1 /*
2 * linux/kernel/capability.c
3 *
4 * Copyright (C) 1997 Andrew Main <zefram@fysh.org>
5 *
6 * Integrated into 2.1.97+, Andrew G. Morgan <morgan@kernel.org>
7 * 30 May 2002: Cleanup, Robert M. Love <rml@tech9.net>
8 */
9
10 #include <linux/audit.h>
11 #include <linux/capability.h>
12 #include <linux/mm.h>
13 #include <linux/module.h>
14 #include <linux/security.h>
15 #include <linux/syscalls.h>
16 #include <linux/pid_namespace.h>
17 #include <asm/uaccess.h>
18 #include "cred-internals.h"
19
20 /*
21 * Leveraged for setting/resetting capabilities
22 */
23
24 const kernel_cap_t __cap_empty_set = CAP_EMPTY_SET;
25 const kernel_cap_t __cap_full_set = CAP_FULL_SET;
26 const kernel_cap_t __cap_init_eff_set = CAP_INIT_EFF_SET;
27
28 EXPORT_SYMBOL(__cap_empty_set);
29 EXPORT_SYMBOL(__cap_full_set);
30 EXPORT_SYMBOL(__cap_init_eff_set);
31
32 #ifdef CONFIG_SECURITY_FILE_CAPABILITIES
33 int file_caps_enabled = 1;
34
file_caps_disable(char * str)35 static int __init file_caps_disable(char *str)
36 {
37 file_caps_enabled = 0;
38 return 1;
39 }
40 __setup("no_file_caps", file_caps_disable);
41 #endif
42
43 /*
44 * More recent versions of libcap are available from:
45 *
46 * http://www.kernel.org/pub/linux/libs/security/linux-privs/
47 */
48
warn_legacy_capability_use(void)49 static void warn_legacy_capability_use(void)
50 {
51 static int warned;
52 if (!warned) {
53 char name[sizeof(current->comm)];
54
55 printk(KERN_INFO "warning: `%s' uses 32-bit capabilities"
56 " (legacy support in use)\n",
57 get_task_comm(name, current));
58 warned = 1;
59 }
60 }
61
62 /*
63 * Version 2 capabilities worked fine, but the linux/capability.h file
64 * that accompanied their introduction encouraged their use without
65 * the necessary user-space source code changes. As such, we have
66 * created a version 3 with equivalent functionality to version 2, but
67 * with a header change to protect legacy source code from using
68 * version 2 when it wanted to use version 1. If your system has code
69 * that trips the following warning, it is using version 2 specific
70 * capabilities and may be doing so insecurely.
71 *
72 * The remedy is to either upgrade your version of libcap (to 2.10+,
73 * if the application is linked against it), or recompile your
74 * application with modern kernel headers and this warning will go
75 * away.
76 */
77
warn_deprecated_v2(void)78 static void warn_deprecated_v2(void)
79 {
80 static int warned;
81
82 if (!warned) {
83 char name[sizeof(current->comm)];
84
85 printk(KERN_INFO "warning: `%s' uses deprecated v2"
86 " capabilities in a way that may be insecure.\n",
87 get_task_comm(name, current));
88 warned = 1;
89 }
90 }
91
92 /*
93 * Version check. Return the number of u32s in each capability flag
94 * array, or a negative value on error.
95 */
cap_validate_magic(cap_user_header_t header,unsigned * tocopy)96 static int cap_validate_magic(cap_user_header_t header, unsigned *tocopy)
97 {
98 __u32 version;
99
100 if (get_user(version, &header->version))
101 return -EFAULT;
102
103 switch (version) {
104 case _LINUX_CAPABILITY_VERSION_1:
105 warn_legacy_capability_use();
106 *tocopy = _LINUX_CAPABILITY_U32S_1;
107 break;
108 case _LINUX_CAPABILITY_VERSION_2:
109 warn_deprecated_v2();
110 /*
111 * fall through - v3 is otherwise equivalent to v2.
112 */
113 case _LINUX_CAPABILITY_VERSION_3:
114 *tocopy = _LINUX_CAPABILITY_U32S_3;
115 break;
116 default:
117 if (put_user((u32)_KERNEL_CAPABILITY_VERSION, &header->version))
118 return -EFAULT;
119 return -EINVAL;
120 }
121
122 return 0;
123 }
124
125 /*
126 * The only thing that can change the capabilities of the current
127 * process is the current process. As such, we can't be in this code
128 * at the same time as we are in the process of setting capabilities
129 * in this process. The net result is that we can limit our use of
130 * locks to when we are reading the caps of another process.
131 */
cap_get_target_pid(pid_t pid,kernel_cap_t * pEp,kernel_cap_t * pIp,kernel_cap_t * pPp)132 static inline int cap_get_target_pid(pid_t pid, kernel_cap_t *pEp,
133 kernel_cap_t *pIp, kernel_cap_t *pPp)
134 {
135 int ret;
136
137 if (pid && (pid != task_pid_vnr(current))) {
138 struct task_struct *target;
139
140 read_lock(&tasklist_lock);
141
142 target = find_task_by_vpid(pid);
143 if (!target)
144 ret = -ESRCH;
145 else
146 ret = security_capget(target, pEp, pIp, pPp);
147
148 read_unlock(&tasklist_lock);
149 } else
150 ret = security_capget(current, pEp, pIp, pPp);
151
152 return ret;
153 }
154
155 /**
156 * sys_capget - get the capabilities of a given process.
