internally catch binascii errors

[lukn]

File "/whatever/is/my/funny/project.py", line xxx, in functionname
    valid = d.verify()
  File "/usr/lib/python3.6/site-packages/dkim/__init__.py", line 879, in verify
    return self.verify_sig(sig, include_headers, sigheaders[idx], dnsfunc)
  File "/usr/lib/python3.6/site-packages/dkim/__init__.py", line 674, in verify_sig
    pk, self.keysize, ktag = load_pk_from_dns(name, dnsfunc)
  File "/usr/lib/python3.6/site-packages/dkim/__init__.py", line 447, in load_pk_from_dns
    pk = parse_public_key(base64.b64decode(pub[b'p']))
  File "/usr/lib64/python3.6/base64.py", line 87, in b64decode
    return binascii.a2b_base64(s)
binascii.Error: Incorrect padding

such errors occur due to broken public keys in DNS records. as there is not much that could be done about this, such binascii errors should be caught internally and just logged.

I guess verification should be considered as failed in such cases...

[Scott Kitterman (kitterman)]

Catch binascii related key format errors (LP: #1854477)

[Scott Kitterman (kitterman)]

It's now treated like other key errors. You'll get a keyerror if there is a logger.

[Scott Kitterman (kitterman)]

2019-12-09 Version 1.0.0
    - Add support for RFC 8460 tlsrpt DKIM signature processing (LP: #1847020)
    - Add async support with aiodns for DKIM verification (ARC not supported)
      (LP: #1847002)
    - Add new timeout parameter to enable DNS lookup timeouts to be adjusted
    - Add new DKIM.present function to allow applications to test if a DKIM
      signature is present without doing validation (LP: #1851141)
    - Support signature verification with RSAPublicKey formatted keys
      since, although rare, they are RFC 6376 specified (LP: #1851862)
    - Drop usage of pymilter Milter.dns in dnsplug since it doesn't support
      havine a timeout passed to it
    - Catch binascii related key format errors (LP: #1854477)