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snappy-fox/snappy-fox.c

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/**
* Snappy-fox -- Firefox Morgue Cache de-compressor
* Copyright (C) 2021 Davide Berardi <berardi.dav@gmail.com>
*
* 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 3 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, see <https://www.gnu.org/licenses/>.
*/
#define _POSIX_C_SOURCE 1
#include <errno.h>
#include <stdint.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <getopt.h>
#define MAX_COMPRESSED_DATA_SIZE 16777211
#define MAX_UNCOMPRESSED_DATA_SIZE 65536
#ifdef DEBUG
#define prdebug(f...) fprintf(stderr, "[ DEBUG ]"), fprintf(stderr, f)
#define prinfo(f...) fprintf(stderr, "[ INFO ]"), fprintf(stderr, f)
#else
#define prdebug(f...)
#define prinfo(f...)
#endif
#define prbanner(f...) fprintf(stderr, f)
#define prerror(f...) fprintf(stderr, "[ ERROR ]"), fprintf(stderr, f)
#ifndef VERSION
#define VERSION "unknown"
#endif
/* Flags */
/* Unframed file stream, by default assume framed file */
static uint32_t unframed_stream = 0;
/* Ignore offset errors, by default consider them as fatal errors*/
static uint32_t ignore_offset_errors = 0;
/* Byte to substitute offset corrupted values with */
static uint8_t offset_dummy_byte = 0xff;
/* Read offset */
static uint32_t read_offset = 0;
/* Consider CRC Errors */
static uint32_t consider_crc_errors = 0;
/* CRC related functions */
static const uint32_t crc32c_table[] = {
0x00000000, 0xf26b8303, 0xe13b70f7, 0x1350f3f4, 0xc79a971f,
0x35f1141c, 0x26a1e7e8, 0xd4ca64eb, 0x8ad958cf, 0x78b2dbcc,
0x6be22838, 0x9989ab3b, 0x4d43cfd0, 0xbf284cd3, 0xac78bf27,
0x5e133c24, 0x105ec76f, 0xe235446c, 0xf165b798, 0x030e349b,
0xd7c45070, 0x25afd373, 0x36ff2087, 0xc494a384, 0x9a879fa0,
0x68ec1ca3, 0x7bbcef57, 0x89d76c54, 0x5d1d08bf, 0xaf768bbc,
0xbc267848, 0x4e4dfb4b, 0x20bd8ede, 0xd2d60ddd, 0xc186fe29,
0x33ed7d2a, 0xe72719c1, 0x154c9ac2, 0x061c6936, 0xf477ea35,
0xaa64d611, 0x580f5512, 0x4b5fa6e6, 0xb93425e5, 0x6dfe410e,
0x9f95c20d, 0x8cc531f9, 0x7eaeb2fa, 0x30e349b1, 0xc288cab2,
0xd1d83946, 0x23b3ba45, 0xf779deae, 0x05125dad, 0x1642ae59,
0xe4292d5a, 0xba3a117e, 0x4851927d, 0x5b016189, 0xa96ae28a,
0x7da08661, 0x8fcb0562, 0x9c9bf696, 0x6ef07595, 0x417b1dbc,
0xb3109ebf, 0xa0406d4b, 0x522bee48, 0x86e18aa3, 0x748a09a0,
0x67dafa54, 0x95b17957, 0xcba24573, 0x39c9c670, 0x2a993584,
0xd8f2b687, 0x0c38d26c, 0xfe53516f, 0xed03a29b, 0x1f682198,
0x5125dad3, 0xa34e59d0, 0xb01eaa24, 0x42752927, 0x96bf4dcc,
0x64d4cecf, 0x77843d3b, 0x85efbe38, 0xdbfc821c, 0x2997011f,
0x3ac7f2eb, 0xc8ac71e8, 0x1c661503, 0xee0d9600, 0xfd5d65f4,
0x0f36e6f7, 0x61c69362, 0x93ad1061, 0x80fde395, 0x72966096,
0xa65c047d, 0x5437877e, 0x4767748a, 0xb50cf789, 0xeb1fcbad,
0x197448ae, 0x0a24bb5a, 0xf84f3859, 0x2c855cb2, 0xdeeedfb1,
0xcdbe2c45, 0x3fd5af46, 0x7198540d, 0x83f3d70e, 0x90a324fa,
