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ssh: add diffie-hellman-group16-sha512 kex
This group is disabled by default because it is a bit slower than the others. The group18-sha512 variant is too slow to include. Benchstat results including diffie-hellman-group18-sha512: name time/op Kexes/diffie-hellman-group-exchange-sha256-12 22.6ms ± 9% Kexes/diffie-hellman-group18-sha512-12 1.15s ±11% Kexes/ecdh-sha2-nistp384-12 3.91ms ± 6% Kexes/ecdh-sha2-nistp256-12 304µs ± 5% Kexes/[email protected] 413µs ± 7% Kexes/ecdh-sha2-nistp521-12 11.6ms ±13% Kexes/curve25519-sha256-12 361µs ± 5% Kexes/diffie-hellman-group-exchange-sha1-12 22.9ms ± 9% Kexes/diffie-hellman-group1-sha1-12 3.59ms ± 6% Kexes/diffie-hellman-group14-sha1-12 22.1ms ±11% Kexes/diffie-hellman-group14-sha256-12 21.6ms ± 8% Kexes/diffie-hellman-group16-sha512-12 138ms ± 9% name alloc/op Kexes/diffie-hellman-group-exchange-sha256-12 67.8kB ± 1% Kexes/diffie-hellman-group18-sha512-12 243kB ± 9% Kexes/ecdh-sha2-nistp384-12 13.9kB ± 0% Kexes/ecdh-sha2-nistp256-12 12.1kB ± 0% Kexes/[email protected] 8.22kB ± 0% Kexes/ecdh-sha2-nistp521-12 16.5kB ± 0% Kexes/curve25519-sha256-12 8.22kB ± 0% Kexes/diffie-hellman-group-exchange-sha1-12 67.5kB ± 0% Kexes/diffie-hellman-group1-sha1-12 34.9kB ± 0% Kexes/diffie-hellman-group14-sha1-12 61.9kB ± 0% Kexes/diffie-hellman-group14-sha256-12 62.0kB ± 0% Kexes/diffie-hellman-group16-sha512-12 117kB ± 0% name allocs/op Kexes/diffie-hellman-group-exchange-sha256-12 314 ± 0% Kexes/diffie-hellman-group18-sha512-12 271 ± 4% Kexes/ecdh-sha2-nistp384-12 243 ± 0% Kexes/ecdh-sha2-nistp256-12 213 ± 0% Kexes/[email protected] 168 ± 0% Kexes/ecdh-sha2-nistp521-12 245 ± 0% Kexes/curve25519-sha256-12 168 ± 0% Kexes/diffie-hellman-group-exchange-sha1-12 314 ± 0% Kexes/diffie-hellman-group1-sha1-12 255 ± 0% Kexes/diffie-hellman-group14-sha1-12 255 ± 0% Kexes/diffie-hellman-group14-sha256-12 255 ± 0% Kexes/diffie-hellman-group16-sha512-12 256 ± 0% Change-Id: Id119401fda7e417675325f37e3d442e70585206c Reviewed-on: https://go-review.googlesource.com/c/crypto/+/506839 Run-TryBot: Filippo Valsorda <[email protected]> TryBot-Result: Gopher Robot <[email protected]> Reviewed-by: Cherry Mui <[email protected]> Auto-Submit: Filippo Valsorda <[email protected]> Reviewed-by: David Chase <[email protected]> Reviewed-by: Filippo Valsorda <[email protected]>
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‎ssh/common.go‎

Lines changed: 5 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -49,7 +49,8 @@ var supportedKexAlgos = []string{
4949
// P384 and P521 are not constant-time yet, but since we don't
5050
// reuse ephemeral keys, using them for ECDH should be OK.
5151
kexAlgoECDH256, kexAlgoECDH384, kexAlgoECDH521,
52-
kexAlgoDH14SHA256, kexAlgoDH14SHA1, kexAlgoDH1SHA1,
52+
kexAlgoDH14SHA256, kexAlgoDH16SHA512, kexAlgoDH14SHA1,
53+
kexAlgoDH1SHA1,
5354
}
5455

5556
// serverForbiddenKexAlgos contains key exchange algorithms, that are forbidden
@@ -59,8 +60,9 @@ var serverForbiddenKexAlgos = map[string]struct{}{
5960
kexAlgoDHGEXSHA256: {}, // server half implementation is only minimal to satisfy the automated tests
6061
}
6162

