Combine lzma_options_block validation needed by both Block

encoder and decoder, and put the shared things to
block_private.h. Improved the checks a little so that
they may detect too big Compressed Size at initialization
time if lzma_options_block.total_size or .total_limit is
known.

Allow encoding and decoding Blocks with combinations of
fields that are not allowed by the file format specification.
Doing this requires that the application passes such a
combination in lzma_options_lzma; liblzma doesn't do that,
but it's not impossible that someone could find them useful
in some custom file format.

1 files changed, 50 insertions, 0 deletions

diff --git a/src/liblzma/common/block_private.h b/src/liblzma/common/block_private.h
index 8e2db319..16d95b9f 100644
--- a/src/liblzma/common/block_private.h
+++ b/src/liblzma/common/block_private.h
@@ -43,4 +43,54 @@ is_size_valid(lzma_vli size, lzma_vli reference)
 	return reference == LZMA_VLI_VALUE_UNKNOWN || reference == size;
 }
 
+
+/// If any of these tests fail, the caller has to return LZMA_PROG_ERROR.
+static inline bool
+validate_options_1(const lzma_options_block *options)
+{
+	return options == NULL
+			|| !lzma_vli_is_valid(options->compressed_size)
+			|| !lzma_vli_is_valid(options->uncompressed_size)
+			|| !lzma_vli_is_valid(options->total_size)
+			|| !lzma_vli_is_valid(options->total_limit)
+			|| !lzma_vli_is_valid(options->uncompressed_limit);
+}
+
+
+/// If any of these tests fail, the encoder has to return LZMA_PROG_ERROR
+/// because something is going horribly wrong if such values get passed
+/// to the encoder. In contrast, the decoder has to return LZMA_DATA_ERROR,
+/// since these tests failing indicate that something is wrong in the Stream.
+static inline bool
+validate_options_2(const lzma_options_block *options)
+{
+	if ((options->uncompressed_size != LZMA_VLI_VALUE_UNKNOWN
+				&& options->uncompressed_size
+					> options->uncompressed_limit)
+			|| (options->total_size != LZMA_VLI_VALUE_UNKNOWN
+				&& options->total_size
+					> options->total_limit)
+			|| (!options->has_eopm && options->uncompressed_size
+				== LZMA_VLI_VALUE_UNKNOWN)
+			|| options->header_size > options->total_size)
+		return true;
+
+	if (options->compressed_size != LZMA_VLI_VALUE_UNKNOWN) {
+		// Calculate a rough minimum possible valid Total Size of
+		// this Block, and check that total_size and total_limit
+		// are big enough. Note that the real minimum size can be
+		// bigger due to the Check, Uncompressed Size, Backwards
+		// Size, pr Padding being present. A rough check here is
+		// enough for us to catch the most obvious errors as early
+		// as possible.
+		const lzma_vli total_min = options->compressed_size
+				+ (lzma_vli)(options->header_size);
+		if (total_min > options->total_size
+				|| total_min > options->total_limit)
+			return true;
+	}
+
+	return false;
+}
+
 #endif