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ramips: Add a tool to create JCG factory images

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This tool creates factory images for JCG routers.
Details can be found in the header comment of jcgimage.c.

Signed-off-by: Reinhard Max <reinhard@m4x.de>
Reviewed-by: Torsten Duwe <duwe@lst.de>

SVN-Revision: 48888
This commit is contained in:
John Crispin 2016-03-03 20:24:30 +00:00
parent 15517811e4
commit 678dcef7a5
2 changed files with 393 additions and 0 deletions
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1
tools/firmware-utils/Makefile
View file

@ -75,6 +75,7 @@ define Host/Compile
$(call cc,dgn3500sum)
$(call cc,edimax_fw_header, -Wall)
$(call cc,mkmerakifw sha1, -Wall)
$(call cc,jcgimage, -lz -Wall)
endef
define Host/Install

392
tools/firmware-utils/src/jcgimage.c Normal file
View file

@ -0,0 +1,392 @@
/*
* jcgimage - Create a JCG firmware image
*
* Copyright (C) 2015 Reinhard Max <reinhard@m4x.de>
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*
*/
/*
* JCG firmware update images consist of a 512 byte header and a
* modified uImage (details below) as the payload.
*
* The payload is obfuscated by XORing it with a key that is generated
* from parts of the header. Fortunately only non-essential parts of
* the header are used for this and zeroing them results in a zero
* key, effectively disabling the obfuscation and allowing us to use
* clear text payloads.
*
* The mandatory parts of the header are:
*
* - A magic string of "YSZJ" at offset 0.
* - A value of 1 at offset 39 (header format version?)
* - A CRC32 checksum of the payload at offset 504.
* - A CRC32 checksum of the header at offset 508.
*
* An image constructed by these rules will be accepted by JCG's
* U-Boot in resuce mode via TFTP and the payload will be written to
* the flash starting at offset 0x00050000.
*
* JCG's U-Boot does check the content or size of the payload
* image. If it is too large, it wraps around and overwrites U-Boot,
* requiring JTAG to revive the board. To prevent such bricking from
* happening, this tool refuses to build such overlong images.
*
* Two more conditions have to be met for a JCG image to be accepted
* as a valid update by the web interface of the stock firware:
*
* - The bytes at offsets 109 and 111 in the header must be a binary
* representation of the first two components of the firmware
* version as displayed in the update web form, or it will be
* rejected as "incorrect product".
*
* - The payload must start with a valid uImage header whose data
* CRC checksum matches the whole rest of the update file rather
* than just the number of bytes specified in the size field of the
* header.
*
* This last condition is met by JCG's original firmware images,
* because they have both, kernel and rootfs inside the uImage and
* abuse the last four bytes of the name field to record the offset of
* the file system from the start of the uImage header. This tool
* produces such images when called with -k and -r, which are meant to
* repack the original firmware after modifying the file systen,
* e.g. to add debugging tools and enable shell access.
*
* In contrast, OpenWrt sysupgrade images consist of a uImage that
* only contains the kernel and has the rootfs appended to it. Hence,
* the CRC over kernel and file system does not match the one in the
* uImage header. Fixing this by adjusting the uImage header is not
* possible, because it makes the uImage unusable for booting. Instead
* we append four "patch" bytes to the end of the file system, that
* are calculated to force the checksum of kernel+fs to be the same as
* for the kernel alone.
*
*/
#include <zlib.h>
