mirror of
https://codeberg.org/forgejo/forgejo.git
synced 2024-08-22 04:28:06 +02:00
383 lines
9.9 KiB
Go
383 lines
9.9 KiB
Go
// Copyright 2011 The Go Authors. All rights reserved.
|
|
// Use of this source code is governed by a BSD-style
|
|
// license that can be found in the LICENSE file.
|
|
|
|
package ssh
|
|
|
|
import (
|
|
"crypto"
|
|
"crypto/rand"
|
|
"fmt"
|
|
"io"
|
|
"math"
|
|
"sync"
|
|
|
|
_ "crypto/sha1"
|
|
_ "crypto/sha256"
|
|
_ "crypto/sha512"
|
|
)
|
|
|
|
// These are string constants in the SSH protocol.
|
|
const (
|
|
compressionNone = "none"
|
|
serviceUserAuth = "ssh-userauth"
|
|
serviceSSH = "ssh-connection"
|
|
)
|
|
|
|
// supportedCiphers lists ciphers we support but might not recommend.
|
|
var supportedCiphers = []string{
|
|
"aes128-ctr", "aes192-ctr", "aes256-ctr",
|
|
"aes128-gcm@openssh.com",
|
|
chacha20Poly1305ID,
|
|
"arcfour256", "arcfour128", "arcfour",
|
|
aes128cbcID,
|
|
tripledescbcID,
|
|
}
|
|
|
|
// preferredCiphers specifies the default preference for ciphers.
|
|
var preferredCiphers = []string{
|
|
"aes128-gcm@openssh.com",
|
|
chacha20Poly1305ID,
|
|
"aes128-ctr", "aes192-ctr", "aes256-ctr",
|
|
}
|
|
|
|
// supportedKexAlgos specifies the supported key-exchange algorithms in
|
|
// preference order.
|
|
var supportedKexAlgos = []string{
|
|
kexAlgoCurve25519SHA256,
|
|
// P384 and P521 are not constant-time yet, but since we don't
|
|
// reuse ephemeral keys, using them for ECDH should be OK.
|
|
kexAlgoECDH256, kexAlgoECDH384, kexAlgoECDH521,
|
|
kexAlgoDH14SHA1, kexAlgoDH1SHA1,
|
|
}
|
|
|
|
// supportedHostKeyAlgos specifies the supported host-key algorithms (i.e. methods
|
|
// of authenticating servers) in preference order.
|
|
var supportedHostKeyAlgos = []string{
|
|
CertAlgoRSAv01, CertAlgoDSAv01, CertAlgoECDSA256v01,
|
|
CertAlgoECDSA384v01, CertAlgoECDSA521v01, CertAlgoED25519v01,
|
|
|
|
KeyAlgoECDSA256, KeyAlgoECDSA384, KeyAlgoECDSA521,
|
|
KeyAlgoRSA, KeyAlgoDSA,
|
|
|
|
KeyAlgoED25519,
|
|
}
|
|
|
|
// supportedMACs specifies a default set of MAC algorithms in preference order.
|
|
// This is based on RFC 4253, section 6.4, but with hmac-md5 variants removed
|
|
// because they have reached the end of their useful life.
|
|
var supportedMACs = []string{
|
|
"hmac-sha2-256-etm@openssh.com", "hmac-sha2-256", "hmac-sha1", "hmac-sha1-96",
|
|
}
|
|
|
|
var supportedCompressions = []string{compressionNone}
|
|
|
|
// hashFuncs keeps the mapping of supported algorithms to their respective
|
|
// hashes needed for signature verification.
|
|
var hashFuncs = map[string]crypto.Hash{
|
|
KeyAlgoRSA: crypto.SHA1,
|
|
KeyAlgoDSA: crypto.SHA1,
|
|
KeyAlgoECDSA256: crypto.SHA256,
|
|
KeyAlgoECDSA384: crypto.SHA384,
|
|
KeyAlgoECDSA521: crypto.SHA512,
|
|
CertAlgoRSAv01: crypto.SHA1,
|
|
CertAlgoDSAv01: crypto.SHA1,
|
|
CertAlgoECDSA256v01: crypto.SHA256,
|
|
CertAlgoECDSA384v01: crypto.SHA384,
|
|
CertAlgoECDSA521v01: crypto.SHA512,
|
|
}
|
|
|
|
// unexpectedMessageError results when the SSH message that we received didn't
|
|
// match what we wanted.
|
|
func unexpectedMessageError(expected, got uint8) error {
|
|
return fmt.Errorf("ssh: unexpected message type %d (expected %d)", got, expected)
|
|
}
|
|
|
|
// parseError results from a malformed SSH message.
|
|
func parseError(tag uint8) error {
|
|
return fmt.Errorf("ssh: parse error in message type %d", tag)
|
|
}
|
|
|
|
func findCommon(what string, client []string, server []string) (common string, err error) {
|
|
for _, c := range client {
|
|
for _, s := range server {
|
|
if c == s {
|
|
return c, nil
|
|
}
|
|
}
|
|
}
|
|
return "", fmt.Errorf("ssh: no common algorithm for %s; client offered: %v, server offered: %v", what, client, server)
|
|
}
|
|
|
|
type directionAlgorithms struct {
|
|
Cipher string
|
|
MAC string
|
|
Compression string
|
|
}
|
|
|
|
// rekeyBytes returns a rekeying intervals in bytes.
