commit 398b795c87387d25c889a3bf700b387cd120520e Author: Daniel Martí <mvdan@mvdan.cc> Date: Sat Mar 21 21:48:36 2015 +0100 Simplify some err and return logic --- transports/obfs2/obfs2.go | 70 ++++++++++++++++++------------------ transports/obfs3/obfs3.go | 54 ++++++++++++++-------------- transports/obfs4/handshake_ntor.go | 5 ++- transports/obfs4/obfs4.go | 63 +++++++++++++++----------------- transports/obfs4/packet.go | 17 ++++----- transports/obfs4/statefile.go | 6 ++-- transports/scramblesuit/conn.go | 32 +++++++++-------- 7 files changed, 118 insertions(+), 129 deletions(-) diff --git a/transports/obfs2/obfs2.go b/transports/obfs2/obfs2.go index f8efac1..bc2532b 100644 --- a/transports/obfs2/obfs2.go +++ b/transports/obfs2/obfs2.go @@ -187,7 +187,7 @@ func newObfs2ServerConn(conn net.Conn) (c *obfs2Conn, err error) { return } -func (conn *obfs2Conn) handshake() (err error) { +func (conn *obfs2Conn) handshake() error { // Each begins by generating a seed and a padding key as follows. // The initiator generates: // @@ -202,8 +202,8 @@ func (conn *obfs2Conn) handshake() (err error) { // Each then generates a random number PADLEN in range from 0 through // MAX_PADDING (inclusive). var seed [seedLen]byte - if err = csrand.Bytes(seed[:]); err != nil { - return + if err := csrand.Bytes(seed[:]); err != nil { + return err } var padMagic []byte if conn.isInitiator { @@ -218,8 +218,8 @@ func (conn *obfs2Conn) handshake() (err error) { binary.BigEndian.PutUint32(hsBlob[0:4], magicValue) binary.BigEndian.PutUint32(hsBlob[4:8], padLen) if padLen > 0 { - if err = csrand.Bytes(hsBlob[8:]); err != nil { - return + if err := csrand.Bytes(hsBlob[8:]); err != nil { + return err } } @@ -230,25 +230,25 @@ func (conn *obfs2Conn) handshake() (err error) { // and the responder sends: // // RESP_SEED | E(RESP_PAD_KEY, UINT32(MAGIC_VALUE) | UINT32(PADLEN) | WR(PADLEN)) - var txBlock cipher.Block - if txBlock, err = aes.NewCipher(padKey); err != nil { - return + txBlock, err := aes.NewCipher(padKey) + if err != nil { + return err } txStream := cipher.NewCTR(txBlock, padIV) conn.tx = &cipher.StreamWriter{S: txStream, W: conn.Conn} - if _, err = conn.Conn.Write(seed[:]); err != nil { - return + if _, err := conn.Conn.Write(seed[:]); err != nil { + return err } - if _, err = conn.Write(hsBlob); err != nil { - return + if _, err := conn.Write(hsBlob); err != nil { + return err } // Upon receiving the SEED from the other party, each party derives // the other party's padding key value as above, and decrypts the next // 8 bytes of the key establishment message. var peerSeed [seedLen]byte - if _, err = io.ReadFull(conn.Conn, peerSeed[:]); err != nil { - return + if _, err := io.ReadFull(conn.Conn, peerSeed[:]); err != nil { + return err } var peerPadMagic []byte if conn.isInitiator { @@ -257,46 +257,44 @@ func (conn *obfs2Conn) handshake() (err error) { peerPadMagic = []byte(initiatorPadString) } peerKey, peerIV := hsKdf(peerPadMagic, peerSeed[:], !conn.isInitiator) - var rxBlock cipher.Block - if rxBlock, err = aes.NewCipher(peerKey); err != nil { - return + rxBlock, err := aes.NewCipher(peerKey) + if err != nil { + return err } rxStream := cipher.NewCTR(rxBlock, peerIV) conn.rx = &cipher.StreamReader{S: rxStream, R: conn.Conn} hsHdr := make([]byte, hsLen) - if _, err = io.ReadFull(conn, hsHdr[:]); err != nil { - return + if _, err := io.ReadFull(conn, hsHdr[:]); err != nil { + return err } // If the MAGIC_VALUE does not match, or the PADLEN value is greater than // MAX_PADDING, the party receiving it should close the connection // immediately. if peerMagic := binary.BigEndian.Uint32(hsHdr[0:4]); peerMagic != magicValue { - err = fmt.Errorf("invalid magic value: %x", peerMagic) - return + return fmt.Errorf("invalid magic value: %x", peerMagic) } padLen = binary.BigEndian.Uint32(hsHdr[4:8]) if padLen > maxPadding { - err = fmt.Errorf("padlen too