Adding sni_challenge verification

ca/sni_challenge/make.sh

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+#!/bin/bash
+#Quick script to compile/load sni_support
+#Will change to something more appropriate in the future
+
+#Modify python path
+
+swig -python sni_support.i
+gcc -fpic -I/home/james/virtualenvs/chocolate/include/python2.7 -c sni_support_wrap.c sni_support.c
+gcc -shared sni_support_wrap.o sni_support.o -o _sni_support.so 

ca/sni_challenge/sni_support.c

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+#include <openssl/ssl.h>
+#include <openssl/x509v3.h>
+#include <openssl/objects.h>
+#include "sni_support.h"
+
+void set_sni_ext(SSL *ctx, char *servername) {
+  SSL_set_tlsext_host_name(ctx, servername);
+}
+
+int get_nid(X509_EXTENSION *ext) {
+  return OBJ_obj2nid(X509_EXTENSION_get_object(ext));
+}
+
+binary_data_t get_unknown_value(X509_EXTENSION *ext) {
+  binary_data_t result;
+  result.size = ext->value->length;
+  result.data = (unsigned char *)ext->value->data;
+  return result;
+} 

ca/sni_challenge/sni_support.h

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+#ifndef SNI_SUPPORT_H
+#define SNI_SUPPORT_H
+
+typedef struct binary_data {
+  int size;
+  unsigned char* data;
+} binary_data_t;
+
+void set_sni_ext(SSL *ctx, char *servername);
+int get_nid(X509_EXTENSION *ext);
+binary_data_t get_unknown_value(X509_EXTENSION *ext);
+
+#endif

ca/sni_challenge/sni_support.i

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+%module sni_support
+%{
+  #include <openssl/ssl.h>
+  #include <openssl/x509v3.h>
+  #include "sni_support.h"
+%}
+
+%typemap(out) binary_data_t {
+    $result = PyString_FromStringAndSize($1.data,$1.size);
+}
+
+%include "sni_support.h"
+

ca/sni_challenge/verify_sni_challenge.py

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+import M2Crypto
+import sni_support
+import hmac
+import hashlib
+
+S_SIZE = 20
+
+def check(one, two, three, four, five):
+    print "done"
+    return 0
+
+def byteToHex(byteStr):
+    return ''.join(["%02X" % ord(x) for x in byteStr]).strip()
+
+def check_challenge_value(ext_value, sharedSecret):
+    s = ext_value[0:S_SIZE]
+    mac = ext_value[S_SIZE:]
+    expected_mac = hmac.new(sharedSecret, str(s), hashlib.sha256).digest()
+
+    #print "s: ", byteToHex(s)
+    #print "mac: ", byteToHex(mac)
+    #print "expected_mac: ", byteToHex(expected_mac)
+    #print type(mac)
+    #print type(expected_mac)
+
+    if mac == expected_mac:
+        return True
+    return False 
+
+def verify_challenge(address, sharedSecret, encryptedValue):
+    sni_name = byteToHex(encryptedValue[0]) + ".com"
+
+    context = M2Crypto.SSL.Context()
+    context.set_allow_unknown_ca(True)
+    context.set_verify(M2Crypto.SSL.verify_none, 4)
+
+    conn = M2Crypto.SSL.Connection(context)
+    sni_support.set_sni_ext(conn.ssl, sni_name)
+    conn.connect((address, 443))
+
+    cert_chain = conn.get_peer_cert_chain()
+    
+    #Ensure certificate chain form is correct
+    if len(cert_chain) != 1:
+        return False, "Incorrect number of certificates in chain"
+
+    for i in range(0,cert_chain[0].get_ext_count()):
+        ext = cert_chain[0].get_ext_at(i)
+
+        if sni_support.get_nid(ext.x509_ext) == 0:
+
+            valid = check_challenge_value(sni_support.get_unknown_value(ext.x509_ext), sharedSecret)
+            if valid:
+                return True, "Challenge completed successfully"
+            else:
+                return False, "Certificate extension does not check out"
+
+
+def main():
+    #Testing the example sni_challenge
+    from Crypto.PublicKey import RSA
+
+    testkey = RSA.importKey(open("/home/james/Documents/apache_choc/testing.key").read())
+
+    #the second parameter is ignored
+    #https://www.dlitz.net/software/pycrypto/api/current/
+    encryptedValue = testkey.encrypt('0x12345678', 0)
+    valid, response = verify_challenge("127.0.0.1", '0x12345678', encryptedValue)
+    print response
+
+if __name__ == "__main__":
+    main()