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3e1c2515 | 1 | /* Common capabilities, needed by capability.o. |
1da177e4 LT |
2 | * |
3 | * This program is free software; you can redistribute it and/or modify | |
4 | * it under the terms of the GNU General Public License as published by | |
5 | * the Free Software Foundation; either version 2 of the License, or | |
6 | * (at your option) any later version. | |
7 | * | |
8 | */ | |
9 | ||
c59ede7b | 10 | #include <linux/capability.h> |
3fc689e9 | 11 | #include <linux/audit.h> |
1da177e4 LT |
12 | #include <linux/module.h> |
13 | #include <linux/init.h> | |
14 | #include <linux/kernel.h> | |
15 | #include <linux/security.h> | |
16 | #include <linux/file.h> | |
17 | #include <linux/mm.h> | |
18 | #include <linux/mman.h> | |
19 | #include <linux/pagemap.h> | |
20 | #include <linux/swap.h> | |
1da177e4 LT |
21 | #include <linux/skbuff.h> |
22 | #include <linux/netlink.h> | |
23 | #include <linux/ptrace.h> | |
24 | #include <linux/xattr.h> | |
25 | #include <linux/hugetlb.h> | |
b5376771 | 26 | #include <linux/mount.h> |
b460cbc5 | 27 | #include <linux/sched.h> |
3898b1b4 AM |
28 | #include <linux/prctl.h> |
29 | #include <linux/securebits.h> | |
3486740a | 30 | #include <linux/user_namespace.h> |
40401530 | 31 | #include <linux/binfmts.h> |
72c2d582 | 32 | |
b5f22a59 SH |
33 | /* |
34 | * If a non-root user executes a setuid-root binary in | |
35 | * !secure(SECURE_NOROOT) mode, then we raise capabilities. | |
36 | * However if fE is also set, then the intent is for only | |
37 | * the file capabilities to be applied, and the setuid-root | |
38 | * bit is left on either to change the uid (plausible) or | |
39 | * to get full privilege on a kernel without file capabilities | |
40 | * support. So in that case we do not raise capabilities. | |
41 | * | |
42 | * Warn if that happens, once per boot. | |
43 | */ | |
d7627467 | 44 | static void warn_setuid_and_fcaps_mixed(const char *fname) |
b5f22a59 SH |
45 | { |
46 | static int warned; | |
47 | if (!warned) { | |
48 | printk(KERN_INFO "warning: `%s' has both setuid-root and" | |
49 | " effective capabilities. Therefore not raising all" | |
50 | " capabilities.\n", fname); | |
51 | warned = 1; | |
52 | } | |
53 | } | |
54 | ||
1da177e4 LT |
55 | int cap_netlink_send(struct sock *sk, struct sk_buff *skb) |
56 | { | |
1da177e4 LT |
57 | return 0; |
58 | } | |
59 | ||
1d045980 DH |
60 | /** |
61 | * cap_capable - Determine whether a task has a particular effective capability | |
3699c53c | 62 | * @cred: The credentials to use |
3486740a | 63 | * @ns: The user namespace in which we need the capability |
1d045980 DH |
64 | * @cap: The capability to check for |
65 | * @audit: Whether to write an audit message or not | |
66 | * | |
67 | * Determine whether the nominated task has the specified capability amongst | |
68 | * its effective set, returning 0 if it does, -ve if it does not. | |
69 | * | |
3699c53c DH |
70 | * NOTE WELL: cap_has_capability() cannot be used like the kernel's capable() |
71 | * and has_capability() functions. That is, it has the reverse semantics: | |
72 | * cap_has_capability() returns 0 when a task has a capability, but the | |
73 | * kernel's capable() and has_capability() returns 1 for this case. | |
a6dbb1ef | 74 | */ |
6a9de491 EP |
75 | int cap_capable(const struct cred *cred, struct user_namespace *targ_ns, |
76 | int cap, int audit) | |
1da177e4 | 77 | { |
3486740a SH |
78 | for (;;) { |
79 | /* The creator of the user namespace has all caps. */ | |
80 | if (targ_ns != &init_user_ns && targ_ns->creator == cred->user) | |
81 | return 0; | |
82 | ||
83 | /* Do we have the necessary capabilities? */ | |
84 | if (targ_ns == cred->user->user_ns) | |
85 | return cap_raised(cred->cap_effective, cap) ? 0 : -EPERM; | |
86 | ||
87 | /* Have we tried all of the parent namespaces? */ | |
88 | if (targ_ns == &init_user_ns) | |
89 | return -EPERM; | |
90 | ||
91 | /* | |
92 | *If you have a capability in a parent user ns, then you have | |
93 | * it over all children user namespaces as well. | |
94 | */ | |
95 | targ_ns = targ_ns->creator->user_ns; | |
96 | } | |
97 | ||
98 | /* We never get here */ | |
1da177e4 LT |
99 | } |
100 | ||
1d045980 DH |
101 | /** |
102 | * cap_settime - Determine whether the current process may set the system clock | |
103 | * @ts: The time to set | |
104 | * @tz: The timezone to set | |
105 | * | |
106 | * Determine whether the current process may set the system clock and timezone | |
107 | * information, returning 0 if permission granted, -ve if denied. | |
108 | */ | |
1e6d7679 | 109 | int cap_settime(const struct timespec *ts, const struct timezone *tz) |
1da177e4 LT |
110 | { |
111 | if (!capable(CAP_SYS_TIME)) | |
112 | return -EPERM; | |
113 | return 0; | |
114 | } | |
115 | ||
1d045980 | 116 | /** |
9e48858f | 117 | * cap_ptrace_access_check - Determine whether the current process may access |
1d045980 DH |
