tssh和ssh连接算法有差异，openssh可以连，但tssh连不上

[ViCrack]

我发现某次连接ssh，tss连接不上，但是OpenSSH是可以连的

我执行了--debug和ssh -vv进行对比日志，下面是AI说的，不知道是不是这个算法选的原因

同一台服务器、同一把 RSA 密钥

对比两份日志的关键差异：

✅ 普通 ssh 成功时

关键行：

Server accepts key: default RSA SHA256:xxxxxxxxx...
signing using rsa-sha2-512
Authenticated ... using "publickey"


也就是说：

使用的 key：SHA256:xxxxxxxxx...

签名算法：rsa-sha2-512

认证成功

❌ tssh 失败时

关键行：

sign with algorithm [rsa-sha2-256]
unable to authenticate


也就是说：

使用的 key：同一把（SHA256:xxxxxxxxx...）

签名算法：rsa-sha2-256

服务器拒绝

🎯 结论

问题不是 key。
问题是 签名算法不同。

普通 ssh 使用：

rsa-sha2-512


而 tssh 使用：

rsa-sha2-256


服务器虽然在 KEX 阶段声明支持：

rsa-sha2-512,rsa-sha2-256


但实际 authorized_keys 校验时，很可能存在限制（例如旧 sshd 或策略限制）。

OpenSSH 在 9.x 中默认优先使用 rsa-sha2-512。
tssh 当前版本优先使用 rsa-sha2-256。

这就是认证失败的原因。

tssh日志如下（有修改）

debug: tssh version: trzsz ssh 0.1.24-4d86ba8
debug: open C:\Users\cdgfa.tssh.conf success
debug: Language = Chinese
debug: open config [C:\Users\cdgfa.ssh\config] success
debug: decode config [C:\Users\cdgfa.ssh\config] success
debug: extended config [C:\Users\cdgfa.ssh\password] does not exist
debug: no extended config [DnsSrvName] for [example.com]
debug: no extended config [UdpMode] for [example.com]
debug: new ssh agent client [\.\pipe\openssh-ssh-agent] success
debug: will attempt key: ssh-agent ssh-rsa SHA256:sdfdsjiogfkoprejtihierbgytretertrt
debug: add auth method: public key authentication
debug: disable auth method: gssapi-with-mic authentication
debug: add auth method: keyboard interactive authentication
debug: add auth method: password authentication
debug: add UserKnownHostsFile: C:\Users\cdgfa.ssh\known_hosts
debug: UserKnownHostsFile [C:\Users\cdgfa.ssh\known_hosts2] does not exist
debug: GlobalKnownHostsFile [/etc/ssh/ssh_known_hosts] does not exist
debug: GlobalKnownHostsFile [/etc/ssh/ssh_known_hosts2] does not exist
debug: login to [example.com] addr: example.com:22
debug: sign with algorithm [rsa-sha2-256]: SHA256:sdfdsjiogfkoprejtihierbgytretertrt
login to [example.com] new conn [example.com:22] failed: ssh: handshake failed: ssh: unable to authenticate, attempted methods [none publickey], no supported methods remain

ssh日志如下

debug1: Server accepts key: default RSA SHA256:xxxx...
debug3: sign_and_send_pubkey: using publickey-hostbound-v00@openssh.com with RSA SHA256:xxxxx...
debug3: sign_and_send_pubkey: signing using rsa-sha2-512 SHA256:xxxxx...

可以看到tssh日志中使用了rsa-sha2-256，ssh中使用了rsa-sha2-512

[lonnywong]

服务器声明支持 rsa-sha2-256，但是用 rsa-sha2-256 却登录失败？tssh 是 go 的 ssh 库自动选择的。

[lonnywong]

@ViCrack 你可以试试改下面这行代码：

trzsz-ssh/tssh/login.go

Line 491 in 4d44e1c

HostKeyAlgorithms: hostKeyAlgorithms,

分别改成下面的，看看效果如何：

		HostKeyAlgorithms: []string{ssh.KeyAlgoRSASHA512},

		HostKeyAlgorithms: []string{ssh.KeyAlgoRSASHA256, ssh.KeyAlgoRSASHA512},

		HostKeyAlgorithms: []string{ssh.KeyAlgoRSASHA512, ssh.KeyAlgoRSASHA256},

[ViCrack]

@lonnywong

改了，但是没用，一样连不上，虽然选择算法上跟ssh有差异那么看起来应该不是根本原因所在。

我研究了一下，可能跟我最近用了Bitwarden的SSH代理有关，开启了之后Bitwarden会接管\.\pipe\openssh-ssh-agent，此时ssh是可以连接的，而tssh就连不了，从日志中看到还是照样连了new ssh agent client拿到了正确的key（和ssh-add -l输出一样），算法是rsa-sha2-256

