]> git.decadent.org.uk Git - nfs-utils.git/blobdiff - utils/gssd/krb5_util.c
Clean up gssd_get_single_krb5_cred and its debugging messages
[nfs-utils.git] / utils / gssd / krb5_util.c
index d29b8397445bb85fb2a4f6038645fd4e83a29cc2..5d433b121ee26b96f2319fec04eda6eca638dc18 100644 (file)
 
 #include <stdio.h>
 #include <stdlib.h>
+#include <unistd.h>
 #include <string.h>
 #include <dirent.h>
+#include <netdb.h>
+#include <ctype.h>
 #include <errno.h>
 #include <time.h>
 #include <gssapi/gssapi.h>
@@ -131,10 +134,11 @@ static int select_krb5_ccache(const struct dirent *d);
 static int gssd_find_existing_krb5_ccache(uid_t uid, struct dirent **d);
 static int gssd_get_single_krb5_cred(krb5_context context,
                krb5_keytab kt, struct gssd_k5_kt_princ *ple);
-static int gssd_have_realm_ple(krb5_data *realm);
+static int gssd_have_realm_ple(void *realm);
 static int gssd_process_krb5_keytab(krb5_context context, krb5_keytab kt,
                char *kt_name);
 
+
 /*
  * Called from the scandir function to weed out potential krb5
  * credentials cache files
@@ -158,7 +162,7 @@ select_krb5_ccache(const struct dirent *d)
 }
 
 /*
- * Look in the GSSD_DEFAULT_CRED_DIR for files that look like they
+ * Look in the ccachedir for files that look like they
  * are Kerberos Credential Cache files for a given UID.  Return
  * non-zero and the dirent pointer for the entry most likely to be
  * what we want. Otherwise, return zero and no dirent pointer.
@@ -178,78 +182,73 @@ gssd_find_existing_krb5_ccache(uid_t uid, struct dirent **d)
        struct dirent *best_match_dir = NULL;
        struct stat best_match_stat, tmp_stat;
 
