To save typing, my .ssh/config started with "User = bart",
which was intended to apply globally unless overriden by the
"User" setting for a particularly connection. Although I
may be mistaken, I think the manual implies that this is
supposed to work.
Sadly, it doesn't; with this configuration, when publickey
authentication fails, rather than fall back to password
authentication the client simply repeatedly sends some bogus
public key until the server dies. Here's a trace:
OpenSSH_5.5p1 Debian-5, OpenSSL 0.9.8o 01 Jun 2010
debug1: Reading configuration data /home/bart/.ssh/config
debug1: Applying options for test
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: Applying options for *
debug1: Connecting to bartfan.po8.org [192.168.1.7] port 22.
debug1: Connection established.
debug1: identity file /home/bart/.ssh/id-rsa-test type 1
debug1: Checking blacklist file /usr/share/ssh/blacklist.RSA-4096
debug1: Checking blacklist file /etc/ssh/blacklist.RSA-4096
debug1: identity file /home/bart/.ssh/id-rsa-test-cert type -1
debug1: Remote protocol version 2.0, remote software version OpenSSH_5.5p1 Debian-5
debug1: match: OpenSSH_5.5p1 Debian-5 pat OpenSSH*
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_5.5p1 Debian-5
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<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 'bartfan.po8.org' is known and matches the RSA host key.
debug1: Found key in /home/bart/.ssh/known_hosts:59
debug1: ssh_rsa_verify: signature correct
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug1: SSH2_MSG_NEWKEYS received
debug1: Roaming not allowed by server
debug1: SSH2_MSG_SERVICE_REQUEST sent
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug1: Authentications that can continue: publickey,password
debug1: Next authentication method: publickey
debug1: Offering public key: /home/bart/.ssh/id-rsa-test
debug1: Authentications that can continue: publickey,password
debug1: Offering public key: bart@bartfan
debug1: Authentications that can continue: publickey,password
debug1: Offering public key: bart@bartfan
debug1: Authentications that can continue: publickey,password
debug1: Offering public key: bart@bartfan
debug1: Authentications that can continue: publickey,password
debug1: Offering public key: bart@bartfan
debug1: Authentications that can continue: publickey,password
debug1: Offering public key: bart@bartfan
Received disconnect from 192.168.1.7: 2: Too many authentication failures for bart
Moving the "User" option to be private to each connection in
the config file seems to solve the problem.