Enabling upstream server verification. Added flags --verify_upstream_cert,

--upstream-trusted-cadir, and --upstream-trusted-ca.

libmproxy/proxy/config.py

@@ -52,6 +52,9 @@ class ProxyConfig:
             ssl_version_server=tcp.SSL_DEFAULT_METHOD,
             ssl_ports=TRANSPARENT_SSL_PORTS,
             spoofed_ssl_port=None,
+            ssl_verify_upstream_cert=False,
+            ssl_upstream_trusted_cadir=None,
+            ssl_upstream_trusted_ca=None
     ):
         self.host = host
         self.port = port
@@ -100,6 +103,13 @@ class ProxyConfig:
             self.openssl_method_server = ssl_version_server
         else:
             self.openssl_method_server = tcp.SSL_VERSIONS[ssl_version_server]
+        
+        if ssl_verify_upstream_cert:
+            self.openssl_verification_mode_server = SSL.VERIFY_PEER
+        else:
+            self.openssl_verification_mode_server = SSL.VERIFY_NONE
+        self.openssl_trusted_cadir_server = ssl_upstream_trusted_cadir
+        self.openssl_trusted_ca_server = ssl_upstream_trusted_ca
 
         self.openssl_options_client = tcp.SSL_DEFAULT_OPTIONS
         self.openssl_options_server = tcp.SSL_DEFAULT_OPTIONS
@@ -203,7 +213,10 @@ def process_proxy_options(parser, options):
         ssl_version_client=options.ssl_version_client,
         ssl_version_server=options.ssl_version_server,
         ssl_ports=ssl_ports,
-        spoofed_ssl_port=spoofed_ssl_port
+        spoofed_ssl_port=spoofed_ssl_port,
+        ssl_verify_upstream_cert=options.ssl_verify_upstream_cert,
+        ssl_upstream_trusted_cadir=options.ssl_upstream_trusted_cadir,
+        ssl_upstream_trusted_ca=options.ssl_upstream_trusted_ca
     )
 
 
@@ -242,6 +255,23 @@ def ssl_option_group(parser):
         action="store_true", dest="no_upstream_cert",
         help="Don't connect to upstream server to look up certificate details."
     )
+    group.add_argument(
+        "--verify-upstream-cert", default=False,
+        action="store_true", dest="ssl_verify_upstream_cert",
+        help="Verify upstream server SSL/TLS certificates and fail if invalid "
+             "or not present."
+    )
+    group.add_argument(
+        "--upstream-trusted-cadir", default=None, action="store",
+        dest="ssl_upstream_trusted_cadir",
+        help="Path to a directory of trusted CA certificates for upstream "
+             "server verification prepared using the c_rehash tool."
+    )
+    group.add_argument(
+        "--upstream-trusted-ca", default=None, action="store",
+        dest="ssl_upstream_trusted_ca",
+        help="Path to a PEM formatted trusted CA certificate."
+    )
     group.add_argument(
         "--ssl-port",
         action="append",

libmproxy/proxy/server.py

@@ -235,8 +235,18 @@ class ConnectionHandler:
                     sni,
                     method=self.config.openssl_method_server,
                     options=self.config.openssl_options_server,
+                    verify_options=self.config.openssl_verification_mode_server,
+                    ca_path=self.config.openssl_trusted_cadir_server,
+                    ca_pemfile=self.config.openssl_trusted_ca_server,
                     cipher_list=self.config.ciphers_server,
                 )
+                ssl_cert_err = self.server_conn.ssl_verification_error
+                if ssl_cert_err is not None:
+                    self.log(
+                        "SSL verification failed for upstream server at depth %s with error: %s" % 
+                            (ssl_cert_err['depth'], ssl_cert_err['errno']),
+                        "error")
+                    self.log("Ignoring server verification error, continuing with connection", "error")
             except tcp.NetLibError as v:
                 e = ProxyError(502, repr(v))
                 # Workaround for https://github.com/mitmproxy/mitmproxy/issues/427
@@ -246,6 +256,13 @@ class ConnectionHandler:
                 if client and "handshake failure" in e.message:
                     self.server_conn.may_require_sni = e
                 else:
+                    ssl_cert_err = self.server_conn.ssl_verification_error
+                    if ssl_cert_err is not None:
+                        self.log(
+                            "SSL verification failed for upstream server at depth %s with error: %s" % 
+                                (ssl_cert_err['depth'], ssl_cert_err['errno']),
+                            "error")
+                        self.log("Aborting connection attempt", "error")
                     raise e
         if client:
             if self.client_conn.ssl_established:

