wip

Signed-off-by: Pin <wf6DJd8a3xSSCZbn@protonmail.com>

.gitignore

@@ -0,0 +1,7 @@
+*.png
+*.out
+*.woo
+*.wow
+*.gch
+vgcore.*
+bin/

Makefile

@@ -0,0 +1,23 @@
+LIBRARIES = `pkg-config --libs zlib libsodium` -Iinclude
+SOURCES = ./src/* ./cmd/pspng.c
+OUTPUT_DIR = ./bin
+OUTPUT = -o ${OUTPUT_DIR}/PROG
+INSTALL_OUTPUT = ${OUTPUT_DIR}/PROG
+
+build: output_dir
+	gcc -Wall -pthread ${LIBRARIES} ${SOURCES} ${OUTPUT:PROG=pspng}
+
+debug: output_dir
+	gcc -Wall -g -pthread ${LIBRARIES} ${SOURCES} ${OUTPUT:PROG=pspng}
+
+install:
+	mv ${INSTALL_OUTPUT:PROG=pspng} /usr/bin/
+
+output_dir:
+	mkdir -p ${OUTPUT_DIR}
+
+clean:
+	rm -rf $(OUTPUT_DIR) **.h.gch
+
+memcheck: debug
+	valgrind --tool=memcheck --leak-check=yes --show-reachable=yes --num-callers=20 --track-fds=yes -s ${OUTPUT_DIR}/pspng

