-Cleaned up lib code with gometalinter.v1

-Added -h opt to demo client (hmac)

README.md

@@ -1,3 +1,23 @@
+/*  Herradura - a Key exchange scheme in the style of Diffie-Hellman Key Exchange.
+    Copyright (C) 2017 Omar Alejandro Herrera Reyna
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+    golang implementation by Russ Magee (rmagee_at_gmail.com) */
+
+--
+
 This is a drop-in replacement for the golang/pkg/net facilities
 (net.Dial(), net.Listen(), net.Accept() and net.Conn type) using the
 experimental HerraduraKEx 'secure' key exchange algorithm, first released at
@@ -28,6 +48,6 @@ $ go install .
 $ cd demo/
 $ go build client.go && go build server.go
 
-[ in separate shell windows ]
+[ in separate shells ]
 [A]$ ./server
 [B]$ ./client

demo/client.go

@@ -15,11 +15,13 @@ import (
 // Compare to 'clientp.go' in this directory to see the equivalence.
 func main() {
 	var cAlg string
+	var hAlg string
 	
 	flag.StringVar(&cAlg, "c", "C_AES_256", "cipher [\"C_AES_256\" | \"C_TWOFISH_128\" | \"C_BLOWFISH_64\"]")
+	flag.StringVar(&hAlg, "h", "H_SHA256", "hmac [\"H_SHA256\"]")
 	flag.Parse()
 
-	conn, err := hkex.Dial("tcp", "localhost:2000", cAlg)
+	conn, err := hkex.Dial("tcp", "localhost:2000", cAlg, hAlg)
 	if err != nil {
 		// handle error
 		fmt.Println("Err!")

herradurakex.go

@@ -1,20 +1,10 @@
-/*  Herradura - a Key exchange scheme in the style of Diffie-Hellman Key Exchange.
-    Copyright (C) 2017 Omar Alejandro Herrera Reyna
-
-    This program is free software: you can redistribute it and/or modify
-    it under the terms of the GNU General Public License as published by
-    the Free Software Foundation, either version 3 of the License, or
-    (at your option) any later version.
-
-    This program is distributed in the hope that it will be useful,
-    but WITHOUT ANY WARRANTY; without even the implied warranty of
-    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-    GNU General Public License for more details.
-
-    You should have received a copy of the GNU General Public License
-    along with this program.  If not, see <https://www.gnu.org/licenses/>.
-
-    golang implementation by Russ Magee (rmagee_at_gmail.com) */
+// Package herradurakex - socket lib conforming to
+// golang.org/pkg/net Conn interface, with
+// experimental key exchange algorithm by
+// Omar Alejandro Herrera Reyna
+// (https://github.com/Caume/HerraduraKEx)
+//
+// See README.md for full license info.
 package herradurakex
 
 /* This is the core KEx algorithm. For client/server net support code,
@@ -38,7 +28,8 @@ type HerraduraKEx struct {
 	fa           *big.Int
 }
 
-// Return a new HerraduraKEx struct.
+// New returns a HerraduraKEx struct.
+//
 //   i - internal (private) random nonce
 //   p - public (exchanged) random nonce (typically 1/4 bitsize of i)
 //
@@ -76,16 +67,16 @@ func (h *HerraduraKEx) rand() (v *big.Int) {
 	return v
 }
 
-// Return max value for an n-bit big.Int
-func (h *HerraduraKEx) getMax() (v *big.Int) {
-	v = big.NewInt(0)
+// getMax returns the max value for an n-bit big.Int
+func (h *HerraduraKEx) getMax() (n *big.Int) {
+	n = big.NewInt(0)
 	var max big.Int
 
 	for i := 0; i < h.intSz; i++ {
-		max.SetBit(v, i, 1)
+		max.SetBit(n, i, 1)
 	}
-	v = &max
-	return v
+	n = &max
+	return n
 }
 
 func (h *HerraduraKEx) bitX(x *big.Int, pos int) (ret int64) {
@@ -120,8 +111,6 @@ func (h *HerraduraKEx) fscx(up, down *big.Int) (result *big.Int) {
 // This is the iteration function using the result of the previous iteration
 // as the first parameter and the second parameter of the first iteration.
 func (h *HerraduraKEx) fscxRevolve(x, y *big.Int, passes int) (result *big.Int) {
-	result = big.NewInt(0)
-
 	result = x
 	for count := 0; count < passes; count++ {
 		result = h.fscx(result, y)
@@ -129,13 +118,13 @@ func (h *HerraduraKEx) fscxRevolve(x, y *big.Int, passes int) (result *big.Int)
 	return result
 }
 
