better corruption check by calculating the number of fill bytes

[rsbs2] / extract.c

#include <sys/stat.h>
#include <sys/types.h>
#include <limits.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <strings.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <libgen.h>
#include "rsb-lz.h"
#include "extract.h"

struct file_entry* get_next_file(unsigned char *fw, int len)
{
	static unsigned char *pos;
	static unsigned char *start;
	static unsigned char *end;
	static struct file_entry fent;
	int name_length;

	if (fw != NULL && len != 0) {
		pos = fw + 0x28;

#if 0
		printf("Start of filesystem: 0x%08x\n", *((unsigned int*)pos));
#endif
		start = fw;
		pos = fw + *((unsigned int*)pos);
		end = fw + len;
	}

	fent.unknown = *pos;
	pos++;

	if (fent.unknown == 0x00) {
		/* EOF */
		int fill = (4 - ((pos - start) % 4)) % 4;
		int i;

		for (i = 0; i < fill; i++) {
			if (*pos != 0xff) {
				fprintf(stderr, "Wrong fill byte after EOF: 0x%02x, aborting!\n", *pos);
				exit(1);
			}
			pos++;
		}

		if (pos != end) {
			fprintf(stderr, "EOF marker not at end-of-file %p <-> %p, aborting!\n", pos, end);
			exit(1);
		}

		return NULL;
	}


	name_length = *((unsigned int*)pos);
	pos += 4;

	fent.length = *((unsigned int*)pos);
	pos += 4;

	if ((fent.length > (end - pos)) ||
	    (name_length > (end - pos))) {
		printf("EOF reached without hitting EOF marker, aborting "
			"(unknown: 0x%02x, namelen: 0x%08x, contentlen: 0x%08x!\n",
			fent.unknown, name_length, fent.length);
		exit(1);
	}

	fent.name = (char*)pos;
	pos += name_length;

	fent.start = pos;
	pos += fent.length;

	return &fent;
}

void extract_files(unsigned char *fw, int len)
{
	struct file_entry *fent;

	fent = get_next_file(fw, len);
	
	while (fent) {
		printf("%s: unknown: 0x%02x, length: %d",
			fent->name, fent->unknown, fent->length);

		if (fent->length > 0) {
			write_file(fent->name, fent->start, fent->length);
			if (*((unsigned int*)fent->start) == LZ_MAGIC) {
				char *lzname;

				if ((lzname = strdup(fent->name)) == NULL) {
					perror("strdup");
					exit(1);
				}

				if (!strcmp(lzname + strlen(lzname) - 4 , ".lz")) {
					fprintf(stderr, "Ugh, can't derive filename...\n");
					exit(1);
				}
				lzname[strlen(lzname) - 3] = 0x00;

				printf("%s: packed file found", lzname);

				extract_lz_file(fent->start, (unsigned char*)lzname);
				free(lzname);
			} else if (!strcmp(fent->name, "firmware")) {
				unsigned char *lzpos;
				char lzname[128];

				bzero(lzname, sizeof(lzname));
				strcpy(lzname, "firmware.");

				lzpos = fent->start + *((unsigned int*)(fent->start + 0x20));
				memcpy(lzname + strlen(lzname), lzpos - 4, 4);
				lzpos += 4;
				if (*((unsigned int*)(lzpos)) == LZ_MAGIC) {
					printf("%s: compressed firmware part found", lzname);
					extract_lz_file(lzpos, (unsigned char*)lzname);
				}
			}
		} else {
			printf(", ignoring...\n");
		}
		fent = get_next_file(NULL, 0);
	}
}

void mkdir_p(char *dir)
{
	char *copy, *parent;

	if ((dir == NULL) || (!strcmp(dir, ".")))
		return;

	if ((copy = strdup(dir)) == NULL) {
		perror("strdup");
		exit(1);
	}
	parent = dirname(copy);
	mkdir_p(parent);

	errno = 0;
	if (mkdir(dir, 0755) == -1) {
		if (errno != EEXIST) {
			fprintf(stderr, "%s: ", dir);
			perror("mkdir");
			exit(1);
		}
	}
	free(copy);
}

void write_file(char *fname, unsigned char *buf, int len)
{
	char filename[PATH_MAX];
	char *filename_c, *dirn;
	int fd;
	int remaining;
	int ret;

	strcpy(filename, "extracted/");
	strcat(filename, fname);

	if ((filename_c = strdup(filename)) == NULL) {
		perror("strdup");
		exit(1);
	}
	dirn = dirname(filename_c);
	mkdir_p(dirn);
	free(filename_c);

	if ((fd = open(filename, O_WRONLY|O_CREAT, 0644)) == -1) {
		fprintf(stderr, "%s: ", filename);
		perror("open");
		exit(1);
	}

	remaining = len;

	while(remaining) {
		ret = write(fd, buf + (len - remaining), remaining);
		if (ret < 0) {
			perror("write");
			exit(1);
		}
		remaining -= ret;
	}

	printf(", %s written.\n", filename);

	close(fd);
}