Handle migration from pre-1.7 databases with master key kvno != 1

krb5_dbe_lookup_mkvno assumes an mkvno of 1 for entries with no
explicit tl_data.  We've seen at least one pre-1.7 KDB with a master
kvno of 0, violating this assumption.  Fix this as follows:

* krb5_dbe_lookup_mkvno outputs 0 instead of 1 if no tl_data exists.
* A new function krb5_dbe_get_mkvno translates this 0 value to the
  minimum version number in the mkey_list.  (krb5_dbe_lookup_mkvno
  cannot do this as it doesn't take the mkey_list as a parameter.)
* Call sites to krb5_dbe_lookup_mkvno are converted to
  krb5_dbe_get_mkvno, except for an LDAP case where it is acceptable
  to store 0 if the mkvno is unknown.

ticket: 6650
target_version: 1.7.1
tags: pullup

git-svn-id: svn://anonsvn.mit.edu/krb5/trunk@23676 dc483132-0cff-0310-8789-dd5450dbe970

1 files changed, 34 insertions, 2 deletions

diff --git a/src/lib/kdb/kdb5.c b/src/lib/kdb/kdb5.c
index cd9f716974..83dde5137d 100644
--- a/src/lib/kdb/kdb5.c
+++ b/src/lib/kdb/kdb5.c
@@ -1591,7 +1591,7 @@ krb5_dbe_find_mkey(krb5_context         context,
     krb5_error_code retval;
     krb5_keylist_node *cur_keyblock = mkey_list;
 
-    retval = krb5_dbe_lookup_mkvno(context, entry, &mkvno);
+    retval = krb5_dbe_get_mkvno(context, entry, mkey_list, &mkvno);
     if (retval)
         return (retval);
 
@@ -1852,7 +1852,7 @@ krb5_dbe_lookup_mkvno(krb5_context      context,
         return (code);
 
     if (tl_data.tl_data_length == 0) {
-        *mkvno = 1; /* default for princs that lack the KRB5_TL_MKVNO data */
+        *mkvno = 0; /* Indicates KRB5_TL_MKVNO data not present */
         return (0);
     } else if (tl_data.tl_data_length != 2) {
         return (KRB5_KDB_TRUNCATED_RECORD);
@@ -1864,6 +1864,38 @@ krb5_dbe_lookup_mkvno(krb5_context      context,
 }
 
 krb5_error_code
+krb5_dbe_get_mkvno(krb5_context        context,
+                   krb5_db_entry     * entry,
+                   krb5_keylist_node * mkey_list,
+                   krb5_kvno         * mkvno)
+{
+    krb5_error_code code;
+    krb5_kvno kvno;
+
+    if (mkey_list == NULL)
+        return EINVAL;
+
+    /* Output the value from entry tl_data if present. */
+    code = krb5_dbe_lookup_mkvno(context, entry, &kvno);
+    if (code != 0)
+        return code;
+    if (kvno != 0) {
+        *mkvno = kvno;
+        return 0;
+    }
+
+    /* Determine the minimum kvno in mkey_list and output that. */
+    kvno = (krb5_kvno) -1;
+    while (mkey_list != NULL) {
+        if (mkey_list->kvno < kvno)
+            kvno = mkey_list->kvno;
+        mkey_list = mkey_list->next;
+    }
+    *mkvno = kvno;
+    return 0;
+}
+
+krb5_error_code
 krb5_dbe_update_mkvno(krb5_context    context,
                       krb5_db_entry * entry,
                       krb5_kvno       mkvno)