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/*
* message-id.c -- construct the body of a Message-ID or Content-ID
* header field
*
* This code is Copyright (c) 2012, by the authors of nmh. See the
* COPYRIGHT file in the root directory of the nmh distribution for
* complete copyright information.
*/
#include <h/mh.h>
#include <sys/time.h> /* for gettimeofday() */
static enum {
NMH_MESSAGE_ID_LOCALNAME,
NMH_MESSAGE_ID_RANDOM
} message_id_style = NMH_MESSAGE_ID_LOCALNAME;
static char message_id_[BUFSIZ];
/* Convert name of message id style to integer value and store it. */
int
save_message_id_style (const char *value) {
if (! strcasecmp (value, "localname")) {
message_id_style = NMH_MESSAGE_ID_LOCALNAME;
return 0;
} else if (! strcasecmp (value, "random")) {
message_id_style = NMH_MESSAGE_ID_RANDOM;
return 0;
} else {
return 1;
}
}
char *
message_id (time_t tclock, int content_id) {
switch (message_id_style) {
case NMH_MESSAGE_ID_LOCALNAME: {
char *format = content_id ? "<%d.%ld.%%d@%s>" : "<%d.%ld@%s>";
snprintf (message_id_, sizeof message_id_, format,
(int) getpid (), (long) tclock, LocalName (1));
break;
}
case NMH_MESSAGE_ID_RANDOM: {
char *format = content_id
? "<%d-%ld.%06ld%%d@%.*s.%.*s.%.*s>"
: "<%d-%ld.%06ld@%.*s.%.*s.%.*s>";
/* Use a sequence of digits divisible by 3 because that will
expand to base64 without any waste. Must be shorter than 58,
see below. */
unsigned char rnd[9];
/* The part after the '@' is divided into thirds. The base64
encoded string will be 4/3 the size of rnd. */
size_t one_third = sizeof rnd * 4/3/3;
if (m_rand (rnd, sizeof rnd) == 0) {
struct timeval now;
/* All we really need is 4 * [sizeof rnd/3] + 2, as long as
the base64 encoding stays shorter than 76 bytes so embedded
newlines aren't necessary. But use double the sizeof rnd
just to be safe. */
unsigned char rnd_base64[2 * sizeof rnd];
unsigned char *cp;
int i;
writeBase64 (rnd, sizeof rnd, rnd_base64);
for (i = strlen ((const char *) rnd_base64) - 1;
i > 0 && iscntrl (rnd_base64[i]);
--i) {
/* Remove trailing newline. rnd_base64 had better be
shorter than 76 characters, so don't bother to look for
embedded newlines. */
rnd_base64[i] = '\0';
}
/* Try to make the base64 string look a little more like a
hostname by replacing + with - and / with _. */
for (cp = rnd_base64; *cp; ++cp) {
if (*cp == '+') {
*cp = '-';
} else if (*cp == '/') {
*cp = '_';
}
}
/* gettimeofday() and getpid() shouldn't fail on POSIX platforms. */
gettimeofday (&now, 0);
/* The format string inserts a couple of dots, for the benefit
of spam filters that want to see a message id with a final
part that resembles a hostname. */
snprintf (message_id_, sizeof message_id_, format,
getpid (), (long) now.tv_sec, (long) now.tv_usec,
one_third, rnd_base64,
one_third, &rnd_base64[one_third],
one_third, &rnd_base64[2*one_third]);
}
break;
}
}
return message_id_;
}
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