lzma_stream_footer_decode(lzma_stream_flags *options, const uint8_t *in)
{
uint32_t crc;
// Magic
if (memcmp(in + sizeof(uint32_t) * 2 + LZMA_STREAM_FLAGS_SIZE,
lzma_footer_magic, sizeof(lzma_footer_magic)) != 0)
return LZMA_FORMAT_ERROR;
// CRC32
crc = lzma_crc32(in + sizeof(uint32_t),
sizeof(uint32_t) + LZMA_STREAM_FLAGS_SIZE, 0);
if (crc != unaligned_read32le(in))
return LZMA_DATA_ERROR;
// Stream Flags
if (stream_flags_decode(options, in + sizeof(uint32_t) * 2))
return LZMA_OPTIONS_ERROR;
// Backward Size
options->backward_size = unaligned_read32le(in + sizeof(uint32_t));
options->backward_size = (options->backward_size + 1) * 4;
return LZMA_OK;
}
lzma_stream_header_decode(lzma_stream_flags *options, const uint8_t *in)
{
// Magic
if (memcmp(in, lzma_header_magic, sizeof(lzma_header_magic)) != 0)
return LZMA_FORMAT_ERROR;
// Verify the CRC32 so we can distinguish between corrupt
// and unsupported files.
const uint32_t crc = lzma_crc32(in + sizeof(lzma_header_magic),
LZMA_STREAM_FLAGS_SIZE, 0);
if (crc != unaligned_read32le(in + sizeof(lzma_header_magic)
+ LZMA_STREAM_FLAGS_SIZE))
return LZMA_DATA_ERROR;
// Stream Flags
if (stream_flags_decode(options, in + sizeof(lzma_header_magic)))
return LZMA_OPTIONS_ERROR;
// Set Backward Size to indicate unknown value. That way
// lzma_stream_flags_compare() can be used to compare Stream Header
// and Stream Footer while keeping it useful also for comparing
// two Stream Footers.
options->backward_size = LZMA_VLI_UNKNOWN;
return LZMA_OK;
}
extern lzma_ret
lzma_simple_props_decode(void **options, const lzma_allocator *allocator,
const uint8_t *props, size_t props_size)
{
if (props_size == 0)
return LZMA_OK;
if (props_size != 4) {
return LZMA_OPTIONS_ERROR;
}
lzma_options_bcj *opt = lzma_alloc(
sizeof(lzma_options_bcj), allocator);
if (opt == NULL)
return LZMA_MEM_ERROR;
opt->start_offset = unaligned_read32le(props);
// Don't leave an options structure allocated if start_offset is zero.
if (opt->start_offset == 0)
lzma_free(opt, allocator);
else
*options = opt;
return LZMA_OK;
}
lzma_block_header_decode(lzma_block *block,
lzma_allocator *allocator, const uint8_t *in)
{
const size_t filter_count = (in[1] & 3) + 1;
size_t in_size;
size_t i;
// Start after the Block Header Size and Block Flags fields.
size_t in_pos = 2;
// NOTE: We consider the header to be corrupt not only when the
// CRC32 doesn't match, but also when variable-length integers
// are invalid or over 63 bits, or if the header is too small
// to contain the claimed information.
// Initialize the filter options array. This way the caller can
// safely free() the options even if an error occurs in this function.
for (i = 0; i <= LZMA_FILTERS_MAX; ++i) {
block->filters[i].id = LZMA_VLI_UNKNOWN;
block->filters[i].options = NULL;
}
// Always zero for now.
block->version = 0;
// Validate Block Header Size and Check type. The caller must have
// already set these, so it is a programming error if this test fails.
if (lzma_block_header_size_decode(in[0]) != block->header_size
|| (unsigned int)(block->check) > LZMA_CHECK_ID_MAX)
return LZMA_PROG_ERROR;
// Exclude the CRC32 field.
in_size = block->header_size - 4;
// Verify CRC32
if (lzma_crc32(in, in_size, 0) != unaligned_read32le(in + in_size))
return LZMA_DATA_ERROR;
// Check for unsupported flags.
if (in[1] & 0x3C)
return LZMA_OPTIONS_ERROR;
// Compressed Size
if (in[1] & 0x40) {
return_if_error(lzma_vli_decode(&block->compressed_size,
NULL, in, &in_pos, in_size));
// Validate Compressed Size. This checks that it isn't zero
// and that the total size of the Block is a valid VLI.
if (lzma_block_unpadded_size(block) == 0)
return LZMA_DATA_ERROR;
} else {
block->compressed_size = LZMA_VLI_UNKNOWN;
}
// Uncompressed Size
if (in[1] & 0x80)
return_if_error(lzma_vli_decode(&block->uncompressed_size,
NULL, in, &in_pos, in_size));
else
block->uncompressed_size = LZMA_VLI_UNKNOWN;
// Filter Flags
for (i = 0; i < filter_count; ++i) {
const lzma_ret ret = lzma_filter_flags_decode(
&block->filters[i], allocator,
in, &in_pos, in_size);
if (ret != LZMA_OK) {
free_properties(block, allocator);
return ret;
}
}
// Padding
while (in_pos < in_size) {
if (in[in_pos++] != 0x00) {
free_properties(block, allocator);
// Possibly some new field present so use
// LZMA_OPTIONS_ERROR instead of LZMA_DATA_ERROR.
return LZMA_OPTIONS_ERROR;
}
}
return LZMA_OK;
}
