avc_get_initial_context - Linux

Overview

avc_get_initial_context is a Linux command that allows unprivileged processes to obtain an initial security context (ISC) from the Security Enhanced Linux (SELinux) policy. This capability is commonly used by unprivileged processes to allow access to objects or perform actions that would otherwise be prohibited.

Syntax

avc_get_initial_context [options] <target_sid> <source_sid> <target_class> <target_perm>

Options/Flags

• -c, –class: Specify the class of the target object.
• -p, –perm: Specify the permission to check for the target object.
• -u, –source_user: Specify the user name of the source subject.
• -r, –role: Specify the role name of the source subject.
• -t, –type: Specify the type of the target subject.
• -h, –help: Display usage help.

Examples

To check if an unprivileged user can read a file labeled as confidential, use:

avc_get_initial_context -p read -t file -c unlabeled user_u:role_u conf_t:file

To obtain an ISC for a script that allows it to access a specific directory, use:

avc_get_initial_context -r script_r -t file -c dir -p write /usr/bin/audit2allow

Common Issues

• Permission denied: Ensure that the user or role has the appropriate privileges to access the target object.
• Invalid target class or permission: Verify that the specified target class and permission are valid.

Integration

avc_get_initial_context can be combined with other SELinux tools to further enhance security. For example, it can be used with the semanage command to create or modify SELinux policies.

Related Commands

• getenforce
• sestatus
• semanage