blob: 09479f71ee2eda7da05fce5d0554a3fef9370238 [file] [log] [blame]
Thomas Gleixner2874c5f2019-05-27 08:55:01 +02001// SPDX-License-Identifier: GPL-2.0-or-later
James Morris3e1c2512009-10-20 13:48:33 +09002/* Common capabilities, needed by capability.o.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003 */
4
Randy.Dunlapc59ede72006-01-11 12:17:46 -08005#include <linux/capability.h>
Eric Paris3fc689e2008-11-11 21:48:18 +11006#include <linux/audit.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -07007#include <linux/init.h>
8#include <linux/kernel.h>
Casey Schauflerb1d9e6b2015-05-02 15:11:42 -07009#include <linux/lsm_hooks.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070010#include <linux/file.h>
11#include <linux/mm.h>
12#include <linux/mman.h>
13#include <linux/pagemap.h>
14#include <linux/swap.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070015#include <linux/skbuff.h>
16#include <linux/netlink.h>
17#include <linux/ptrace.h>
18#include <linux/xattr.h>
19#include <linux/hugetlb.h>
Serge E. Hallynb5376772007-10-16 23:31:36 -070020#include <linux/mount.h>
Serge E. Hallynb460cbc2007-10-18 23:39:52 -070021#include <linux/sched.h>
Andrew G. Morgan3898b1b2008-04-28 02:13:40 -070022#include <linux/prctl.h>
23#include <linux/securebits.h>
Serge E. Hallyn34867402011-03-23 16:43:17 -070024#include <linux/user_namespace.h>
Al Viro40401532012-02-13 03:58:52 +000025#include <linux/binfmts.h>
Jonghwan Choi51b79be2012-04-18 17:23:04 -040026#include <linux/personality.h>
Christian Brauner7bc23ab2022-06-28 14:16:10 +020027#include <linux/mnt_idmapping.h>
Andrew Morgan72c2d582007-10-18 03:05:59 -070028
Serge E. Hallynb5f22a52009-04-02 18:47:14 -050029/*
30 * If a non-root user executes a setuid-root binary in
31 * !secure(SECURE_NOROOT) mode, then we raise capabilities.
32 * However if fE is also set, then the intent is for only
33 * the file capabilities to be applied, and the setuid-root
34 * bit is left on either to change the uid (plausible) or
35 * to get full privilege on a kernel without file capabilities
36 * support. So in that case we do not raise capabilities.
37 *
38 * Warn if that happens, once per boot.
39 */
David Howellsd7627462010-08-17 23:52:56 +010040static void warn_setuid_and_fcaps_mixed(const char *fname)
Serge E. Hallynb5f22a52009-04-02 18:47:14 -050041{
42 static int warned;
43 if (!warned) {
44 printk(KERN_INFO "warning: `%s' has both setuid-root and"
45 " effective capabilities. Therefore not raising all"
46 " capabilities.\n", fname);
47 warned = 1;
48 }
49}
50
David Howells1d045982008-11-14 10:39:24 +110051/**
52 * cap_capable - Determine whether a task has a particular effective capability
David Howells3699c532009-01-06 22:27:01 +000053 * @cred: The credentials to use
Randy Dunlap049ae602021-04-11 17:55:28 -070054 * @targ_ns: The user namespace in which we need the capability
David Howells1d045982008-11-14 10:39:24 +110055 * @cap: The capability to check for
Micah Mortone88ed482019-02-25 14:17:10 -080056 * @opts: Bitmask of options defined in include/linux/security.h
David Howells1d045982008-11-14 10:39:24 +110057 *
58 * Determine whether the nominated task has the specified capability amongst
59 * its effective set, returning 0 if it does, -ve if it does not.
60 *
David Howells3699c532009-01-06 22:27:01 +000061 * NOTE WELL: cap_has_capability() cannot be used like the kernel's capable()
62 * and has_capability() functions. That is, it has the reverse semantics:
63 * cap_has_capability() returns 0 when a task has a capability, but the
64 * kernel's capable() and has_capability() returns 1 for this case.
Andrew G. Morgana6dbb1e2008-01-21 17:18:30 -080065 */
Eric Paris6a9de492012-01-03 12:25:14 -050066int cap_capable(const struct cred *cred, struct user_namespace *targ_ns,
Micah Mortonc1a85a02019-01-07 16:10:53 -080067 int cap, unsigned int opts)
Linus Torvalds1da177e2005-04-16 15:20:36 -070068{
Eric W. Biederman520d9ea2012-12-13 18:06:40 -080069 struct user_namespace *ns = targ_ns;
Serge E. Hallyn34867402011-03-23 16:43:17 -070070
Eric W. Biederman520d9ea2012-12-13 18:06:40 -080071 /* See if cred has the capability in the target user namespace
72 * by examining the target user namespace and all of the target
73 * user namespace's parents.
74 */
75 for (;;) {
Serge E. Hallyn34867402011-03-23 16:43:17 -070076 /* Do we have the necessary capabilities? */
Eric W. Biederman520d9ea2012-12-13 18:06:40 -080077 if (ns == cred->user_ns)
Serge E. Hallyn34867402011-03-23 16:43:17 -070078 return cap_raised(cred->cap_effective, cap) ? 0 : -EPERM;
79
Kirill Tkhai64db4c72017-05-02 20:11:52 +030080 /*
81 * If we're already at a lower level than we're looking for,
82 * we're done searching.
83 */
84 if (ns->level <= cred->user_ns->level)
Serge E. Hallyn34867402011-03-23 16:43:17 -070085 return -EPERM;
86
Eric W. Biederman520d9ea2012-12-13 18:06:40 -080087 /*
88 * The owner of the user namespace in the parent of the
89 * user namespace has all caps.
90 */
91 if ((ns->parent == cred->user_ns) && uid_eq(ns->owner, cred->euid))
92 return 0;
93
Serge E. Hallyn34867402011-03-23 16:43:17 -070094 /*
Eric W. Biederman520d9ea2012-12-13 18:06:40 -080095 * If you have a capability in a parent user ns, then you have
Serge E. Hallyn34867402011-03-23 16:43:17 -070096 * it over all children user namespaces as well.
97 */
Eric W. Biederman520d9ea2012-12-13 18:06:40 -080098 ns = ns->parent;
Serge E. Hallyn34867402011-03-23 16:43:17 -070099 }
100
101 /* We never get here */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700102}
103
David Howells1d045982008-11-14 10:39:24 +1100104/**
105 * cap_settime - Determine whether the current process may set the system clock
106 * @ts: The time to set
107 * @tz: The timezone to set
108 *
109 * Determine whether the current process may set the system clock and timezone
110 * information, returning 0 if permission granted, -ve if denied.
111 */
Baolin Wang457db292016-04-08 14:02:11 +0800112int cap_settime(const struct timespec64 *ts, const struct timezone *tz)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700113{
114 if (!capable(CAP_SYS_TIME))
115 return -EPERM;
116 return 0;
117}
118
David Howells1d045982008-11-14 10:39:24 +1100119/**
Ingo Molnar9e488582009-05-07 19:26:19 +1000120 * cap_ptrace_access_check - Determine whether the current process may access
David Howells1d045982008-11-14 10:39:24 +1100121 * another
122 * @child: The process to be accessed
123 * @mode: The mode of attachment.
124 *
Serge E. Hallyn8409cca2011-03-23 16:43:20 -0700125 * If we are in the same or an ancestor user_ns and have all the target
126 * task's capabilities, then ptrace access is allowed.
127 * If we have the ptrace capability to the target user_ns, then ptrace
128 * access is allowed.
129 * Else denied.
130 *
David Howells1d045982008-11-14 10:39:24 +1100131 * Determine whether a process may access another, returning 0 if permission
132 * granted, -ve if denied.
133 */
Ingo Molnar9e488582009-05-07 19:26:19 +1000134int cap_ptrace_access_check(struct task_struct *child, unsigned int mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700135{
David Howellsc69e8d92008-11-14 10:39:19 +1100136 int ret = 0;
Serge E. Hallyn8409cca2011-03-23 16:43:20 -0700137 const struct cred *cred, *child_cred;
Jann Horncaaee622016-01-20 15:00:04 -0800138 const kernel_cap_t *caller_caps;
David Howellsc69e8d92008-11-14 10:39:19 +1100139
140 rcu_read_lock();
Serge E. Hallyn8409cca2011-03-23 16:43:20 -0700141 cred = current_cred();
142 child_cred = __task_cred(child);
Jann Horncaaee622016-01-20 15:00:04 -0800143 if (mode & PTRACE_MODE_FSCREDS)
144 caller_caps = &cred->cap_effective;
145 else
146 caller_caps = &cred->cap_permitted;
Eric W. Biedermanc4a4d602011-11-16 23:15:31 -0800147 if (cred->user_ns == child_cred->user_ns &&
Jann Horncaaee622016-01-20 15:00:04 -0800148 cap_issubset(child_cred->cap_permitted, *caller_caps))
Serge E. Hallyn8409cca2011-03-23 16:43:20 -0700149 goto out;
Eric W. Biedermanc4a4d602011-11-16 23:15:31 -0800150 if (ns_capable(child_cred->user_ns, CAP_SYS_PTRACE))
Serge E. Hallyn8409cca2011-03-23 16:43:20 -0700151 goto out;
152 ret = -EPERM;
153out:
David Howellsc69e8d92008-11-14 10:39:19 +1100154 rcu_read_unlock();
155 return ret;
David Howells5cd9c582008-08-14 11:37:28 +0100156}
157
David Howells1d045982008-11-14 10:39:24 +1100158/**
159 * cap_ptrace_traceme - Determine whether another process may trace the current
160 * @parent: The task proposed to be the tracer
161 *
Serge E. Hallyn8409cca2011-03-23 16:43:20 -0700162 * If parent is in the same or an ancestor user_ns and has all current's
163 * capabilities, then ptrace access is allowed.
164 * If parent has the ptrace capability to current's user_ns, then ptrace
165 * access is allowed.
166 * Else denied.
167 *
David Howells1d045982008-11-14 10:39:24 +1100168 * Determine whether the nominated task is permitted to trace the current
169 * process, returning 0 if permission is granted, -ve if denied.
170 */
David Howells5cd9c582008-08-14 11:37:28 +0100171int cap_ptrace_traceme(struct task_struct *parent)
172{
David Howellsc69e8d92008-11-14 10:39:19 +1100173 int ret = 0;
Serge E. Hallyn8409cca2011-03-23 16:43:20 -0700174 const struct cred *cred, *child_cred;
David Howellsc69e8d92008-11-14 10:39:19 +1100175
176 rcu_read_lock();
Serge E. Hallyn8409cca2011-03-23 16:43:20 -0700177 cred = __task_cred(parent);
178 child_cred = current_cred();
Eric W. Biedermanc4a4d602011-11-16 23:15:31 -0800179 if (cred->user_ns == child_cred->user_ns &&
Serge E. Hallyn8409cca2011-03-23 16:43:20 -0700180 cap_issubset(child_cred->cap_permitted, cred->cap_permitted))
181 goto out;
Eric W. Biedermanc4a4d602011-11-16 23:15:31 -0800182 if (has_ns_capability(parent, child_cred->user_ns, CAP_SYS_PTRACE))
Serge E. Hallyn8409cca2011-03-23 16:43:20 -0700183 goto out;
184 ret = -EPERM;
185out:
David Howellsc69e8d92008-11-14 10:39:19 +1100186 rcu_read_unlock();
187 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700188}
189
David Howells1d045982008-11-14 10:39:24 +1100190/**
191 * cap_capget - Retrieve a task's capability sets
192 * @target: The task from which to retrieve the capability sets
193 * @effective: The place to record the effective set
194 * @inheritable: The place to record the inheritable set
195 * @permitted: The place to record the permitted set
196 *
197 * This function retrieves the capabilities of the nominated task and returns
198 * them to the caller.
