zip_open.c

/*
  zip_open.c -- open zip archive by name
  Copyright (C) 1999-2012 Dieter Baron and Thomas Klausner

  This file is part of libzip, a library to manipulate ZIP archives.
  The authors can be contacted at <libzip@nih.at>

  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 <sys/stat.h>
#include <errno.h>
#include <limits.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "zipint.h"

static void set_error(int *, const struct zip_error *, int);
static struct zip *_zip_allocate_new(const char *, unsigned int, int *);
static zip_int64_t _zip_checkcons(FILE *, struct zip_cdir *, struct zip_error *);
static void _zip_check_torrentzip(struct zip *, const struct zip_cdir *);
static struct zip_cdir *_zip_find_central_dir(FILE *, unsigned int, int *, off_t);
static int _zip_file_exists(const char *, unsigned int, int *);
static int _zip_headercomp(const struct zip_dirent *, const struct zip_dirent *);
static unsigned char *_zip_memmem(const unsigned char *, size_t,
				  const unsigned char *, size_t);
static struct zip_cdir *_zip_readcdir(FILE *, off_t, unsigned char *, const unsigned char *,
				 size_t, unsigned int, struct zip_error *);
static struct zip_cdir *_zip_read_eocd(const unsigned char *, const unsigned char *, off_t,
				       size_t, unsigned int, struct zip_error *);
static struct zip_cdir *_zip_read_eocd64(FILE *, const unsigned char *, const unsigned char *,
					 off_t, size_t, unsigned int, struct zip_error *);



ZIP_EXTERN struct zip *
zip_open(const char *fn, int _flags, int *zep)
{
    FILE *fp;
    unsigned int flags;

    if (_flags < 0) {
        if (zep)
            *zep = ZIP_ER_INVAL;
        return NULL;
    }
    flags = (unsigned int)_flags;

    switch (_zip_file_exists(fn, flags, zep)) {
    case -1:
	return NULL;
    case 0:
	return _zip_allocate_new(fn, flags, zep);
    default:
	if (flags & ZIP_TRUNCATE) {
	    FILE *f;

	    if ((f = fopen(fn, "rb")) == NULL) {
		set_error(zep, NULL, ZIP_ER_OPEN);
		return NULL;
	    }
	    fclose(f);
	    return _zip_allocate_new(fn, flags, zep);
	}
	break;
    }

    if ((fp=fopen(fn, "rb")) == NULL) {
	set_error(zep, NULL, ZIP_ER_OPEN);
	return NULL;
    }

    return _zip_open(fn, fp, flags, zep);
}


ZIP_EXTERN int
zip_archive_set_tempdir(struct zip *za, const char *tempdir)
{
    char *new_tempdir;

    if (tempdir) {
        if ((new_tempdir = strdup(tempdir)) == NULL) {
            _zip_error_set(&za->error, ZIP_ER_MEMORY, errno);
            return -1;
        }
    }
    else
        new_tempdir = NULL;

    free(za->tempdir);
    za->tempdir = new_tempdir;

    return 0;
}


struct zip *
_zip_open(const char *fn, FILE *fp, unsigned int flags, int *zep)
{
    struct zip *za;
    struct zip_cdir *cdir;
    off_t len;

    if (fseeko(fp, 0, SEEK_END) < 0) {
	*zep = ZIP_ER_SEEK;
	return NULL;
    }
    len = ftello(fp);

    /* treat empty files as empty archives */
    if (len == 0) {
	if ((za=_zip_allocate_new(fn, flags, zep)) == NULL)
	    fclose(fp);
	else
	    za->zp = fp;
	return za;
    }

    cdir = _zip_find_central_dir(fp, flags, zep, len);
    if (cdir == NULL) {
	fclose(fp);
	return NULL;
    }

    if ((za=_zip_allocate_new(fn, flags, zep)) == NULL) {
	_zip_cdir_free(cdir);
	fclose(fp);
	return NULL;
    }

    za->entry = cdir->entry;
    za->nentry = cdir->nentry;
    za->nentry_alloc = cdir->nentry_alloc;
    za->comment_orig = cdir->comment;

    za->zp = fp;

