[PATCH v3] dco: make key state desync recoverable

From: Ralf Lici <[email protected]>

If installing a DCO key succeeds, always record the slot in the
corresponding key_state. The installed-key counter only tracks whether
the number of kernel slots grew, but a successful KEY_NEW still means
that this key_state is associated with the selected DCO slot.

Also replace DCO key-state assertions in dco_update_keys() with error
returns. This preserves the invariant checks but lets the existing
caller restart the connection instead of aborting the process if
userspace ever detects inconsistent DCO key state.

Github: https://github.com/OpenVPN/openvpn-private-issues/issues/143
Change-Id: I4d0887839b4a13a92e92250d1b315dec949698f3
Signed-off-by: Ralf Lici <[email protected]>
Acked-by: Antonio Quartulli <[email protected]>
Gerrit URL: https://gerrit.openvpn.net/c/openvpn/+/1795
---

This change was reviewed on Gerrit and approved by at least one
developer. I request to merge it to master.

Gerrit URL: https://gerrit.openvpn.net/c/openvpn/+/1795
This mail reflects revision 3 of this Change.

Acked-by according to Gerrit (reflected above):
Antonio Quartulli <[email protected]>

        
diff --git a/src/openvpn/dco.c b/src/openvpn/dco.c
index e944547..2584368 100644
--- a/src/openvpn/dco.c
+++ b/src/openvpn/dco.c
@@ -73,9 +73,12 @@
 
     int ret = dco_new_key(multi->dco, multi->dco_peer_id, ks->key_id, slot, encrypt_key, encrypt_iv,
                           decrypt_key, decrypt_iv, ciphername, epoch);
-    if ((ret == 0) && (multi->dco_keys_installed < 2))
+    if (ret == 0)
     {
-        multi->dco_keys_installed++;
+        if (multi->dco_keys_installed < 2)
+        {
+            multi->dco_keys_installed++;
+        }
         ks->dco_status =
             (slot == OVPN_KEY_SLOT_PRIMARY) ? DCO_INSTALLED_PRIMARY : DCO_INSTALLED_SECONDARY;
     }
@@ -166,7 +169,13 @@
     /* if we have a primary key, it must have been installed already (keys
      * are installed upon generation in the TLS code)
      */
-    ASSERT(primary->dco_status != DCO_NOT_INSTALLED);
+    if (primary->dco_status == DCO_NOT_INSTALLED)
+    {
+        msg(D_DCO, "DCO key state mismatch: selected primary key is not installed "
+                   "(peer_id=%d, key_id=%d, dco_keys_installed=%d)",
+            multi->dco_peer_id, primary->key_id, multi->dco_keys_installed);
+        return false;
+    }
 
     struct key_state *secondary = dco_get_secondary_key(multi, primary);
     /* if the current primary key was installed as secondary in DCO,
@@ -190,6 +199,14 @@
                 primary->key_id);
         }
 
+        if (secondary && secondary->dco_status != DCO_INSTALLED_PRIMARY)
+        {
+            msg(D_DCO, "DCO key state mismatch: expected old primary key is not installed as DCO primary before swap "
+                       "(peer_id=%d, new_primary_key_id=%d, old_primary_key_id=%d, old_primary_dco_status=%d, dco_keys_installed=%d)",
+                multi->dco_peer_id, primary->key_id, secondary->key_id, secondary->dco_status, multi->dco_keys_installed);
+            return false;
+        }
+
         int ret = dco_swap_keys(dco, multi->dco_peer_id);
         if (ret < 0)
         {
@@ -200,7 +217,6 @@
         primary->dco_status = DCO_INSTALLED_PRIMARY;
         if (secondary)
         {
-            ASSERT(secondary->dco_status == DCO_INSTALLED_PRIMARY);
             secondary->dco_status = DCO_INSTALLED_SECONDARY;
         }
     }