gssd: Add options to rpc.gssd to allow for the use of $HOME/.k5identity files

Since commit 2f682f25c642fcfe7c511d04bc9d67e732282348 $HOME
has been set to '/' to avoid a deadlock when accessing
Kerberized NFS shares. While this works for most use cases,
users who depend on the use of $HOME/.k5identity files are
negatively impacted by this commit. This patch allows for
users to use their $HOME/.k5identity to access subsequent
Kerberized resources based on the credentials in said file.

The default set by commit 2f682f25c still remains the same,
but a user can pass '-H' to change rpc.gssd behavior to not
set $HOME to '/'. Setting 'set-home=0' in /etc/nfs.conf
has the same effect as passing '-H' directly to rpc.gssd.

Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1868087

Signed-off-by: Jacob Shivers <jshivers@redhat.com>
Signed-off-by: Steve Dickson <steved@redhat.com>

4 files changed, 41 insertions, 10 deletions

diff --git a/nfs.conf b/nfs.conf
index e69ec16d..5b080015 100644
--- a/nfs.conf
+++ b/nfs.conf
@@ -24,6 +24,7 @@
 # keytab-file=/etc/krb5.keytab
 # cred-cache-directory=
 # preferred-realm=
+# set-home=1
 #
 [lockd]
 # port=0
diff --git a/systemd/nfs.conf.man b/systemd/nfs.conf.man
index d2187f8a..7fa35d44 100644
--- a/systemd/nfs.conf.man
+++ b/systemd/nfs.conf.man
@@ -253,7 +253,8 @@ Recognized values:
 .BR rpc-timeout ,
 .BR keytab-file ,
 .BR cred-cache-directory ,
-.BR preferred-realm .
+.BR preferred-realm ,
+.BR set-home .
 
 See
 .BR rpc.gssd (8)
diff --git a/utils/gssd/gssd.c b/utils/gssd/gssd.c
index 85bc4b07..1541d371 100644
--- a/utils/gssd/gssd.c
+++ b/utils/gssd/gssd.c
@@ -87,6 +87,8 @@ unsigned int  context_timeout = 0;
 unsigned int  rpc_timeout = 5;
 char *preferred_realm = NULL;
 char *ccachedir = NULL;
+/* set $HOME to "/" by default */
+static bool set_home = true;
 /* Avoid DNS reverse lookups on server names */
 static bool avoid_dns = true;
 static bool use_gssproxy = false;
@@ -900,7 +902,7 @@ sig_die(int signal)
 static void
 usage(char *progname)
 {
-	fprintf(stderr, "usage: %s [-f] [-l] [-M] [-n] [-v] [-r] [-p pipefsdir] [-k keytab] [-d ccachedir] [-t timeout] [-R preferred realm] [-D]\n",
+	fprintf(stderr, "usage: %s [-f] [-l] [-M] [-n] [-v] [-r] [-p pipefsdir] [-k keytab] [-d ccachedir] [-t timeout] [-R preferred realm] [-D] [-H]\n",
 		progname);
 	exit(1);
 }
@@ -941,6 +943,7 @@ read_gss_conf(void)
 		preferred_realm = s;
 
 	use_gssproxy = conf_get_bool("gssd", "use-gss-proxy", use_gssproxy);
+	set_home = conf_get_bool("gssd", "set-home", set_home);
 }
 
 int
@@ -961,7 +964,7 @@ main(int argc, char *argv[])
 	verbosity = conf_get_num("gssd", "verbosity", verbosity);
 	rpc_verbosity = conf_get_num("gssd", "rpc-verbosity", rpc_verbosity);
 
-	while ((opt = getopt(argc, argv, "DfvrlmnMp:k:d:t:T:R:")) != -1) {
+	while ((opt = getopt(argc, argv, "HDfvrlmnMp:k:d:t:T:R:")) != -1) {
 		switch (opt) {
 			case 'f':
 				fg = 1;
@@ -1009,6 +1012,9 @@ main(int argc, char *argv[])
 			case 'D':
 				avoid_dns = false;
 				break;
+			case 'H':
+				set_home = false;
+				break;
 			default:
 				usage(argv[0]);
 				break;
@@ -1018,13 +1024,19 @@ main(int argc, char *argv[])
 	/*
 	 * Some krb5 routines try to scrape info out of files in the user's
 	 * home directory. This can easily deadlock when that homedir is on a
-	 * kerberized NFS mount. By setting $HOME unconditionally to "/", we
-	 * prevent this behavior in routines that use $HOME in preference to
-	 * the results of getpw*.
+	 * kerberized NFS mount. By setting $HOME to "/" by default, we prevent
+	 * this behavior in routines that use $HOME in preference to the results
+	 * of getpw*.
+	 *
+	 * Some users do not use Kerberized home dirs and need $HOME to remain
+	 * unchanged. Those users can leave $HOME unchanged by setting set_home
+	 * to false.
 	 */
-	if (setenv("HOME", "/", 1)) {
-		printerr(0, "gssd: Unable to set $HOME: %s\n", strerror(errno));
-		exit(1);
+	if (set_home) {
+		if (setenv("HOME", "/", 1)) {
+			printerr(0, "gssd: Unable to set $HOME: %s\n", strerror(errno));
+			exit(1);
+		}
 	}
 
 	if (use_gssproxy) {
diff --git a/utils/gssd/gssd.man b/utils/gssd/gssd.man
index 26095a89..9ae6def9 100644
--- a/utils/gssd/gssd.man
+++ b/utils/gssd/gssd.man
@@ -8,7 +8,7 @@
 rpc.gssd \- RPCSEC_GSS daemon
 .SH SYNOPSIS
 .B rpc.gssd
-.RB [ \-DfMnlvr ]
+.RB [ \-DfMnlvrH ]
 .RB [ \-k
 .IR keytab ]
 .RB [ \-p
@@ -282,6 +282,16 @@ The default timeout is set to 5 seconds.
 If you get messages like "WARNING: can't create tcp rpc_clnt to server
 %servername% for user with uid %uid%: RPC: Remote system error -
 Connection timed out", you should consider an increase of this timeout.
+.TP
+.B -H
+Avoids setting $HOME to "/". This allows rpc.gssd to read per user k5identity
+files versus trying to read /.k5identity for each user.
+
+If
+.B \-H
+is not set, rpc.gssd will use the first match found in
+/var/kerberos/krb5/user/$EUID/client.keytab and will not use a principal based on
+host and/or service parameters listed in $HOME/.k5identity.
 .SH CONFIGURATION FILE
 Many of the options that can be set on the command line can also be
 controlled through values set in the
@@ -339,6 +349,13 @@ Equivalent to
 .B preferred-realm
 Equivalent to
 .BR -R .
+.TP
+.B set-home
+Setting to
+.B false
+is equivalent to providing the
+.B -H
+flag.
 .P
 In addtion, the following value is recognized from the
 .B [general]