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528 lines
15 KiB
Go
528 lines
15 KiB
Go
// hkexnet.go - net.Conn compatible channel setup with encrypted/HMAC
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// negotiation
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// Copyright (c) 2017-2018 Russell Magee
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// Licensed under the terms of the MIT license (see LICENSE.mit in this
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// distribution)
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//
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// golang implementation by Russ Magee (rmagee_at_gmail.com)
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package hkexsh
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// Implementation of HKEx-wrapped versions of the golang standard
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// net package interfaces, allowing clients and servers to simply replace
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// 'net.Dial' and 'net.Listen' with 'hkex.Dial' and 'hkex.Listen'.
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import (
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"bytes"
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"crypto/cipher"
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"encoding/binary"
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"encoding/hex"
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"errors"
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"fmt"
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"hash"
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"io"
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"log"
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"math/big"
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"net"
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"strings"
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"sync"
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"time"
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)
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const (
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CSONone = iota // No error, normal packet
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CSOHmacInvalid // HMAC mismatch detected on remote end
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CSOTermSize // set term size (rows:cols)
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CSOChaff // Dummy packet, do not pass beyond decryption
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)
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/*---------------------------------------------------------------------*/
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type WinSize struct {
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Rows uint16
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Cols uint16
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}
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// Conn is a HKex connection - a drop-in replacement for net.Conn
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type Conn struct {
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c net.Conn // which also implements io.Reader, io.Writer, ...
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h *HerraduraKEx
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cipheropts uint32 // post-KEx cipher/hmac options
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opts uint32 // post-KEx protocol options (caller-defined)
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WinCh chan WinSize
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Rows uint16
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Cols uint16
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Rwmut sync.Mutex
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r cipher.Stream //read cipherStream
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rm hash.Hash
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w cipher.Stream //write cipherStream
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wm hash.Hash
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dBuf *bytes.Buffer //decrypt buffer for Read()
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}
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// ConnOpts returns the cipher/hmac options value, which is sent to the
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// peer but is not itself part of the KEx.
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//
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// (Used for protocol-level negotiations after KEx such as
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// cipher/HMAC algorithm options etc.)
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func (c Conn) ConnOpts() uint32 {
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return c.cipheropts
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}
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// SetConnOpts sets the cipher/hmac options value, which is sent to the
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// peer as part of KEx but not part of the KEx itself.
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//
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// opts - bitfields for cipher and hmac alg. to use after KEx
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func (c *Conn) SetConnOpts(copts uint32) {
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c.cipheropts = copts
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}
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// Opts returns the protocol options value, which is sent to the peer
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// but is not itself part of the KEx or connection (cipher/hmac) setup.
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//
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// Consumers of this lib may use this for protocol-level options not part
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// of the KEx or encryption info used by the connection.
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func (c Conn) Opts() uint32 {
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return c.opts
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}
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// SetOpts sets the protocol options value, which is sent to the peer
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// but is not itself part of the KEx or connection (cipher/hmac) setup.
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//
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// Consumers of this lib may use this for protocol-level options not part
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// of the KEx of encryption info used by the connection.
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//
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// opts - a uint32, caller-defined
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func (c *Conn) SetOpts(opts uint32) {
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c.opts = opts
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}
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func (c *Conn) applyConnExtensions(extensions ...string) {
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for _, s := range extensions {
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switch s {
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case "C_AES_256":
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log.Println("[extension arg = C_AES_256]")
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c.cipheropts &= (0xFFFFFF00)
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c.cipheropts |= CAlgAES256
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break
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case "C_TWOFISH_128":
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log.Println("[extension arg = C_TWOFISH_128]")
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c.cipheropts &= (0xFFFFFF00)
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c.cipheropts |= CAlgTwofish128
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break
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case "C_BLOWFISH_64":
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log.Println("[extension arg = C_BLOWFISH_64]")
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c.cipheropts &= (0xFFFFFF00)
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c.cipheropts |= CAlgBlowfish64
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break
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case "H_SHA256":
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log.Println("[extension arg = H_SHA256]")
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c.cipheropts &= (0xFFFF00FF)
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c.cipheropts |= (HmacSHA256 << 8)
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break
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default:
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log.Printf("[Dial ext \"%s\" ignored]\n", s)
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break
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}
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}
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}
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// Dial as net.Dial(), but with implicit HKEx PeerD read on connect
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// Can be called like net.Dial(), defaulting to C_AES_256/H_SHA256,
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// or additional option arguments can be passed amongst the following:
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//
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// "C_AES_256" | "C_TWOFISH_128"
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//
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// "H_SHA256"
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func Dial(protocol string, ipport string, extensions ...string) (hc *Conn, err error) {
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// Open raw Conn c
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c, err := net.Dial(protocol, ipport)
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if err != nil {
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return nil, err
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}
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// Init hkexnet.Conn hc over net.Conn c
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hc = &Conn{c: c, h: New(0, 0), dBuf: new(bytes.Buffer)}
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hc.applyConnExtensions(extensions...)
