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libpng/contrib/tools/pngfix.c

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/* pngfix.c
*
* Copyright (c) 2014-2015 John Cunningham Bowler
*
* Last changed in libpng 1.6.20 [(PENDING RELEASE)]
*
* This code is released under the libpng license.
* For conditions of distribution and use, see the disclaimer
* and license in png.h
*
* Tool to check and fix the zlib inflate 'too far back' problem.
* See the usage message for more information.
*/
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <ctype.h>
#include <limits.h>
#include <errno.h>
#include <assert.h>
#define implies(x,y) assert(!(x) || (y))
#ifdef __GNUC__
/* This is used to fix the error:
*
* pngfix.c:
* In function 'zlib_advance':
* pngfix.c:181:13: error: assuming signed overflow does not
* occur when simplifying conditional to constant [-Werror=strict-overflow]
*/
# define FIX_GCC volatile
#else
# define FIX_GCC
#endif
#define PROGRAM_NAME "pngfix"
/* Define the following to use this program against your installed libpng,
* rather than the one being built here:
*/
#ifdef PNG_FREESTANDING_TESTS
# include <png.h>
#else
# include "../../png.h"
#endif
#if PNG_LIBPNG_VER < 10603 /* 1.6.3 */
# error "pngfix will not work with libpng prior to 1.6.3"
#endif
#ifdef PNG_SETJMP_SUPPORTED
#include <setjmp.h>
#if defined(PNG_READ_SUPPORTED) && defined(PNG_EASY_ACCESS_SUPPORTED) &&\
(defined(PNG_READ_DEINTERLACE_SUPPORTED) ||\
defined(PNG_READ_INTERLACING_SUPPORTED))
/* zlib.h defines the structure z_stream, an instance of which is included
* in this structure and is required for decompressing the LZ compressed
* data in PNG files.
*/
#ifndef ZLIB_CONST
/* We must ensure that zlib uses 'const' in declarations. */
# define ZLIB_CONST
#endif
#include <zlib.h>
#ifdef const
/* zlib.h sometimes #defines const to nothing, undo this. */
# undef const
#endif
/* zlib.h has mediocre z_const use before 1.2.6, this stuff is for compatibility
* with older builds.
*/
#if ZLIB_VERNUM < 0x1260
# define PNGZ_MSG_CAST(s) constcast(char*,s)
# define PNGZ_INPUT_CAST(b) constcast(png_bytep,b)
#else
# define PNGZ_MSG_CAST(s) (s)
# define PNGZ_INPUT_CAST(b) (b)
#endif
#ifndef PNG_MAXIMUM_INFLATE_WINDOW
# error "pngfix not supported in this libpng version"
#endif
#if ZLIB_VERNUM >= 0x1240
/* Copied from pngpriv.h */
#ifdef __cplusplus
# define voidcast(type, value) static_cast<type>(value)
# define constcast(type, value) const_cast<type>(value)
# define aligncast(type, value) \
static_cast<type>(static_cast<void*>(value))
# define aligncastconst(type, value) \
static_cast<type>(static_cast<const void*>(value))
#else
# define voidcast(type, value) (value)
# define constcast(type, value) ((type)(value))
# define aligncast(type, value) ((void*)(value))
# define aligncastconst(type, value) ((const void*)(value))
#endif /* __cplusplus */
#if PNG_LIBPNG_VER < 10700
/* Chunk tags (copied from pngpriv.h) */
#define PNG_32b(b,s) ((png_uint_32)(b) << (s))
#define PNG_U32(b1,b2,b3,b4) \
(PNG_32b(b1,24) | PNG_32b(b2,16) | PNG_32b(b3,8) | PNG_32b(b4,0))
/* Constants for known chunk types. */
#define png_IDAT PNG_U32( 73, 68, 65, 84)
#define png_IEND PNG_U32( 73, 69, 78, 68)
#define png_IHDR PNG_U32( 73, 72, 68, 82)
#define png_PLTE PNG_U32( 80, 76, 84, 69)
#define png_bKGD PNG_U32( 98, 75, 71, 68)
#define png_cHRM PNG_U32( 99, 72, 82, 77)
#define png_fRAc PNG_U32(102, 82, 65, 99) /* registered, not defined */
#define png_gAMA PNG_U32(103, 65, 77, 65)
#define png_gIFg PNG_U32(103, 73, 70, 103)
#define png_gIFt PNG_U32(103, 73, 70, 116) /* deprecated */
#define png_gIFx PNG_U32(103, 73, 70, 120)
#define png_hIST PNG_U32(104, 73, 83, 84)
#define png_iCCP PNG_U32(105, 67, 67, 80)
#define png_iTXt PNG_U32(105, 84, 88, 116)
#define png_oFFs PNG_U32(111, 70, 70, 115)
#define png_pCAL PNG_U32(112, 67, 65, 76)
#define png_pHYs PNG_U32(112, 72, 89, 115)
#define png_sBIT PNG_U32(115, 66, 73, 84)
#define png_sCAL PNG_U32(115, 67, 65, 76)
#define png_sPLT PNG_U32(115, 80, 76, 84)
#define png_sRGB PNG_U32(115, 82, 71, 66)
#define png_sTER PNG_U32(115, 84, 69, 82)
#define png_tEXt PNG_U32(116, 69, 88, 116)
#define png_tIME PNG_U32(116, 73, 77, 69)
#define png_tRNS PNG_U32(116, 82, 78, 83)
#define png_zTXt PNG_U32(122, 84, 88, 116)
#endif
/* The 8-byte signature as a pair of 32-bit quantities */
#define sig1 PNG_U32(137, 80, 78, 71)
#define sig2 PNG_U32( 13, 10, 26, 10)
/* Is the chunk critical? */
#define CRITICAL(chunk) (((chunk) & PNG_U32(32,0,0,0)) == 0)
/* Is it safe to copy? */
#define SAFE_TO_COPY(chunk) (((chunk) & PNG_U32(0,0,0,32)) != 0)
/* Fix ups for builds with limited read support */
#ifndef PNG_ERROR_TEXT_SUPPORTED
# define png_error(a,b) png_err(a)
#endif
/********************************* UTILITIES **********************************/
/* UNREACHED is a value to cause an assert to fail. Because of the way the
* assert macro is written the string "UNREACHED" is produced in the error
* message.
*/
#define UNREACHED 0
/* 80-bit number handling - a PNG image can be up to (2^31-1)x(2^31-1) 8-byte
* (16-bit RGBA) pixels in size; that's less than 2^65 bytes or 2^68 bits, so
* arithmetic of 80-bit numbers is sufficient. This representation uses an
* arbitrary length array of png_uint_16 digits (0..65535). The representation
* is little endian.
*
* The arithmetic functions take zero to two uarb values together with the
* number of digits in those values and write the result to the given uarb
* (always the first argument) returning the number of digits in the result.
* If the result is negative the return value is also negative (this would
* normally be an error).
*/
typedef png_uint_16 udigit; /* A 'unum' is an array of these */
typedef png_uint_16p uarb;
typedef png_const_uint_16p uarbc;
#define UDIGITS(unum) ((sizeof unum)/(sizeof (udigit))
/* IMPORTANT: only apply this to an array, applied to a pointer the result
* will typically be '2', which is not useful.
*/
static int
uarb_set(uarb result, png_alloc_size_t val)
/* Set (initialize) 'result' to 'val'. The size required for 'result' must
* be determined by the caller from a knowledge of the maximum for 'val'.
*/
{
int ndigits = 0;
while (val > 0)
{
result[ndigits++] = (png_uint_16)(val & 0xffff);
val >>= 16;
}
return ndigits;
}
static int
uarb_copy(uarb to, uarb from, int idigits)
/* Copy a uarb, may reduce the digit count */
{
int d, odigits;
for (d=odigits=0; d<idigits; ++d)
if ((to[d] = from[d]) != 0)
odigits = d+1;
return odigits;
}
static int
uarb_inc(uarb num, int in_digits, png_int_32 add)
/* This is a signed 32-bit add, except that to avoid overflow the value added
* or subtracted must be no more than 2^31-65536. A negative result
* indicates a negative number (which is an error below). The size of
* 'num' should be max(in_digits+1,2) for arbitrary 'add' but can be just
* in_digits+1 if add is known to be in the range -65535..65535.
*/
{
FIX_GCC int out_digits = 0;
while (out_digits < in_digits)
{
add += num[out_digits];
num[out_digits++] = (png_uint_16)(add & 0xffff);
add >>= 16;
}
while (add != 0 && add != (-1))
{
num[out_digits++] = (png_uint_16)(add & 0xffff);
add >>= 16;
}
if (add == 0)
{
while (out_digits > 0 && num[out_digits-1] == 0)
--out_digits;
return out_digits; /* may be 0 */
}
else /* negative result */
{
while (out_digits > 1 && num[out_digits-1] == 0xffff)
--out_digits;
return -out_digits;
}
}
static int
uarb_add32(uarb num, int in_digits, png_uint_32 add)
/* As above but this works with any 32-bit value and only does 'add' */
{
if (in_digits > 0)
{
in_digits = uarb_inc(num, in_digits, add & 0xffff);
return uarb_inc(num+1, in_digits-1, add >> 16)+1;
}
return uarb_set(num, add);
}
static int
uarb_mult_digit(uarb acc, int a_digits, uarb num, FIX_GCC int n_digits,
png_uint_16 val)
/* Primitive one-digit multiply - 'val' must be 0..65535. Note that this
* primitive is a multiply and accumulate - the result of *num * val is added
* to *acc.
*
* This is a one-digit multiply, so the product may be up to one digit longer
* than 'num', however the add to 'acc' means that the caller must ensure
* that 'acc' is at least one digit longer than this *and* at least one digit
* longer than the current length of 'acc'. (Or the caller must otherwise
* ensure 'adigits' is adequate from knowledge of the values.)
*/
{
/* The digits in *acc, *num and val are in the range 0..65535, so the
* result below is at most (65535*65535)+2*65635 = 65535*(65535+2), which is
* exactly 0xffffffff.
*/
if (val > 0 && n_digits > 0) /* Else the product is 0 */
{
png_uint_32 carry = 0;
int out_digits = 0;
while (out_digits < n_digits || carry > 0)
{
if (out_digits < a_digits)
carry += acc[out_digits];
if (out_digits < n_digits)
carry += (png_uint_32)num[out_digits] * val;
acc[out_digits++] = (png_uint_16)(carry & 0xffff);
carry >>= 16;
}
/* So carry is 0 and all the input digits have been consumed. This means
* that it is possible to skip any remaining digits in acc.
*/
if (out_digits > a_digits)
return out_digits;
}
return a_digits;
}
static int
uarb_mult32(uarb acc, int a_digits, uarb num, int n_digits, png_uint_32 val)
/* calculate acc += num * val, 'val' may be any 32-bit value, 'acc' and 'num'
* may be any value, returns the number of digits in 'acc'.
*/
{
if (n_digits > 0 && val > 0)
{
a_digits = uarb_mult_digit(acc, a_digits, num, n_digits,
(png_uint_16)(val & 0xffff));
/* Because n_digits and val are >0 the following must be true: */
assert(a_digits > 0);
val >>= 16;
if (val > 0)
a_digits = uarb_mult_digit(acc+1, a_digits-1, num, n_digits,
(png_uint_16)val) + 1;
}
return a_digits;
}
static int
uarb_shift(uarb inout, int ndigits, unsigned int right_shift)
/* Shift inout right by right_shift bits, right_shift must be in the range
* 1..15
*/
{
FIX_GCC int i = ndigits;
png_uint_16 carry = 0;
assert(right_shift >= 1 && right_shift <= 15);
while (--i >= 0)
{
png_uint_16 temp = (png_uint_16)(carry | (inout[i] >> right_shift));
/* Bottom bits to top bits of carry */
carry = (png_uint_16)((inout[i] << (16-right_shift)) & 0xffff);
inout[i] = temp;
/* The shift may reduce ndigits */
if (i == ndigits-1 && temp == 0)
ndigits = i;
}
return ndigits;
}
static int
uarb_cmp(uarb a, int adigits, uarb b, int bdigits)
/* Return -1/0/+1 according as a<b/a==b/a>b */
{
if (adigits < bdigits)
return -1;
if (adigits > bdigits)
return 1;
while (adigits-- > 0)
if (a[adigits] < b[adigits])
return -1;
else if (a[adigits] > b[adigits])
return 1;
return 0;
}
#if 0 /*UNUSED*/
static int
uarb_eq32(uarb num, int digits, png_uint_32 val)
/* Return true if the uarb is equal to 'val' */
{
switch (digits)
{
case 0: return val == 0;
case 1: return val == num[0];
case 2: return (val & 0xffff) == num[0] && (val >> 16) == num[1];
default: return 0;
}
}
#endif
static void
uarb_printx(uarb num, int digits, FILE *out)
/* Print 'num' as a hexadecimal number (easier than decimal!) */
{
while (digits > 0)
if (num[--digits] > 0)
{
fprintf(out, "0x%x", num[digits]);
while (digits > 0)
fprintf(out, "%.4x", num[--digits]);
}
else if (digits == 0) /* the number is 0 */
fputs("0x0", out);
}
static void
uarb_print(uarb num, int digits, FILE *out)
/* Prints 'num' as a decimal if it will fit in an unsigned long, else as a
* hexadecimal number. Notice that the results vary for images over 4GByte
* in a system dependent way, and the hexadecimal form doesn't work very well
* in awk script input.
*
*
* TODO: write uarb_div10
*/
{
if (digits * sizeof (udigit) > sizeof (unsigned long))
uarb_printx(num, digits, out);
else
{
unsigned long n = 0;
while (digits > 0)
n = (n << 16) + num[--digits];
fprintf(out, "%lu", n);
}
}
/* Generate random bytes. This uses a boring repeatable algorithm and it
* is implemented here so that it gives the same set of numbers on every
* architecture. It's a linear congruential generator (Knuth or Sedgewick
* "Algorithms") but it comes from the 'feedback taps' table in Horowitz and
* Hill, "The Art of Electronics" (Pseudo-Random Bit Sequences and Noise
* Generation.)
