source: vbox/trunk/src/libs/liblzma-5.4.1/common/index_hash.c

///////////////////////////////////////////////////////////////////////////////
//
/// \file       index_hash.c
/// \brief      Validates Index by using a hash function
//
//  Author:     Lasse Collin
//
//  This file has been put into the public domain.
//  You can do whatever you want with this file.
//
///////////////////////////////////////////////////////////////////////////////

#include "common.h"
#include "index.h"
#include "check.h"


typedef struct {
        /// Sum of the Block sizes (including Block Padding)
        lzma_vli blocks_size;

        /// Sum of the Uncompressed Size fields
        lzma_vli uncompressed_size;

        /// Number of Records
        lzma_vli count;

        /// Size of the List of Index Records as bytes
        lzma_vli index_list_size;

        /// Check calculated from Unpadded Sizes and Uncompressed Sizes.
        lzma_check_state check;

} lzma_index_hash_info;


struct lzma_index_hash_s {
        enum {
                SEQ_BLOCK,
                SEQ_COUNT,
                SEQ_UNPADDED,
                SEQ_UNCOMPRESSED,
                SEQ_PADDING_INIT,
                SEQ_PADDING,
                SEQ_CRC32,
        } sequence;

        /// Information collected while decoding the actual Blocks.
        lzma_index_hash_info blocks;

        /// Information collected from the Index field.
        lzma_index_hash_info records;

        /// Number of Records not fully decoded
        lzma_vli remaining;

        /// Unpadded Size currently being read from an Index Record.
        lzma_vli unpadded_size;

        /// Uncompressed Size currently being read from an Index Record.
        lzma_vli uncompressed_size;

        /// Position in variable-length integers when decoding them from
        /// the List of Records.
        size_t pos;

        /// CRC32 of the Index
        uint32_t crc32;
};


extern LZMA_API(lzma_index_hash *)
lzma_index_hash_init(lzma_index_hash *index_hash,
                const lzma_allocator *allocator)
{
        if (index_hash == NULL) {
                index_hash = lzma_alloc(sizeof(lzma_index_hash), allocator);
                if (index_hash == NULL)
                        return NULL;
        }

        index_hash->sequence = SEQ_BLOCK;
        index_hash->blocks.blocks_size = 0;
        index_hash->blocks.uncompressed_size = 0;
        index_hash->blocks.count = 0;
        index_hash->blocks.index_list_size = 0;
        index_hash->records.blocks_size = 0;
        index_hash->records.uncompressed_size = 0;
        index_hash->records.count = 0;
        index_hash->records.index_list_size = 0;
        index_hash->unpadded_size = 0;
        index_hash->uncompressed_size = 0;
        index_hash->pos = 0;
        index_hash->crc32 = 0;

        // These cannot fail because LZMA_CHECK_BEST is known to be supported.
        (void)lzma_check_init(&index_hash->blocks.check, LZMA_CHECK_BEST);
        (void)lzma_check_init(&index_hash->records.check, LZMA_CHECK_BEST);

        return index_hash;
}


extern LZMA_API(void)
lzma_index_hash_end(lzma_index_hash *index_hash,
                const lzma_allocator *allocator)
{
        lzma_free(index_hash, allocator);
        return;
}


extern LZMA_API(lzma_vli)
lzma_index_hash_size(const lzma_index_hash *index_hash)
{
        // Get the size of the Index from ->blocks instead of ->records for
        // cases where application wants to know the Index Size before
        // decoding the Index.
        return index_size(index_hash->blocks.count,
                        index_hash->blocks.index_list_size);
}


/// Updates the sizes and the hash without any validation.
static void
hash_append(lzma_index_hash_info *info, lzma_vli unpadded_size,
                lzma_vli uncompressed_size)
{
        info->blocks_size += vli_ceil4(unpadded_size);
        info->uncompressed_size += uncompressed_size;
        info->index_list_size += lzma_vli_size(unpadded_size)
                        + lzma_vli_size(uncompressed_size);
        ++info->count;

        const lzma_vli sizes[2] = { unpadded_size, uncompressed_size };
        lzma_check_update(&info->check, LZMA_CHECK_BEST,
                        (const uint8_t *)(sizes), sizeof(sizes));

        return;
}


extern LZMA_API(lzma_ret)
lzma_index_hash_append(lzma_index_hash *index_hash, lzma_vli unpadded_size,
                lzma_vli uncompressed_size)
{
        // Validate the arguments.
        if (index_hash == NULL || index_hash->sequence != SEQ_BLOCK
                        || unpadded_size < UNPADDED_SIZE_MIN
                        || unpadded_size > UNPADDED_SIZE_MAX
                        || uncompressed_size > LZMA_VLI_MAX)
                return LZMA_PROG_ERROR;

        // Update the hash.
        hash_append(&index_hash->blocks, unpadded_size, uncompressed_size);

        // Validate the properties of *info are still in allowed limits.
        if (index_hash->blocks.blocks_size > LZMA_VLI_MAX
                        || index_hash->blocks.uncompressed_size > LZMA_VLI_MAX
                        || index_size(index_hash->blocks.count,
                                        index_hash->blocks.index_list_size)
                                > LZMA_BACKWARD_SIZE_MAX
                        || index_stream_size(index_hash->blocks.blocks_size,
                                        index_hash->blocks.count,
                                        index_hash->blocks.index_list_size)
                                > LZMA_VLI_MAX)
                return LZMA_DATA_ERROR;

        return LZMA_OK;
}


extern LZMA_API(lzma_ret)
lzma_index_hash_decode(lzma_index_hash *index_hash, const uint8_t *in,
                size_t *in_pos, size_t in_size)
{
        // Catch zero input buffer here, because in contrast to Index encoder
        // and decoder functions, applications call this function directly
        // instead of via lzma_code(), which does the buffer checking.
        if (*in_pos >= in_size)
                return LZMA_BUF_ERROR;

