Windows 11の標準でインストールされている ssh-keygen コマンドをオプションなしで実行してキーを作成し、それを使ってOracle Cloud上にLinuxインスタンスを立てた。
普通にTera Termやsshコマンドでは正常にログインできた。
Oracle CloudのWeb UI上にあるCloud Shellにはsshログインができる機能がある。(アプローチ4: OCI Cloud ShellでのSSH秘密キーを使用したコンピュート・インスタンスのプライベートIPアドレスへのSSH経由の接続)
Cloud Shellに作成した秘密鍵をアップロードして、ログインを試みた・・・
ociユーザ@cloudshell:~ (ap-tokyo-1)$ ssh -i id_ed25519 opc@10.0.0.xxx
sign_and_send_pubkey: no mutual signature supported
opc@10.0.0.xxx: Permission denied (publickey,gssapi-keyex,gssapi-with-mic).
ociユーザ@cloudshell:~ (ap-tokyo-1)$
エラーでログインできない
-vvv オプションをつけて実行してみる
ociユーザ@cloudshell:~ (ap-tokyo-1)$ ssh -i id_ed25519 opc@10.0.0.xxx
sign_and_send_pubkey: no mutual signature supported
opc@10.0.0.xxx: Permission denied (publickey,gssapi-keyex,gssapi-with-mic).
ociユーザ@cloudshell:~ (ap-tokyo-1)$ ssh -vvv -i id_ed25519 opc@10.0.0.xxx
OpenSSH_8.0p1, OpenSSL 1.1.1k FIPS 25 Mar 2021
debug1: Reading configuration data /home/ociユーザ/.ssh/config
debug1: Reading configuration data /etc/ssh/ssh_config
debug3: /etc/ssh/ssh_config line 52: Including file /etc/ssh/ssh_config.d/05-redhat.conf depth 0
debug1: Reading configuration data /etc/ssh/ssh_config.d/05-redhat.conf
debug2: checking match for 'final all' host 10.0.0.xxx originally 10.0.0.xxx
debug3: /etc/ssh/ssh_config.d/05-redhat.conf line 3: not matched 'final'
debug2: match not found
debug3: /etc/ssh/ssh_config.d/05-redhat.conf line 5: Including file /etc/crypto-policies/back-ends/openssh.config depth 1 (parse only)
debug1: Reading configuration data /etc/crypto-policies/back-ends/openssh.config
debug3: kex names ok: [ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group14-sha256,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512]
debug1: configuration requests final Match pass
debug2: resolve_canonicalize: hostname 10.0.0.xxx is address
debug1: re-parsing configuration
debug1: Reading configuration data /home/ociユーザ/.ssh/config
debug1: Reading configuration data /etc/ssh/ssh_config
debug3: /etc/ssh/ssh_config line 52: Including file /etc/ssh/ssh_config.d/05-redhat.conf depth 0
debug1: Reading configuration data /etc/ssh/ssh_config.d/05-redhat.conf
debug2: checking match for 'final all' host 10.0.0.xxx originally 10.0.0.xxx
debug3: /etc/ssh/ssh_config.d/05-redhat.conf line 3: matched 'final'
debug2: match found
debug3: /etc/ssh/ssh_config.d/05-redhat.conf line 5: Including file /etc/crypto-policies/back-ends/openssh.config depth 1
debug1: Reading configuration data /etc/crypto-policies/back-ends/openssh.config
debug3: kex names ok: [ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group14-sha256,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512]
debug1: FIPS mode initialized
debug2: ssh_connect_direct
debug1: Connecting to 10.0.0.xxx [10.0.0.xxx] port 22.
debug1: Connection established.
