archival/libunarchive/decompress_uncompress.c

   1 /* vi: set sw=4 ts=4: */
   2 #include "libbb.h"
   3
   4 /* uncompress for busybox -- (c) 2002 Robert Griebl
   5  *
   6  * based on the original compress42.c source
   7  * (see disclaimer below)
   8  */
   9
  10
  11 /* (N)compress42.c - File compression ala IEEE Computer, Mar 1992.
  12  *
  13  * Authors:
  14  *   Spencer W. Thomas   (decvax!harpo!utah-cs!utah-gr!thomas)
  15  *   Jim McKie           (decvax!mcvax!jim)
  16  *   Steve Davies        (decvax!vax135!petsd!peora!srd)
  17  *   Ken Turkowski       (decvax!decwrl!turtlevax!ken)
  18  *   James A. Woods      (decvax!ihnp4!ames!jaw)
  19  *   Joe Orost           (decvax!vax135!petsd!joe)
  20  *   Dave Mack           (csu@alembic.acs.com)
  21  *   Peter Jannesen, Network Communication Systems
  22  *                       (peter@ncs.nl)
  23  *
  24  * marc@suse.de : a small security fix for a buffer overflow
  25  *
  26  * [... History snipped ...]
  27  *
  28  */
  29 #include <stdio.h>
  30 #include <string.h>
  31 #include <unistd.h>
  32
  33 /* Default input buffer size */
  34 #define IBUFSIZ 2048
  35
  36 /* Default output buffer size */
  37 #define OBUFSIZ 2048
  38
  39 /* Defines for third byte of header */
  40 #define MAGIC_1         (char_type)'\037'       /* First byte of compressed file               */
  41 #define MAGIC_2         (char_type)'\235'       /* Second byte of compressed file              */
  42 #define BIT_MASK        0x1f    /* Mask for 'number of compresssion bits'       */
  43                                                         /* Masks 0x20 and 0x40 are free.                */
  44                                                         /* I think 0x20 should mean that there is       */
  45                                                         /* a fourth header byte (for expansion).        */
  46 #define BLOCK_MODE      0x80    /* Block compresssion if table is full and      */
  47                         /* compression rate is dropping flush tables    */
  48                         /* the next two codes should not be changed lightly, as they must not   */
  49                         /* lie within the contiguous general code space.                        */
  50 #define FIRST   257             /* first free entry                             */
  51 #define CLEAR   256             /* table clear output code                      */
  52
  53 #define INIT_BITS 9             /* initial number of bits/code */
  54
  55
  56 /* machine variants which require cc -Dmachine:  pdp11, z8000, DOS */
  57 #define FAST
  58
  59 #define HBITS           17      /* 50% occupancy */
  60 #define HSIZE      (1<<HBITS)
  61 #define HMASK      (HSIZE-1)
  62 #define HPRIME           9941
  63 #define BITS               16
  64 #undef  MAXSEG_64K
  65 #define MAXCODE(n)      (1L << (n))
  66
  67 #define htabof(i)                               htab[i]
  68 #define codetabof(i)                    codetab[i]
  69 #define tab_prefixof(i)                 codetabof(i)
  70 #define tab_suffixof(i)                 ((unsigned char *)(htab))[i]
  71 #define de_stack                                ((unsigned char *)&(htab[HSIZE-1]))
  72 #define clear_htab()                    memset(htab, -1, HSIZE)
  73 #define clear_tab_prefixof()    memset(codetab, 0, 256);
  74
  75
  76 /*
  77  * Decompress stdin to stdout.  This routine adapts to the codes in the
  78  * file building the "string" table on-the-fly; requiring no table to
  79  * be stored in the compressed file.  The tables used herein are shared
  80  * with those of the compress() routine.  See the definitions above.
