Add support for external account binding; add OCSP responder

.dockerignore

@@ -5,6 +5,7 @@
 !controller.py
 !dns_server.py
 !acme_tlsalpn.py
+!ocsp.py
 !create-pebble-config.py
 !README.md
 !LICENSE

Dockerfile

@@ -1,7 +1,7 @@
 FROM golang:1.13-stretch as builder
 # Install pebble
 ARG PEBBLE_REMOTE=
-ARG PEBBLE_CHECKOUT="746c32eb265131059a2a340388a4bc7c37405cfc"
+ARG PEBBLE_CHECKOUT="05f79ba495ab6a27cbbc32e20b44afac52eb9914"
 ENV GOPATH=/go
 RUN go get -v -u github.com/letsencrypt/pebble/... && \
     cd /go/src/github.com/letsencrypt/pebble && \
@@ -23,6 +23,6 @@ COPY --from=builder /go/bin /go/bin
 COPY --from=builder /go/pkg /go/pkg
 COPY --from=builder /go/src/github.com/letsencrypt/pebble/test /go/src/github.com/letsencrypt/pebble/test
 # Setup controller.py and run.sh
-ADD run.sh controller.py dns_server.py acme_tlsalpn.py create-pebble-config.py LICENSE LICENSE-acme README.md /root/
-EXPOSE 5000 6000 14000
+ADD run.sh controller.py dns_server.py acme_tlsalpn.py ocsp.py create-pebble-config.py LICENSE LICENSE-acme README.md /root/
+EXPOSE 5000 14000
 CMD [ "/bin/sh", "-c", "/root/run.sh" ]

controller.py

@@ -29,13 +29,14 @@
 
 from functools import partial
 
-from flask import Flask
-from flask import request
+from flask import Flask, request
 
 from acme_tlsalpn import ALPNChallengeServer, gen_ss_cert
+
 from OpenSSL import crypto
 
 from dns_server import DNSServer
+from ocsp import get_ocsp_response
 
 
 app = Flask(__name__)
@@ -218,20 +219,35 @@ def get_root_certificate_minica():
         return f.read()
 
 
-@app.route('/root-certificate-for-ca/<int:index>')
-def get_root_certificate_pebble(index):
+def _pebble_urlopen(fragment, *args, **kwargs):
     ctx = ssl.create_default_context()
     ctx.check_hostname = False
     ctx.verify_mode = ssl.CERT_NONE
-    return urllib.request.urlopen("https://localhost:15000/roots/{0}".format(index), context=ctx).read()
+    url = "https://localhost:15000{0}".format(fragment)
+    log('(internal call to {0})'.format(url))
+    return urllib.request.urlopen(url, *args, context=ctx, **kwargs)
+
+
+@app.route('/root-certificate-for-ca/<int:index>')
+def get_root_certificate_pebble(index):
+    return _pebble_urlopen("/roots/{0}".format(index)).read()
 
 
 @app.route('/intermediate-certificate-for-ca/<int:index>')
 def get_intermediate_certificate_pebble(index):
-    ctx = ssl.create_default_context()
-    ctx.check_hostname = False
-    ctx.verify_mode = ssl.CERT_NONE
-    return urllib.request.urlopen("https://localhost:15000/intermediates/{0}".format(index), context=ctx).read()
+    return _pebble_urlopen("/intermediates/{0}".format(index)).read()
+
+
+@app.route('/ocsp/<string:data>', methods=['GET'])
+def ocsp_get(data):
+    log('Received OCSP GET request')
+    return get_ocsp_response(base64.urlsafe_b64decode(data), _pebble_urlopen, log=log)
+
+
+@app.route('/ocsp', methods=['POST'])
+def ocsp_post():
+    log('Received OCSP POST request')
+    return get_ocsp_response(request.data, _pebble_urlopen, log=log)
 
 
 if __name__ == "__main__":

create-pebble-config.py

@@ -32,7 +32,16 @@
     "privateKey": "test/certs/localhost/key.pem",
     "httpPort": 5000,
     "tlsPort": 5001,
-    "ocspResponderURL": "http://{0}:6000".format(own_ip),  # will be added later
+    "ocspResponderURL": "http://{0}:5000/ocsp".format(own_ip),  # will be added later
+    "externalAccountBindingRequired": False,
+    "externalAccountMACKeys": {
+      "kid-1": "zWNDZM6eQGHWpSRTPal5eIUYFTu7EajVIoguysqZ9wG44nMEtx3MUAsUDkMTQ12W",
+      "kid-2": "b10lLJs8l1GPIzsLP0s6pMt8O0XVGnfTaCeROxQM0BIt2XrJMDHJZBM5NuQmQJQH",
+      "kid-3": "zWNDZM6eQGHWpSRTPal5eIUYFTu7EajVIoguysqZ9wG44nMEtx3MUAsUDkMTQ12W",
+      "kid-4": "b10lLJs8l1GPIzsLP0s6pMt8O0XVGnfTaCeROxQM0BIt2XrJMDHJZBM5NuQmQJQH",
+      "kid-5": "zWNDZM6eQGHWpSRTPal5eIUYFTu7EajVIoguysqZ9wG44nMEtx3MUAsUDkMTQ12W",
+      "kid-6": "b10lLJs8l1GPIzsLP0s6pMt8O0XVGnfTaCeROxQM0BIt2XrJMDHJZBM5NuQmQJQH"
+    }
   }
 }
 

