Putty: Getting Server refused our key Error - ssh

Question

I created key pair using puttygen.exe (client is windows 8). On server (Ubuntu 12.04.3 LTS), I have put my public key in ~/.ssh/authorized_keys. The public key is this:
ssh-rsa AAAAB3NzaC1yc2EAAAABJQAAAQEAopfM6RHOgnuc4Aftn3t4k5UIAT3StCAbn/vg/IMbphbXadshC+79sIlRq3P4zGzMjFTP4hKnzu6ehLV5lmj/qorq3SKT+bPO5Qrac3VbIlrGvuBFDDjP82I2Hwg3HzlsFTstqk++KToapaTYZ7jENEYyPl2wnzITJnt//+4U1o6juoXTKgdNE02hHnRZyHOV/bnkZyJJCEwJv5U0eXSThQnhmXtUxGT8U0HQNFiXfqIIVllhWiCnyrhhIaKz/CIJNAd2VmzyJzQtJtTQX8aWSNVrZju6Sv2/RncTNvsACdNgjjh/FH8PQXaep00jlJ3MOdsC8vz6VSPFbh6iKy1oLQ== rsa-key-20131231
So it's correct (one line, no comments, starts with ssh-rsa, etc.)
.ssh dir permission level is 700, authorized_keys file permission is 600. Both directory and file owned by the actual user that I try to log in.
When I try connecting I'm getting 'server refused our key' and server asks for password. That's all. Nothing is logged to /var/log/auth.log when attempting to log in with the key.
I've looked everywhere and all articles and tips mention setting chmod 600 and 700 for the file/directory and formatting the key correctly. I've done all this still getting 'refused our key' error and I'm out of ideas.

Answer 1

OK, there was a small typo in my key. Apparently when pasting to file the first letter was cut off and it started with sh-rsa instead of ssh-rsa.
nrathathaus - your answer was very helpful, thanks a lot, this answer is credited to you :) I did like you said and set this in sshd_conf:
LogLevel DEBUG3
By looking at the logs I realized that sshd reads the key correctly but rejects it because of the incorrect identifier.

Answer 2

Adding a few thoughts as other answers helped, but were not exact fit.
First of all, as mentioned in accepted answer, edit
/etc/ssh/sshd_config
and set log level:
LogLevel DEBUG3
Then restart sshd on the server to have it use the changed log level, e.g.:
sudo service ssh restart
Then try to authenticate, and when it fails, look for log file:
/var/log/secure
It will have errors you are looking for.

Answer 3

In my case I had to change the permissions of /home/user from 0755 to 0700 as well.

Answer 4

In my case, is a permission problem.
I changed the log level to DEBUG3, and in /var/log/secure I see this line:
Authentication refused: bad ownership or modes for directory
Googled and I found this post:
https://www.daveperrett.com/articles/2010/09/14/ssh-authentication-refused/
chmod g-w /home/$USER
chmod 700 /home/$USER/.ssh
chmod 600 /home/$USER/.ssh/authorized_keys
Basically, it tells me to:
get rid of group w permission of your user home dir
change permission to 700 of the .ssh dir
change permission to 600 of the authorized_keys file.
And that works.
Another thing is that even I enabled root login, I cannot get root to work. Better use another user.

