SSH with Cron: RSA key not accepted

cronkey-authenticationsshUbuntu

I am trying to get ssh to work in cron, and it seems like I have tried all the standard tricks with no luck at all. I can run a non-interactive ssh by using

>./some_script_with_ssh

in bash. It's only when I try to use it in cron that it fails. Any help I could get would be greatly appreciated.

Below are some of the data requested in similar questions:

My user's crontab

PATH = /home/zach/.ssh/:/usr/bin
52 * * * * ssh -vvv my_account@my_remote "touch temp.temp"

Printout from the email cron sent me

OpenSSH_7.3p1 Ubuntu-1, OpenSSL 1.0.2g  1 Mar 2016
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 19: Applying options for *
debug2: resolving "my_remote" port 22
debug2: ssh_connect_direct: needpriv 0
debug1: Connecting to my_remote [IP_HERE] port 22.
debug1: Connection established.
debug1: identity file /home/zach/.ssh/id_rsa type 1
debug1: key_load_public: No such file or directory
debug1: identity file /home/zach/.ssh/id_rsa-cert type -1
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_7.3p1 Ubuntu-1
debug1: Remote protocol version 2.0, remote software version OpenSSH_6.2
debug1: match: OpenSSH_6.2 pat OpenSSH* compat 0x04000000
debug2: fd 3 setting O_NONBLOCK
debug1: Authenticating to my_remote:22 as 'my_account'
debug3: hostkeys_foreach: reading file "/home/zach/.ssh/known_hosts"
debug3: record_hostkey: found key type ECDSA in file /home/zach/.ssh/known_hosts:1
debug3: load_hostkeys: loaded 1 keys from my_remote
debug3: order_hostkeyalgs: prefer hostkeyalgs: ecdsa-sha2-nistp256-cert-v01@openssh.com,ecdsa-sha2-nistp384-cert-v01@openssh.com,ecdsa-sha2-nistp521-cert-v01@openssh.com,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@libssh.org,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha256,diffie-hellman-group14-sha1,ext-info-c
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,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,ssh-ed25519-cert-v01@openssh.com,ssh-rsa-cert-v01@openssh.com,ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa
debug2: ciphers ctos: chacha20-poly1305@openssh.com,aes128-ctr,aes192-ctr,aes256-ctr,aes128-gcm@openssh.com,aes256-gcm@openssh.com,aes128-cbc,aes192-cbc,aes256-cbc,3des-cbc
debug2: ciphers stoc: chacha20-poly1305@openssh.com,aes128-ctr,aes192-ctr,aes256-ctr,aes128-gcm@openssh.com,aes256-gcm@openssh.com,aes128-cbc,aes192-cbc,aes256-cbc,3des-cbc
debug2: MACs ctos: umac-64-etm@openssh.com,umac-128-etm@openssh.com,hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,hmac-sha1-etm@openssh.com,umac-64@openssh.com,umac-128@openssh.com,hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: MACs stoc: umac-64-etm@openssh.com,umac-128-etm@openssh.com,hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,hmac-sha1-etm@openssh.com,umac-64@openssh.com,umac-128@openssh.com,hmac-sha2-256,hmac-sha2-512,hmac-sha1
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: ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1
debug2: host key algorithms: ssh-rsa,ssh-dss,ecdsa-sha2-nistp256
debug2: ciphers ctos: aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-gcm@openssh.com,aes256-gcm@openssh.com,aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,rijndael-cbc@lysator.liu.se
debug2: ciphers stoc: aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-gcm@openssh.com,aes256-gcm@openssh.com,aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,rijndael-cbc@lysator.liu.se
debug2: MACs ctos: hmac-md5-etm@openssh.com,hmac-sha1-etm@openssh.com,umac-64-etm@openssh.com,umac-128-etm@openssh.com,hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,hmac-ripemd160-etm@openssh.com,hmac-sha1-96-etm@openssh.com,hmac-md5-96-etm@openssh.com,hmac-md5,hmac-sha1,umac-64@openssh.com,umac-128@openssh.com,hmac-sha2-256,hmac-sha2-512,hmac-ripemd160,hmac-ripemd160@openssh.com,hmac-sha1-96,hmac-md5-96
debug2: MACs stoc: hmac-md5-etm@openssh.com,hmac-sha1-etm@openssh.com,umac-64-etm@openssh.com,umac-128-etm@openssh.com,hmac-sha2-256-etm@openssh.com,hmac-sha2-512-etm@openssh.com,hmac-ripemd160-etm@openssh.com,hmac-sha1-96-etm@openssh.com,hmac-md5-96-etm@openssh.com,hmac-md5,hmac-sha1,umac-64@openssh.com,umac-128@openssh.com,hmac-sha2-256,hmac-sha2-512,hmac-ripemd160,hmac-ripemd160@openssh.com,hmac-sha1-96,hmac-md5-96