+       memset(&best_match_stat, 0, sizeof(best_match_stat));
        *d = NULL;
-       n = scandir(GSSD_DEFAULT_CRED_DIR, &namelist, select_krb5_ccache, 0);
+       n = scandir(ccachedir, &namelist, select_krb5_ccache, 0);
        if (n < 0) {
                perror("scandir looking for krb5 credentials caches");
        }
        else if (n > 0) {
-               char substring[128];
-               char fullstring[128];
                char statname[1024];
-               snprintf(substring, sizeof(substring), "_%d_", uid);
-               snprintf(fullstring, sizeof(fullstring), "_%d", uid);
                for (i = 0; i < n; i++) {
                        printerr(3, "CC file '%s' being considered\n",
                                 namelist[i]->d_name);
-                       if (strstr(namelist[i]->d_name, substring) ||
-                           !strcmp(namelist[i]->d_name, fullstring)) {
-                               snprintf(statname, sizeof(statname),
-                                        "%s/%s", GSSD_DEFAULT_CRED_DIR,
-                                        namelist[i]->d_name);
-                               if (stat(statname, &tmp_stat)) {
-                                       printerr(0, "Error doing stat "
-                                                   "on file '%s'\n",
-                                                statname);
-                                       continue;
-                               }
-                               if (!S_ISREG(tmp_stat.st_mode)) {
-                                       printerr(3, "File '%s' is not "
-                                                   "a regular file\n",
-                                                statname);
-                                       continue;
-                               }
-                               printerr(3, "CC file '%s' matches "
-                                           "name check and has "
-                                           "mtime of %u\n",
-                                        namelist[i]->d_name,
-                                        tmp_stat.st_mtime);
-                               /* if more than one match is found,
-                                * return the most recent (the one
-                                * with the latest mtime),
-                                * and don't free the dirent */
-                               if (!found) {
+                       snprintf(statname, sizeof(statname),
+                                "%s/%s", ccachedir, namelist[i]->d_name);
+                       if (lstat(statname, &tmp_stat)) {
+                               printerr(0, "Error doing stat on file '%s'\n",
+                                        statname);
+                               free(namelist[i]);
+                               continue;
+                       }
+                       /* Only pick caches owned by the user (uid) */
+                       if (tmp_stat.st_uid != uid) {
+                               printerr(3, "'%s' owned by %u, not %u\n",
+                                        statname, tmp_stat.st_uid, uid);
+                               free(namelist[i]);
+                               continue;
+                       }
+                       if (!S_ISREG(tmp_stat.st_mode)) {
+                               printerr(3, "'%s' is not a regular file\n",
+                                        statname);
+                               free(namelist[i]);
+                               continue;
+                       }
+                       printerr(3, "CC file '%s' matches owner check and has "
+                                "mtime of %u\n",
+                                namelist[i]->d_name, tmp_stat.st_mtime);
+                       /*
+                        * if more than one match is found, return the most
+                        * recent (the one with the latest mtime), and
+                        * don't free the dirent
+                        */
+                       if (!found) {
+                               best_match_dir = namelist[i];
+                               best_match_stat = tmp_stat;
+                               found++;
+                       }
+                       else {
+                               /*
+                                * If the current match has an mtime later
+                                * than the one we are looking at, then use
+                                * the current match.  Otherwise, we still
+                                * have the best match.
+                                */
+                               if (tmp_stat.st_mtime >
+                                           best_match_stat.st_mtime) {
+                                       free(best_match_dir);
                                        best_match_dir = namelist[i];
                                        best_match_stat = tmp_stat;
-                                       found++;
                                }
                                else {
-                                       /*
-                                        * If the current match has
-                                        * an mtime later than the
-                                        * one we are looking at,
-                                        * then use the current match.
-                                        * Otherwise, we still have
-                                        * the best match.
-                                        */
-                                       if (tmp_stat.st_mtime >
-                                                   best_match_stat.st_mtime) {
-                                               free(best_match_dir);
-                                               best_match_dir = namelist[i];
-                                               best_match_stat = tmp_stat;
-                                       }
-                                       else {
-                                               free(namelist[i]);
-                                       }
-                                       printerr(3, "CC file '%s' is our "
-                                                   "current best match "
-                                                   "with mtime of %u\n",
-                                                best_match_dir->d_name,
-                                                best_match_stat.st_mtime);
+                                       free(namelist[i]);
                                }
+                               printerr(3, "CC file '%s' is our "
+                                           "current best match "
+                                           "with mtime of %u\n",
+                                        best_match_dir->d_name,
+                                        best_match_stat.st_mtime);
                        }
-                       else
-                               free(namelist[i]);
                }
                free(namelist);
        }
@@ -280,26 +279,30 @@ limit_krb5_enctypes(struct rpc_gss_sec *sec, uid_t uid)
 {
        u_int maj_stat, min_stat;
        gss_cred_id_t credh;
+       gss_OID_set_desc  desired_mechs;
        krb5_enctype enctypes[] = { ENCTYPE_DES_CBC_CRC };
        int num_enctypes = sizeof(enctypes) / sizeof(enctypes[0]);
 
+       /* We only care about getting a krb5 cred */
+       desired_mechs.count = 1;
+       desired_mechs.elements = &krb5oid;
+
        maj_stat = gss_acquire_cred(&min_stat, NULL, 0,
-                                   GSS_C_NULL_OID_SET, GSS_C_INITIATE,
+                                   &desired_mechs, GSS_C_INITIATE,
                                    &credh, NULL, NULL);
 
        if (maj_stat != GSS_S_COMPLETE) {
-               printerr(0, "WARNING: error from gss_acquire_cred "
-                       "for user with uid %d (%s)\n",
-                       uid, error_message(min_stat));
+               pgsserr("gss_acquire_cred",
+                       maj_stat, min_stat, &krb5oid);
                return -1;
        }
 
        maj_stat = gss_set_allowable_enctypes(&min_stat, credh, &krb5oid,
                                             num_enctypes, &enctypes);
        if (maj_stat != GSS_S_COMPLETE) {
-               printerr(0, "WARNING: error from gss_set_allowable_enctypes "
-                       "for user with uid %d (%s)\n",
-                       uid, error_message(min_stat));
+               pgsserr("gss_set_allowable_enctypes",
+                       maj_stat, min_stat, &krb5oid);
+               gss_release_cred(&min_stat, &credh);
                return -1;
        }
        sec->cred = credh;
@@ -330,6 +333,8 @@ gssd_get_single_krb5_cred(krb5_context context,
        char cc_name[BUFSIZ];
        int code;
        time_t now = time(0);
+       char *cache_type;
+       char *pname = NULL;
 
        memset(&my_creds, 0, sizeof(my_creds));
 
