source: vbox/trunk/src/libs/liblzma-5.8.1/common/lzip_decoder.c@ 108911

// SPDX-License-Identifier: 0BSD

///////////////////////////////////////////////////////////////////////////////
//
/// \file       lzip_decoder.c
/// \brief      Decodes .lz (lzip) files
//
//  Author:     Michał Górny
//              Lasse Collin
//
///////////////////////////////////////////////////////////////////////////////

#include "lzip_decoder.h"
#include "lzma_decoder.h"
#include "check.h"


// .lz format version 0 lacks the 64-bit Member size field in the footer.
#define LZIP_V0_FOOTER_SIZE 12
#define LZIP_V1_FOOTER_SIZE 20
#define LZIP_FOOTER_SIZE_MAX LZIP_V1_FOOTER_SIZE

// lc/lp/pb are hardcoded in the .lz format.
#define LZIP_LC 3
#define LZIP_LP 0
#define LZIP_PB 2


typedef struct {
        enum {
                SEQ_ID_STRING,
                SEQ_VERSION,
                SEQ_DICT_SIZE,
                SEQ_CODER_INIT,
                SEQ_LZMA_STREAM,
                SEQ_MEMBER_FOOTER,
        } sequence;

        /// .lz member format version
        uint32_t version;

        /// CRC32 of the uncompressed data in the .lz member
        uint32_t crc32;

        /// Uncompressed size of the .lz member
        uint64_t uncompressed_size;

        /// Compressed size of the .lz member
        uint64_t member_size;

        /// Memory usage limit
        uint64_t memlimit;

        /// Amount of memory actually needed
        uint64_t memusage;

        /// If true, LZMA_GET_CHECK is returned after decoding the header
        /// fields. As all files use CRC32 this is redundant but it's
        /// implemented anyway since the initialization functions supports
        /// all other flags in addition to LZMA_TELL_ANY_CHECK.
        bool tell_any_check;

        /// If true, we won't calculate or verify the CRC32 of
        /// the uncompressed data.
        bool ignore_check;

        /// If true, we will decode concatenated .lz members and stop if
        /// non-.lz data is seen after at least one member has been
        /// successfully decoded.
        bool concatenated;

        /// When decoding concatenated .lz members, this is true as long as
        /// we are decoding the first .lz member. This is needed to avoid
        /// incorrect LZMA_FORMAT_ERROR in case there is non-.lz data at
        /// the end of the file.
        bool first_member;

        /// Reading position in the header and footer fields
        size_t pos;

        /// Buffer to hold the .lz footer fields
        uint8_t buffer[LZIP_FOOTER_SIZE_MAX];

        /// Options decoded from the .lz header that needed to initialize
        /// the LZMA1 decoder.
        lzma_options_lzma options;

        /// LZMA1 decoder
        lzma_next_coder lzma_decoder;

} lzma_lzip_coder;


static lzma_ret
lzip_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_lzip_coder *coder = coder_ptr;

        while (true)
        switch (coder->sequence) {
        case SEQ_ID_STRING: {
                // The "ID string" or magic bytes are "LZIP" in US-ASCII.
                const uint8_t lzip_id_string[4] = { 0x4C, 0x5A, 0x49, 0x50 };

                while (coder->pos < sizeof(lzip_id_string)) {
                        if (*in_pos >= in_size) {
                                // If we are on the 2nd+ concatenated member
                                // and the input ends before we can read
                                // the magic bytes, we discard the bytes that
                                // were already read (up to 3) and finish.
                                // See the reasoning below.
                                return !coder->first_member
                                                && action == LZMA_FINISH
                                        ? LZMA_STREAM_END : LZMA_OK;
                        }

                        if (in[*in_pos] != lzip_id_string[coder->pos]) {
                                // The .lz format allows putting non-.lz data
                                // at the end of the file. If we have seen
                                // at least one valid .lz member already,
                                // then we won't consume the byte at *in_pos
                                // and will return LZMA_STREAM_END. This way
                                // apps can easily locate and read the non-.lz
                                // data after the .lz member(s).
                                //
                                // NOTE: If the first 1-3 bytes of the non-.lz
                                // data match the .lz ID string then the first
                                // 1-3 bytes of the junk will get ignored by
                                // us. If apps want to properly locate the
                                // trailing data they must ensure that the
                                // first byte of their custom data isn't the
                                // same as the first byte of .lz ID string.
                                // With the liblzma API we cannot rewind the
                                // input position across calls to lzma_code().
                                return !coder->first_member
                                        ? LZMA_STREAM_END : LZMA_FORMAT_ERROR;
                        }

