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///////////////////////////////////////////////////////////////////////////////
//
/// \file index_decoder.c
/// \brief Decodes the Index field
//
// Author: Lasse Collin
//
// This file has been put into the public domain.
// You can do whatever you want with this file.
//
///////////////////////////////////////////////////////////////////////////////
#include "index.h"
#include "check.h"
struct lzma_coder_s {
enum {
SEQ_INDICATOR,
SEQ_COUNT,
SEQ_MEMUSAGE,
SEQ_UNPADDED,
SEQ_UNCOMPRESSED,
SEQ_PADDING_INIT,
SEQ_PADDING,
SEQ_CRC32,
} sequence;
/// Memory usage limit
uint64_t memlimit;
/// Target Index
lzma_index *index;
/// Pointer give by the application, which is set after
/// successful decoding.
lzma_index **index_ptr;
/// Number of Records left to decode.
lzma_vli count;
/// The most recent Unpadded Size field
lzma_vli unpadded_size;
/// The most recent Uncompressed Size field
lzma_vli uncompressed_size;
/// Position in integers
size_t pos;
/// CRC32 of the List of Records field
uint32_t crc32;
};
static lzma_ret
index_decode(lzma_coder *coder, const lzma_allocator *allocator,
const uint8_t *restrict in, size_t *restrict in_pos,
size_t in_size,
uint8_t *restrict out lzma_attribute((__unused__)),
size_t *restrict out_pos lzma_attribute((__unused__)),
size_t out_size lzma_attribute((__unused__)),
lzma_action action lzma_attribute((__unused__)))
{
// Similar optimization as in index_encoder.c
const size_t in_start = *in_pos;
lzma_ret ret = LZMA_OK;
while (*in_pos < in_size)
switch (coder->sequence) {
case SEQ_INDICATOR:
// Return LZMA_DATA_ERROR instead of e.g. LZMA_PROG_ERROR or
// LZMA_FORMAT_ERROR, because a typical usage case for Index
// decoder is when parsing the Stream backwards. If seeking
// backward from the Stream Footer gives us something that
// doesn't begin with Index Indicator, the file is considered
// corrupt, not "programming error" or "unrecognized file
// format". One could argue that the application should
// verify the Index Indicator before trying to decode the
// Index, but well, I suppose it is simpler this way.
if (in[(*in_pos)++] != 0x00)
return LZMA_DATA_ERROR;
coder->sequence = SEQ_COUNT;
break;
case SEQ_COUNT:
ret = lzma_vli_decode(&coder->count, &coder->pos,
in, in_pos, in_size);
if (ret != LZMA_STREAM_END)
goto out;
coder->pos = 0;
coder->sequence = SEQ_MEMUSAGE;
// Fall through
case SEQ_MEMUSAGE:
if (lzma_index_memusage(1, coder->count) > coder->memlimit) {
ret = LZMA_MEMLIMIT_ERROR;
goto out;
}
// Tell the Index handling code how many Records this
// Index has to allow it to allocate memory more efficiently.
lzma_index_prealloc(coder->index, coder->count);
ret = LZMA_OK;
coder->sequence = coder->count == 0
? SEQ_PADDING_INIT : SEQ_UNPADDED;
break;
case SEQ_UNPADDED:
case SEQ_UNCOMPRESSED: {
lzma_vli *size = coder->sequence == SEQ_UNPADDED
? &coder->unpadded_size
: &coder->uncompressed_size;
ret = lzma_vli_decode(size, &coder->pos,
in, in_pos, in_size);
if (ret != LZMA_STREAM_END)
goto out;
ret = LZMA_OK;
coder->pos = 0;
if (coder->sequence == SEQ_UNPADDED) {
// Validate that encoded Unpadded Size isn't too small
// or too big.
if (coder->unpadded_size < UNPADDED_SIZE_MIN
|| coder->unpadded_size
> UNPADDED_SIZE_MAX)
return LZMA_DATA_ERROR;
coder->sequence = SEQ_UNCOMPRESSED;
} else {
// Add the decoded Record to the Index.
return_if_error(lzma_index_append(
coder->index, allocator,
coder->unpadded_size,
coder->uncompressed_size));
// Check if this was the last Record.
coder->sequence = --coder->count == 0
? SEQ_PADDING_INIT
: SEQ_UNPADDED;
}
break;
}
case SEQ_PADDING_INIT:
coder->pos = lzma_index_padding_size(coder->index);
coder->sequence = SEQ_PADDING;
// Fall through
case SEQ_PADDING:
if (coder->pos > 0) {
--coder->pos;
if (in[(*in_pos)++] != 0x00)
return LZMA_DATA_ERROR;
break;
}
// Finish the CRC32 calculation.
coder->crc32 = lzma_crc32(in + in_start,
*in_pos - in_start, coder->crc32);
coder->sequence = SEQ_CRC32;
// Fall through
case SEQ_CRC32:
do {
if (*in_pos == in_size)
return LZMA_OK;
if (((coder->crc32 >> (coder->pos * 8)) & 0xFF)
!= in[(*in_pos)++])
return LZMA_DATA_ERROR;
} while (++coder->pos < 4);
// Decoding was successful, now we can let the application
// see the decoded Index.
