2 * message-id.c -- construct the body of a Message-ID or Content-ID
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.
11 #include <unistd.h> /* for getpid() */
12 #include <sys/time.h> /* for gettimeofday() */
17 NMH_MESSAGE_ID_LOCALNAME,
19 } message_id_style = NMH_MESSAGE_ID_LOCALNAME;
20 static char message_id_[BUFSIZ];
23 /* Convert name of message id style to integer value and store it. */
25 save_message_id_style (const char *value) {
26 if (! mh_strcasecmp (value, "localname")) {
27 message_id_style = NMH_MESSAGE_ID_LOCALNAME;
29 } else if (! mh_strcasecmp (value, "random")) {
30 message_id_style = NMH_MESSAGE_ID_RANDOM;
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>";
44 snprintf (message_id_, sizeof message_id_, format,
45 (int) getpid (), (long) tclock, LocalName (1));
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,
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;
62 if (m_rand (rnd, sizeof rnd) == 0) {
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
68 unsigned char rnd_base64[2 * sizeof rnd];
72 writeBase64 (rnd, sizeof rnd, rnd_base64);
74 for (i = strlen ((const char *) rnd_base64) - 1;
75 i > 0 && iscntrl (rnd_base64[i]);
77 /* Remove trailing newline. rnd_base64 had better be
78 shorter than 76 characters, so don't bother to look for
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) {
88 } else if (*cp == '/') {
93 /* gettimeofday() and getpid() shouldn't fail on POSIX platforms. */
94 gettimeofday (&now, 0);
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]);