Allow leading/trailing data when looking for certificates
When parsing the list of certificates provided for signing
verification the parser did not allow leading or trailing
data, like headers you might find in openSSL exported PKCS#12
values:
Bag Attributes
2.16.840.1.113730.5.1.1.1: CT,C,C
localKeyID: 00 9B 92 61 B3 05 7F EE 42 9B 6A AF DE 5B 08 ...
friendlyName: CA Signing Certificate
subject=/O=ACME/CN=CA Signing Certificate
issuer=/O=ACME/CN=CA Signing Certificate
https://pagure.io/certmonger/issue/93