you know nothing server

http://pygotham.org/talks/67
I know nothing :(

Transcript

1. you know nothing server (encrypted messaging) A32A8211
2. Hi, I’m @jamesonjlee
3. (secure data storage api)
4. So
5. Encrypted Messaging
6. Why?
7. It’s a hard problem.
8. Yes? $36.3M Munies $60M Munies
9. No?
10. ¯\_(ツ)_/¯
11. Disclaimer
12. I don’t actually “know” crypto
13. Don’t believe in what I am saying blindly
14. End Disclaimer
15. So
16. Let’s say you have a (super) secret (business) plan
18. A Classic (cryptographic) Story !
19. !
22. !
23. !
25. “Crypto” • HMAC (SHA) • Symmetric (AES) • Asymmetric (RSA) • Hybrid (mix-and-match)
26. Asymmetric Private Key <-> Public Key Public Key (Encrypt) Private Key (Decrypt, Sign, Auth)
28. Choose Wisely RSA DSA …?
29. GPG • Gnu Privacy Guard implements OpenPGP • https://www.gnupg.org/gph/en/manual.html • (openpgp is a hybrid cipher)
30. ! encrypts a message for using ’s Pub-Key
31. ! store the encrypted message on ’s server
32. retrieves the message from ’s server
33. decrypt’s using ’s Private Key
34. code - server setup from flask import Flask, json from flask.ext.sqlalchemy import SQLAlchemy import config ! app = Flask(__name__) app.config.from_object(config) db = SQLAlchemy(app) ! class Message(db.Model): id = db.Column(db.Integer, primary_key=True) recipient = db.Column(db.String(128), index=True, nullable=False) message = db.Column(db.Text, nullable=False) ! def __init__(self, recipient, message): self.recipient = recipient self.message = message
35. code - server @app.route('/message/<string:recipient_id>', methods=['GET']) def get_message_by_sig(recipient_id): messages = Message.query.filter(Message.recipient == recipient_id).all() return json.dumps(messages), 200 ! @app.route('/message/<string:recipient_id>', methods=['POST']) def add_message_by_sig(recipient_id): message = request.get_json() message = Message(recipient=recipient_id, message=message) db.session.add(message) db.session.commit() return 'OK', 200
36. code - client class Client(object): def __init__(self, host, port, passphrase): self.host = "{host}:{port}".format(host=host, port=port) self.passphrase = passphrase self.gpg, self.fp = get_or_gen_gpg(passphrase) self.secret = ‘' ! def get_messages(self): url = self.host + "/message/{}".format(self.fp) resp = requests.get(url, auth=(self.secret, '')) decrypted = [] for message in resp.json(): decrypted.append(self._decrypt(message)) print decrypted ! def send_message(self, message): url = self.host + "/message/{}".format(self.fp) encrypted_message = self._encrypt(message) payload = json.dumps(encrypted_message) resp = requests.post(url, payload=payload, auth=(self.secret, '')) print resp.json()
37. code - client encrypt/decrypt def _encrypt(self, message, recipient): encrypted_data = self.gpg.encrypt( message, recipients=[recipient], sign=self.fp, passphrase=passphrase) return encrypted_data ! def _decrypt(self, message): decrypted_data = gpg.decrypt( str(encrypted_data), passphrase=passphrase) return decrypted_data
38. There are some holes..
39. Who is you?
40. You is who?
41. Verify?
42. Verify!
43. Client? <——> Server?
44. Client? <— NSA —> Server?
45. Identity Verification • I am USER, are you SERVER + key • I am SERVER key, are you USER key + key2 • (encrypted with key2) • I am USER, you are SERVER • Then all communication by “key2” until expiry
46. SSL/TLS Handshake! http://www-01.ibm.com/support/knowledgecenter/SSFKSJ_7.1.0/com.ibm.mq.doc/sy10660_.htm?lang=en
