feature/2018.03.13_add-fingerprint-1

[ntrepid8]

• update ExPublicKey.RSAPublicKey
  • add get_fingerprint/2
  • add encode_der/1
  • add decode_der/2
  • add optional colons in fingerprint
• update ExPublicKey.RSAPrivateKey
  • add decode_der/1
  • add encode_der/1
  • add get_public/1
  • add get_fingerprint/2
• update ExPublicKeyTest
• update ExPublicKey.RSAPrivateKey inspect/2
  • include the fingerprint
  • handle pretty printing
• add ExPublicKey.RSAPublicKey inspect/2
  • include the fingerprint
  • handle pretty printing
• update ExPublicKey
  • verify ret_code in generate_rsa_openssl_fallback/1

[ntrepid8]

@obrok what are you thoughts on updating the inspect output to include the SHA256 fingerprint?

#ExPublicKey.RSAPrivateKey<
     fingerprint_sha256=7a:40:1c:b9:4b:b8:a5:bb:6b:98:b6:1b:8b:7a:24:8d:45:9b:e5:54
      17:7e:66:26:7e:95:11:9d:39:14:7b:b2>

It also works for the public key struct:

#ExPublicKey.RSAPublicKey<
     fingerprint_sha256=7a:40:1c:b9:4b:b8:a5:bb:6b:98:b6:1b:8b:7a:24:8d:45:9b:e5:54
      17:7e:66:26:7e:95:11:9d:39:14:7b:b2>

I calculated the fingerprints so they would match a fingerprint generated by openssl as described in these AWS docs:

• https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ec2-key-pairs.html#verify-key-pair-fingerprints