*
* (Copied from contrib/libtests/pngvalid.c)
*/
static void
make_random_bytes(png_uint_32* seed, void* pv, size_t size)
{
png_uint_32 u0 = seed[0], u1 = seed[1];
png_bytep bytes = voidcast(png_bytep, pv);
/* There are thirty-three bits; the next bit in the sequence is bit-33 XOR
* bit-20. The top 1 bit is in u1, the bottom 32 are in u0.
*/
size_t i;
for (i=0; i<size; ++i)
{
/* First generate 8 new bits then shift them in at the end. */
png_uint_32 u = ((u0 >> (20-8)) ^ ((u1 << 7) | (u0 >> (32-7)))) & 0xff;
u1 <<= 8;
u1 |= u0 >> 24;
u0 <<= 8;
u0 |= u;
*bytes++ = (png_byte)u;
}
seed[0] = u0;
seed[1] = u1;
}
/* Clear an object to a random value. */
static void
clear(void *pv, size_t size)
{
static png_uint_32 clear_seed[2] = { 0x12345678, 0x9abcdef0 };
make_random_bytes(clear_seed, pv, size);
}
#define CLEAR(object) clear(&(object), sizeof (object))
/* Copied from unreleased 1.7 code.
*
* CRC checking uses a local pre-built implementation of the Ethernet CRC32.
* This is to avoid a function call to the zlib DLL and to optimize the
* byte-by-byte case.
*/
static png_uint_32 crc_table[256] =
{
0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
0x2d02ef8d
};
/* The CRC calculated here *IS* conditioned, the corresponding value used by
* zlib and the result value is obtained by XORing with CRC_INIT, which is also
* the first value that must be passed in (for the first byte) to crc_one_byte.
*/
#define CRC_INIT 0xffffffff
static png_uint_32
crc_one_byte(png_uint_32 crc, int b)
{
return crc_table[(crc ^ b) & 0xff] ^ (crc >> 8);
}
static png_uint_32
crc_init_4(png_uint_32 value)
{
/* This is an alternative to the algorithm used in zlib, which requires four
* separate tables to parallelize the four byte operations, it only works for
* a CRC of the first four bytes of the stream, but this is what happens in
* the parser below where length+chunk-name is read and chunk-name used to
* initialize the CRC. Notice that the calculation here avoids repeated
* conditioning (xor with 0xffffffff) by storing the conditioned value.
*/
png_uint_32 crc = crc_table[(~value >> 24)] ^ 0xffffff;
crc = crc_table[(crc ^ (value >> 16)) & 0xff] ^ (crc >> 8);
crc = crc_table[(crc ^ (value >> 8)) & 0xff] ^ (crc >> 8);
return crc_table[(crc ^ value) & 0xff] ^ (crc >> 8);
}
static int
chunk_type_valid(png_uint_32 c)
/* Bit whacking approach to chunk name validation that is intended to avoid
* branches. The cost is that it uses a lot of 32-bit constants, which might
* be bad on some architectures.
*/
{
png_uint_32 t;
/* Remove bit 5 from all but the reserved byte; this means every
* 8-bit unit must be in the range 65-90 to be valid. So bit 5
* must be zero, bit 6 must be set and bit 7 zero.
*/
c &= ~PNG_U32(32,32,0,32);
t = (c & ~0x1f1f1f1f) ^ 0x40404040;
/* Subtract 65 for each 8-bit quantity, this must not overflow
* and each byte must then be in the range 0-25.
*/
c -= PNG_U32(65,65,65,65);
t |=c ;
/* Subtract 26, handling the overflow which should set the top
* three bits of each byte.
*/
c -= PNG_U32(25,25,25,26);
t |= ~c;
return (t & 0xe0e0e0e0) == 0;
}
/**************************** CONTROL INFORMATION *****************************/
/* Information about a sequence of IDAT chunks, the chunks have been re-synced
* using sync_stream below and the new lengths are recorded here. Because the
* number of chunks is unlimited this is handled using a linked list of these
* structures.
*/
struct IDAT_list
{
struct IDAT_list *next; /* Linked list */
unsigned int length; /* Actual length of the array below */
unsigned int count; /* Number of entries that are valid */
# define IDAT_INIT_LENGTH 16
png_uint_32 lengths[IDAT_INIT_LENGTH];
};
static void
IDAT_list_init(struct IDAT_list *list)
{
CLEAR(*list);
list->next = NULL;
list->length = IDAT_INIT_LENGTH;
}
static size_t
IDAT_list_size(struct IDAT_list *list, unsigned int length)
/* Return the size in bytes of an IDAT_list of the given length. */
{
if (list != NULL)
length = list->length;
return sizeof *list - sizeof list->lengths +
length * sizeof list->lengths[0];
}
static void
IDAT_list_end(struct IDAT_list *IDAT_list)
{
struct IDAT_list *list = IDAT_list->next;
CLEAR(*IDAT_list);
while (list != NULL)
{
struct IDAT_list *next = list->next;
clear(list, IDAT_list_size(list, 0));
free(list);
list = next;
}
}
static struct IDAT_list *
IDAT_list_extend(struct IDAT_list *tail)
{
/* Use the previous cached value if available. */
struct IDAT_list *next = tail->next;
if (next == NULL)
{
/* Insert a new, malloc'ed, block of IDAT information buffers, this
* one twice as large as the previous one:
*/
unsigned int length = 2 * tail->length;
if (length < tail->length) /* arithmetic overflow */
length = tail->length;
next = voidcast(IDAT_list*, malloc(IDAT_list_size(NULL, length)));
CLEAR(*next);
/* The caller must handle this: */
if (next == NULL)
return NULL;
next->next = NULL;
next->length = length;
tail->next = next;
}
return next;
}
/* GLOBAL CONTROL STRUCTURE */
struct global
{
/* PUBLIC GLOBAL VARIABLES: OWNER INITIALIZE */
unsigned int errors :1; /* print file errors to stderr */
unsigned int warnings :1; /* print libpng warnings to stderr */
unsigned int optimize_zlib :1; /* Run optimization search */
unsigned int quiet :2; /* don't output summaries */
unsigned int verbose :3; /* various internal tracking */
unsigned int skip :3; /* Non-critical chunks to skip */
# define SKIP_NONE 0
# define SKIP_BAD_CRC 1 /* Chunks with a bad CRC */
# define SKIP_UNSAFE 2 /* Chunks not safe to copy */
# define SKIP_UNUSED 3 /* Chunks not used by libpng */
# define SKIP_TRANSFORM 4 /* Chunks only used in transforms */
# define SKIP_COLOR 5 /* Everything but tRNS, sBIT, gAMA and sRGB */
# define SKIP_ALL 6 /* Everything but tRNS and sBIT */
png_uint_32 idat_max; /* 0 to perform no re-chunking */
int status_code; /* Accumulated status code */
# define TOO_FAR_BACK 0x01 /* found a too-far-back error */
# define CRC_ERROR 0x02 /* fixed an invalid CRC */
# define STREAM_ERROR 0x04 /* damaged PNG stream (may be fixable) */
# define TRUNCATED 0x08 /* truncated but still readable */
# define FILE_ERROR 0x10 /* could not read the file */
# define WRITE_ERROR 0x20 /* write error (this terminates the read) */
# define INTERNAL_ERROR 0x40 /* internal limits/errors encountered */
/* PUBLIC GLOBAL VARIABLES: USED INTERNALLY BY IDAT READ CODE */
struct IDAT_list idat_cache; /* Cache of file IDAT information buffers */
/* The structure is shared across all uses of this global control
* structure to avoid reallocation between IDAT streams.
*/
};
static int
global_end(struct global *global)
{
int rc;
IDAT_list_end(&global->idat_cache);
rc = global->status_code;
CLEAR(*global);
return rc;
}
static void
global_init(struct global *global)
/* Call this once (and only once) to initialize the control */
{
CLEAR(*global);
/* Globals */
global->errors = 0;
global->warnings = 0;
global->quiet = 0;
global->verbose = 0;
global->idat_max = 0; /* no re-chunking of IDAT */
global->optimize_zlib = 0;
global->skip = SKIP_NONE;
global->status_code = 0;
IDAT_list_init(&global->idat_cache);
}
static int
skip_chunk_type(const struct global *global, png_uint_32 type)
/* Return true if this chunk is to be skipped according to the --strip
* option. This code needs to recognize all known ancillary chunks in order
* to handle the --strip=unsafe option.
*/
{
/* Never strip critical chunks: */
if (CRITICAL(type))
return 0;
switch (type)
{
/* Chunks that are treated as, effectively, critical because they affect
* correct interpretation of the pixel values:
*/
case png_tRNS: case png_sBIT:
return 0;
/* Chunks that specify gamma encoding which should therefore only be
* removed the the user insists:
*/
case png_gAMA: case png_sRGB:
if (global->skip >= SKIP_ALL)
return 1;
return 0;
/* Chunks that affect color interpretation - not used by libpng and rarely
* used by applications, but technically still required for correct
* interpretation of the image data:
*/
case png_cHRM: case png_iCCP:
if (global->skip >= SKIP_COLOR)
return 1;
return 0;
/* Other chunks that are used by libpng in image transformations (as
* opposed to known chunks that have get/set APIs but are not otherwise
* used.)
*/
case png_bKGD:
if (global->skip >= SKIP_TRANSFORM)
return 1;
return 0;
/* All other chunks that libpng knows about and affect neither image
* interpretation nor libpng transforms - chunks that are effectively
* unused by libpng even though libpng might recognize and store them.
*/
case png_fRAc: case png_gIFg: case png_gIFt: case png_gIFx: case png_hIST:
case png_iTXt: case png_oFFs: case png_pCAL: case png_pHYs: case png_sCAL:
case png_sPLT: case png_sTER: case png_tEXt: case png_tIME: case png_zTXt:
if (global->skip >= SKIP_UNUSED)
return 1;
return 0;
/* Chunks that libpng does not know about (notice that this depends on the
* list above including all known chunks!) The decision here depends on
* whether the safe-to-copy bit is set in the chunk type.
*/
default:
if (SAFE_TO_COPY(type))
{
if (global->skip >= SKIP_UNUSED) /* as above */
return 1;
}
else if (global->skip >= SKIP_UNSAFE)
return 1;
return 0;
}
}
/* PER-FILE CONTROL STRUCTURE */
struct chunk;
struct IDAT;
struct file
{
/* ANCESTORS */
struct global *global;
/* PUBLIC PER-FILE VARIABLES: CALLER INITIALIZE */
const char * file_name;
const char * out_name; /* Name of output file (if required) */
/* PUBLIC PER-FILE VARIABLES: SET BY PNG READ CODE */
/* File specific result codes */
int status_code; /* Set to a bit mask of the following: */
int read_errno; /* Records a read error errno */
int write_errno; /* Records a write error errno */
/* IHDR information */
png_uint_32 width;
png_uint_32 height;
png_byte bit_depth;
png_byte color_type;
png_byte compression_method;
png_byte filter_method;
png_byte interlace_method;
udigit image_bytes[5];
int image_digits;
/* PROTECTED PER-FILE VARIABLES: USED BY THE READ CODE */
FILE * file; /* Original PNG file */
FILE * out; /* If a new one is being written */
jmp_buf jmpbuf; /* Set while reading a PNG */
/* PROTECTED CHUNK SPECIFIC VARIABLES: USED BY CHUNK CODE */
/* The following variables are used during reading to record the length, type
* and data position of the *next* chunk or, right at the start, the
* signature (in length,type).
*
* When a chunk control structure is instantiated these values are copied
* into the structure and can then be overritten with the data for the next
* chunk.
*/
fpos_t data_pos; /* Position of first byte of chunk data */
png_uint_32 length; /* First word (length or signature start) */
png_uint_32 type; /* Second word (type or signature end) */
png_uint_32 crc; /* Running chunk CRC (used by read_chunk) */
/* These counts are maintained by the read and write routines below and are
* reset by the chunk handling code. They record the total number of bytes
* read or written for the chunk, including the header (length,type) bytes.
*/
png_uint_32 read_count; /* Count of bytes read (in the chunk) */
png_uint_32 write_count; /* Count of bytes written (in the chunk) */
int state; /* As defined here: */
# define STATE_SIGNATURE 0 /* The signature is being written */
# define STATE_CHUNKS 1 /* Non-IDAT chunks are being written */
# define STATE_IDAT 2 /* An IDAT stream is being written */
/* Two pointers used to enable clean-up in the event of fatal errors and to
* hold state about the parser process (only one of each at present.)
*/
struct chunk * chunk;
struct IDAT * idat;
/* Interface to allocate a new chunk or IDAT control structure. The result
* is returned by setting one or other of the above variables. Note that the
* relevant initializer is called by the allocator function. The alloc_ptr
* is used only by the implementation of the allocate function.
*/
void * alloc_ptr;
void (*alloc)(struct file*,int idat);
/* idat: allocate IDAT not chunk */
};
/* Valid longjmp (stop) codes are: */
#define LIBPNG_WARNING_CODE 1 /* generic png_error */
#define LIBPNG_ERROR_CODE 2 /* generic png_error */
#define ZLIB_ERROR_CODE 3 /* generic zlib error */
#define INVALID_ERROR_CODE 4 /* detected an invalid PNG */
#define READ_ERROR_CODE 5 /* read failed */
#define WRITE_ERROR_CODE 6 /* error in write */
#define UNEXPECTED_ERROR_CODE 7 /* unexpected (internal?) error */
static void
emit_string(const char *str, FILE *out)
/* Print a string with spaces replaced by '_' and non-printing characters by
* an octal escape.
*/
{
for (; *str; ++str)
if (isgraph(UCHAR_MAX & *str))
putc(*str, out);
else if (isspace(UCHAR_MAX & *str))
putc('_', out);
else
fprintf(out, "\\%.3o", *str);
}
static const char *
strcode(int code)
{
switch (code)
{
case LIBPNG_WARNING_CODE: return "warning";
case LIBPNG_ERROR_CODE: return "libpng";
case ZLIB_ERROR_CODE: return "zlib";
case INVALID_ERROR_CODE: return "invalid";
case READ_ERROR_CODE: return "read";
case WRITE_ERROR_CODE: return "write";
case UNEXPECTED_ERROR_CODE: return "unexpected";
default: return "INVALID";
}
}
static void
emit_error(struct file *file, int code, const char *what)
/* Generic error message routine, takes a 'stop' code but can be used
* elsewhere. Always outputs a message.
