Write an example obfs4 bridge line to "obfs4_bridgeline.txt".

Write an example client bridge line suitable for use with the running
obfs4 server instance to "obfs4_bridgeline.txt" for the convenience of
bridge operators.

1 files changed, 35 insertions, 3 deletions

diff --git a/transports/obfs4/statefile.go b/transports/obfs4/statefile.go
index 8690178..1e00f32 100644
--- a/transports/obfs4/statefile.go
+++ b/transports/obfs4/statefile.go
@@ -42,7 +42,8 @@ import (
 )
 
 const (
-	stateFile = "obfs4_state.json"
+	stateFile  = "obfs4_state.json"
+	bridgeFile = "obfs4_bridgeline.txt"
 )
 
 type jsonServerState struct {
@@ -91,10 +92,10 @@ func serverStateFromArgs(stateDir string, args *pt.Args) (*obfs4ServerState, err
 		js.IATMode = iatMode
 	}
 
-	return serverStateFromJSONServerState(&js)
+	return serverStateFromJSONServerState(stateDir, &js)
 }
 
-func serverStateFromJSONServerState(js *jsonServerState) (*obfs4ServerState, error) {
+func serverStateFromJSONServerState(stateDir string, js *jsonServerState) (*obfs4ServerState, error) {
 	var err error
 
 	st := new(obfs4ServerState)
@@ -112,6 +113,11 @@ func serverStateFromJSONServerState(js *jsonServerState) (*obfs4ServerState, err
 	}
 	st.iatMode = js.IATMode
 
+	// Generate a human readable summary of the configured endpoint.
+	if err = newBridgeFile(stateDir, st); err != nil {
+		return nil, err
+	}
+
 	return st, nil
 }
 
@@ -170,3 +176,29 @@ func newJSONServerState(stateDir string, js *jsonServerState) (err error) {
 
 	return nil
 }
+
+func newBridgeFile(stateDir string, st *obfs4ServerState) (err error) {
+	const prefix = "# obfs4 torrc client bridge line\n" +
+		"#\n" +
+		"# This file is an automatically generated bridge line based on\n" +
+		"# the current obfs4proxy configuration.  EDITING IT WILL HAVE\n" +
+		"# NO EFFECT.\n" +
+		"#\n" +
+		"# Before distributing this Bridge, edit the placeholder fields\n" +
+		"# to contain the actual values:\n" +
+		"#  <IP ADDRESS>  - The public IP address of your obfs4 bridge.\n" +
+		"#  <PORT>        - The TCP/IP port of your obfs4 bridge.\n" +
+		"#  <FINGERPRINT> - The bridge's fingerprint.\n\n"
+
+	bridgeLine := fmt.Sprintf("Bridge obfs4 <IP ADDRESS>:<PORT> <FINGERPRINT> node-id=%s public-key=%s iat-mode=%d\n",
+		st.nodeID.Hex(),
+		st.identityKey.Public().Hex(),
+		st.iatMode)
+
+	tmp := []byte(prefix + bridgeLine)
+	if err = ioutil.WriteFile(path.Join(stateDir, bridgeFile), tmp, 0600); err != nil {
+		return err
+	}
+
+	return nil
+}