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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 Braunera793d792021-12-03 12:16:59 +010027#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. */
Christian Braunerbd303362021-12-03 12:17:07 +0100422 kroot = mapped_kuid_fs(mnt_userns, fs_ns, kroot);
Christian Brauner71bc3562021-01-21 14:19:29 +0100423
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
Christian Brauner44720712021-12-03 12:17:03 +0100492 * @fs_userns: user namespace of the filesystem
Christian Braunere65ce2a2021-01-21 14:19:27 +0100493 *
494 * If the inode has been found through an idmapped mount the user namespace of
495 * the vfsmount must be passed through @mnt_userns. This function will then
496 * take care to map the inode according to @mnt_userns before checking
497 * permissions. On non-idmapped mounts or if permission checking is to be
498 * performed on the raw inode simply passs init_user_ns.
499 */
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500500static kuid_t rootid_from_xattr(const void *value, size_t size,
Christian Braunere65ce2a2021-01-21 14:19:27 +0100501 struct user_namespace *task_ns,
Christian Brauner44720712021-12-03 12:17:03 +0100502 struct user_namespace *mnt_userns,
503 struct user_namespace *fs_userns)
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500504{
505 const struct vfs_ns_cap_data *nscap = value;
Christian Braunere65ce2a2021-01-21 14:19:27 +0100506 kuid_t rootkid;
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500507 uid_t rootid = 0;
508
509 if (size == XATTR_CAPS_SZ_3)
510 rootid = le32_to_cpu(nscap->rootid);
511
Christian Braunere65ce2a2021-01-21 14:19:27 +0100512 rootkid = make_kuid(task_ns, rootid);
Christian Brauner44720712021-12-03 12:17:03 +0100513 return mapped_kuid_user(mnt_userns, fs_userns, rootkid);
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500514}
515
Eric Biggersdc32b5c2018-01-01 09:28:31 -0600516static bool validheader(size_t size, const struct vfs_cap_data *cap)
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500517{
Eric Biggersdc32b5c2018-01-01 09:28:31 -0600518 return is_v2header(size, cap) || is_v3header(size, cap);
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500519}
520
Christian Braunere65ce2a2021-01-21 14:19:27 +0100521/**
522 * cap_convert_nscap - check vfs caps
523 *
524 * @mnt_userns: user namespace of the mount the inode was found from
525 * @dentry: used to retrieve inode to check permissions on
526 * @ivalue: vfs caps value which may be modified by this function
527 * @size: size of @ivalue
528 *
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500529 * User requested a write of security.capability. If needed, update the
530 * xattr to change from v2 to v3, or to fixup the v3 rootid.
531 *
Christian Braunere65ce2a2021-01-21 14:19:27 +0100532 * If the inode has been found through an idmapped mount the user namespace of
533 * the vfsmount must be passed through @mnt_userns. This function will then
534 * take care to map the inode according to @mnt_userns before checking
535 * permissions. On non-idmapped mounts or if permission checking is to be
536 * performed on the raw inode simply passs init_user_ns.
537 *
Randy Dunlap049ae602021-04-11 17:55:28 -0700538 * Return: On success, return the new size; on error, return < 0.
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500539 */
Christian Braunere65ce2a2021-01-21 14:19:27 +0100540int cap_convert_nscap(struct user_namespace *mnt_userns, struct dentry *dentry,
541 const void **ivalue, size_t size)
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500542{
543 struct vfs_ns_cap_data *nscap;
544 uid_t nsrootid;
545 const struct vfs_cap_data *cap = *ivalue;
546 __u32 magic, nsmagic;
547 struct inode *inode = d_backing_inode(dentry);
548 struct user_namespace *task_ns = current_user_ns(),
Eric W. Biederman3b0c2d32021-03-12 15:07:09 -0600549 *fs_ns = inode->i_sb->s_user_ns;
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500550 kuid_t rootid;
551 size_t newsize;
552
553 if (!*ivalue)
554 return -EINVAL;
Eric Biggersdc32b5c2018-01-01 09:28:31 -0600555 if (!validheader(size, cap))
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500556 return -EINVAL;
Christian Braunere65ce2a2021-01-21 14:19:27 +0100557 if (!capable_wrt_inode_uidgid(mnt_userns, inode, CAP_SETFCAP))
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500558 return -EPERM;
Christian Braunerbd303362021-12-03 12:17:07 +0100559 if (size == XATTR_CAPS_SZ_2 && (mnt_userns == fs_ns))
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500560 if (ns_capable(inode->i_sb->s_user_ns, CAP_SETFCAP))
561 /* user is privileged, just write the v2 */
562 return size;
563
Christian Braunerbd303362021-12-03 12:17:07 +0100564 rootid = rootid_from_xattr(*ivalue, size, task_ns, mnt_userns, fs_ns);
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500565 if (!uid_valid(rootid))
566 return -EINVAL;
567
568 nsrootid = from_kuid(fs_ns, rootid);
569 if (nsrootid == -1)
570 return -EINVAL;
571
572 newsize = sizeof(struct vfs_ns_cap_data);
573 nscap = kmalloc(newsize, GFP_ATOMIC);
574 if (!nscap)
575 return -ENOMEM;
576 nscap->rootid = cpu_to_le32(nsrootid);
577 nsmagic = VFS_CAP_REVISION_3;
578 magic = le32_to_cpu(cap->magic_etc);
579 if (magic & VFS_CAP_FLAGS_EFFECTIVE)
580 nsmagic |= VFS_CAP_FLAGS_EFFECTIVE;
581 nscap->magic_etc = cpu_to_le32(nsmagic);
582 memcpy(&nscap->data, &cap->data, sizeof(__le32) * 2 * VFS_CAP_U32);
583
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500584 *ivalue = nscap;
585 return newsize;
586}
587
David Howells1d045982008-11-14 10:39:24 +1100588/*
589 * Calculate the new process capability sets from the capability sets attached
590 * to a file.
591 */
Eric Parisc0b00442008-11-11 21:48:10 +1100592static inline int bprm_caps_from_vfs_caps(struct cpu_vfs_cap_data *caps,
David Howellsa6f76f22008-11-14 10:39:24 +1100593 struct linux_binprm *bprm,
Zhi Li4d49f672011-08-11 13:27:50 +0800594 bool *effective,
Richard Guy Briggsfc7eadf2017-10-11 20:57:07 -0400595 bool *has_fcap)
Serge E. Hallynb5376772007-10-16 23:31:36 -0700596{
David Howellsa6f76f22008-11-14 10:39:24 +1100597 struct cred *new = bprm->cred;
Eric Parisc0b00442008-11-11 21:48:10 +1100598 unsigned i;
599 int ret = 0;
600
601 if (caps->magic_etc & VFS_CAP_FLAGS_EFFECTIVE)
David Howellsa6f76f22008-11-14 10:39:24 +1100602 *effective = true;
Eric Parisc0b00442008-11-11 21:48:10 +1100603
Zhi Li4d49f672011-08-11 13:27:50 +0800604 if (caps->magic_etc & VFS_CAP_REVISION_MASK)
Richard Guy Briggsfc7eadf2017-10-11 20:57:07 -0400605 *has_fcap = true;
Zhi Li4d49f672011-08-11 13:27:50 +0800606
Eric Parisc0b00442008-11-11 21:48:10 +1100607 CAP_FOR_EACH_U32(i) {
608 __u32 permitted = caps->permitted.cap[i];
609 __u32 inheritable = caps->inheritable.cap[i];
610
611 /*
612 * pP' = (X & fP) | (pI & fI)
Andy Lutomirski58319052015-09-04 15:42:45 -0700613 * The addition of pA' is handled later.