test/data/trusted-cadir/8117bdb9.0

@@ -0,0 +1 @@
+trusted-ca.pem

test/data/trusted-cadir/9d45e6a9.0

@@ -0,0 +1 @@
+trusted-ca.pem

test/data/trusted-cadir/trusted-ca.pem

@@ -0,0 +1,14 @@
+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----

test/data/trusted-server.crt

@@ -0,0 +1,33 @@
+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----
+-----BEGIN RSA PRIVATE KEY-----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+-----END RSA PRIVATE KEY-----

test/data/untrusted-server.crt

@@ -0,0 +1,32 @@
+# untrusted-interm.crt, self-signed
+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----
+-----BEGIN RSA PRIVATE KEY-----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+-----END RSA PRIVATE KEY-----

test/test_proxy.py

@@ -9,6 +9,8 @@ from libpathod import test
 from netlib import http, tcp
 import mock
 
+from OpenSSL import SSL
+
 
 def test_proxy_error():
     p = ProxyError(111, "msg")
@@ -133,6 +135,20 @@ class TestProcessProxyOptions:
             "--singleuser",
             "test")
 
+    def test_verify_upstream_cert(self):
+        p = self.assert_noerr("--verify-upstream-cert")
+        assert p.openssl_verification_mode_server == SSL.VERIFY_PEER
+
+    def test_upstream_trusted_cadir(self):
+        expected_dir = "/path/to/a/ca/dir"
+        p = self.assert_noerr("--upstream-trusted-cadir", expected_dir)
+        assert p.openssl_trusted_cadir_server == expected_dir
+
+    def test_upstream_trusted_ca(self):
+        expected_file = "/path/to/a/cert/file"
+        p = self.assert_noerr("--upstream-trusted-ca", expected_file)
+        assert p.openssl_trusted_ca_server == expected_file
+
 
 class TestProxyServer:
     # binding to 0.0.0.0:1 works without special permissions on Windows

test/test_server.py

@@ -9,6 +9,7 @@ import tutils
 import tservers
 from libmproxy.protocol import KILL, Error
 from libmproxy.protocol.http import CONTENT_MISSING
+from OpenSSL import SSL
 
 """
     Note that the choice of response code in these tests matters more than you
@@ -348,6 +349,65 @@ class TestHTTPSCertfile(tservers.HTTPProxTest, CommonMixin):
         assert self.pathod("304")
 
 
+class TestHTTPSUpstreamServerVerificationWTrustedCert(tservers.HTTPProxTest):
+    """
+    Test upstream server certificate verification with a trusted server cert.
+    """
+    ssl = True
+    ssloptions = pathod.SSLOptions(
+        cn = "trusted-cert",
+        certs = [
+            ("trusted-cert", tutils.test_data.path("data/trusted-server.crt"))
+        ])
+
+    def test_verification_w_cadir(self):
+        self.config.openssl_verification_mode_server = SSL.VERIFY_PEER
+        self.config.openssl_trusted_cadir_server = tutils.test_data.path(
+            "data/trusted-cadir/")
+        
+        self.pathoc()
+
+    def test_verification_w_pemfile(self):
+        self.config.openssl_verification_mode_server = SSL.VERIFY_PEER
+        self.config.openssl_trusted_ca_server = tutils.test_data.path(
+            "data/trusted-cadir/trusted-ca.pem")
+
+        self.pathoc()
+
+
+class TestHTTPSUpstreamServerVerificationWBadCert(tservers.HTTPProxTest):
+    """
+    Test upstream server certificate verification with an untrusted server cert.
+    """
+    ssl = True
+    ssloptions = pathod.SSLOptions(
+        cn = "untrusted-cert",
+        certs = [
+             ("untrusted-cert", tutils.test_data.path("data/untrusted-server.crt"))
+        ])
+
+    def test_default_verification_w_bad_cert(self):
+        """Should use no verification."""
+        self.config.openssl_trusted_ca_server = tutils.test_data.path(
+            "data/trusted-cadir/trusted-ca.pem")
+
+        self.pathoc()
+
+    def test_no_verification_w_bad_cert(self):
+        self.config.openssl_verification_mode_server = SSL.VERIFY_NONE
+        self.config.openssl_trusted_ca_server = tutils.test_data.path(
+            "data/trusted-cadir/trusted-ca.pem")
+
+        self.pathoc()
+
+    def test_verification_w_bad_cert(self):
+        self.config.openssl_verification_mode_server = SSL.VERIFY_PEER
+        self.config.openssl_trusted_ca_server = tutils.test_data.path(
+            "data/trusted-cadir/trusted-ca.pem")
+
+        tutils.raises("SSL handshake error", self.pathoc)
+
+
 class TestHTTPSNoCommonName(tservers.HTTPProxTest):
     """
     Test what happens if we get a cert without common name back.