first stab at simple mailer
Simon 'corecode' Schubert
corecode at fs.ei.tum.de
Tue Mar 20 14:48:03 PDT 2007
Hey,
again and again people are complaining about why sendmail is in base and why not postfix, etc. We keep saying that we do need a mail delivery/transport agent, for stuff such as periodic, cron, etc.
But that doesn't mean that we need sendmail. Actually a much simpler mailer would do: one that just delivers locally (and if possible, remote) and does nothing else.
I've started writing such a mailer which can be used to replace sendmail for the most basic mail jobs. I consider this in an early stage of development, but much of the functionality is already there. Please review the code/concept and give me feedback.
How it works:
- binary will be setgid mail or such.
- mail gets accepted from stdin
- mail gets written to spool dir
- per recipient one child is being forked
- childs try delivering
- on timeout a bounce is created
- if the system goes down, /etc/rc would start the mailer in queue processing mode, which does the same like above except for reading the mail from stdin. instead it reads the queue.
What is still missing:
- SMTP delivery
- alias expansion
- proper sysexit codes
What I am not sure about:
- should the mailer block until all recipients are served or should it (like now) daemonize instantly
comments welcome! (and contributions as well)
latest development version is always at <http://ww2.fs.ei.tum.de/~corecode/git?p=dma.git>
attached current version.
cheers
simon
--
Serve - BSD +++ RENT this banner advert +++ ASCII Ribbon /"\
Work - Mac +++ space for low €€€ NOW!1 +++ Campaign \ /
Party Enjoy Relax | http://dragonflybsd.org Against HTML \
Dude 2c 2 the max ! http://golden-apple.biz Mail + News / \
#include <sys/param.h>
#include <sys/queue.h>
#include <sys/stat.h>
#include <dirent.h>
#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <inttypes.h>
#include <paths.h>
#include <pwd.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <syslog.h>
#include <unistd.h>
#define VERSION "DragonFly Mail Agent 0.1"
#define MIN_RETRY 300 /* 5 minutes */
#define MAX_RETRY (3*60*60) /* retry at least every 3 hours */
#define MAX_TIMEOUT (5*24*60*60) /* give up after 5 days */
#define SPOOL_PATH "/tmp/spool"/*"/var/spool/mqueue"*/
struct qitem {
LIST_ENTRY(qitem) next;
const char *sender;
char *addr;
char *queuefn;
char *queueid;
FILE *queuef;
off_t hdrlen;
int remote;
};
LIST_HEAD(queueh, qitem);
struct queue {
struct queueh queue;
uintmax_t id;
int mailfd;
char *tmpf;
};
static void deliver(struct qitem *);
struct tmpf {
SLIST_ENTRY(tmpf) next;
char *name;
};
static SLIST_HEAD(, tmpf) tmpfs = SLIST_HEAD_INITIALIZER(tmpfs);
static int daemonize = 1;
static char *
hostname(void)
{
static char name[MAXHOSTNAMELEN+1];
if (gethostname(name, sizeof(name)) != 0)
strcpy(name, "(unknown hostname)");
return name;
}
static char *
set_from(const char *osender)
{
char *sender;
if (osender) {
sender = strdup(osender);
if (sender == NULL)
return (NULL);
} else {
if (asprintf(&sender, "%s@%s", getlogin(), hostname()) <= 0)
return (NULL);
}
if (strchr(sender, '\n') != NULL) {
errno = EINVAL;
return (NULL);
}
return (sender);
}
static int
add_recp(struct queue *queue, const char *str, const char *sender, int expand)
{
struct qitem *it, *tit;
struct passwd *pw;
char *host;
#if 0
if (expand)
/* XXX add alias processing */
#endif
it = calloc(1, sizeof(*it));
if (it == NULL)
return (-1);
it->addr = strdup(str);
if (it->addr == NULL)
return (-1);
it->sender = sender;
if ((host = strrchr(it->addr, '@')) != NULL) {
/* Remote address */
if (strcmp(host + 1, hostname()) == 0 ||
strcmp(host + 1, "localhost") == 0) {
/* It is really a local thingy */
*host = 0;
goto local;
}
/* XXX validate address/host? */
it->remote = 1;
} else {
local:
/* Local destination, check */
pw = getpwnam(it->addr);
if (expand && pw == NULL)
goto out;
it->remote = 0;
endpwent();
}
LIST_FOREACH(tit, &queue->queue, next) {
/* weed out duplicate dests */
if (strcmp(tit->addr, it->addr) == 0) {
free(it->addr);
free(it);
return (0);
}
}
LIST_INSERT_HEAD(&queue->queue, it, next);
return (0);
out:
free(it->addr);
free(it);
return (-1);
}
static void
deltmp(void)
{
struct tmpf *t;
SLIST_FOREACH(t, &tmpfs, next) {
unlink(t->name);
}
}
static int
gentempf(struct queue *queue)
{
char fn[PATH_MAX+1];
struct tmpf *t;
int fd;
if (snprintf(fn, sizeof(fn), "%s/%s", SPOOL_PATH, "tmp_XXXXXXXXXX") <= 0)
return (-1);
fd = mkstemp(fn);
if (fd < 0)
return (-1);
queue->mailfd = fd;
queue->tmpf = strdup(fn);
if (queue->tmpf == NULL) {
unlink(fn);
return (-1);
}
t = malloc(sizeof(*t));
if (t != NULL) {
t->name = queue->tmpf;
SLIST_INSERT_HEAD(&tmpfs, t, next);
}
return (0);
}
/*
* spool file format:
*
* envelope-from
* queue-id1 envelope-to1
* queue-id2 envelope-to2
* ...