*/
{
const char *reason;
int err = 0;
switch (code)
{
case LIBPNG_WARNING_CODE: reason = "libpng warning:"; break;
case LIBPNG_ERROR_CODE: reason = "libpng error:"; break;
case ZLIB_ERROR_CODE: reason = "zlib error:"; break;
case INVALID_ERROR_CODE: reason = "invalid"; break;
case READ_ERROR_CODE: reason = "read failure:";
err = file->read_errno;
break;
case WRITE_ERROR_CODE: reason = "write error";
err = file->write_errno;
break;
case UNEXPECTED_ERROR_CODE: reason = "unexpected error:";
err = file->read_errno;
if (err == 0)
err = file->write_errno;
break;
default: reason = "INVALID (internal error):"; break;
}
if (err != 0)
fprintf(stderr, "%s: %s %s [%s]\n", file->file_name, reason, what,
strerror(err));
else
fprintf(stderr, "%s: %s %s\n", file->file_name, reason, what);
}
static void chunk_end(struct chunk **);
static void IDAT_end(struct IDAT **);
static int
file_end(struct file *file)
{
int rc;
/* If either of the chunk pointers are set end them here, the IDAT structure
* must be deallocated first as it may deallocate the chunk structure.
*/
if (file->idat != NULL)
IDAT_end(&file->idat);
if (file->chunk != NULL)
chunk_end(&file->chunk);
rc = file->status_code;
if (file->file != NULL)
(void)fclose(file->file);
if (file->out != NULL)
{
/* NOTE: this is bitwise |, all the following functions must execute and
* must succeed.
*/
if (ferror(file->out) | fflush(file->out) | fclose(file->out))
{
perror(file->out_name);
emit_error(file, READ_ERROR_CODE, "output write error");
rc |= WRITE_ERROR;
}
}
/* Accumulate the result codes */
file->global->status_code |= rc;
CLEAR(*file);
return rc; /* status code: non-zero on read or write error */
}
static int
file_init(struct file *file, struct global *global, const char *file_name,
const char *out_name, void *alloc_ptr, void (*alloc)(struct file*,int))
/* Initialize a file control structure. This will open the given files as
* well. The status code returned is 0 on success, non zero (using the flags
* above) on a file open error.
*/
{
CLEAR(*file);
file->global = global;
file->file_name = file_name;
file->out_name = out_name;
file->status_code = 0;
file->read_errno = 0;
file->write_errno = 0;
file->file = NULL;
file->out = NULL;
/* jmpbuf is garbage: must be set by read_png */
file->read_count = 0;
file->state = STATE_SIGNATURE;
file->chunk = NULL;
file->idat = NULL;
file->alloc_ptr = alloc_ptr;
file->alloc = alloc;
/* Open the files: */
assert(file_name != NULL);
file->file = fopen(file_name, "rb");
if (file->file == NULL)
{
file->read_errno = errno;
file->status_code |= FILE_ERROR;
/* Always output: please give a readable file! */
perror(file_name);
return FILE_ERROR;
}
if (out_name != NULL)
{
file->out = fopen(out_name, "wb");
if (file->out == NULL)
{
file->write_errno = errno;
file->status_code |= WRITE_ERROR;
perror(out_name);
return WRITE_ERROR;
}
}
return 0;
}
static void
log_error(struct file *file, int code, const char *what)
/* Like emit_error but checks the global 'errors' flag */
{
if (file->global->errors)
emit_error(file, code, what);
}
static char
type_char(png_uint_32 v)
{
/* In fact because chunk::chunk_type is validated prior to any call to this
* function it will always return a-zA-Z, but the extra codes are just there
* to help in finding internal (programming) errors. Note that the code only
* ever considers the low 7 bits of the value (so it is not necessary for the
* type_name function to mask of the byte.)
*/
if (v & 32)
return "!abcdefghijklmnopqrstuvwxyz56789"[(v-96)&31];
else
return "@ABCDEFGHIJKLMNOPQRSTUVWXYZ01234"[(v-64)&31];
}
static void
type_name(png_uint_32 type, FILE *out)
{
putc(type_char(type >> 24), out);
putc(type_char(type >> 16), out);
putc(type_char(type >> 8), out);
putc(type_char(type ), out);
}
static void
type_sep(FILE *out)
{
putc(':', out);
putc(' ', out);
}
static png_uint_32 current_type(struct file *file, int code);
PNG_NORETURN static void
stop(struct file *file, int code, const char *what)
/* Return control when a PNG file cannot be read. This outputs an 'ERR'
* summary line too.
*/
{
log_error(file, code, what);
/* The chunk being read is typically identified by file->chunk or, if this is
* NULL, by file->type. This may be wrong if libpng reads ahead, but this
* only happens with IDAT where libpng reads the header then jumps around
* finding errors in the previous chunks. We know that is happening because
* we are at the start of the IDAT (i.e. no IDAT data has yet been written.)
*
* SUMMARY FORMAT (stop):
*
* IDAT ERR status code read-errno write-errno message file
*
* 'uncompressed' will be 0 if there was a problem in the IHDR. The errno
* values are emit_string(strerror(errno)).
*/
if (file->global->quiet < 2) /* need two quiets to stop this. */
{
png_uint_32 type;
if (file->chunk != NULL)
type = current_type(file, code); /* Gropes in struct chunk and IDAT */
else
type = file->type;
if (type)
type_name(type, stdout);
else /* magic: an IDAT header, produces bogons for too many IDATs */
fputs("HEAD", stdout); /* not a registered chunk! */
printf(" ERR %.2x %s ", file->status_code, strcode(code));
/* This only works one strerror at a time, because of the way strerror is
* implemented.
*/
emit_string(strerror(file->read_errno), stdout);
putc(' ', stdout);
emit_string(strerror(file->write_errno), stdout);
putc(' ', stdout);
emit_string(what, stdout);
putc(' ', stdout);
fputs(file->file_name, stdout);
putc('\n', stdout);
}
file->status_code |= FILE_ERROR;
longjmp(file->jmpbuf, code);
}
PNG_NORETURN static void
stop_invalid(struct file *file, const char *what)
{
stop(file, INVALID_ERROR_CODE, what);
}
static void
type_message(struct file *file, png_uint_32 type, const char *what)
/* Error message for a chunk; the chunk name comes from 'type' */
{
if (file->global->errors)
{
fputs(file->file_name, stderr);
type_sep(stderr);
type_name(type, stderr);
type_sep(stderr);
fputs(what, stderr);
putc('\n', stderr);
}
}
/* Input file positioning - we jump around in the input file while reading
* stuff, these wrappers deal with the error handling.
*/
static void
file_getpos(struct file *file, fpos_t *pos)
{
if (fgetpos(file->file, pos))
{
/* This is unexpected, so perror it */
perror(file->file_name);
stop(file, READ_ERROR_CODE, "fgetpos");
}
}
static void
file_setpos(struct file *file, const fpos_t *pos)
{
if (fsetpos(file->file, pos))
{
perror(file->file_name);
stop(file, READ_ERROR_CODE, "fsetpos");
}
}
static void
getpos(struct file *file)
/* Get the current position and store it in 'data_pos'. The corresponding
* setpos() function is chunk specific because it uses the copy of the
* position for the specific chunk.
*/
{
file_getpos(file, &file->data_pos);
}
/* Read utility - read a single byte, returns a value in the range 0..255 or EOF
* on a read error. In the latter case status_code and read_errno are updated
* appropriately.
*/
static int
read_byte(struct file *file)
{
int ch = getc(file->file);
if (ch >= 0 && ch <= 255)
{
++(file->read_count);
return ch;
}
else if (ch != EOF)
{
file->status_code |= INTERNAL_ERROR;
file->read_errno = ERANGE; /* out of range character */
/* This is very unexpected; an error message is always output: */
emit_error(file, UNEXPECTED_ERROR_CODE, "file read");
}
# ifdef EINTR
else if (errno == EINTR) /* Interrupted, try again */
{
errno = 0;
return read_byte(file);
}
# endif
else
{
/* An error, it doesn't really matter what the error is but it gets
* recorded anyway.
*/
if (ferror(file->file))
file->read_errno = errno;
else if (feof(file->file))
file->read_errno = 0; /* I.e. a regular EOF, no error */
else /* unexpected */
file->read_errno = EDOM;
}
/* 'TRUNCATED' is used for all cases of failure to read a byte, because of
* the way libpng works a byte read is never attempted unless the byte is
* expected to be there, so EOF should not occur.
*/
file->status_code |= TRUNCATED;
return EOF;
}
static png_byte
reread_byte(struct file *file)
/* Read a byte when an error is not expected to happen because the byte has
* been read before without error.
*/
{
int ch = getc(file->file);
if (errno != 0)
file->read_errno = errno;
if (ch < 0 || ch > 255)
stop(file, UNEXPECTED_ERROR_CODE, "reread");
return (png_byte)ch;
}
static png_uint_32
reread_4(struct file *file)
/* The same but for a four byte quantity */
{
png_uint_32 result = 0;
int i = 0;
while (++i <= 4)
result = (result << 8) + reread_byte(file);
return result;
}
static void
skip_12(struct file *file)
/* Skip exactly 12 bytes in the input stream - used to skip a CRC and chunk
* header that has been read before.
*/
{
/* Since the chunks were read before this shouldn't fail: */
if (fseek(file->file, 12, SEEK_CUR) != 0)
{
if (errno != 0)
file->read_errno = errno;
stop(file, UNEXPECTED_ERROR_CODE, "reskip");
}
}
static void
write_byte(struct file *file, int b)
/* Write one byte to the output - this causes a fatal error if the write
* fails and the read of this PNG file immediately terminates. Just
* increments the write count if there is no output file.
*/
{
if (file->out != NULL)
{
if (putc(b, file->out) != b)
{
file->write_errno = errno;
file->status_code |= WRITE_ERROR;
stop(file, WRITE_ERROR_CODE, "write byte");
}
}
++(file->write_count);
}
/* Derivatives of the read/write functions. */
static unsigned int
read_4(struct file *file, png_uint_32 *pu)
/* Read four bytes, returns the number of bytes read successfully and, if all
* four bytes are read, assigns the result to *pu.
*/
{
unsigned int i = 0;
png_uint_32 val = 0;
do
{
int ch = read_byte(file);
if (ch == EOF)
return i;
val = (val << 8) + ch;
} while (++i < 4);
*pu = val;
return i;
}
/* CRC handling - read but calculate the CRC while doing so. */
static int
crc_read_many(struct file *file, png_uint_32 length)
/* Reads 'length' bytes and updates the CRC, returns true on success, false
* if the input is truncated.
*/
{
if (length > 0)
{
png_uint_32 crc = file->crc;
do
{
int ch = read_byte(file);
if (ch == EOF)
return 0; /* Truncated */
crc = crc_one_byte(crc, ch);
}
while (--length > 0);
file->crc = crc;
}
return 1; /* OK */
}
static int
calc_image_size(struct file *file)
/* Fill in the image_bytes field given the IHDR information, calls stop on
* error.
*/
{
png_uint_16 pd = file->bit_depth;
switch (file->color_type)
{
default:
stop_invalid(file, "IHDR: colour type");
invalid_bit_depth:
stop_invalid(file, "IHDR: bit depth");
case 0: /* g */
if (pd != 1 && pd != 2 && pd != 4 && pd != 8 && pd != 16)
goto invalid_bit_depth;
break;
case 3:
if (pd != 1 && pd != 2 && pd != 4 && pd != 8)
goto invalid_bit_depth;
break;
case 2: /* rgb */
if (pd != 8 && pd != 16)
goto invalid_bit_depth;
pd = (png_uint_16)(pd * 3);
break;
case 4: /* ga */
if (pd != 8 && pd != 16)
goto invalid_bit_depth;
pd = (png_uint_16)(pd * 2);
break;
case 6: /* rgba */
if (pd != 8 && pd != 16)
goto invalid_bit_depth;
pd = (png_uint_16)(pd * 4);
break;
}
if (file->width < 1 || file->width > 0x7fffffff)
stop_invalid(file, "IHDR: width");
else if (file->height < 1 || file->height > 0x7fffffff)
stop_invalid(file, "IHDR: height");
else if (file->compression_method != 0)
stop_invalid(file, "IHDR: compression method");
else if (file->filter_method != 0)
stop_invalid(file, "IHDR: filter method");
else switch (file->interlace_method)
{
case PNG_INTERLACE_ADAM7:
/* Interlacing makes the image larger because of the replication of
* both the filter byte and the padding to a byte boundary.
*/
{
int pass;
int image_digits = 0;
udigit row_width[2], row_bytes[3];
for (pass=0; pass<=6; ++pass)
{
png_uint_32 pw = PNG_PASS_COLS(file->width, pass);
if (pw > 0)
{
int digits;
/* calculate 1+((pw*pd+7)>>3) in row_bytes */
digits = uarb_mult_digit(row_bytes, uarb_set(row_bytes, 7),
row_width, uarb_set(row_width, pw), pd);
digits = uarb_shift(row_bytes, digits, 3);
digits = uarb_inc(row_bytes, digits, 1);
/* Add row_bytes * pass-height to the file image_bytes field
*/
image_digits = uarb_mult32(file->image_bytes, image_digits,
row_bytes, digits,
PNG_PASS_ROWS(file->height, pass));
}
}
file->image_digits = image_digits;
}
break;
case PNG_INTERLACE_NONE:
{
int digits;
udigit row_width[2], row_bytes[3];
/* As above, but use image_width in place of the pass width: */
digits = uarb_mult_digit(row_bytes, uarb_set(row_bytes, 7),
row_width, uarb_set(row_width, file->width), pd);
digits = uarb_shift(row_bytes, digits, 3);
digits = uarb_inc(row_bytes, digits, 1);
/* Set row_bytes * image-height to the file image_bytes field */
file->image_digits = uarb_mult32(file->image_bytes, 0,
row_bytes, digits, file->height);
}
break;
default:
stop_invalid(file, "IHDR: interlace method");
}
assert(file->image_digits >= 1 && file->image_digits <= 5);
return 1;
}
/* PER-CHUNK CONTROL STRUCTURE
* This structure is instantiated for each chunk, except for the IDAT chunks
* where one chunk control structure is used for the whole of a single stream of
* IDAT chunks (see the IDAT control structure below).
