On Mon Aug 31, 2020 at 6:56 PM PDT, Damien Miller wrote:
> On Mon, 31 Aug 2020, [email protected] wrote:
>
> > >Synopsis:  ecdsa-sk no longer works with latest snapshot
> > >Category:
> > >Environment:
> >     System      : OpenBSD 6.7
> >     Details     : OpenBSD 6.7-current (GENERIC.MP) #52: Sun Aug 30 17:55:06 
> > MDT 2020
> >                      
> > [email protected]:/usr/src/sys/arch/amd64/compile/GENERIC.MP
> > 
> >     Architecture: OpenBSD.amd64
> >     Machine     : amd64
> > >Description:
> >     As of a recent snapshot, my Yubikey with an ecdsa-sk key no longer
> >     works with ssh. Where the ssh process would typically pause to confirm
> >     presence, now it fails immediately with the following:
> > 
> >             Confirm user presence for key ECDSA-SK SHA256:____
> >             sign_and_send_pubkey: signing failed for ECDSA-SK "$keypath": 
> > invalid format
> >             $user@$ip: Permission denied (publickey).
> > >How-To-Repeat:
> >     1. Insert a single Yubikey into a USB port.
> >     2. Generate an ecdsa-sk key with normal options, i.e. not a resident
> >        key.
> >     3. Attempt to ssh into any service that uses your ecdsa-sk key.
> > 
> >     This can be reproduced with or without ssh-agent running.
>
> Hi,
>
> Thanks for the report - plase send the output of a failing ssh session
> in verbose mode, i.e.
>
> ssh -vvv user@host
>
> Thanks,
> Damien

Hi Damien,

Sure thing. Please see the output of `ssh -vvv user@host` below.