cmd/pspng.c

@@ -0,0 +1,620 @@
+#pragma GCC optimize("O0")
+
+#include <endian.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <string.h>
+#include <stdlib.h>
+#include <sodium.h>
+#include <getopt.h>
+#include <pthread.h>
+#include "crc_util.h"
+#include "CRCLib.h"
+#include "pspng.h"
+#include "compress_util.h"
+
+//#define MAX_IDAT_SIZE 16384
+#define MAX_WINDOW_SIZE 32768
+#define MAX_IDAT_SIZE 8192
+
+const long idat_signature = 1229209940;
+const long iend_signature = 1229278788;
+
+unsigned long first_idat(unsigned char *addr) {
+	int idat_found = 0;
+	unsigned long offset = 8;
+	long jump_offset = 0;
+	unsigned long header_type = 0;
+	while(idat_found == 0) {
+		jump_offset = check_header_length(addr, offset);
+		header_type = check_header_length(addr, offset+4);
+		if(header_type == idat_signature) {
+			idat_found = 1;
+		} else {
+			offset = offset + jump_offset + 12;
+		}
+	}
+	return offset;
+}
+
+int total_idat(unsigned char *addr) {
+	int searching = 0;
+	int found_idat = 0;
+	unsigned long offset = 0;
+	unsigned long idat_length = 0;
+	unsigned long header_type = 0;
+
+	unsigned long first_idat_offset = first_idat(addr);
+	offset = first_idat_offset;
+
+	while(searching == 0) {
+		found_idat++;
+		idat_length = check_header_length(addr, offset);
+		// Jumping Offset + IDAT LENGTH + 3 bytes for 2 CRCs and 1 LEN fields
+		offset = offset+12+idat_length;
+		header_type = check_header_length(addr, offset+4);
+		if(header_type != idat_signature) {
+			searching = 1;
+		}
+	}
+	return found_idat;
+}
+
+int update_file_crc(unsigned char *addr, unsigned long offset , unsigned int crc_num) {
+	int startCRC = 8 + offset + check_header_length(addr, offset);
+	unsigned char new_crc;
+	for(int i = 0; i < 4; i++) {
+		new_crc = crc_num >> (8*(3-i)) & 0xFF;
+		addr[startCRC+i] = new_crc;
+	}
+	return 0;
+}
+
+static void random_window_bit_change(unsigned char *data, int width, int rounds, int color_range, size_t length, size_t offset) {
+	size_t random_num = 0;
+	size_t filter_chunk_byte = 0;
+	size_t change_num = 0;
+	long prior_chuck_check = 0;
+	for (int i = 0; i < rounds; i++) {
+		random_num = 0;
+		do {
+			random_num = randombytes_uniform(length) + offset;
+			filter_chunk_byte = (random_num - (random_num % ((width * color_range) + 1)));
+		} while((random_num % ((width * color_range) + 1)) == 0);
+
+		if(data[filter_chunk_byte] == 0) {
+			// None Filter Type Change
+			if(data[random_num] == 255) {
+				data[random_num]--;
+			} else {
+				data[random_num]++;
+			}
+		} else if(data[filter_chunk_byte] == 1) {
+			// Sub Filter Type Change
+			if(data[random_num] == 255) {
+				data[random_num]--;
+				change_num = 1;
+			} else {
+				data[random_num]++;
+				change_num = -1;
+			}
+			// Starting after random change
+			for(int j = 1; j < 2; j++) {
+				data[random_num+(color_range * j)] = (data[random_num+(color_range * j)] + change_num) % 256;
+			}
+		} else if(data[filter_chunk_byte] == 2) {
+			printf("2\n");
+			if(data[random_num] == 255) {
+				data[random_num]--;
+			} else {
+				data[random_num]++;
+			}
+		} else if(data[filter_chunk_byte] == 3) {
+			// Average Filter Type Change
+			//printf("HEE: %d\n", data[(filter_chunk_byte - (width * color_range))-1]);
+			prior_chuck_check = filter_chunk_byte;
+			do {
+				//printf("C: %d\n", data[prior_chuck_check]);
+				prior_chuck_check = (prior_chuck_check - (width * color_range)-1);
+				//printf("CH: %ld\n", prior_chuck_check);
+			} while(prior_chuck_check >= 0);
+
+			if(data[random_num] == 255) {
+				data[random_num]--;
+			} else {
+				data[random_num]++;
+			}
+		} else if(data[filter_chunk_byte] == 4) {
+			printf("4\n");
+			if(data[random_num] == 255) {
+				data[random_num]--;
+			} else {
+				data[random_num]++;
+			}
+		} else {
+			printf("ERROR ;( %ld\n", filter_chunk_byte);
+		}
+
+	}
+	return;
+}
+
+static int verify_crc_chunks(unsigned char *data, size_t data_length, int crc_depth, unsigned int max_data_length, char message, size_t iteration) {
+	unsigned char* testing_chunk;
+	unsigned int crc_check = 0;
+	unsigned int test_data_length = 0;
+	unsigned int crc_check_length;
+	int rounds = 0;
+
+	for(int i = 0; i < crc_depth; i++) {
+		if((max_data_length * (i+1)) > data_length) {
+			test_data_length = (data_length - (max_data_length * i));
+			testing_chunk = calloc(test_data_length+4, sizeof(unsigned char));
+			// If this is met we need to stop verification
+			i = crc_depth;
+		} else {
+			test_data_length = max_data_length;
