src/src/mime.c

   1 /*************************************************
   2 *     Exim - an Internet mail transport agent    *
   3 *************************************************/
   4
   5 /* Copyright (c) Tom Kistner <tom@duncanthrax.net> 2004, 2015 */
   6 /* License: GPL */
   7
   8 #include "exim.h"
   9 #ifdef WITH_CONTENT_SCAN        /* entire file */
  10 #include "mime.h"
  11 #include <sys/stat.h>
  12
  13 FILE *mime_stream = NULL;
  14 uschar *mime_current_boundary = NULL;
  15
  16 static mime_header mime_header_list[] = {
  17   { US"content-type:",              13, &mime_content_type },
  18   { US"content-disposition:",       20, &mime_content_disposition },
  19   { US"content-transfer-encoding:", 26, &mime_content_transfer_encoding },
  20   { US"content-id:",                11, &mime_content_id },
  21   { US"content-description:",       20, &mime_content_description }
  22 };
  23
  24 static int mime_header_list_size = nelem(mime_header_list);
  25
  26 static mime_parameter mime_parameter_list[] = {
  27   { US"name=",     5, &mime_filename },
  28   { US"filename=", 9, &mime_filename },
  29   { US"charset=",  8, &mime_charset  },
  30   { US"boundary=", 9, &mime_boundary }
  31 };
  32
  33
  34 /*************************************************
  35 * set MIME anomaly level + text                  *
  36 *************************************************/
  37
  38 /* Small wrapper to set the two expandables which
  39    give info on detected "problems" in MIME
  40    encodings. Indexes are defined in mime.h. */
  41
  42 void
  43 mime_set_anomaly(int idx)
  44 {
  45 struct anom {
  46   int level;
  47   const uschar * text;
  48 } anom[] = { {1, CUS"Broken Quoted-Printable encoding detected"},
  49              {2, CUS"Broken BASE64 encoding detected"} };
  50
  51 mime_anomaly_level = anom[idx].level;
  52 mime_anomaly_text =  anom[idx].text;
  53 }
  54
  55
  56 /*************************************************
  57 * decode quoted-printable chars                  *
  58 *************************************************/
  59
  60 /* gets called when we hit a =
  61    returns: new pointer position
  62    result code in c:
  63           -2 - decode error
  64           -1 - soft line break, no char
  65            0-255 - char to write
  66 */
  67
  68 static uschar *
  69 mime_decode_qp_char(uschar *qp_p, int *c)
  70 {
  71 uschar *initial_pos = qp_p;
  72
  73 /* advance one char */
  74 qp_p++;
  75
  76 /* Check for two hex digits and decode them */
  77 if (isxdigit(*qp_p) && isxdigit(qp_p[1]))
  78   {
  79   /* Do hex conversion */
  80   *c = (isdigit(*qp_p) ? *qp_p - '0' : toupper(*qp_p) - 'A' + 10) <<4;
  81   qp_p++;
  82   *c |= isdigit(*qp_p) ? *qp_p - '0' : toupper(*qp_p) - 'A' + 10;
  83   return qp_p + 1;
  84   }
  85
  86 /* tab or whitespace may follow just ignore it if it precedes \n */
  87 while (*qp_p == '\t' || *qp_p == ' ' || *qp_p == '\r')
  88   qp_p++;
  89
  90 if (*qp_p == '\n')      /* hit soft line break */
  91   {
  92   *c = -1;
  93   return qp_p;
  94   }
  95
  96 /* illegal char here */
  97 *c = -2;
  98 return initial_pos;
  99 }
 100
 101
 102 /* just dump MIME part without any decoding */
 103 static ssize_t
 104 mime_decode_asis(FILE* in, FILE* out, uschar* boundary)
 105 {
 106   ssize_t len, size = 0;
 107   uschar buffer[MIME_MAX_LINE_LENGTH];
 108
 109   while(fgets(CS buffer, MIME_MAX_LINE_LENGTH, mime_stream) != NULL)
 110     {
 111     if (boundary != NULL
 112        && Ustrncmp(buffer, "--", 2) == 0
 113        && Ustrncmp((buffer+2), boundary, Ustrlen(boundary)) == 0
 114        )
 115       break;
 116
 117     len = Ustrlen(buffer);
