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

   1 /* message_id.c -- construct the body of a Message-ID or Content-ID
   2  *                 header field
   3  *
   4  * This code is Copyright (c) 2012, by the authors of nmh.  See the
   5  * COPYRIGHT file in the root directory of the nmh distribution for
   6  * complete copyright information.
   7  */
   8
   9 #include <h/mh.h>
  10 #include "m_rand.h"
  11 #include "message_id.h"
  12 #include <sys/time.h>  /* for gettimeofday() */
  13 #include "base64.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 (! strcasecmp (value, "localname")) {
  27     message_id_style = NMH_MESSAGE_ID_LOCALNAME;
  28     return 0;
  29   }
  30   if (! strcasecmp (value, "random")) {
  31     message_id_style = NMH_MESSAGE_ID_RANDOM;
  32     return 0;
  33   }
  34   return 1;
  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 #define P(fmt) \
  43     snprintf(message_id_, sizeof message_id_, \
  44         (fmt), (int)getpid(), (long)tclock, LocalName(1))
  45
  46             if (content_id)
  47                 P("<%d.%ld.%%d@%s>");
  48             else
  49                 P("<%d.%ld@%s>");
  50 #undef P
  51       break;
  52     }
  53
  54     case NMH_MESSAGE_ID_RANDOM: {
  55       /* Use a sequence of digits divisible by 3 because that will
  56          expand to base64 without any waste.  Must be shorter than 58,
  57          see below. */
  58       unsigned char rnd[9];
  59       /* The part after the '@' is divided into thirds.  The base64
  60          encoded string will be 4/3 the size of rnd. */
  61       size_t one_third = sizeof rnd * 4/3/3;
  62
  63       if (m_rand (rnd, sizeof rnd) == 0) {
  64         struct timeval now;
  65         /* All we really need is 4 * [sizeof rnd/3] + 2, as long as
  66            the base64 encoding stays shorter than 76 bytes so embedded
  67            newlines aren't necessary.  But use double the sizeof rnd
  68            just to be safe. */
  69         unsigned char rnd_base64[2 * sizeof rnd];
  70         unsigned char *cp;
  71         int i;
  72
  73         writeBase64 (rnd, sizeof rnd, rnd_base64);
  74
  75         for (i = strlen ((const char *) rnd_base64) - 1;
  76              i > 0  &&  iscntrl (rnd_base64[i]);
  77              --i) {
  78           /* Remove trailing newline.  rnd_base64 had better be
  79              shorter than 76 characters, so don't bother to look for
  80              embedded newlines. */
  81           rnd_base64[i] = '\0';
  82         }
  83
  84         /* Try to make the base64 string look a little more like a
  85            hostname by replacing + with - and / with _. */
  86         for (cp = rnd_base64; *cp; ++cp) {
  87           if (*cp == '+') {
  88             *cp = '-';
  89           } else if (*cp == '/') {
  90             *cp = '_';
  91           }
  92         }
  93
  94         /* gettimeofday() and getpid() shouldn't fail on POSIX platforms. */
  95         gettimeofday (&now, 0);
  96
  97         /* The format string inserts a couple of dots, for the benefit
  98            of spam filters that want to see a message id with a final
  99            part that resembles a hostname. */
 100 #define P(fmt) \
 101     snprintf(message_id_, sizeof message_id_, (fmt), \
 102         getpid(), (long)now.tv_sec, (long)now.tv_usec, \
 103         (int)one_third, rnd_base64, \
 104         (int)one_third, &rnd_base64[one_third], \
 105         (int)one_third, &rnd_base64[2*one_third])
 106
 107             if (content_id)
 108                 P("<%d-%ld.%06ld%%d@%.*s.%.*s.%.*s>");
 109             else
 110                 P("<%d-%ld.%06ld@%.*s.%.*s.%.*s>");
 111 #undef P
 112       }
 113
 114       break;
 115     }
 116   }
 117
 118   return message_id_;
 119 }