Best,

Evan

OpenSSH_8.3, LibreSSL 3.2.1
debug1: Reading configuration data /home/$myuser/.ssh/config
debug1: /home/$myuser/.ssh/config line 1: Applying options for *
debug1: /home/$myuser/.ssh/config line 11: Applying options for $myserver
debug1: Reading configuration data /etc/ssh/ssh_config
debug2: resolve_canonicalize: hostname $myip is address
debug3: expanded UserKnownHostsFile '~/.ssh/known_hosts' -> 
'/home/$myuser/.ssh/known_hosts'
debug3: expanded UserKnownHostsFile '~/.ssh/known_hosts2' -> 
'/home/$myuser/.ssh/known_hosts2'
debug1: auto-mux: Trying existing master
debug1: Control socket 
"/home/$myuser/.ssh/31c0e4a977b4607445212bb8627b62f6ee34b72e.sock" does not 
exist
debug2: ssh_connect_direct
debug1: Connecting to $myip [$myip] port 22.
debug1: Connection established.
debug1: identity file /home/$myuser/.ssh/id_rsa type 0
debug1: identity file /home/$myuser/.ssh/id_rsa-cert type -1
debug1: identity file /home/$myuser/.ssh/id_dsa type -1
debug1: identity file /home/$myuser/.ssh/id_dsa-cert type -1
debug1: identity file /home/$myuser/.ssh/id_ecdsa type -1
debug1: identity file /home/$myuser/.ssh/id_ecdsa-cert type -1
debug1: identity file /home/$myuser/.ssh/id_ecdsa_sk type 10
debug1: identity file /home/$myuser/.ssh/id_ecdsa_sk-cert type -1
debug1: identity file /home/$myuser/.ssh/id_ed25519 type -1
debug1: identity file /home/$myuser/.ssh/id_ed25519-cert type -1
debug1: identity file /home/$myuser/.ssh/id_ed25519_sk type -1
debug1: identity file /home/$myuser/.ssh/id_ed25519_sk-cert type -1
debug1: identity file /home/$myuser/.ssh/id_xmss type -1
debug1: identity file /home/$myuser/.ssh/id_xmss-cert type -1
debug1: Local version string SSH-2.0-OpenSSH_8.3
debug1: Remote protocol version 2.0, remote software version OpenSSH_8.3
debug1: match: OpenSSH_8.3 pat OpenSSH* compat 0x04000000
debug2: fd 3 setting O_NONBLOCK
debug1: Authenticating to $myip:22 as '$myuser'
debug3: hostkeys_foreach: reading file "/home/$myuser/.ssh/known_hosts"
debug3: record_hostkey: found key type ECDSA in file 
/home/$myuser/.ssh/known_hosts:61
debug3: load_hostkeys: loaded 1 keys from $myip
debug3: order_hostkeyalgs: prefer hostkeyalgs: 
[email protected],[email protected],[email protected],ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521
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: 
curve25519-sha256,[email protected],ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,diffie-hellman-group14-sha256,ext-info-c
debug2: host key algorithms: 
[email protected],[email protected],[email protected],ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],ssh-ed25519,[email protected],rsa-sha2-512,rsa-sha2-256,ssh-rsa
debug2: ciphers ctos: 
[email protected],aes128-ctr,aes192-ctr,aes256-ctr,[email protected],[email protected]
debug2: ciphers stoc: 
[email protected],aes128-ctr,aes192-ctr,aes256-ctr,[email protected],[email protected]
debug2: MACs ctos: 
[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: MACs stoc: 
[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: compression ctos: none,[email protected],zlib
debug2: compression stoc: none,[email protected],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,[email protected],ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,diffie-hellman-group14-sha256
debug2: host key algorithms: 
rsa-sha2-512,rsa-sha2-256,ssh-rsa,ecdsa-sha2-nistp256,ssh-ed25519
debug2: ciphers ctos: 
[email protected],aes128-ctr,aes192-ctr,aes256-ctr,[email protected],[email protected]
debug2: ciphers stoc: 
[email protected],aes128-ctr,aes192-ctr,aes256-ctr,[email protected],[email protected]
debug2: MACs ctos: 
[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: MACs stoc: 
[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: compression ctos: none,[email protected]
debug2: compression stoc: none,[email protected]
debug2: languages ctos: 
debug2: languages stoc: 
debug2: first_kex_follows 0 
debug2: reserved 0 
debug1: kex: algorithm: curve25519-sha256
debug1: kex: host key algorithm: ecdsa-sha2-nistp256
debug1: kex: server->client cipher: [email protected] MAC: 
<implicit> compression: none
debug1: kex: client->server cipher: [email protected] MAC: 
<implicit> compression: none
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:P7DtIw7f2H9affC1tQbNzaZt6eIAXWH9E54tUp8kFKo
debug3: hostkeys_foreach: reading file "/home/$myuser/.ssh/known_hosts"
debug3: record_hostkey: found key type ECDSA in file 