0x62c8a7f9, 0xb602c312, 0x44694011, 0x5739b3e5, 0xa55230e6,
0xfb410cc2, 0x092a8fc1, 0x1a7a7c35, 0xe811ff36, 0x3cdb9bdd,
0xceb018de, 0xdde0eb2a, 0x2f8b6829, 0x82f63b78, 0x709db87b,
0x63cd4b8f, 0x91a6c88c, 0x456cac67, 0xb7072f64, 0xa457dc90,
0x563c5f93, 0x082f63b7, 0xfa44e0b4, 0xe9141340, 0x1b7f9043,
0xcfb5f4a8, 0x3dde77ab, 0x2e8e845f, 0xdce5075c, 0x92a8fc17,
0x60c37f14, 0x73938ce0, 0x81f80fe3, 0x55326b08, 0xa759e80b,
0xb4091bff, 0x466298fc, 0x1871a4d8, 0xea1a27db, 0xf94ad42f,
0x0b21572c, 0xdfeb33c7, 0x2d80b0c4, 0x3ed04330, 0xccbbc033,
0xa24bb5a6, 0x502036a5, 0x4370c551, 0xb11b4652, 0x65d122b9,
0x97baa1ba, 0x84ea524e, 0x7681d14d, 0x2892ed69, 0xdaf96e6a,
0xc9a99d9e, 0x3bc21e9d, 0xef087a76, 0x1d63f975, 0x0e330a81,
0xfc588982, 0xb21572c9, 0x407ef1ca, 0x532e023e, 0xa145813d,
0x758fe5d6, 0x87e466d5, 0x94b49521, 0x66df1622, 0x38cc2a06,
0xcaa7a905, 0xd9f75af1, 0x2b9cd9f2, 0xff56bd19, 0x0d3d3e1a,
0x1e6dcdee, 0xec064eed, 0xc38d26c4, 0x31e6a5c7, 0x22b65633,
0xd0ddd530, 0x0417b1db, 0xf67c32d8, 0xe52cc12c, 0x1747422f,
0x49547e0b, 0xbb3ffd08, 0xa86f0efc, 0x5a048dff, 0x8ecee914,
0x7ca56a17, 0x6ff599e3, 0x9d9e1ae0, 0xd3d3e1ab, 0x21b862a8,
0x32e8915c, 0xc083125f, 0x144976b4, 0xe622f5b7, 0xf5720643,
0x07198540, 0x590ab964, 0xab613a67, 0xb831c993, 0x4a5a4a90,
0x9e902e7b, 0x6cfbad78, 0x7fab5e8c, 0x8dc0dd8f, 0xe330a81a,
0x115b2b19, 0x020bd8ed, 0xf0605bee, 0x24aa3f05, 0xd6c1bc06,
0xc5914ff2, 0x37faccf1, 0x69e9f0d5, 0x9b8273d6, 0x88d28022,
0x7ab90321, 0xae7367ca, 0x5c18e4c9, 0x4f48173d, 0xbd23943e,
0xf36e6f75, 0x0105ec76, 0x12551f82, 0xe03e9c81, 0x34f4f86a,
0xc69f7b69, 0xd5cf889d, 0x27a40b9e, 0x79b737ba, 0x8bdcb4b9,
0x988c474d, 0x6ae7c44e, 0xbe2da0a5, 0x4c4623a6, 0x5f16d052,
0xad7d5351
};
static uint32_t crc32c_lookup(uint8_t index) {
return crc32c_table[index & 0xff];
}
static void crc32c(uint32_t *crc, const uint8_t *data, size_t len)
{
int i = 0;
for (i = 0 ; i < len; ++i) {
uint32_t tabval = crc32c_lookup(*crc ^ data[i]);
*crc = tabval ^ (*crc >> 8);
}
}
static void crc32c_init(uint32_t *crc) {
/* Initial value is 0 */
*crc = 0xffffffff;
}
static void crc32c_fini(uint32_t *crc) {
/* Final step is to reverse the CRC Value */
*crc ^= 0xffffffff;
/* Mask the CRC */
*crc = ((*crc >> 15) | (*crc << 17)) + 0xa282ead8;
}
/* Logarithm base two of the number */
static uint32_t log2_32(uint32_t n) {
int32_t i = 0;
for (i = 31; i >= 0; --i) {
if (n & (1ul << i))
return i + 1;
}
return 0;
}
static int check_overflow_shift(uint8_t c, uint32_t shift, uint32_t length) {
/* Trivial check */
if (c == 0 || shift == 0)
return 0;
/* The right value will overflow the number */
if (7*shift + log2_32(c) > 31)
return 1;
return 0;
}
static uint32_t get_length(uint8_t *data, uint32_t length, uint32_t *bytes) {
uint32_t l = 0;
uint32_t shift = 0;
uint8_t c = 0;
uint8_t cbit = 1;
while (cbit != 0) {
c = *data;
/* Return error */
if (check_overflow_shift(c, shift, length))