debug: tssh version: trzsz ssh 0.1.24-4d86ba8
debug: C:\Users\asdsadf\.config\tssh\tssh.conf or C:\Users\asdsadf\.tssh.conf does not exist
debug: open config [C:\Users\asdsadf\.ssh\config] success
debug: decode config [C:\Users\asdsadf\.ssh\config] success
debug: extended config [C:\Users\asdsadf\.ssh\password] does not exist
debug: no extended config [DnsSrvName] for [aaaaaaaaaaaaa]
debug: no extended config [UdpMode] for [aaaaaaaaaaaaa]
debug: new ssh agent client [\\.\pipe\openssh-ssh-agent] success
debug: will attempt key: ssh-agent ssh-rsa SHA256:xxxxxxxxxxxxxxxxxxxxxxx
debug: add auth method: public key authentication
debug: disable auth method: gssapi-with-mic authentication
debug: add auth method: keyboard interactive authentication
debug: add auth method: password authentication
debug: add UserKnownHostsFile: C:\Users\asdsadf\.ssh\known_hosts
debug: UserKnownHostsFile [C:\Users\asdsadf\.ssh\known_hosts2] does not exist
debug: GlobalKnownHostsFile [/etc/ssh/ssh_known_hosts] does not exist
debug: GlobalKnownHostsFile [/etc/ssh/ssh_known_hosts2] does not exist
debug: login to [aaaaaaaaaaaaa] addr: aaaaaaaaaaaaa:22
debug: sign with algorithm [rsa-sha2-256]: SHA256:xxxxxxxxxxxxxxxxxxxxxxx
login to [aaaaaaaaaaaaa] new conn [aaaaaaaaaaaaa:22] failed: ssh: handshake failed: ssh: unable to authenticate, attempted methods [none publickey], no supported methods remain

当我关掉了SSH代理，tssh又能连上了，可以看到连不上ssh agent，默认拿了id_rsa （此时输出的key也是正确的，和ssh agent一样），不知道这是什么原因

debug: tssh version: trzsz ssh 0.1.24-4d86ba8
debug: C:\Users\asdsadsad\.config\tssh\tssh.conf or C:\Users\asdsadsad\.tssh.conf does not exist
debug: open config [C:\Users\asdsadsad\.ssh\config] success
debug: decode config [C:\Users\asdsadsad\.ssh\config] success
debug: extended config [C:\Users\asdsadsad\.ssh\password] does not exist
debug: no extended config [DnsSrvName] for [dddaaaaaaaaaaaaaaa]
debug: no extended config [UdpMode] for [dddaaaaaaaaaaaaaaa]
debug: new ssh agent client [\\.\pipe\openssh-ssh-agent] success
Warning: get ssh agent signers failed: agent: failed to list keys
debug: will attempt key: C:\Users\asdsadsad\.ssh\id_rsa ssh-rsa SHA256:cccccccccccccccccccccccc
debug: add auth method: public key authentication
debug: disable auth method: gssapi-with-mic authentication
debug: add auth method: keyboard interactive authentication
debug: add auth method: password authentication
debug: add UserKnownHostsFile: C:\Users\asdsadsad\.ssh\known_hosts
debug: UserKnownHostsFile [C:\Users\asdsadsad\.ssh\known_hosts2] does not exist
debug: GlobalKnownHostsFile [/etc/ssh/ssh_known_hosts] does not exist
debug: GlobalKnownHostsFile [/etc/ssh/ssh_known_hosts2] does not exist
debug: login to [dddaaaaaaaaaaaaaaa] addr: dddaaaaaaaaaaaaaaa:22
debug: sign with algorithm [rsa-sha2-256]: SHA256:cccccccccccccccccccccccc
debug: login to [dddaaaaaaaaaaaaaaa] success

如下参考：
https://help.ppgg.in/docs/password-manager/developer-tools/ssh/ssh-agent

[lonnywong]

可能与 SSH agent restriction 有关 #182 (comment)

[ViCrack]

那就不清楚了，一开始我还以为是加密算法的问题。
我这边没有用过ssh-add -h的命令，密钥是直接在Bitwarden界面上添加的，也没看到Bitwarden有什么限制某些主机才能用ssh密钥的功能。

[lonnywong]

@ViCrack 改下面这行代码，看看报什么错？

trzsz-ssh/tssh/auth_method.go

Line 95 in 4d44e1c

return signer.SignWithAlgorithm(rand, data, algorithm)

@@ -92,7 +92,11 @@ func (s *sshSigner) SignWithAlgorithm(rand io.Reader, data []byte, algorithm str
                if enableDebugLogging {
                        debug("sign with algorithm [%s]: %s", algorithm, ssh.FingerprintSHA256(s.pubKey))
                }
-               return signer.SignWithAlgorithm(rand, data, algorithm)
+               signature, err := signer.SignWithAlgorithm(rand, data, algorithm)
+               if err != nil {
+                       warning("sign with [%s] [%s] failed: %v", algorithm, ssh.FingerprintSHA256(s.pubKey), err)
+               }
+               return signature, err
        }

[ViCrack]

没有报错，warning那行没输出

[ViCrack]

@lonnywong 我看到bitwarden有个bug没修复，bitwarden/clients#16681

看起来是用rsa-sha2-256签名，但是key返回是&{rsa-sha2-512

不知道会不会跟这个issue有关

[lonnywong]

估计就是这个原因了，go 选了 256，却得到 512 的签名。

[ViCrack]

我尝试强制改成ssh.KeyAlgoRSASHA512的签名算法，发现可以连接了

可能正因为ssh在256和512中优先选择了rsa-sha2-512的签名算法，所以能连接成功

bitwarden本身就有bug，再加上go ssh按理来说最好跟openssh一样优先选择一个更安全的算法

[lonnywong]

tssh 已实现优先 rsa-sha2-512，不过 go ssh 有个 bug https://go.dev/cl/746020 ，要等它修复。