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