Eric Parisc0b00442008-11-11 21:48:10 +1100614 */
David Howellsa6f76f22008-11-14 10:39:24 +1100615 new->cap_permitted.cap[i] =
616 (new->cap_bset.cap[i] & permitted) |
617 (new->cap_inheritable.cap[i] & inheritable);
Eric Parisc0b00442008-11-11 21:48:10 +1100618
David Howellsa6f76f22008-11-14 10:39:24 +1100619 if (permitted & ~new->cap_permitted.cap[i])
620 /* insufficient to execute correctly */
Eric Parisc0b00442008-11-11 21:48:10 +1100621 ret = -EPERM;
Eric Parisc0b00442008-11-11 21:48:10 +1100622 }
623
624 /*
625 * For legacy apps, with no internal support for recognizing they
626 * do not have enough capabilities, we return an error if they are
627 * missing some "forced" (aka file-permitted) capabilities.
628 */
David Howellsa6f76f22008-11-14 10:39:24 +1100629 return *effective ? ret : 0;
Eric Parisc0b00442008-11-11 21:48:10 +1100630}
631
Christian Brauner71bc3562021-01-21 14:19:29 +0100632/**
633 * get_vfs_caps_from_disk - retrieve vfs caps from disk
634 *
635 * @mnt_userns: user namespace of the mount the inode was found from
636 * @dentry: dentry from which @inode is retrieved
637 * @cpu_caps: vfs capabilities
638 *
David Howells1d045982008-11-14 10:39:24 +1100639 * Extract the on-exec-apply capability sets for an executable file.
Christian Brauner71bc3562021-01-21 14:19:29 +0100640 *
641 * If the inode has been found through an idmapped mount the user namespace of
642 * the vfsmount must be passed through @mnt_userns. This function will then
643 * take care to map the inode according to @mnt_userns before checking
644 * permissions. On non-idmapped mounts or if permission checking is to be
645 * performed on the raw inode simply passs init_user_ns.
David Howells1d045982008-11-14 10:39:24 +1100646 */
Christian Brauner71bc3562021-01-21 14:19:29 +0100647int get_vfs_caps_from_disk(struct user_namespace *mnt_userns,
648 const struct dentry *dentry,
649 struct cpu_vfs_cap_data *cpu_caps)
Eric Parisc0b00442008-11-11 21:48:10 +1100650{
David Howellsc6f493d2015-03-17 22:26:22 +0000651 struct inode *inode = d_backing_inode(dentry);
Serge E. Hallynb5376772007-10-16 23:31:36 -0700652 __u32 magic_etc;
Andrew Morgane338d262008-02-04 22:29:42 -0800653 unsigned tocopy, i;
Eric Parisc0b00442008-11-11 21:48:10 +1100654 int size;
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500655 struct vfs_ns_cap_data data, *nscaps = &data;
656 struct vfs_cap_data *caps = (struct vfs_cap_data *) &data;
657 kuid_t rootkuid;
Colin Ian King76ba89c72017-09-04 18:50:05 +0100658 struct user_namespace *fs_ns;
Eric Parisc0b00442008-11-11 21:48:10 +1100659
660 memset(cpu_caps, 0, sizeof(struct cpu_vfs_cap_data));
661
Andreas Gruenbacher5d6c3192016-09-29 17:48:42 +0200662 if (!inode)
Eric Parisc0b00442008-11-11 21:48:10 +1100663 return -ENODATA;
664
Colin Ian King76ba89c72017-09-04 18:50:05 +0100665 fs_ns = inode->i_sb->s_user_ns;
Andreas Gruenbacher5d6c3192016-09-29 17:48:42 +0200666 size = __vfs_getxattr((struct dentry *)dentry, inode,
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500667 XATTR_NAME_CAPS, &data, XATTR_CAPS_SZ);
David Howellsa6f76f22008-11-14 10:39:24 +1100668 if (size == -ENODATA || size == -EOPNOTSUPP)
Eric Parisc0b00442008-11-11 21:48:10 +1100669 /* no data, that's ok */
670 return -ENODATA;
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500671
Eric Parisc0b00442008-11-11 21:48:10 +1100672 if (size < 0)
673 return size;
Serge E. Hallynb5376772007-10-16 23:31:36 -0700674
Andrew Morgane338d262008-02-04 22:29:42 -0800675 if (size < sizeof(magic_etc))
Serge E. Hallynb5376772007-10-16 23:31:36 -0700676 return -EINVAL;
677
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500678 cpu_caps->magic_etc = magic_etc = le32_to_cpu(caps->magic_etc);
Serge E. Hallynb5376772007-10-16 23:31:36 -0700679
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500680 rootkuid = make_kuid(fs_ns, 0);
David Howellsa6f76f22008-11-14 10:39:24 +1100681 switch (magic_etc & VFS_CAP_REVISION_MASK) {
Andrew Morgane338d262008-02-04 22:29:42 -0800682 case VFS_CAP_REVISION_1:
683 if (size != XATTR_CAPS_SZ_1)
684 return -EINVAL;
685 tocopy = VFS_CAP_U32_1;
686 break;
687 case VFS_CAP_REVISION_2:
688 if (size != XATTR_CAPS_SZ_2)
689 return -EINVAL;
690 tocopy = VFS_CAP_U32_2;
691 break;
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500692 case VFS_CAP_REVISION_3:
693 if (size != XATTR_CAPS_SZ_3)
694 return -EINVAL;
695 tocopy = VFS_CAP_U32_3;
696 rootkuid = make_kuid(fs_ns, le32_to_cpu(nscaps->rootid));
697 break;
698
Serge E. Hallynb5376772007-10-16 23:31:36 -0700699 default:
700 return -EINVAL;
701 }
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500702 /* Limit the caps to the mounter of the filesystem
703 * or the more limited uid specified in the xattr.
704 */
Christian Braunerbd303362021-12-03 12:17:07 +0100705 rootkuid = mapped_kuid_fs(mnt_userns, fs_ns, rootkuid);
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500706 if (!rootid_owns_currentns(rootkuid))
707 return -ENODATA;
Andrew Morgane338d262008-02-04 22:29:42 -0800708
Andrew G. Morgan5459c162008-07-23 21:28:24 -0700709 CAP_FOR_EACH_U32(i) {
Eric Parisc0b00442008-11-11 21:48:10 +1100710 if (i >= tocopy)
711 break;
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500712 cpu_caps->permitted.cap[i] = le32_to_cpu(caps->data[i].permitted);
713 cpu_caps->inheritable.cap[i] = le32_to_cpu(caps->data[i].inheritable);
Andrew Morgane338d262008-02-04 22:29:42 -0800714 }
David Howellsa6f76f22008-11-14 10:39:24 +1100715
Eric Paris7d8b6c62014-07-23 15:36:26 -0400716 cpu_caps->permitted.cap[CAP_LAST_U32] &= CAP_LAST_U32_VALID_MASK;
717 cpu_caps->inheritable.cap[CAP_LAST_U32] &= CAP_LAST_U32_VALID_MASK;
718
Richard Guy Briggs2fec30e2019-01-23 21:36:25 -0500719 cpu_caps->rootid = rootkuid;
720
Eric Parisc0b00442008-11-11 21:48:10 +1100721 return 0;
Serge E. Hallynb5376772007-10-16 23:31:36 -0700722}
723
David Howells1d045982008-11-14 10:39:24 +1100724/*
725 * Attempt to get the on-exec apply capability sets for an executable file from
726 * its xattrs and, if present, apply them to the proposed credentials being
727 * constructed by execve().
