From d15ace2d81783a92474e2dbe6c02f20589aa70f0 Mon Sep 17 00:00:00 2001
From: Andreas Schneider <asn@samba.org>
Date: Mon, 9 Aug 2021 17:20:31 +0200
Subject: [PATCH] CVE-2020-25719 s4:kdc: Check if the pac is valid before
 updating it

BUG: https://bugzilla.samba.org/show_bug.cgi?id=14561

Signed-off-by: Andreas Schneider <asn@samba.org>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
Conflict: remove selftest/knownfail_heimdal_kdc selftest/knownfail_mit_kdc
---
 source4/kdc/mit_samba.c        |  9 +++++++++
 source4/kdc/wdc-samba4.c       | 17 +++++++++++++++++
 4 files changed, 32 insertions(+), 35 deletions(-)

diff --git a/source4/kdc/mit_samba.c b/source4/kdc/mit_samba.c
index d0e68ec8ea4..592f6a3bac4 100644
--- a/source4/kdc/mit_samba.c
+++ b/source4/kdc/mit_samba.c
@@ -512,6 +512,15 @@ krb5_error_code mit_samba_reget_pac(struct mit_samba_context *ctx,
 		client_skdc_entry =
 			talloc_get_type_abort(client->e_data,
 					      struct samba_kdc_entry);
+
+		/*
+		 * Check the objectSID of the client and pac data are the same.
+		 * Does a parse and SID check, but no crypto.
+		 */
+		code = samba_kdc_validate_pac_blob(context, client_skdc_entry, *pac);
+		if (code != 0) {
+			goto done;
+		}
 	}
 
 	if (server == NULL) {
diff --git a/source4/kdc/wdc-samba4.c b/source4/kdc/wdc-samba4.c
index ac9d7d51733..ed6e9fb9b63 100644
--- a/source4/kdc/wdc-samba4.c
+++ b/source4/kdc/wdc-samba4.c
@@ -137,6 +137,23 @@ static krb5_error_code samba_wdc_reget_pac2(krb5_context context,
 		return ENOMEM;
 	}
 
+	if (client != NULL) {
+		struct samba_kdc_entry *client_skdc_entry = NULL;
+
+		client_skdc_entry = talloc_get_type_abort(client->ctx,
+							  struct samba_kdc_entry);
+
+		/*
+		 * Check the objectSID of the client and pac data are the same.
+		 * Does a parse and SID check, but no crypto.
+		 */
+		ret = samba_kdc_validate_pac_blob(context, client_skdc_entry, *pac);
+		if (ret != 0) {
+			talloc_free(mem_ctx);
+			return ret;
+		}
+	}
+
 	/* If the krbtgt was generated by an RODC, and we are not that
 	 * RODC, then we need to regenerate the PAC - we can't trust
 	 * it */
-- 
2.33.0

