per XPG, gethostname() with a short buffer returns truncated data - not ENOMEM.

As permitted, make the truncated buffer be NUL terminated.
make getdomainname() match.

4 files changed, 69 insertions, 16 deletions

diff --git a/lib/libc/gen/getdomainname.3 b/lib/libc/gen/getdomainname.3
index 42c620c1ed1..fe4d944c3a7 100644
--- a/lib/libc/gen/getdomainname.3
+++ b/lib/libc/gen/getdomainname.3
@@ -1,4 +1,4 @@
-.\"	$OpenBSD: getdomainname.3,v 1.5 1998/05/13 08:50:54 deraadt Exp $
+.\"	$OpenBSD: getdomainname.3,v 1.6 1998/07/07 07:12:52 deraadt Exp $
 .\"
 .\" Copyright (c) 1983, 1991, 1993
 .\"	The Regents of the University of California.  All rights reserved.
@@ -53,8 +53,8 @@ The parameter
 .Fa namelen
 specifies the size of the 
 .Fa name
-array.  The returned name is null-terminated unless insufficient
-space is provided.
+array.  If insufficient space is provided, the returned name is truncated.
+The returned name is always null-terminated.
 .Pp
 .Fn Setdomainname
 sets the domain name of the host machine to be
@@ -92,7 +92,11 @@ Domain names are limited to
 .Dv MAXHOSTNAMELEN
 (from
 .Ao Pa sys/param.h Ac )
-characters, currently 256.
+characters, currently 256.  This includes the terminating NUL character.
+.Pp
+If the buffer passed to
+.Fn getdomainname
+is too small, other operating systems may not gaurantee termination with NUL.
 .Sh HISTORY
 The
 .Nm
diff --git a/lib/libc/gen/gethostname.3 b/lib/libc/gen/gethostname.3
index 881ba586e92..32b46fb9e1e 100644
--- a/lib/libc/gen/gethostname.3
+++ b/lib/libc/gen/gethostname.3
@@ -1,4 +1,4 @@
-.\"	$OpenBSD: gethostname.3,v 1.5 1998/05/13 08:50:56 deraadt Exp $
+.\"	$OpenBSD: gethostname.3,v 1.6 1998/07/07 07:12:53 deraadt Exp $
 .\"
 .\" Copyright (c) 1983, 1991, 1993
 .\"	The Regents of the University of California.  All rights reserved.
@@ -53,8 +53,8 @@ The parameter
 .Fa namelen
 specifies the size of the 
 .Fa name
-array.  The returned name is null-terminated unless insufficient
-space is provided.
+array.  If insufficient space is provided, the returned name is truncated.
+The returned name is always null-terminated.
 .Pp
 .Fn Sethostname
 sets the name of the host machine to be
@@ -90,9 +90,20 @@ Host names are limited to
 .Dv MAXHOSTNAMELEN
 (from
 .Ao Pa sys/param.h Ac )
-characters, currently 256.
+characters, currently 256.  This includes the terminating NUL character.
+.Pp
+If the buffer passed to
+.Fn getdomainname
+is smaller than
+.Dv MAXHOSTNAMELEN ,
+other operating systems may not gaurantee termination with NUL.
 .Sh HISTORY
 The
 .Nm
 function call appeared in
 .Bx 4.2 .
+.Sh STANDARDS
+The
+.Nm
+function call conforms to
+.St -xpg4.2 .
diff --git a/sys/kern/kern_sysctl.c b/sys/kern/kern_sysctl.c
index c0d0316cfa7..bf8ec43273d 100644
--- a/sys/kern/kern_sysctl.c
+++ b/sys/kern/kern_sysctl.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: kern_sysctl.c,v 1.25 1998/06/02 06:10:28 deraadt Exp $	*/
+/*	$OpenBSD: kern_sysctl.c,v 1.26 1998/07/07 07:12:40 deraadt Exp $	*/
 /*	$NetBSD: kern_sysctl.c,v 1.17 1996/05/20 17:49:05 mrg Exp $	*/
 