118 | * another |
119 | * @child: The process to be accessed | |
120 | * @mode: The mode of attachment. | |
121 | * | |
8409cca7 SH |
122 | * If we are in the same or an ancestor user_ns and have all the target |
123 | * task's capabilities, then ptrace access is allowed. | |
124 | * If we have the ptrace capability to the target user_ns, then ptrace | |
125 | * access is allowed. | |
126 | * Else denied. | |
127 | * | |
1d045980 DH |
128 | * Determine whether a process may access another, returning 0 if permission |
129 | * granted, -ve if denied. | |
130 | */ | |
9e48858f | 131 | int cap_ptrace_access_check(struct task_struct *child, unsigned int mode) |
1da177e4 | 132 | { |
c69e8d9c | 133 | int ret = 0; |
8409cca7 | 134 | const struct cred *cred, *child_cred; |
c69e8d9c DH |
135 | |
136 | rcu_read_lock(); | |
8409cca7 SH |
137 | cred = current_cred(); |
138 | child_cred = __task_cred(child); | |
139 | if (cred->user->user_ns == child_cred->user->user_ns && | |
140 | cap_issubset(child_cred->cap_permitted, cred->cap_permitted)) | |
141 | goto out; | |
142 | if (ns_capable(child_cred->user->user_ns, CAP_SYS_PTRACE)) | |
143 | goto out; | |
144 | ret = -EPERM; | |
145 | out: | |
c69e8d9c DH |
146 | rcu_read_unlock(); |
147 | return ret; | |
5cd9c58f DH |
148 | } |
149 | ||
1d045980 DH |
150 | /** |
151 | * cap_ptrace_traceme - Determine whether another process may trace the current | |
152 | * @parent: The task proposed to be the tracer | |
153 | * | |
8409cca7 SH |
154 | * If parent is in the same or an ancestor user_ns and has all current's |
155 | * capabilities, then ptrace access is allowed. | |
156 | * If parent has the ptrace capability to current's user_ns, then ptrace | |
157 | * access is allowed. | |
158 | * Else denied. | |
159 | * | |
1d045980 DH |
160 | * Determine whether the nominated task is permitted to trace the current |
161 | * process, returning 0 if permission is granted, -ve if denied. | |
162 | */ | |
5cd9c58f DH |
163 | int cap_ptrace_traceme(struct task_struct *parent) |
164 | { | |
c69e8d9c | 165 | int ret = 0; |
8409cca7 | 166 | const struct cred *cred, *child_cred; |
c69e8d9c DH |
167 | |
168 | rcu_read_lock(); | |
8409cca7 SH |
169 | cred = __task_cred(parent); |
170 | child_cred = current_cred(); | |
171 | if (cred->user->user_ns == child_cred->user->user_ns && | |
172 | cap_issubset(child_cred->cap_permitted, cred->cap_permitted)) | |
173 | goto out; | |
174 | if (has_ns_capability(parent, child_cred->user->user_ns, CAP_SYS_PTRACE)) | |
175 | goto out; | |
176 | ret = -EPERM; | |
177 | out: | |
c69e8d9c DH |
178 | rcu_read_unlock(); |
179 | return ret; | |
1da177e4 LT |
180 | } |
181 | ||
1d045980 DH |
182 | /** |
183 | * cap_capget - Retrieve a task's capability sets | |
184 | * @target: The task from which to retrieve the capability sets | |
185 | * @effective: The place to record the effective set | |
186 | * @inheritable: The place to record the inheritable set | |
187 | * @permitted: The place to record the permitted set | |
188 | * | |
189 | * This function retrieves the capabilities of the nominated task and returns | |
190 | * them to the caller. | |
191 | */ | |
192 | int cap_capget(struct task_struct *target, kernel_cap_t *effective, | |
193 | kernel_cap_t *inheritable, kernel_cap_t *permitted) | |
1da177e4 | 194 | { |
c69e8d9c | 195 | const struct cred *cred; |
b6dff3ec | 196 | |
1da177e4 | 197 | /* Derived from kernel/capability.c:sys_capget. */ |
c69e8d9c DH |
198 | rcu_read_lock(); |
199 | cred = __task_cred(target); | |
b6dff3ec DH |
200 | *effective = cred->cap_effective; |
201 | *inheritable = cred->cap_inheritable; | |
202 | *permitted = cred->cap_permitted; | |
c69e8d9c | 203 | rcu_read_unlock(); |
1da177e4 LT |
204 | return 0; |
205 | } | |
206 | ||
1d045980 DH |
207 | /* |
208 | * Determine whether the inheritable capabilities are limited to the old | |
209 | * permitted set. Returns 1 if they are limited, 0 if they are not. | |
210 | */ | |
72c2d582 AM |
211 | static inline int cap_inh_is_capped(void) |
212 | { | |
72c2d582 | 213 | |
1d045980 DH |
214 | /* they are so limited unless the current task has the CAP_SETPCAP |
215 | * capability | |
216 | */ | |
6a9de491 EP |
217 | if (cap_capable(current_cred(), current_cred()->user->user_ns, |
218 | CAP_SETPCAP, SECURITY_CAP_AUDIT) == 0) | |
1d045980 | 219 | return 0; |
1d045980 | 220 | return 1; |
1209726c | 221 | } |
72c2d582 | 222 | |
1d045980 DH |
223 | /** |
224 | * cap_capset - Validate and apply proposed changes to current's capabilities | |
225 | * @new: The proposed new credentials; alterations should be made here | |
226 | * @old: The current task's current credentials | |
227 | * @effective: A pointer to the proposed new effective capabilities set | |
228 | * @inheritable: A pointer to the proposed new inheritable capabilities set | |
229 | * @permitted: A pointer to the proposed new permitted capabilities set | |
230 | * | |