#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <libgen.h>
#include <stdlib.h>
#include <errno.h>
#include <err.h>
#include <time.h>
#include <sys/mman.h>
#include <arpa/inet.h>
#include <assert.h>
/*
* JCG Firmware image header
*/
#define JH_MAGIC 0x59535a4a /* "YSZJ" */
struct jcg_header {
uint32_t jh_magic;
uint8_t jh_version[32]; /* Firmware version string. Fill with
zeros to avoid encryption */
uint32_t jh_type; /* must be 1 */
uint8_t jh_info[64]; /* Firmware info string. Fill with
zeros to avoid encryption */
uint32_t jh_time; /* Image creation time in seconds since
* the Epoch. Does not seem to be used
* by the stock firmware. */
uint16_t jh_major; /* Major fimware version */
uint16_t jh_minor; /* Minor fimrmware version */
uint8_t jh_unknown[392]; /* Apparently unused and all zeros */
uint32_t jh_dcrc; /* CRC checksum of the payload */
uint32_t jh_hcrc; /* CRC checksum of the header */
};
/*
* JCG uses a modified uImage header that replaces the last four bytes
* of the image name with the length of the kernel in the image.
*/
#define IH_MAGIC 0x27051956 /* Image Magic Number */
#define IH_NMLEN 28 /* Image Name Length */
struct uimage_header {
uint32_t ih_magic; /* Image Header Magic Number */
uint32_t ih_hcrc; /* Image Header CRC Checksum */
uint32_t ih_time; /* Image Creation Timestamp */
uint32_t ih_size; /* Image Data Size */
uint32_t ih_load; /* Data Load Address */
uint32_t ih_ep; /* Entry Point Address */
uint32_t ih_dcrc; /* Image Data CRC Checksum */
uint8_t ih_os; /* Operating System */
uint8_t ih_arch; /* CPU architecture */
uint8_t ih_type; /* Image Type */
uint8_t ih_comp; /* Compression Type */
uint8_t ih_name[IH_NMLEN];/* Image Name */
uint32_t ih_fsoff; /* Offset of the file system partition */
};
/*
* Open the named file and return its size and file descriptor.
* Exit in case of errors.
*/
int
opensize(char *name, size_t *size)
{
struct stat s;
int fd = open(name, O_RDONLY);
if (fd < 0) {
err(1, "cannot open \"%s\"", name);
}
if (fstat(fd, &s) == -1) {
err(1, "cannot stat \"%s\"", name);
}
*size = s.st_size;
return fd;
}
/*
* Write the JCG header
*/
void
mkjcgheader(struct jcg_header *h, size_t psize, char *version)
{
uLong crc;
uint16_t major = 0, minor = 0;
void *payload = (void *)h + sizeof(*h);
if (version != NULL) {
if (sscanf(version, "%hu.%hu", &major, &minor) != 2) {
err(1, "cannot parse version \"%s\"", version);
}
}
memset(h, 0, sizeof(*h));
h->jh_magic = htonl(JH_MAGIC);
h->jh_type = htonl(1);
h->jh_time = htonl(time(NULL));
h->jh_major = htons(major);
h->jh_minor = htons(minor);
/* CRC over JCG payload (uImage) */
crc = crc32(0L, Z_NULL, 0);
crc = crc32(crc, payload, psize);
h->jh_dcrc = htonl(crc);
/* CRC over JCG header */
crc = crc32(0L, Z_NULL, 0);
crc = crc32(crc, (void *)h, sizeof(*h));
h->jh_hcrc = htonl(crc);
}
/*
* Write the uImage header
*/
void
mkuheader(struct uimage_header *h, size_t ksize, size_t fsize)
{
uLong crc;
void *payload = (void *)h + sizeof(*h);
// printf("mkuheader: %p, %zd, %zd\n", h, ksize, fsize);
memset(h, 0, sizeof(*h));
h->ih_magic = htonl(IH_MAGIC);
h->ih_time = htonl(time(NULL));
h->ih_size = htonl(ksize + fsize);
h->ih_load = htonl(0x80000000);
h->ih_ep = htonl(0x80292000);
h->ih_os = 0x05;
h->ih_arch = 0x05;
h->ih_type = 0x02;
h->ih_comp = 0x03;
h->ih_fsoff = htonl(sizeof(*h) + ksize);
strcpy((char *)h->ih_name, "Linux Kernel Image");
/* CRC over uImage payload (kernel and file system) */
crc = crc32(0L, Z_NULL, 0);
crc = crc32(crc, payload, ntohl(h->ih_size));
h->ih_dcrc = htonl(crc);
printf("CRC1: %08lx\n", crc);
/* CRC over uImage header */
crc = crc32(0L, Z_NULL, 0);
crc = crc32(crc, (void *)h, sizeof(*h));
h->ih_hcrc = htonl(crc);
printf("CRC2: %08lx\n", crc);
