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Disable ssh password authentication, when the current user is logged in via ssh using public key authentication

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This commit is contained in:
Michael Kroes 2016-03-28 07:28:12 +02:00
parent df92a10eba
commit 75d2831fd8
1 changed files with 36 additions and 0 deletions
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36
setup/system.sh
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@ -4,6 +4,42 @@ source setup/functions.sh # load our functions
# Basic System Configuration
# -------------------------
# ### Disable password login via SSH
# We will disable password based login via ssh only if the user that logged in:
#
# - Is using an ssh connection
# - Used a public key to authenticate
# - The user still has that key in authorized_keys
#
# The /var/log/auth.log will contain entries for logins that used public
# key authentication. We will try to find an entry for the user. If we
# find a record matching the user and the current ip address we will lookup
# the key finger print in the authorized keys of the user
#
# Sudo makes the use of $SSH_CLIENT client impossible, so we have to use pinky
USERNAME_THAT_WAS_USED_TO_LOG_IN=$(logname)
IP_ADDRESS_OF_USER=$(pinky -w $USERNAME_THAT_WAS_USED_TO_LOG_IN | tail -n+2 | tail -n1 | awk '{print $(NF)}')
if [ ! -z "$IP_ADDRESS_OF_USER" ]; then
HOMEDIRECTORY_OF_USER=$(grep "$USERNAME_THAT_WAS_USED_TO_LOG_IN" /etc/passwd | cut -d":" -f6)
LOG_ENTRY_TO_SEARCH_FOR="ssh.* Accepted publickey for $USERNAME_THAT_WAS_USED_TO_LOG_IN from $IP_ADDRESS_OF_USER"
SSH_PUB_KEY_USED_TO_LOG_IN=$(grep "$LOG_ENTRY_TO_SEARCH_FOR" /var/log/auth.log* | tail -n 1 | awk '{print $(NF)}')
if [ ! -z "$SSH_PUB_KEY_USED_TO_LOG_IN" ]; then
if [ -e "$HOMEDIRECTORY_OF_USER"/.ssh/authorized_keys ]; then
if ssh-keygen -l -f "$HOMEDIRECTORY_OF_USER"/.ssh/authorized_keys | grep -q -i "$SSH_PUB_KEY_USED_TO_LOG_IN"; then
# Public key used to log in is still in authorized_keys so we can safely disable
# password based logins
echo "Disabling password authentication for ssh"
tools/editconf.py /etc/ssh/sshd_config -s \
PasswordAuthentication=yes
restart_service ssh
fi
fi
fi
fi
# ### Add swap space to the system
# If the physical memory of the system is below 2GB it is wise to create a