diff options
| -rw-r--r-- | image/main.c | 23 |
1 files changed, 23 insertions, 0 deletions
diff --git a/image/main.c b/image/main.c index 378a0d42..b7e06885 100644 --- a/image/main.c +++ b/image/main.c @@ -408,6 +408,29 @@ static const u32 crc32c_rev_table[256] = { 0x588982AFL,0x5D65F45EL,0x53516F4DL,0x56BD19BCL }; +/* + * Calculate a 4-byte suffix to match desired CRC32C + * + * @current_crc: CRC32C checksum of all bytes before the suffix + * @desired_crc: the checksum that we want to get after adding the suffix + * + * Outputs: @suffix: pointer to where the suffix will be written (4-bytes) + */ +static void find_collision_calc_suffix(unsigned long current_crc, + unsigned long desired_crc, + char *suffix) +{ + int i; + + for(i = 3; i >= 0; i--) { + desired_crc = (desired_crc << 8) + ^ crc32c_rev_table[desired_crc >> 24 & 0xFF] + ^ ((current_crc >> i * 8) & 0xFF); + } + for (i = 0; i < 4; i++) + suffix[i] = (desired_crc >> i * 8) & 0xFF; +} + static int find_collision_brute_force(struct name *val, u32 name_len) { unsigned long checksum; |