SSHD Gives error could not open Authorized Keys, although permissions seem correct

问题

I'm unable to login to SSH because of the following error in /var/log/secure (according to the debug logs):

Dec 19 18:01:05 hostname sshd[25119]: debug1: trying public key file /root/.ssh/authorized_keys
Dec 19 18:01:05 hostname sshd[25119]: debug1: Could not open authorized keys '/root/.ssh/authorized_keys': Permission denied

I have the following permissions set on root

chmod 700 ~/.ssh
chmod 600 ~/.ssh/authorized_keys
chmod go-wrx ~

ls -lah gives the following output for those directories:

drwx------.   6 root root 4.0K Dec 19 17:46 root
drwx------.  2 root root 4.0K Dec 19 17:41 .ssh
-rw-------. 1 root root  416 Dec 19 17:12 authorized_keys

I know the key I'm using is correct, as I just setup another server with it without any problems.

I'm running: CentOS release 6.4 (Final)

I've added my sshd config in case there's something misconfigured in there that might be causing the issue:

#       $OpenBSD: sshd_config,v 1.80 2008/07/02 02:24:18 djm Exp $

# This is the sshd server system-wide configuration file.  See
# sshd_config(5) for more information.

# This sshd was compiled with PATH=/usr/local/bin:/bin:/usr/bin

# The strategy used for options in the default sshd_config shipped with
# OpenSSH is to specify options with their default value where
# possible, but leave them commented.  Uncommented options change a
# default value.

#Port 22
#AddressFamily any
#ListenAddress 0.0.0.0
#ListenAddress ::

# Disable legacy (protocol version 1) support in the server for new
# installations. In future the default will change to require explicit
# activation of protocol 1
Protocol 2

# HostKey for protocol version 1
#HostKey /etc/ssh/ssh_host_key
# HostKeys for protocol version 2
#HostKey /etc/ssh/ssh_host_rsa_key
#HostKey /etc/ssh/ssh_host_dsa_key

# Lifetime and size of ephemeral version 1 server key
#KeyRegenerationInterval 1h
#ServerKeyBits 1024

# Logging
# obsoletes QuietMode and FascistLogging
#SyslogFacility AUTH
SyslogFacility AUTHPRIV
LogLevel DEBUG

# Authentication:

#LoginGraceTime 2m
PermitRootLogin yes
StrictModes no
#MaxAuthTries 6
#MaxSessions 10

RSAAuthentication yes
PubkeyAuthentication yes
AuthorizedKeysFile      .ssh/authorized_keys
#AuthorizedKeysCommand none
#AuthorizedKeysCommandRunAs nobody

# For this to work you will also need host keys in /etc/ssh/ssh_known_hosts
#RhostsRSAAuthentication no
# similar for protocol version 2
#HostbasedAuthentication no
# Change to yes if you don't trust ~/.ssh/known_hosts for
# RhostsRSAAuthentication and HostbasedAuthentication
#IgnoreUserKnownHosts no
# Don't read the user's ~/.rhosts and ~/.shosts files
IgnoreRhosts yes

# To disable tunneled clear text passwords, change to no here!
#PasswordAuthentication yes
#PermitEmptyPasswords no
PasswordAuthentication yes

# Change to no to disable s/key passwords
#ChallengeResponseAuthentication yes
ChallengeResponseAuthentication no

# Kerberos options
#KerberosAuthentication no
#KerberosOrLocalPasswd yes
#KerberosTicketCleanup yes
#KerberosGetAFSToken no
#KerberosUseKuserok yes

# GSSAPI options
#GSSAPIAuthentication no
GSSAPIAuthentication yes
#GSSAPICleanupCredentials yes
GSSAPICleanupCredentials yes
#GSSAPIStrictAcceptorCheck yes
#GSSAPIKeyExchange no

# Set this to 'yes' to enable PAM authentication, account processing,
# and session processing. If this is enabled, PAM authentication will
# be allowed through the ChallengeResponseAuthentication and
# PasswordAuthentication.  Depending on your PAM configuration,
# PAM authentication via ChallengeResponseAuthentication may bypass
# the setting of "PermitRootLogin without-password".
# If you just want the PAM account and session checks to run without
# PAM authentication, then enable this but set PasswordAuthentication
# and ChallengeResponseAuthentication to 'no'.
#UsePAM no
UsePAM yes

# Accept locale-related environment variables
AcceptEnv LANG LC_CTYPE LC_NUMERIC LC_TIME LC_COLLATE LC_MONETARY LC_MESSAGES
AcceptEnv LC_PAPER LC_NAME LC_ADDRESS LC_TELEPHONE LC_MEASUREMENT
AcceptEnv LC_IDENTIFICATION LC_ALL LANGUAGE
AcceptEnv XMODIFIERS

#AllowAgentForwarding yes
#AllowTcpForwarding yes
#GatewayPorts no
#X11Forwarding no
X11Forwarding yes
#X11DisplayOffset 10
#X11UseLocalhost yes
#PrintMotd yes
#PrintLastLog yes
#TCPKeepAlive yes
#UseLogin no
#UsePrivilegeSeparation yes
#PermitUserEnvironment no
#Compression delayed
#ClientAliveInterval 0
#ClientAliveCountMax 3
#ShowPatchLevel no
UseDNS no
#PidFile /var/run/sshd.pid
#MaxStartups 10:30:100
#PermitTunnel no
#ChrootDirectory none

# no default banner path
#Banner none

# override default of no subsystems
Subsystem       sftp    /usr/libexec/openssh/sftp-server

# Example of overriding settings on a per-user basis
#Match User anoncvs
#       X11Forwarding no
#       AllowTcpForwarding no
#       ForceCommand cvs server

Any ideas would be much appreciated.

