tplink-safeloader: add support to split & extract firmwares

Split the oem firmware upgrade images into seperate files.
Useful when analysing oem firmware files.

Signed-off-by: Alexander Couzens <lynxis@fe80.eu>

tools/firmware-utils/src/tplink-safeloader.c

@@ -46,6 +46,7 @@
 
 #include <sys/types.h>
 #include <sys/stat.h>
+#include <limits.h>
 
 #include "md5.h"
 
@@ -1379,6 +1380,9 @@ static void usage(const char *argv0) {
 		"Usage: %s [OPTIONS...]\n"
 		"\n"
 		"Options:\n"
+		"  -h              show this help\n"
+		"\n"
+		"Create a new image:\n"
 		"  -B <board>      create image for the board specified with <board>\n"
 		"  -k <file>       read kernel image from the file <file>\n"
 		"  -r <file>       read rootfs image from the file <file>\n"
@@ -1386,7 +1390,9 @@ static void usage(const char *argv0) {
 		"  -V <rev>        sets the revision number to <rev>\n"
 		"  -j              add jffs2 end-of-filesystem markers\n"
 		"  -S              create sysupgrade instead of factory image\n"
-		"  -h              show this help\n",
+		"Extract an old image:\n"
+		"  -x <file>       extract all oem firmware partition\n"
+		"  -d <dir>        destination to extract the firmware partition\n",
 		argv0
 	);
 };
@@ -1403,8 +1409,232 @@ static const struct device_info *find_board(const char *id)
 	return NULL;
 }
 
+static int add_flash_partition(
+		struct flash_partition_entry *part_list,
+		size_t max_entries,
+		const char *name,
+		unsigned long base,
+		unsigned long size)
+{
+	int ptr = 0;
+	/* check if the list has a free entry */
+	for (int ptr=0; ptr<max_entries; ptr++, part_list++) {
+		if (part_list->name == NULL &&
+				part_list->base == 0 &&
+				part_list->size == 0)
+			break;
+	}
+
+	if (ptr == max_entries) {
+		error(1, 0, "No free flash part entry available.");
+	}
+
+	part_list->name = calloc(1, strlen(name) + 1);
+	memcpy((char *)part_list->name, name, strlen(name));
+	part_list->base = base;
+	part_list->size = size;
+
+	return 0;
+}
+
+/** read the partition table into struct flash_partition_entry */
+static int read_partition_table(
+		FILE *file, long offset,
+		struct flash_partition_entry *entries, size_t max_entries,
+		int type)
+{
+	char buf[2048];
+	char *ptr, *end;
+	const char *parthdr = NULL;
+	const char *fwuphdr = "fwup-ptn";
+	const char *flashhdr = "partition";
+
+	/* TODO: search for the partition table */
+
+	switch(type) {
+		case 0:
+			parthdr = fwuphdr;
+			break;
+		case 1:
+			parthdr = flashhdr;
+			break;
+		default:
+			error(1, 0, "Invalid partition table");
+	}
+
+	if (fseek(file, offset, SEEK_SET) < 0)
+		error(1, errno, "Can not seek in the firmware");
+
+	if (fread(buf, 1, 2048, file) < 0)
+		error(1, errno, "Can not read fwup-ptn from the firmware");
+
+	buf[2047] = '\0';
+
+	/* look for the partition header */
+	if (memcmp(buf, parthdr, strlen(parthdr)) != 0) {
+		fprintf(stderr, "DEBUG: can not find fwuphdr\n");
+		return 1;
+	}
+
+	ptr = buf;
+	end = buf + sizeof(buf);
+	while ((ptr + strlen(parthdr)) < end &&
+			memcmp(ptr, parthdr, strlen(parthdr)) == 0) {
+		char *end_part;
+		char *end_element;
+
+		char name[32] = { 0 };
+		int name_len = 0;
+		unsigned long base = 0;
+		unsigned long size = 0;
+
+		end_part = memchr(ptr, '\n', (end - ptr));
+		if (end_part == NULL) {
+			/* in theory this should never happen, because a partition always ends with 0x09, 0x0D, 0x0A */
+			break;
+		}
+
+		for (int i=0; i<=4; i++) {
+			if (end_part <= ptr)
+				break;
+
+			end_element = memchr(ptr, 0x20, (end_part - ptr));
+			if (end_element == NULL) {
+				error(1, errno, "Ignoring the rest of the partition entries.");
+				break;
+			}
+
+			switch (i) {
+				/* partition header */
+				case 0:
+					ptr = end_element + 1;
+					continue;
+				/* name */
+				case 1:
+					name_len = (end_element - ptr) > 31 ? 31 : (end_element - ptr);
+					strncpy(name, ptr, name_len);
+					name[name_len] = '\0';
+					ptr = end_element + 1;
+					continue;
+
+				/* string "base" */
+				case 2:
+					ptr = end_element + 1;
+					continue;
+
+				/* actual base */
+				case 3:
+					base = strtoul(ptr, NULL, 16);
+					ptr = end_element + 1;
+					continue;
+
+				/* string "size" */
+				case 4:
+					ptr = end_element + 1;
+					/* actual size. The last element doesn't have a sepeartor */
+					size = strtoul(ptr, NULL, 16);
+					/* the part ends with 0x09, 0x0d, 0x0a */
+					ptr = end_part + 1;
+					add_flash_partition(entries, max_entries, name, base, size);
+					continue;
+			}
+		}
+	}
+
+	return 0;
+}
+
+static void write_partition(
+		FILE *input_file,
+		size_t firmware_offset,
+		struct flash_partition_entry *entry,
+		FILE *output_file)
+{
+	char buf[4096];
+	size_t offset;
+
+	fseek(input_file, entry->base + firmware_offset, SEEK_SET);
+
+	for (offset = 0; sizeof(buf) + offset <= entry->size; offset += sizeof(buf)) {
+		if (fread(buf, sizeof(buf), 1, input_file) < 0)
+			error(1, errno, "Can not read partition from input_file");
+
+		if (fwrite(buf, sizeof(buf), 1, output_file) < 0)
+			error(1, errno, "Can not write partition to output_file");
+	}
+	/* write last chunk smaller than buffer */
+	if (offset < entry->size) {
+		offset = entry->size - offset;
+		if (fread(buf, offset, 1, input_file) < 0)
+			error(1, errno, "Can not read partition from input_file");
+		if (fwrite(buf, offset, 1, output_file) < 0)
+			error(1, errno, "Can not write partition to output_file");
+	}
+}
+
+static int extract_firmware_partition(FILE *input_file, size_t firmware_offset, struct flash_partition_entry *entry, const char *output_directory)
+{
+	FILE *output_file;
+	char output[PATH_MAX];
+
+	snprintf(output, PATH_MAX, "%s/%s", output_directory, entry->name);
+	output_file = fopen(output, "wb+");
+	if (output_file == NULL) {
+		error(1, errno, "Can not open output file %s", output);
+	}
+
+	write_partition(input_file, firmware_offset, entry, output_file);
+
+	fclose(output_file);
+
+	return 0;
+}
+
+/** extract all partitions from the firmware file */
+static int extract_firmware(const char *input, const char *output_directory)
+{
+	struct flash_partition_entry entries[16] = { 0 };
+	size_t max_entries = 16;
+	size_t firmware_offset = 0x1014;
+	FILE *input_file;
+
+	struct stat statbuf;
+
+	/* check input file */
+	if (stat(input, &statbuf)) {
+		error(1, errno, "Can not read input firmware %s", input);
+	}
+
+	/* check if output directory exists */
+	if (stat(output_directory, &statbuf)) {
+		error(1, errno, "Failed to stat output directory %s", output_directory);
+	}
+
+	if ((statbuf.st_mode & S_IFMT) != S_IFDIR) {
+		error(1, errno, "Given output directory is not a directory %s", output_directory);
+	}
+
+	input_file = fopen(input, "rb");
+
+	if (read_partition_table(input_file, firmware_offset, entries, 16, 0) != 0) {
+		error(1, 0, "Error can not read the partition table (fwup-ptn)");
+	}
+
+	for (int i=0; i<max_entries; i++) {
+		if (entries[i].name == NULL &&
+				entries[i].base == 0 &&
+				entries[i].size == 0)
+			continue;
+
+		extract_firmware_partition(input_file, firmware_offset, &entries[i], output_directory);
+	}
+
+	return 0;
+}
+
 int main(int argc, char *argv[]) {
 	const char *board = NULL, *kernel_image = NULL, *rootfs_image = NULL, *output = NULL;
+	const char *extract_image = NULL, *output_directory = NULL;
 	bool add_jffs2_eof = false, sysupgrade = false;
 	unsigned rev = 0;
 	const struct device_info *info;
@@ -1413,7 +1643,7 @@ int main(int argc, char *argv[]) {
 	while (true) {
 		int c;
 