+			testing_chunk = calloc(test_data_length+4, sizeof(unsigned char));
+		}
+		// Setting first chunk to IDAT
+		testing_chunk[0] = 0x49;
+		testing_chunk[1] = 0x44;
+		testing_chunk[2] = 0x41;
+		testing_chunk[3] = 0x54;
+		for(int j = 0; j < test_data_length; j++) {
+			testing_chunk[j+4] = data[(test_data_length*rounds)+j+(MAX_WINDOW_SIZE*iteration)];
+		}
+		crc_check_length = test_data_length+4;
+		crc_check = crc(testing_chunk, crc_check_length);
+		
+		if ((crc_check >> (8*3)) != message ) {
+			free(testing_chunk);
+			return 1;
+		}
+		printf("FOUND: %c\n", message);
+		// Used as an alternative to i
+		// Since i needs to be changed it max data length is met
+		rounds++;
+	}
+	free(testing_chunk);
+	return 0;
+}
+
+static int crc_embed_data(unsigned char *data, unsigned int data_length, int bit_width, int color_range, unsigned int sliding_window, char message, size_t offset , size_t iteration) {
+	unsigned char *check_data;
+	size_t check_data_length = 0;
+
+	random_window_bit_change(data, bit_width, 2, color_range, sliding_window, offset);
+
+	// Compressing data for test
+	zlib_compress_data(data, data_length, &check_data, &check_data_length);
+
+	int match_crc = verify_crc_chunks(check_data, check_data_length, 1, MAX_IDAT_SIZE, message, iteration);
+
+	if(match_crc == 0) {
+		printf("COM SIZE: %zu\n", check_data_length);
+		free(check_data);
+		return 0;
+	}
+	free(check_data);
+	return 1;
+}
+
+void *random_data_change_thread_call(void *w) {
+	struct EMBED_THREAD_STRUCT *data = w;
+	unsigned char* temp_color_data = calloc(data->uncom_data_len, sizeof(unsigned char));
+	char cur_message;
+	int searching = 1;
+	do {
+		// Creating temporary data set
+		memcpy(temp_color_data, data->data, data->uncom_data_len);
+
+		// Look into testing these values more
+		if(data->uncom_data_len > 800000) {
+			data->data_len = 90000 + (90000 * data->cur_iteration);
+		} else {
+			data->data_len = data->uncom_data_len;
+		}
+		if(data->uncom_data_len > 16000) {
+			data->win_size = 9000 + (9000 * data->cur_iteration);
+		} else {
+			data->win_size = data->uncom_data_len;
+		}
+
+		cur_message = data->message[data->cur_iteration];
+
+		searching = crc_embed_data(temp_color_data, data->data_len, data->width, data->color_range, data->win_size, cur_message, data->cur_offset, data->cur_iteration);
+
+		pthread_mutex_lock(&data->mutex_lock);
+		if (searching == 0 && *data->searching == 1) {
+			*data->searching = searching;
+			printf("CUR MESSAGE: %c\n", cur_message);
+			memcpy(data->data, temp_color_data, data->uncom_data_len);
+			pthread_mutex_unlock(&data->mutex_lock);
+			break;
+		}
+		pthread_mutex_unlock(&data->mutex_lock);
+
+	} while(*data->searching == 1);
+	free(temp_color_data);
+	pthread_exit(0);
+}
+
+size_t generate_offset(unsigned char *data, size_t data_len, size_t iteration) {
+	unsigned char *com_data_buff = NULL;
+	unsigned char *uncom_data_buff = NULL;
+	size_t com_data_size = 0;
+	size_t uncom_data_size = 0;
+
+	printf("Gen Offset\n");
+	zlib_compress_data(data, data_len, &com_data_buff, &com_data_size);
+
+	zlib_decompress_data(com_data_buff, (MAX_WINDOW_SIZE * (iteration+1)), &uncom_data_buff, &uncom_data_size);
+
+	printf("NEW SIZE: %zu\n", uncom_data_size);
+
+	free(com_data_buff);
+	free(uncom_data_buff);
+	return uncom_data_size;
+}
+
+void random_data_change(unsigned char *color_data, unsigned char *width, size_t length, char *message) {
+	int searching = 1;
+	int core_count = 24;
+	unsigned int sliding_window = 0;
+	unsigned int compress_data_length = 0;
+	// Needs to be turned into a variable
+	int color_range = 3;
+	int waiting = 0;
+	// Union for width type cast
+	union {
+		uint32_t width_int;
+		unsigned char width_array[4];
+	}w;
+	memcpy(w.width_array, width, 4);
+
+	struct EMBED_THREAD_STRUCT *t_data = malloc(sizeof(struct EMBED_THREAD_STRUCT));
+
+	if(pthread_mutex_init(&t_data->mutex_lock, NULL) != 0) {
+		printf("Mutex Lock Error\n");
+		return;
+	}
+	t_data->searching = &searching;
+	t_data->message = message;
+	t_data->data = color_data;
+	t_data->data_len = compress_data_length;
+	t_data->uncom_data_len = length;
+	t_data->cur_offset = 0;
+	t_data->width = be32toh(w.width_int);
+	t_data->color_range = color_range;
+	t_data->win_size = sliding_window;
+	pthread_t tid;
+	t_data->thread_id = tid;
+	for(int j = 0; j < strlen(message); j++) {
+		// Setting Iteration bit and searching
+		t_data->cur_iteration = j;
+		*t_data->searching = 1;
+		for(int i = 0; i < core_count; i++) {