 118     if (fwrite(buffer, 1, (size_t)len, out) < len)
 119       return -1;
 120     size += len;
 121     } /* while */
 122   return size;
 123 }
 124
 125
 126
 127 /* decode quoted-printable MIME part */
 128 static ssize_t
 129 mime_decode_qp(FILE* in, FILE* out, uschar* boundary)
 130 {
 131 uschar ibuf[MIME_MAX_LINE_LENGTH], obuf[MIME_MAX_LINE_LENGTH];
 132 uschar *ipos, *opos;
 133 ssize_t len, size = 0;
 134
 135 while (fgets(CS ibuf, MIME_MAX_LINE_LENGTH, in) != NULL)
 136   {
 137   if (boundary != NULL
 138      && Ustrncmp(ibuf, "--", 2) == 0
 139      && Ustrncmp((ibuf+2), boundary, Ustrlen(boundary)) == 0
 140      )
 141     break; /* todo: check for missing boundary */
 142
 143   ipos = ibuf;
 144   opos = obuf;
 145
 146   while (*ipos != 0)
 147     {
 148     if (*ipos == '=')
 149       {
 150       int decode_qp_result;
 151
 152       ipos = mime_decode_qp_char(ipos, &decode_qp_result);
 153
 154       if (decode_qp_result == -2)
 155         {
 156         /* Error from decoder. ipos is unchanged. */
 157         mime_set_anomaly(MIME_ANOMALY_BROKEN_QP);
 158         *opos = '=';
 159         ++opos;
 160         ++ipos;
 161         }
 162       else if (decode_qp_result == -1)
 163         break;
 164       else if (decode_qp_result >= 0)
 165         {
 166         *opos = decode_qp_result;
 167         ++opos;
 168         }
 169       }
 170     else
 171       {
 172       *opos = *ipos;
 173       ++opos;
 174       ++ipos;
 175       }
 176     }
 177   /* something to write? */
 178   len = opos - obuf;
 179   if (len > 0)
 180     {
 181     if (fwrite(obuf, 1, len, out) != len) return -1; /* error */
 182     size += len;
 183     }
 184   }
 185 return size;
 186 }
 187
 188
 189 static FILE *
 190 mime_get_decode_file(uschar *pname, uschar *fname)
 191 {
 192 FILE *f = NULL;
 193 uschar *filename;
 194
 195 filename = (uschar *)malloc(2048);
 196
 197 if (pname && fname)
 198   {
 199   (void)string_format(filename, 2048, "%s/%s", pname, fname);
 200   f = modefopen(filename,"wb+",SPOOL_MODE);
 201   }
 202 else if (!pname)
 203   f = modefopen(fname,"wb+",SPOOL_MODE);
 204 else if (!fname)
 205   {
 206   int file_nr = 0;
 207   int result = 0;
 208
 209   /* must find first free sequential filename */
 210   do
 211     {
 212     struct stat mystat;
 213     (void)string_format(filename, 2048,
 214       "%s/%s-%05u", pname, message_id, file_nr++);
 215     /* security break */
 216     if (file_nr >= 1024)
 217       break;
 218     result = stat(CS filename, &mystat);
 219     } while(result != -1);
 220
 221   f = modefopen(filename, "wb+", SPOOL_MODE);
 222   }
 223
 224 /* set expansion variable */
 225 mime_decoded_filename = filename;
 226
 227 return f;
 228 }
 229
 230
 231 int
 232 mime_decode(const uschar **listptr)
 233 {
 234 int sep = 0;
 235 const uschar *list = *listptr;
 236 uschar *option;
 237 uschar option_buffer[1024];
 238 uschar decode_path[1024];
 239 FILE *decode_file = NULL;
 240 long f_pos = 0;
 241 ssize_t size_counter = 0;
 242 ssize_t (*decode_function)(FILE*, FILE*, uschar*);
 243
 244 if (mime_stream == NULL)
 245   return FAIL;
 246
 247 f_pos = ftell(mime_stream);
 248
 249 /* build default decode path (will exist since MBOX must be spooled up) */
 250 (void)string_format(decode_path,1024,"%s/scan/%s",spool_directory,message_id);
 251
 252 /* try to find 1st option */
 253 if ((option = string_nextinlist(&list, &sep,
 254                                 option_buffer,
 255                                 sizeof(option_buffer))) != NULL)
 256   {
 257   /* parse 1st option */
 258   if ( (Ustrcmp(option,"false") == 0) || (Ustrcmp(option,"0") == 0) )
 259     /* explicitly no decoding */
