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/*
* .xz Stream decoder
*
* Author: Lasse Collin <lasse.collin@tukaani.org>
*
* This file has been put into the public domain.
* You can do whatever you want with this file.
*/
#include "xz_private.h"
#include "xz_stream.h"
/* Hash used to validate the Index field */
struct xz_dec_hash {
vli_type unpadded;
vli_type uncompressed;
uint32_t crc32;
};
struct xz_dec {
/* Position in dec_main() */
enum {
SEQ_STREAM_HEADER,
SEQ_BLOCK_START,
SEQ_BLOCK_HEADER,
SEQ_BLOCK_UNCOMPRESS,
SEQ_BLOCK_PADDING,
SEQ_BLOCK_CHECK,
SEQ_INDEX,
SEQ_INDEX_PADDING,
SEQ_INDEX_CRC32,
SEQ_STREAM_FOOTER
} sequence;
/* Position in variable-length integers and Check fields */
uint32_t pos;
/* Variable-length integer decoded by dec_vli() */
vli_type vli;
/* Saved in_pos and out_pos */
size_t in_start;
size_t out_start;
/* CRC32 value in Block or Index */
uint32_t crc32;
/* Type of the integrity check calculated from uncompressed data */
enum xz_check check_type;
/* Operation mode */
enum xz_mode mode;
/*
* True if the next call to xz_dec_run() is allowed to return
* XZ_BUF_ERROR.
*/
bool allow_buf_error;
/* Information stored in Block Header */
struct {
/*
* Value stored in the Compressed Size field, or
* VLI_UNKNOWN if Compressed Size is not present.
*/
vli_type compressed;
/*
* Value stored in the Uncompressed Size field, or
* VLI_UNKNOWN if Uncompressed Size is not present.
*/
vli_type uncompressed;
/* Size of the Block Header field */
uint32_t size;
} block_header;
/* Information collected when decoding Blocks */
struct {
/* Observed compressed size of the current Block */
vli_type compressed;
/* Observed uncompressed size of the current Block */
vli_type uncompressed;
/* Number of Blocks decoded so far */
vli_type count;
/*
* Hash calculated from the Block sizes. This is used to
* validate the Index field.
*/
struct xz_dec_hash hash;
} block;
/* Variables needed when verifying the Index field */
struct {
/* Position in dec_index() */
enum {
SEQ_INDEX_COUNT,
SEQ_INDEX_UNPADDED,
SEQ_INDEX_UNCOMPRESSED
} sequence;
/* Size of the Index in bytes */
vli_type size;
/* Number of Records (matches block.count in valid files) */
vli_type count;
/*
* Hash calculated from the Records (matches block.hash in
* valid files).
*/
struct xz_dec_hash hash;
} index;
/*
* Temporary buffer needed to hold Stream Header, Block Header,
* and Stream Footer. The Block Header is the biggest (1 KiB)
* so we reserve space according to that. buf[] has to be aligned
* to a multiple of four bytes; the size_t variables before it
* should guarantee this.
*/
struct {
size_t pos;
size_t size;
uint8_t buf[1024];
} temp;
struct xz_dec_lzma2 *lzma2;
#ifdef XZ_DEC_BCJ
struct xz_dec_bcj *bcj;
bool bcj_active;
#endif
};
#ifdef XZ_DEC_ANY_CHECK
/* Sizes of the Check field with different Check IDs */
static const uint8_t check_sizes[16] = {
0,
4, 4, 4,
8, 8, 8,
16, 16, 16,
32, 32, 32,
64, 64, 64
};
#endif
/*
* Fill s->temp by copying data starting from b->in[b->in_pos]. Caller
* must have set s->temp.pos to indicate how much data we are supposed
* to copy into s->temp.buf. Return true once s->temp.pos has reached
* s->temp.size.
*/
static bool fill_temp(struct xz_dec *s, struct xz_buf *b)
{
size_t copy_size = min_t(size_t,
b->in_size - b->in_pos, s->temp.size - s->temp.pos);
memcpy(s->temp.buf + s->temp.pos, b->in + b->in_pos, copy_size);
b->in_pos += copy_size;
s->temp.pos += copy_size;
if (s->temp.pos == s->temp.size) {
s->temp.pos = 0;
return true;
}
return false;
}
/* Decode a variable-length integer (little-endian base-128 encoding) */
static enum xz_ret dec_vli(struct xz_dec *s, const uint8_t *in,
size_t *in_pos, size_t in_size)
{
uint8_t byte;
if (s->pos == 0)
s->vli = 0;
while (*in_pos < in_size) {
byte = in[*in_pos];
++*in_pos;
s->vli |= (vli_type)(byte & 0x7F) << s->pos;
if ((byte & 0x80) == 0) {
/* Don't allow non-minimal encodings. */
if (byte == 0 && s->pos != 0)
return XZ_DATA_ERROR;
s->pos = 0;
return XZ_STREAM_END;
}
s->pos += 7;
if (s->pos == 7 * VLI_BYTES_MAX)
return XZ_DATA_ERROR;
}
return XZ_OK;
}
/*
* Decode the Compressed Data field from a Block. Update and validate
* the observed compressed and uncompressed sizes of the Block so that
* they don't exceed the values possibly stored in the Block Header
* (validation assumes that no integer overflow occurs, since vli_type
* is normally uint64_t). Update the CRC32 if presence of the CRC32
* field was indicated in Stream Header.
*
* Once the decoding is finished, validate that the observed sizes match
* the sizes possibly stored in the Block Header. Update the hash and
* Block count, which are later used to validate the Index field.
*/
static enum xz_ret dec_block(struct xz_dec *s, struct xz_buf *b)
{
enum xz_ret ret;
s->in_start = b->in_pos;
s->out_start = b->out_pos;
#ifdef XZ_DEC_BCJ
if (s->bcj_active)
ret = xz_dec_bcj_run(s->bcj, s->lzma2, b);
else
#endif
ret = xz_dec_lzma2_run(s->lzma2, b);
s->block.compressed += b->in_pos - s->in_start;
s->block.uncompressed += b->out_pos - s->out_start;
/*
* There is no need to separately check for VLI_UNKNOWN, since
* the observed sizes are always smaller than VLI_UNKNOWN.
*/
if (s->block.compressed > s->block_header.compressed
|| s->block.uncompressed
> s->block_header.uncompressed)
return XZ_DATA_ERROR;
if (s->check_type == XZ_CHECK_CRC32)
s->crc32 = xz_crc32(b->out + s->out_start,
b->out_pos - s->out_
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