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+/*
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+ * Copyright (c) 2014, Psiphon Inc.
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+ * All rights reserved.
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+ *
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+ * This program is free software: you can redistribute it and/or modify
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+ * it under the terms of the GNU General Public License as published by
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+ * the Free Software Foundation, either version 3 of the License, or
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+ * (at your option) any later version.
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+ *
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+ * This program is distributed in the hope that it will be useful,
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+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
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+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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+ * GNU General Public License for more details.
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+ *
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+ * You should have received a copy of the GNU General Public License
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+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
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+ *
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+ */
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+
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+/*
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+Copyright (c) 2012 The Go Authors. All rights reserved.
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+
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+Redistribution and use in source and binary forms, with or without
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+modification, are permitted provided that the following conditions are
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+met:
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+
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+ * Redistributions of source code must retain the above copyright
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+notice, this list of conditions and the following disclaimer.
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+ * Redistributions in binary form must reproduce the above
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+copyright notice, this list of conditions and the following disclaimer
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+in the documentation and/or other materials provided with the
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+distribution.
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+ * Neither the name of Google Inc. nor the names of its
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+contributors may be used to endorse or promote products derived from
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+this software without specific prior written permission.
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+
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+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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+*/
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+
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+// Fork of https://github.com/getlantern/tlsdialer (http://gopkg.in/getlantern/tlsdialer.v1)
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+// which itself is a "Fork of crypto/tls.Dial and DialWithDialer"
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+
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+// Adds two capabilities to tlsdialer:
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+//
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+// 1. HTTP proxy support, so the dialer may be used with http.Transport.
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+//
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+// 2. Support for self-signed Psiphon server certificates, which Go's certificate
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+// verification rejects due to two short comings:
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+// - lack of IP address SANs.
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+// see: "...because it doesn't contain any IP SANs" case in crypto/x509/verify.go
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+// - non-compliant constraint configuration (RFC 5280, 4.2.1.9).
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+// see: CheckSignatureFrom() in crypto/x509/x509.go
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+// Since the client has to be able to handle existing Psiphon server certificates,
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+// we need to be able to perform some form of verification in these cases.
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+
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+// tlsdialer:
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+// package tlsdialer contains a customized version of crypto/tls.Dial that
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+// allows control over whether or not to send the ServerName extension in the
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+// client handshake.
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+
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+package psiphon
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+
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+import (
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+ "bytes"
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+ "crypto/tls"
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+ "crypto/x509"
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+ "errors"
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+ "fmt"
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+ "io"
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+ "log"
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+ "net"
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+ "strings"
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+ "time"
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+)
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+
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+type timeoutError struct{}
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+
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+func (timeoutError) Error() string { return "tls: DialWithDialer timed out" }
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+func (timeoutError) Timeout() bool { return true }
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+func (timeoutError) Temporary() bool { return true }
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+
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+// CustomTLSConfig contains parameters to determine the behavior
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+// of CustomTLSDial.
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+// httpProxyAddress - use the specified HTTP proxy (HTTP CONNECT) if not blank
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+// sendServerName - use SNI (tlsdialer functionality)
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+// verifyLegacyCertificate - special case self-signed server certificate
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+// case. Ignores IP SANs and basic constraints. No certificate chain. Just
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+// checks that the server presented the specified certificate.
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+// tlsConfig - a tls.Config use in the non-verifyLegacyCertificate case.
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+type CustomTLSConfig struct {
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+ httpProxyAddress string
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+ sendServerName bool
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+ verifyLegacyCertificate *x509.Certificate
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+ tlsConfig *tls.Config
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+}
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+
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+// tlsdialer:
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+// Like crypto/tls.Dial, but with the ability to control whether or not to
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+// send the ServerName extension in client handshakes through the sendServerName
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+// flag.
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+//
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+// Note - if sendServerName is false, the VerifiedChains field on the
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+// connection's ConnectionState will never get populated.
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+func CustomTLSDial(network, addr string, config *CustomTLSConfig) (*tls.Conn, error) {
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+ return CustomTLSDialWithDialer(new(net.Dialer), network, addr, config)
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+}
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+
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+// tlsdialer:
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+// Like crypto/tls.DialWithDialer, but with the ability to control whether or
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+// not to send the ServerName extension in client handshakes through the
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+// sendServerName flag.
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+//
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+// Note - if sendServerName is false, the VerifiedChains field on the
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+// connection's ConnectionState will never get populated.
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+func CustomTLSDialWithDialer(dialer *net.Dialer, network, addr string, config *CustomTLSConfig) (*tls.Conn, error) {
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+ // We want the Timeout and Deadline values from dialer to cover the
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+ // whole process: TCP connection and TLS handshake. This means that we
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+ // also need to start our own timers now.