Answer 5

Running Windows 8.1 I ran into the server refused our key problem.
Following the guide: https://winscp.net/eng/docs/guide_windows_openssh_server
It was easy to make a connection using the Windows login username and password. However, authenticating with the username in combination with a private key, the response was server refused our key.
Getting it to work with a public key came down to the permissions on the file:
C:\ProgramData\ssh\administrators_authorized_keys
This is a helpful page: https://github.com/PowerShell/Win32-OpenSSH/wiki/Troubleshooting-Steps
Stop the two OpenSSH services, then open a command prompt with admin permissions. Then run:
C:\OpenSSH-Win32>c:\OpenSSH-Win32\sshd.exe -ddd
Note: specify the full path to the exe otherwise sshd complains.
This creates a one-time use connection listener. The -ddd is verbose level 3.
After making a connection, scanning the logs revealed:
debug1: trying public key file __PROGRAMDATA__/ssh/administrators_authorized_keys
debug3: Failed to open file:C:/ProgramData/ssh/administrators_authorized_keys error:2
debug1: Could not open authorized keys '__PROGRAMDATA__/ssh/administrators_authorized_keys':
No such file or directory
Had to create the file: C:\ProgramData\ssh\administrators_authorized_keys
And copy the public key text into it, e.g: ssh-rsa AAAA................MmpfXUCj rsa-key-20190505
And then save the file. I saved the file as UTF-8 with the BOM. Didn't test ANSI.
Then running the one-time command line again, in the logs showed:
debug1: trying public key file __PROGRAMDATA__/ssh/administrators_authorized_keys
debug3: Bad permissions. Try removing permissions for user: S-1-5-11 on file C:/ProgramData/ssh/administrators_authorized_keys.
Authentication refused.
S-1-5-11 is the name given to the System.
To fix the Bad permissions, right click on the administrators_authorized_keys file, goto the Security Tab , click the Advanced button and remove inherited permissions.
Then delete all Group or user names: except for the Windows login username, e.g: YourMachineName\username
The permissions for that username should be Read Allow, Write Deny everything else is unchecked. The owner of the file should also be YourMachineName\username
This fixed the problem.
Other Useful links:
Download OpenSSH-Win32.zip from: https://github.com/PowerShell/Win32-OpenSSH/releases
C# example of how to use the WinSCPnet.dll to make a connection to the OpenSSH server: https://winscp.net/eng/docs/library#csharp
Here is the code snippet to make a connection using the WinSCPnet.dll:
static void WinSCPTest() {
SessionOptions ops = new SessionOptions {
Protocol = Protocol.Sftp,
PortNumber = 22,
HostName = "192.168.1.188",
UserName = "user123",
//Password = "Password1",
SshHostKeyFingerprint = #"ssh-rsa 2048 qu0f........................ddowUUXA="
};
ops.SshPrivateKeyPath = #"C:\temp\rsa-key-20190505.ppk";
using (Session session = new Session()) {
session.Open(ops);
MessageBox.Show("success");
}
}
Replace SshHostKeyFingerprint and SshPrivateKeyPath with your own values.
Edit: added screenshot of administrators_authorized_keys file permissions:
When OpenSSH SSH Server is running as a Service, then only System should have permission. However, if running sshd.exe from the command prompt, then the current user should be the only one listed (read allow, write deny).

Answer 6

The simple solution i found was to move the authorized_keys file away from the hidden .ssh directory and put it in the system ssh directory:
/etc/ssh/keys/authorized_keys
As soon as I did this it worked with no problems.

Answer 7

having same issue in windows server 2008 r2 and explored a lot to solve, finally did that by following:
open C:\Program Files (x86)\OpenSSH\etc\sshd_config with textpad or any other text editor
remove comment from following lines, after removing they should look like following:
RSAAuthentication yes
PubkeyAuthentication yes
AuthorizedKeysFile .ssh/authorized_keys
save it and try to login with private key now.
have fun.

Answer 8

I'm adding this answer to help anyone, like me, who spent hours scouring the internet without success.
YOUR HOME FOLDER MIGHT BE ENCRYPTED.
Or for that matter any folder in which your "authorized_keys" file is nested. Man, that would have saved me a lot of time. To check, go perform
ls -A
on the directory whose encryption status you would like to determine. If the folder contains a folder named ".encryptfs" the answer is, yes, that folder is encrypted. This will impede your ability to access the "authorized_keys" file containing the public ssh key needed for verification.
To fix this, place the "authorized_key" file in a directory tree that contains no encryption.

Answer 9

After adding key, login as ec2-user if you are using an Amazon Linux machine
If its ubuntu machine then use ubuntu

Answer 10

Thanks to nrathaus and /var/log/auth.log investigation on debug level comes the following.
Another reason is that your home directory may have permissions different than 755.

Answer 11

In my case it was caused by (/etc/ssh/sshd_config):
PermitRootLogin no
Changed to yes, restarted the service and got in normally.