199 */
200int cap_capget(struct task_struct *target, kernel_cap_t *effective,
201 kernel_cap_t *inheritable, kernel_cap_t *permitted)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700202{
David Howellsc69e8d92008-11-14 10:39:19 +1100203 const struct cred *cred;
David Howellsb6dff3e2008-11-14 10:39:16 +1100204
Linus Torvalds1da177e2005-04-16 15:20:36 -0700205 /* Derived from kernel/capability.c:sys_capget. */
David Howellsc69e8d92008-11-14 10:39:19 +1100206 rcu_read_lock();
207 cred = __task_cred(target);
David Howellsb6dff3e2008-11-14 10:39:16 +1100208 *effective = cred->cap_effective;
209 *inheritable = cred->cap_inheritable;
210 *permitted = cred->cap_permitted;
David Howellsc69e8d92008-11-14 10:39:19 +1100211 rcu_read_unlock();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700212 return 0;
213}
214
David Howells1d045982008-11-14 10:39:24 +1100215/*
216 * Determine whether the inheritable capabilities are limited to the old
217 * permitted set. Returns 1 if they are limited, 0 if they are not.
218 */
Andrew Morgan72c2d582007-10-18 03:05:59 -0700219static inline int cap_inh_is_capped(void)
220{
David Howells1d045982008-11-14 10:39:24 +1100221 /* they are so limited unless the current task has the CAP_SETPCAP
222 * capability
Andrew Morgan72c2d582007-10-18 03:05:59 -0700223 */
Eric W. Biedermanc4a4d602011-11-16 23:15:31 -0800224 if (cap_capable(current_cred(), current_cred()->user_ns,
Micah Mortonc1a85a02019-01-07 16:10:53 -0800225 CAP_SETPCAP, CAP_OPT_NONE) == 0)
David Howells1d045982008-11-14 10:39:24 +1100226 return 0;
David Howells1d045982008-11-14 10:39:24 +1100227 return 1;
Andrew Morgan72c2d582007-10-18 03:05:59 -0700228}
229
David Howells1d045982008-11-14 10:39:24 +1100230/**
231 * cap_capset - Validate and apply proposed changes to current's capabilities
232 * @new: The proposed new credentials; alterations should be made here
233 * @old: The current task's current credentials
234 * @effective: A pointer to the proposed new effective capabilities set
235 * @inheritable: A pointer to the proposed new inheritable capabilities set
236 * @permitted: A pointer to the proposed new permitted capabilities set
237 *
238 * This function validates and applies a proposed mass change to the current
239 * process's capability sets. The changes are made to the proposed new
240 * credentials, and assuming no error, will be committed by the caller of LSM.
241 */
David Howellsd84f4f92008-11-14 10:39:23 +1100242int cap_capset(struct cred *new,
243 const struct cred *old,
244 const kernel_cap_t *effective,
245 const kernel_cap_t *inheritable,
246 const kernel_cap_t *permitted)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700247{
David Howellsd84f4f92008-11-14 10:39:23 +1100248 if (cap_inh_is_capped() &&
249 !cap_issubset(*inheritable,
250 cap_combine(old->cap_inheritable,
251 old->cap_permitted)))
Andrew Morgan72c2d582007-10-18 03:05:59 -0700252 /* incapable of using this inheritable set */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700253 return -EPERM;
David Howellsd84f4f92008-11-14 10:39:23 +1100254
Serge E. Hallyn3b7391d2008-02-04 22:29:45 -0800255 if (!cap_issubset(*inheritable,
David Howellsd84f4f92008-11-14 10:39:23 +1100256 cap_combine(old->cap_inheritable,
257 old->cap_bset)))
Serge E. Hallyn3b7391d2008-02-04 22:29:45 -0800258 /* no new pI capabilities outside bounding set */
259 return -EPERM;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700260
261 /* verify restrictions on target's new Permitted set */
David Howellsd84f4f92008-11-14 10:39:23 +1100262 if (!cap_issubset(*permitted, old->cap_permitted))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700263 return -EPERM;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700264
265 /* verify the _new_Effective_ is a subset of the _new_Permitted_ */
David Howellsd84f4f92008-11-14 10:39:23 +1100266 if (!cap_issubset(*effective, *permitted))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700267 return -EPERM;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700268
David Howellsd84f4f92008-11-14 10:39:23 +1100269 new->cap_effective = *effective;
270 new->cap_inheritable = *inheritable;
271 new->cap_permitted = *permitted;
Andy Lutomirski58319052015-09-04 15:42:45 -0700272
273 /*
274 * Mask off ambient bits that are no longer both permitted and
275 * inheritable.
276 */
277 new->cap_ambient = cap_intersect(new->cap_ambient,
278 cap_intersect(*permitted,
279 *inheritable));
280 if (WARN_ON(!cap_ambient_invariant_ok(new)))
281 return -EINVAL;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700282 return 0;
283}
284
David Howells1d045982008-11-14 10:39:24 +1100285/**
286 * cap_inode_need_killpriv - Determine if inode change affects privileges
287 * @dentry: The inode/dentry in being changed with change marked ATTR_KILL_PRIV
288 *
289 * Determine if an inode having a change applied that's marked ATTR_KILL_PRIV
290 * affects the security markings on that inode, and if it is, should
Stefan Bergerab5348c2017-07-26 22:27:05 -0400291 * inode_killpriv() be invoked or the change rejected.
David Howells1d045982008-11-14 10:39:24 +1100292 *
Randy Dunlap049ae602021-04-11 17:55:28 -0700293 * Return: 1 if security.capability has a value, meaning inode_killpriv()
Stefan Bergerab5348c2017-07-26 22:27:05 -0400294 * is required, 0 otherwise, meaning inode_killpriv() is not required.
David Howells1d045982008-11-14 10:39:24 +1100295 */
Serge E. Hallynb5376772007-10-16 23:31:36 -0700296int cap_inode_need_killpriv(struct dentry *dentry)
297{
David Howellsc6f493d2015-03-17 22:26:22 +0000298 struct inode *inode = d_backing_inode(dentry);
Serge E. Hallynb5376772007-10-16 23:31:36 -0700299 int error;
300
Andreas Gruenbacher5d6c3192016-09-29 17:48:42 +0200301 error = __vfs_getxattr(dentry, inode, XATTR_NAME_CAPS, NULL, 0);
302 return error > 0;
Serge E. Hallynb5376772007-10-16 23:31:36 -0700303}
304
David Howells1d045982008-11-14 10:39:24 +1100305/**
306 * cap_inode_killpriv - Erase the security markings on an inode
Christian Brauner71bc3562021-01-21 14:19:29 +0100307 *
308 * @mnt_userns: user namespace of the mount the inode was found from
309 * @dentry: The inode/dentry to alter
David Howells1d045982008-11-14 10:39:24 +1100310 *
311 * Erase the privilege-enhancing security markings on an inode.
312 *
Christian Brauner71bc3562021-01-21 14:19:29 +0100313 * If the inode has been found through an idmapped mount the user namespace of
314 * the vfsmount must be passed through @mnt_userns. This function will then
315 * take care to map the inode according to @mnt_userns before checking
316 * permissions. On non-idmapped mounts or if permission checking is to be
317 * performed on the raw inode simply passs init_user_ns.
318 *
Randy Dunlap049ae602021-04-11 17:55:28 -0700319 * Return: 0 if successful, -ve on error.
David Howells1d045982008-11-14 10:39:24 +1100320 */
Christian Brauner71bc3562021-01-21 14:19:29 +0100321int cap_inode_killpriv(struct user_namespace *mnt_userns, struct dentry *dentry)
Serge E. Hallynb5376772007-10-16 23:31:36 -0700322{
Andreas Gruenbacher5d6c3192016-09-29 17:48:42 +0200323 int error;
Serge E. Hallynb5376772007-10-16 23:31:36 -0700324
Christian Brauner71bc3562021-01-21 14:19:29 +0100325 error = __vfs_removexattr(mnt_userns, dentry, XATTR_NAME_CAPS);
Andreas Gruenbacher5d6c3192016-09-29 17:48:42 +0200326 if (error == -EOPNOTSUPP)
327 error = 0;
328 return error;
Serge E. Hallynb5376772007-10-16 23:31:36 -0700329}
330
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500331static bool rootid_owns_currentns(kuid_t kroot)
332{
333 struct user_namespace *ns;
334
335 if (!uid_valid(kroot))
336 return false;
337
338 for (ns = current_user_ns(); ; ns = ns->parent) {
339 if (from_kuid(ns, kroot) == 0)
340 return true;
341 if (ns == &init_user_ns)
342 break;
343 }
344
345 return false;
346}
347
348static __u32 sansflags(__u32 m)
349{
350 return m & ~VFS_CAP_FLAGS_EFFECTIVE;
351}
352
Eric Biggersdc32b5c2018-01-01 09:28:31 -0600353static bool is_v2header(size_t size, const struct vfs_cap_data *cap)
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500354{
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500355 if (size != XATTR_CAPS_SZ_2)
356 return false;
Eric Biggersdc32b5c2018-01-01 09:28:31 -0600357 return sansflags(le32_to_cpu(cap->magic_etc)) == VFS_CAP_REVISION_2;
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500358}
359
Eric Biggersdc32b5c2018-01-01 09:28:31 -0600360static bool is_v3header(size_t size, const struct vfs_cap_data *cap)
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500361{
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500362 if (size != XATTR_CAPS_SZ_3)
363 return false;
Eric Biggersdc32b5c2018-01-01 09:28:31 -0600364 return sansflags(le32_to_cpu(cap->magic_etc)) == VFS_CAP_REVISION_3;
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500365}
366
367/*
368 * getsecurity: We are called for security.* before any attempt to read the
369 * xattr from the inode itself.
370 *
371 * This gives us a chance to read the on-disk value and convert it. If we
372 * return -EOPNOTSUPP, then vfs_getxattr() will call the i_op handler.
373 *
374 * Note we are not called by vfs_getxattr_alloc(), but that is only called
375 * by the integrity subsystem, which really wants the unconverted values -
376 * so that's good.
