▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄ ██ ██ █▌ - DISABLING BASH_HISTORY AND/OR LOGGING ALL USER'S CMDS - █▌ █▌ █▌ █ ▐▌ █ Once you have logged out of your shell by default bash will store the last ▐▌ █ 500 previous cmds (commands), and/or 500 lines, you executed to your ▐▌ █ .bash_history file for easy recall on future sessions (Ctrl+R or ! or !!). ▐▌ █ Even passwords that were entered as plain text, such as: ▐▌ █ mysqladmin -u root password 'new-password' ▐▌ █ If you take a look at hack logs, many have "cat .bash_history". HERE is a ▐▌ █ an infamous example, search for: cat .bash_history ▐▌ █ ▐▌ █ I've listed a number of different methods to disable it, limit it, or stop ▐▌ █ users from altering their own .bash_history for auditing needs. Depending ▐▌ █ on your own needs select a method/s. ▐▌ █ ▐▌ █ QUICK METHOD: ▐▌ █ TO VIEW YOUR .BASH_HISTORY: ▐▌ █ SOME COMMON BASH VARIABLES: ▐▌ █ VARIABLE NOTES: ▐▌ █ DISABLE .BASH_HISTORY - INCLUDING CURRENT SESSION'S KEYSTROKES: ▐▌ █ DISABLE .BASH_HISTORY - WHILE RETAINING CURRENT SESSION'S KEYSTROKE: ▐▌ █ TEMPORARILY DISABLE YOUR .BASH_HISTORY: ▐▌ █ LIMIT (not disable) .BASH_HISTORY FOR ALL USERS: ▐▌ █ PREVENT USERS MODIFYING THEIR .BASH_HISTORY: ▐▌ █ ▐▌ █ QUICK METHOD: ▐▌ █ ````````````` ▐▌ █ Quick method to completely disable your own .bash_history, without reading ▐▌ █ any further: ▐▌ █ Remove the file: ▐▌ █ rm ~/.bash_history -rf ▐▌ █ Clear your current history stored in RAM: ▐▌ █ history -c ▐▌ █ Change your settings: ▐▌ █ export HISTFILESIZE=0 ▐▌ █ export HISTSIZE=0 ▐▌ █ unset HISTFILE ▐▌ █ Logout, login, done. ▐▌ █ ▐▌ █ Or even faster method to send .bash_history to a black hole: ▐▌ █ rm ~/.bash_history ▐▌ █ ln /dev/null ~/.bash_history -sf ▐▌ █ Logout, login, done. ▐▌ █ ▐▌ █ TO VIEW YOUR .BASH_HISTORY: ▐▌ █ ``````````````````````````` ▐▌ █ history ▐▌ █ or ▐▌ █ ls -al .bash_history ▐▌ █ cat ~/.bash_history ▐▌ █ The number of cmds that history will show (cmd number on left column) ▐▌ █ might be larger than the default 500 as it includes your current session's ▐▌ █ cmds and what is in .bash_history. ▐▌ █ To view your top 10 bash cmds in your present history: ▐▌ █ history | awk '{print $2}' | awk 'BEGIN {FS="|"}{print $1}' | sort | uniq -c | sort -n | tail | sort -nr █ You can re-execute any cmd on the list by entering the item number ▐▌ █ preceded with ! ▐▌ █ For example if on the list is the cmd above as 502, to re-execute it: ▐▌ █ !502 ▐▌ █ Or to re-execute the previous cmd: ▐▌ █ !! ▐▌ █ ▐▌ █ SOME COMMON BASH VARIABLES: ▐▌ █ ``````````````````````````` ▐▌ █ Can skip this section; not needed to read/do: ▐▌ █ Here is a list of some of the variables, with a brief description. Don't ▐▌ █ worry if these don't make sense now, you'll see how to use them below. ▐▌ █ Bash man page is HERE or in your shell prompt: man bash ▐▌ █ ▐▌ █ HISTFILE ▐▌ █ Set the name/path of bash history. Default is ~/.bash_history. If ▐▌ █ 'unset' bash history is not saved after exiting. ▐▌ █ HISTFILESIZE ▐▌ █ Set the maximum number of lines to be saved in .bash_history ▐▌ █ HISTSIZE ▐▌ █ Set the number of commands to remember/store in .bash_history ▐▌ █ HISTTIMEFORMAT ▐▌ █ Time stamp the commands. Example: export HISTTIMEFORMAT='%Y-%m-%d %H:%M' ▐▌ █ HISTCONTROL ▐▌ █ Here you can have a colon separated list of 'values' controlling what is ▐▌ █ stored in .bash_history. Here are a few of them: ▐▌ █ ignorespace - cmds that begin with a space will not be saved. ▐▌ █ ignoredups - cmds matching previous