*/
struct chunk
{
/* ANCESTORS */
struct file * file;
struct global * global;
/* PUBLIC IDAT INFORMATION: SET BY THE ZLIB CODE */
udigit uncompressed_bytes[5];
int uncompressed_digits;
udigit compressed_bytes[5];
int compressed_digits;
/* PUBLIC PER-CHUNK INFORMATION: USED BY CHUNK READ CODE */
/* This information is filled in by chunk_init from the data in the file
* control structure, but chunk_length may be changed later.
*/
fpos_t chunk_data_pos; /* Position of first byte of chunk data */
png_uint_32 chunk_length; /* From header (or modified below) */
png_uint_32 chunk_type; /* From header */
/* PUBLIC PER-CHUNK INFORMATION: FOR THE CHUNK WRITE CODE */
png_uint_32 write_crc; /* Output CRC (may differ from read_crc) */
png_uint_32 rewrite_offset; /* Count of bytes before rewrite. */
int rewrite_length; /* Number of bytes left to change */
png_byte rewrite_buffer[2]; /* Buffer of new byte values */
};
static void
chunk_message(struct chunk *chunk, const char *message)
{
type_message(chunk->file, chunk->chunk_type, message);
}
static void
chunk_end(struct chunk **chunk_var)
{
struct chunk *chunk = *chunk_var;
*chunk_var = NULL;
CLEAR(*chunk);
}
static void
chunk_init(struct chunk * const chunk, struct file * const file)
/* When a chunk is initialized the file length/type/pos are copied into the
* corresponding chunk fields and the new chunk is registered in the file
* structure. There can only be one chunk at a time.
*
* NOTE: this routine must onely be called from the file alloc routine!
*/
{
assert(file->chunk == NULL);
CLEAR(*chunk);
chunk->file = file;
chunk->global = file->global;
chunk->chunk_data_pos = file->data_pos;
chunk->chunk_length = file->length;
chunk->chunk_type = file->type;
/* Compresssed/uncompressed size information (from the zlib control structure
* that is used to check the compressed data in a chunk.)
*/
chunk->uncompressed_digits = 0;
chunk->compressed_digits = 0;
file->chunk = chunk;
}
static png_uint_32
current_type(struct file *file, int code)
/* Guess the actual chunk type that causes a stop() */
{
/* This may return png_IDAT for errors detected (late) in the header; that
* includes any inter-chunk consistency check that libpng performs. Assume
* that if the chunk_type is png_IDAT and the file write count is 8 this is
* what is happening.
*/
if (file->chunk != NULL)
{
png_uint_32 type = file->chunk->chunk_type;
/* This is probably wrong for the excess IDATs case, because then libpng
* whines about too many of them (apparently in some cases erroneously)
* when the header is read.
*/
if (code <= LIBPNG_ERROR_CODE && type == png_IDAT &&
file->write_count == 8)
type = 0; /* magic */
return type;
}
else
return file->type;
}
static void
setpos(struct chunk *chunk)
/* Reset the position to 'chunk_data_pos' - the start of the data for this
* chunk. As a side effect the read_count in the file is reset to 8, just
* after the length/type header.
*/
{
chunk->file->read_count = 8;
file_setpos(chunk->file, &chunk->chunk_data_pos);
}
/* Specific chunk handling - called for each chunk header, all special chunk
* processing is initiated in these functions.
*/
/* The next functions handle special processing for those chunks with LZ data,
* the data is identified and checked for validity. If there are problems which
* cannot be corrected the routines return false, otherwise true (although
* modification to the zlib header may be required.)
*
* The compressed data is in zlib format (RFC1950) and consequently has a
* minimum length of 7 bytes.
*/
static int zlib_check(struct file *file, png_uint_32 offset);
static int
process_zTXt_iCCP(struct file *file)
/* zTXt and iCCP have exactly the same form - keyword, null, compression
* method then compressed data.
*/
{
struct chunk *chunk = file->chunk;
png_uint_32 length;
png_uint_32 index = 0;
assert(chunk != NULL && file->idat == NULL);
length = chunk->chunk_length;
setpos(chunk);
while (length >= 9)
{
--length;
++index;
if (reread_byte(file) == 0) /* keyword null terminator */
{
--length;
++index;
(void)reread_byte(file); /* compression method */
return zlib_check(file, index);
}
}
chunk_message(chunk, "too short");
return 0; /* skip */
}
static int
process_iTXt(struct file *file)
{
/* Like zTXt but more fields. */
struct chunk *chunk = file->chunk;
png_uint_32 length;
png_uint_32 index = 0;
assert(chunk != NULL && file->idat == NULL);
length = chunk->chunk_length;
setpos(chunk);
while (length >= 5)
{
--length;
++index;
if (reread_byte(file) == 0) /* keyword null terminator */
{
--length;
++index;
if (reread_byte(file) == 0) /* uncompressed text */
return 1; /* nothing to check */
--length;
++index;
(void)reread_byte(file); /* compression method */
/* Skip the language tag (null terminated). */
while (length >= 9)
{
--length;
++index;
if (reread_byte(file) == 0) /* terminator */
{
/* Skip the translated keyword */
while (length >= 8)
{
--length;
++index;
if (reread_byte(file) == 0) /* terminator */
return zlib_check(file, index);
}
}
}
/* Ran out of bytes in the compressed case. */
break;
}
}
log_error(file, INVALID_ERROR_CODE, "iTXt chunk length");
return 0; /* skip */
}
/* IDAT READ/WRITE CONTROL STRUCTURE */
struct IDAT
{
/* ANCESTORS */
struct file * file;
struct global * global;
/* PROTECTED IDAT INFORMATION: SET BY THE IDAT READ CODE */
struct IDAT_list *idat_list_head; /* START of the list of IDAT information */
struct IDAT_list *idat_list_tail; /* *END* of the list of IDAT information */
/* PROTECTED IDAT INFORMATION: USED BY THE IDAT WRITE CODE */
struct IDAT_list *idat_cur; /* Current list entry */
unsigned int idat_count; /* And the *current* index into the list */
png_uint_32 idat_index; /* Index of *next* input byte to write */
png_uint_32 idat_length; /* Cache of current chunk length */
};
/* NOTE: there is currently no IDAT_reset, so a stream cannot contain more than
* one IDAT sequence (i.e. MNG is not supported).
*/
static void
IDAT_end(struct IDAT **idat_var)
{
struct IDAT *idat = *idat_var;
struct file *file = idat->file;
*idat_var = NULL;
CLEAR(*idat);
assert(file->chunk != NULL);
chunk_end(&file->chunk);
/* Regardless of why the IDAT was killed set the state back to CHUNKS (it may
* already be CHUNKS because the state isn't changed until process_IDAT
* returns; a stop will cause IDAT_end to be entered in state CHUNKS!)
*/
file->state = STATE_CHUNKS;
}
static void
IDAT_init(struct IDAT * const idat, struct file * const file)
/* When the chunk is png_IDAT instantiate an IDAT control structure in place
* of a chunk control structure. The IDAT will instantiate a chunk control
* structure using the file alloc routine.
*
* NOTE: this routine must only be called from the file alloc routine!
*/
{
assert(file->chunk == NULL);
assert(file->idat == NULL);
CLEAR(*idat);
idat->file = file;
idat->global = file->global;
/* Initialize the tail to the pre-allocated buffer and set the count to 0
* (empty.)
*/
idat->global->idat_cache.count = 0;
idat->idat_list_head = idat->idat_list_tail = &idat->global->idat_cache;
/* Now the chunk. The allocator calls the initializer of the new chunk and
* stores the result in file->chunk:
*/
file->alloc(file, 0/*chunk*/);
assert(file->chunk != NULL);
/* And store this for cleanup (and to check for double alloc or failure to
* free.)
*/
file->idat = idat;
}
static png_uint_32
rechunk_length(struct IDAT *idat)
/* Return the length for the next IDAT chunk, taking into account
* rechunking.
*/
{
png_uint_32 len = idat->global->idat_max;
if (len == 0) /* use original chunk lengths */
{
const struct IDAT_list *cur;
unsigned int count;
if (idat->idat_index == 0) /* at the new chunk (first time) */
return idat->idat_length; /* use the cache */
/* Otherwise rechunk_length is called at the end of a chunk for the length
* of the next one.
*/
cur = idat->idat_cur;
count = idat->idat_count;
assert(idat->idat_index == idat->idat_length &&
idat->idat_length == cur->lengths[count]);
/* Return length of the *next* chunk */
if (++count < cur->count)
return cur->lengths[count];
/* End of this list */
assert(cur != idat->idat_list_tail);
cur = cur->next;
assert(cur != NULL && cur->count > 0);
return cur->lengths[0];
}
else /* rechunking */
{
/* The chunk size is the lesser of file->idat_max and the number
* of remaining bytes.
*/
png_uint_32 have = idat->idat_length - idat->idat_index;
if (len > have)
{
struct IDAT_list *cur = idat->idat_cur;
unsigned int j = idat->idat_count+1; /* the next IDAT in the list */
do
{
/* Add up the remaining bytes. This can't overflow because the
* individual lengths are always <= 0x7fffffff, so when we add two
* of them overflow is not possible.
*/
assert(cur != NULL);
for (;;)
{
/* NOTE: IDAT_list::count here, not IDAT_list::length */
for (; j < cur->count; ++j)
{
have += cur->lengths[j];
if (len <= have)
return len;
}
/* If this was the end return the count of the available bytes */
if (cur == idat->idat_list_tail)
return have;
cur = cur->next;
j = 0;
}
}
while (len > have);
}
return len;
}
}
static int
process_IDAT(struct file *file)
/* Process the IDAT stream, this is the more complex than the preceding
* cases because the compressed data is spread across multiple IDAT chunks
* (typically). Rechunking of the data is not handled here; all this
* function does is establish whether the zlib header needs to be modified.
*
* Initially the function returns false, indicating that the chunk should not
* be written. It does this until the last IDAT chunk is passed in, then it
* checks the zlib data and returns true.
*
* It does not return false on a fatal error; it calls stop instead.
*
* The caller must have an instantiated (IDAT) control structure and it must
* have extent over the whole read of the IDAT stream. For a PNG this means
* the whole PNG read, for MNG it could have lesser extent.
*/
{
struct IDAT_list *list;
assert(file->idat != NULL && file->chunk != NULL);
/* We need to first check the entire sequence of IDAT chunks to ensure the
* stream is in sync. Do this by building a list of all the chunks and
* recording the length of each because the length may have been fixed up by
* sync_stream below.
*
* At the end of the list of chunks, where the type of the next chunk is not
* png_IDAT, process the whole stream using the list data to check validity
* then return control to the start and rewrite everything.
*/
list = file->idat->idat_list_tail;
if (list->count == list->length)
{
list = IDAT_list_extend(list);
if (list == NULL)
stop(file, READ_ERROR_CODE, "out of memory");
/* Move to the next block */
list->count = 0;
file->idat->idat_list_tail = list;
}
/* And fill in the next IDAT information buffer. */
list->lengths[(list->count)++] = file->chunk->chunk_length;
/* The type of the next chunk was recorded in the file control structure by
* the caller, if this is png_IDAT return 'skip' to the caller.
*/
if (file->type == png_IDAT)
return 0; /* skip this for the moment */
/* This is the final IDAT chunk, so run the tests to check for the too far
* back error and possibly optimize the window bits. This means going back
* to the start of the first chunk data, which is stored in the original
* chunk allocation.
*/
setpos(file->chunk);
if (zlib_check(file, 0))
{
struct IDAT *idat;
int cmp;
/* The IDAT stream was successfully uncompressed; see whether it
* contained the correct number of bytes of image data.
*/
cmp = uarb_cmp(file->image_bytes, file->image_digits,
file->chunk->uncompressed_bytes, file->chunk->uncompressed_digits);
if (cmp < 0)
type_message(file, png_IDAT, "extra uncompressed data");
else if (cmp > 0)
stop(file, LIBPNG_ERROR_CODE, "IDAT: uncompressed data too small");
/* Return the stream to the start of the first IDAT chunk; the length
* is set in the write case below but the input chunk variables must be
* set (once) here:
*/
setpos(file->chunk);
idat = file->idat;
idat->idat_cur = idat->idat_list_head;
idat->idat_length = idat->idat_cur->lengths[0];
idat->idat_count = 0; /* Count of chunks read in current list */
idat->idat_index = 0; /* Index into chunk data */
/* Update the chunk length to the correct value for the IDAT chunk: */
file->chunk->chunk_length = rechunk_length(idat);
/* Change the state to writing IDAT chunks */
file->state = STATE_IDAT;
return 1;
}
else /* Failure to decompress the IDAT stream; give up. */
stop(file, ZLIB_ERROR_CODE, "could not uncompress IDAT");
}
/* ZLIB CONTROL STRUCTURE */
struct zlib
{
/* ANCESTORS */
struct IDAT * idat; /* NOTE: May be NULL */
struct chunk * chunk;
struct file * file;
struct global *global;
/* GLOBAL ZLIB INFORMATION: SET BY THE CALLER */
png_uint_32 rewrite_offset;
/* GLOBAL ZLIB INFORMATION: SET BY THE ZLIB READ CODE */
udigit compressed_bytes[5];
int compressed_digits;
udigit uncompressed_bytes[5];
int uncompressed_digits;
int file_bits; /* window bits from the file */
int ok_bits; /* Set <16 on a successful read */
int cksum; /* Set on a checksum error */
/* PROTECTED ZLIB INFORMATION: USED BY THE ZLIB ROUTINES */
z_stream z;
png_uint_32 extra_bytes; /* Count of extra compressed bytes */
int state;
int rc; /* Last return code */
int window_bits; /* 0 if no change */
png_byte header[2];
};
static const char *
zlib_flevel(struct zlib *zlib)
{
switch (zlib->header[1] >> 6)
{
case 0: return "supfast";
case 1: return "stdfast";
case 2: return "default";
case 3: return "maximum";
default: assert(UNREACHED);
}
return "COMPILER BUG";
}
static const char *
zlib_rc(struct zlib *zlib)
/* Return a string for the zlib return code */
{
switch (zlib->rc)
{
case Z_OK: return "Z_OK";
case Z_STREAM_END: return "Z_STREAM_END";
case Z_NEED_DICT: return "Z_NEED_DICT";
case Z_ERRNO: return "Z_ERRNO";
case Z_STREAM_ERROR: return "Z_STREAM_ERROR";
case Z_DATA_ERROR: return "Z_DATA_ERROR";
case Z_MEM_ERROR: return "Z_MEM_ERROR";
case Z_BUF_ERROR: return "Z_BUF_ERROR";
case Z_VERSION_ERROR: return "Z_VERSION_ERROR";
default: return "Z_*INVALID_RC*";
}
}
static void
zlib_message(struct zlib *zlib, int unexpected)
/* Output a message given a zlib rc */
{
if (zlib->global->errors)
{
const char *reason = zlib->z.msg;
if (reason == NULL)
reason = "[no message]";
fputs(zlib->file->file_name, stderr);
type_sep(stderr);
type_name(zlib->chunk->chunk_type, stderr);
fprintf(stderr, ": %szlib error: %d (%s) (%s)\n",
unexpected ? "unexpected " : "", zlib->rc, zlib_rc(zlib), reason);
}
}
static void
zlib_end(struct zlib *zlib)
{
/* Output the summary line now; this ensures a summary line always gets
* output regardless of the manner of exit.
