1CAP_GET_PROC(3) Linux Programmer's Manual CAP_GET_PROC(3)
2
6 cap_get_proc, cap_set_proc, capgetp, cap_get_bound, cap_drop_bound -
7 capability manipulation on processes
8
10 #include <sys/capability.h>
11 cap_t cap_get_proc(void);
13 int cap_set_proc(cap_t cap_p);
15 int cap_get_bound(cap_value_t cap);
17 CAP_IS_SUPPORTED(cap_value_t cap);
19 int cap_drop_bound(cap_value_t cap);
21 #include <sys/types.h>
23 cap_t cap_get_pid(pid_t pid);
25 Link with -lcap.
27
29 cap_get_proc() allocates a capability state in working storage, sets
30 its state to that of the calling process, and returns a pointer to this
31 newly created capability state. The caller should free any releasable
32 memory, when the capability state in working storage is no longer
33 required, by calling cap_free() with the cap_t as an argument.
34 cap_set_proc() sets the values for all capability flags for all capa‐
36 bilities to the capability state identified by cap_p. The new capabil‐
37 ity state of the process will be completely determined by the contents
38 of cap_p upon successful return from this function. If any flag in
39 cap_p is set for any capability not currently permitted for the calling
40 process, the function will fail, and the capability state of the
41 process will remain unchanged.
42 cap_get_pid() returns cap_d, see cap_init(3), with the process capabil‐
44 ities of the process indicated by pid. This information can also be
45 obtained from the /proc/<pid>/status file.
46 cap_get_bound() with a cap as an argument returns the current value of
48 this bounding set capability flag in effect for the current process.
49 This operation is unpriveged. Note, a macro function CAP_IS_SUP‐
50 PORTED(cap_value_t cap) is provided that evaluates to true (1) if the
51 system supports the specified capability, cap. If the system does not
52 support the capability, this function returns 0. This macro works by
53 testing for an error condition with cap_get_bound().
54 cap_drop_bound() can be used to lower the specified bounding set capa‐
56 bility, cap, To complete successfully, the prevailing effective capa‐
57 bility set must have a raised CAP_SETPCAP.
58
60 The functions cap_get_proc() and cap_get_pid() return a non-NULL value
61 on success, and NULL on failure.
62 The function cap_get_bound() returns -1 if the requested capability is
64 unknown, otherwise the return value reflects the current state of that
65 capability in the prevailing bounding set. Note, a macro function,
66 The functions cap_set_proc() and cap_drop_bound() return zero for suc‐
68 cess, and -1 on failure.
69 On failure, errno is set to EINVAL, EPERM, or ENOMEM.
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73 cap_set_proc() and cap_get_proc() are specified in the withdrawn
74 POSIX.1e draft specification. cap_get_pid() is a Linux extension.
75
77 The library also supports the deprecated functions:
78 int capgetp(pid_t pid, cap_t cap_d);
80 int capsetp(pid_t pid, cap_t cap_d);
82 capgetp() attempts to obtain the capabilities of some other process;
84 storing the capabilities in a pre-allocated cap_d.See cap_init() for
85 information on allocating an empty capability set. This function,
86 capgetp(), is deprecated, you should use cap_get_pid().
87 capsetp() attempts to set the capabilities of some other process(es),
89 pid. If pid is positive it refers to a specific process; if it is
90 zero, it refers to the current process; -1 refers to all processes
91 other than the current process and process '1' (typically init(8));
92 other negative values refer to the -pid process group. In order to use
93 this function, the kernel must support it and the current process must
94 have CAP_SETPCAP raised in its Effective capability set. The capabili‐
95 ties set in the target process(es) are those contained in cap_d. Ker‐
96 nels that support filesystem capabilities redefine the semantics of
97 CAP_SETPCAP and on such systems this function will always fail for any
98 target not equal to the current process. capsetp() returns zero for
99 success, and -1 on failure.
100 Where supported by the kernel, the function capsetp() should be used
102 with care. It existed, primarily, to overcome an early lack of support
103 for capabilities in the filesystems supported by Linux. Note that, by
104 default, the only processes that have CAP_SETPCAP available to them are
105 processes started as a kernel thread. (Typically this includes
106 init(8), kflushd and kswapd). You will need to recompile the kernel to
107 modify this default.
108
110 The code segment below raises the CAP_FOWNER and CAP_SETFCAP effective
111 capabilities for the caller:
112 cap_t caps;
114 cap_value_t cap_list[2];
115 if (!CAP_IS_SUPPORTED(CAP_SETFCAP))
117 /* handle error */
118 caps = cap_get_proc();
120 if (caps == NULL)
121 /* handle error */;
122 cap_list[0] = CAP_FOWNER;
124 cap_list[1] = CAP_SETFCAP;
125 if (cap_set_flag(caps, CAP_EFFECTIVE, 2, cap_list, CAP_SET) == -1)
126 /* handle error */;
127 if (cap_set_proc(caps) == -1)
129 /* handle error */;
130 if (cap_free(caps) == -1)
132 /* handle error */;
133
135 libcap(3), cap_clear(3), cap_copy_ext(3), cap_from_text(3),
136 cap_get_file(3), cap_init(3), capabilities(7)
137 2008-05-11 CAP_GET_PROC(3)