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 1.91 2014/11/28 02:46:39 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
  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 = 0;
  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 (ulen > 0 && (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), 0, NULL,
 151                     TEXTTEST, text)) == 0)
 152                         rv = -1;
 153         }
 154
 155         /* Now try to discover other details about the file. */
 156         for (i = 0; i < ulen; i++) {
 157                 if (ubuf[i] == '\n') {
 158                         if (seen_cr)
 159                                 n_crlf++;
 160                         else
 161                                 n_lf++;
 162                         last_line_end = i;
 163                 } else if (seen_cr)
 164                         n_cr++;
 165
 166                 seen_cr = (ubuf[i] == '\r');
 167                 if (seen_cr)
 168                         last_line_end = i;
 169
 170                 if (ubuf[i] == 0x85) { /* X3.64/ECMA-43 "next line" character */
 171                         n_nel++;
 172                         last_line_end = i;
 173                 }
 174
 175                 /* If this line is _longer_ than MAXLINELEN, remember it. */
 176                 if (i > last_line_end + MAXLINELEN)
 177                         has_long_lines = 1;
 178
 179                 if (ubuf[i] == '\033')
 180                         has_escapes = 1;
 181                 if (ubuf[i] == '\b')
 182                         has_backspace = 1;
 183         }
 184
 185         /* Beware, if the data has been truncated, the final CR could have
 186            been followed by a LF.  If we have HOWMANY bytes, it indicates
 187            that the data might have been truncated, probably even before
 188            this function was called. */
 189         if (seen_cr && nbytes < HOWMANY)
 190                 n_cr++;
 191
 192         if (strcmp(type, "binary") == 0) {
 193                 rv = 0;
 194                 goto done;
 195         }
 196         if (mime) {
 197                 if (!file_printedlen(ms) && (mime & MAGIC_MIME_TYPE) != 0) {
 198                         if (subtype_mime) {
 199                                 if (file_printf(ms, "%s", subtype_mime) == -1)
 200                                         goto done;
 201                         } else {
 202                                 if (file_printf(ms, "text/plain") == -1)
 203                                         goto done;
 204                         }
 205                 }
 206         } else {
 207                 if (file_printedlen(ms)) {
 208                         switch (file_replace(ms, " text$", ", ")) {
 209                         case 0:
 210                                 switch (file_replace(ms, " text executable$",
 211                                     ", ")) {
 212                                 case 0:
 213                                         if (file_printf(ms, ", ") == -1)
 214                                                 goto done;
 215                                         break;
 216                                 case -1:
 217                                         goto done;
 218                                 default:
 219                                         executable = 1;
 220                                         break;
 221                                 }
 222                                 break;
 223                         case -1:
 224                                 goto done;
 225                         default:
 226                                 break;
 227                         }
 228                 }
 229
 230                 if (file_printf(ms, "%s", code) == -1)
 231                         goto done;
 232
 233                 if (subtype) {
 234                         if (file_printf(ms, " %s", subtype) == -1)
 235                                 goto done;
 236                 }
 237
 238                 if (file_printf(ms, " %s", type) == -1)
 239                         goto done;
 240
 241                 if (executable)
 242                         if (file_printf(ms, " executable") == -1)
 243                                 goto done;
 244
 245                 if (has_long_lines)
 246                         if (file_printf(ms, ", with very long lines") == -1)
 247                                 goto done;
 248
 249                 /*
 250                  * Only report line terminators if we find one other than LF,
 251                  * or if we find none at all.