+			pthread_create(&tid, NULL, random_data_change_thread_call, t_data);
+		}
+		// Waiting for all threads to complete
+		waiting = 0;
+		do {
+			pthread_join(tid, NULL);
+			waiting++;
+		} while(waiting!=core_count);
+		pthread_mutex_destroy(&t_data->mutex_lock);
+
+		// Only generate new offset if not last char in message
+		if(j != (strlen(message) - 1)) {
+			t_data->cur_offset = generate_offset(color_data, t_data->uncom_data_len, j);
+		}
+	}
+	return;
+}
+
+void build_png_file(struct PNG_FILE_STRUCT *png_file, char *out_file_name) {
+	FILE *fp;
+	unsigned char *full_data;
+	unsigned int int_crc;
+	unsigned char new_crc[4];
+	unsigned char IEND_DATA[12] = { 0x00, 0x00, 0x00, 0x00, 0x49, 0x45, 0x4E, 0x44, 0xAE, 0x42, 0x60, 0x82};
+
+	fp = fopen(out_file_name, "w");
+
+	union{
+		unsigned char data[sizeof(struct PNG_START_FILE_STRUCT)];
+		struct PNG_START_FILE_STRUCT png_data;
+	}start_data;
+
+	start_data.png_data = png_file->png_start_data;
+
+	printf("IHDR SIZE: %zu\n", sizeof(struct PNG_START_FILE_STRUCT));
+
+	// IHDR Data
+	for(int i = 0; i < sizeof(start_data.data); i++) {
+		fputc(start_data.data[i], fp);
+	}
+
+	// Generating IDAT CHUNKS
+	int idat_loop = 0;
+	uint32_t current_len = 0;
+	do {
+		// Setting IDAT length chunk variable
+		if ((be32toh(png_file->png_idat_data.idat_data_length)-(MAX_IDAT_SIZE*idat_loop)) > MAX_IDAT_SIZE) {
+			current_len = MAX_IDAT_SIZE;
+		} else {
+			current_len = (be32toh(png_file->png_idat_data.idat_data_length)-(MAX_IDAT_SIZE*idat_loop));
+		}
+
+		// IDAT LENGTH WRITE
+		for(int i = 0; i < 4; i++) {
+			//fputc(png_file->png_idat_data.idat_length[i], fp);
+			fputc(current_len >> (8*(3-i)), fp);
+		}
+		// IDAT HEADER WRITE
+		for(int i = 0; i < 4; i++) {
+			fputc(png_file->png_idat_data.idat_header[i], fp);
+		}
+		// IDAT DATA WRITE
+		//for(int i = 0; i < be32toh(png_file->png_idat_data.idat_data_length); i++) {
+		for(int i = 0; i < current_len; i++) {
+			fputc(png_file->png_idat_data.idat_data[i+(MAX_IDAT_SIZE*idat_loop)], fp);
+		}
+
+		// Generating CRC
+		//unsigned char *full_data = malloc(be32toh(png_file->png_idat_data.idat_data_length)+4);
+		full_data = malloc(current_len+4);
+		for(int i = 0; i < 4; i++) {
+			full_data[i] = png_file->png_idat_data.idat_header[i];
+		}
+		for(int i = 0; i < current_len; i++) {
+			full_data[i+4] = png_file->png_idat_data.idat_data[i+(MAX_IDAT_SIZE*idat_loop)];
+		}
+	
+		int_crc = crc(full_data, current_len+4);
+	
+		// IDAT CRC WRITE
+		for(int i = 0; i < 4; i++) {
+			new_crc[i] = int_crc >> (8*(3-i)) & 0xFF;
+			fputc(new_crc[i], fp);
+		}
+
+		// Adding to loop count
+		idat_loop++;
+	} while((idat_loop-1) < (be32toh(png_file->png_idat_data.idat_data_length) / MAX_IDAT_SIZE));
+
+	// IEND Data
+	for(int i = 0; i < 12; i++) {
+		fputc(IEND_DATA[i], fp);
+	}
+	free(full_data);
+	fclose(fp);
+}
+
+unsigned char* populate_idat_array(unsigned char *addr, unsigned long offset, size_t *idat_byte_length) {
+	size_t size = 8;
+	//size_t idat_byte_length = 0;
+	size_t idat_length = 0;
+	//unsigned char* idat_data = calloc(size, sizeof(unsigned char));
+	unsigned char* idat_data = calloc(size, sizeof(unsigned char));
+
+	for(size_t i = 0; i < total_idat(addr); i++) {
+		idat_length = check_header_length(addr, offset);
+		for(size_t j = 0; j < idat_length; j++) {
+			if(*idat_byte_length == size) {
+				size *= 2;
+				idat_data = reallocarray(idat_data, size, sizeof(unsigned char));
+			}
+			idat_data[*idat_byte_length] = addr[offset+8+j];
+			*idat_byte_length += 1;
+		}
+		// Offset 3 bytes for 2 length fields and 1 crc
+		offset = offset + idat_length + 12;
+	}
+	return idat_data;
+}
+
+int change_idat_content(unsigned char *addr, struct PNG_FILE_STRUCT *png_file, char *message, int accuracy, unsigned long offset, char *out_file_name) {
+	if(accuracy > 4) {
+		printf("Warning, accuracy cannot be larger than 4");
+		return EXIT_FAILURE;
+	}
+	if(accuracy > 2) {
+		printf("Notice, this could take a long time...");
+	}
+	if(total_idat(addr) < strlen(message)) {
+		printf("Warning, message exceeds IDAT amount\n");
+		exit(EXIT_FAILURE);
+	}
+
+	size_t idat_byte_length = 0;
+	unsigned char *idat_data = populate_idat_array(addr, offset, &idat_byte_length);
+
+	unsigned char* temp_idat_data = calloc(idat_byte_length, sizeof(unsigned char));
+	memcpy(temp_idat_data, idat_data, idat_byte_length);
+
+	// Decompressing Data
+	unsigned char *uncom_data_buff = NULL;
+	size_t uncom_data_size = 0;
+	zlib_decompress_data(temp_idat_data, idat_byte_length, &uncom_data_buff, &uncom_data_size);