377 */
Christian Brauner71bc3562021-01-21 14:19:29 +0100378int cap_inode_getsecurity(struct user_namespace *mnt_userns,
379 struct inode *inode, const char *name, void **buffer,
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500380 bool alloc)
381{
382 int size, ret;
383 kuid_t kroot;
Miklos Szeredif2b00be2021-01-28 10:22:48 +0100384 u32 nsmagic, magic;
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500385 uid_t root, mappedroot;
386 char *tmpbuf = NULL;
387 struct vfs_cap_data *cap;
Miklos Szeredif2b00be2021-01-28 10:22:48 +0100388 struct vfs_ns_cap_data *nscap = NULL;
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500389 struct dentry *dentry;
390 struct user_namespace *fs_ns;
391
392 if (strcmp(name, "capability") != 0)
393 return -EOPNOTSUPP;
394
Eddie.Horng355139a2018-07-20 15:30:00 +0800395 dentry = d_find_any_alias(inode);
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500396 if (!dentry)
397 return -EINVAL;
398
399 size = sizeof(struct vfs_ns_cap_data);
Christian Brauner71bc3562021-01-21 14:19:29 +0100400 ret = (int)vfs_getxattr_alloc(mnt_userns, dentry, XATTR_NAME_CAPS,
Tycho Andersenc7c7a1a12021-01-21 14:19:28 +0100401 &tmpbuf, size, GFP_NOFS);
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500402 dput(dentry);
403
Arnd Bergmann82e5d8c2021-03-22 17:02:41 +0100404 if (ret < 0 || !tmpbuf)
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500405 return ret;
406
407 fs_ns = inode->i_sb->s_user_ns;
408 cap = (struct vfs_cap_data *) tmpbuf;
Eric Biggersdc32b5c2018-01-01 09:28:31 -0600409 if (is_v2header((size_t) ret, cap)) {
Miklos Szeredif2b00be2021-01-28 10:22:48 +0100410 root = 0;
411 } else if (is_v3header((size_t) ret, cap)) {
412 nscap = (struct vfs_ns_cap_data *) tmpbuf;
413 root = le32_to_cpu(nscap->rootid);
414 } else {
415 size = -EINVAL;
416 goto out_free;
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500417 }
418
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500419 kroot = make_kuid(fs_ns, root);
420
Christian Brauner71bc3562021-01-21 14:19:29 +0100421 /* If this is an idmapped mount shift the kuid. */
422 kroot = kuid_into_mnt(mnt_userns, kroot);
423
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500424 /* If the root kuid maps to a valid uid in current ns, then return
425 * this as a nscap. */
426 mappedroot = from_kuid(current_user_ns(), kroot);
427 if (mappedroot != (uid_t)-1 && mappedroot != (uid_t)0) {
Miklos Szeredif2b00be2021-01-28 10:22:48 +0100428 size = sizeof(struct vfs_ns_cap_data);
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500429 if (alloc) {
Miklos Szeredif2b00be2021-01-28 10:22:48 +0100430 if (!nscap) {
431 /* v2 -> v3 conversion */
432 nscap = kzalloc(size, GFP_ATOMIC);
433 if (!nscap) {
434 size = -ENOMEM;
435 goto out_free;
436 }
437 nsmagic = VFS_CAP_REVISION_3;
438 magic = le32_to_cpu(cap->magic_etc);
439 if (magic & VFS_CAP_FLAGS_EFFECTIVE)
440 nsmagic |= VFS_CAP_FLAGS_EFFECTIVE;
441 memcpy(&nscap->data, &cap->data, sizeof(__le32) * 2 * VFS_CAP_U32);
442 nscap->magic_etc = cpu_to_le32(nsmagic);
443 } else {
444 /* use allocated v3 buffer */
445 tmpbuf = NULL;
446 }
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500447 nscap->rootid = cpu_to_le32(mappedroot);
Miklos Szeredif2b00be2021-01-28 10:22:48 +0100448 *buffer = nscap;
449 }
450 goto out_free;
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500451 }
452
453 if (!rootid_owns_currentns(kroot)) {
Miklos Szeredif2b00be2021-01-28 10:22:48 +0100454 size = -EOVERFLOW;
455 goto out_free;
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500456 }
457
458 /* This comes from a parent namespace. Return as a v2 capability */
459 size = sizeof(struct vfs_cap_data);
460 if (alloc) {
Miklos Szeredif2b00be2021-01-28 10:22:48 +0100461 if (nscap) {
462 /* v3 -> v2 conversion */
463 cap = kzalloc(size, GFP_ATOMIC);
464 if (!cap) {
465 size = -ENOMEM;
466 goto out_free;
467 }
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500468 magic = VFS_CAP_REVISION_2;
469 nsmagic = le32_to_cpu(nscap->magic_etc);
470 if (nsmagic & VFS_CAP_FLAGS_EFFECTIVE)
471 magic |= VFS_CAP_FLAGS_EFFECTIVE;
472 memcpy(&cap->data, &nscap->data, sizeof(__le32) * 2 * VFS_CAP_U32);
473 cap->magic_etc = cpu_to_le32(magic);
Tetsuo Handa1f578172018-04-10 15:15:16 +0900474 } else {
Miklos Szeredif2b00be2021-01-28 10:22:48 +0100475 /* use unconverted v2 */
476 tmpbuf = NULL;
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500477 }
Miklos Szeredif2b00be2021-01-28 10:22:48 +0100478 *buffer = cap;
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500479 }
Miklos Szeredif2b00be2021-01-28 10:22:48 +0100480out_free:
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500481 kfree(tmpbuf);
482 return size;
483}
484
Christian Braunere65ce2a2021-01-21 14:19:27 +0100485/**
486 * rootid_from_xattr - translate root uid of vfs caps
487 *
488 * @value: vfs caps value which may be modified by this function
489 * @size: size of @ivalue
490 * @task_ns: user namespace of the caller
491 * @mnt_userns: user namespace of the mount the inode was found from
492 *
493 * If the inode has been found through an idmapped mount the user namespace of
494 * the vfsmount must be passed through @mnt_userns. This function will then
495 * take care to map the inode according to @mnt_userns before checking
496 * permissions. On non-idmapped mounts or if permission checking is to be
497 * performed on the raw inode simply passs init_user_ns.
498 */
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500499static kuid_t rootid_from_xattr(const void *value, size_t size,
Christian Braunere65ce2a2021-01-21 14:19:27 +0100500 struct user_namespace *task_ns,
501 struct user_namespace *mnt_userns)
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500502{
503 const struct vfs_ns_cap_data *nscap = value;
Christian Braunere65ce2a2021-01-21 14:19:27 +0100504 kuid_t rootkid;
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500505 uid_t rootid = 0;
506
507 if (size == XATTR_CAPS_SZ_3)
508 rootid = le32_to_cpu(nscap->rootid);
509
Christian Braunere65ce2a2021-01-21 14:19:27 +0100510 rootkid = make_kuid(task_ns, rootid);
511 return kuid_from_mnt(mnt_userns, rootkid);
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500512}
513
Eric Biggersdc32b5c2018-01-01 09:28:31 -0600514static bool validheader(size_t size, const struct vfs_cap_data *cap)
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500515{
Eric Biggersdc32b5c2018-01-01 09:28:31 -0600516 return is_v2header(size, cap) || is_v3header(size, cap);
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500517}
518
Christian Braunere65ce2a2021-01-21 14:19:27 +0100519/**
520 * cap_convert_nscap - check vfs caps
521 *
522 * @mnt_userns: user namespace of the mount the inode was found from
523 * @dentry: used to retrieve inode to check permissions on
524 * @ivalue: vfs caps value which may be modified by this function
525 * @size: size of @ivalue
526 *
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500527 * User requested a write of security.capability. If needed, update the
528 * xattr to change from v2 to v3, or to fixup the v3 rootid.
529 *
Christian Braunere65ce2a2021-01-21 14:19:27 +0100530 * If the inode has been found through an idmapped mount the user namespace of
531 * the vfsmount must be passed through @mnt_userns. This function will then
532 * take care to map the inode according to @mnt_userns before checking
533 * permissions. On non-idmapped mounts or if permission checking is to be
534 * performed on the raw inode simply passs init_user_ns.
535 *
Randy Dunlap049ae602021-04-11 17:55:28 -0700536 * Return: On success, return the new size; on error, return < 0.
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500537 */
Christian Braunere65ce2a2021-01-21 14:19:27 +0100538int cap_convert_nscap(struct user_namespace *mnt_userns, struct dentry *dentry,
539 const void **ivalue, size_t size)
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500540{
541 struct vfs_ns_cap_data *nscap;
542 uid_t nsrootid;
543 const struct vfs_cap_data *cap = *ivalue;
544 __u32 magic, nsmagic;
545 struct inode *inode = d_backing_inode(dentry);
546 struct user_namespace *task_ns = current_user_ns(),
Eric W. Biederman3b0c2d32021-03-12 15:07:09 -0600547 *fs_ns = inode->i_sb->s_user_ns;
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500548 kuid_t rootid;
549 size_t newsize;
550
551 if (!*ivalue)
552 return -EINVAL;
Eric Biggersdc32b5c2018-01-01 09:28:31 -0600553 if (!validheader(size, cap))
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500554 return -EINVAL;
Christian Braunere65ce2a2021-01-21 14:19:27 +0100555 if (!capable_wrt_inode_uidgid(mnt_userns, inode, CAP_SETFCAP))
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500556 return -EPERM;
Christian Braunere65ce2a2021-01-21 14:19:27 +0100557 if (size == XATTR_CAPS_SZ_2 && (mnt_userns == &init_user_ns))
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500558 if (ns_capable(inode->i_sb->s_user_ns, CAP_SETFCAP))
559 /* user is privileged, just write the v2 */
560 return size;
561
Christian Braunere65ce2a2021-01-21 14:19:27 +0100562 rootid = rootid_from_xattr(*ivalue, size, task_ns, mnt_userns);
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500563 if (!uid_valid(rootid))
564 return -EINVAL;
565
566 nsrootid = from_kuid(fs_ns, rootid);
567 if (nsrootid == -1)
568 return -EINVAL;
569
570 newsize = sizeof(struct vfs_ns_cap_data);
571 nscap = kmalloc(newsize, GFP_ATOMIC);
572 if (!nscap)
573 return -ENOMEM;
574 nscap->rootid = cpu_to_le32(nsrootid);
575 nsmagic = VFS_CAP_REVISION_3;
576 magic = le32_to_cpu(cap->magic_etc);
577 if (magic & VFS_CAP_FLAGS_EFFECTIVE)
578 nsmagic |= VFS_CAP_FLAGS_EFFECTIVE;
579 nscap->magic_etc = cpu_to_le32(nsmagic);
580 memcpy(&nscap->data, &cap->data, sizeof(__le32) * 2 * VFS_CAP_U32);
581
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500582 *ivalue = nscap;
583 return newsize;
584}
585
David Howells1d045982008-11-14 10:39:24 +1100586/*
587 * Calculate the new process capability sets from the capability sets attached
588 * to a file.
