blob: 28f4d25480dfa018afd0703f714443f14843079d [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>
Andrew Morgan72c2d582007-10-18 03:05:59 -070027
Serge E. Hallynb5f22a52009-04-02 18:47:14 -050028/*
29 * If a non-root user executes a setuid-root binary in
30 * !secure(SECURE_NOROOT) mode, then we raise capabilities.
31 * However if fE is also set, then the intent is for only
32 * the file capabilities to be applied, and the setuid-root
33 * bit is left on either to change the uid (plausible) or
34 * to get full privilege on a kernel without file capabilities
35 * support. So in that case we do not raise capabilities.
36 *
37 * Warn if that happens, once per boot.
38 */
David Howellsd7627462010-08-17 23:52:56 +010039static void warn_setuid_and_fcaps_mixed(const char *fname)
Serge E. Hallynb5f22a52009-04-02 18:47:14 -050040{
41 static int warned;
42 if (!warned) {
43 printk(KERN_INFO "warning: `%s' has both setuid-root and"
44 " effective capabilities. Therefore not raising all"
45 " capabilities.\n", fname);
46 warned = 1;
47 }
48}
49
David Howells1d045982008-11-14 10:39:24 +110050/**
51 * cap_capable - Determine whether a task has a particular effective capability
David Howells3699c532009-01-06 22:27:01 +000052 * @cred: The credentials to use
Serge E. Hallyn34867402011-03-23 16:43:17 -070053 * @ns: The user namespace in which we need the capability
David Howells1d045982008-11-14 10:39:24 +110054 * @cap: The capability to check for
Micah Mortone88ed482019-02-25 14:17:10 -080055 * @opts: Bitmask of options defined in include/linux/security.h
David Howells1d045982008-11-14 10:39:24 +110056 *
57 * Determine whether the nominated task has the specified capability amongst
58 * its effective set, returning 0 if it does, -ve if it does not.
59 *
David Howells3699c532009-01-06 22:27:01 +000060 * NOTE WELL: cap_has_capability() cannot be used like the kernel's capable()
61 * and has_capability() functions. That is, it has the reverse semantics:
62 * cap_has_capability() returns 0 when a task has a capability, but the
63 * kernel's capable() and has_capability() returns 1 for this case.
Andrew G. Morgana6dbb1e2008-01-21 17:18:30 -080064 */
Eric Paris6a9de492012-01-03 12:25:14 -050065int cap_capable(const struct cred *cred, struct user_namespace *targ_ns,
Micah Mortonc1a85a02019-01-07 16:10:53 -080066 int cap, unsigned int opts)
Linus Torvalds1da177e2005-04-16 15:20:36 -070067{
Eric W. Biederman520d9ea2012-12-13 18:06:40 -080068 struct user_namespace *ns = targ_ns;
Serge E. Hallyn34867402011-03-23 16:43:17 -070069
Eric W. Biederman520d9ea2012-12-13 18:06:40 -080070 /* See if cred has the capability in the target user namespace
71 * by examining the target user namespace and all of the target
72 * user namespace's parents.
73 */
74 for (;;) {
Serge E. Hallyn34867402011-03-23 16:43:17 -070075 /* Do we have the necessary capabilities? */
Eric W. Biederman520d9ea2012-12-13 18:06:40 -080076 if (ns == cred->user_ns)
Serge E. Hallyn34867402011-03-23 16:43:17 -070077 return cap_raised(cred->cap_effective, cap) ? 0 : -EPERM;
78
Kirill Tkhai64db4c72017-05-02 20:11:52 +030079 /*
80 * If we're already at a lower level than we're looking for,
81 * we're done searching.
82 */
83 if (ns->level <= cred->user_ns->level)
Serge E. Hallyn34867402011-03-23 16:43:17 -070084 return -EPERM;
85
Eric W. Biederman520d9ea2012-12-13 18:06:40 -080086 /*
87 * The owner of the user namespace in the parent of the
88 * user namespace has all caps.
89 */
90 if ((ns->parent == cred->user_ns) && uid_eq(ns->owner, cred->euid))
91 return 0;
92
Serge E. Hallyn34867402011-03-23 16:43:17 -070093 /*
Eric W. Biederman520d9ea2012-12-13 18:06:40 -080094 * If you have a capability in a parent user ns, then you have
Serge E. Hallyn34867402011-03-23 16:43:17 -070095 * it over all children user namespaces as well.
96 */
Eric W. Biederman520d9ea2012-12-13 18:06:40 -080097 ns = ns->parent;
Serge E. Hallyn34867402011-03-23 16:43:17 -070098 }
99
100 /* We never get here */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700101}
102
David Howells1d045982008-11-14 10:39:24 +1100103/**
104 * cap_settime - Determine whether the current process may set the system clock
105 * @ts: The time to set
106 * @tz: The timezone to set
107 *
108 * Determine whether the current process may set the system clock and timezone
109 * information, returning 0 if permission granted, -ve if denied.
110 */
Baolin Wang457db292016-04-08 14:02:11 +0800111int cap_settime(const struct timespec64 *ts, const struct timezone *tz)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700112{
113 if (!capable(CAP_SYS_TIME))
114 return -EPERM;
115 return 0;
116}
117
David Howells1d045982008-11-14 10:39:24 +1100118/**
Ingo Molnar9e488582009-05-07 19:26:19 +1000119 * cap_ptrace_access_check - Determine whether the current process may access
David Howells1d045982008-11-14 10:39:24 +1100120 * another
121 * @child: The process to be accessed
122 * @mode: The mode of attachment.
123 *
Serge E. Hallyn8409cca2011-03-23 16:43:20 -0700124 * If we are in the same or an ancestor user_ns and have all the target
125 * task's capabilities, then ptrace access is allowed.
126 * If we have the ptrace capability to the target user_ns, then ptrace
127 * access is allowed.
128 * Else denied.
129 *
David Howells1d045982008-11-14 10:39:24 +1100130 * Determine whether a process may access another, returning 0 if permission
131 * granted, -ve if denied.
132 */
Ingo Molnar9e488582009-05-07 19:26:19 +1000133int cap_ptrace_access_check(struct task_struct *child, unsigned int mode)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700134{
David Howellsc69e8d92008-11-14 10:39:19 +1100135 int ret = 0;
Serge E. Hallyn8409cca2011-03-23 16:43:20 -0700136 const struct cred *cred, *child_cred;
Jann Horncaaee622016-01-20 15:00:04 -0800137 const kernel_cap_t *caller_caps;
David Howellsc69e8d92008-11-14 10:39:19 +1100138
139 rcu_read_lock();
Serge E. Hallyn8409cca2011-03-23 16:43:20 -0700140 cred = current_cred();
141 child_cred = __task_cred(child);
Jann Horncaaee622016-01-20 15:00:04 -0800142 if (mode & PTRACE_MODE_FSCREDS)
143 caller_caps = &cred->cap_effective;
144 else
145 caller_caps = &cred->cap_permitted;
Eric W. Biedermanc4a4d602011-11-16 23:15:31 -0800146 if (cred->user_ns == child_cred->user_ns &&
Jann Horncaaee622016-01-20 15:00:04 -0800147 cap_issubset(child_cred->cap_permitted, *caller_caps))
Serge E. Hallyn8409cca2011-03-23 16:43:20 -0700148 goto out;
Eric W. Biedermanc4a4d602011-11-16 23:15:31 -0800149 if (ns_capable(child_cred->user_ns, CAP_SYS_PTRACE))
Serge E. Hallyn8409cca2011-03-23 16:43:20 -0700150 goto out;
151 ret = -EPERM;
152out:
David Howellsc69e8d92008-11-14 10:39:19 +1100153 rcu_read_unlock();
154 return ret;
David Howells5cd9c582008-08-14 11:37:28 +0100155}
156
David Howells1d045982008-11-14 10:39:24 +1100157/**
158 * cap_ptrace_traceme - Determine whether another process may trace the current
159 * @parent: The task proposed to be the tracer
160 *
Serge E. Hallyn8409cca2011-03-23 16:43:20 -0700161 * If parent is in the same or an ancestor user_ns and has all current's
162 * capabilities, then ptrace access is allowed.
163 * If parent has the ptrace capability to current's user_ns, then ptrace
164 * access is allowed.
165 * Else denied.
166 *
David Howells1d045982008-11-14 10:39:24 +1100167 * Determine whether the nominated task is permitted to trace the current
168 * process, returning 0 if permission is granted, -ve if denied.
169 */
David Howells5cd9c582008-08-14 11:37:28 +0100170int cap_ptrace_traceme(struct task_struct *parent)
171{
David Howellsc69e8d92008-11-14 10:39:19 +1100172 int ret = 0;
Serge E. Hallyn8409cca2011-03-23 16:43:20 -0700173 const struct cred *cred, *child_cred;
David Howellsc69e8d92008-11-14 10:39:19 +1100174
175 rcu_read_lock();
Serge E. Hallyn8409cca2011-03-23 16:43:20 -0700176 cred = __task_cred(parent);
177 child_cred = current_cred();
Eric W. Biedermanc4a4d602011-11-16 23:15:31 -0800178 if (cred->user_ns == child_cred->user_ns &&
Serge E. Hallyn8409cca2011-03-23 16:43:20 -0700179 cap_issubset(child_cred->cap_permitted, cred->cap_permitted))
180 goto out;
Eric W. Biedermanc4a4d602011-11-16 23:15:31 -0800181 if (has_ns_capability(parent, child_cred->user_ns, CAP_SYS_PTRACE))
Serge E. Hallyn8409cca2011-03-23 16:43:20 -0700182 goto out;
183 ret = -EPERM;
184out:
David Howellsc69e8d92008-11-14 10:39:19 +1100185 rcu_read_unlock();
186 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700187}
188
David Howells1d045982008-11-14 10:39:24 +1100189/**
190 * cap_capget - Retrieve a task's capability sets
191 * @target: The task from which to retrieve the capability sets
192 * @effective: The place to record the effective set
193 * @inheritable: The place to record the inheritable set
194 * @permitted: The place to record the permitted set
195 *
196 * This function retrieves the capabilities of the nominated task and returns
197 * them to the caller.
198 */
199int cap_capget(struct task_struct *target, kernel_cap_t *effective,
200 kernel_cap_t *inheritable, kernel_cap_t *permitted)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700201{
David Howellsc69e8d92008-11-14 10:39:19 +1100202 const struct cred *cred;
David Howellsb6dff3e2008-11-14 10:39:16 +1100203
Linus Torvalds1da177e2005-04-16 15:20:36 -0700204 /* Derived from kernel/capability.c:sys_capget. */
David Howellsc69e8d92008-11-14 10:39:19 +1100205 rcu_read_lock();
206 cred = __task_cred(target);
David Howellsb6dff3e2008-11-14 10:39:16 +1100207 *effective = cred->cap_effective;
208 *inheritable = cred->cap_inheritable;
209 *permitted = cred->cap_permitted;
David Howellsc69e8d92008-11-14 10:39:19 +1100210 rcu_read_unlock();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700211 return 0;
212}
213
David Howells1d045982008-11-14 10:39:24 +1100214/*
215 * Determine whether the inheritable capabilities are limited to the old
216 * permitted set. Returns 1 if they are limited, 0 if they are not.
