Android SELinux AVC Print Code

Introduction

Android SELinux (Security-Enhanced Linux) is a mandatory access control (MAC) system implemented in the Android operating system to provide an additional layer of security. AVC stands for Access Vector Cache and is used to log SELinux denials in the system. In this article, we will discuss how to print AVC messages in Android using code examples.

Printing AVC Messages

To print AVC messages in Android, we need to use the avc_audit_denied function which is defined in the SELinux library. This function logs AVC denials to the kernel ring buffer and then to the audit subsystem where they can be viewed using tools like dmesg or logcat.

Here is a code example of how to print AVC messages in Android:

#include <selinux/avc.h>

void print_avc_message() {
    char *scontext = "u:r:untrusted_app:s0";
    char *tcontext = "u:r:system_server:s0";
    char *tclass = "service_manager";
    char *perm = "call";

    avc_audit_denied(scontext, tcontext, tclass, perm, NULL);
}

In the code above, we call the avc_audit_denied function with the source context u:r:untrusted_app:s0, target context u:r:system_server:s0, target class service_manager, and permission call. This will log an AVC denial message related to the specified access.

Sequence Diagram

Here is a sequence diagram showing the flow of printing AVC messages in Android:

sequenceDiagram
    participant App
    participant SELinux
    participant Kernel
    App->>+SELinux: avc_audit_denied()
    SELinux->>+Kernel: Log AVC denial
    Kernel-->>-SELinux: AVC denial logged

Conclusion

In this article, we have discussed how to print AVC messages in Android using code examples. By logging AVC denials, developers can better understand the interactions between different processes and enforce security policies in the system. SELinux AVC print code is an essential tool for debugging and securing Android applications.

By following the steps outlined in this article, developers can effectively utilize SELinux in Android and enhance the security of their applications.

Remember to always pay attention to SELinux AVC messages and act on them promptly to ensure the integrity and security of your Android system.