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  * Copyright (c) The Exim Maintainers 2015 - 2018
   8  */
   9
  10 #include "exim.h"
  11 #ifdef WITH_CONTENT_SCAN        /* entire file */
  12 #include "mime.h"
  13 #include <sys/stat.h>
  14
  15 FILE *mime_stream = NULL;
  16 uschar *mime_current_boundary = NULL;
  17
  18 static mime_header mime_header_list[] = {
  19   /*    name                    namelen         value */
  20   { US"content-type:",              13, &mime_content_type },
  21   { US"content-disposition:",       20, &mime_content_disposition },
  22   { US"content-transfer-encoding:", 26, &mime_content_transfer_encoding },
  23   { US"content-id:",                11, &mime_content_id },
  24   { US"content-description:",       20, &mime_content_description }
  25 };
  26
  27 static int mime_header_list_size = nelem(mime_header_list);
  28
  29 static mime_parameter mime_parameter_list[] = {
  30   /*    name    namelen  value */
  31   { US"name=",     5, &mime_filename },
  32   { US"filename=", 9, &mime_filename },
  33   { US"charset=",  8, &mime_charset  },
  34   { US"boundary=", 9, &mime_boundary }
  35 };
  36
  37
  38 /*************************************************
  39 * set MIME anomaly level + text                  *
  40 *************************************************/
  41
  42 /* Small wrapper to set the two expandables which
  43    give info on detected "problems" in MIME
  44    encodings. Indexes are defined in mime.h. */
  45
  46 void
  47 mime_set_anomaly(int idx)
  48 {
  49 struct anom {
  50   int level;
  51   const uschar * text;
  52 } anom[] = { {1, CUS"Broken Quoted-Printable encoding detected"},
  53              {2, CUS"Broken BASE64 encoding detected"} };
  54
  55 mime_anomaly_level = anom[idx].level;
  56 mime_anomaly_text =  anom[idx].text;
  57 }
  58
  59
  60 /*************************************************
  61 * decode quoted-printable chars                  *
  62 *************************************************/
  63
  64 /* gets called when we hit a =
  65    returns: new pointer position
  66    result code in c:
  67           -2 - decode error
  68           -1 - soft line break, no char
  69            0-255 - char to write
  70 */
  71
  72 static uschar *
  73 mime_decode_qp_char(uschar *qp_p, int *c)
  74 {
  75 uschar *initial_pos = qp_p;
  76
  77 /* advance one char */
  78 qp_p++;
  79
  80 /* Check for two hex digits and decode them */
  81 if (isxdigit(*qp_p) && isxdigit(qp_p[1]))
  82   {
  83   /* Do hex conversion */
  84   *c = (isdigit(*qp_p) ? *qp_p - '0' : toupper(*qp_p) - 'A' + 10) <<4;
  85   qp_p++;
  86   *c |= isdigit(*qp_p) ? *qp_p - '0' : toupper(*qp_p) - 'A' + 10;
  87   return qp_p + 1;
  88   }
  89
  90 /* tab or whitespace may follow just ignore it if it precedes \n */
  91 while (*qp_p == '\t' || *qp_p == ' ' || *qp_p == '\r')
  92   qp_p++;
  93
  94 if (*qp_p == '\n')      /* hit soft line break */
  95   {
  96   *c = -1;
  97   return qp_p;
  98   }
  99
 100 /* illegal char here */
 101 *c = -2;
 102 return initial_pos;
 103 }
 104
 105
 106 /* just dump MIME part without any decoding */
 107 static ssize_t
 108 mime_decode_asis(FILE* in, FILE* out, uschar* boundary)
 109 {
 110 ssize_t len, size = 0;
 111 uschar buffer[MIME_MAX_LINE_LENGTH];
 112
 113 while(fgets(CS buffer, MIME_MAX_LINE_LENGTH, mime_stream) != NULL)
 114   {
 115   if (boundary != NULL
 116      && Ustrncmp(buffer, "--", 2) == 0
 117      && Ustrncmp((buffer+2), boundary, Ustrlen(boundary)) == 0
