mirror of https://gogs.blitter.com/RLabs/xs
-Added error checking for all stages of hkex.Conn.Accept() and GetStream()
-Server will log such errors without panic/exit -Const added but not yet used for 'chaff' packets
This commit is contained in:
Russ Magee
parent
c56d4d9ad9
commit
50f0433579
29
hkexchan.go
29
hkexchan.go
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@ -15,11 +15,11 @@ import (
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"crypto/aes"
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"crypto/cipher"
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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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"log"
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"math/big"
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"os"
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"golang.org/x/crypto/blowfish"
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"golang.org/x/crypto/twofish"
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@ -46,12 +46,11 @@ const (
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/* Support functionality to set up encryption after a channel has
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been negotiated via hkexnet.go
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*/
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func (hc Conn) getStream(keymat *big.Int) (rc cipher.Stream, mc hash.Hash) {
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func (hc Conn) getStream(keymat *big.Int) (rc cipher.Stream, mc hash.Hash, err error) {
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var key []byte
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var block cipher.Block
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var iv []byte
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var ivlen int
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var err error
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copts := hc.cipheropts & 0xFF
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// TODO: each cipher alg case should ensure len(keymat.Bytes())
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@ -93,7 +92,8 @@ func (hc Conn) getStream(keymat *big.Int) (rc cipher.Stream, mc hash.Hash) {
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default:
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log.Printf("[invalid cipher (%d)]\n", copts)
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fmt.Printf("DOOFUS SET A VALID CIPHER ALG (%d)\n", copts)
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os.Exit(1)
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err = errors.New("hkexchan: INVALID CIPHER ALG")
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//os.Exit(1)
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}
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hopts := (hc.cipheropts >> 8) & 0xFF
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@ -109,20 +109,19 @@ func (hc Conn) getStream(keymat *big.Int) (rc cipher.Stream, mc hash.Hash) {
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default:
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log.Printf("[invalid hmac (%d)]\n", hopts)
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fmt.Printf("DOOFUS SET A VALID HMAC ALG (%d)\n", hopts)
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os.Exit(1)
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err = errors.New("hkexchan: INVALID HMAC ALG")
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return
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//os.Exit(1)
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}
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if err != nil {
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panic(err)
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// Feed the IV into the hmac: all traffic in the connection must
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// feed its data into the hmac afterwards, so both ends can xor
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// that with the stream to detect corruption.
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_, _ = mc.Write(iv)
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var currentHash []byte
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currentHash = mc.Sum(currentHash)
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log.Printf("Channel init hmac(iv):%s\n", hex.EncodeToString(currentHash))
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}
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// Feed the IV into the hmac: all traffic in the connection must
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// feed its data into the hmac afterwards, so both ends can xor
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// that with the stream to detect corruption.
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_, _ = mc.Write(iv)
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var currentHash []byte
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currentHash = mc.Sum(currentHash)
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log.Printf("Channel init hmac(iv):%s\n", hex.EncodeToString(currentHash))
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return
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}
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54
hkexnet.go
54
hkexnet.go
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@ -28,6 +28,12 @@ import (
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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 detect on remote end
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csoChaff // This packet is a dummy, do not process beyond decryption
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)
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/*---------------------------------------------------------------------*/
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// Conn is a HKex connection - a drop-in replacement for net.Conn
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@ -149,8 +155,8 @@ func Dial(protocol string, ipport string, extensions ...string) (hc *Conn, err e
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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 = hc.getStream(hc.h.fa)
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hc.w, hc.wm = hc.getStream(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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@ -262,11 +268,13 @@ func (hl HKExListener) Accept() (hc Conn, err error) {
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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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@ -279,8 +287,8 @@ func (hl HKExListener) Accept() (hc Conn, err error) {
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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 = hc.getStream(hc.h.fa)
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hc.w, hc.wm = hc.getStream(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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@ -303,9 +311,9 @@ func (c Conn) Read(b []byte) (n int, err error) {
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var hmacIn [4]uint8