entries will not be saved. ▐▌ █ ignoreboth - ignoredups and ignorespace combined. ▐▌ █ erasedups - erases previous duplicate cmds in history before the new cmd ▐▌ █ is saved. I prefer using this line over ignoredups with HISTTIMEFORMAT ▐▌ █ as the latest occurance of the cmd is saved. ▐▌ █ Here is an example using the above: ▐▌ █ export HISTCONTROL=ignorespace:erasedups ▐▌ █ HISTIGNORE ▐▌ █ Here you can have a colon separated list of 'patterns' controlling what ▐▌ █ is stored in .bash_history. ▐▌ █ "[ ]*" - cmds that begin with a space will not be saved. ▐▌ █ "&" - cmds matching previous entries will not be saved. ▐▌ █ Here is an example that will ignore duplicate cmds, cmds that begin with ▐▌ █ a space, and the exit cmd: ▐▌ █ export HISTIGNORE='&:[ ]*:exit' ▐▌ █ PROMPT_COMMAND ▐▌ █ To execute a set command prior to each of your primary commands. For ▐▌ █ example if open multiple shell sessions and do not want each one ▐▌ █ overwriting your .bash_history on exit you could do this: ▐▌ █ export PROMPT_COMMAND=history -a; history -n ▐▌ █ Or to save, append and reload history after each cmd executes: ▐▌ █ export PROMPT_COMMAND='history -a; history -r; $PROMPT_COMMAND' ▐▌ █ shopt -s histappend ▐▌ █ TMOUT ▐▌ █ The number of seconds until the shell session automatically terminates ▐▌ █ if it doesn't receive input. A 0 value means the shell will not ▐▌ █ automatically terminate. ▐▌ █ ▐▌ █ VARIABLE NOTES: ▐▌ █ ``````````````` ▐▌ █ 1) To activate the changes to a user's variables, the user will need to ▐▌ █ logout then back in (or open a new session or run the altered file). ▐▌ █ ▐▌ █ 2) To list your own environment variables: ▐▌ █ env ▐▌ █ ▐▌ █ If for example you have previously entered the cmd: ▐▌ █ export HISTCONTROL=ignorespace ▐▌ █ You'll see 'HISTCONTROL=ignorespace' in the output of env. ▐▌ █ ▐▌ █ To view a specific variable, precede that variable with: echo $ ▐▌ █ If there is no reply, it hasn't been manually set, and is at the default. ▐▌ █ For example: ▐▌ █ echo $HISTFILESIZE ▐▌ █ echo $HISTSIZE ▐▌ █ echo $TMOUT ▐▌ █ ▐▌ █ 3) To remove a variable that you have set use 'unset'. ▐▌ █ For example if you have done: ▐▌ █ export HISTSIZE=500 ▐▌ █ then remove that with: ▐▌ █ unset HISTSIZE ▐▌ █ ▐▌ █ 4) Keep in mind that if you change a user's bash environment variable, ▐▌ █ they can change it back if the correct permissions are not set. I'll go ▐▌ █ over that in the section 'PREVENT USERS MODIFYING THEIR .BASH_HISTORY'. ▐▌ █ ▐▌ █ 5) You might need to replace the double quotes " with single quotes ' in ▐▌ █ the variables below if you receive an error. ▐▌ █ ▐▌ █ ▐▌ █ DISABLE .BASH_HISTORY - INCLUDING CURRENT SESSION'S KEYSTROKES: ▐▌ █ ``````````````````````````````````````````````````````````````` ▐▌ █ With this method you will not be able to recall previous cmds (Ctrl+r). ▐▌ █ ▐▌ █ FOR YOURSELF: ▐▌ █ Clear your current history: ▐▌ █ history -c ▐▌ █ Remove the file: ▐▌ █ rm ~/.bash_history -rf ▐▌ █ Change your settings: ▐▌ █ export HISTFILESIZE=0 ▐▌ █ export HISTSIZE=0 ▐▌ █ unset HISTFILE ▐▌ █ ▐▌ █ (or you could add those settings to your ~/.bash_profile) ▐▌ █ ▐▌ █ FOR A SPECIFIED USER (replace 'user' with user's name): ▐▌ █ su ▐▌ █ Clear their history: ▐▌ █ history -c /home/user/.bash_history ▐▌ █ Remove the file: ▐▌ █ rm /home/user/.bash_history -rf ▐▌ █ Change their settings: ▐▌ █ echo "export HISTFILESIZE=0" >> /home/user/.bash_profile ▐▌ █ echo "export HISTSIZE=0" >> /home/user/.bash_profile ▐▌ █ echo "unset HISTFILE" >> /home/user/.bash_profile ▐▌ █ ▐▌ █ FOR ALL USERS: ▐▌ █ su ▐▌ █ pico /etc/profile ▐▌ █ Add these lines at the end of the file: ▐▌ █ export HISTFILESIZE=0 ▐▌ █ export HISTSIZE=0 ▐▌ █ unset HISTFILE ▐▌ █ ln /dev/null ~/.bash_history -sf ▐▌ █ ▐▌ █ You'll need to remove all users .bash_history files. Find them first to be ▐▌ █ sure these are the files you want to remove: ▐▌ █ find /home -type f -name .bash_history ▐▌ █ ▐▌ █ If your output above is correct, then to remove all of those files: ▐▌ █ find /home -type f -name .bash_history \ ▐▌ █ -exec rm -f {} \; ▐▌ █ ▐▌ █ Or: ▐▌ █ pico /etc/bash.bashrc ▐▌ █ Add these lines at the end: ▐▌ █ export HISTFILE= ▐▌ █ ln /dev/null ~/.bash_history -sf ▐▌ █ ▐▌ █ Or you could add these lines instead: ▐▌ █ export HISTSIZE=0 ▐▌ █ ln /dev/null ~/.bash_history -sf ▐▌ █ ▐▌ █ Or you could: ▐▌ █ echo "unset HISTFILE" >> /etc/profile ▐▌ █ ▐▌ █ As you can see there are a number of methods that can be applied to all ▐▌ █ users including root. ▐▌ █ ▐▌ █ FOR ROOT: ▐▌ █ su ▐▌ █ Clear root history: ▐▌ █ history -c /root/.bash_history ▐▌ █ Or: ▐▌ █ cat /dev/null > /root/.bash_history ▐▌ █ Send bash history to a black hole: ▐▌ █ ln /dev/null /root/.bash_history -sf ▐▌ █ rm /root/.bash_history -f ▐▌ █ ▐▌ █ Or you can add the settings: ▐▌ █ pico /root/.bash_profile ▐▌ █ If that file doesn't exist then: ▐▌ █ pico /root/.bashrc ▐▌ █ or ▐▌ █ pico /root/.profile ▐▌ █ Paste these lines at the bottom: ▐▌ █ export HISTFILESIZE=0 ▐▌ █ export HISTSIZE=0 ▐▌ █ unset HISTFILE ▐▌ █ ▐▌ █ If you choose to do this for root you should consider a logging program ▐▌ █ to monitor root actions and if possible have the logs sent live to another ▐▌ █ server. ▐▌ █ ▐▌ █ DISABLE .BASH_HISTORY - WHILE RETAINING CURRENT SESSION'S KEYSTROKE: ▐▌ █ ```````````````````````````````````````````````````````````````````` ▐▌ █ To be able to recall the current session's recent cmds (Ctrl+r) for ▐▌ █ example to 30 lines, in all the statements above for 'export HISTSIZE=0' ▐▌ █ change to: ▐▌ █ export HISTSIZE=30 ▐▌ █ ▐▌ █ Or you could: ▐▌ █ export HISTFILE=/dev/null ▐▌ █ ▐▌ █ Or you could: ▐▌ █ pico ~/.bashrc ▐▌ █ Add this line: ▐▌ █ HISTFILE=/dev/null ▐▌ █ ▐▌ █ TEMPORARILY DISABLE YOUR .BASH_HISTORY: ▐▌ █ ``````````````````````````````````````` ▐▌ █ If you want to temporarily disable the logging of your commands, first: ▐▌ █ unset HISTFILE ▐▌ █ Or you could: ▐▌ █ export HISTFILE=/dev/null ▐▌ █ Run your cmds, then reset it: ▐▌ █ export HISTFILE=~/.bash_history ▐▌ █ Or if you didn't care to save the .previous .bash_history and kill ▐▌ █ everything without a wait, after you are finished (not recommended) log ▐▌ █ out with this cmd: ▐▌ █ rm ~/.bash_history -f && kill -9 $$ ▐▌ █ ▐▌ █ LIMIT (not disable) .BASH_HISTORY FOR ALL USERS: ▐▌ █ ```````````````````````````````````````````````` ▐▌ █ pico /etc/profile ▐▌ █ Add these lines at the end, or adjust if already there to limit users to ▐▌ █ 20 previous cmds: ▐▌ █ HISTFILESIZE=30 ▐▌ █ HISTSIZE=30 ▐▌ █ ▐▌ █ PREVENT USERS MODIFYING THEIR .BASH_HISTORY: ▐▌ █ ```````````````````````````````````````````` ▐▌ █ Keep in mind that the methods below for bash are not impossible to bypass, ▐▌ █ as clever users can find ways around this such as few methods that I have ▐▌ █ read about and listed below. ▐▌ █ ▐▌ █ 1) To not allow users (or even root) to modify, move, or delete their ▐▌ █ .bash_history you need to set an attribute to append only (replace user ▐▌ █ with the user's name): ▐▌ █ su ▐▌ █ chattr +a /home/user/.bash_history ▐▌ █ FreeBSD it would be: sappnd /home/user/.bash_history ▐▌ █ ▐▌ █ You should also set append only to all the other bash configuration files. ▐▌ █ When users logs in, bash reads first from /etc/profile, then the first ▐▌ █ three in this order: ▐▌ █ chattr +a /home/user/.bash_profile ▐▌ █ chattr +a /home/user/.bash_login ▐▌ █ chattr +a /home/user/.profile ▐▌ █ chattr +a /home/user/.bashrc ▐▌ █ chattr +a /home/user/.bash_logout ▐▌ █ ▐▌ █ .bashrc is read when ▐▌ █ A. another interactive shell is started, for example by entering: bash and ▐▌ █ B. When it is referred to from the other .bash files containing .bashrc in ▐▌ █ their body - so that means in every case. ▐▌ █ ▐▌ █ Here is an example to change the perms to +a on all the files listed ▐▌ █ above, in all the users /home directory, in mass: ▐▌ █ You might want to search files first to know you have all/only the correct ▐▌ █ files: ▐▌ █ find /home -type f -name .bash\* ▐▌ █ find /home -type f -name .profile ▐▌ █ ▐▌ █ Then to change to the perms: ▐▌ █ find /home -type f -name .bash\* \ ▐▌ █ -exec chattr +a {} \; ▐▌ █ find /home -type f -name .profile \ ▐▌ █ -exec chattr +a {} \; ▐▌ █ ▐▌ █ Even for root to edit files that are set to chattr +a that attribute must ▐▌ █ be removed first. ▐▌ █ To view chattr attributes on the file: ▐▌ █ lsattr .bash_history ▐▌ █ Output would be: -----a------------- ▐▌ █ To remove an 'a' attribute: ▐▌ █ chattr -a .bash_history ▐▌ █ Or if lsattr replied with an 'i' then -i. The i attribute is immutable- no ▐▌ █ append ability. ▐▌ █ To know more about chattr view HERE, or man chattr ▐▌ █ ▐▌ █ 2) Then you need to set the variables so that each cmd a user executes is ▐▌ █ logged immediately, and variables are set to read only so that users can't ▐▌ █ change them such as the size, location, and log all cmds. To do this: ▐▌ █ pico /etc/profile ▐▌ █ Add the following lines to the bottom of the file: ▐▌ if [ "$BASH" ]; then PROMPT_COMMAND="history -a;$PROMPT_COMMAND"; readonly PROMPT_COMMAND readonly HISTSIZE readonly HISTFILE readonly HISTFILESIZE readonly HISTCMD readonly HOME readonly HISTIGNORE readonly HISTCONTROL fi █ ▐▌ █ 3) Disable access to other shells programs on the system so the users must ▐▌ █ use bash. Some of the more common ones are csh, tcsh and ksh. ▐▌ █ To find location of program; which [program], for example: ▐▌ █ which csh ▐▌ █ which tcsh ▐▌ █ ▐▌ █ chmod 750 /bin/csh ▐▌ █ chmod 750 /usr/bin/tcsh ▐▌ █ ▐▌ █ On standard Debian install there is csh (/bin/csh) and tcsh ▐▌ █ (/usr/bin/tcsh). Find out what other shells are installed on your own ▐▌ █ system. ▐▌ █ ▐▌ █ 4) Doing this tho will still not prevent a way out of the above settings ▐▌ █ for bash. ▐▌ █ Here are a few examples a user could type in to bypass the steps above: ▐▌ █ Bash will mimic sh, not using the configurations files related to bash: ▐▌ █ /bin/sh ▐▌ █ Or if it exist: ▐▌ █ /bin/rbash ▐▌ █ Then user is able to bypass logging for current session by: ▐▌ █ unset HISTFILE ▐▌ █ ▐▌ █ Or a user can launch bash with variables to not read the .bashrc file: ▐▌ █ /bin/bash --norc ▐▌ █ HISTFILE= ▐▌ █ ▐▌ █ //---------------------------------------------------------------------- ▐▌ █ ▐▌ █ If you find mistakes, have suggestions, and or questions please post at ▐▌ █ mewbies forum HERE - thank you. ▐▌ █ ▐▌ █ Last update on 20 Jul '10 ▐▌ █ ▐▌ █▌ █▌ █▌ - mewbies.com - █▌ █▌ █▌ ██▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄██
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