+
+	printf("ORIG UNCOM LEN: %zu\n", uncom_data_size);
+
+	// Start data testing
+	random_data_change(uncom_data_buff, png_file->png_start_data.file_width, uncom_data_size, message);
+	
+	//return 0;
+	// Compress Data
+	unsigned char *com_data_buff;
+	size_t com_data_size = 0;
+	zlib_compress_data(uncom_data_buff, uncom_data_size, &com_data_buff, &com_data_size);
+
+	printf("COM LEN: %zu\n", com_data_size);
+
+	png_file->png_idat_data.idat_data = calloc(com_data_size, sizeof(unsigned char));
+
+	png_file->png_idat_data.idat_data_length = be32toh(com_data_size);
+
+	for(size_t i = 0; i < com_data_size; i++) {
+		png_file->png_idat_data.idat_data[i] = com_data_buff[i];
+	}
+
+	// Build PNG File
+	build_png_file(png_file, out_file_name);
+
+	// Freeing used memory
+	free(uncom_data_buff);
+	free(com_data_buff);
+	free(idat_data);
+	free(temp_idat_data);
+	free(png_file->png_idat_data.idat_data);
+
+	return 0;
+}
+
+// This is where it all starts
+int main(int argc, char **argv) {
+	FILE *fp;
+	size_t i = 0;
+	unsigned long offset = 0;
+	int uncompress_call = 0;
+	int compress_call = 0;
+	struct PNG_FILE_STRUCT png_file_data;
+	char *in_file_name = NULL;
+	char *out_file_name = NULL;
+	char *message = NULL;
+
+	static const struct option long_options[] = {
+		{"help", no_argument, NULL, 'h'},
+		{"file", required_argument, NULL, 'f'},
+		{"outfile", required_argument, NULL, 'o'},
+		{"message", required_argument, NULL, 'm'},
+		{"compress", no_argument, NULL, 'c'},
+		{"uncompress", no_argument, NULL, 'u'},
+		{0, 0, 0, 0}
+	};
+
+	const char* usage =
+		"Usage: pspng [options]\n\n"
+		"  -c  --compress       	Compress Message\n"
+		"  -u  --uncompress     	Currently used for debugging\n"
+		"  -h, --help			Shows help message\n"
+		"  -f, --file			Denotes input file\n"
+		"  -o, --outfile		Denotes output file\n"
+		"  -m, --message		Encoded message\n"
+		"\n";
+
+	int c;
+	while (1) {
+		int option_index = 0;
+		c = getopt_long(argc, argv, "hf:o:m:uc", long_options ,&option_index);
+		if(c == -1) {
+			break;
+		}
+		switch(c) {
+			case 'h':
+				printf("%s", usage);
+				exit(EXIT_SUCCESS);
+			case 'f':
+				in_file_name = optarg;
+				break;
+			case 'o':
+				out_file_name = optarg;
+				break;
+			case 'm':
+				message = optarg;
+				break;
+			case 'c':
+				compress_call = 1;
+				break;
+			case 'u':
+				uncompress_call = 1;
+				break;
+		}
+	}
+
+	if(in_file_name == NULL) {
+		printf("Input file required!\n");
+		exit(EXIT_FAILURE);
+	}
+	
+	if(compress_call == 1) { 
+		if(out_file_name == NULL) {
+			printf("Output file required!\n");
+			exit(EXIT_FAILURE);
+		} else if(message == NULL) {
+			printf("Message required!\n");
+			exit(EXIT_FAILURE);
+		}
+	}
+
+	if(sodium_init() == -1) {
+		return EXIT_FAILURE;
+	}
+
+	fp = fopen(in_file_name, "rt");
+	if (fp == NULL) {
+		printf("File error\n");
+		exit(EXIT_FAILURE);
+	}
+
+
+	unsigned char *file_data = file_to_char_array(fp, &i);
+	fclose(fp);
+
+	populate_start_png(file_data, &png_file_data.png_start_data);
+
+	offset = first_idat(file_data);
+
+	if(uncompress_call == 1) {
+		size_t idat_byte_length = 0;
+		unsigned long cur_idat_len = 0;
+		//unsigned char message_data[8192];
+		unsigned char* idat_data = populate_idat_array(file_data, offset, &idat_byte_length);
+
+		//for(int i = 0; i < idat_byte_length; i++) {
+			//printf("%02X ", idat_data[i]);
+		//}
+		printf("\nDecompressed Data:\n\n");
+		// Decompressing data
+		//unsigned char *uncom_data_buff = NULL;
+		//size_t uncom_data_size = 0;
+		//zlib_decompress_data(idat_data, idat_byte_length, &uncom_data_buff, &uncom_data_size);
+		//for(int i = 0; i < uncom_data_size; i++) {
+		//	printf("%02X ", uncom_data_buff[i]);
+		//}
+		//printf("\n");
+
+		do {
+			for(int j = 0; j < 64; j++) {
+				cur_idat_len = 0;
+				for(int i = 0; i < 4; i++) {
+					cur_idat_len += (file_data[offset+i] << (24-(8*i)));
+				}
+					//printf("%c", file_data[offset+cur_idat_len+8]);
+				if((j % 4) == 0) {
+					printf("%c", file_data[offset+cur_idat_len+8]);
+				}
+				// Offset Plus idat length + 3 bytes
+				offset += cur_idat_len + 12;
+			}
+		} while(offset < idat_byte_length);
+
+		free(idat_data);
+		free(file_data);
+		return EXIT_SUCCESS;
+	}
+
+	if(compress_call == 1) {
+		populate_idat_png(file_data, &png_file_data.png_idat_data, offset);
+	
+		change_idat_content(file_data, &png_file_data, message, 1, offset, out_file_name);
+	
+		free(file_data);
+		return EXIT_SUCCESS;
+	}
+
+	free(file_data);
+	return EXIT_FAILURE;
+}