 252                  */
 253                 if ((n_crlf == 0 && n_cr == 0 && n_nel == 0 && n_lf == 0) ||
 254                     (n_crlf != 0 || n_cr != 0 || n_nel != 0)) {
 255                         if (file_printf(ms, ", with") == -1)
 256                                 goto done;
 257
 258                         if (n_crlf == 0 && n_cr == 0 && n_nel == 0 && n_lf == 0) {
 259                                 if (file_printf(ms, " no") == -1)
 260                                         goto done;
 261                         } else {
 262                                 if (n_crlf) {
 263                                         if (file_printf(ms, " CRLF") == -1)
 264                                                 goto done;
 265                                         if (n_cr || n_lf || n_nel)
 266                                                 if (file_printf(ms, ",") == -1)
 267                                                         goto done;
 268                                 }
 269                                 if (n_cr) {
 270                                         if (file_printf(ms, " CR") == -1)
 271                                                 goto done;
 272                                         if (n_lf || n_nel)
 273                                                 if (file_printf(ms, ",") == -1)
 274                                                         goto done;
 275                                 }
 276                                 if (n_lf) {
 277                                         if (file_printf(ms, " LF") == -1)
 278                                                 goto done;
 279                                         if (n_nel)
 280                                                 if (file_printf(ms, ",") == -1)
 281                                                         goto done;
 282                                 }
 283                                 if (n_nel)
 284                                         if (file_printf(ms, " NEL") == -1)
 285                                                 goto done;
 286                         }
 287
 288                         if (file_printf(ms, " line terminators") == -1)
 289                                 goto done;
 290                 }
 291
 292                 if (has_escapes)
 293                         if (file_printf(ms, ", with escape sequences") == -1)
 294                                 goto done;
 295                 if (has_backspace)
 296                         if (file_printf(ms, ", with overstriking") == -1)
 297                                 goto done;
 298         }
 299         rv = 1;
 300 done:
 301         free(utf8_buf);
 302
 303         return rv;
 304 }
 305
 306 /*
 307  * Encode Unicode string as UTF-8, returning pointer to character
 308  * after end of string, or NULL if an invalid character is found.
 309  */
 310 private unsigned char *
 311 encode_utf8(unsigned char *buf, size_t len, unichar *ubuf, size_t ulen)
 312 {
 313         size_t i;
 314         unsigned char *end = buf + len;
 315
 316         for (i = 0; i < ulen; i++) {
 317                 if (ubuf[i] <= 0x7f) {
 318                         if (end - buf < 1)
 319                                 return NULL;
 320                         *buf++ = (unsigned char)ubuf[i];
 321                 } else if (ubuf[i] <= 0x7ff) {
 322                         if (end - buf < 2)
 323                                 return NULL;
 324                         *buf++ = (unsigned char)((ubuf[i] >> 6) + 0xc0);
 325                         *buf++ = (unsigned char)((ubuf[i] & 0x3f) + 0x80);
 326                 } else if (ubuf[i] <= 0xffff) {
 327                         if (end - buf < 3)
 328                                 return NULL;
 329                         *buf++ = (unsigned char)((ubuf[i] >> 12) + 0xe0);
 330                         *buf++ = (unsigned char)(((ubuf[i] >> 6) & 0x3f) + 0x80);
 331                         *buf++ = (unsigned char)((ubuf[i] & 0x3f) + 0x80);
 332                 } else if (ubuf[i] <= 0x1fffff) {
 333                         if (end - buf < 4)
 334                                 return NULL;
 335                         *buf++ = (unsigned char)((ubuf[i] >> 18) + 0xf0);
 336                         *buf++ = (unsigned char)(((ubuf[i] >> 12) & 0x3f) + 0x80);
 337                         *buf++ = (unsigned char)(((ubuf[i] >>  6) & 0x3f) + 0x80);
 338                         *buf++ = (unsigned char)((ubuf[i] & 0x3f) + 0x80);
 339                 } else if (ubuf[i] <= 0x3ffffff) {
 340                         if (end - buf < 5)
 341                                 return NULL;
 342                         *buf++ = (unsigned char)((ubuf[i] >> 24) + 0xf8);
 343                         *buf++ = (unsigned char)(((ubuf[i] >> 18) & 0x3f) + 0x80);
 344                         *buf++ = (unsigned char)(((ubuf[i] >> 12) & 0x3f) + 0x80);
 345                         *buf++ = (unsigned char)(((ubuf[i] >>  6) & 0x3f) + 0x80);
 346                         *buf++ = (unsigned char)((ubuf[i] & 0x3f) + 0x80);
 347                 } else if (ubuf[i] <= 0x7fffffff) {
 348                         if (end - buf < 6)
 349                                 return NULL;
 350                         *buf++ = (unsigned char)((ubuf[i] >> 30) + 0xfc);
 351                         *buf++ = (unsigned char)(((ubuf[i] >> 24) & 0x3f) + 0x80);
 352                         *buf++ = (unsigned char)(((ubuf[i] >> 18) & 0x3f) + 0x80);
 353                         *buf++ = (unsigned char)(((ubuf[i] >> 12) & 0x3f) + 0x80);
 354                         *buf++ = (unsigned char)(((ubuf[i] >>  6) & 0x3f) + 0x80);
 355                         *buf++ = (unsigned char)((ubuf[i] & 0x3f) + 0x80);
 356                 } else /* Invalid character */
 357                         return NULL;
 358         }
 359
 360         return buf;
 361 }