contrib/file/src/ascmagic.c

   1 /*
   2  * Copyright (c) Ian F. Darwin 1986-1995.
   3  * Software written by Ian F. Darwin and others;
   4  * maintained 1995-present by Christos Zoulas and others.
   5  *
   6  * Redistribution and use in source and binary forms, with or without
   7  * modification, are permitted provided that the following conditions
   8  * are met:
   9  * 1. Redistributions of source code must retain the above copyright
  10  *    notice immediately at the beginning of the file, without modification,
  11  *    this list of conditions, and the following disclaimer.
  12  * 2. Redistributions in binary form must reproduce the above copyright
  13  *    notice, this list of conditions and the following disclaimer in the
  14  *    documentation and/or other materials provided with the distribution.
  15  *
  16  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  17  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  18  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  19  * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR
  20  * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  21  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  22  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  23  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  24  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  25  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  26  * SUCH DAMAGE.
  27  */
  28 /*
  29  * ASCII magic -- try to detect text encoding.
  30  *
  31  * Extensively modified by Eric Fischer <enf@pobox.com> in July, 2000,
  32  * to handle character codes other than ASCII on a unified basis.
  33  */
  34
  35 #include "file.h"
  36
  37 #ifndef lint
  38 FILE_RCSID("@(#)$File: ascmagic.c,v 1.81 2011/03/15 22:16:29 christos Exp $")
  39 #endif  /* lint */
  40
  41 #include "magic.h"
  42 #include <string.h>
  43 #include <memory.h>
  44 #include <ctype.h>
  45 #include <stdlib.h>
  46 #ifdef HAVE_UNISTD_H
  47 #include <unistd.h>
  48 #endif
  49 #include "names.h"
  50
  51 #define MAXLINELEN 300  /* longest sane line length */
  52 #define ISSPC(x) ((x) == ' ' || (x) == '\t' || (x) == '\r' || (x) == '\n' \
  53                   || (x) == 0x85 || (x) == '\f')
  54
  55 private int ascmatch(const unsigned char *, const unichar *, size_t);
  56 private unsigned char *encode_utf8(unsigned char *, size_t, unichar *, size_t);
  57 private size_t trim_nuls(const unsigned char *, size_t);
  58
  59 /*
  60  * Undo the NUL-termination kindly provided by process()
  61  * but leave at least one byte to look at
  62  */
  63 private size_t
  64 trim_nuls(const unsigned char *buf, size_t nbytes)
  65 {
  66         while (nbytes > 1 && buf[nbytes - 1] == '\0')
  67                 nbytes--;
  68
  69         return nbytes;
  70 }
  71
  72 protected int
  73 file_ascmagic(struct magic_set *ms, const unsigned char *buf, size_t nbytes)
  74 {
  75         unichar *ubuf = NULL;
  76         size_t ulen;
  77         int rv = 1;
  78
  79         const char *code = NULL;
  80         const char *code_mime = NULL;
  81         const char *type = NULL;
  82
  83         if (ms->flags & MAGIC_APPLE)
  84                 return 0;
  85
  86         nbytes = trim_nuls(buf, nbytes);
  87
  88         /* If file doesn't look like any sort of text, give up. */
  89         if (file_encoding(ms, buf, nbytes, &ubuf, &ulen, &code, &code_mime,
  90             &type) == 0) {
  91                 rv = 0;
  92                 goto done;
  93         }
  94
  95         rv = file_ascmagic_with_encoding(ms, buf, nbytes, ubuf, ulen, code,
  96             type);
  97
  98  done:
  99         if (ubuf)
 100                 free(ubuf);
 101
 102         return rv;
 103 }
 104
 105 protected int
 106 file_ascmagic_with_encoding(struct magic_set *ms, const unsigned char *buf,
 107     size_t nbytes, unichar *ubuf, size_t ulen, const char *code,
 108     const char *type)
 109 {
 110         unsigned char *utf8_buf = NULL, *utf8_end;
 111         size_t mlen, i;
 112         const struct names *p;
 113         int rv = -1;
 114         int mime = ms->flags & MAGIC_MIME;
 115
 116         const char *subtype = NULL;
 117         const char *subtype_mime = NULL;
 118
 119         int has_escapes = 0;
 120         int has_backspace = 0;
 121         int seen_cr = 0;
 122
 123         int n_crlf = 0;
 124         int n_lf = 0;
 125         int n_cr = 0;
 126         int n_nel = 0;
 127         int score, curtype, executable = 0;
 128
 129         size_t last_line_end = (size_t)-1;
 130         int has_long_lines = 0;
 131
 132         if (ms->flags & MAGIC_APPLE)
 133                 return 0;
 134
 135         nbytes = trim_nuls(buf, nbytes);
 136
 137         /* If we have fewer than 2 bytes, give up. */
 138         if (nbytes <= 1) {
 139                 rv = 0;
 140                 goto done;
 141         }
 142
 143         if ((ms->flags & MAGIC_NO_CHECK_SOFT) == 0) {
 144                 /* Convert ubuf to UTF-8 and try text soft magic */