*/
if (!zlib->global->quiet)
{
if (zlib->ok_bits < 16) /* stream was read ok */
{
const char *reason;
if (zlib->cksum)
reason = "CHK"; /* checksum error */
else if (zlib->ok_bits > zlib->file_bits)
reason = "TFB"; /* fixing a too-far-back error */
else if (zlib->ok_bits == zlib->file_bits)
reason = "OK ";
else
reason = "OPT"; /* optimizing window bits */
/* SUMMARY FORMAT (for a successful zlib inflate):
*
* IDAT reason flevel file-bits ok-bits compressed uncompressed file
*/
type_name(zlib->chunk->chunk_type, stdout);
printf(" %s %s %d %d ", reason, zlib_flevel(zlib), zlib->file_bits,
zlib->ok_bits);
uarb_print(zlib->compressed_bytes, zlib->compressed_digits, stdout);
putc(' ', stdout);
uarb_print(zlib->uncompressed_bytes, zlib->uncompressed_digits,
stdout);
putc(' ', stdout);
fputs(zlib->file->file_name, stdout);
putc('\n', stdout);
}
else
{
/* This is a zlib read error; the chunk will be skipped. For an IDAT
* stream this will also cause a fatal read error (via stop()).
*
* SUMMARY FORMAT:
*
* IDAT SKP flevel file-bits z-rc compressed message file
*
* z-rc is the zlib failure code; message is the error message with
* spaces replaced by '-'. The compressed byte count indicates where
* in the zlib stream the error occurred.
*/
type_name(zlib->chunk->chunk_type, stdout);
printf(" SKP %s %d %s ", zlib_flevel(zlib), zlib->file_bits,
zlib_rc(zlib));
uarb_print(zlib->compressed_bytes, zlib->compressed_digits, stdout);
putc(' ', stdout);
emit_string(zlib->z.msg ? zlib->z.msg : "[no_message]", stdout);
putc(' ', stdout);
fputs(zlib->file->file_name, stdout);
putc('\n', stdout);
}
}
if (zlib->state >= 0)
{
zlib->rc = inflateEnd(&zlib->z);
if (zlib->rc != Z_OK)
zlib_message(zlib, 1/*unexpected*/);
}
CLEAR(*zlib);
}
static int
zlib_reset(struct zlib *zlib, int window_bits)
/* Reinitializes a zlib with a different window_bits */
{
assert(zlib->state >= 0); /* initialized by zlib_init */
zlib->z.next_in = Z_NULL;
zlib->z.avail_in = 0;
zlib->z.next_out = Z_NULL;
zlib->z.avail_out = 0;
zlib->window_bits = window_bits;
zlib->compressed_digits = 0;
zlib->uncompressed_digits = 0;
zlib->state = 0; /* initialized, once */
zlib->rc = inflateReset2(&zlib->z, 0);
if (zlib->rc != Z_OK)
{
zlib_message(zlib, 1/*unexpected*/);
return 0;
}
return 1;
}
static int
zlib_init(struct zlib *zlib, struct IDAT *idat, struct chunk *chunk,
int window_bits, png_uint_32 offset)
/* Initialize a zlib_control; the result is true/false */
{
CLEAR(*zlib);
zlib->idat = idat;
zlib->chunk = chunk;
zlib->file = chunk->file;
zlib->global = chunk->global;
zlib->rewrite_offset = offset; /* never changed for this zlib */
/* *_out does not need to be set: */
zlib->z.next_in = Z_NULL;
zlib->z.avail_in = 0;
zlib->z.zalloc = Z_NULL;
zlib->z.zfree = Z_NULL;
zlib->z.opaque = Z_NULL;
zlib->state = -1;
zlib->window_bits = window_bits;
zlib->compressed_digits = 0;
zlib->uncompressed_digits = 0;
/* These values are sticky across reset (in addition to the stuff in the
* first block, which is actually constant.)
*/
zlib->file_bits = 24;
zlib->ok_bits = 16; /* unset */
zlib->cksum = 0; /* set when a checksum error is detected */
/* '0' means use the header; inflateInit2 should always succeed because it
* does nothing apart from allocating the internal zstate.
*/
zlib->rc = inflateInit2(&zlib->z, 0);
if (zlib->rc != Z_OK)
{
zlib_message(zlib, 1/*unexpected*/);
return 0;
}
else
{
zlib->state = 0; /* initialized */
return 1;
}
}
static int
max_window_bits(uarbc size, int ndigits)
/* Return the zlib stream window bits required for data of the given size. */
{
png_uint_16 cb;
if (ndigits > 1)
return 15;
cb = size[0];
if (cb > 16384) return 15;
if (cb > 8192) return 14;
if (cb > 4096) return 13;
if (cb > 2048) return 12;
if (cb > 1024) return 11;
if (cb > 512) return 10;
if (cb > 256) return 9;
return 8;
}
static int
zlib_advance(struct zlib *zlib, png_uint_32 nbytes)
/* Read nbytes compressed bytes; the stream will be initialized if required.
* Bytes are always being reread and errors are fatal. The return code is as
* follows:
*
* -1: saw the "too far back" error
* 0: ok, keep going
* 1: saw Z_STREAM_END (zlib->extra_bytes indicates too much data)
* 2: a zlib error that cannot be corrected (error message already
* output if required.)
*/
# define ZLIB_TOO_FAR_BACK (-1)
# define ZLIB_OK 0
# define ZLIB_STREAM_END 1
# define ZLIB_FATAL 2
{
int state = zlib->state;
int endrc = ZLIB_OK;
png_uint_32 in_bytes = 0;
struct file *file = zlib->file;
assert(state >= 0);
while (in_bytes < nbytes && endrc == ZLIB_OK)
{
png_uint_32 out_bytes;
int flush;
png_byte bIn = reread_byte(file);
png_byte bOut;
switch (state)
{
case 0: /* first header byte */
{
int file_bits = 8+(bIn >> 4);
int new_bits = zlib->window_bits;
zlib->file_bits = file_bits;
/* Check against the existing value - it may not need to be
* changed. Note that a bogus file_bits is allowed through once,
* to see if it works, but the window_bits value is set to 15,
* the maximum.
*/
if (new_bits == 0) /* no change */
zlib->window_bits = ((file_bits > 15) ? 15 : file_bits);
else if (new_bits != file_bits) /* rewrite required */
bIn = (png_byte)((bIn & 0xf) + ((new_bits-8) << 4));
}
zlib->header[0] = bIn;
zlib->state = state = 1;
break;
case 1: /* second header byte */
{
int b2 = bIn & 0xe0; /* top 3 bits */
/* The checksum calculation, on the first 11 bits: */
b2 += 0x1f - ((zlib->header[0] << 8) + b2) % 0x1f;
/* Update the checksum byte if required: */
if (bIn != b2)
{
/* If the first byte wasn't changed this indicates an error in
* the checksum calculation; signal this by setting 'cksum'.
*/
if (zlib->file_bits == zlib->window_bits)
zlib->cksum = 1;
bIn = (png_byte)b2;
}
}
zlib->header[1] = bIn;
zlib->state = state = 2;
break;
default: /* After the header bytes */
break;
}
/* For some streams, perhaps only those compressed with 'superfast
* compression' (which results in a lot of copying) Z_BUF_ERROR can happen
* immediately after all output has been flushed on the next input byte.
* This is handled below when Z_BUF_ERROR is detected by adding an output
* byte.
*/
zlib->z.next_in = &bIn;
zlib->z.avail_in = 1;
zlib->z.next_out = &bOut;
zlib->z.avail_out = 0; /* Initially */
/* Initially use Z_NO_FLUSH in an attempt to persuade zlib to look at this
* byte without confusing what is going on with output.
*/
flush = Z_NO_FLUSH;
out_bytes = 0;
/* NOTE: expression 3 is only evaluted on 'continue', because of the
* 'break' at the end of this loop below.
*/
for (;endrc == ZLIB_OK;
flush = Z_SYNC_FLUSH,
zlib->z.next_out = &bOut,
zlib->z.avail_out = 1,
++out_bytes)
{
zlib->rc = inflate(&zlib->z, flush);
out_bytes -= zlib->z.avail_out;
switch (zlib->rc)
{
case Z_BUF_ERROR:
if (zlib->z.avail_out == 0)
continue; /* Try another output byte. */
if (zlib->z.avail_in == 0)
break; /* Try another input byte */
/* Both avail_out and avail_in are 1 yet zlib returned a code
* indicating no progress was possible. This is unexpected.
*/
zlib_message(zlib, 1/*unexpected*/);
endrc = ZLIB_FATAL; /* stop processing */
break;
case Z_OK:
/* Zlib is supposed to have made progress: */
assert(zlib->z.avail_out == 0 || zlib->z.avail_in == 0);
continue;
case Z_STREAM_END:
/* This is the successful end. */
zlib->state = 3; /* end of stream */
endrc = ZLIB_STREAM_END;
break;
case Z_NEED_DICT:
zlib_message(zlib, 0/*stream error*/);
endrc = ZLIB_FATAL;
break;
case Z_DATA_ERROR:
/* The too far back error can be corrected, others cannot: */
if (zlib->z.msg != NULL &&
strcmp(zlib->z.msg, "invalid distance too far back") == 0)
{
endrc = ZLIB_TOO_FAR_BACK;
break;
}
/* FALL THROUGH */
default:
zlib_message(zlib, 0/*stream error*/);
endrc = ZLIB_FATAL;
break;
} /* switch (inflate rc) */
/* Control gets here when further output is not possible; endrc may
* still be ZLIB_OK if more input is required.
*/
break;
} /* for (output bytes) */
/* Keep a running count of output byte produced: */
zlib->uncompressed_digits = uarb_add32(zlib->uncompressed_bytes,
zlib->uncompressed_digits, out_bytes);
/* Keep going, the loop will terminate when endrc is no longer set to
* ZLIB_OK or all the input bytes have been consumed; meanwhile keep
* adding input bytes.
*/
assert(zlib->z.avail_in == 0 || endrc != ZLIB_OK);
in_bytes += 1 - zlib->z.avail_in;
} /* while (input bytes) */
assert(in_bytes == nbytes || endrc != ZLIB_OK);
/* Update the running total of input bytes consumed */
zlib->compressed_digits = uarb_add32(zlib->compressed_bytes,
zlib->compressed_digits, in_bytes - zlib->z.avail_in);
/* At the end of the stream update the chunk with the accumulated
* information if it is an improvement:
*/
if (endrc == ZLIB_STREAM_END && zlib->window_bits < zlib->ok_bits)
{
struct chunk *chunk = zlib->chunk;
chunk->uncompressed_digits = uarb_copy(chunk->uncompressed_bytes,
zlib->uncompressed_bytes, zlib->uncompressed_digits);
chunk->compressed_digits = uarb_copy(chunk->compressed_bytes,
zlib->compressed_bytes, zlib->compressed_digits);
chunk->rewrite_buffer[0] = zlib->header[0];
chunk->rewrite_buffer[1] = zlib->header[1];
if (zlib->window_bits != zlib->file_bits || zlib->cksum)
{
/* A rewrite is required */
chunk->rewrite_offset = zlib->rewrite_offset;
chunk->rewrite_length = 2;
}
else
{
chunk->rewrite_offset = 0;
chunk->rewrite_length = 0;
}
if (in_bytes < nbytes)
chunk_message(chunk, "extra compressed data");
zlib->extra_bytes = nbytes - in_bytes;
zlib->ok_bits = zlib->window_bits;
}
return endrc;
}
static int
zlib_run(struct zlib *zlib)
/* Like zlib_advance but also handles a stream of IDAT chunks. */
{
/* The 'extra_bytes' field is set by zlib_advance if there is extra
* compressed data in the chunk it handles (if it sees Z_STREAM_END before
* all the input data has been used.) This function uses the value to update
* the correct chunk length, so the problem should only ever be detected once
* for each chunk. zlib_advance outputs the error message, though see the
* IDAT specific check below.
*/
zlib->extra_bytes = 0;
if (zlib->idat != NULL)
{
struct IDAT_list *list = zlib->idat->idat_list_head;
struct IDAT_list *last = zlib->idat->idat_list_tail;
int skip = 0;
/* 'rewrite_offset' is the offset of the LZ data within the chunk, for
* IDAT it should be 0:
*/
assert(zlib->rewrite_offset == 0);
/* Process each IDAT_list in turn; the caller has left the stream
* positioned at the start of the first IDAT chunk data.
*/
for (;;)
{
const unsigned int count = list->count;
unsigned int i;
for (i = 0; i<count; ++i)
{
int rc;
if (skip > 0) /* Skip CRC and next IDAT header */
skip_12(zlib->file);
skip = 12; /* for the next time */
rc = zlib_advance(zlib, list->lengths[i]);
switch (rc)
{
case ZLIB_OK: /* keep going */
break;
case ZLIB_STREAM_END: /* stop */
/* There may be extra chunks; if there are and one of them is
* not zero length output the 'extra data' message. Only do
* this check if errors are being output.
