The GNU history utility keeps a record of the commands a user enters during a shell/terminal session. By default, 1,000 historical commands are stored, but the number can be changed using the $HISTSIZE and $HISTFILESIZE variables. The history is logged in a hidden file named “.bash_history” in the user’s home directory.
Simply running the history command on a shell will print out all the commands that have been executed during a session. You can replay any of the historically run commands using the “!” sign. For example, “!5” will run the command present on the fifth line of your bash history.
You can also search your history for any previously run commands. grep history | git will filter out all the git commands from your history. You can also press ctrl + R to start a recursive search of your history. During a recursive search, matching results will start appearing as you type a keyword.
The bash history file can also contain sensitive information like API keys, secrets, and passwords.
Bash users often enter their passwords and other sensitive information on the command line, which ends up getting stored in the bash history file. For example, a user may run the following command to log in to a SQL Server database:
SQLCMD -S mydatabase -U admin -P p@@sw0rd
This command will end up in the bash history, along with the plaintext password.
On a compromised system, malicious actors can search this file for credentials and other exploitable information.
Orca can detect passwords in the shell history. Orca uses pattern matching techniques on each line of the bash history file to look for different password execution types. Some password examples that Orca can detect and alert on are as follows:
Use the command set +o history to temporarily turn history saving on or off.
Set HISTIGNORE=”*[Pp][Aa][Ss][Ss][Ww][Oo][Rr][Dd]*” to ensure that any command with the word password isn’t stored in bash history. Note: The $HISTIGNORE environment variable controls which commands are entered into the history and which are ignored.
Educate people to not enter passwords via the command line. A relatively safer alternative is to provide passwords via the standard input (stdin) stream.
Use the command history –d to clear a specific line from a history file. You can also clear the entire history using history -c.
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