return MAX_UNCOMPRESSED_DATA_SIZE + 1;
cbit = c & 0x80;
c = c & ~0x80;
l |= c << (7*shift);
data++;
shift++;
(*bytes)++;
}
return l;
}
static int32_t parse_literal(uint8_t *cdata, uint32_t cidx, uint32_t clength,
uint8_t *data, uint32_t *idx, uint32_t length) {
int32_t lenval = 0;
uint32_t bytes_to_read = 0;
uint32_t offsetval = 0;
uint32_t lenval_u = 0;
uint32_t clen = (uint32_t)(cdata[cidx] & 0xfc) >> 2;
if (clen < 60) {
bytes_to_read = 0;
} else {
bytes_to_read = clen - 59;
clen = 0;
memcpy(&clen, &cdata[cidx + 1], bytes_to_read);
}
clen += 1;
offsetval = cidx + bytes_to_read + 1;
if (offsetval > clength)
return -1;
/* Check integer overflow */
lenval_u = clen + bytes_to_read +1;
if (lenval_u > (uint32_t)(UINT32_MAX / 2))
return -1;
lenval = (int32_t)lenval_u;
if (*idx > length || clen > length)
return -1;
if (*idx + clen > length)
return -1;
prdebug("Copying literal %d bytes at (u:%d c:%d (%u))\n",
clen, *idx, offsetval, offsetval);
memcpy(&data[*idx], &cdata[offsetval], clen);
*idx += clen;
return lenval;
}
static int offsetread(uint8_t *data, uint32_t *idx, uint32_t length,
uint32_t clen, uint32_t coff) {
int ret = 0;
uint32_t i;
prdebug("Copying %d bytes offset %d (pos: %d)\n",
clen, coff, *idx);
/* Ignore invalid offset */
if (*idx < coff || coff == 0)
ret = -1;
if (*idx + clen > length)
ret = -1;
/* Check if we can ignore errors */
if (ret != 0 && !ignore_offset_errors) {
prerror("Offset error\n");
} else if (ret != 0 && ignore_offset_errors) {
prinfo("Ignoring offset errors\n");
for (i = 0; i < clen; ++i)
data[*idx+i] = offset_dummy_byte;
*idx = *idx + clen;
ret = 0;
} else if (coff >= clen) {
memcpy(&data[*idx], &data[*idx - coff], clen);
*idx += clen;
} else {
for (i = 0; i < clen / coff ; ++i) {
memcpy(&data[*idx], &data[*idx - coff], coff);
*idx += coff;
}
memcpy(&data[*idx], &data[*idx - coff], clen % coff);
*idx += clen % coff;
}
return ret;
}
static int32_t parse_copy1(uint8_t *cdata, uint32_t cidx, uint32_t clength,
uint8_t *data, uint32_t *idx, uint32_t length) {
int ret = 0;
uint32_t clen = (uint32_t)((cdata[cidx] & 0x1c) >> 2) + 4;
uint32_t coff = (uint32_t)((cdata[cidx] & 0xe0)) << 3;
coff |= cdata[cidx+1];
if ((ret = offsetread(data, idx, length, clen, coff)) != 0)
return ret;
return 2;
}
static int32_t parse_copy2(uint8_t *cdata, uint32_t cidx, uint32_t clength,
uint8_t *data, uint32_t *idx, uint32_t length) {
int ret = 0;
uint32_t clen = (uint32_t)((cdata[cidx] & 0xfc) >> 2) + 1;
uint32_t coff = 0;
memcpy(&coff, &cdata[cidx+1], 2);
if ((ret = offsetread(data, idx, length, clen, coff)) != 0)
return ret;
return 3;
}
static int32_t parse_copy4(uint8_t *cdata, uint32_t cidx, uint32_t clength,
uint8_t *data, uint32_t *idx, uint32_t length) {
int ret = 0;
uint32_t clen = (uint32_t)((cdata[cidx] & 0xfc) >> 2) + 1;
uint32_t coff = 0;
memcpy(&coff, &cdata[cidx+1], 4);
if ((ret = offsetread(data, idx, length, clen, coff)) != 0)
