verify payment requests with tlslite and pyasn1 (pure python) instead of m2Crypto

lib/paymentrequest.py

@@ -1,3 +1,22 @@
+#!/usr/bin/env python
+#
+# Electrum - lightweight Bitcoin client
+# Copyright (C) 2014 Thomas Voegtlin
+#
+# This program 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.
+#
+# This program 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 this program. If not, see <http://www.gnu.org/licenses/>.
+
+
 import hashlib
 import httplib
 import os.path
@@ -24,6 +43,7 @@ except ImportError:
 import bitcoin
 import util
 import transaction
+import x509
 
 
 REQUEST_HEADERS = {'Accept': 'application/bitcoin-paymentrequest', 'User-Agent': 'Electrum'}
@@ -39,12 +59,10 @@ PR_ERROR   = 4     # could not parse
 
 ca_list = {}
 
+
+
+
 def load_certificates():
-    try:
-        from M2Crypto import X509
-    except:
-        print_error("ERROR: Could not import M2Crypto")
-        return False
 
     ca_path = os.path.expanduser("~/.electrum/ca/ca-bundle.crt")
     try:
@@ -62,14 +80,20 @@ def load_certificates():
         else:
             c += line
         if line == "-----END CERTIFICATE-----\n":
-            x = X509.load_cert_string(c)
-            ca_list[x.get_fingerprint()] = x
+            x = x509.X509()
+            try:
+                x.parse(c)
+            except Exception as e:
+                print "cannot parse cert:", e
+            ca_list[x.getFingerprint()] = x
     ca_f.close()
+    util.print_error("%d certificates"%len(ca_list))
     return True
 
 load_certificates()
 
 
+
 class PaymentRequest:
     def __init__(self, config):
         self.config = config
@@ -130,19 +154,13 @@ class PaymentRequest:
 
 
     def verify(self):
-        try:
-            from M2Crypto import X509
-        except:
-            self.error = "cannot import M2Crypto"
-            return False
 
         if not ca_list:
             self.error = "Trusted certificate authorities list not found"
             return False
 
         paymntreq = self.data
-        sig = paymntreq.signature
-        if not sig:
+        if not paymntreq.signature:
             self.error = "No signature"
             return 
 
@@ -150,86 +168,79 @@ class PaymentRequest:
         cert.ParseFromString(paymntreq.pki_data)
         cert_num = len(cert.certificate)
 
-        x509_1 = X509.load_cert_der_string(cert.certificate[0])
-        if self.domain != x509_1.get_subject().CN:
-            validcert = False
-            try:
-                SANs = x509_1.get_ext("subjectAltName").get_value().split(",")
-                for s in SANs:
-                    s = s.strip()
-                    if s.startswith("DNS:") and s[4:] == self.domain:
-                        validcert = True
-                        print "Match SAN DNS"
-                    elif s.startswith("IP:") and s[3:] == self.domain:
-                        validcert = True
-                        print "Match SAN IP"
-                    elif s.startswith("email:") and s[6:] == self.domain:
-                        validcert = True
-                        print "Match SAN email"
-            except Exception, e:
-                print "ERROR: No SAN data"
-            if not validcert:
-                ###TODO: check for wildcards
-                self.error = "ERROR: Certificate Subject Domain Mismatch and SAN Mismatch"
-                return
-
-        x509 = []
-        CA_OU = ''
-
-        if cert_num > 1:
-            for i in range(cert_num - 1):
-                x509.append(X509.load_cert_der_string(cert.certificate[i+1]))
-                if x509[i].check_ca() == 0:
+        x509_chain = []
+        for i in range(cert_num):
+            x = x509.X509()
+            x.parseBinary(bytearray(cert.certificate[i]))
+            x.slow_parse()
+            x509_chain.append(x)
+            if i == 0:
+                if not x.check_name(self.domain):
+                    self.error = "Certificate Domain Mismatch"
+                    return
+            else:
+                if not x.check_ca():
                     self.error = "ERROR: Supplied CA Certificate Error"
                     return
-            for i in range(cert_num - 1):
-                if i == 0:
-                    if x509_1.verify(x509[i].get_pubkey()) != 1:
-                        self.error = "ERROR: Certificate not Signed by Provided CA Certificate Chain"
-                        return
-                else:
-                    if x509[i-1].verify(x509[i].get_pubkey()) != 1:
-                        self.error = "ERROR: CA Certificate not Signed by Provided CA Certificate Chain"
-                        return
-
-            supplied_CA_fingerprint = x509[cert_num-2].get_fingerprint()
-            supplied_CA_CN = x509[cert_num-2].get_subject().CN
-            CA_match = False
 
