source: xz/vendor/current/src/liblzma/common/block_decoder.c@ 1993

///////////////////////////////////////////////////////////////////////////////
//
/// \file       block_decoder.c
/// \brief      Decodes .xz Blocks
//
//  Author:     Lasse Collin
//
//  This file has been put into the public domain.
//  You can do whatever you want with this file.
//
///////////////////////////////////////////////////////////////////////////////

#include "block_decoder.h"
#include "filter_decoder.h"
#include "check.h"


typedef struct {
        enum {
                SEQ_CODE,
                SEQ_PADDING,
                SEQ_CHECK,
        } sequence;

        /// The filters in the chain; initialized with lzma_raw_decoder_init().
        lzma_next_coder next;

        /// Decoding options; we also write Compressed Size and Uncompressed
        /// Size back to this structure when the decoding has been finished.
        lzma_block *block;

        /// Compressed Size calculated while decoding
        lzma_vli compressed_size;

        /// Uncompressed Size calculated while decoding
        lzma_vli uncompressed_size;

        /// Maximum allowed Compressed Size; this takes into account the
        /// size of the Block Header and Check fields when Compressed Size
        /// is unknown.
        lzma_vli compressed_limit;

        /// Position when reading the Check field
        size_t check_pos;

        /// Check of the uncompressed data
        lzma_check_state check;

        /// True if the integrity check won't be calculated and verified.
        bool ignore_check;
} lzma_block_coder;


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;
}


static lzma_ret
block_decode(void *coder_ptr, const lzma_allocator *allocator,
                const uint8_t *restrict in, size_t *restrict in_pos,
                size_t in_size, uint8_t *restrict out,
                size_t *restrict out_pos, size_t out_size, lzma_action action)
{
        lzma_block_coder *coder = coder_ptr;

        switch (coder->sequence) {
        case SEQ_CODE: {
                const size_t in_start = *in_pos;
                const size_t out_start = *out_pos;

                const lzma_ret ret = coder->next.code(coder->next.coder,
                                allocator, in, in_pos, in_size,
                                out, out_pos, out_size, 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;

                if (!coder->ignore_check)
                        lzma_check_update(&coder->check, coder->block->check,
                                        out + out_start, out_used);

                if (ret != LZMA_STREAM_END)
                        return ret;

                // Compressed and Uncompressed Sizes are now at their final
                // values. Verify that they match the values given to us.
                if (!is_size_valid(coder->compressed_size,
                                        coder->block->compressed_size)
                                || !is_size_valid(coder->uncompressed_size,
                                        coder->block->uncompressed_size))
                        return LZMA_DATA_ERROR;

                // Copy the values into coder->block. The caller
                // may use this information to construct Index.
                coder->block->compressed_size = coder->compressed_size;
                coder->block->uncompressed_size = coder->uncompressed_size;

                coder->sequence = SEQ_PADDING;
        }

        // Fall through

        case SEQ_PADDING:
                // Compressed Data is padded to a multiple of four bytes.
                while (coder->compressed_size & 3) {
                        if (*in_pos >= in_size)
                                return LZMA_OK;

                        // We use compressed_size here just get the Padding
                        // right. The actual Compressed Size was stored to
                        // coder->block already, and won't be modified by
                        // us anymore.
                        ++coder->compressed_size;

                        if (in[(*in_pos)++] != 0x00)
                                return LZMA_DATA_ERROR;
                }

                if (coder->block->check == LZMA_CHECK_NONE)
                        return LZMA_STREAM_END;

                if (!coder->ignore_check)
                        lzma_check_finish(&coder->check, coder->block->check);

                coder->sequence = SEQ_CHECK;

        // Fall through

        case SEQ_CHECK: {
                const size_t check_size = lzma_check_size(coder->block->check);
                lzma_bufcpy(in, in_pos, in_size, coder->block->raw_check,
                                &coder->check_pos, check_size);
                if (coder->check_pos < check_size)
                        return LZMA_OK;

                // Validate the Check only if we support it.
                // coder->check.buffer may be uninitialized
                // when the Check ID is not supported.
                if (!coder->ignore_check
                                && lzma_check_is_supported(coder->block->check)
                                && memcmp(coder->block->raw_check,
                                        coder->check.buffer.u8,
                                        check_size) != 0)
                        return LZMA_DATA_ERROR;

                return LZMA_STREAM_END;
        }
        }

        return LZMA_PROG_ERROR;
}


static void
block_decoder_end(void *coder_ptr, const lzma_allocator *allocator)
{
        lzma_block_coder *coder = coder_ptr;
        lzma_next_end(&coder->next, allocator);
        lzma_free(coder, allocator);
        return;
}


extern lzma_ret
lzma_block_decoder_init(lzma_next_coder *next, const lzma_allocator *allocator,
                lzma_block *block)
{
        lzma_next_coder_init(&lzma_block_decoder_init, next, allocator);

        // Validate the options. lzma_block_unpadded_size() does that for us
        // except for Uncompressed Size and filters. Filters are validated
        // by the raw decoder.
        if (lzma_block_unpadded_size(block) == 0
                        || !lzma_vli_is_valid(block->uncompressed_size))
                return LZMA_PROG_ERROR;

        // Allocate *next->coder if needed.
        lzma_block_coder *coder = next->coder;
        if (coder == NULL) {
                coder = lzma_alloc(sizeof(lzma_block_coder), allocator);
                if (coder == NULL)
                        return LZMA_MEM_ERROR;

                next->coder = coder;
                next->code = &block_decode;
                next->end = &block_decoder_end;
                coder->next = LZMA_NEXT_CODER_INIT;
        }

        // Basic initializations
        coder->sequence = SEQ_CODE;
        coder->block = block;
        coder->compressed_size = 0;
        coder->uncompressed_size = 0;

        // If Compressed Size is not known, we calculate the maximum allowed
        // value so that encoded size of the Block (including Block Padding)
        // is still a valid VLI and a multiple of four.
        coder->compressed_limit
                        = block->compressed_size == LZMA_VLI_UNKNOWN
                                ? (LZMA_VLI_MAX & ~LZMA_VLI_C(3))
                                        - block->header_size
                                        - lzma_check_size(block->check)
                                : block->compressed_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).
        coder->check_pos = 0;
        lzma_check_init(&coder->check, block->check);

        coder->ignore_check = block->version >= 1
                        ? block->ignore_check : false;

        // Initialize the filter chain.
        return lzma_raw_decoder_init(&coder->next, allocator,
                        block->filters);
}


extern LZMA_API(lzma_ret)
lzma_block_decoder(lzma_stream *strm, lzma_block *block)
{
        lzma_next_strm_init(lzma_block_decoder_init, strm, block);

        strm->internal->supported_actions[LZMA_RUN] = true;
        strm->internal->supported_actions[LZMA_FINISH] = true;

        return LZMA_OK;
}