217 */
Andrew Morgan72c2d582007-10-18 03:05:59 -0700218static inline int cap_inh_is_capped(void)
219{
David Howells1d045982008-11-14 10:39:24 +1100220 /* they are so limited unless the current task has the CAP_SETPCAP
221 * capability
Andrew Morgan72c2d582007-10-18 03:05:59 -0700222 */
Eric W. Biedermanc4a4d602011-11-16 23:15:31 -0800223 if (cap_capable(current_cred(), current_cred()->user_ns,
Micah Mortonc1a85a02019-01-07 16:10:53 -0800224 CAP_SETPCAP, CAP_OPT_NONE) == 0)
David Howells1d045982008-11-14 10:39:24 +1100225 return 0;
David Howells1d045982008-11-14 10:39:24 +1100226 return 1;
Andrew Morgan72c2d582007-10-18 03:05:59 -0700227}
228
David Howells1d045982008-11-14 10:39:24 +1100229/**
230 * cap_capset - Validate and apply proposed changes to current's capabilities
231 * @new: The proposed new credentials; alterations should be made here
232 * @old: The current task's current credentials
233 * @effective: A pointer to the proposed new effective capabilities set
234 * @inheritable: A pointer to the proposed new inheritable capabilities set
235 * @permitted: A pointer to the proposed new permitted capabilities set
236 *
237 * This function validates and applies a proposed mass change to the current
238 * process's capability sets. The changes are made to the proposed new
239 * credentials, and assuming no error, will be committed by the caller of LSM.
240 */
David Howellsd84f4f92008-11-14 10:39:23 +1100241int cap_capset(struct cred *new,
242 const struct cred *old,
243 const kernel_cap_t *effective,
244 const kernel_cap_t *inheritable,
245 const kernel_cap_t *permitted)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700246{
David Howellsd84f4f92008-11-14 10:39:23 +1100247 if (cap_inh_is_capped() &&
248 !cap_issubset(*inheritable,
249 cap_combine(old->cap_inheritable,
250 old->cap_permitted)))
Andrew Morgan72c2d582007-10-18 03:05:59 -0700251 /* incapable of using this inheritable set */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700252 return -EPERM;
David Howellsd84f4f92008-11-14 10:39:23 +1100253
Serge E. Hallyn3b7391d2008-02-04 22:29:45 -0800254 if (!cap_issubset(*inheritable,
David Howellsd84f4f92008-11-14 10:39:23 +1100255 cap_combine(old->cap_inheritable,
256 old->cap_bset)))
Serge E. Hallyn3b7391d2008-02-04 22:29:45 -0800257 /* no new pI capabilities outside bounding set */
258 return -EPERM;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700259
260 /* verify restrictions on target's new Permitted set */
David Howellsd84f4f92008-11-14 10:39:23 +1100261 if (!cap_issubset(*permitted, old->cap_permitted))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700262 return -EPERM;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700263
264 /* verify the _new_Effective_ is a subset of the _new_Permitted_ */
David Howellsd84f4f92008-11-14 10:39:23 +1100265 if (!cap_issubset(*effective, *permitted))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700266 return -EPERM;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700267
David Howellsd84f4f92008-11-14 10:39:23 +1100268 new->cap_effective = *effective;
269 new->cap_inheritable = *inheritable;
270 new->cap_permitted = *permitted;
Andy Lutomirski58319052015-09-04 15:42:45 -0700271
272 /*
273 * Mask off ambient bits that are no longer both permitted and
274 * inheritable.
275 */
276 new->cap_ambient = cap_intersect(new->cap_ambient,
277 cap_intersect(*permitted,
278 *inheritable));
279 if (WARN_ON(!cap_ambient_invariant_ok(new)))
280 return -EINVAL;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700281 return 0;
282}
283
David Howells1d045982008-11-14 10:39:24 +1100284/**
285 * cap_inode_need_killpriv - Determine if inode change affects privileges
286 * @dentry: The inode/dentry in being changed with change marked ATTR_KILL_PRIV
287 *
288 * Determine if an inode having a change applied that's marked ATTR_KILL_PRIV
289 * affects the security markings on that inode, and if it is, should
Stefan Bergerab5348c2017-07-26 22:27:05 -0400290 * inode_killpriv() be invoked or the change rejected.
David Howells1d045982008-11-14 10:39:24 +1100291 *
Stefan Bergerab5348c2017-07-26 22:27:05 -0400292 * Returns 1 if security.capability has a value, meaning inode_killpriv()
293 * is required, 0 otherwise, meaning inode_killpriv() is not required.
David Howells1d045982008-11-14 10:39:24 +1100294 */
Serge E. Hallynb5376772007-10-16 23:31:36 -0700295int cap_inode_need_killpriv(struct dentry *dentry)
296{
David Howellsc6f493d2015-03-17 22:26:22 +0000297 struct inode *inode = d_backing_inode(dentry);
Serge E. Hallynb5376772007-10-16 23:31:36 -0700298 int error;
299
Andreas Gruenbacher5d6c3192016-09-29 17:48:42 +0200300 error = __vfs_getxattr(dentry, inode, XATTR_NAME_CAPS, NULL, 0);
301 return error > 0;
Serge E. Hallynb5376772007-10-16 23:31:36 -0700302}
303
David Howells1d045982008-11-14 10:39:24 +1100304/**
305 * cap_inode_killpriv - Erase the security markings on an inode
Christian Brauner71bc3562021-01-21 14:19:29 +0100306 *
307 * @mnt_userns: user namespace of the mount the inode was found from
308 * @dentry: The inode/dentry to alter
David Howells1d045982008-11-14 10:39:24 +1100309 *
310 * Erase the privilege-enhancing security markings on an inode.
311 *
Christian Brauner71bc3562021-01-21 14:19:29 +0100312 * If the inode has been found through an idmapped mount the user namespace of
313 * the vfsmount must be passed through @mnt_userns. This function will then
314 * take care to map the inode according to @mnt_userns before checking
315 * permissions. On non-idmapped mounts or if permission checking is to be
316 * performed on the raw inode simply passs init_user_ns.
317 *
David Howells1d045982008-11-14 10:39:24 +1100318 * Returns 0 if successful, -ve on error.
319 */
Christian Brauner71bc3562021-01-21 14:19:29 +0100320int cap_inode_killpriv(struct user_namespace *mnt_userns, struct dentry *dentry)
Serge E. Hallynb5376772007-10-16 23:31:36 -0700321{
Andreas Gruenbacher5d6c3192016-09-29 17:48:42 +0200322 int error;
Serge E. Hallynb5376772007-10-16 23:31:36 -0700323
Christian Brauner71bc3562021-01-21 14:19:29 +0100324 error = __vfs_removexattr(mnt_userns, dentry, XATTR_NAME_CAPS);
Andreas Gruenbacher5d6c3192016-09-29 17:48:42 +0200325 if (error == -EOPNOTSUPP)
326 error = 0;
327 return error;
Serge E. Hallynb5376772007-10-16 23:31:36 -0700328}
329
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500330static bool rootid_owns_currentns(kuid_t kroot)
331{
332 struct user_namespace *ns;
333
334 if (!uid_valid(kroot))
335 return false;
336
337 for (ns = current_user_ns(); ; ns = ns->parent) {
338 if (from_kuid(ns, kroot) == 0)
339 return true;
340 if (ns == &init_user_ns)
341 break;
342 }
343
344 return false;
345}
346
347static __u32 sansflags(__u32 m)
348{
349 return m & ~VFS_CAP_FLAGS_EFFECTIVE;
350}
351
Eric Biggersdc32b5c2018-01-01 09:28:31 -0600352static bool is_v2header(size_t size, const struct vfs_cap_data *cap)
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500353{
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500354 if (size != XATTR_CAPS_SZ_2)
355 return false;
Eric Biggersdc32b5c2018-01-01 09:28:31 -0600356 return sansflags(le32_to_cpu(cap->magic_etc)) == VFS_CAP_REVISION_2;
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500357}
358
Eric Biggersdc32b5c2018-01-01 09:28:31 -0600359static bool is_v3header(size_t size, const struct vfs_cap_data *cap)
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500360{
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500361 if (size != XATTR_CAPS_SZ_3)
362 return false;
Eric Biggersdc32b5c2018-01-01 09:28:31 -0600363 return sansflags(le32_to_cpu(cap->magic_etc)) == VFS_CAP_REVISION_3;
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500364}
365
366/*
367 * getsecurity: We are called for security.* before any attempt to read the
368 * xattr from the inode itself.
369 *
370 * This gives us a chance to read the on-disk value and convert it. If we
371 * return -EOPNOTSUPP, then vfs_getxattr() will call the i_op handler.
372 *
373 * Note we are not called by vfs_getxattr_alloc(), but that is only called
374 * by the integrity subsystem, which really wants the unconverted values -
375 * so that's good.