231 | * This function validates and applies a proposed mass change to the current | |
232 | * process's capability sets. The changes are made to the proposed new | |
233 | * credentials, and assuming no error, will be committed by the caller of LSM. | |
234 | */ | |
d84f4f99 DH |
235 | int cap_capset(struct cred *new, |
236 | const struct cred *old, | |
237 | const kernel_cap_t *effective, | |
238 | const kernel_cap_t *inheritable, | |
239 | const kernel_cap_t *permitted) | |
1da177e4 | 240 | { |
d84f4f99 DH |
241 | if (cap_inh_is_capped() && |
242 | !cap_issubset(*inheritable, | |
243 | cap_combine(old->cap_inheritable, | |
244 | old->cap_permitted))) | |
72c2d582 | 245 | /* incapable of using this inheritable set */ |
1da177e4 | 246 | return -EPERM; |
d84f4f99 | 247 | |
3b7391de | 248 | if (!cap_issubset(*inheritable, |
d84f4f99 DH |
249 | cap_combine(old->cap_inheritable, |
250 | old->cap_bset))) | |
3b7391de SH |
251 | /* no new pI capabilities outside bounding set */ |
252 | return -EPERM; | |
1da177e4 LT |
253 | |
254 | /* verify restrictions on target's new Permitted set */ | |
d84f4f99 | 255 | if (!cap_issubset(*permitted, old->cap_permitted)) |
1da177e4 | 256 | return -EPERM; |
1da177e4 LT |
257 | |
258 | /* verify the _new_Effective_ is a subset of the _new_Permitted_ */ | |
d84f4f99 | 259 | if (!cap_issubset(*effective, *permitted)) |
1da177e4 | 260 | return -EPERM; |
1da177e4 | 261 | |
d84f4f99 DH |
262 | new->cap_effective = *effective; |
263 | new->cap_inheritable = *inheritable; | |
264 | new->cap_permitted = *permitted; | |
1da177e4 LT |
265 | return 0; |
266 | } | |
267 | ||
1d045980 DH |
268 | /* |
269 | * Clear proposed capability sets for execve(). | |
270 | */ | |
b5376771 SH |
271 | static inline void bprm_clear_caps(struct linux_binprm *bprm) |
272 | { | |
a6f76f23 | 273 | cap_clear(bprm->cred->cap_permitted); |
b5376771 SH |
274 | bprm->cap_effective = false; |
275 | } | |
276 | ||
1d045980 DH |
277 | /** |
278 | * cap_inode_need_killpriv - Determine if inode change affects privileges | |
279 | * @dentry: The inode/dentry in being changed with change marked ATTR_KILL_PRIV | |
280 | * | |
281 | * Determine if an inode having a change applied that's marked ATTR_KILL_PRIV | |
282 | * affects the security markings on that inode, and if it is, should | |
283 | * inode_killpriv() be invoked or the change rejected? | |
284 | * | |
285 | * Returns 0 if granted; +ve if granted, but inode_killpriv() is required; and | |
286 | * -ve to deny the change. | |
287 | */ | |
b5376771 SH |
288 | int cap_inode_need_killpriv(struct dentry *dentry) |
289 | { | |
290 | struct inode *inode = dentry->d_inode; | |
291 | int error; | |
292 | ||
acfa4380 | 293 | if (!inode->i_op->getxattr) |
b5376771 SH |
294 | return 0; |
295 | ||
296 | error = inode->i_op->getxattr(dentry, XATTR_NAME_CAPS, NULL, 0); | |
297 | if (error <= 0) | |
298 | return 0; | |
299 | return 1; | |
300 | } | |
301 | ||
1d045980 DH |
302 | /** |
303 | * cap_inode_killpriv - Erase the security markings on an inode | |
304 | * @dentry: The inode/dentry to alter | |
305 | * | |
306 | * Erase the privilege-enhancing security markings on an inode. | |
307 | * | |
308 | * Returns 0 if successful, -ve on error. | |
309 | */ | |
b5376771 SH |
310 | int cap_inode_killpriv(struct dentry *dentry) |
311 | { | |
312 | struct inode *inode = dentry->d_inode; | |
313 | ||
acfa4380 | 314 | if (!inode->i_op->removexattr) |
b5376771 SH |
315 | return 0; |
316 | ||
317 | return inode->i_op->removexattr(dentry, XATTR_NAME_CAPS); | |
318 | } | |
319 | ||
1d045980 DH |
320 | /* |
321 | * Calculate the new process capability sets from the capability sets attached | |
322 | * to a file. | |
323 | */ | |
c0b00441 | 324 | static inline int bprm_caps_from_vfs_caps(struct cpu_vfs_cap_data *caps, |
a6f76f23 | 325 | struct linux_binprm *bprm, |
4d49f671 ZL |
326 | bool *effective, |
327 | bool *has_cap) | |
b5376771 | 328 | { |
a6f76f23 | 329 | struct cred *new = bprm->cred; |
c0b00441 EP |
330 | unsigned i; |
331 | int ret = 0; | |
332 | ||
333 | if (caps->magic_etc & VFS_CAP_FLAGS_EFFECTIVE) | |
a6f76f23 | 334 | *effective = true; |
c0b00441 | 335 | |
4d49f671 ZL |
336 | if (caps->magic_etc & VFS_CAP_REVISION_MASK) |
337 | *has_cap = true; | |
338 | ||
c0b00441 EP |
339 | CAP_FOR_EACH_U32(i) { |
340 | __u32 permitted = caps->permitted.cap[i]; | |
341 | __u32 inheritable = caps->inheritable.cap[i]; | |
342 | ||
343 | /* | |
344 | * pP' = (X & fP) | (pI & fI) | |
345 | */ | |
a6f76f23 DH |
346 | new->cap_permitted.cap[i] = |
347 | (new->cap_bset.cap[i] & permitted) | | |
348 | (new->cap_inheritable.cap[i] & inheritable); | |
c0b00441 | 349 | |
a6f76f23 DH |
350 | if (permitted & ~new->cap_permitted.cap[i]) |
351 | /* insufficient to execute correctly */ | |
c0b00441 | 352 | ret = -EPERM; |
c0b00441 EP |
353 | } |
354 | ||
355 | /* | |
356 | * For legacy apps, with no internal support for recognizing they | |
357 | * do not have enough capabilities, we return an error if they are | |