728 */
Eric W. Biederman56305aa2020-05-29 22:00:54 -0500729static int get_file_caps(struct linux_binprm *bprm, struct file *file,
730 bool *effective, bool *has_fcap)
Serge E. Hallynb5376772007-10-16 23:31:36 -0700731{
Serge E. Hallynb5376772007-10-16 23:31:36 -0700732 int rc = 0;
Eric Parisc0b00442008-11-11 21:48:10 +1100733 struct cpu_vfs_cap_data vcaps;
Serge E. Hallynb5376772007-10-16 23:31:36 -0700734
Kees Cookee67ae72017-07-18 15:25:28 -0700735 cap_clear(bprm->cred->cap_permitted);
Serge Hallyn3318a382008-10-30 11:52:23 -0500736
Serge E. Hallyn1f29fae2008-11-05 16:08:52 -0600737 if (!file_caps_enabled)
738 return 0;
739
Eric W. Biederman56305aa2020-05-29 22:00:54 -0500740 if (!mnt_may_suid(file->f_path.mnt))
Serge E. Hallynb5376772007-10-16 23:31:36 -0700741 return 0;
Andy Lutomirski380cf5b2016-06-23 16:41:05 -0500742
743 /*
744 * This check is redundant with mnt_may_suid() but is kept to make
745 * explicit that capability bits are limited to s_user_ns and its
746 * descendants.
747 */
Eric W. Biederman56305aa2020-05-29 22:00:54 -0500748 if (!current_in_userns(file->f_path.mnt->mnt_sb->s_user_ns))
Seth Forsheed07b8462015-09-23 15:16:04 -0500749 return 0;
Serge E. Hallynb5376772007-10-16 23:31:36 -0700750
Christian Brauner71bc3562021-01-21 14:19:29 +0100751 rc = get_vfs_caps_from_disk(file_mnt_user_ns(file),
752 file->f_path.dentry, &vcaps);
Eric Parisc0b00442008-11-11 21:48:10 +1100753 if (rc < 0) {
754 if (rc == -EINVAL)
Serge E. Hallyn8db6c342017-05-08 13:11:56 -0500755 printk(KERN_NOTICE "Invalid argument reading file caps for %s\n",
756 bprm->filename);
Eric Parisc0b00442008-11-11 21:48:10 +1100757 else if (rc == -ENODATA)
758 rc = 0;
Serge E. Hallynb5376772007-10-16 23:31:36 -0700759 goto out;
760 }
Serge E. Hallynb5376772007-10-16 23:31:36 -0700761
Richard Guy Briggsfc7eadf2017-10-11 20:57:07 -0400762 rc = bprm_caps_from_vfs_caps(&vcaps, bprm, effective, has_fcap);
Serge E. Hallynb5376772007-10-16 23:31:36 -0700763
764out:
Serge E. Hallynb5376772007-10-16 23:31:36 -0700765 if (rc)
Kees Cookee67ae72017-07-18 15:25:28 -0700766 cap_clear(bprm->cred->cap_permitted);
Serge E. Hallynb5376772007-10-16 23:31:36 -0700767
768 return rc;
769}
770
Richard Guy Briggs9304b462017-10-11 20:57:08 -0400771static inline bool root_privileged(void) { return !issecure(SECURE_NOROOT); }
772
Richard Guy Briggs81a6a012017-10-11 20:57:09 -0400773static inline bool __is_real(kuid_t uid, struct cred *cred)
774{ return uid_eq(cred->uid, uid); }
775
776static inline bool __is_eff(kuid_t uid, struct cred *cred)
777{ return uid_eq(cred->euid, uid); }
778
779static inline bool __is_suid(kuid_t uid, struct cred *cred)
780{ return !__is_real(uid, cred) && __is_eff(uid, cred); }
781
Richard Guy Briggsdb1a8922017-10-11 20:57:05 -0400782/*
783 * handle_privileged_root - Handle case of privileged root
784 * @bprm: The execution parameters, including the proposed creds
785 * @has_fcap: Are any file capabilities set?
786 * @effective: Do we have effective root privilege?
787 * @root_uid: This namespace' root UID WRT initial USER namespace
788 *
789 * Handle the case where root is privileged and hasn't been neutered by
790 * SECURE_NOROOT. If file capabilities are set, they won't be combined with
791 * set UID root and nothing is changed. If we are root, cap_permitted is
792 * updated. If we have become set UID root, the effective bit is set.
793 */
Richard Guy Briggsfc7eadf2017-10-11 20:57:07 -0400794static void handle_privileged_root(struct linux_binprm *bprm, bool has_fcap,
Richard Guy Briggsdb1a8922017-10-11 20:57:05 -0400795 bool *effective, kuid_t root_uid)
796{
797 const struct cred *old = current_cred();
798 struct cred *new = bprm->cred;
799
Richard Guy Briggs9304b462017-10-11 20:57:08 -0400800 if (!root_privileged())
Richard Guy Briggsdb1a8922017-10-11 20:57:05 -0400801 return;
802 /*
803 * If the legacy file capability is set, then don't set privs
804 * for a setuid root binary run by a non-root user. Do set it
805 * for a root user just to cause least surprise to an admin.
806 */
Richard Guy Briggs81a6a012017-10-11 20:57:09 -0400807 if (has_fcap && __is_suid(root_uid, new)) {
Richard Guy Briggsdb1a8922017-10-11 20:57:05 -0400808 warn_setuid_and_fcaps_mixed(bprm->filename);
809 return;
810 }
811 /*
812 * To support inheritance of root-permissions and suid-root
813 * executables under compatibility mode, we override the
814 * capability sets for the file.
815 */
Richard Guy Briggs81a6a012017-10-11 20:57:09 -0400816 if (__is_eff(root_uid, new) || __is_real(root_uid, new)) {
Richard Guy Briggsdb1a8922017-10-11 20:57:05 -0400817 /* pP' = (cap_bset & ~0) | (pI & ~0) */
818 new->cap_permitted = cap_combine(old->cap_bset,
819 old->cap_inheritable);
820 }
821 /*
822 * If only the real uid is 0, we do not set the effective bit.
823 */
Richard Guy Briggs81a6a012017-10-11 20:57:09 -0400824 if (__is_eff(root_uid, new))
Richard Guy Briggsdb1a8922017-10-11 20:57:05 -0400825 *effective = true;
826}
827
Richard Guy Briggs4c7e7152017-10-11 20:57:06 -0400828#define __cap_gained(field, target, source) \
829 !cap_issubset(target->cap_##field, source->cap_##field)
830#define __cap_grew(target, source, cred) \
831 !cap_issubset(cred->cap_##target, cred->cap_##source)
832#define __cap_full(field, cred) \
833 cap_issubset(CAP_FULL_SET, cred->cap_##field)
Richard Guy Briggs81a6a012017-10-11 20:57:09 -0400834
835static inline bool __is_setuid(struct cred *new, const struct cred *old)
836{ return !uid_eq(new->euid, old->uid); }
837
838static inline bool __is_setgid(struct cred *new, const struct cred *old)
839{ return !gid_eq(new->egid, old->gid); }
840
Richard Guy Briggs9fbc2c72017-10-11 20:57:10 -0400841/*
Richard Guy Briggsdbbbe112017-10-11 20:57:14 -0400842 * 1) Audit candidate if current->cap_effective is set
Richard Guy Briggs9fbc2c72017-10-11 20:57:10 -0400843 *
844 * We do not bother to audit if 3 things are true:
845 * 1) cap_effective has all caps
Richard Guy Briggs588fb2c2017-10-11 20:57:13 -0400846 * 2) we became root *OR* are were already root
Richard Guy Briggs9fbc2c72017-10-11 20:57:10 -0400847 * 3) root is supposed to have all caps (SECURE_NOROOT)
848 * Since this is just a normal root execing a process.
849 *
850 * Number 1 above might fail if you don't have a full bset, but I think
851 * that is interesting information to audit.