}
/*
* Calculate a "patch" value and write it into the last four bytes of
* buf, so that the CRC32 checksum of the whole buffer is dcrc.
*
* Based on: SAR-PR-2006-05: Reversing CRC – Theory and Practice.
* Martin Stigge, Henryk Plötz, Wolf Müller, Jens-Peter Redlich.
* http://sar.informatik.hu-berlin.de/research/publications/#SAR-PR-2006-05
*/
void
craftcrc(uint32_t dcrc, uint8_t *buf, size_t len)
{
int i;
uint32_t a;
uint32_t patch = 0;
uint32_t crc = crc32(0L, Z_NULL, 0);
a = ~dcrc;
for (i = 0; i < 32; i++) {
if (patch & 1) {
patch = (patch >> 1) ^ 0xedb88320L;
} else {
patch >>= 1;
}
if (a & 1) {
patch ^= 0x5b358fd3L;
}
a >>= 1;
}
patch ^= ~crc32(crc, buf, len - 4);
for (i = 0; i < 4; i++) {
buf[len - 4 + i] = patch & 0xff;
patch >>= 8;
}
/* Verify that we actually get the desired result */
crc = crc32(0L, Z_NULL, 0);
crc = crc32(crc, buf, len);
if (crc != dcrc) {
errx(1, "CRC patching is broken: wanted %08x, but got %08x.", dcrc, crc);
}
}
void
usage() {
fprintf(stderr, "Usage:\n"
" jcgimage -o outputfile -u uImage [-v version]\n"
" jcgimage -o outputfile -k kernel -f rootfs [-v version]\n");
exit(1);
}
#define MODE_UNKNOWN 0
#define MODE_UIMAGE 1
#define MODE_KR 2
/* The output image must not be larger than 4MiB - 5*64kiB */
#define MAXSIZE (size_t)(4 * 1024 * 1024 - 5 * 64 * 1024)
int
main(int argc, char **argv)
{
struct jcg_header *jh;
struct uimage_header *uh;
int c;
char *imagefile = NULL;
char *file1 = NULL;
char *file2 = NULL;
char *version = NULL;
int mode = MODE_UNKNOWN;
int fdo, fd1, fd2;
size_t size1, size2, sizeu, sizeo, off1, off2;
void *map;
/* Make sure the headers have the right size */
assert(sizeof(struct jcg_header) == 512);
assert(sizeof(struct uimage_header) == 64);
while ((c = getopt(argc, argv, "o:k:f:u:v:h")) != -1) {
switch (c) {
case 'o':
imagefile = optarg;
break;
case 'k':
if (mode == MODE_UIMAGE)
errx(1,"-k cannot be combined with -u");
mode = MODE_KR;
file1 = optarg;
break;
case 'f':
if (mode == MODE_UIMAGE)
errx(1,"-f cannot be combined with -u");
mode = MODE_KR;
file2 = optarg;
break;
case 'u':
if (mode == MODE_KR)
errx(1,"-u cannot be combined with -k and -r");
mode = MODE_UIMAGE;
file1 = optarg;
break;
case 'v':
version = optarg;
break;
case 'h':
default:
usage();
}
}
if (optind != argc) {
errx(1, "illegal arg \"%s\"", argv[optind]);
}
if (imagefile == NULL) {
errx(1, "no output file specified");
}
if (mode == MODE_UNKNOWN)
errx(1, "specify either -u or -k and -r");
if (mode == MODE_KR) {
if (file1 == NULL || file2 == NULL)
errx(1,"need -k and -r");
fd2 = opensize(file2, &size2);
}
fd1 = opensize(file1, &size1);
if (mode == MODE_UIMAGE) {
off1 = sizeof(*jh);
sizeu = size1 + 4;
sizeo = sizeof(*jh) + sizeu;
} else {
off1 = sizeof(*jh) + sizeof(*uh);
off2 = sizeof(*jh) + sizeof(*uh) + size1;
sizeu = sizeof(*uh) + size1 + size2;
sizeo = sizeof(*jh) + sizeu;
}
if (sizeo > MAXSIZE)
errx(1,"payload too large: %zd > %zd\n", sizeo, MAXSIZE);
fdo = open(imagefile, O_RDWR | O_CREAT | O_TRUNC, 00644);
if (fdo < 0)
err(1, "cannot open \"%s\"", imagefile);
if (ftruncate(fdo, sizeo) == -1) {
err(1, "cannot grow \"%s\" to %zd bytes", imagefile, sizeo);
}
map = mmap(NULL, sizeo, PROT_READ|PROT_WRITE, MAP_SHARED, fdo, 0);
uh = map + sizeof(*jh);
if (map == MAP_FAILED) {
err(1, "cannot mmap \"%s\"", imagefile);
}
if (read(fd1, map + off1, size1) != size1)
err(1, "cannot copy %s", file1);
if (mode == MODE_KR) {
if (read(fd2, map+off2, size2) != size2)
err(1, "cannot copy %s", file2);
mkuheader(uh, size1, size2);
} else if (mode == MODE_UIMAGE) {
craftcrc(ntohl(uh->ih_dcrc), (void*)uh + sizeof(*uh),
sizeu - sizeof(*uh));
}
mkjcgheader(map, sizeu, version);
munmap(map, sizeo);
close(fdo);
return 0;
}