LXR busybox/archival/libarchive/decompress

   1/* vi: set sw=4 ts=4: */
   2/* uncompress for busybox -- (c) 2002 Robert Griebl
   3 *
   4 * based on the original compress42.c source
   5 * (see disclaimer below)
   6 */
   7
   8/* (N)compress42.c - File compression ala IEEE Computer, Mar 1992.
   9 *
  10 * Authors:
  11 *   Spencer W. Thomas   (decvax!harpo!utah-cs!utah-gr!thomas)
  12 *   Jim McKie           (decvax!mcvax!jim)
  13 *   Steve Davies        (decvax!vax135!petsd!peora!srd)
  14 *   Ken Turkowski       (decvax!decwrl!turtlevax!ken)
  15 *   James A. Woods      (decvax!ihnp4!ames!jaw)
  16 *   Joe Orost           (decvax!vax135!petsd!joe)
  17 *   Dave Mack           (csu@alembic.acs.com)
  18 *   Peter Jannesen, Network Communication Systems
  19 *                       (peter@ncs.nl)
  20 *
  21 * marc@suse.de : a small security fix for a buffer overflow
  22 *
  23 * [... History snipped ...]
  24 *
  25 */
  26
  27#include "libbb.h"
  28#include "archive.h"
  29
  30
  31/* Default input buffer size */
  32#define IBUFSIZ 2048
  33
  34/* Default output buffer size */
  35#define OBUFSIZ 2048
  36
  37/* Defines for third byte of header */
  38#define BIT_MASK        0x1f    /* Mask for 'number of compresssion bits'       */
  39                                /* Masks 0x20 and 0x40 are free.                */
  40                                /* I think 0x20 should mean that there is       */
  41                                /* a fourth header byte (for expansion).        */
  42#define BLOCK_MODE      0x80    /* Block compression if table is full and       */
  43                                /* compression rate is dropping flush tables    */
  44                                /* the next two codes should not be changed lightly, as they must not   */
  45                                /* lie within the contiguous general code space.                        */
  46#define FIRST   257     /* first free entry */
  47#define CLEAR   256     /* table clear output code */
  48
  49#define INIT_BITS 9     /* initial number of bits/code */
  50
  51
  52/* machine variants which require cc -Dmachine:  pdp11, z8000, DOS */
  53#define HBITS      17   /* 50% occupancy */
  54#define HSIZE      (1<<HBITS)
  55#define HMASK      (HSIZE-1)    /* unused */
  56#define HPRIME     9941         /* unused */
  57#define BITS       16
  58#define BITS_STR   "16"
  59#undef  MAXSEG_64K              /* unused */
  60#define MAXCODE(n) (1L << (n))
  61
  62#define htabof(i)               htab[i]
  63#define codetabof(i)            codetab[i]
  64#define tab_prefixof(i)         codetabof(i)
  65#define tab_suffixof(i)         ((unsigned char *)(htab))[i]
  66#define de_stack                ((unsigned char *)&(htab[HSIZE-1]))
  67#define clear_tab_prefixof()    memset(codetab, 0, 256)
  68
  69/*
  70 * Decompress stdin to stdout.  This routine adapts to the codes in the
  71 * file building the "string" table on-the-fly; requiring no table to
  72 * be stored in the compressed file.
  73 */
  74
  75IF_DESKTOP(long long) int FAST_FUNC
  76unpack_Z_stream(int fd_in, int fd_out)
  77{
  78        IF_DESKTOP(long long total_written = 0;)
  79        IF_DESKTOP(long long) int retval = -1;
  80        unsigned char *stackp;
  81        long code;
  82        int finchar;
  83        long oldcode;
  84        long incode;
  85        int inbits;
  86        int posbits;
  87        int outpos;
  88        int insize;
  89        int bitmask;
  90        long free_ent;
  91        long maxcode;
  92        long maxmaxcode;
  93        int n_bits;
  94        int rsize = 0;
  95        unsigned char *inbuf; /* were eating insane amounts of stack - */
  96        unsigned char *outbuf; /* bad for some embedded targets */
  97        unsigned char *htab;
  98        unsigned short *codetab;
  99
 100        /* Hmm, these were statics - why?! */
 101        /* user settable max # bits/code */
 102        int maxbits; /* = BITS; */
 103        /* block compress mode -C compatible with 2.0 */
 104        int block_mode; /* = BLOCK_MODE; */
 105
 106        inbuf = xzalloc(IBUFSIZ + 64);
 107        outbuf = xzalloc(OBUFSIZ + 2048);
 108        htab = xzalloc(HSIZE);  /* wsn't zeroed out before, maybe can xmalloc? */
 109        codetab = xzalloc(HSIZE * sizeof(codetab[0]));
 110
 111        insize = 0;
 112
 113        /* xread isn't good here, we have to return - caller may want
 114         * to do some cleanup (e.g. delete incomplete unpacked file etc) */
 115        if (full_read(fd_in, inbuf, 1) != 1) {
 116                bb_error_msg("short read");
 117                goto err;
 118        }
 119
 120        maxbits = inbuf[0] & BIT_MASK;
 121        block_mode = inbuf[0] & BLOCK_MODE;
 122        maxmaxcode = MAXCODE(maxbits);
 123
 124        if (maxbits > BITS) {
 125                bb_error_msg("compressed with %d bits, can only handle "
 126                                BITS_STR" bits", maxbits);
 127                goto err;
 128        }
 129
 130        n_bits = INIT_BITS;
 131        maxcode = MAXCODE(INIT_BITS) - 1;
 132        bitmask = (1 << INIT_BITS) - 1;
 133        oldcode = -1;
 134        finchar = 0;
 135        outpos = 0;
 136        posbits = 0 << 3;
 137
 138        free_ent = ((block_mode) ? FIRST : 256);
 139
 140        /* As above, initialize the first 256 entries in the table. */
 141        /*clear_tab_prefixof(); - done by xzalloc */
 142
 143        for (code = 255; code >= 0; --code) {
 144                tab_suffixof(code) = (unsigned char) code;
 145        }
 146
 147        do {
 148 resetbuf:
 149                {
 150                        int i;
 151                        int e;
 152                        int o;
 153
 154                        o = posbits >> 3;
 155                        e = insize - o;
 156
 157                        for (i = 0; i < e; ++i)
 158                                inbuf[i] = inbuf[i + o];
 159
 160                        insize = e;
 161                        posbits = 0;
 162                }
 163
