Pileus Git - ~andy/fetchmail/blob - rfc822.c

   1 /*****************************************************************************
   2
   3 NAME:
   4    rfc822.c -- code for slicing and dicing RFC822 mail headers
   5
   6 ENTRY POINTS:
   7    nextaddr() -- parse the next address out of an RFC822 header
   8    reply_hack() -- append hostname to local header addresses
   9
  10 THEORY:
  11    How to parse RFC822 headers in C. This is not a fully conformant
  12 implementation of RFC822 or RFC2822, but it has been in production use
  13 in a widely-deployed MTA (fetcmail) since 1996 without complaints.
  14 Really perverse combinations of quoting and commenting could break it.
  15
  16 AUTHOR:
  17    Eric S. Raymond <esr@thyrsus.com>, 1997.  This source code example
  18 is part of fetchmail and the Unix Cookbook, and are released under the
  19 MIT license.  Compile with -DMAIN to build the demonstrator.
  20
  21 ******************************************************************************/
  22 #include  <stdio.h>
  23 #include  <ctype.h>
  24 #include  <string.h>
  25 #include  <stdlib.h>
  26
  27 #include "fetchmail.h"
  28
  29 #ifndef MAIN
  30 #include "i18n.h"
  31 #else
  32 #include  <unistd.h>
  33 static int verbose;
  34 char *program_name = "rfc822";
  35 #endif /* MAIN */
  36
  37 #ifndef TRUE
  38 #define TRUE 1
  39 #define FALSE 0
  40 #endif
  41
  42 #define HEADER_END(p)   ((p)[0] == '\n' && ((p)[1] != ' ' && (p)[1] != '\t'))
  43
  44 unsigned char *reply_hack(
  45         unsigned char *buf              /* header to be hacked */,
  46         const unsigned char *host       /* server hostname */,
  47         size_t *length)
  48 /* hack message headers so replies will work properly */
  49 {
  50     unsigned char *from, *cp, last_nws = '\0', *parens_from = NULL;
  51     int parendepth, state, has_bare_name_part, has_host_part;
  52 #ifndef MAIN
  53     int addresscount = 1;
  54 #endif /* MAIN */
  55
  56     if (strncasecmp("From:", buf, 5)
  57         && strncasecmp("To:", buf, 3)
  58         && strncasecmp("Reply-To:", buf, 9)
  59         && strncasecmp("Return-Path:", buf, 12)
  60         && strncasecmp("Cc:", buf, 3)
  61         && strncasecmp("Bcc:", buf, 4)
  62         && strncasecmp("Resent-From:", buf, 12)
  63         && strncasecmp("Resent-To:", buf, 10)
  64         && strncasecmp("Resent-Cc:", buf, 10)
  65         && strncasecmp("Resent-Bcc:", buf, 11)
  66         && strncasecmp("Apparently-From:", buf, 16)
  67         && strncasecmp("Apparently-To:", buf, 14)
  68         && strncasecmp("Sender:", buf, 7)
  69         && strncasecmp("Resent-Sender:", buf, 14)
  70        ) {
  71         return(buf);
  72     }
  73
  74 #ifndef MAIN
  75     if (outlevel >= O_DEBUG)
  76         report_build(stdout, GT_("About to rewrite %s"), buf);
  77
  78     /* make room to hack the address; buf must be malloced */
  79     for (cp = buf; *cp; cp++)
  80         if (*cp == ',' || isspace(*cp))
  81             addresscount++;
  82     buf = (unsigned char *)xrealloc(buf, strlen(buf) + addresscount * (strlen(host) + 1) + 1);
  83 #endif /* MAIN */
  84
  85     /*
  86      * This is going to foo up on some ill-formed addresses.
  87      * Note that we don't rewrite the fake address <> in order to
  88      * avoid screwing up bounce suppression with a null Return-Path.
