/*
  $NiH: zip_open.c,v 1.28 2005/01/11 19:01:53 dillo Exp $

  zip_open.c -- open zip archive
  Copyright (C) 1999, 2003, 2004 Dieter Baron and Thomas Klausner

  This file is part of libzip, a library to manipulate ZIP archives.
  The authors can be contacted at <nih@giga.or.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 <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>

#include "zip.h"
#include "zipint.h"

static void set_error(int *, struct zip_error *, int);
static int _zip_checkcons(FILE *, struct zip_cdir *, struct zip_error *);
static int _zip_headercomp(struct zip_dirent *, int,
			   struct zip_dirent *, int);
static void *_zip_memdup(const void *, size_t, struct zip_error *);
static unsigned char *_zip_memmem(const unsigned char *, int,
				  const unsigned char *, int);
static struct zip_cdir *_zip_readcdir(FILE *, unsigned char *, unsigned char *,
				 int, struct zip_error *);



struct zip *
zip_open(const char *fn, int flags, int *zep)
{
    FILE *fp;
    unsigned char *buf, *match;
    int a, i, buflen, best;
    struct zip *za;
    struct zip_cdir *cdir, *cdirnew;
    long len;
    struct stat st;
    struct zip_error error, err2;

    if (fn == NULL) {
	set_error(zep, NULL, ZIP_ER_INVAL);
	return NULL;
    }
    
    if (stat(fn, &st) != 0) {
	if (flags & ZIP_CREATE) {
	    if ((za=_zip_new(&error)) == NULL) {
		set_error(zep, &error, 0);
		return NULL;
	    }
	    
	    za->zn = strdup(fn);
	    if (!za->zn) {
		_zip_free(za);
		set_error(zep, NULL, ZIP_ER_MEMORY);
		return NULL;
	    }
	    return za;
	}
	else {
	    set_error(zep, NULL, ZIP_ER_OPEN);
	    return NULL;
	}
    }
    else if ((flags & ZIP_EXCL)) {
	set_error(zep, NULL, ZIP_ER_EXISTS);
	return NULL;
    }
    /* ZIP_CREATE gets ignored if file exists and not ZIP_EXCL,
       just like open() */
    
    if ((fp=fopen(fn, "rb")) == NULL) {
	set_error(zep, NULL, ZIP_ER_OPEN);
	return NULL;
    }
    
    clearerr(fp);
    fseek(fp, 0, SEEK_END);
    len = ftell(fp);
    i = fseek(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);
	fclose(fp);
	return NULL;
    }

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

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

    if (ferror(fp)) {
	set_error(zep, NULL, ZIP_ER_READ);
	free(buf);
	fclose(fp);
	return NULL;
    }
    
    best = -1;
    cdir = NULL;
    match = buf;
    while ((match=_zip_memmem(match, buflen-(match-buf)-18,
			      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, match-1, buflen, &err2)) == NULL)
	    continue;	    

	if (cdir) {
	    if (best <= 0)
		best = _zip_checkcons(fp, cdir, &err2);
	    a = _zip_checkcons(fp, cdirnew, &err2);
	    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, &err2);
	    else
		best = 0;
	}
	cdirnew = NULL;
    }

    free(buf);
    
    if (best < 0) {
	/* no consistent eocd found */
	set_error(zep, NULL, ZIP_ER_NOZIP);
	_zip_cdir_free(cdir);
	fclose(fp);
	return NULL;
    }

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

    za->zp = fp;
    za->cdir = cdir;
    
    if ((za->zn=strdup(fn)) == NULL) {
	set_error(zep, NULL, ZIP_ER_MEMORY);
	_zip_free(za);
	return NULL;
    }

    if ((za->entry=malloc(sizeof(*(za->entry))*cdir->nentry)) == NULL) {
	set_error(zep, NULL, ZIP_ER_MEMORY);
	_zip_free(za);
	return NULL;
    }
    for (i=0; i<cdir->nentry; i++)
	_zip_entry_new(za);

    return za;
}



static void
set_error(int *zep, 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, unsigned char *buf, unsigned char *eocd, int buflen,
	      struct zip_error *error)
{
    struct zip_cdir *cd;
    unsigned char *cdp, **bufp;
    int i, comlen, nentry;

    comlen = buf + buflen - eocd - EOCDLEN;
    if (comlen < 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;
    }

    cdp = eocd + 8;
    /* number of cdir-entries on this disk */
    i = _zip_read2(&cdp);
    /* number of cdir-entries */
    nentry = _zip_read2(&cdp);

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

    cd->size = _zip_read4(&cdp);
    cd->offset = _zip_read4(&cdp);
    cd->comment = NULL;
    cd->comment_len = _zip_read2(&cdp);