376 */
Christian Brauner71bc3562021-01-21 14:19:29 +0100377int cap_inode_getsecurity(struct user_namespace *mnt_userns,
378 struct inode *inode, const char *name, void **buffer,
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500379 bool alloc)
380{
381 int size, ret;
382 kuid_t kroot;
Miklos Szeredif2b00be2021-01-28 10:22:48 +0100383 u32 nsmagic, magic;
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500384 uid_t root, mappedroot;
385 char *tmpbuf = NULL;
386 struct vfs_cap_data *cap;
Miklos Szeredif2b00be2021-01-28 10:22:48 +0100387 struct vfs_ns_cap_data *nscap = NULL;
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500388 struct dentry *dentry;
389 struct user_namespace *fs_ns;
390
391 if (strcmp(name, "capability") != 0)
392 return -EOPNOTSUPP;
393
Eddie.Horng355139a2018-07-20 15:30:00 +0800394 dentry = d_find_any_alias(inode);
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500395 if (!dentry)
396 return -EINVAL;
397
398 size = sizeof(struct vfs_ns_cap_data);
Christian Brauner71bc3562021-01-21 14:19:29 +0100399 ret = (int)vfs_getxattr_alloc(mnt_userns, dentry, XATTR_NAME_CAPS,
Tycho Andersenc7c7a1a12021-01-21 14:19:28 +0100400 &tmpbuf, size, GFP_NOFS);
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500401 dput(dentry);
402
403 if (ret < 0)
404 return ret;
405
406 fs_ns = inode->i_sb->s_user_ns;
407 cap = (struct vfs_cap_data *) tmpbuf;
Eric Biggersdc32b5c2018-01-01 09:28:31 -0600408 if (is_v2header((size_t) ret, cap)) {
Miklos Szeredif2b00be2021-01-28 10:22:48 +0100409 root = 0;
410 } else if (is_v3header((size_t) ret, cap)) {
411 nscap = (struct vfs_ns_cap_data *) tmpbuf;
412 root = le32_to_cpu(nscap->rootid);
413 } else {
414 size = -EINVAL;
415 goto out_free;
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500416 }
417
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500418 kroot = make_kuid(fs_ns, root);
419
Christian Brauner71bc3562021-01-21 14:19:29 +0100420 /* If this is an idmapped mount shift the kuid. */
421 kroot = kuid_into_mnt(mnt_userns, kroot);
422
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500423 /* If the root kuid maps to a valid uid in current ns, then return
424 * this as a nscap. */
425 mappedroot = from_kuid(current_user_ns(), kroot);
426 if (mappedroot != (uid_t)-1 && mappedroot != (uid_t)0) {
Miklos Szeredif2b00be2021-01-28 10:22:48 +0100427 size = sizeof(struct vfs_ns_cap_data);
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500428 if (alloc) {
Miklos Szeredif2b00be2021-01-28 10:22:48 +0100429 if (!nscap) {
430 /* v2 -> v3 conversion */
431 nscap = kzalloc(size, GFP_ATOMIC);
432 if (!nscap) {
433 size = -ENOMEM;
434 goto out_free;
435 }
436 nsmagic = VFS_CAP_REVISION_3;
437 magic = le32_to_cpu(cap->magic_etc);
438 if (magic & VFS_CAP_FLAGS_EFFECTIVE)
439 nsmagic |= VFS_CAP_FLAGS_EFFECTIVE;
440 memcpy(&nscap->data, &cap->data, sizeof(__le32) * 2 * VFS_CAP_U32);
441 nscap->magic_etc = cpu_to_le32(nsmagic);
442 } else {
443 /* use allocated v3 buffer */
444 tmpbuf = NULL;
445 }
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500446 nscap->rootid = cpu_to_le32(mappedroot);
Miklos Szeredif2b00be2021-01-28 10:22:48 +0100447 *buffer = nscap;
448 }
449 goto out_free;
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500450 }
451
452 if (!rootid_owns_currentns(kroot)) {
Miklos Szeredif2b00be2021-01-28 10:22:48 +0100453 size = -EOVERFLOW;
454 goto out_free;
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500455 }
456
457 /* This comes from a parent namespace. Return as a v2 capability */
458 size = sizeof(struct vfs_cap_data);
459 if (alloc) {
Miklos Szeredif2b00be2021-01-28 10:22:48 +0100460 if (nscap) {
461 /* v3 -> v2 conversion */
462 cap = kzalloc(size, GFP_ATOMIC);
463 if (!cap) {
464 size = -ENOMEM;
465 goto out_free;
466 }
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500467 magic = VFS_CAP_REVISION_2;
468 nsmagic = le32_to_cpu(nscap->magic_etc);
469 if (nsmagic & VFS_CAP_FLAGS_EFFECTIVE)
470 magic |= VFS_CAP_FLAGS_EFFECTIVE;
471 memcpy(&cap->data, &nscap->data, sizeof(__le32) * 2 * VFS_CAP_U32);
472 cap->magic_etc = cpu_to_le32(magic);
Tetsuo Handa1f578172018-04-10 15:15:16 +0900473 } else {
Miklos Szeredif2b00be2021-01-28 10:22:48 +0100474 /* use unconverted v2 */
475 tmpbuf = NULL;
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500476 }
Miklos Szeredif2b00be2021-01-28 10:22:48 +0100477 *buffer = cap;
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500478 }
Miklos Szeredif2b00be2021-01-28 10:22:48 +0100479out_free:
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500480 kfree(tmpbuf);
481 return size;
482}
483
Christian Braunere65ce2a2021-01-21 14:19:27 +0100484/**
485 * rootid_from_xattr - translate root uid of vfs caps
486 *
487 * @value: vfs caps value which may be modified by this function
488 * @size: size of @ivalue
489 * @task_ns: user namespace of the caller
490 * @mnt_userns: user namespace of the mount the inode was found from
491 *
492 * If the inode has been found through an idmapped mount the user namespace of
493 * the vfsmount must be passed through @mnt_userns. This function will then
494 * take care to map the inode according to @mnt_userns before checking
495 * permissions. On non-idmapped mounts or if permission checking is to be
496 * performed on the raw inode simply passs init_user_ns.
497 */
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500498static kuid_t rootid_from_xattr(const void *value, size_t size,
Christian Braunere65ce2a2021-01-21 14:19:27 +0100499 struct user_namespace *task_ns,
500 struct user_namespace *mnt_userns)
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500501{
502 const struct vfs_ns_cap_data *nscap = value;
Christian Braunere65ce2a2021-01-21 14:19:27 +0100503 kuid_t rootkid;
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500504 uid_t rootid = 0;
505
506 if (size == XATTR_CAPS_SZ_3)
507 rootid = le32_to_cpu(nscap->rootid);
508
Christian Braunere65ce2a2021-01-21 14:19:27 +0100509 rootkid = make_kuid(task_ns, rootid);
510 return kuid_from_mnt(mnt_userns, rootkid);
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500511}
512
Eric Biggersdc32b5c2018-01-01 09:28:31 -0600513static bool validheader(size_t size, const struct vfs_cap_data *cap)
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500514{
Eric Biggersdc32b5c2018-01-01 09:28:31 -0600515 return is_v2header(size, cap) || is_v3header(size, cap);
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500516}
517
Christian Braunere65ce2a2021-01-21 14:19:27 +0100518/**
519 * cap_convert_nscap - check vfs caps
520 *
521 * @mnt_userns: user namespace of the mount the inode was found from
522 * @dentry: used to retrieve inode to check permissions on
523 * @ivalue: vfs caps value which may be modified by this function
524 * @size: size of @ivalue
525 *
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500526 * User requested a write of security.capability. If needed, update the
527 * xattr to change from v2 to v3, or to fixup the v3 rootid.
528 *
Christian Braunere65ce2a2021-01-21 14:19:27 +0100529 * If the inode has been found through an idmapped mount the user namespace of
530 * the vfsmount must be passed through @mnt_userns. This function will then
531 * take care to map the inode according to @mnt_userns before checking
532 * permissions. On non-idmapped mounts or if permission checking is to be
533 * performed on the raw inode simply passs init_user_ns.
534 *
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500535 * If all is ok, we return the new size, on error return < 0.
536 */
Christian Braunere65ce2a2021-01-21 14:19:27 +0100537int cap_convert_nscap(struct user_namespace *mnt_userns, struct dentry *dentry,
538 const void **ivalue, size_t size)
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500539{
540 struct vfs_ns_cap_data *nscap;
541 uid_t nsrootid;
542 const struct vfs_cap_data *cap = *ivalue;
543 __u32 magic, nsmagic;
544 struct inode *inode = d_backing_inode(dentry);
545 struct user_namespace *task_ns = current_user_ns(),
Eric W. Biederman95ebabd2020-12-17 09:42:00 -0600546 *fs_ns = inode->i_sb->s_user_ns,
547 *ancestor;
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
Eric W. Biederman95ebabd2020-12-17 09:42:00 -0600570 /*
571 * Do not allow allow adding a v3 filesystem capability xattr
572 * if the rootid field is ambiguous.
573 */
574 for (ancestor = task_ns->parent; ancestor; ancestor = ancestor->parent) {
575 if (from_kuid(ancestor, rootid) == 0)
576 return -EINVAL;
577 }
578
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500579 newsize = sizeof(struct vfs_ns_cap_data);
580 nscap = kmalloc(newsize, GFP_ATOMIC);
581 if (!nscap)
582 return -ENOMEM;
583 nscap->rootid = cpu_to_le32(nsrootid);
584 nsmagic = VFS_CAP_REVISION_3;
585 magic = le32_to_cpu(cap->magic_etc);
586 if (magic & VFS_CAP_FLAGS_EFFECTIVE)
587 nsmagic |= VFS_CAP_FLAGS_EFFECTIVE;
588 nscap->magic_etc = cpu_to_le32(nsmagic);
589 memcpy(&nscap->data, &cap->data, sizeof(__le32) * 2 * VFS_CAP_U32);
590
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500591 *ivalue = nscap;
592 return newsize;
593}
594
David Howells1d045982008-11-14 10:39:24 +1100595/*
596 * Calculate the new process capability sets from the capability sets attached
597 * to a file.
598 */
Eric Parisc0b00442008-11-11 21:48:10 +1100599static inline int bprm_caps_from_vfs_caps(struct cpu_vfs_cap_data *caps,
David Howellsa6f76f22008-11-14 10:39:24 +1100600 struct linux_binprm *bprm,
Zhi Li4d49f672011-08-11 13:27:50 +0800601 bool *effective,
Richard Guy Briggsfc7eadf2017-10-11 20:57:07 -0400602 bool *has_fcap)
Serge E. Hallynb5376772007-10-16 23:31:36 -0700603{
David Howellsa6f76f22008-11-14 10:39:24 +1100604 struct cred *new = bprm->cred;
Eric Parisc0b00442008-11-11 21:48:10 +1100605 unsigned i;
606 int ret = 0;
607
608 if (caps->magic_etc & VFS_CAP_FLAGS_EFFECTIVE)
David Howellsa6f76f22008-11-14 10:39:24 +1100609 *effective = true;
Eric Parisc0b00442008-11-11 21:48:10 +1100610
Zhi Li4d49f672011-08-11 13:27:50 +0800611 if (caps->magic_etc & VFS_CAP_REVISION_MASK)
Richard Guy Briggsfc7eadf2017-10-11 20:57:07 -0400612 *has_fcap = true;
Zhi Li4d49f672011-08-11 13:27:50 +0800613
Eric Parisc0b00442008-11-11 21:48:10 +1100614 CAP_FOR_EACH_U32(i) {
615 __u32 permitted = caps->permitted.cap[i];
616 __u32 inheritable = caps->inheritable.cap[i];
617
618 /*
619 * pP' = (X & fP) | (pI & fI)
Andy Lutomirski58319052015-09-04 15:42:45 -0700620 * The addition of pA' is handled later.