  81  */
  82
  83 USE_DESKTOP(long long) int
  84 uncompress(int fd_in, int fd_out)
  85 {
  86         USE_DESKTOP(long long total_written = 0;)
  87         unsigned char *stackp;
  88         long int code;
  89         int finchar;
  90         long int oldcode;
  91         long int incode;
  92         int inbits;
  93         int posbits;
  94         int outpos;
  95         int insize;
  96         int bitmask;
  97         long int free_ent;
  98         long int maxcode;
  99         long int maxmaxcode;
 100         int n_bits;
 101         int rsize = 0;
 102         RESERVE_CONFIG_UBUFFER(inbuf, IBUFSIZ + 64);
 103         RESERVE_CONFIG_UBUFFER(outbuf, OBUFSIZ + 2048);
 104         unsigned char htab[HSIZE];
 105         unsigned short codetab[HSIZE];
 106
 107         /* Hmm, these were statics - why?! */
 108         /* user settable max # bits/code */
 109         int maxbits; /* = BITS; */
 110         /* block compress mode -C compatible with 2.0 */
 111         int block_mode; /* = BLOCK_MODE; */
 112
 113         memset(inbuf, 0, IBUFSIZ + 64);
 114         memset(outbuf, 0, OBUFSIZ + 2048);
 115
 116         insize = 0;
 117
 118         /* xread isn't good here, we have to return - caller may want
 119          * to do some cleanup (e.g. delete incomplete unpacked file etc) */
 120         if (full_read(fd_in, inbuf, 1) != 1) {
 121                 bb_error_msg("short read");
 122                 return -1;
 123         }
 124
 125         maxbits = inbuf[0] & BIT_MASK;
 126         block_mode = inbuf[0] & BLOCK_MODE;
 127         maxmaxcode = MAXCODE(maxbits);
 128
 129         if (maxbits > BITS) {
 130                 bb_error_msg("compressed with %d bits, can only handle "
 131                                 "%d bits", maxbits, BITS);
 132                 return -1;
 133         }
 134
 135         n_bits = INIT_BITS;
 136         maxcode = MAXCODE(INIT_BITS) - 1;
 137         bitmask = (1 << INIT_BITS) - 1;
 138         oldcode = -1;
 139         finchar = 0;
 140         outpos = 0;
 141         posbits = 0 << 3;
 142
 143         free_ent = ((block_mode) ? FIRST : 256);
 144
 145         /* As above, initialize the first 256 entries in the table. */
 146         clear_tab_prefixof();
 147
 148         for (code = 255; code >= 0; --code) {
 149                 tab_suffixof(code) = (unsigned char) code;
 150         }
 151
 152         do {
 153  resetbuf:
 154                 {
 155                         int i;
 156                         int e;
 157                         int o;
 158
 159                         o = posbits >> 3;
 160                         e = insize - o;
 161
 162                         for (i = 0; i < e; ++i)
 163                                 inbuf[i] = inbuf[i + o];
 164
 165                         insize = e;
 166                         posbits = 0;
 167                 }
 168
 169                 if (insize < (int) (IBUFSIZ + 64) - IBUFSIZ) {
 170                         rsize = safe_read(fd_in, inbuf + insize, IBUFSIZ);
 171 //error check??
