Extract Certificate Transparency SCTs from stapled OCSP responses

third_party/tlslite/tlslite/messages.py

Index: third_party/tlslite/tlslite/messages.py
diff --git a/third_party/tlslite/tlslite/messages.py b/third_party/tlslite/tlslite/messages.py
index 296f422b33743cff288a39fbdf3ea567a2337340..497ef6048df786d96f62b317c24e933019f35219 100644
--- a/third_party/tlslite/tlslite/messages.py
+++ b/third_party/tlslite/tlslite/messages.py
@@ -132,6 +132,7 @@ class ClientHello(HandshakeMsg):
         self.srp_username = None        # a string
         self.channel_id = False
         self.support_signed_cert_timestamps = False
+        self.status_request = False
 
     def create(self, version, random, session_id, cipher_suites,
                certificate_types=None, srp_username=None):
@@ -182,6 +183,19 @@ class ClientHello(HandshakeMsg):
                         if extLength:
                             raise SyntaxError()
                         self.support_signed_cert_timestamps = True
+                    elif extType == ExtensionType.status_request:
+                        # Extension contents are currently ignored.
+                        # According to RFC 6066, this is not strictly forbidden
+                        # (although it is suboptimal):
+                        # Servers that receive a client hello containing the
+                        # "status_request" extension MAY return a suitable
+                        # certificate status response to the client along with
+                        # their certificate.  If OCSP is requested, they
+                        # SHOULD use the information contained in the extension
+                        # when selecting an OCSP responder and SHOULD include
+                        # request_extensions in the OCSP request.
+                        p.getFixBytes(extLength)
+                        self.status_request = True
                     else:
                         p.getFixBytes(extLength)
                     soFar += 4 + extLength
@@ -230,6 +244,7 @@ class ServerHello(HandshakeMsg):
         self.compression_method = 0
         self.channel_id = False
         self.signed_cert_timestamps = None
+        self.status_request = False
 
     def create(self, version, random, session_id, cipher_suite,
                certificate_type):
@@ -282,6 +297,9 @@ class ServerHello(HandshakeMsg):
         if self.signed_cert_timestamps:
             extLength += 4 + len(self.signed_cert_timestamps)
 
+        if self.status_request:
+            extLength += 4
+
         if extLength != 0:
             w.add(extLength, 2)
 
@@ -299,6 +317,10 @@ class ServerHello(HandshakeMsg):
             w.add(ExtensionType.signed_cert_timestamps, 2)
             w.addVarSeq(stringToBytes(self.signed_cert_timestamps), 1, 2)
 
+        if self.status_request:
+            w.add(ExtensionType.status_request, 2)
+            w.add(0, 2)
+
         return HandshakeMsg.postWrite(self, w, trial)
 
 class Certificate(HandshakeMsg):
@@ -367,6 +389,37 @@ class Certificate(HandshakeMsg):
             raise AssertionError()
         return HandshakeMsg.postWrite(self, w, trial)
 
+class CertificateStatus(HandshakeMsg):
+    def __init__(self):
+        self.contentType = ContentType.handshake
+
+    def create(self, ocsp_response):
+        self.ocsp_response = ocsp_response
+        return self
+
+    # Defined for the sake of completeness, even though we currently only
+    # support sending the status message (server-side), not requesting
+    # or receiving it (client-side).
+    def parse(self, p):
+        p.startLengthCheck(3)
+        status_type = p.get(1)
+        # Only one type is specified, so hardwire it.
+        if status_type != CertificateStatusType.ocsp:
+            raise SyntaxError()
+        ocsp_response = p.getVarBytes(3)
+        if not ocsp_response:
+            # Can't be empty
+            raise SyntaxError()
+        self.ocsp_response = ocsp_response
+        return self
+
+    def write(self, trial=False):
+        w = HandshakeMsg.preWrite(self, HandshakeType.certificate_status,
+                                  trial)
+        w.add(CertificateStatusType.ocsp, 1)
+        w.addVarSeq(stringToBytes(self.ocsp_response), 1, 3)
+        return HandshakeMsg.postWrite(self, w, trial)
+
 class CertificateRequest(HandshakeMsg):
     def __init__(self):
         self.contentType = ContentType.handshake