contrib/file/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 1.84 2011/12/08 12:38:24 rrt 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
  50 #define MAXLINELEN 300  /* longest sane line length */
  51 #define ISSPC(x) ((x) == ' ' || (x) == '\t' || (x) == '\r' || (x) == '\n' \
  52                   || (x) == 0x85 || (x) == '\f')
  53
  54 private unsigned char *encode_utf8(unsigned char *, size_t, unichar *, size_t);
  55 private size_t trim_nuls(const unsigned char *, size_t);
  56
  57 /*
  58  * Undo the NUL-termination kindly provided by process()
  59  * but leave at least one byte to look at
  60  */
  61 private size_t
  62 trim_nuls(const unsigned char *buf, size_t nbytes)
  63 {
  64         while (nbytes > 1 && buf[nbytes - 1] == '\0')
  65                 nbytes--;
  66
  67         return nbytes;
  68 }
  69
  70 protected int
  71 file_ascmagic(struct magic_set *ms, const unsigned char *buf, size_t nbytes,
  72         int text)
  73 {
  74         unichar *ubuf = NULL;
  75         size_t ulen;
  76         int rv = 1;
  77
  78         const char *code = NULL;
  79         const char *code_mime = NULL;
  80         const char *type = NULL;
  81
  82         if (ms->flags & MAGIC_APPLE)
  83                 return 0;
  84
  85         nbytes = trim_nuls(buf, nbytes);
  86
  87         /* If file doesn't look like any sort of text, give up. */
  88         if (file_encoding(ms, buf, nbytes, &ubuf, &ulen, &code, &code_mime,
  89             &type) == 0)
  90                 rv = 0;
  91         else
  92                 rv = file_ascmagic_with_encoding(ms, buf, nbytes, ubuf, ulen, code,
  93                                                  type, text);
  94
  95         free(ubuf);
  96
  97         return rv;
  98 }
  99
 100 protected int
 101 file_ascmagic_with_encoding(struct magic_set *ms, const unsigned char *buf,
 102     size_t nbytes, unichar *ubuf, size_t ulen, const char *code,
 103     const char *type, int text)
 104 {
 105         unsigned char *utf8_buf = NULL, *utf8_end;
 106         size_t mlen, i;
 107         int rv = -1;
 108         int mime = ms->flags & MAGIC_MIME;
 109
 110         const char *subtype = NULL;
 111         const char *subtype_mime = NULL;
 112
 113         int has_escapes = 0;
 114         int has_backspace = 0;
 115         int seen_cr = 0;
 116
 117         int n_crlf = 0;
 118         int n_lf = 0;
 119         int n_cr = 0;
 120         int n_nel = 0;
 121         int executable = 0;
 122
 123         size_t last_line_end = (size_t)-1;
 124         int has_long_lines = 0;
 125
 126         if (ms->flags & MAGIC_APPLE)
 127                 return 0;
 128
 129         nbytes = trim_nuls(buf, nbytes);
 130
 131         /* If we have fewer than 2 bytes, give up. */
 132         if (nbytes <= 1) {
 133                 rv = 0;
 134                 goto done;
 135         }
 136
 137         if ((ms->flags & MAGIC_NO_CHECK_SOFT) == 0) {
 138                 /* Convert ubuf to UTF-8 and try text soft magic */
 139                 /* malloc size is a conservative overestimate; could be
 140                    improved, or at least realloced after conversion. */
 141                 mlen = ulen * 6;
 142                 if ((utf8_buf = CAST(unsigned char *, malloc(mlen))) == NULL) {
 143                         file_oomem(ms, mlen);
 144                         goto done;
 145                 }
 146                 if ((utf8_end = encode_utf8(utf8_buf, mlen, ubuf, ulen))
 147                     == NULL)
 148                         goto done;
 149                 if ((rv = file_softmagic(ms, utf8_buf,
 150                     (size_t)(utf8_end - utf8_buf), TEXTTEST, text)) == 0)
 151                         rv = -1;
 152         }
 153
 154         /* Now try to discover other details about the file. */
 155         for (i = 0; i < ulen; i++) {
 156                 if (ubuf[i] == '\n') {
 157                         if (seen_cr)
 158                                 n_crlf++;
 159                         else
 160                                 n_lf++;
 161                         last_line_end = i;
 162                 } else if (seen_cr)
 163                         n_cr++;
 164
 165                 seen_cr = (ubuf[i] == '\r');
 166                 if (seen_cr)
 167                         last_line_end = i;
 168
 169                 if (ubuf[i] == 0x85) { /* X3.64/ECMA-43 "next line" character */
 170                         n_nel++;
 171                         last_line_end = i;
 172                 }
 173
 174                 /* If this line is _longer_ than MAXLINELEN, remember it. */
 175                 if (i > last_line_end + MAXLINELEN)
 176                         has_long_lines = 1;
 177
 178                 if (ubuf[i] == '\033')
 179                         has_escapes = 1;
 180                 if (ubuf[i] == '\b')
 181                         has_backspace = 1;
 182         }
 183
 184         /* Beware, if the data has been truncated, the final CR could have
 185            been followed by a LF.  If we have HOWMANY bytes, it indicates
 186            that the data might have been truncated, probably even before
 187            this function was called. */
 188         if (seen_cr && nbytes < HOWMANY)
 189                 n_cr++;
 190
 191         if (strcmp(type, "binary") == 0) {
 192                 rv = 0;
 193                 goto done;