Answer 12

I have solved this problem,puttygen is a third-party software, ssh key which generated by it didn't be used directly, so you must make some changes.
For example, it look like this
---- BEGIN SSH2 PUBLIC KEY ----
Comment: "rsa-key-20170502"
AAAAB3NzaC1yc2EAAAABJQAAAQEAr4Ffd3LD1pa7KVSBDU+lq0M7vNvLp6TewkP7
*******C4eq1cdJACBPyjqUCoz00r+LqkGA6sIFGooeVuUXTOxbYULuNQ==
---- END SSH2 PUBLIC KEY ----
I omit some of the alphabets in the middle, replaced by *, if not, StackOverflow told me that the code format is wrong, do not let me post。
this is my ssh key generated by puttygen, you must change to this
ssh-rsa AAAAB3NzaC1yc2EAAAABJQAAAQEAr4Ffd3LD1pa7KVSBDU+lq0M7vNvLp6TewkP7wfvKGWWR7wxA8GEXJsM01FQw5hYWbNF0CDI7nCMXDUEDOzO1xKtNoaidlLA0qGl67bHaF5t+0mE+dZBGqK7jG9L8/KU/b66/tuZnqFqBjLkT+lS8MDo1okJOScuLSilk9oT5ZiqxsD24sdEcUE62S8Qwu7roVEAWU3hHNpnMK+1szlPBCVpbjcQTdiv1MjsOHJXY2PWx6DAIBii+/N+IdGzoFdhq+Yo/RGWdr1Zw/LSwqKDq1SmrpToW9uWVdAxeC4eq1cdJACBPyjqUCoz00r+LqkGA6sIFGooeVuUXTOxbYULuNQ== yourname#hostname
In my case, I have deleted some comments, such as
---- BEGIN SSH2 PUBLIC KEY ----
Comment: "rsa-key-20170502"
---- END SSH2 PUBLIC KEY ----
and add ssh-rsa at the beginning,
add yourname#hostname at the last.
note: not delete== in the last and you must change "yourname" and "hostname" for you, In my case, is uaskh#mycomputer,yourname is that you want to log in your vps .when all these things have done,you could to upload public-key to uaskh's home~/.ssh/authorized_keys by cat public-key >> ~/.ssh/authorized_keys then sudo chmod 700 ~/.ssh sudo chmod 600 ~/.ssh/authorized_keys then you must to modify /etc/ssh/sshd_config, RSAAuthentication yes PubkeyAuthentication yes AuthorizedKeysFile .ssh/authorized_keys my operating system is CentOS 7,This is my first time to anwser question,I will try my efforts to do ,Thank you!

Answer 13

I encountered this problem today and my issue was that when copying the public key from file, new line characters are included as well. You can use ":set list" in vim to see all the hidden new lines and make sure to delete all the new lines except for the last one. Also, my key was missing "ssh-rsa " in the beginning. Make sure you have that as well.

Answer 14

The equivilent of an SSH command:
ssh -i <path_to_pem_file> ec2-user#calendar.com
In Windows, first use PuTTYGen to convert the pem file to a ppk file.
Open PuTTYGen
File/Load the private pem key (or an OpenSSH key)
In the Open FileDialog, use the drop down to select "All files" (it only shows ppk file formats not pem, also OpenSSH key files that can be converted like pem files don't have a file extension)
File/Save private key (*.ppk)
The same settings in Putty as the SSH command:
Open Putty
Session/Hostname: calendar.com
Connection/Data/Auto-login username: ec2-user
Connection/SSH/Auth/PrivateKeyFile Path: the file path to the PPK file

Answer 15

OpenSSH disable the ssh-rsa signature scheme by default in the next
release.
In the SSH protocol, the "ssh-rsa" signature scheme uses the SHA-1
hash algorithm in conjunction with the RSA public key algorithm. It is
now possible1 to perform chosen-prefix attacks against the SHA-1
algorithm for less than USD$50K.
Source
So, update the key.

Answer 16

For those receiving this error from Windows Server, I received this same error and it was a user account issue. With many organizations, group policy for Administrators may not allow setting up SSH Server and connections. With that type of setup, this must be done from Local Admin account. Might be worth looking into if you have confirmed there are not any typos in the public key.

Answer 17

In my case, I had to disable SELinux on Centos6.6 to get it working :)
Edit /etc/selinux/config and set the following and then reboot the host.
selinux=disabled
BTW...forgot to mention that I had to set the LogLevel=DEBUG3 to identify the issue.

Answer 18

I had the same error on solaris but found in /var/adm/splunk-auth.log the following:
sshd: [auth.debug] debug1: PAM conv function returns PAM_SUCCESS
sshd: [auth.notice] Excessive (3) login failures for weblogic: locking account.
sshd: [auth.debug] ldap pam_sm_authenticate(sshd-kbdint weblogic), flags = 1
sshd: [auth.info] Keyboard-interactive (PAM) userauth failed[9] while authenticating: Authentication failed
In /etc/shadow the account was locked:
weblogic:*LK*UP:16447::::::3
Removed the "*LK*" part:
weblogic:UP:16447::::::3
and I could use ssh with authorized_keys as usual.

Answer 19

I have this issue where sshd only reads from authorized_keys2.
Copying or renaming the file fixed the problem for me.
cd ~/.ssh
sudo cat authorized_keys >> authorized_keys2
P.S. I'm using Putty from Windows and used PuTTyKeygen for key pair generation.

Answer 20

I was facing similar issue when trying to logon through Mobaxterm. The private key was generated through puttygen. Regenerating the key helped in my case.

