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

// SPDX-License-Identifier: 0BSD

///////////////////////////////////////////////////////////////////////////////
//
/// \file       alone_decoder.c
/// \brief      Decoder for LZMA_Alone files
//
//  Author:     Lasse Collin
//
///////////////////////////////////////////////////////////////////////////////

#include "alone_decoder.h"
#include "lzma_decoder.h"
#include "lz_decoder.h"


typedef struct {
        lzma_next_coder next;

        enum {
                SEQ_PROPERTIES,
                SEQ_DICTIONARY_SIZE,
                SEQ_UNCOMPRESSED_SIZE,
                SEQ_CODER_INIT,
                SEQ_CODE,
        } sequence;

        /// If true, reject files that are unlikely to be .lzma files.
        /// If false, more non-.lzma files get accepted and will give
        /// LZMA_DATA_ERROR either immediately or after a few output bytes.
        bool picky;

        /// Position in the header fields
        size_t pos;

        /// Uncompressed size decoded from the header
        lzma_vli uncompressed_size;

        /// Memory usage limit
        uint64_t memlimit;

        /// Amount of memory actually needed (only an estimate)
        uint64_t memusage;

        /// Options decoded from the header needed to initialize
        /// the LZMA decoder
        lzma_options_lzma options;
} lzma_alone_coder;


static lzma_ret
alone_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_alone_coder *coder = coder_ptr;

        while (*out_pos < out_size
                        && (coder->sequence == SEQ_CODE || *in_pos < in_size))
        switch (coder->sequence) {
        case SEQ_PROPERTIES:
                if (lzma_lzma_lclppb_decode(&coder->options, in[*in_pos]))
                        return LZMA_FORMAT_ERROR;

                coder->sequence = SEQ_DICTIONARY_SIZE;
                ++*in_pos;
                break;

        case SEQ_DICTIONARY_SIZE:
                coder->options.dict_size
                                |= (size_t)(in[*in_pos]) << (coder->pos * 8);

                if (++coder->pos == 4) {
                        if (coder->picky && coder->options.dict_size
                                        != UINT32_MAX) {
                                // A hack to ditch tons of false positives:
                                // We allow only dictionary sizes that are
                                // 2^n or 2^n + 2^(n-1). LZMA_Alone created
                                // only files with 2^n, but accepts any
                                // dictionary size.
                                uint32_t d = coder->options.dict_size - 1;
                                d |= d >> 2;
                                d |= d >> 3;
                                d |= d >> 4;
                                d |= d >> 8;
                                d |= d >> 16;
                                ++d;

                                if (d != coder->options.dict_size)
                                        return LZMA_FORMAT_ERROR;
                        }

                        coder->pos = 0;
                        coder->sequence = SEQ_UNCOMPRESSED_SIZE;
                }

                ++*in_pos;
                break;

        case SEQ_UNCOMPRESSED_SIZE:
                coder->uncompressed_size
                                |= (lzma_vli)(in[*in_pos]) << (coder->pos * 8);
                ++*in_pos;
                if (++coder->pos < 8)
                        break;

                // Another hack to ditch false positives: Assume that
                // if the uncompressed size is known, it must be less
                // than 256 GiB.
                //
                // FIXME? Without picky we allow > LZMA_VLI_MAX which doesn't
                // really matter in this specific situation (> LZMA_VLI_MAX is
                // safe in the LZMA decoder) but it's somewhat weird still.
                if (coder->picky
                                && coder->uncompressed_size != LZMA_VLI_UNKNOWN
                                && coder->uncompressed_size
                                        >= (LZMA_VLI_C(1) << 38))
                        return LZMA_FORMAT_ERROR;

                // Use LZMA_FILTER_LZMA1EXT features to specify the
                // uncompressed size and that the end marker is allowed
                // even when the uncompressed size is known. Both .lzma
                // header and LZMA1EXT use UINT64_MAX indicate that size
                // is unknown.
                coder->options.ext_flags = LZMA_LZMA1EXT_ALLOW_EOPM;
                lzma_set_ext_size(coder->options, coder->uncompressed_size);

                // Calculate the memory usage so that it is ready
                // for SEQ_CODER_INIT.
                coder->memusage = lzma_lzma_decoder_memusage(&coder->options)
                                + LZMA_MEMUSAGE_BASE;

                coder->pos = 0;
                coder->sequence = SEQ_CODER_INIT;
                FALLTHROUGH;

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

                lzma_filter_info filters[2] = {
                        {
                                .id = LZMA_FILTER_LZMA1EXT,
                                .init = &lzma_lzma_decoder_init,
                                .options = &coder->options,
                        }, {
                                .init = NULL,
                        }
                };

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

                coder->sequence = SEQ_CODE;
                break;
        }

        case SEQ_CODE: {
                return coder->next.code(coder->next.coder,
                                allocator, in, in_pos, in_size,
                                out, out_pos, out_size, action);
        }

        default:
                return LZMA_PROG_ERROR;
        }

        return LZMA_OK;
}


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


static lzma_ret
alone_decoder_memconfig(void *coder_ptr, uint64_t *memusage,
                uint64_t *old_memlimit, uint64_t new_memlimit)
{
        lzma_alone_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_alone_decoder_init(lzma_next_coder *next, const lzma_allocator *allocator,
                uint64_t memlimit, bool picky)
{
        lzma_next_coder_init(&lzma_alone_decoder_init, next, allocator);

        lzma_alone_coder *coder = next->coder;

        if (coder == NULL) {
                coder = lzma_alloc(sizeof(lzma_alone_coder), allocator);
                if (coder == NULL)
                        return LZMA_MEM_ERROR;

                next->coder = coder;
                next->code = &alone_decode;
                next->end = &alone_decoder_end;
                next->memconfig = &alone_decoder_memconfig;
                coder->next = LZMA_NEXT_CODER_INIT;
        }

        coder->sequence = SEQ_PROPERTIES;
        coder->picky = picky;
        coder->pos = 0;
        coder->options.dict_size = 0;
        coder->options.preset_dict = NULL;
        coder->options.preset_dict_size = 0;
        coder->uncompressed_size = 0;
        coder->memlimit = my_max(1, memlimit);
        coder->memusage = LZMA_MEMUSAGE_BASE;

        return LZMA_OK;
}


extern LZMA_API(lzma_ret)
lzma_alone_decoder(lzma_stream *strm, uint64_t memlimit)
{
        lzma_next_strm_init(lzma_alone_decoder_init, strm, memlimit, false);

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

        return LZMA_OK;
}