Bug 18205 - openssh fails to restart correctly denying access to remote machine
Summary: openssh fails to restart correctly denying access to remote machine
Status: CLOSED DUPLICATE of bug 18023
Alias: None
Product: Red Hat Linux
Classification: Retired
Component: openssh   
(Show other bugs)
Version: 7.0
Hardware: i386 Linux
Target Milestone: ---
Assignee: Nalin Dahyabhai
QA Contact:
Keywords: Security
Depends On:
TreeView+ depends on / blocked
Reported: 2000-10-03 11:33 UTC by Andy Nash
Modified: 2008-05-01 15:37 UTC (History)
1 user (show)

Fixed In Version:
Doc Type: Bug Fix
Doc Text:
Story Points: ---
Clone Of:
Last Closed: 2000-10-03 17:32:58 UTC
Type: ---
Regression: ---
Mount Type: ---
Documentation: ---
Verified Versions:
Category: ---
oVirt Team: ---
RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: ---

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Description Andy Nash 2000-10-03 11:33:59 UTC
i have installed 7.0 clean with a custom server installation, including 
openssh. everything functions correctly except:

when restarting sshd like this:

/etc/rc.d/init.d/sshd restart (or condrestart, or stop start)

the existing ssh session remains alive, but no new sessions can be 
started. in addition, restarting a second time causes the existing session 
to also be dropped.

this has the following effect:

no access can be gained to the server until sshd is restarted from the 
console (assuming telnet is blocked)

i have no idea whether it is possible, but could someone use this to cause 
sshd to restart - denying access to the sysadm - in order to hide their 
activities or as a DOS attack?

below is the /etc/ssh/sshd_config file:

# This is ssh server systemwide configuration file.

Port 22
Protocol 2,1
#ListenAddress ::
HostKey /etc/ssh/ssh_host_key
ServerKeyBits 768
LoginGraceTime 600
KeyRegenerationInterval 3600
PermitRootLogin no
# Don't read ~/.rhosts and ~/.shosts files
IgnoreRhosts yes
# Uncomment if you don't trust ~/.ssh/known_hosts for 
#IgnoreUserKnownHosts yes
StrictModes yes
X11Forwarding no
X11DisplayOffset 10
PrintMotd yes
KeepAlive yes

# Logging
SyslogFacility AUTH
LogLevel INFO
#obsoletes QuietMode and FascistLogging

RhostsAuthentication no
# For this to work you will also need host keys in /etc/ssh_known_hosts
RhostsRSAAuthentication no
RSAAuthentication yes

# To disable tunneled clear text passwords, change to no here!
PasswordAuthentication no
PermitEmptyPasswords no
# Uncomment to disable s/key passwords
#SkeyAuthentication no

# To change Kerberos options
#KerberosAuthentication no
#KerberosOrLocalPasswd yes
#AFSTokenPassing no
#KerberosTicketCleanup no

# Kerberos TGT Passing does only work with the AFS kaserver
#KerberosTgtPassing yes

CheckMail no
UseLogin no

Subsystem       sftp    /usr/local/sbin/sftpd

Comment 1 Andy Nash 2000-10-03 17:43:08 UTC
ooops! i have now found an earlier bug report which pertains to the same 
problem - 18023 - updated init scripts have apparently been prepared, and will 
be included in a future bugfix release.

you're too fast for me!

Andy Nash

*** This bug has been marked as a duplicate of 18023 ***

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