Richard Guy Briggsdbbbe112017-10-11 20:57:14 -0400852 *
853 * A number of other conditions require logging:
854 * 2) something prevented setuid root getting all caps
855 * 3) non-setuid root gets fcaps
856 * 4) non-setuid root gets ambient
Richard Guy Briggs9fbc2c72017-10-11 20:57:10 -0400857 */
Richard Guy Briggsdbbbe112017-10-11 20:57:14 -0400858static inline bool nonroot_raised_pE(struct cred *new, const struct cred *old,
859 kuid_t root, bool has_fcap)
Richard Guy Briggs9fbc2c72017-10-11 20:57:10 -0400860{
861 bool ret = false;
862
Richard Guy Briggsdbbbe112017-10-11 20:57:14 -0400863 if ((__cap_grew(effective, ambient, new) &&
864 !(__cap_full(effective, new) &&
865 (__is_eff(root, new) || __is_real(root, new)) &&
866 root_privileged())) ||
867 (root_privileged() &&
868 __is_suid(root, new) &&
869 !__cap_full(effective, new)) ||
870 (!__is_setuid(new, old) &&
871 ((has_fcap &&
872 __cap_gained(permitted, new, old)) ||
873 __cap_gained(ambient, new, old))))
874
Richard Guy Briggs02ebbaf2017-10-11 20:57:11 -0400875 ret = true;
Richard Guy Briggsdbbbe112017-10-11 20:57:14 -0400876
Richard Guy Briggs9fbc2c72017-10-11 20:57:10 -0400877 return ret;
878}
879
David Howells1d045982008-11-14 10:39:24 +1100880/**
Eric W. Biederman56305aa2020-05-29 22:00:54 -0500881 * cap_bprm_creds_from_file - Set up the proposed credentials for execve().
David Howells1d045982008-11-14 10:39:24 +1100882 * @bprm: The execution parameters, including the proposed creds
Eric W. Biederman56305aa2020-05-29 22:00:54 -0500883 * @file: The file to pull the credentials from
David Howells1d045982008-11-14 10:39:24 +1100884 *
885 * Set up the proposed credentials for a new execution context being
886 * constructed by execve(). The proposed creds in @bprm->cred is altered,
Randy Dunlap049ae602021-04-11 17:55:28 -0700887 * which won't take effect immediately.
888 *
889 * Return: 0 if successful, -ve on error.
David Howellsa6f76f22008-11-14 10:39:24 +1100890 */
Eric W. Biederman56305aa2020-05-29 22:00:54 -0500891int cap_bprm_creds_from_file(struct linux_binprm *bprm, struct file *file)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700892{
Eric W. Biederman56305aa2020-05-29 22:00:54 -0500893 /* Process setpcap binaries and capabilities for uid 0 */
David Howellsa6f76f22008-11-14 10:39:24 +1100894 const struct cred *old = current_cred();
895 struct cred *new = bprm->cred;
Richard Guy Briggsfc7eadf2017-10-11 20:57:07 -0400896 bool effective = false, has_fcap = false, is_setid;
Serge E. Hallynb5376772007-10-16 23:31:36 -0700897 int ret;
Eric W. Biederman18815a12012-02-07 16:45:47 -0800898 kuid_t root_uid;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700899
Andy Lutomirski58319052015-09-04 15:42:45 -0700900 if (WARN_ON(!cap_ambient_invariant_ok(old)))
901 return -EPERM;
902
Eric W. Biederman56305aa2020-05-29 22:00:54 -0500903 ret = get_file_caps(bprm, file, &effective, &has_fcap);
David Howellsa6f76f22008-11-14 10:39:24 +1100904 if (ret < 0)
905 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700906
Eric W. Biederman18815a12012-02-07 16:45:47 -0800907 root_uid = make_kuid(new->user_ns, 0);
908
Richard Guy Briggsfc7eadf2017-10-11 20:57:07 -0400909 handle_privileged_root(bprm, has_fcap, &effective, root_uid);
Serge E. Hallynb5376772007-10-16 23:31:36 -0700910
Eric Parisd52fc5d2012-04-17 16:26:54 -0400911 /* if we have fs caps, clear dangerous personality flags */
Richard Guy Briggs4c7e7152017-10-11 20:57:06 -0400912 if (__cap_gained(permitted, new, old))
Eric W. Biederman56305aa2020-05-29 22:00:54 -0500913 bprm->per_clear |= PER_CLEAR_ON_SETID;
Eric Parisd52fc5d2012-04-17 16:26:54 -0400914
David Howellsa6f76f22008-11-14 10:39:24 +1100915 /* Don't let someone trace a set[ug]id/setpcap binary with the revised
Andy Lutomirski259e5e62012-04-12 16:47:50 -0500916 * credentials unless they have the appropriate permit.
917 *
918 * In addition, if NO_NEW_PRIVS, then ensure we get no new privs.
David Howellsa6f76f22008-11-14 10:39:24 +1100919 */
Richard Guy Briggs81a6a012017-10-11 20:57:09 -0400920 is_setid = __is_setuid(new, old) || __is_setgid(new, old);
Andy Lutomirski58319052015-09-04 15:42:45 -0700921
Richard Guy Briggs4c7e7152017-10-11 20:57:06 -0400922 if ((is_setid || __cap_gained(permitted, new, old)) &&
Eric W. Biederman9227dd22017-01-23 17:26:31 +1300923 ((bprm->unsafe & ~LSM_UNSAFE_PTRACE) ||
Eric W. Biederman20523132017-01-23 17:17:26 +1300924 !ptracer_capable(current, new->user_ns))) {
David Howellsa6f76f22008-11-14 10:39:24 +1100925 /* downgrade; they get no more than they had, and maybe less */
Eric W. Biederman70169422016-11-17 01:38:35 -0600926 if (!ns_capable(new->user_ns, CAP_SETUID) ||
Andy Lutomirski259e5e62012-04-12 16:47:50 -0500927 (bprm->unsafe & LSM_UNSAFE_NO_NEW_PRIVS)) {
David Howellsa6f76f22008-11-14 10:39:24 +1100928 new->euid = new->uid;
929 new->egid = new->gid;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700930 }
Serge E. Hallynb3a222e2009-11-23 16:21:30 -0600931 new->cap_permitted = cap_intersect(new->cap_permitted,
932 old->cap_permitted);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700933 }
934
David Howellsa6f76f22008-11-14 10:39:24 +1100935 new->suid = new->fsuid = new->euid;
936 new->sgid = new->fsgid = new->egid;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700937
Andy Lutomirski58319052015-09-04 15:42:45 -0700938 /* File caps or setid cancels ambient. */
Richard Guy Briggsfc7eadf2017-10-11 20:57:07 -0400939 if (has_fcap || is_setid)
Andy Lutomirski58319052015-09-04 15:42:45 -0700940 cap_clear(new->cap_ambient);
941
942 /*
943 * Now that we've computed pA', update pP' to give:
944 * pP' = (X & fP) | (pI & fI) | pA'
945 */
946 new->cap_permitted = cap_combine(new->cap_permitted, new->cap_ambient);
947
948 /*
949 * Set pE' = (fE ? pP' : pA'). Because pA' is zero if fE is set,
950 * this is the same as pE' = (fE ? pP' : 0) | pA'.