Eric Parisc0b00442008-11-11 21:48:10 +1100621 */
David Howellsa6f76f22008-11-14 10:39:24 +1100622 new->cap_permitted.cap[i] =
623 (new->cap_bset.cap[i] & permitted) |
624 (new->cap_inheritable.cap[i] & inheritable);
Eric Parisc0b00442008-11-11 21:48:10 +1100625
David Howellsa6f76f22008-11-14 10:39:24 +1100626 if (permitted & ~new->cap_permitted.cap[i])
627 /* insufficient to execute correctly */
Eric Parisc0b00442008-11-11 21:48:10 +1100628 ret = -EPERM;
Eric Parisc0b00442008-11-11 21:48:10 +1100629 }
630
631 /*
632 * For legacy apps, with no internal support for recognizing they
633 * do not have enough capabilities, we return an error if they are
634 * missing some "forced" (aka file-permitted) capabilities.
635 */
David Howellsa6f76f22008-11-14 10:39:24 +1100636 return *effective ? ret : 0;
Eric Parisc0b00442008-11-11 21:48:10 +1100637}
638
Christian Brauner71bc3562021-01-21 14:19:29 +0100639/**
640 * get_vfs_caps_from_disk - retrieve vfs caps from disk
641 *
642 * @mnt_userns: user namespace of the mount the inode was found from
643 * @dentry: dentry from which @inode is retrieved
644 * @cpu_caps: vfs capabilities
645 *
David Howells1d045982008-11-14 10:39:24 +1100646 * Extract the on-exec-apply capability sets for an executable file.
Christian Brauner71bc3562021-01-21 14:19:29 +0100647 *
648 * If the inode has been found through an idmapped mount the user namespace of
649 * the vfsmount must be passed through @mnt_userns. This function will then
650 * take care to map the inode according to @mnt_userns before checking
651 * permissions. On non-idmapped mounts or if permission checking is to be
652 * performed on the raw inode simply passs init_user_ns.
David Howells1d045982008-11-14 10:39:24 +1100653 */
Christian Brauner71bc3562021-01-21 14:19:29 +0100654int get_vfs_caps_from_disk(struct user_namespace *mnt_userns,
655 const struct dentry *dentry,
656 struct cpu_vfs_cap_data *cpu_caps)
Eric Parisc0b00442008-11-11 21:48:10 +1100657{
David Howellsc6f493d2015-03-17 22:26:22 +0000658 struct inode *inode = d_backing_inode(dentry);
Serge E. Hallynb5376772007-10-16 23:31:36 -0700659 __u32 magic_etc;
Andrew Morgane338d262008-02-04 22:29:42 -0800660 unsigned tocopy, i;
Eric Parisc0b00442008-11-11 21:48:10 +1100661 int size;
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500662 struct vfs_ns_cap_data data, *nscaps = &data;
663 struct vfs_cap_data *caps = (struct vfs_cap_data *) &data;
664 kuid_t rootkuid;
Colin Ian King76ba89c72017-09-04 18:50:05 +0100665 struct user_namespace *fs_ns;
Eric Parisc0b00442008-11-11 21:48:10 +1100666
667 memset(cpu_caps, 0, sizeof(struct cpu_vfs_cap_data));
668
Andreas Gruenbacher5d6c3192016-09-29 17:48:42 +0200669 if (!inode)
Eric Parisc0b00442008-11-11 21:48:10 +1100670 return -ENODATA;
671
Colin Ian King76ba89c72017-09-04 18:50:05 +0100672 fs_ns = inode->i_sb->s_user_ns;
Andreas Gruenbacher5d6c3192016-09-29 17:48:42 +0200673 size = __vfs_getxattr((struct dentry *)dentry, inode,
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500674 XATTR_NAME_CAPS, &data, XATTR_CAPS_SZ);
David Howellsa6f76f22008-11-14 10:39:24 +1100675 if (size == -ENODATA || size == -EOPNOTSUPP)
Eric Parisc0b00442008-11-11 21:48:10 +1100676 /* no data, that's ok */
677 return -ENODATA;
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500678
Eric Parisc0b00442008-11-11 21:48:10 +1100679 if (size < 0)
680 return size;
Serge E. Hallynb5376772007-10-16 23:31:36 -0700681
Andrew Morgane338d262008-02-04 22:29:42 -0800682 if (size < sizeof(magic_etc))
Serge E. Hallynb5376772007-10-16 23:31:36 -0700683 return -EINVAL;
684
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500685 cpu_caps->magic_etc = magic_etc = le32_to_cpu(caps->magic_etc);
Serge E. Hallynb5376772007-10-16 23:31:36 -0700686
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500687 rootkuid = make_kuid(fs_ns, 0);
David Howellsa6f76f22008-11-14 10:39:24 +1100688 switch (magic_etc & VFS_CAP_REVISION_MASK) {
Andrew Morgane338d262008-02-04 22:29:42 -0800689 case VFS_CAP_REVISION_1:
690 if (size != XATTR_CAPS_SZ_1)
691 return -EINVAL;
692 tocopy = VFS_CAP_U32_1;
693 break;
694 case VFS_CAP_REVISION_2:
695 if (size != XATTR_CAPS_SZ_2)
696 return -EINVAL;
697 tocopy = VFS_CAP_U32_2;
698 break;
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500699 case VFS_CAP_REVISION_3:
700 if (size != XATTR_CAPS_SZ_3)
701 return -EINVAL;
702 tocopy = VFS_CAP_U32_3;
703 rootkuid = make_kuid(fs_ns, le32_to_cpu(nscaps->rootid));
704 break;
705
Serge E. Hallynb5376772007-10-16 23:31:36 -0700706 default:
707 return -EINVAL;
708 }
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500709 /* Limit the caps to the mounter of the filesystem
710 * or the more limited uid specified in the xattr.
711 */
Christian Brauner71bc3562021-01-21 14:19:29 +0100712 rootkuid = kuid_into_mnt(mnt_userns, rootkuid);
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500713 if (!rootid_owns_currentns(rootkuid))
714 return -ENODATA;
Andrew Morgane338d262008-02-04 22:29:42 -0800715
Andrew G. Morgan5459c162008-07-23 21:28:24 -0700716 CAP_FOR_EACH_U32(i) {
Eric Parisc0b00442008-11-11 21:48:10 +1100717 if (i >= tocopy)
718 break;
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500719 cpu_caps->permitted.cap[i] = le32_to_cpu(caps->data[i].permitted);
720 cpu_caps->inheritable.cap[i] = le32_to_cpu(caps->data[i].inheritable);
Andrew Morgane338d262008-02-04 22:29:42 -0800721 }
David Howellsa6f76f22008-11-14 10:39:24 +1100722
Eric Paris7d8b6c62014-07-23 15:36:26 -0400723 cpu_caps->permitted.cap[CAP_LAST_U32] &= CAP_LAST_U32_VALID_MASK;
724 cpu_caps->inheritable.cap[CAP_LAST_U32] &= CAP_LAST_U32_VALID_MASK;
725
Richard Guy Briggs2fec30e2019-01-23 21:36:25 -0500726 cpu_caps->rootid = rootkuid;
727
Eric Parisc0b00442008-11-11 21:48:10 +1100728 return 0;
Serge E. Hallynb5376772007-10-16 23:31:36 -0700729}
730
David Howells1d045982008-11-14 10:39:24 +1100731/*
732 * Attempt to get the on-exec apply capability sets for an executable file from
733 * its xattrs and, if present, apply them to the proposed credentials being
734 * constructed by execve().
735 */
Eric W. Biederman56305aa2020-05-29 22:00:54 -0500736static int get_file_caps(struct linux_binprm *bprm, struct file *file,
737 bool *effective, bool *has_fcap)
Serge E. Hallynb5376772007-10-16 23:31:36 -0700738{
Serge E. Hallynb5376772007-10-16 23:31:36 -0700739 int rc = 0;
Eric Parisc0b00442008-11-11 21:48:10 +1100740 struct cpu_vfs_cap_data vcaps;
Serge E. Hallynb5376772007-10-16 23:31:36 -0700741
Kees Cookee67ae72017-07-18 15:25:28 -0700742 cap_clear(bprm->cred->cap_permitted);
Serge Hallyn3318a382008-10-30 11:52:23 -0500743
Serge E. Hallyn1f29fae2008-11-05 16:08:52 -0600744 if (!file_caps_enabled)
745 return 0;
746
Eric W. Biederman56305aa2020-05-29 22:00:54 -0500747 if (!mnt_may_suid(file->f_path.mnt))
Serge E. Hallynb5376772007-10-16 23:31:36 -0700748 return 0;
Andy Lutomirski380cf5b2016-06-23 16:41:05 -0500749
750 /*
751 * This check is redundant with mnt_may_suid() but is kept to make
752 * explicit that capability bits are limited to s_user_ns and its
753 * descendants.
754 */
Eric W. Biederman56305aa2020-05-29 22:00:54 -0500755 if (!current_in_userns(file->f_path.mnt->mnt_sb->s_user_ns))
Seth Forsheed07b8462015-09-23 15:16:04 -0500756 return 0;
Serge E. Hallynb5376772007-10-16 23:31:36 -0700757
Christian Brauner71bc3562021-01-21 14:19:29 +0100758 rc = get_vfs_caps_from_disk(file_mnt_user_ns(file),
759 file->f_path.dentry, &vcaps);
Eric Parisc0b00442008-11-11 21:48:10 +1100760 if (rc < 0) {
761 if (rc == -EINVAL)
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500762 printk(KERN_NOTICE "Invalid argument reading file caps for %s\n",
763 bprm->filename);
Eric Parisc0b00442008-11-11 21:48:10 +1100764 else if (rc == -ENODATA)
765 rc = 0;
Serge E. Hallynb5376772007-10-16 23:31:36 -0700766 goto out;
767 }
Serge E. Hallynb5376772007-10-16 23:31:36 -0700768
Richard Guy Briggsfc7eadf2017-10-11 20:57:07 -0400769 rc = bprm_caps_from_vfs_caps(&vcaps, bprm, effective, has_fcap);
Serge E. Hallynb5376772007-10-16 23:31:36 -0700770
771out:
Serge E. Hallynb5376772007-10-16 23:31:36 -0700772 if (rc)
Kees Cookee67ae72017-07-18 15:25:28 -0700773 cap_clear(bprm->cred->cap_permitted);
Serge E. Hallynb5376772007-10-16 23:31:36 -0700774
775 return rc;
776}
777
Richard Guy Briggs9304b462017-10-11 20:57:08 -0400778static inline bool root_privileged(void) { return !issecure(SECURE_NOROOT); }
779
Richard Guy Briggs81a6a012017-10-11 20:57:09 -0400780static inline bool __is_real(kuid_t uid, struct cred *cred)
781{ return uid_eq(cred->uid, uid); }
782
783static inline bool __is_eff(kuid_t uid, struct cred *cred)
784{ return uid_eq(cred->euid, uid); }
785
786static inline bool __is_suid(kuid_t uid, struct cred *cred)
787{ return !__is_real(uid, cred) && __is_eff(uid, cred); }
788
Richard Guy Briggsdb1a8922017-10-11 20:57:05 -0400789/*
790 * handle_privileged_root - Handle case of privileged root
791 * @bprm: The execution parameters, including the proposed creds
792 * @has_fcap: Are any file capabilities set?