long: %d", padLen) - return + return fmt.Errorf("padlen too long: %d", padLen) } // Otherwise, it should read the remaining PADLEN bytes of padding data // and discard them. tmp := make([]byte, padLen) - if _, err = io.ReadFull(conn.Conn, tmp); err != nil { // Note: Skips AES. - return + if _, err := io.ReadFull(conn.Conn, tmp); err != nil { // Note: Skips AES. + return err } // Derive the actual keys. - if err = conn.kdf(seed[:], peerSeed[:]); err != nil { - return + if err := conn.kdf(seed[:], peerSeed[:]); err != nil { + return err } - return + return nil } -func (conn *obfs2Conn) kdf(seed, peerSeed []byte) (err error) { +func (conn *obfs2Conn) kdf(seed, peerSeed []byte) error { // Additional keys are then derived as: // // INIT_SECRET = MAC("Initiator obfuscated data", INIT_SEED|RESP_SEED) @@ -315,16 +313,16 @@ func (conn *obfs2Conn) kdf(seed, peerSeed []byte) (err error) { } initKey, initIV := hsKdf([]byte(initiatorKdfString), combSeed, true) - var initBlock cipher.Block - if initBlock, err = aes.NewCipher(initKey); err != nil { - return + initBlock, err := aes.NewCipher(initKey) + if err != nil { + return err } initStream := cipher.NewCTR(initBlock, initIV) respKey, respIV := hsKdf([]byte(responderKdfString), combSeed, false) - var respBlock cipher.Block - if respBlock, err = aes.NewCipher(respKey); err != nil { - return + respBlock, err := aes.NewCipher(respKey) + if err != nil { + return err } respStream := cipher.NewCTR(respBlock, respIV) @@ -336,7 +334,7 @@ func (conn *obfs2Conn) kdf(seed, peerSeed []byte) (err error) { conn.rx.S = initStream } - return + return nil } func hsKdf(magic, seed []byte, isInitiator bool) (padKey, padIV []byte) { diff --git a/transports/obfs3/obfs3.go b/transports/obfs3/obfs3.go index 53409db..d215c49 100644 --- a/transports/obfs3/obfs3.go +++ b/transports/obfs3/obfs3.go @@ -166,56 +166,56 @@ func newObfs3ServerConn(conn net.Conn) (c *obfs3Conn, err error) { return } -func (conn *obfs3Conn) handshake() (err error) { +func (conn *obfs3Conn) handshake() error { // The party who opens the connection is the 'initiator'; the one who // accepts it is the 'responder'. Each begins by generating a // UniformDH keypair, and a random number PADLEN in [0, MAX_PADDING/2]. // Both parties then send: // // PUB_KEY | WR(PADLEN) - var privateKey *uniformdh.PrivateKey - if privateKey, err = uniformdh.GenerateKey(csrand.Reader); err != nil { - return + privateKey, err := uniformdh.GenerateKey(csrand.Reader) + if err != nil { + return err } padLen := csrand.IntRange(0, maxPadding/2) blob := make([]byte, uniformdh.Size+padLen) - var publicKey []byte - if publicKey, err = privateKey.PublicKey.Bytes(); err != nil { - return + publicKey, err := privateKey.PublicKey.Bytes() + if err != nil { + return err } copy(blob[0:], publicKey) - if err = csrand.Bytes(blob[uniformdh.Size:]); err != nil { - return + if err := csrand.Bytes(blob[uniformdh.Size:]); err != nil { + return err } - if _, err = conn.Conn.Write(blob); err != nil { - return + if _, err := conn.Conn.Write(blob); err != nil { + return err } // Read the public key from the peer. rawPeerPublicKey := make([]byte, uniformdh.Size) - if _, err = io.ReadFull(conn.Conn, rawPeerPublicKey); err != nil { - return + if _, err := io.ReadFull(conn.Conn, rawPeerPublicKey); err != nil { + return err } var peerPublicKey uniformdh.PublicKey - if err = peerPublicKey.SetBytes(rawPeerPublicKey); err != nil { - return + if err := peerPublicKey.SetBytes(rawPeerPublicKey); err != nil { + return err } // After retrieving the public key of the other end, each party // completes the DH key exchange and generates a shared-secret for the // session (named SHARED_SECRET). - var sharedSecret []byte - if sharedSecret, err = uniformdh.Handshake(privateKey, &peerPublicKey); err != nil { - return + sharedSecret, err := uniformdh.Handshake(privateKey, &peerPublicKey) + if err != nil { + return err } - if err = conn.kdf(sharedSecret); err != nil { - return + if err := conn.kdf(sharedSecret); err != nil { + return err } - return + return nil } -func (conn *obfs3Conn) kdf(sharedSecret []byte) (err error) { +func (conn *obfs3Conn) kdf(sharedSecret []byte) error { // Using that shared-secret each party derives its encryption keys as // follows: // @@ -248,14 +248,14 @@ func (conn *obfs3Conn) kdf(sharedSecret []byte) (err error) { // // Note: To have this be the last place where the shared secret is used, // also generate the magic value to send/scan for here. - var initBlock cipher.Block - if initBlock, err = aes.NewCipher(initSecret[:keyLen]); err != nil { + initBlock, err := aes.NewCipher(initSecret[:keyLen]) + if err != nil { return err } initStream := cipher.NewCTR(initBlock, initSecret[keyLen:]) - var respBlock cipher.Block - if respBlock, err = aes.NewCipher(respSecret[:keyLen]); err != nil { + respBlock, err := aes.NewCipher(respSecret[:keyLen]) + if err != nil { return err } respStream := cipher.NewCTR(respBlock, respSecret[keyLen:]) @@ -272,7 +272,7 @@ func (conn *obfs3Conn) kdf(sharedSecret []byte) (err error) { conn.rxMagic = initMagic } - return + return nil } func (conn *obfs3Conn) findPeerMagic() error { diff --git a/transports/obfs4/handshake_ntor.go b/transports/obfs4/handshake_ntor.go index 8dcf0c8..57de460 100644 --- a/transports/obfs4/handshake_ntor.go +++ b/transports/obfs4/handshake_ntor.go @@ -417,10 +417,9 @@ func findMarkMac(mark, buf []byte, startPos, maxPos int, fromTail bool) (pos int func makePad(padLen int) ([]byte, error) { pad := make([]byte, padLen) - err := csrand.Bytes(pad) - if err != nil { + if err := csrand.Bytes(pad); err != nil { return nil, err } - return pad, err + return pad, nil } diff --git a/transports/obfs4/obfs4.go b/transports/obfs4/obfs4.go index 256f549..07af9ab 100644 --- a/transports/obfs4/obfs4.go +++ b/transports/obfs4/obfs4.go @@ -105,16 +105,15 @@ func (t *Transport) ClientFactory(stateDir string) (base.ClientFactory, error) { // ServerFactory returns a new obfs4ServerFactory instance. func (t *Transport) ServerFactory(stateDir string, args *pt.Args) (base.ServerFactory, error) { - var err error - - var st *obfs4ServerState - if st, err = serverStateFromArgs(stateDir, args); err != nil { + st, err := serverStateFromArgs(stateDir, args) + if err != nil { return nil, err } var iatSeed *drbg.Seed if st.iatMode != iatNone { iatSeedSrc := sha256.Sum256(st.drbgSeed.Bytes()[:]) + var err error iatSeed, err = drbg.SeedFromBytes(iatSeedSrc[:]) if err != nil { return nil, err @@ -152,8 +151,6 @@ func (cf *obfs4ClientFactory) Transport() base.Transport { } func (cf *obfs4ClientFactory) ParseArgs(args *pt.Args) (interface{}, error) { - var err error - var nodeID *ntor.NodeID var publicKey *ntor.PublicKey @@ -161,8 +158,8 @@ func (cf *obfs4ClientFactory) ParseArgs(args *pt.Args) (interface{}, error) { // for the Node ID and Public Key. certStr, ok := args.Get(certArg) if ok { - var cert *obfs4ServerCert - if cert, err = serverCertFromString(certStr); err != nil { + cert, err := serverCertFromString(certStr) + if err != nil { return nil, err } nodeID, publicKey = cert.unpack() @@ -173,6 +170,7 @@ func (cf *obfs4ClientFactory) ParseArgs(args *pt.Args) (interface{}, error) { if !ok { return nil, fmt.Errorf("missing argument '%s'", nodeIDArg) } + var err error if nodeID, err = ntor.NodeIDFromHex(nodeIDStr); err != nil { return nil, err } @@ -191,8 +189,7 @@ func (cf *obfs4ClientFactory) ParseArgs(args *pt.Args) (interface{}, error) { if !ok { return nil, fmt.Errorf("missing argument '%s'", iatArg) } - var iatMode int - iatMode, err = strconv.Atoi(iatStr) + iatMode, err := strconv.Atoi(iatStr) if err != nil || iatMode < iatNone || iatMode > iatParanoid { return nil, fmt.Errorf("invalid iat-mode '%d'", iatMode) } @@ -343,16 +340,15 @@ func (conn *obfs4Conn) clientHandshake(nodeID *ntor.NodeID, peerIdentityKey *nto // Consume the server handshake. var hsBuf [maxHandshakeLength]byte for { - var n int - if n, err = conn.Conn.Read(hsBuf[:]); err != nil { + n, err := conn.Conn.Read(hsBuf[:]) + if err != nil { // The Read() could have returned data and an error, but there is // no point in continuing on an EOF or whatever. return err } conn.receiveBuffer.Write(hsBuf[:n]) - var seed []byte - n, seed, err = hs.parseServerHandshake(conn.receiveBuffer.Bytes()) + n, seed, err := hs.parseServerHandshake(conn.receiveBuffer.Bytes()) if err == ErrMarkNotFoundYet { continue } else if err != nil { @@ -369,39 +365,38 @@ func (conn *obfs4Conn) clientHandshake(nodeID *ntor.NodeID, peerIdentityKey *nto } } -func (conn *obfs4Conn) serverHandshake(sf *obfs4ServerFactory, sessionKey *ntor.Keypair) (err error) { +func (conn *obfs4Conn) serverHandshake(sf *obfs4ServerFactory, sessionKey *ntor.Keypair) error { if !conn.isServer { return fmt.Errorf("serverHandshake called on client connection") } // Generate the server handshake, and arm the base timeout. hs := newServerHandshake(sf.nodeID, sf.identityKey, sessionKey) - if err = conn.Conn.SetDeadline(time.Now().Add(serverHandshakeTimeout)); err != nil { - return + if err := conn.Conn.SetDeadline(time.Now().Add(serverHandshakeTimeout)); err != nil { + return err } // Consume the client handshake. var hsBuf [maxHandshakeLength]byte for { - var n int - if n, err = conn.Conn.Read(hsBuf[:]); err != nil { + n, err := conn.Conn.Read(hsBuf[:]) + if err != nil { // The Read() could have returned data and an error, but there is // no point in continuing on an EOF or whatever. - return + return err } conn.receiveBuffer.Write(hsBuf[:n]) - var seed []byte - seed, err = hs.parseClientHandshake(sf.replayFilter, conn.receiveBuffer.Bytes()) + seed, err := hs.parseClientHandshake(sf.replayFilter, conn.receiveBuffer.Bytes()) if err == ErrMarkNotFoundYet { continue } else if err != nil { - return + return err } conn.receiveBuffer.Reset() - if err = conn.Conn.SetDeadline(time.Time{}); err != nil { - return + if err := conn.Conn.SetDeadline(time.Time{}); err != nil { + return nil } // Use the derived key material to intialize the link crypto. @@ -422,26 +417,24 @@ func (conn *obfs4Conn) serverHandshake(sf *obfs4ServerFactory, sessionKey *ntor. // handshake_ntor.go. // Generate/send the response. - var blob []byte - blob, err = hs.generateHandshake() + blob, err := hs.generateHandshake() if err != nil { - return + return err } var frameBuf bytes.Buffer - _, err = frameBuf.Write(blob) - if err != nil { - return + if _, err = frameBuf.Write(blob); err != nil { + return err } // Send the PRNG seed as the first packet. - if err = conn.makePacket(&frameBuf, packetTypePrngSeed, sf.lenSeed.Bytes()[:], 0); err != nil { - return + if err := conn.makePacket(&frameBuf, packetTypePrngSeed, sf.lenSeed.Bytes()[:], 0); err != nil { + return err } if _, err = conn.Conn.Write(frameBuf.Bytes()); err != nil { - return + return err } - return + return nil } func (conn *obfs4Conn) Read(b []byte) (n int, err error) { diff --git a/transports/obfs4/packet.go b/transports/obfs4/packet.go index 9865c82..461ad54 100644 --- a/transports/obfs4/packet.go +++ b/transports/obfs4/packet.go @@ -69,7 +69,7 @@ func (e InvalidPayloadLengthError) Error() string { var zeroPadBytes [maxPacketPaddingLength]byte -func (conn *obfs4Conn) makePacket(w io.Writer, pktType uint8, data []byte, padLen uint16) (err error) { +func (conn *obfs4Conn) makePacket(w io.Writer, pktType uint8, data []byte, padLen uint16) error { var pkt [framing.MaximumFramePayloadLength]byte if len(data)+int(padLen) > maxPacketPayloadLength { @@ -93,22 +93,19 @@ func (conn *obfs4Conn) makePacket(w io.Writer, pktType uint8, data []byte, padLe // Encode the packet in an AEAD frame. var frame [framing.MaximumSegmentLength]byte - frameLen := 0 - frameLen, err = conn.encoder.Encode(frame[:], pkt[:pktLen]) + frameLen, err := conn.encoder.Encode(frame[:], pkt[:pktLen]) if err != nil { // All encoder errors are fatal. - return + return err } - var wrLen int - wrLen, err = w.Write(frame[:frameLen]) + wrLen, err := w.Write(frame[:frameLen]) if err != nil { - return + return err } else if wrLen < frameLen { - err = io.ErrShortWrite - return + return io.ErrShortWrite } - return + return nil } func (conn *obfs4Conn) readPackets() (err error) { diff --git a/transports/obfs4/statefile.go b/transports/obfs4/statefile.go index 0838180..6c34f35 100644 --- a/transports/obfs4/statefile.go +++ b/transports/obfs4/statefile.go @@ -183,7 +183,7 @@ func jsonServerStateFromFile(stateDir string, js *jsonServerState) error { return err } - if err = json.Unmarshal(f, js); err != nil { + if err := json.Unmarshal(f, js); err != nil { return fmt.Errorf("failed to load statefile '%s': %s", fPath, err) } @@ -227,7 +227,7 @@ func newJSONServerState(stateDir string, js *jsonServerState) (err error) { return nil } -func newBridgeFile(stateDir string, st *obfs4ServerState) (err error) { +func newBridgeFile(stateDir string, st *obfs4ServerState) error { const prefix = "# obfs4 torrc client bridge line\n" + "#\n" + "# This file is an automatically generated bridge line based on\n" + @@ -244,7 +244,7 @@ func newBridgeFile(stateDir string, st *obfs4ServerState) (err error) { st.clientString()) tmp := []byte(prefix + bridgeLine) - if err = ioutil.WriteFile(path.Join(stateDir, bridgeFile), tmp, 0600); err != nil { + if err := ioutil.WriteFile(path.Join(stateDir, bridgeFile), tmp, 0600); err != nil { return err } diff --git a/transports/scramblesuit/conn.go b/transports/scramblesuit/conn.go index b77bc5f..b8a27c7 100644 --- a/transports/scramblesuit/conn.go +++ b/transports/scramblesuit/conn.go @@ -441,20 +441,23 @@ handshakeUDH: } } -func (conn *ssConn) initCrypto(seed []byte) (err error) { +func (conn *ssConn) initCrypto(seed []byte) error { // Use HKDF-SHA256 (Expand only, no Extract) to generate session keys from // initial keying material. okm := hkdfExpand(sha256.New, seed, nil, kdfSecretLength) - if conn.txCrypto, err = newCryptoState(okm[0:32], okm[32:40], okm[80:112]); err != nil { - return + var err error + conn.txCrypto, err = newCryptoState(okm[0:32], okm[32:40], okm[80:112]) + if err != nil { + return err } - if conn.rxCrypto, err = newCryptoState(okm[40:72], okm[72:80], okm[112:144]); err != nil { - return + conn.rxCrypto, err = newCryptoState(okm[40:72], okm[72:80], okm[112:144]) + if err != nil { + return err } - return + return nil } -func (conn *ssConn) padBurst(burst *bytes.Buffer, sampleLen int) (err error) { +func (conn *ssConn) padBurst(burst *bytes.Buffer, sampleLen int) error { // Burst contains the fully encrypted+MACed outgoing payload that will be // written to the network. Pad it out so that the last segment (based on // the ScrambleSuit MTU) is sampleLen bytes. @@ -473,18 +476,17 @@ func (conn *ssConn) padBurst(burst *bytes.Buffer, sampleLen int) (err error) { } if padLen == 0 { - return - } else if padLen > maxSegmentLength { + return nil + } + if padLen > maxSegmentLength { // Note: packetmorpher.py: getPadding is slightly wrong and only // accounts for one of the two packet headers. - if err = conn.makePacket(burst, pktPayload, nil, 700-pktOverhead); err != nil { - return + if err := conn.makePacket(burst, pktPayload, nil, 700-pktOverhead); err != nil { + return err } - err = conn.makePacket(burst, pktPayload, nil, padLen-(700+2*pktOverhead)) - } else { - err = conn.makePacket(burst, pktPayload, nil, padLen-pktOverhead) + return conn.makePacket(burst, pktPayload, nil, padLen-(700+2*pktOverhead)) } - return + return conn.makePacket(burst, pktPayload, nil, padLen-pktOverhead) } func newScrambleSuitClientConn(conn net.Conn, tStore *ssTicketStore, ca *ssClientArgs) (net.Conn, error) {