*/
if (zlib->global->errors && zlib->extra_bytes == 0)
{
struct IDAT_list *check = list;
int j = i+1, jcount = count;
for (;;)
{
for (; j<jcount; ++j)
if (check->lengths[j] > 0)
{
chunk_message(zlib->chunk,
"extra compressed data");
goto end_check;
}
if (check == last)
break;
check = check->next;
jcount = check->count;
j = 0;
}
}
end_check:
/* Terminate the list at the current position, reducing the
* length of the last IDAT too if required.
*/
list->lengths[i] -= zlib->extra_bytes;
list->count = i+1;
zlib->idat->idat_list_tail = list;
/* FALL THROUGH */
default:
return rc;
}
}
/* At the end of the compressed data and Z_STREAM_END was not seen. */
if (list == last)
return ZLIB_OK;
list = list->next;
}
}
else
{
struct chunk *chunk = zlib->chunk;
int rc;
assert(zlib->rewrite_offset < chunk->chunk_length);
rc = zlib_advance(zlib, chunk->chunk_length - zlib->rewrite_offset);
/* The extra bytes in the chunk are handled now by adjusting the chunk
* length to exclude them; the zlib data is always stored at the end of
* the PNG chunk (although clearly this is not necessary.) zlib_advance
* has already output a warning message.
*/
chunk->chunk_length -= zlib->extra_bytes;
return rc;
}
}
static int /* global function; not a member function */
zlib_check(struct file *file, png_uint_32 offset)
/* Check the stream of zlib compressed data in either idat (if given) or (if
* not) chunk. In fact it is zlib_run that handles the difference in reading
* a single chunk and a list of IDAT chunks.
*
* In either case the input file must be positioned at the first byte of zlib
* compressed data (the first header byte).
*
* The return value is true on success, including the case where the zlib
* header may need to be rewritten, and false on an unrecoverable error.
*
* In the case of IDAT chunks 'offset' should be 0.
*/
{
fpos_t start_pos;
struct zlib zlib;
/* Record the start of the LZ data to allow a re-read. */
file_getpos(file, &start_pos);
/* First test the existing (file) window bits: */
if (zlib_init(&zlib, file->idat, file->chunk, 0/*window bits*/, offset))
{
int min_bits, max_bits, rc;
/* The first run using the existing window bits. */
rc = zlib_run(&zlib);
switch (rc)
{
case ZLIB_TOO_FAR_BACK:
/* too far back error */
file->status_code |= TOO_FAR_BACK;
min_bits = zlib.window_bits + 1;
max_bits = 15;
break;
case ZLIB_STREAM_END:
if (!zlib.global->optimize_zlib &&
zlib.window_bits == zlib.file_bits && !zlib.cksum)
{
/* The trivial case where the stream is ok and optimization was
* not requested.
*/
zlib_end(&zlib);
return 1;
}
max_bits = max_window_bits(zlib.uncompressed_bytes,
zlib.uncompressed_digits);
if (zlib.ok_bits < max_bits)
max_bits = zlib.ok_bits;
min_bits = 8;
/* cksum is set if there is an error in the zlib header checksum
* calculation in the original file (and this may be the only reason
* a rewrite is required). We can't rely on the file window bits in
* this case, so do the optimization anyway.
*/
if (zlib.cksum)
chunk_message(zlib.chunk, "zlib checkum");
break;
case ZLIB_OK:
/* Truncated stream; unrecoverable, gets converted to ZLIB_FATAL */
zlib.z.msg = PNGZ_MSG_CAST("[truncated]");
zlib_message(&zlib, 0/*expected*/);
/* FALL THROUGH */
default:
/* Unrecoverable error; skip the chunk; a zlib_message has already
* been output.
*/
zlib_end(&zlib);
return 0;
}
/* Optimize window bits or fix a too-far-back error. min_bits and
* max_bits have been set appropriately, ok_bits records the bit value
* known to work.
*/
while (min_bits < max_bits || max_bits < zlib.ok_bits/*if 16*/)
{
int test_bits = (min_bits + max_bits) >> 1;
if (zlib_reset(&zlib, test_bits))
{
file_setpos(file, &start_pos);
rc = zlib_run(&zlib);
switch (rc)
{
case ZLIB_TOO_FAR_BACK:
min_bits = test_bits+1;
if (min_bits > max_bits)
{
/* This happens when the stream really is damaged and it
* contains a distance code that addresses bytes before
* the start of the uncompressed data.
*/
assert(test_bits == 15);
/* Output the error that wasn't output before: */
if (zlib.z.msg == NULL)
zlib.z.msg = PNGZ_MSG_CAST(
"invalid distance too far back");
zlib_message(&zlib, 0/*stream error*/);
zlib_end(&zlib);
return 0;
}
break;
case ZLIB_STREAM_END: /* success */
max_bits = test_bits;
break;
default:
/* A fatal error; this happens if a too-far-back error was
* hiding a more serious error, zlib_advance has already
* output a zlib_message.
*/
zlib_end(&zlib);
return 0;
}
}
else /* inflateReset2 failed */
{
zlib_end(&zlib);
return 0;
}
}
/* The loop guarantees this */
assert(zlib.ok_bits == max_bits);
zlib_end(&zlib);
return 1;
}
else /* zlib initialization failed - skip the chunk */
{
zlib_end(&zlib);
return 0;
}
}
/***************************** LIBPNG CALLBACKS *******************************/
/* The strategy here is to run a regular libpng PNG file read but examine the
* input data (from the file) before passing it to libpng so as to be aware of
* the state we expect libpng to be in. Warning and error callbacks are also
* intercepted so that they can be quieted and interpreted. Interpretation
* depends on a somewhat risky string match for known error messages; let us
* hope that this can be fixed in the next version of libpng.
*
* The control structure is pointed to by the libpng error pointer. It contains
* that set of structures which must persist across multiple read callbacks,
* which is pretty much everything except the 'zlib' control structure.
*
* The file structure is instantiated in the caller of the per-file routine, but
* the per-file routine contains the chunk and IDAT control structures.
*/
/* The three routines read_chunk, process_chunk and sync_stream can only be
* called via a call to read_chunk and only exit at a return from process_chunk.
* These routines could have been written as one confusing large routine,
* instead this code relies on the compiler to do tail call elimination. The
* possible calls are as follows:
*
* read_chunk
* -> sync_stream
* -> process_chunk
* -> process_chunk
* -> read_chunk
* returns
*/
static void read_chunk(struct file *file);
static void
process_chunk(struct file *file, png_uint_32 file_crc, png_uint_32 next_length,
png_uint_32 next_type)
/* Called when the chunk data has been read, next_length and next_type
* will be set for the next chunk (or 0 if this is IEND).
*
* When this routine returns, chunk_length and chunk_type will be set for the
* next chunk to write because if a chunk is skipped this return calls back
* to read_chunk.
*/
{
const png_uint_32 type = file->type;
if (file->global->verbose > 1)
{
fputs(" ", stderr);
type_name(file->type, stderr);
fprintf(stderr, " %lu 0x%.8x 0x%.8x\n", (unsigned long)file->length,
file->crc ^ 0xffffffff, file_crc);
}
/* The basic structure seems correct but the CRC may not match, in this
* case assume that it is simply a bad CRC, either wrongly calculated or
* because of damaged stream data.
*/
if ((file->crc ^ 0xffffffff) != file_crc)
{
/* The behavior is set by the 'skip' setting; if it is anything other
* than SKIP_BAD_CRC ignore the bad CRC and return the chunk, with a
* corrected CRC and possibly processed, to libpng. Otherwise skip the
* chunk, which will result in a fatal error if the chunk is critical.
*/
file->status_code |= CRC_ERROR;
/* Ignore the bad CRC */
if (file->global->skip != SKIP_BAD_CRC)
type_message(file, type, "bad CRC");
/* This will cause an IEND with a bad CRC to stop */
else if (CRITICAL(type))
stop(file, READ_ERROR_CODE, "bad CRC in critical chunk");
else
{
type_message(file, type, "skipped: bad CRC");
/* NOTE: this cannot be reached for IEND because it is critical. */
goto skip_chunk;
}
}
/* Check for other 'skip' cases and handle these; these only apply to
* ancillary chunks (and not tRNS, which should probably have been a critical
* chunk.)
*/
if (skip_chunk_type(file->global, type))
goto skip_chunk;
/* The chunk may still be skipped if problems are detected in the LZ data,
* however the LZ data check requires a chunk. Handle this by instantiating
* a chunk unless an IDAT is already instantiated (IDAT control structures
* instantiate their own chunk.)
*/
if (type != png_IDAT)
file->alloc(file, 0/*chunk*/);
else if (file->idat == NULL)
file->alloc(file, 1/*IDAT*/);
else
{
/* The chunk length must be updated for process_IDAT */
assert(file->chunk != NULL);
assert(file->chunk->chunk_type == png_IDAT);
file->chunk->chunk_length = file->length;
}
/* Record the 'next' information too, now that the original values for
* this chunk have been copied. Notice that the IDAT chunks only make a
* copy of the position of the first chunk, this is fine - process_IDAT does
* not need the position of this chunk.
*/
file->length = next_length;
file->type = next_type;
getpos(file);
/* Do per-type processing, note that if this code does not return from the
* function the chunk will be skipped. The rewrite is cancelled here so that
* it can be set in the per-chunk processing.
*/
file->chunk->rewrite_length = 0;
file->chunk->rewrite_offset = 0;
switch (type)
{
default:
return;
case png_IHDR:
/* Read this now and update the control structure with the information
* it contains. The header is validated completely to ensure this is a
* PNG.
*/
{
struct chunk *chunk = file->chunk;
if (chunk->chunk_length != 13)
stop_invalid(file, "IHDR length");
/* Read all the IHDR information and validate it. */
setpos(chunk);
file->width = reread_4(file);
file->height = reread_4(file);
file->bit_depth = reread_byte(file);
file->color_type = reread_byte(file);
file->compression_method = reread_byte(file);
file->filter_method = reread_byte(file);
file->interlace_method = reread_byte(file);
/* This validates all the fields, and calls stop_invalid if
* there is a problem.
*/
calc_image_size(file);
}
return;
/* Ancillary chunks that require further processing: */
case png_zTXt: case png_iCCP:
if (process_zTXt_iCCP(file))
return;
chunk_end(&file->chunk);
file_setpos(file, &file->data_pos);
break;
case png_iTXt:
if (process_iTXt(file))
return;
chunk_end(&file->chunk);
file_setpos(file, &file->data_pos);
break;
case png_IDAT:
if (process_IDAT(file))
return;
/* First pass: */
assert(next_type == png_IDAT);
break;
}
/* Control reaches this point if the chunk must be skipped. For chunks other
* than IDAT this means that the zlib compressed data is fatally damanged and
* the chunk will not be passed to libpng. For IDAT it means that the end of
* the IDAT stream has not yet been reached and we must handle the next
* (IDAT) chunk. If the LZ data in an IDAT stream cannot be read 'stop' must
* be used to halt parsing of the PNG.
*/
read_chunk(file);
return;
/* This is the generic code to skip the current chunk; simply jump to the
* next one.
*/
skip_chunk:
file->length = next_length;
file->type = next_type;
getpos(file);
read_chunk(file);
}
static png_uint_32
get32(png_bytep buffer, int offset)
/* Read a 32-bit value from an 8-byte circular buffer (used only below).
*/
{
return
(buffer[ offset & 7] << 24) +
(buffer[(offset+1) & 7] << 16) +
(buffer[(offset+2) & 7] << 8) +
(buffer[(offset+3) & 7] );
}
static void
sync_stream(struct file *file)
/* The stream seems to be messed up, attempt to resync from the current chunk
* header. Executes stop on a fatal error, otherwise calls process_chunk.
*/
{
png_uint_32 file_crc;
file->status_code |= STREAM_ERROR;
if (file->global->verbose)
{
fputs(" SYNC ", stderr);
type_name(file->type, stderr);
putc('\n', stderr);
}
/* Return to the start of the chunk data */
file_setpos(file, &file->data_pos);
file->read_count = 8;
if (read_4(file, &file_crc) == 4) /* else completely truncated */
{
/* Ignore the recorded chunk length, proceed through the data looking for
* a leading sequence of bytes that match the CRC in the following four
* bytes. Each time a match is found check the next 8 bytes for a valid
* length, chunk-type pair.
*/
png_uint_32 length;
png_uint_32 type = file->type;
png_uint_32 crc = crc_init_4(type);
png_byte buffer[8];
unsigned int nread = 0, nused = 0;
for (length=0; length <= 0x7fffffff; ++length)
{
int ch;
if ((crc ^ 0xffffffff) == file_crc)
{
/* A match on the CRC; for IEND this is sufficient, but for anything
* else expect a following chunk header.
*/
if (type == png_IEND)
{
file->length = length;
process_chunk(file, file_crc, 0, 0);
return;
}
else
{
/* Need 8 bytes */
while (nread < 8+nused)
{
ch = read_byte(file);
if (ch == EOF)
goto truncated;
buffer[(nread++) & 7] = (png_byte)ch;
}
/* Prevent overflow */
nread -= nused & ~7;
nused -= nused & ~7; /* or, nused &= 7 ;-) */
/* Examine the 8 bytes for a valid chunk header. */
{
png_uint_32 next_length = get32(buffer, nused);
if (next_length < 0x7fffffff)
{
png_uint_32 next_type = get32(buffer, nused+4);
if (chunk_type_valid(next_type))
{
file->read_count -= 8;
process_chunk(file, file_crc, next_length, next_type);
return;
}
}
/* Not valid, keep going. */
}
}
}
/* This catches up with the circular buffer which gets filled above
* while checking a chunk header. This code is slightly tricky - if
* the chunk_type is IEND the buffer will never be used, if it is not
* the code will always read ahead exactly 8 bytes and pass this on to
* process_chunk. So the invariant that IEND leaves the file position
* after the IEND CRC and other chunk leave it after the *next* chunk
* header is not broken.
