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I am having wierd issue with openSSH connecting to remote server. I can connect it with userID and password, but when I use the public key authentication, it shows the following lines in the putty.log and quits.

=~=~=~=~=~=~=~=~=~=~=~= PuTTY log 2011.06.02 13:44:04 =~=~=~=~=~=~=~=~=~=~=~=
Using username "******".

Authenticating with public key "comment-----"
Last login: Wed Jun  1 17:27:13 2011 from ****.com

ANd then the putty quits.

I went thru different posts, where they talk about shell cmd and other stuffs and I am lost now.

Both the machines are running in windows with openssh. Can anybody guide me from where to start now.

ANy help is appreciated.

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Enabling debugging in your putty might be a place to start. If you are able to connect from that same machine using a password without the key enabled I would suspect something in your authorized_keys file on the destination machine, so you might want to look there. – Neil Neely Jun 2 '11 at 19:37
You mention you are running OpenSSH on Windows. How exactly are you doing that. Via Cygwin, CopSSH, or something else? If you have a full Cygwin on the server, can you use ssh on the server to make a connection to the localhost? Have you considered at least temporarily installing Cygwin on a client, and using that to attempt to connect? – Zoredache Jun 2 '11 at 23:50
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4 Answers

up vote 2 down vote

Puttygen generates an SSH2 aka Tectia or ssh.com public key when you use the 'Save public key' button, not a OpenSSH key. Different servers need a different type of key.

In puttygen load your private key file, and copy the line that looks like this ssh-rsa AAAAB3... from the dialog box labeled 'Public key for pasting into OpenSSH authorized_keys file'.

Puttygen public key

OpenSSH Public key

ssh-rsa AAAB3NzaC1yc2EAAAABJQAAAIBQ2Si6NjLR40YTI+9Z/TTBSYUykO1RjAX3GA2Zs15v7wiBVz3JoeLXFAmXRApdWCHCsmZIAjiX+qC0Ks1MY4suphDQv1ZfJE1xmhRwqr7h4f+/i0QmGI05lr/yJqwSashUIF4YWqgC14ov57VtaiCp//GTU29exME/JX3FzzxVmw== rsa-key-20110602

ssh.com Public key

---- BEGIN SSH2 PUBLIC KEY ----
Comment: "rsa-key-20110602"
AAAAB3NzaC1yc2EAAAABJQAAAIBQ2Si6NjLR40YTI+9Z/TTBSYUykO1RjAX3GA2Z
s15v7wiBVz3JoeLXFAmXRApdWCHCsmZIAjiX+qC0Ks1MY4suphDQv1ZfJE1xmhRw
qr7h4f+/i0QmGI05lr/yJqwSashUIF4YWqgC14ov57VtaiCp//GTU29exME/JX3F
zzxVmw==
---- END SSH2 PUBLIC KEY ----
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yes it looks the same ....it starts with ssh-rsa AAA- - - - - -...thanks – user54898 Jun 2 '11 at 21:34
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up vote 1 down vote

I think your public and/or private key may be corrupt.

Are you saying the server uses Windows too? In that case I don't know where to look for the keys, but usually they're called id_rsa and id_rsa.pub. What is in id_rsa.pub? And what is in the file authorized_keys?

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@Eduardo Ivanec public/private were generated by puttygen and public key was pasted on the authorized_keys in the server and private file with .pkk extension was supplied from putty. If there was sth wrong with keys then, wouldnt it be saying , key invalid or refused..... – user54898 Jun 2 '11 at 19:50
@user54898, puttygen generates a public key in a format that isn't appropriate for OpenSSH if you click the button. – Zoredache Jun 2 '11 at 20:52
i mean i copy pasted to authorized_keys file. it was in correct format. – user54898 Jun 2 '11 at 21:21
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up vote 0 down vote

Check the authorized_keys file on the server - the server may be forcing a command based on the key you're using to authenticate, which could explain the different behaviour when logging in with a public key instead of a password.

To check this look for a command= string somewhere in the file.

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I did a search but I could not find anything..... – user54898 Jun 2 '11 at 19:51
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up vote 0 down vote

Another possibility is the permissions on the authorized_keys file itself. As you are on windows, I am unfamiliar with that side, but in the *nix world, if the ssh daemon sees that your authorized_keys file is world readable it will refuse to honor it.

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Can you tell me how to see the log files in windows except putty.log(Which doesnot give enough info), – user54898 Jun 2 '11 at 22:28
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