debug1: identity file id_ed25519 type -1
debug1: identity file id_ed25519-cert type -1
debug1: Local version string SSH-2.0-OpenSSH_8.0
debug1: Remote protocol version 2.0, remote software version OpenSSH_8.0
debug1: match: OpenSSH_8.0 pat OpenSSH* compat 0x04000000
debug2: fd 3 setting O_NONBLOCK
debug1: Authenticating to 10.0.0.xxx:22 as 'opc'
debug3: hostkeys_foreach: reading file "/home/ociユーザ/.ssh/known_hosts"
debug3: record_hostkey: found key type ECDSA in file /home/ociユーザ/.ssh/known_hosts:2
debug3: load_hostkeys: loaded 1 keys from 10.0.0.xxx
debug3: order_hostkeyalgs: have matching best-preference key type ecdsa-sha2-nistp256-cert-v01@openssh.com, using HostkeyAlgorithms verbatim
debug3: send packet: type 20
debug1: SSH2_MSG_KEXINIT sent
debug3: receive packet: type 20
debug1: SSH2_MSG_KEXINIT received
debug2: local client KEXINIT proposal
debug2: KEX algorithms: ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group14-sha256,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,ext-info-c,kex-strict-c-v00@openssh.com
debug2: host key algorithms: ecdsa-sha2-nistp256-cert-v01@openssh.com,ecdsa-sha2-nistp384-cert-v01@openssh.com,ecdsa-sha2-nistp521-cert-v01@openssh.com,rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-256-cert-v01@openssh.com,ssh-rsa-cert-v01@openssh.com,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,rsa-sha2-512,rsa-sha2-256,ssh-rsa
debug2: ciphers ctos: aes256-gcm@openssh.com,aes256-ctr,aes256-cbc,aes128-gcm@openssh.com,aes128-ctr,aes128-cbc
debug2: ciphers stoc: aes256-gcm@openssh.com,aes256-ctr,aes256-cbc,aes128-gcm@openssh.com,aes128-ctr,aes128-cbc
debug2: MACs ctos: hmac-sha2-256-etm@openssh.com,hmac-sha1-etm@openssh.com,hmac-sha2-512-etm@openssh.com,hmac-sha2-256,hmac-sha1,hmac-sha2-512
debug2: MACs stoc: hmac-sha2-256-etm@openssh.com,hmac-sha1-etm@openssh.com,hmac-sha2-512-etm@openssh.com,hmac-sha2-256,hmac-sha1,hmac-sha2-512
debug2: compression ctos: none,zlib@openssh.com,zlib
debug2: compression stoc: none,zlib@openssh.com,zlib
debug2: languages ctos:
debug2: languages stoc:
debug2: first_kex_follows 0
debug2: reserved 0
debug2: peer server KEXINIT proposal
debug2: KEX algorithms: curve25519-sha256,curve25519-sha256@libssh.org,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group14-sha256,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,kex-strict-s-v00@openssh.com
debug2: host key algorithms: rsa-sha2-512,rsa-sha2-256,ssh-rsa,ecdsa-sha2-nistp256,ssh-ed25519
debug2: ciphers ctos: aes256-gcm@openssh.com,chacha20-poly1305@openssh.com,aes256-ctr,aes256-cbc,aes128-gcm@openssh.com,aes128-ctr,aes128-cbc
debug2: ciphers stoc: aes256-gcm@openssh.com,chacha20-poly1305@openssh.com,aes256-ctr,aes256-cbc,aes128-gcm@openssh.com,aes128-ctr,aes128-cbc
debug2: MACs ctos: hmac-sha2-256-etm@openssh.com,hmac-sha1-etm@openssh.com,umac-128-etm@openssh.com,hmac-sha2-512-etm@openssh.com,hmac-sha2-256,hmac-sha1,umac-128@openssh.com,hmac-sha2-512
debug2: MACs stoc: hmac-sha2-256-etm@openssh.com,hmac-sha1-etm@openssh.com,umac-128-etm@openssh.com,hmac-sha2-512-etm@openssh.com,hmac-sha2-256,hmac-sha1,umac-128@openssh.com,hmac-sha2-512
debug2: compression ctos: none,zlib@openssh.com
debug2: compression stoc: none,zlib@openssh.com
debug2: languages ctos:
debug2: languages stoc:
debug2: first_kex_follows 0
debug2: reserved 0
debug3: will use strict KEX ordering
debug1: kex: algorithm: ecdh-sha2-nistp256
debug1: kex: host key algorithm: ecdsa-sha2-nistp256
debug1: kex: server->client cipher: aes256-gcm@openssh.com MAC: <implicit> compression: none
debug1: kex: client->server cipher: aes256-gcm@openssh.com MAC: <implicit> compression: none
debug1: kex: ecdh-sha2-nistp256 need=32 dh_need=32
debug1: kex: ecdh-sha2-nistp256 need=32 dh_need=32
debug3: send packet: type 30
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
debug3: receive packet: type 31
debug1: Server host key: ecdsa-sha2-nistp256 SHA256:+MsXOEwNhjYX3Cf67ITrWyMo9+tni8bnXb+phZ/DMU0
debug3: hostkeys_foreach: reading file "/home/ociユーザ/.ssh/known_hosts"
debug3: record_hostkey: found key type ECDSA in file /home/ociユーザ/.ssh/known_hosts:2
debug3: load_hostkeys: loaded 1 keys from 10.0.0.xxx
debug1: Host '10.0.0.xxx' is known and matches the ECDSA host key.
