/*

  zip_source_crc.c -- pass-through source that calculates CRC32 and size

  Copyright (C) 2009-2025 Dieter Baron and Thomas Klausner

  This file is part of libzip, a library to manipulate ZIP archives.

  The authors can be contacted at <info@libzip.org>

  Redistribution and use in source and binary forms, with or without

  modification, are permitted provided that the following conditions

  are met:

  1. Redistributions of source code must retain the above copyright

     notice, this list of conditions and the following disclaimer.

  2. Redistributions in binary form must reproduce the above copyright

     notice, this list of conditions and the following disclaimer in

     the documentation and/or other materials provided with the

     distribution.

  3. The names of the authors may not be used to endorse or promote

     products derived from this software without specific prior

     written permission.

  THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS

  OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED

  WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE

  ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY

  DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL

  DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE

  GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS

  INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER

  IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR

  OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN

  IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

*/

#include <limits.h>

#include <stdlib.h>

#include <zlib.h>

#include "zipint.h"

struct crc_context {

    int validate;     /* whether to check CRC on EOF and return error on mismatch */

    int crc_complete; /* whether CRC was computed for complete file */

    zip_error_t error;

    zip_uint64_t size;

    zip_uint64_t position;     /* current reading position */

    zip_uint64_t crc_position; /* how far we've computed the CRC */

    zip_uint32_t crc;

};

static void crc_context_free(struct crc_context *ctx);

static struct crc_context *crc_context_new(void);

static void crc_context_read_init(struct crc_context *ctx);

static zip_int64_t crc_read(zip_source_t *, void *, void *, zip_uint64_t, zip_source_cmd_t);

static zip_int64_t validate_crc(struct crc_context *ctx, zip_source_t *src);

zip_source_t *zip_source_crc_create(zip_source_t *src, int validate, zip_error_t *error) {

    struct crc_context *ctx;

    zip_source_t *new_src;

    if (src == NULL) {

        zip_error_set(error, ZIP_ER_INVAL, 0);

        return NULL;

    }

    if ((ctx = crc_context_new()) == NULL) {

        zip_error_set(error, ZIP_ER_MEMORY, 0);

        return NULL;

    }

    ctx->validate = validate;

    new_src = zip_source_layered_create(src, crc_read, ctx, error);

    if (new_src == NULL) {

        crc_context_free(ctx);

        return NULL;

    }

    return new_src;

}

static zip_int64_t crc_read(zip_source_t *src, void *_ctx, void *data, zip_uint64_t len, zip_source_cmd_t cmd) {

    struct crc_context *ctx;

    zip_int64_t n;

    ctx = (struct crc_context *)_ctx;

    switch (cmd) {

    case ZIP_SOURCE_OPEN:

        crc_context_read_init(ctx);

        return 0;

    case ZIP_SOURCE_READ:

        if ((n = zip_source_read(src, data, len)) < 0) {

            zip_error_set_from_source(&ctx->error, src);

            return -1;

        }

        if (n == 0) {

            return validate_crc(ctx, src);

        }

        else {

            /*

             We can only compute the CRC data in the correct order. So we update the CRC for data read this time that starts at ctx->crc_position.

             If we already computed the CRC for the whole file, or if there is a gap between ctx->crc_position and the start of new data, or if we already computed the CRC for all new data read, we don't update the CRC.

             ctx->position is the position of the first byte in data.

             ctx->crc_position is the position of the first byte in data that has not been included  in the CRC yet.

             Therefore, we want to compute the CRC for data[ctx->crc_position - ctx->position .. n-1].

            */

            if (!ctx->crc_complete && ctx->position <= ctx->crc_position && ctx->crc_position < ctx->position + (zip_uint64_t)n) {

                zip_uint64_t i, nn;

                for (i = ctx->crc_position - ctx->position; i < (zip_uint64_t)n; i += nn) {

                    nn = ZIP_MIN(UINT_MAX, (zip_uint64_t)n - i);

                    ctx->crc = (zip_uint32_t)crc32(ctx->crc, (const Bytef *)data + i, (uInt)nn);

                    ctx->crc_position += nn;

                }

            }

        }

        ctx->position += (zip_uint64_t)n;

        return n;

    case ZIP_SOURCE_CLOSE: {

        zip_int64_t ret = zip_source_at_eof(src);

        if (ret < 0) {

            zip_error_set_from_source(&ctx->error, src);

            return -1;

        }

        else if (ret == 1) {

            return validate_crc(ctx, src);

        }

        else {

            return 0;

        }

    }

    case ZIP_SOURCE_STAT: {

        zip_stat_t *st;

        st = (zip_stat_t *)data;

        if (ctx->crc_complete) {

            if ((st->valid & ZIP_STAT_SIZE) && st->size != ctx->size) {

                zip_error_set(&ctx->error, ZIP_ER_DATA_LENGTH, 0);

                return -1;

            }

            /* TODO: Set comp_size, comp_method, encryption_method?