 194         }
 195         if (mime) {
 196                 if (!file_printedlen(ms) && (mime & MAGIC_MIME_TYPE) != 0) {
 197                         if (subtype_mime) {
 198                                 if (file_printf(ms, "%s", subtype_mime) == -1)
 199                                         goto done;
 200                         } else {
 201                                 if (file_printf(ms, "text/plain") == -1)
 202                                         goto done;
 203                         }
 204                 }
 205         } else {
 206                 if (file_printedlen(ms)) {
 207                         switch (file_replace(ms, " text$", ", ")) {
 208                         case 0:
 209                                 switch (file_replace(ms, " text executable$",
 210                                     ", ")) {
 211                                 case 0:
 212                                         if (file_printf(ms, ", ") == -1)
 213                                                 goto done;
 214                                 case -1:
 215                                         goto done;
 216                                 default:
 217                                         executable = 1;
 218                                         break;
 219                                 }
 220                                 break;
 221                         case -1:
 222                                 goto done;
 223                         default:
 224                                 break;
 225                         }
 226                 }
 227
 228                 if (file_printf(ms, "%s", code) == -1)
 229                         goto done;
 230
 231                 if (subtype) {
 232                         if (file_printf(ms, " %s", subtype) == -1)
 233                                 goto done;
 234                 }
 235
 236                 if (file_printf(ms, " %s", type) == -1)
 237                         goto done;
 238
 239                 if (executable)
 240                         if (file_printf(ms, " executable") == -1)
 241                                 goto done;
 242
 243                 if (has_long_lines)
 244                         if (file_printf(ms, ", with very long lines") == -1)
 245                                 goto done;
 246
 247                 /*
 248                  * Only report line terminators if we find one other than LF,
 249                  * or if we find none at all.
 250                  */
 251                 if ((n_crlf == 0 && n_cr == 0 && n_nel == 0 && n_lf == 0) ||
 252                     (n_crlf != 0 || n_cr != 0 || n_nel != 0)) {
 253                         if (file_printf(ms, ", with") == -1)
 254                                 goto done;
 255
 256                         if (n_crlf == 0 && n_cr == 0 && n_nel == 0 && n_lf == 0) {
 257                                 if (file_printf(ms, " no") == -1)
 258                                         goto done;
 259                         } else {
 260                                 if (n_crlf) {
 261                                         if (file_printf(ms, " CRLF") == -1)
 262                                                 goto done;
 263                                         if (n_cr || n_lf || n_nel)
 264                                                 if (file_printf(ms, ",") == -1)
 265                                                         goto done;
 266                                 }
 267                                 if (n_cr) {
 268                                         if (file_printf(ms, " CR") == -1)
 269                                                 goto done;
 270                                         if (n_lf || n_nel)
 271                                                 if (file_printf(ms, ",") == -1)
 272                                                         goto done;
 273                                 }
 274                                 if (n_lf) {
 275                                         if (file_printf(ms, " LF") == -1)
 276                                                 goto done;
 277                                         if (n_nel)
 278                                                 if (file_printf(ms, ",") == -1)
 279                                                         goto done;
 280                                 }
 281                                 if (n_nel)
 282                                         if (file_printf(ms, " NEL") == -1)
 283                                                 goto done;
 284                         }
 285
 286                         if (file_printf(ms, " line terminators") == -1)
 287                                 goto done;
 288                 }
 289
 290                 if (has_escapes)
 291                         if (file_printf(ms, ", with escape sequences") == -1)
 292                                 goto done;
 293                 if (has_backspace)
 294                         if (file_printf(ms, ", with overstriking") == -1)
 295                                 goto done;
 296         }
 297         rv = 1;
 298 done:
 299         free(utf8_buf);
 300
 301         return rv;
 302 }
 303
 304 /*
 305  * Encode Unicode string as UTF-8, returning pointer to character
 306  * after end of string, or NULL if an invalid character is found.