ocsp.py

@@ -0,0 +1,190 @@
+# -*- coding: utf-8 -*-
+# (c) 2018 Felix Fontein (@felixfontein) <felix@fontein.de>
+#
+# Written by Felix Fontein <felix@fontein.de>
+# This file is part of Ansible
+#
+# Ansible is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# Ansible is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with Ansible.  If not, see <http://www.gnu.org/licenses/>.
+
+import datetime
+import json
+import os
+import urllib
+import traceback
+
+from flask import Response
+
+from cryptography import x509
+from cryptography.x509 import ocsp
+from cryptography.hazmat.backends import default_backend
+from cryptography.hazmat.primitives import hashes
+from cryptography.hazmat.primitives import serialization
+
+
+SAMPLE_REQUEST_CACHE = {}
+
+
+def _get_sample_request_for_root(root, hash_algorithm, pebble_urlopen):
+    '''
+    Returns an OCSP sample request for this root, together with the intermediate certificate and its key.
+    '''
+    cache_key = (root, hash_algorithm.name)
+    if cache_key in SAMPLE_REQUEST_CACHE:
+        return SAMPLE_REQUEST_CACHE[cache_key]
+
+    # Get hold of intermediate certificate with key
+    intermediate = x509.load_pem_x509_certificate(
+        pebble_urlopen("/intermediates/{0}".format(root)).read(),
+        backend=default_backend())
+    intermediate_key = serialization.load_pem_private_key(
+        pebble_urlopen("/intermediate-keys/{0}".format(root)).read(),
+        None,
+        backend=default_backend())
+
+    one_day = datetime.timedelta(1, 0, 0)
+    builder = x509.CertificateBuilder()
+    builder = builder.subject_name(intermediate.subject)
+    builder = builder.issuer_name(intermediate.subject)
+    builder = builder.not_valid_before(datetime.datetime.today() - one_day)
+    builder = builder.not_valid_after(datetime.datetime.today() + one_day)
+    builder = builder.serial_number(x509.random_serial_number())
+    builder = builder.public_key(intermediate.public_key())
+    certificate = builder.sign(
+        private_key=intermediate_key,
+        algorithm=hashes.SHA256(),
+        backend=default_backend())
+
+    req = ocsp.OCSPRequestBuilder()
+    req = req.add_certificate(certificate, intermediate, hash_algorithm)
+    req = req.build()
+
+    result = req, intermediate, intermediate_key
+    SAMPLE_REQUEST_CACHE[cache_key] = result
+    return result
+
+
+RECOVATION_REASONS = {
+    1: x509.ReasonFlags.key_compromise,
+    2: x509.ReasonFlags.ca_compromise,
+    3: x509.ReasonFlags.affiliation_changed,
+    4: x509.ReasonFlags.superseded,
+    5: x509.ReasonFlags.cessation_of_operation,
+    6: x509.ReasonFlags.certificate_hold,
+    7: x509.ReasonFlags.privilege_withdrawn,
+    8: x509.ReasonFlags.aa_compromise,
+}
+
+
+def _get_ocsp_response(data, pebble_urlopen, log):
+    try:
+        ocsp_request = ocsp.load_der_ocsp_request(data)
+    except Exception:
+        log('Error while decoding OCSP request')
+        return ocsp.OCSPResponseBuilder.build_unsuccessful(
+            ocsp.OCSPResponseStatus.MALFORMED_REQUEST)
+
+    log('OCSP request for certificate # {0}'.format(ocsp_request.serial_number))
+
+    # Process possible extensions
+    nonce = None
+    for ext in ocsp_request.extensions:
+        if isinstance(ext.value, x509.OCSPNonce):
+            nonce = ext.value.nonce
+            continue
+        if ext.critical:
+            return ocsp.OCSPResponseBuilder.build_unsuccessful(
+                ocsp.OCSPResponseStatus.MALFORMED_REQUEST)
+
+    # Determine issuer
+    root_count = int(os.environ.get('PEBBLE_ALTERNATE_ROOTS') or '0') + 1
+    for root in range(root_count):
+        req, intermediate, intermediate_key = _get_sample_request_for_root(
+            root, ocsp_request.hash_algorithm, pebble_urlopen)
+        if req.issuer_key_hash == ocsp_request.issuer_key_hash and req.issuer_name_hash == ocsp_request.issuer_name_hash:
+            log('Identified intermediate certificate {0}'.format(intermediate.subject))
+            break
+        intermediate = None
+        intermediate_key = None
+    if intermediate is None or intermediate_key is None:
+        log(ocsp_request.issuer_key_hash, ocsp_request.issuer_name_hash)
+        log('Cannot identify intermediate certificate')
+        return ocsp.OCSPResponseBuilder.build_unsuccessful(
+            ocsp.OCSPResponseStatus.UNAUTHORIZED)
+
+    serial_hex = hex(ocsp_request.serial_number)[2:]
+    if len(serial_hex) % 2 == 1:
+        serial_hex = '0' + serial_hex
+    try:
+        url = pebble_urlopen("/cert-status-by-serial/{0}".format(serial_hex))
+    except urllib.error.HTTPError as e:
+        if e.code == 404:
+            log('Unknown certificate with # {0}'.format(ocsp_request.serial_number))
+            return ocsp.OCSPResponseBuilder.build_unsuccessful(
+                ocsp.OCSPResponseStatus.UNAUTHORIZED)
+        raise
+
+    data = json.loads(url.read())
+    log('Pebble result on certificate:', json.dumps(data, sort_keys=True, indent=2))
+
+    cert = x509.load_pem_x509_certificate(
+        data['Certificate'].encode('utf-8'), backend=default_backend())
+
+    now = datetime.datetime.now()
+    if data['Status'] == 'Revoked':
+        cert_status = ocsp.OCSPCertStatus.REVOKED
+        revoked_at = data.get('RevokedAt')
+        if revoked_at is not None:
+            revoked_at = ' '.join(revoked_at.split(' ')[:2])  # remove time zones
+            if '.' in revoked_at:
+                revoked_at = revoked_at[:revoked_at.index('.')]  # remove milli- or nanoseconds
+            revoked_at = datetime.datetime.strptime(revoked_at, '%Y-%m-%d %H:%M:%S')
+        revocation_time = revoked_at,
+        revocation_reason = RECOVATION_REASONS.get(data.get('Reason'), x509.ReasonFlags.unspecified)
+    elif data['Status'] == 'Valid':
+        cert_status = ocsp.OCSPCertStatus.GOOD
+        revocation_time = None
+        revocation_reason = None
+    else:
+        log('Unknown certificate status "{0}"'.format(data['Status']))
+        return ocsp.OCSPResponseBuilder.build_unsuccessful(
+            ocsp.OCSPResponseStatus.INTERNAL_ERROR)
+
+    response = ocsp.OCSPResponseBuilder()
+    response = response.add_response(
+        cert=cert,
+        issuer=intermediate,
+        algorithm=ocsp_request.hash_algorithm,
+        cert_status=cert_status,
+        this_update=now,
+        next_update=None,
+        revocation_time=revocation_time,
+        revocation_reason=revocation_reason)
+    response = response.responder_id(
+        ocsp.OCSPResponderEncoding.HASH,
+        intermediate)
+    if nonce is not None:
+        response = response.add_extension(x509.OCSPNonce(nonce), False)
+    return response.sign(intermediate_key, hashes.SHA256())
+
+
+def get_ocsp_response(data, pebble_urlopen, log=lambda *args: print(args)):
+    try:
+        response = _get_ocsp_response(data, pebble_urlopen, log=log)
+    except Exception as e:
+        log('Error while processing OCSP request: {0}'.format(e), traceback.format_exc())
+        response = ocsp.OCSPResponseBuilder.build_unsuccessful(
+            ocsp.OCSPResponseStatus.INTERNAL_ERROR)
+    return Response(
+        response.public_bytes(serialization.Encoding.DER),
+        mimetype='application/ocsp-response')