 118      )
 119     break;
 120
 121   len = Ustrlen(buffer);
 122   if (fwrite(buffer, 1, (size_t)len, out) < len)
 123     return -1;
 124   size += len;
 125   } /* while */
 126 return size;
 127 }
 128
 129
 130
 131 /* decode quoted-printable MIME part */
 132 static ssize_t
 133 mime_decode_qp(FILE* in, FILE* out, uschar* boundary)
 134 {
 135 uschar ibuf[MIME_MAX_LINE_LENGTH], obuf[MIME_MAX_LINE_LENGTH];
 136 uschar *ipos, *opos;
 137 ssize_t len, size = 0;
 138
 139 while (fgets(CS ibuf, MIME_MAX_LINE_LENGTH, in) != NULL)
 140   {
 141   if (boundary != NULL
 142      && Ustrncmp(ibuf, "--", 2) == 0
 143      && Ustrncmp((ibuf+2), boundary, Ustrlen(boundary)) == 0
 144      )
 145     break; /* todo: check for missing boundary */
 146
 147   ipos = ibuf;
 148   opos = obuf;
 149
 150   while (*ipos != 0)
 151     {
 152     if (*ipos == '=')
 153       {
 154       int decode_qp_result;
 155
 156       ipos = mime_decode_qp_char(ipos, &decode_qp_result);
 157
 158       if (decode_qp_result == -2)
 159         {
 160         /* Error from decoder. ipos is unchanged. */
 161         mime_set_anomaly(MIME_ANOMALY_BROKEN_QP);
 162         *opos++ = '=';
 163         ++ipos;
 164         }
 165       else if (decode_qp_result == -1)
 166         break;
 167       else if (decode_qp_result >= 0)
 168         *opos++ = decode_qp_result;
 169       }
 170     else
 171       *opos++ = *ipos++;
 172     }
 173   /* something to write? */
 174   len = opos - obuf;
 175   if (len > 0)
 176     {
 177     if (fwrite(obuf, 1, len, out) != len) return -1; /* error */
 178     size += len;
 179     }
 180   }
 181 return size;
 182 }
 183
 184
 185 /*
 186  * Return open filehandle for combo of path and file.
 187  * Side-effect: set mime_decoded_filename, to copy in allocated mem
 188  */
 189 static FILE *
 190 mime_get_decode_file(uschar *pname, uschar *fname)
 191 {
 192 if (pname && fname)
 193   mime_decoded_filename = string_sprintf("%s/%s", pname, fname);
 194 else if (!pname)
 195   mime_decoded_filename = string_copy(fname);
 196 else if (!fname)
 197   {
 198   int file_nr = 0;
 199   int result = 0;
 200
 201   /* must find first free sequential filename */
 202   do
 203     {
 204     struct stat mystat;
 205     mime_decoded_filename = string_sprintf("%s/%s-%05u", pname, message_id, file_nr++);
 206     /* security break */
 207     if (file_nr >= 1024)
 208       break;
 209     result = stat(CS mime_decoded_filename, &mystat);
 210     } while(result != -1);
 211   }
 212
 213 return modefopen(mime_decoded_filename, "wb+", SPOOL_MODE);
 214 }
 215
 216
 217 int
 218 mime_decode(const uschar **listptr)
 219 {
 220 int sep = 0;
 221 const uschar *list = *listptr;
 222 uschar * option;
 223 uschar * decode_path;
 224 FILE *decode_file = NULL;
 225 long f_pos = 0;
 226 ssize_t size_counter = 0;
 227 ssize_t (*decode_function)(FILE*, FILE*, uschar*);
 228
 229 if (!mime_stream || (f_pos = ftell(mime_stream)) < 0)
 230   return FAIL;
 231
 232 /* build default decode path (will exist since MBOX must be spooled up) */
 233 decode_path = string_sprintf("%s/scan/%s", spool_directory, message_id);
 234
 235 /* try to find 1st option */
 236 if ((option = string_nextinlist(&list, &sep, NULL, 0)))
 237   {
 238   /* parse 1st option */
 239   if ((Ustrcmp(option,"false") == 0) || (Ustrcmp(option,"0") == 0))
 240     /* explicitly no decoding */
 241     return FAIL;
 242
 243   if (Ustrcmp(option,"default") == 0)
 244     /* explicit default path + file names */
 245     goto DEFAULT_PATH;