    _zip_check_torrentzip(za, cdir);

    za->ch_flags = za->flags;

    free(cdir);

    return za;
}



static void
set_error(int *zep, const struct zip_error *err, int ze)
{
    int se;

    if (err) {
	_zip_error_get(err, &ze, &se);
	if (zip_error_get_sys_type(ze) == ZIP_ET_SYS)
	    errno = se;
    }

    if (zep)
	*zep = ze;
}



/* _zip_readcdir:
   tries to find a valid end-of-central-directory at the beginning of
   buf, and then the corresponding central directory entries.
   Returns a struct zip_cdir which contains the central directory
   entries, or NULL if unsuccessful. */

static struct zip_cdir *
_zip_readcdir(FILE *fp, off_t buf_offset, unsigned char *buf, const unsigned char *eocd, size_t buflen,
	      unsigned int flags, struct zip_error *error)
{
    struct zip_cdir *cd;
    const unsigned char *cdp;
    const unsigned char **bufp;
    zip_int64_t tail_len, comment_len;
    zip_uint64_t i, left;

    tail_len = buf + buflen - eocd - EOCDLEN;
    if (tail_len < 0) {
	/* not enough bytes left for comment */
	_zip_error_set(error, ZIP_ER_NOZIP, 0);
	return NULL;
    }

    /* check for end-of-central-dir magic */
    if (memcmp(eocd, EOCD_MAGIC, 4) != 0) {
	_zip_error_set(error, ZIP_ER_NOZIP, 0);
	return NULL;
    }

    if (memcmp(eocd+4, "\0\0\0\0", 4) != 0) {
	_zip_error_set(error, ZIP_ER_MULTIDISK, 0);
	return NULL;
    }

    if (eocd-EOCD64LOCLEN >= buf && memcmp(eocd-EOCD64LOCLEN, EOCD64LOC_MAGIC, 4) == 0)
	cd = _zip_read_eocd64(fp, eocd-EOCD64LOCLEN, buf, buf_offset, buflen, flags, error);
    else
	cd = _zip_read_eocd(eocd, buf, buf_offset, buflen, flags, error);

    if (cd == NULL)
	return NULL;

    cdp = eocd + 20;
    comment_len = _zip_read2(&cdp);

    if ((zip_uint64_t)cd->offset+(zip_uint64_t)cd->size > (zip_uint64_t)buf_offset + (zip_uint64_t)(eocd-buf)) {
	/* cdir spans past EOCD record */
	_zip_error_set(error, ZIP_ER_INCONS, 0);
	_zip_cdir_free(cd);
	return NULL;
    }

    if (tail_len < comment_len || ((flags & ZIP_CHECKCONS) && tail_len != comment_len)) {
	_zip_error_set(error, ZIP_ER_INCONS, 0);
	_zip_cdir_free(cd);
	return NULL;
    }

    if (comment_len) {
	if ((cd->comment=_zip_string_new(eocd+EOCDLEN, (zip_uint16_t)comment_len, ZIP_FL_ENC_GUESS, error)) == NULL) {
	    _zip_cdir_free(cd);
	    return NULL;
	}
    }

    if (cd->offset >= buf_offset) {
	/* if buffer already read in, use it */
	cdp = buf + (cd->offset - buf_offset);
	bufp = &cdp;
    }
    else {
	/* go to start of cdir and read it entry by entry */
	bufp = NULL;
	clearerr(fp);
	fseeko(fp, cd->offset, SEEK_SET);
	/* possible consistency check: cd->offset =
	   len-(cd->size+cd->comment_len+EOCDLEN) ? */
	if (ferror(fp) || (ftello(fp) != cd->offset)) {
	    /* seek error or offset of cdir wrong */
	    if (ferror(fp))
		_zip_error_set(error, ZIP_ER_SEEK, errno);
	    else
		_zip_error_set(error, ZIP_ER_NOZIP, 0);
	    _zip_cdir_free(cd);
	    return NULL;
	}
    }

    left = (zip_uint64_t)cd->size;
    i=0;
    while (i<cd->nentry && left > 0) {
	if ((cd->entry[i].orig=_zip_dirent_new()) == NULL
	    || (_zip_dirent_read(cd->entry[i].orig, fp, bufp, &left, 0, error)) < 0) {
	    _zip_cdir_free(cd);
	    return NULL;
	}
	i++;
    }
    if (i != cd->nentry || ((flags & ZIP_CHECKCONS) && left != 0)) {
        _zip_error_set(error, ZIP_ER_INCONS, 0);
        _zip_cdir_free(cd);
        return NULL;
    }

    return cd;
}



/* _zip_checkcons:
   Checks the consistency of the central directory by comparing central
   directory entries with local headers and checking for plausible
   file and header offsets. Returns -1 if not plausible, else the
   difference between the lowest and the highest fileposition reached */

static zip_int64_t
_zip_checkcons(FILE *fp, struct zip_cdir *cd, struct zip_error *error)
{
    zip_uint64_t i;
    zip_uint64_t min, max, j;
    struct zip_dirent temp;