|
|
func (a *directionAlgorithms) rekeyBytes() int64 {
|
|
// According to RFC4344 block ciphers should rekey after
|
|
// 2^(BLOCKSIZE/4) blocks. For all AES flavors BLOCKSIZE is
|
|
// 128.
|
|
switch a.Cipher {
|
|
case "aes128-ctr", "aes192-ctr", "aes256-ctr", gcmCipherID, aes128cbcID:
|
|
return 16 * (1 << 32)
|
|
|
|
}
|
|
|
|
// For others, stick with RFC4253 recommendation to rekey after 1 Gb of data.
|
|
return 1 << 30
|
|
}
|
|
|
|
type algorithms struct {
|
|
kex string
|
|
hostKey string
|
|
w directionAlgorithms
|
|
r directionAlgorithms
|
|
}
|
|
|
|
func findAgreedAlgorithms(clientKexInit, serverKexInit *kexInitMsg) (algs *algorithms, err error) {
|
|
result := &algorithms{}
|
|
|
|
result.kex, err = findCommon("key exchange", clientKexInit.KexAlgos, serverKexInit.KexAlgos)
|
|
if err != nil {
|
|
return
|
|
}
|
|
|
|
result.hostKey, err = findCommon("host key", clientKexInit.ServerHostKeyAlgos, serverKexInit.ServerHostKeyAlgos)
|
|
if err != nil {
|
|
return
|
|
}
|
|
|
|
result.w.Cipher, err = findCommon("client to server cipher", clientKexInit.CiphersClientServer, serverKexInit.CiphersClientServer)
|
|
if err != nil {
|
|
return
|
|
}
|
|
|
|
result.r.Cipher, err = findCommon("server to client cipher", clientKexInit.CiphersServerClient, serverKexInit.CiphersServerClient)
|
|
if err != nil {
|
|
return
|
|
}
|
|
|
|
result.w.MAC, err = findCommon("client to server MAC", clientKexInit.MACsClientServer, serverKexInit.MACsClientServer)
|
|
if err != nil {
|
|
return
|
|
}
|
|
|
|
result.r.MAC, err = findCommon("server to client MAC", clientKexInit.MACsServerClient, serverKexInit.MACsServerClient)
|
|
if err != nil {
|
|
return
|
|
}
|
|
|
|
result.w.Compression, err = findCommon("client to server compression", clientKexInit.CompressionClientServer, serverKexInit.CompressionClientServer)
|
|
if err != nil {
|
|
return
|
|
}
|
|
|
|
result.r.Compression, err = findCommon("server to client compression", clientKexInit.CompressionServerClient, serverKexInit.CompressionServerClient)
|
|
if err != nil {
|
|
return
|
|
}
|
|
|
|
return result, nil
|
|
}
|
|
|
|
// If rekeythreshold is too small, we can't make any progress sending
|
|
// stuff.
|
|
const minRekeyThreshold uint64 = 256
|
|
|
|
// Config contains configuration data common to both ServerConfig and
|
|
// ClientConfig.
|
|
type Config struct {
|
|
// Rand provides the source of entropy for cryptographic
|
|
// primitives. If Rand is nil, the cryptographic random reader
|
|
// in package crypto/rand will be used.
|
|
Rand io.Reader
|
|
|
|
// The maximum number of bytes sent or received after which a
|
|
// new key is negotiated. It must be at least 256. If
|
|
// unspecified, a size suitable for the chosen cipher is used.
|
|
RekeyThreshold uint64
|
|
|
|
// The allowed key exchanges algorithms. If unspecified then a
|
|
// default set of algorithms is used.
|
|
KeyExchanges []string
|
|
|
|
// The allowed cipher algorithms. If unspecified then a sensible
|
|
// default is used.
|
|
Ciphers []string
|
|
|
|
// The allowed MAC algorithms. If unspecified then a sensible default
|
|
// is used.
|
|
MACs []string
|
|
}
|
|
|
|
// SetDefaults sets sensible values for unset fields in config. This is
|
|
// exported for testing: Configs passed to SSH functions are copied and have
|
|
// default values set automatically.
|
|
func (c *Config) SetDefaults() {
|
|
if c.Rand == nil {
|
|
c.Rand = rand.Reader
|
|
}
|
|
if c.Ciphers == nil {
|
|
c.Ciphers = preferredCiphers
|
|
}
|
|
var ciphers []string
|
|
for _, c := range c.Ciphers {
|
|
if cipherModes[c] != nil {
|
|
// reject the cipher if we have no cipherModes definition
|
|
ciphers = append(ciphers, c)
|
|
}
|
|
}
|
|
c.Ciphers = ciphers
|
|
|
|
if c.KeyExchanges == nil {
|
|
c.KeyExchanges = supportedKexAlgos
|
|
}
|
|
|
|
if c.MACs == nil {
|
|
c.MACs = supportedMACs
|
|
}
|
|
|
|
if c.RekeyThreshold == 0 {
|
|
// cipher specific default
|
|
} else if c.RekeyThreshold < minRekeyThreshold {
|
|
c.RekeyThreshold = minRekeyThreshold
|
|
} else if c.RekeyThreshold >= math.MaxInt64 {
|
|
// Avoid weirdness if somebody uses -1 as a threshold.