358 | * missing some "forced" (aka file-permitted) capabilities. | |
359 | */ | |
a6f76f23 | 360 | return *effective ? ret : 0; |
c0b00441 EP |
361 | } |
362 | ||
1d045980 DH |
363 | /* |
364 | * Extract the on-exec-apply capability sets for an executable file. | |
365 | */ | |
c0b00441 EP |
366 | int get_vfs_caps_from_disk(const struct dentry *dentry, struct cpu_vfs_cap_data *cpu_caps) |
367 | { | |
368 | struct inode *inode = dentry->d_inode; | |
b5376771 | 369 | __u32 magic_etc; |
e338d263 | 370 | unsigned tocopy, i; |
c0b00441 EP |
371 | int size; |
372 | struct vfs_cap_data caps; | |
373 | ||
374 | memset(cpu_caps, 0, sizeof(struct cpu_vfs_cap_data)); | |
375 | ||
acfa4380 | 376 | if (!inode || !inode->i_op->getxattr) |
c0b00441 EP |
377 | return -ENODATA; |
378 | ||
379 | size = inode->i_op->getxattr((struct dentry *)dentry, XATTR_NAME_CAPS, &caps, | |
380 | XATTR_CAPS_SZ); | |
a6f76f23 | 381 | if (size == -ENODATA || size == -EOPNOTSUPP) |
c0b00441 EP |
382 | /* no data, that's ok */ |
383 | return -ENODATA; | |
c0b00441 EP |
384 | if (size < 0) |
385 | return size; | |
b5376771 | 386 | |
e338d263 | 387 | if (size < sizeof(magic_etc)) |
b5376771 SH |
388 | return -EINVAL; |
389 | ||
c0b00441 | 390 | cpu_caps->magic_etc = magic_etc = le32_to_cpu(caps.magic_etc); |
b5376771 | 391 | |
a6f76f23 | 392 | switch (magic_etc & VFS_CAP_REVISION_MASK) { |
e338d263 AM |
393 | case VFS_CAP_REVISION_1: |
394 | if (size != XATTR_CAPS_SZ_1) | |
395 | return -EINVAL; | |
396 | tocopy = VFS_CAP_U32_1; | |
397 | break; | |
398 | case VFS_CAP_REVISION_2: | |
399 | if (size != XATTR_CAPS_SZ_2) | |
400 | return -EINVAL; | |
401 | tocopy = VFS_CAP_U32_2; | |
402 | break; | |
b5376771 SH |
403 | default: |
404 | return -EINVAL; | |
405 | } | |
e338d263 | 406 | |
5459c164 | 407 | CAP_FOR_EACH_U32(i) { |
c0b00441 EP |
408 | if (i >= tocopy) |
409 | break; | |
410 | cpu_caps->permitted.cap[i] = le32_to_cpu(caps.data[i].permitted); | |
411 | cpu_caps->inheritable.cap[i] = le32_to_cpu(caps.data[i].inheritable); | |
e338d263 | 412 | } |
a6f76f23 | 413 | |
c0b00441 | 414 | return 0; |
b5376771 SH |
415 | } |
416 | ||
1d045980 DH |
417 | /* |
418 | * Attempt to get the on-exec apply capability sets for an executable file from | |
419 | * its xattrs and, if present, apply them to the proposed credentials being | |
420 | * constructed by execve(). | |
421 | */ | |
4d49f671 | 422 | static int get_file_caps(struct linux_binprm *bprm, bool *effective, bool *has_cap) |
b5376771 SH |
423 | { |
424 | struct dentry *dentry; | |
425 | int rc = 0; | |
c0b00441 | 426 | struct cpu_vfs_cap_data vcaps; |
b5376771 | 427 | |
3318a386 SH |
428 | bprm_clear_caps(bprm); |
429 | ||
1f29fae2 SH |
430 | if (!file_caps_enabled) |
431 | return 0; | |
432 | ||
3318a386 | 433 | if (bprm->file->f_vfsmnt->mnt_flags & MNT_NOSUID) |
b5376771 | 434 | return 0; |
b5376771 SH |
435 | |
436 | dentry = dget(bprm->file->f_dentry); | |
b5376771 | 437 | |
c0b00441 EP |
438 | rc = get_vfs_caps_from_disk(dentry, &vcaps); |
439 | if (rc < 0) { | |
440 | if (rc == -EINVAL) | |
441 | printk(KERN_NOTICE "%s: get_vfs_caps_from_disk returned %d for %s\n", | |
442 | __func__, rc, bprm->filename); | |
443 | else if (rc == -ENODATA) | |
444 | rc = 0; | |
b5376771 SH |
445 | goto out; |
446 | } | |
b5376771 | 447 | |
4d49f671 | 448 | rc = bprm_caps_from_vfs_caps(&vcaps, bprm, effective, has_cap); |
a6f76f23 DH |
449 | if (rc == -EINVAL) |
450 | printk(KERN_NOTICE "%s: cap_from_disk returned %d for %s\n", | |
451 | __func__, rc, bprm->filename); | |
b5376771 SH |
452 | |
453 | out: | |
454 | dput(dentry); | |
455 | if (rc) | |
456 | bprm_clear_caps(bprm); | |
457 | ||
458 | return rc; | |
459 | } | |
460 | ||
1d045980 DH |
461 | /** |
462 | * cap_bprm_set_creds - Set up the proposed credentials for execve(). | |
463 | * @bprm: The execution parameters, including the proposed creds | |
464 | * | |
465 | * Set up the proposed credentials for a new execution context being | |
466 | * constructed by execve(). The proposed creds in @bprm->cred is altered, | |
467 | * which won't take effect immediately. Returns 0 if successful, -ve on error. | |
a6f76f23 DH |
468 | */ |
469 | int cap_bprm_set_creds(struct linux_binprm *bprm) | |
1da177e4 | 470 | { |
a6f76f23 DH |
471 | const struct cred *old = current_cred(); |
472 | struct cred *new = bprm->cred; | |
7d8db180 | 473 | bool effective, has_cap = false; |
b5376771 | 474 | int ret; |
1da177e4 | 475 | |
a6f76f23 | 476 | effective = false; |
4d49f671 | 477 | ret = get_file_caps(bprm, &effective, &has_cap); |
a6f76f23 DH |
478 | if (ret < 0) |
479 | return ret; | |
1da177e4 | 480 | |
5459c164 | 481 | if (!issecure(SECURE_NOROOT)) { |
b5f22a59 SH |
482 | /* |
483 | * If the legacy file capability is set, then don't set privs | |
484 | * for a setuid root binary run by a non-root user. Do set it | |
485 | * for a root user just to cause least surprise to an admin. | |