951 */
Eric Paris4bf2ea72011-04-01 17:08:28 -0400952 if (effective)
953 new->cap_effective = new->cap_permitted;
954 else
Andy Lutomirski58319052015-09-04 15:42:45 -0700955 new->cap_effective = new->cap_ambient;
956
957 if (WARN_ON(!cap_ambient_invariant_ok(new)))
958 return -EPERM;
959
Richard Guy Briggsdbbbe112017-10-11 20:57:14 -0400960 if (nonroot_raised_pE(new, old, root_uid, has_fcap)) {
Richard Guy Briggs9fbc2c72017-10-11 20:57:10 -0400961 ret = audit_log_bprm_fcaps(bprm, new, old);
962 if (ret < 0)
963 return ret;
Eric Paris3fc689e2008-11-11 21:48:18 +1100964 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700965
David Howellsd84f4f92008-11-14 10:39:23 +1100966 new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
Andy Lutomirski58319052015-09-04 15:42:45 -0700967
968 if (WARN_ON(!cap_ambient_invariant_ok(new)))
969 return -EPERM;
970
Kees Cook46d98eb2017-07-18 15:25:27 -0700971 /* Check for privilege-elevated exec. */
Richard Guy Briggs02ebbaf2017-10-11 20:57:11 -0400972 if (is_setid ||
973 (!__is_real(root_uid, new) &&
974 (effective ||
975 __cap_grew(permitted, ambient, new))))
Eric W. Biederman56305aa2020-05-29 22:00:54 -0500976 bprm->secureexec = 1;
Serge E. Hallynb5376772007-10-16 23:31:36 -0700977
Kees Cookee67ae72017-07-18 15:25:28 -0700978 return 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700979}
980
David Howells1d045982008-11-14 10:39:24 +1100981/**
982 * cap_inode_setxattr - Determine whether an xattr may be altered
983 * @dentry: The inode/dentry being altered
984 * @name: The name of the xattr to be changed
985 * @value: The value that the xattr will be changed to
986 * @size: The size of value
987 * @flags: The replacement flag
988 *
989 * Determine whether an xattr may be altered or set on an inode, returning 0 if
990 * permission is granted, -ve if denied.
991 *
992 * This is used to make sure security xattrs don't get updated or set by those
993 * who aren't privileged to do so.
994 */
David Howells8f0cfa52008-04-29 00:59:41 -0700995int cap_inode_setxattr(struct dentry *dentry, const char *name,
996 const void *value, size_t size, int flags)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700997{
Eric W. Biedermanb1d749c52017-04-21 19:14:32 -0500998 struct user_namespace *user_ns = dentry->d_sb->s_user_ns;
999
Serge E. Hallyn8db6c342017-05-08 13:11:56 -05001000 /* Ignore non-security xattrs */
1001 if (strncmp(name, XATTR_SECURITY_PREFIX,
Carmeli Tamirc5eaab12019-07-06 11:07:38 -04001002 XATTR_SECURITY_PREFIX_LEN) != 0)
Serge E. Hallynb5376772007-10-16 23:31:36 -07001003 return 0;
David Howells1d045982008-11-14 10:39:24 +11001004
Serge E. Hallyn8db6c342017-05-08 13:11:56 -05001005 /*
1006 * For XATTR_NAME_CAPS the check will be done in
1007 * cap_convert_nscap(), called by setxattr()
1008 */
1009 if (strcmp(name, XATTR_NAME_CAPS) == 0)
1010 return 0;
1011
Eric W. Biedermanb1d749c52017-04-21 19:14:32 -05001012 if (!ns_capable(user_ns, CAP_SYS_ADMIN))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001013 return -EPERM;
1014 return 0;
1015}
1016
David Howells1d045982008-11-14 10:39:24 +11001017/**
1018 * cap_inode_removexattr - Determine whether an xattr may be removed
Christian Brauner71bc3562021-01-21 14:19:29 +01001019 *
1020 * @mnt_userns: User namespace of the mount the inode was found from
1021 * @dentry: The inode/dentry being altered
1022 * @name: The name of the xattr to be changed
David Howells1d045982008-11-14 10:39:24 +11001023 *
1024 * Determine whether an xattr may be removed from an inode, returning 0 if
1025 * permission is granted, -ve if denied.
1026 *
Christian Brauner71bc3562021-01-21 14:19:29 +01001027 * If the inode has been found through an idmapped mount the user namespace of
1028 * the vfsmount must be passed through @mnt_userns. This function will then
1029 * take care to map the inode according to @mnt_userns before checking
1030 * permissions. On non-idmapped mounts or if permission checking is to be
1031 * performed on the raw inode simply passs init_user_ns.
1032 *
David Howells1d045982008-11-14 10:39:24 +11001033 * This is used to make sure security xattrs don't get removed by those who
1034 * aren't privileged to remove them.
1035 */
Christian Brauner71bc3562021-01-21 14:19:29 +01001036int cap_inode_removexattr(struct user_namespace *mnt_userns,
1037 struct dentry *dentry, const char *name)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001038{
Eric W. Biedermanb1d749c52017-04-21 19:14:32 -05001039 struct user_namespace *user_ns = dentry->d_sb->s_user_ns;
1040
Serge E. Hallyn8db6c342017-05-08 13:11:56 -05001041 /* Ignore non-security xattrs */
1042 if (strncmp(name, XATTR_SECURITY_PREFIX,
Carmeli Tamirc5eaab12019-07-06 11:07:38 -04001043 XATTR_SECURITY_PREFIX_LEN) != 0)
Serge E. Hallyn8db6c342017-05-08 13:11:56 -05001044 return 0;
1045
1046 if (strcmp(name, XATTR_NAME_CAPS) == 0) {
1047 /* security.capability gets namespaced */
1048 struct inode *inode = d_backing_inode(dentry);
1049 if (!inode)
1050 return -EINVAL;
Christian Brauner71bc3562021-01-21 14:19:29 +01001051 if (!capable_wrt_inode_uidgid(mnt_userns, inode, CAP_SETFCAP))
Serge E. Hallynb5376772007-10-16 23:31:36 -07001052 return -EPERM;
1053 return 0;
David Howells1d045982008-11-14 10:39:24 +11001054 }
1055
Eric W. Biedermanb1d749c52017-04-21 19:14:32 -05001056 if (!ns_capable(user_ns, CAP_SYS_ADMIN))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001057 return -EPERM;
1058 return 0;
1059}
1060
David Howellsa6f76f22008-11-14 10:39:24 +11001061/*
Linus Torvalds1da177e2005-04-16 15:20:36 -07001062 * cap_emulate_setxuid() fixes the effective / permitted capabilities of
1063 * a process after a call to setuid, setreuid, or setresuid.
1064 *
1065 * 1) When set*uiding _from_ one of {r,e,s}uid == 0 _to_ all of
1066 * {r,e,s}uid != 0, the permitted and effective capabilities are
1067 * cleared.
1068 *
1069 * 2) When set*uiding _from_ euid == 0 _to_ euid != 0, the effective
1070 * capabilities of the process are cleared.
1071 *
1072 * 3) When set*uiding _from_ euid != 0 _to_ euid == 0, the effective
1073 * capabilities are set to the permitted capabilities.
1074 *
David Howellsa6f76f22008-11-14 10:39:24 +11001075 * fsuid is handled elsewhere. fsuid == 0 and {r,e,s}uid!= 0 should
Linus Torvalds1da177e2005-04-16 15:20:36 -07001076 * never happen.
1077 *
David Howellsa6f76f22008-11-14 10:39:24 +11001078 * -astor
Linus Torvalds1da177e2005-04-16 15:20:36 -07001079 *
1080 * cevans - New behaviour, Oct '99
1081 * A process may, via prctl(), elect to keep its capabilities when it
1082 * calls setuid() and switches away from uid==0. Both permitted and
1083 * effective sets will be retained.
1084 * Without this change, it was impossible for a daemon to drop only some
1085 * of its privilege. The call to setuid(!=0) would drop all privileges!
1086 * Keeping uid 0 is not an option because uid 0 owns too many vital
1087 * files..
1088 * Thanks to Olaf Kirch and Peter Benie for spotting this.
1089 */
David Howellsd84f4f92008-11-14 10:39:23 +11001090static inline void cap_emulate_setxuid(struct cred *new, const struct cred *old)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001091{
Eric W. Biederman18815a12012-02-07 16:45:47 -08001092 kuid_t root_uid = make_kuid(old->user_ns, 0);
1093
1094 if ((uid_eq(old->uid, root_uid) ||
1095 uid_eq(old->euid, root_uid) ||
1096 uid_eq(old->suid, root_uid)) &&
1097 (!uid_eq(new->uid, root_uid) &&
1098 !uid_eq(new->euid, root_uid) &&
Andy Lutomirski58319052015-09-04 15:42:45 -07001099 !uid_eq(new->suid, root_uid))) {
1100 if (!issecure(SECURE_KEEP_CAPS)) {
1101 cap_clear(new->cap_permitted);
1102 cap_clear(new->cap_effective);
1103 }
1104
1105 /*
1106 * Pre-ambient programs expect setresuid to nonroot followed
1107 * by exec to drop capabilities. We should make sure that
1108 * this remains the case.