 260     return FAIL;
 261
 262   if (Ustrcmp(option,"default") == 0)
 263     /* explicit default path + file names */
 264     goto DEFAULT_PATH;
 265
 266   if (option[0] == '/')
 267     {
 268     struct stat statbuf;
 269
 270     memset(&statbuf,0,sizeof(statbuf));
 271
 272     /* assume either path or path+file name */
 273     if ( (stat(CS option, &statbuf) == 0) && S_ISDIR(statbuf.st_mode) )
 274       /* is directory, use it as decode_path */
 275       decode_file = mime_get_decode_file(option, NULL);
 276     else
 277       /* does not exist or is a file, use as full file name */
 278       decode_file = mime_get_decode_file(NULL, option);
 279     }
 280   else
 281     /* assume file name only, use default path */
 282     decode_file = mime_get_decode_file(decode_path, option);
 283   }
 284 else
 285   {
 286   /* no option? patch default path */
 287 DEFAULT_PATH:
 288   decode_file = mime_get_decode_file(decode_path, NULL);
 289   }
 290
 291 if (!decode_file)
 292   return DEFER;
 293
 294 /* decode according to mime type */
 295 decode_function =
 296   !mime_content_transfer_encoding
 297   ? mime_decode_asis    /* no encoding, dump as-is */
 298   : Ustrcmp(mime_content_transfer_encoding, "base64") == 0
 299   ? mime_decode_base64
 300   : Ustrcmp(mime_content_transfer_encoding, "quoted-printable") == 0
 301   ? mime_decode_qp
 302   : mime_decode_asis;   /* unknown encoding type, just dump as-is */
 303
 304 size_counter = decode_function(mime_stream, decode_file, mime_current_boundary);
 305
 306 clearerr(mime_stream);
 307 if (fseek(mime_stream, f_pos, SEEK_SET))
 308   return DEFER;
 309
 310 if (fclose(decode_file) != 0 || size_counter < 0)
 311   return DEFER;
 312
 313 /* round up to the next KiB */
 314 mime_content_size = (size_counter + 1023) / 1024;
 315
 316 return OK;
 317 }
 318
 319
 320 static int
 321 mime_get_header(FILE *f, uschar *header)
 322 {
 323 int c = EOF;
 324 int done = 0;
 325 int header_value_mode = 0;
 326 int header_open_brackets = 0;
 327 int num_copied = 0;
 328
 329 while(!done)
 330   {
 331   if ((c = fgetc(f)) == EOF) break;
 332
 333   /* always skip CRs */
 334   if (c == '\r') continue;
 335
 336   if (c == '\n')
 337     {
 338     if (num_copied > 0)
 339       {
 340       /* look if next char is '\t' or ' ' */
 341       if ((c = fgetc(f)) == EOF) break;
 342       if ( (c == '\t') || (c == ' ') ) continue;
 343       (void)ungetc(c,f);
 344       }
 345     /* end of the header, terminate with ';' */
 346     c = ';';
 347     done = 1;
 348     }
 349
 350   /* skip control characters */
 351   if (c < 32) continue;
 352
 353   if (header_value_mode)
 354     {
 355     /* --------- value mode ----------- */
 356     /* skip leading whitespace */
 357     if ( ((c == '\t') || (c == ' ')) && (header_value_mode == 1) )
 358       continue;
 359
 360       /* we have hit a non-whitespace char, start copying value data */
 361       header_value_mode = 2;
 362
 363       if (c == '"')       /* flip "quoted" mode */
 364         header_value_mode = header_value_mode==2 ? 3 : 2;
 365
 366       /* leave value mode on unquoted ';' */
 367       if (header_value_mode == 2 && c == ';') {
 368         header_value_mode = 0;
 369       };
 370       /* -------------------------------- */
 371     }
 372   else
 373     {
 374     /* -------- non-value mode -------- */
 375     /* skip whitespace + tabs */
 376     if ( (c == ' ') || (c == '\t') )
 377       continue;
 378     if (c == '\\')
 379       {
 380       /* quote next char. can be used
 381       to escape brackets. */
 382       if ((c = fgetc(f)) == EOF) break;
 383       }
 384     else if (c == '(')
 385       {