@@ -346,6 +351,9 @@ gssd_get_single_krb5_cred(krb5_context context,
                goto out;
        }
 
+       if ((krb5_unparse_name(context, ple->princ, &pname)))
+               pname = NULL;
+
        krb5_get_init_creds_opt_init(&options);
        krb5_get_init_creds_opt_set_address_list(&options, NULL);
 
@@ -354,17 +362,12 @@ gssd_get_single_krb5_cred(krb5_context context,
        printerr(0, "WARNING: Using (debug) short machine cred lifetime!\n");
        krb5_get_init_creds_opt_set_tkt_life(&options, 5*60);
 #endif
-        if ((code = krb5_get_init_creds_keytab(context, &my_creds, ple->princ,
-                                         kt, 0, 0, &options))) {
-               char *pname;
-               if ((krb5_unparse_name(context, ple->princ, &pname))) {
-                       pname = NULL;
-               }
+       if ((code = krb5_get_init_creds_keytab(context, &my_creds, ple->princ,
+                                              kt, 0, NULL, &options))) {
                printerr(0, "WARNING: %s while getting initial ticket for "
-                           "principal '%s' from keytab '%s'\n",
+                        "principal '%s' using keytab '%s'\n",
                         error_message(code),
                         pname ? pname : "<unparsable>", kt_name);
-               if (pname) krb5_free_unparsed_name(context, pname);
                goto out;
        }
 
@@ -372,14 +375,21 @@ gssd_get_single_krb5_cred(krb5_context context,
         * Initialize cache file which we're going to be using
         */
 
-       snprintf(cc_name, sizeof(cc_name), "FILE:%s/%s%s_%s",
+       if (use_memcache)
+           cache_type = "MEMORY";
+       else
+           cache_type = "FILE";
+       snprintf(cc_name, sizeof(cc_name), "%s:%s/%s%s_%s",
+               cache_type,
                GSSD_DEFAULT_CRED_DIR, GSSD_DEFAULT_CRED_PREFIX,
                GSSD_DEFAULT_MACHINE_CRED_SUFFIX, ple->realm);
        ple->endtime = my_creds.times.endtime;
+       if (ple->ccname != NULL)
+               free(ple->ccname);
        ple->ccname = strdup(cc_name);
        if (ple->ccname == NULL) {
                printerr(0, "ERROR: no storage to duplicate credentials "
-                           "cache name\n");
+                           "cache name '%s'\n", cc_name);
                code = ENOMEM;
                goto out;
        }
@@ -400,8 +410,11 @@ gssd_get_single_krb5_cred(krb5_context context,
        }
 
        code = 0;
-       printerr(1, "Using (machine) credentials cache: '%s'\n", cc_name);
+       printerr(2, "Successfully obtained machine credentials for "
+                "principal '%s' stored in ccache '%s'\n", pname, cc_name);
   out:
+       if (pname)
+               k5_free_unparsed_name(context, pname);
        if (ccache)
                krb5_cc_close(context, ccache);
        krb5_free_cred_contents(context, &my_creds);
@@ -416,13 +429,22 @@ gssd_get_single_krb5_cred(krb5_context context,
  *     1 => found ple for given realm
  */
 static int
-gssd_have_realm_ple(krb5_data *realm)
+gssd_have_realm_ple(void *r)
 {
        struct gssd_k5_kt_princ *ple;
+#ifdef HAVE_KRB5
+       krb5_data *realm = (krb5_data *)r;
+#else
+       char *realm = (char *)r;
+#endif
 
        for (ple = gssd_k5_kt_princ_list; ple; ple = ple->next) {
+#ifdef HAVE_KRB5
                if ((realm->length == strlen(ple->realm)) &&
                    (strncmp(realm->data, ple->realm, realm->length) == 0)) {
+#else
+               if (strcmp(realm, ple->realm) == 0) {
+#endif
                    return 1;
                }
        }
@@ -431,7 +453,7 @@ gssd_have_realm_ple(krb5_data *realm)
 