-		c = getopt(argc, argv, "B:k:r:o:V:jSh");
+		c = getopt(argc, argv, "B:k:r:o:V:jSh:x:d:");
 		if (c == -1)
 			break;
 
@@ -1450,27 +1680,43 @@ int main(int argc, char *argv[]) {
 			usage(argv[0]);
 			return 0;
 
+		case 'd':
+			output_directory = optarg;
+			break;
+
+		case 'x':
+			extract_image = optarg;
+			break;
+
 		default:
 			usage(argv[0]);
 			return 1;
 		}
 	}
 
-	if (!board)
-		error(1, 0, "no board has been specified");
-	if (!kernel_image)
-		error(1, 0, "no kernel image has been specified");
-	if (!rootfs_image)
-		error(1, 0, "no rootfs image has been specified");
-	if (!output)
-		error(1, 0, "no output filename has been specified");
+	if (extract_image || output_directory) {
+		if (!extract_image)
+			error(1, 0, "No factory/oem image given via -x <file>. Output directory is only valid with -x");
+		if (!output_directory)
+			error(1, 0, "Can not extract an image without output directory. Use -d <dir>");
+		extract_firmware(extract_image, output_directory);
+	} else {
+		if (!board)
+			error(1, 0, "no board has been specified");
+		if (!kernel_image)
+			error(1, 0, "no kernel image has been specified");
+		if (!rootfs_image)
+			error(1, 0, "no rootfs image has been specified");
+		if (!output)
+			error(1, 0, "no output filename has been specified");
 
-	info = find_board(board);
+		info = find_board(board);
 
-	if (info == NULL)
-		error(1, 0, "unsupported board %s", board);
+		if (info == NULL)
+			error(1, 0, "unsupported board %s", board);
 
-	build_image(output, kernel_image, rootfs_image, rev, add_jffs2_eof, sysupgrade, info);
+		build_image(output, kernel_image, rootfs_image, rev, add_jffs2_eof, sysupgrade, info);
+	}
 
 	return 0;
 }