include/CRCLib.h

@@ -0,0 +1,55 @@
+/*
+ * Code Implemented From: https://www.w3.org/TR/PNG/#D-CRCAppendix
+*/
+
+/* Table of CRCs of all 8-bit messages. */
+unsigned long crc_table[256];
+   
+/* Flag: has the table been computed? Initially false. */
+int crc_table_computed = 0;
+   
+/* Make the table for a fast CRC. */
+void make_crc_table(void)
+{
+  unsigned long c;
+  int n, k;
+   
+  for (n = 0; n < 256; n++) {
+    c = (unsigned long) n;
+    for (k = 0; k < 8; k++) {
+      if (c & 1)
+        c = 0xedb88320L ^ (c >> 1);
+      else
+        c = c >> 1;
+    }
+    crc_table[n] = c;
+  }
+  crc_table_computed = 1;
+}
+  
+
+/* Update a running CRC with the bytes buf[0..len-1]--the CRC
+   should be initialized to all 1's, and the transmitted value
+   is the 1's complement of the final running CRC (see the
+   crc() routine below). */
+   
+unsigned long update_crc(unsigned long crc, unsigned char *buf,
+                         int len)
+{
+  unsigned long c = crc;
+  int n;
+   
+  if (!crc_table_computed)
+    make_crc_table();
+  for (n = 0; n < len; n++) {
+    c = crc_table[(c ^ buf[n]) & 0xff] ^ (c >> 8);
+  }
+  return c;
+}
+   
+/* Return the CRC of the bytes buf[0..len-1]. */
+unsigned long crc(unsigned char *buf, int len)
+{
+  return update_crc(0xffffffffL, buf, len) ^ 0xffffffffL;
+}
+