*coder->index_ptr = coder->index;
// Make index NULL so we don't free it unintentionally.
coder->index = NULL;
return LZMA_STREAM_END;
default:
assert(0);
return LZMA_PROG_ERROR;
}
out:
// Update the CRC32,
coder->crc32 = lzma_crc32(in + in_start,
*in_pos - in_start, coder->crc32);
return ret;
}
static void
index_decoder_end(lzma_coder *coder, const lzma_allocator *allocator)
{
lzma_index_end(coder->index, allocator);
lzma_free(coder, allocator);
return;
}
static lzma_ret
index_decoder_memconfig(lzma_coder *coder, uint64_t *memusage,
uint64_t *old_memlimit, uint64_t new_memlimit)
{
*memusage = lzma_index_memusage(1, coder->count);
*old_memlimit = coder->memlimit;
if (new_memlimit != 0) {
if (new_memlimit < *memusage)
return LZMA_MEMLIMIT_ERROR;
coder->memlimit = new_memlimit;
}
return LZMA_OK;
}
static lzma_ret
index_decoder_reset(lzma_coder *coder, const lzma_allocator *allocator,
lzma_index **i, uint64_t memlimit)
{
// Remember the pointer given by the application. We will set it
// to point to the decoded Index only if decoding is successful.
// Before that, keep it NULL so that applications can always safely
// pass it to lzma_index_end() no matter did decoding succeed or not.
coder->index_ptr = i;
*i = NULL;
// We always allocate a new lzma_index.
coder->index = lzma_index_init(allocator);
if (coder->index == NULL)
return LZMA_MEM_ERROR;
// Initialize the rest.
coder->sequence = SEQ_INDICATOR;
coder->memlimit = memlimit;
coder->count = 0; // Needs to be initialized due to _memconfig().
coder->pos = 0;
coder->crc32 = 0;
return LZMA_OK;
}
static lzma_ret
index_decoder_init(lzma_next_coder *next, const lzma_allocator *allocator,
lzma_index **i, uint64_t memlimit)
{
lzma_next_coder_init(&index_decoder_init, next, allocator);
if (i == NULL || memlimit == 0)
return LZMA_PROG_ERROR;
if (next->coder == NULL) {
next->coder = lzma_alloc(sizeof(lzma_coder), allocator);
if (next->coder == NULL)
return LZMA_MEM_ERROR;
next->code = &index_decode;
next->end = &index_decoder_end;
next->memconfig = &index_decoder_memconfig;
next->coder->index = NULL;
} else {
lzma_index_end(next->coder->index, allocator);
}
return index_decoder_reset(next->coder, allocator, i, memlimit);
}
extern LZMA_API(lzma_ret)
lzma_index_decoder(lzma_stream *strm, lzma_index **i, uint64_t memlimit)
{
lzma_next_strm_init(index_decoder_init, strm, i, memlimit);
strm->internal->supported_actions[LZMA_RUN] = true;
strm->internal->supported_actions[LZMA_FINISH] = true;
return LZMA_OK;
}
extern LZMA_API(lzma_ret)
lzma_index_buffer_decode(lzma_index **i, uint64_t *memlimit,
const lzma_allocator *allocator,
const uint8_t *in, size_t *in_pos, size_t in_size)
{
// Sanity checks
if (i == NULL || memlimit == NULL
|| in == NULL || in_pos == NULL || *in_pos > in_size)
return LZMA_PROG_ERROR;
// Initialize the decoder.
lzma_coder coder;
return_if_error(index_decoder_reset(&coder, allocator, i, *memlimit));
// Store the input start position so that we can restore it in case
// of an error.
const size_t in_start = *in_pos;
// Do the actual decoding.
lzma_ret ret = index_decode(&coder, allocator, in, in_pos, in_size,
NULL, NULL, 0, LZMA_RUN);
if (ret == LZMA_STREAM_END) {
ret = LZMA_OK;
} else {
// Something went wrong, free the Index structure and restore
// the input position.
lzma_index_end(coder.index, allocator);
*in_pos = in_start;
if (ret == LZMA_OK) {
// The input is truncated or otherwise corrupt.
// Use LZMA_DATA_ERROR instead of LZMA_BUF_ERROR
// like lzma_vli_decode() does in single-call mode.
ret = LZMA_DATA_ERROR;
} else if (ret == LZMA_MEMLIMIT_ERROR) {
// Tell the caller how much memory would have
// been needed.
*memlimit = lzma_index_memusage(1, coder.count);
}
}
return ret;
}