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 1.105 2019/06/08 20:49:14 christos Exp $")
  39 #endif  /* lint */
  40
  41 #include "magic.h"
  42 #include <string.h>
  43 #include <ctype.h>
  44 #include <stdlib.h>
  45 #ifdef HAVE_UNISTD_H
  46 #include <unistd.h>
  47 #endif
  48
  49 #define MAXLINELEN 300  /* longest sane line length */
  50 #define ISSPC(x) ((x) == ' ' || (x) == '\t' || (x) == '\r' || (x) == '\n' \
  51                   || (x) == 0x85 || (x) == '\f')
  52
  53 private unsigned char *encode_utf8(unsigned char *, size_t, unichar *, size_t);
  54 private size_t trim_nuls(const unsigned char *, size_t);
  55
  56 /*
  57  * Undo the NUL-termination kindly provided by process()
  58  * but leave at least one byte to look at
  59  */
  60 private size_t
  61 trim_nuls(const unsigned char *buf, size_t nbytes)
  62 {
  63         while (nbytes > 1 && buf[nbytes - 1] == '\0')
  64                 nbytes--;
  65
  66         return nbytes;
  67 }
  68
  69 protected int
  70 file_ascmagic(struct magic_set *ms, const struct buffer *b, int text)
  71 {
  72         unichar *ubuf = NULL;
  73         size_t ulen = 0;
  74         int rv = 1;
  75         struct buffer bb;
  76
  77         const char *code = NULL;
  78         const char *code_mime = NULL;
  79         const char *type = NULL;
  80
  81         bb = *b;
  82         bb.flen = trim_nuls(CAST(const unsigned char *, b->fbuf), b->flen);
  83         /*
  84          * Avoid trimming at an odd byte if the original buffer was evenly
  85          * sized; this avoids losing the last character on UTF-16 LE text
  86          */
  87         if ((bb.flen & 1) && !(b->flen & 1))
  88                 bb.flen++;
  89
  90         /* If file doesn't look like any sort of text, give up. */
  91         if (file_encoding(ms, &bb, &ubuf, &ulen, &code, &code_mime,
  92             &type) == 0)
  93                 rv = 0;
  94         else
  95                 rv = file_ascmagic_with_encoding(ms, &bb,
  96                     ubuf, ulen, code, type, text);
  97
  98         free(ubuf);
  99
 100         return rv;
 101 }
 102
 103 protected int
 104 file_ascmagic_with_encoding(struct magic_set *ms,
 105     const struct buffer *b, unichar *ubuf, size_t ulen, const char *code,
 106     const char *type, int text)
 107 {
 108         struct buffer bb;
 109         const unsigned char *buf = CAST(const unsigned char *, b->fbuf);
 110         size_t nbytes = b->flen;
 111         unsigned char *utf8_buf = NULL, *utf8_end;
 112         size_t mlen, i, len;
 113         int rv = -1;
 114         int mime = ms->flags & MAGIC_MIME;
 115         int need_separator = 0;
 116
 117         const char *subtype = NULL;
 118         const char *subtype_mime = NULL;
 119
 120         int has_escapes = 0;
 121         int has_backspace = 0;
 122         int seen_cr = 0;
 123
 124         int n_crlf = 0;
 125         int n_lf = 0;
 126         int n_cr = 0;
 127         int n_nel = 0;
 128         int executable = 0;
 129
 130         size_t last_line_end = CAST(size_t, -1);
 131         int has_long_lines = 0;
 132
 133         nbytes = trim_nuls(buf, nbytes);
 134
 135         /* If we have fewer than 2 bytes, give up. */
 136         if (nbytes <= 1) {
 137                 rv = 0;
 138                 goto done;
 139         }
 140
 141         if (ulen > 0 && (ms->flags & MAGIC_NO_CHECK_SOFT) == 0) {
 142                 /* Convert ubuf to UTF-8 and try text soft magic */
 143                 /* malloc size is a conservative overestimate; could be
 144                    improved, or at least realloced after conversion. */
 145                 mlen = ulen * 6;
 146                 if ((utf8_buf = CAST(unsigned char *, malloc(mlen))) == NULL) {
 147                         file_oomem(ms, mlen);
 148                         goto done;
 149                 }
 150                 if ((utf8_end = encode_utf8(utf8_buf, mlen, ubuf, ulen))
 151                     == NULL)
 152                         goto done;
 153                 buffer_init(&bb, b->fd, &b->st, utf8_buf,
 154                     CAST(size_t, utf8_end - utf8_buf));
 155
 156                 if ((rv = file_softmagic(ms, &bb, NULL, NULL,
 157                     TEXTTEST, text)) == 0)
 158                         rv = -1;
 159                 else
 160                         need_separator = 1;
 161                 buffer_fini(&bb);
 162                 if ((ms->flags & (MAGIC_APPLE|MAGIC_EXTENSION))) {
 163                         rv = rv == -1 ? 0 : 1;
 164                         goto done;
 165                 }
 166         }
 167         if ((ms->flags & (MAGIC_APPLE|MAGIC_EXTENSION)))
 168                 return 0;
 169
 170         /* Now try to discover other details about the file. */