47. code - reinvented client def authenticate(self): if not self.secret: self.secret = generate_random_string() if not self.session: self._challenge_server() return self.secret ! def _challenge_server(self): url = self.host + "/authenticate/{}".format(self.fp) message = self._encrypt(self.secret, self.server_fp) ! response = request.post(url, data=payload) if response.ok: msg = json.loads(self._decrypt(response.text)) if msg['key'] == self.secret: self.secret = msg['key2'] self.session = True else: raise Exception('Bad Server Authentication') else: self.authenticate()
48. code - reinvented server @app.route('/authenticate/<string:recipient_id>', methods=['POST']) def authenticate_person(recipient_id): key = util.gpg_decrypt(app.gpg, request.data, config.SERVER_PASSPHRASE) key2 = util.generate_random_string(32) body = { 'key': str(key), 'key2': key2 } msg = json.dumps(body) server_fp = util.get_fp_from_gpg(app.gpg, config.SERVER_KEY_FP) encrypted = util.gpg_encrypt( app.gpg, server_fp, msg, recipient_id, config.SERVER_PASSPHRASE) return str(encrypted), 200
50. Nope
51. :(
52. code - reinvented client def authenticate(self): if not self.secret: self.secret = generate_random_string() if not self.session: self._challenge_server() return self.secret ! def _challenge_server(self): url = self.host + "/authenticate/{}".format(self.fp) message = self._encrypt(self.secret, self.server_fp) ! response = request.post(url, data=payload) if response.ok: msg = json.loads(self._decrypt(response.text)) if msg['key'] == self.secret: self.secret = msg['key2'] self.session = True else: raise Exception('Bad Server Authentication') else: self.authenticate()
53. code - reinvented server @app.route('/authenticate/<string:recipient_id>', methods=['POST']) def authenticate_person(recipient_id): key = util.gpg_decrypt(app.gpg, request.data, config.SERVER_PASSPHRASE) key2 = util.generate_random_string(32) body = { 'key': str(key), 'key2': key2 } msg = json.dumps(body) server_fp = util.get_fp_from_gpg(app.gpg, config.SERVER_KEY_FP) encrypted = util.gpg_encrypt( app.gpg, server_fp, msg, recipient_id, config.SERVER_PASSPHRASE) return str(encrypted), 200
54. You is who?
55. Identity Distribution
56. Public Key Infrastructure
58. Web of Trust
60. WoT vs PKI
61. wot wot, wot, wot • http://pgp.mit.edu • http://keyserver.pgp.com
62. wot wot, wot, wot • http://pgp.mit.edu • http://keyserver.pgp.com • …
63. wot wot, wot, wot • http://pgp.mit.edu • http://keyserver.pgp.com • … • … • … • … • …
64. wot wot, wot, wot • http://pgp.mit.edu • http://keyserver.pgp.com • … • … • … • … • … • … • … • … • … • … • …
66. ! http://sks-keyservers.net/
68. ¯\_(ツ)_/¯
69. (new!) https://keybase.io
70. code - keyserver class PubKey(db.Model): id = db.Column(db.Integer, primary_key=True) fingerprint = db.Column(db.String(128), index=True, nullable=False) pub_key = db.Column(db.Text, nullable=False) ! def __init__(self, fingerprint, pub_key): self.fingerprint = fingerprint self.pub_key = pub_key
71. code - keyserver @app.route('/identify/<string:fingerprint>', methods=['GET']) def get_fingerprint_pub_key(fingerprint): pub_key = PubKey.query.filter(PubKey.fingerprint==fingerprint).first() if pub_key: return pub_key.pub_key, '200' else: return 'Unknown Fingerprint', 404 ! @app.route('/identify/<string:fingerprint>', methods=['POST']) def add_fingerprint_pub_key(fingerprint): pub_key = PubKey(fingerprint, request.form.get('keyfile')) db.session.add(pub_key) db.session.commit() return 'OK', 200
73. ¯\_(ツ)_/¯
74. What done? Swimming Pool Cloud
76. Anonymous!
77. demo-ish
78. final thoughts
79. Forward Secrecy
80. Plausible Deniability
81. Cool Stuffs • DNSSEC • Off-The-Record • Perfect Forward Secrecy • GPG Internals • MFA Possession Factors (http://pyvideo.org/ video/2699/multi-factor-authentication- possession-factors)
82. just sign mine Don’t just sign random keys
83. Don’t just sign random keys
84. Tanks! source on github: jamesonjlee/simple-secret-app