1 files changed, 156 insertions, 0 deletions
diff --git a/transports/obfs4/statefile.go b/transports/obfs4/statefile.go
new file mode 100644
index 0000000..814a545
--- /dev/null
+++ b/transports/obfs4/statefile.go
@@ -0,0 +1,156 @@
+/*
+ * Copyright (c) 2014, Yawning Angel <yawning at torproject dot org>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ *  * Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ *
+ *  * Redistributions in binary form must reproduce the above copyright notice,
+ *    this list of conditions and the following disclaimer in the documentation
+ *    and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+package obfs4
+
+import (
+	"encoding/base64"
+	"encoding/json"
+	"fmt"
+	"io/ioutil"
+	"os"
+	"path"
+
+	"git.torproject.org/pluggable-transports/goptlib.git"
+	"git.torproject.org/pluggable-transports/obfs4.git/common/csrand"
+	"git.torproject.org/pluggable-transports/obfs4.git/common/drbg"
+	"git.torproject.org/pluggable-transports/obfs4.git/common/ntor"
+)
+
+const (
+	stateFile = "obfs4_state.json"
+)
+
+type jsonServerState struct {
+	NodeID     string `json:"node-id"`
+	PrivateKey string `json:"private-key"`
+	PublicKey  string `json:"public-key"`
+	DrbgSeed   string `json:"drbgSeed"`
+}
+
+type obfs4ServerState struct {
+	nodeID      *ntor.NodeID
+	identityKey *ntor.Keypair
+	drbgSeed    *drbg.Seed
+}
+
+func serverStateFromArgs(stateDir string, args *pt.Args) (*obfs4ServerState, error) {
+	var js jsonServerState
+	var nodeIDOk, privKeyOk, seedOk bool
+
+	js.NodeID, nodeIDOk = args.Get(nodeIDArg)
+	js.PrivateKey, privKeyOk = args.Get(privateKeyArg)
+	js.DrbgSeed, seedOk = args.Get(seedArg)
+
+	if !privKeyOk && !nodeIDOk && !seedOk {
+		if err := jsonServerStateFromFile(stateDir, &js); err != nil {
+			return nil, err
+		}
+	} else if !privKeyOk {
+		return nil, fmt.Errorf("missing argument '%s'", privateKeyArg)
+	} else if !nodeIDOk {
+		return nil, fmt.Errorf("missing argument '%s'", nodeIDArg)
+	} else if !seedOk {
+		return nil, fmt.Errorf("missing argument '%s'", seedArg)
+	}
+
+	return serverStateFromJSONServerState(&js)
+}
+
+func serverStateFromJSONServerState(js *jsonServerState) (*obfs4ServerState, error) {
+	var err error
+
+	st := new(obfs4ServerState)
+	if st.nodeID, err = ntor.NodeIDFromBase64(js.NodeID); err != nil {
+		return nil, err
+	}
+	if st.identityKey, err = ntor.KeypairFromBase64(js.PrivateKey); err != nil {
+		return nil, err
+	}
+	var rawSeed []byte
+	if rawSeed, err = base64.StdEncoding.DecodeString(js.DrbgSeed); err != nil {
+		return nil, err
+	}
+	if st.drbgSeed, err = drbg.SeedFromBytes(rawSeed); err != nil {
+		return nil, err
+	}
+
+	return st, nil
+}
+
+func jsonServerStateFromFile(stateDir string, js *jsonServerState) error {
+	f, err := ioutil.ReadFile(path.Join(stateDir, stateFile))
+	if err != nil {
+		if os.IsNotExist(err) {
+			if err = newJSONServerState(stateDir, js); err == nil {
+				return nil
+			}
+		}
+		return err
+	}
+
+	if err = json.Unmarshal(f, js); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func newJSONServerState(stateDir string, js *jsonServerState) (err error) {
+	// Generate everything a server needs, using the cryptographic PRNG.
+	var st obfs4ServerState
+	rawID := make([]byte, ntor.NodeIDLength)
+	if err = csrand.Bytes(rawID); err != nil {
+		return
+	}
+	if st.nodeID, err = ntor.NewNodeID(rawID); err != nil {
+		return
+	}
+	if st.identityKey, err = ntor.NewKeypair(false); err != nil {
+		return
+	}
+	if st.drbgSeed, err = drbg.NewSeed(); err != nil {
+		return
+	}
+
+	// Encode it into JSON format and write the state file.
+	js.NodeID = st.nodeID.Base64()
+	js.PrivateKey = st.identityKey.Private().Base64()
+	js.PublicKey = st.identityKey.Public().Base64()
+	js.DrbgSeed = st.drbgSeed.Base64()
+
+	var encoded []byte
+	if encoded, err = json.Marshal(js); err != nil {
+		return
+	}
+
+	if err = ioutil.WriteFile(path.Join(stateDir, stateFile), encoded, 0600); err != nil {
+		return err
+	}
+
+	return nil
+}