 246
 247   if (option[0] == '/')
 248     {
 249     struct stat statbuf;
 250
 251     memset(&statbuf,0,sizeof(statbuf));
 252
 253     /* assume either path or path+file name */
 254     if ( (stat(CS option, &statbuf) == 0) && S_ISDIR(statbuf.st_mode) )
 255       /* is directory, use it as decode_path */
 256       decode_file = mime_get_decode_file(option, NULL);
 257     else
 258       /* does not exist or is a file, use as full file name */
 259       decode_file = mime_get_decode_file(NULL, option);
 260     }
 261   else
 262     /* assume file name only, use default path */
 263     decode_file = mime_get_decode_file(decode_path, option);
 264   }
 265 else
 266   {
 267   /* no option? patch default path */
 268 DEFAULT_PATH:
 269   decode_file = mime_get_decode_file(decode_path, NULL);
 270   }
 271
 272 if (!decode_file)
 273   return DEFER;
 274
 275 /* decode according to mime type */
 276 decode_function =
 277   !mime_content_transfer_encoding
 278   ? mime_decode_asis    /* no encoding, dump as-is */
 279   : Ustrcmp(mime_content_transfer_encoding, "base64") == 0
 280   ? mime_decode_base64
 281   : Ustrcmp(mime_content_transfer_encoding, "quoted-printable") == 0
 282   ? mime_decode_qp
 283   : mime_decode_asis;   /* unknown encoding type, just dump as-is */
 284
 285 size_counter = decode_function(mime_stream, decode_file, mime_current_boundary);
 286
 287 clearerr(mime_stream);
 288 if (fseek(mime_stream, f_pos, SEEK_SET))
 289   return DEFER;
 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   else
 353     {
 354     /* -------- non-value mode -------- */
 355     /* skip whitespace + tabs */
 356     if ( (c == ' ') || (c == '\t') )
 357       continue;
 358     if (c == '\\')
 359       {
 360       /* quote next char. can be used
 361       to escape brackets. */
 362       if ((c = fgetc(f)) == EOF) break;
 363       }
 364     else if (c == '(')
 365       {
 366       header_open_brackets++;
 367       continue;
 368       }
 369     else if ((c == ')') && header_open_brackets)
 370       {
 371       header_open_brackets--;
 372       continue;
 373       }
 374     else if ( (c == '=') && !header_open_brackets ) /* enter value mode */
 375       header_value_mode = 1;
 376
 377     /* skip chars while we are in a comment */
 378     if (header_open_brackets > 0)
 379       continue;
 380     /* -------------------------------- */
 381     }
 382
 383   /* copy the char to the buffer */
 384   header[num_copied++] = (uschar)c;
 385
 386   /* break if header buffer is full */
 387   if (num_copied > MIME_MAX_HEADER_SIZE-1)
 388     done = 1;
 389   }
 390
 391 if ((num_copied > 0) && (header[num_copied-1] != ';'))
 392   header[num_copied-1] = ';';
 393
 394 /* 0-terminate */
 395 header[num_copied] = '\0';
 396
 397 /* return 0 for EOF or empty line */
 398 return c == EOF || num_copied == 1 ? 0 : 1;
 399 }
 400
 401
 402 /* reset all per-part mime variables */
 403 static void
 404 mime_vars_reset(void)
 405 {
 406 mime_anomaly_level     = 0;
 407 mime_anomaly_text      = NULL;
 408 mime_boundary          = NULL;
 409 mime_charset           = NULL;
 410 mime_decoded_filename  = NULL;
 411 mime_filename          = NULL;
 412 mime_content_description = NULL;
 413 mime_content_disposition = NULL;
 414 mime_content_id        = NULL;
 415 mime_content_transfer_encoding = NULL;
 416 mime_content_type      = NULL;
 417 mime_is_multipart      = 0;
 418 mime_content_size      = 0;
 419 }
 420
 421
 422 /* Grab a parameter value, dealing with quoting.
