如何生成“ssh-rsa”密钥而不是“rsa-sha2-512”

Question

我有很多服务器，我已经为其正确生成了密钥、设置了权限并且能够在没有密码的情况下进行 ssh/scp。然而，有一台机器有点不同，我认为我已经找到了不同之处。

不同之处在于，在没有密码的情况下我无法连接的机器上，ssh 正在接受密钥：

debug1: Server accepts key: pkalg ssh-rsa blen 279

和我的所有其他机器都接受：

debug1: Server accepts key: pkalg rsa-sha2-512 blen 279

在创建 ssh 密钥时，我总是设置参数“-t rsa”，但我不确定生成哪种密钥。你能帮我创建 rsa-sha2-512 的 ssh-rsa 密钥吗？最后一件事 - 我无法修改 /etc/ssh/sshd_config 来更改某些内容。

ssh 日志的完整转储如下： 我可以连接到的一个：

OpenSSH_7.4p1, OpenSSL 1.0.2k-fips  26 Jan 2017
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 58: Applying options for *
debug1: Connecting to HOSTNAME [IP] port 22.
debug1: Connection established.
debug1: identity file /SOMEPATH/SOMEDIR/SOMEFOLDER/.ssh/id_rsa type 1
debug1: key_load_public: No such file or directory
debug1: identity file /SOMEPATH/SOMEDIR/SOMEFOLDER/.ssh/id_rsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /SOMEPATH/SOMEDIR/SOMEFOLDER/.ssh/id_dsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /SOMEPATH/SOMEDIR/SOMEFOLDER/.ssh/id_dsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /SOMEPATH/SOMEDIR/SOMEFOLDER/.ssh/id_ecdsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /SOMEPATH/SOMEDIR/SOMEFOLDER/.ssh/id_ecdsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /SOMEPATH/SOMEDIR/SOMEFOLDER/.ssh/id_ed25519 type -1
debug1: key_load_public: No such file or directory
debug1: identity file /SOMEPATH/SOMEDIR/SOMEFOLDER/.ssh/id_ed25519-cert type -1
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_7.4
debug1: Remote protocol version 2.0, remote software version OpenSSH_7.4
debug1: match: OpenSSH_7.4 pat OpenSSH* compat 0x04000000
debug1: Authenticating to HOSTNAME:22 as 'SOMEUSER'
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug1: kex: algorithm: curve25519-sha256
debug1: kex: host key algorithm: ecdsa-sha2-nistp256
debug1: kex: server->client cipher: chacha20-poly1305@openssh.com MAC: <implicit> compression: none
debug1: kex: client->server cipher: chacha20-poly1305@openssh.com MAC: <implicit> compression: none
debug1: kex: curve25519-sha256 need=64 dh_need=64
debug1: kex: curve25519-sha256 need=64 dh_need=64
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
debug1: Server host key: ecdsa-sha2-nistp256 SHA256:###HASH###
debug1: Host 'HOSTNAME' is known and matches the ECDSA host key.
debug1: Found key in /SOMEPATH/SOMEDIR/SOMEFOLDER/.ssh/known_hosts:2
debug1: rekey after ###HASH### blocks
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug1: SSH2_MSG_NEWKEYS received
debug1: rekey after ###HASH### blocks
debug1: SSH2_MSG_EXT_INFO received
debug1: kex_input_ext_info: server-sig-algs=<rsa-sha2-256,rsa-sha2-512>
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug1: Authentications that can continue: publickey,gssapi-keyex,gssapi-with-mic,password
debug1: Next authentication method: gssapi-keyex
debug1: No valid Key exchange context
debug1: Next authentication method: gssapi-with-mic
debug1: Unspecified GSS failure.  Minor code may provide more information
No Kerberos credentials available (default cache: FILE:/tmp/krb5cc_38000069)

debug1: Unspecified GSS failure.  Minor code may provide more information
No Kerberos credentials available (default cache: FILE:/tmp/krb5cc_38000069)

debug1: Next authentication method: publickey
debug1: Offering RSA public key: /SOMEPATH/SOMEDIR/SOMEFOLDER/.ssh/id_rsa
debug1: Server accepts key: pkalg rsa-sha2-512 blen 279
debug1: Authentication succeeded (publickey).
Authenticated to HOSTNAME ([IP]:22).
debug1: channel 0: new [client-session]
debug1: Requesting no-more-sessions@openssh.com
debug1: Entering interactive session.
debug1: pledge: network
debug1: client_input_global_request: rtype hostkeys-00@openssh.com want_reply 0
debug1: Sending environment.
debug1: Sending env LANG = en_US.UTF-8

