Initial experiments: HMAC on stream

demo/server/server.go

@@ -75,7 +75,7 @@ func runShellAs(who string, cmd string, interactive bool, conn hkex.Conn) (err e
 	var uid, gid uint32
 	fmt.Sscanf(u.Uid, "%d", &uid)
 	fmt.Sscanf(u.Gid, "%d", &gid)
-	fmt.Println("uid:", uid, "gid:", gid)
+	log.Println("uid:", uid, "gid:", gid)
 
 	// Need to clear server's env and set key vars of the
 	// target user. This isn't perfect (TERM doesn't seem to
@@ -155,14 +155,14 @@ func main() {
 	}
 	defer l.Close()
 
-	fmt.Println("Serving on", laddr)
+	log.Println("Serving on", laddr)
 	for {
 		// Wait for a connection.
 		conn, err := l.Accept()
 		if err != nil {
 			log.Fatal(err)
 		}
-		fmt.Println("Accepted client")
+		log.Println("Accepted client")
 
 		// Handle the connection in a new goroutine.
 		// The loop then returns to accepting, so that
@@ -179,7 +179,7 @@ func main() {
 
 			n, err := fmt.Fscanf(c, "%d %d %d %d\n", &len1, &len2, &len3, &len4)
 			if err != nil || n < 4 {
-				fmt.Println("[Bad cmdSpec fmt]")
+				log.Println("[Bad cmdSpec fmt]")
 				return err
 			}
 			//fmt.Printf("  lens:%d %d %d %d\n", len1, len2, len3, len4)
@@ -187,27 +187,27 @@ func main() {
 			rec.op = make([]byte, len1, len1)
 			_, err = io.ReadFull(c, rec.op)
 			if err != nil {
-				fmt.Println("[Bad cmdSpec.op]")
+				log.Println("[Bad cmdSpec.op]")
 				return err
 			}
 			rec.who = make([]byte, len2, len2)
 			_, err = io.ReadFull(c, rec.who)
 			if err != nil {
-				fmt.Println("[Bad cmdSpec.who]")
+				log.Println("[Bad cmdSpec.who]")
 				return err
 			}
 
 			rec.cmd = make([]byte, len3, len3)
 			_, err = io.ReadFull(c, rec.cmd)
 			if err != nil {
-				fmt.Println("[Bad cmdSpec.cmd]")
+				log.Println("[Bad cmdSpec.cmd]")
 				return err
 			}
 
 			rec.authCookie = make([]byte, len4, len4)
 			_, err = io.ReadFull(c, rec.authCookie)
 			if err != nil {
-				fmt.Println("[Bad cmdSpec.authCookie]")
+				log.Println("[Bad cmdSpec.authCookie]")
 				return err
 			}
 
@@ -229,19 +229,19 @@ func main() {
 				// Returned hopefully via an EOF or exit/logout;
 				// Clear current op so user can enter next, or EOF
 				rec.op[0] = 0
-				fmt.Println("[Command complete]")
+				log.Println("[Command complete]")
 			} else if rec.op[0] == 's' {
 				log.Println("[Running shell]")
 				runShellAs(string(rec.who), string(rec.cmd), true, conn)
 				// Returned hopefully via an EOF or exit/logout;
 				// Clear current op so user can enter next, or EOF
 				rec.op[0] = 0
-				fmt.Println("[Exiting shell]")
+				log.Println("[Exiting shell]")
 			} else {
 				log.Println("[Bad cmdSpec]")
 			}
 			return
 		}(conn)
 	} //endfor
-	fmt.Println("[Exiting]")
+	log.Println("[Exiting]")
 }

herradurakex.go

@@ -25,7 +25,6 @@ package herradurakex
 
     golang implementation by Russ Magee (rmagee_at_gmail.com) */
 
-
 /* This is the core KEx algorithm. For client/server net support code,
 See hkexnet.go for a golang/pkg/net for the compatible Conn interface
 using this to transparently negotiate keys and secure a network channel. */
@@ -148,6 +147,7 @@ func (h *HerraduraKEx) FA() {
 	h.fa = h.fscxRevolve(h.PeerD, h.b, h.intSz-h.pubSz)
 	h.fa.Xor(h.fa, h.a)
 }
+
 // Output HerraduraKEx type value as a string. Implements Stringer interface.
 func (h *HerraduraKEx) String() string {
 	return fmt.Sprintf("s:%d p:%d\na:%s\nb:%s\nd:->%s\n<-PeerD:%s\nfa:%s",

hkexauth.go

@@ -5,7 +5,6 @@ package herradurakex
 import (
 	"bytes"
 	"encoding/csv"
-	"fmt"
 	"io"
 	"io/ioutil"
 	"log"
@@ -19,7 +18,7 @@ func AuthUser(username string, auth string, fname string) (valid bool, allowedCm
 	b, e := ioutil.ReadFile(fname)
 	if e != nil {
 		valid = false
-		fmt.Println("ERROR: Cannot read hkexsh.passwd file!")
+		log.Println("ERROR: Cannot read hkexsh.passwd file!")
 		log.Fatal(e)
 	}
 	r := csv.NewReader(bytes.NewReader(b))
@@ -46,8 +45,6 @@ func AuthUser(username string, auth string, fname string) (valid bool, allowedCm
 			}
 			break
 		}
-
-		//fmt.Println(record)
 	}
 	return
 }

hkexchan.go

@@ -8,6 +8,7 @@ import (
 	"crypto"
 	"crypto/aes"
 	"crypto/cipher"
+	"encoding/hex"
 	"fmt"
 	"hash"
 	"log"
@@ -43,6 +44,7 @@ been negotiated via hkexnet.go
 func (hc Conn) getStream(keymat *big.Int) (rc cipher.Stream, mc hash.Hash) {
 	var key []byte
 	var block cipher.Block
+	var iv []byte
 	var ivlen int
 	var err error
 