486 | */ | |
4d49f671 | 487 | if (has_cap && new->uid != 0 && new->euid == 0) { |
b5f22a59 SH |
488 | warn_setuid_and_fcaps_mixed(bprm->filename); |
489 | goto skip; | |
490 | } | |
5459c164 AM |
491 | /* |
492 | * To support inheritance of root-permissions and suid-root | |
493 | * executables under compatibility mode, we override the | |
494 | * capability sets for the file. | |
495 | * | |
a6f76f23 | 496 | * If only the real uid is 0, we do not set the effective bit. |
5459c164 | 497 | */ |
a6f76f23 | 498 | if (new->euid == 0 || new->uid == 0) { |
5459c164 | 499 | /* pP' = (cap_bset & ~0) | (pI & ~0) */ |
a6f76f23 DH |
500 | new->cap_permitted = cap_combine(old->cap_bset, |
501 | old->cap_inheritable); | |
1da177e4 | 502 | } |
a6f76f23 DH |
503 | if (new->euid == 0) |
504 | effective = true; | |
1da177e4 | 505 | } |
b5f22a59 | 506 | skip: |
b5376771 | 507 | |
d52fc5dd EP |
508 | /* if we have fs caps, clear dangerous personality flags */ |
509 | if (!cap_issubset(new->cap_permitted, old->cap_permitted)) | |
510 | bprm->per_clear |= PER_CLEAR_ON_SETID; | |
511 | ||
512 | ||
a6f76f23 DH |
513 | /* Don't let someone trace a set[ug]id/setpcap binary with the revised |
514 | * credentials unless they have the appropriate permit | |
515 | */ | |
516 | if ((new->euid != old->uid || | |
517 | new->egid != old->gid || | |
518 | !cap_issubset(new->cap_permitted, old->cap_permitted)) && | |
519 | bprm->unsafe & ~LSM_UNSAFE_PTRACE_CAP) { | |
520 | /* downgrade; they get no more than they had, and maybe less */ | |
521 | if (!capable(CAP_SETUID)) { | |
522 | new->euid = new->uid; | |
523 | new->egid = new->gid; | |
1da177e4 | 524 | } |
b3a222e5 SH |
525 | new->cap_permitted = cap_intersect(new->cap_permitted, |
526 | old->cap_permitted); | |
1da177e4 LT |
527 | } |
528 | ||
a6f76f23 DH |
529 | new->suid = new->fsuid = new->euid; |
530 | new->sgid = new->fsgid = new->egid; | |
1da177e4 | 531 | |
4bf2ea77 EP |
532 | if (effective) |
533 | new->cap_effective = new->cap_permitted; | |
534 | else | |
535 | cap_clear(new->cap_effective); | |
a6f76f23 | 536 | bprm->cap_effective = effective; |
1da177e4 | 537 | |
3fc689e9 EP |
538 | /* |
539 | * Audit candidate if current->cap_effective is set | |
540 | * | |
541 | * We do not bother to audit if 3 things are true: | |
542 | * 1) cap_effective has all caps | |
543 | * 2) we are root | |
544 | * 3) root is supposed to have all caps (SECURE_NOROOT) | |
545 | * Since this is just a normal root execing a process. | |
546 | * | |
547 | * Number 1 above might fail if you don't have a full bset, but I think | |
548 | * that is interesting information to audit. | |
549 | */ | |
d84f4f99 DH |
550 | if (!cap_isclear(new->cap_effective)) { |
551 | if (!cap_issubset(CAP_FULL_SET, new->cap_effective) || | |
a6f76f23 DH |
552 | new->euid != 0 || new->uid != 0 || |
553 | issecure(SECURE_NOROOT)) { | |
554 | ret = audit_log_bprm_fcaps(bprm, new, old); | |
555 | if (ret < 0) | |
556 | return ret; | |
557 | } | |
3fc689e9 | 558 | } |
1da177e4 | 559 | |
d84f4f99 | 560 | new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS); |
a6f76f23 | 561 | return 0; |
1da177e4 LT |
562 | } |
563 | ||
1d045980 DH |
564 | /** |
565 | * cap_bprm_secureexec - Determine whether a secure execution is required | |
566 | * @bprm: The execution parameters | |
567 | * | |
568 | * Determine whether a secure execution is required, return 1 if it is, and 0 | |
569 | * if it is not. | |
570 | * | |
571 | * The credentials have been committed by this point, and so are no longer | |
572 | * available through @bprm->cred. | |
a6f76f23 DH |
573 | */ |
574 | int cap_bprm_secureexec(struct linux_binprm *bprm) | |
1da177e4 | 575 | { |
c69e8d9c | 576 | const struct cred *cred = current_cred(); |
b6dff3ec DH |
577 | |
578 | if (cred->uid != 0) { | |
b5376771 SH |
579 | if (bprm->cap_effective) |
580 | return 1; | |
a6f76f23 | 581 | if (!cap_isclear(cred->cap_permitted)) |
b5376771 SH |
582 | return 1; |
583 | } | |
584 | ||
b6dff3ec DH |
585 | return (cred->euid != cred->uid || |
586 | cred->egid != cred->gid); | |
1da177e4 LT |
587 | } |
588 | ||
1d045980 DH |
589 | /** |
590 | * cap_inode_setxattr - Determine whether an xattr may be altered | |
591 | * @dentry: The inode/dentry being altered | |
592 | * @name: The name of the xattr to be changed | |
593 | * @value: The value that the xattr will be changed to | |
594 | * @size: The size of value | |
595 | * @flags: The replacement flag | |
596 | * | |
597 | * Determine whether an xattr may be altered or set on an inode, returning 0 if | |
598 | * permission is granted, -ve if denied. | |
599 | * | |
600 | * This is used to make sure security xattrs don't get updated or set by those | |
601 | * who aren't privileged to do so. | |
602 | */ | |
8f0cfa52 DH |
603 | int cap_inode_setxattr(struct dentry *dentry, const char *name, |
604 | const void *value, size_t size, int flags) | |
1da177e4 | 605 | { |
b5376771 SH |