* <empty line>
* mail data
*
* queue ids are unique, formed from the inode of the spool file
* and a unique identifier.
*/
static int
preparespool(struct queue *queue, const char *sender)
{
char line[1000]; /* by RFC2822 */
struct stat st;
int error;
struct qitem *it;
FILE *queuef;
off_t hdrlen;
error = snprintf(line, sizeof(line), "%s\n", sender);
if (error < 0 || (size_t)error >= sizeof(line)) {
errno = E2BIG;
return (-1);
}
if (write(queue->mailfd, line, error) != error)
return (-1);
queuef = fdopen(queue->mailfd, "r+");
if (queuef == NULL)
return (-1);
/*
* Assign queue id to each dest.
*/
if (fstat(queue->mailfd, &st) != 0)
return (-1);
queue->id = st.st_ino;
LIST_FOREACH(it, &queue->queue, next) {
if (asprintf(&it->queueid, "%"PRIxMAX".%"PRIxPTR,
queue->id, (uintptr_t)it) <= 0)
return (-1);
if (asprintf(&it->queuefn, "%s/%s",
SPOOL_PATH, it->queueid) <= 0)
return (-1);
/* File may not exist yet */
if (stat(it->queuefn, &st) == 0)
return (-1);
it->queuef = queuef;
error = snprintf(line, sizeof(line), "%s %s\n",
it->queueid, it->addr);
if (error < 0 || (size_t)error >= sizeof(line))
return (-1);
if (write(queue->mailfd, line, error) != error)
return (-1);
}
line[0] = '\n';
if (write(queue->mailfd, line, 1) != 1)
return (-1);
hdrlen = lseek(queue->mailfd, 0, SEEK_CUR);
LIST_FOREACH(it, &queue->queue, next) {
it->hdrlen = hdrlen;
}
return (0);
}
static char *
rfc822date(void)
{
static char str[50];
size_t error;
time_t now;
now = time(NULL);
error = strftime(str, sizeof(str), "%a, %d %b %Y %T %z",
localtime(&now));
if (error == 0)
strcpy(str, "(date fail)");
return (str);
}
static int
readmail(struct queue *queue, const char *sender, int nodot)
{
char line[1000]; /* by RFC2822 */
size_t linelen;
int error;
error = snprintf(line, sizeof(line), "\
Received: from %s (uid %d)\n\
\t(envelope-from %s)\n\
\tid %"PRIxMAX"\n\
\tby %s (%s);\n\
\t%s\n",
getlogin(), getuid(),
sender,
queue->id,
hostname(), VERSION,
rfc822date());
if (error < 0 || (size_t)error >= sizeof(line))
return (-1);
if (write(queue->mailfd, line, error) != error)
return (-1);
while (!feof(stdin)) {
if (fgets(line, sizeof(line), stdin) == NULL)
break;
linelen = strlen(line);
if (linelen == 0 || line[linelen - 1] != '\n') {
errno = EINVAL; /* XXX mark permanent errors */
return (-1);
}
if (!nodot && linelen == 2 && line[0] == '.')
