unzip.c

   1 /* unzip.c -- decompress files in gzip or pkzip format.
   2  * Copyright (C) 1992-1993 Jean-loup Gailly
   3  * This is free software; you can redistribute it and/or modify it under the
   4  * terms of the GNU General Public License, see the file COPYING.
   5  *
   6  * The code in this file is derived from the file funzip.c written
   7  * and put in the public domain by Mark Adler.
   8  */
   9
  10 /*
  11    This version can extract files in gzip or pkzip format.
  12    For the latter, only the first entry is extracted, and it has to be
  13    either deflated or stored.
  14  */
  15
  16 #ifdef RCSID
  17 static char rcsid[] = "$Id: unzip.c,v 0.13 1993/06/10 13:29:00 jloup Exp $";
  18 #endif
  19
  20 #include "tailor.h"
  21 #include "gzip.h"
  22 #include "crypt.h"
  23
  24 /* PKZIP header definitions */
  25 #define LOCSIG 0x04034b50L      /* four-byte lead-in (lsb first) */
  26 #define LOCFLG 6                /* offset of bit flag */
  27 #define  CRPFLG 1               /*  bit for encrypted entry */
  28 #define  EXTFLG 8               /*  bit for extended local header */
  29 #define LOCHOW 8                /* offset of compression method */
  30 #define LOCTIM 10               /* file mod time (for decryption) */
  31 #define LOCCRC 14               /* offset of crc */
  32 #define LOCSIZ 18               /* offset of compressed size */
  33 #define LOCLEN 22               /* offset of uncompressed length */
  34 #define LOCFIL 26               /* offset of file name field length */
  35 #define LOCEXT 28               /* offset of extra field length */
  36 #define LOCHDR 30               /* size of local header, including sig */
  37 #define EXTHDR 16               /* size of extended local header, inc sig */
  38
  39
  40 /* Globals */
  41
  42 int decrypt;        /* flag to turn on decryption */
  43 char *key;          /* not used--needed to link crypt.c */
  44 int pkzip = 0;      /* set for a pkzip file */
  45 int ext_header = 0; /* set if extended local header */
  46
  47 /* ===========================================================================
  48  * Check zip file and advance inptr to the start of the compressed data.
  49  * Get ofname from the local header if necessary.
  50  */
  51 int check_zipfile(in)
  52     int in;   /* input file descriptors */
  53 {
  54     uch *h = inbuf + inptr; /* first local header */
  55
  56     ifd = in;
  57
  58     /* Check validity of local header, and skip name and extra fields */
  59     inptr += LOCHDR + SH(h + LOCFIL) + SH(h + LOCEXT);
  60
  61     if (inptr > insize || LG(h) != LOCSIG) {
  62         fprintf(stderr, "\n%s: %s: not a valid zip file\n",
  63                 progname, ifname);
  64         exit_code = ERROR;
  65         return ERROR;
  66     }
  67     method = h[LOCHOW];
  68     if (method != STORED && method != DEFLATED) {
  69         fprintf(stderr,
  70                 "\n%s: %s: first entry not deflated or stored -- use unzip\n",
  71                 progname, ifname);
  72         exit_code = ERROR;
  73         return ERROR;
  74     }
  75
  76     /* If entry encrypted, decrypt and validate encryption header */
  77     if ((decrypt = h[LOCFLG] & CRPFLG) != 0) {
  78         fprintf(stderr, "\n%s: %s: encrypted file -- use unzip\n",
  79                 progname, ifname);
  80         exit_code = ERROR;
  81         return ERROR;
  82     }
  83
  84     /* Save flags for unzip() */
  85     ext_header = (h[LOCFLG] & EXTFLG) != 0;
  86     pkzip = 1;
  87
  88     /* Get ofname and time stamp from local header (to be done) */
  89     return OK;
  90 }
  91
  92 /* ===========================================================================
  93  * Unzip in to out.  This routine works on both gzip and pkzip files.