 423
 424 Arguments:
 425  str    Input string.  Updated on return to point to terminating ; or NUL
 426
 427 Return:
 428  Allocated string with parameter value
 429 */
 430 static uschar *
 431 mime_param_val(uschar ** sp)
 432 {
 433 uschar * s = *sp;
 434 gstring * val = NULL;
 435
 436 /* debug_printf_indent("   considering paramval '%s'\n", s); */
 437
 438 while (*s && *s != ';')         /* ; terminates */
 439   if (*s == '"')
 440     {
 441     s++;                        /* skip opening " */
 442     while (*s && *s != '"')     /* " protects ; */
 443       val = string_catn(val, s++, 1);
 444     if (*s) s++;                /* skip closing " */
 445     }
 446   else
 447     val = string_catn(val, s++, 1);
 448 *sp = s;
 449 return string_from_gstring(val);
 450 }
 451
 452 static uschar *
 453 mime_next_semicolon(uschar * s)
 454 {
 455 while (*s && *s != ';')         /* ; terminates */
 456   if (*s == '"')
 457     {
 458     s++;                        /* skip opening " */
 459     while (*s && *s != '"')     /* " protects ; */
 460       s++;
 461     if (*s) s++;                /* skip closing " */
 462     }
 463   else
 464     s++;
 465 return s;
 466 }
 467
 468
 469 static uschar *
 470 rfc2231_to_2047(const uschar * fname, const uschar * charset, int * len)
 471 {
 472 gstring * val = string_catn(NULL, US"=?", 2);
 473 uschar c;
 474
 475 if (charset)
 476   val = string_cat(val, charset);
 477 val = string_catn(val, US"?Q?", 3);
 478
 479 while ((c = *fname))
 480   if (c == '%' && isxdigit(fname[1]) && isxdigit(fname[2]))
 481     {
 482     val = string_catn(val, US"=", 1);
 483     val = string_catn(val, ++fname, 2);
 484     fname += 2;
 485     }
 486   else
 487     val = string_catn(val, fname++, 1);
 488
 489 val = string_catn(val, US"?=", 2);
 490 *len = val->ptr;
 491 return string_from_gstring(val);
 492 }
 493
 494
 495 int
 496 mime_acl_check(uschar *acl, FILE *f, struct mime_boundary_context *context,
 497     uschar **user_msgptr, uschar **log_msgptr)
 498 {
 499 int rc = OK;
 500 uschar * header = NULL;
 501 struct mime_boundary_context nested_context;
 502
 503 /* reserve a line buffer to work in.  Assume tainted data. */
 504 header = store_get(MIME_MAX_HEADER_SIZE+1, TRUE);
 505
 506 /* Not actually used at the moment, but will be vital to fixing
 507  * some RFC 2046 nonconformance later... */
 508 nested_context.parent = context;
 509
 510 /* loop through parts */
 511 while(1)
 512   {
 513   /* reset all per-part mime variables */
 514   mime_vars_reset();
 515
 516   /* If boundary is null, we assume that *f is positioned on the start of
 517   headers (for example, at the very beginning of a message.  If a boundary is
 518   given, we must first advance to it to reach the start of the next header
 519   block.  */
 520
 521   /* NOTE -- there's an error here -- RFC2046 specifically says to
 522    * check for outer boundaries.  This code doesn't do that, and
 523    * I haven't fixed this.
 524    *
 525    * (I have moved partway towards adding support, however, by adding
 526    * a "parent" field to my new boundary-context structure.)
 527    */
 528   if (context) for (;;)
 529     {
 530     if (!fgets(CS header, MIME_MAX_HEADER_SIZE, f))
 531       {
 532       /* Hit EOF or read error. Ugh. */
 533       DEBUG(D_acl) debug_printf_indent("MIME: Hit EOF ...\n");
 534       return rc;
 535       }
 536
 537     /* boundary line must start with 2 dashes */
 538     if (  Ustrncmp(header, "--", 2) == 0
 539        && Ustrncmp(header+2, context->boundary, Ustrlen(context->boundary)) == 0
 540        )
 541       {                 /* found boundary */
 542       if (Ustrncmp((header+2+Ustrlen(context->boundary)), "--", 2) == 0)
 543         {
 544         /* END boundary found */
 545         DEBUG(D_acl) debug_printf_indent("MIME: End boundary found %s\n",
 546           context->boundary);
 547         return rc;
 548         }
 549
 550       DEBUG(D_acl) debug_printf_indent("MIME: Next part with boundary %s\n",
 551         context->boundary);
 552       break;
 553       }
 554     }
 555
 556   /* parse headers, set up expansion variables */
 557   while (mime_get_header(f, header))
 558
 559     /* look for interesting headers */
 560     for (struct mime_header * mh = mime_header_list;
 561          mh < mime_header_list + mime_header_list_size;
 562          mh++) if (strncmpic(mh->name, header, mh->namelen) == 0)
 563       {
 564       uschar * p = header + mh->namelen;
 565       uschar * q;
 566
 567       /* grab the value (normalize to lower case)
 568       and copy to its corresponding expansion variable */
 569
 570       for (q = p; *q != ';' && *q; q++) ;