include/compress_util.h

@@ -0,0 +1,8 @@
+#include <stdio.h>
+#include <zlib.h>
+#include <stddef.h>
+#include <assert.h>
+#include <errno.h>
+
+void zlib_decompress_data(unsigned char *data_chunk, size_t file_length, unsigned char **buff, size_t *sz);
+void zlib_compress_data(unsigned char *data_chunk, size_t file_length, unsigned char **buff, size_t *sz);

include/crc_util.h

@@ -0,0 +1,58 @@
+#include <stdio.h>
+#include <stdint.h>
+
+#pragma once
+
+// PNG File Struct
+struct PNG_START_FILE_STRUCT {
+	unsigned char file_sig[8];
+	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 {
+	union{
+		unsigned char idat_length[4];
+		uint32_t idat_data_length;
+	};
+	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;
+	struct PNG_IDAT_FILE_STRUCT png_idat_data;
+};
+
+struct EMBED_THREAD_STRUCT {
+	pthread_mutex_t mutex_lock;
+	pthread_t thread_id;
+	int *searching;
+	unsigned char *data;
+	unsigned int data_len;
+	size_t uncom_data_len;
+	size_t cur_offset;
+	size_t cur_iteration;
+	int width;
+	int color_range;
+	unsigned int win_size;
+	char *message;
+};
+
+extern const long png_signature[8];
+
+unsigned long 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);

include/pspng.h

@@ -0,0 +1,7 @@
+#pragma once
+
+int check_file_header(char *addr);
+unsigned long first_idat(unsigned char *addr);
+int total_idat(unsigned char *addr);
+void build_png_file(struct PNG_FILE_STRUCT *png_file, char *out_file_name);
+int change_idat_content(unsigned char *addr, struct PNG_FILE_STRUCT *png_file, char *message, int accuracy, unsigned long offset, char *out_file_name);

src/compress_util.c

@@ -0,0 +1,132 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <assert.h>
+#include <errno.h>
+#include "compress_util.h"
+
+#define CHUNK 1024 
+
+/*
+ * Built from exmaple provided in: https://zlib.net/zlib_how.html
+*/
+void zlib_decompress_data(unsigned char *data_chunk, size_t file_length, unsigned char **buff, size_t *sz) {
+        int ret;
+        unsigned int have;
+        z_stream strm;
+        // Adding one to zero here
+        unsigned char out[CHUNK];
+        unsigned char in[CHUNK];
+
+        errno=0;
+        FILE *data_stream = fmemopen(data_chunk, file_length, "r");
+        FILE *of = open_memstream((char**)buff, sz);
+        if(data_stream == NULL) {
+                perror("F MEM OPEN");
+        }
+
+        strm.zalloc = Z_NULL;
+        strm.zfree = Z_NULL;
+        strm.opaque = Z_NULL;
+        strm.avail_in = 0;
+        strm.next_in = Z_NULL;
+        ret = inflateInit(&strm);
+        if(ret != Z_OK) {
+                return;
+        }
+
+        do {
+                strm.avail_in = fread(in, 1, CHUNK, data_stream);
+                if(ferror(data_stream)) {
+                        (void)inflateEnd(&strm);
+                        return;
+                }
+                if(strm.avail_in == 0) {
+                        break;
+                }
+                strm.next_in = in;
+        
+                do {
+                        strm.avail_out = CHUNK;
+                        strm.next_out = out;
+                        ret = inflate(&strm, Z_NO_FLUSH);
+                        assert(ret != Z_STREAM_ERROR);
+                        switch(ret) {
+                                case Z_NEED_DICT:
+                                        ret = Z_DATA_ERROR;
+                                case Z_DATA_ERROR:
+                                case Z_MEM_ERROR:
+                                        (void)inflateEnd(&strm);
+                                        printf("Error: %d\n", ret);
+                                        printf("MSG: %s\n", (char*)strm.msg);
+                                        return;
+                        }
+                        have = CHUNK - strm.avail_out;
+                        fwrite(out, 1, have, of);
+                } while(strm.avail_out == 0);
+        } while(ret != Z_STREAM_END);
+
+        (void)inflateEnd(&strm);
+
+        fclose(data_stream);
+        fclose(of);
+}
+
+/*
+ * Built from exmaple provided in: https://zlib.net/zlib_how.html
+*/
+void zlib_compress_data(unsigned char *data_chunk, size_t file_length, unsigned char **buff, size_t *sz) {
+        int ret, flush;
+        unsigned int have;
+        z_stream strm;
+        unsigned char in[CHUNK];
+        unsigned char out[CHUNK];
+        int level = 9;
+        int method = Z_DEFLATED;
+        int windowBits = 10;
+        int memLevel = 9;
+        //int strategy = Z_DEFAULT_STRATEGY;
+        int strategy = Z_FILTERED;
+
+        FILE *data_stream = fmemopen(data_chunk, file_length, "r");
+        FILE *out_data_stream = NULL;
+        out_data_stream = open_memstream((char**)buff, sz);
+
+        strm.zalloc = Z_NULL;
+        strm.zfree = Z_NULL;
+        strm.opaque = Z_NULL;
+        ret = deflateInit2(&strm, level, method, windowBits, memLevel, strategy);
+        if (ret != Z_OK) {
+                return;
+        }
+
+        do {
+                strm.avail_in = fread(in, 1, CHUNK, data_stream);
+                if (ferror(data_stream)) {
+                        (void)deflateEnd(&strm);
+                        return;
+                }
+                flush = feof(data_stream) ? Z_FINISH : Z_NO_FLUSH;
+                strm.next_in = in;
+
+                do {
+                        strm.avail_out = CHUNK;
+                        strm.next_out = out;
+
+                        ret = deflate(&strm, flush);
+                        assert(ret != Z_STREAM_ERROR);
+                        have = CHUNK - strm.avail_out;
+                        if(fwrite(out, 1, have, out_data_stream) != have || ferror(out_data_stream)) {
+                                (void)deflateEnd(&strm);
+                                return;
+                        }
+                } while(strm.avail_out == 0);
+                assert(strm.avail_in == 0);
+
+        } while(flush != Z_FINISH);
+        assert(ret == Z_STREAM_END);
+
+        fclose(data_stream);
+        fclose(out_data_stream);
+
+        (void)deflateEnd(&strm);
+}