*/
if (nread <= nused)
{
ch = read_byte(file);
if (ch == EOF)
goto truncated;
}
else
ch = buffer[(++nused) & 7];
crc = crc_one_byte(crc, file_crc >> 24);
file_crc = (file_crc << 8) + ch;
}
/* Control gets to here if when 0x7fffffff bytes (plus 8) have been read,
* ok, treat this as a damaged stream too:
*/
}
truncated:
stop(file, READ_ERROR_CODE, "damaged PNG stream");
}
static void
read_chunk(struct file *file)
/* On entry file::data_pos must be set to the position of the first byte
* of the chunk data *and* the input file must be at this position. This
* routine (via process_chunk) instantiates a chunk or IDAT control structure
* based on file::length and file::type and also resets these fields and
* file::data_pos for the chunk after this one. For an IDAT chunk the whole
* stream of IDATs will be read, until something other than an IDAT is
* encountered, and the file fields will be set for the chunk after the end
* of the stream of IDATs.
*
* For IEND the file::type field will be set to 0, and nothing beyond the end
* of the IEND chunk will have been read.
*/
{
png_uint_32 length = file->length;
png_uint_32 type = file->type;
/* After IEND file::type is set to 0, if libpng attempts to read
* more data at this point this is a bug in libpng.
*/
if (type == 0)
stop(file, UNEXPECTED_ERROR_CODE, "read beyond IEND");
if (file->global->verbose > 2)
{
fputs(" ", stderr);
type_name(type, stderr);
fprintf(stderr, " %lu\n", (unsigned long)length);
}
/* Start the read_crc calculation with the chunk type, then read to the end
* of the chunk data (without processing it in any way) to check that it is
* all there and calculate the CRC.
*/
file->crc = crc_init_4(type);
if (crc_read_many(file, length)) /* else it was truncated */
{
png_uint_32 file_crc; /* CRC read from file */
unsigned int nread = read_4(file, &file_crc);
if (nread == 4)
{
if (type != png_IEND) /* do not read beyond IEND */
{
png_uint_32 next_length;
nread += read_4(file, &next_length);
if (nread == 8 && next_length <= 0x7fffffff)
{
png_uint_32 next_type;
nread += read_4(file, &next_type);
if (nread == 12 && chunk_type_valid(next_type))
{
/* Adjust the read count back to the correct value for this
* chunk.
*/
file->read_count -= 8;
process_chunk(file, file_crc, next_length, next_type);
return;
}
}
}
else /* IEND */
{
process_chunk(file, file_crc, 0, 0);
return;
}
}
}
/* Control gets to here if the the stream seems invalid or damaged in some
* way. Either there was a problem reading all the expected data (this
* chunk's data, its CRC and the length and type of the next chunk) or the
* next chunk length/type are invalid. Notice that the cases that end up
* here all correspond to cases that would otherwise terminate the read of
* the PNG file.
*/
sync_stream(file);
}
/* This returns a file* from a png_struct in an implementation specific way. */
static struct file *get_control(png_const_structrp png_ptr);
static void PNGCBAPI
error_handler(png_structp png_ptr, png_const_charp message)
{
stop(get_control(png_ptr), LIBPNG_ERROR_CODE, message);
}
static void PNGCBAPI
warning_handler(png_structp png_ptr, png_const_charp message)
{
struct file *file = get_control(png_ptr);
if (file->global->warnings)
emit_error(file, LIBPNG_WARNING_CODE, message);
}
/* Read callback - this is where the work gets done to check the stream before
* passing it to libpng
*/
static void PNGCBAPI
read_callback(png_structp png_ptr, png_bytep buffer, size_t count)
/* Return 'count' bytes to libpng in 'buffer' */
{
struct file *file = get_control(png_ptr);
png_uint_32 type, length; /* For the chunk be *WRITTEN* */
struct chunk *chunk;
/* libpng should always ask for at least one byte */
if (count == 0)
stop(file, UNEXPECTED_ERROR_CODE, "read callback for 0 bytes");
/* The callback always reads ahead by 8 bytes - the signature or chunk header
* - these bytes are stored in chunk_length and chunk_type. This block is
* executed once for the signature and once for the first chunk right at the
* start.
*/
if (file->read_count < 8)
{
assert(file->read_count == 0);
assert((file->status_code & TRUNCATED) == 0);
(void)read_4(file, &file->length);
if (file->read_count == 4)
(void)read_4(file, &file->type);
if (file->read_count < 8)
{
assert((file->status_code & TRUNCATED) != 0);
stop(file, READ_ERROR_CODE, "not a PNG (too short)");
}
if (file->state == STATE_SIGNATURE)
{
if (file->length != sig1 || file->type != sig2)
stop(file, LIBPNG_ERROR_CODE, "not a PNG (signature)");
/* Else write it (this is the initialization of write_count, prior to
* this it contains CLEAR garbage.)
*/
file->write_count = 0;
}
else
{
assert(file->state == STATE_CHUNKS);
/* The first chunk must be a well formed IHDR (this could be relaxed to
* use the checks in process_chunk, but that seems unnecessary.)
*/
if (file->length != 13 || file->type != png_IHDR)
stop(file, LIBPNG_ERROR_CODE, "not a PNG (IHDR)");
/* The position of the data must be stored too */
getpos(file);
}
}
/* Retrieve previous state (because the read callbacks are made pretty much
* byte-by-byte in the sequential reader prior to 1.7).
*/
chunk = file->chunk;
if (chunk != NULL)
{
length = chunk->chunk_length;
type = chunk->chunk_type;
}
else
{
/* This is the signature case; for IDAT and other chunks these values will
* be overwritten when read_chunk is called below.
*/
length = file->length;
type = file->type;
}
do
{
png_uint_32 b;
/* Complete the read of a chunk; as a side effect this also instantiates
* a chunk control structure and sets the file length/type/data_pos fields
* for the *NEXT* chunk header.
*
* NOTE: at an IDAT any following IDAT chunks will also be read and the
* next_ fields will refer to the chunk after the last IDAT.
*
* NOTE: read_chunk only returns when it has read a chunk that must now be
* written.
*/
if (file->state != STATE_SIGNATURE && chunk == NULL)
{
assert(file->read_count == 8);
assert(file->idat == NULL);
read_chunk(file);
chunk = file->chunk;
assert(chunk != NULL);
/* Do the initialization that was not done before. */
length = chunk->chunk_length;
type = chunk->chunk_type;
/* And start writing the new chunk. */
file->write_count = 0;
}
/* The chunk_ fields describe a chunk that must be written, or hold the
* signature. Write the header first. In the signature case this
* rewrites the signature.
*/
switch (file->write_count)
{
case 0: b = length >> 24; break;
case 1: b = length >> 16; break;
case 2: b = length >> 8; break;
case 3: b = length ; break;
case 4: b = type >> 24; break;
case 5: b = type >> 16; break;
case 6: b = type >> 8; break;
case 7: b = type ; break;
case 8:
/* The header has been written. If this is really the signature
* that's all that is required and we can go to normal chunk
* processing.
*/
if (file->state == STATE_SIGNATURE)
{
/* The signature has been written, the tail call to read_callback
* below (it's just a goto to the start with a decent compiler)
* will read the IHDR header ahead and validate it.
*/
assert(length == sig1 && type == sig2);
file->read_count = 0; /* Forces a header read */
file->state = STATE_CHUNKS; /* IHDR: checked above */
read_callback(png_ptr, buffer, count);
return;
}
else
{
assert(chunk != NULL);
/* Set up for write, notice that repositioning the input stream
* is only necessary if something is to be read from it. Also
* notice that for the IDAT stream this must only happen once -
* on the first IDAT - to get back to the start of the list and
* this is done inside process_IDAT:
*/
chunk->write_crc = crc_init_4(type);
if (file->state != STATE_IDAT && length > 0)
setpos(chunk);
}
/* FALL THROUGH */
default:
assert(chunk != NULL);
/* NOTE: the arithmetic below overflows and gives a large positive
* png_uint_32 value until the whole chunk data has been written.
*/
switch (file->write_count - length)
{
/* Write the chunk data, normally this just comes from
* the file. The only exception is for that part of a
* chunk which is zlib data and which must be rewritten,
* and IDAT chunks which can be completely
* reconstructed.
*/
default:
if (file->state == STATE_IDAT)
{
struct IDAT *idat = file->idat;
assert(idat != NULL);
/* Read an IDAT byte from the input stream of IDAT chunks.
* Because the IDAT stream can be re-chunked this stream is
* held in the struct IDAT members. The chunk members, in
* particular chunk_length (and therefore the length local)
* refer to the output chunk.
*/
while (idat->idat_index >= idat->idat_length)
{
/* Advance one chunk */
struct IDAT_list *cur = idat->idat_cur;
assert(idat->idat_index == idat->idat_length);
assert(cur != NULL && cur->count > 0);
/* NOTE: IDAT_list::count here, not IDAT_list::length */
if (++(idat->idat_count) >= cur->count)
{
assert(idat->idat_count == cur->count);
/* Move on to the next IDAT_list: */
cur = cur->next;
/* This is an internal error - read beyond the end of
* the pre-calculated stream.
*/
if (cur == NULL || cur->count == 0)
stop(file, UNEXPECTED_ERROR_CODE,
"read beyond end of IDAT");
idat->idat_count = 0;
idat->idat_cur = cur;
}
idat->idat_index = 0;
/* Zero length IDAT chunks are permitted, so the length
* here may be 0.
*/
idat->idat_length = cur->lengths[idat->idat_count];
/* And skip 12 bytes to the next chunk data */
skip_12(file);
}
/* The index is always that of the next byte, the rest of
* the information is always the current IDAT chunk and the
* current list.
*/
++(idat->idat_index);
}
/* Read the byte from the stream. */
b = reread_byte(file);
/* If the byte must be rewritten handle that here */
if (chunk->rewrite_length > 0)
{
if (chunk->rewrite_offset > 0)
--(chunk->rewrite_offset);
else
{
b = chunk->rewrite_buffer[0];
memmove(chunk->rewrite_buffer, chunk->rewrite_buffer+1,
(sizeof chunk->rewrite_buffer)-
(sizeof chunk->rewrite_buffer[0]));
--(chunk->rewrite_length);
}
}
chunk->write_crc = crc_one_byte(chunk->write_crc, b);
break;
/* The CRC is written at:
*
* chunk_write == chunk_length+8..chunk_length+11
*
* so 8 to 11. The CRC is not (yet) conditioned.
*/
case 8: b = chunk->write_crc >> 24; goto write_crc;
case 9: b = chunk->write_crc >> 16; goto write_crc;
case 10: b = chunk->write_crc >> 8; goto write_crc;
case 11:
/* This must happen before the chunk_end below: */
b = chunk->write_crc;
if (file->global->verbose > 2)
{
fputs(" ", stderr);
type_name(type, stderr);
fprintf(stderr, " %lu 0x%.8x\n", (unsigned long)length,
chunk->write_crc ^ 0xffffffff);
}
/* The IDAT stream is written without a call to read_chunk
* until the end is reached. rechunk_length() calculates the
* length of the output chunks. Control gets to this point at
* the end of an *output* chunk - the length calculated by
* rechunk_length. If this corresponds to the end of the
* input stream stop writing IDAT chunks, otherwise continue.
*/
if (file->state == STATE_IDAT &&
(file->idat->idat_index < file->idat->idat_length ||
1+file->idat->idat_count < file->idat->idat_cur->count ||
file->idat->idat_cur != file->idat->idat_list_tail))
{
/* Write another IDAT chunk. Call rechunk_length to
* calculate the length required.
*/
length = chunk->chunk_length = rechunk_length(file->idat);
assert(type == png_IDAT);
file->write_count = 0; /* for the new chunk */
--(file->write_count); /* fake out the increment below */
}
else
{
/* Entered at the end of a non-IDAT chunk and at the end of
* the IDAT stream. The rewrite should have been cleared.
*/
if (chunk->rewrite_length > 0 || chunk->rewrite_offset > 0)
stop(file, UNEXPECTED_ERROR_CODE, "pending rewrite");
/* This is the last byte so reset chunk_read for the next
* chunk and move the input file to the position after the
* *next* chunk header if required.
*/
file->read_count = 8;
file_setpos(file, &file->data_pos);
if (file->idat == NULL)
chunk_end(&file->chunk);
else
IDAT_end(&file->idat);
}
write_crc:
b ^= 0xff; /* conditioning */
break;
}
break;
}
/* Write one byte */
b &= 0xff;
*buffer++ = (png_byte)b;
--count;
write_byte(file, (png_byte)b); /* increments chunk_write */
}
while (count > 0);
}
/* Bundle the file and an uninitialized chunk and IDAT control structure
* together to allow implementation of the chunk/IDAT allocate routine.
*/
struct control
{
struct file file;
struct chunk chunk;
struct IDAT idat;
};
static int
control_end(struct control *control)
{
return file_end(&control->file);
}
static struct file *
get_control(png_const_structrp png_ptr)
{
/* This just returns the (file*). The chunk and idat control structures
* don't always exist.
*/
struct control *control = voidcast(struct control*,
png_get_error_ptr(png_ptr));
return &control->file;
}
static void
allocate(struct file *file, int allocate_idat)
{
struct control *control = voidcast(struct control*, file->alloc_ptr);
if (allocate_idat)
{
assert(file->idat == NULL);
IDAT_init(&control->idat, file);
}
else /* chunk */
{
assert(file->chunk == NULL);
chunk_init(&control->chunk, file);
}
}
static int
control_init(struct control *control, struct global *global,
const char *file_name, const char *out_name)
/* This wraps file_init(&control::file) and simply returns the result from
* file_init.
*/
{
return file_init(&control->file, global, file_name, out_name, control,
allocate);
}
static int
read_png(struct control *control)
/* Read a PNG, return 0 on success else an error (status) code; a bit mask as
* defined for file::status_code as above.
*/
{
png_structp png_ptr;
png_infop info_ptr = NULL;
volatile int rc;
png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, control,
error_handler, warning_handler);
if (png_ptr == NULL)
{
/* This is not really expected. */
log_error(&control->file, LIBPNG_ERROR_CODE, "OOM allocating png_struct");
control->file.status_code |= INTERNAL_ERROR;
return LIBPNG_ERROR_CODE;
}
rc = setjmp(control->file.jmpbuf);
if (rc == 0)
{
# ifdef PNG_SET_USER_LIMITS_SUPPORTED
/* Remove any limits on the size of PNG files that can be read,
* without this we may reject files based on built-in safety
* limits.