debug1: Found key in /home/ociユーザ/.ssh/known_hosts:2
debug3: send packet: type 21
debug1: resetting send seqnr 3
debug2: set_newkeys: mode 1
debug1: rekey out after 4294967296 blocks
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug3: receive packet: type 21
debug1: resetting read seqnr 3
debug1: SSH2_MSG_NEWKEYS received
debug2: set_newkeys: mode 0
debug1: rekey in after 4294967296 blocks
debug1: Will attempt key: id_ed25519 explicit
debug2: pubkey_prepare: done
debug3: send packet: type 5
debug3: receive packet: type 7
debug1: SSH2_MSG_EXT_INFO received
debug1: kex_input_ext_info: server-sig-algs=<ssh-ed25519,ssh-rsa,rsa-sha2-256,rsa-sha2-512,ssh-dss,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521>
debug3: receive packet: type 6
debug2: service_accept: ssh-userauth
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug3: send packet: type 50
debug3: receive packet: type 51
debug1: Authentications that can continue: publickey,gssapi-keyex,gssapi-with-mic
debug3: start over, passed a different list publickey,gssapi-keyex,gssapi-with-mic
debug3: preferred gssapi-with-mic,publickey,keyboard-interactive,password
debug3: authmethod_lookup gssapi-with-mic
debug3: remaining preferred: publickey,keyboard-interactive,password
debug3: authmethod_is_enabled gssapi-with-mic
debug1: Next authentication method: gssapi-with-mic
debug1: Unspecified GSS failure. Minor code may provide more information
No Kerberos credentials available (default cache: KEYRING:persistent:1101)
debug1: Unspecified GSS failure. Minor code may provide more information
No Kerberos credentials available (default cache: KEYRING:persistent:1101)
debug2: we did not send a packet, disable method
debug3: authmethod_lookup publickey
debug3: remaining preferred: keyboard-interactive,password
debug3: authmethod_is_enabled publickey
debug1: Next authentication method: publickey
debug1: Trying private key: id_ed25519
debug3: sign_and_send_pubkey: ED25519 SHA256:G5Z69XeB+E4FrMlaatSWDSt7LIrU8BI+f5EL+Ak5xXs
sign_and_send_pubkey: no mutual signature supported
debug2: we did not send a packet, disable method
debug1: No more authentication methods to try.
opc@10.0.0.xxx: Permission denied (publickey,gssapi-keyex,gssapi-with-mic).
ociユーザ@cloudshell:~ (ap-tokyo-1)$
もしかしてWindows 11 でキーを作成する際に ed25519 で作成されていることが原因なのかな？と ecdsa 形式で作成してみることにした。
> ssh-keygen -t ecdsa -f ecdsa-key
Generating public/private ecdsa key pair.
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in ecdsa-key
Your public key has been saved in ecdsa-key.pub
The key fingerprint is:
SHA256:N1BTF6JhBg2xFd9FrhZUv28Fib8bb696KF2ElgiIgNQ osakanataro@windowspc
The key's randomart image is:
+---[ECDSA 256]---+
|.oo. . .+=Ooo +++|
|. E. . .*.= * +.|
| o.+.oo= o|
| .. +..+.|
| S o. .+..|
| . . .+.o|
| . oo o|
| . o .=.|
| ..+.o+|
+----[SHA256]-----+
>
これで作成された公開鍵をLinuxインスタンス上の~/.ssh/authorized_keys に登録
OCIのCloud Shell上には秘密鍵をアップロードしてログインを実行
ociユーザ@cloudshell:~ (ap-tokyo-1)$ ssh -i ecdsa-key opc@10.0.0.xxx
Activate the web console with: systemctl enable --now cockpit.socket
Last login: Thu Aug 14 18:57:03 2025 from 10.0.0.xxx
[opc@wordpress ~]$
ログイン成功
というわけで、Oracle CloudのCloud shellでは ed25519 の公開鍵は使えないようです。
