x509: use SKI and AKI to find parent certificate if it is missing

lib/paymentrequest.py

@@ -44,7 +44,7 @@ REQUEST_HEADERS = {'Accept': 'application/bitcoin-paymentrequest', 'User-Agent':
 ACK_HEADERS = {'Content-Type':'application/bitcoin-payment','Accept':'application/bitcoin-paymentack','User-Agent':'Electrum'}
 
 ca_path = requests.certs.where()
-ca_list = x509.load_certificates(ca_path)
+ca_list, ca_keyID = x509.load_certificates(ca_path)
 
 
 # status of payment requests
@@ -142,15 +142,17 @@ class PaymentRequest:
             return False
         # if the root CA is not supplied, add it to the chain
         ca = x509_chain[cert_num-1]
-        if ca.get_common_name() not in ca_list:
-            x = ca_list.get(ca.get_issuer())
-            if x:
-                x509_chain.append(x)
+        if ca.getFingerprint() not in ca_list:
+            keyID = ca.get_issuer_keyID()
+            f = ca_keyID.get(keyID)
+            if f:
+                root = ca_list[f]
+                x509_chain.append(root)
             else:
                 self.error = "Supplied CA Not Found in Trusted CA Store."
                 return False
         # verify the chain of signatures
-        cert_num = len(cert.certificate)
+        cert_num = len(x509_chain)
         for i in range(1, cert_num):
             x = x509_chain[i]
             prev_x = x509_chain[i-1]

lib/x509.py

@@ -50,9 +50,6 @@ PREFIX_RSA_SHA512 = bytearray([0x30,0x51,0x30,0x0d,0x06,0x09,0x60,0x86,0x48,0x01
 class CertificateError(Exception):
     pass
 
-def decode_str(data):
-    encoding = 'utf-16-be' if isinstance(data, BMPString) else 'utf-8'
-    return bytes(data).decode(encoding)
 
 def decode_OID(s):
     s = map(ord, s)
@@ -69,33 +66,31 @@ def decode_OID(s):
     return '.'.join(map(str,r))
 
 
+def asn1_get_children(der, i):
+    nodes = []
+    ii = asn1_node_first_child(der,i)
+    nodes.append(ii)
+    while ii[2]<i[2]:
+        ii = asn1_node_next(der,ii)
+        nodes.append(ii)
+    return nodes
+
+def asn1_get_sequence(s):
+    return map(lambda j: asn1_get_value(s, j), asn1_get_children(s, asn1_node_root(s)))
+
+def asn1_get_dict(der, i):
+    p = {}
+    for ii in asn1_get_children(der, i):
+        for iii in asn1_get_children(der, ii):
+            iiii = asn1_node_first_child(der, iii)
+            oid = decode_OID(asn1_get_value_of_type(der, iiii, 'OBJECT IDENTIFIER'))
+            iiii = asn1_node_next(der, iiii)
+            value = asn1_get_value(der, iiii)
+            p[oid] = value
+    return p
+
 
 class X509(tlslite.X509):
-    """Child class of tlslite.X509 that uses pyasn1 to parse cert
-    information. Note: pyasn1 is a lot slower than tlslite, so we
-    should try to do everything in tlslite.
-    """
-
-    def get_children(self, der, i):
-        nodes = []
-        ii = asn1_node_first_child(der,i)
-        while True:
-            nodes.append(ii)
-            ii = asn1_node_next(der,ii)
-            if ii[0] > i[2]:
-                break
-        return nodes
-    
-    def get_dict(self, der, i):
-        p = {}
-        for ii in self.get_children(der, i):
-            for iii in self.get_children(der, ii):
-                iiii = asn1_node_first_child(der, iii)
-                oid = decode_OID(asn1_get_value_of_type(der, iiii, 'OBJECT IDENTIFIER'))
-                iiii = asn1_node_next(der, iiii)
-                value = asn1_get_value(der, iiii)
-                p[oid] = value
-        return p
 
     def parseBinary(self, b):
 
