liblzma: Add support for lzma_block.ignore_check.

Note that this slightly changes how lzma_block_header_decode()
has been documented. Earlier it said that the .version is set
to the lowest required value, but now it says that the .version
field is kept unchanged if possible. In practice this doesn't
affect any old code, because before this commit the only
possible .version was 0.

6 files changed, 28 insertions, 10 deletions

diff --git a/src/liblzma/common/block_buffer_encoder.c b/src/liblzma/common/block_buffer_encoder.c
index dcd574e9..39e263aa 100644
--- a/src/liblzma/common/block_buffer_encoder.c
+++ b/src/liblzma/common/block_buffer_encoder.c
@@ -233,7 +233,7 @@ block_buffer_encode(lzma_block *block, const lzma_allocator *allocator,
 
 	// The contents of the structure may depend on the version so
 	// check the version before validating the contents of *block.
-	if (block->version != 0)
+	if (block->version > 1)
 		return LZMA_OPTIONS_ERROR;
 
 	if ((unsigned int)(block->check) > LZMA_CHECK_ID_MAX
diff --git a/src/liblzma/common/block_decoder.c b/src/liblzma/common/block_decoder.c
index cee6c782..685c3b03 100644
--- a/src/liblzma/common/block_decoder.c
+++ b/src/liblzma/common/block_decoder.c
@@ -45,6 +45,9 @@ struct lzma_coder_s {
 
 	/// Check of the uncompressed data
 	lzma_check_state check;
+
+	/// True if the integrity check won't be calculated and verified.
+	bool ignore_check;
 };
 
 
@@ -97,8 +100,9 @@ block_decode(lzma_coder *coder, const lzma_allocator *allocator,
 					coder->block->uncompressed_size))
 			return LZMA_DATA_ERROR;
 
-		lzma_check_update(&coder->check, coder->block->check,
-				out + out_start, out_used);
+		if (!coder->ignore_check)
+			lzma_check_update(&coder->check, coder->block->check,
+					out + out_start, out_used);
 
 		if (ret != LZMA_STREAM_END)
 			return ret;
@@ -140,7 +144,9 @@ block_decode(lzma_coder *coder, const lzma_allocator *allocator,
 		if (coder->block->check == LZMA_CHECK_NONE)
 			return LZMA_STREAM_END;
 
-		lzma_check_finish(&coder->check, coder->block->check);
+		if (!coder->ignore_check)
+			lzma_check_finish(&coder->check, coder->block->check);
+
 		coder->sequence = SEQ_CHECK;
 
 	// Fall through
@@ -155,7 +161,8 @@ block_decode(lzma_coder *coder, const lzma_allocator *allocator,
 		// Validate the Check only if we support it.
 		// coder->check.buffer may be uninitialized
 		// when the Check ID is not supported.
-		if (lzma_check_is_supported(coder->block->check)
+		if (!coder->ignore_check
+				&& lzma_check_is_supported(coder->block->check)
 				&& memcmp(coder->block->raw_check,
 					coder->check.buffer.u8,
 					check_size) != 0)
@@ -224,6 +231,9 @@ lzma_block_decoder_init(lzma_next_coder *next, const lzma_allocator *allocator,
 	next->coder->check_pos = 0;
 	lzma_check_init(&next->coder->check, block->check);
 
+	next->coder->ignore_check = block->version >= 1
+			? block->ignore_check : false;
+
 	// Initialize the filter chain.
 	return lzma_raw_decoder_init(&next->coder->next, allocator,
 			block->filters);
diff --git a/src/liblzma/common/block_encoder.c b/src/liblzma/common/block_encoder.c
index 15f55f7a..def58641 100644
--- a/src/liblzma/common/block_encoder.c
+++ b/src/liblzma/common/block_encoder.c
@@ -166,7 +166,7 @@ lzma_block_encoder_init(lzma_next_coder *next, const lzma_allocator *allocator,
 
 	// The contents of the structure may depend on the version so
 	// check the version first.
-	if (block->version != 0)
+	if (block->version > 1)
 		return LZMA_OPTIONS_ERROR;
 
 	// If the Check ID is not supported, we cannot calculate the check and
diff --git a/src/liblzma/common/block_header_decoder.c b/src/liblzma/common/block_header_decoder.c
index 416642cd..1dd982f6 100644
--- a/src/liblzma/common/block_header_decoder.c
+++ b/src/liblzma/common/block_header_decoder.c
@@ -46,8 +46,16 @@ lzma_block_header_decode(lzma_block *block,
 		block->filters[i].options = NULL;
 	}
 
-	// Always zero for now.
-	block->version = 0;
+	// Versions 0 and 1 are supported. If a newer version was specified,
+	// we need to downgrade it.
+	if (block->version > 1)
+		block->version = 1;
+
+	// This isn't a Block Header option, but since the decompressor will
+	// read it if version >= 1, it's better to initialize it here than
+	// to expect the caller to do it since in almost all cases this
+	// should be false.
+	block->ignore_check = false;
 
 	// Validate Block Header Size and Check type. The caller must have
 	// already set these, so it is a programming error if this test fails.
diff --git a/src/liblzma/common/block_header_encoder.c b/src/liblzma/common/block_header_encoder.c
index 707dd0cb..5c5f5424 100644
--- a/src/liblzma/common/block_header_encoder.c
+++ b/src/liblzma/common/block_header_encoder.c
@@ -17,7 +17,7 @@
 extern LZMA_API(lzma_ret)
 lzma_block_header_size(lzma_block *block)
 {
-	if (block->version != 0)
+	if (block->version > 1)
 		return LZMA_OPTIONS_ERROR;
 
 	// Block Header Size + Block Flags + CRC32.
diff --git a/src/liblzma/common/block_util.c b/src/liblzma/common/block_util.c
index 62c93454..00c7fe8d 100644
--- a/src/liblzma/common/block_util.c
+++ b/src/liblzma/common/block_util.c
@@ -51,7 +51,7 @@ lzma_block_unpadded_size(const lzma_block *block)
 	// NOTE: This function is used for validation too, so it is
 	// essential that these checks are always done even if
 	// Compressed Size is unknown.
-	if (block == NULL || block->version != 0
+	if (block == NULL || block->version > 1
 			|| block->header_size < LZMA_BLOCK_HEADER_SIZE_MIN
 			|| block->header_size > LZMA_BLOCK_HEADER_SIZE_MAX
 			|| (block->header_size & 3)