Account for the OS returning an empty certificate chain.

net/data/ssl/scripts/generate-test-certs.sh

 #!/bin/sh
 
 # Copyright 2013 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.
 
 # This script generates a set of test (end-entity, intermediate, root)
 # certificates that can be used to test fetching of an intermediate via AIA.
 
 try() {
@@ skipping 132 matching lines @@
     -config ../scripts/ee.cnf -newkey rsa:2048 -text \
     -out ../certificates/punycodetest.pem
 
 ## Reject intranet hostnames in "publicly" trusted certs
 # 365 * 3 = 1095
 SUBJECT_NAME="req_dn" \
   try openssl req -x509 -days 1095 \
     -config ../scripts/ee.cnf -newkey rsa:2048 -text \
     -out ../certificates/reject_intranet_hosts.pem
 
+## Leaf certificate with a large key; Apple's certificate verifier rejects with
+## a fatal error if the key is bigger than 4096 bits.
+try openssl req -x509 -days 3650 \
+    -config ../scripts/ee.cnf -newkey rsa:4104 -text \
+    -sha256 \
+    -out ../certificates/large_key.pem
+
 ## Validity too long unit test support.
 try openssl req -config ../scripts/ee.cnf \
   -newkey rsa:2048 -text -out ../certificates/10_year_validity.req
 CA_COMMON_NAME="Test Root CA" \
   try openssl ca \
     -batch \
     -extensions user_cert \
     -startdate 081030000000Z \
     -enddate   181029000000Z \
     -in ../certificates/10_year_validity.req \
@@ skipping 136 matching lines @@
 ## Block a leaf cert by issuer-hash-and-serial. However, this will be issued
 ## from an intermediate CA issued underneath a root.
 try python crlsetutil.py -o ../certificates/crlset_by_intermediate_serial.raw \
 <<CRLSETBYINTERMEDIATESERIAL
 {
   "BlockedByHash": {
     "../certificates/quic_intermediate.crt": [3]
   }
 }
 CRLSETBYINTERMEDIATESERIAL