793 * @effective: Do we have effective root privilege?
794 * @root_uid: This namespace' root UID WRT initial USER namespace
795 *
796 * Handle the case where root is privileged and hasn't been neutered by
797 * SECURE_NOROOT. If file capabilities are set, they won't be combined with
798 * set UID root and nothing is changed. If we are root, cap_permitted is
799 * updated. If we have become set UID root, the effective bit is set.
800 */
Richard Guy Briggsfc7eadf2017-10-11 20:57:07 -0400801static void handle_privileged_root(struct linux_binprm *bprm, bool has_fcap,
Richard Guy Briggsdb1a8922017-10-11 20:57:05 -0400802 bool *effective, kuid_t root_uid)
803{
804 const struct cred *old = current_cred();
805 struct cred *new = bprm->cred;
806
Richard Guy Briggs9304b462017-10-11 20:57:08 -0400807 if (!root_privileged())
Richard Guy Briggsdb1a8922017-10-11 20:57:05 -0400808 return;
809 /*
810 * If the legacy file capability is set, then don't set privs
811 * for a setuid root binary run by a non-root user. Do set it
812 * for a root user just to cause least surprise to an admin.
813 */
Richard Guy Briggs81a6a012017-10-11 20:57:09 -0400814 if (has_fcap && __is_suid(root_uid, new)) {
Richard Guy Briggsdb1a8922017-10-11 20:57:05 -0400815 warn_setuid_and_fcaps_mixed(bprm->filename);
816 return;
817 }
818 /*
819 * To support inheritance of root-permissions and suid-root
820 * executables under compatibility mode, we override the
821 * capability sets for the file.
822 */
Richard Guy Briggs81a6a012017-10-11 20:57:09 -0400823 if (__is_eff(root_uid, new) || __is_real(root_uid, new)) {
Richard Guy Briggsdb1a8922017-10-11 20:57:05 -0400824 /* pP' = (cap_bset & ~0) | (pI & ~0) */
825 new->cap_permitted = cap_combine(old->cap_bset,
826 old->cap_inheritable);
827 }
828 /*
829 * If only the real uid is 0, we do not set the effective bit.
830 */
Richard Guy Briggs81a6a012017-10-11 20:57:09 -0400831 if (__is_eff(root_uid, new))
Richard Guy Briggsdb1a8922017-10-11 20:57:05 -0400832 *effective = true;
833}
834
Richard Guy Briggs4c7e7152017-10-11 20:57:06 -0400835#define __cap_gained(field, target, source) \
836 !cap_issubset(target->cap_##field, source->cap_##field)
837#define __cap_grew(target, source, cred) \
838 !cap_issubset(cred->cap_##target, cred->cap_##source)
839#define __cap_full(field, cred) \
840 cap_issubset(CAP_FULL_SET, cred->cap_##field)
Richard Guy Briggs81a6a012017-10-11 20:57:09 -0400841
842static inline bool __is_setuid(struct cred *new, const struct cred *old)
843{ return !uid_eq(new->euid, old->uid); }
844
845static inline bool __is_setgid(struct cred *new, const struct cred *old)
846{ return !gid_eq(new->egid, old->gid); }
847
Richard Guy Briggs9fbc2c72017-10-11 20:57:10 -0400848/*
Richard Guy Briggsdbbbe112017-10-11 20:57:14 -0400849 * 1) Audit candidate if current->cap_effective is set
Richard Guy Briggs9fbc2c72017-10-11 20:57:10 -0400850 *
851 * We do not bother to audit if 3 things are true:
852 * 1) cap_effective has all caps
Richard Guy Briggs588fb2c2017-10-11 20:57:13 -0400853 * 2) we became root *OR* are were already root
Richard Guy Briggs9fbc2c72017-10-11 20:57:10 -0400854 * 3) root is supposed to have all caps (SECURE_NOROOT)
855 * Since this is just a normal root execing a process.
856 *
857 * Number 1 above might fail if you don't have a full bset, but I think
858 * that is interesting information to audit.
Richard Guy Briggsdbbbe112017-10-11 20:57:14 -0400859 *
860 * A number of other conditions require logging:
861 * 2) something prevented setuid root getting all caps
862 * 3) non-setuid root gets fcaps
863 * 4) non-setuid root gets ambient
Richard Guy Briggs9fbc2c72017-10-11 20:57:10 -0400864 */
Richard Guy Briggsdbbbe112017-10-11 20:57:14 -0400865static inline bool nonroot_raised_pE(struct cred *new, const struct cred *old,
866 kuid_t root, bool has_fcap)
Richard Guy Briggs9fbc2c72017-10-11 20:57:10 -0400867{
868 bool ret = false;
869
Richard Guy Briggsdbbbe112017-10-11 20:57:14 -0400870 if ((__cap_grew(effective, ambient, new) &&
871 !(__cap_full(effective, new) &&
872 (__is_eff(root, new) || __is_real(root, new)) &&
873 root_privileged())) ||
874 (root_privileged() &&
875 __is_suid(root, new) &&
876 !__cap_full(effective, new)) ||
877 (!__is_setuid(new, old) &&
878 ((has_fcap &&
879 __cap_gained(permitted, new, old)) ||
880 __cap_gained(ambient, new, old))))
881
Richard Guy Briggs02ebbaf2017-10-11 20:57:11 -0400882 ret = true;
Richard Guy Briggsdbbbe112017-10-11 20:57:14 -0400883
Richard Guy Briggs9fbc2c72017-10-11 20:57:10 -0400884 return ret;
885}
886
David Howells1d045982008-11-14 10:39:24 +1100887/**
Eric W. Biederman56305aa2020-05-29 22:00:54 -0500888 * cap_bprm_creds_from_file - Set up the proposed credentials for execve().
David Howells1d045982008-11-14 10:39:24 +1100889 * @bprm: The execution parameters, including the proposed creds
Eric W. Biederman56305aa2020-05-29 22:00:54 -0500890 * @file: The file to pull the credentials from
David Howells1d045982008-11-14 10:39:24 +1100891 *
892 * Set up the proposed credentials for a new execution context being
893 * constructed by execve(). The proposed creds in @bprm->cred is altered,
894 * which won't take effect immediately. Returns 0 if successful, -ve on error.
David Howellsa6f76f22008-11-14 10:39:24 +1100895 */
Eric W. Biederman56305aa2020-05-29 22:00:54 -0500896int cap_bprm_creds_from_file(struct linux_binprm *bprm, struct file *file)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700897{
Eric W. Biederman56305aa2020-05-29 22:00:54 -0500898 /* Process setpcap binaries and capabilities for uid 0 */
David Howellsa6f76f22008-11-14 10:39:24 +1100899 const struct cred *old = current_cred();
900 struct cred *new = bprm->cred;
Richard Guy Briggsfc7eadf2017-10-11 20:57:07 -0400901 bool effective = false, has_fcap = false, is_setid;
Serge E. Hallynb5376772007-10-16 23:31:36 -0700902 int ret;
Eric W. Biederman18815a12012-02-07 16:45:47 -0800903 kuid_t root_uid;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700904
Andy Lutomirski58319052015-09-04 15:42:45 -0700905 if (WARN_ON(!cap_ambient_invariant_ok(old)))
906 return -EPERM;
907
Eric W. Biederman56305aa2020-05-29 22:00:54 -0500908 ret = get_file_caps(bprm, file, &effective, &has_fcap);
David Howellsa6f76f22008-11-14 10:39:24 +1100909 if (ret < 0)
910 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700911
Eric W. Biederman18815a12012-02-07 16:45:47 -0800912 root_uid = make_kuid(new->user_ns, 0);
913
Richard Guy Briggsfc7eadf2017-10-11 20:57:07 -0400914 handle_privileged_root(bprm, has_fcap, &effective, root_uid);
Serge E. Hallynb5376772007-10-16 23:31:36 -0700915
Eric Parisd52fc5d2012-04-17 16:26:54 -0400916 /* if we have fs caps, clear dangerous personality flags */
Richard Guy Briggs4c7e7152017-10-11 20:57:06 -0400917 if (__cap_gained(permitted, new, old))
Eric W. Biederman56305aa2020-05-29 22:00:54 -0500918 bprm->per_clear |= PER_CLEAR_ON_SETID;
Eric Parisd52fc5d2012-04-17 16:26:54 -0400919
David Howellsa6f76f22008-11-14 10:39:24 +1100920 /* Don't let someone trace a set[ug]id/setpcap binary with the revised
Andy Lutomirski259e5e62012-04-12 16:47:50 -0500921 * credentials unless they have the appropriate permit.
922 *
923 * In addition, if NO_NEW_PRIVS, then ensure we get no new privs.
David Howellsa6f76f22008-11-14 10:39:24 +1100924 */
Richard Guy Briggs81a6a012017-10-11 20:57:09 -0400925 is_setid = __is_setuid(new, old) || __is_setgid(new, old);
Andy Lutomirski58319052015-09-04 15:42:45 -0700926
Richard Guy Briggs4c7e7152017-10-11 20:57:06 -0400927 if ((is_setid || __cap_gained(permitted, new, old)) &&
Eric W. Biederman9227dd22017-01-23 17:26:31 +1300928 ((bprm->unsafe & ~LSM_UNSAFE_PTRACE) ||
Eric W. Biederman20523132017-01-23 17:17:26 +1300929 !ptracer_capable(current, new->user_ns))) {
David Howellsa6f76f22008-11-14 10:39:24 +1100930 /* downgrade; they get no more than they had, and maybe less */
Eric W. Biederman70169422016-11-17 01:38:35 -0600931 if (!ns_capable(new->user_ns, CAP_SETUID) ||
Andy Lutomirski259e5e62012-04-12 16:47:50 -0500932 (bprm->unsafe & LSM_UNSAFE_NO_NEW_PRIVS)) {
David Howellsa6f76f22008-11-14 10:39:24 +1100933 new->euid = new->uid;
934 new->egid = new->gid;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700935 }
Serge E. Hallynb3a222e2009-11-23 16:21:30 -0600936 new->cap_permitted = cap_intersect(new->cap_permitted,
937 old->cap_permitted);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700938 }
939
David Howellsa6f76f22008-11-14 10:39:24 +1100940 new->suid = new->fsuid = new->euid;
941 new->sgid = new->fsgid = new->egid;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700942
Andy Lutomirski58319052015-09-04 15:42:45 -0700943 /* File caps or setid cancels ambient. */
Richard Guy Briggsfc7eadf2017-10-11 20:57:07 -0400944 if (has_fcap || is_setid)
Andy Lutomirski58319052015-09-04 15:42:45 -0700945 cap_clear(new->cap_ambient);
946
947 /*
948 * Now that we've computed pA', update pP' to give:
949 * pP' = (X & fP) | (pI & fI) | pA'
950 */
951 new->cap_permitted = cap_combine(new->cap_permitted, new->cap_ambient);
952
953 /*
954 * Set pE' = (fE ? pP' : pA'). Because pA' is zero if fE is set,
955 * this is the same as pE' = (fE ? pP' : 0) | pA'.
