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 1.107 2020/06/08 19:58:36 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
 119         int has_escapes = 0;
 120         int has_backspace = 0;
 121         int seen_cr = 0;
 122
 123         int n_crlf = 0;
 124         int n_lf = 0;
 125         int n_cr = 0;
 126         int n_nel = 0;
 127         int executable = 0;
 128
 129         size_t last_line_end = CAST(size_t, -1);
 130         int has_long_lines = 0;
 131
 132         nbytes = trim_nuls(buf, nbytes);
 133
 134         /* If we have fewer than 2 bytes, give up. */
 135         if (nbytes <= 1) {
 136                 rv = 0;
 137                 goto done;
 138         }
 139
 140         if (ulen > 0 && (ms->flags & MAGIC_NO_CHECK_SOFT) == 0) {
 141                 /* Convert ubuf to UTF-8 and try text soft magic */
 142                 /* malloc size is a conservative overestimate; could be
 143                    improved, or at least realloced after conversion. */
 144                 mlen = ulen * 6;
 145                 if ((utf8_buf = CAST(unsigned char *, malloc(mlen))) == NULL) {
 146                         file_oomem(ms, mlen);
 147                         goto done;
 148                 }
 149                 if ((utf8_end = encode_utf8(utf8_buf, mlen, ubuf, ulen))
 150                     == NULL)
 151                         goto done;
 152                 buffer_init(&bb, b->fd, &b->st, utf8_buf,
 153                     CAST(size_t, utf8_end - utf8_buf));
 154
 155                 if ((rv = file_softmagic(ms, &bb, NULL, NULL,
 156                     TEXTTEST, text)) == 0)
 157                         rv = -1;
 158                 else
 159                         need_separator = 1;
 160                 buffer_fini(&bb);
 161                 if ((ms->flags & (MAGIC_APPLE|MAGIC_EXTENSION))) {
 162                         rv = rv == -1 ? 0 : 1;
 163                         goto done;
 164                 }
 165         }
 166
 167         if ((ms->flags & (MAGIC_APPLE|MAGIC_EXTENSION))) {
 168                 rv = 0;
 169                 goto done;
 170         }
 171
 172         /* Now try to discover other details about the file. */
 173         for (i = 0; i < ulen; i++) {
 174                 if (ubuf[i] == '\n') {
 175                         if (seen_cr)
 176                                 n_crlf++;
 177                         else
 178                                 n_lf++;
 179                         last_line_end = i;
 180                 } else if (seen_cr)
 181                         n_cr++;
 182
 183                 seen_cr = (ubuf[i] == '\r');
 184                 if (seen_cr)
 185                         last_line_end = i;
 186
 187                 if (ubuf[i] == 0x85) { /* X3.64/ECMA-43 "next line" character */
 188                         n_nel++;
 189                         last_line_end = i;
 190                 }
 191
 192                 /* If this line is _longer_ than MAXLINELEN, remember it. */
 193                 if (i > last_line_end + MAXLINELEN)
 194                         has_long_lines = 1;
 195
 196                 if (ubuf[i] == '\033')
 197                         has_escapes = 1;
 198                 if (ubuf[i] == '\b')
 199                         has_backspace = 1;
 200         }
 201
 202         /* Beware, if the data has been truncated, the final CR could have
 203            been followed by a LF.  If we have ms->bytes_max bytes, it indicates
 204            that the data might have been truncated, probably even before
 205            this function was called. */
 206         if (seen_cr && nbytes < ms->bytes_max)
 207                 n_cr++;
 208
 209         if (strcmp(type, "binary") == 0) {
 210                 rv = 0;
 211                 goto done;
 212         }
 213         len = file_printedlen(ms);
 214         if (mime) {
 215                 if ((mime & MAGIC_MIME_TYPE) != 0) {
 216                         if (len) {
 217                                 /*
 218                                  * Softmagic printed something, we
 219                                  * are either done, or we need a separator
 220                                  */
 221                                 if ((ms->flags & MAGIC_CONTINUE) == 0) {
 222                                         rv = 1;
 223                                         goto done;
 224                                 }
 225                                 if (need_separator && file_separator(ms) == -1)
 226                                         goto done;
 227                         } else {
 228                                 if (file_printf(ms, "text/plain") == -1)
 229                                         goto done;
 230                         }
 231                 }
 232         } else {
 233                 if (len) {
 234                         switch (file_replace(ms, " text$", ", ")) {
 235                         case 0:
 236                                 switch (file_replace(ms, " text executable$",
 237                                     ", ")) {
 238                                 case 0:
 239                                         if (file_printf(ms, ", ") == -1)
 240                                                 goto done;
 241                                         break;
 242                                 case -1:
 243                                         goto done;
 244                                 default:
 245                                         executable = 1;
 246                                         break;
 247                                 }
 248                                 break;
 249                         case -1:
 250                                 goto done;
 251                         default:
 252                                 break;
 253                         }
 254                 }
 255
 256                 if (file_printf(ms, "%s", code) == -1)
 257                         goto done;
 258
 259                 if (subtype) {
 260                         if (file_printf(ms, " %s", subtype) == -1)
 261                                 goto done;
 262                 }
 263
 264                 if (file_printf(ms, " %s", type) == -1)
 265                         goto done;
 266
 267                 if (executable)
 268                         if (file_printf(ms, " executable") == -1)
 269                                 goto done;
 270
 271                 if (has_long_lines)
 272                         if (file_printf(ms, ", with very long lines") == -1)
 273                                 goto done;
 274
 275                 /*
 276                  * Only report line terminators if we find one other than LF,
 277                  * or if we find none at all.
