diplodocus.org Git - nmh/blob - sbr/message_id.c

   1 /*
   2  * message-id.c -- construct the body of a Message-ID or Content-ID
   3  *                 header field
   4  *
   5  * This code is Copyright (c) 2012, by the authors of nmh.  See the
   6  * COPYRIGHT file in the root directory of the nmh distribution for
   7  * complete copyright information.
   8  */
   9
  10 #include <h/mh.h>
  11 #include <unistd.h>    /* for getpid() */
  12 #include <sys/time.h>  /* for gettimeofday() */
  13 #include <stdio.h>
  14
  15
  16 static enum {
  17   NMH_MESSAGE_ID_LOCALNAME,
  18   NMH_MESSAGE_ID_RANDOM
  19 } message_id_style = NMH_MESSAGE_ID_LOCALNAME;
  20 static char message_id_[BUFSIZ];
  21
  22
  23 /* Convert name of message id style to integer value and store it. */
  24 int
  25 save_message_id_style (const char *value) {
  26   if (! mh_strcasecmp (value, "localname")) {
  27     message_id_style = NMH_MESSAGE_ID_LOCALNAME;
  28     return 0;
  29   } else if (! mh_strcasecmp (value, "random")) {
  30     message_id_style = NMH_MESSAGE_ID_RANDOM;
  31     return 0;
  32   } else {
  33     return 1;
  34   }
  35 }
  36
  37
  38 char *
  39 message_id (time_t tclock, int content_id) {
  40   switch (message_id_style) {
  41     case NMH_MESSAGE_ID_LOCALNAME: {
  42       char *format = content_id  ?  "<%d.%ld.%%d@%s>"  :  "<%d.%ld@%s>";
  43
  44       snprintf (message_id_, sizeof message_id_, format,
  45                 (int) getpid (), (long) tclock, LocalName (1));
  46
  47       break;
  48     }
  49
  50     case NMH_MESSAGE_ID_RANDOM: {
  51       char *format = content_id
  52         ?  "<%d-%ld.%06ld%%d@%.*s.%.*s.%.*s>"
  53         :  "<%d-%ld.%06ld@%.*s.%.*s.%.*s>";
  54       /* Use a sequence of digits divisible by 3 because that will
  55          expand to base64 without any waste.  Must be shorter than 58,
  56          see below. */
  57       unsigned char rnd[9];
  58       /* The part after the '@' is divided into thirds.  The base64
  59          encoded string will be 4/3 the size of rnd. */
  60       size_t one_third = sizeof rnd * 4/3/3;
  61
  62       if (m_rand (rnd, sizeof rnd) == 0) {
  63         struct timeval now;
  64         /* All we really need is 4 * [sizeof rnd/3] + 2, as long as
  65            the base64 encoding stays shorter than 76 bytes so embedded
  66            newlines aren't necessary.  But use double the sizeof rnd
  67            just to be safe. */
  68         unsigned char rnd_base64[2 * sizeof rnd];
  69         unsigned char *cp;
  70         int i;
  71
  72         writeBase64 (rnd, sizeof rnd, rnd_base64);
  73
  74         for (i = strlen ((const char *) rnd_base64) - 1;
  75              i > 0  &&  iscntrl (rnd_base64[i]);
  76              --i) {
  77           /* Remove trailing newline.  rnd_base64 had better be
  78              shorter than 76 characters, so don't bother to look for
  79              embedded newlines. */
  80           rnd_base64[i] = '\0';
  81         }
  82
  83         /* Try to make the base64 string look a little more like a
  84            hostname by replacing + with - and / with _. */
  85         for (cp = rnd_base64; *cp; ++cp) {
  86           if (*cp == '+') {
  87             *cp = '-';
  88           } else if (*cp == '/') {
  89             *cp = '_';
  90           }
  91         }
  92
  93         /* gettimeofday() and getpid() shouldn't fail on POSIX platforms. */
  94         gettimeofday (&now, 0);
  95
  96         /* The format string inserts a couple of dots, for the benefit
  97            of spam filters that want to see a message id with a final
  98            part that resembles a hostname. */
  99         snprintf (message_id_, sizeof message_id_, format,
 100                   getpid (), (long) now.tv_sec, (long) now.tv_usec,
 101                   one_third, rnd_base64,
 102                   one_third, &rnd_base64[one_third],
 103                   one_third, &rnd_base64[2*one_third]);
 104       }
 105
 106       break;
 107     }
 108   }
 109
 110   return message_id_;
 111 }