Answer 21

As my experience, I suggest you should generate keys from putty, should not generate from linux side. Because the key will be old PEM format. Anyway, just my suggestion. I did as steps below and worked fine with me and with my team.
Generate a key pair with PuTTYGen.exe on your local (type: RSA, length: 2048 bits).
Save private/public key as "id_rsa.ppk/id_rsa.pub" files on your local.
Create "authorized_keys" file on your local, then enter the public key in "id_rsa.pub" to "authorized_keys".
Remember content has to begin with "ssh-rsa" and one line only.
Use WinScp (or putty command) to copy "authorized_keys & id_rsa.pub" from your local to your linux-user-home "/home/$USER/.ssh/".
Run these commands:
chmod 700 .ssh
chmod 600 .ssh/authorized_keys
chown $USER:$USER .ssh -R
Test your connect setting by load the private key "id_rsa.ppk" in the PuTTY.exe profile, then click open (put your passphrase if have).

Answer 22

check your key, this should be a rsa (id_rsa.pub) key today and no longer a dss (id_dsa.pub) key, use puttygen 0.70 and choose RSA on type of key to generate, replace the public key on host ~/.ssh/authorized_keys

Answer 23

Oh my God I spent days trying to fix this. So here is what worked for me. I went back to the root fold like this:
cd /root/
mkdir .ssh
cd .ssh
chmod 700 .ssh
nano -w authorized_keys
service ssh restart
So I used root to logging via Putty and it worked. so try to do the same with the user you want to use in putty.

Answer 24

In the case of mine it was a wrong user:group attribution. I solved setting the right user and group:
sudo chown [user]:[group] -R /home/[user]

Answer 25

This helps to me:
# /etc/ssh/sshd_config
PubkeyAuthentication yes
PubkeyAcceptedKeyTypes=+ssh-rsa
# temporarily added:
LogLevel DEBUG3
# gentoo
# tail -n 50 /var/log/messages
and restart sshd
/etc/init.d/sshd restart

Answer 26

If you run Putty in a version before 0.75, then updating Putty should solve the problem.
Newer version of openSSH (as in Ubuntu 22.04) have deprecated the use of the SHA1 hashing algorithm during the login, but Putty used SHA1 until version 0.74.
If sshd log file on the server shows
$ sudo grep 'sshd' /var/log/auth.log
sshd[113232]: userauth_pubkey: key type ssh-rsa not in PubkeyAcceptedAlgorithms [preauth]
then this in fact causing the error, and should be gone after Putty has been updated.

Answer 27

I'm using a PUTTYgen file with psftp, and I encountered this problem on my Windows Server when we were required to create new keys for a client. The private_key_name.ppk file and the open_ssh.txt file must be in the same directory for the connection to work.

Answer 28

In my case home on nfs was 777, needed to be 750. That fixed the issue.

Answer 29

When using Cpanel you can check if the key is authorized in
SSH Access >> Public keys >> Manage >> Authorize or Deauthorize.

Answer 30

if you get this error in /var/log/secure
error: key_read: key_from_blob AA
AAB3NzaC1yc2EAAAABJQAAAQEAoo3PFwX04NFG+rKz93l7em1BsUBzjHPMsswD
it means your key is having space, if you generated key through puttgen when you view .ppk file, it will look like this:
AAAAB3NzaC1yc2EAAAABJQAAAQEAoo3PFwX04NFG+rKz93l7em1BsUBzjHPMsswD
al74MLaJyhQD0pE23NS1izahbo1sJGnSJu2VJ//zxidSsba6xa6OvmeiKTwCz0E5
GMefdGVdpdbTlv99qjBl1+Nw1tDnHIC0+v9XmeZERQfCds9Kp1UivfReoYImntBC
gLtNyqRYrSu8csJCt7E1oY8QK6WP1vfYgAQ2taGyS9+g7FHyyf5VY2vH3oWzzbqz
xjsSLAv3zEQSm1LzSw9Pvc8iwasFyUMBOPj31CKQYTXyX8KpJTr0Zb7oqMauBE5L
VwxZhlcJHbj0FsMbF/+GRjvgexymCi3bHmwGQ6FEADNd0RkhdQ==
and when you try to paste it you will get an error in reading key, so try to edit key and make it one line and try it
this should look like something
ssh-rsa AAAAB3NzaC1yc2EAAAABJQAAAQEAoo3PFwX04NFG+rKz93l7em1BsUBzjHPMsswDal74MLaJyhQD0pE23NS1izahbo1sJGnSJu2VJ//zxidSsba6xa6OvmeiKTwCz0E5GMefdGVdpdbTlv99qjBl1+Nw1tDnHIC0+v9XmeZERQfCds9Kp1UivfReoYImntBCgLtNyqRYrSu8csJCt7E1oY8QK6WP1vfYgAQ2taGyS9+g7FHyyf5VY2vH3oWzzbqzxjsSLAv3zEQSm1LzSw9Pvc8iwasFyUMBOPj31CKQYTXyX8KpJTr0Zb7oqMauBE5LVwxZhlcJHbj0FsMbF/+GRjvgexymCi3bHmwGQ6FEADNd0RkhdQ== username#domainname