Use getservbyname(3) for port numbers

[Christian Weisgerber]

[Reposted from tech at openbsd.org]

Is there a reason ssh doesn't consult services(5) for port numbers?

This has irked me forever.  I'd rather write ssh -L icb:localhost:icb
instead of ssh -L 7326, wait, 7236, uhm, grep icb /etc/services...

I don't think there is any syntactic ambiguity since Unix sockets
already must contain a '/'.

The patch below adds this:
* Try to resolve a port specification with getservbyname(3) if a
  numeric conversion fails.
* Make the "Port" option in ssh_config handle its argument as a
  port rather than a plain integer.

All other command line switches and configuration file options
already use a2port().

This passes the existing regression tests.

Index: misc.c
===================================================================
RCS file: /cvs/src/usr.bin/ssh/misc.c,v
retrieving revision 1.131
diff -u -p -r1.131 misc.c
--- misc.c	27 Jul 2018 05:13:02 -0000	1.131
+++ misc.c	30 Aug 2018 23:59:07 -0000
@@ -36,6 +36,7 @@
 #include <netinet/in.h>
 #include <netinet/ip.h>
 #include <netinet/tcp.h>
+#include <arpa/inet.h>
 
 #include <ctype.h>
 #include <errno.h>
@@ -299,13 +300,16 @@ pwcopy(struct passwd *pw)
 int
 a2port(const char *s)
 {
+	struct servent *se;
 	long long port;
 	const char *errstr;
 
 	port = strtonum(s, 0, 65535, &errstr);
-	if (errstr != NULL)
-		return -1;
-	return (int)port;
+	if (errstr == NULL)
+		return (int)port;
+	if ((se = getservbyname(s, "tcp")) != NULL)
+		return ntohs(se->s_port);
+	return -1;
 }
 
 int
Index: readconf.c
===================================================================
RCS file: /cvs/src/usr.bin/ssh/readconf.c,v
retrieving revision 1.297
diff -u -p -r1.297 readconf.c
--- readconf.c	12 Aug 2018 20:19:13 -0000	1.297
+++ readconf.c	30 Aug 2018 23:14:38 -0000
@@ -1142,7 +1142,20 @@ parse_command:
 		return 0;
 
 	case oPort:
-		intptr = &options->port;
+		arg = strdelim(&s);
+		if (!arg || *arg == '\0')
+			fatal("%.200s line %d: Missing argument.",
+			    filename, linenum);
+		value = a2port(arg);
+		if (value <= 0)
+			fatal("%.200s line %d: Bad port '%s'.",
+			    filename, linenum, arg);
+		if (*activep && options->port == -1)
+			options->port = value;
+		break;
+
+	case oConnectionAttempts:
+		intptr = &options->connection_attempts;
 parse_int:
 		arg = strdelim(&s);
 		if ((errstr = atoi_err(arg, &value)) != NULL)
@@ -1151,10 +1164,6 @@ parse_int:
 		if (*activep && *intptr == -1)
 			*intptr = value;
 		break;
-
-	case oConnectionAttempts:
-		intptr = &options->connection_attempts;
-		goto parse_int;
 
 	case oCiphers:
 		arg = strdelim(&s);
-- 
Christian "naddy" Weisgerber                          naddy at mips.inka.de