-            x = ca_list.get(supplied_CA_fingerprint)
-            if x:
-                CA_OU = x.get_subject().OU
-                CA_match = True
-                if x.get_subject().CN != supplied_CA_CN:
-                    print "ERROR: Trusted CA CN Mismatch; however CA has trusted fingerprint"
-                    print "Payment will continue with manual verification."
-            else:
-                print "ERROR: Supplied CA Not Found in Trusted CA Store."
-                print "Payment will continue with manual verification."
-        else:
+        if not cert_num > 1:
             self.error = "ERROR: CA Certificate Chain Not Provided by Payment Processor"
             return False
 
+        for i in range(1, cert_num):
+            x = x509_chain[i]
+            prev_x = x509_chain[i-1]
+
+            algo, sig, data = prev_x.extract_sig()
+            if algo.getComponentByName('algorithm') != x509.ALGO_RSA_SHA1:
+                self.error = "Algorithm not suported"
+                return
+
+            sig = bytearray(sig[5:])
+            pubkey = x.publicKey
+            verify = pubkey.hashAndVerify(sig, data)
+            if not verify:
+                self.error = "Certificate not Signed by Provided CA Certificate Chain"
+                return
+
+        ca = x509_chain[cert_num-1]
+        supplied_CA_fingerprint = ca.getFingerprint()
+        supplied_CA_names = ca.extract_names()
+        CA_OU = supplied_CA_names['OU']
+
+        x = ca_list.get(supplied_CA_fingerprint)
+        if x:
+            x.slow_parse()
+            names = x.extract_names()
+            CA_match = True
+            if names['CN'] != supplied_CA_names['CN']:
+                print "ERROR: Trusted CA CN Mismatch; however CA has trusted fingerprint"
+                print "Payment will continue with manual verification."
+        else:
+            CA_match = False
+
+        pubkey0 = x509_chain[0].publicKey
+        sig = paymntreq.signature
         paymntreq.signature = ''
         s = paymntreq.SerializeToString()
-        pubkey_1 = x509_1.get_pubkey()
+        sigBytes = bytearray(sig)
+        msgBytes = bytearray(s)
 
         if paymntreq.pki_type == "x509+sha256":
-            pubkey_1.reset_context(md="sha256")
+            hashBytes = bytearray(hashlib.sha256(msgBytes).digest())
+            prefixBytes = bytearray([0x30,0x31,0x30,0x0d,0x06,0x09,0x60,0x86,0x48,0x01,0x65,0x03,0x04,0x02,0x01,0x05,0x00,0x04,0x20])
+            verify = pubkey0.verify(sigBytes, prefixBytes + hashBytes)
         elif paymntreq.pki_type == "x509+sha1":
-            pubkey_1.reset_context(md="sha1")
+            verify = pubkey0.hashAndVerify(sigBytes, msgBytes)
         else:
             self.error = "ERROR: Unsupported PKI Type for Message Signature"
             return False
 
-        pubkey_1.verify_init()
-        pubkey_1.verify_update(s)
-        if pubkey_1.verify_final(sig) != 1:
+        if not verify:
             self.error = "ERROR: Invalid Signature for Payment Request Data"
             return False
 
         ### SIG Verified
-
         self.details = pay_det = paymentrequest_pb2.PaymentDetails()
         self.details.ParseFromString(paymntreq.serialized_payment_details)
 
@@ -241,6 +252,8 @@ class PaymentRequest:
 
         if CA_match:
             self.status = 'Signed by Trusted CA:\n' + CA_OU
+        else:
+            self.status = "Supplied CA Not Found in Trusted CA Store."
 