157 * @header: pointer to struct that contains capability version and
158 * target pid data
159 * @dataptr: pointer to struct that contains the effective, permitted,
160 * and inheritable capabilities that are returned
161 *
162 * Returns 0 on success and < 0 on error.
163 */
SYSCALL_DEFINE2(capget,cap_user_header_t,header,cap_user_data_t,dataptr)164 SYSCALL_DEFINE2(capget, cap_user_header_t, header, cap_user_data_t, dataptr)
165 {
166 int ret = 0;
167 pid_t pid;
168 unsigned tocopy;
169 kernel_cap_t pE, pI, pP;
170
171 ret = cap_validate_magic(header, &tocopy);
172 if (ret != 0)
173 return ret;
174
175 if (get_user(pid, &header->pid))
176 return -EFAULT;
177
178 if (pid < 0)
179 return -EINVAL;
180
181 ret = cap_get_target_pid(pid, &pE, &pI, &pP);
182 if (!ret) {
183 struct __user_cap_data_struct kdata[_KERNEL_CAPABILITY_U32S];
184 unsigned i;
185
186 for (i = 0; i < tocopy; i++) {
187 kdata[i].effective = pE.cap[i];
188 kdata[i].permitted = pP.cap[i];
189 kdata[i].inheritable = pI.cap[i];
190 }
191
192 /*
193 * Note, in the case, tocopy < _KERNEL_CAPABILITY_U32S,
194 * we silently drop the upper capabilities here. This
195 * has the effect of making older libcap
196 * implementations implicitly drop upper capability
197 * bits when they perform a: capget/modify/capset
198 * sequence.
199 *
200 * This behavior is considered fail-safe
201 * behavior. Upgrading the application to a newer
202 * version of libcap will enable access to the newer
203 * capabilities.
204 *
205 * An alternative would be to return an error here
206 * (-ERANGE), but that causes legacy applications to
207 * unexpectidly fail; the capget/modify/capset aborts
208 * before modification is attempted and the application
209 * fails.
210 */
211 if (copy_to_user(dataptr, kdata, tocopy
212 * sizeof(struct __user_cap_data_struct))) {
213 return -EFAULT;
214 }
215 }
216
217 return ret;
218 }
219
220 /**
221 * sys_capset - set capabilities for a process or (*) a group of processes
222 * @header: pointer to struct that contains capability version and
223 * target pid data
224 * @data: pointer to struct that contains the effective, permitted,
225 * and inheritable capabilities
226 *
227 * Set capabilities for the current process only. The ability to any other
228 * process(es) has been deprecated and removed.
229 *
230 * The restrictions on setting capabilities are specified as:
231 *
232 * I: any raised capabilities must be a subset of the old permitted
233 * P: any raised capabilities must be a subset of the old permitted
234 * E: must be set to a subset of new permitted
235 *
236 * Returns 0 on success and < 0 on error.
237 */
SYSCALL_DEFINE2(capset,cap_user_header_t,header,const cap_user_data_t,data)238 SYSCALL_DEFINE2(capset, cap_user_header_t, header, const cap_user_data_t, data)
239 {
240 struct __user_cap_data_struct kdata[_KERNEL_CAPABILITY_U32S];
241 unsigned i, tocopy;
242 kernel_cap_t inheritable, permitted, effective;
243 struct cred *new;
244 int ret;
245 pid_t pid;
246
247 ret = cap_validate_magic(header, &tocopy);
248 if (ret != 0)
249 return ret;
250
251 if (get_user(pid, &header->pid))
252 return -EFAULT;
253
254 /* may only affect current now */
255 if (pid != 0 && pid != task_pid_vnr(current))
256 return -EPERM;
257
258 if (copy_from_user(&kdata, data,
259 tocopy * sizeof(struct __user_cap_data_struct)))
260 return -EFAULT;
261
262 for (i = 0; i < tocopy; i++) {
263 effective.cap[i] = kdata[i].effective;
264 permitted.cap[i] = kdata[i].permitted;
265 inheritable.cap[i] = kdata[i].inheritable;
266 }
267 while (i < _KERNEL_CAPABILITY_U32S) {
268 effective.cap[i] = 0;
269 permitted.cap[i] = 0;
270 inheritable.cap[i] = 0;
271 i++;
272 }
273
274 new = prepare_creds();
275 if (!new)
276 return -ENOMEM;
277
278 ret = security_capset(new, current_cred(),
279 &effective, &inheritable, &permitted);
280 if (ret < 0)
281 goto error;
282
283 audit_log_capset(pid, new, current_cred());
284
285 return commit_creds(new);
286
287 error:
288 abort_creds(new);
289 return ret;
290 }
291
292 /**
293 * capable - Determine if the current task has a superior capability in effect
294 * @cap: The capability to be tested for
295 *
296 * Return true if the current task has the given superior capability currently
297 * available for use, false if not.
298 *
299 * This sets PF_SUPERPRIV on the task if the capability is available on the
300 * assumption that it's about to be used.
301 */
capable(int cap)302 int capable(int cap)
303 {
304 if (unlikely(!cap_valid(cap))) {
305 printk(KERN_CRIT "capable() called with invalid cap=%u\n", cap);
306 BUG();
307 }
308
309 if (security_capable(cap) == 0) {
310 current->flags |= PF_SUPERPRIV;
311 return 1;
312 }
313 return 0;
314 }
315 EXPORT_SYMBOL(capable);
316