回答1:

If the permissions are correct, SELinux might still be preventing sshd from opening the file.

Try fixing the labels inside the .ssh directory (and maybe $HOME):

restorecon -FRvv ~/.ssh

(I'm intentionally not suggesting disabling SELinux or setting it to the permissive mode.)

回答2:

I was struggling to use key authentication as well.

Could not open authorized keys '/home/myUserName/.ssh/authorized_keys2': Permission denied

Had checked all the above things when I ended up here (first link on google). I realize that this is an old post but I will add it here in case somebody else has the same problem as me and end up here.

I had owner of the authorized_keys file to "root", so changing it with:

chown myUserName authorized_keys2

Solved it for me.

回答3:

In case if SELinux enabled:

$ getenforce
Enforcing

to temporary enable pub-key ssl login to non-standard user home directory location run:

$ sudo chcon -t ssh_home_t /srv/jenkins/.ssh/authorized_keys /srv/jenkins/.ssh

$ ls -ldZ /srv/jenkins/.ssh/authorized_keys /srv/jenkins/.ssh/
drwxr-xr-x. jenkins jenkins system_u:object_r:ssh_home_t:s0  /srv/jenkins/.ssh/
-rw-r--r--. jenkins jenkins system_u:object_r:ssh_home_t:s0  /srv/jenkins/.ssh/authorized_keys

See https://linux.die.net/man/8/ssh_selinux for the details.

To make SELinux settings permanent run:

$ sudo semanage fcontext -a -t ssh_home_t /srv/jenkins/.ssh/authorized_keys
$ sudo semanage fcontext -a -t ssh_home_t /srv/jenkins/.ssh
$ sudo restorecon -R -v /srv/jenkins/.ssh/

You hit this if you are on modern RHEL, Oracle Linux, CentOS.

回答4:

Check the /home directory permissions. It should be

drwxr-xr-x. 9 root root 113 Jun 28 22:57 home

and then your home directory detail:

drwxr----- 5 user group 124 May 18 17:00 User drwx------ 2 user group 29 May 18 12:05 .ssh -rw------- 1 user group 2235 Jun 28 23:09 authorized_keys

My error messages in logs

/var/log/secure > sshd[22565]: error: Received disconnect from X.X.X.X: 14: No supported authentication methods available [preauth]

On client side

ssh user@X.X.X.X Permission denied (publickey). ssh -vvv user@X.X.X.X ... debug2: we did not send a packet, disable method debug1: No more authentication methods to try. Permission denied (publickey).
On server side

service sshd stop
run sshd debug mode:
/usr/sbin/sshd -ddd

... debug1: trying public key file /home/USER/.ssh/authorized_keys debug1: Could not open authorized keys '/home/USER/.ssh/authorized_keys': Permission denied ...

回答5:

A couple ideas to check:

Can you cat authorized_keys? What does the file look like?
Is your sshd configured to allow root login? This is generally frowned upon,
Are you doing it as root or as a sudoer?

回答6:

Don't do chmod on ~/.ssh/.... Try to write the exact path: /root/.ssh/..., since sometimes (when using su etc), the ~ can be setup incorrectly. Check and post the permissions again for the full path without using ~ in the command.
Once you are absolutely sure the permissions are OK, check if your sshd is actually running under user root: ps -A u | grep sshd.

回答7:

A couple of things to double-check:

Are you sure you copied the PUBLIC key to the authorized_keys, not the private key? :-)
Do cat -tv authorized_keys. Any ^M characters at the end of each line? Do a dos2unix on authorized_keys
Did you restart the ssh daemon after making configuration changes?

回答8:

I encountered this same issue and got it solved by changing both .ssh and authorized_keys's owner at the same time: chown MyUsername:Myusername .ssh chown MyUsername:Myusername .ssh/authorized_keys

Thanks to @niclaslindgren.

And BTW, it's no matter with whether there is ^M in authorized_keys or not, I had tested and proved it, it works with both the ways

回答9:

I'm going to throw my answer in here as well since I just wasted the last hour trying to figure out a workaround for another hour I wasted previously on Azure.

This does not work:

AuthorizedKeyFiles ~/.ssh/authorized_keys

Generating server-side logs using an alternate port (i.e. /usr/sbin/sshd -ddd -p 12345) reveals the following when using the above configuration:

debug1: trying public key file /root/.ssh/authorized_keys
debug1: Could not open authorized keys '/root/.ssh/authorized_keys': Permission denied

Either of these are correct, however:

AuthorizedKeyFiles /home/%u/.ssh/authorized_keys

AuthorizedKeyFiles .ssh/authorized_keys

See also: https://www.ssh.com/ssh/authorized_keys/openssh

来源：https://stackoverflow.com/questions/20688844/sshd-gives-error-could-not-open-authorized-keys-although-permissions-seem-corre

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ssh

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