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