589 */
Eric Parisc0b00442008-11-11 21:48:10 +1100590static inline int bprm_caps_from_vfs_caps(struct cpu_vfs_cap_data *caps,
David Howellsa6f76f22008-11-14 10:39:24 +1100591 struct linux_binprm *bprm,
Zhi Li4d49f672011-08-11 13:27:50 +0800592 bool *effective,
Richard Guy Briggsfc7eadf2017-10-11 20:57:07 -0400593 bool *has_fcap)
Serge E. Hallynb5376772007-10-16 23:31:36 -0700594{
David Howellsa6f76f22008-11-14 10:39:24 +1100595 struct cred *new = bprm->cred;
Eric Parisc0b00442008-11-11 21:48:10 +1100596 unsigned i;
597 int ret = 0;
598
599 if (caps->magic_etc & VFS_CAP_FLAGS_EFFECTIVE)
David Howellsa6f76f22008-11-14 10:39:24 +1100600 *effective = true;
Eric Parisc0b00442008-11-11 21:48:10 +1100601
Zhi Li4d49f672011-08-11 13:27:50 +0800602 if (caps->magic_etc & VFS_CAP_REVISION_MASK)
Richard Guy Briggsfc7eadf2017-10-11 20:57:07 -0400603 *has_fcap = true;
Zhi Li4d49f672011-08-11 13:27:50 +0800604
Eric Parisc0b00442008-11-11 21:48:10 +1100605 CAP_FOR_EACH_U32(i) {
606 __u32 permitted = caps->permitted.cap[i];
607 __u32 inheritable = caps->inheritable.cap[i];
608
609 /*
610 * pP' = (X & fP) | (pI & fI)
Andy Lutomirski58319052015-09-04 15:42:45 -0700611 * The addition of pA' is handled later.
Eric Parisc0b00442008-11-11 21:48:10 +1100612 */
David Howellsa6f76f22008-11-14 10:39:24 +1100613 new->cap_permitted.cap[i] =
614 (new->cap_bset.cap[i] & permitted) |
615 (new->cap_inheritable.cap[i] & inheritable);
Eric Parisc0b00442008-11-11 21:48:10 +1100616
David Howellsa6f76f22008-11-14 10:39:24 +1100617 if (permitted & ~new->cap_permitted.cap[i])
618 /* insufficient to execute correctly */
Eric Parisc0b00442008-11-11 21:48:10 +1100619 ret = -EPERM;
Eric Parisc0b00442008-11-11 21:48:10 +1100620 }
621
622 /*
623 * For legacy apps, with no internal support for recognizing they
624 * do not have enough capabilities, we return an error if they are
625 * missing some "forced" (aka file-permitted) capabilities.
626 */
David Howellsa6f76f22008-11-14 10:39:24 +1100627 return *effective ? ret : 0;
Eric Parisc0b00442008-11-11 21:48:10 +1100628}
629
Christian Brauner71bc3562021-01-21 14:19:29 +0100630/**
631 * get_vfs_caps_from_disk - retrieve vfs caps from disk
632 *
633 * @mnt_userns: user namespace of the mount the inode was found from
634 * @dentry: dentry from which @inode is retrieved
635 * @cpu_caps: vfs capabilities
636 *
David Howells1d045982008-11-14 10:39:24 +1100637 * Extract the on-exec-apply capability sets for an executable file.
Christian Brauner71bc3562021-01-21 14:19:29 +0100638 *
639 * If the inode has been found through an idmapped mount the user namespace of
640 * the vfsmount must be passed through @mnt_userns. This function will then
641 * take care to map the inode according to @mnt_userns before checking
642 * permissions. On non-idmapped mounts or if permission checking is to be
643 * performed on the raw inode simply passs init_user_ns.
David Howells1d045982008-11-14 10:39:24 +1100644 */
Christian Brauner71bc3562021-01-21 14:19:29 +0100645int get_vfs_caps_from_disk(struct user_namespace *mnt_userns,
646 const struct dentry *dentry,
647 struct cpu_vfs_cap_data *cpu_caps)
Eric Parisc0b00442008-11-11 21:48:10 +1100648{
David Howellsc6f493d2015-03-17 22:26:22 +0000649 struct inode *inode = d_backing_inode(dentry);
Serge E. Hallynb5376772007-10-16 23:31:36 -0700650 __u32 magic_etc;
Andrew Morgane338d262008-02-04 22:29:42 -0800651 unsigned tocopy, i;
Eric Parisc0b00442008-11-11 21:48:10 +1100652 int size;
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500653 struct vfs_ns_cap_data data, *nscaps = &data;
654 struct vfs_cap_data *caps = (struct vfs_cap_data *) &data;
655 kuid_t rootkuid;
Colin Ian King76ba89c72017-09-04 18:50:05 +0100656 struct user_namespace *fs_ns;
Eric Parisc0b00442008-11-11 21:48:10 +1100657
658 memset(cpu_caps, 0, sizeof(struct cpu_vfs_cap_data));
659
Andreas Gruenbacher5d6c3192016-09-29 17:48:42 +0200660 if (!inode)
Eric Parisc0b00442008-11-11 21:48:10 +1100661 return -ENODATA;
662
Colin Ian King76ba89c72017-09-04 18:50:05 +0100663 fs_ns = inode->i_sb->s_user_ns;
Andreas Gruenbacher5d6c3192016-09-29 17:48:42 +0200664 size = __vfs_getxattr((struct dentry *)dentry, inode,
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500665 XATTR_NAME_CAPS, &data, XATTR_CAPS_SZ);
David Howellsa6f76f22008-11-14 10:39:24 +1100666 if (size == -ENODATA || size == -EOPNOTSUPP)
Eric Parisc0b00442008-11-11 21:48:10 +1100667 /* no data, that's ok */
668 return -ENODATA;
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500669
Eric Parisc0b00442008-11-11 21:48:10 +1100670 if (size < 0)
671 return size;
Serge E. Hallynb5376772007-10-16 23:31:36 -0700672
Andrew Morgane338d262008-02-04 22:29:42 -0800673 if (size < sizeof(magic_etc))
Serge E. Hallynb5376772007-10-16 23:31:36 -0700674 return -EINVAL;
675
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500676 cpu_caps->magic_etc = magic_etc = le32_to_cpu(caps->magic_etc);
Serge E. Hallynb5376772007-10-16 23:31:36 -0700677
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500678 rootkuid = make_kuid(fs_ns, 0);
David Howellsa6f76f22008-11-14 10:39:24 +1100679 switch (magic_etc & VFS_CAP_REVISION_MASK) {
Andrew Morgane338d262008-02-04 22:29:42 -0800680 case VFS_CAP_REVISION_1:
681 if (size != XATTR_CAPS_SZ_1)
682 return -EINVAL;
683 tocopy = VFS_CAP_U32_1;
684 break;
685 case VFS_CAP_REVISION_2:
686 if (size != XATTR_CAPS_SZ_2)
687 return -EINVAL;
688 tocopy = VFS_CAP_U32_2;
689 break;
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500690 case VFS_CAP_REVISION_3:
691 if (size != XATTR_CAPS_SZ_3)
692 return -EINVAL;
693 tocopy = VFS_CAP_U32_3;
694 rootkuid = make_kuid(fs_ns, le32_to_cpu(nscaps->rootid));
695 break;
696
Serge E. Hallynb5376772007-10-16 23:31:36 -0700697 default:
698 return -EINVAL;
699 }
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500700 /* Limit the caps to the mounter of the filesystem
701 * or the more limited uid specified in the xattr.
702 */
Christian Brauner71bc3562021-01-21 14:19:29 +0100703 rootkuid = kuid_into_mnt(mnt_userns, rootkuid);
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500704 if (!rootid_owns_currentns(rootkuid))
705 return -ENODATA;
Andrew Morgane338d262008-02-04 22:29:42 -0800706
Andrew G. Morgan5459c162008-07-23 21:28:24 -0700707 CAP_FOR_EACH_U32(i) {
Eric Parisc0b00442008-11-11 21:48:10 +1100708 if (i >= tocopy)
709 break;
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500710 cpu_caps->permitted.cap[i] = le32_to_cpu(caps->data[i].permitted);
711 cpu_caps->inheritable.cap[i] = le32_to_cpu(caps->data[i].inheritable);
Andrew Morgane338d262008-02-04 22:29:42 -0800712 }
David Howellsa6f76f22008-11-14 10:39:24 +1100713
Eric Paris7d8b6c62014-07-23 15:36:26 -0400714 cpu_caps->permitted.cap[CAP_LAST_U32] &= CAP_LAST_U32_VALID_MASK;
715 cpu_caps->inheritable.cap[CAP_LAST_U32] &= CAP_LAST_U32_VALID_MASK;
716
Richard Guy Briggs2fec30e2019-01-23 21:36:25 -0500717 cpu_caps->rootid = rootkuid;
718
Eric Parisc0b00442008-11-11 21:48:10 +1100719 return 0;
Serge E. Hallynb5376772007-10-16 23:31:36 -0700720}
721
David Howells1d045982008-11-14 10:39:24 +1100722/*
723 * Attempt to get the on-exec apply capability sets for an executable file from
724 * its xattrs and, if present, apply them to the proposed credentials being
725 * constructed by execve().
726 */
Eric W. Biederman56305aa2020-05-29 22:00:54 -0500727static int get_file_caps(struct linux_binprm *bprm, struct file *file,
728 bool *effective, bool *has_fcap)
Serge E. Hallynb5376772007-10-16 23:31:36 -0700729{
Serge E. Hallynb5376772007-10-16 23:31:36 -0700730 int rc = 0;
Eric Parisc0b00442008-11-11 21:48:10 +1100731 struct cpu_vfs_cap_data vcaps;
Serge E. Hallynb5376772007-10-16 23:31:36 -0700732
Kees Cookee67ae72017-07-18 15:25:28 -0700733 cap_clear(bprm->cred->cap_permitted);
Serge Hallyn3318a382008-10-30 11:52:23 -0500734
Serge E. Hallyn1f29fae2008-11-05 16:08:52 -0600735 if (!file_caps_enabled)
736 return 0;
737
Eric W. Biederman56305aa2020-05-29 22:00:54 -0500738 if (!mnt_may_suid(file->f_path.mnt))
Serge E. Hallynb5376772007-10-16 23:31:36 -0700739 return 0;
Andy Lutomirski380cf5b2016-06-23 16:41:05 -0500740
741 /*
742 * This check is redundant with mnt_may_suid() but is kept to make
743 * explicit that capability bits are limited to s_user_ns and its
744 * descendants.
745 */
Eric W. Biederman56305aa2020-05-29 22:00:54 -0500746 if (!current_in_userns(file->f_path.mnt->mnt_sb->s_user_ns))
Seth Forsheed07b8462015-09-23 15:16:04 -0500747 return 0;
Serge E. Hallynb5376772007-10-16 23:31:36 -0700748
Christian Brauner71bc3562021-01-21 14:19:29 +0100749 rc = get_vfs_caps_from_disk(file_mnt_user_ns(file),
750 file->f_path.dentry, &vcaps);
Eric Parisc0b00442008-11-11 21:48:10 +1100751 if (rc < 0) {
752 if (rc == -EINVAL)
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500753 printk(KERN_NOTICE "Invalid argument reading file caps for %s\n",
754 bprm->filename);
Eric Parisc0b00442008-11-11 21:48:10 +1100755 else if (rc == -ENODATA)
756 rc = 0;
Serge E. Hallynb5376772007-10-16 23:31:36 -0700757 goto out;
758 }
Serge E. Hallynb5376772007-10-16 23:31:36 -0700759
Richard Guy Briggsfc7eadf2017-10-11 20:57:07 -0400760 rc = bprm_caps_from_vfs_caps(&vcaps, bprm, effective, has_fcap);
Serge E. Hallynb5376772007-10-16 23:31:36 -0700761
762out:
Serge E. Hallynb5376772007-10-16 23:31:36 -0700763 if (rc)
Kees Cookee67ae72017-07-18 15:25:28 -0700764 cap_clear(bprm->cred->cap_permitted);
Serge E. Hallynb5376772007-10-16 23:31:36 -0700765
766 return rc;
767}
768
Richard Guy Briggs9304b462017-10-11 20:57:08 -0400769static inline bool root_privileged(void) { return !issecure(SECURE_NOROOT); }
770
Richard Guy Briggs81a6a012017-10-11 20:57:09 -0400771static inline bool __is_real(kuid_t uid, struct cred *cred)
772{ return uid_eq(cred->uid, uid); }
773
774static inline bool __is_eff(kuid_t uid, struct cred *cred)
775{ return uid_eq(cred->euid, uid); }
776
777static inline bool __is_suid(kuid_t uid, struct cred *cred)
778{ return !__is_real(uid, cred) && __is_eff(uid, cred); }
779
Richard Guy Briggsdb1a8922017-10-11 20:57:05 -0400780/*
781 * handle_privileged_root - Handle case of privileged root
782 * @bprm: The execution parameters, including the proposed creds
783 * @has_fcap: Are any file capabilities set?
