How do I configure SSH so it doesn't try all the identity files automatically?
Solution 1
user76528's short answer is correct, but I just had this problem and thought some elaboration would be useful. You might also care about this solution if you've wondered "Why is ssh ignoring my identityfile configuration option"?
Firstly, unlike every other option in ssh_config, ssh does not use the first IdentityFile
that it finds. Instead the IdentityFile
option adds that file to a list of identities used. You may stack multiple IdentityFile
options, and the ssh client will try them all until the server accepts one or rejects the connection.
Second, if you use an ssh-agent, ssh will automatically try to use the keys in the agent, even if you have not specified them with in ssh_config's IdentityFile (or -i) option. This is a common reason you might get the Too many authentication failures for user
error. Using the IdentitiesOnly yes
option will disable this behavior.
If you ssh as multiple users to multiple systems, I recommend putting IdentitiesOnly yes
in your global section of ssh_config, and putting each IdentityFile
within the appropriate Host subsections.
Solution 2
I generally do it like so:
$ ssh -o IdentitiesOnly=yes -F /dev/null -i ~/path/to/some_id_rsa [email protected]
The options are as follows:
-o IdentitiesOnly=yes
- tells SSH to only use keys that are provided via the CLI and none from the$HOME/.ssh
or via ssh-agent-F /dev/null
- disables the use of$HOME/.ssh/config
-i ~/path/to/some_id_rsa
- the key that you explicitly want to use for the connection
Example
$ ssh -v -o IdentitiesOnly=yes -F /dev/null -i ~/my_id_rsa [email protected]
OpenSSH_6.2p2, OSSLShim 0.9.8r 8 Dec 2011
debug1: Reading configuration data /dev/null
debug1: Connecting to someserver.mydom.com [10.128.12.124] port 22.
debug1: Connection established.
debug1: identity file /Users/sammingolelli/my_id_rsa type 1
debug1: identity file /Users/sammingolelli/my_id_rsa-cert type -1
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_6.2
debug1: Remote protocol version 2.0, remote software version OpenSSH_5.3
debug1: match: OpenSSH_5.3 pat OpenSSH_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: Server host key: RSA f5:60:30:71:8c:a3:da:a3:fe:b1:6d:0b:20:87:23:e1
debug1: Host 'someserver' is known and matches the RSA host key.
debug1: Found key in /Users/sammingolelli/.ssh/known_hosts:103
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,gssapi-keyex,gssapi-with-mic,password
debug1: Next authentication method: publickey
debug1: Offering RSA public key: /Users/sammingolelli/my_id_rsa
debug1: Server accepts key: pkalg ssh-rsa blen 535
debug1: read PEM private key done: type RSA
debug1: Authentication succeeded (publickey).
Authenticated to someserver.mydom.com ([10.128.12.124]:22).
debug1: channel 0: new [client-session]
debug1: Requesting [email protected]
debug1: Entering interactive session.
Last login: Tue Dec 8 19:03:24 2015 from 153.65.219.15
someserver$
Notice in the above output that ssh
has only identified the my_id_rsa
private key via the CLI and that it uses it to connect to someserver.
Specifically these sections:
debug1: identity file /Users/sammingolelli/my_id_rsa type 1
debug1: identity file /Users/sammingolelli/my_id_rsa-cert type -1
and:
debug1: Next authentication method: publickey
debug1: Offering RSA public key: /Users/sammingolelli/my_id_rsa
debug1: Server accepts key: pkalg ssh-rsa blen 535
debug1: read PEM private key done: type RSA
debug1: Authentication succeeded (publickey).
Solution 3
In the scenario where you have many keys, you will invariably run into the "Too many Authentication Failures" error. If you have a password, and want to simply use the password to login, here is how you do it.
To use ONLY password authentication and NOT use Public-key, and NOT use the somewhat misleading "keyboard-interactive" (which is a superset including password), you can do this from the command line:
ssh -o PreferredAuthentications=password [email protected]
Solution 4
Use IdentityFile but Keep Using ssh-agent to Avoid Passphrase Reprompts
The accepted solution of using IdentitiesOnly yes
means you'll never be able to take advantage of ssh-agent, resulting in repeated prompts for your passphrase when loading your key.