606 | if (!strcmp(name, XATTR_NAME_CAPS)) { |
607 | if (!capable(CAP_SETFCAP)) | |
608 | return -EPERM; | |
609 | return 0; | |
1d045980 DH |
610 | } |
611 | ||
612 | if (!strncmp(name, XATTR_SECURITY_PREFIX, | |
c5b60b5e | 613 | sizeof(XATTR_SECURITY_PREFIX) - 1) && |
1da177e4 LT |
614 | !capable(CAP_SYS_ADMIN)) |
615 | return -EPERM; | |
616 | return 0; | |
617 | } | |
618 | ||
1d045980 DH |
619 | /** |
620 | * cap_inode_removexattr - Determine whether an xattr may be removed | |
621 | * @dentry: The inode/dentry being altered | |
622 | * @name: The name of the xattr to be changed | |
623 | * | |
624 | * Determine whether an xattr may be removed from an inode, returning 0 if | |
625 | * permission is granted, -ve if denied. | |
626 | * | |
627 | * This is used to make sure security xattrs don't get removed by those who | |
628 | * aren't privileged to remove them. | |
629 | */ | |
8f0cfa52 | 630 | int cap_inode_removexattr(struct dentry *dentry, const char *name) |
1da177e4 | 631 | { |
b5376771 SH |
632 | if (!strcmp(name, XATTR_NAME_CAPS)) { |
633 | if (!capable(CAP_SETFCAP)) | |
634 | return -EPERM; | |
635 | return 0; | |
1d045980 DH |
636 | } |
637 | ||
638 | if (!strncmp(name, XATTR_SECURITY_PREFIX, | |
c5b60b5e | 639 | sizeof(XATTR_SECURITY_PREFIX) - 1) && |
1da177e4 LT |
640 | !capable(CAP_SYS_ADMIN)) |
641 | return -EPERM; | |
642 | return 0; | |
643 | } | |
644 | ||
a6f76f23 | 645 | /* |
1da177e4 LT |
646 | * cap_emulate_setxuid() fixes the effective / permitted capabilities of |
647 | * a process after a call to setuid, setreuid, or setresuid. | |
648 | * | |
649 | * 1) When set*uiding _from_ one of {r,e,s}uid == 0 _to_ all of | |
650 | * {r,e,s}uid != 0, the permitted and effective capabilities are | |
651 | * cleared. | |
652 | * | |
653 | * 2) When set*uiding _from_ euid == 0 _to_ euid != 0, the effective | |
654 | * capabilities of the process are cleared. | |
655 | * | |
656 | * 3) When set*uiding _from_ euid != 0 _to_ euid == 0, the effective | |
657 | * capabilities are set to the permitted capabilities. | |
658 | * | |
a6f76f23 | 659 | * fsuid is handled elsewhere. fsuid == 0 and {r,e,s}uid!= 0 should |
1da177e4 LT |
660 | * never happen. |
661 | * | |
a6f76f23 | 662 | * -astor |
1da177e4 LT |
663 | * |
664 | * cevans - New behaviour, Oct '99 | |
665 | * A process may, via prctl(), elect to keep its capabilities when it | |
666 | * calls setuid() and switches away from uid==0. Both permitted and | |
667 | * effective sets will be retained. | |
668 | * Without this change, it was impossible for a daemon to drop only some | |
669 | * of its privilege. The call to setuid(!=0) would drop all privileges! | |
670 | * Keeping uid 0 is not an option because uid 0 owns too many vital | |
671 | * files.. | |
672 | * Thanks to Olaf Kirch and Peter Benie for spotting this. | |
673 | */ | |
d84f4f99 | 674 | static inline void cap_emulate_setxuid(struct cred *new, const struct cred *old) |
1da177e4 | 675 | { |
d84f4f99 DH |
676 | if ((old->uid == 0 || old->euid == 0 || old->suid == 0) && |
677 | (new->uid != 0 && new->euid != 0 && new->suid != 0) && | |
3898b1b4 | 678 | !issecure(SECURE_KEEP_CAPS)) { |
d84f4f99 DH |
679 | cap_clear(new->cap_permitted); |
680 | cap_clear(new->cap_effective); | |
1da177e4 | 681 | } |
d84f4f99 DH |
682 | if (old->euid == 0 && new->euid != 0) |
683 | cap_clear(new->cap_effective); | |
684 | if (old->euid != 0 && new->euid == 0) | |
685 | new->cap_effective = new->cap_permitted; | |
1da177e4 LT |
686 | } |
687 | ||
1d045980 DH |
688 | /** |
689 | * cap_task_fix_setuid - Fix up the results of setuid() call | |
690 | * @new: The proposed credentials | |
691 | * @old: The current task's current credentials | |
692 | * @flags: Indications of what has changed | |
693 | * | |
694 | * Fix up the results of setuid() call before the credential changes are | |
695 | * actually applied, returning 0 to grant the changes, -ve to deny them. | |
696 | */ | |
d84f4f99 | 697 | int cap_task_fix_setuid(struct cred *new, const struct cred *old, int flags) |
1da177e4 LT |
698 | { |
699 | switch (flags) { | |
700 | case LSM_SETID_RE: | |
701 | case LSM_SETID_ID: | |
702 | case LSM_SETID_RES: | |
1d045980 DH |
703 | /* juggle the capabilities to follow [RES]UID changes unless |
704 | * otherwise suppressed */ | |
d84f4f99 DH |
705 | if (!issecure(SECURE_NO_SETUID_FIXUP)) |
706 | cap_emulate_setxuid(new, old); | |
1da177e4 | 707 | break; |
1da177e4 | 708 | |
1d045980 DH |
709 | case LSM_SETID_FS: |
710 | /* juggle the capabilties to follow FSUID changes, unless | |
711 | * otherwise suppressed | |
712 | * | |
d84f4f99 DH |
713 | * FIXME - is fsuser used for all CAP_FS_MASK capabilities? |
714 | * if not, we might be a bit too harsh here. | |
715 | */ | |
716 | if (!issecure(SECURE_NO_SETUID_FIXUP)) { | |
1d045980 | 717 | if (old->fsuid == 0 && new->fsuid != 0) |
d84f4f99 DH |
718 | new->cap_effective = |
719 | cap_drop_fs_set(new->cap_effective); | |
1d045980 DH |
