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 1.110 2021/12/06 15:33:00 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, file_unichar_t *,
  54     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 struct buffer *b, int text)
  72 {
  73         file_unichar_t *ubuf = NULL;
  74         size_t ulen = 0;
  75         int rv = 1;
  76         struct buffer bb;
  77
  78         const char *code = NULL;
  79         const char *code_mime = NULL;
  80         const char *type = NULL;
  81
  82         bb = *b;
  83         bb.flen = trim_nuls(CAST(const unsigned char *, b->fbuf), b->flen);
  84         /*
  85          * Avoid trimming at an odd byte if the original buffer was evenly
  86          * sized; this avoids losing the last character on UTF-16 LE text
  87          */
  88         if ((bb.flen & 1) && !(b->flen & 1))
  89                 bb.flen++;
  90
  91         /* If file doesn't look like any sort of text, give up. */
  92         if (file_encoding(ms, &bb, &ubuf, &ulen, &code, &code_mime,
  93             &type) == 0)
  94                 rv = 0;
  95         else
  96                 rv = file_ascmagic_with_encoding(ms, &bb,
  97                     ubuf, ulen, code, type, text);
  98
  99         free(ubuf);
 100
 101         return rv;
 102 }
 103
 104 protected int
 105 file_ascmagic_with_encoding(struct magic_set *ms, const struct buffer *b,
 106     file_unichar_t *ubuf, size_t ulen, const char *code, const char *type,
 107     int text)
 108 {
 109         struct buffer bb;
 110         const unsigned char *buf = CAST(const unsigned char *, b->fbuf);
 111         size_t nbytes = b->flen;
 112         unsigned char *utf8_buf = NULL, *utf8_end;
 113         size_t mlen, i, len;
 114         int rv = -1;
 115         int mime = ms->flags & MAGIC_MIME;
 116         int need_separator = 0;
 117
 118         const char *subtype = 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         size_t 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
 168         if ((ms->flags & (MAGIC_APPLE|MAGIC_EXTENSION))) {
 169                 rv = 0;
 170                 goto done;
 171         }
 172
 173         /* Now try to discover other details about the file. */
 174         for (i = 0; i < ulen; i++) {
 175                 if (ubuf[i] == '\n') {
 176                         if (seen_cr)
 177                                 n_crlf++;
 178                         else
 179                                 n_lf++;
 180                         last_line_end = i;
 181                 } else if (seen_cr)
 182                         n_cr++;
 183
 184                 seen_cr = (ubuf[i] == '\r');
 185                 if (seen_cr)
 186                         last_line_end = i;
 187
 188                 if (ubuf[i] == 0x85) { /* X3.64/ECMA-43 "next line" character */
 189                         n_nel++;
 190                         last_line_end = i;
 191                 }
 192
 193                 /* If this line is _longer_ than MAXLINELEN, remember it. */
 194                 if (i > last_line_end + MAXLINELEN) {
 195                         size_t ll = i - last_line_end;
 196                         if (ll > has_long_lines)
 197                                 has_long_lines = ll;
 198                 }
 199
 200                 if (ubuf[i] == '\033')
 201                         has_escapes = 1;
 202                 if (ubuf[i] == '\b')
 203                         has_backspace = 1;
 204         }
 205
 206         /* Beware, if the data has been truncated, the final CR could have
 207            been followed by a LF.  If we have ms->bytes_max bytes, it indicates
 208            that the data might have been truncated, probably even before
 209            this function was called. */
 210         if (seen_cr && nbytes < ms->bytes_max)
 211                 n_cr++;
 212
 213         if (strcmp(type, "binary") == 0) {
 214                 rv = 0;
 215                 goto done;
 216         }
 217         len = file_printedlen(ms);
 218         if (mime) {
 219                 if ((mime & MAGIC_MIME_TYPE) != 0) {
 220                         if (len) {
 221                                 /*
 222                                  * Softmagic printed something, we
 223                                  * are either done, or we need a separator
 224                                  */
 225                                 if ((ms->flags & MAGIC_CONTINUE) == 0) {
 226                                         rv = 1;
 227                                         goto done;
 228                                 }
 229                                 if (need_separator && file_separator(ms) == -1)
 230                                         goto done;
 231                         } else {
 232                                 if (file_printf(ms, "text/plain") == -1)
 233                                         goto done;
 234                         }
 235                 }
 236         } else {
 237                 if (len) {
 238                         switch (file_replace(ms, " text$", ", ")) {
 239                         case 0:
 240                                 switch (file_replace(ms, " text executable$",
 241                                     ", ")) {
 242                                 case 0:
 243                                         if (file_printf(ms, ", ") == -1)
 244                                                 goto done;
 245                                         break;
 246                                 case -1:
 247                                         goto done;
 248                                 default:
 249                                         executable = 1;
 250                                         break;
 251                                 }
 252                                 break;
 253                         case -1:
 254                                 goto done;
 255                         default:
 256                                 break;
 257                         }
 258                 }
 259
 260                 if (file_printf(ms, "%s", code) == -1)
 261                         goto done;
 262
 263                 if (subtype) {
 264                         if (file_printf(ms, " %s", subtype) == -1)
 265                                 goto done;
 266                 }
 267
 268                 if (file_printf(ms, " %s", type) == -1)
 269                         goto done;
 270
 271                 if (executable)
 272                         if (file_printf(ms, " executable") == -1)
 273                                 goto done;
 274
 275                 if (has_long_lines)
 276                         if (file_printf(ms, ", with very long lines (%"
 277                             SIZE_T_FORMAT "u)", has_long_lines) == -1)
 278                                 goto done;
 279
 280                 /*
 281                  * Only report line terminators if we find one other than LF,
 282                  * or if we find none at all.