-// Return the D (FSCX Revolved) value, input to generate FA
+// D returns the D (FSCX Revolved) value, input to generate FA
 // (the value for peer KEx)
 func (h *HerraduraKEx) D() *big.Int {
 	return h.d
 }
 
-// Return the FA value, which must be sent to peer for KEx.
+// FA returns the FA value, which must be sent to peer for KEx.
 func (h *HerraduraKEx) FA() {
 	h.fa = h.fscxRevolve(h.PeerD, h.b, h.intSz-h.pubSz)
 	h.fa.Xor(h.fa, h.a)

hkexchan.go

@@ -34,17 +34,16 @@ import (
 
 // Available ciphers for hkex.Conn
 const (
-	C_AES_256     = iota
-	C_TWOFISH_128 // golang.org/x/crypto/twofish
-	C_BLOWFISH_64 // golang.org/x/crypto/blowfish
-	C_NONE_DISALLOWED
+	CAlgAES256     = iota
+	CAlgTwofish128 // golang.org/x/crypto/twofish
+	CAlgBlowfish64 // golang.org/x/crypto/blowfish
+	CAlgNoneDisallowed
 )
 
 // Available HMACs for hkex.Conn (TODO: not currently used)
 const (
-	H_BOGUS = iota
-	H_SHA256
-	H_NONE_DISALLOWED
+	HmacSHA256 = iota
+	HmacNoneDisallowed
 )
 
 /*TODO: HMAC derived from HKEx FA.*/
@@ -61,29 +60,26 @@ func (hc Conn) getStream(keymat *big.Int) (ret cipher.Stream) {
 	// TODO: each cipher alg case should ensure len(keymat.Bytes())
 	// is >= 2*cipher.BlockSize (enough for both key and iv)
 	switch copts {
-	case C_AES_256:
+	case CAlgAES256:
 		key = keymat.Bytes()[0:aes.BlockSize]
 		block, err = aes.NewCipher(key)
 		ivlen = aes.BlockSize
-		iv := make([]byte, aes.BlockSize)
-		iv = keymat.Bytes()[aes.BlockSize : aes.BlockSize+ivlen]
+		iv := keymat.Bytes()[aes.BlockSize : aes.BlockSize+ivlen]
 		ret = cipher.NewOFB(block, iv)
 		fmt.Printf("[cipher AES_256 (%d)]\n", copts)
 		break
-	case C_TWOFISH_128:
+	case CAlgTwofish128:
 		key = keymat.Bytes()[0:twofish.BlockSize]
 		block, err = twofish.NewCipher(key)
 		ivlen = twofish.BlockSize
-		iv := make([]byte, twofish.BlockSize)
-		iv = keymat.Bytes()[twofish.BlockSize : twofish.BlockSize+ivlen]
+		iv := keymat.Bytes()[twofish.BlockSize : twofish.BlockSize+ivlen]
 		ret = cipher.NewOFB(block, iv)
 		fmt.Printf("[cipher TWOFISH_128 (%d)]\n", copts)
 		break
-	case C_BLOWFISH_64:
+	case CAlgBlowfish64:
 		key = keymat.Bytes()[0:blowfish.BlockSize]
 		block, err = blowfish.NewCipher(key)
 		ivlen = blowfish.BlockSize
-		iv := make([]byte, blowfish.BlockSize)
 		// N.b. Bounds enforcement of differing cipher algorithms
 		// ------------------------------------------------------
 		// cipher/aes and x/cipher/twofish appear to allow one to
@@ -93,23 +89,19 @@ func (hc Conn) getStream(keymat *big.Int) (ret cipher.Stream) {
 		//
 		// I assume the other two check bounds and only
 		// copy what's needed whereas blowfish does no such check.
-		iv = keymat.Bytes()[blowfish.BlockSize : blowfish.BlockSize+ivlen]
+		iv := keymat.Bytes()[blowfish.BlockSize : blowfish.BlockSize+ivlen]
 		ret = cipher.NewOFB(block, iv)
 		fmt.Printf("[cipher BLOWFISH_64 (%d)]\n", copts)
 		break
 	default:
 		fmt.Printf("DOOFUS SET A VALID CIPHER ALG (%d)\n", copts)
-		block, err = nil, nil
 		os.Exit(1)
 	}
 