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+ timeout := dialer.Timeout
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+
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+ if !dialer.Deadline.IsZero() {
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+ deadlineTimeout := dialer.Deadline.Sub(time.Now())
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+ if timeout == 0 || deadlineTimeout < timeout {
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+ timeout = deadlineTimeout
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+ }
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+ }
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+
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+ var errChannel chan error
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+
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+ if timeout != 0 {
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+ errChannel = make(chan error, 2)
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+ time.AfterFunc(timeout, func() {
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+ errChannel <- timeoutError{}
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+ })
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+ }
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+
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+ dialAddr := addr
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+ if config.httpProxyAddress != "" {
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+ dialAddr = config.httpProxyAddress
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+ }
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+
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+ rawConn, err := dialer.Dial(network, dialAddr)
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+ if err != nil {
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+ return nil, err
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+ }
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+
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+ colonPos := strings.LastIndex(addr, ":")
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+ if colonPos == -1 {
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+ colonPos = len(addr)
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+ }
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+ hostname := addr[:colonPos]
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+
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+ tlsConfig := config.tlsConfig
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+ if tlsConfig == nil {
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+ tlsConfig = &tls.Config{}
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+ }
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+
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+ serverName := tlsConfig.ServerName
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+
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+ // If no ServerName is set, infer the ServerName
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+ // from the hostname we're connecting to.
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+ if serverName == "" {
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+ serverName = hostname
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+ }
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+
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+ // copy config so we can tweak it
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+ tlsConfigCopy := new(tls.Config)
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+ *tlsConfigCopy = *tlsConfig
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+
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+ if config.sendServerName {
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+ // Set the ServerName and rely on the usual logic in
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+ // tls.Conn.Handshake() to do its verification
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+ tlsConfigCopy.ServerName = serverName
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+ } else {
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+ // Disable verification in tls.Conn.Handshake(). We'll verify manually
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+ // after handshaking
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+ tlsConfigCopy.InsecureSkipVerify = true
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+ }
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+
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+ conn := tls.Client(rawConn, tlsConfigCopy)
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+
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+ establishConnection := func(rawConn net.Conn, conn *tls.Conn) error {
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+ // TODO: use the proxy request/response code from net/http/transport.go
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+ if config.httpProxyAddress != "" {
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+ connectRequest := fmt.Sprintf(
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+ "CONNECT %s HTTP/1.1\r\nHost: %s\r\nConnection: Keep-Alive\r\n\r\n",
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+ addr, hostname)
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+ _, err := rawConn.Write([]byte(connectRequest))
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+ if err != nil {
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+ return err
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+ }
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+ expectedResponse := []byte("HTTP/1.1 200 OK\r\n\r\n")
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+ readBuffer := make([]byte, len(expectedResponse))
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+ _, err = io.ReadFull(rawConn, readBuffer)
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+ if err != nil {
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+ return err
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+ }
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+ if !bytes.Equal(readBuffer, expectedResponse) {
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+ return fmt.Errorf("unexpected HTTP proxy response: %s", string(readBuffer))
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+ }
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+ }
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+ return conn.Handshake()
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+ }
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+
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+ if timeout == 0 {
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+ err = establishConnection(rawConn, conn)
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+ } else {
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+ go func() {
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+ errChannel <- establishConnection(rawConn, conn)
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+ }()
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+ err = <-errChannel
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+ }
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+
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+ log.Printf("TEMP tlsDialer establishConnection done: %+v", conn.ConnectionState())
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+
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+ if err == nil && config.verifyLegacyCertificate != nil {
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+ err = verifyLegacyCertificate(conn, config.verifyLegacyCertificate)
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+ } else if err == nil && !config.sendServerName && !tlsConfig.InsecureSkipVerify {
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+ // Manually verify certificates
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+ err = verifyServerCerts(conn, serverName, tlsConfigCopy)
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+ }
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+
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+ if err != nil {
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+ rawConn.Close()
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+ return nil, err
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+ }
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+
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+ return conn, nil
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+}
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+
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+func verifyLegacyCertificate(conn *tls.Conn, expectedCertificate *x509.Certificate) error {
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+ certs := conn.ConnectionState().PeerCertificates
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+ if len(certs) < 1 {
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+ return errors.New("no certificate to verify")
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+ }
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+ if !bytes.Equal(certs[0].Raw, expectedCertificate.Raw) {
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+ return errors.New("unexpected certificate")
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+ }
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+ return nil
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+}
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+
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+func verifyServerCerts(conn *tls.Conn, serverName string, config *tls.Config) error {
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+ certs := conn.ConnectionState().PeerCertificates
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+
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+ opts := x509.VerifyOptions{
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+ Roots: config.RootCAs,
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+ CurrentTime: time.Now(),
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+ DNSName: serverName,
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+ Intermediates: x509.NewCertPool(),
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+ }
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+
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+ for i, cert := range certs {
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+ if i == 0 {
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+ continue
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+ }
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+ opts.Intermediates.AddCert(cert)
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+ }
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+ _, err := certs[0].Verify(opts)
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+ return err
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+}
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Rod Hynes