kdb: store mkey list in context and permit NULL mkey for kdb_dbe_decrypt_key_data

Previously, code needed to run a loop to find the current master key,
possibly fetch a new master key list and try finding the master key
again around each key decryption.  This was not universally done;
there are cases where only the current master key was used.  In
addition, the correct ideom for decrypting key data is too complicated
and is potentially unavailable to plugins that do not have access to
the master key.  Instead, store the master key list in the dal_handle
whenever it is fetched and permit a NULL master key for
krb5_dbe_decrypt_key_data.

* Remove APIs for krb5_db_{get|set}_mkey_list
* krb5_db_fetch_mkey_list: memoize master key list in dal_handle
* krb5_db_free_mkey_list: don't free the memoized list; arrange for it to be freed later
* krb5_dbe_decrypt_key_data: Search for correct master key on NULL argument
* change call sites to take advantage

ticket: 6778

git-svn-id: svn://anonsvn.mit.edu/krb5/trunk@24314 dc483132-0cff-0310-8789-dd5450dbe970

1 files changed, 76 insertions, 35 deletions

diff --git a/src/lib/kdb/kdb5.c b/src/lib/kdb/kdb5.c
index 9786503005..c549689870 100644
--- a/src/lib/kdb/kdb5.c
+++ b/src/lib/kdb/kdb5.c
@@ -1,6 +1,6 @@
 /* -*- mode: c; c-basic-offset: 4; indent-tabs-mode: nil -*- */
 /*
- * Copyright 2006, 2009 by the Massachusetts Institute of Technology.
+ * Copyright 2006, 2009, 2010 by the Massachusetts Institute of Technology.
  * All Rights Reserved.
  *
  * Export of this software from the United States of America may
@@ -549,17 +549,23 @@ static krb5_error_code
 kdb_free_lib_handle(krb5_context kcontext)
 {
     krb5_error_code status = 0;
+    krb5_keylist_node *old_keylist = kcontext->dal_handle->master_keylist;
 
     status = kdb_free_library(kcontext->dal_handle->lib_handle);
     if (status)
         return status;
-
+    /* The dal_handle holds an alias to the most recent mkey_list*/
+    if (kcontext->dal_handle->free_keylist) {
+        kcontext->dal_handle->master_keylist = NULL; /*force freeing*/
+        krb5_db_free_mkey_list(kcontext, old_keylist);
+    }
+    krb5_free_principal(kcontext, kcontext->dal_handle->master_princ);
     free(kcontext->dal_handle);
     kcontext->dal_handle = NULL;
     return 0;
 }
 
-static krb5_error_code
+static  krb5_error_code
 get_vftabl(krb5_context kcontext, kdb_vftabl **vftabl_ptr)
 {
     krb5_error_code status;
@@ -989,35 +995,6 @@ krb5_db_iterate(krb5_context kcontext,
 }
 
 krb5_error_code
-krb5_db_set_mkey_list(krb5_context kcontext,
-                      krb5_keylist_node * keylist)
-{
-    krb5_error_code status = 0;
-    kdb_vftabl *v;
-
-    status = get_vftabl(kcontext, &v);
-    if (status)
-        return status;
-    if (v->set_master_key_list == NULL)
-        return KRB5_PLUGIN_OP_NOTSUPP;
-    return v->set_master_key_list(kcontext, keylist);
-}
-
-krb5_error_code
-krb5_db_get_mkey_list(krb5_context kcontext, krb5_keylist_node ** keylist)
-{
-    krb5_error_code status = 0;
-    kdb_vftabl *v;
-
-    status = get_vftabl(kcontext, &v);
-    if (status)
-        return status;
-    if (v->get_master_key_list == NULL)
-        return KRB5_PLUGIN_OP_NOTSUPP;
-    return v->get_master_key_list(kcontext, keylist);
-}
-
-krb5_error_code
 krb5_db_fetch_mkey_list(krb5_context     context,
                         krb5_principal        mname,
                         const krb5_keyblock * mkey,
@@ -1026,11 +1003,28 @@ krb5_db_fetch_mkey_list(krb5_context     context,
 {
     kdb_vftabl *v;
     krb5_error_code status = 0;
+    krb5_keylist_node *local_keylist;
 
