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-rw-r--r--transports/obfs2/obfs2.go70
1 files changed, 34 insertions, 36 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) {