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 "h/mts.h"
  11 #include "m_rand.h"
  12 #include "message_id.h"
  13 #include <sys/time.h>  /* for gettimeofday() */
  14 #include "base64.h"
  15
  16
  17 static enum {
  18   NMH_MESSAGE_ID_LOCALNAME,
  19   NMH_MESSAGE_ID_RANDOM
  20 } message_id_style = NMH_MESSAGE_ID_LOCALNAME;
  21 static char message_id_[BUFSIZ];
  22
  23
  24 /* Convert name of message id style to integer value and store it. */
  25 int
  26 save_message_id_style (const char *value)
  27 {
  28   if (! strcasecmp (value, "localname")) {
  29     message_id_style = NMH_MESSAGE_ID_LOCALNAME;
  30     return 0;
  31   }
  32   if (! strcasecmp (value, "random")) {
  33     message_id_style = NMH_MESSAGE_ID_RANDOM;
  34     return 0;
  35   }
  36   return 1;
  37 }
  38
  39
  40 char *
  41 message_id (time_t tclock, int content_id)
  42 {
  43   switch (message_id_style) {
  44     case NMH_MESSAGE_ID_LOCALNAME: {
  45 #define P(fmt) \
  46     snprintf(message_id_, sizeof message_id_, \
  47         (fmt), (int)getpid(), (long)tclock, LocalName(1))
  48
  49             if (content_id)
  50                 P("<%d.%ld.%%d@%s>");
  51             else
  52                 P("<%d.%ld@%s>");
  53 #undef P
  54       break;
  55     }
  56
  57     case NMH_MESSAGE_ID_RANDOM: {
  58       /* Use a sequence of digits divisible by 3 because that will
  59          expand to base64 without any waste.  Must be shorter than 58,
  60          see below. */
  61       unsigned char rnd[9];
  62       /* The part after the '@' is divided into thirds.  The base64
  63          encoded string will be 4/3 the size of rnd. */
  64       size_t one_third = sizeof rnd * 4/3/3;
  65
  66       if (m_rand (rnd, sizeof rnd) == 0) {
  67         struct timeval now;
  68         /* All we really need is 4 * [sizeof rnd/3] + 2, as long as
  69            the base64 encoding stays shorter than 76 bytes so embedded
  70            newlines aren't necessary.  But use double the sizeof rnd
  71            just to be safe. */
  72         unsigned char rnd_base64[2 * sizeof rnd];
  73         unsigned char *cp;
  74         int i;
  75
  76         writeBase64 (rnd, sizeof rnd, rnd_base64);
  77
  78         for (i = strlen ((const char *) rnd_base64) - 1;
  79              i > 0  &&  iscntrl (rnd_base64[i]);
  80              --i) {
  81           /* Remove trailing newline.  rnd_base64 had better be
  82              shorter than 76 characters, so don't bother to look for
  83              embedded newlines. */
  84           rnd_base64[i] = '\0';
  85         }
  86
  87         /* Try to make the base64 string look a little more like a
  88            hostname by replacing + with - and / with _. */
  89         for (cp = rnd_base64; *cp; ++cp) {
  90           if (*cp == '+') {
  91             *cp = '-';
  92           } else if (*cp == '/') {
  93             *cp = '_';
  94           }
  95         }
  96
  97         /* gettimeofday() and getpid() shouldn't fail on POSIX platforms. */
  98         gettimeofday (&now, 0);
  99
 100         /* The format string inserts a couple of dots, for the benefit
 101            of spam filters that want to see a message id with a final
 102            part that resembles a hostname. */
 103 #define P(fmt) \
 104     snprintf(message_id_, sizeof message_id_, (fmt), \
 105         getpid(), (long)now.tv_sec, (long)now.tv_usec, \
 106         (int)one_third, rnd_base64, \
 107         (int)one_third, &rnd_base64[one_third], \
 108         (int)one_third, &rnd_base64[2*one_third])
 109
 110             if (content_id)
 111                 P("<%d-%ld.%06ld%%d@%.*s.%.*s.%.*s>");
 112             else
 113                 P("<%d-%ld.%06ld@%.*s.%.*s.%.*s>");
 114 #undef P
 115       }
 116
 117       break;
 118     }
 119   }
 120
 121   return message_id_;
 122 }