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xs
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hmac tampering indication implemented -- local and remote-side

This commit is contained in:
Russ Magee 2018-04-15 13:29:06 -07:00
parent b45784e07b
commit c56d4d9ad9
1 changed files with 18 additions and 4 deletions
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20
hkexnet.go
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@ -17,6 +17,7 @@ import (
"crypto/cipher" "crypto/cipher"
"encoding/binary" "encoding/binary"
"encoding/hex" "encoding/hex"
"errors"
"fmt" "fmt"
"hash" "hash"
"io" "io"
@ -298,9 +299,18 @@ func (c Conn) Read(b []byte) (n int, err error) {
break break
} }
var ctrlStatOp uint8
var hmacIn [4]uint8 var hmacIn [4]uint8
var payloadLen uint32 var payloadLen uint32
// Read ctrl/status opcode (for now, set nonzero on hmac mismatch)
err = binary.Read(c.c, binary.BigEndian, &ctrlStatOp)
if ctrlStatOp != 0 {
// Other side indicated channel tampering, close channel
c.Close()
return 1, errors.New("** ALERT - remote end detected HMAC mismatch - possible channel tampering **")
}
// Read the hmac and payload len first // Read the hmac and payload len first
err = binary.Read(c.c, binary.BigEndian, &hmacIn) err = binary.Read(c.c, binary.BigEndian, &hmacIn)
// Normal client 'exit' from interactive session will cause // Normal client 'exit' from interactive session will cause
@ -362,10 +372,10 @@ func (c Conn) Read(b []byte) (n int, err error) {
hTmp := c.rm.Sum(nil)[0:4] hTmp := c.rm.Sum(nil)[0:4]
log.Printf("<%04x) HMAC:(i)%s (c)%02x\r\n", decryptN, hex.EncodeToString([]byte(hmacIn[0:])), hTmp) log.Printf("<%04x) HMAC:(i)%s (c)%02x\r\n", decryptN, hex.EncodeToString([]byte(hmacIn[0:])), hTmp)
// Puke if hmac didn't match, corrupted channel // Log alert if hmac didn't match, corrupted channel
if !bytes.Equal(hTmp, []byte(hmacIn[0:])) || hmacIn[0] > 0xf8 { if !bytes.Equal(hTmp, []byte(hmacIn[0:])) /*|| hmacIn[0] > 0xf8*/ {
fmt.Println("** ALERT - hmac mismatch, possible channel tampering **") fmt.Println("** ALERT - hmac mismatch, possible channel tampering **")
c.Close() _, _ = c.c.Write([]byte{0x1})
} }
} }
retN := c.dBuf.Len() retN := c.dBuf.Len()
@ -407,6 +417,10 @@ func (c Conn) Write(b []byte) (n int, err error) {
} }
log.Printf(" ->ctext:\r\n%s\r\n", hex.Dump(wb.Bytes())) log.Printf(" ->ctext:\r\n%s\r\n", hex.Dump(wb.Bytes()))
var ctrlStatOp byte
ctrlStatOp = 0x00
_ = binary.Write(c.c, binary.BigEndian, &ctrlStatOp)
// Write hmac LSB, payloadLen followed by payload // Write hmac LSB, payloadLen followed by payload
_ = binary.Write(c.c, binary.BigEndian, hmacOut) _ = binary.Write(c.c, binary.BigEndian, hmacOut)
_ = binary.Write(c.c, binary.BigEndian, payloadLen) _ = binary.Write(c.c, binary.BigEndian, payloadLen)