784 * @effective: Do we have effective root privilege?
785 * @root_uid: This namespace' root UID WRT initial USER namespace
786 *
787 * Handle the case where root is privileged and hasn't been neutered by
788 * SECURE_NOROOT. If file capabilities are set, they won't be combined with
789 * set UID root and nothing is changed. If we are root, cap_permitted is
790 * updated. If we have become set UID root, the effective bit is set.
791 */
Richard Guy Briggsfc7eadf2017-10-11 20:57:07 -0400792static void handle_privileged_root(struct linux_binprm *bprm, bool has_fcap,
Richard Guy Briggsdb1a8922017-10-11 20:57:05 -0400793 bool *effective, kuid_t root_uid)
794{
795 const struct cred *old = current_cred();
796 struct cred *new = bprm->cred;
797
Richard Guy Briggs9304b462017-10-11 20:57:08 -0400798 if (!root_privileged())
Richard Guy Briggsdb1a8922017-10-11 20:57:05 -0400799 return;
800 /*
801 * If the legacy file capability is set, then don't set privs
802 * for a setuid root binary run by a non-root user. Do set it
803 * for a root user just to cause least surprise to an admin.
804 */
Richard Guy Briggs81a6a012017-10-11 20:57:09 -0400805 if (has_fcap && __is_suid(root_uid, new)) {
Richard Guy Briggsdb1a8922017-10-11 20:57:05 -0400806 warn_setuid_and_fcaps_mixed(bprm->filename);
807 return;
808 }
809 /*
810 * To support inheritance of root-permissions and suid-root
811 * executables under compatibility mode, we override the
812 * capability sets for the file.
813 */
Richard Guy Briggs81a6a012017-10-11 20:57:09 -0400814 if (__is_eff(root_uid, new) || __is_real(root_uid, new)) {
Richard Guy Briggsdb1a8922017-10-11 20:57:05 -0400815 /* pP' = (cap_bset & ~0) | (pI & ~0) */
816 new->cap_permitted = cap_combine(old->cap_bset,
817 old->cap_inheritable);
818 }
819 /*
820 * If only the real uid is 0, we do not set the effective bit.
821 */
Richard Guy Briggs81a6a012017-10-11 20:57:09 -0400822 if (__is_eff(root_uid, new))
Richard Guy Briggsdb1a8922017-10-11 20:57:05 -0400823 *effective = true;
824}
825
Richard Guy Briggs4c7e7152017-10-11 20:57:06 -0400826#define __cap_gained(field, target, source) \
827 !cap_issubset(target->cap_##field, source->cap_##field)
828#define __cap_grew(target, source, cred) \
829 !cap_issubset(cred->cap_##target, cred->cap_##source)
830#define __cap_full(field, cred) \
831 cap_issubset(CAP_FULL_SET, cred->cap_##field)
Richard Guy Briggs81a6a012017-10-11 20:57:09 -0400832
833static inline bool __is_setuid(struct cred *new, const struct cred *old)
834{ return !uid_eq(new->euid, old->uid); }
835
836static inline bool __is_setgid(struct cred *new, const struct cred *old)
837{ return !gid_eq(new->egid, old->gid); }
838
Richard Guy Briggs9fbc2c72017-10-11 20:57:10 -0400839/*
Richard Guy Briggsdbbbe112017-10-11 20:57:14 -0400840 * 1) Audit candidate if current->cap_effective is set
Richard Guy Briggs9fbc2c72017-10-11 20:57:10 -0400841 *
842 * We do not bother to audit if 3 things are true:
843 * 1) cap_effective has all caps
Richard Guy Briggs588fb2c2017-10-11 20:57:13 -0400844 * 2) we became root *OR* are were already root
Richard Guy Briggs9fbc2c72017-10-11 20:57:10 -0400845 * 3) root is supposed to have all caps (SECURE_NOROOT)
846 * Since this is just a normal root execing a process.
847 *
848 * Number 1 above might fail if you don't have a full bset, but I think
849 * that is interesting information to audit.
Richard Guy Briggsdbbbe112017-10-11 20:57:14 -0400850 *
851 * A number of other conditions require logging:
852 * 2) something prevented setuid root getting all caps
853 * 3) non-setuid root gets fcaps
854 * 4) non-setuid root gets ambient
Richard Guy Briggs9fbc2c72017-10-11 20:57:10 -0400855 */
Richard Guy Briggsdbbbe112017-10-11 20:57:14 -0400856static inline bool nonroot_raised_pE(struct cred *new, const struct cred *old,
857 kuid_t root, bool has_fcap)
Richard Guy Briggs9fbc2c72017-10-11 20:57:10 -0400858{
859 bool ret = false;
860
Richard Guy Briggsdbbbe112017-10-11 20:57:14 -0400861 if ((__cap_grew(effective, ambient, new) &&
862 !(__cap_full(effective, new) &&
863 (__is_eff(root, new) || __is_real(root, new)) &&
864 root_privileged())) ||
865 (root_privileged() &&
866 __is_suid(root, new) &&
867 !__cap_full(effective, new)) ||
868 (!__is_setuid(new, old) &&
869 ((has_fcap &&
870 __cap_gained(permitted, new, old)) ||
871 __cap_gained(ambient, new, old))))
872
Richard Guy Briggs02ebbaf2017-10-11 20:57:11 -0400873 ret = true;
Richard Guy Briggsdbbbe112017-10-11 20:57:14 -0400874
Richard Guy Briggs9fbc2c72017-10-11 20:57:10 -0400875 return ret;
876}
877
David Howells1d045982008-11-14 10:39:24 +1100878/**
Eric W. Biederman56305aa2020-05-29 22:00:54 -0500879 * cap_bprm_creds_from_file - Set up the proposed credentials for execve().
David Howells1d045982008-11-14 10:39:24 +1100880 * @bprm: The execution parameters, including the proposed creds
Eric W. Biederman56305aa2020-05-29 22:00:54 -0500881 * @file: The file to pull the credentials from
David Howells1d045982008-11-14 10:39:24 +1100882 *
883 * Set up the proposed credentials for a new execution context being
884 * constructed by execve(). The proposed creds in @bprm->cred is altered,
Randy Dunlap049ae602021-04-11 17:55:28 -0700885 * which won't take effect immediately.
886 *
887 * Return: 0 if successful, -ve on error.
David Howellsa6f76f22008-11-14 10:39:24 +1100888 */
Eric W. Biederman56305aa2020-05-29 22:00:54 -0500889int cap_bprm_creds_from_file(struct linux_binprm *bprm, struct file *file)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700890{
Eric W. Biederman56305aa2020-05-29 22:00:54 -0500891 /* Process setpcap binaries and capabilities for uid 0 */
David Howellsa6f76f22008-11-14 10:39:24 +1100892 const struct cred *old = current_cred();
893 struct cred *new = bprm->cred;
Richard Guy Briggsfc7eadf2017-10-11 20:57:07 -0400894 bool effective = false, has_fcap = false, is_setid;
Serge E. Hallynb5376772007-10-16 23:31:36 -0700895 int ret;
Eric W. Biederman18815a12012-02-07 16:45:47 -0800896 kuid_t root_uid;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700897
Andy Lutomirski58319052015-09-04 15:42:45 -0700898 if (WARN_ON(!cap_ambient_invariant_ok(old)))
899 return -EPERM;
900
Eric W. Biederman56305aa2020-05-29 22:00:54 -0500901 ret = get_file_caps(bprm, file, &effective, &has_fcap);
David Howellsa6f76f22008-11-14 10:39:24 +1100902 if (ret < 0)
903 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700904
Eric W. Biederman18815a12012-02-07 16:45:47 -0800905 root_uid = make_kuid(new->user_ns, 0);
906
Richard Guy Briggsfc7eadf2017-10-11 20:57:07 -0400907 handle_privileged_root(bprm, has_fcap, &effective, root_uid);
Serge E. Hallynb5376772007-10-16 23:31:36 -0700908
Eric Parisd52fc5d2012-04-17 16:26:54 -0400909 /* if we have fs caps, clear dangerous personality flags */
Richard Guy Briggs4c7e7152017-10-11 20:57:06 -0400910 if (__cap_gained(permitted, new, old))
Eric W. Biederman56305aa2020-05-29 22:00:54 -0500911 bprm->per_clear |= PER_CLEAR_ON_SETID;
Eric Parisd52fc5d2012-04-17 16:26:54 -0400912
David Howellsa6f76f22008-11-14 10:39:24 +1100913 /* Don't let someone trace a set[ug]id/setpcap binary with the revised
Andy Lutomirski259e5e62012-04-12 16:47:50 -0500914 * credentials unless they have the appropriate permit.
915 *
916 * In addition, if NO_NEW_PRIVS, then ensure we get no new privs.
David Howellsa6f76f22008-11-14 10:39:24 +1100917 */
Richard Guy Briggs81a6a012017-10-11 20:57:09 -0400918 is_setid = __is_setuid(new, old) || __is_setgid(new, old);
Andy Lutomirski58319052015-09-04 15:42:45 -0700919
Richard Guy Briggs4c7e7152017-10-11 20:57:06 -0400920 if ((is_setid || __cap_gained(permitted, new, old)) &&
Eric W. Biederman9227dd22017-01-23 17:26:31 +1300921 ((bprm->unsafe & ~LSM_UNSAFE_PTRACE) ||
Eric W. Biederman20523132017-01-23 17:17:26 +1300922 !ptracer_capable(current, new->user_ns))) {
David Howellsa6f76f22008-11-14 10:39:24 +1100923 /* downgrade; they get no more than they had, and maybe less */
Eric W. Biederman70169422016-11-17 01:38:35 -0600924 if (!ns_capable(new->user_ns, CAP_SETUID) ||
Andy Lutomirski259e5e62012-04-12 16:47:50 -0500925 (bprm->unsafe & LSM_UNSAFE_NO_NEW_PRIVS)) {
David Howellsa6f76f22008-11-14 10:39:24 +1100926 new->euid = new->uid;
927 new->egid = new->gid;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700928 }
Serge E. Hallynb3a222e2009-11-23 16:21:30 -0600929 new->cap_permitted = cap_intersect(new->cap_permitted,
930 old->cap_permitted);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700931 }
932
David Howellsa6f76f22008-11-14 10:39:24 +1100933 new->suid = new->fsuid = new->euid;
934 new->sgid = new->fsgid = new->egid;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700935
Andy Lutomirski58319052015-09-04 15:42:45 -0700936 /* File caps or setid cancels ambient. */
Richard Guy Briggsfc7eadf2017-10-11 20:57:07 -0400937 if (has_fcap || is_setid)
Andy Lutomirski58319052015-09-04 15:42:45 -0700938 cap_clear(new->cap_ambient);
939
940 /*
941 * Now that we've computed pA', update pP' to give:
942 * pP' = (X & fP) | (pI & fI) | pA'
943 */
944 new->cap_permitted = cap_combine(new->cap_permitted, new->cap_ambient);
945
946 /*
947 * Set pE' = (fE ? pP' : pA'). Because pA' is zero if fE is set,
948 * this is the same as pE' = (fE ? pP' : 0) | pA'.
