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-rw-r--r--src/liblzma/common/block_decoder.c79
1 files changed, 54 insertions, 25 deletions
diff --git a/src/liblzma/common/block_decoder.c b/src/liblzma/common/block_decoder.c
index 075bd279..4827e0f0 100644
--- a/src/liblzma/common/block_decoder.c
+++ b/src/liblzma/common/block_decoder.c
@@ -40,6 +40,9 @@ typedef struct {
/// is unknown.
lzma_vli compressed_limit;
+ /// Maximum allowed Uncompressed Size.
+ lzma_vli uncompressed_limit;
+
/// Position when reading the Check field
size_t check_pos;
@@ -52,21 +55,6 @@ typedef struct {
static inline bool
-update_size(lzma_vli *size, lzma_vli add, lzma_vli limit)
-{
- if (limit > LZMA_VLI_MAX)
- limit = LZMA_VLI_MAX;
-
- if (limit < *size || limit - *size < add)
- return true;
-
- *size += add;
-
- return false;
-}
-
-
-static inline bool
is_size_valid(lzma_vli size, lzma_vli reference)
{
return reference == LZMA_VLI_UNKNOWN || reference == size;
@@ -86,21 +74,54 @@ block_decode(void *coder_ptr, const lzma_allocator *allocator,
const size_t in_start = *in_pos;
const size_t out_start = *out_pos;
+ // Limit the amount of input and output space that we give
+ // to the raw decoder based on the information we have
+ // (or don't have) from Block Header.
+ const size_t in_stop = *in_pos + (size_t)my_min(
+ in_size - *in_pos,
+ coder->compressed_limit - coder->compressed_size);
+ const size_t out_stop = *out_pos + (size_t)my_min(
+ out_size - *out_pos,
+ coder->uncompressed_limit - coder->uncompressed_size);
+
const lzma_ret ret = coder->next.code(coder->next.coder,
- allocator, in, in_pos, in_size,
- out, out_pos, out_size, action);
+ allocator, in, in_pos, in_stop,
+ out, out_pos, out_stop, action);
const size_t in_used = *in_pos - in_start;
const size_t out_used = *out_pos - out_start;
- // NOTE: We compare to compressed_limit here, which prevents
- // the total size of the Block growing past LZMA_VLI_MAX.
- if (update_size(&coder->compressed_size, in_used,
- coder->compressed_limit)
- || update_size(&coder->uncompressed_size,
- out_used,
- coder->block->uncompressed_size))
- return LZMA_DATA_ERROR;
+ // Because we have limited the input and output sizes,
+ // we know that these cannot grow too big or overflow.
+ coder->compressed_size += in_used;
+ coder->uncompressed_size += out_used;
+
+ if (ret == LZMA_OK) {
+ const bool comp_done = coder->compressed_size
+ == coder->block->compressed_size;
+ const bool uncomp_done = coder->uncompressed_size
+ == coder->block->uncompressed_size;
+
+ // If both input and output amounts match the sizes
+ // in Block Header but we still got LZMA_OK instead
+ // of LZMA_STREAM_END, the file is broken.
+ if (comp_done && uncomp_done)
+ return LZMA_DATA_ERROR;
+
+ // If the decoder has consumed all the input that it
+ // needs but it still couldn't fill the output buffer
+ // or return LZMA_STREAM_END, the file is broken.
+ if (comp_done && *out_pos < out_size)
+ return LZMA_DATA_ERROR;
+
+ // If the decoder has produced all the output but
+ // it still didn't return LZMA_STREAM_END or consume
+ // more input (for example, detecting an end of
+ // payload marker may need more input but produce
+ // no output) the file is broken.
+ if (uncomp_done && *in_pos < in_size)
+ return LZMA_DATA_ERROR;
+ }
if (!coder->ignore_check)
lzma_check_update(&coder->check, coder->block->check,
@@ -230,6 +251,14 @@ lzma_block_decoder_init(lzma_next_coder *next, const lzma_allocator *allocator,
- lzma_check_size(block->check)
: block->compressed_size;
+ // With Uncompressed Size this is simpler. If Block Header lacks
+ // the size info, then LZMA_VLI_MAX is the maximum possible
+ // Uncompressed Size.
+ coder->uncompressed_limit
+ = block->uncompressed_size == LZMA_VLI_UNKNOWN
+ ? LZMA_VLI_MAX
+ : block->uncompressed_size;
+
// Initialize the check. It's caller's problem if the Check ID is not
// supported, and the Block decoder cannot verify the Check field.
// Caller can test lzma_check_is_supported(block->check).