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Date: Mon, 5 Oct 2015 17:00:52 +0200
From: "Jason A. Donenfeld" <Jason@...c4.com>
To: oss-security <oss-security@...ts.openwall.com>, cve-assign@...re.org
Subject: CVE Request: OpenSMTPD <= 5.7.2 buffer overflow
Hello,
As reported in [1], OpenSMTPD <= 5.7.2 has a remotely exploitable
buffer overflow. This overflow requires a CVE. A PoC is attached to
[1].
OpenSMTPD 5.7.3 was released with fixes, and the release notes follow
below. There may be other vulnerabilities also fixed by this release.
A full diff follows for analysis and additional CVE assignment, in
case that is necessary.
Thanks,
Jason
[1] http://seclists.org/oss-sec/2015/q4/25
---------- Forwarded message ----------
From: Gilles Chehade <gilles@...lp.org>
Date: Mon, Oct 5, 2015 at 3:30 PM
Subject: Announce: OpenSMTPD 5.7.3 released
To: misc@...nsmtpd.org
[snipped]
Issues fixed in this release (since 5.7.2):
===========================================
- fix an mda buffer truncation bug which allows a user to create forward
files that pass session checks but fail delivery later down the chain,
within the user mda [0]
- fix remote buffer overflow in unprivileged pony process [1]
- reworked offline enqueue to better protect against hardlink attacks [2]
[0] reported by Holger Jahn
[1] reported by Jason A. Donenfeld
[2] reported by Qualys Security
------ DIFF -----
diff -ru opensmtpd-5.7.2p1/smtpd/enqueue.c opensmtpd-5.7.3p1/smtpd/enqueue.c
--- opensmtpd-5.7.2p1/smtpd/enqueue.c 2015-10-02 01:46:21.000000000 +0200
+++ opensmtpd-5.7.3p1/smtpd/enqueue.c 2015-10-05 13:33:41.000000000 +0200
@@ -795,12 +795,25 @@
FILE *fp;
int i, fd, ch;
mode_t omode;
+ uint64_t rnd;
+ int ret;
if (ckdir(PATH_SPOOL PATH_OFFLINE, 01777, 0, 0, 0) == 0)
errx(EX_UNAVAILABLE, "error in offline directory setup");
- if (! bsnprintf(path, sizeof(path), "%s%s/%lld.XXXXXXXXXX", PATH_SPOOL,
- PATH_OFFLINE, (long long int) time(NULL)))
+ do {
+ rnd = generate_uid();
+ if (! bsnprintf(path, sizeof(path),
"%s%s/%016"PRIx64, PATH_SPOOL,
+ PATH_OFFLINE, rnd))
+ err(EX_UNAVAILABLE, "snprintf");
+ ret = mkdir(path, 0700);
+ if (ret == -1)
+ if (errno != EEXIST)
+ err(EX_UNAVAILABLE, "mkdir");
+ } while (ret == -1);
+
+ if (! bsnprintf(path, sizeof(path),
"%s%s/%016"PRIx64"/%lld.XXXXXXXXXX", PATH_SPOOL,
+ PATH_OFFLINE, rnd, (long long int) time(NULL)))
err(EX_UNAVAILABLE, "snprintf");
omode = umask(7077);
diff -ru opensmtpd-5.7.2p1/smtpd/filter.c opensmtpd-5.7.3p1/smtpd/filter.c
--- opensmtpd-5.7.2p1/smtpd/filter.c 2015-10-02 01:46:21.000000000 +0200
+++ opensmtpd-5.7.3p1/smtpd/filter.c 2015-10-05 13:33:41.000000000 +0200
@@ -728,7 +728,6 @@
struct filter_session *s = io->arg;
size_t len, n;
char *data;
- char buf[65535];
log_trace(TRACE_FILTERS, "filter: filter_tx_io(%p, %s)", s,
io_strevent(evt));
@@ -736,10 +735,9 @@
case IO_DATAIN:
data = iobuf_data(&s->ibuf);
len = iobuf_len(&s->ibuf);
- memmove(buf, data, len);
- buf[len] = 0;
- log_trace(TRACE_FILTERS, "filter: filter_tx_io:
datain (%zu) for req %016"PRIx64": %s",
- len, s->id, buf);
+
+ log_trace(TRACE_FILTERS, "filter: filter_tx_io:
datain (%zu) for req %016"PRIx64"",
+ len, s->id);
n = fwrite(data, 1, len, s->ofile);
if (n != len) {
diff -ru opensmtpd-5.7.2p1/smtpd/mda.c opensmtpd-5.7.3p1/smtpd/mda.c
--- opensmtpd-5.7.2p1/smtpd/mda.c 2015-10-02 01:46:21.000000000 +0200
+++ opensmtpd-5.7.3p1/smtpd/mda.c 2015-10-05 13:33:41.000000000 +0200
@@ -286,8 +286,17 @@
deliver.userinfo = *userinfo;
(void)strlcpy(deliver.user, userinfo->username,
sizeof(deliver.user));
- (void)strlcpy(deliver.to, e->buffer,
