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 1.95 2016/05/03 16:10:37 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         nbytes = trim_nuls(buf, nbytes);
  83
  84         /* If file doesn't look like any sort of text, give up. */
  85         if (file_encoding(ms, buf, nbytes, &ubuf, &ulen, &code, &code_mime,
  86             &type) == 0)
  87                 rv = 0;
  88         else
  89                 rv = file_ascmagic_with_encoding(ms, buf, nbytes, ubuf, ulen, code,
  90                                                  type, text);
  91
  92         free(ubuf);
  93
  94         return rv;
  95 }
  96
  97 protected int
  98 file_ascmagic_with_encoding(struct magic_set *ms, const unsigned char *buf,
  99     size_t nbytes, unichar *ubuf, size_t ulen, const char *code,
 100     const char *type, int text)
 101 {
 102         unsigned char *utf8_buf = NULL, *utf8_end;
 103         size_t mlen, i;
 104         int rv = -1;
 105         int mime = ms->flags & MAGIC_MIME;
 106
 107         const char *subtype = NULL;
 108         const char *subtype_mime = NULL;
 109
 110         int has_escapes = 0;
 111         int has_backspace = 0;
 112         int seen_cr = 0;
 113
 114         int n_crlf = 0;
 115         int n_lf = 0;
 116         int n_cr = 0;
 117         int n_nel = 0;
 118         int executable = 0;
 119
 120         size_t last_line_end = (size_t)-1;
 121         int has_long_lines = 0;
 122
 123         nbytes = trim_nuls(buf, nbytes);
 124
 125         /* If we have fewer than 2 bytes, give up. */
 126         if (nbytes <= 1) {
 127                 rv = 0;
 128                 goto done;
 129         }
 130
 131         if (ulen > 0 && (ms->flags & MAGIC_NO_CHECK_SOFT) == 0) {
 132                 /* Convert ubuf to UTF-8 and try text soft magic */
 133                 /* malloc size is a conservative overestimate; could be
 134                    improved, or at least realloced after conversion. */
 135                 mlen = ulen * 6;
 136                 if ((utf8_buf = CAST(unsigned char *, malloc(mlen))) == NULL) {
 137                         file_oomem(ms, mlen);
 138                         goto done;
 139                 }
 140                 if ((utf8_end = encode_utf8(utf8_buf, mlen, ubuf, ulen))
 141                     == NULL)
 142                         goto done;
 143                 if ((rv = file_softmagic(ms, utf8_buf,
 144                     (size_t)(utf8_end - utf8_buf), NULL, NULL,
 145                     TEXTTEST, text)) == 0)
 146                         rv = -1;
 147                 if ((ms->flags & (MAGIC_APPLE|MAGIC_EXTENSION)))
 148                         return rv == -1 ? 0 : 1;
 149         }
 150         if ((ms->flags & (MAGIC_APPLE|MAGIC_EXTENSION)))
 151                 return 0;
 152
 153         /* Now try to discover other details about the file. */
 154         for (i = 0; i < ulen; i++) {
 155                 if (ubuf[i] == '\n') {
 156                         if (seen_cr)
 157                                 n_crlf++;
 158                         else
 159                                 n_lf++;
 160                         last_line_end = i;
 161                 } else if (seen_cr)
 162                         n_cr++;
 163
 164                 seen_cr = (ubuf[i] == '\r');
 165                 if (seen_cr)
 166                         last_line_end = i;
 167
 168                 if (ubuf[i] == 0x85) { /* X3.64/ECMA-43 "next line" character */
 169                         n_nel++;
 170                         last_line_end = i;
 171                 }
 172
 173                 /* If this line is _longer_ than MAXLINELEN, remember it. */
 174                 if (i > last_line_end + MAXLINELEN)
 175                         has_long_lines = 1;
 176
 177                 if (ubuf[i] == '\033')
 178                         has_escapes = 1;
 179                 if (ubuf[i] == '\b')
 180                         has_backspace = 1;
 181         }
 182
 183         /* Beware, if the data has been truncated, the final CR could have
 184            been followed by a LF.  If we have ms->bytes_max bytes, it indicates
 185            that the data might have been truncated, probably even before
 186            this function was called. */
 187         if (seen_cr && nbytes < ms->bytes_max)
 188                 n_cr++;
 189
 190         if (strcmp(type, "binary") == 0) {
 191                 rv = 0;
 192                 goto done;
 193         }
 194         if (mime) {
 195                 if (!file_printedlen(ms) && (mime & MAGIC_MIME_TYPE) != 0) {
 196                         if (subtype_mime) {
 197                                 if (file_printf(ms, "%s", subtype_mime) == -1)
 198                                         goto done;
 199                         } else {
 200                                 if (file_printf(ms, "text/plain") == -1)
 201                                         goto done;
 202                         }
 203                 }
 204         } else {
 205                 if (file_printedlen(ms)) {
 206                         switch (file_replace(ms, " text$", ", ")) {
 207                         case 0:
 208                                 switch (file_replace(ms, " text executable$",
 209                                     ", ")) {
 210                                 case 0:
 211                                         if (file_printf(ms, ", ") == -1)
 212                                                 goto done;
 213                                         break;
 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 }