@@ -54,7 +56,7 @@ func (hc Conn) getStream(keymat *big.Int) (rc cipher.Stream, mc hash.Hash) {
 		key = keymat.Bytes()[0:aes.BlockSize]
 		block, err = aes.NewCipher(key)
 		ivlen = aes.BlockSize
-		iv := keymat.Bytes()[aes.BlockSize : aes.BlockSize+ivlen]
+		iv = keymat.Bytes()[aes.BlockSize : aes.BlockSize+ivlen]
 		rc = cipher.NewOFB(block, iv)
 		log.Printf("[cipher AES_256 (%d)]\n", copts)
 		break
@@ -62,7 +64,7 @@ func (hc Conn) getStream(keymat *big.Int) (rc cipher.Stream, mc hash.Hash) {
 		key = keymat.Bytes()[0:twofish.BlockSize]
 		block, err = twofish.NewCipher(key)
 		ivlen = twofish.BlockSize
-		iv := keymat.Bytes()[twofish.BlockSize : twofish.BlockSize+ivlen]
+		iv = keymat.Bytes()[twofish.BlockSize : twofish.BlockSize+ivlen]
 		rc = cipher.NewOFB(block, iv)
 		log.Printf("[cipher TWOFISH_128 (%d)]\n", copts)
 		break
@@ -79,7 +81,7 @@ func (hc Conn) getStream(keymat *big.Int) (rc cipher.Stream, mc hash.Hash) {
 		//
 		// 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]
 		rc = cipher.NewOFB(block, iv)
 		log.Printf("[cipher BLOWFISH_64 (%d)]\n", copts)
 		break
@@ -109,5 +111,13 @@ func (hc Conn) getStream(keymat *big.Int) (rc cipher.Stream, mc hash.Hash) {
 		panic(err)
 	}
 
+	// Feed the IV into the hmac: all traffic in the connection must
+	// feed its data into the hmac afterwards, so both ends can xor
+	// that with the stream to detect corruption.
+	_, _ = mc.Write(iv)
+	var currentHash []byte
+	currentHash = mc.Sum(currentHash)
+	log.Printf("Channel init hmac(iv):%s\n", hex.EncodeToString(currentHash))
+
 	return
 }

hkexnet.go

@@ -27,10 +27,10 @@ import (
 	"encoding/hex"
 	"fmt"
 	"hash"
-	"io"
 	"log"
 	"math/big"
 	"net"
+	"strings"
 	"time"
 )
 
@@ -289,25 +289,27 @@ func (hl HKExListener) Accept() (hc Conn, err error) {
 //
 // See go doc io.Reader
 func (c Conn) Read(b []byte) (n int, err error) {
-	log.Printf("[Decrypting...]\n")
+	//log.Printf("[Decrypting...]\r\n")
 
-	//c.c.SetReadDeadline(time.Now().Add(1 * time.Second))
 	n, err = c.c.Read(b)
+	// Normal client 'exit' from interactive session will cause
+	// (on server side) err.Error() == "<iface/addr info ...>: use of closed network connection"
 	if err != nil && err.Error() != "EOF" {
-		//if neterr, ok := err.(net.Error); ok {
-		//	fmt.Printf("[Read() timeout - %s]\n", neterr)
-		//} else {
-		//	panic(err)
-		//}
+		if !strings.HasSuffix(err.Error(), "use of closed network connection") {
+			log.Println("unexpected Read() err:", err)
+		} else {
+			log.Println("[Client hung up]")
+		}
 	}
-	log.Printf("  ctext:%+v\n", b[:n]) // print only used portion
+	log.Printf("  <:ctext:\r\n%s\r\n", hex.Dump(b[:n])) //EncodeToString(b[:n])) // print only used portion
+
 	db := bytes.NewBuffer(b[:n])
 	// 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: c.r, R: db}
 	n, err = rs.Read(b)
-	log.Printf("  ptext:%+v\n", b[:n])
+	log.Printf("  <-ptext:\r\n%s\r\n", hex.Dump(b[:n])) //EncodeToString(b[:n]))
 	return
 }
 
@@ -315,8 +317,8 @@ func (c Conn) Read(b []byte) (n int, err error) {
 //
 // See go doc io.Writer
 func (c Conn) Write(b []byte) (n int, err error) {
-	log.Printf("[Encrypting...]\n")
-	log.Printf("  ptext:%+v\n", b)
+	//log.Printf("[Encrypting...]\r\n")
+	log.Printf("  :>ptext:\r\n%s\r\n", hex.Dump(b)) //EncodeToString(b))
 	var wb bytes.Buffer
 	// The StreamWriter acts like a pipe, forwarding whatever is
 	// written to it through the cipher, encrypting as it goes
@@ -325,7 +327,7 @@ func (c Conn) Write(b []byte) (n int, err error) {
 	if err != nil {
 		panic(err)
 	}
-	log.Printf("  ctext:%+v\n", wb.Bytes())
+	log.Printf("  ->ctext:\r\n%s\r\n", hex.Dump(wb.Bytes())) //EncodeToString(b)) // print only used portion
 	n, err = c.c.Write(wb.Bytes())
 	return
 }