Add a key purpose parameter to Certificate PathBuilder.

net/data/verify_certificate_chain_unittest/generate-constrained-root-bad-eku.py

+#!/usr/bin/python
+# Copyright (c) 2017 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 trust anchor. The trust anchor
+has an EKU that restricts it to clientAuth. Verification is expected to fail as
+the end-entity is verified for serverAuth, and the trust anchor enforces
+constraints."""
+
+import common
+
+# 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('extendedKeyUsage', 'clientAuth')
+
+# Intermediate certificate.
+intermediate = common.create_intermediate_certificate('Intermediate', root)
+
+# Target certificate.
+target = common.create_end_entity_certificate('Target', intermediate)
+
+chain = [target, intermediate]
+trusted = common.TrustAnchor(root, constrained=True)
+time = common.DEFAULT_TIME
+key_purpose = common.KEY_PURPOSE_SERVER_AUTH
+verify_result = False
+errors = """----- Certificate i=2 -----
+ERROR: The extended key usage does not include server auth
+
+"""
+
+common.write_test_file(__doc__, chain, trusted, time, key_purpose,
+                       verify_result, errors)