 /*
  * Process the given keytab file and create a list of principals we
- * might use to perform mount operations.
+ * might use as machine credentials.
  *
  * Returns:
  *     0 => Sucess
@@ -448,9 +470,8 @@ gssd_process_krb5_keytab(krb5_context context, krb5_keytab kt, char *kt_name)
 
        /*
         * Look through each entry in the keytab file and determine
-        * if we might want to use it later to do a mount.  If so,
-        * save info in the global principal list
-        * (gssd_k5_kt_princ_list).
+        * if we might want to use it as machine credentials.  If so,
+        * save info in the global principal list (gssd_k5_kt_princ_list).
         * Note: (ple == principal list entry)
         */
        if ((code = krb5_kt_start_seq_get(context, kt, &cursor))) {
@@ -468,20 +489,20 @@ gssd_process_krb5_keytab(krb5_context context, krb5_keytab kt, char *kt_name)
                        printerr(0, "WARNING: Skipping keytab entry because "
                                    "we failed to unparse principal name: %s\n",
                                 error_message(code));
+                       krb5_kt_free_entry(context, &kte);
                        continue;
                }
                printerr(2, "Processing keytab entry for principal '%s'\n",
                         pname);
-               if ( (kte.principal->data[0].length == GSSD_SERVICE_NAME_LEN) &&
-                    (strncmp(kte.principal->data[0].data, GSSD_SERVICE_NAME,
-                             GSSD_SERVICE_NAME_LEN) == 0) &&
-                    (!gssd_have_realm_ple(&kte.principal->realm)) ) {
-                       printerr(2, "We will use this entry (%s)\n", pname);
+               /* Just use the first keytab entry found for each realm */
+               if ((!gssd_have_realm_ple((void *)&kte.principal->realm)) ) {
+                       printerr(2, "We WILL use this entry (%s)\n", pname);
                        ple = malloc(sizeof(struct gssd_k5_kt_princ));
                        if (ple == NULL) {
                                printerr(0, "ERROR: could not allocate storage "
                                            "for principal list entry\n");
-                               krb5_free_unparsed_name(context, pname);
+                               k5_free_unparsed_name(context, pname);
+                               krb5_kt_free_entry(context, &kte);
                                retval = ENOMEM;
                                goto out;
                        }
@@ -490,13 +511,18 @@ gssd_process_krb5_keytab(krb5_context context, krb5_keytab kt, char *kt_name)
                        ple->ccname = NULL;
                        ple->endtime = 0;
                        if ((ple->realm =
+#ifdef HAVE_KRB5
                                strndup(kte.principal->realm.data,
                                        kte.principal->realm.length))
+#else
+                               strdup(kte.principal->realm))
+#endif
                                        == NULL) {
                                printerr(0, "ERROR: %s while copying realm to "
                                            "principal list entry\n",
                                         "not enough memory");
-                               krb5_free_unparsed_name(context, pname);
+                               k5_free_unparsed_name(context, pname);
+                               krb5_kt_free_entry(context, &kte);
                                retval = ENOMEM;
                                goto out;
                        }
@@ -505,7 +531,8 @@ gssd_process_krb5_keytab(krb5_context context, krb5_keytab kt, char *kt_name)
                                printerr(0, "ERROR: %s while copying principal "
                                            "to principal list entry\n",
                                        error_message(code));
-                               krb5_free_unparsed_name(context, pname);
+                               k5_free_unparsed_name(context, pname);
+                               krb5_kt_free_entry(context, &kte);
                                retval = code;
                                goto out;
                        }
@@ -520,7 +547,8 @@ gssd_process_krb5_keytab(krb5_context context, krb5_keytab kt, char *kt_name)
                        printerr(2, "We will NOT use this entry (%s)\n",
                                pname);
                }
-               krb5_free_unparsed_name(context, pname);
+               k5_free_unparsed_name(context, pname);
+               krb5_kt_free_entry(context, &kte);
        }
 
        if ((code = krb5_kt_end_seq_get(context, kt, &cursor))) {
@@ -565,6 +593,403 @@ gssd_set_krb5_ccache_name(char *ccname)
 #endif
 }
 
