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lantiq: fritz_cal_extract with reverse option for AVM FritzBox 7430
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This implementation of fritz_cal_extract can also retrieve firmware
data stored in reverse byte order, as found in the AVM 7430 device.

This is done by intermediate storage in a buffer presumably large enough
to hold the complete data set. Currently, this buffer size is 128kB + 1kB
(some extra space for skipped data).

In the usual case of "forward" data, this implementation should behave
like the original implementation in all common cases. limit [-l] will
determine the amount of data read and size of buffer allocated.

However, if you are reading reversed data or didn't set a limit, the buffer
may be too small to hold all data. In this case, you can choose a higher
limit [-l] to enforce a sufficient buffer size.

Signed-off-by: Dustin Gathmann <[email protected]>
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@dzzinstant
dzzinstant committed Sep 9, 2024
1 parent 5eb8b77 commit 05b3eef
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324 changes: 198 additions & 126 deletions package/utils/fritz-tools/src/fritz_cal_extract.c
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Original file line number Diff line number Diff line change
Expand Up @@ -8,6 +8,9 @@
* that is Not copyrighted -- provided to the public domain
* Version 1.4 11 December 2005 Mark Adler
*
* Modifications to also handle calibration data in reversed byte order
* (c) 2024 by <[email protected]>.
*
* 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
Expand All @@ -28,106 +31,126 @@
#include <assert.h>
#include <unistd.h>
#include <stdint.h>
#include <stdbool.h>
#include <stdlib.h>
#include <endian.h>
#include <errno.h>
#include "zlib.h"

#define CHUNK 1024
#define DEFAULT_BUFFERSIZE (129 * 1024)

#define MIN(a,b) (((a)<(b))?(a):(b))

static inline size_t special_min(size_t a, size_t b)
/* Reverse byte order in data buffer.
* 'top' is position of last valid data byte = (datasize - 1)
*/
static void buffer_reverse(unsigned char *data, unsigned int top)
{
return a == 0 ? b : (a < b ? a : b);
register unsigned char swapbyte;
const unsigned int center = top / 2;

for (unsigned int bottom = 0; bottom < center; ++bottom, --top) {
swapbyte = data[bottom];
data[bottom] = data[top];
data[top] = swapbyte;
}
}

/* Decompress from file source to file dest until stream ends or EOF.
inf() returns Z_OK on success, Z_MEM_ERROR if memory could not be
allocated for processing, Z_DATA_ERROR if the deflate data is
invalid or incomplete, Z_VERSION_ERROR if the version of zlib.h and
the version of the library linked do not match, or Z_ERRNO if there
is an error reading or writing the files. */
static int inf(FILE *source, FILE *dest, size_t limit, size_t skip)
/* Decompress from file source to data buffer until stream ends
* or *limit bytes have been written to buffer.
*
* On call, 'limit' must reference a variable containing the intended
* number of bytes to retrieve (must be <= allocated buffer size).
*
* Return values (success):
* Z_END_STREAM if complete data was retrieved (*limit == size of complete data),
* or Z_OK if data was retrieved up to limit (*limit == original value).
*
* Return values (failure):
* Z_MEM_ERROR if memory could not be allocated for processing,
* Z_DATA_ERROR if the deflate data is invalid or incomplete,
* Z_VERSION_ERROR if the version of zlib.h and the version of the
* library linked do not match, or
* Z_ERRNO if there is an error reading or writing the files.
*/
static int inflate_to_buffer(FILE *source, unsigned char *buf, size_t *limit)
{
int ret;
size_t have;
z_stream strm;
unsigned char in[CHUNK];
unsigned char out[CHUNK];

/* allocate inflate state */
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 ret;

/* decompress until deflate stream ends or end of file */
do {
strm.avail_in = fread(in, 1, CHUNK, source);
if (ferror(source)) {
(void)inflateEnd(&strm);
return Z_ERRNO;
}
if (strm.avail_in == 0)
break;
strm.next_in = in;

