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jpeg.c
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jpeg.c
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/*
JPEG the Ripper
Copyright (c) 2005,2022 github.com/rusq
Redistribution and use in source and binary forms, with or without modification,
are permitted provided that the following conditions are met:
1. Redistributions of source code must retain the above copyright notice, this
list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright notice,
this list of conditions and the following disclaimer in the documentation
and/or other materials provided with the distribution.
3. Neither the name of the copyright holder nor the names of its contributors
may be used to endorse or promote products derived from this software without
specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include <stdio.h>
#include <stdlib.h>
#include "jpeg.h"
#include "log.h"
#define _JPEG_MARKER 0xff
#define _JPEG_SOI 0xd8
#define _JPEG_APP0 0xe0
#define _JPEG_APP1 0xe1
#define _JPEG_DQT 0xdb
#define _JPEG_COMMENT 0xfe
/* jpeg_marker describes the jpeg marker format */
struct jpeg_marker {
unsigned char marker;
unsigned char tag;
};
typedef struct jpeg_marker *jpeg_marker_ptr;
/* section_size is the JPEG section size, use SECTION_SIZE macro to calculate
size in bytes */
struct section_size {
unsigned char b1;
unsigned char b2;
};
typedef struct section_size *section_size_ptr;
#define SECTION_SIZE(ss) ss.b1 * 256 + ss.b2 - sizeof(struct jpeg_marker)
typedef struct {
unsigned char tag;
char *name;
} _tag_name;
_tag_name _tag_names[] = {
{_JPEG_SOI, "start of image"}, {_JPEG_APP0, "app0"}, {_JPEG_APP1, "app1"},
{_JPEG_DQT, "quantisation tables"}, {_JPEG_COMMENT, "comment"},
};
size_t _tag_names_sz = sizeof(_tag_names) / sizeof(_tag_name);
/* tag_name returns the tag name string for the tag. If the tag is not found it
returns NULL */
char *tag_name(unsigned char tag) {
size_t i;
for (i = 0; i < _tag_names_sz; i++) {
if (_tag_names[i].tag == tag) {
return _tag_names[i].name;
}
}
return NULL;
}
/* read_marker attempts to read the jpeg marker from the file f. It returns
RET_ERROR on failure, or RET_OK on success. jt will be populated with values.
*/
int read_marker(jpeg_marker_ptr jt, FILE *f) {
char *tn;
if (fread(jt, sizeof(*jt), 1, f) == 0) {
perror("failed to read the marker");
return RET_ERROR;
}
if (jt->marker != 0xff) {
fprintf(stderr, "not a marker\n");
return RET_ERROR;
}
tn = tag_name(jt->tag);
if (tn == NULL) {
tn = "unknown";
}
lverbose("read_marker: read marker with tag: %s\n", tn);
return RET_OK;
}
/* read_section_size should be called immediately after read_marker. It will
attempt to read the section size from the file f. On success it returns RET_OK
and ss is populated with values from the file. Use SECTION_SIZE macro to
calculate integer size of the section. On error it returns RET_ERROR. */
int read_section_size(section_size_ptr ss, FILE *f) {
if (fread(ss, sizeof(*ss), 1, f) == 0) {
perror("failed to read section size");
return RET_ERROR;
}
lverbose("read_section_size: [%02X, %02X], size: %d\n", ss->b1, ss->b2, SECTION_SIZE((*ss)));
return RET_OK;
}
/* jpeg_hdr_size returns the header size in bytes. It will return RET_ERROR on error. */
long jpeg_hdr_size(FILE *f) {
struct jpeg_marker jt;
struct section_size ss;
long initial_pos;
if ((initial_pos = ftell(f)) == -1) {
perror("failed to determine current file position");
return RET_ERROR;
}
/* read the first tag */
if (!read_marker(&jt, f)) {
llog("failed to read marker 1");
return RET_ERROR;
}
if (jt.tag != _JPEG_SOI) {
llog("unexpected tag");
return RET_ERROR;
}
/* read the following tag */
if (!read_marker(&jt, f)) {
perror("failed to read marker 2");
return RET_ERROR;
}
switch (jt.tag) {
default:
llog("unexpected tag: %X\n", jt.tag);
return RET_ERROR;
case _JPEG_APP0:;
}
if (!read_section_size(&ss, f)) {
return RET_ERROR;
}
/* skip */
if (fseek(f, SECTION_SIZE(ss), SEEK_CUR) == -1) {
perror("unable to seek");
return RET_ERROR;
}
if (!read_marker(&jt, f)) {
return RET_ERROR;
}
/* search for quantisation tables */
while (jt.tag != _JPEG_DQT) {
if (!read_section_size(&ss, f)) {
return RET_ERROR;
}
lverbose("\tskipping section size: %d\n", SECTION_SIZE(ss));
if (fseek(f, SECTION_SIZE(ss), SEEK_CUR) == -1) {
perror("seek failed");
return RET_ERROR;
}
if (!read_marker(&jt, f)) {
return RET_ERROR;
}
}
return ftell(f) - sizeof(struct jpeg_marker) - initial_pos;
}