CAP_GET_PROC(3)

NAME
cap_get_proc, cap_set_proc, capgetp - capability manipulation on processes

SYNOPSIS
#include <sys/capability.h>

cap_t cap_get_proc(void);

int cap_set_proc(cap_t cap_p);

cap_t capgetp(pid_t pid, cap_t cap_d);

Link with -lcap.

DESCRIPTION
cap_get_proc() allocates a capability state in working storage, sets its state to that of the calling process, and returns a pointer to this newly created capability state. The caller should free any releasable memory, when the capability state in working storage is no longer required, by calling cap_free() with the cap_t as an argument.

cap_set_proc() sets the values for all capability flags for all capabilities to the capability state identified by cap_p. The new capability state of the process will be completely determined by the contents of cap_p upon successful return from this function. If any flag in cap_p is set for any capability not currently permitted for the calling process, the function will fail, and the capability state of the process will remain unchanged.

capgetp() fills an existing cap_d, see cap_init(3), with the process capabilities of the process indicated by pid. This information can also be obtained from the /proc/<pid>/status file.

RETURN VALUE
cap_get_proc() returns a non-NULL value on success, and NULL on failure.

cap_set_proc() and capgetp() return zero for success, and -1 on failure.

On failure, errno is set to EINVAL, EPERM, or ENOMEM.

CONFORMING TO
cap_set_proc() and cap_get_proc() are specified in the withdrawn POSIX.1e draft specification. capgetp() and capsetp() (described below) are Linux extensions.

NOTES
The library also supports the deprecated function:

cap_t capsetp(pid_t pid, cap_t cap_d);

capsetp() attempts to set the capabilities of some other process(es), pid. If pid is positive it refers to a specific process; if it is zero, it refers to the current process; -1 refers to all processes other than the current process and process '1' (typically init(8)); other negative values refer to the -pid process group. In order to use this function, the kernel must support it and the current process must have CAP_SETPCAP raised in its Effective capability set. The capabilities set in the target process(es) are those contained in cap_d. Kernels that support filesystem capabilities redefine the semantics of CAP_SETPCAP and on such systems this function will always fail for any target not equal to the current process. capsetp() returns zero for success, and -1 on failure. Where supported by the kernel, the function capsetp() should be used with care. It existed, primarily, to overcome an early lack of support for capabilities in the filesystems supported by Linux. Note that, by default, the only processes that have CAP_SETPCAP available to them are processes started as a kernel thread. (Typically this includes init(8), kflushd and kswapd). You will need to recompile the kernel to modify this default.

EXAMPLE
The code segment below raises the CAP_FOWNER and CAP_SETFCAP effective capabilities for the caller:
    cap_t caps;
    cap_value_t cap_list[2];
    caps = cap_get_proc();
    if (caps == NULL)
        /* handle error */;
    cap_list[0] = CAP_FOWNER;
    cap_list[1] = CAP_SETFCAP;
    if (cap_set_flag(caps, CAP_EFFECTIVE, 2, cap_list, CAP_SET) == -1)
        /* handle error */;
    if (cap_set_proc(caps) == -1)
        /* handle error */;
    if (cap_free(caps) == -1)
        /* handle error */;

SEE ALSO
cap_clear(3), cap_copy_ext(3), cap_from_text(3), cap_get_file(3), cap_init(3), capabilities(7)