 307  */
 308 private unsigned char *
 309 encode_utf8(unsigned char *buf, size_t len, unichar *ubuf, size_t ulen)
 310 {
 311         size_t i;
 312         unsigned char *end = buf + len;
 313
 314         for (i = 0; i < ulen; i++) {
 315                 if (ubuf[i] <= 0x7f) {
 316                         if (end - buf < 1)
 317                                 return NULL;
 318                         *buf++ = (unsigned char)ubuf[i];
 319                 } else if (ubuf[i] <= 0x7ff) {
 320                         if (end - buf < 2)
 321                                 return NULL;
 322                         *buf++ = (unsigned char)((ubuf[i] >> 6) + 0xc0);
 323                         *buf++ = (unsigned char)((ubuf[i] & 0x3f) + 0x80);
 324                 } else if (ubuf[i] <= 0xffff) {
 325                         if (end - buf < 3)
 326                                 return NULL;
 327                         *buf++ = (unsigned char)((ubuf[i] >> 12) + 0xe0);
 328                         *buf++ = (unsigned char)(((ubuf[i] >> 6) & 0x3f) + 0x80);
 329                         *buf++ = (unsigned char)((ubuf[i] & 0x3f) + 0x80);
 330                 } else if (ubuf[i] <= 0x1fffff) {
 331                         if (end - buf < 4)
 332                                 return NULL;
 333                         *buf++ = (unsigned char)((ubuf[i] >> 18) + 0xf0);
 334                         *buf++ = (unsigned char)(((ubuf[i] >> 12) & 0x3f) + 0x80);
 335                         *buf++ = (unsigned char)(((ubuf[i] >>  6) & 0x3f) + 0x80);
 336                         *buf++ = (unsigned char)((ubuf[i] & 0x3f) + 0x80);
 337                 } else if (ubuf[i] <= 0x3ffffff) {
 338                         if (end - buf < 5)
 339                                 return NULL;
 340                         *buf++ = (unsigned char)((ubuf[i] >> 24) + 0xf8);
 341                         *buf++ = (unsigned char)(((ubuf[i] >> 18) & 0x3f) + 0x80);
 342                         *buf++ = (unsigned char)(((ubuf[i] >> 12) & 0x3f) + 0x80);
 343                         *buf++ = (unsigned char)(((ubuf[i] >>  6) & 0x3f) + 0x80);
 344                         *buf++ = (unsigned char)((ubuf[i] & 0x3f) + 0x80);
 345                 } else if (ubuf[i] <= 0x7fffffff) {
 346                         if (end - buf < 6)
 347                                 return NULL;
 348                         *buf++ = (unsigned char)((ubuf[i] >> 30) + 0xfc);
 349                         *buf++ = (unsigned char)(((ubuf[i] >> 24) & 0x3f) + 0x80);
 350                         *buf++ = (unsigned char)(((ubuf[i] >> 18) & 0x3f) + 0x80);
 351                         *buf++ = (unsigned char)(((ubuf[i] >> 12) & 0x3f) + 0x80);
 352                         *buf++ = (unsigned char)(((ubuf[i] >>  6) & 0x3f) + 0x80);
 353                         *buf++ = (unsigned char)((ubuf[i] & 0x3f) + 0x80);
 354                 } else /* Invalid character */
 355                         return NULL;
 356         }
 357
 358         return buf;
 359 }