949 */
Eric Paris4bf2ea72011-04-01 17:08:28 -0400950 if (effective)
951 new->cap_effective = new->cap_permitted;
952 else
Andy Lutomirski58319052015-09-04 15:42:45 -0700953 new->cap_effective = new->cap_ambient;
954
955 if (WARN_ON(!cap_ambient_invariant_ok(new)))
956 return -EPERM;
957
Richard Guy Briggsdbbbe112017-10-11 20:57:14 -0400958 if (nonroot_raised_pE(new, old, root_uid, has_fcap)) {
Richard Guy Briggs9fbc2c72017-10-11 20:57:10 -0400959 ret = audit_log_bprm_fcaps(bprm, new, old);
960 if (ret < 0)
961 return ret;
Eric Paris3fc689e2008-11-11 21:48:18 +1100962 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700963
David Howellsd84f4f92008-11-14 10:39:23 +1100964 new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
Andy Lutomirski58319052015-09-04 15:42:45 -0700965
966 if (WARN_ON(!cap_ambient_invariant_ok(new)))
967 return -EPERM;
968
Kees Cook46d98eb2017-07-18 15:25:27 -0700969 /* Check for privilege-elevated exec. */
Richard Guy Briggs02ebbaf2017-10-11 20:57:11 -0400970 if (is_setid ||
971 (!__is_real(root_uid, new) &&
972 (effective ||
973 __cap_grew(permitted, ambient, new))))
Eric W. Biederman56305aa2020-05-29 22:00:54 -0500974 bprm->secureexec = 1;
Serge E. Hallynb5376772007-10-16 23:31:36 -0700975
Kees Cookee67ae72017-07-18 15:25:28 -0700976 return 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700977}
978
David Howells1d045982008-11-14 10:39:24 +1100979/**
980 * cap_inode_setxattr - Determine whether an xattr may be altered
981 * @dentry: The inode/dentry being altered
982 * @name: The name of the xattr to be changed
983 * @value: The value that the xattr will be changed to
984 * @size: The size of value
985 * @flags: The replacement flag
986 *
987 * Determine whether an xattr may be altered or set on an inode, returning 0 if
988 * permission is granted, -ve if denied.
989 *
990 * This is used to make sure security xattrs don't get updated or set by those
991 * who aren't privileged to do so.
992 */
David Howells8f0cfa52008-04-29 00:59:41 -0700993int cap_inode_setxattr(struct dentry *dentry, const char *name,
994 const void *value, size_t size, int flags)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700995{
Eric W. Biedermanb1d749c2017-04-21 19:14:32 -0500996 struct user_namespace *user_ns = dentry->d_sb->s_user_ns;
997
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500998 /* Ignore non-security xattrs */
999 if (strncmp(name, XATTR_SECURITY_PREFIX,
Carmeli Tamirc5eaab12019-07-06 11:07:38 -04001000 XATTR_SECURITY_PREFIX_LEN) != 0)
Serge E. Hallynb5376772007-10-16 23:31:36 -07001001 return 0;
David Howells1d045982008-11-14 10:39:24 +11001002
Serge E. Hallyn8db6c342017-05-08 13:11:56 -05001003 /*
1004 * For XATTR_NAME_CAPS the check will be done in
1005 * cap_convert_nscap(), called by setxattr()
1006 */
1007 if (strcmp(name, XATTR_NAME_CAPS) == 0)
1008 return 0;
1009
Eric W. Biedermanb1d749c2017-04-21 19:14:32 -05001010 if (!ns_capable(user_ns, CAP_SYS_ADMIN))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001011 return -EPERM;
1012 return 0;
1013}
1014
David Howells1d045982008-11-14 10:39:24 +11001015/**
1016 * cap_inode_removexattr - Determine whether an xattr may be removed
Christian Brauner71bc3562021-01-21 14:19:29 +01001017 *
1018 * @mnt_userns: User namespace of the mount the inode was found from
1019 * @dentry: The inode/dentry being altered
1020 * @name: The name of the xattr to be changed
David Howells1d045982008-11-14 10:39:24 +11001021 *
1022 * Determine whether an xattr may be removed from an inode, returning 0 if
1023 * permission is granted, -ve if denied.
1024 *
Christian Brauner71bc3562021-01-21 14:19:29 +01001025 * If the inode has been found through an idmapped mount the user namespace of
1026 * the vfsmount must be passed through @mnt_userns. This function will then
1027 * take care to map the inode according to @mnt_userns before checking
1028 * permissions. On non-idmapped mounts or if permission checking is to be
1029 * performed on the raw inode simply passs init_user_ns.
1030 *
David Howells1d045982008-11-14 10:39:24 +11001031 * This is used to make sure security xattrs don't get removed by those who
1032 * aren't privileged to remove them.
1033 */
Christian Brauner71bc3562021-01-21 14:19:29 +01001034int cap_inode_removexattr(struct user_namespace *mnt_userns,
1035 struct dentry *dentry, const char *name)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001036{
Eric W. Biedermanb1d749c2017-04-21 19:14:32 -05001037 struct user_namespace *user_ns = dentry->d_sb->s_user_ns;
1038
Serge E. Hallyn8db6c342017-05-08 13:11:56 -05001039 /* Ignore non-security xattrs */
1040 if (strncmp(name, XATTR_SECURITY_PREFIX,
Carmeli Tamirc5eaab12019-07-06 11:07:38 -04001041 XATTR_SECURITY_PREFIX_LEN) != 0)
Serge E. Hallyn8db6c342017-05-08 13:11:56 -05001042 return 0;
1043
1044 if (strcmp(name, XATTR_NAME_CAPS) == 0) {
1045 /* security.capability gets namespaced */
1046 struct inode *inode = d_backing_inode(dentry);
1047 if (!inode)
1048 return -EINVAL;
Christian Brauner71bc3562021-01-21 14:19:29 +01001049 if (!capable_wrt_inode_uidgid(mnt_userns, inode, CAP_SETFCAP))
Serge E. Hallynb5376772007-10-16 23:31:36 -07001050 return -EPERM;
1051 return 0;
David Howells1d045982008-11-14 10:39:24 +11001052 }
1053
Eric W. Biedermanb1d749c2017-04-21 19:14:32 -05001054 if (!ns_capable(user_ns, CAP_SYS_ADMIN))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001055 return -EPERM;
1056 return 0;
1057}
1058
David Howellsa6f76f22008-11-14 10:39:24 +11001059/*
Linus Torvalds1da177e2005-04-16 15:20:36 -07001060 * cap_emulate_setxuid() fixes the effective / permitted capabilities of
1061 * a process after a call to setuid, setreuid, or setresuid.
1062 *
1063 * 1) When set*uiding _from_ one of {r,e,s}uid == 0 _to_ all of
1064 * {r,e,s}uid != 0, the permitted and effective capabilities are
1065 * cleared.
1066 *
1067 * 2) When set*uiding _from_ euid == 0 _to_ euid != 0, the effective
1068 * capabilities of the process are cleared.
1069 *
1070 * 3) When set*uiding _from_ euid != 0 _to_ euid == 0, the effective
1071 * capabilities are set to the permitted capabilities.
1072 *
David Howellsa6f76f22008-11-14 10:39:24 +11001073 * fsuid is handled elsewhere. fsuid == 0 and {r,e,s}uid!= 0 should
Linus Torvalds1da177e2005-04-16 15:20:36 -07001074 * never happen.
1075 *
David Howellsa6f76f22008-11-14 10:39:24 +11001076 * -astor
Linus Torvalds1da177e2005-04-16 15:20:36 -07001077 *
1078 * cevans - New behaviour, Oct '99
1079 * A process may, via prctl(), elect to keep its capabilities when it
1080 * calls setuid() and switches away from uid==0. Both permitted and
1081 * effective sets will be retained.
1082 * Without this change, it was impossible for a daemon to drop only some
1083 * of its privilege. The call to setuid(!=0) would drop all privileges!
1084 * Keeping uid 0 is not an option because uid 0 owns too many vital
1085 * files..
1086 * Thanks to Olaf Kirch and Peter Benie for spotting this.
1087 */
David Howellsd84f4f92008-11-14 10:39:23 +11001088static inline void cap_emulate_setxuid(struct cred *new, const struct cred *old)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001089{
Eric W. Biederman18815a12012-02-07 16:45:47 -08001090 kuid_t root_uid = make_kuid(old->user_ns, 0);
1091
1092 if ((uid_eq(old->uid, root_uid) ||
1093 uid_eq(old->euid, root_uid) ||
1094 uid_eq(old->suid, root_uid)) &&
1095 (!uid_eq(new->uid, root_uid) &&
1096 !uid_eq(new->euid, root_uid) &&
Andy Lutomirski58319052015-09-04 15:42:45 -07001097 !uid_eq(new->suid, root_uid))) {
1098 if (!issecure(SECURE_KEEP_CAPS)) {
1099 cap_clear(new->cap_permitted);
1100 cap_clear(new->cap_effective);
1101 }
1102
1103 /*
1104 * Pre-ambient programs expect setresuid to nonroot followed
1105 * by exec to drop capabilities. We should make sure that
1106 * this remains the case.
1107 */
1108 cap_clear(new->cap_ambient);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001109 }
Eric W. Biederman18815a12012-02-07 16:45:47 -08001110 if (uid_eq(old->euid, root_uid) && !uid_eq(new->euid, root_uid))
David Howellsd84f4f92008-11-14 10:39:23 +11001111 cap_clear(new->cap_effective);
Eric W. Biederman18815a12012-02-07 16:45:47 -08001112 if (!uid_eq(old->euid, root_uid) && uid_eq(new->euid, root_uid))
David Howellsd84f4f92008-11-14 10:39:23 +11001113 new->cap_effective = new->cap_permitted;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001114}
1115
David Howells1d045982008-11-14 10:39:24 +11001116/**
1117 * cap_task_fix_setuid - Fix up the results of setuid() call
1118 * @new: The proposed credentials
1119 * @old: The current task's current credentials
1120 * @flags: Indications of what has changed
1121 *
1122 * Fix up the results of setuid() call before the credential changes are
Randy Dunlap049ae602021-04-11 17:55:28 -07001123 * actually applied.
1124 *
1125 * Return: 0 to grant the changes, -ve to deny them.