|
|
c.RekeyThreshold = math.MaxInt64
|
|
}
|
|
}
|
|
|
|
// buildDataSignedForAuth returns the data that is signed in order to prove
|
|
// possession of a private key. See RFC 4252, section 7.
|
|
func buildDataSignedForAuth(sessionID []byte, req userAuthRequestMsg, algo, pubKey []byte) []byte {
|
|
data := struct {
|
|
Session []byte
|
|
Type byte
|
|
User string
|
|
Service string
|
|
Method string
|
|
Sign bool
|
|
Algo []byte
|
|
PubKey []byte
|
|
}{
|
|
sessionID,
|
|
msgUserAuthRequest,
|
|
req.User,
|
|
req.Service,
|
|
req.Method,
|
|
true,
|
|
algo,
|
|
pubKey,
|
|
}
|
|
return Marshal(data)
|
|
}
|
|
|
|
func appendU16(buf []byte, n uint16) []byte {
|
|
return append(buf, byte(n>>8), byte(n))
|
|
}
|
|
|
|
func appendU32(buf []byte, n uint32) []byte {
|
|
return append(buf, byte(n>>24), byte(n>>16), byte(n>>8), byte(n))
|
|
}
|
|
|
|
func appendU64(buf []byte, n uint64) []byte {
|
|
return append(buf,
|
|
byte(n>>56), byte(n>>48), byte(n>>40), byte(n>>32),
|
|
byte(n>>24), byte(n>>16), byte(n>>8), byte(n))
|
|
}
|
|
|
|
func appendInt(buf []byte, n int) []byte {
|
|
return appendU32(buf, uint32(n))
|
|
}
|
|
|
|
func appendString(buf []byte, s string) []byte {
|
|
buf = appendU32(buf, uint32(len(s)))
|
|
buf = append(buf, s...)
|
|
return buf
|
|
}
|
|
|
|
func appendBool(buf []byte, b bool) []byte {
|
|
if b {
|
|
return append(buf, 1)
|
|
}
|
|
return append(buf, 0)
|
|
}
|
|
|
|
// newCond is a helper to hide the fact that there is no usable zero
|
|
// value for sync.Cond.
|
|
func newCond() *sync.Cond { return sync.NewCond(new(sync.Mutex)) }
|
|
|
|
// window represents the buffer available to clients
|
|
// wishing to write to a channel.
|
|
type window struct {
|
|
*sync.Cond
|
|
win uint32 // RFC 4254 5.2 says the window size can grow to 2^32-1
|
|
writeWaiters int
|
|
closed bool
|
|
}
|
|
|
|
// add adds win to the amount of window available
|
|
// for consumers.
|
|
func (w *window) add(win uint32) bool {
|
|
// a zero sized window adjust is a noop.
|
|
if win == 0 {
|
|
return true
|
|
}
|
|
w.L.Lock()
|
|
if w.win+win < win {
|
|
w.L.Unlock()
|
|
return false
|
|
}
|
|
w.win += win
|
|
// It is unusual that multiple goroutines would be attempting to reserve
|
|
// window space, but not guaranteed. Use broadcast to notify all waiters
|
|
// that additional window is available.
|
|
w.Broadcast()
|
|
w.L.Unlock()
|
|
return true
|
|
}
|
|
|
|
// close sets the window to closed, so all reservations fail
|
|
// immediately.
|
|
func (w *window) close() {
|
|
w.L.Lock()
|
|
w.closed = true
|
|
w.Broadcast()
|
|
w.L.Unlock()
|
|
}
|
|
|
|
// reserve reserves win from the available window capacity.
|
|
// If no capacity remains, reserve will block. reserve may
|
|
// return less than requested.
|
|
func (w *window) reserve(win uint32) (uint32, error) {
|
|
var err error
|
|
w.L.Lock()
|
|
w.writeWaiters++
|
|
w.Broadcast()
|
|
for w.win == 0 && !w.closed {
|
|
w.Wait()
|
|
}
|
|
w.writeWaiters--
|
|
if w.win < win {
|
|
win = w.win
|
|
}
|
|
w.win -= win
|
|
if w.closed {
|
|
err = io.EOF
|
|
}
|
|
w.L.Unlock()
|
|
return win, err
|
|
}
|
|
|
|
// waitWriterBlocked waits until some goroutine is blocked for further
|
|
// writes. It is used in tests only.
|
|
func (w *window) waitWriterBlocked() {
|
|
w.Cond.L.Lock()
|
|
for w.writeWaiters == 0 {
|
|
w.Cond.Wait()
|
|
}
|
|
w.Cond.L.Unlock()
|
|
}
|