         self.payment_url = self.details.payment_url
 

lib/x509.py

@@ -0,0 +1,214 @@
+#!/usr/bin/env python
+#
+# Electrum - lightweight Bitcoin client
+# Copyright (C) 2014 Thomas Voegtlin
+#
+# This program 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.
+#
+# This program 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 this program. If not, see <http://www.gnu.org/licenses/>.
+
+
+from datetime import datetime, timedelta
+
+try:
+    import pyasn1
+except ImportError:
+    sys.exit("Error: pyasn1 does not seem to be installed. Try 'sudo pip install pyasn1'")
+
+try:
+    import tlslite
+except ImportError:
+    sys.exit("Error: tlslite does not seem to be installed. Try 'sudo pip install tlslite'")
+
+
+
+from pyasn1.codec.der import decoder, encoder
+from pyasn1.type.univ import Any, ObjectIdentifier, OctetString
+from pyasn1.type.char import BMPString, IA5String, UTF8String
+from pyasn1.type.useful import GeneralizedTime
+from pyasn1_modules.rfc2459 import (Certificate, DirectoryString,
+                                    SubjectAltName, GeneralNames,
+                                    GeneralName)
+from pyasn1_modules.rfc2459 import id_ce_subjectAltName as SUBJECT_ALT_NAME
+from pyasn1_modules.rfc2459 import id_at_commonName as COMMON_NAME
+from pyasn1_modules.rfc2459 import id_at_organizationalUnitName as OU_NAME
+from pyasn1_modules.rfc2459 import id_ce_basicConstraints, BasicConstraints
+XMPP_ADDR = ObjectIdentifier('1.3.6.1.5.5.7.8.5')
+SRV_NAME = ObjectIdentifier('1.3.6.1.5.5.7.8.7')
+ALGO_RSA_SHA1 = ObjectIdentifier('1.2.840.113549.1.1.5')
+
+
+class CertificateError(Exception):
+    pass
+
+def decode_str(data):
+    encoding = 'utf-16-be' if isinstance(data, BMPString) else 'utf-8'
+    return bytes(data).decode(encoding)
+
+
+class X509(tlslite.X509):
+    """ Child class of tlslite.X509 that uses pyasn1 """
+
+    def slow_parse(self):
+        self.cert = decoder.decode(str(self.bytes), asn1Spec=Certificate())[0]
+        self.tbs = self.cert.getComponentByName('tbsCertificate')
+        self.subject = self.tbs.getComponentByName('subject')
+        self.extensions = self.tbs.getComponentByName('extensions') or []
+
+    def extract_names(self):
+        results = {'CN': None,
+                   'DNS': set(),
+                   'SRV': set(),
+                   'URI': set(),
+                   'XMPPAddr': set(), 
+                   'OU': None,}
+  
+        # Extract the CommonName(s) from the cert.
+        for rdnss in self.subject:
+            for rdns in rdnss:
+                for name in rdns:
+                    oid = name.getComponentByName('type')
+                    value = name.getComponentByName('value')
+  
+                    if oid == COMMON_NAME:
+                        value = decoder.decode(value, asn1Spec=DirectoryString())[0]
+                        value = decode_str(value.getComponent())
+                        results['CN'] = value
+
+                    elif oid == OU_NAME:
+                        value = decoder.decode(value, asn1Spec=DirectoryString())[0]
+                        value = decode_str(value.getComponent())
+                        results['OU'] = value
+
+        # Extract the Subject Alternate Names (DNS, SRV, URI, XMPPAddr)
+        for extension in self.extensions:
+            oid = extension.getComponentByName('extnID')
+            if oid != SUBJECT_ALT_NAME:
+                continue
+  
+            value = decoder.decode(extension.getComponentByName('extnValue'),
+                               asn1Spec=OctetString())[0]
+            sa_names = decoder.decode(value, asn1Spec=SubjectAltName())[0]
+            for name in sa_names:
+                name_type = name.getName()
+                if name_type == 'dNSName':
+                    results['DNS'].add(decode_str(name.getComponent()))
+                if name_type == 'uniformResourceIdentifier':
+                    value = decode_str(name.getComponent())
+                    if value.startswith('xmpp:'):
+                        results['URI'].add(value[5:])
+                elif name_type == 'otherName':
+                    name = name.getComponent()
+  