David Howells1d045982008-11-14 10:39:24 +11001126 */
David Howellsd84f4f92008-11-14 10:39:23 +11001127int cap_task_fix_setuid(struct cred *new, const struct cred *old, int flags)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001128{
1129 switch (flags) {
1130 case LSM_SETID_RE:
1131 case LSM_SETID_ID:
1132 case LSM_SETID_RES:
David Howells1d045982008-11-14 10:39:24 +11001133 /* juggle the capabilities to follow [RES]UID changes unless
1134 * otherwise suppressed */
David Howellsd84f4f92008-11-14 10:39:23 +11001135 if (!issecure(SECURE_NO_SETUID_FIXUP))
1136 cap_emulate_setxuid(new, old);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001137 break;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001138
David Howells1d045982008-11-14 10:39:24 +11001139 case LSM_SETID_FS:
1140 /* juggle the capabilties to follow FSUID changes, unless
1141 * otherwise suppressed
1142 *
David Howellsd84f4f92008-11-14 10:39:23 +11001143 * FIXME - is fsuser used for all CAP_FS_MASK capabilities?
1144 * if not, we might be a bit too harsh here.
1145 */
1146 if (!issecure(SECURE_NO_SETUID_FIXUP)) {
Eric W. Biederman18815a12012-02-07 16:45:47 -08001147 kuid_t root_uid = make_kuid(old->user_ns, 0);
1148 if (uid_eq(old->fsuid, root_uid) && !uid_eq(new->fsuid, root_uid))
David Howellsd84f4f92008-11-14 10:39:23 +11001149 new->cap_effective =
1150 cap_drop_fs_set(new->cap_effective);
David Howells1d045982008-11-14 10:39:24 +11001151
Eric W. Biederman18815a12012-02-07 16:45:47 -08001152 if (!uid_eq(old->fsuid, root_uid) && uid_eq(new->fsuid, root_uid))
David Howellsd84f4f92008-11-14 10:39:23 +11001153 new->cap_effective =
1154 cap_raise_fs_set(new->cap_effective,
1155 new->cap_permitted);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001156 }
David Howellsd84f4f92008-11-14 10:39:23 +11001157 break;
David Howells1d045982008-11-14 10:39:24 +11001158
Linus Torvalds1da177e2005-04-16 15:20:36 -07001159 default:
1160 return -EINVAL;
1161 }
1162
1163 return 0;
1164}
1165
Serge E. Hallynb5376772007-10-16 23:31:36 -07001166/*
1167 * Rationale: code calling task_setscheduler, task_setioprio, and
1168 * task_setnice, assumes that
1169 * . if capable(cap_sys_nice), then those actions should be allowed
1170 * . if not capable(cap_sys_nice), but acting on your own processes,
1171 * then those actions should be allowed
1172 * This is insufficient now since you can call code without suid, but
1173 * yet with increased caps.
1174 * So we check for increased caps on the target process.
1175 */
Serge E. Hallynde45e802008-09-26 22:27:47 -04001176static int cap_safe_nice(struct task_struct *p)
Serge E. Hallynb5376772007-10-16 23:31:36 -07001177{
Serge Hallynf54fb862013-07-23 13:18:53 -05001178 int is_subset, ret = 0;
David Howellsc69e8d92008-11-14 10:39:19 +11001179
1180 rcu_read_lock();
1181 is_subset = cap_issubset(__task_cred(p)->cap_permitted,
1182 current_cred()->cap_permitted);
Serge Hallynf54fb862013-07-23 13:18:53 -05001183 if (!is_subset && !ns_capable(__task_cred(p)->user_ns, CAP_SYS_NICE))
1184 ret = -EPERM;
David Howellsc69e8d92008-11-14 10:39:19 +11001185 rcu_read_unlock();
1186
Serge Hallynf54fb862013-07-23 13:18:53 -05001187 return ret;
Serge E. Hallynb5376772007-10-16 23:31:36 -07001188}
1189
David Howells1d045982008-11-14 10:39:24 +11001190/**
1191 * cap_task_setscheduler - Detemine if scheduler policy change is permitted
1192 * @p: The task to affect
David Howells1d045982008-11-14 10:39:24 +11001193 *
1194 * Detemine if the requested scheduler policy change is permitted for the
Randy Dunlap049ae602021-04-11 17:55:28 -07001195 * specified task.
1196 *
1197 * Return: 0 if permission is granted, -ve if denied.
David Howells1d045982008-11-14 10:39:24 +11001198 */
KOSAKI Motohirob0ae1982010-10-15 04:21:18 +09001199int cap_task_setscheduler(struct task_struct *p)
Serge E. Hallynb5376772007-10-16 23:31:36 -07001200{
1201 return cap_safe_nice(p);
1202}
1203
David Howells1d045982008-11-14 10:39:24 +11001204/**
Randy Dunlap049ae602021-04-11 17:55:28 -07001205 * cap_task_setioprio - Detemine if I/O priority change is permitted
David Howells1d045982008-11-14 10:39:24 +11001206 * @p: The task to affect
1207 * @ioprio: The I/O priority to set
1208 *
1209 * Detemine if the requested I/O priority change is permitted for the specified
Randy Dunlap049ae602021-04-11 17:55:28 -07001210 * task.
1211 *
1212 * Return: 0 if permission is granted, -ve if denied.
David Howells1d045982008-11-14 10:39:24 +11001213 */
1214int cap_task_setioprio(struct task_struct *p, int ioprio)
Serge E. Hallynb5376772007-10-16 23:31:36 -07001215{
1216 return cap_safe_nice(p);
1217}
1218
David Howells1d045982008-11-14 10:39:24 +11001219/**
Randy Dunlap049ae602021-04-11 17:55:28 -07001220 * cap_task_setnice - Detemine if task priority change is permitted
David Howells1d045982008-11-14 10:39:24 +11001221 * @p: The task to affect
1222 * @nice: The nice value to set
1223 *
1224 * Detemine if the requested task priority change is permitted for the
Randy Dunlap049ae602021-04-11 17:55:28 -07001225 * specified task.
1226 *
1227 * Return: 0 if permission is granted, -ve if denied.
David Howells1d045982008-11-14 10:39:24 +11001228 */
1229int cap_task_setnice(struct task_struct *p, int nice)
Serge E. Hallynb5376772007-10-16 23:31:36 -07001230{
1231 return cap_safe_nice(p);
1232}
1233
Serge E. Hallyn3b7391d2008-02-04 22:29:45 -08001234/*
David Howells1d045982008-11-14 10:39:24 +11001235 * Implement PR_CAPBSET_DROP. Attempt to remove the specified capability from
1236 * the current task's bounding set. Returns 0 on success, -ve on error.
Serge E. Hallyn3b7391d2008-02-04 22:29:45 -08001237 */
Tetsuo Handa6d6f3322014-07-22 21:20:01 +09001238static int cap_prctl_drop(unsigned long cap)
Serge E. Hallyn3b7391d2008-02-04 22:29:45 -08001239{
Tetsuo Handa6d6f3322014-07-22 21:20:01 +09001240 struct cred *new;
1241
Eric W. Biederman160da842013-07-02 10:04:54 -07001242 if (!ns_capable(current_user_ns(), CAP_SETPCAP))
Serge E. Hallyn3b7391d2008-02-04 22:29:45 -08001243 return -EPERM;
1244 if (!cap_valid(cap))
1245 return -EINVAL;
David Howellsd84f4f92008-11-14 10:39:23 +11001246
Tetsuo Handa6d6f3322014-07-22 21:20:01 +09001247 new = prepare_creds();
1248 if (!new)
1249 return -ENOMEM;
David Howellsd84f4f92008-11-14 10:39:23 +11001250 cap_lower(new->cap_bset, cap);
Tetsuo Handa6d6f3322014-07-22 21:20:01 +09001251 return commit_creds(new);
Serge E. Hallyn3b7391d2008-02-04 22:29:45 -08001252}
Andrew G. Morgan3898b1b2008-04-28 02:13:40 -07001253
David Howells1d045982008-11-14 10:39:24 +11001254/**
1255 * cap_task_prctl - Implement process control functions for this security module
1256 * @option: The process control function requested
Randy Dunlap049ae602021-04-11 17:55:28 -07001257 * @arg2: The argument data for this function
1258 * @arg3: The argument data for this function
1259 * @arg4: The argument data for this function
1260 * @arg5: The argument data for this function
David Howells1d045982008-11-14 10:39:24 +11001261 *
1262 * Allow process control functions (sys_prctl()) to alter capabilities; may
1263 * also deny access to other functions not otherwise implemented here.
1264 *
Randy Dunlap049ae602021-04-11 17:55:28 -07001265 * Return: 0 or +ve on success, -ENOSYS if this function is not implemented
David Howells1d045982008-11-14 10:39:24 +11001266 * here, other -ve on error. If -ENOSYS is returned, sys_prctl() and other LSM
1267 * modules will consider performing the function.
1268 */
Andrew G. Morgan3898b1b2008-04-28 02:13:40 -07001269int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3,
David Howellsd84f4f92008-11-14 10:39:23 +11001270 unsigned long arg4, unsigned long arg5)
Andrew G. Morgan3898b1b2008-04-28 02:13:40 -07001271{
Tetsuo Handa6d6f3322014-07-22 21:20:01 +09001272 const struct cred *old = current_cred();
David Howellsd84f4f92008-11-14 10:39:23 +11001273 struct cred *new;
David Howellsd84f4f92008-11-14 10:39:23 +11001274
Andrew G. Morgan3898b1b2008-04-28 02:13:40 -07001275 switch (option) {
1276 case PR_CAPBSET_READ:
1277 if (!cap_valid(arg2))
Tetsuo Handa6d6f3322014-07-22 21:20:01 +09001278 return -EINVAL;
1279 return !!cap_raised(old->cap_bset, arg2);
David Howellsd84f4f92008-11-14 10:39:23 +11001280
Andrew G. Morgan3898b1b2008-04-28 02:13:40 -07001281 case PR_CAPBSET_DROP:
Tetsuo Handa6d6f3322014-07-22 21:20:01 +09001282 return cap_prctl_drop(arg2);
Andrew G. Morgan3898b1b2008-04-28 02:13:40 -07001283
1284 /*
1285 * The next four prctl's remain to assist with transitioning a
1286 * system from legacy UID=0 based privilege (when filesystem
1287 * capabilities are not in use) to a system using filesystem
1288 * capabilities only - as the POSIX.1e draft intended.
1289 *
1290 * Note:
1291 *
1292 * PR_SET_SECUREBITS =
1293 * issecure_mask(SECURE_KEEP_CAPS_LOCKED)
1294 * | issecure_mask(SECURE_NOROOT)
1295 * | issecure_mask(SECURE_NOROOT_LOCKED)
1296 * | issecure_mask(SECURE_NO_SETUID_FIXUP)
1297 * | issecure_mask(SECURE_NO_SETUID_FIXUP_LOCKED)
1298 *
1299 * will ensure that the current process and all of its
1300 * children will be locked into a pure
1301 * capability-based-privilege environment.