    if (cd->nentry) {
	max = cd->entry[0].orig->offset;
	min = cd->entry[0].orig->offset;
    }
    else
	min = max = 0;

    for (i=0; i<cd->nentry; i++) {
	if (cd->entry[i].orig->offset < min)
	    min = cd->entry[i].orig->offset;
	if (min > (zip_uint64_t)cd->offset) {
	    _zip_error_set(error, ZIP_ER_NOZIP, 0);
	    return -1;
	}

	j = cd->entry[i].orig->offset + cd->entry[i].orig->comp_size
	    + _zip_string_length(cd->entry[i].orig->filename) + LENTRYSIZE;
	if (j > max)
	    max = j;
	if (max > (zip_uint64_t)cd->offset) {
	    _zip_error_set(error, ZIP_ER_NOZIP, 0);
	    return -1;
	}

	if (fseeko(fp, (off_t)cd->entry[i].orig->offset, SEEK_SET) != 0) {
	    _zip_error_set(error, ZIP_ER_SEEK, errno);
	    return -1;
	}

	if (_zip_dirent_read(&temp, fp, NULL, NULL, 1, error) == -1)
	    return -1;

	if (_zip_headercomp(cd->entry[i].orig, &temp) != 0) {
	    _zip_error_set(error, ZIP_ER_INCONS, 0);
	    _zip_dirent_finalize(&temp);
	    return -1;
	}

	cd->entry[i].orig->extra_fields = _zip_ef_merge(cd->entry[i].orig->extra_fields, temp.extra_fields);
	cd->entry[i].orig->local_extra_fields_read = 1;
	temp.extra_fields = NULL;

	_zip_dirent_finalize(&temp);
    }

    return (max-min) < ZIP_INT64_MAX ? (zip_int64_t)(max-min) : ZIP_INT64_MAX;
}



/* _zip_check_torrentzip:
   check whether ZA has a valid TORRENTZIP comment, i.e. is torrentzipped */

static void
_zip_check_torrentzip(struct zip *za, const struct zip_cdir *cdir)
{
    uLong crc_got, crc_should;
    char buf[8+1];
    char *end;

    if (za->zp == NULL || cdir == NULL)
	return;

    if (_zip_string_length(cdir->comment) != TORRENT_SIG_LEN+8
	|| strncmp((const char *)cdir->comment->raw, TORRENT_SIG, TORRENT_SIG_LEN) != 0)
	return;

    memcpy(buf, cdir->comment->raw+TORRENT_SIG_LEN, 8);
    buf[8] = '\0';
    errno = 0;
    crc_should = strtoul(buf, &end, 16);
    if ((crc_should == UINT_MAX && errno != 0) || (end && *end))
	return;

    if (_zip_filerange_crc(za->zp, cdir->offset, cdir->size, &crc_got, NULL) < 0)
	return;

    if (crc_got == crc_should)
	za->flags |= ZIP_AFL_TORRENT;
}




/* _zip_headercomp:
   compares a central directory entry and a local file header
   Return 0 if they are consistent, -1 if not. */

static int
_zip_headercomp(const struct zip_dirent *central, const struct zip_dirent *local)
{
    if ((central->version_needed != local->version_needed)
#if 0
	/* some zip-files have different values in local
	   and global headers for the bitflags */
	|| (central->bitflags != local->bitflags)
#endif
	|| (central->comp_method != local->comp_method)
	|| (central->last_mod != local->last_mod)
	|| !_zip_string_equal(central->filename, local->filename))
	return -1;


    if ((central->crc != local->crc) || (central->comp_size != local->comp_size)
	|| (central->uncomp_size != local->uncomp_size)) {
	/* InfoZip stores valid values in local header even when data descriptor is used.
	   This is in violation of the appnote. */
	if (((local->bitflags & ZIP_GPBF_DATA_DESCRIPTOR) == 0
	     || local->crc != 0 || local->comp_size != 0 || local->uncomp_size != 0))
	    return -1;
    }

    return 0;
}



static struct zip *
_zip_allocate_new(const char *fn, unsigned int flags, int *zep)
{
    struct zip *za;
    struct zip_error error;

    if ((za=_zip_new(&error)) == NULL) {
	set_error(zep, &error, 0);
	return NULL;
    }

    if (fn == NULL)
	za->zn = NULL;
    else {
	za->zn = strdup(fn);
	if (!za->zn) {
	    zip_discard(za);
	    set_error(zep, NULL, ZIP_ER_MEMORY);
	    return NULL;
	}
    }
    za->open_flags = flags;
    return za;
}