 571       *mh->value = string_copynlc(p, q-p);
 572       DEBUG(D_acl) debug_printf_indent("MIME: found %s header, value is '%s'\n",
 573         mh->name, *mh->value);
 574
 575       if (*(p = q)) p++;                        /* jump past the ; */
 576
 577         {
 578         uschar * mime_fname = NULL;
 579         uschar * mime_fname_rfc2231 = NULL;
 580         uschar * mime_filename_charset = NULL;
 581         BOOL decoding_failed = FALSE;
 582
 583         /* grab all param=value tags on the remaining line,
 584         check if they are interesting */
 585
 586         while (*p)
 587           {
 588           DEBUG(D_acl) debug_printf_indent("MIME:   considering paramlist '%s'\n", p);
 589
 590           if (  !mime_filename
 591              && strncmpic(CUS"content-disposition:", header, 20) == 0
 592              && strncmpic(CUS"filename*", p, 9) == 0
 593              )
 594             {                                   /* RFC 2231 filename */
 595             uschar * q;
 596
 597             /* find value of the filename */
 598             p += 9;
 599             while(*p != '=' && *p) p++;
 600             if (*p) p++;                        /* p is filename or NUL */
 601             q = mime_param_val(&p);             /* p now trailing ; or NUL */
 602
 603             if (q && *q)
 604               {
 605               uschar * temp_string, * err_msg;
 606               int slen;
 607
 608               /* build up an un-decoded filename over successive
 609               filename*= parameters (for use when 2047 decode fails) */
 610
 611               mime_fname_rfc2231 = string_sprintf("%#s%s",
 612                 mime_fname_rfc2231, q);
 613
 614               if (!decoding_failed)
 615                 {
 616                 int size;
 617                 if (!mime_filename_charset)
 618                   {
 619                   uschar * s = q;
 620
 621                   /* look for a ' in the "filename" */
 622                   while(*s != '\'' && *s) s++;  /* s is 1st ' or NUL */
 623
 624                   if ((size = s-q) > 0)
 625                     mime_filename_charset = string_copyn(q, size);
 626
 627                   if (*(p = s)) p++;
 628                   while(*p == '\'') p++;        /* p is after 2nd ' */
 629                   }
 630                 else
 631                   p = q;
 632
 633                 DEBUG(D_acl) debug_printf_indent("MIME:    charset %s fname '%s'\n",
 634                   mime_filename_charset ? mime_filename_charset : US"<NULL>", p);
 635
 636                 temp_string = rfc2231_to_2047(p, mime_filename_charset, &slen);
 637                 DEBUG(D_acl) debug_printf_indent("MIME:    2047-name %s\n", temp_string);
 638
 639                 temp_string = rfc2047_decode(temp_string, FALSE, NULL, ' ',
 640                   NULL, &err_msg);
 641                 DEBUG(D_acl) debug_printf_indent("MIME:    plain-name %s\n", temp_string);
 642
 643                 if (!temp_string || (size = Ustrlen(temp_string))  == slen)
 644                   decoding_failed = TRUE;
 645                 else
 646                   /* build up a decoded filename over successive
 647                   filename*= parameters */
 648
 649                   mime_filename = mime_fname = mime_fname
 650                     ? string_sprintf("%s%s", mime_fname, temp_string)
 651                     : temp_string;
 652                 }
 653               }
 654             }
 655
 656           else
 657             /* look for interesting parameters */
 658             for (mime_parameter * mp = mime_parameter_list;
 659                  mp < mime_parameter_list + nelem(mime_parameter_list);
 660                  mp++
 661                 ) if (strncmpic(mp->name, p, mp->namelen) == 0)
 662               {
 663               uschar * q;
 664               uschar * dummy_errstr;
 665
 666               /* grab the value and copy to its expansion variable */
 667               p += mp->namelen;
 668               q = mime_param_val(&p);           /* p now trailing ; or NUL */
 669
 670               *mp->value = q && *q
 671                 ? rfc2047_decode(q, check_rfc2047_length, NULL, 32, NULL,
 672                     &dummy_errstr)
 673                 : NULL;
 674               DEBUG(D_acl) debug_printf_indent(
 675                 "MIME:  found %s parameter in %s header, value '%s'\n",
 676                 mp->name, mh->name, *mp->value);
 677
 678               break;                    /* done matching param names */
 679               }
 680
 681
 682           /* There is something, but not one of our interesting parameters.