                        ++*in_pos;
                        ++coder->pos;
                }

                coder->pos = 0;

                coder->crc32 = 0;
                coder->uncompressed_size = 0;
                coder->member_size = sizeof(lzip_id_string);

                coder->sequence = SEQ_VERSION;
                FALLTHROUGH;
        }

        case SEQ_VERSION:
                if (*in_pos >= in_size)
                        return LZMA_OK;

                coder->version = in[(*in_pos)++];

                // We support version 0 and unextended version 1.
                if (coder->version > 1)
                        return LZMA_OPTIONS_ERROR;

                ++coder->member_size;
                coder->sequence = SEQ_DICT_SIZE;

                // .lz versions 0 and 1 use CRC32 as the integrity check
                // so if the application wanted to know that
                // (LZMA_TELL_ANY_CHECK) we can tell it now.
                if (coder->tell_any_check)
                        return LZMA_GET_CHECK;

                FALLTHROUGH;

        case SEQ_DICT_SIZE: {
                if (*in_pos >= in_size)
                        return LZMA_OK;

                const uint32_t ds = in[(*in_pos)++];
                ++coder->member_size;

                // The five lowest bits are for the base-2 logarithm of
                // the dictionary size and the highest three bits are
                // the fractional part (0/16 to 7/16) that will be
                // subtracted to get the final value.
                //
                // For example, with 0xB5:
                //     b2log = 21
                //     fracnum = 5
                //     dict_size = 2^21 - 2^21 * 5 / 16 = 1408 KiB
                const uint32_t b2log = ds & 0x1F;
                const uint32_t fracnum = ds >> 5;

                // The format versions 0 and 1 allow dictionary size in the
                // range [4 KiB, 512 MiB].
                if (b2log < 12 || b2log > 29 || (b2log == 12 && fracnum > 0))
                        return LZMA_DATA_ERROR;

                //   2^[b2log] - 2^[b2log] * [fracnum] / 16
                // = 2^[b2log] - [fracnum] * 2^([b2log] - 4)
                coder->options.dict_size = (UINT32_C(1) << b2log)
                                - (fracnum << (b2log - 4));

                assert(coder->options.dict_size >= 4096);
                assert(coder->options.dict_size <= (UINT32_C(512) << 20));

                coder->options.preset_dict = NULL;
                coder->options.lc = LZIP_LC;
                coder->options.lp = LZIP_LP;
                coder->options.pb = LZIP_PB;

                // Calculate the memory usage.
                coder->memusage = lzma_lzma_decoder_memusage(&coder->options)
                                + LZMA_MEMUSAGE_BASE;

                // Initialization is a separate step because if we return
                // LZMA_MEMLIMIT_ERROR we need to be able to restart after
                // the memlimit has been increased.
                coder->sequence = SEQ_CODER_INIT;
                FALLTHROUGH;
        }

        case SEQ_CODER_INIT: {
                if (coder->memusage > coder->memlimit)
                        return LZMA_MEMLIMIT_ERROR;

                const lzma_filter_info filters[2] = {
                        {
                                .id = LZMA_FILTER_LZMA1,
                                .init = &lzma_lzma_decoder_init,
                                .options = &coder->options,
                        }, {
                                .init = NULL,
                        }
                };

                return_if_error(lzma_next_filter_init(&coder->lzma_decoder,
                                allocator, filters));

                coder->crc32 = 0;
                coder->sequence = SEQ_LZMA_STREAM;
                FALLTHROUGH;
        }

        case SEQ_LZMA_STREAM: {
                const size_t in_start = *in_pos;
                const size_t out_start = *out_pos;

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

                const size_t out_used = *out_pos - out_start;

                coder->member_size += *in_pos - in_start;
                coder->uncompressed_size += out_used;