1109 */
1110 cap_clear(new->cap_ambient);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001111 }
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 cap_clear(new->cap_effective);
Eric W. Biederman18815a12012-02-07 16:45:47 -08001114 if (!uid_eq(old->euid, root_uid) && uid_eq(new->euid, root_uid))
David Howellsd84f4f92008-11-14 10:39:23 +11001115 new->cap_effective = new->cap_permitted;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001116}
1117
David Howells1d045982008-11-14 10:39:24 +11001118/**
1119 * cap_task_fix_setuid - Fix up the results of setuid() call
1120 * @new: The proposed credentials
1121 * @old: The current task's current credentials
1122 * @flags: Indications of what has changed
1123 *
1124 * Fix up the results of setuid() call before the credential changes are
Randy Dunlap049ae602021-04-11 17:55:28 -07001125 * actually applied.
1126 *
1127 * Return: 0 to grant the changes, -ve to deny them.
David Howells1d045982008-11-14 10:39:24 +11001128 */
David Howellsd84f4f92008-11-14 10:39:23 +11001129int cap_task_fix_setuid(struct cred *new, const struct cred *old, int flags)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001130{
1131 switch (flags) {
1132 case LSM_SETID_RE:
1133 case LSM_SETID_ID:
1134 case LSM_SETID_RES:
David Howells1d045982008-11-14 10:39:24 +11001135 /* juggle the capabilities to follow [RES]UID changes unless
1136 * otherwise suppressed */
David Howellsd84f4f92008-11-14 10:39:23 +11001137 if (!issecure(SECURE_NO_SETUID_FIXUP))
1138 cap_emulate_setxuid(new, old);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001139 break;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001140
David Howells1d045982008-11-14 10:39:24 +11001141 case LSM_SETID_FS:
1142 /* juggle the capabilties to follow FSUID changes, unless
1143 * otherwise suppressed
1144 *
David Howellsd84f4f92008-11-14 10:39:23 +11001145 * FIXME - is fsuser used for all CAP_FS_MASK capabilities?
1146 * if not, we might be a bit too harsh here.
1147 */
1148 if (!issecure(SECURE_NO_SETUID_FIXUP)) {
Eric W. Biederman18815a12012-02-07 16:45:47 -08001149 kuid_t root_uid = make_kuid(old->user_ns, 0);
1150 if (uid_eq(old->fsuid, root_uid) && !uid_eq(new->fsuid, root_uid))
David Howellsd84f4f92008-11-14 10:39:23 +11001151 new->cap_effective =
1152 cap_drop_fs_set(new->cap_effective);
David Howells1d045982008-11-14 10:39:24 +11001153
Eric W. Biederman18815a12012-02-07 16:45:47 -08001154 if (!uid_eq(old->fsuid, root_uid) && uid_eq(new->fsuid, root_uid))
David Howellsd84f4f92008-11-14 10:39:23 +11001155 new->cap_effective =
1156 cap_raise_fs_set(new->cap_effective,
1157 new->cap_permitted);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001158 }
David Howellsd84f4f92008-11-14 10:39:23 +11001159 break;
David Howells1d045982008-11-14 10:39:24 +11001160
Linus Torvalds1da177e2005-04-16 15:20:36 -07001161 default:
1162 return -EINVAL;
1163 }
1164
1165 return 0;
1166}
1167
Serge E. Hallynb5376772007-10-16 23:31:36 -07001168/*
1169 * Rationale: code calling task_setscheduler, task_setioprio, and
1170 * task_setnice, assumes that
1171 * . if capable(cap_sys_nice), then those actions should be allowed
1172 * . if not capable(cap_sys_nice), but acting on your own processes,
1173 * then those actions should be allowed
1174 * This is insufficient now since you can call code without suid, but
1175 * yet with increased caps.
1176 * So we check for increased caps on the target process.
1177 */
Serge E. Hallynde45e802008-09-26 22:27:47 -04001178static int cap_safe_nice(struct task_struct *p)
Serge E. Hallynb5376772007-10-16 23:31:36 -07001179{
Serge Hallynf54fb862013-07-23 13:18:53 -05001180 int is_subset, ret = 0;
David Howellsc69e8d92008-11-14 10:39:19 +11001181
1182 rcu_read_lock();
1183 is_subset = cap_issubset(__task_cred(p)->cap_permitted,
1184 current_cred()->cap_permitted);
Serge Hallynf54fb862013-07-23 13:18:53 -05001185 if (!is_subset && !ns_capable(__task_cred(p)->user_ns, CAP_SYS_NICE))
1186 ret = -EPERM;
David Howellsc69e8d92008-11-14 10:39:19 +11001187 rcu_read_unlock();
1188
Serge Hallynf54fb862013-07-23 13:18:53 -05001189 return ret;
Serge E. Hallynb5376772007-10-16 23:31:36 -07001190}
1191
David Howells1d045982008-11-14 10:39:24 +11001192/**
1193 * cap_task_setscheduler - Detemine if scheduler policy change is permitted
1194 * @p: The task to affect
David Howells1d045982008-11-14 10:39:24 +11001195 *
1196 * Detemine if the requested scheduler policy change is permitted for the
Randy Dunlap049ae602021-04-11 17:55:28 -07001197 * specified task.
1198 *
1199 * Return: 0 if permission is granted, -ve if denied.
David Howells1d045982008-11-14 10:39:24 +11001200 */
KOSAKI Motohirob0ae1982010-10-15 04:21:18 +09001201int cap_task_setscheduler(struct task_struct *p)
Serge E. Hallynb5376772007-10-16 23:31:36 -07001202{
1203 return cap_safe_nice(p);
1204}
1205
David Howells1d045982008-11-14 10:39:24 +11001206/**
Randy Dunlap049ae602021-04-11 17:55:28 -07001207 * cap_task_setioprio - Detemine if I/O priority change is permitted
David Howells1d045982008-11-14 10:39:24 +11001208 * @p: The task to affect
1209 * @ioprio: The I/O priority to set
1210 *
1211 * Detemine if the requested I/O priority change is permitted for the specified
Randy Dunlap049ae602021-04-11 17:55:28 -07001212 * task.
1213 *
1214 * Return: 0 if permission is granted, -ve if denied.
David Howells1d045982008-11-14 10:39:24 +11001215 */
1216int cap_task_setioprio(struct task_struct *p, int ioprio)
Serge E. Hallynb5376772007-10-16 23:31:36 -07001217{
1218 return cap_safe_nice(p);
1219}
1220
David Howells1d045982008-11-14 10:39:24 +11001221/**
Randy Dunlap049ae602021-04-11 17:55:28 -07001222 * cap_task_setnice - Detemine if task priority change is permitted
David Howells1d045982008-11-14 10:39:24 +11001223 * @p: The task to affect
1224 * @nice: The nice value to set
1225 *
1226 * Detemine if the requested task priority change is permitted for the
Randy Dunlap049ae602021-04-11 17:55:28 -07001227 * specified task.
1228 *
1229 * Return: 0 if permission is granted, -ve if denied.