 283                  */
 284                 if ((n_crlf == 0 && n_cr == 0 && n_nel == 0 && n_lf == 0) ||
 285                     (n_crlf != 0 || n_cr != 0 || n_nel != 0)) {
 286                         if (file_printf(ms, ", with") == -1)
 287                                 goto done;
 288
 289                         if (n_crlf == 0 && n_cr == 0 &&
 290                             n_nel == 0 && n_lf == 0) {
 291                                 if (file_printf(ms, " no") == -1)
 292                                         goto done;
 293                         } else {
 294                                 if (n_crlf) {
 295                                         if (file_printf(ms, " CRLF") == -1)
 296                                                 goto done;
 297                                         if (n_cr || n_lf || n_nel)
 298                                                 if (file_printf(ms, ",") == -1)
 299                                                         goto done;
 300                                 }
 301                                 if (n_cr) {
 302                                         if (file_printf(ms, " CR") == -1)
 303                                                 goto done;
 304                                         if (n_lf || n_nel)
 305                                                 if (file_printf(ms, ",") == -1)
 306                                                         goto done;
 307                                 }
 308                                 if (n_lf) {
 309                                         if (file_printf(ms, " LF") == -1)
 310                                                 goto done;
 311                                         if (n_nel)
 312                                                 if (file_printf(ms, ",") == -1)
 313                                                         goto done;
 314                                 }
 315                                 if (n_nel)
 316                                         if (file_printf(ms, " NEL") == -1)
 317                                                 goto done;
 318                         }
 319
 320                         if (file_printf(ms, " line terminators") == -1)
 321                                 goto done;
 322                 }
 323
 324                 if (has_escapes)
 325                         if (file_printf(ms, ", with escape sequences") == -1)
 326                                 goto done;
 327                 if (has_backspace)
 328                         if (file_printf(ms, ", with overstriking") == -1)
 329                                 goto done;
 330         }
 331         rv = 1;
 332 done:
 333         free(utf8_buf);
 334
 335         return rv;
 336 }
 337
 338 /*
 339  * Encode Unicode string as UTF-8, returning pointer to character
 340  * after end of string, or NULL if an invalid character is found.
 341  */
 342 private unsigned char *
 343 encode_utf8(unsigned char *buf, size_t len, file_unichar_t *ubuf, size_t ulen)
 344 {
 345         size_t i;
 346         unsigned char *end = buf + len;
 347
 348         for (i = 0; i < ulen; i++) {
 349                 if (ubuf[i] <= 0x7f) {
 350                         if (end - buf < 1)
 351                                 return NULL;
 352                         *buf++ = CAST(unsigned char, ubuf[i]);
 353                         continue;
 354                 }
 355                 if (ubuf[i] <= 0x7ff) {
 356                         if (end - buf < 2)
 357                                 return NULL;
 358                         *buf++ = CAST(unsigned char, (ubuf[i] >> 6) + 0xc0);
 359                         goto out1;
 360                 }
 361                 if (ubuf[i] <= 0xffff) {
 362                         if (end - buf < 3)
 363                                 return NULL;
 364                         *buf++ = CAST(unsigned char, (ubuf[i] >> 12) + 0xe0);
 365                         goto out2;
 366                 }
 367                 if (ubuf[i] <= 0x1fffff) {
 368                         if (end - buf < 4)
 369                                 return NULL;
 370                         *buf++ = CAST(unsigned char, (ubuf[i] >> 18) + 0xf0);
 371                         goto out3;
 372                 }
 373                 if (ubuf[i] <= 0x3ffffff) {
 374                         if (end - buf < 5)
 375                                 return NULL;
 376                         *buf++ = CAST(unsigned char, (ubuf[i] >> 24) + 0xf8);
 377                         goto out4;
 378                 }
 379                 if (ubuf[i] <= 0x7fffffff) {
 380                         if (end - buf < 6)
 381                                 return NULL;
 382                         *buf++ = CAST(unsigned char, (ubuf[i] >> 30) + 0xfc);
 383                         goto out5;
 384                 }
 385                 /* Invalid character */
 386                 return NULL;
 387         out5:   *buf++ = CAST(unsigned char, ((ubuf[i] >> 24) & 0x3f) + 0x80);
 388         out4:   *buf++ = CAST(unsigned char, ((ubuf[i] >> 18) & 0x3f) + 0x80);
 389         out3:   *buf++ = CAST(unsigned char, ((ubuf[i] >> 12) & 0x3f) + 0x80);
 390         out2:   *buf++ = CAST(unsigned char, ((ubuf[i] >>  6) & 0x3f) + 0x80);
 391         out1:   *buf++ = CAST(unsigned char, ((ubuf[i] >>  0) & 0x3f) + 0x80);
 392         }
 393
 394         return buf;
 395 }