Elide the error out from most logs unless unsafeLogging is set.

The Golang runtime will happily splatter the remote IP address and port
in the error's string representation for network related errors.  While
useful for debugging, this is unacceptable from a privacy standpoint.

obfs4proxy/obfs4proxy.go

@@ -167,7 +167,11 @@ func clientHandler(f base.ClientFactory, conn *pt.SocksConn, proxyURI *url.URL)
 		// the configuration phase.
 		dialer, err := proxy.FromURL(proxyURI, proxy.Direct)
 		if err != nil {
-			log.Printf("[ERROR]: %s(%s) - failed to obtain proxy dialer: %s", name, addrStr, err)
+			if unsafeLogging {
+				log.Printf("[ERROR]: %s(%s) - failed to obtain proxy dialer: %s", name, addrStr, err)
+			} else {
+				log.Printf("[ERROR]: %s(%s) - failed to obtain proxy dialer", name, addrStr)
+			}
 			conn.Reject()
 			return
 		}
@@ -191,18 +195,26 @@ func clientHandler(f base.ClientFactory, conn *pt.SocksConn, proxyURI *url.URL)
 	// bytes back and forth.
 	remote, err := f.WrapConn(remoteConn, args)
 	if err != nil {
-		log.Printf("[ERROR]: %s(%s) - handshake failed: %s", name, addrStr, err)
+		if unsafeLogging {
+			log.Printf("[ERROR]: %s(%s) - handshake failed: %s", name, addrStr, err)
+		} else {
+			log.Printf("[ERROR]: %s(%s) - handshake failed", name, addrStr)
+		}
 		conn.Reject()
 		return
 	}
 	err = conn.Grant(remoteConn.RemoteAddr().(*net.TCPAddr))
 	if err != nil {
-		log.Printf("[ERROR]: %s(%s) - SOCKS grant failed: %s", name, addrStr, err)
+		if unsafeLogging {
+			log.Printf("[ERROR]: %s(%s) - SOCKS grant failed: %s", name, addrStr, err)
+		} else {
+			log.Printf("[ERROR]: %s(%s) - SOCKS grant failed", name, addrStr)
+		}
 		return
 	}
 
 	err = copyLoop(conn, remote)
-	if err != nil {
+	if err != nil && unsafeLogging {
 		log.Printf("[INFO]: %s(%s) - closed connection: %s", name, addrStr, err)
 	} else {
 		log.Printf("[INFO]: %s(%s) - closed connection", name, addrStr)
@@ -282,20 +294,28 @@ func serverHandler(f base.ServerFactory, conn net.Conn, info *pt.ServerInfo) {
 	// Instantiate the server transport method and handshake.
 	remote, err := f.WrapConn(conn)
 	if err != nil {
-		log.Printf("[ERROR]: %s(%s) - handshake failed: %s", name, addrStr, err)
+		if unsafeLogging {
+			log.Printf("[ERROR]: %s(%s) - handshake failed: %s", name, addrStr, err)
+		} else {
+			log.Printf("[ERROR]: %s(%s) - handshake failed", name, addrStr)
+		}
 		return
 	}
 
 	// Connect to the orport.
 	orConn, err := pt.DialOr(info, conn.RemoteAddr().String(), name)
 	if err != nil {
-		log.Printf("[ERROR]: %s(%s) - failed to connect to ORPort: %s", name, addrStr, err)
+		if unsafeLogging {
+			log.Printf("[ERROR]: %s(%s) - failed to connect to ORPort: %s", name, addrStr, err)
+		} else {
+			log.Printf("[ERROR]: %s(%s) - failed to connect to ORPort", name, addrStr)
+		}
 		return
 	}
 	defer orConn.Close()
 
 	err = copyLoop(orConn, remote)
-	if err != nil {
+	if err != nil && unsafeLogging {
 		log.Printf("[INFO]: %s(%s) - closed connection: %s", name, addrStr, err)
 	} else {
 		log.Printf("[INFO]: %s(%s) - closed connection", name, addrStr)