956 */
Eric Paris4bf2ea72011-04-01 17:08:28 -0400957 if (effective)
958 new->cap_effective = new->cap_permitted;
959 else
Andy Lutomirski58319052015-09-04 15:42:45 -0700960 new->cap_effective = new->cap_ambient;
961
962 if (WARN_ON(!cap_ambient_invariant_ok(new)))
963 return -EPERM;
964
Richard Guy Briggsdbbbe112017-10-11 20:57:14 -0400965 if (nonroot_raised_pE(new, old, root_uid, has_fcap)) {
Richard Guy Briggs9fbc2c72017-10-11 20:57:10 -0400966 ret = audit_log_bprm_fcaps(bprm, new, old);
967 if (ret < 0)
968 return ret;
Eric Paris3fc689e2008-11-11 21:48:18 +1100969 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700970
David Howellsd84f4f92008-11-14 10:39:23 +1100971 new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
Andy Lutomirski58319052015-09-04 15:42:45 -0700972
973 if (WARN_ON(!cap_ambient_invariant_ok(new)))
974 return -EPERM;
975
Kees Cook46d98eb2017-07-18 15:25:27 -0700976 /* Check for privilege-elevated exec. */
Richard Guy Briggs02ebbaf2017-10-11 20:57:11 -0400977 if (is_setid ||
978 (!__is_real(root_uid, new) &&
979 (effective ||
980 __cap_grew(permitted, ambient, new))))
Eric W. Biederman56305aa2020-05-29 22:00:54 -0500981 bprm->secureexec = 1;
Serge E. Hallynb5376772007-10-16 23:31:36 -0700982
Kees Cookee67ae72017-07-18 15:25:28 -0700983 return 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700984}
985
David Howells1d045982008-11-14 10:39:24 +1100986/**
987 * cap_inode_setxattr - Determine whether an xattr may be altered
988 * @dentry: The inode/dentry being altered
989 * @name: The name of the xattr to be changed
990 * @value: The value that the xattr will be changed to
991 * @size: The size of value
992 * @flags: The replacement flag
993 *
994 * Determine whether an xattr may be altered or set on an inode, returning 0 if
995 * permission is granted, -ve if denied.
996 *
997 * This is used to make sure security xattrs don't get updated or set by those
998 * who aren't privileged to do so.
999 */
David Howells8f0cfa52008-04-29 00:59:41 -07001000int cap_inode_setxattr(struct dentry *dentry, const char *name,
1001 const void *value, size_t size, int flags)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001002{
Eric W. Biedermanb1d749c52017-04-21 19:14:32 -05001003 struct user_namespace *user_ns = dentry->d_sb->s_user_ns;
1004
Serge E. Hallyn8db6c342017-05-08 13:11:56 -05001005 /* Ignore non-security xattrs */
1006 if (strncmp(name, XATTR_SECURITY_PREFIX,
Carmeli Tamirc5eaab12019-07-06 11:07:38 -04001007 XATTR_SECURITY_PREFIX_LEN) != 0)
Serge E. Hallynb5376772007-10-16 23:31:36 -07001008 return 0;
David Howells1d045982008-11-14 10:39:24 +11001009
Serge E. Hallyn8db6c342017-05-08 13:11:56 -05001010 /*
1011 * For XATTR_NAME_CAPS the check will be done in
1012 * cap_convert_nscap(), called by setxattr()
1013 */
1014 if (strcmp(name, XATTR_NAME_CAPS) == 0)
1015 return 0;
1016
Eric W. Biedermanb1d749c52017-04-21 19:14:32 -05001017 if (!ns_capable(user_ns, CAP_SYS_ADMIN))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001018 return -EPERM;
1019 return 0;
1020}
1021
David Howells1d045982008-11-14 10:39:24 +11001022/**
1023 * cap_inode_removexattr - Determine whether an xattr may be removed
Christian Brauner71bc3562021-01-21 14:19:29 +01001024 *
1025 * @mnt_userns: User namespace of the mount the inode was found from
1026 * @dentry: The inode/dentry being altered
1027 * @name: The name of the xattr to be changed
David Howells1d045982008-11-14 10:39:24 +11001028 *
1029 * Determine whether an xattr may be removed from an inode, returning 0 if
1030 * permission is granted, -ve if denied.
1031 *
Christian Brauner71bc3562021-01-21 14:19:29 +01001032 * If the inode has been found through an idmapped mount the user namespace of
1033 * the vfsmount must be passed through @mnt_userns. This function will then
1034 * take care to map the inode according to @mnt_userns before checking
1035 * permissions. On non-idmapped mounts or if permission checking is to be
1036 * performed on the raw inode simply passs init_user_ns.
1037 *
David Howells1d045982008-11-14 10:39:24 +11001038 * This is used to make sure security xattrs don't get removed by those who
1039 * aren't privileged to remove them.
1040 */
Christian Brauner71bc3562021-01-21 14:19:29 +01001041int cap_inode_removexattr(struct user_namespace *mnt_userns,
1042 struct dentry *dentry, const char *name)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001043{
Eric W. Biedermanb1d749c52017-04-21 19:14:32 -05001044 struct user_namespace *user_ns = dentry->d_sb->s_user_ns;
1045
Serge E. Hallyn8db6c342017-05-08 13:11:56 -05001046 /* Ignore non-security xattrs */
1047 if (strncmp(name, XATTR_SECURITY_PREFIX,
Carmeli Tamirc5eaab12019-07-06 11:07:38 -04001048 XATTR_SECURITY_PREFIX_LEN) != 0)
Serge E. Hallyn8db6c342017-05-08 13:11:56 -05001049 return 0;
1050
1051 if (strcmp(name, XATTR_NAME_CAPS) == 0) {
1052 /* security.capability gets namespaced */
1053 struct inode *inode = d_backing_inode(dentry);
1054 if (!inode)
1055 return -EINVAL;
Christian Brauner71bc3562021-01-21 14:19:29 +01001056 if (!capable_wrt_inode_uidgid(mnt_userns, inode, CAP_SETFCAP))
Serge E. Hallynb5376772007-10-16 23:31:36 -07001057 return -EPERM;
1058 return 0;
David Howells1d045982008-11-14 10:39:24 +11001059 }
1060
Eric W. Biedermanb1d749c52017-04-21 19:14:32 -05001061 if (!ns_capable(user_ns, CAP_SYS_ADMIN))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001062 return -EPERM;
1063 return 0;
1064}
1065
David Howellsa6f76f22008-11-14 10:39:24 +11001066/*
Linus Torvalds1da177e2005-04-16 15:20:36 -07001067 * cap_emulate_setxuid() fixes the effective / permitted capabilities of
1068 * a process after a call to setuid, setreuid, or setresuid.
1069 *
1070 * 1) When set*uiding _from_ one of {r,e,s}uid == 0 _to_ all of
1071 * {r,e,s}uid != 0, the permitted and effective capabilities are
1072 * cleared.
1073 *
1074 * 2) When set*uiding _from_ euid == 0 _to_ euid != 0, the effective
1075 * capabilities of the process are cleared.
1076 *
1077 * 3) When set*uiding _from_ euid != 0 _to_ euid == 0, the effective
1078 * capabilities are set to the permitted capabilities.
1079 *
David Howellsa6f76f22008-11-14 10:39:24 +11001080 * fsuid is handled elsewhere. fsuid == 0 and {r,e,s}uid!= 0 should
Linus Torvalds1da177e2005-04-16 15:20:36 -07001081 * never happen.
1082 *
David Howellsa6f76f22008-11-14 10:39:24 +11001083 * -astor
Linus Torvalds1da177e2005-04-16 15:20:36 -07001084 *
1085 * cevans - New behaviour, Oct '99
1086 * A process may, via prctl(), elect to keep its capabilities when it
1087 * calls setuid() and switches away from uid==0. Both permitted and
1088 * effective sets will be retained.
1089 * Without this change, it was impossible for a daemon to drop only some
1090 * of its privilege. The call to setuid(!=0) would drop all privileges!
1091 * Keeping uid 0 is not an option because uid 0 owns too many vital
1092 * files..
1093 * Thanks to Olaf Kirch and Peter Benie for spotting this.
1094 */
David Howellsd84f4f92008-11-14 10:39:23 +11001095static inline void cap_emulate_setxuid(struct cred *new, const struct cred *old)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001096{
Eric W. Biederman18815a12012-02-07 16:45:47 -08001097 kuid_t root_uid = make_kuid(old->user_ns, 0);
1098
1099 if ((uid_eq(old->uid, root_uid) ||
1100 uid_eq(old->euid, root_uid) ||
1101 uid_eq(old->suid, root_uid)) &&
1102 (!uid_eq(new->uid, root_uid) &&
1103 !uid_eq(new->euid, root_uid) &&
Andy Lutomirski58319052015-09-04 15:42:45 -07001104 !uid_eq(new->suid, root_uid))) {
1105 if (!issecure(SECURE_KEEP_CAPS)) {
1106 cap_clear(new->cap_permitted);
1107 cap_clear(new->cap_effective);
1108 }
1109
1110 /*
1111 * Pre-ambient programs expect setresuid to nonroot followed
1112 * by exec to drop capabilities. We should make sure that
1113 * this remains the case.
1114 */
1115 cap_clear(new->cap_ambient);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001116 }
Eric W. Biederman18815a12012-02-07 16:45:47 -08001117 if (uid_eq(old->euid, root_uid) && !uid_eq(new->euid, root_uid))
David Howellsd84f4f92008-11-14 10:39:23 +11001118 cap_clear(new->cap_effective);
Eric W. Biederman18815a12012-02-07 16:45:47 -08001119 if (!uid_eq(old->euid, root_uid) && uid_eq(new->euid, root_uid))
David Howellsd84f4f92008-11-14 10:39:23 +11001120 new->cap_effective = new->cap_permitted;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001121}
1122
David Howells1d045982008-11-14 10:39:24 +11001123/**
1124 * cap_task_fix_setuid - Fix up the results of setuid() call
1125 * @new: The proposed credentials
1126 * @old: The current task's current credentials
1127 * @flags: Indications of what has changed
1128 *
1129 * Fix up the results of setuid() call before the credential changes are
1130 * actually applied, returning 0 to grant the changes, -ve to deny them.
