s4-kdc: default kvno for inter-domain trusts to zero

the exact value doesn't matter, as both Samba and windows check
against the latest password, but the old default of -1 caused ASN.1
parsing errors on windows, which prevented it answering TGS requests

thanks to Hongwei Sun for finding this from a ttt trace

Pair-Programmed-With: Andrew Bartlett <abartlet@samba.org>

1 files changed, 9 insertions, 1 deletions

diff --git a/source4/kdc/db-glue.c b/source4/kdc/db-glue.c
index cdc318a4a8..52bacd0f9d 100644
--- a/source4/kdc/db-glue.c
+++ b/source4/kdc/db-glue.c
@@ -896,7 +896,15 @@ static krb5_error_code samba_kdc_trust_message2entry(krb5_context context,
 		goto out;
 	}
 
-	entry_ex->entry.kvno = -1;
+	entry_ex->entry.kvno = 0;
+	/*
+	  we usually don't have a TRUST_AUTH_TYPE_VERSION field, as
+	  windows doesn't create one, so we rely on the fact that both
+	  windows and Samba don't actually check the kvno and instead
+	  just check against the latest password blob. If we do have a
+	  TRUST_AUTH_TYPE_VERSION field then we do use it, otherwise
+	  we just use 0.
+	 */
 	for (i=0; i < password_blob.count; i++) {
 		if (password_blob.current.array[i].AuthType == TRUST_AUTH_TYPE_VERSION) {
 			entry_ex->entry.kvno = password_blob.current.array[i].AuthInfo.version.version;