                // Don't update the CRC32 if the integrity check will be
                // ignored or if there was no new output. The latter is
                // important in case out == NULL to avoid null pointer + 0
                // which is undefined behavior.
                if (!coder->ignore_check && out_used > 0)
                        coder->crc32 = lzma_crc32(out + out_start, out_used,
                                        coder->crc32);

                if (ret != LZMA_STREAM_END)
                        return ret;

                coder->sequence = SEQ_MEMBER_FOOTER;
                FALLTHROUGH;
        }

        case SEQ_MEMBER_FOOTER: {
                // The footer of .lz version 0 lacks the Member size field.
                // This is the only difference between version 0 and
                // unextended version 1 formats.
                const size_t footer_size = coder->version == 0
                                ? LZIP_V0_FOOTER_SIZE
                                : LZIP_V1_FOOTER_SIZE;

                // Copy the CRC32, Data size, and Member size fields to
                // the internal buffer.
                lzma_bufcpy(in, in_pos, in_size, coder->buffer, &coder->pos,
                                footer_size);

                // Return if we didn't get the whole footer yet.
                if (coder->pos < footer_size)
                        return LZMA_OK;

                coder->pos = 0;
                coder->member_size += footer_size;

                // Check that the footer fields match the observed data.
                if (!coder->ignore_check
                                && coder->crc32 != read32le(&coder->buffer[0]))
                        return LZMA_DATA_ERROR;

                if (coder->uncompressed_size != read64le(&coder->buffer[4]))
                        return LZMA_DATA_ERROR;

                if (coder->version > 0) {
                        // .lz version 0 has no Member size field.
                        if (coder->member_size != read64le(&coder->buffer[12]))
                                return LZMA_DATA_ERROR;
                }

                // Decoding is finished if we weren't requested to decode
                // more than one .lz member.
                if (!coder->concatenated)
                        return LZMA_STREAM_END;

                coder->first_member = false;
                coder->sequence = SEQ_ID_STRING;
                break;
        }

        default:
                assert(0);
                return LZMA_PROG_ERROR;
        }

        // Never reached
}


static void
lzip_decoder_end(void *coder_ptr, const lzma_allocator *allocator)
{
        lzma_lzip_coder *coder = coder_ptr;
        lzma_next_end(&coder->lzma_decoder, allocator);
        lzma_free(coder, allocator);
        return;
}


static lzma_check
lzip_decoder_get_check(const void *coder_ptr lzma_attribute((__unused__)))
{
        return LZMA_CHECK_CRC32;
}


static lzma_ret
lzip_decoder_memconfig(void *coder_ptr, uint64_t *memusage,
                uint64_t *old_memlimit, uint64_t new_memlimit)
{
        lzma_lzip_coder *coder = coder_ptr;

        *memusage = coder->memusage;
        *old_memlimit = coder->memlimit;

        if (new_memlimit != 0) {
                if (new_memlimit < coder->memusage)
                        return LZMA_MEMLIMIT_ERROR;

                coder->memlimit = new_memlimit;
        }

        return LZMA_OK;
}


extern lzma_ret
lzma_lzip_decoder_init(
                lzma_next_coder *next, const lzma_allocator *allocator,
                uint64_t memlimit, uint32_t flags)
{
        lzma_next_coder_init(&lzma_lzip_decoder_init, next, allocator);

        if (flags & ~LZMA_SUPPORTED_FLAGS)
                return LZMA_OPTIONS_ERROR;

        lzma_lzip_coder *coder = next->coder;
        if (coder == NULL) {
                coder = lzma_alloc(sizeof(lzma_lzip_coder), allocator);
                if (coder == NULL)
                        return LZMA_MEM_ERROR;

                next->coder = coder;
                next->code = &lzip_decode;
                next->end = &lzip_decoder_end;
                next->get_check = &lzip_decoder_get_check;
                next->memconfig = &lzip_decoder_memconfig;

                coder->lzma_decoder = LZMA_NEXT_CODER_INIT;
        }

        coder->sequence = SEQ_ID_STRING;
        coder->memlimit = my_max(1, memlimit);
        coder->memusage = LZMA_MEMUSAGE_BASE;
        coder->tell_any_check = (flags & LZMA_TELL_ANY_CHECK) != 0;
        coder->ignore_check = (flags & LZMA_IGNORE_CHECK) != 0;
        coder->concatenated = (flags & LZMA_CONCATENATED) != 0;
        coder->first_member = true;
        coder->pos = 0;

        return LZMA_OK;
}


extern LZMA_API(lzma_ret)
lzma_lzip_decoder(lzma_stream *strm, uint64_t memlimit, uint32_t flags)
{
        lzma_next_strm_init(lzma_lzip_decoder_init, strm, memlimit, flags);

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

        return LZMA_OK;
}