我无法连接的第二个：

OpenSSH_7.4p1, OpenSSL 1.0.2k-fips  26 Jan 2017
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 58: Applying options for *
debug1: Connecting to HOSTNAME [IP] port 22.
debug1: Connection established.
debug1: identity file /SOMEPATH/SOMEDIR/SOMEFOLDER/.ssh/id_rsa type 1
debug1: key_load_public: No such file or directory
debug1: identity file /SOMEPATH/SOMEDIR/SOMEFOLDER/.ssh/id_rsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /SOMEPATH/SOMEDIR/SOMEFOLDER/.ssh/id_dsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /SOMEPATH/SOMEDIR/SOMEFOLDER/.ssh/id_dsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /SOMEPATH/SOMEDIR/SOMEFOLDER/.ssh/id_ecdsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /SOMEPATH/SOMEDIR/SOMEFOLDER/.ssh/id_ecdsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /SOMEPATH/SOMEDIR/SOMEFOLDER/.ssh/id_ed25519 type -1
debug1: key_load_public: No such file or directory
debug1: identity file /SOMEPATH/SOMEDIR/SOMEFOLDER/.ssh/id_ed25519-cert type -1
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_7.4
debug1: Remote protocol version 2.0, remote software version Sun_SSH_1.1.8
debug1: no match: Sun_SSH_1.1.8
debug1: Authenticating to HOSTNAME:22 as 'USERNAME'
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug1: kex: algorithm: diffie-hellman-group-exchange-sha256
debug1: kex: host key algorithm: ssh-rsa
debug1: kex: server->client cipher: aes128-ctr MAC: hmac-sha2-256 compression: none
debug1: kex: client->server cipher: aes128-ctr MAC: hmac-sha2-256 compression: none
debug1: kex: diffie-hellman-group-exchange-sha256 need=32 dh_need=32
debug1: kex: diffie-hellman-group-exchange-sha256 need=32 dh_need=32
debug1: SSH2_MSG_KEX_DH_GEX_REQUEST(1024<8192<8192) sent
debug1: got SSH2_MSG_KEX_DH_GEX_GROUP
debug1: SSH2_MSG_KEX_DH_GEX_INIT sent
debug1: got SSH2_MSG_KEX_DH_GEX_REPLY
debug1: Server host key: ssh-rsa SHA256:###HASH###
debug1: Host 'HOSTNAME' is known and matches the RSA host key.
debug1: Found key in /SOMEPATH/SOMEDIR/SOMEFOLDER/.ssh/known_hosts:13
debug1: rekey after ###HASH### blocks
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug1: SSH2_MSG_NEWKEYS received
debug1: rekey after ###HASH### blocks
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug1: Authentications that can continue: gssapi-keyex,gssapi-with-mic,publickey,password,keyboard-interactive
debug1: Next authentication method: gssapi-keyex
debug1: No valid Key exchange context
debug1: Next authentication method: gssapi-with-mic
debug1: Unspecified GSS failure.  Minor code may provide more information
No Kerberos credentials available (default cache: FILE:/tmp/krb5cc_38000069)

debug1: Unspecified GSS failure.  Minor code may provide more information
No Kerberos credentials available (default cache: FILE:/tmp/krb5cc_38000069)

debug1: Next authentication method: publickey
debug1: Offering RSA public key: /SOMEPATH/SOMEDIR/SOMEFOLDER/.ssh/id_rsa
debug1: Server accepts key: pkalg ssh-rsa blen 279
debug1: Authentications that can continue: gssapi-keyex,gssapi-with-mic,publickey,password,keyboard-interactive
debug1: Trying private key: /SOMEPATH/SOMEDIR/SOMEFOLDER/.ssh/id_dsa
debug1: Trying private key: /SOMEPATH/SOMEDIR/SOMEFOLDER/.ssh/id_ecdsa
debug1: Trying private key: /SOMEPATH/SOMEDIR/SOMEFOLDER/.ssh/id_ed25519
debug1: Next authentication method: keyboard-interactive
Password:

我用来生成密钥的命令：

ssh-keygen -b 2048 -t rsa -E sha256 -f filename

我也尝试过：

• 创建具有不同参数的密钥：

  -t rsa1; -t ecdsa; -b 1024; -b 2048;

Answer 1

RSA 密钥本身既不是“SHA1”也不是“SHA2” ——密钥格​​式根本不涉及任何哈希算法。私钥只由两个大数字组成，与证书不同，没有附加签名。

然而，SSH 并没有为每个公钥算法使用哪种哈希算法留下很大的灵活性——例如，最初规定每当使用“ssh-rsa”密钥进行签名时，它都将与 SHA1 一起使用，而不是其他任何东西。因此，为了允许人们使用他们现有的 RSA 密钥，必须纯粹为连接握手创建新的签名算法名称——pkalg rsa-sha2-512仍然意味着使用相同的 ssh-rsa 密钥，只用 SHA2 执行签名。

通常，当客户端和服务器都声称支持此功能时，会通过协议启用此功能。如果要为错误地声称支持 rsa-sha2 的服务器禁用它，则可以在 OpenSSH 客户端中自定义PubkeyAcceptedKeyTypes：

ssh -o "PubkeyAcceptedKeyTypes=ssh-rsa" [...]

但这对您的情况无济于事，因为客户端已经正确检测到服务器不支持带有 SHA2 的 RSA。您的问题很可能完全出在其他地方。