Spencer/PNG_CC
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Pin
2021-10-14 01:27:38 -04:00
parent 7534150326
commit 6166af2b41
4 changed files with 104 additions and 9 deletions
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1
.gitignore vendored
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@@ -2,4 +2,5 @@
*.out
*.woo
*.wow
*.gch
bin/

9
cmd/crc.c
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@@ -123,7 +123,6 @@ int change_idat_content(unsigned char *addr, unsigned char *message, int accurac
int prop_found = 0;
long size = 1;
long rounds = 0;
size_t idat_byte_length = 0;
unsigned char* idat_data = calloc(size, sizeof(unsigned char));
for(size_t i = 0; i <= idat_length; i++) {
@@ -167,6 +166,8 @@ int main() {
FILE *fp;
size_t i = 0;
unsigned long offset = 0;
struct PNG_START_FILE_STRUCT png_start_file_data;
struct PNG_IDAT_FILE_STRUCT png_idat_file_data;
unsigned char *message = malloc(sizeof(char));
message[0] = '\0';
@@ -184,7 +185,13 @@ int main() {
unsigned char *file_data = file_to_char_array(fp, &i);
fclose(fp);
populate_start_png(file_data, &png_start_file_data);
offset = first_idat(file_data);
printf("Off: %ld\n", offset);
populate_idat_png(file_data, &png_idat_file_data, offset);
change_idat_content(file_data, message, 1, offset);
free(file_data);
free(message);

32
include/crc_util.h
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@@ -1,15 +1,29 @@
#include <stdio.h>
// PNG File Struct
struct PNG_FILE_STRUCT {
struct PNG_START_FILE_STRUCT {
unsigned char file_sig[8];
int file_width;
int file_height;
int bit_depth;
int color_type;
int compression_method;
int filter_method;
int interlace_method;
unsigned char ihdr_length[4];
unsigned char ihdr_header[4];
unsigned char file_width[4];
unsigned char file_height[4];
unsigned char bit_depth[1];
unsigned char color_type[1];
unsigned char compression_method[1];
unsigned char filter_method[1];
unsigned char interlace_method[1];
unsigned char ihdr_crc[4];
};
struct PNG_IDAT_FILE_STRUCT {
unsigned char idat_length[4];
unsigned char idat_header[4];
unsigned char idat_crc[4];
unsigned char idat_data[];
};
struct PNG_FILE_STRUCT {
struct PNG_START_FILE_STRUCT png_start_data;
};
extern const long png_signature[8];
@@ -18,3 +32,5 @@ int check_header_length(unsigned char *addr, long offset);
int check_file_header(char *addr);
int create_cc_file(unsigned char *addr, unsigned long file_length);
unsigned char* file_to_char_array(FILE *in_file, size_t* size);
void populate_start_png(unsigned char *addr, struct PNG_START_FILE_STRUCT *png_data);
void populate_idat_png(unsigned char *addr, struct PNG_IDAT_FILE_STRUCT *png_data, unsigned long offset);

71
src/crc_util.c
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@@ -27,6 +27,77 @@ int check_file_header(char *addr) {
}
void populate_idat_png(unsigned char *addr, struct PNG_IDAT_FILE_STRUCT *png_data, unsigned long offset) {
unsigned long cur_idat_length = 0;
for(int i = 0; i < 4; i++){
png_data->idat_length[i] = addr[i+offset];
}
for(int i = 0; i < 4; i++){
cur_idat_length += (png_data->idat_length[i] << (24-(8*i)));
}
printf("\n%ld\n", cur_idat_length);
}
void populate_start_png(unsigned char *addr, struct PNG_START_FILE_STRUCT *png_data) {
for(int i = 0; i < 8; i++) {
png_data->file_sig[i] = addr[i];
printf("%02X ", png_data->file_sig[i]);
}
printf("\n");
for(int i = 0; i < 4; i++) {
png_data->ihdr_length[i] = addr[i+8];
printf("%02X ", png_data->ihdr_length[i]);
}
printf("\n");
for(int i = 0; i < 4; i++) {
png_data->ihdr_header[i] = addr[i+12];
printf("%02X ", png_data->ihdr_header[i]);
}
printf("\n");
for(int i = 0; i < 4; i++) {
png_data->file_width[i] = addr[i+16];
printf("%02X ", png_data->file_width[i]);
}
printf("\n");
for(int i = 0; i < 4; i++) {
png_data->file_height[i] = addr[i+20];
printf("%02X ", png_data->file_height[i]);
}
printf("\n");
for(int i = 0; i < 1; i++) {
png_data->bit_depth[i] = addr[i+24];
printf("%02X ", png_data->bit_depth[i]);
}
printf("\n");
for(int i = 0; i < 1; i++) {
png_data->color_type[i] = addr[i+25];
printf("%02X ", png_data->color_type[i]);
}
printf("\n");
for(int i = 0; i < 1; i++) {
png_data->compression_method[i] = addr[i+26];
printf("%02X ", png_data->compression_method[i]);
}
printf("\n");
for(int i = 0; i < 1; i++) {
png_data->filter_method[i] = addr[i+27];
printf("%02X ", png_data->filter_method[i]);
}
printf("\n");
for(int i = 0; i < 1; i++) {
png_data->interlace_method[i] = addr[i+28];
printf("%02X ", png_data->interlace_method[i]);
}
printf("\n");
for(int i = 0; i < 4; i++) {
png_data->ihdr_crc[i] = addr[i+29];
printf("%02X ", png_data->ihdr_crc[i]);
}
printf("\n");
}
int create_cc_file(unsigned char *addr, unsigned long file_length) {
FILE *fp;
fp = fopen("png2.png", "w");