break;
if ((size_t)write(queue->mailfd, line, linelen) != linelen)
return (-1);
}
if (fsync(queue->mailfd) != 0)
return (-1);
return (0);
}
static int
linkspool(struct queue *queue)
{
struct qitem *it;
LIST_FOREACH(it, &queue->queue, next) {
if (link(queue->tmpf, it->queuefn) != 0)
goto delfiles;
}
unlink(queue->tmpf);
return (0);
delfiles:
LIST_FOREACH(it, &queue->queue, next) {
unlink(it->queuefn);
}
return (-1);
}
static struct qitem *
go_background(struct queue *queue)
{
struct sigaction sa;
struct qitem *it;
pid_t pid;
if (daemonize && daemon(0, 0) != 0) {
syslog(LOG_ERR, "can not daemonize: %m");
exit(1);
}
daemonize = 0;
bzero(&sa, sizeof(sa));
sa.sa_flags = SA_NOCLDWAIT;
sa.sa_handler = SIG_IGN;
sigaction(SIGCHLD, &sa, NULL);
LIST_FOREACH(it, &queue->queue, next) {
/* No need to fork for the last dest */
if (LIST_NEXT(it, next) == NULL)
return (it);
pid = fork();
switch (pid) {
case -1:
syslog(LOG_ERR, "can not fork: %m");
exit(1);
break;
case 0:
/*
* Child:
*
* return and deliver mail
*/
return (it);
default:
/*
* Parent:
*
* fork next child
*/
break;
}
}
syslog(LOG_CRIT, "reached dead code");
exit(1);
}
static void
bounce(struct qitem *it, const char *reason)
{
struct queue bounceq;
struct qitem *bit;
char line[1000];
int error;
/* Don't bounce bounced mails */
if (it->sender[0] == 0) {
syslog(LOG_CRIT, "%s: delivery panic: can't bounce a bounce",
it->queueid);
exit(1);
}
syslog(LOG_ERR, "%s: delivery failed, bouncing",
it->queueid);
LIST_INIT(&bounceq.queue);
if (add_recp(&bounceq, it->sender, "", 1) != 0)
goto fail;
if (gentempf(&bounceq) != 0)
goto fail;
if (preparespool(&bounceq, "") != 0)
goto fail;
bit = LIST_FIRST(&bounceq.queue);
error = fprintf(bit->queuef, "\
Received: from MAILER-DAEMON\n\
\tid %"PRIxMAX"\n\
\tby %s (%s);\n\
\t%s\n\
X-Original-To: <%s>\n\
From: MAILER-DAEMON <>\n\
To: %s\n\
Subject: Mail delivery failed\n\
Message-Id: <%"PRIxMAX"@%s>\n\
Date: %s\n\
\n\
This is the %s at %s.\n\
\n\
There was an error delivering your mail to <%s>.\n\
\n\
%s\n\
\n\
Message headers follow.\n\
\n\
",
bounceq.id,
hostname(), VERSION,
rfc822date(),
it->addr,
it->sender,
bounceq.id, hostname(),
rfc822date(),
VERSION, hostname(),
it->addr,
reason);
if (error < 0)
goto fail;
if (fflush(bit->queuef) != 0)
goto fail;
if (fseek(it->queuef, it->hdrlen, SEEK_SET) != 0)
goto fail;
while (!feof(it->queuef)) {
if (fgets(line, sizeof(line), it->queuef) == NULL)
break;
if (line[0] == '\n')
break;
write(bounceq.mailfd, line, strlen(line));
}
if (fsync(bounceq.mailfd) != 0)
goto fail;
if (linkspool(&bounceq) != 0)
goto fail;
/* bounce is safe */
unlink(it->queuefn);
fclose(it->queuef);
bit = go_background(&bounceq);
deliver(bit);
/* NOTREACHED */
fail:
syslog(LOG_CRIT, "%s: error creating bounce: %m", it->queueid);
unlink(it->queuefn);
exit(1);
}
static int
deliver_local(struct qitem *it, const char **errmsg)
{
char fn[PATH_MAX+1];
char line[1000];
size_t linelen;
int mbox;
int error;
off_t mboxlen;
time_t now = time(NULL);
error = snprintf(fn, sizeof(fn), "%s/%s", _PATH_MAILDIR, it->addr);
if (error < 0 || (size_t)error >= sizeof(fn)) {
syslog(LOG_ERR, "%s: local delivery deferred: %m",
it->queueid);
return (1);
}
mbox = open(fn, O_WRONLY|O_EXLOCK|O_APPEND);
if (mbox < 0) {
