Patches that include a '-H' flag and man page entry.
The default is to maintain behavior since
2f682f25c642fcfe7c511d04bc9d67e732282348, but passing '-H' avoids
$HOME being set to '/'.
Also included a patch for /etc/nfs.conf to add 'set-home=1'. Setting
it to false is equivalent to passing '-H' to rpc.gssd.
Regards,
Jacob Shivers
On Mon, Jan 4, 2021 at 11:00 AM Jacob Shivers <jshivers@xxxxxxxxxx> wrote:
>
> Hello,
>
> I completely missed this so please excuse the delay.
>
> > On 11/23/20 1:17 PM, Jacob Shivers wrote:
> > > Commit 2f682f25c642fcfe7c511d04bc9d67e732282348 changed existing
> > > behavior to avoid a deadlock for users using Kerberized NFS home dirs.
> > >
> > > However, this also prevents users leveraging their own k5identity
> > > files under their home directory and instead rpc.gssd uses a
> > > system-wide /.k5identity file. For users expecting to use their own
> > > k5identity file this is certainly unexpected.
> > So how is the deadlock not happening when ~/.k5identity is on a NFS
> > home directory? What am I missing?
> They are not using NFS for home directories. They are accessing
> systems with a local fs backing the /home
>
> > > Below is some pseudo code that was proposed and would just add a flag
> > > allowing for the behavior prior to
> > > 2f682f25c642fcfe7c511d04bc9d67e732282348:
> > >
> > > /* psudo code snippet starts here */
> > > /*
> > > * 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
> > > + * kerberized NFS mount. Some users may not have $HOME on NFS.
> > > + * By default setting $HOME unconditionally to "/", we
> > > * prevent this behavior in routines that use $HOME in preference to
> > > * the results of getpw*.
> > > + * Users who have $HOME on krb5-NFS should set
> > > `--home-not-kerberized` in argv
> > > + * Users who have $HOME on krb5-NFS but want to use their
> > > $HOME anyway should set NFS_HOME_ACCESSIBLE=TRUE
> > > */
> > > + if (argv == '--home-not-kerberized') ||
> > > (getenv("NFS_HOME_ACCESSIBLE") == 'TRUE') {
> > > + log.debug('Not masking $HOME, this breaks on Kerberized $HOME');
> > > + }
> > > + else {
> > > + log.debug('Assuming $HOME requires Kerberos, use
> > > `--home-not-kerberized` to change this behavior');
> > > if (setenv("HOME", "/", 1)) {
> > > printerr(1, "Unable to set $HOME: %s\n", strerror(errn));
> > > exit(1);
> > > }
> > > + }
> > > /* psudo code snippet ends here */
> > In general I'm pretty reluctant to add flags but what is needed
> > to do so is a company single letter flag '-H' and a man page
> > entry describing the flag.
> Ok.
>
> > >
> > > While acknowledging the use of this flag for Kerberized NFS home dirs
> > > is undesirable and would cause a deadlock, there should be no issue
> > > for users not using Kerberized NFS home dirs.
> > What apps are you using that is seeing this problem?
> It is just when accessing the Kerberized NFS share. Other Kerberos
> aware services/applications check for the existence of ~/.k5identify
> before reading /var/kerberos/krb5/user/${EUID}/client.keytab. rpc.gssd
> no longer does this and the intent of the patch would be to add
> granularity to choose the behavior or rpc.gssd with respect to
> scanning for a k5identity file.
>
> If any additional information is required, please inform me.
>
> Thanks,
>
> Jacob Shivers
diff --git a/nfs.conf b/nfs.conf
index 9fcf1bf..4c41666 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/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/systemd/nfs.conf.man b/systemd/nfs.conf.man
index 16e0ec4..ee54041 100644
--- a/systemd/nfs.conf.man
+++ b/systemd/nfs.conf.man
@@ -243,7 +243,8 @@ 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.man b/utils/gssd/gssd.man
index 26095a8..b6444ab 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),
