Make decryption of master key list more robust

krb5_def_fetch_mkey_list was incorrectly filtering mkey_aux entries
when searching the list for an entry which can be decrypted with the
stashed master key.  This bug was masked in most cases by the mkvno
heuristic.

Remove the mkvno heuristic, since performance is not an issue for this
rarely-performed operation, and remove the incorrect enctype
comparison in the brute-force search.

ticket: 6652
target_version: 1.8
tags: pullup

git-svn-id: svn://anonsvn.mit.edu/krb5/trunk@23677 dc483132-0cff-0310-8789-dd5450dbe970

1 files changed, 13 insertions, 37 deletions

diff --git a/src/lib/kdb/kdb_default.c b/src/lib/kdb/kdb_default.c
index 4a4cf8739..225a5074e 100644
--- a/src/lib/kdb/kdb_default.c
+++ b/src/lib/kdb/kdb_default.c
@@ -542,49 +542,25 @@ krb5_def_fetch_mkey_list(krb5_context        context,
     }
 
     if (!found_key) {
-        /*
-         * Note the mkvno may provide a hint as to which mkey_aux tuple to
-         * decrypt.
-         */
         if ((retval = krb5_dbe_lookup_mkey_aux(context, &master_entry,
                                                &mkey_aux_data_list)))
             goto clean_n_exit;
 
-        /* mkvno may be 0 in some cases like keyboard and should be ignored */
-        if (mkvno != 0) {
-            /* for performance sake, try decrypting with matching kvno */
-            for (aux_data_entry = mkey_aux_data_list; aux_data_entry != NULL;
-                 aux_data_entry = aux_data_entry->next) {
-
-                if (aux_data_entry->mkey_kvno == mkvno) {
-                    if (krb5_dbekd_decrypt_key_data(context, mkey,
-                                                    &aux_data_entry->latest_mkey,
-                                                    &cur_mkey, NULL) == 0) {
-                        found_key = TRUE;
-                        break;
-                    }
-                }
+        for (aux_data_entry = mkey_aux_data_list; aux_data_entry != NULL;
+             aux_data_entry = aux_data_entry->next) {
+
+            if (krb5_dbekd_decrypt_key_data(context, mkey,
+                                             &aux_data_entry->latest_mkey,
+                                             &cur_mkey, NULL) == 0) {
+                found_key = TRUE;
+                break;
             }
         }
-        if (!found_key) {
-            /* given the importance of acquiring the latest mkey, try brute force */
-            for (aux_data_entry = mkey_aux_data_list; aux_data_entry != NULL;
-                 aux_data_entry = aux_data_entry->next) {
-
-                if (mkey->enctype == aux_data_entry->latest_mkey.key_data_type[0] &&
-                    (krb5_dbekd_decrypt_key_data(context, mkey,
-                                                 &aux_data_entry->latest_mkey,
-                                                 &cur_mkey, NULL) == 0)) {
-                    found_key = TRUE;
-                    break;
-                }
-            }
-            if (found_key != TRUE) {
-                krb5_set_error_message (context, KRB5_KDB_BADMASTERKEY,
-                                        "Unable to decrypt latest master key with the provided master key\n");
-                retval = KRB5_KDB_BADMASTERKEY;
-                goto clean_n_exit;
-            }
+        if (found_key != TRUE) {
+            krb5_set_error_message (context, KRB5_KDB_BADMASTERKEY,
+                                    "Unable to decrypt latest master key with the provided master key\n");
+            retval = KRB5_KDB_BADMASTERKEY;
+            goto clean_n_exit;
         }
     }