720 | |
721 | if (old->fsuid != 0 && new->fsuid == 0) | |
d84f4f99 DH |
722 | new->cap_effective = |
723 | cap_raise_fs_set(new->cap_effective, | |
724 | new->cap_permitted); | |
1da177e4 | 725 | } |
d84f4f99 | 726 | break; |
1d045980 | 727 | |
1da177e4 LT |
728 | default: |
729 | return -EINVAL; | |
730 | } | |
731 | ||
732 | return 0; | |
733 | } | |
734 | ||
b5376771 SH |
735 | /* |
736 | * Rationale: code calling task_setscheduler, task_setioprio, and | |
737 | * task_setnice, assumes that | |
738 | * . if capable(cap_sys_nice), then those actions should be allowed | |
739 | * . if not capable(cap_sys_nice), but acting on your own processes, | |
740 | * then those actions should be allowed | |
741 | * This is insufficient now since you can call code without suid, but | |
742 | * yet with increased caps. | |
743 | * So we check for increased caps on the target process. | |
744 | */ | |
de45e806 | 745 | static int cap_safe_nice(struct task_struct *p) |
b5376771 | 746 | { |
c69e8d9c DH |
747 | int is_subset; |
748 | ||
749 | rcu_read_lock(); | |
750 | is_subset = cap_issubset(__task_cred(p)->cap_permitted, | |
751 | current_cred()->cap_permitted); | |
752 | rcu_read_unlock(); | |
753 | ||
754 | if (!is_subset && !capable(CAP_SYS_NICE)) | |
b5376771 SH |
755 | return -EPERM; |
756 | return 0; | |
757 | } | |
758 | ||
1d045980 DH |
759 | /** |
760 | * cap_task_setscheduler - Detemine if scheduler policy change is permitted | |
761 | * @p: The task to affect | |
1d045980 DH |
762 | * |
763 | * Detemine if the requested scheduler policy change is permitted for the | |
764 | * specified task, returning 0 if permission is granted, -ve if denied. | |
765 | */ | |
b0ae1981 | 766 | int cap_task_setscheduler(struct task_struct *p) |
b5376771 SH |
767 | { |
768 | return cap_safe_nice(p); | |
769 | } | |
770 | ||
1d045980 DH |
771 | /** |
772 | * cap_task_ioprio - Detemine if I/O priority change is permitted | |
773 | * @p: The task to affect | |
774 | * @ioprio: The I/O priority to set | |
775 | * | |
776 | * Detemine if the requested I/O priority change is permitted for the specified | |
777 | * task, returning 0 if permission is granted, -ve if denied. | |
778 | */ | |
779 | int cap_task_setioprio(struct task_struct *p, int ioprio) | |
b5376771 SH |
780 | { |
781 | return cap_safe_nice(p); | |
782 | } | |
783 | ||
1d045980 DH |
784 | /** |
785 | * cap_task_ioprio - Detemine if task priority change is permitted | |
786 | * @p: The task to affect | |
787 | * @nice: The nice value to set | |
788 | * | |
789 | * Detemine if the requested task priority change is permitted for the | |
790 | * specified task, returning 0 if permission is granted, -ve if denied. | |
791 | */ | |
792 | int cap_task_setnice(struct task_struct *p, int nice) | |
b5376771 SH |
793 | { |
794 | return cap_safe_nice(p); | |
795 | } | |
796 | ||
3b7391de | 797 | /* |
1d045980 DH |
798 | * Implement PR_CAPBSET_DROP. Attempt to remove the specified capability from |
799 | * the current task's bounding set. Returns 0 on success, -ve on error. | |
3b7391de | 800 | */ |
d84f4f99 | 801 | static long cap_prctl_drop(struct cred *new, unsigned long cap) |
3b7391de SH |
802 | { |
803 | if (!capable(CAP_SETPCAP)) | |
804 | return -EPERM; | |
805 | if (!cap_valid(cap)) | |
806 | return -EINVAL; | |
d84f4f99 DH |
807 | |
808 | cap_lower(new->cap_bset, cap); | |
3b7391de SH |
809 | return 0; |
810 | } | |
3898b1b4 | 811 | |
1d045980 DH |
812 | /** |
813 | * cap_task_prctl - Implement process control functions for this security module | |
814 | * @option: The process control function requested | |
815 | * @arg2, @arg3, @arg4, @arg5: The argument data for this function | |
816 | * | |
817 | * Allow process control functions (sys_prctl()) to alter capabilities; may | |
818 | * also deny access to other functions not otherwise implemented here. | |
819 | * | |
820 | * Returns 0 or +ve on success, -ENOSYS if this function is not implemented | |
821 | * here, other -ve on error. If -ENOSYS is returned, sys_prctl() and other LSM | |
822 | * modules will consider performing the function. | |
823 | */ | |
3898b1b4 | 824 | int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3, |
d84f4f99 | 825 | unsigned long arg4, unsigned long arg5) |
3898b1b4 | 826 | { |
d84f4f99 | 827 | struct cred *new; |
3898b1b4 AM |
828 | long error = 0; |
829 | ||
d84f4f99 DH |
830 | new = prepare_creds(); |
831 | if (!new) | |
832 | return -ENOMEM; | |
833 | ||
3898b1b4 AM |
834 | switch (option) { |
835 | case PR_CAPBSET_READ: | |
d84f4f99 | 836 | error = -EINVAL; |
3898b1b4 | 837 | if (!cap_valid(arg2)) |
d84f4f99 DH |
838 | goto error; |
839 | error = !!cap_raised(new->cap_bset, arg2); | |
840 | goto no_change; | |
841 | ||
3898b1b4 | 842 | case PR_CAPBSET_DROP: |
d84f4f99 DH |
843 | error = cap_prctl_drop(new, arg2); |
844 | if (error < 0) | |
845 | goto error; | |
846 | goto changed; | |
3898b1b4 AM |
847 | |
848 | /* | |
