getcon(3)

💖 NAME 💖

okay so bestie, this whole page is about getting and setting SELinux security contexts of a process, and also freeing the memory that comes with them. it's giving "I just want to know who I am" but for processes, fr fr.

• getcon, getprevcon, getpidcon — get SELinux security context of a process 🫶
• freecon, freeconary — free memory associated with SELinux security contexts 🧹
• getpeercon — get security context of a peer socket 🧚
• setcon — set current security context of a process 👑

and yes, this is from the SELinux API documentation (that's the manual name, mwah) 💅

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✨ SYNOPSIS ✨

like, here's the tea, all of it, character for character:

#include <selinux/selinux.h>

int getcon(char **context);

int getcon_raw(char **context);

int getprevcon(char **context);

int getprevcon_raw(char **context);

int getpidcon(pid_t pid, char **context);

int getpidcon_raw(pid_t pid, char **context);

int getpidprevcon(pid_t pid, char **context);

int getpidprevcon_raw(pid_t pid, char **context);

int getpeercon(int fd, char **context);

int getpeercon_raw(int fd, char **context);

void freecon(char *con);

void freeconary(char **con);

int setcon(const char *context);

int setcon_raw(const char *context);

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🌸 DESCRIPTION 🌸

getcon()

retrieves the context of the current process 💖 and omg, it must be free'd with freecon() or you're gonna leak memory and that's not the vibe.

getprevcon()

same as getcon but it gets the context before the last exec. like, who was I before I became who I am now 🦋

getpidcon()

returns the process context for the specified PID, which must be free'd with freecon() ✨

getpidprevcon()

returns the process context before the last exec for the specified PID, which must be free'd with freecon() 🌈

getpeercon()

retrieves the context of the peer socket, which must be free'd with freecon() 🧚 (yes, the socket's bestie context. iconique.)

freecon()

frees the memory allocated for a security context 🎀

If con is NULL, no operation is performed. (so like, chill, nothing happens, it's fine 💀)

freeconary()

frees the memory allocated for a context array 🧹

If con is NULL, no operation is performed. (same energy, no notes.)

setcon()

sets the current security context of the process to a new value 👑 okay but listen, this one is highkey serious, so pay attention bestie:

use of this function requires that the entire application be trusted to maintain any desired separation between the old and new security contexts. that is not the same as exec-based transitions performed via setexeccon(3). When possible, decompose your application and use setexeccon(3) and execve(3) instead. periodt.

Since access to file descriptors is revalidated upon use by SELinux, the new context must be explicitly authorized in the policy to use the descriptors opened by the old context if that is desired 😭 Otherwise, attempts by the process to use any existing descriptors (including stdin, stdout, and stderr) after performing the setcon() will fail. like not "hmm that's unfortunate" fail, fail fail.

A multi-threaded application can perform a setcon() prior to creating any child threads, in which case all of the child threads will inherit the new context 💜 However, prior to Linux 2.6.28, setcon() would fail if there are any other threads running in the same process, since this would yield an inconsistency among the security contexts of threads sharing the same memory space. Since Linux 2.6.28, setcon() is permitted for threads within a multi-threaded process if the new security context is bounded by the old security context, where the bounded relation is defined through typebounds statements in the policy and guarantees that the new security context has a subset of the permissions of the old security context. slay, but like, carefully.

If the process was being ptraced at the time of the setcon() operation, ptrace permission will be revalidated against the new context and the setcon() will fail if it is not allowed by policy 🙈

*_raw()

getcon_raw(), getprevcon_raw(), getpidcon_raw(), getpidprevcon_raw(), getpeercon_raw() and setcon_raw() behave identically to their non-raw counterparts but do not perform context translation. no translation, just raw vibes, iykyk 💅

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⭐ RETURN VALUE ⭐

On error -1 is returned with errno set. On success 0 is returned. that's it, that's the whole mood 💀✨

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🎀 NOTES 🎀

The retrieval functions might return success and set *context to NULL if and only if SELinux is not enabled. so like, check that bestie, don't get got 🙈

Querying a foreign process via its PID, e.g. getpidcon() or getpidprevcon(), is inherently racy and therefore should never be relied upon for security purposes. NEVER. no cap. 🔥

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🦋 SEE ALSO 🦋

• selinux(8)
• setexeccon(3)

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okay that's the whole page bestie, you ate 💅 go forth and query contexts responsibly 🫶

this masterpiece was brought to you by russell@coker.com.au, dated 21 December 2011 💖 and honestly? iconic for it. bye bestie, love u, free your cons 🌸✨