  94  *
  95  * IN assertions: the buffer inbuf contains already the beginning of
  96  *   the compressed data, from offsets inptr to insize-1 included.
  97  *   The magic header has already been checked. The output buffer is cleared.
  98  */
  99 int unzip(in, out)
 100     int in, out;   /* input and output file descriptors */
 101 {
 102     ulg orig_crc = 0;       /* original crc */
 103     ulg orig_len = 0;       /* original uncompressed length */
 104     int n;
 105     int res;
 106     uch buf[EXTHDR];        /* extended local header */
 107
 108     ifd = in;
 109     ofd = out;
 110
 111     updcrc(NULL, 0);           /* initialize crc */
 112
 113     if (pkzip && !ext_header) {  /* crc and length at the end otherwise */
 114         orig_crc = LG(inbuf + LOCCRC);
 115         orig_len = LG(inbuf + LOCLEN);
 116     }
 117
 118     /* Decompress */
 119     if (method == DEFLATED)  {
 120       res = inflate();
 121
 122         if (res == 3) {
 123             error("out of memory");
 124         } else if (res != 0) {
 125             error("invalid compressed data--format violated");
 126         }
 127
 128     } else if (pkzip && method == STORED) {
 129
 130         register ulg n = LG(inbuf + LOCLEN);
 131
 132         if (n != LG(inbuf + LOCSIZ) - (decrypt ? RAND_HEAD_LEN : 0)) {
 133
 134             fprintf(stderr, "len %ld, siz %ld\n", n, LG(inbuf + LOCSIZ));
 135             error("invalid compressed data--length mismatch");
 136         }
 137         while (n--) {
 138             uch c = (uch)get_byte();
 139 #ifdef CRYPT
 140             if (decrypt) zdecode(c);
 141 #endif
 142             put_ubyte(c);
 143         }
 144         flush_window();
 145     } else {
 146         error("internal error, invalid method");
 147     }
 148
 149     /* Get the crc and original length */
 150     if (!pkzip) {
 151         /* crc32  (see algorithm.doc)
 152          * uncompressed input size modulo 2^32
 153          */
 154         for (n = 0; n < 8; n++) {
 155             buf[n] = (uch)get_byte(); /* may cause an error if EOF */
 156         }
 157         orig_crc = LG(buf);
 158         orig_len = LG(buf+4);
 159
 160     } else if (ext_header) {  /* If extended header, check it */
 161         /* signature - 4bytes: 0x50 0x4b 0x07 0x08
 162          * CRC-32 value
 163          * compressed size 4-bytes
 164          * uncompressed size 4-bytes
 165          */
 166         for (n = 0; n < EXTHDR; n++) {
 167             buf[n] = (uch)get_byte(); /* may cause an error if EOF */
 168         }
 169         orig_crc = LG(buf+4);
 170         orig_len = LG(buf+12);
 171     }
 172
 173     /* Validate decompression */
 174     if (orig_crc != updcrc(outbuf, 0)) {
 175         error("invalid compressed data--crc error");
 176     }
 177     if (orig_len != (ulg)bytes_out) {
 178         error("invalid compressed data--length error");
 179     }
 180
 181     /* Check if there are more entries in a pkzip file */
 182     if (pkzip && inptr + 4 < insize && LG(inbuf+inptr) == LOCSIG) {
 183         if (to_stdout) {
 184             WARN((stderr,
 185                   "%s: %s has more than one entry--rest ignored\n",
 186                   progname, ifname));
 187         } else {
 188             /* Don't destroy the input zip file */
 189             fprintf(stderr,
 190                     "%s: %s has more than one entry -- unchanged\n",
 191                     progname, ifname);
 192             exit_code = ERROR;
 193             ext_header = pkzip = 0;
 194             return ERROR;
 195         }
 196     }
 197     ext_header = pkzip = 0; /* for next file */
 198     return OK;
 199 }