+                    oid = name.getComponentByName('type-id')
+                    value = name.getComponentByName('value')
+  
+                    if oid == XMPP_ADDR:
+                        value = decoder.decode(value, asn1Spec=UTF8String())[0]
+                        results['XMPPAddr'].add(decode_str(value))
+                    elif oid == SRV_NAME:
+                        value = decoder.decode(value, asn1Spec=IA5String())[0]
+                        results['SRV'].add(decode_str(value))
+        return results
+
+
+    def check_ca(self):
+        for extension in self.extensions:
+            oid = extension.getComponentByName('extnID')
+            if oid != id_ce_basicConstraints:
+                continue
+            value = decoder.decode(extension.getComponentByName('extnValue'),
+                               asn1Spec=OctetString())[0]
+            constraints = decoder.decode(value, asn1Spec=BasicConstraints())[0]
+            return bool(constraints[0])
+
+    def extract_sig(self):
+        signature = self.cert.getComponentByName('signatureValue')
+        algorithm = self.cert.getComponentByName('signatureAlgorithm')
+        data = encoder.encode(self.tbs)
+        s = encoder.encode(signature)
+        return algorithm, s, data
+
+
+    def extract_pubkey(self):
+        pki = self.tbs.getComponentByName('subjectPublicKeyInfo')
+        algo = pki.getComponentByName('algorithm')
+        algorithm = algo.getComponentByName('algorithm')
+        parameters = algo.getComponentByName('parameters')
+        subjectPublicKey = pki.getComponentByName('subjectPublicKey')
+        return algorithm, parameters, encoder.encode(subjectPublicKey)
+
+
+    def extract_dates(self):
+        validity = self.tbs.getComponentByName('validity')
+        not_before = validity.getComponentByName('notBefore')
+        not_before = str(not_before.getComponent())
+        not_after = validity.getComponentByName('notAfter')
+        not_after = str(not_after.getComponent())
+        if isinstance(not_before, GeneralizedTime):
+            not_before = datetime.strptime(not_before, '%Y%m%d%H%M%SZ')
+        else:
+            not_before = datetime.strptime(not_before, '%y%m%d%H%M%SZ')
+        if isinstance(not_after, GeneralizedTime):
+            not_after = datetime.strptime(not_after, '%Y%m%d%H%M%SZ')
+        else:
+            not_after = datetime.strptime(not_after, '%y%m%d%H%M%SZ')
+        return not_before, not_after
+
+    def get_ttl(self):
+        not_before, not_after = self.extract_dates()
+        if not_after is None:
+            return None
+        return not_after - datetime.utcnow()
+
+    def check_name(self, expected):
+        not_before, not_after = self.extract_dates()
+        cert_names = self.extract_names()
+        now = datetime.utcnow()
+        if not_before > now:
+            raise CertificateError(
+                'Certificate has not entered its valid date range.')
+        if not_after <= now:
+            raise CertificateError(
+                'Certificate has expired.')
+        if '.' in expected:
+            expected_wild = expected[expected.index('.'):]
+        else:
+            expected_wild = expected
+        expected_srv = '_xmpp-client.%s' % expected
+        for name in cert_names['XMPPAddr']:
+            if name == expected:
+                return True
+        for name in cert_names['SRV']:
+            if name == expected_srv or name == expected:
+                return True
+        for name in cert_names['DNS']:
+            if name == expected:
+                return True
+            if name.startswith('*'):
+                if '.' in name:
+                    name_wild = name[name.index('.'):]
+                else:
+                    name_wild = name
+                if expected_wild == name_wild:
+                    return True
+        for name in cert_names['URI']:
+            if name == expected:
+                return True
+        if cert_names['CN'] == expected:
+            return True
+        raise CertificateError(
+            'Could not match certficate against hostname: %s' % expected)
+
+
+class X509CertChain(tlslite.X509CertChain):
+    pass