Add scripts to generate simple test data for certificate verification.

net/data/verify_certificate_chain_unittest/generate-violates-basic-constraints-pathlen-0.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.
+
+import os
+import sys
+
+sys.path.insert(0, os.path.dirname(__file__))
+import common
+
+description = """Certificate chain with 2 intermediaries. The first
+intermediary has a basic constraints path length of 0, so it is a violation for
+it to have a subordinate intermediary."""
+
+common.Init(__file__)
+
+# Self-signed root certificate (part of trust store).
+root = common.CreateSelfSignedRootCertificate('Root')
+
+# Intermediary with pathlen 0
+intermediary1 = common.CreateIntermediaryCertificate('Intermediary1', root)
+intermediary1.GetExtensions().SetProperty('basicConstraints',
+                                          'critical,CA:true,pathlen:0')
+
+# Another intermediary (with the same pathlen restriction)
+intermediary2 = common.CreateIntermediaryCertificate('Intermediary2',
+                                                     intermediary1)
+intermediary2.GetExtensions().SetProperty('basicConstraints',
+                                          'critical,CA:true,pathlen:0')
+
+# Target certificate.
+target = common.CreateEndEntityCertificate('Target', intermediary2)
+
+chain = [target, intermediary2, intermediary1]
+trusted = [root]
+time = common.DEFAULT_TIME
+verify_result = False
+
+common.WriteTestFile(description, chain, trusted, time, verify_result)