return ret;
return 5;
}
static int32_t parse_compressed_type(uint8_t compressed_type,
uint8_t *cdata, uint32_t cidx, uint32_t clen,
uint8_t *data, uint32_t *idx, uint32_t len) {
switch (compressed_type) {
case 0:
/* Literal stream */
prdebug("Found Literal stream\n");
return parse_literal(cdata, cidx, clen, data, idx, len);
case 1:
/* 1 byte offset */
prdebug("Found single byte offset stream\n");
return parse_copy1(cdata, cidx, clen, data, idx, len);
case 2:
/* 2 byte offset */
prdebug("Found two bytes offset stream\n");
return parse_copy2(cdata, cidx, clen, data, idx, len);
case 3:
/* 4 byte offset */
prdebug("Found four bytes offset stream\n");
return parse_copy4(cdata, cidx, clen, data, idx, len);
default:
prerror("Impossible compressed type!\n");
return -1;
}
}
static int snappy_uncompress(FILE *out, uint8_t *cdata, size_t clength,
uint8_t *data, size_t length, uint32_t *idx, uint32_t *crc) {
int32_t off = 0;
uint32_t cidx = 0;
uint32_t bytes = 0;
uint32_t len = 0;
uint8_t ctype = 0;
crc32c_init(crc);
*idx = 0;
prdebug("Decompressing %ld bytes\n", clength);
len = get_length(cdata, clength, &bytes);
prdebug("Uncompressed Length %d\n", len);
if (len > MAX_UNCOMPRESSED_DATA_SIZE)
return -1;
cidx = bytes;
while (cidx < clength && *idx < length) {
ctype = cdata[cidx] & 0x03;
off = parse_compressed_type(ctype, cdata, cidx, clength,
data, idx, len);
if (off < 0) {
/* Calculate CRC */
crc32c(crc, data, *idx);
crc32c_fini(crc);
if (fwrite(data, 1, *idx, out) != *idx)
return off;
return off;
}
cidx += off;
}
crc32c(crc, data, *idx);
crc32c_fini(crc);
return 0;
}
static FILE *open_read_file(const char *file) {
FILE *in = stdin;
if (strcmp(file, "-") != 0)
in = fopen(file, "rb");
prdebug("Opening IN file: %s\n", file);
if (in == NULL)
return in;
if (read_offset != 0) {
prinfo("Seeking to offset %d\n", read_offset);
fseek(in, read_offset, SEEK_SET);
}
return in;
}
static FILE *open_write_file(const char *file) {
FILE *out = stdout;
if (strcmp(file, "-") != 0)
out = fopen(file, "wb");
prdebug("Opening OUT file: %s\n", file);
return out;
}
static int close_file(FILE *f) {
if (f == stdin || f == stdout)
return 0;
return fclose(f);
}
static uint8_t get_chunktype(FILE *in) {
uint8_t chunktype;
if (fread(&chunktype, 1, 1, in) != 1)
return 0x27;
return chunktype;
}
static int parse_stream_identifier(FILE *in) {
uint8_t stream_identifier[9];
uint8_t reference_identifier[] = {
0x06, 0x00, 0x00, 0x73,
0x4e, 0x61, 0x50, 0x70,
0x59
};
if (fread(stream_identifier, 9, 1, in) < 1)
return -1;
if (memcmp(reference_identifier, stream_identifier, 9) != 0)
return -1;
return 0;
}
static int parse_compressed_data_chunk(FILE *in, FILE *out) {
int ret = 0;
size_t r = 0;
uint8_t *c_data = NULL;
uint8_t *data = NULL;
/* Compressed data */
uint32_t c_length = 0;
uint32_t c_read_length = 0;
uint32_t crc = 0;
uint32_t idx = 0;