 164                if (insize < (int) (IBUFSIZ + 64) - IBUFSIZ) {
 165                        rsize = safe_read(fd_in, inbuf + insize, IBUFSIZ);
 166                        if (rsize < 0)
 167                                bb_error_msg_and_die(bb_msg_read_error);
 168                        insize += rsize;
 169                }
 170
 171                inbits = ((rsize > 0) ? (insize - insize % n_bits) << 3 :
 172                                  (insize << 3) - (n_bits - 1));
 173
 174                while (inbits > posbits) {
 175                        if (free_ent > maxcode) {
 176                                posbits =
 177                                        ((posbits - 1) +
 178                                         ((n_bits << 3) -
 179                                          (posbits - 1 + (n_bits << 3)) % (n_bits << 3)));
 180                                ++n_bits;
 181                                if (n_bits == maxbits) {
 182                                        maxcode = maxmaxcode;
 183                                } else {
 184                                        maxcode = MAXCODE(n_bits) - 1;
 185                                }
 186                                bitmask = (1 << n_bits) - 1;
 187                                goto resetbuf;
 188                        }
 189                        {
 190                                unsigned char *p = &inbuf[posbits >> 3];
 191
 192                                code = ((((long) (p[0])) | ((long) (p[1]) << 8) |
 193                                         ((long) (p[2]) << 16)) >> (posbits & 0x7)) & bitmask;
 194                        }
 195                        posbits += n_bits;
 196
 197
 198                        if (oldcode == -1) {
 199                                if (code >= 256)
 200                                        bb_error_msg_and_die("corrupted data"); /* %ld", code); */
 201                                oldcode = code;
 202                                finchar = (int) oldcode;
 203                                outbuf[outpos++] = (unsigned char) finchar;
 204                                continue;
 205                        }
 206
 207                        if (code == CLEAR && block_mode) {
 208                                clear_tab_prefixof();
 209                                free_ent = FIRST - 1;
 210                                posbits =
 211                                        ((posbits - 1) +
 212                                         ((n_bits << 3) -
 213                                          (posbits - 1 + (n_bits << 3)) % (n_bits << 3)));
 214                                n_bits = INIT_BITS;
 215                                maxcode = MAXCODE(INIT_BITS) - 1;
 216                                bitmask = (1 << INIT_BITS) - 1;
 217                                goto resetbuf;
 218                        }
 219
 220                        incode = code;
 221                        stackp = de_stack;
 222
 223                        /* Special case for KwKwK string. */
 224                        if (code >= free_ent) {
 225                                if (code > free_ent) {
 226                                        unsigned char *p;
 227
 228                                        posbits -= n_bits;
 229                                        p = &inbuf[posbits >> 3];
 230
 231                                        bb_error_msg
 232                                                ("insize:%d posbits:%d inbuf:%02X %02X %02X %02X %02X (%d)",
 233                                                 insize, posbits, p[-1], p[0], p[1], p[2], p[3],
 234                                                 (posbits & 07));
 235                                        bb_error_msg("corrupted data");
 236                                        goto err;
 237                                }
 238
 239                                *--stackp = (unsigned char) finchar;
 240                                code = oldcode;
 241                        }
 242
 243                        /* Generate output characters in reverse order */
 244                        while ((long) code >= (long) 256) {
 245                                if (stackp <= &htabof(0))
 246                                        bb_error_msg_and_die("corrupted data");
 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                                                        xwrite(fd_out, outbuf, outpos);
 272                                                        IF_DESKTOP(total_written += outpos;)
 273                                                        outpos = 0;
 274                                                }
 275                                                stackp += i;
 276                                                i = de_stack - stackp;
 277                                        } while (i > 0);
 278                                } else {
 279                                        memcpy(outbuf + outpos, stackp, i);
 280                                        outpos += i;
 281                                }
 282                        }
 283
 284                        /* Generate the new entry. */
 285                        code = free_ent;
 286                        if (code < maxmaxcode) {
 287                                tab_prefixof(code) = (unsigned short) oldcode;
 288                                tab_suffixof(code) = (unsigned char) finchar;
 289                                free_ent = code + 1;
 290                        }
 291
 292                        /* Remember previous code.  */
 293                        oldcode = incode;
 294                }
 295
 296        } while (rsize > 0);
 297
 298        if (outpos > 0) {
 299                xwrite(fd_out, outbuf, outpos);
 300                IF_DESKTOP(total_written += outpos;)
 301        }
 302
 303        retval = IF_DESKTOP(total_written) + 0;
 304 err:
 305        free(inbuf);
 306        free(outbuf);
 307        free(htab);
 308        free(codetab);
 309        return retval;
 310}
 311