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
debug1: kex: algorithm: ecdh-sha2-nistp256
debug1: kex: host key algorithm: ecdsa-sha2-nistp256
debug1: kex: server->client cipher: aes128-ctr MAC: umac-64-etm@openssh.com compression: none
debug1: kex: client->server cipher: aes128-ctr MAC: umac-64-etm@openssh.com compression: none
debug3: send packet: type 30
debug1: sending SSH2_MSG_KEX_ECDH_INIT
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
debug3: receive packet: type 31
debug1: Server host key: ecdsa-sha2-nistp256 SHA256:K8vzLDbyV5JKlcnHsIj6BK/yR4OTJaY4fFuHpsg0FdE
debug3: hostkeys_foreach: reading file "/home/zach/.ssh/known_hosts"
debug3: record_hostkey: found key type ECDSA in file /home/zach/.ssh/known_hosts:1
debug3: load_hostkeys: loaded 1 keys from my_remote
debug3: hostkeys_foreach: reading file "/home/zach/.ssh/known_hosts"
debug3: record_hostkey: found key type ECDSA in file /home/zach/.ssh/known_hosts:2
debug3: load_hostkeys: loaded 1 keys from 128.97.70.146
debug1: Host 'my_remote' is known and matches the ECDSA host key.
debug1: Found key in /home/zach/.ssh/known_hosts:1
debug3: send packet: type 21
debug2: set_newkeys: mode 1
debug1: rekey after 4294967296 blocks
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug3: receive packet: type 21
debug2: set_newkeys: mode 0
debug1: rekey after 4294967296 blocks
debug1: SSH2_MSG_NEWKEYS received
debug2: key: /home/zach/.ssh/id_rsa (0x55f6f6440f50)
debug3: send packet: type 5
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-with-mic,password,keyboard-interactive
debug3: start over, passed a different list publickey,gssapi-with-mic,password,keyboard-interactive
debug3: preferred publickey,keyboard-interactive
debug3: authmethod_lookup publickey
debug3: remaining preferred: keyboard-interactive
debug3: authmethod_is_enabled publickey
debug1: Next authentication method: publickey
debug1: Offering RSA public key: /home/zach/.ssh/id_rsa
debug3: send_pubkey_test
debug3: send packet: type 50
debug2: we sent a publickey packet, wait for reply
debug3: receive packet: type 60
debug1: Server accepts key: pkalg ssh-rsa blen 279
debug2: input_userauth_pk_ok: fp SHA256:jsePXa9FO8c9f0bVwdgvXMJQ2GyHVqz5spaO13EQ0/M
debug3: sign_and_send_pubkey: RSA SHA256:jsePXa9FO8c9f0bVwdgvXMJQ2GyHVqz5spaO13EQ0/M
debug1: read_passphrase: can't open /dev/tty: No such device or address
debug2: no passphrase given, try next key
debug2: we did not send a packet, disable method
debug3: authmethod_lookup keyboard-interactive
debug3: remaining preferred:
debug3: authmethod_is_enabled keyboard-interactive
debug1: Next authentication method: keyboard-interactive
debug2: userauth_kbdint
debug3: send packet: type 50
debug2: we sent a keyboard-interactive packet, wait for reply
debug3: receive packet: type 60
debug2: input_userauth_info_req
debug2: input_userauth_info_req: num_prompts 1
debug1: read_passphrase: can't open /dev/tty: No such device or address
debug3: send packet: type 61
debug3: receive packet: type 51
debug1: Authentications that can continue: publickey,gssapi-with-mic,password,keyboard-interactive
debug2: userauth_kbdint
debug3: send packet: type 50
debug2: we sent a keyboard-interactive packet, wait for reply
debug3: receive packet: type 60
debug2: input_userauth_info_req
debug2: input_userauth_info_req: num_prompts 1
debug1: read_passphrase: can't open /dev/tty: No such device or address
debug3: send packet: type 61
debug3: receive packet: type 51
debug1: Authentications that can continue: publickey,gssapi-with-mic,password,keyboard-interactive
debug2: userauth_kbdint
debug3: send packet: type 50
debug2: we sent a keyboard-interactive packet, wait for reply
debug3: receive packet: type 60
debug2: input_userauth_info_req
debug2: input_userauth_info_req: num_prompts 1
debug1: read_passphrase: can't open /dev/tty: No such device or address
debug3: send packet: type 61
debug3: receive packet: type 51
debug1: Authentications that can continue: publickey,gssapi-with-mic,password,keyboard-interactive
debug2: we did not send a packet, disable method
debug1: No more authentication methods to try.
Permission denied (publickey,gssapi-with-mic,password,keyboard-interactive).