@@ -123,7 +118,7 @@ class X509(tlslite.X509):
 
         # issuer
         issuer = asn1_node_next(der, sig_algo)
-        self.issuer = self.get_dict(der, issuer)
+        self.issuer = asn1_get_dict(der, issuer)
 
         # validity
         validity = asn1_node_next(der, issuer)
@@ -134,26 +129,31 @@ class X509(tlslite.X509):
 
         # subject
         subject = asn1_node_next(der, validity)
-        self.subject = self.get_dict(der, subject)
+        self.subject = asn1_get_dict(der, subject)
         subject_pki = asn1_node_next(der, subject)
 
-        # optional fields: issuer_uid, subject_uid, extensions
-        i = subject_pki
+        # extensions
         self.CA = False
-        while True:
+        self.AKI = None
+        self.SKI = None
+        i = subject_pki
+        while i[2] < cert[2]:
             i = asn1_node_next(der, i)
-            if i[0] > cert[2]:
-                break
-            for ii in self.get_children(der, i):
-                for iii in self.get_children(der, ii):
-                    iiii = asn1_node_first_child(der, iii)
-                    oid = decode_OID(asn1_get_value_of_type(der, iiii, 'OBJECT IDENTIFIER'))
-                    iiii = asn1_node_next(der, iiii)
-                    value = asn1_get_value(der, iiii)
-                    if oid == '2.5.29.19':   # basic constraints
-                        self.CA = value
-                    else:
-                        pass
+            d = asn1_get_dict(der, i)
+            for oid, value in d.items():
+                if oid == '2.5.29.19':
+                    # Basic Constraints
+                    self.CA = bool(value)
+                elif oid == '2.5.29.14':
+                    # Subject Key Identifier
+                    r = asn1_node_root(value)
+                    value = asn1_get_value_of_type(value, r, 'OCTET STRING')
+                    self.SKI = value.encode('hex')
+                elif oid == '2.5.29.35':
+                    # Authority Key Identifier
+                    self.AKI = asn1_get_sequence(value)[0].encode('hex')
+                else:
+                    pass
 
         # cert signature
         cert_sig_algo = asn1_node_next(der, cert)
@@ -162,13 +162,16 @@ class X509(tlslite.X509):
         cert_sig = asn1_node_next(der, cert_sig_algo)
         self.signature = asn1_get_value(der, cert_sig)[1:]
         
+    def get_keyID(self):
+        # http://security.stackexchange.com/questions/72077/validating-an-ssl-certificate-chain-according-to-rfc-5280-am-i-understanding-th
+        return self.SKI if self.SKI else repr(self.subject)
+
+    def get_issuer_keyID(self):
+        return self.AKI if self.AKI else repr(self.issuer)
 
     def get_common_name(self):
         return self.subject.get('2.5.4.3', 'unknown')
 
-    def get_issuer(self):
-        return self.issuer.get('2.5.4.3', 'unknown')
-
     def get_signature(self):
         return self.cert_sig_algo, self.signature, self.data
 
@@ -198,6 +201,7 @@ class X509CertChain(tlslite.X509CertChain):
 @profiler
 def load_certificates(ca_path):
     ca_list = {}
+    ca_keyID = {}
     with open(ca_path, 'r') as f:
         s = f.read()
     bList = tlslite.utils.pem.dePemList(s, "CERTIFICATE")
@@ -206,10 +210,12 @@ def load_certificates(ca_path):
         try:
             x.parseBinary(b)
             x.check_date()
-        except Exception as e:
+        except BaseException as e:
             util.print_error("cert error:", e)
             continue
-        ca_list[x.get_common_name()] = x
 
+        fp = x.getFingerprint()
+        ca_list[fp] = x
+        ca_keyID[x.get_keyID()] = fp
 
-    return ca_list
+    return ca_list, ca_keyID