 145                 /* malloc size is a conservative overestimate; could be
 146                    improved, or at least realloced after conversion. */
 147                 mlen = ulen * 6;
 148                 if ((utf8_buf = CAST(unsigned char *, malloc(mlen))) == NULL) {
 149                         file_oomem(ms, mlen);
 150                         goto done;
 151                 }
 152                 if ((utf8_end = encode_utf8(utf8_buf, mlen, ubuf, ulen))
 153                     == NULL)
 154                         goto done;
 155                 if ((rv = file_softmagic(ms, utf8_buf,
 156                     (size_t)(utf8_end - utf8_buf), TEXTTEST)) != 0)
 157                         goto subtype_identified;
 158                 else
 159                         rv = -1;
 160         }
 161
 162         /* look for tokens from names.h - this is expensive! */
 163         if ((ms->flags & MAGIC_NO_CHECK_TOKENS) != 0)
 164                 goto subtype_identified;
 165
 166         i = 0;
 167         score = 0;
 168         curtype = -1;
 169         while (i < ulen) {
 170                 size_t end;
 171
 172                 /* skip past any leading space */
 173                 while (i < ulen && ISSPC(ubuf[i]))
 174                         i++;
 175                 if (i >= ulen)
 176                         break;
 177
 178                 /* find the next whitespace */
 179                 for (end = i + 1; end < nbytes; end++)
 180                         if (ISSPC(ubuf[end]))
 181                                 break;
 182
 183                 /* compare the word thus isolated against the token list */
 184                 for (p = names; p < names + NNAMES; p++) {
 185                         if (ascmatch((const unsigned char *)p->name, ubuf + i,
 186                             end - i)) {
 187                                 if (curtype == -1)
 188                                         curtype = p->type;
 189                                 else if (curtype != p->type) {
 190                                         score = p->score;
 191                                         curtype = p->type;
 192                                 } else
 193                                         score += p->score;
 194                                 if (score > 1) {
 195                                         subtype = types[p->type].human;
 196                                         subtype_mime = types[p->type].mime;
 197                                         goto subtype_identified;
 198                                 }
 199                         }
 200                 }
 201
 202                 i = end;
 203         }
 204
 205 subtype_identified:
 206
 207         /* Now try to discover other details about the file. */
 208         for (i = 0; i < ulen; i++) {
 209                 if (ubuf[i] == '\n') {
 210                         if (seen_cr)
 211                                 n_crlf++;
 212                         else
 213                                 n_lf++;
 214                         last_line_end = i;
 215                 } else if (seen_cr)
 216                         n_cr++;
 217
 218                 seen_cr = (ubuf[i] == '\r');
 219                 if (seen_cr)
 220                         last_line_end = i;
 221
 222                 if (ubuf[i] == 0x85) { /* X3.64/ECMA-43 "next line" character */
 223                         n_nel++;
 224                         last_line_end = i;
 225                 }
 226
 227                 /* If this line is _longer_ than MAXLINELEN, remember it. */
 228                 if (i > last_line_end + MAXLINELEN)
 229                         has_long_lines = 1;
 230
 231                 if (ubuf[i] == '\033')
 232                         has_escapes = 1;
 233                 if (ubuf[i] == '\b')
 234                         has_backspace = 1;
 235         }
 236
 237         /* Beware, if the data has been truncated, the final CR could have
 238            been followed by a LF.  If we have HOWMANY bytes, it indicates
 239            that the data might have been truncated, probably even before
 240            this function was called. */
 241         if (seen_cr && nbytes < HOWMANY)
 242                 n_cr++;
 243
 244         if (strcmp(type, "binary") == 0) {
 245                 rv = 0;
 246                 goto done;
 247         }
 248         if (mime) {
 249                 if (!file_printedlen(ms) && (mime & MAGIC_MIME_TYPE) != 0) {
 250                         if (subtype_mime) {
 251                                 if (file_printf(ms, "%s", subtype_mime) == -1)
 252                                         goto done;
 253                         } else {
 254                                 if (file_printf(ms, "text/plain") == -1)
 255                                         goto done;
 256                         }
 257                 }
 258         } else {
 259                 if (file_printedlen(ms)) {
 260                         switch (file_replace(ms, " text$", ", ")) {
 261                         case 0:
 262                                 switch (file_replace(ms, " text executable$",
 263                                     ", ")) {
 264                                 case 0:
 265                                         if (file_printf(ms, ", ") == -1)
 266                                                 goto done;
 267                                 case -1:
 268                                         goto done;
 269                                 default:
 270                                         executable = 1;
 271                                         break;
 272                                 }
 273                                 break;
 274                         case -1:
 275                                 goto done;
 276                         default:
 277                                 break;
 278                         }
 279                 }
 280
 281                 if (file_printf(ms, "%s", code) == -1)
 282                         goto done;
 283
 284                 if (subtype) {
 285                         if (file_printf(ms, " %s", subtype) == -1)
 286                                 goto done;
 287                 }
 288
 289                 if (file_printf(ms, " %s", type) == -1)
 290                         goto done;
 291
 292                 if (executable)
 293                         if (file_printf(ms, " executable") == -1)
 294                                 goto done;
 295
 296                 if (has_long_lines)
 297                         if (file_printf(ms, ", with very long lines") == -1)
 298                                 goto done;
 299
 300                 /*
 301                  * Only report line terminators if we find one other than LF,
 302                  * or if we find none at all.
 303                  */
 304                 if ((n_crlf == 0 && n_cr == 0 && n_nel == 0 && n_lf == 0) ||
 305                     (n_crlf != 0 || n_cr != 0 || n_nel != 0)) {
 306                         if (file_printf(ms, ", with") == -1)
 307                                 goto done;
 308
 309                         if (n_crlf == 0 && n_cr == 0 && n_nel == 0 && n_lf == 0) {
 310                                 if (file_printf(ms, " no") == -1)
 311                                         goto done;
 312                         } else {
 313                                 if (n_crlf) {
 314                                         if (file_printf(ms, " CRLF") == -1)
 315                                                 goto done;
 316                                         if (n_cr || n_lf || n_nel)
 317                                                 if (file_printf(ms, ",") == -1)
 318                                                         goto done;
 319                                 }
 320                                 if (n_cr) {
 321                                         if (file_printf(ms, " CR") == -1)
 322                                                 goto done;
 323                                         if (n_lf || n_nel)
 324                                                 if (file_printf(ms, ",") == -1)
 325                                                         goto done;
 326                                 }
 327                                 if (n_lf) {
 328                                         if (file_printf(ms, " LF") == -1)
 329                                                 goto done;
 330                                         if (n_nel)
 331                                                 if (file_printf(ms, ",") == -1)
 332                                                         goto done;
 333                                 }
 334                                 if (n_nel)
 335                                         if (file_printf(ms, " NEL") == -1)
 336                                                 goto done;
 337                         }
 338
 339                         if (file_printf(ms, " line terminators") == -1)
 340                                 goto done;
 341                 }
 342
 343                 if (has_escapes)
 344                         if (file_printf(ms, ", with escape sequences") == -1)
 345                                 goto done;
 346                 if (has_backspace)
 347                         if (file_printf(ms, ", with overstriking") == -1)
 348                                 goto done;
 349         }
 350         rv = 1;
 351 done:
 352         if (utf8_buf)
 353                 free(utf8_buf);
 354
 355         return rv;
 356 }
 357
 358 private int
 359 ascmatch(const unsigned char *s, const unichar *us, size_t ulen)
 360 {
 361         size_t i;
 362
 363         for (i = 0; i < ulen; i++) {
 364                 if (s[i] != us[i])
 365                         return 0;
 366         }
 367
 368         if (s[i])
 369                 return 0;
 370         else
 371                 return 1;
 372 }
 373
 374 /*
 375  * Encode Unicode string as UTF-8, returning pointer to character
 376  * after end of string, or NULL if an invalid character is found.
