Validate keytab at startup

In addition to validating the keytab everytime a TGT is requested, we
also validate the keytab on back end startup to give early warning that
the keytab is not usable.

Fixes: #556

2 files changed, 19 insertions, 48 deletions

diff --git a/src/providers/ldap/ldap_child.c b/src/providers/ldap/ldap_child.c
index 17c26855..f51040a7 100644
--- a/src/providers/ldap/ldap_child.c
+++ b/src/providers/ldap/ldap_child.c
@@ -143,10 +143,6 @@ static int ldap_child_get_tgt_sync(TALLOC_CTX *memctx,
     krb5_error_code krberr;
     krb5_timestamp kdc_time_offset;
     int kdc_time_offset_usec;
-    krb5_kt_cursor cursor;
-    krb5_keytab_entry entry;
-    char *principal;
-    bool found;
     int ret;
 
     krberr = krb5_init_context(&context);
@@ -227,50 +223,9 @@ static int ldap_child_get_tgt_sync(TALLOC_CTX *memctx,
     }
 
     /* Verify the keytab */
-    krberr = krb5_kt_start_seq_get(context, keytab, &cursor);
-    if (krberr) {
-        DEBUG(0, ("Cannot read keytab [%s].\n", keytab_name));
-
-        sss_log(SSS_LOG_ERR, "Error reading keytab file [%s]: [%d][%s]. "
-                             "Unable to create GSSAPI-encrypted LDAP connection.",
-                             keytab_name, krberr,
-                             sss_krb5_get_error_message(context, krberr));
-
-        ret = EFAULT;
-        goto done;
-    }
-
-    found = false;
-    while((ret = krb5_kt_next_entry(context, keytab, &entry, &cursor)) == 0){
-        krb5_unparse_name(context, entry.principal, &principal);
-        if (strcmp(full_princ, principal) == 0) {
-            found = true;
-        }
-        free(principal);
-        krb5_free_keytab_entry_contents(context, &entry);
-
-        if (found) {
-            break;
-        }
-    }
-    krberr = krb5_kt_end_seq_get(context, keytab, &cursor);
-    if (krberr) {
-        DEBUG(0, ("Could not close keytab.\n"));
-        sss_log(SSS_LOG_ERR, "Could not close keytab file [%s].",
-                             keytab_name);
-        ret = EFAULT;
-        goto done;
-    }
-
-    if (!found) {
-        DEBUG(0, ("Principal [%s] not found in keytab [%s]\n",
-                  full_princ, keytab_name));
-        sss_log(SSS_LOG_ERR, "Error processing keytab file [%s]: "
-                             "Principal [%s] was not found. "
-                             "Unable to create GSSAPI-encrypted LDAP connection.",
-                             keytab_name, full_princ);
-
-        ret = EFAULT;
+    ret = sss_krb5_verify_keytab_ex(full_princ, keytab_name, context, keytab);
+    if (ret) {
+        DEBUG(2, ("Unable to verify principal is present in the keytab\n"));
         goto done;
     }
 
diff --git a/src/providers/ldap/sdap_child_helpers.c b/src/providers/ldap/sdap_child_helpers.c
index 58b757ef..1b122485 100644
--- a/src/providers/ldap/sdap_child_helpers.c
+++ b/src/providers/ldap/sdap_child_helpers.c
@@ -29,6 +29,7 @@
 #include <fcntl.h>
 
 #include "util/util.h"
+#include "util/sss_krb5.h"
 #include "providers/ldap/ldap_common.h"
 #include "providers/ldap/sdap_async_private.h"
 #include "providers/child_common.h"
@@ -455,6 +456,21 @@ int setup_child(struct sdap_id_ctx *ctx)
         return EOK;
     }
 
+    if (mech && (strcasecmp(mech, "GSSAPI") == 0)) {
+        ret = sss_krb5_verify_keytab(dp_opt_get_string(ctx->opts->basic,
+                                                       SDAP_SASL_AUTHID),
+                                     dp_opt_get_string(ctx->opts->basic,
+                                                       SDAP_KRB5_REALM),
+                                     dp_opt_get_string(ctx->opts->basic,
+                                                       SDAP_KRB5_KEYTAB));
+
+        if (ret != EOK) {
+            DEBUG(0, ("Could not verify keytab\n"))
+            return ret;
+        }
+
+    }
+
     if (debug_to_file != 0 && ldap_child_debug_fd == -1) {
         ret = open_debug_file_ex("ldap_child", &debug_filep);
         if (ret != EOK) {