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// Send hkexnet.Conn parameters to remote side
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// d is value for Herradura key exchange
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fmt.Fprintf(c, "0x%s\n%08x:%08x\n", hc.h.d.Text(16),
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hc.cipheropts, hc.opts)
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d := big.NewInt(0)
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_, err = fmt.Fscanln(c, d)
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if err != nil {
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return nil, err
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}
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_, err = fmt.Fscanf(c, "%08x:%08x\n",
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&hc.cipheropts, &hc.opts)
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if err != nil {
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return nil, err
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}
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hc.h.PeerD = d
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log.Printf("** D:%s\n", hc.h.d.Text(16))
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log.Printf("**(c)** peerD:%s\n", hc.h.PeerD.Text(16))
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hc.h.FA()
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log.Printf("**(c)** FA:%s\n", hc.h.fa)
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hc.r, hc.rm, err = hc.getStream(hc.h.fa)
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hc.w, hc.wm, err = hc.getStream(hc.h.fa)
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return
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}
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// Close a hkex.Conn
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func (c Conn) Close() (err error) {
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err = c.c.Close()
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log.Println("[Conn Closing]")
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return
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}
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// LocalAddr returns the local network address.
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func (c Conn) LocalAddr() net.Addr {
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return c.c.LocalAddr()
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}
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// RemoteAddr returns the remote network address.
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func (c Conn) RemoteAddr() net.Addr {
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return c.c.RemoteAddr()
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}
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// SetDeadline sets the read and write deadlines associated
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// with the connection. It is equivalent to calling both
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// SetReadDeadline and SetWriteDeadline.
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//
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// A deadline is an absolute time after which I/O operations
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// fail with a timeout (see type Error) instead of
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// blocking. The deadline applies to all future and pending
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// I/O, not just the immediately following call to Read or
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// Write. After a deadline has been exceeded, the connection
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// can be refreshed by setting a deadline in the future.
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//
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// An idle timeout can be implemented by repeatedly extending
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// the deadline after successful Read or Write calls.
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//
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// A zero value for t means I/O operations will not time out.
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func (c Conn) SetDeadline(t time.Time) error {
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return c.SetDeadline(t)
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}
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// SetWriteDeadline sets the deadline for future Write calls
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// and any currently-blocked Write call.
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// Even if write times out, it may return n > 0, indicating that
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// some of the data was successfully written.
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// A zero value for t means Write will not time out.
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func (c Conn) SetWriteDeadline(t time.Time) error {
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return c.SetWriteDeadline(t)
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}
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// SetReadDeadline sets the deadline for future Read calls
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// and any currently-blocked Read call.
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// A zero value for t means Read will not time out.
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func (c Conn) SetReadDeadline(t time.Time) error {
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return c.SetReadDeadline(t)
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}
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/*---------------------------------------------------------------------*/
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// HKExListener is a Listener conforming to net.Listener
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//
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// See go doc net.Listener
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type HKExListener struct {
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l net.Listener
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}
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// Listen for a connection
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//
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// See go doc net.Listen
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func Listen(protocol string, ipport string) (hl HKExListener, e error) {
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l, err := net.Listen(protocol, ipport)
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if err != nil {
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return HKExListener{nil}, err
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}
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log.Println("[Listening]")
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hl.l = l
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return
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}
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// Close a hkex Listener - closes the Listener.
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// Any blocked Accept operations will be unblocked and return errors.
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//
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// See go doc net.Listener.Close
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func (hl HKExListener) Close() error {
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log.Println("[Listener Closed]")
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return hl.l.Close()
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}
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// Addr returns a the listener's network address.