+/*
+ * Given a principal, find a matching ple structure
+ */
+static struct gssd_k5_kt_princ *
+find_ple_by_princ(krb5_context context, krb5_principal princ)
+{
+       struct gssd_k5_kt_princ *ple;
+
+       for (ple = gssd_k5_kt_princ_list; ple != NULL; ple = ple->next) {
+               if (krb5_principal_compare(context, ple->princ, princ))
+                       return ple;
+       }
+       /* no match found */
+       return NULL;
+}
+
+/*
+ * Create, initialize, and add a new ple structure to the global list
+ */
+static struct gssd_k5_kt_princ *
+new_ple(krb5_context context, krb5_principal princ)
+{
+       struct gssd_k5_kt_princ *ple = NULL, *p;
+       krb5_error_code code;
+       char *default_realm;
+       int is_default_realm = 0;
+
+       ple = malloc(sizeof(struct gssd_k5_kt_princ));
+       if (ple == NULL)
+               goto outerr;
+       memset(ple, 0, sizeof(*ple));
+
+#ifdef HAVE_KRB5
+       ple->realm = strndup(princ->realm.data,
+                            princ->realm.length);
+#else
+       ple->realm = strdup(princ->realm);
+#endif
+       if (ple->realm == NULL)
+               goto outerr;
+       code = krb5_copy_principal(context, princ, &ple->princ);
+       if (code)
+               goto outerr;
+
+       /*
+        * Add new entry onto the list (if this is the default
+        * realm, always add to the front of the list)
+        */
+
+       code = krb5_get_default_realm(context, &default_realm);
+       if (code == 0) {
+               if (strcmp(ple->realm, default_realm) == 0)
+                       is_default_realm = 1;
+               k5_free_default_realm(context, default_realm);
+       }
+
+       if (is_default_realm) {
+               ple->next = gssd_k5_kt_princ_list;
+               gssd_k5_kt_princ_list = ple;
+       } else {
+               p = gssd_k5_kt_princ_list;
+               while (p != NULL && p->next != NULL)
+                       p = p->next;
+               if (p == NULL)
+                       gssd_k5_kt_princ_list = ple;
+               else
+                       p->next = ple;
+       }
+
+       return ple;
+outerr:
+       if (ple) {
+               if (ple->realm)
+                       free(ple->realm);
+               free(ple);
+       }
+       return NULL;
+}
+
+/*
+ * Given a principal, find an existing ple structure, or create one
+ */
+static struct gssd_k5_kt_princ *
+get_ple_by_princ(krb5_context context, krb5_principal princ)
+{
+       struct gssd_k5_kt_princ *ple;
+
+       /* Need to serialize list if we ever become multi-threaded! */
+
+       ple = find_ple_by_princ(context, princ);
+       if (ple == NULL) {
+               ple = new_ple(context, princ);
+       }
+
+       return ple;
+}
+
+/*
+ * Given a (possibly unqualified) hostname,
+ * return the fully qualified (lower-case!) hostname
+ */
+static int
+get_full_hostname(const char *inhost, char *outhost, int outhostlen)
+{
+       struct addrinfo *addrs = NULL;
+       struct addrinfo hints;
+       int retval;
+       char *c;
+
+       memset(&hints, 0, sizeof(hints));
+       hints.ai_socktype = SOCK_STREAM;
+       hints.ai_family = PF_UNSPEC;
+       hints.ai_flags = AI_CANONNAME;
+
+       /* Get full target hostname */
+       retval = getaddrinfo(inhost, NULL, &hints, &addrs);
+       if (retval) {
+               printerr(0, "%s while getting full hostname for '%s'\n",
+                        gai_strerror(retval), inhost);
+               goto out;
+       }
+       strncpy(outhost, addrs->ai_canonname, outhostlen);
+       freeaddrinfo(addrs);
+       for (c = outhost; *c != '\0'; c++)
+           *c = tolower(*c);
+
+       printerr(3, "Full hostname for '%s' is '%s'\n", inhost, outhost);
+       retval = 0;
+out:
+       return retval;
+}
+
+/* 
+ * If principal matches the given realm and service name,
+ * and has *any* instance (hostname), return 1.
+ * Otherwise return 0, indicating no match.
+ */
+static int
+realm_and_service_match(krb5_context context, krb5_principal p,
+                       const char *realm, const char *service)
+{
+#ifdef HAVE_KRB5
+       /* Must have two components */
+       if (p->length != 2)
+               return 0;
+       if ((strlen(realm) == p->realm.length)
+           && (strncmp(realm, p->realm.data, p->realm.length) == 0)
+           && (strlen(service) == p->data[0].length)
+           && (strncmp(service, p->data[0].data, p->data[0].length) == 0))
+               return 1;
+#else
+       const char *name, *inst;
+
+       if (p->name.name_string.len != 2)
+               return 0;
+       name = krb5_principal_get_comp_string(context, p, 0);
+       inst = krb5_principal_get_comp_string(context, p, 1);
+       if (name == NULL || inst == NULL)
+               return 0;
+       if ((strcmp(realm, p->realm) == 0)
+           && (strcmp(service, name) == 0))
+               return 1;
+#endif
+       return 0;
+}
+
+/*
+ * Search the given keytab file looking for an entry with the given
+ * service name and realm, ignoring hostname (instance).
+ *
+ * Returns:
+ *     0 => No error
+ *     non-zero => An error occurred