uint32_t uncompressed_crc = 0;
c_data = malloc(MAX_COMPRESSED_DATA_SIZE);
if (c_data == NULL) {
ret = -1;
goto exit_point;
}
data = malloc(MAX_UNCOMPRESSED_DATA_SIZE);
if (data == NULL) {
ret = -1;
goto free_c_data;
}
r = fread(&c_length, 1, 3, in);
if (r == 0) {
ret = 0;
goto return_point;
} else if (r < 3) {
ret = -1;
goto return_point;
}
r = fread(&crc, 1, 4, in);
if (r == 0) {
ret = 0;
goto return_point;
} else if (r < 4) {
ret = -1;
goto return_point;
}
if (c_length > MAX_COMPRESSED_DATA_SIZE) {
ret = -1;
goto return_point;
}
c_length--;
prdebug("Compressed data chunk, len %d\n", c_length);
if (c_length > MAX_COMPRESSED_DATA_SIZE) {
ret = -1;
goto return_point;
}
c_read_length = fread(c_data, 1, c_length - 3, in);
if ((ret = snappy_uncompress(out, c_data, c_read_length,
data, MAX_UNCOMPRESSED_DATA_SIZE, &idx,
&uncompressed_crc)) != 0) {
goto return_point;
}
prinfo("End of decompression %lx\n", ftell(in));
if (crc != uncompressed_crc) {
prinfo("Corrupted File! Expected CRC: %08x Calculated CRC: %08x\n", crc, uncompressed_crc);
if (consider_crc_errors) {
ret = -1;
goto return_point;
}
}
if (fwrite(data, 1, idx, out) < idx) {
perror("fwrite");
ret = -1;
goto return_point;
}
return_point:
free(data);
free_c_data:
free(c_data);
exit_point:
return ret;
}
static int parse_unknown_chunktype(uint8_t chunktype) {
if (chunktype == 0x27) {
return 0;
} else if (chunktype > 0x27 && chunktype <= 0x7f) {
prerror("[frame] Unskippable chunk encountered %02hhx\n",
(unsigned char) chunktype);
return 1;
} else {
prerror("[frame] Skipping chunk %02hhx\n",
(unsigned char) chunktype);
return 0;
}
}
static int parse_chunk(FILE *in, FILE *out, uint8_t chunktype) {
prinfo("Got chunk %d\n", chunktype);
switch (chunktype) {
case 0xff:
return parse_stream_identifier(in);
case 0x00:
return parse_compressed_data_chunk(in, out);
case 0x01:
/* TODO */
// return parse_uncompressed_data_chunk(in, out);
return -1;
case 0xfe:
/* TODO */
// return parse_padding(in, out);
return -1;
default:
return parse_unknown_chunktype(chunktype);
}
}
static int snappy_decompress_unframed(FILE *in, FILE *out) {
int ret = 0;
int32_t r = 0;
uint32_t read_head = 0;
uint32_t write_head = 0;
uint8_t *inbuf, *outbuf;
int32_t read_size = MAX_COMPRESSED_DATA_SIZE;
int32_t write_size = MAX_COMPRESSED_DATA_SIZE;
inbuf = malloc(read_size);
if (inbuf == NULL) {
ret = -1;
goto return_point;
}
outbuf = malloc(write_size);
if (outbuf == NULL) {
ret = -1;
goto free_in;
}
read_size = fread(inbuf, 1, read_size, in);
if (read_size <= 0) {
ret = read_size;
goto free_out;
}
while (read_head < read_size) {
/* Skip unvalid compressed types, sledge */
uint8_t ctype = inbuf[read_head] & 0x03;
r = parse_compressed_type(ctype, inbuf, read_head, read_size,
outbuf, &write_head, write_size);
if (r < 0) {
prerror("parse_compressed_type: %d\n", r);
return r;
}
read_head += r;