                    After all, this only works for uncompressed data. */

            st->size = ctx->size;

            st->crc = ctx->crc;

            st->comp_size = ctx->size;

            st->comp_method = ZIP_CM_STORE;

            st->encryption_method = ZIP_EM_NONE;

            st->valid |= ZIP_STAT_SIZE | ZIP_STAT_CRC | ZIP_STAT_COMP_SIZE | ZIP_STAT_COMP_METHOD | ZIP_STAT_ENCRYPTION_METHOD;

        }

        return 0;

    }

    case ZIP_SOURCE_ERROR:

        return zip_error_to_data(&ctx->error, data, len);

    case ZIP_SOURCE_FREE:

        crc_context_free(ctx);

        return 0;

    case ZIP_SOURCE_SUPPORTS: {

        zip_int64_t mask = zip_source_supports(src);

        if (mask < 0) {

            zip_error_set_from_source(&ctx->error, src);

            return -1;

        }

        mask &= ~zip_source_make_command_bitmap(ZIP_SOURCE_BEGIN_WRITE, ZIP_SOURCE_COMMIT_WRITE, ZIP_SOURCE_ROLLBACK_WRITE, ZIP_SOURCE_SEEK_WRITE, ZIP_SOURCE_TELL_WRITE, ZIP_SOURCE_REMOVE, ZIP_SOURCE_GET_FILE_ATTRIBUTES, -1);

        mask |= zip_source_make_command_bitmap(ZIP_SOURCE_FREE, -1);

        return mask;

    }

    case ZIP_SOURCE_SEEK: {

        zip_int64_t new_position;

        zip_source_args_seek_t *args = ZIP_SOURCE_GET_ARGS(zip_source_args_seek_t, data, len, &ctx->error);

        if (args == NULL) {

            return -1;

        }

        if (zip_source_seek(src, args->offset, args->whence) < 0 || (new_position = zip_source_tell(src)) < 0) {

            zip_error_set_from_source(&ctx->error, src);

            return -1;

        }

        ctx->position = (zip_uint64_t)new_position;

        return 0;

    }

    case ZIP_SOURCE_TELL:

        return (zip_int64_t)ctx->position;

    default:

        return zip_source_pass_to_lower_layer(src, data, len, cmd);

    }

}

zip_int64_t validate_crc(struct crc_context *ctx, zip_source_t *src) {

    struct zip_stat st;

    ctx->size = ctx->position;

    if (ctx->validate) {

        if (zip_source_stat(src, &st) < 0) {

            zip_error_set_from_source(&ctx->error, src);

            return -1;

        }

    }

    if (ctx->crc_position == ctx->position) {

        ctx->crc_complete = 1;

        if (ctx->validate) {

            if ((st.valid & ZIP_STAT_CRC) && st.crc != ctx->crc) {

                zip_error_set(&ctx->error, ZIP_ER_CRC, 0);

                return -1;

            }

        }

    }

    if (ctx->validate) {

        if ((st.valid & ZIP_STAT_SIZE) && st.size != ctx->size) {

            /* We don't have the index here, but the caller should know which file they are reading from. */

            zip_error_set(&ctx->error, ZIP_ER_INCONS, MAKE_DETAIL_WITH_INDEX(ZIP_ER_DETAIL_INVALID_FILE_LENGTH, MAX_DETAIL_INDEX));

            return -1;

        }

    }

    return 0;

}

static struct crc_context *crc_context_new(void) {

    struct crc_context *ctx;

    if ((ctx = (struct crc_context *)malloc(sizeof(*ctx))) == NULL) {

        return NULL;

    }

    zip_error_init(&ctx->error);

    ctx->validate = 0;

    crc_context_read_init(ctx);

    return ctx;

}

static void crc_context_free(struct crc_context *ctx) {

    if (ctx == NULL) {

        return;

    }

    zip_error_fini(&ctx->error);

    free(ctx);

}

static void crc_context_read_init(struct crc_context *ctx) {

    ctx->position = 0;

    ctx->crc_complete = 0;

    ctx->crc_position = 0;

    ctx->crc = (zip_uint32_t)crc32(0, NULL, 0);

    ctx->size = 0;

}