+ *
+ * If a keytab entry is found, "found" is set to one, and the keytab
+ * entry is returned in "kte".  Otherwise, "found" is zero, and the
+ * value of "kte" is unpredictable.
+ */
+static int
+gssd_search_krb5_keytab(krb5_context context, krb5_keytab kt,
+                       const char *realm, const char *service,
+                       int *found, krb5_keytab_entry *kte)
+{
+       krb5_kt_cursor cursor;
+       krb5_error_code code;
+       struct gssd_k5_kt_princ *ple;
+       int retval = -1;
+       char kt_name[BUFSIZ];
+       char *pname;
+
+       if (found == NULL) {
+               retval = EINVAL;
+               goto out;
+       }
+       *found = 0;
+
+       /*
+        * Look through each entry in the keytab file and determine
+        * if we might want to use it as machine credentials.  If so,
+        * save info in the global principal list (gssd_k5_kt_princ_list).
+        */
+       if ((code = krb5_kt_get_name(context, kt, kt_name, BUFSIZ))) {
+               printerr(0, "ERROR: %s attempting to get keytab name\n",
+                        error_message(code));
+               retval = code;
+               goto out;
+       }
+       if ((code = krb5_kt_start_seq_get(context, kt, &cursor))) {
+               printerr(0, "ERROR: %s while beginning keytab scan "
+                           "for keytab '%s'\n",
+                       error_message(code), kt_name);
+               retval = code;
+               goto out;
+       }
+
+       while ((code = krb5_kt_next_entry(context, kt, kte, &cursor)) == 0) {
+               if ((code = krb5_unparse_name(context, kte->principal,
+                                             &pname))) {
+                       printerr(0, "WARNING: Skipping keytab entry because "
+                                "we failed to unparse principal name: %s\n",
+                                error_message(code));
+                       k5_free_kt_entry(context, kte);
+                       continue;
+               }
+               printerr(4, "Processing keytab entry for principal '%s'\n",
+                        pname);
+               /* Use the first matching keytab entry found */
+               if ((realm_and_service_match(context, kte->principal, realm,
+                                            service))) {
+                       printerr(4, "We WILL use this entry (%s)\n", pname);
+                       ple = get_ple_by_princ(context, kte->principal);
+                       /*
+                        * Return, don't free, keytab entry if
+                        * we were successful!
+                        */
+                       if (ple == NULL) {
+                               retval = ENOMEM;
+                               k5_free_kt_entry(context, kte);
+                       } else {
+                               retval = 0;
+                               *found = 1;
+                       }
+                       k5_free_unparsed_name(context, pname);
+                       break;
+               }
+               else {
+                       printerr(4, "We will NOT use this entry (%s)\n",
+                               pname);
+               }
+               k5_free_unparsed_name(context, pname);
+               k5_free_kt_entry(context, kte);
+       }
+
+       if ((code = krb5_kt_end_seq_get(context, kt, &cursor))) {
+               printerr(0, "WARNING: %s while ending keytab scan for "
+                           "keytab '%s'\n",
+                        error_message(code), kt_name);
+       }
+
+       retval = 0;
+  out:
+       return retval;
+}
+
+/*
+ * Find a keytab entry to use for a given target hostname.
+ * Tries to find the most appropriate keytab to use given the
+ * name of the host we are trying to connect with.
+ */
+static int
+find_keytab_entry(krb5_context context, krb5_keytab kt, const char *hostname,
+                 krb5_keytab_entry *kte)
+{
+       krb5_error_code code;
+       const char *svcnames[] = { "root", "nfs", "host", NULL };
+       char **realmnames = NULL;
+       char myhostname[NI_MAXHOST], targethostname[NI_MAXHOST];
+       int i, j, retval;
+       char *default_realm = NULL;
+       char *realm;
+       int tried_all = 0, tried_default = 0;
+       krb5_principal princ;
+
+
+       /* Get full target hostname */
+       retval = get_full_hostname(hostname, targethostname,
+                                  sizeof(targethostname));
+       if (retval)
+               goto out;
+
+       /* Get full local hostname */
+       retval = gethostname(myhostname, sizeof(myhostname));
+       if (retval) {
+               printerr(1, "%s while getting local hostname\n",
+                        error_message(retval));
+               goto out;
+       }
+       retval = get_full_hostname(myhostname, myhostname, sizeof(myhostname));
+       if (retval)
+               goto out;
+
+       code = krb5_get_default_realm(context, &default_realm);
+       if (code) {
+               retval = code;
+               printerr(1, "%s while getting default realm name\n",
+                        error_message(code));