 386       header_open_brackets++;
 387       continue;
 388       }
 389     else if ((c == ')') && header_open_brackets)
 390       {
 391       header_open_brackets--;
 392       continue;
 393       }
 394     else if ( (c == '=') && !header_open_brackets ) /* enter value mode */
 395       header_value_mode = 1;
 396
 397     /* skip chars while we are in a comment */
 398     if (header_open_brackets > 0)
 399       continue;
 400     /* -------------------------------- */
 401     }
 402
 403   /* copy the char to the buffer */
 404   header[num_copied++] = (uschar)c;
 405
 406   /* break if header buffer is full */
 407   if (num_copied > MIME_MAX_HEADER_SIZE-1)
 408     done = 1;
 409   }
 410
 411 if ((num_copied > 0) && (header[num_copied-1] != ';'))
 412   header[num_copied-1] = ';';
 413
 414 /* 0-terminate */
 415 header[num_copied] = '\0';
 416
 417 /* return 0 for EOF or empty line */
 418 if ((c == EOF) || (num_copied == 1))
 419   return 0;
 420 else
 421   return 1;
 422 }
 423
 424
 425 static void
 426 mime_vars_reset(void)
 427 {
 428 mime_anomaly_level     = 0;
 429 mime_anomaly_text      = NULL;
 430 mime_boundary          = NULL;
 431 mime_charset           = NULL;
 432 mime_decoded_filename  = NULL;
 433 mime_filename          = NULL;
 434 mime_content_description = NULL;
 435 mime_content_disposition = NULL;
 436 mime_content_id        = NULL;
 437 mime_content_transfer_encoding = NULL;
 438 mime_content_type      = NULL;
 439 mime_is_multipart      = 0;
 440 mime_content_size      = 0;
 441 }
 442
 443
 444 /* Grab a parameter value, dealing with quoting.
 445
 446 Arguments:
 447  str    Input string.  Updated on return to point to terminating ; or NUL
 448
 449 Return:
 450  Allocated string with parameter value
 451 */
 452 static uschar *
 453 mime_param_val(uschar ** sp)
 454 {
 455 uschar * s = *sp;
 456 uschar * val = NULL;
 457 int size = 0, ptr = 0;
 458
 459 /* debug_printf("   considering paramval '%s'\n", s); */
 460
 461 while (*s && *s != ';')         /* ; terminates */
 462   if (*s == '"')
 463     {
 464     s++;                        /* skip opening " */
 465     while (*s && *s != '"')     /* " protects ; */
 466       val = string_cat(val, &size, &ptr, s++, 1);
 467     if (*s) s++;                /* skip closing " */
 468     }
 469   else
 470     val = string_cat(val, &size, &ptr, s++, 1);
 471 if (val) val[ptr] = '\0';
 472 *sp = s;
 473 return val;
 474 }
 475
 476 static uschar *
 477 mime_next_semicolon(uschar * s)
 478 {
 479 while (*s && *s != ';')         /* ; terminates */
 480   if (*s == '"')
 481     {
 482     s++;                        /* skip opening " */
 483     while (*s && *s != '"')     /* " protects ; */
 484       s++;
 485     if (*s) s++;                /* skip closing " */
 486     }
 487   else
 488     s++;
 489 return s;
 490 }
 491
 492
 493 static uschar *
 494 rfc2231_to_2047(const uschar * fname, const uschar * charset, int * len)
 495 {
 496 int size = 0, ptr = 0;
 497 uschar * val = string_cat(NULL, &size, &ptr, US"=?", 2);
 498 uschar c;
 499
 500 if (charset)
 501   val = string_cat(val, &size, &ptr, charset, Ustrlen(charset));
 502 val = string_cat(val, &size, &ptr, US"?Q?", 3);
 503
 504 while ((c = *fname))
 505   if (c == '%' && isxdigit(fname[1]) && isxdigit(fname[2]))
 506     {
 507     val = string_cat(val, &size, &ptr, US"=", 1);
 508     val = string_cat(val, &size, &ptr, ++fname, 2);
 509     fname += 2;
 510     }
 511   else
 512     val = string_cat(val, &size, &ptr, fname++, 1);
 513
 514 val = string_cat(val, &size, &ptr, US"?=", 2);
 515 val[*len = ptr] = '\0';
 516 return val;
 517 }
 518
 519
 520 int