     status = get_vftabl(context, &v);
     if (status)
         return status;
-    return v->fetch_master_key_list(context, mname, mkey, mkvno, mkey_list);
+    if (!context->dal_handle->master_princ) {
+        status = krb5_copy_principal(context, mname, &context->dal_handle->master_princ);
+        if (status)
+            return status;
+    }
+    if (mkey_list == NULL)
+        mkey_list = &local_keylist;
+    status =  v->fetch_master_key_list(context, mname, mkey, mkvno, mkey_list);
+    if (status == 0) {
+        /* The dal_handle holds an alias to the most recent master_keylist*/
+        krb5_keylist_node *old_keylist = context->dal_handle->master_keylist;
+        context->dal_handle->master_keylist = *mkey_list;
+        if (context->dal_handle->free_keylist)
+            krb5_db_free_mkey_list(context, old_keylist);
+        context->dal_handle->free_keylist = (mkey_list == &local_keylist);
+    }
+    return status;
 }
 
 void
@@ -1039,6 +1033,19 @@ krb5_db_free_mkey_list(krb5_context    context,
 {
     krb5_keylist_node *cur, *prev;
 
+    /*
+     * The dal_handle holds onto the most recent master
+     * keylist that has been fetched throughout the lifetime of the context; if
+     * this function is called on that keylist, then the dal_handle is updated to
+     * indicate that the keylist should be freed on next call to
+     * krb5_db_fetch_mkey_list() or when the database is closed. Otherwise, the
+     * master_keylist is freed. Either way, the caller must not access this master
+     * keylist after calling this function.
+     */
+    if (context&& context->dal_handle->master_keylist == mkey_list) {
+        context->dal_handle->free_keylist = 1;
+        return;
+    }
     for (cur = mkey_list; cur != NULL;) {
         prev = cur;
         cur = cur->next;
@@ -2177,6 +2184,27 @@ krb5_db_promote(krb5_context kcontext, char **db_args)
     return status;
 }
 
+static krb5_error_code
+decrypt_iterator(krb5_context kcontext,
+                 const krb5_key_data        * key_data,
+                 krb5_keyblock      * dbkey,
+                 krb5_keysalt       * keysalt)
+{
+    krb5_error_code status = 0;
+    kdb_vftabl *v;
+    krb5_keylist_node *n = kcontext->dal_handle->master_keylist;
+    status = get_vftabl(kcontext, &v);
+    if (status)
+        return status;
+    for (;n; n = n->next) {
+        krb5_clear_error_message(kcontext);
+        status= v->decrypt_key_data(kcontext, &n->keyblock, key_data, dbkey, keysalt);
+        if (status == 0)
+            return 0;
+    }
+    return status;
+}
+
 krb5_error_code
 krb5_dbe_decrypt_key_data( krb5_context         kcontext,
                            const krb5_keyblock        * mkey,
@@ -2186,11 +2214,24 @@ krb5_dbe_decrypt_key_data( krb5_context         kcontext,
 {
     krb5_error_code status = 0;
     kdb_vftabl *v;
-
+    krb5_keylist_node *n = kcontext->dal_handle->master_keylist;
     status = get_vftabl(kcontext, &v);
     if (status)
         return status;
-    return v->decrypt_key_data(kcontext, mkey, key_data, dbkey, keysalt);
+    if (mkey ||!n)
+        return v->decrypt_key_data(kcontext, mkey, key_data, dbkey, keysalt);
+    status = decrypt_iterator(kcontext, key_data, dbkey, keysalt);
+    if (status == 0)
+        return 0;
+    if (kcontext->dal_handle->master_keylist) {
+        /* Try reloading master keys*/
+        krb5_keyblock *cur_mkey = &kcontext->dal_handle->master_keylist->keyblock;
+        if (krb5_db_fetch_mkey_list(kcontext, kcontext->dal_handle->master_princ,
+                                    cur_mkey, -1, NULL) == 0) {
+            return decrypt_iterator(kcontext, key_data, dbkey, keysalt);
+        }
+    }
+    return status;
 }
 
 krb5_error_code