62-
// preferredKexAlgos specifies the default preference for key-exchange algorithms
63-
// in preference order.
63+
// preferredKexAlgos specifies the default preference for key-exchange
64+
// algorithms in preference order. The diffie-hellman-group16-sha512 algorithm
65+
// is disabled by default because it is a bit slower than the others.
6466
var preferredKexAlgos = []string{
6567
kexAlgoCurve25519SHA256, kexAlgoCurve25519SHA256LibSSH,
6668
kexAlgoECDH256, kexAlgoECDH384, kexAlgoECDH521,

‎ssh/kex.go‎

Lines changed: 12 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -23,6 +23,7 @@ const (
2323
kexAlgoDH1SHA1 = "diffie-hellman-group1-sha1"
2424
kexAlgoDH14SHA1 = "diffie-hellman-group14-sha1"
2525
kexAlgoDH14SHA256 = "diffie-hellman-group14-sha256"
26+
kexAlgoDH16SHA512 = "diffie-hellman-group16-sha512"
2627
kexAlgoECDH256 = "ecdh-sha2-nistp256"
2728
kexAlgoECDH384 = "ecdh-sha2-nistp384"
2829
kexAlgoECDH521 = "ecdh-sha2-nistp521"
@@ -430,6 +431,17 @@ func init() {
430431
hashFunc: crypto.SHA256,
431432
}
432433

434+
// This is the group called diffie-hellman-group16-sha512 in RFC
435+
// 8268 and Oakley Group 16 in RFC 3526.
436+
p, _ = new(big.Int).SetString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
437+
438+
kexAlgoMap[kexAlgoDH16SHA512] = &dhGroup{
439+
g: new(big.Int).SetInt64(2),
440+
p: p,
441+
pMinus1: new(big.Int).Sub(p, bigOne),
442+
hashFunc: crypto.SHA512,
443+
}
444+
433445
kexAlgoMap[kexAlgoECDH521] = &ecdh{elliptic.P521()}
434446
kexAlgoMap[kexAlgoECDH384] = &ecdh{elliptic.P384()}
435447
kexAlgoMap[kexAlgoECDH256] = &ecdh{elliptic.P256()}

‎ssh/kex_test.go‎

Lines changed: 41 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -8,6 +8,7 @@ package ssh
88

99
import (
1010
"crypto/rand"
11+
"fmt"
1112
"reflect"
1213
"sync"
1314
"testing"
@@ -63,3 +64,43 @@ func TestKexes(t *testing.T) {
6364
})
6465
}
6566
}
67+
68+
func BenchmarkKexes(b *testing.B) {
69+
type kexResultErr struct {
70+
result *kexResult
71+
err error
72+
}
73+
74+
for name, kex := range kexAlgoMap {
75+
b.Run(name, func(b *testing.B) {
76+
for i := 0; i < b.N; i++ {
77+
t1, t2 := memPipe()
78+
79+
s := make(chan kexResultErr, 1)
80+
c := make(chan kexResultErr, 1)
81+
var magics handshakeMagics
82+
83+
go func() {
84+
r, e := kex.Client(t1, rand.Reader, &magics)
85+
t1.Close()
86+
c <- kexResultErr{r, e}
87+
}()
88+
go func() {
89+
r, e := kex.Server(t2, rand.Reader, &magics, testSigners["ecdsa"].(AlgorithmSigner), testSigners["ecdsa"].PublicKey().Type())
90+
t2.Close()
91+
s <- kexResultErr{r, e}
92+
}()
93+
94+
clientRes := <-c
95+
serverRes := <-s
96+
97+
if clientRes.err != nil {
98+
panic(fmt.Sprintf("client: %v", clientRes.err))
99+
}
100+
if serverRes.err != nil {
101+
panic(fmt.Sprintf("server: %v", serverRes.err))
102+
}
103+
}
104+
})
105+
}
106+
}

‎ssh/test/session_test.go‎

Lines changed: 3 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -410,6 +410,9 @@ func TestKeyExchanges(t *testing.T) {
410410
// are not included in the default list of supported kex so we have to add them
411411
// here manually.
412412
kexOrder = append(kexOrder, "diffie-hellman-group-exchange-sha1", "diffie-hellman-group-exchange-sha256")
413+
// The key exchange algorithms diffie-hellman-group16-sha512 is disabled by
414+
// default so we add it here manually.
415+
kexOrder = append(kexOrder, "diffie-hellman-group16-sha512")
413416
for _, kex := range kexOrder {
414417
t.Run(kex, func(t *testing.T) {
415418
server := newServer(t)

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