/* run inflate() on input until output buffer not full */
do {
strm.avail_out = CHUNK;
strm.next_out = out;
ret = inflate(&strm, Z_NO_FLUSH);
assert(ret != Z_STREAM_ERROR); /* state not clobbered */
switch (ret) {
case Z_NEED_DICT:
ret = Z_DATA_ERROR; /* and fall through */
case Z_DATA_ERROR:
case Z_MEM_ERROR:
(void)inflateEnd(&strm);
return ret;
}
have = special_min(limit, CHUNK - strm.avail_out) - skip;
if (fwrite(&out[skip], have, 1, dest) != 1 || ferror(dest)) {
(void)inflateEnd(&strm);
return Z_ERRNO;
}
skip = 0;
limit -= have;
} while (strm.avail_out == 0 && limit > 0);

/* done when inflate() says it's done */
} while (ret != Z_STREAM_END && limit > 0);

/* clean up and return */
(void)inflateEnd(&strm);
return (limit == 0 ? Z_OK : (ret == Z_STREAM_END ? Z_OK : Z_DATA_ERROR));
int ret;
z_stream strm;
unsigned char in[CHUNK];

/* allocate inflate state */
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 ret;

/* set data buffer as stream output */
strm.avail_out = *limit;
strm.next_out = buf;

/* decompress until deflate stream ends or end of file */
do {
strm.avail_in = fread(in, 1, CHUNK, source);
if (ferror(source)) {
(void)inflateEnd(&strm);
return Z_ERRNO;
}
if (strm.avail_in == 0)
break;
strm.next_in = in;

/* run inflate(), fill data buffer with all available output */
ret = inflate(&strm, Z_FINISH);
assert(ret != Z_STREAM_ERROR); /* state not clobbered */

switch (ret) {
case Z_NEED_DICT:
ret = Z_DATA_ERROR; /* and fall through */
case Z_DATA_ERROR:
case Z_MEM_ERROR:
(void)inflateEnd(&strm);
return ret;
}
/* done when inflate() says it's done or limit reached */
} while (ret != Z_STREAM_END && strm.avail_out > 0);

/* set limit to end of retrieved data */
assert(strm.total_out <= *limit);
*limit = strm.total_out;

/* clean up and return */
(void)inflateEnd(&strm);
return (ret == Z_STREAM_END ? Z_STREAM_END : (strm.avail_out == 0 ? Z_OK : Z_DATA_ERROR));
}

/* report a zlib or i/o error */
static void zerr(int ret)
{
switch (ret) {
case Z_ERRNO:
if (ferror(stdin))
fputs("error reading stdin\n", stderr);
if (ferror(stdout))
fputs("error writing stdout\n", stderr);
break;
case Z_STREAM_ERROR:
fputs("invalid compression level\n", stderr);
break;
case Z_DATA_ERROR:
fputs("invalid or incomplete deflate data\n", stderr);
break;
case Z_MEM_ERROR:
fputs("out of memory\n", stderr);
break;
case Z_VERSION_ERROR:
fputs("zlib version mismatch!\n", stderr);
}
switch (ret) {
case Z_ERRNO:
if (ferror(stdin))
fputs("error reading stdin\n", stderr);
if (ferror(stdout))
fputs("error writing stdout\n", stderr);
break;
case Z_STREAM_ERROR:
fputs("invalid compression level\n", stderr);
break;
case Z_DATA_ERROR:
fputs("invalid or incomplete deflate data\n", stderr);
break;
case Z_MEM_ERROR:
fputs("out of memory\n", stderr);
break;
case Z_VERSION_ERROR:
fputs("zlib version mismatch!\n", stderr);
}
}

static unsigned int get_num(char *str)
Expand All @@ -140,7 +163,8 @@ static unsigned int get_num(char *str)

