Add -l option to gssd to force legacy behaviour

Implement a new option -l to force gssd to ignore its kernel's crypto
capabilities and use just the Single DES legacy encryption types to be
compatible with old servers. This is only relevant if those servers have
strong keys in their keytab.

Signed-off-by: Steve Dickson <steved@redhat.com>
Tested-by: Michael Weiser <weiser@science-computing.de>

diff --git a/utils/gssd/gssd.c b/utils/gssd/gssd.c
index d53795e30fc472465d4fe1187e4ae443e7bf82ec..782525566acc56ec46eeda628072b39d72de5655 100644 (file)
--- a/utils/gssd/gssd.c
+++ b/utils/gssd/gssd.c
@@ -85,7 +85,7 @@ sig_hup(int signal)
 static void
 usage(char *progname)
 {
-       fprintf(stderr, "usage: %s [-f] [-M] [-n] [-v] [-r] [-p pipefsdir] [-k keytab] [-d ccachedir] [-t timeout] [-R preferred realm]\n",
+       fprintf(stderr, "usage: %s [-f] [-l] [-M] [-n] [-v] [-r] [-p pipefsdir] [-k keytab] [-d ccachedir] [-t timeout] [-R preferred realm]\n",
                progname);
        exit(1);
 }
@@ -102,7 +102,7 @@ main(int argc, char *argv[])
        char *progname;
 
        memset(ccachesearch, 0, sizeof(ccachesearch));
-       while ((opt = getopt(argc, argv, "fvrmnMp:k:d:t:R:")) != -1) {
+       while ((opt = getopt(argc, argv, "fvrlmnMp:k:d:t:R")) != -1) {
                switch (opt) {
                        case 'f':
                                fg = 1;
@@ -143,6 +143,13 @@ main(int argc, char *argv[])
                        case 'R':
                                preferred_realm = strdup(optarg);
                                break;
+                       case 'l':
+#ifdef HAVE_SET_ALLOWABLE_ENCTYPES
+                               limit_to_legacy_enctypes = 1;
+#else 
+                               errx(1, "Setting encryption type not support by Kerberos libraries.");
+#endif
+                               break;
                        default:
                                usage(argv[0]);
                                break;

diff --git a/utils/gssd/gssd.man b/utils/gssd/gssd.man
index 073379d37597103e7d416307e90061d5a043c5c8..d8138faf0e3f8ac4ce1f15c37c886bf2238bb060 100644 (file)
--- a/utils/gssd/gssd.man
+++ b/utils/gssd/gssd.man
@@ -6,7 +6,7 @@
 .SH NAME
 rpc.gssd \- rpcsec_gss daemon
 .SH SYNOPSIS
-.B "rpc.gssd [-f] [-n] [-k keytab] [-p pipefsdir] [-v] [-r] [-d ccachedir]"
+.B "rpc.gssd [-f] [-n] [-k keytab] [-l] [-p pipefsdir] [-v] [-r] [-d ccachedir]"
 .SH DESCRIPTION
 The rpcsec_gss protocol gives a means of using the gss-api generic security
 api to provide security for protocols using rpc (in particular, nfs).  Before
@@ -70,6 +70,30 @@ for "machine credentials" is now:
 If this search order does not use the correct key then provide a
 keytab file that contains only correct keys.
 .TP
+.B -l
+Tells
+.B rpc.gssd
+to limit session keys to Single DES even if the kernel supports stronger
+encryption types. Service ticket encryption is still governed by what
+the KDC believes the target server supports. This way the client can
+access a server that has strong keys in its keytab for ticket decryption
+but whose kernel only supports Single DES.
+.IP
+The alternative is to put only Single DES keys in the server's keytab
+and limit encryption types for its principal to Single DES on the KDC
+which will cause service tickets for this server to be encrypted using
+only Single DES and (as a side-effect) contain only Single DES session
+keys.
+.IP
+This legacy behaviour is only required for older servers
+(pre nfs-utils-1.2.4). If the server has a recent kernel, Kerberos
+implementation and nfs-utils it will work just fine with stronger
+encryption.
+.IP
+.B Note:
+This option is only available with Kerberos libraries that 
+support setable encryption types.
+.TP
 .B -p path
 Tells
 .B rpc.gssd

diff --git a/utils/gssd/krb5_util.c b/utils/gssd/krb5_util.c
index 4b13fa1f5c2ac2e1fd64d2036fe0c6c6ad1a0e63..887d118f3b19277196dcf75b5c532cb3c3376e92 100644 (file)
--- a/utils/gssd/krb5_util.c
+++ b/utils/gssd/krb5_util.c
@@ -129,6 +129,10 @@
 /* Global list of principals/cache file names for machine credentials */
 struct gssd_k5_kt_princ *gssd_k5_kt_princ_list = NULL;
 
+#ifdef HAVE_SET_ALLOWABLE_ENCTYPES
+int limit_to_legacy_enctypes = 0;
+#endif
+
 /*==========================*/
 /*===  Internal routines ===*/
 /*==========================*/
@@ -1342,7 +1346,7 @@ limit_krb5_enctypes(struct rpc_gss_sec *sec)
         * If we failed for any reason to produce global
         * list of supported enctypes, use local default here.
         */
-       if (krb5_enctypes == NULL)
+       if (krb5_enctypes == NULL || limit_to_legacy_enctypes)
                maj_stat = gss_set_allowable_enctypes(&min_stat, credh,
                                        &krb5oid, num_enctypes, enctypes);
        else

diff --git a/utils/gssd/krb5_util.h b/utils/gssd/krb5_util.h
index b42b91edf932b0e616e06ed3167f2dd22da81ffe..cd6e107326923449375f0a93e81b0a5cf8d0a342 100644 (file)
--- a/utils/gssd/krb5_util.h
+++ b/utils/gssd/krb5_util.h
@@ -36,6 +36,7 @@ char *gssd_k5_err_msg(krb5_context context, krb5_error_code code);
 void gssd_k5_get_default_realm(char **def_realm);
 
 #ifdef HAVE_SET_ALLOWABLE_ENCTYPES
+extern int limit_to_legacy_enctypes;
 int limit_krb5_enctypes(struct rpc_gss_sec *sec);
 #endif