getcap

The getcap command in Linux is used to display the capabilities of files. Capabilities are a finer-grained way to grant specific privileges to executables, rather than giving them full root privileges through setuid. This allows for better security practices by reducing the potential impact of vulnerabilities in privileged executables.

Overview of getcap

Purpose

The primary purpose of getcap is to list the capabilities of a specified file. This helps administrators understand what specific privileges a file has been granted.

Basic Usage

The general syntax for getcap is:

getcap [options] <file> [file...]

• <file>: The path to the file whose capabilities you want to display.

Example Usages

1. Displaying Capabilities of a Single File

   To display the capabilities of a single file, simply provide the path to the file:

   getcap /path/to/file

   Example:

   getcap /usr/bin/ping

   Output:

   /usr/bin/ping = cap_net_raw+ep

   This output indicates that the ping command has the cap_net_raw capability with ep (effective and permitted) flags.

2. Displaying Capabilities of Multiple Files

   You can list capabilities for multiple files by specifying their paths:

   getcap /path/to/file1 /path/to/file2

   Example:

   getcap /usr/bin/ping /usr/sbin/tcpdump

3. Displaying Capabilities Recursively

   To display capabilities of all files in a directory recursively, use the -r option:

   getcap -r /path/to/directory

   Example:

   getcap -r /usr/bin

Capabilities Overview

Capabilities are divided into different categories and can be set with specific flags. Here are some common capabilities:

• cap_net_raw: Allow raw socket operations.

• cap_net_admin: Perform various network-related operations.

• cap_sys_admin: Perform various system administration tasks.

• cap_sys_ptrace: Trace arbitrary processes using ptrace.

Example Capabilities and Their Meanings

• cap_net_raw+ep: Grants the file the ability to perform raw network operations (cap_net_raw) with effective (e) and permitted (p) flags.

• cap_net_admin+eip: Grants the file network administration capabilities with effective (e), inheritable (i), and permitted (p) flags.

Conclusion

getcap is a useful command for displaying the capabilities of files in a Linux system. By granting specific capabilities to executables, administrators can improve security by limiting the privileges of these executables to only those necessary for their operation.