- spamd(8)'s -l accepts an IP address as argument to bind(2) and it calls

inet_pton(3) to check if it's valid and since that function doesn't provide
a proper errno (POSIX doesn't mandate to do so) then if a string is given we
may get this message:
spamd: inet_pton: Undefined error: 0

- Instead replace that code to use getaddrinfo(3) from which is possible to get
a proper error message, and at the same time being able to parse IPs and
hostnames (if either the IP or host is not local then the next bind(2) will
fail)

- By default without arguments, spamd(8) will still bind(2) to 127.0.0.1 as
it did before

With feedback from deraadt@ and OK beck@

1 files changed, 17 insertions, 11 deletions

diff --git a/libexec/spamd/spamd.c b/libexec/spamd/spamd.c
index 86a97ebed1b..22acebf2072 100644
--- a/libexec/spamd/spamd.c
+++ b/libexec/spamd/spamd.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: spamd.c,v 1.147 2016/11/30 07:54:36 mestre Exp $	*/
+/*	$OpenBSD: spamd.c,v 1.148 2017/01/17 23:28:04 mestre Exp $	*/
 
 /*
  * Copyright (c) 2015 Henning Brauer <henning@openbsd.org>
@@ -1236,6 +1236,10 @@ main(int argc, char *argv[])
 	const char *errstr;
 	char *sync_iface = NULL;
 	char *sync_baddr = NULL;
+	struct addrinfo hints, *res;
+	char *addr;
+	char portstr[6];
+	int error;
 
 	tzset();
 	openlog_r("spamd", LOG_PID | LOG_NDELAY, LOG_DAEMON, &sdata);
@@ -1426,18 +1430,20 @@ main(int argc, char *argv[])
 	    sizeof(one)) == -1)
 		return (-1);
 
-	memset(&sin, 0, sizeof sin);
-	sin.sin_len = sizeof(sin);
-	if (bind_address) {
-		if (inet_pton(AF_INET, bind_address, &sin.sin_addr) != 1)
-			err(1, "inet_pton");
-	} else
-		sin.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
-	sin.sin_family = AF_INET;
-	sin.sin_port = htons(port);
+	memset(&hints, 0, sizeof(hints));
+	hints.ai_family = AF_INET;
+	addr = bind_address;
+	snprintf(portstr, sizeof(portstr), "%hu", port);
 
-	if (bind(smtplisten, (struct sockaddr *)&sin, sizeof sin) == -1)
+	if ((error = getaddrinfo(addr, portstr, &hints, &res)) != 0) {
+		errx(1, "getaddrinfo: %s", gai_strerror(error));
+	}
+
+	if (bind(smtplisten, res->ai_addr, res->ai_addrlen) == -1) {
+		freeaddrinfo(res);
 		err(1, "bind");
+	}
+	freeaddrinfo(res);
 
 	memset(&lin, 0, sizeof sin);
 	lin.sin_len = sizeof(sin);