David Howells1d045982008-11-14 10:39:24 +11001230 */
1231int cap_task_setnice(struct task_struct *p, int nice)
Serge E. Hallynb5376772007-10-16 23:31:36 -07001232{
1233 return cap_safe_nice(p);
1234}
1235
Serge E. Hallyn3b7391d2008-02-04 22:29:45 -08001236/*
David Howells1d045982008-11-14 10:39:24 +11001237 * Implement PR_CAPBSET_DROP. Attempt to remove the specified capability from
1238 * the current task's bounding set. Returns 0 on success, -ve on error.
Serge E. Hallyn3b7391d2008-02-04 22:29:45 -08001239 */
Tetsuo Handa6d6f3322014-07-22 21:20:01 +09001240static int cap_prctl_drop(unsigned long cap)
Serge E. Hallyn3b7391d2008-02-04 22:29:45 -08001241{
Tetsuo Handa6d6f3322014-07-22 21:20:01 +09001242 struct cred *new;
1243
Eric W. Biederman160da842013-07-02 10:04:54 -07001244 if (!ns_capable(current_user_ns(), CAP_SETPCAP))
Serge E. Hallyn3b7391d2008-02-04 22:29:45 -08001245 return -EPERM;
1246 if (!cap_valid(cap))
1247 return -EINVAL;
David Howellsd84f4f92008-11-14 10:39:23 +11001248
Tetsuo Handa6d6f3322014-07-22 21:20:01 +09001249 new = prepare_creds();
1250 if (!new)
1251 return -ENOMEM;
David Howellsd84f4f92008-11-14 10:39:23 +11001252 cap_lower(new->cap_bset, cap);
Tetsuo Handa6d6f3322014-07-22 21:20:01 +09001253 return commit_creds(new);
Serge E. Hallyn3b7391d2008-02-04 22:29:45 -08001254}
Andrew G. Morgan3898b1b2008-04-28 02:13:40 -07001255
David Howells1d045982008-11-14 10:39:24 +11001256/**
1257 * cap_task_prctl - Implement process control functions for this security module
1258 * @option: The process control function requested
Randy Dunlap049ae602021-04-11 17:55:28 -07001259 * @arg2: The argument data for this function
1260 * @arg3: The argument data for this function
1261 * @arg4: The argument data for this function
1262 * @arg5: The argument data for this function
David Howells1d045982008-11-14 10:39:24 +11001263 *
1264 * Allow process control functions (sys_prctl()) to alter capabilities; may
1265 * also deny access to other functions not otherwise implemented here.
1266 *
Randy Dunlap049ae602021-04-11 17:55:28 -07001267 * Return: 0 or +ve on success, -ENOSYS if this function is not implemented
David Howells1d045982008-11-14 10:39:24 +11001268 * here, other -ve on error. If -ENOSYS is returned, sys_prctl() and other LSM
1269 * modules will consider performing the function.
1270 */
Andrew G. Morgan3898b1b2008-04-28 02:13:40 -07001271int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3,
David Howellsd84f4f92008-11-14 10:39:23 +11001272 unsigned long arg4, unsigned long arg5)
Andrew G. Morgan3898b1b2008-04-28 02:13:40 -07001273{
Tetsuo Handa6d6f3322014-07-22 21:20:01 +09001274 const struct cred *old = current_cred();
David Howellsd84f4f92008-11-14 10:39:23 +11001275 struct cred *new;
David Howellsd84f4f92008-11-14 10:39:23 +11001276
Andrew G. Morgan3898b1b2008-04-28 02:13:40 -07001277 switch (option) {
1278 case PR_CAPBSET_READ:
1279 if (!cap_valid(arg2))
Tetsuo Handa6d6f3322014-07-22 21:20:01 +09001280 return -EINVAL;
1281 return !!cap_raised(old->cap_bset, arg2);
David Howellsd84f4f92008-11-14 10:39:23 +11001282
Andrew G. Morgan3898b1b2008-04-28 02:13:40 -07001283 case PR_CAPBSET_DROP:
Tetsuo Handa6d6f3322014-07-22 21:20:01 +09001284 return cap_prctl_drop(arg2);
Andrew G. Morgan3898b1b2008-04-28 02:13:40 -07001285
1286 /*
1287 * The next four prctl's remain to assist with transitioning a
1288 * system from legacy UID=0 based privilege (when filesystem
1289 * capabilities are not in use) to a system using filesystem
1290 * capabilities only - as the POSIX.1e draft intended.
1291 *
1292 * Note:
1293 *
1294 * PR_SET_SECUREBITS =
1295 * issecure_mask(SECURE_KEEP_CAPS_LOCKED)
1296 * | issecure_mask(SECURE_NOROOT)
1297 * | issecure_mask(SECURE_NOROOT_LOCKED)
1298 * | issecure_mask(SECURE_NO_SETUID_FIXUP)
1299 * | issecure_mask(SECURE_NO_SETUID_FIXUP_LOCKED)
1300 *
1301 * will ensure that the current process and all of its
1302 * children will be locked into a pure
1303 * capability-based-privilege environment.
1304 */
1305 case PR_SET_SECUREBITS:
Tetsuo Handa6d6f3322014-07-22 21:20:01 +09001306 if ((((old->securebits & SECURE_ALL_LOCKS) >> 1)
1307 & (old->securebits ^ arg2)) /*[1]*/
1308 || ((old->securebits & SECURE_ALL_LOCKS & ~arg2)) /*[2]*/
David Howellsd84f4f92008-11-14 10:39:23 +11001309 || (arg2 & ~(SECURE_ALL_LOCKS | SECURE_ALL_BITS)) /*[3]*/
Eric Paris6a9de492012-01-03 12:25:14 -05001310 || (cap_capable(current_cred(),
Micah Mortonc1a85a02019-01-07 16:10:53 -08001311 current_cred()->user_ns,
1312 CAP_SETPCAP,
1313 CAP_OPT_NONE) != 0) /*[4]*/
Andrew G. Morgan3898b1b2008-04-28 02:13:40 -07001314 /*
1315 * [1] no changing of bits that are locked
1316 * [2] no unlocking of locks
1317 * [3] no setting of unsupported bits
1318 * [4] doing anything requires privilege (go read about
1319 * the "sendmail capabilities bug")
1320 */
David Howellsd84f4f92008-11-14 10:39:23 +11001321 )
1322 /* cannot change a locked bit */
Tetsuo Handa6d6f3322014-07-22 21:20:01 +09001323 return -EPERM;
1324
1325 new = prepare_creds();
1326 if (!new)
1327 return -ENOMEM;
David Howellsd84f4f92008-11-14 10:39:23 +11001328 new->securebits = arg2;
Tetsuo Handa6d6f3322014-07-22 21:20:01 +09001329 return commit_creds(new);
David Howellsd84f4f92008-11-14 10:39:23 +11001330
Andrew G. Morgan3898b1b2008-04-28 02:13:40 -07001331 case PR_GET_SECUREBITS:
Tetsuo Handa6d6f3322014-07-22 21:20:01 +09001332 return old->securebits;
Andrew G. Morgan3898b1b2008-04-28 02:13:40 -07001333
Andrew G. Morgan3898b1b2008-04-28 02:13:40 -07001334 case PR_GET_KEEPCAPS:
Tetsuo Handa6d6f3322014-07-22 21:20:01 +09001335 return !!issecure(SECURE_KEEP_CAPS);
David Howellsd84f4f92008-11-14 10:39:23 +11001336
Andrew G. Morgan3898b1b2008-04-28 02:13:40 -07001337 case PR_SET_KEEPCAPS:
1338 if (arg2 > 1) /* Note, we rely on arg2 being unsigned here */
Tetsuo Handa6d6f3322014-07-22 21:20:01 +09001339 return -EINVAL;
David Howellsd84f4f92008-11-14 10:39:23 +11001340 if (issecure(SECURE_KEEP_CAPS_LOCKED))