static int
_zip_file_exists(const char *fn, unsigned int flags, int *zep)
{
    struct stat st;

    if (fn == NULL) {
	set_error(zep, NULL, ZIP_ER_INVAL);
	return -1;
    }

    if (stat(fn, &st) != 0) {
	if (flags & ZIP_CREATE)
	    return 0;
	else {
	    set_error(zep, NULL, ZIP_ER_OPEN);
	    return -1;
	}
    }
    else if ((flags & ZIP_EXCL)) {
	set_error(zep, NULL, ZIP_ER_EXISTS);
	return -1;
    }
    /* ZIP_CREATE gets ignored if file exists and not ZIP_EXCL,
       just like open() */

    return 1;
}



static struct zip_cdir *
_zip_find_central_dir(FILE *fp, unsigned int flags, int *zep, off_t len)
{
    struct zip_cdir *cdir, *cdirnew;
    unsigned char *buf, *match;
    off_t buf_offset;
    size_t buflen;
    zip_int64_t a, i;
    zip_int64_t best;
    struct zip_error zerr;

    if (len < (off_t)EOCDLEN) {
        set_error(zep, NULL, ZIP_ER_NOZIP);
        return NULL;
    }

    i = fseeko(fp, -(len < CDBUFSIZE ? len : CDBUFSIZE), SEEK_END);
    if (i == -1 && errno != EFBIG) {
	/* seek before start of file on my machine */
	set_error(zep, NULL, ZIP_ER_SEEK);
	return NULL;
    }
    buf_offset = ftello(fp);

    /* 64k is too much for stack */
    if ((buf=(unsigned char *)malloc(CDBUFSIZE)) == NULL) {
	set_error(zep, NULL, ZIP_ER_MEMORY);
	return NULL;
    }

    clearerr(fp);
    buflen = fread(buf, 1, CDBUFSIZE, fp);

    if (ferror(fp)) {
	set_error(zep, NULL, ZIP_ER_READ);
	free(buf);
	return NULL;
    }

    best = -1;
    cdir = NULL;
    match = buf+ (buflen < CDBUFSIZE ? 0 : EOCD64LOCLEN);
    _zip_error_set(&zerr, ZIP_ER_NOZIP, 0);

    while ((match=_zip_memmem(match, buflen-(size_t)(match-buf)-(EOCDLEN-4),
			      (const unsigned char *)EOCD_MAGIC, 4))!=NULL) {
	/* found match -- check, if good */
	/* to avoid finding the same match all over again */
	match++;
	if ((cdirnew=_zip_readcdir(fp, buf_offset, buf, match-1, buflen, flags,
				   &zerr)) == NULL)
	    continue;

	if (cdir) {
	    if (best <= 0)
		best = _zip_checkcons(fp, cdir, &zerr);
	    a = _zip_checkcons(fp, cdirnew, &zerr);
	    if (best < a) {
		_zip_cdir_free(cdir);
		cdir = cdirnew;
		best = a;
	    }
	    else
		_zip_cdir_free(cdirnew);
	}
	else {
	    cdir = cdirnew;
	    if (flags & ZIP_CHECKCONS)
		best = _zip_checkcons(fp, cdir, &zerr);
	    else
		best = 0;
	}
	cdirnew = NULL;
    }

    free(buf);

    if (best < 0) {
	set_error(zep, &zerr, 0);
	_zip_cdir_free(cdir);
	return NULL;
    }

    return cdir;
}



static unsigned char *
_zip_memmem(const unsigned char *big, size_t biglen, const unsigned char *little, size_t littlelen)
{
    const unsigned char *p;

    if ((biglen < littlelen) || (littlelen == 0))
	return NULL;
    p = big-1;
    while ((p=(const unsigned char *)
	        memchr(p+1, little[0], (size_t)(big-(p+1))+(size_t)(biglen-littlelen)+1)) != NULL) {
	if (memcmp(p+1, little+1, littlelen-1)==0)
	    return (unsigned char *)p;
    }

    return NULL;
}



static struct zip_cdir *
_zip_read_eocd(const unsigned char *eocd, const unsigned char *buf, off_t buf_offset, size_t buflen,
	       unsigned int flags, struct zip_error *error)
{
    struct zip_cdir *cd;
    const unsigned char *cdp;
    zip_uint64_t i, nentry, size, offset;

    if (eocd+EOCDLEN > buf+buflen) {
	_zip_error_set(error, ZIP_ER_INCONS, 0);
	return NULL;
    }

    cdp = eocd + 8;