 	hopts := (hc.cipheropts >> 8) & 0xFF
 	switch hopts {
-	case H_BOGUS:
-		fmt.Printf("[nop H_BOGUS (%d)]\n", hopts)
-		break
-	case H_SHA256:
-		fmt.Printf("[nop H_SHA256 (%d)]\n", hopts)
+	case HmacSHA256:
+		fmt.Printf("[nop HmacSHA256 (%d)]\n", hopts)
 		break
 	default:
 		fmt.Printf("DOOFUS SET A VALID HMAC ALG (%d)\n", hopts)

hkexnet.go

@@ -31,7 +31,7 @@ import (
 
 /*---------------------------------------------------------------------*/
 
-// A HKex connection - drop-in replacement for net.Conn
+// Conn is a HKex connection - a drop-in replacement for net.Conn
 type Conn struct {
 	c          net.Conn // which also implements io.Reader, io.Writer, ...
 	h          *HerraduraKEx
@@ -41,24 +41,25 @@ type Conn struct {
 	w          cipher.Stream
 }
 
-// Return the cipher/hmac options value, which is sent to the peer but is
-// not itself part of the KEx.
+// ConnOpts returns the cipher/hmac options value, which is sent to the
+// peer but is not itself part of the KEx.
+//
 // (Used for protocol-level negotiations after KEx such as
 // cipher/HMAC algorithm options etc.)
 func (c *Conn) ConnOpts() uint32 {
 	return c.cipheropts
 }
 
-// Set cipher/hmac options value, which is sent to the peer as part of
-// KEx but not part of the KEx itself.
+// SetConnOpts sets the cipher/hmac options value, which is sent to the
+// peer as part of KEx but not part of the KEx itself.
 //
 // opts - bitfields for cipher and hmac alg. to use after KEx
 func (c *Conn) SetConnOpts(copts uint32) {
 	c.cipheropts = copts
 }
 
-// Return the protocol options value, which is sent to the peer but is
-// not itself part of the KEx or connection (cipher/hmac) setup.
+// Opts returns the protocol options value, which is sent to the peer
+// but is not itself part of the KEx or connection (cipher/hmac) setup.
 //
 // Consumers of this lib may use this for protocol-level options not part
 // of the KEx or encryption info used by the connection.
@@ -66,9 +67,9 @@ func (c *Conn) Opts() uint32 {
 	return c.opts
 }
 
-// Set the protocol options value, which is sent to the peer but is
-// not itself part of the KEx or connection (cipher/hmac) setup.
-
+// SetOpts sets the protocol options value, which is sent to the peer
+// but is not itself part of the KEx or connection (cipher/hmac) setup.
+//
 // Consumers of this lib may use this for protocol-level options not part
 // of the KEx of encryption info used by the connection.
 //
@@ -77,26 +78,28 @@ func (c *Conn) SetOpts(opts uint32) {
 	c.opts = opts
 }
 
-func (hc *Conn) applyConnExtensions(extensions ...string) {
+func (c *Conn) applyConnExtensions(extensions ...string) {
 	for _, s := range extensions {
 		switch s {
 		case "C_AES_256":
-			hc.cipheropts &= (0xFFFFFF00)
-			hc.cipheropts |= C_AES_256
+			fmt.Println("[extension arg = C_AES_256]")
+			c.cipheropts &= (0xFFFFFF00)
+			c.cipheropts |= CAlgAES256
 			break
 		case "C_TWOFISH_128":
 			fmt.Println("[extension arg = C_TWOFISH_128]")
-			hc.cipheropts &= (0xFFFFFF00)
-			hc.cipheropts |= C_TWOFISH_128
+			c.cipheropts &= (0xFFFFFF00)
+			c.cipheropts |= CAlgTwofish128
 			break
 		case "C_BLOWFISH_64":
 			fmt.Println("[extension arg = C_BLOWFISH_64]")
-			hc.cipheropts &= (0xFFFFFF00)
-			hc.cipheropts |= C_BLOWFISH_64
+			c.cipheropts &= (0xFFFFFF00)
+			c.cipheropts |= CAlgBlowfish64
 			break
 		case "H_SHA256":
-			hc.cipheropts &= (0xFFFF00FF)
-			hc.cipheropts |= (H_SHA256 << 8)
+			fmt.Println("[extension arg = H_SHA256]")
+			c.cipheropts &= (0xFFFF00FF)
+			c.cipheropts |= (HmacSHA256 << 8)
 			break
 		default:
 			fmt.Printf("[Dial ext \"%s\" ignored]\n", s)
@@ -147,20 +150,24 @@ func Dial(protocol string, ipport string, extensions ...string) (hc *Conn, err e
 }
 