1302 */
1303 case PR_SET_SECUREBITS:
Tetsuo Handa6d6f3322014-07-22 21:20:01 +09001304 if ((((old->securebits & SECURE_ALL_LOCKS) >> 1)
1305 & (old->securebits ^ arg2)) /*[1]*/
1306 || ((old->securebits & SECURE_ALL_LOCKS & ~arg2)) /*[2]*/
David Howellsd84f4f92008-11-14 10:39:23 +11001307 || (arg2 & ~(SECURE_ALL_LOCKS | SECURE_ALL_BITS)) /*[3]*/
Eric Paris6a9de492012-01-03 12:25:14 -05001308 || (cap_capable(current_cred(),
Micah Mortonc1a85a02019-01-07 16:10:53 -08001309 current_cred()->user_ns,
1310 CAP_SETPCAP,
1311 CAP_OPT_NONE) != 0) /*[4]*/
Andrew G. Morgan3898b1b2008-04-28 02:13:40 -07001312 /*
1313 * [1] no changing of bits that are locked
1314 * [2] no unlocking of locks
1315 * [3] no setting of unsupported bits
1316 * [4] doing anything requires privilege (go read about
1317 * the "sendmail capabilities bug")
1318 */
David Howellsd84f4f92008-11-14 10:39:23 +11001319 )
1320 /* cannot change a locked bit */
Tetsuo Handa6d6f3322014-07-22 21:20:01 +09001321 return -EPERM;
1322
1323 new = prepare_creds();
1324 if (!new)
1325 return -ENOMEM;
David Howellsd84f4f92008-11-14 10:39:23 +11001326 new->securebits = arg2;
Tetsuo Handa6d6f3322014-07-22 21:20:01 +09001327 return commit_creds(new);
David Howellsd84f4f92008-11-14 10:39:23 +11001328
Andrew G. Morgan3898b1b2008-04-28 02:13:40 -07001329 case PR_GET_SECUREBITS:
Tetsuo Handa6d6f3322014-07-22 21:20:01 +09001330 return old->securebits;
Andrew G. Morgan3898b1b2008-04-28 02:13:40 -07001331
Andrew G. Morgan3898b1b2008-04-28 02:13:40 -07001332 case PR_GET_KEEPCAPS:
Tetsuo Handa6d6f3322014-07-22 21:20:01 +09001333 return !!issecure(SECURE_KEEP_CAPS);
David Howellsd84f4f92008-11-14 10:39:23 +11001334
Andrew G. Morgan3898b1b2008-04-28 02:13:40 -07001335 case PR_SET_KEEPCAPS:
1336 if (arg2 > 1) /* Note, we rely on arg2 being unsigned here */
Tetsuo Handa6d6f3322014-07-22 21:20:01 +09001337 return -EINVAL;
David Howellsd84f4f92008-11-14 10:39:23 +11001338 if (issecure(SECURE_KEEP_CAPS_LOCKED))
Tetsuo Handa6d6f3322014-07-22 21:20:01 +09001339 return -EPERM;
1340
1341 new = prepare_creds();
1342 if (!new)
1343 return -ENOMEM;
David Howellsd84f4f92008-11-14 10:39:23 +11001344 if (arg2)
1345 new->securebits |= issecure_mask(SECURE_KEEP_CAPS);
Andrew G. Morgan3898b1b2008-04-28 02:13:40 -07001346 else
David Howellsd84f4f92008-11-14 10:39:23 +11001347 new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
Tetsuo Handa6d6f3322014-07-22 21:20:01 +09001348 return commit_creds(new);
Andrew G. Morgan3898b1b2008-04-28 02:13:40 -07001349
Andy Lutomirski58319052015-09-04 15:42:45 -07001350 case PR_CAP_AMBIENT:
1351 if (arg2 == PR_CAP_AMBIENT_CLEAR_ALL) {
1352 if (arg3 | arg4 | arg5)
1353 return -EINVAL;
1354
1355 new = prepare_creds();
1356 if (!new)
1357 return -ENOMEM;
1358 cap_clear(new->cap_ambient);
1359 return commit_creds(new);
1360 }
1361
1362 if (((!cap_valid(arg3)) | arg4 | arg5))
1363 return -EINVAL;
1364
1365 if (arg2 == PR_CAP_AMBIENT_IS_SET) {
1366 return !!cap_raised(current_cred()->cap_ambient, arg3);
1367 } else if (arg2 != PR_CAP_AMBIENT_RAISE &&
1368 arg2 != PR_CAP_AMBIENT_LOWER) {
1369 return -EINVAL;
1370 } else {
1371 if (arg2 == PR_CAP_AMBIENT_RAISE &&
1372 (!cap_raised(current_cred()->cap_permitted, arg3) ||
1373 !cap_raised(current_cred()->cap_inheritable,
Andy Lutomirski746bf6d2015-09-04 15:42:51 -07001374 arg3) ||
1375 issecure(SECURE_NO_CAP_AMBIENT_RAISE)))
Andy Lutomirski58319052015-09-04 15:42:45 -07001376 return -EPERM;
1377
1378 new = prepare_creds();
1379 if (!new)
1380 return -ENOMEM;
1381 if (arg2 == PR_CAP_AMBIENT_RAISE)
1382 cap_raise(new->cap_ambient, arg3);
1383 else
1384 cap_lower(new->cap_ambient, arg3);
1385 return commit_creds(new);
1386 }
1387
Andrew G. Morgan3898b1b2008-04-28 02:13:40 -07001388 default:
1389 /* No functionality available - continue with default */
Tetsuo Handa6d6f3322014-07-22 21:20:01 +09001390 return -ENOSYS;
Andrew G. Morgan3898b1b2008-04-28 02:13:40 -07001391 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001392}
1393
David Howells1d045982008-11-14 10:39:24 +11001394/**
David Howells1d045982008-11-14 10:39:24 +11001395 * cap_vm_enough_memory - Determine whether a new virtual mapping is permitted
1396 * @mm: The VM space in which the new mapping is to be made
1397 * @pages: The size of the mapping
1398 *
1399 * Determine whether the allocation of a new virtual mapping by the current
Randy Dunlap049ae602021-04-11 17:55:28 -07001400 * task is permitted.
1401 *
1402 * Return: 1 if permission is granted, 0 if not.
David Howells1d045982008-11-14 10:39:24 +11001403 */
Alan Cox34b4e4a2007-08-22 14:01:28 -07001404int cap_vm_enough_memory(struct mm_struct *mm, long pages)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001405{
1406 int cap_sys_admin = 0;
1407
Micah Mortonc1a85a02019-01-07 16:10:53 -08001408 if (cap_capable(current_cred(), &init_user_ns,
1409 CAP_SYS_ADMIN, CAP_OPT_NOAUDIT) == 0)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001410 cap_sys_admin = 1;
Micah Mortonc1a85a02019-01-07 16:10:53 -08001411
Casey Schauflerb1d9e6b2015-05-02 15:11:42 -07001412 return cap_sys_admin;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001413}
Eric Paris7c738752009-07-31 12:53:58 -04001414
Randy Dunlap049ae602021-04-11 17:55:28 -07001415/**
Al Virod0077942012-05-30 13:11:37 -04001416 * cap_mmap_addr - check if able to map given addr
1417 * @addr: address attempting to be mapped
1418 *
1419 * If the process is attempting to map memory below dac_mmap_min_addr they need
1420 * CAP_SYS_RAWIO. The other parameters to this function are unused by the
Randy Dunlap049ae602021-04-11 17:55:28 -07001421 * capability security module.
1422 *
1423 * Return: 0 if this mapping should be allowed or -EPERM if not.
Al Virod0077942012-05-30 13:11:37 -04001424 */
1425int cap_mmap_addr(unsigned long addr)
1426{
1427 int ret = 0;
1428
1429 if (addr < dac_mmap_min_addr) {
1430 ret = cap_capable(current_cred(), &init_user_ns, CAP_SYS_RAWIO,
Micah Mortonc1a85a02019-01-07 16:10:53 -08001431 CAP_OPT_NONE);
Al Virod0077942012-05-30 13:11:37 -04001432 /* set PF_SUPERPRIV if it turns out we allow the low mmap */
1433 if (ret == 0)
1434 current->flags |= PF_SUPERPRIV;
1435 }
1436 return ret;
1437}
1438
Al Viroe5467852012-05-30 13:30:51 -04001439int cap_mmap_file(struct file *file, unsigned long reqprot,
1440 unsigned long prot, unsigned long flags)
Eric Paris7c738752009-07-31 12:53:58 -04001441{
Al Viroe5467852012-05-30 13:30:51 -04001442 return 0;
Eric Paris7c738752009-07-31 12:53:58 -04001443}
Casey Schauflerb1d9e6b2015-05-02 15:11:42 -07001444
1445#ifdef CONFIG_SECURITY
1446
YueHaibingd1c59472019-06-11 21:48:15 +08001447static struct security_hook_list capability_hooks[] __lsm_ro_after_init = {
Casey Schauflerb1d9e6b2015-05-02 15:11:42 -07001448 LSM_HOOK_INIT(capable, cap_capable),
1449 LSM_HOOK_INIT(settime, cap_settime),
1450 LSM_HOOK_INIT(ptrace_access_check, cap_ptrace_access_check),
1451 LSM_HOOK_INIT(ptrace_traceme, cap_ptrace_traceme),
1452 LSM_HOOK_INIT(capget, cap_capget),
1453 LSM_HOOK_INIT(capset, cap_capset),
Eric W. Biederman56305aa2020-05-29 22:00:54 -05001454 LSM_HOOK_INIT(bprm_creds_from_file, cap_bprm_creds_from_file),
Casey Schauflerb1d9e6b2015-05-02 15:11:42 -07001455 LSM_HOOK_INIT(inode_need_killpriv, cap_inode_need_killpriv),
1456 LSM_HOOK_INIT(inode_killpriv, cap_inode_killpriv),
Serge E. Hallyn8db6c342017-05-08 13:11:56 -05001457 LSM_HOOK_INIT(inode_getsecurity, cap_inode_getsecurity),
Casey Schauflerb1d9e6b2015-05-02 15:11:42 -07001458 LSM_HOOK_INIT(mmap_addr, cap_mmap_addr),
1459 LSM_HOOK_INIT(mmap_file, cap_mmap_file),
1460 LSM_HOOK_INIT(task_fix_setuid, cap_task_fix_setuid),
1461 LSM_HOOK_INIT(task_prctl, cap_task_prctl),
1462 LSM_HOOK_INIT(task_setscheduler, cap_task_setscheduler),
1463 LSM_HOOK_INIT(task_setioprio, cap_task_setioprio),
1464 LSM_HOOK_INIT(task_setnice, cap_task_setnice),
1465 LSM_HOOK_INIT(vm_enough_memory, cap_vm_enough_memory),
1466};
1467
Kees Cookd117a152018-09-14 15:40:45 -07001468static int __init capability_init(void)
Casey Schauflerb1d9e6b2015-05-02 15:11:42 -07001469{
Casey Schauflerd69dece52017-01-18 17:09:05 -08001470 security_add_hooks(capability_hooks, ARRAY_SIZE(capability_hooks),
1471 "capability");
Kees Cookd117a152018-09-14 15:40:45 -07001472 return 0;
Casey Schauflerb1d9e6b2015-05-02 15:11:42 -07001473}
1474
Kees Cookd117a152018-09-14 15:40:45 -07001475DEFINE_LSM(capability) = {
1476 .name = "capability",
1477 .order = LSM_ORDER_FIRST,
1478 .init = capability_init,
1479};
1480
Casey Schauflerb1d9e6b2015-05-02 15:11:42 -07001481#endif /* CONFIG_SECURITY */