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Diffstat (limited to '')
-rw-r--r-- | src/liblzma/common/stream_flags_decoder.c | 88 |
1 files changed, 88 insertions, 0 deletions
diff --git a/src/liblzma/common/stream_flags_decoder.c b/src/liblzma/common/stream_flags_decoder.c new file mode 100644 index 0000000..b8d263b --- /dev/null +++ b/src/liblzma/common/stream_flags_decoder.c @@ -0,0 +1,88 @@ +/////////////////////////////////////////////////////////////////////////////// +// +/// \file stream_flags_decoder.c +/// \brief Decodes Stream Header and Stream Footer from .xz files +// +// Author: Lasse Collin +// +// This file has been put into the public domain. +// You can do whatever you want with this file. +// +/////////////////////////////////////////////////////////////////////////////// + +#include "stream_flags_common.h" + + +static bool +stream_flags_decode(lzma_stream_flags *options, const uint8_t *in) +{ + // Reserved bits must be unset. + if (in[0] != 0x00 || (in[1] & 0xF0)) + return true; + + options->version = 0; + options->check = in[1] & 0x0F; + + return false; +} + + +extern LZMA_API(lzma_ret) +lzma_stream_header_decode(lzma_stream_flags *options, const uint8_t *in) +{ + // Magic + if (memcmp(in, lzma_header_magic, sizeof(lzma_header_magic)) != 0) + return LZMA_FORMAT_ERROR; + + // Verify the CRC32 so we can distinguish between corrupt + // and unsupported files. + const uint32_t crc = lzma_crc32(in + sizeof(lzma_header_magic), + LZMA_STREAM_FLAGS_SIZE, 0); + if (crc != read32le(in + sizeof(lzma_header_magic) + + LZMA_STREAM_FLAGS_SIZE)) { +#ifndef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION + return LZMA_DATA_ERROR; +#endif + } + + // Stream Flags + if (stream_flags_decode(options, in + sizeof(lzma_header_magic))) + return LZMA_OPTIONS_ERROR; + + // Set Backward Size to indicate unknown value. That way + // lzma_stream_flags_compare() can be used to compare Stream Header + // and Stream Footer while keeping it useful also for comparing + // two Stream Footers. + options->backward_size = LZMA_VLI_UNKNOWN; + + return LZMA_OK; +} + + +extern LZMA_API(lzma_ret) +lzma_stream_footer_decode(lzma_stream_flags *options, const uint8_t *in) +{ + // Magic + if (memcmp(in + sizeof(uint32_t) * 2 + LZMA_STREAM_FLAGS_SIZE, + lzma_footer_magic, sizeof(lzma_footer_magic)) != 0) + return LZMA_FORMAT_ERROR; + + // CRC32 + const uint32_t crc = lzma_crc32(in + sizeof(uint32_t), + sizeof(uint32_t) + LZMA_STREAM_FLAGS_SIZE, 0); + if (crc != read32le(in)) { +#ifndef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION + return LZMA_DATA_ERROR; +#endif + } + + // Stream Flags + if (stream_flags_decode(options, in + sizeof(uint32_t) * 2)) + return LZMA_OPTIONS_ERROR; + + // Backward Size + options->backward_size = read32le(in + sizeof(uint32_t)); + options->backward_size = (options->backward_size + 1) * 4; + + return LZMA_OK; +} |