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//
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// See go doc net.Listener.Addr
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func (hl HKExListener) Addr() net.Addr {
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return hl.l.Addr()
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}
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// Accept a client connection, conforming to net.Listener.Accept()
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//
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// See go doc net.Listener.Accept
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func (hl HKExListener) Accept() (hc Conn, err error) {
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// Open raw Conn c
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c, err := hl.l.Accept()
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if err != nil {
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return Conn{c: nil, h: nil, cipheropts: 0, opts: 0,
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r: nil, w: nil}, err
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}
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log.Println("[Accepted]")
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hc = Conn{c: c, h: New(0, 0), WinCh: make(chan WinSize, 1),
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dBuf: new(bytes.Buffer)}
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// Read in hkexnet.Conn parameters over raw Conn c
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// d is value for Herradura key exchange
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d := big.NewInt(0)
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_, err = fmt.Fscanln(c, d)
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log.Printf("[Got d:%v]", d)
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if err != nil {
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return hc, err
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}
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_, err = fmt.Fscanf(c, "%08x:%08x\n",
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&hc.cipheropts, &hc.opts)
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log.Printf("[Got cipheropts, opts:%v, %v]", hc.cipheropts, hc.opts)
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if err != nil {
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return hc, err
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}
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hc.h.PeerD = d
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log.Printf("** D:%s\n", hc.h.d.Text(16))
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log.Printf("**(s)** peerD:%s\n", hc.h.PeerD.Text(16))
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hc.h.FA()
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log.Printf("**(s)** FA:%s\n", hc.h.fa)
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fmt.Fprintf(c, "0x%s\n%08x:%08x\n", hc.h.d.Text(16),
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hc.cipheropts, hc.opts)
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hc.r, hc.rm, err = hc.getStream(hc.h.fa)
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hc.w, hc.wm, err = hc.getStream(hc.h.fa)
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return
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}
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/*---------------------------------------------------------------------*/
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// Read into a byte slice
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//
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// See go doc io.Reader
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func (c Conn) Read(b []byte) (n int, err error) {
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//log.Printf("[Decrypting...]\r\n")
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log.Printf("Read() requests %d bytes\n", len(b))
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for {
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//log.Printf("c.dBuf.Len(): %d\n", c.dBuf.Len())
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if c.dBuf.Len() > 0 /* len(b) */ {
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break
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}
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var ctrlStatOp uint8
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var hmacIn [4]uint8
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var payloadLen uint32
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// Read ctrl/status opcode (CSOHmacInvalid on hmac mismatch)
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err = binary.Read(c.c, binary.BigEndian, &ctrlStatOp)
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log.Printf("[ctrlStatOp: %v]\n", ctrlStatOp)
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if ctrlStatOp == CSOHmacInvalid {
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// Other side indicated channel tampering, close channel
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c.Close()
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return 1, errors.New("** ALERT - remote end detected HMAC mismatch - possible channel tampering **")
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}
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// Read the hmac and payload len first
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err = binary.Read(c.c, binary.BigEndian, &hmacIn)
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// Normal client 'exit' from interactive session will cause
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// (on server side) err.Error() == "<iface/addr info ...>: use of closed network connection"
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if err != nil {
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if !strings.HasSuffix(err.Error(), "use of closed network connection") {
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log.Println("unexpected Read() err:", err)
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} else {
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log.Println("[Client hung up]")
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}
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return 0, err
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}
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err = binary.Read(c.c, binary.BigEndian, &payloadLen)
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if err != nil {
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if err.Error() != "EOF" {
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panic(err)
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// Cannot just return 0, err here - client won't hang up properly
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// when 'exit' from shell. TODO: try server sending ctrlStatOp to
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// indicate to Reader? -rlm 20180428
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}
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}
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if payloadLen > 16384 {
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log.Printf("[Insane payloadLen:%v]\n", payloadLen)
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c.Close()
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return 1, errors.New("Insane payloadLen")
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}
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//log.Println("payloadLen:", payloadLen)
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var payloadBytes = make([]byte, payloadLen)
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n, err = io.ReadFull(c.c, payloadBytes)
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//log.Print(" << Read ", n, " payloadBytes")
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// Normal client 'exit' from interactive session will cause
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// (on server side) err.Error() == "<iface/addr info ...>: use of closed network connection"
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if err != nil && err.Error() != "EOF" {
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if !strings.HasSuffix(err.Error(), "use of closed network connection") {
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log.Println("unexpected Read() err:", err)
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} else {
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log.Println("[Client hung up]")
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}
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}