 521 mime_acl_check(uschar *acl, FILE *f, struct mime_boundary_context *context,
 522     uschar **user_msgptr, uschar **log_msgptr)
 523 {
 524 int rc = OK;
 525 uschar * header = NULL;
 526 struct mime_boundary_context nested_context;
 527
 528 /* reserve a line buffer to work in */
 529 header = store_get(MIME_MAX_HEADER_SIZE+1);
 530
 531 /* Not actually used at the moment, but will be vital to fixing
 532  * some RFC 2046 nonconformance later... */
 533 nested_context.parent = context;
 534
 535 /* loop through parts */
 536 while(1)
 537   {
 538   /* reset all per-part mime variables */
 539   mime_vars_reset();
 540
 541   /* If boundary is null, we assume that *f is positioned on the start of
 542   headers (for example, at the very beginning of a message.  If a boundary is
 543   given, we must first advance to it to reach the start of the next header
 544   block.  */
 545
 546   /* NOTE -- there's an error here -- RFC2046 specifically says to
 547    * check for outer boundaries.  This code doesn't do that, and
 548    * I haven't fixed this.
 549    *
 550    * (I have moved partway towards adding support, however, by adding
 551    * a "parent" field to my new boundary-context structure.)
 552    */
 553   if (context) for (;;)
 554     {
 555     if (!fgets(CS header, MIME_MAX_HEADER_SIZE, f))
 556       {
 557       /* Hit EOF or read error. Ugh. */
 558       DEBUG(D_acl) debug_printf("MIME: Hit EOF ...\n");
 559       return rc;
 560       }
 561
 562     /* boundary line must start with 2 dashes */
 563     if (  Ustrncmp(header, "--", 2) == 0
 564        && Ustrncmp(header+2, context->boundary, Ustrlen(context->boundary)) == 0
 565        )
 566       {                 /* found boundary */
 567       if (Ustrncmp((header+2+Ustrlen(context->boundary)), "--", 2) == 0)
 568         {
 569         /* END boundary found */
 570         DEBUG(D_acl) debug_printf("MIME: End boundary found %s\n",
 571           context->boundary);
 572         return rc;
 573         }
 574
 575       DEBUG(D_acl) debug_printf("MIME: Next part with boundary %s\n",
 576         context->boundary);
 577       break;
 578       }
 579     }
 580
 581   /* parse headers, set up expansion variables */
 582   while (mime_get_header(f, header))
 583     {
 584     struct mime_header * mh;
 585
 586     /* look for interesting headers */
 587     for (mh = mime_header_list;
 588          mh < mime_header_list + mime_header_list_size;
 589          mh++) if (strncmpic(mh->name, header, mh->namelen) == 0)
 590       {
 591       uschar * p = header + mh->namelen;
 592       uschar * q;
 593
 594       /* grab the value (normalize to lower case)
 595       and copy to its corresponding expansion variable */
 596
 597       for (q = p; *q != ';' && *q; q++) ;
 598       *mh->value = string_copynlc(p, q-p);
 599       DEBUG(D_acl) debug_printf("MIME: found %s header, value is '%s'\n",
 600         mh->name, *mh->value);
 601
 602       if (*(p = q)) p++;                        /* jump past the ; */
 603
 604         {
 605         uschar * mime_fname = NULL;
 606         uschar * mime_fname_rfc2231 = NULL;
 607         uschar * mime_filename_charset = NULL;
 608         BOOL decoding_failed = FALSE;
 609
 610         /* grab all param=value tags on the remaining line,
 611         check if they are interesting */
 612
 613         while (*p)
 614           {
 615           mime_parameter * mp;
 616
 617           DEBUG(D_acl) debug_printf("MIME:   considering paramlist '%s'\n", p);
 618
 619           if (  !mime_filename
 620              && strncmpic(CUS"content-disposition:", header, 20) == 0
 621              && strncmpic(CUS"filename*", p, 9) == 0
 622              )