syslog(LOG_ERR, "%s: local delivery deferred: can not open `%s': %m",
it->queueid, fn);
return (1);
}
mboxlen = lseek(mbox, 0, SEEK_CUR);
if (fseek(it->queuef, it->hdrlen, SEEK_SET) != 0) {
syslog(LOG_ERR, "%s: local delivery deferred: can not seek: %m",
it->queueid);
return (1);
}
error = snprintf(line, sizeof(line), "From %s\t%s", it->sender, ctime(&now));
if (error < 0 || (size_t)error >= sizeof(line)) {
syslog(LOG_ERR, "%s: local delivery deferred: can not write header: %m",
it->queueid);
return (1);
}
if (write(mbox, line, error) != error)
goto wrerror;
while (!feof(it->queuef)) {
if (fgets(line, sizeof(line), it->queuef) == NULL)
break;
linelen = strlen(line);
if (linelen == 0 || line[linelen - 1] != '\n') {
syslog(LOG_CRIT, "%s: local delivery failed: corrupted queue file",
it->queueid);
*errmsg = "corrupted queue file";
error = -1;
goto chop;
}
if (strncmp(line, "From ", 5) == 0) {
const char *gt = ">";
if (write(mbox, gt, 1) != 1)
goto wrerror;
}
if ((size_t)write(mbox, line, linelen) != linelen)
goto wrerror;
}
line[0] = '\n';
if (write(mbox, line, 1) != 1)
goto wrerror;
close(mbox);
return (0);
wrerror:
syslog(LOG_ERR, "%s: local delivery failed: write error: %m",
it->queueid);
error = 1;
chop:
if (ftruncate(mbox, mboxlen) != 0)
syslog(LOG_WARNING, "%s: error recovering mbox `%s': %m",
it->queueid, fn);
close(mbox);
return (error);
}
static void
deliver(struct qitem *it)
{
int error;
unsigned int backoff = MIN_RETRY;
const char *errmsg = "unknown bounce reason";
struct timeval now;
struct stat st;
syslog(LOG_INFO, "%s: mail from=<%s> to=<%s>",
it->queueid, it->sender, it->addr);
retry:
syslog(LOG_INFO, "%s: trying delivery",
it->queueid);
if (it->remote) {
errmsg = "remote delivery not implemented";
error = -1;/* XXX implement me */
} else
error = deliver_local(it, &errmsg);
switch (error) {
case 0:
unlink(it->queuefn);
syslog(LOG_INFO, "%s: delivery successful",
it->queueid);
exit(0);
case 1:
if (stat(it->queuefn, &st) != 0) {
syslog(LOG_ERR, "%s: lost queue file `%s'",
it->queueid, it->queuefn);
exit(1);
}
if (gettimeofday(&now, NULL) == 0 &&
(now.tv_sec - st.st_mtimespec.tv_sec > MAX_TIMEOUT)) {
char *msg;
if (asprintf(&msg,
"Could not deliver for the last %d seconds. Giving up.",
MAX_TIMEOUT) > 0)
errmsg = msg;
goto bounce;
}
sleep(backoff);
backoff *= 2;
if (backoff > MAX_RETRY)
backoff = MAX_RETRY;
goto retry;
case -1:
default:
break;
}
bounce:
bounce(it, errmsg);
/* NOTREACHED */
}
static void
run_queue(void)
{
struct stat st;
struct qitem *it;
struct queue queue, itmqueue;
DIR *spooldir;
struct dirent *de;
char line[1000];
char *fn;
FILE *queuef;
char *sender;
char *addr;
char *queueid;
char *queuefn;
off_t hdrlen;
int fd;
LIST_INIT(&queue.queue);
spooldir = opendir(SPOOL_PATH);
if (spooldir == NULL)
err(1, "reading queue");
while ((de = readdir(spooldir)) != NULL) {
sender = NULL;
queuef = NULL;
queueid = NULL;
queuefn = NULL;
fn = NULL;
LIST_INIT(&itmqueue.queue);
/* ignore temp files */
if (strncmp(de->d_name, "tmp_", 4) == 0 ||
de->d_type != DT_REG)
continue;
if (asprintf(&queuefn, "%s/%s", SPOOL_PATH, de->d_name) < 0)
goto fail;
fd = open(queuefn, O_RDONLY|O_EXLOCK|O_NONBLOCK);
if (fd < 0) {
/* Ignore locked files */
if (errno == EWOULDBLOCK)
continue;
goto skip_item;
}