+               goto out;
+       }
+
+       /*
+        * Get the realm name(s) for the target hostname.
+        * In reality, this function currently only returns a
+        * single realm, but we code with the assumption that
+        * someday it may actually return a list.
+        */
+       code = krb5_get_host_realm(context, targethostname, &realmnames);
+       if (code) {
+               printerr(0, "ERROR: %s while getting realm(s) for host '%s'\n",
+                        error_message(code), targethostname);
+               retval = code;
+               goto out;
+       }
+
+       /*
+        * Try the "appropriate" realm first, and if nothing found for that
+        * realm, try the default realm (if it hasn't already been tried).
+        */
+       i = 0;
+       realm = realmnames[i];
+       while (1) {
+               if (realm == NULL) {
+                       tried_all = 1;
+                       if (!tried_default)
+                               realm = default_realm;
+               }
+               if (tried_all && tried_default)
+                       break;
+               if (strcmp(realm, default_realm) == 0)
+                       tried_default = 1;
+               for (j = 0; svcnames[j] != NULL; j++) {
+                       code = krb5_build_principal_ext(context, &princ,
+                                                       strlen(realm),
+                                                       realm,
+                                                       strlen(svcnames[j]),
+                                                       svcnames[j],
+                                                       strlen(myhostname),
+                                                       myhostname,
+                                                       NULL);
+                       if (code) {
+                               printerr(1, "%s while building principal for "
+                                        "'%s/%s@%s'\n", error_message(code),
+                                        svcnames[j], myhostname, realm);
+                               continue;
+                       }
+                       code = krb5_kt_get_entry(context, kt, princ, 0, 0, kte);
+                       krb5_free_principal(context, princ);
+                       if (code) {
+                               printerr(3, "%s while getting keytab entry for "
+                                        "'%s/%s@%s'\n", error_message(code),
+                                        svcnames[j], myhostname, realm);
+                       } else {
+                               printerr(3, "Success getting keytab entry for "
+                                        "'%s/%s@%s'\n",
+                                        svcnames[j], myhostname, realm);
+                               retval = 0;
+                               goto out;
+                       }
+                       retval = code;
+               }
+               /*
+                * Nothing found with our hostname instance, now look for
+                * names with any instance (they must have an instance)
+                */
+               for (j = 0; svcnames[j] != NULL; j++) {
+                       int found = 0;
+                       code = gssd_search_krb5_keytab(context, kt, realm,
+                                                      svcnames[j], &found, kte);
+                       if (!code && found) {
+                               printerr(3, "Success getting keytab entry for "
+                                        "%s/*@%s\n", svcnames[j], realm);
+                               retval = 0;
+                               goto out;
+                       }
+               }
+               if (!tried_all) {
+                       i++;
+                       realm = realmnames[i];
+               }
+       }
+out:
+       if (default_realm)
+               k5_free_default_realm(context, default_realm);
+       if (realmnames)
+               krb5_free_host_realm(context, realmnames);
+       return retval;
+}
+
 /*==========================*/
 /*===  External routines ===*/
 /*==========================*/
@@ -588,13 +1013,12 @@ gssd_setup_krb5_user_gss_ccache(uid_t uid, char *servername)
        memset(buf, 0, sizeof(buf));
        if (gssd_find_existing_krb5_ccache(uid, &d)) {
                snprintf(buf, sizeof(buf), "FILE:%s/%s",
-                       GSSD_DEFAULT_CRED_DIR, d->d_name);
+                       ccachedir, d->d_name);
                free(d);
        }
        else
                snprintf(buf, sizeof(buf), "FILE:%s/%s%u",
-                       GSSD_DEFAULT_CRED_DIR,
-                       GSSD_DEFAULT_CRED_PREFIX, uid);
+                       ccachedir, GSSD_DEFAULT_CRED_PREFIX, uid);
        printerr(2, "using %s as credentials cache for client with "
                    "uid %u for server %s\n", buf, uid, servername);
        gssd_set_krb5_ccache_name(buf);
@@ -726,18 +1150,19 @@ gssd_get_krb5_machine_cred_list(char ***list)
        retval = -1;
        *list = (char **) NULL;
 