 171         for (i = 0; i < ulen; i++) {
 172                 if (ubuf[i] == '\n') {
 173                         if (seen_cr)
 174                                 n_crlf++;
 175                         else
 176                                 n_lf++;
 177                         last_line_end = i;
 178                 } else if (seen_cr)
 179                         n_cr++;
 180
 181                 seen_cr = (ubuf[i] == '\r');
 182                 if (seen_cr)
 183                         last_line_end = i;
 184
 185                 if (ubuf[i] == 0x85) { /* X3.64/ECMA-43 "next line" character */
 186                         n_nel++;
 187                         last_line_end = i;
 188                 }
 189
 190                 /* If this line is _longer_ than MAXLINELEN, remember it. */
 191                 if (i > last_line_end + MAXLINELEN)
 192                         has_long_lines = 1;
 193
 194                 if (ubuf[i] == '\033')
 195                         has_escapes = 1;
 196                 if (ubuf[i] == '\b')
 197                         has_backspace = 1;
 198         }
 199
 200         /* Beware, if the data has been truncated, the final CR could have
 201            been followed by a LF.  If we have ms->bytes_max bytes, it indicates
 202            that the data might have been truncated, probably even before
 203            this function was called. */
 204         if (seen_cr && nbytes < ms->bytes_max)
 205                 n_cr++;
 206
 207         if (strcmp(type, "binary") == 0) {
 208                 rv = 0;
 209                 goto done;
 210         }
 211         len = file_printedlen(ms);
 212         if (mime) {
 213                 if ((mime & MAGIC_MIME_TYPE) != 0) {
 214                         if (len) {
 215                                 /*
 216                                  * Softmagic printed something, we
 217                                  * are either done, or we need a separator
 218                                  */
 219                                 if ((ms->flags & MAGIC_CONTINUE) == 0) {
 220                                         rv = 1;
 221                                         goto done;
 222                                 }
 223                                 if (need_separator && file_separator(ms) == -1)
 224                                         goto done;
 225                         }
 226                         if (subtype_mime) {
 227                                 if (file_printf(ms, "%s", subtype_mime) == -1)
 228                                         goto done;
 229                         } else {
 230                                 if (file_printf(ms, "text/plain") == -1)
 231                                         goto done;
 232                         }
 233                 }
 234         } else {
 235                 if (len) {
 236                         switch (file_replace(ms, " text$", ", ")) {
 237                         case 0:
 238                                 switch (file_replace(ms, " text executable$",
 239                                     ", ")) {
 240                                 case 0:
 241                                         if (file_printf(ms, ", ") == -1)
 242                                                 goto done;
 243                                         break;
 244                                 case -1:
 245                                         goto done;
 246                                 default:
 247                                         executable = 1;
 248                                         break;
 249                                 }
 250                                 break;
 251                         case -1:
 252                                 goto done;
 253                         default:
 254                                 break;
 255                         }
 256                 }
 257
 258                 if (file_printf(ms, "%s", code) == -1)
 259                         goto done;
 260
 261                 if (subtype) {
 262                         if (file_printf(ms, " %s", subtype) == -1)
 263                                 goto done;
 264                 }
 265
 266                 if (file_printf(ms, " %s", type) == -1)
 267                         goto done;
 268
 269                 if (executable)
 270                         if (file_printf(ms, " executable") == -1)
 271                                 goto done;
 272
 273                 if (has_long_lines)
 274                         if (file_printf(ms, ", with very long lines") == -1)
 275                                 goto done;
 276
 277                 /*
 278                  * Only report line terminators if we find one other than LF,
 279                  * or if we find none at all.