  89      */
  90
  91     parendepth = state = 0;
  92     has_host_part = has_bare_name_part = FALSE;
  93     for (from = buf; *from; from++)
  94     {
  95 #ifdef MAIN
  96         if (verbose)
  97         {
  98             printf("state %d: %s", state, (char *)buf);
  99             printf("%*s^\n", from - buf + 10, " ");
 100         }
 101 #endif /* MAIN */
 102         if (state != 2)
 103         {
 104             if (*from == '(')
 105                 ++parendepth;
 106             else if (*from == ')')
 107                 --parendepth;
 108         }
 109
 110         if (!parendepth && !has_host_part)
 111             switch (state)
 112             {
 113             case 0:     /* before header colon */
 114                 if (*from == ':')
 115                     state = 1;
 116                 break;
 117
 118             case 1:     /* we've seen the colon, we're looking for addresses */
 119                 if (!isspace(*from))
 120                     last_nws = *from;
 121                 if (*from == '<')
 122                     state = 3;
 123                 else if (*from == '@' || *from == '!')
 124                     has_host_part = TRUE;
 125                 else if (*from == '"')
 126                     state = 2;
 127                 /*
 128                  * Not expanding on last non-WS == ';' deals with groupnames,
 129                  * an obscure misfeature described in sections
 130                  * 6.1, 6.2.6, and A.1.5 of the RFC822 standard.
 131                  */
 132                 else if ((*from == ',' || HEADER_END(from))
 133                          && has_bare_name_part
 134                          && !has_host_part
 135                          && last_nws != ';')
 136                 {
 137                     int hostlen;
 138                     unsigned char *p;
 139
 140                     p = from;
 141                     if (parens_from)
 142                         from = parens_from;
 143                     while (isspace(*from) || (*from == ','))
 144                         --from;
 145                     from++;
 146                     hostlen = strlen(host);
 147                     for (cp = from + strlen(from); cp >= from; --cp)
 148                         cp[hostlen+1] = *cp;
 149                     *from++ = '@';
 150                     memcpy(from, host, hostlen);
 151                     from = p + hostlen + 1;
 152                     has_host_part = TRUE;
 153                 }
 154                 else if (from[1] == '('
 155                          && has_bare_name_part
 156                          && !has_host_part
 157                          && last_nws != ';' && last_nws != ')')
 158                 {
 159                     parens_from = from;
 160                 }
 161                 else if (!isspace(*from))
 162                     has_bare_name_part = TRUE;
 163                 break;
 164
 165             case 2:     /* we're in a string */
 166                 if (*from == '"')
 167                 {
 168                     char        *bp;
 169                     int         bscount;
 170
 171                     bscount = 0;
 172                     for (bp = from - 1; *bp == '\\'; bp--)
 173                         bscount++;
 174                     if (!(bscount % 2))
 175                         state = 1;
 176                 }
 177                 break;
 178
 179             case 3:     /* we're in a <>-enclosed address */
 180                 if (*from == '@' || *from == '!')
 181                     has_host_part = TRUE;
 182                 else if (*from == '>' && (from > buf && from[-1] != '<'))
 183                 {
 184                     state = 1;
 185                     if (!has_host_part)
 186                     {
 187                         int hostlen;
 188
 189                         hostlen = strlen(host);
 190                         for (cp = from + strlen(from); cp >= from; --cp)
 191                             cp[hostlen+1] = *cp;
 192                         *from++ = '@';
 193                         memcpy(from, host, hostlen);
 194                         from += hostlen;
 195                         has_host_part = TRUE;
 196                     }
 197                 }
 198                 break;
 199             }
 200
 201         /*
 202          * If we passed a comma, reset everything.