-       /* Refresh machine credentials */
-       if ((retval = gssd_refresh_krb5_machine_creds())) {
-               goto out;
-       }
-
        if ((l = (char **) malloc(listsize * sizeof(char *))) == NULL) {
                retval = ENOMEM;
                goto out;
        }
 
+       /* Need to serialize list if we ever become multi-threaded! */
+
        for (ple = gssd_k5_kt_princ_list; ple; ple = ple->next) {
                if (ple->ccname) {
+                       /* Make sure cred is up-to-date before returning it */
+                       retval = gssd_refresh_krb5_machine_credential(NULL, ple);
+                       if (retval)
+                               continue;
                        if (i + 1 > listsize) {
                                listsize += listinc;
                                l = (char **)
@@ -817,3 +1242,68 @@ gssd_destroy_krb5_machine_creds(void)
        krb5_free_context(context);
 }
 
+/*
+ * Obtain (or refresh if necessary) Kerberos machine credentials
+ */
+int
+gssd_refresh_krb5_machine_credential(char *hostname,
+                                    struct gssd_k5_kt_princ *ple)
+{
+       krb5_error_code code = 0;
+       krb5_context context;
+       krb5_keytab kt = NULL;;
+       int retval = 0;
+
+       if (hostname == NULL && ple == NULL)
+               return EINVAL;
+
+       code = krb5_init_context(&context);
+       if (code) {
+               printerr(0, "ERROR: %s: %s while initializing krb5 context\n",
+                        __FUNCTION__, error_message(code));
+               retval = code;
+               goto out;
+       }
+
+       if ((code = krb5_kt_resolve(context, keytabfile, &kt))) {
+               printerr(0, "ERROR: %s: %s while resolving keytab '%s'\n",
+                        __FUNCTION__, error_message(code), keytabfile);
+               goto out;
+       }
+
+       if (ple == NULL) {
+               krb5_keytab_entry kte;
+
+               code = find_keytab_entry(context, kt, hostname, &kte);
+               if (code) {
+                       printerr(0, "ERROR: %s: no usable keytab entry found "
+                                "in keytab %s for connection with host %s\n",
+                                __FUNCTION__, keytabfile, hostname);
+                       retval = code;
+                       goto out;
+               }
+
+               ple = get_ple_by_princ(context, kte.principal);
+               k5_free_kt_entry(context, &kte);
+               if (ple == NULL) {
+                       char *pname;
+                       if ((krb5_unparse_name(context, kte.principal, &pname))) {
+                               pname = NULL;
+                       }
+                       printerr(0, "ERROR: %s: Could not locate or create "
+                                "ple struct for principal %s for connection "
+                                "with host %s\n",
+                                __FUNCTION__, pname ? pname : "<unparsable>",
+                                hostname);
+                       if (pname) k5_free_unparsed_name(context, pname);
+                       goto out;
+               }
+       }
+       retval = gssd_get_single_krb5_cred(context, kt, ple);
+out:
+       if (kt)
+               krb5_kt_close(context, kt);
+       krb5_free_context(context);
+       return retval;
+}
+