1131 */
David Howellsd84f4f92008-11-14 10:39:23 +11001132int cap_task_fix_setuid(struct cred *new, const struct cred *old, int flags)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001133{
1134 switch (flags) {
1135 case LSM_SETID_RE:
1136 case LSM_SETID_ID:
1137 case LSM_SETID_RES:
David Howells1d045982008-11-14 10:39:24 +11001138 /* juggle the capabilities to follow [RES]UID changes unless
1139 * otherwise suppressed */
David Howellsd84f4f92008-11-14 10:39:23 +11001140 if (!issecure(SECURE_NO_SETUID_FIXUP))
1141 cap_emulate_setxuid(new, old);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001142 break;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001143
David Howells1d045982008-11-14 10:39:24 +11001144 case LSM_SETID_FS:
1145 /* juggle the capabilties to follow FSUID changes, unless
1146 * otherwise suppressed
1147 *
David Howellsd84f4f92008-11-14 10:39:23 +11001148 * FIXME - is fsuser used for all CAP_FS_MASK capabilities?
1149 * if not, we might be a bit too harsh here.
1150 */
1151 if (!issecure(SECURE_NO_SETUID_FIXUP)) {
Eric W. Biederman18815a12012-02-07 16:45:47 -08001152 kuid_t root_uid = make_kuid(old->user_ns, 0);
1153 if (uid_eq(old->fsuid, root_uid) && !uid_eq(new->fsuid, root_uid))
David Howellsd84f4f92008-11-14 10:39:23 +11001154 new->cap_effective =
1155 cap_drop_fs_set(new->cap_effective);
David Howells1d045982008-11-14 10:39:24 +11001156
Eric W. Biederman18815a12012-02-07 16:45:47 -08001157 if (!uid_eq(old->fsuid, root_uid) && uid_eq(new->fsuid, root_uid))
David Howellsd84f4f92008-11-14 10:39:23 +11001158 new->cap_effective =
1159 cap_raise_fs_set(new->cap_effective,
1160 new->cap_permitted);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001161 }
David Howellsd84f4f92008-11-14 10:39:23 +11001162 break;
David Howells1d045982008-11-14 10:39:24 +11001163
Linus Torvalds1da177e2005-04-16 15:20:36 -07001164 default:
1165 return -EINVAL;
1166 }
1167
1168 return 0;
1169}
1170
Serge E. Hallynb5376772007-10-16 23:31:36 -07001171/*
1172 * Rationale: code calling task_setscheduler, task_setioprio, and
1173 * task_setnice, assumes that
1174 * . if capable(cap_sys_nice), then those actions should be allowed
1175 * . if not capable(cap_sys_nice), but acting on your own processes,
1176 * then those actions should be allowed
1177 * This is insufficient now since you can call code without suid, but
1178 * yet with increased caps.
1179 * So we check for increased caps on the target process.
1180 */
Serge E. Hallynde45e802008-09-26 22:27:47 -04001181static int cap_safe_nice(struct task_struct *p)
Serge E. Hallynb5376772007-10-16 23:31:36 -07001182{
Serge Hallynf54fb862013-07-23 13:18:53 -05001183 int is_subset, ret = 0;
David Howellsc69e8d92008-11-14 10:39:19 +11001184
1185 rcu_read_lock();
1186 is_subset = cap_issubset(__task_cred(p)->cap_permitted,
1187 current_cred()->cap_permitted);
Serge Hallynf54fb862013-07-23 13:18:53 -05001188 if (!is_subset && !ns_capable(__task_cred(p)->user_ns, CAP_SYS_NICE))
1189 ret = -EPERM;
David Howellsc69e8d92008-11-14 10:39:19 +11001190 rcu_read_unlock();
1191
Serge Hallynf54fb862013-07-23 13:18:53 -05001192 return ret;
Serge E. Hallynb5376772007-10-16 23:31:36 -07001193}
1194
David Howells1d045982008-11-14 10:39:24 +11001195/**
1196 * cap_task_setscheduler - Detemine if scheduler policy change is permitted
1197 * @p: The task to affect
David Howells1d045982008-11-14 10:39:24 +11001198 *
1199 * Detemine if the requested scheduler policy change is permitted for the
1200 * specified task, returning 0 if permission is granted, -ve if denied.
1201 */
KOSAKI Motohirob0ae1982010-10-15 04:21:18 +09001202int cap_task_setscheduler(struct task_struct *p)
Serge E. Hallynb5376772007-10-16 23:31:36 -07001203{
1204 return cap_safe_nice(p);
1205}
1206
David Howells1d045982008-11-14 10:39:24 +11001207/**
1208 * cap_task_ioprio - Detemine if I/O priority change is permitted
1209 * @p: The task to affect
1210 * @ioprio: The I/O priority to set
1211 *
1212 * Detemine if the requested I/O priority change is permitted for the specified
1213 * task, returning 0 if permission is granted, -ve if denied.
1214 */
1215int cap_task_setioprio(struct task_struct *p, int ioprio)
Serge E. Hallynb5376772007-10-16 23:31:36 -07001216{
1217 return cap_safe_nice(p);
1218}
1219
David Howells1d045982008-11-14 10:39:24 +11001220/**
1221 * cap_task_ioprio - Detemine if task priority change is permitted
1222 * @p: The task to affect
1223 * @nice: The nice value to set
1224 *
1225 * Detemine if the requested task priority change is permitted for the
1226 * specified task, returning 0 if permission is granted, -ve if denied.
1227 */
1228int cap_task_setnice(struct task_struct *p, int nice)
Serge E. Hallynb5376772007-10-16 23:31:36 -07001229{
1230 return cap_safe_nice(p);
1231}
1232
Serge E. Hallyn3b7391d2008-02-04 22:29:45 -08001233/*
David Howells1d045982008-11-14 10:39:24 +11001234 * Implement PR_CAPBSET_DROP. Attempt to remove the specified capability from
1235 * the current task's bounding set. Returns 0 on success, -ve on error.
Serge E. Hallyn3b7391d2008-02-04 22:29:45 -08001236 */
Tetsuo Handa6d6f3322014-07-22 21:20:01 +09001237static int cap_prctl_drop(unsigned long cap)
Serge E. Hallyn3b7391d2008-02-04 22:29:45 -08001238{
Tetsuo Handa6d6f3322014-07-22 21:20:01 +09001239 struct cred *new;
1240
Eric W. Biederman160da842013-07-02 10:04:54 -07001241 if (!ns_capable(current_user_ns(), CAP_SETPCAP))
Serge E. Hallyn3b7391d2008-02-04 22:29:45 -08001242 return -EPERM;
1243 if (!cap_valid(cap))
1244 return -EINVAL;
David Howellsd84f4f92008-11-14 10:39:23 +11001245
Tetsuo Handa6d6f3322014-07-22 21:20:01 +09001246 new = prepare_creds();
1247 if (!new)
1248 return -ENOMEM;
David Howellsd84f4f92008-11-14 10:39:23 +11001249 cap_lower(new->cap_bset, cap);
Tetsuo Handa6d6f3322014-07-22 21:20:01 +09001250 return commit_creds(new);
Serge E. Hallyn3b7391d2008-02-04 22:29:45 -08001251}
Andrew G. Morgan3898b1b2008-04-28 02:13:40 -07001252
David Howells1d045982008-11-14 10:39:24 +11001253/**
1254 * cap_task_prctl - Implement process control functions for this security module
1255 * @option: The process control function requested
1256 * @arg2, @arg3, @arg4, @arg5: The argument data for this function
1257 *
1258 * Allow process control functions (sys_prctl()) to alter capabilities; may
1259 * also deny access to other functions not otherwise implemented here.
1260 *
1261 * Returns 0 or +ve on success, -ENOSYS if this function is not implemented
1262 * here, other -ve on error. If -ENOSYS is returned, sys_prctl() and other LSM
1263 * modules will consider performing the function.
1264 */
Andrew G. Morgan3898b1b2008-04-28 02:13:40 -07001265int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3,
David Howellsd84f4f92008-11-14 10:39:23 +11001266 unsigned long arg4, unsigned long arg5)
Andrew G. Morgan3898b1b2008-04-28 02:13:40 -07001267{
Tetsuo Handa6d6f3322014-07-22 21:20:01 +09001268 const struct cred *old = current_cred();
David Howellsd84f4f92008-11-14 10:39:23 +11001269 struct cred *new;
David Howellsd84f4f92008-11-14 10:39:23 +11001270
Andrew G. Morgan3898b1b2008-04-28 02:13:40 -07001271 switch (option) {
1272 case PR_CAPBSET_READ:
1273 if (!cap_valid(arg2))
Tetsuo Handa6d6f3322014-07-22 21:20:01 +09001274 return -EINVAL;
1275 return !!cap_raised(old->cap_bset, arg2);
David Howellsd84f4f92008-11-14 10:39:23 +11001276
Andrew G. Morgan3898b1b2008-04-28 02:13:40 -07001277 case PR_CAPBSET_DROP:
Tetsuo Handa6d6f3322014-07-22 21:20:01 +09001278 return cap_prctl_drop(arg2);
Andrew G. Morgan3898b1b2008-04-28 02:13:40 -07001279
1280 /*
1281 * The next four prctl's remain to assist with transitioning a
1282 * system from legacy UID=0 based privilege (when filesystem
1283 * capabilities are not in use) to a system using filesystem
1284 * capabilities only - as the POSIX.1e draft intended.
1285 *
1286 * Note:
1287 *
1288 * PR_SET_SECUREBITS =
1289 * issecure_mask(SECURE_KEEP_CAPS_LOCKED)
1290 * | issecure_mask(SECURE_NOROOT)
1291 * | issecure_mask(SECURE_NOROOT_LOCKED)
1292 * | issecure_mask(SECURE_NO_SETUID_FIXUP)
1293 * | issecure_mask(SECURE_NO_SETUID_FIXUP_LOCKED)
1294 *
1295 * will ensure that the current process and all of its
1296 * children will be locked into a pure
1297 * capability-based-privilege environment.