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log.Printf(" <:ctext:\r\n%s\r\n", hex.Dump(payloadBytes[:n]))
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db := bytes.NewBuffer(payloadBytes[:n]) //copying payloadBytes to db
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// The StreamReader acts like a pipe, decrypting
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// whatever is available and forwarding the result
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// to the parameter of Read() as a normal io.Reader
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rs := &cipher.StreamReader{S: c.r, R: db}
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// The caller isn't necessarily reading the full payload so we need
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// to decrypt ot an intermediate buffer, draining it on demand of caller
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decryptN, err := rs.Read(payloadBytes)
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log.Printf(" <-ptext:\r\n%s\r\n", hex.Dump(payloadBytes[:n]))
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if err != nil {
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panic(err)
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}
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// Throw away pkt if it's chaff (ie., caller to Read() won't see this data)
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if ctrlStatOp == CSOChaff {
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log.Printf("[Chaff pkt, discarded (len %d)]\n", decryptN)
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} else if ctrlStatOp == CSOTermSize {
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fmt.Sscanf(string(payloadBytes), "%d %d", &c.Rows, &c.Cols)
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log.Printf("[TermSize pkt: rows %v cols %v]\n", c.Rows, c.Cols)
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c.WinCh <- WinSize{c.Rows, c.Cols}
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} else {
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c.dBuf.Write(payloadBytes)
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//log.Printf("c.dBuf: %s\n", hex.Dump(c.dBuf.Bytes()))
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}
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// Re-calculate hmac, compare with received value
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c.rm.Write(payloadBytes)
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hTmp := c.rm.Sum(nil)[0:4]
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log.Printf("<%04x) HMAC:(i)%s (c)%02x\r\n", decryptN, hex.EncodeToString([]byte(hmacIn[0:])), hTmp)
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// Log alert if hmac didn't match, corrupted channel
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if !bytes.Equal(hTmp, []byte(hmacIn[0:])) /*|| hmacIn[0] > 0xf8*/ {
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fmt.Println("** ALERT - detected HMAC mismatch, possible channel tampering **")
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_, _ = c.c.Write([]byte{CSOHmacInvalid})
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}
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}
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retN := c.dBuf.Len()
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if retN > len(b) {
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retN = len(b)
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}
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log.Printf("Read() got %d bytes\n", retN)
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copy(b, c.dBuf.Next(retN))
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//log.Printf("As Read() returns, c.dBuf is %d long: %s\n", c.dBuf.Len(), hex.Dump(c.dBuf.Bytes()))
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return retN, nil
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}
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// Write a byte slice
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//
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// See go doc io.Writer
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func (c Conn) Write(b []byte) (n int, err error) {
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n, err = c.WritePacket(b, CSONone)
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return n, err
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}
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// Write a byte slice with specified ctrlStatusOp byte
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func (c Conn) WritePacket(b []byte, op byte) (n int, err error) {
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//log.Printf("[Encrypting...]\r\n")
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var hmacOut []uint8
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var payloadLen uint32
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log.Printf(" :>ptext:\r\n%s\r\n", hex.Dump(b))
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payloadLen = uint32(len(b))
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// Testing: '`1' will trigger a chaff packet
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//if payloadLen == 2 && string(b) == "`1" {
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// op = CSOChaff
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//}
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// Calculate hmac on payload
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c.wm.Write(b)
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hmacOut = c.wm.Sum(nil)[0:4]
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log.Printf(" (%04x> HMAC(o):%s\r\n", payloadLen, hex.EncodeToString(hmacOut))
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var wb bytes.Buffer
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// The StreamWriter acts like a pipe, forwarding whatever is
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// written to it through the cipher, encrypting as it goes
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ws := &cipher.StreamWriter{S: c.w, W: &wb}
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_, err = ws.Write(b)
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if err != nil {
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panic(err)
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}
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log.Printf(" ->ctext:\r\n%s\r\n", hex.Dump(wb.Bytes()))
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ctrlStatOp := op
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//{
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_ = binary.Write(c.c, binary.BigEndian, &ctrlStatOp)
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// Write hmac LSB, payloadLen followed by payload
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_ = binary.Write(c.c, binary.BigEndian, hmacOut)
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_ = binary.Write(c.c, binary.BigEndian, payloadLen)
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n, err = c.c.Write(wb.Bytes())
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//}
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if err != nil {
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//panic(err)
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log.Println(err)
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}
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return
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}
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// hkexsh.Copy() is a modified version of io.Copy() with locking,
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// on a passed-in mutex, around the actual call to Write() to permit
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// multiple producers to write hkexsh buffers to the same destination.
|
|
//
|
|
// (Used to generate chaff during sessions)
|
|
func Copy(m *sync.Mutex, dst io.Writer, src io.Reader) (written int64, err error) {
|
|
// // If the reader has a WriteTo method, use it to do the copy.
|
|
// // Avoids an allocation and a copy.
|
|
// if wt, ok := src.(io.WriterTo); ok {
|
|
// return wt.WriteTo(dst)
|
|
// }
|
|
// // Similarly, if the writer has a ReadFrom method, use it to do the copy.
|
|
// if rt, ok := dst.(io.ReaderFrom); ok {
|
|
// return rt.ReadFrom(src)
|
|
// }
|
|
|
|
buf := make([]byte, 32*1024)
|
|
for {
|
|
nr, er := src.Read(buf)
|
|
if nr > 0 {
|
|
m.Lock()
|
|
nw, ew := dst.Write(buf[0:nr])
|
|
m.Unlock()
|
|
if nw > 0 {
|
|
written += int64(nw)
|
|
}
|
|
if ew != nil {
|
|
err = ew
|
|
break
|
|
}
|
|
if nr != nw {
|
|
err = io.ErrShortWrite
|
|
break
|
|
}
|
|
}
|
|
if er != nil {
|
|
if er != io.EOF {
|
|
err = er
|
|
}
|
|
break
|
|
}
|
|
}
|
|
return written, err
|
|
}
|