 /*-
@@ -246,13 +246,13 @@ kern_sysctl(name, namelen, oldp, oldlenp, newp, newlen, p)
 		securelevel = level;
 		return (0);
 	case KERN_HOSTNAME:
-		error = sysctl_string(oldp, oldlenp, newp, newlen,
+		error = sysctl_tstring(oldp, oldlenp, newp, newlen,
 		    hostname, sizeof(hostname));
 		if (newp && !error)
 			hostnamelen = newlen;
 		return (error);
 	case KERN_DOMAINNAME:
-		error = sysctl_string(oldp, oldlenp, newp, newlen,
+		error = sysctl_tstring(oldp, oldlenp, newp, newlen,
 		    domainname, sizeof(domainname));
 		if (newp && !error)
 			domainnamelen = newlen;
@@ -479,16 +479,52 @@ sysctl_string(oldp, oldlenp, newp, newlen, str, maxlen)
 	char *str;
 	int maxlen;
 {
+	return sysctl__string(oldp, oldlenp, newp, newlen, str, maxlen, 0);
+}
+
+int
+sysctl_tstring(oldp, oldlenp, newp, newlen, str, maxlen)
+	void *oldp;
+	size_t *oldlenp;
+	void *newp;
+	size_t newlen;
+	char *str;
+	int maxlen;
+{
+	return sysctl__string(oldp, oldlenp, newp, newlen, str, maxlen, 1);
+}
+
+int
+sysctl__string(oldp, oldlenp, newp, newlen, str, maxlen, trunc)
+	void *oldp;
+	size_t *oldlenp;
+	void *newp;
+	size_t newlen;
+	char *str;
+	int maxlen;
+	int trunc;
+{
 	int len, error = 0;
+	char c;
 
 	len = strlen(str) + 1;
-	if (oldp && *oldlenp < len)
-		return (ENOMEM);
+	if (oldp && *oldlenp < len) {
+		if (trunc == 0 || *oldlenp == 0)
+			return (ENOMEM);
+	}
 	if (newp && newlen >= maxlen)
 		return (EINVAL);
 	if (oldp) {
-		*oldlenp = len;
-		error = copyout(str, oldp, len);
+		if (trunc && *oldlenp < len) {
+			/* XXX save & zap NUL terminator while copying */
+			c = str[*oldlenp-1];
+			str[*oldlenp-1] = '\0';
+			error = copyout(str, oldp, *oldlenp);
+			str[*oldlenp-1] = c;
+		} else {
+			*oldlenp = len;
+			error = copyout(str, oldp, len);
+		}
 	}
 	if (error == 0 && newp) {
 		error = copyin(newp, str, newlen);
diff --git a/sys/sys/sysctl.h b/sys/sys/sysctl.h
index 4b47e752a8c..59e51573884 100644
--- a/sys/sys/sysctl.h
+++ b/sys/sys/sysctl.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: sysctl.h,v 1.25 1998/06/02 06:10:30 deraadt Exp $	*/
+/*	$OpenBSD: sysctl.h,v 1.26 1998/07/07 07:12:51 deraadt Exp $	*/
 /*	$NetBSD: sysctl.h,v 1.16 1996/04/09 20:55:36 cgd Exp $	*/
 
 /*
@@ -383,6 +383,8 @@ typedef int (sysctlfn)
 int sysctl_int __P((void *, size_t *, void *, size_t, int *));
 int sysctl_rdint __P((void *, size_t *, void *, int));
 int sysctl_string __P((void *, size_t *, void *, size_t, char *, int));
+int sysctl_tstring __P((void *, size_t *, void *, size_t, char *, int));
+int sysctl__string __P((void *, size_t *, void *, size_t, char *, int, int));
 int sysctl_rdstring __P((void *, size_t *, void *, char *));
 int sysctl_rdstruct __P((void *, size_t *, void *, void *, int));
 int sysctl_struct __P((void *, size_t *, void *, size_t, void *, int));