 683              Advance past the next semicolon */
 684           p = mime_next_semicolon(p);
 685           if (*p) p++;
 686           }                             /* param scan on line */
 687
 688         if (strncmpic(CUS"content-disposition:", header, 20) == 0)
 689           {
 690           if (decoding_failed) mime_filename = mime_fname_rfc2231;
 691
 692           DEBUG(D_acl) debug_printf_indent(
 693             "MIME:  found %s parameter in %s header, value is '%s'\n",
 694             "filename", mh->name, mime_filename);
 695           }
 696         }
 697       }
 698
 699   /* set additional flag variables (easier access) */
 700   if (  mime_content_type
 701      && Ustrncmp(mime_content_type,"multipart",9) == 0
 702      )
 703     mime_is_multipart = 1;
 704
 705   /* Make a copy of the boundary pointer.
 706      Required since mime_boundary is global
 707      and can be overwritten further down in recursion */
 708   nested_context.boundary = mime_boundary;
 709
 710   /* raise global counter */
 711   mime_part_count++;
 712
 713   /* copy current file handle to global variable */
 714   mime_stream = f;
 715   mime_current_boundary = context ? context->boundary : 0;
 716
 717   /* Note the context */
 718   mime_is_coverletter = !(context && context->context == MBC_ATTACHMENT);
 719
 720   /* call ACL handling function */
 721   rc = acl_check(ACL_WHERE_MIME, NULL, acl, user_msgptr, log_msgptr);
 722
 723   mime_stream = NULL;
 724   mime_current_boundary = NULL;
 725
 726   if (rc != OK) break;
 727
 728   /* If we have a multipart entity and a boundary, go recursive */
 729   if (  mime_content_type && nested_context.boundary
 730      && Ustrncmp(mime_content_type,"multipart",9) == 0)
 731     {
 732     DEBUG(D_acl)
 733       debug_printf_indent("MIME: Entering multipart recursion, boundary '%s'\n",
 734         nested_context.boundary);
 735
 736     nested_context.context =
 737       context && context->context == MBC_ATTACHMENT
 738       ? MBC_ATTACHMENT
 739       :    Ustrcmp(mime_content_type,"multipart/alternative") == 0
 740         || Ustrcmp(mime_content_type,"multipart/related") == 0
 741       ? MBC_COVERLETTER_ALL
 742       : MBC_COVERLETTER_ONESHOT;
 743
 744     rc = mime_acl_check(acl, f, &nested_context, user_msgptr, log_msgptr);
 745     if (rc != OK) break;
 746     }
 747   else if (  mime_content_type
 748           && Ustrncmp(mime_content_type,"message/rfc822",14) == 0)
 749     {
 750     const uschar * rfc822name = NULL;
 751     uschar * filename;
 752     int file_nr = 0;
 753     int result = 0;
 754
 755     /* must find first free sequential filename */
 756     for (gstring * g = string_get(64); result != -1; g->ptr = 0)
 757       {
 758       struct stat mystat;
 759       g = string_fmt_append(g,
 760         "%s/scan/%s/__rfc822_%05u", spool_directory, message_id, file_nr++);
 761       /* security break */
 762       if (file_nr >= 128)
 763         goto NO_RFC822;
 764       result = stat(CS (filename = string_from_gstring(g)), &mystat);
 765       }
 766
 767     rfc822name = filename;
 768
 769     /* decode RFC822 attachment */
 770     mime_decoded_filename = NULL;
 771     mime_stream = f;
 772     mime_current_boundary = context ? context->boundary : NULL;
 773     mime_decode(&rfc822name);
 774     mime_stream = NULL;
 775     mime_current_boundary = NULL;
 776     if (!mime_decoded_filename)         /* decoding failed */
 777       {
 778       log_write(0, LOG_MAIN,
 779            "MIME acl condition warning - could not decode RFC822 MIME part to file.");
 780       rc = DEFER;
 781       goto out;
 782       }
 783     mime_decoded_filename = NULL;
 784     }
 785
 786 NO_RFC822:
 787   /* If the boundary of this instance is NULL, we are finished here */
 788   if (!context) break;
 789
 790   if (context->context == MBC_COVERLETTER_ONESHOT)
 791     context->context = MBC_ATTACHMENT;
 792   }
 793
 794 out:
 795 mime_vars_reset();
 796 return rc;
 797 }
 798
 799 #endif  /*WITH_CONTENT_SCAN*/
 800
 801 /* vi: sw ai sw=2
 802 */