fix two possible local DoS

smtpd/control.c

@@ -73,9 +73,11 @@ extern const char *backend_stat;
 
 static uint32_t			connid = 0;
 static struct tree		ctl_conns;
+static struct tree		ctl_count;
 static struct stat_digest	digest;
 
-#define	CONTROL_FD_RESERVE	5
+#define	CONTROL_FD_RESERVE		5
+#define	CONTROL_MAXCONN_PER_CLIENT	5
 
 static void
 control_imsg(struct mproc *p, struct imsg *imsg)
@@ -282,6 +284,7 @@ control(void)
 	signal(SIGHUP, SIG_IGN);
 
 	tree_init(&ctl_conns);
+	tree_init(&ctl_count);
 
 	memset(&digest, 0, sizeof digest);
 	digest.startup = time(NULL);
@@ -330,6 +333,9 @@ control_accept(int listenfd, short event, void *arg)
 	socklen_t		 len;
 	struct sockaddr_un	 sun;
 	struct ctl_conn		*c;
+	size_t			*count;
+	uid_t			 euid;
+	gid_t			 egid;
 
 	if (getdtablesize() - getdtablecount() < CONTROL_FD_RESERVE)
 		goto pause;
@@ -346,16 +352,30 @@ control_accept(int listenfd, short event, void *arg)
 
 	session_socket_blockmode(connfd, BM_NONBLOCK);
 
-	c = xcalloc(1, sizeof(*c), "control_accept");
-	if (getpeereid(connfd, &c->euid, &c->egid) == -1)
+	if (getpeereid(connfd, &euid, &egid) == -1)
 		fatal("getpeereid");
+
+	count = tree_get(&ctl_count, euid);
+	if (count == NULL)
+		count = xcalloc(1, sizeof *count, "control_accept");
+
+	if (*count == CONTROL_MAXCONN_PER_CLIENT) {
+		close(connfd);
+		return;
+	}
+	(*count)++;
+
+	c = xcalloc(1, sizeof(*c), "control_accept");
+	c->euid = euid;
+	c->egid = egid;
 	c->id = ++connid;
 	c->mproc.proc = PROC_CLIENT;
 	c->mproc.handler = control_dispatch_ext;
 	c->mproc.data = c;
 	mproc_init(&c->mproc, connfd);
 	mproc_enable(&c->mproc);
 	tree_xset(&ctl_conns, c->id, c);
+	tree_set(&ctl_count, c->euid, count);
 
 	stat_backend->increment("control.session", 1);
 	return;
@@ -368,6 +388,16 @@ control_accept(int listenfd, short event, void *arg)
 static void
 control_close(struct ctl_conn *c)
 {
+	size_t	*count;
+
+	count = tree_get(&ctl_count, c->euid);
+	(*count)--;
+	if (*count == 0) {
+		tree_xpop(&ctl_count, c->euid);
+		free(count);
+	}
+	else
+		tree_set(&ctl_count, c->euid, count);
 	tree_xpop(&ctl_conns, c->id);
 	mproc_clear(&c->mproc);
 	free(c);

smtpd/mproc.c

@@ -188,6 +188,14 @@ mproc_dispatch(int fd, short event, void *arg)
 
 	for (;;) {
 		if ((n = imsg_get(&p->imsgbuf, &imsg)) == -1) {
+
+			if (smtpd_process == PROC_CONTROL &&
+			    p->proc == PROC_CLIENT) {
+				log_warnx("warn: client sent invalid imsg "
+				    "over control socket");
+				p->handler(p, NULL);
+				return;
+			}
 			log_warn("fatal: %s: error in imsg_get for %s",
 			    proc_name(smtpd_process),  p->name);
 			fatalx(NULL);