    /* number of cdir-entries on this disk */
    i = _zip_read2(&cdp);
    /* number of cdir-entries */
    nentry = _zip_read2(&cdp);

    if (nentry != i) {
	_zip_error_set(error, ZIP_ER_NOZIP, 0);
	return NULL;
    }

    size = _zip_read4(&cdp);
    offset = _zip_read4(&cdp);

    if (size > ZIP_OFF_MAX || offset > ZIP_OFF_MAX || offset+size > ZIP_OFF_MAX) {
        _zip_error_set(error, ZIP_ER_SEEK, EFBIG);
        return NULL;
    }

    if (offset+size > (zip_uint64_t)(buf_offset + (eocd-buf))) {
	/* cdir spans past EOCD record */
	_zip_error_set(error, ZIP_ER_INCONS, 0);
	return NULL;
    }

    if ((flags & ZIP_CHECKCONS) && offset+size != (zip_uint64_t)(buf_offset + (eocd-buf))) {
	_zip_error_set(error, ZIP_ER_INCONS, 0);
	return NULL;
    }

    if ((cd=_zip_cdir_new(nentry, error)) == NULL)
	return NULL;

    cd->size = (off_t)size;
    cd->offset = (off_t)offset;

    return cd;
}



static struct zip_cdir *
_zip_read_eocd64(FILE *f, const zip_uint8_t *eocd64loc, const zip_uint8_t *buf,
		 off_t buf_offset, size_t buflen, unsigned int flags, struct zip_error *error)
{
    struct zip_cdir *cd;
    zip_uint64_t offset;
    const zip_uint8_t *cdp;
    zip_uint8_t eocd[EOCD64LEN];
    zip_uint64_t eocd_offset;
    zip_uint64_t size, nentry, i;

    cdp = eocd64loc+8;
    eocd_offset = _zip_read8(&cdp);

    if (eocd_offset > ZIP_OFF_MAX || eocd_offset + EOCD64LEN > ZIP_OFF_MAX) {
        _zip_error_set(error, ZIP_ER_SEEK, EFBIG);
        return NULL;
    }

    if (eocd64loc < buf || (off_t)eocd_offset+EOCD64LEN > (buf_offset+(eocd64loc-buf))) {
	_zip_error_set(error, ZIP_ER_INCONS, 0);
	return NULL;
    }

    if ((off_t)eocd_offset >= buf_offset && (off_t)eocd_offset+EOCD64LEN <= buf_offset+(ssize_t)buflen)
	cdp = buf+((off_t)eocd_offset-buf_offset);
    else {
	if (fseeko(f, (off_t)eocd_offset, SEEK_SET) != 0) {
	    _zip_error_set(error, ZIP_ER_SEEK, errno);
	    return NULL;
	}

	clearerr(f);
	if (fread(eocd, 1, EOCD64LEN, f) < EOCD64LEN) {
            _zip_error_set(error, ZIP_ER_READ, errno);
            return NULL;
        }

	if (ferror(f)) {
	    _zip_error_set(error, ZIP_ER_READ, errno);
	    return NULL;
	}

	cdp = eocd;
    }

    if (memcmp(cdp, EOCD64_MAGIC, 4) != 0) {
	_zip_error_set(error, ZIP_ER_INCONS, 0);
	return NULL;
    }
    cdp += 4;

    size = _zip_read8(&cdp);

    if ((flags & ZIP_CHECKCONS) && size+eocd_offset+12 != (zip_uint64_t)(buf_offset+(eocd64loc-buf))) {
	_zip_error_set(error, ZIP_ER_INCONS, 0);
	return NULL;
    }

    cdp += 4; /* skip version made by/needed */
    cdp += 8; /* skip num disks */

    nentry = _zip_read8(&cdp);
    i = _zip_read8(&cdp);

    if (nentry != i) {
	_zip_error_set(error, ZIP_ER_MULTIDISK, 0);
	return NULL;
    }

    size = _zip_read8(&cdp);
    offset = _zip_read8(&cdp);

    if (size > ZIP_OFF_MAX || offset > ZIP_OFF_MAX || offset+size > ZIP_OFF_MAX) {
        _zip_error_set(error, ZIP_ER_SEEK, EFBIG);
        return NULL;
    }
    if ((flags & ZIP_CHECKCONS) && offset+size != eocd_offset) {
	_zip_error_set(error, ZIP_ER_INCONS, 0);
	return NULL;
    }

    if ((cd=_zip_cdir_new(nentry, error)) == NULL)
	return NULL;


    cd->size = (off_t)size;
    cd->offset = (off_t)offset;

    return cd;
}