*/
png_set_user_limits(png_ptr, 0x7fffffff, 0x7fffffff);
png_set_chunk_cache_max(png_ptr, 0);
png_set_chunk_malloc_max(png_ptr, 0);
# endif
png_set_read_fn(png_ptr, control, read_callback);
info_ptr = png_create_info_struct(png_ptr);
if (info_ptr == NULL)
png_error(png_ptr, "OOM allocating info structure");
if (control->file.global->verbose)
fprintf(stderr, " INFO\n");
png_read_info(png_ptr, info_ptr);
{
png_uint_32 height = png_get_image_height(png_ptr, info_ptr);
int passes = png_set_interlace_handling(png_ptr);
int pass;
png_start_read_image(png_ptr);
for (pass = 0; pass < passes; ++pass)
{
png_uint_32 y = height;
/* NOTE: this skips asking libpng to return either version of
* the image row, but libpng still reads the rows.
*/
while (y-- > 0)
png_read_row(png_ptr, NULL, NULL);
}
}
if (control->file.global->verbose)
fprintf(stderr, " END\n");
/* Make sure to read to the end of the file: */
png_read_end(png_ptr, info_ptr);
}
png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
return rc;
}
static int
one_file(struct global *global, const char *file_name, const char *out_name)
{
int rc;
struct control control;
if (global->verbose)
fprintf(stderr, "FILE %s -> %s\n", file_name,
out_name ? out_name : "<none>");
/* Although control_init can return a failure code the structure is always
* initialized, so control_end can be used to accumulate any status codes.
*/
rc = control_init(&control, global, file_name, out_name);
if (rc == 0)
rc = read_png(&control);
rc |= control_end(&control);
return rc;
}
static void
usage(const char *prog)
{
/* ANSI C-90 limits strings to 509 characters, so use a string array: */
size_t i;
static const char *usage_string[] = {
" Tests, optimizes and optionally fixes the zlib header in PNG files.",
" Optionally, when fixing, strips ancilliary chunks from the file.",
0,
"OPTIONS",
" OPERATION",
" By default files are just checked for readability with a summary of the",
" of zlib issues founds for each compressed chunk and the IDAT stream in",
" the file.",
" --optimize (-o):",
" Find the smallest deflate window size for the compressed data.",
" --strip=[none|crc|unsafe|unused|transform|color|all]:",
" none (default): Retain all chunks.",
" crc: Remove chunks with a bad CRC.",
" unsafe: Remove chunks that may be unsafe to retain if the image data",
" is modified. This is set automatically if --max is given but",
" may be cancelled by a later --strip=none.",
" unused: Remove chunks not used by libpng when decoding an image.",
" This retains any chunks that might be used by libpng image",
" transformations.",
" transform: unused+bKGD.",
" color: transform+iCCP and cHRM.",
" all: color+gAMA and sRGB.",
" Only ancillary chunks are ever removed. In addition the tRNS and sBIT",
" chunks are never removed as they affect exact interpretation of the",
" image pixel values. The following known chunks are treated specially",
" by the above options:",
" gAMA, sRGB [all]: These specify the gamma encoding used for the pixel",
" values.",
" cHRM, iCCP [color]: These specify how colors are encoded. iCCP also",
" specifies the exact encoding of a pixel value; however, in",
" practice most programs will ignore it.",
" bKGD [transform]: This is used by libpng transforms."
" --max=<number>:",
" Use IDAT chunks sized <number>. If no number is given the the IDAT",
" chunks will be the maximum size permitted; 2^31-1 bytes. If the option",
" is omitted the original chunk sizes will not be changed. When the",
" option is given --strip=unsafe is set automatically. This may be",
" cancelled if you know that all unknown unsafe-to-copy chunks really are",
" safe to copy across an IDAT size change. This is true of all chunks",
" that have ever been formally proposed as PNG extensions.",
" MESSAGES",
" By default the program only outputs summaries for each file.",
" --quiet (-q):",
" Do not output the summaries except for files that cannot be read. With",
" two --quiets these are not output either.",
" --errors (-e):",
" Output errors from libpng and the program (except too-far-back).",
" --warnings (-w):",
" Output warnings from libpng.",
" OUTPUT",
" By default nothing is written.",
" --out=<file>:",
" Write the optimized/corrected version of the next PNG to <file>. This",
" overrides the following two options",
" --suffix=<suffix>:",
" Set --out=<name><suffix> for all following files unless overridden on",
" a per-file basis by explicit --out.",
" --prefix=<prefix>:",
" Set --out=<prefix><name> for all the following files unless overridden",
" on a per-file basis by explicit --out.",
" These two options can be used together to produce a suffix and prefix.",
" INTERNAL OPTIONS",
#if 0 /*NYI*/
#ifdef PNG_MAXIMUM_INFLATE_WINDOW
" --test:",
" Test the PNG_MAXIMUM_INFLATE_WINDOW option. Setting this disables",
" output as this would produce a broken file.",
#endif
#endif
0,
"EXIT CODES",
" *** SUBJECT TO CHANGE ***",
" The program exit code is value in the range 0..127 holding a bit mask of",
" the following codes. Notice that the results for each file are combined",
" together - check one file at a time to get a meaningful error code!",
" 0x01: The zlib too-far-back error existed in at least one chunk.",
" 0x02: At least one chunk had a CRC error.",
" 0x04: A chunk length was incorrect.",
" 0x08: The file was truncated.",
" Errors less than 16 are potentially recoverable, for a single file if the",
" exit code is less than 16 the file could be read (with corrections if a",
" non-zero code is returned).",
" 0x10: The file could not be read, even with corrections.",
" 0x20: The output file could not be written.",
" 0x40: An unexpected, potentially internal, error occurred.",
" If the command line arguments are incorrect the program exits with exit",
" 255. Some older operating systems only support 7-bit exit codes, on those",
" systems it is suggested that this program is first tested by supplying",
" invalid arguments.",
0,
"DESCRIPTION",
" " PROGRAM_NAME ":",
" checks each PNG file on the command line for errors. By default errors are",
" not output and the program just returns an exit code and prints a summary.",
" With the --quiet (-q) option the summaries are suppressed too and the",
" program only outputs unexpected errors (internal errors and file open",
" errors).",
" Various known problems in PNG files are fixed while the file is being read",
" The exit code says what problems were fixed. In particular the zlib error:",
0,
" \"invalid distance too far back\"",
0,
" caused by an incorrect optimization of a zlib stream is fixed in any",
" compressed chunk in which it is encountered. An integrity problem of the",
" PNG stream caused by a bug in libpng which wrote an incorrect chunk length",
" is also fixed. Chunk CRC errors are automatically fixed up.",
0,
" Setting one of the \"OUTPUT\" options causes the possibly modified file to",
" be written to a new file.",
0,
" Notice that some PNG files with the zlib optimization problem can still be",
" read by libpng under some circumstances. This program will still detect",
" and, if requested, correct the error.",
0,
" The program will reliably process all files on the command line unless",
" either an invalid argument causes the usage message (this message) to be",
" produced or the program crashes.",
0,
" The summary lines describe issues encountered with the zlib compressed",
" stream of a chunk. They have the following format, which is SUBJECT TO",
" CHANGE in the future:",
0,
" chunk reason comp-level p1 p2 p3 p4 file",
0,
" p1 through p4 vary according to the 'reason'. There are always 8 space",
" separated fields. Reasons specific formats are:",
0,
" chunk ERR status code read-errno write-errno message file",
" chunk SKP comp-level file-bits zlib-rc compressed message file",
" chunk ??? comp-level file-bits ok-bits compressed uncompress file",
0,
" The various fields are",
0,
"$1 chunk: The chunk type of a chunk in the file or 'HEAD' if a problem",
" is reported by libpng at the start of the IDAT stream.",
"$2 reason: One of:",
" CHK: A zlib header checksum was detected and fixed.",
" TFB: The zlib too far back error was detected and fixed.",
" OK : No errors were detected in the zlib stream and optimization",
" was not requested, or was not possible.",
" OPT: The zlib stream window bits value could be improved (and was).",
" SKP: The chunk was skipped because of a zlib issue (zlib-rc) with",
" explanation 'message'",
" ERR: The read of the file was aborted. The parameters explain why.",
"$3 status: For 'ERR' the accumulated status code from 'EXIT CODES' above.",
" This is printed as a 2 digit hexadecimal value",
" comp-level: The recorded compression level (FLEVEL) of a zlib stream",
" expressed as a string {supfast,stdfast,default,maximum}",
"$4 code: The file exit code; where stop was called, as a fairly terse",
" string {warning,libpng,zlib,invalid,read,write,unexpected}.",
" file-bits: The zlib window bits recorded in the file.",
"$5 read-errno: A system errno value from a read translated by strerror(3).",
" zlib-rc: A zlib return code as a string (see zlib.h).",
" ok-bits: The smallest zlib window bits value that works.",
"$6 write-errno:A system errno value from a write translated by strerror(3).",
" compressed: The count of compressed bytes in the zlib stream, when the",
" reason is 'SKP'; this is a count of the bytes read from the",
" stream when the fatal error was encountered.",
"$7 message: An error message (spaces replaced by _, as in all parameters),",
" uncompress: The count of bytes from uncompressing the zlib stream; this",
" may not be the same as the number of bytes in the image.",
"$8 file: The name of the file (this may contain spaces).",
};
fprintf(stderr, "Usage: %s {[options] png-file}\n", prog);
for (i=0; i < (sizeof usage_string)/(sizeof usage_string[0]); ++i)
{
if (usage_string[i] != 0)
fputs(usage_string[i], stderr);
fputc('\n', stderr);
}
exit(255);
}
int
main(int argc, const char **argv)
{
char temp_name[FILENAME_MAX+1];
const char * prog = *argv;
const char * outfile = NULL;
const char * suffix = NULL;
const char * prefix = NULL;
int done = 0; /* if at least one file is processed */
struct global global;
global_init(&global);
while (--argc > 0)
{
++argv;
if (strcmp(*argv, "--debug") == 0)
{
/* To help debugging problems: */
global.errors = global.warnings = 1;
global.quiet = 0;
global.verbose = 7;
}
else if (strncmp(*argv, "--max=", 6) == 0)
{
global.idat_max = (png_uint_32)atol(6+*argv);
if (global.skip < SKIP_UNSAFE)
global.skip = SKIP_UNSAFE;
}
else if (strcmp(*argv, "--max") == 0)
{
global.idat_max = 0x7fffffff;
if (global.skip < SKIP_UNSAFE)
global.skip = SKIP_UNSAFE;
}
else if (strcmp(*argv, "--optimize") == 0 || strcmp(*argv, "-o") == 0)
global.optimize_zlib = 1;
else if (strncmp(*argv, "--out=", 6) == 0)
outfile = 6+*argv;
else if (strncmp(*argv, "--suffix=", 9) == 0)
suffix = 9+*argv;
else if (strncmp(*argv, "--prefix=", 9) == 0)
prefix = 9+*argv;
else if (strcmp(*argv, "--strip=none") == 0)
global.skip = SKIP_NONE;
else if (strcmp(*argv, "--strip=crc") == 0)
global.skip = SKIP_BAD_CRC;
else if (strcmp(*argv, "--strip=unsafe") == 0)
global.skip = SKIP_UNSAFE;
else if (strcmp(*argv, "--strip=unused") == 0)
global.skip = SKIP_UNUSED;
else if (strcmp(*argv, "--strip=transform") == 0)
global.skip = SKIP_TRANSFORM;
else if (strcmp(*argv, "--strip=color") == 0)
global.skip = SKIP_COLOR;
else if (strcmp(*argv, "--strip=all") == 0)
global.skip = SKIP_ALL;
else if (strcmp(*argv, "--errors") == 0 || strcmp(*argv, "-e") == 0)
global.errors = 1;
else if (strcmp(*argv, "--warnings") == 0 || strcmp(*argv, "-w") == 0)
global.warnings = 1;
else if (strcmp(*argv, "--quiet") == 0 || strcmp(*argv, "-q") == 0)
{
if (global.quiet)
global.quiet = 2;
else
global.quiet = 1;
}
else if (strcmp(*argv, "--verbose") == 0 || strcmp(*argv, "-v") == 0)
++global.verbose;
#if 0
/* NYI */
# ifdef PNG_MAXIMUM_INFLATE_WINDOW
else if (strcmp(*argv, "--test") == 0)
++set_option;
# endif
#endif
else if ((*argv)[0] == '-')
usage(prog);
else
{
size_t outlen = strlen(*argv);
if (outfile == NULL) /* else this takes precedence */
{
/* Consider the prefix/suffix options */
if (prefix != NULL)
{
size_t prefixlen = strlen(prefix);
if (prefixlen+outlen > FILENAME_MAX)
{
fprintf(stderr, "%s: output file name too long: %s%s%s\n",
prog, prefix, *argv, suffix ? suffix : "");
global.status_code |= WRITE_ERROR;
continue;
}
memcpy(temp_name, prefix, prefixlen);
memcpy(temp_name+prefixlen, *argv, outlen);
outlen += prefixlen;
outfile = temp_name;
}
else if (suffix != NULL)
memcpy(temp_name, *argv, outlen);
temp_name[outlen] = 0;
if (suffix != NULL)
{
size_t suffixlen = strlen(suffix);
if (outlen+suffixlen > FILENAME_MAX)
{
fprintf(stderr, "%s: output file name too long: %s%s\n",
prog, *argv, suffix);
global.status_code |= WRITE_ERROR;
continue;
}
memcpy(temp_name+outlen, suffix, suffixlen);
outlen += suffixlen;
temp_name[outlen] = 0;
outfile = temp_name;
}
}
(void)one_file(&global, *argv, outfile);
++done;
outfile = NULL;
}
}
if (!done)
usage(prog);
return global_end(&global);
}
#else /* ZLIB_VERNUM < 0x1240 */
int
main(void)
{
fprintf(stderr,
"pngfix needs libpng with a zlib >=1.2.4 (not 0x%x)\n",
ZLIB_VERNUM);
return 77;
}
#endif /* ZLIB_VERNUM */
#else /* No read support */
int
main(void)
{
fprintf(stderr, "pngfix does not work without read deinterlace support\n");
return 77;
}
#endif /* PNG_READ_SUPPORTED && PNG_EASY_ACCESS_SUPPORTED */
#else /* No setjmp support */
int
main(void)
{
fprintf(stderr, "pngfix does not work without setjmp support\n");
return 77;
}
#endif /* PNG_SETJMP_SUPPORTED */
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