 623             {                                   /* RFC 2231 filename */
 624             uschar * q;
 625
 626             /* find value of the filename */
 627             p += 9;
 628             while(*p != '=' && *p) p++;
 629             if (*p) p++;                        /* p is filename or NUL */
 630             q = mime_param_val(&p);             /* p now trailing ; or NUL */
 631
 632             if (q && *q)
 633               {
 634               uschar * temp_string, * err_msg;
 635               int slen;
 636
 637               /* build up an un-decoded filename over successive
 638               filename*= parameters (for use when 2047 decode fails) */
 639
 640               mime_fname_rfc2231 = string_sprintf("%#s%s",
 641                 mime_fname_rfc2231, q);
 642
 643               if (!decoding_failed)
 644                 {
 645                 int size;
 646                 if (!mime_filename_charset)
 647                   {
 648                   uschar * s = q;
 649
 650                   /* look for a ' in the "filename" */
 651                   while(*s != '\'' && *s) s++;  /* s is 1st ' or NUL */
 652
 653                   if ((size = s-q) > 0)
 654                     mime_filename_charset = string_copyn(q, size);
 655
 656                   if (*(p = s)) p++;
 657                   while(*p == '\'') p++;        /* p is after 2nd ' */
 658                   }
 659                 else
 660                   p = q;
 661
 662                 DEBUG(D_acl) debug_printf("MIME:    charset %s fname '%s'\n",
 663                   mime_filename_charset ? mime_filename_charset : US"<NULL>", p);
 664
 665                 temp_string = rfc2231_to_2047(p, mime_filename_charset, &slen);
 666                 DEBUG(D_acl) debug_printf("MIME:    2047-name %s\n", temp_string);
 667
 668                 temp_string = rfc2047_decode(temp_string, FALSE, NULL, ' ',
 669                   NULL, &err_msg);
 670                 DEBUG(D_acl) debug_printf("MIME:    plain-name %s\n", temp_string);
 671
 672                 size = Ustrlen(temp_string);
 673
 674                 if (size == slen)
 675                   decoding_failed = TRUE;
 676                 else
 677                   /* build up a decoded filename over successive
 678                   filename*= parameters */
 679
 680                   mime_filename = mime_fname = mime_fname
 681                     ? string_sprintf("%s%s", mime_fname, temp_string)
 682                     : temp_string;
 683                 }
 684               }
 685             }
 686
 687           else
 688             /* look for interesting parameters */
 689             for (mp = mime_parameter_list;
 690                  mp < mime_parameter_list + nelem(mime_parameter_list);
 691                  mp++
 692                 ) if (strncmpic(mp->name, p, mp->namelen) == 0)
 693               {
 694               uschar * q;
 695               uschar * dummy_errstr;
 696
 697               /* grab the value and copy to its expansion variable */
 698               p += mp->namelen;
 699               q = mime_param_val(&p);           /* p now trailing ; or NUL */
 700
 701               *mp->value = q && *q
 702                 ? rfc2047_decode(q, check_rfc2047_length, NULL, 32, NULL,
 703                     &dummy_errstr)
 704                 : NULL;
 705               DEBUG(D_acl) debug_printf(
 706                 "MIME:  found %s parameter in %s header, value '%s'\n",
 707                 mp->name, mh->name, *mp->value);
 708
 709               break;                    /* done matching param names */
 710               }
 711
 712
 713           /* There is something, but not one of our interesting parameters.