 280                  */
 281                 if ((n_crlf == 0 && n_cr == 0 && n_nel == 0 && n_lf == 0) ||
 282                     (n_crlf != 0 || n_cr != 0 || n_nel != 0)) {
 283                         if (file_printf(ms, ", with") == -1)
 284                                 goto done;
 285
 286                         if (n_crlf == 0 && n_cr == 0 && n_nel == 0 && n_lf == 0) {
 287                                 if (file_printf(ms, " no") == -1)
 288                                         goto done;
 289                         } else {
 290                                 if (n_crlf) {
 291                                         if (file_printf(ms, " CRLF") == -1)
 292                                                 goto done;
 293                                         if (n_cr || n_lf || n_nel)
 294                                                 if (file_printf(ms, ",") == -1)
 295                                                         goto done;
 296                                 }
 297                                 if (n_cr) {
 298                                         if (file_printf(ms, " CR") == -1)
 299                                                 goto done;
 300                                         if (n_lf || n_nel)
 301                                                 if (file_printf(ms, ",") == -1)
 302                                                         goto done;
 303                                 }
 304                                 if (n_lf) {
 305                                         if (file_printf(ms, " LF") == -1)
 306                                                 goto done;
 307                                         if (n_nel)
 308                                                 if (file_printf(ms, ",") == -1)
 309                                                         goto done;
 310                                 }
 311                                 if (n_nel)
 312                                         if (file_printf(ms, " NEL") == -1)
 313                                                 goto done;
 314                         }
 315
 316                         if (file_printf(ms, " line terminators") == -1)
 317                                 goto done;
 318                 }
 319
 320                 if (has_escapes)
 321                         if (file_printf(ms, ", with escape sequences") == -1)
 322                                 goto done;
 323                 if (has_backspace)
 324                         if (file_printf(ms, ", with overstriking") == -1)
 325                                 goto done;
 326         }
 327         rv = 1;
 328 done:
 329         free(utf8_buf);
 330
 331         return rv;
 332 }
 333
 334 /*
 335  * Encode Unicode string as UTF-8, returning pointer to character
 336  * after end of string, or NULL if an invalid character is found.
 337  */
 338 private unsigned char *
 339 encode_utf8(unsigned char *buf, size_t len, unichar *ubuf, size_t ulen)
 340 {
 341         size_t i;
 342         unsigned char *end = buf + len;
 343
 344         for (i = 0; i < ulen; i++) {
 345                 if (ubuf[i] <= 0x7f) {
 346                         if (end - buf < 1)
 347                                 return NULL;
 348                         *buf++ = CAST(unsigned char, ubuf[i]);
 349                 } else if (ubuf[i] <= 0x7ff) {
 350                         if (end - buf < 2)
 351                                 return NULL;
 352                         *buf++ = CAST(unsigned char, (ubuf[i] >> 6) + 0xc0);
 353                         *buf++ = CAST(unsigned char, (ubuf[i] & 0x3f) + 0x80);
 354                 } else if (ubuf[i] <= 0xffff) {
 355                         if (end - buf < 3)
 356                                 return NULL;
 357                         *buf++ = CAST(unsigned char, (ubuf[i] >> 12) + 0xe0);
 358                         *buf++ = CAST(unsigned char, ((ubuf[i] >> 6) & 0x3f) + 0x80);
 359                         *buf++ = CAST(unsigned char, (ubuf[i] & 0x3f) + 0x80);
 360                 } else if (ubuf[i] <= 0x1fffff) {
 361                         if (end - buf < 4)
 362                                 return NULL;
 363                         *buf++ = CAST(unsigned char, (ubuf[i] >> 18) + 0xf0);
 364                         *buf++ = CAST(unsigned char, ((ubuf[i] >> 12) & 0x3f) + 0x80);
 365                         *buf++ = CAST(unsigned char, ((ubuf[i] >>  6) & 0x3f) + 0x80);
 366                         *buf++ = CAST(unsigned char, (ubuf[i] & 0x3f) + 0x80);
 367                 } else if (ubuf[i] <= 0x3ffffff) {
 368                         if (end - buf < 5)
 369                                 return NULL;
 370                         *buf++ = CAST(unsigned char, (ubuf[i] >> 24) + 0xf8);
 371                         *buf++ = CAST(unsigned char, ((ubuf[i] >> 18) & 0x3f) + 0x80);
 372                         *buf++ = CAST(unsigned char, ((ubuf[i] >> 12) & 0x3f) + 0x80);
 373                         *buf++ = CAST(unsigned char, ((ubuf[i] >>  6) & 0x3f) + 0x80);
 374                         *buf++ = CAST(unsigned char, (ubuf[i] & 0x3f) + 0x80);
 375                 } else if (ubuf[i] <= 0x7fffffff) {
 376                         if (end - buf < 6)
 377                                 return NULL;
 378                         *buf++ = CAST(unsigned char, (ubuf[i] >> 30) + 0xfc);
 379                         *buf++ = CAST(unsigned char, ((ubuf[i] >> 24) & 0x3f) + 0x80);
 380                         *buf++ = CAST(unsigned char, ((ubuf[i] >> 18) & 0x3f) + 0x80);
 381                         *buf++ = CAST(unsigned char, ((ubuf[i] >> 12) & 0x3f) + 0x80);
 382                         *buf++ = CAST(unsigned char, ((ubuf[i] >>  6) & 0x3f) + 0x80);
 383                         *buf++ = CAST(unsigned char, (ubuf[i] & 0x3f) + 0x80);
 384                 } else /* Invalid character */
 385                         return NULL;
 386         }
 387
 388         return buf;
 389 }