// SPDX-License-Identifier: 0BSD

///////////////////////////////////////////////////////////////////////////////

//

/// \file       index_hash.c

/// \brief      Validates Index by using a hash function

//

//  Author:     Lasse Collin

//

///////////////////////////////////////////////////////////////////////////////

#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;

    FALLTHROUGH;

  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;

    FALLTHROUGH;

  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.

  //

  // Avoid null pointer + 0 (undefined behavior) in "in + in_start".

  // In such a case we had no input and thus in_used == 0.

  {

    const size_t in_used = *in_pos - in_start;

    if (in_used > 0)

      index_hash->crc32 = lzma_crc32(in + in_start,

          in_used, index_hash->crc32);

  }

  return ret;

}