To keep using ssh-agent
and avoid the 'Too many authentication failures' errors, try this:
Remove any interactive console startup scripts that automatically load keys into
ssh-agent
.add
AddKeysToAgent yes
to your client's ssh config. This will prompt you for the passphrase on first connect, but then add the key to your agent.use
ssh-add -D
when you get 'too many authentication' errors. This simply 'resets' (deletes) your ssh-agent cache. Then attempt the connection again within the same session. You will be prompted for a passphrase, and once accepted, it will be added to your agent. Since you'll have only one key in your agent, you will be allowed to connect. ssh-agent is then still there for future connections during the same session to avoid reprompts.Host ex example.com User joe HostName example.com PreferredAuthentications publickey,password IdentityFile /path/to/id_rsa AddKeysToAgent yes
Solution 5
The ssh client and the ssh-agent
is communicating through a Unix domain socket whose name is specified to the client by the SSH_AUTH_SOCK
environment variable (set by the agent upon its startup).
Thus, to prevent a single invocation of the client from querying the agent this variable can be set explicitly to something invalid, like an empty string;
$ SSH_AUTH_SOCK= ssh user@server
A client invocation like this will fail communicating with the agent and only be able to offer the identities available as files in ~/.ssh/
, or any specified on the command line using -i
, to the server.
debug1: pubkey_prepare: ssh_get_authentication_socket: Connection refused
cwd
Updated on September 18, 2022Comments
-
cwd over 1 year
I have been putting my ssh identity files inside my
~/.ssh/
folder. I have probably about 30 files in there.When I connect to servers, I will specify the identity file to use with something like
ssh -i ~/.ssh/client1-identity [email protected]
However, if I do not specify an identity file, and just use something like this:
ssh [email protected]
I get the error
Too many authentication failures for user123
I understand that is because if no identity file is specified, and ssh can find identity files, then it will try all of them.
I also understand that I can edit the
~/.ssh/config
file and specify something like:Host example.com PreferredAuthentications keyboard-interactive,password
in order to prevent that connection from trying known identity files.
So, I guess I could move my identity files outside of the
~/.ssh/
directory, or I could specify each host that I want to disable identity-file authentication for in the config file, but is there any way to tell SSH by default not to search for identity files? Or to specify the ones it will search for?-
Admin about 13 yearsRe "I understand that is because..." - use
ssh -v
to find out for sure.
-
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chrishiestand almost 12 yearsThe question asked about how to limit which public keys are used. This answer disables public key authentication entirely.
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CodeGrue over 10 yearsnicely explained, thank you. It's not obvious that that parameter 'IdentitiesOnly' means TakeOnlyWhatIExplicitlySpecifyThenFailoverToPassword. And apparently, the ./ssh/id_rsa key is still listed.
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Admin almost 10 yearsAn example would be nice
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jamix about 9 yearsPutting
IdentitiesOnly yes
in the global section of ssh_config is what did it for me. Thanks! -
Ryder over 8 yearsThank you for the detailed comment. I used to use ('\' for newline)
Host * \ IdentityFile ~/.ssh/mykey
as a configuration option, and at first it seemed odd that having a different entry for a specific site, e.g.Host special \ IdentityFile ~/.ssh/specialkey \ IdentitiesOnly yes
continued to supplymykey
instead ofspecialkey
. It certainly was unclear, until I realized (from your answer) that the IdentityFile entries are stacked in an order of evaluation and the last-defined one will be used. RemovingIdentityFile ~/.ssh/mykey
solved the issue, and the correct, single key was used. -
leden over 7 yearsThanks, this is the only complete solution. Apparently,
-F /dev/null
is the missing piece in the other answers. -
Admin over 7 yearsIsn't it:
IdentitiesOnly yes
(without the "=")? -
Admin over 7 years@DimitriosMistriotis According to the ssh_config man page, either is acceptable:
Configuration options may be separated by whitespace or optional whitespace and exactly one '='; the latter format is useful to avoid the need to quote whitespace when specifying configuration options using the ssh, scp, and sftp -o option.
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vfclists over 6 yearsWill at accept keys added to keychain?
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Admin about 6 yearsBefore I tried this, I noticed my
git pull/push
commands were trying every single identity loaded in my agent. It wasn't a problem till at one point I had too many keys. -
rsuarez almost 5 yearsThis is a great answer. It's simple and works when you're using commands that use SSH "under the hood", like git. A pity I can't upvote it more.
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Admin over 4 years
IdentitiesOnly
may not always work, you may have to exclude a host specifically; see superuser.com/questions/859661/… -
user541686 almost 4 years+1 Set
IdentityAgent
tonone
if you need to set this in your config file. -
Admin almost 4 years**If your SSH agent is still prompting you for a password, see the answer below.
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Admin about 2 yearsThis is counterintuitive. the
identity_file
man page option should mention that it is possible that the supplied key will not be used at all.