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Merge pull request #78 from szabadka/master

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Implement some stricter format checks in the decoder.
This commit is contained in:
szabadka 2015-04-22 14:43:06 +02:00
commit 5ded136348
1 changed files with 41 additions and 8 deletions
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49
dec/decode.c
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@ -86,12 +86,21 @@ static BROTLI_INLINE int DecodeVarLenUint8(BrotliBitReader* br) {
return 0;
}
/* Advances the bit reader position to the next byte boundary and verifies
that any skipped bits are set to zero. */
static BROTLI_INLINE int JumpToByteBoundary(BrotliBitReader* br) {
uint32_t new_bit_pos = (br->bit_pos_ + 7) & (uint32_t)(~7UL);
uint32_t pad_bits = BrotliReadBits(br, (int)(new_bit_pos - br->bit_pos_));
return pad_bits == 0;
}
static int DecodeMetaBlockLength(BrotliBitReader* br,
int* meta_block_length,
int* input_end,
int* is_metadata,
int* is_uncompressed) {
int size_nibbles;
int size_bytes;
int i;
*input_end = (int)BrotliReadBits(br, 1);
*meta_block_length = 0;
@ -107,13 +116,25 @@ static int DecodeMetaBlockLength(BrotliBitReader* br,
if (BrotliReadBits(br, 1) != 0) {
return 0;
}
size_nibbles = 2 * (int)BrotliReadBits(br, 2);
if (size_nibbles == 0) {
size_bytes = (int)BrotliReadBits(br, 2);
if (size_bytes == 0) {
return 1;
}
}
for (i = 0; i < size_nibbles; ++i) {
*meta_block_length |= (int)BrotliReadBits(br, 4) << (i * 4);
for (i = 0; i < size_bytes; ++i) {
int next_byte = (int)BrotliReadBits(br, 8);
if (i + 1 == size_bytes && size_bytes > 1 && next_byte == 0) {
return 0;
}
*meta_block_length |= next_byte << (i * 8);
}
} else {
for (i = 0; i < size_nibbles; ++i) {
int next_nibble = (int)BrotliReadBits(br, 4);
if (i + 1 == size_nibbles && size_nibbles > 4 && next_nibble == 0) {
return 0;
}
*meta_block_length |= next_nibble << (i * 4);
}
}
++(*meta_block_length);
if (!*input_end && !*is_metadata) {
@ -264,7 +285,10 @@ static BrotliResult ReadHuffmanCode(int alphabet_size,
}
memset(s->code_lengths, 0, (size_t)alphabet_size);
for (i = 0; i < num_symbols; ++i) {
symbols[i] = (int)BrotliReadBits(br, max_bits) % alphabet_size;
symbols[i] = (int)BrotliReadBits(br, max_bits);
if (symbols[i] >= alphabet_size) {
return BROTLI_RESULT_ERROR;
}
s->code_lengths[symbols[i]] = 2;
}
s->code_lengths[symbols[0]] = 1;
@ -992,7 +1016,10 @@ BrotliResult BrotliDecompressStreaming(BrotliInput input, BrotliOutput output,
}
BROTLI_LOG_UINT(s->meta_block_remaining_len);
if (s->is_metadata) {
BrotliSetBitPos(br, (s->br.bit_pos_ + 7) & (uint32_t)(~7UL));
if (!JumpToByteBoundary(&s->br)) {
result = BROTLI_RESULT_ERROR;
break;
}
s->state = BROTLI_STATE_METADATA;
break;
}
@ -1001,7 +1028,10 @@ BrotliResult BrotliDecompressStreaming(BrotliInput input, BrotliOutput output,
break;
}
if (s->is_uncompressed) {
BrotliSetBitPos(br, (s->br.bit_pos_ + 7) & (uint32_t)(~7UL));
if (!JumpToByteBoundary(&s->br)) {
result = BROTLI_RESULT_ERROR;
break;
}
s->state = BROTLI_STATE_UNCOMPRESSED;
break;
}
@ -1451,6 +1481,9 @@ BrotliResult BrotliDecompressStreaming(BrotliInput input, BrotliOutput output,
result = BROTLI_RESULT_ERROR;
}
}
if (!JumpToByteBoundary(&s->br)) {
result = BROTLI_RESULT_ERROR;
}
return result;
default:
printf("Unknown state %d\n", s->state);