requirements.txt

@@ -1,15 +1,15 @@
 # Requirements
-Flask==1.1.1
-pyOpenSSL==19.0.0
-dnslib==0.9.10
+Flask==1.1.2
+pyOpenSSL==19.1.0
+dnslib==0.9.14
+cryptography==3.0
 
 # Implicit requirements to make Python part reproducable
-Jinja2==2.10.3
+Jinja2==2.11.2
 MarkupSafe==1.1.1
-Werkzeug==0.16.0
-cffi==1.13.2
-click==7.0
-cryptography==2.8
+Werkzeug==1.0.1
+cffi==1.14.1
+click==7.1.2
 itsdangerous==1.1.0
-pycparser==2.19
-six==1.12.0
+pycparser==2.20
+six==1.15.0

run.sh

@@ -2,14 +2,14 @@
 set -e
 # Our internal BIND (started by Controller) is the official DNS resolver for this container
 echo nameserver 127.0.0.1 > /etc/resolv.conf
-# Start controller in background
-export CONTROLLER_PORT=5000
-export GOPATH=/go
-/usr/local/bin/python /root/controller.py &
 # Make Pebble sleep at most 5 seconds between auth checks (default is 15 seconds)
 export PEBBLE_VA_SLEEPTIME=5
 # Add three alternate roots with intermediate certs
 export PEBBLE_ALTERNATE_ROOTS=3
+# Start controller in background
+export CONTROLLER_PORT=5000
+export GOPATH=/go
+/usr/local/bin/python /root/controller.py &
 # Create Pebble config
 /usr/local/bin/python /root/create-pebble-config.py /go/src/github.com/letsencrypt/pebble/test/config/pebble-config.json
 # Start Pebble