 172                         insize += rsize;
 173                 }
 174
 175                 inbits = ((rsize > 0) ? (insize - insize % n_bits) << 3 :
 176                                   (insize << 3) - (n_bits - 1));
 177
 178                 while (inbits > posbits) {
 179                         if (free_ent > maxcode) {
 180                                 posbits =
 181                                         ((posbits - 1) +
 182                                          ((n_bits << 3) -
 183                                           (posbits - 1 + (n_bits << 3)) % (n_bits << 3)));
 184                                 ++n_bits;
 185                                 if (n_bits == maxbits) {
 186                                         maxcode = maxmaxcode;
 187                                 } else {
 188                                         maxcode = MAXCODE(n_bits) - 1;
 189                                 }
 190                                 bitmask = (1 << n_bits) - 1;
 191                                 goto resetbuf;
 192                         }
 193                         {
 194                                 unsigned char *p = &inbuf[posbits >> 3];
 195
 196                                 code = ((((long) (p[0])) | ((long) (p[1]) << 8) |
 197                                          ((long) (p[2]) << 16)) >> (posbits & 0x7)) & bitmask;
 198                         }
 199                         posbits += n_bits;
 200
 201
 202                         if (oldcode == -1) {
 203                                 oldcode = code;
 204                                 finchar = (int) oldcode;
 205                                 outbuf[outpos++] = (unsigned char) finchar;
 206                                 continue;
 207                         }
 208
 209                         if (code == CLEAR && block_mode) {
 210                                 clear_tab_prefixof();
 211                                 free_ent = FIRST - 1;
 212                                 posbits =
 213                                         ((posbits - 1) +
 214                                          ((n_bits << 3) -
 215                                           (posbits - 1 + (n_bits << 3)) % (n_bits << 3)));
 216                                 n_bits = INIT_BITS;
 217                                 maxcode = MAXCODE(INIT_BITS) - 1;
 218                                 bitmask = (1 << INIT_BITS) - 1;
 219                                 goto resetbuf;
 220                         }
 221
 222                         incode = code;
 223                         stackp = de_stack;
 224
 225                         /* Special case for KwKwK string. */
 226                         if (code >= free_ent) {
 227                                 if (code > free_ent) {
 228                                         unsigned char *p;
 229
 230                                         posbits -= n_bits;
 231                                         p = &inbuf[posbits >> 3];
 232
 233                                         bb_error_msg
 234                                                 ("insize:%d posbits:%d inbuf:%02X %02X %02X %02X %02X (%d)",
 235                                                  insize, posbits, p[-1], p[0], p[1], p[2], p[3],
 236                                                  (posbits & 07));
 237                                         bb_error_msg("uncompress: corrupt input");
 238                                         return -1;
 239                                 }
 240
 241                                 *--stackp = (unsigned char) finchar;
 242                                 code = oldcode;
 243                         }
 244
 245                         /* Generate output characters in reverse order */
 246                         while ((long int) code >= (long int) 256) {
 247                                 *--stackp = tab_suffixof(code);
 248                                 code = tab_prefixof(code);
 249                         }
 250
 251                         finchar = tab_suffixof(code);
 252                         *--stackp = (unsigned char) finchar;
 253
 254                         /* And put them out in forward order */
 255                         {
 256                                 int i;
 257
 258                                 i = de_stack - stackp;
 259                                 if (outpos + i >= OBUFSIZ) {
 260                                         do {
 261                                                 if (i > OBUFSIZ - outpos) {
 262                                                         i = OBUFSIZ - outpos;
 263                                                 }
 264
 265                                                 if (i > 0) {
 266                                                         memcpy(outbuf + outpos, stackp, i);
 267                                                         outpos += i;
 268                                                 }
 269
 270                                                 if (outpos >= OBUFSIZ) {
 271                                                         full_write(fd_out, outbuf, outpos);
 272 //error check??
 273                                                         USE_DESKTOP(total_written += outpos;)
 274                                                         outpos = 0;
 275                                                 }
 276                                                 stackp += i;
 277                                                 i = de_stack - stackp;
 278                                         } while (i > 0);
 279                                 } else {
 280                                         memcpy(outbuf + outpos, stackp, i);
 281                                         outpos += i;
 282                                 }
 283                         }
 284
 285                         /* Generate the new entry. */
 286                         code = free_ent;
 287                         if (code < maxmaxcode) {
 288                                 tab_prefixof(code) = (unsigned short) oldcode;
 289                                 tab_suffixof(code) = (unsigned char) finchar;
 290                                 free_ent = code + 1;
 291                         }
 292
 293                         /* Remember previous code.  */
 294                         oldcode = incode;
 295                 }
 296
 297         } while (rsize > 0);
 298
 299         if (outpos > 0) {
 300                 full_write(fd_out, outbuf, outpos);
 301 //error check??
 302                 USE_DESKTOP(total_written += outpos;)
 303         }
 304
 305         RELEASE_CONFIG_BUFFER(inbuf);
 306         RELEASE_CONFIG_BUFFER(outbuf);
 307         return USE_DESKTOP(total_written) + 0;
 308 }