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ssh: invert algorithm choices on the server
At the protocol level, SSH lets client and server specify different algorithms for the read and write half of the connection. This has never worked correctly, as Client-to-Server was always interpreted as the "write" side, even if we were the server. This has never been a problem because, apparently, there are no clients that insist on different algorithm choices running against Go SSH servers. Since the SSH package does not expose a mechanism to specify algorithms for read/write separately, there is end-to-end for this change, so add a unittest instead. Change-Id: Ie3aa781630a3bb7a3b0e3754cb67b3ce12581544 Reviewed-on: https://go-review.googlesource.com/c/crypto/+/172538 Reviewed-by: Filippo Valsorda <filippo@golang.org> Run-TryBot: Filippo Valsorda <filippo@golang.org> TryBot-Result: Gobot Gobot <gobot@golang.org>
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,176 @@ | ||
| // Copyright 2019 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 ( | ||
| "reflect" | ||
| "testing" | ||
| ) | ||
|
|
||
| func TestFindAgreedAlgorithms(t *testing.T) { | ||
| initKex := func(k *kexInitMsg) { | ||
| if k.KexAlgos == nil { | ||
| k.KexAlgos = []string{"kex1"} | ||
| } | ||
| if k.ServerHostKeyAlgos == nil { | ||
| k.ServerHostKeyAlgos = []string{"hostkey1"} | ||
| } | ||
| if k.CiphersClientServer == nil { | ||
| k.CiphersClientServer = []string{"cipher1"} | ||
|
|
||
| } | ||
| if k.CiphersServerClient == nil { | ||
| k.CiphersServerClient = []string{"cipher1"} | ||
|
|
||
| } | ||
| if k.MACsClientServer == nil { | ||
| k.MACsClientServer = []string{"mac1"} | ||
|
|
||
| } | ||
| if k.MACsServerClient == nil { | ||
| k.MACsServerClient = []string{"mac1"} | ||
|
|
||
| } | ||
| if k.CompressionClientServer == nil { | ||
| k.CompressionClientServer = []string{"compression1"} | ||
|
|
||
| } | ||
| if k.CompressionServerClient == nil { | ||
| k.CompressionServerClient = []string{"compression1"} | ||
|
|
||
| } | ||
| if k.LanguagesClientServer == nil { | ||
| k.LanguagesClientServer = []string{"language1"} | ||
|
|
||
| } | ||
| if k.LanguagesServerClient == nil { | ||
| k.LanguagesServerClient = []string{"language1"} | ||
|
|
||
| } | ||
| } | ||
|
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| initDirAlgs := func(a *directionAlgorithms) { | ||
| if a.Cipher == "" { | ||
| a.Cipher = "cipher1" | ||
| } | ||
| if a.MAC == "" { | ||
| a.MAC = "mac1" | ||
| } | ||
| if a.Compression == "" { | ||
| a.Compression = "compression1" | ||
| } | ||
| } | ||
|
|
||
| initAlgs := func(a *algorithms) { | ||
| if a.kex == "" { | ||
| a.kex = "kex1" | ||
| } | ||
| if a.hostKey == "" { | ||
| a.hostKey = "hostkey1" | ||
| } | ||
| initDirAlgs(&a.r) | ||
| initDirAlgs(&a.w) | ||
| } | ||
|
|
||
| type testcase struct { | ||
| name string | ||
| clientIn, serverIn kexInitMsg | ||
| wantClient, wantServer algorithms | ||
| wantErr bool | ||
| } | ||
|
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| cases := []testcase{ | ||
| testcase{ | ||
| name: "standard", | ||
| }, | ||
|
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| testcase{ | ||
| name: "no common hostkey", | ||
| serverIn: kexInitMsg{ | ||
| ServerHostKeyAlgos: []string{"hostkey2"}, | ||
| }, | ||
| wantErr: true, | ||
| }, | ||
|
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||
| testcase{ | ||
| name: "no common kex", | ||
| serverIn: kexInitMsg{ | ||
| KexAlgos: []string{"kex2"}, | ||
| }, | ||
| wantErr: true, | ||
| }, | ||
|
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| testcase{ | ||
| name: "no common cipher", | ||
| serverIn: kexInitMsg{ | ||
| CiphersClientServer: []string{"cipher2"}, | ||
| }, | ||
| wantErr: true, | ||
| }, | ||
|
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| testcase{ | ||
| name: "client decides cipher", | ||
| serverIn: kexInitMsg{ | ||
| CiphersClientServer: []string{"cipher1", "cipher2"}, | ||
| CiphersServerClient: []string{"cipher2", "cipher3"}, | ||
| }, | ||
| clientIn: kexInitMsg{ | ||
| CiphersClientServer: []string{"cipher2", "cipher1"}, | ||
| CiphersServerClient: []string{"cipher3", "cipher2"}, | ||
| }, | ||
| wantClient: algorithms{ | ||
| r: directionAlgorithms{ | ||
| Cipher: "cipher3", | ||
| }, | ||
| w: directionAlgorithms{ | ||
| Cipher: "cipher2", | ||
| }, | ||
| }, | ||
| wantServer: algorithms{ | ||
| w: directionAlgorithms{ | ||
| Cipher: "cipher3", | ||
| }, | ||
| r: directionAlgorithms{ | ||
| Cipher: "cipher2", | ||
| }, | ||
| }, | ||
| }, | ||
|
|
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| // TODO(hanwen): fix and add tests for AEAD ignoring | ||
| // the MACs field | ||
| } | ||
|
|
||
| for i := range cases { | ||
| initKex(&cases[i].clientIn) | ||
| initKex(&cases[i].serverIn) | ||
| initAlgs(&cases[i].wantClient) | ||
| initAlgs(&cases[i].wantServer) | ||
| } | ||
|
|
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| for _, c := range cases { | ||
| t.Run(c.name, func(t *testing.T) { | ||
| serverAlgs, serverErr := findAgreedAlgorithms(false, &c.clientIn, &c.serverIn) | ||
| clientAlgs, clientErr := findAgreedAlgorithms(true, &c.clientIn, &c.serverIn) | ||
|
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| serverHasErr := serverErr != nil | ||
| clientHasErr := clientErr != nil | ||
| if c.wantErr != serverHasErr || c.wantErr != clientHasErr { | ||
| t.Fatalf("got client/server error (%v, %v), want hasError %v", | ||
| clientErr, serverErr, c.wantErr) | ||
|
|
||
| } | ||
| if c.wantErr { | ||
| return | ||
| } | ||
|
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| if !reflect.DeepEqual(serverAlgs, &c.wantServer) { | ||
| t.Errorf("server: got algs %#v, want %#v", serverAlgs, &c.wantServer) | ||
| } | ||
| if !reflect.DeepEqual(clientAlgs, &c.wantClient) { | ||
| t.Errorf("server: got algs %#v, want %#v", clientAlgs, &c.wantClient) | ||
| } | ||
| }) | ||
| } | ||
| } |
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