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var payloadLen uint32
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// Read ctrl/status opcode (for now, set nonzero on hmac mismatch)
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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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if ctrlStatOp != 0 {
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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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@ -328,14 +336,19 @@ func (c Conn) Read(b []byte) (n int, err error) {
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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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} // else {
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// return 0, err
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//}
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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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panic("Insane payloadLen")
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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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@ -364,8 +377,14 @@ func (c Conn) Read(b []byte) (n int, err error) {
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if err != nil {
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panic(err)
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}
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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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// 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]\n")
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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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@ -374,10 +393,11 @@ func (c Conn) Read(b []byte) (n int, err error) {
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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 - hmac mismatch, possible channel tampering **")
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_, _ = c.c.Write([]byte{0x1})
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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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@ -416,11 +436,11 @@ func (c Conn) Write(b []byte) (n int, err error) {
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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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var ctrlStatOp byte
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ctrlStatOp = 0x00
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ctrlStatOp = csoNone
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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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@ -19,7 +19,7 @@ import (
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"os/user"
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"github.com/jameskeane/bcrypt"
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hkexsh "blitter.com/hkexsh"
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hkexsh "blitter.com/go/hkexsh"
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)
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func main() {
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@ -18,7 +18,7 @@ import (
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"strings"
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"sync"
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hkexsh "blitter.com/hkexsh"
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hkexsh "blitter.com/go/hkexsh"
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isatty "github.com/mattn/go-isatty"
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)
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@ -18,8 +18,8 @@ import (
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"os/user"
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"syscall"
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hkexsh "blitter.com/hkexsh"
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"blitter.com/hkexsh/spinsult"
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hkexsh "blitter.com/go/hkexsh"
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"blitter.com/go/hkexsh/spinsult"
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"github.com/kr/pty"
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)
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@ -171,90 +171,93 @@ func main() {
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// Wait for a connection.
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conn, err := l.Accept()
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if err != nil {
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log.Fatal(err)
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}
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log.Println("Accepted client")
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log.Printf("Accept() got error(%v), hanging up.\n", err)
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conn.Close()
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//log.Fatal(err)
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} else {
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log.Println("Accepted client")
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// Handle the connection in a new goroutine.
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// The loop then returns to accepting, so that
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// multiple connections may be served concurrently.
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go func(c hkexsh.Conn) (e error) {
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defer c.Close()
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// Handle the connection in a new goroutine.
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// The loop then returns to accepting, so that
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// multiple connections may be served concurrently.
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go func(c hkexsh.Conn) (e error) {
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defer c.Close()
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//We use io.ReadFull() here to guarantee we consume
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//just the data we want for the cmdSpec, and no more.
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//Otherwise data will be sitting in the channel that isn't
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//passed down to the command handlers.
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var rec cmdSpec
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var len1, len2, len3, len4 uint32
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//We use io.ReadFull() here to guarantee we consume
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//just the data we want for the cmdSpec, and no more.
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//Otherwise data will be sitting in the channel that isn't
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//passed down to the command handlers.
