Replace MD5 with a cryptographically secure random IV generation

- edgeview has the mode of using encryption for the payload, and it was
  using static md5 IV value. this patch is to fix with the secure random
  dynamic IV generation for the encryption op.

Signed-off-by: naiming-zededa <naiming@zededa.com>

Author: naiming-zededa

pkg/edgeview/src/crypto.go

@@ -10,7 +10,6 @@ import (
 	"crypto/cipher"
 	"crypto/ecdsa"
 	"crypto/hmac"
-	"crypto/md5"
 	"crypto/rand"
 	"crypto/rsa"
 	"crypto/sha256"
@@ -34,7 +33,6 @@ const hashBytesNum = 32 // Hmac Sha256 Hash is 32 bytes fixed
 var (
 	nonceOpEncrption bool
 	nonceHash        [32]byte         // JWT Nonce with Sha256Sum for encryption
-	viBytes          [16]byte         // vi 16 bytes data for encryption
 	jwtNonce         string           // JWT session Nonce for authentication
 	clientAuthType   types.EvAuthType // edgeview client authentication type
 	evSSHPrivateKey  string           // path to Edgeview SSH private key
@@ -47,6 +45,7 @@ type envelopeMsg struct {
 	Message    []byte             `json:"message"`
 	Sha256Hash [hashBytesNum]byte `json:"sha256Hash"`
 	Signature  []byte             // Field to store the cert auth signature
+	IV         []byte             `json:"iv,omitempty"`
 }
 
 // LoadPublicKey loads a public key from a PEM file and determines its type (RSA or EC)
@@ -178,6 +177,13 @@ func addEnvelopeAndWriteWss(msg []byte, isText bool, clientAuthNeeded bool) erro
 	return err
 }
 
+func rawTextMsgWriteWss(msg []byte) error {
+	wssWrMutex.Lock()
+	err := websocketConn.WriteMessage(websocket.TextMessage, msg)
+	wssWrMutex.Unlock()
+	return err
+}
+
 func addEvelopeToData(msg []byte) []byte {
 	if nonceOpEncrption {
 		return encryptData(msg)
@@ -208,14 +214,15 @@ func signAuthenData(msg []byte) []byte {
 }
 
 func encryptData(msg []byte) []byte {
-	eMsg, err := encryptEvMsg(msg)
+	iv, eMsg, err := encryptEvMsg(msg)
 	if err != nil {
 		log.Errorf("encrypt failed %v", err)
 		return nil
 	}
 	jmsg := envelopeMsg{
 		Message:    eMsg,
 		Sha256Hash: sha256.Sum256(msg),
+		IV:         iv,
 	}
 
 	jdata, err := json.Marshal(jmsg)
@@ -284,7 +291,7 @@ func verifyEnvelopeData(data []byte, checkClientAuth bool) (bool, bool, []byte,
 	}
 
 	if nonceOpEncrption {
-		ok, msg := decryptEvMsg(envelope.Message)
+		ok, msg := decryptEvMsg(envelope.IV, envelope.Message)
 		if !ok {
 			return true, false, nil, keyComment
 		}
@@ -304,24 +311,37 @@ func verifyEnvelopeData(data []byte, checkClientAuth bool) (bool, bool, []byte,
 	return true, true, envelope.Message, keyComment
 }
 
-func encryptEvMsg(msg []byte) ([]byte, error) {
+func encryptEvMsg(msg []byte) ([]byte, []byte, error) {
 	block, err := aes.NewCipher(nonceHash[:])
 	if err != nil {
-		return nil, err
+		return nil, nil, err
 	}
 
-	cfb := cipher.NewCFBEncrypter(block, viBytes[:])
+	iv := make([]byte, aes.BlockSize)
+	if _, err := rand.Read(iv); err != nil {
+		return nil, nil, err
+	}
+
+	cfb := cipher.NewCFBEncrypter(block, iv)
 	cipherText := make([]byte, len(msg))
 	cfb.XORKeyStream(cipherText, msg)
-	return cipherText, nil
+
+	return iv, cipherText, nil
 }
 
-func decryptEvMsg(data []byte) (bool, []byte) {
+func decryptEvMsg(iv, data []byte) (bool, []byte) {
+	if len(iv) != aes.BlockSize {
+		// can not use encryption for sending this message, otherwise client side won't be able to decrypt
+		_ = rawTextMsgWriteWss([]byte(fmt.Sprintf("Edgeview encrypted message missing or invalid IV. Need Edgeview Client version %s or higher\n", encMinVersion)))
+		return false, nil
+	}
+
 	block, err := aes.NewCipher(nonceHash[:])
 	if err != nil {
 		return false, nil
 	}
-	cfb := cipher.NewCFBDecrypter(block, viBytes[:])
+
+	cfb := cipher.NewCFBDecrypter(block, iv)
 	plainText := make([]byte, len(data))
 	cfb.XORKeyStream(plainText, data)
 	return true, plainText
@@ -335,7 +355,6 @@ func encryptVarInit(jdata types.EvjwtInfo) {
 	nonceOpEncrption = jdata.Enc
 	if nonceOpEncrption {
 		nonceHash = sha256.Sum256([]byte(jdata.Key))
-		viBytes = md5.Sum([]byte(jdata.Key))
 	}
 }
 

pkg/edgeview/src/edge-view.go

@@ -44,13 +44,14 @@ const (
 	agentName         = "edgeview"
 	closeMessage      = "+++Done+++"
 	tarCopyDoneMsg    = "+++TarCopyDone+++"
-	edgeViewVersion   = "0.8.6" // set the version now to 0.8.6
+	edgeViewVersion   = "0.8.7"
 	cpLogFileString   = "copy-logfiles"
 	clientIPMsg       = "YourEndPointIPAddr:"
 	serverRateMsg     = "ServerRateLimit:disable"
 	tcpPktRate        = MbpsToBytes * 5 * 1.2 // 125k Bytes * 5 * 1.2, or 5Mbits add 20%
 	tcpPktBurst       = 65536                 // burst allow bytes
 	tarMinVersion     = "0.8.5"               // for tar operation, expect client to have newer version
+	encMinVersion     = "0.8.7"               // for encryption operation, expect client to have newer version
 	verifyFailed      = "+++Verify failed+++"
 	keepaliveInterval = 30 * time.Second // interval for sending websocket ping messages
 )