- sizeof(deliver.to));
+ if (strlcpy(deliver.to, e->buffer,
+ sizeof(deliver.to))
+ >= sizeof(deliver.to)) {
+ mda_queue_tempfail(e->id,
+ "mda command too long",
+ ESC_OTHER_MAIL_SYSTEM_STATUS);
+ mda_log(e, "TempFail",
+ "mda command too long");
+ mda_done(s);
+ return;
+ }
break;
case A_MBOX:
diff -ru opensmtpd-5.7.2p1/smtpd/smtpd.c opensmtpd-5.7.3p1/smtpd/smtpd.c
--- opensmtpd-5.7.2p1/smtpd/smtpd.c 2015-10-02 01:46:21.000000000 +0200
+++ opensmtpd-5.7.3p1/smtpd/smtpd.c 2015-10-05 13:33:41.000000000 +0200
@@ -50,9 +50,11 @@
#include <errno.h>
#include <event.h>
#include <fcntl.h>
+#include <fts.h>
#include <grp.h> /* needed for setgroups */
#include <imsg.h>
#include <inttypes.h>
+#include <libgen.h>
#ifdef HAVE_LOGIN_CAP_H
#include <login_cap.h>
#endif
@@ -440,8 +442,10 @@
"couldn't enqueue offline "
"message %s; smtpctl %s",
child->path, cause);
- else
+ else {
unlink(child->path);
+ rmdir(dirname(child->path));
+ }
free(child->path);
offline_done();
break;
@@ -1075,28 +1079,43 @@
static void
offline_scan(int fd, short ev, void *arg)
{
- DIR *dir = arg;
- struct dirent *d;
+ char *path_argv[2];
+ FTS *fts = arg;
+ FTSENT *e;
int n = 0;
- if (dir == NULL) {
+ path_argv[0] = PATH_SPOOL PATH_OFFLINE;
+ path_argv[1] = NULL;
+
+ if (fts == NULL) {
log_debug("debug: smtpd: scanning offline queue...");
- if ((dir = opendir(PATH_SPOOL PATH_OFFLINE)) == NULL)
- errx(1, "smtpd: opendir");
+ fts = fts_open(path_argv, FTS_PHYSICAL | FTS_NOCHDIR, NULL);
+ if (fts == NULL) {
+ log_warn("fts_open: %s", path_argv[0]);
+ return;
+ }
}
- while ((d = readdir(dir)) != NULL) {
- if (d->d_type != DT_REG)
+ while ((e = fts_read(fts)) != NULL) {
+ if (e->fts_info != FTS_F)
+ continue;
+
+ /* offline files must be at depth 2 */
+ if (e->fts_level != 2)
+ continue;
+
+ /* offline file owner must match parent directory owner */
+ if (e->fts_statp->st_uid != e->fts_parent->fts_statp->st_uid)
continue;
- if (offline_add(d->d_name)) {
+ if (offline_add(e->fts_accpath)) {
log_warnx("warn: smtpd: "
- "could not add offline message %s", d->d_name);
+ "could not add offline message %s", e->fts_name);
continue;
}
if ((n++) == OFFLINE_READMAX) {
- evtimer_set(&offline_ev, offline_scan, dir);
+ evtimer_set(&offline_ev, offline_scan, fts);
offline_timeout.tv_sec = 0;
offline_timeout.tv_usec = 100000;
evtimer_add(&offline_ev, &offline_timeout);
@@ -1105,24 +1124,19 @@
}
log_debug("debug: smtpd: offline scanning done");
- closedir(dir);
+ fts_close(fts);
}
static int
offline_enqueue(char *name)
{
- char t[PATH_MAX], *path;
+ char *path;
struct stat sb;
pid_t pid;
struct child *child;
struct passwd *pw;
- if (!bsnprintf(t, sizeof t, "%s/%s", PATH_SPOOL PATH_OFFLINE, name)) {
- log_warnx("warn: smtpd: path name too long");
- return (-1);
- }
-
- if ((path = strdup(t)) == NULL) {
+ if ((path = strdup(name)) == NULL) {
log_warn("warn: smtpd: strdup");
return (-1);
}
diff -ru opensmtpd-5.7.2p1/smtpd/smtpd.h opensmtpd-5.7.3p1/smtpd/smtpd.h
--- opensmtpd-5.7.2p1/smtpd/smtpd.h 2015-10-02 01:46:21.000000000 +0200
+++ opensmtpd-5.7.3p1/smtpd/smtpd.h 2015-10-05 13:33:41.000000000 +0200
@@ -67,7 +67,7 @@
#ifndef SMTPD_NAME
#define SMTPD_NAME "OpenSMTPD"
#endif
-#define SMTPD_VERSION "5.7.2p1"
+#define SMTPD_VERSION "5.7.3p1"
#define SMTPD_SESSION_TIMEOUT 300
#define SMTPD_BACKLOG 5
@@ -684,7 +684,7 @@
};
struct deliver {
- char to[SMTPD_MAXMAILADDRSIZE];
+ char to[EXPAND_BUFFER];
char from[SMTPD_MAXMAILADDRSIZE];
char dest[SMTPD_MAXMAILADDRSIZE];
char user[SMTPD_VUSERNAME_SIZE];
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