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var rec cmdSpec
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var len1, len2, len3, len4 uint32
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n, err := fmt.Fscanf(c, "%d %d %d %d\n", &len1, &len2, &len3, &len4)
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log.Printf("cmdSpec read:%d %d %d %d\n", len1, len2, len3, len4)
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n, err := fmt.Fscanf(c, "%d %d %d %d\n", &len1, &len2, &len3, &len4)
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log.Printf("cmdSpec read:%d %d %d %d\n", len1, len2, len3, len4)
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if err != nil || n < 4 {
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log.Println("[Bad cmdSpec fmt]")
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return err
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}
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//fmt.Printf(" lens:%d %d %d %d\n", len1, len2, len3, len4)
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if err != nil || n < 4 {
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log.Println("[Bad cmdSpec fmt]")
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return err
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}
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//fmt.Printf(" lens:%d %d %d %d\n", len1, len2, len3, len4)
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rec.op = make([]byte, len1, len1)
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_, err = io.ReadFull(c, rec.op)
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if err != nil {
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log.Println("[Bad cmdSpec.op]")
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return err
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}
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rec.who = make([]byte, len2, len2)
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_, err = io.ReadFull(c, rec.who)
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if err != nil {
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log.Println("[Bad cmdSpec.who]")
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return err
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}
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rec.op = make([]byte, len1, len1)
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_, err = io.ReadFull(c, rec.op)
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if err != nil {
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log.Println("[Bad cmdSpec.op]")
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return err
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}
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rec.who = make([]byte, len2, len2)
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_, err = io.ReadFull(c, rec.who)
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if err != nil {
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log.Println("[Bad cmdSpec.who]")
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return err
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}
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rec.cmd = make([]byte, len3, len3)
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_, err = io.ReadFull(c, rec.cmd)
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if err != nil {
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log.Println("[Bad cmdSpec.cmd]")
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return err
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}
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rec.cmd = make([]byte, len3, len3)
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_, err = io.ReadFull(c, rec.cmd)
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if err != nil {
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log.Println("[Bad cmdSpec.cmd]")
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return err
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}
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rec.authCookie = make([]byte, len4, len4)
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_, err = io.ReadFull(c, rec.authCookie)
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if err != nil {
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log.Println("[Bad cmdSpec.authCookie]")
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return err
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}
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rec.authCookie = make([]byte, len4, len4)
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_, err = io.ReadFull(c, rec.authCookie)
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if err != nil {
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log.Println("[Bad cmdSpec.authCookie]")
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return err
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}
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log.Printf("[cmdSpec: op:%c who:%s cmd:%s auth:****]\n",
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rec.op[0], string(rec.who), string(rec.cmd))
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log.Printf("[cmdSpec: op:%c who:%s cmd:%s auth:****]\n",
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rec.op[0], string(rec.who), string(rec.cmd))
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valid, allowedCmds := hkexsh.AuthUser(string(rec.who), string(rec.authCookie), "/etc/hkexsh.passwd")
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if !valid {
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log.Println("Invalid user", string(rec.who))
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c.Write([]byte(rejectUserMsg()))
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valid, allowedCmds := hkexsh.AuthUser(string(rec.who), string(rec.authCookie), "/etc/hkexsh.passwd")
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if !valid {
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log.Println("Invalid user", string(rec.who))
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c.Write([]byte(rejectUserMsg()))
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return
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}
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log.Printf("[allowedCmds:%s]\n", allowedCmds)
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if rec.op[0] == 'c' {
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// Non-interactive command
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log.Println("[Running command]")
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runShellAs(string(rec.who), string(rec.cmd), false, conn)
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// Returned hopefully via an EOF or exit/logout;
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// Clear current op so user can enter next, or EOF
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rec.op[0] = 0
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log.Println("[Command complete]")
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} else if rec.op[0] == 's' {
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log.Println("[Running shell]")
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runShellAs(string(rec.who), string(rec.cmd), true, conn)
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// Returned hopefully via an EOF or exit/logout;
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// Clear current op so user can enter next, or EOF
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rec.op[0] = 0
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log.Println("[Exiting shell]")
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} else {
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log.Println("[Bad cmdSpec]")
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}
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return
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}
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log.Printf("[allowedCmds:%s]\n", allowedCmds)
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if rec.op[0] == 'c' {
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// Non-interactive command
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log.Println("[Running command]")
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runShellAs(string(rec.who), string(rec.cmd), false, conn)
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// Returned hopefully via an EOF or exit/logout;
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// Clear current op so user can enter next, or EOF
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rec.op[0] = 0
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log.Println("[Command complete]")
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} else if rec.op[0] == 's' {
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log.Println("[Running shell]")
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runShellAs(string(rec.who), string(rec.cmd), true, conn)
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// Returned hopefully via an EOF or exit/logout;
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// Clear current op so user can enter next, or EOF
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rec.op[0] = 0
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log.Println("[Exiting shell]")
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} else {
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log.Println("[Bad cmdSpec]")
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}
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return
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}(conn)
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}(conn)
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} // Accept() success
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} //endfor
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log.Println("[Exiting]")
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}
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