1298 */
1299 case PR_SET_SECUREBITS:
Tetsuo Handa6d6f3322014-07-22 21:20:01 +09001300 if ((((old->securebits & SECURE_ALL_LOCKS) >> 1)
1301 & (old->securebits ^ arg2)) /*[1]*/
1302 || ((old->securebits & SECURE_ALL_LOCKS & ~arg2)) /*[2]*/
David Howellsd84f4f92008-11-14 10:39:23 +11001303 || (arg2 & ~(SECURE_ALL_LOCKS | SECURE_ALL_BITS)) /*[3]*/
Eric Paris6a9de492012-01-03 12:25:14 -05001304 || (cap_capable(current_cred(),
Micah Mortonc1a85a02019-01-07 16:10:53 -08001305 current_cred()->user_ns,
1306 CAP_SETPCAP,
1307 CAP_OPT_NONE) != 0) /*[4]*/
Andrew G. Morgan3898b1b2008-04-28 02:13:40 -07001308 /*
1309 * [1] no changing of bits that are locked
1310 * [2] no unlocking of locks
1311 * [3] no setting of unsupported bits
1312 * [4] doing anything requires privilege (go read about
1313 * the "sendmail capabilities bug")
1314 */
David Howellsd84f4f92008-11-14 10:39:23 +11001315 )
1316 /* cannot change a locked bit */
Tetsuo Handa6d6f3322014-07-22 21:20:01 +09001317 return -EPERM;
1318
1319 new = prepare_creds();
1320 if (!new)
1321 return -ENOMEM;
David Howellsd84f4f92008-11-14 10:39:23 +11001322 new->securebits = arg2;
Tetsuo Handa6d6f3322014-07-22 21:20:01 +09001323 return commit_creds(new);
David Howellsd84f4f92008-11-14 10:39:23 +11001324
Andrew G. Morgan3898b1b2008-04-28 02:13:40 -07001325 case PR_GET_SECUREBITS:
Tetsuo Handa6d6f3322014-07-22 21:20:01 +09001326 return old->securebits;
Andrew G. Morgan3898b1b2008-04-28 02:13:40 -07001327
Andrew G. Morgan3898b1b2008-04-28 02:13:40 -07001328 case PR_GET_KEEPCAPS:
Tetsuo Handa6d6f3322014-07-22 21:20:01 +09001329 return !!issecure(SECURE_KEEP_CAPS);
David Howellsd84f4f92008-11-14 10:39:23 +11001330
Andrew G. Morgan3898b1b2008-04-28 02:13:40 -07001331 case PR_SET_KEEPCAPS:
1332 if (arg2 > 1) /* Note, we rely on arg2 being unsigned here */
Tetsuo Handa6d6f3322014-07-22 21:20:01 +09001333 return -EINVAL;
David Howellsd84f4f92008-11-14 10:39:23 +11001334 if (issecure(SECURE_KEEP_CAPS_LOCKED))
Tetsuo Handa6d6f3322014-07-22 21:20:01 +09001335 return -EPERM;
1336
1337 new = prepare_creds();
1338 if (!new)
1339 return -ENOMEM;
David Howellsd84f4f92008-11-14 10:39:23 +11001340 if (arg2)
1341 new->securebits |= issecure_mask(SECURE_KEEP_CAPS);
Andrew G. Morgan3898b1b2008-04-28 02:13:40 -07001342 else
David Howellsd84f4f92008-11-14 10:39:23 +11001343 new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
Tetsuo Handa6d6f3322014-07-22 21:20:01 +09001344 return commit_creds(new);
Andrew G. Morgan3898b1b2008-04-28 02:13:40 -07001345
Andy Lutomirski58319052015-09-04 15:42:45 -07001346 case PR_CAP_AMBIENT:
1347 if (arg2 == PR_CAP_AMBIENT_CLEAR_ALL) {
1348 if (arg3 | arg4 | arg5)
1349 return -EINVAL;
1350
1351 new = prepare_creds();
1352 if (!new)
1353 return -ENOMEM;
1354 cap_clear(new->cap_ambient);
1355 return commit_creds(new);
1356 }
1357
1358 if (((!cap_valid(arg3)) | arg4 | arg5))
1359 return -EINVAL;
1360
1361 if (arg2 == PR_CAP_AMBIENT_IS_SET) {
1362 return !!cap_raised(current_cred()->cap_ambient, arg3);
1363 } else if (arg2 != PR_CAP_AMBIENT_RAISE &&
1364 arg2 != PR_CAP_AMBIENT_LOWER) {
1365 return -EINVAL;
1366 } else {
1367 if (arg2 == PR_CAP_AMBIENT_RAISE &&
1368 (!cap_raised(current_cred()->cap_permitted, arg3) ||
1369 !cap_raised(current_cred()->cap_inheritable,
Andy Lutomirski746bf6d2015-09-04 15:42:51 -07001370 arg3) ||
1371 issecure(SECURE_NO_CAP_AMBIENT_RAISE)))
Andy Lutomirski58319052015-09-04 15:42:45 -07001372 return -EPERM;
1373
1374 new = prepare_creds();
1375 if (!new)
1376 return -ENOMEM;
1377 if (arg2 == PR_CAP_AMBIENT_RAISE)
1378 cap_raise(new->cap_ambient, arg3);
1379 else
1380 cap_lower(new->cap_ambient, arg3);
1381 return commit_creds(new);
1382 }
1383
Andrew G. Morgan3898b1b2008-04-28 02:13:40 -07001384 default:
1385 /* No functionality available - continue with default */
Tetsuo Handa6d6f3322014-07-22 21:20:01 +09001386 return -ENOSYS;
Andrew G. Morgan3898b1b2008-04-28 02:13:40 -07001387 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001388}
1389
David Howells1d045982008-11-14 10:39:24 +11001390/**
David Howells1d045982008-11-14 10:39:24 +11001391 * cap_vm_enough_memory - Determine whether a new virtual mapping is permitted
1392 * @mm: The VM space in which the new mapping is to be made
1393 * @pages: The size of the mapping
1394 *
1395 * Determine whether the allocation of a new virtual mapping by the current
Casey Schauflerb1d9e6b2015-05-02 15:11:42 -07001396 * task is permitted, returning 1 if permission is granted, 0 if not.
David Howells1d045982008-11-14 10:39:24 +11001397 */
Alan Cox34b4e4a2007-08-22 14:01:28 -07001398int cap_vm_enough_memory(struct mm_struct *mm, long pages)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001399{
1400 int cap_sys_admin = 0;
1401
Micah Mortonc1a85a02019-01-07 16:10:53 -08001402 if (cap_capable(current_cred(), &init_user_ns,
1403 CAP_SYS_ADMIN, CAP_OPT_NOAUDIT) == 0)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001404 cap_sys_admin = 1;
Micah Mortonc1a85a02019-01-07 16:10:53 -08001405
Casey Schauflerb1d9e6b2015-05-02 15:11:42 -07001406 return cap_sys_admin;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001407}
Eric Paris7c738752009-07-31 12:53:58 -04001408
1409/*
Al Virod0077942012-05-30 13:11:37 -04001410 * cap_mmap_addr - check if able to map given addr
1411 * @addr: address attempting to be mapped
1412 *
1413 * If the process is attempting to map memory below dac_mmap_min_addr they need
1414 * CAP_SYS_RAWIO. The other parameters to this function are unused by the
1415 * capability security module. Returns 0 if this mapping should be allowed
1416 * -EPERM if not.
1417 */
1418int cap_mmap_addr(unsigned long addr)
1419{
1420 int ret = 0;
1421
1422 if (addr < dac_mmap_min_addr) {
1423 ret = cap_capable(current_cred(), &init_user_ns, CAP_SYS_RAWIO,
Micah Mortonc1a85a02019-01-07 16:10:53 -08001424 CAP_OPT_NONE);
Al Virod0077942012-05-30 13:11:37 -04001425 /* set PF_SUPERPRIV if it turns out we allow the low mmap */
1426 if (ret == 0)
1427 current->flags |= PF_SUPERPRIV;
1428 }
1429 return ret;
1430}
1431
Al Viroe5467852012-05-30 13:30:51 -04001432int cap_mmap_file(struct file *file, unsigned long reqprot,
1433 unsigned long prot, unsigned long flags)
Eric Paris7c738752009-07-31 12:53:58 -04001434{
Al Viroe5467852012-05-30 13:30:51 -04001435 return 0;
Eric Paris7c738752009-07-31 12:53:58 -04001436}
Casey Schauflerb1d9e6b2015-05-02 15:11:42 -07001437
1438#ifdef CONFIG_SECURITY
1439
YueHaibingd1c59472019-06-11 21:48:15 +08001440static struct security_hook_list capability_hooks[] __lsm_ro_after_init = {
Casey Schauflerb1d9e6b2015-05-02 15:11:42 -07001441 LSM_HOOK_INIT(capable, cap_capable),
1442 LSM_HOOK_INIT(settime, cap_settime),
1443 LSM_HOOK_INIT(ptrace_access_check, cap_ptrace_access_check),
1444 LSM_HOOK_INIT(ptrace_traceme, cap_ptrace_traceme),
1445 LSM_HOOK_INIT(capget, cap_capget),
1446 LSM_HOOK_INIT(capset, cap_capset),
Eric W. Biederman56305aa2020-05-29 22:00:54 -05001447 LSM_HOOK_INIT(bprm_creds_from_file, cap_bprm_creds_from_file),
Casey Schauflerb1d9e6b2015-05-02 15:11:42 -07001448 LSM_HOOK_INIT(inode_need_killpriv, cap_inode_need_killpriv),
1449 LSM_HOOK_INIT(inode_killpriv, cap_inode_killpriv),
Serge E. Hallyn8db6c342017-05-08 13:11:56 -05001450 LSM_HOOK_INIT(inode_getsecurity, cap_inode_getsecurity),
Casey Schauflerb1d9e6b2015-05-02 15:11:42 -07001451 LSM_HOOK_INIT(mmap_addr, cap_mmap_addr),
1452 LSM_HOOK_INIT(mmap_file, cap_mmap_file),
1453 LSM_HOOK_INIT(task_fix_setuid, cap_task_fix_setuid),
1454 LSM_HOOK_INIT(task_prctl, cap_task_prctl),
1455 LSM_HOOK_INIT(task_setscheduler, cap_task_setscheduler),
1456 LSM_HOOK_INIT(task_setioprio, cap_task_setioprio),
1457 LSM_HOOK_INIT(task_setnice, cap_task_setnice),
1458 LSM_HOOK_INIT(vm_enough_memory, cap_vm_enough_memory),
1459};
1460
Kees Cookd117a152018-09-14 15:40:45 -07001461static int __init capability_init(void)
Casey Schauflerb1d9e6b2015-05-02 15:11:42 -07001462{
Casey Schauflerd69dece52017-01-18 17:09:05 -08001463 security_add_hooks(capability_hooks, ARRAY_SIZE(capability_hooks),
1464 "capability");
Kees Cookd117a152018-09-14 15:40:45 -07001465 return 0;
Casey Schauflerb1d9e6b2015-05-02 15:11:42 -07001466}
1467
Kees Cookd117a152018-09-14 15:40:45 -07001468DEFINE_LSM(capability) = {
1469 .name = "capability",
1470 .order = LSM_ORDER_FIRST,
1471 .init = capability_init,
1472};
1473
Casey Schauflerb1d9e6b2015-05-02 15:11:42 -07001474#endif /* CONFIG_SECURITY */