Permissions on local RSA data

>ls -l ~/.ssh/
total 12
-rw------- 1 zach zach 1766 Dec 22 13:47 id_rsa
-rw-r--r-- 1 zach zach  419 Dec  4  2015 id_rsa.pub
-rw-r--r-- 1 zach zach 1332 Dec 21 13:51 known_hosts

Permissions on local home

>ls -l ~/..
total 20
drwx------  2 root root 16384 Jul 17  2015 lost+found
drwx------ 67 zach zach  4096 Dec 22 16:05 zach

Permissions on local ~/.ssh folder

drwx------  2 zach zach    4096 Dec 22 15:11 .ssh

Permissions on remote home

drwx------ 31 my_account       grad      4096 Dec 22 13:57 my_account

Permissions on remote RSA data

> ls -l ~/.ssh/
total 12
-rwx------ 1 my_account grad 419 Dec  4  2015 authorized_keys
-rw------- 1 my_account grad  36 Dec 20 22:45 config
-rw------- 1 my_account grad 223 Sep 10 14:51 known_hosts

Permissions on remote ~/.ssh folder

> ls -l ~
drwx------  2 my_account grad   4096 Dec 20 22:45 .ssh

Local /etc/ssh/ssh_config

host *
    passwordauthentication no
    stricthostkeychecking no
    identityfile ~/.ssh/id_rsa
    sendenv lang lc_*
    hashknownhosts yes

Remote /etc/ssh/ssh_config

> cat /etc/ssh/ssh_config
Host *
    Protocol            2
    ServerAliveInterval     120
    TCPKeepAlive        no
    ConnectTimeout      5
    NoHostAuthenticationForLocalhost    yes
    PreferredAuthentications    gssapi-with-mic,publickey,keyboard-interactive,password
    GSSAPIAuthentication    yes
    SendEnv         "LOGNAME LANG LC_*"
    ForwardX11Trusted       yes

My ssh key is not password protected.

>env | grep SSH
SSH_AGENT_LAUNCHER=gnome-keyring
SSH_AUTH_SOCK=/run/user/1000/keyring/ssh (I am user 1000)

I have also tried to use the -n, -T, -t, and -t -t options for ssh with no noticeable difference.

Best Answer

debug1: Offering RSA public key: /home/zach/.ssh/id_rsa
debug3: send_pubkey_test
debug3: send packet: type 50
debug2: we sent a publickey packet, wait for reply
debug3: receive packet: type 60
debug1: Server accepts key: pkalg ssh-rsa blen 279
debug2: input_userauth_pk_ok: fp SHA256:jsePXa9FO8c9f0bVwdgvXMJQ2GyHVqz5spaO13EQ0/M
debug3: sign_and_send_pubkey: RSA SHA256:jsePXa9FO8c9f0bVwdgvXMJQ2GyHVqz5spaO13EQ0/M
debug1: read_passphrase: can't open /dev/tty: No such device or address
debug2: no passphrase given, try next key

Your key is passphrase protected, but you probably didn't notice, because you are using gnome-keyring which takes care of that. So what are the possibilities:

  • Use separate key, which is not encrypted for cron jobs, becuase you still don't have a reasonable and secure way how to provide passphrase in cron job. This is preferred.

  • If you don't mind storing passphrase in plaintext, use sshpass:

    sshpass -p your_passhprase -vvv my_account@my_remote "touch temp.temp"
    
  • Other possibility is to try to "hijack" the connection to your gnome-keyring (using SSH_AUTH_SOCK environment variable). But note that this might not work always (once you log out of your graphical session, the gnome-keyring will not be running anymore and you will see the failures again:

    SSH_AUTH_SOCK=/run/user/1000/keyring/ssh ssh -vvv my_account@my_remote "touch temp.temp"
    
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