849 | * The next four prctl's remain to assist with transitioning a | |
850 | * system from legacy UID=0 based privilege (when filesystem | |
851 | * capabilities are not in use) to a system using filesystem | |
852 | * capabilities only - as the POSIX.1e draft intended. | |
853 | * | |
854 | * Note: | |
855 | * | |
856 | * PR_SET_SECUREBITS = | |
857 | * issecure_mask(SECURE_KEEP_CAPS_LOCKED) | |
858 | * | issecure_mask(SECURE_NOROOT) | |
859 | * | issecure_mask(SECURE_NOROOT_LOCKED) | |
860 | * | issecure_mask(SECURE_NO_SETUID_FIXUP) | |
861 | * | issecure_mask(SECURE_NO_SETUID_FIXUP_LOCKED) | |
862 | * | |
863 | * will ensure that the current process and all of its | |
864 | * children will be locked into a pure | |
865 | * capability-based-privilege environment. | |
866 | */ | |
867 | case PR_SET_SECUREBITS: | |
d84f4f99 DH |
868 | error = -EPERM; |
869 | if ((((new->securebits & SECURE_ALL_LOCKS) >> 1) | |
870 | & (new->securebits ^ arg2)) /*[1]*/ | |
871 | || ((new->securebits & SECURE_ALL_LOCKS & ~arg2)) /*[2]*/ | |
872 | || (arg2 & ~(SECURE_ALL_LOCKS | SECURE_ALL_BITS)) /*[3]*/ | |
6a9de491 | 873 | || (cap_capable(current_cred(), |
3486740a | 874 | current_cred()->user->user_ns, CAP_SETPCAP, |
3699c53c | 875 | SECURITY_CAP_AUDIT) != 0) /*[4]*/ |
3898b1b4 AM |
876 | /* |
877 | * [1] no changing of bits that are locked | |
878 | * [2] no unlocking of locks | |
879 | * [3] no setting of unsupported bits | |
880 | * [4] doing anything requires privilege (go read about | |
881 | * the "sendmail capabilities bug") | |
882 | */ | |
d84f4f99 DH |
883 | ) |
884 | /* cannot change a locked bit */ | |
885 | goto error; | |
886 | new->securebits = arg2; | |
887 | goto changed; | |
888 | ||
3898b1b4 | 889 | case PR_GET_SECUREBITS: |
d84f4f99 DH |
890 | error = new->securebits; |
891 | goto no_change; | |
3898b1b4 | 892 | |
3898b1b4 AM |
893 | case PR_GET_KEEPCAPS: |
894 | if (issecure(SECURE_KEEP_CAPS)) | |
895 | error = 1; | |
d84f4f99 DH |
896 | goto no_change; |
897 | ||
3898b1b4 | 898 | case PR_SET_KEEPCAPS: |
d84f4f99 | 899 | error = -EINVAL; |
3898b1b4 | 900 | if (arg2 > 1) /* Note, we rely on arg2 being unsigned here */ |
d84f4f99 DH |
901 | goto error; |
902 | error = -EPERM; | |
903 | if (issecure(SECURE_KEEP_CAPS_LOCKED)) | |
904 | goto error; | |
905 | if (arg2) | |
906 | new->securebits |= issecure_mask(SECURE_KEEP_CAPS); | |
3898b1b4 | 907 | else |
d84f4f99 DH |
908 | new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS); |
909 | goto changed; | |
3898b1b4 AM |
910 | |
911 | default: | |
912 | /* No functionality available - continue with default */ | |
d84f4f99 DH |
913 | error = -ENOSYS; |
914 | goto error; | |
3898b1b4 AM |
915 | } |
916 | ||
917 | /* Functionality provided */ | |
d84f4f99 DH |
918 | changed: |
919 | return commit_creds(new); | |
920 | ||
921 | no_change: | |
d84f4f99 DH |
922 | error: |
923 | abort_creds(new); | |
924 | return error; | |
1da177e4 LT |
925 | } |
926 | ||
1d045980 DH |
927 | /** |
928 | * cap_vm_enough_memory - Determine whether a new virtual mapping is permitted | |
929 | * @mm: The VM space in which the new mapping is to be made | |
930 | * @pages: The size of the mapping | |
931 | * | |
932 | * Determine whether the allocation of a new virtual mapping by the current | |
933 | * task is permitted, returning 0 if permission is granted, -ve if not. | |
934 | */ | |
34b4e4aa | 935 | int cap_vm_enough_memory(struct mm_struct *mm, long pages) |
1da177e4 LT |
936 | { |
937 | int cap_sys_admin = 0; | |
938 | ||
6a9de491 | 939 | if (cap_capable(current_cred(), &init_user_ns, CAP_SYS_ADMIN, |
3699c53c | 940 | SECURITY_CAP_NOAUDIT) == 0) |
1da177e4 | 941 | cap_sys_admin = 1; |
34b4e4aa | 942 | return __vm_enough_memory(mm, pages, cap_sys_admin); |
1da177e4 | 943 | } |
7c73875e EP |
944 | |
945 | /* | |
946 | * cap_file_mmap - check if able to map given addr | |
947 | * @file: unused | |
948 | * @reqprot: unused | |
949 | * @prot: unused | |
950 | * @flags: unused | |
951 | * @addr: address attempting to be mapped | |
952 | * @addr_only: unused | |
953 | * | |
6f262d8e | 954 | * If the process is attempting to map memory below dac_mmap_min_addr they need |
7c73875e EP |
955 | * CAP_SYS_RAWIO. The other parameters to this function are unused by the |
956 | * capability security module. Returns 0 if this mapping should be allowed | |
957 | * -EPERM if not. | |
958 | */ | |
959 | int cap_file_mmap(struct file *file, unsigned long reqprot, | |
960 | unsigned long prot, unsigned long flags, | |
961 | unsigned long addr, unsigned long addr_only) | |
962 | { | |
963 | int ret = 0; | |
964 | ||
a2551df7 | 965 | if (addr < dac_mmap_min_addr) { |
6a9de491 | 966 | ret = cap_capable(current_cred(), &init_user_ns, CAP_SYS_RAWIO, |
7c73875e EP |
967 | SECURITY_CAP_AUDIT); |
968 | /* set PF_SUPERPRIV if it turns out we allow the low mmap */ | |
969 | if (ret == 0) | |
970 | current->flags |= PF_SUPERPRIV; | |
971 | } | |
972 | return ret; | |
973 | } |