 714              Advance past the next semicolon */
 715           p = mime_next_semicolon(p);
 716           if (*p) p++;
 717           }                             /* param scan on line */
 718
 719         if (strncmpic(CUS"content-disposition:", header, 20) == 0)
 720           {
 721           if (decoding_failed) mime_filename = mime_fname_rfc2231;
 722
 723           DEBUG(D_acl) debug_printf(
 724             "MIME:  found %s parameter in %s header, value is '%s'\n",
 725             "filename", mh->name, mime_filename);
 726           }
 727         }
 728       }
 729     }
 730
 731   /* set additional flag variables (easier access) */
 732   if (  mime_content_type
 733      && Ustrncmp(mime_content_type,"multipart",9) == 0
 734      )
 735     mime_is_multipart = 1;
 736
 737   /* Make a copy of the boundary pointer.
 738      Required since mime_boundary is global
 739      and can be overwritten further down in recursion */
 740   nested_context.boundary = mime_boundary;
 741
 742   /* raise global counter */
 743   mime_part_count++;
 744
 745   /* copy current file handle to global variable */
 746   mime_stream = f;
 747   mime_current_boundary = context ? context->boundary : 0;
 748
 749   /* Note the context */
 750   mime_is_coverletter = !(context && context->context == MBC_ATTACHMENT);
 751
 752   /* call ACL handling function */
 753   rc = acl_check(ACL_WHERE_MIME, NULL, acl, user_msgptr, log_msgptr);
 754
 755   mime_stream = NULL;
 756   mime_current_boundary = NULL;
 757
 758   if (rc != OK) break;
 759
 760   /* If we have a multipart entity and a boundary, go recursive */
 761   if ( (mime_content_type != NULL) &&
 762        (nested_context.boundary != NULL) &&
 763        (Ustrncmp(mime_content_type,"multipart",9) == 0) )
 764     {
 765     DEBUG(D_acl)
 766       debug_printf("MIME: Entering multipart recursion, boundary '%s'\n",
 767         nested_context.boundary);
 768
 769     nested_context.context =
 770       context && context->context == MBC_ATTACHMENT
 771       ? MBC_ATTACHMENT
 772       :    Ustrcmp(mime_content_type,"multipart/alternative") == 0
 773         || Ustrcmp(mime_content_type,"multipart/related") == 0
 774       ? MBC_COVERLETTER_ALL
 775       : MBC_COVERLETTER_ONESHOT;
 776
 777     rc = mime_acl_check(acl, f, &nested_context, user_msgptr, log_msgptr);
 778     if (rc != OK) break;
 779     }
 780   else if ( (mime_content_type != NULL) &&
 781           (Ustrncmp(mime_content_type,"message/rfc822",14) == 0) )
 782     {
 783     const uschar *rfc822name = NULL;
 784     uschar filename[2048];
 785     int file_nr = 0;
 786     int result = 0;
 787
 788     /* must find first free sequential filename */
 789     do
 790       {
 791       struct stat mystat;
 792       (void)string_format(filename, 2048,
 793         "%s/scan/%s/__rfc822_%05u", spool_directory, message_id, file_nr++);
 794       /* security break */
 795       if (file_nr >= 128)
 796         goto NO_RFC822;
 797       result = stat(CS filename,&mystat);
 798       } while (result != -1);
 799
 800     rfc822name = filename;
 801
 802     /* decode RFC822 attachment */
 803     mime_decoded_filename = NULL;
 804     mime_stream = f;
 805     mime_current_boundary = context ? context->boundary : NULL;
 806     mime_decode(&rfc822name);
 807     mime_stream = NULL;
 808     mime_current_boundary = NULL;
 809     if (!mime_decoded_filename)         /* decoding failed */
 810       {
 811       log_write(0, LOG_MAIN,
 812            "mime_regex acl condition warning - could not decode RFC822 MIME part to file.");
 813       rc = DEFER;
 814       goto out;
 815       }
 816     mime_decoded_filename = NULL;
 817     }
 818
 819 NO_RFC822:
 820   /* If the boundary of this instance is NULL, we are finished here */
 821   if (!context) break;
 822
 823   if (context->context == MBC_COVERLETTER_ONESHOT)
 824     context->context = MBC_ATTACHMENT;
 825   }
 826
 827 out:
 828 mime_vars_reset();
 829 return rc;
 830 }
 831
 832 #endif  /*WITH_CONTENT_SCAN*/
 833
 834 /* vi: sw ai sw=2
 835 */