 278                  */
 279                 if ((n_crlf == 0 && n_cr == 0 && n_nel == 0 && n_lf == 0) ||
 280                     (n_crlf != 0 || n_cr != 0 || n_nel != 0)) {
 281                         if (file_printf(ms, ", with") == -1)
 282                                 goto done;
 283
 284                         if (n_crlf == 0 && n_cr == 0 && n_nel == 0 && n_lf == 0) {
 285                                 if (file_printf(ms, " no") == -1)
 286                                         goto done;
 287                         } else {
 288                                 if (n_crlf) {
 289                                         if (file_printf(ms, " CRLF") == -1)
 290                                                 goto done;
 291                                         if (n_cr || n_lf || n_nel)
 292                                                 if (file_printf(ms, ",") == -1)
 293                                                         goto done;
 294                                 }
 295                                 if (n_cr) {
 296                                         if (file_printf(ms, " CR") == -1)
 297                                                 goto done;
 298                                         if (n_lf || n_nel)
 299                                                 if (file_printf(ms, ",") == -1)
 300                                                         goto done;
 301                                 }
 302                                 if (n_lf) {
 303                                         if (file_printf(ms, " LF") == -1)
 304                                                 goto done;
 305                                         if (n_nel)
 306                                                 if (file_printf(ms, ",") == -1)
 307                                                         goto done;
 308                                 }
 309                                 if (n_nel)
 310                                         if (file_printf(ms, " NEL") == -1)
 311                                                 goto done;
 312                         }
 313
 314                         if (file_printf(ms, " line terminators") == -1)
 315                                 goto done;
 316                 }
 317
 318                 if (has_escapes)
 319                         if (file_printf(ms, ", with escape sequences") == -1)
 320                                 goto done;
 321                 if (has_backspace)
 322                         if (file_printf(ms, ", with overstriking") == -1)
 323                                 goto done;
 324         }
 325         rv = 1;
 326 done:
 327         free(utf8_buf);
 328
 329         return rv;
 330 }
 331
 332 /*
 333  * Encode Unicode string as UTF-8, returning pointer to character
 334  * after end of string, or NULL if an invalid character is found.
 335  */
 336 private unsigned char *
 337 encode_utf8(unsigned char *buf, size_t len, unichar *ubuf, size_t ulen)
 338 {
 339         size_t i;
 340         unsigned char *end = buf + len;
 341
 342         for (i = 0; i < ulen; i++) {
 343                 if (ubuf[i] <= 0x7f) {
 344                         if (end - buf < 1)
 345                                 return NULL;
 346                         *buf++ = CAST(unsigned char, ubuf[i]);
 347                 } else if (ubuf[i] <= 0x7ff) {
 348                         if (end - buf < 2)
 349                                 return NULL;
 350                         *buf++ = CAST(unsigned char, (ubuf[i] >> 6) + 0xc0);
 351                         *buf++ = CAST(unsigned char, (ubuf[i] & 0x3f) + 0x80);
 352                 } else if (ubuf[i] <= 0xffff) {
 353                         if (end - buf < 3)
 354                                 return NULL;
 355                         *buf++ = CAST(unsigned char, (ubuf[i] >> 12) + 0xe0);
 356                         *buf++ = CAST(unsigned char, ((ubuf[i] >> 6) & 0x3f) + 0x80);
 357                         *buf++ = CAST(unsigned char, (ubuf[i] & 0x3f) + 0x80);
 358                 } else if (ubuf[i] <= 0x1fffff) {
 359                         if (end - buf < 4)
 360                                 return NULL;
 361                         *buf++ = CAST(unsigned char, (ubuf[i] >> 18) + 0xf0);
 362                         *buf++ = CAST(unsigned char, ((ubuf[i] >> 12) & 0x3f) + 0x80);
 363                         *buf++ = CAST(unsigned char, ((ubuf[i] >>  6) & 0x3f) + 0x80);
 364                         *buf++ = CAST(unsigned char, (ubuf[i] & 0x3f) + 0x80);
 365                 } else if (ubuf[i] <= 0x3ffffff) {
 366                         if (end - buf < 5)
 367                                 return NULL;
 368                         *buf++ = CAST(unsigned char, (ubuf[i] >> 24) + 0xf8);
 369                         *buf++ = CAST(unsigned char, ((ubuf[i] >> 18) & 0x3f) + 0x80);
 370                         *buf++ = CAST(unsigned char, ((ubuf[i] >> 12) & 0x3f) + 0x80);
 371                         *buf++ = CAST(unsigned char, ((ubuf[i] >>  6) & 0x3f) + 0x80);
 372                         *buf++ = CAST(unsigned char, (ubuf[i] & 0x3f) + 0x80);
 373                 } else if (ubuf[i] <= 0x7fffffff) {
 374                         if (end - buf < 6)
 375                                 return NULL;
 376                         *buf++ = CAST(unsigned char, (ubuf[i] >> 30) + 0xfc);
 377                         *buf++ = CAST(unsigned char, ((ubuf[i] >> 24) & 0x3f) + 0x80);
 378                         *buf++ = CAST(unsigned char, ((ubuf[i] >> 18) & 0x3f) + 0x80);
 379                         *buf++ = CAST(unsigned char, ((ubuf[i] >> 12) & 0x3f) + 0x80);
 380                         *buf++ = CAST(unsigned char, ((ubuf[i] >>  6) & 0x3f) + 0x80);
 381                         *buf++ = CAST(unsigned char, (ubuf[i] & 0x3f) + 0x80);
 382                 } else /* Invalid character */
 383                         return NULL;
 384         }
 385
 386         return buf;
 387 }