Local system is OS X. I'm attempting to log in using the packaged command-line ssh client. Remote system is CentOS.
I tried again with verbose output:
OpenSSH_5.1p1, OpenSSL 0.9.7l 28 Sep 2006
debug1: Reading configuration data /etc/ssh_config
debug1: Connecting to <remote host> [<remote ip>] port 22.
debug1: Connection established.
debug1: identity file testkey type 1
debug1: Remote protocol version 2.0, remote software version OpenSSH_4.3
debug1: match: OpenSSH_4.3 pat OpenSSH*
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_5.1
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug1: kex: server->client aes128-cbc hmac-md5 none
debug1: kex: client->server aes128-cbc hmac-md5 none
debug1: SSH2_MSG_KEX_DH_GEX_REQUEST(1024<1024<8192) sent
debug1: expecting SSH2_MSG_KEX_DH_GEX_GROUP
debug1: SSH2_MSG_KEX_DH_GEX_INIT sent
debug1: expecting SSH2_MSG_KEX_DH_GEX_REPLY
debug1: Host '<remote host>' is known and matches the RSA host key.
debug1: Found key in /Users/<local username>/.ssh/known_hosts:2
debug1: ssh_rsa_verify: signature correct
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug1: SSH2_MSG_NEWKEYS received
debug1: SSH2_MSG_SERVICE_REQUEST sent
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug1: Authentications that can continue: publickey,gssapi-with-mic,password
debug1: Next authentication method: publickey
debug1: Offering public key: svidgen-testkey
debug1: Authentications that can continue: publickey,gssapi-with-mic,password
debug1: Offering public key: svidgen-testkey
debug1: Authentications that can continue: publickey,gssapi-with-mic,password
debug1: Next authentication method: password
So, my local client appears to be offering the key twice--it's being rejected/ignored by the server, if I'm interpreting this correctly. Is there some additional configuration that may be required server-side?
I've chmodded the server-side .ssh folder to 700 and .ssh/authorized_keys to 600, as recommended by http://sial.org/howto/openssh/publickey-auth/problems/. And, I'm not entirely sure what to try in terms of possible versioning issues--it looks to me like the local ssh client and remote sshd daemon are agreeing on SSH 2.0 protocol. Is that not the protocol that my key pair would be compatible with?