src/crc_util.c

@@ -0,0 +1,92 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include "crc_util.h"
+
+const long png_signature[8] = { 0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a };
+
+unsigned long check_header_length(unsigned char *addr, long offset) {
+        unsigned long res = 0;
+        for( int i = 0; i < 4; i++ ) {
+                res |= addr[offset+i];
+                if (i < 3) {
+                        res <<= 8;
+                }
+        }
+        return res;
+}
+
+int check_file_header(char *addr) {
+        int signature_match = 0;
+        for( int i = 0; i < 8; i++ ) {
+                if (addr[i] != png_signature[i]) {
+                        signature_match = 1;
+                }
+        }
+        printf("Sig Match: %d\n", signature_match);
+        return signature_match;
+
+}
+
+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)));
+	}
+
+	for(int i = 0; i < 4; i++){
+		png_data->idat_header[i] = addr[i+offset+4];
+	}
+}
+
+void populate_start_png(unsigned char *addr, struct PNG_START_FILE_STRUCT *png_data) {
+	union{
+		unsigned char *data;
+		struct PNG_START_FILE_STRUCT *png_data;
+	}png;
+
+	png.png_data = png_data;
+
+	for(int i = 0; i < sizeof(struct PNG_START_FILE_STRUCT); i++) {
+		png.data[i] = addr[i];
+	}
+}
+
+int create_cc_file(unsigned char *addr, unsigned long file_length) {
+        FILE *fp;
+        fp = fopen("png2.png", "w");
+
+        if(fp == NULL) {
+                return EXIT_FAILURE;
+        }
+
+        for(int i = 0; i < file_length; i++){
+                fputc(addr[i], fp);
+        }
+        fclose(fp);
+	return 0;
+}
+
+unsigned char* file_to_char_array(FILE *in_file, size_t* size) {
+        unsigned long c;
+        unsigned long file_data_cap = 8;
+        unsigned char* file_data = calloc(file_data_cap, sizeof(unsigned char));
+
+        for(size_t i = 0;(c = fgetc(in_file)) != EOF; i++) {
+                if(i == file_data_cap) {
+                        file_data_cap *= 2;
+                        file_data = reallocarray(file_data, file_data_cap, sizeof(unsigned char));
+                        if(file_data == NULL) {
+                                perror("FAILED ARRAY RESIZE");
+                                return NULL;
+                        }
+                }
+                file_data[i] = c;
+                *size += 1;
+        }
+        return file_data;
+}
+