 203          */
 204         if ((from > buf && from[-1] == ',') && !parendepth) {
 205           has_host_part = has_bare_name_part = FALSE;
 206           parens_from = NULL;
 207         }
 208     }
 209
 210 #ifndef MAIN
 211     if (outlevel >= O_DEBUG)
 212         report_complete(stdout, GT_("Rewritten version is %s\n"), buf);
 213 #endif /* MAIN */
 214     *length = strlen(buf);
 215     return(buf);
 216 }
 217
 218 unsigned char *nxtaddr(const unsigned char *hdr /* header to be parsed, NUL to continue previous hdr */)
 219 /* parse addresses in succession out of a specified RFC822 header */
 220 {
 221     static unsigned char address[BUFSIZ];
 222     static int tp;
 223     static const unsigned char *hp;
 224     static int  state, oldstate;
 225 #ifdef MAIN
 226     static const unsigned char *orighdr;
 227 #endif /* MAIN */
 228     int parendepth = 0;
 229
 230 #define START_HDR       0       /* before header colon */
 231 #define SKIP_JUNK       1       /* skip whitespace, \n, and junk */
 232 #define BARE_ADDRESS    2       /* collecting address without delimiters */
 233 #define INSIDE_DQUOTE   3       /* inside double quotes */
 234 #define INSIDE_PARENS   4       /* inside parentheses */
 235 #define INSIDE_BRACKETS 5       /* inside bracketed address */
 236 #define ENDIT_ALL       6       /* after last address */
 237
 238 #define NEXTTP()        ((tp < sizeof(address)-1) ? tp++ : tp)
 239
 240     if (hdr)
 241     {
 242         hp = hdr;
 243         state = START_HDR;
 244 #ifdef MAIN
 245         orighdr = hdr;
 246 #endif /* MAIN */
 247         tp = 0;
 248     }
 249
 250     for (; *hp; hp++)
 251     {
 252 #ifdef MAIN
 253         if (verbose)
 254         {
 255             printf("state %d: %s", state, (char *)orighdr);
 256             printf("%*s^\n", hp - orighdr + 10, " ");
 257         }
 258 #endif /* MAIN */
 259
 260         if (state == ENDIT_ALL)         /* after last address */
 261             return(NULL);
 262         else if (HEADER_END(hp))
 263         {
 264             state = ENDIT_ALL;
 265             if (tp)
 266             {
 267                 while (isspace(address[--tp]))
 268                     continue;
 269                 address[++tp] = '\0';
 270                 tp = 0;
 271                 return (address);
 272             }
 273             return((unsigned char *)NULL);
 274         }
 275         else if (*hp == '\\')           /* handle RFC822 escaping */
 276         {
 277             if (state != INSIDE_PARENS)
 278             {
 279                 address[NEXTTP()] = *hp++;      /* take the escape */
 280                 address[NEXTTP()] = *hp;        /* take following unsigned char */
 281             }
 282         }
 283         else switch (state)
 284         {
 285         case START_HDR:   /* before header colon */
 286             if (*hp == ':')
 287                 state = SKIP_JUNK;
 288             break;
 289
 290         case SKIP_JUNK:         /* looking for address start */
 291             if (*hp == '"')     /* quoted string */
 292             {
 293                 oldstate = SKIP_JUNK;
 294                 state = INSIDE_DQUOTE;
 295                 address[NEXTTP()] = *hp;
 296             }
 297             else if (*hp == '(')        /* address comment -- ignore */
 298             {
 299                 parendepth = 1;
 300                 oldstate = SKIP_JUNK;
 301                 state = INSIDE_PARENS;
 302             }
 303             else if (*hp == '<')        /* begin <address> */
 304             {
 305                 state = INSIDE_BRACKETS;
 306                 tp = 0;
 307             }
 308             else if (*hp != ',' && !isspace(*hp))
 309             {
 310                 --hp;
 311                 state = BARE_ADDRESS;
 312             }
 313             break;
 314
 315         case BARE_ADDRESS:      /* collecting address without delimiters */
 316             if (*hp == ',')     /* end of address */
 317             {
 318                 if (tp)
 319                 {
 320                     address[NEXTTP()] = '\0';
 321                     state = SKIP_JUNK;
 322                     tp = 0;
 323                     return(address);
 324                 }
 325             }
 326             else if (*hp == '(')        /* beginning of comment */