queuef = fdopen(fd, "r");
if (queuef == NULL)
goto skip_item;
if (fgets(line, sizeof(line), queuef) == NULL ||
line[0] == 0)
goto skip_item;
line[strlen(line) - 1] = 0; /* chop newline */
sender = strdup(line);
if (sender == NULL)
goto skip_item;
for (;;) {
if (fgets(line, sizeof(line), queuef) == NULL ||
line[0] == 0)
goto skip_item;
if (line[0] == '\n')
break;
line[strlen(line) - 1] = 0;
queueid = strdup(line);
if (queueid == NULL)
goto skip_item;
addr = strchr(queueid, ' ');
if (addr == NULL)
goto skip_item;
*addr++ = 0;
if (fn != NULL)
free(fn);
if (asprintf(&fn, "%s/%s", SPOOL_PATH, queueid) < 0)
goto skip_item;
/* Item has already been delivered? */
if (stat(fn, &st) != 0)
continue;
if (add_recp(&itmqueue, addr, sender, 0) != 0)
goto skip_item;
it = LIST_FIRST(&itmqueue.queue);
it->queuef = queuef;
it->queueid = queueid;
it->queuefn = fn;
fn = NULL;
}
if (LIST_EMPTY(&itmqueue.queue)) {
warnx("queue file without items: `%s'", queuefn);
goto skip_item2;
}
hdrlen = ftell(queuef);
while ((it = LIST_FIRST(&itmqueue.queue)) != NULL) {
it->hdrlen = hdrlen;
LIST_REMOVE(it, next);
LIST_INSERT_HEAD(&queue.queue, it, next);
}
continue;
skip_item:
warn("reading queue: `%s'", queuefn);
skip_item2:
if (sender != NULL)
free(sender);
if (queuefn != NULL)
free(queuefn);
if (fn != NULL)
free(fn);
if (queueid != NULL)
free(queueid);
close(fd);
}
closedir(spooldir);
it = go_background(&queue);
deliver(it);
/* NOTREACHED */
fail:
err(1, "reading queue");
}
/*
* TODO:
*
* - SMTP delivery
* - alias processing
* - use group permissions
* - proper sysexit codes
*/
int
main(int argc, char **argv)
{
char *sender = NULL;
struct qitem *it;
struct queue queue;
int i, ch;
int nodot = 0, doqueue = 0;
atexit(deltmp);
LIST_INIT(&queue.queue);
openlog("dma", LOG_PID|LOG_PERROR, LOG_MAIL);
while ((ch = getopt(argc, argv, "Df:io:qr:")) != -1) {
switch (ch) {
case 'D':
daemonize = 0;
break;
case 'f':
case 'r':
sender = optarg;
break;
case 'o':
/* -oX is being ignored, except for -oi */
if (optarg[0] != 'i')
break;
/* else FALLTRHOUGH */
case 'i':
nodot = 1;
break;
case 'q':
doqueue = 1;
break;
default:
exit(1);
}
}
argc -= optind;
argv += optind;
if (doqueue) {
if (argc != 0)
errx(1, "sending mail and queue pickup is mutually exclusive");
run_queue();
/* NOTREACHED */
}
if ((sender = set_from(sender)) == NULL)
err(1, "setting from address");
for (i = 0; i < argc; i++) {
if (add_recp(&queue, argv[i], sender, 1) != 0)
errx(1, "invalid recipient `%s'\n", argv[i]);
}
if (LIST_EMPTY(&queue.queue))
errx(1, "no recipients");
if (gentempf(&queue) != 0)
err(1, "create temp file");
if (preparespool(&queue, sender) != 0)
err(1, "creating spools (1)");
if (readmail(&queue, sender, nodot) != 0)
err(1, "reading mail");
if (linkspool(&queue) != 0)
err(1, "creating spools (2)");
/* From here on the mail is safe. */
it = go_background(&queue);
deliver(it);
/* NOTREACHED */
return (0);
}
Attachment:
signature.asc
-------------- next part --------------
A non-text attachment was scrubbed...
Name: pgp00009.pgp
Type: application/octet-stream
Size: 252 bytes
Desc: "Description: OpenPGP digital signature"
URL: <http://lists.dragonflybsd.org/pipermail/kernel/attachments/20070320/dd25548e/attachment-0019.obj>
More information about the Kernel
mailing list