 377  */
 378 private unsigned char *
 379 encode_utf8(unsigned char *buf, size_t len, unichar *ubuf, size_t ulen)
 380 {
 381         size_t i;
 382         unsigned char *end = buf + len;
 383
 384         for (i = 0; i < ulen; i++) {
 385                 if (ubuf[i] <= 0x7f) {
 386                         if (end - buf < 1)
 387                                 return NULL;
 388                         *buf++ = (unsigned char)ubuf[i];
 389                 } else if (ubuf[i] <= 0x7ff) {
 390                         if (end - buf < 2)
 391                                 return NULL;
 392                         *buf++ = (unsigned char)((ubuf[i] >> 6) + 0xc0);
 393                         *buf++ = (unsigned char)((ubuf[i] & 0x3f) + 0x80);
 394                 } else if (ubuf[i] <= 0xffff) {
 395                         if (end - buf < 3)
 396                                 return NULL;
 397                         *buf++ = (unsigned char)((ubuf[i] >> 12) + 0xe0);
 398                         *buf++ = (unsigned char)(((ubuf[i] >> 6) & 0x3f) + 0x80);
 399                         *buf++ = (unsigned char)((ubuf[i] & 0x3f) + 0x80);
 400                 } else if (ubuf[i] <= 0x1fffff) {
 401                         if (end - buf < 4)
 402                                 return NULL;
 403                         *buf++ = (unsigned char)((ubuf[i] >> 18) + 0xf0);
 404                         *buf++ = (unsigned char)(((ubuf[i] >> 12) & 0x3f) + 0x80);
 405                         *buf++ = (unsigned char)(((ubuf[i] >>  6) & 0x3f) + 0x80);
 406                         *buf++ = (unsigned char)((ubuf[i] & 0x3f) + 0x80);
 407                 } else if (ubuf[i] <= 0x3ffffff) {
 408                         if (end - buf < 5)
 409                                 return NULL;
 410                         *buf++ = (unsigned char)((ubuf[i] >> 24) + 0xf8);
 411                         *buf++ = (unsigned char)(((ubuf[i] >> 18) & 0x3f) + 0x80);
 412                         *buf++ = (unsigned char)(((ubuf[i] >> 12) & 0x3f) + 0x80);
 413                         *buf++ = (unsigned char)(((ubuf[i] >>  6) & 0x3f) + 0x80);
 414                         *buf++ = (unsigned char)((ubuf[i] & 0x3f) + 0x80);
 415                 } else if (ubuf[i] <= 0x7fffffff) {
 416                         if (end - buf < 6)
 417                                 return NULL;
 418                         *buf++ = (unsigned char)((ubuf[i] >> 30) + 0xfc);
 419                         *buf++ = (unsigned char)(((ubuf[i] >> 24) & 0x3f) + 0x80);
 420                         *buf++ = (unsigned char)(((ubuf[i] >> 18) & 0x3f) + 0x80);
 421                         *buf++ = (unsigned char)(((ubuf[i] >> 12) & 0x3f) + 0x80);
 422                         *buf++ = (unsigned char)(((ubuf[i] >>  6) & 0x3f) + 0x80);
 423                         *buf++ = (unsigned char)((ubuf[i] & 0x3f) + 0x80);
 424                 } else /* Invalid character */
 425                         return NULL;
 426         }
 427
 428         return buf;
 429 }