Support trust anchor constraints, by specifying them as a certificate.

net/data/verify_certificate_chain_unittest/generate-unconstrained-root-basic-constraints-ca-false.py

 #!/usr/bin/python
 # Copyright (c) 2015 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-"""Certificate chain with 1 intermediate and a trusted root. The intermediate
+"""Certificate chain with 1 intermediate and a trust anchor. The trust anchor
 has a basic constraints extension that indicates it is NOT a CA. Verification
-is expected to fail."""
+is expected to succeed as constraints on the root certificate are not applied
+to the trust anchor."""
 
 import common
 
-# Self-signed root certificate (used as trust anchor).
+# Self-signed root certificate (used as trust anchor) with non-CA basic
+# constraints.
 root = common.create_self_signed_root_certificate('Root')
+root.get_extensions().set_property('basicConstraints', 'critical,CA:false')
 
-# Intermediate with incorrect basic constraints.
+# Intermediate certificate.
 intermediate = common.create_intermediate_certificate('Intermediate', root)
-intermediate.get_extensions().set_property('basicConstraints',
-                                           'critical,CA:false')
 
 # Target certificate.
 target = common.create_end_entity_certificate('Target', intermediate)
 
 chain = [target, intermediate]
 trusted = common.TrustAnchor(root, constrained=False)
 time = common.DEFAULT_TIME
-verify_result = False
+verify_result = True
 
 common.write_test_file(__doc__, chain, trusted, time, verify_result)
+