 // Close a hkex.Conn
-func (hc *Conn) Close() (err error) {
-	err = hc.c.Close()
+func (c *Conn) Close() (err error) {
+	err = c.c.Close()
 	fmt.Println("[Conn Closing]")
 	return
 }
 
 /*---------------------------------------------------------------------*/
 
-// A hkex Listener, conforming to net.Listener - returns a hkex.Conn
+// HKExListener is a Listener conforming to net.Listener
+//
+// See go doc net.Listener
 type HKExListener struct {
 	l net.Listener
 }
 
-// hkex.Listen, a drop-in replacement for net.Conn.Listen
+// Listen for a connection
+//
+// See go doc net.Listen
 func Listen(protocol string, ipport string) (hl HKExListener, e error) {
 	l, err := net.Listen(protocol, ipport)
 	if err != nil {
@@ -172,12 +179,16 @@ func Listen(protocol string, ipport string) (hl HKExListener, e error) {
 }
 
 // Close a hkex Listener
-func (hl *HKExListener) Close() {
-	hl.l.Close()
+//
+// See go doc io.Close
+func (hl *HKExListener) Close() error {
 	fmt.Println("[Listener Closed]")
+	return hl.l.Close()
 }
 
 // Accept a client connection, conforming to net.Listener.Accept()
+//
+// See go doc net.Listener.Accept
 func (hl *HKExListener) Accept() (hc Conn, err error) {
 	c, err := hl.l.Accept()
 	if err != nil {
@@ -211,11 +222,14 @@ func (hl *HKExListener) Accept() (hc Conn, err error) {
 	hc.w = hc.getStream(hc.h.fa)
 	return
 }
-
 /*---------------------------------------------------------------------*/
-func (hc Conn) Read(b []byte) (n int, err error) {
+
+// Read into a byte slice
+//
+// See go doc io.Reader
+func (c Conn) Read(b []byte) (n int, err error) {
 	fmt.Printf("[Decrypting...]\n")
-	n, err = hc.c.Read(b)
+	n, err = c.c.Read(b)
 	if err != nil && err.Error() != "EOF" {
 		panic(err)
 	}
@@ -224,22 +238,28 @@ func (hc Conn) Read(b []byte) (n int, err error) {
 	// The StreamReader acts like a pipe, decrypting
 	// whatever is available and forwarding the result
 	// to the parameter of Read() as a normal io.Reader
-	rs := &cipher.StreamReader{S: hc.r, R: db}
+	rs := &cipher.StreamReader{S: c.r, R: db}
 	n, err = rs.Read(b)
 	fmt.Printf("  ptext:%+v\n", b[:n])
 	return
 }
 
-func (hc Conn) Write(b []byte) (n int, err error) {
+// Write a byte slice
+//
+// See go doc io.Writer
+func (c Conn) Write(b []byte) (n int, err error) {
 	fmt.Printf("[Encrypting...]\n")
 	fmt.Printf("  ptext:%+v\n", b)
 	var wb bytes.Buffer
 	// The StreamWriter acts like a pipe, forwarding whatever is
 	// written to it through the cipher, encrypting as it goes
-	ws := &cipher.StreamWriter{S: hc.w, W: &wb}
-	n, err = ws.Write(b)
+	ws := &cipher.StreamWriter{S: c.w, W: &wb}
+	_, err = ws.Write(b)
+	if err != nil {
+		panic(err)
+	}
 	fmt.Printf("  ctext:%+v\n", wb.Bytes())
-	n, err = hc.c.Write(wb.Bytes())
+	n, err = c.c.Write(wb.Bytes())
 	return
 }