execstack Command in Linux

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execstack is a useful Linux command that allows you to manage the executable stack flag of ELF binaries and shared libraries. That type of flag determines whether the stack can execute code, which is useful for security purposes.

By default, most modern systems block code from running on the stack in order to avoid certain types of attacks. However, this may be required for some programs so that they may be able to function properly on the systems. With the help of execstack command, you can manage this since it allows you to set, clear, or query the executable stack flag. For instance, you can use it to mark a binary as needing an executable stack or to see if a binary requires it.

Table of Contents

Here is a comprehensive guide to the options available with the execstack command −

• Installation of execstack in Linux
• Syntax for execstack Command in Linux
• Different Options Available for execstack Command
• Examples of execstack Command in Linux

Installation of execstack in Linux

The execstack command is not pre-installed on most Linux systems by default. However, you can easily install it using your package manager.

For Ubuntu, Debian, Kali Linux, and similar distributions, you can install execstack with the following command −

sudo apt install execstack

You can use the dnf or yum package manager to install execstack on Fedora and CentOS systems −

sudo dnf install execstack

Or

sudo yum install execstack

The Arch Linux users can get execstack on their systems from the following command −

sudo pacman -S execstack

While on SUSE operating system, you can use the below-given command to install execstack −

sudo zypper install execstack

Syntax for execstack Command in Linux

The following is the basic syntax to use the execstack command on Linux system −

execstack [options] command [args]

Where,

• [options] are flags that modify the behavior of the execstack command.
• command is the action you want to perform, such as setting, clearing, or querying the executable stack flag.
• [args] are the arguments, typically the names of the ELF binaries or shared libraries you want to modify or query.

Different Options Available for execstack Command

With execstack command, you can use several options, which can are described below −

Examples of execstack Command in Linux

Let’s explore a few examples of execstack command in Linux −

• Marking a Shared Library as Requiring an Executable Stack
• Marking a Binary as Not Requiring an Executable Stack
• Querying the Executable Stack Status

Marking a Shared Library as Requiring an Executable Stack

You can use the execstack command on Linux to ensure a shared library can execute code from stack. For this process, you can use the execstack command with the -s option. It sets the executable stack flag, indicating that the library needs this capability to function correctly. For example −

execstack -s /usr/lib/libexample.so

This command marks libexample.so as requiring an executable stack.

Marking a Binary as Not Requiring an Executable Stack

The execstack command can also be used to specify that a binary does not need to execute code from the stack. For this process, you can use the -c option with the execstack command. It will help clear the executable stack flag, indicating that the binary does not require this capability. For example −

execstack -c /usr/bin/example

This command marks the example as not requiring an executable stack.

Querying the Executable Stack Status

The execstack command can also be pretty useful in checking whether a file requires an executable stack. This requires the use of -q option that queries the executable stack status. For example −

execstack -q /usr/local/lib/libexample.so /usr/bin/example

This command checks the executable stack status of libexample.so and examples.

Conclusion

The execstack is a powerful command used in Linux for managing the executable stack flag of ELF binaries and shared libraries. Using execstack, you can set, clear, or query the executable stack flag and ensure compatibility and security for your programs.

This tutorial has provided a detailed overview of execstack command, covering everything from installation to practical examples. Following these examples, you will be able to use the command effectively on your Linux system, and enhance both functionality and security.