 327             {
 328                 parendepth = 1;
 329                 oldstate = BARE_ADDRESS;
 330                 state = INSIDE_PARENS;
 331             }
 332             else if (*hp == '<')        /* beginning of real address */
 333             {
 334                 state = INSIDE_BRACKETS;
 335                 tp = 0;
 336             }
 337             else if (*hp == '"')        /* quoted word, copy verbatim */
 338             {
 339                 oldstate = state;
 340                 state = INSIDE_DQUOTE;
 341                 address[NEXTTP()] = *hp;
 342             }
 343             else if (!isspace(*hp))     /* just take it, ignoring whitespace */
 344                 address[NEXTTP()] = *hp;
 345             break;
 346
 347         case INSIDE_DQUOTE:     /* we're in a quoted string, copy verbatim */
 348             if (*hp != '"')
 349                 address[NEXTTP()] = *hp;
 350             else
 351             {
 352                 address[NEXTTP()] = *hp;
 353                 state = oldstate;
 354             }
 355             break;
 356
 357         case INSIDE_PARENS:     /* we're in a parenthesized comment, ignore */
 358             if (*hp == '(')
 359                 ++parendepth;
 360             else if (*hp == ')')
 361                 --parendepth;
 362             if (parendepth == 0)
 363                 state = oldstate;
 364             break;
 365
 366         case INSIDE_BRACKETS:   /* possible <>-enclosed address */
 367             if (*hp == '>')     /* end of address */
 368             {
 369                 address[NEXTTP()] = '\0';
 370                 state = SKIP_JUNK;
 371                 ++hp;
 372                 tp = 0;
 373                 return(address);
 374             }
 375             else if (*hp == '<')        /* nested <> */
 376                 tp = 0;
 377             else if (*hp == '"')        /* quoted address */
 378             {
 379                 address[NEXTTP()] = *hp;
 380                 oldstate = INSIDE_BRACKETS;
 381                 state = INSIDE_DQUOTE;
 382             }
 383             else                        /* just copy address */
 384                 address[NEXTTP()] = *hp;
 385             break;
 386         }
 387     }
 388
 389     return(NULL);
 390 }
 391
 392 #ifdef MAIN
 393 static void parsebuf(unsigned char *longbuf, int reply)
 394 {
 395     unsigned char       *cp;
 396     size_t              dummy;
 397
 398     if (reply)
 399     {
 400         reply_hack(longbuf, "HOSTNAME.NET", &dummy);
 401         printf("Rewritten buffer: %s", (char *)longbuf);
 402     }
 403     else
 404         if ((cp = nxtaddr(longbuf)) != (unsigned char *)NULL)
 405             do {
 406                 printf("\t-> \"%s\"\n", (char *)cp);
 407             } while
 408                 ((cp = nxtaddr((unsigned char *)NULL)) != (unsigned char *)NULL);
 409 }
 410
 411
 412
 413 int main(int argc, char *argv[])
 414 {
 415     unsigned char       buf[BUFSIZ], longbuf[BUFSIZ];
 416     int                 ch, reply;
 417
 418     verbose = reply = FALSE;
 419     while ((ch = getopt(argc, argv, "rv")) != EOF)
 420         switch(ch)
 421         {
 422         case 'r':
 423             reply = TRUE;
 424             break;
 425
 426         case 'v':
 427             verbose = TRUE;
 428             break;
 429         }
 430
 431     while (fgets(buf, sizeof(buf)-1, stdin))
 432     {
 433         if (buf[0] == ' ' || buf[0] == '\t')
 434             strcat(longbuf, buf);
 435         else if (!strncasecmp("From: ", buf, 6)
 436                     || !strncasecmp("To: ", buf, 4)
 437                     || !strncasecmp("Reply-", buf, 6)
 438                     || !strncasecmp("Cc: ", buf, 4)
 439                     || !strncasecmp("Bcc: ", buf, 5))
 440             strcpy(longbuf, buf);
 441         else if (longbuf[0])
 442         {
 443             if (verbose)
 444                 fputs(longbuf, stdout);
 445             parsebuf(longbuf, reply);
 446             longbuf[0] = '\0';
 447         }
 448     }
 449     if (longbuf[0])
 450     {
 451         if (verbose)
 452             fputs(longbuf, stdout);
 453         parsebuf(longbuf, reply);
 454     }
 455     exit(0);
 456 }
 457 #endif /* MAIN */
 458
 459 /* rfc822.c end */