prinfo("offset: %u\n", read_head);
}
r = fwrite(outbuf, 1, write_head, out);
if (r < 0)
ret = r;
free_out:
free(outbuf);
free_in:
free(inbuf);
return_point:
return ret;
}
static int snappy_decompress_framed(FILE *in, FILE *out) {
int ret = 0;
uint8_t chunktype;
while (feof(in) == 0 && ferror(in) == 0 && ret == 0) {
chunktype = get_chunktype(in);
ret = parse_chunk(in, out, chunktype);
prdebug("New run %ld %d %d\n", ftell(in), feof(in), ferror(in));
}
return ret;
}
static void version(const char *progname) {
fprintf(stderr, "%s Version: %s\n", progname, VERSION);
}
static void usage(const char *progname) {
fprintf(stderr, "Usage %s [options] <input file> <output file>\n",
progname);
fprintf(stderr, " files can be specified as - for stdin or stdout\n");
fprintf(stderr, " Options:\n");
fprintf(stderr, " -E --ignore_offset_errors [substitution byte] Ignore any offset errors that occurs\n");
fprintf(stderr, " -O --read_offset [offset] Start reading file from offset\n");
fprintf(stderr, " -u --unframed Assume Unframed stream in input file\n");
fprintf(stderr, " -h --help This Help\n");
fprintf(stderr, " -v --version Print Version and exit\n");
}
int main(int argc, char **argv) {
int c = 0;
int ret = 0;
FILE *in, *out;
int option_idx = 0;
static struct option flags[] = {
{"consider_crc_errors", no_argument, 0, 'C'},
{"ignore_offset_errors", optional_argument, 0, 'E'},
{"read_offset", required_argument, 0, 'O'},
{"unframed", no_argument, 0, 'u'},
{"version", no_argument, 0, 'v'},
{"help", no_argument, 0, 'h'},
{0, 0, 0, 0}
};
while (c != -1) {
c = getopt_long(argc, argv, "CO:E::uhv", flags, &option_idx);
switch (c) {
case 'C':
consider_crc_errors = 1;
break;
case 'E':
ignore_offset_errors = 1;
/* Set the dummy byte to the passed value */
if (optarg != NULL)
offset_dummy_byte = (strtol(optarg, NULL, 0) & 0xff);
break;
case 'O':
if (optarg != NULL)
read_offset = strtol(optarg, NULL, 0);
break;
case 'u':
unframed_stream = 1;
break;
case 'h':
usage(argv[0]);
return 0;
case 'v':
version(argv[0]);
return 0;
default:
prerror("Unknown Option: %c\n", c);
continue;
case -1:
break;
}
}
prdebug("Starting snappy-fox\n");
if (argc - optind < 2) {
usage(argv[0]);
return 1;
}
#ifdef __AFL_LOOP
while (__AFL_LOOP(1000)) {
#endif
in = open_read_file(argv[optind]);
if (in == NULL) {
perror("fopen read");
ret = 1;
goto exit_point;
}
out = open_write_file(argv[optind + 1]);
if (out == NULL) {
perror("fopen write");
ret = 1;
goto close_in;
}
if (unframed_stream == 0)
ret = snappy_decompress_framed(in, out);
else
ret = snappy_decompress_unframed(in, out);
if (ret != 0) {
prerror("decompress %d\n", ret);
goto return_point;
}
return_point:
if (close_file(out) != 0)
perror("close");
close_in:
if (close_file(in) != 0)
perror("close");
exit_point:
prdebug("Exiting %d\n", ret);
#ifdef __AFL_LOOP
}
#endif
return ret;
}
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