        // NOTE: This function has many similarities to index_encode() and
        // index_decode() functions found from index_encoder.c and
        // index_decoder.c. See the comments especially in index_encoder.c.
        const size_t in_start = *in_pos;
        lzma_ret ret = LZMA_OK;

        while (*in_pos < in_size)
        switch (index_hash->sequence) {
        case SEQ_BLOCK:
                // Check the Index Indicator is present.
                if (in[(*in_pos)++] != INDEX_INDICATOR)
                        return LZMA_DATA_ERROR;

                index_hash->sequence = SEQ_COUNT;
                break;

        case SEQ_COUNT: {
                ret = lzma_vli_decode(&index_hash->remaining,
                                &index_hash->pos, in, in_pos, in_size);
                if (ret != LZMA_STREAM_END)
                        goto out;

                // The count must match the count of the Blocks decoded.
                if (index_hash->remaining != index_hash->blocks.count)
                        return LZMA_DATA_ERROR;

                ret = LZMA_OK;
                index_hash->pos = 0;

                // Handle the special case when there are no Blocks.
                index_hash->sequence = index_hash->remaining == 0
                                ? SEQ_PADDING_INIT : SEQ_UNPADDED;
                break;
        }

        case SEQ_UNPADDED:
        case SEQ_UNCOMPRESSED: {
                lzma_vli *size = index_hash->sequence == SEQ_UNPADDED
                                ? &index_hash->unpadded_size
                                : &index_hash->uncompressed_size;

                ret = lzma_vli_decode(size, &index_hash->pos,
                                in, in_pos, in_size);
                if (ret != LZMA_STREAM_END)
                        goto out;

                ret = LZMA_OK;
                index_hash->pos = 0;

                if (index_hash->sequence == SEQ_UNPADDED) {
                        if (index_hash->unpadded_size < UNPADDED_SIZE_MIN
                                        || index_hash->unpadded_size
                                                > UNPADDED_SIZE_MAX)
                                return LZMA_DATA_ERROR;

                        index_hash->sequence = SEQ_UNCOMPRESSED;
                } else {
                        // Update the hash.
                        hash_append(&index_hash->records,
                                        index_hash->unpadded_size,
                                        index_hash->uncompressed_size);

                        // Verify that we don't go over the known sizes. Note
                        // that this validation is simpler than the one used
                        // in lzma_index_hash_append(), because here we know
                        // that values in index_hash->blocks are already
                        // validated and we are fine as long as we don't
                        // exceed them in index_hash->records.
                        if (index_hash->blocks.blocks_size
                                        < index_hash->records.blocks_size
                                        || index_hash->blocks.uncompressed_size
                                        < index_hash->records.uncompressed_size
                                        || index_hash->blocks.index_list_size
                                        < index_hash->records.index_list_size)
                                return LZMA_DATA_ERROR;

                        // Check if this was the last Record.
                        index_hash->sequence = --index_hash->remaining == 0
                                        ? SEQ_PADDING_INIT : SEQ_UNPADDED;
                }

                break;
        }

        case SEQ_PADDING_INIT:
                index_hash->pos = (LZMA_VLI_C(4) - index_size_unpadded(
                                index_hash->records.count,
                                index_hash->records.index_list_size)) & 3;
                index_hash->sequence = SEQ_PADDING;

        // Fall through

        case SEQ_PADDING:
                if (index_hash->pos > 0) {
                        --index_hash->pos;
                        if (in[(*in_pos)++] != 0x00)
                                return LZMA_DATA_ERROR;

                        break;
                }

                // Compare the sizes.
                if (index_hash->blocks.blocks_size
                                != index_hash->records.blocks_size
                                || index_hash->blocks.uncompressed_size
                                != index_hash->records.uncompressed_size
                                || index_hash->blocks.index_list_size
                                != index_hash->records.index_list_size)
                        return LZMA_DATA_ERROR;

                // Finish the hashes and compare them.
                lzma_check_finish(&index_hash->blocks.check, LZMA_CHECK_BEST);
                lzma_check_finish(&index_hash->records.check, LZMA_CHECK_BEST);
                if (memcmp(index_hash->blocks.check.buffer.u8,
                                index_hash->records.check.buffer.u8,
                                lzma_check_size(LZMA_CHECK_BEST)) != 0)
                        return LZMA_DATA_ERROR;

                // Finish the CRC32 calculation.
                index_hash->crc32 = lzma_crc32(in + in_start,
                                *in_pos - in_start, index_hash->crc32);

                index_hash->sequence = SEQ_CRC32;

        // Fall through

        case SEQ_CRC32:
                do {
                        if (*in_pos == in_size)
                                return LZMA_OK;

                        if (((index_hash->crc32 >> (index_hash->pos * 8))
                                        & 0xFF) != in[(*in_pos)++]) {
#ifndef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
                                return LZMA_DATA_ERROR;
#endif
                        }

                } while (++index_hash->pos < 4);

                return LZMA_STREAM_END;

        default:
                assert(0);
                return LZMA_PROG_ERROR;
        }

out:
        // Update the CRC32,
        index_hash->crc32 = lzma_crc32(in + in_start,
                        *in_pos - in_start, index_hash->crc32);

        return ret;
}