static void usage(void)
{
fprintf(stderr, "Usage: fritz_cal_extract [-s seek offset] [-i skip] [-o output file] [-l limit] [infile] -e entry_id\n"
fprintf(stderr, "Usage: fritz_cal_extract -e entry_id [-s seek offset] [-l limit]\n"
"\t[-r reverse extracted data] [-i skip n bytes] [-o output file] [infile]\n"
"Finds and extracts zlib compressed calibration data in the EVA loader\n");
exit(EXIT_FAILURE);
}
Expand All @@ -154,53 +178,59 @@ struct cal_entry {
int main(int argc, char **argv)
{
struct cal_entry cal = { .len = 0 };
unsigned char *buf = NULL;
FILE *in = stdin;
FILE *out = stdout;
size_t datasize = DEFAULT_BUFFERSIZE;
size_t limit = 0, skip = 0;
int initial_offset = 0;
int entry = -1;
bool reversed = false, limit_was_set = true;
int ret;
int opt;

while ((opt = getopt(argc, argv, "s:e:o:l:i:")) != -1) {
while ((opt = getopt(argc, argv, "s:e:o:l:i:r")) != -1) {
switch (opt) {
case 's':
initial_offset = (int)get_num(optarg);
if (errno) {
perror("Failed to parse seek offset");
goto out_bad;
}
break;
case 'e':
entry = (int) htobe16(get_num(optarg));
if (errno) {
perror("Failed to entry id");
goto out_bad;
}
break;
case 'o':
out = fopen(optarg, "w");
if (!out) {
perror("Failed to create output file");
goto out_bad;
}
break;
case 'l':
limit = (size_t)get_num(optarg);
if (errno) {
perror("Failed to parse limit");
goto out_bad;
}
break;
case 'i':
skip = (size_t)get_num(optarg);
if (errno) {
perror("Failed to parse skip");
goto out_bad;
}
break;
default: /* '?' */
usage();
case 's':
initial_offset = (int)get_num(optarg);
if (errno) {
perror("Failed to parse seek offset");
goto out_bad;
}
break;
case 'e':
entry = (int) htobe16(get_num(optarg));
if (errno) {
perror("Failed to entry id");
goto out_bad;
}
break;
case 'o':
out = fopen(optarg, "w");
if (!out) {
perror("Failed to create output file");
goto out_bad;
}
break;
case 'l':
limit = (size_t)get_num(optarg);
if (errno) {
perror("Failed to parse limit");
goto out_bad;
}
break;
case 'i':
skip = (size_t)get_num(optarg);
if (errno) {
perror("Failed to parse skip");
goto out_bad;
}
break;
case 'r':
reversed = true;
break;
default: /* '?' */
usage();
}
}

Expand Down Expand Up @@ -243,9 +273,50 @@ int main(int argc, char **argv)
goto out_bad;
}

ret = inf(in, out, limit, skip);
if (ret == Z_OK)
goto out;
/* Set boundaries. Only keep default datasize if we need complete data
* for reversal and didn't set a higher limit. */
if (!limit) {
limit_was_set = false;
limit = datasize - skip;
}
datasize = (reversed && datasize >= limit + skip) ? datasize : (limit + skip);

/* Create data buffer. */
buf = malloc(datasize);
assert(buf != NULL);

ret = inflate_to_buffer(in, buf, &datasize);

if ((reversed || !limit_was_set) && ret != Z_STREAM_END) { /* didn't read to stream end */
fprintf(stderr, "Failed: Data exceeds buffer size of %u. Refusing to reverse"
" or store incomplete data."
" Use a higher limit [-l] to increase buffer size.\n",
(unsigned int) datasize);
goto out_bad;
}

ret = (ret == Z_STREAM_END) ? Z_OK : ret; /* normalize return value */
if (ret != Z_OK) {
zerr(ret);
goto out_bad;
}

if (reversed)
buffer_reverse(buf, datasize - 1);

if (datasize <= skip) {
fprintf(stderr, "Failed to skip %u bytes, total data size is %u!\n",
(unsigned int)skip, (unsigned int)datasize);
goto out_bad;
}

limit = MIN(limit, datasize - skip);
if (fwrite(&buf[skip], limit, 1, out) != 1 || ferror(out)) {
fprintf(stderr, "Failed to write data buffer to output file");
goto out_bad;
}

goto out;

zerr(ret);

Expand All @@ -257,5 +328,6 @@ int main(int argc, char **argv)
fclose(in);
if (out)
fclose(out);
free(buf);
return ret;
}
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