    /* some zip files are broken; their internal comment length
       says 0, but they have 1 or 2 comment bytes */
    if ((comlen-cd->comment_len < 0) || (comlen-cd->comment_len > 2)
	|| (cd->nentry != i)) {
	/* comment size wrong -- too few or too many left after central dir */
	/* or number of cdir-entries on this disk != number of cdir-entries */
	_zip_error_set(error, ZIP_ER_NOZIP, 0);
	free(cd);
	return NULL;
    }

    if (cd->comment_len)
	if ((cd->comment=_zip_memdup(eocd+EOCDLEN, cd->comment_len, error))
	    == NULL) {
	    free(cd);
	    return NULL;
	}

    cdp = eocd;
    if (cd->size < eocd-buf) {
	/* if buffer already read in, use it */
	cdp = eocd - cd->size;
	bufp = &cdp;
    }
    else {
	/* go to start of cdir and read it entry by entry */
	bufp = NULL;
	clearerr(fp);
	fseek(fp, -(cd->size+cd->comment_len+EOCDLEN), SEEK_END);
	if (ferror(fp) || (ftell(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);
	    free(cd);
	    return NULL;
	}
    }

    for (i=0; i<cd->nentry; i++) {
	if ((_zip_dirent_read(cd->entry+i, fp, bufp, eocd-cdp, 0,
			      error)) < 0) {
	    cd->nentry = i;
	    _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 int
_zip_checkcons(FILE *fp, struct zip_cdir *cd, struct zip_error *error)
{
    int min, max, i, j;
    struct zip_dirent temp;

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

    for (i=0; i<cd->nentry; i++) {
	if (cd->entry[i].offset < min)
	    min = cd->entry[i].offset;
	if (min < 0) {
	    _zip_error_set(error, ZIP_ER_NOZIP, 0);
	    return -1;
	}
	
	j = cd->entry[i].offset + cd->entry[i].comp_size
	    + cd->entry[i].filename_len + LENTRYSIZE;
	if (j > max)
	    max = j;
	if (max > cd->offset) {
	    _zip_error_set(error, ZIP_ER_NOZIP, 0);
	    return -1;
	}
	
	if (fseek(fp, cd->entry[i].offset, SEEK_SET) != 0) {
	    _zip_error_set(error, ZIP_ER_SEEK, 0);
	    return -1;
	}
	
	if (_zip_dirent_read(&temp, fp, NULL, 0, 1, error) == -1)
	    return -1;
	
	if (_zip_headercomp(cd->entry+i, 0, &temp, 1) != 0) {
	    _zip_error_set(error, ZIP_ER_NOZIP, 0);
	    _zip_dirent_finalize(&temp);
	    return -1;
	}
	_zip_dirent_finalize(&temp);
    }

    return max - min;
}



/* _zip_headercomp:
   compares two headers h1 and h2; if they are local headers, set
   local1p or local2p respectively to 1, else 0. Return 0 if they
   are identical, -1 if not. */

static int
_zip_headercomp(struct zip_dirent *h1, int local1p, struct zip_dirent *h2,
	   int local2p)
{
    if ((h1->version_needed != h2->version_needed)
#if 0
	/* some zip-files have different values in local
	   and global headers for the bitflags */
	|| (h1->bitflags != h2->bitflags)
#endif
	|| (h1->comp_method != h2->comp_method)
	|| (h1->last_mod != h2->last_mod)
	|| (h1->crc != h2->crc)
	|| (h1->comp_size != h2->comp_size)
	|| (h1->uncomp_size != h2->uncomp_size)
	|| (h1->filename_len != h2->filename_len)
	|| !h1->filename || !h2->filename
	|| strcmp(h1->filename, h2->filename))
	return -1;

    if ((local1p == local2p)
	&& ((h1->extrafield_len != h2->extrafield_len)
	    || (h1->extrafield_len && h2->extrafield
		&& memcmp(h1->extrafield, h2->extrafield,
			  h1->extrafield_len))))
	return -1;

    /* if either is local, nothing more to check */
    if (local1p || local2p)
	return 0;

    if ((h1->version_madeby != h2->version_madeby)
	|| (h1->disk_number != h2->disk_number)
	|| (h1->int_attrib != h2->int_attrib)
	|| (h1->ext_attrib != h2->ext_attrib)
	|| (h1->offset != h2->offset)
	|| (h1->comment_len != h2->comment_len)
	|| (h1->comment_len && h2->comment
	    && memcmp(h1->comment, h2->comment, h1->comment_len)))
	return -1;

    return 0;
}



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

    return NULL;
}



static void *
_zip_memdup(const void *mem, size_t len, struct zip_error *error)
{
    void *ret;

    ret = malloc(len);
    if (!ret) {
	_zip_error_set(error, ZIP_ER_MEMORY, 0);
	return NULL;
    }

    memcpy(ret, mem, len);

    return ret;
}