/home/$myuser/.ssh/known_hosts:61
debug3: load_hostkeys: loaded 1 keys from $myip
debug1: Host '$myip' is known and matches the ECDSA host key.
debug1: Found key in /home/$myuser/.ssh/known_hosts:61
debug3: send packet: type 21
debug2: set_newkeys: mode 1
debug1: rekey out after 134217728 blocks
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug3: receive packet: type 21
debug1: SSH2_MSG_NEWKEYS received
debug2: set_newkeys: mode 0
debug1: rekey in after 134217728 blocks
debug1: pubkey_prepare: ssh_get_authentication_socket: No such file or directory
debug1: Will attempt key: /home/$myuser/.ssh/id_rsa RSA 
SHA256:2v8Wb4Dtk7c18WbM0BTK11dRHBCZDYZgaUWyLgk35jY
debug1: Will attempt key: /home/$myuser/.ssh/id_dsa 
debug1: Will attempt key: /home/$myuser/.ssh/id_ecdsa 
debug1: Will attempt key: /home/$myuser/.ssh/id_ecdsa_sk ECDSA-SK 
SHA256:GB4xULL7euanCP2PZeL3KAQS9+rbhUepIvy+tYSmfRk authenticator
debug1: Will attempt key: /home/$myuser/.ssh/id_ed25519 
debug1: Will attempt key: /home/$myuser/.ssh/id_ed25519_sk 
debug1: Will attempt key: /home/$myuser/.ssh/id_xmss 
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,[email protected],ssh-rsa,rsa-sha2-256,rsa-sha2-512,ssh-dss,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,[email protected]>
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
debug3: start over, passed a different list publickey
debug3: preferred publickey,keyboard-interactive,password
debug3: authmethod_lookup publickey
debug3: remaining preferred: keyboard-interactive,password
debug3: authmethod_is_enabled publickey
debug1: Next authentication method: publickey
debug1: Offering public key: /home/$myuser/.ssh/id_rsa RSA 
SHA256:2v8Wb4Dtk7c18WbM0BTK11dRHBCZDYZgaUWyLgk35jY
debug3: send packet: type 50
debug2: we sent a publickey packet, wait for reply
debug3: receive packet: type 51
debug1: Authentications that can continue: publickey
debug1: Trying private key: /home/$myuser/.ssh/id_dsa
debug3: no such identity: /home/$myuser/.ssh/id_dsa: No such file or directory
debug1: Trying private key: /home/$myuser/.ssh/id_ecdsa
debug3: no such identity: /home/$myuser/.ssh/id_ecdsa: No such file or directory
debug1: Offering public key: /home/$myuser/.ssh/id_ecdsa_sk ECDSA-SK 
SHA256:GB4xULL7euanCP2PZeL3KAQS9+rbhUepIvy+tYSmfRk authenticator
debug3: send packet: type 50
debug2: we sent a publickey packet, wait for reply
debug3: receive packet: type 60
debug1: Server accepts key: /home/$myuser/.ssh/id_ecdsa_sk ECDSA-SK 
SHA256:GB4xULL7euanCP2PZeL3KAQS9+rbhUepIvy+tYSmfRk authenticator
debug3: sign_and_send_pubkey: ECDSA-SK 
SHA256:GB4xULL7euanCP2PZeL3KAQS9+rbhUepIvy+tYSmfRk
debug3: sign_and_send_pubkey: signing using [email protected] 
SHA256:GB4xULL7euanCP2PZeL3KAQS9+rbhUepIvy+tYSmfRk
debug3: no authentication agent, not adding key
debug3: start_helper: started pid=45801
debug3: ssh_msg_send: type 5
debug3: ssh_msg_recv entering
debug1: start_helper: starting /usr/libexec/ssh-sk-helper 
debug1: ssh-sk-helper: ready to sign with key ECDSA-SK, provider internal: msg 
len 245, compat 0x4000000
debug1: sshsk_sign: provider "internal", key ECDSA-SK, flags 0x01
debug1: sk_probe: 1 device(s) detected
debug1: sk_probe: selecting sk by cred
debug1: sk_open: fido_dev_open /dev/fido/0 failed: FIDO_ERR_INTERNAL
debug1: sk_openv: sk_open failed
debug1: sk_select_by_cred: sk_openv failed
debug1: ssh_sk_sign: failed to find sk
debug1: sshsk_sign: sk_sign failed with code -1
debug1: ssh-sk-helper: Signing failed: invalid format
debug1: ssh-sk-helper: reply len 8
debug3: ssh_msg_send: type 5
debug1: client_converse: helper returned error -4
debug3: reap_helper: pid=45801
debug1: identity_sign: sshkey_sign: invalid format
sign_and_send_pubkey: signing failed for ECDSA-SK 
"/home/$myuser/.ssh/id_ecdsa_sk": invalid format
debug1: Trying private key: /home/$myuser/.ssh/id_ed25519
debug3: no such identity: /home/$myuser/.ssh/id_ed25519: No such file or 
directory
debug1: Trying private key: /home/$myuser/.ssh/id_ed25519_sk
debug3: no such identity: /home/$myuser/.ssh/id_ed25519_sk: No such file or 
directory
debug1: Trying private key: /home/$myuser/.ssh/id_xmss
debug3: no such identity: /home/$myuser/.ssh/id_xmss: No such file or directory
debug2: we did not send a packet, disable method
debug1: No more authentication methods to try.
$myuser@$myip: Permission denied (publickey).

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