Suppose you want to use Linux and OpenSSH to automize your tasks or you just don't want to type the password every time you connect to a server.
You can solve this issue by doing this.
Scenario:
skyline wants to connect to veyron using ssh without a password.
By default, the ssh command has the order to check for authentication: Authentications that can continue: publickey,gssapi-keyex,gssapi-with-mic,password
[0] skyline ~ $ ssh alvaro@veyron -v OpenSSH_5.3p1, OpenSSL 1.0.0-fips 29 Mar 2010 debug1: Reading configuration data /etc/ssh/ssh_config debug1: Applying options for * debug1: Connecting to veyron[10.10.1.194] port 22. debug1: Connection established. debug1: permanently_set_uid: 0/0 debug1: identity file /Users/alvaro/.ssh/identity type -1 debug1: identity file /Users/alvaro/.ssh/id_rsa type 1 debug1: identity file /Users/alvaro/.ssh/id_dsa type -1 debug1: Remote protocol version 2.0, remote software version OpenSSH_5.3 debug1: match: OpenSSH_5.3 pat OpenSSH* debug1: Enabling compatibility mode for protocol 2.0 debug1: Local version string SSH-2.0-OpenSSH_5.3 debug1: SSH2_MSG_KEXINIT sent debug1: SSH2_MSG_KEXINIT received debug1: kex: server->client aes128-ctr hmac-md5 none debug1: kex: client->server aes128-ctr hmac-md5 none debug1: SSH2_MSG_KEX_DH_GEX_REQUEST(1024 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 Credentials cache file '/tmp/krb5cc_0' not found debug1: Unspecified GSS failure. Minor code may provide more information Credentials cache file '/tmp/krb5cc_0' not found debug1: Unspecified GSS failure. Minor code may provide more information debug1: Unspecified GSS failure. Minor code may provide more information debug1: Next authentication method: publickey debug1: Trying private key: /Users/alvaro/.ssh/identity debug1: Offering public key: /Users/alvaro/.ssh/id_rsa debug1: Authentications that can continue: publickey,gssapi-keyex,gssapi-with-mic,password debug1: Trying private key: /Users/alvaro/.ssh/id_dsa debug1: Next authentication method: password alvaro@veyron's password:
Checking the ssh server authorized_keys configuration:
root # grep -e Authorized -e Pubkey /etc/ssh/sshd_config | grep -v '#' PubkeyAuthentication yes AuthorizedKeysFile .ssh/authorized_keys
Generating public/private rsa key pair:
[0] skyline ~ $ ssh-keygen -t rsa Generating public/private rsa key pair. Enter file in which to save the key (/Users/alvaro/.ssh/id_rsa): Created directory '/Users/alvaro/.ssh'. Enter passphrase (empty for no passphrase): Enter same passphrase again: Your identification has been saved in /Users/alvaro/.ssh/id_rsa. Your public key has been saved in /Users/alvaro/.ssh/id_rsa.pub. The key fingerprint is: 53:1d:8a:f8:93:a8:1e:e2:9d:db:f8:ca:3d:73:5a:60 alvaro@skyline The key's randomart image is: +--[ RSA 2048]----+ | . | | . . o . | | . . o . | | o o | | E S | | o . o | | . o . | | . = *o.. | | . O+== | +-----------------+[0] skyline ~ $ ssh alvaro@veyron mkdir -p .ssh Password: [0] skyline ~ $ cat .ssh/id_rsa.pub | ssh alvaro@veyron 'cat >> .ssh/authorized_keys' Password:[0] skyline ~ $ cat .ssh/config Host veyron User alvaro Hostname 10.10.1.194
Verbose connection:
[0] skyline ~ $ ssh alvaro@veyron -v OpenSSH_5.3p1, OpenSSL 1.0.0-fips 29 Mar 2010 debug1: Reading configuration data /etc/ssh/ssh_config debug1: Applying options for * debug1: Connecting to localhost [::1] port 22. debug1: Connection established. debug1: permanently_set_uid: 0/0 debug1: identity file /Users/alvaro/.ssh/identity type -1 debug1: identity file /Users/alvaro/.ssh/id_rsa type 1 debug1: identity file /Users/alvaro/.ssh/id_dsa type -1 debug1: Remote protocol version 2.0, remote software version OpenSSH_5.3 debug1: match: OpenSSH_5.3 pat OpenSSH* debug1: Enabling compatibility mode for protocol 2.0 debug1: Local version string SSH-2.0-OpenSSH_5.3 debug1: SSH2_MSG_KEXINIT sent debug1: SSH2_MSG_KEXINIT received debug1: kex: server->client aes128-ctr hmac-md5 none debug1: kex: client->server aes128-ctr hmac-md5 none debug1: SSH2_MSG_KEX_DH_GEX_REQUEST(1024 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 Credentials cache file '/tmp/krb5cc_0' not found debug1: Unspecified GSS failure. Minor code may provide more information Credentials cache file '/tmp/krb5cc_0' not found debug1: Unspecified GSS failure. Minor code may provide more information debug1: Unspecified GSS failure. Minor code may provide more information debug1: Next authentication method: publickey debug1: Trying private key: /Users/alvaro/.ssh/identity debug1: Offering public key: /Users/alvaro/.ssh/id_rsa debug1: Server accepts key: pkalg ssh-rsa blen 277 debug1: read PEM private key done: type RSA debug1: Authentication succeeded (publickey). debug1: channel 0: new [client-session] debug1: Requesting no-more-sessions@openssh.com debug1: Entering interactive session. debug1: Sending environment. debug1: Sending env LANG = en_US.UTF-8 Last login: Tue Apr 24 14:50:42 CDT 2012 from skyline.headup.ws on ssh alvaro@veyron ~ $
Clean ssh execution:
[0] skyline ~ $ ssh veyron Last login: Tue Apr 24 14:50:42 CDT 2012 from skyline.headup.ws on ssh alvaro@veyron ~ $
