[PATCH 0/1] nfs-utils: Add flag and boolean to control SETENV behavior for $HOME in rpc.gssd

[PATCH 0/1] nfs-utils: Add flag and boolean to control SETENV behavior for $HOME in rpc.gssd

[Jacob Shivers]

A deadlock can occur when accessing NFS home directories when $HOME is
unmodified as Kerberos routines will attempt to access $HOME, but will be
inaccessible due to a lack of a Kerberos ticket. It would then check for the
existence of $HOME/.k5identity, but could not access the file due to not having
a TGT.

The issue was originally reported in:
https://bugzilla.redhat.com/show_bug.cgi?id=1052902

This patch allows for user control of this behavior granting users who do not
have Kerberized home directories access to their .k5identity file.

This addresses the following bugzilla:
https://bugzilla.redhat.com/show_bug.cgi?id=1868087

Jacob Shivers (1):
  gssd: Add options to rpc.gssd to allow for the use of
    $HOME/.k5identity files

 nfs.conf             |  1 +
 systemd/nfs.conf.man |  3 ++-
 utils/gssd/gssd.c    | 28 ++++++++++++++++++++--------
 utils/gssd/gssd.man  | 19 ++++++++++++++++++-
 4 files changed, 41 insertions(+), 10 deletions(-)

-- 
2.29.2

[PATCH 1/1] gssd: Add options to rpc.gssd to allow for the use of $HOME/.k5identity files

[Jacob Shivers]

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 2f682f25c642fcfe7c511d04bc9d67e732282348 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.

Signed-off-by: Jacob Shivers <jshivers@redhat.com>
---
 nfs.conf             |  1 +
 systemd/nfs.conf.man |  3 ++-
 utils/gssd/gssd.c    | 28 ++++++++++++++++++++--------
 utils/gssd/gssd.man  | 19 ++++++++++++++++++-
 4 files changed, 41 insertions(+), 10 deletions(-)

diff --git a/nfs.conf b/nfs.conf
index bebb2e3d1e68..eabe8c7c34c4 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 d2187f8aca1a..7fa35d441eca 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 85bc4b07bebd..1541d3710b24 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 26095a898293..c93cde6a66e5 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
@@ -347,6 +357,13 @@ section:
 .B pipefs-directory
 Equivalent to
 .BR -p .
+.TP
+.B set-home
+Setting to
+.B false
+is equivalent to providing the
+.B -H
+flag.
 
 .SH SEE ALSO
 .BR rpc.svcgssd (8),
-- 
2.29.2

Re: [PATCH 1/1] gssd: Add options to rpc.gssd to allow for the use of $HOME/.k5identity files

[Steve Dickson]

On 3/1/21 4:46 PM, Jacob Shivers wrote:
> 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 2f682f25c642fcfe7c511d04bc9d67e732282348 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.
> 
> Signed-off-by: Jacob Shivers <jshivers@redhat.com>
Committed... (tag: nfs-utils-2-5-4-rc1)

steved.

> ---
>  nfs.conf             |  1 +
>  systemd/nfs.conf.man |  3 ++-
>  utils/gssd/gssd.c    | 28 ++++++++++++++++++++--------
>  utils/gssd/gssd.man  | 19 ++++++++++++++++++-
>  4 files changed, 41 insertions(+), 10 deletions(-)
> 
> diff --git a/nfs.conf b/nfs.conf
> index bebb2e3d1e68..eabe8c7c34c4 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 d2187f8aca1a..7fa35d441eca 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 85bc4b07bebd..1541d3710b24 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 26095a898293..c93cde6a66e5 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
> @@ -347,6 +357,13 @@ section:
>  .B pipefs-directory
>  Equivalent to
>  .BR -p .
> +.TP
> +.B set-home
> +Setting to
> +.B false
> +is equivalent to providing the
> +.B -H
> +flag.
>  
>  .SH SEE ALSO
>  .BR rpc.svcgssd (8),
>