Tetsuo Handa6d6f3322014-07-22 21:20:01 +09001341 return -EPERM;
1342
1343 new = prepare_creds();
1344 if (!new)
1345 return -ENOMEM;
David Howellsd84f4f92008-11-14 10:39:23 +11001346 if (arg2)
1347 new->securebits |= issecure_mask(SECURE_KEEP_CAPS);
Andrew G. Morgan3898b1b2008-04-28 02:13:40 -07001348 else
David Howellsd84f4f92008-11-14 10:39:23 +11001349 new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
Tetsuo Handa6d6f3322014-07-22 21:20:01 +09001350 return commit_creds(new);
Andrew G. Morgan3898b1b2008-04-28 02:13:40 -07001351
Andy Lutomirski58319052015-09-04 15:42:45 -07001352 case PR_CAP_AMBIENT:
1353 if (arg2 == PR_CAP_AMBIENT_CLEAR_ALL) {
1354 if (arg3 | arg4 | arg5)
1355 return -EINVAL;
1356
1357 new = prepare_creds();
1358 if (!new)
1359 return -ENOMEM;
1360 cap_clear(new->cap_ambient);
1361 return commit_creds(new);
1362 }
1363
1364 if (((!cap_valid(arg3)) | arg4 | arg5))
1365 return -EINVAL;
1366
1367 if (arg2 == PR_CAP_AMBIENT_IS_SET) {
1368 return !!cap_raised(current_cred()->cap_ambient, arg3);
1369 } else if (arg2 != PR_CAP_AMBIENT_RAISE &&
1370 arg2 != PR_CAP_AMBIENT_LOWER) {
1371 return -EINVAL;
1372 } else {
1373 if (arg2 == PR_CAP_AMBIENT_RAISE &&
1374 (!cap_raised(current_cred()->cap_permitted, arg3) ||
1375 !cap_raised(current_cred()->cap_inheritable,
Andy Lutomirski746bf6d2015-09-04 15:42:51 -07001376 arg3) ||
1377 issecure(SECURE_NO_CAP_AMBIENT_RAISE)))
Andy Lutomirski58319052015-09-04 15:42:45 -07001378 return -EPERM;
1379
1380 new = prepare_creds();
1381 if (!new)
1382 return -ENOMEM;
1383 if (arg2 == PR_CAP_AMBIENT_RAISE)
1384 cap_raise(new->cap_ambient, arg3);
1385 else
1386 cap_lower(new->cap_ambient, arg3);
1387 return commit_creds(new);
1388 }
1389
Andrew G. Morgan3898b1b2008-04-28 02:13:40 -07001390 default:
1391 /* No functionality available - continue with default */
Tetsuo Handa6d6f3322014-07-22 21:20:01 +09001392 return -ENOSYS;
Andrew G. Morgan3898b1b2008-04-28 02:13:40 -07001393 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001394}
1395
David Howells1d045982008-11-14 10:39:24 +11001396/**
David Howells1d045982008-11-14 10:39:24 +11001397 * cap_vm_enough_memory - Determine whether a new virtual mapping is permitted
1398 * @mm: The VM space in which the new mapping is to be made
1399 * @pages: The size of the mapping
1400 *
1401 * Determine whether the allocation of a new virtual mapping by the current
Randy Dunlap049ae602021-04-11 17:55:28 -07001402 * task is permitted.
1403 *
1404 * Return: 1 if permission is granted, 0 if not.
David Howells1d045982008-11-14 10:39:24 +11001405 */
Alan Cox34b4e4a2007-08-22 14:01:28 -07001406int cap_vm_enough_memory(struct mm_struct *mm, long pages)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001407{
1408 int cap_sys_admin = 0;
1409
Micah Mortonc1a85a02019-01-07 16:10:53 -08001410 if (cap_capable(current_cred(), &init_user_ns,
1411 CAP_SYS_ADMIN, CAP_OPT_NOAUDIT) == 0)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001412 cap_sys_admin = 1;
Micah Mortonc1a85a02019-01-07 16:10:53 -08001413
Casey Schauflerb1d9e6b2015-05-02 15:11:42 -07001414 return cap_sys_admin;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001415}
Eric Paris7c738752009-07-31 12:53:58 -04001416
Randy Dunlap049ae602021-04-11 17:55:28 -07001417/**
Al Virod0077942012-05-30 13:11:37 -04001418 * cap_mmap_addr - check if able to map given addr
1419 * @addr: address attempting to be mapped
1420 *
1421 * If the process is attempting to map memory below dac_mmap_min_addr they need
1422 * CAP_SYS_RAWIO. The other parameters to this function are unused by the
Randy Dunlap049ae602021-04-11 17:55:28 -07001423 * capability security module.
1424 *
1425 * Return: 0 if this mapping should be allowed or -EPERM if not.
Al Virod0077942012-05-30 13:11:37 -04001426 */
1427int cap_mmap_addr(unsigned long addr)
1428{
1429 int ret = 0;
1430
1431 if (addr < dac_mmap_min_addr) {
1432 ret = cap_capable(current_cred(), &init_user_ns, CAP_SYS_RAWIO,
Micah Mortonc1a85a02019-01-07 16:10:53 -08001433 CAP_OPT_NONE);
Al Virod0077942012-05-30 13:11:37 -04001434 /* set PF_SUPERPRIV if it turns out we allow the low mmap */
1435 if (ret == 0)
1436 current->flags |= PF_SUPERPRIV;
1437 }
1438 return ret;
1439}
1440
Al Viroe5467852012-05-30 13:30:51 -04001441int cap_mmap_file(struct file *file, unsigned long reqprot,
1442 unsigned long prot, unsigned long flags)
Eric Paris7c738752009-07-31 12:53:58 -04001443{
Al Viroe5467852012-05-30 13:30:51 -04001444 return 0;
Eric Paris7c738752009-07-31 12:53:58 -04001445}
Casey Schauflerb1d9e6b2015-05-02 15:11:42 -07001446
1447#ifdef CONFIG_SECURITY
1448
YueHaibingd1c59472019-06-11 21:48:15 +08001449static struct security_hook_list capability_hooks[] __lsm_ro_after_init = {
Casey Schauflerb1d9e6b2015-05-02 15:11:42 -07001450 LSM_HOOK_INIT(capable, cap_capable),
1451 LSM_HOOK_INIT(settime, cap_settime),
1452 LSM_HOOK_INIT(ptrace_access_check, cap_ptrace_access_check),
1453 LSM_HOOK_INIT(ptrace_traceme, cap_ptrace_traceme),
1454 LSM_HOOK_INIT(capget, cap_capget),
1455 LSM_HOOK_INIT(capset, cap_capset),
Eric W. Biederman56305aa2020-05-29 22:00:54 -05001456 LSM_HOOK_INIT(bprm_creds_from_file, cap_bprm_creds_from_file),
Casey Schauflerb1d9e6b2015-05-02 15:11:42 -07001457 LSM_HOOK_INIT(inode_need_killpriv, cap_inode_need_killpriv),
1458 LSM_HOOK_INIT(inode_killpriv, cap_inode_killpriv),
Serge E. Hallyn8db6c342017-05-08 13:11:56 -05001459 LSM_HOOK_INIT(inode_getsecurity, cap_inode_getsecurity),
Casey Schauflerb1d9e6b2015-05-02 15:11:42 -07001460 LSM_HOOK_INIT(mmap_addr, cap_mmap_addr),
1461 LSM_HOOK_INIT(mmap_file, cap_mmap_file),
1462 LSM_HOOK_INIT(task_fix_setuid, cap_task_fix_setuid),
1463 LSM_HOOK_INIT(task_prctl, cap_task_prctl),
1464 LSM_HOOK_INIT(task_setscheduler, cap_task_setscheduler),
1465 LSM_HOOK_INIT(task_setioprio, cap_task_setioprio),
1466 LSM_HOOK_INIT(task_setnice, cap_task_setnice),
1467 LSM_HOOK_INIT(vm_enough_memory, cap_vm_enough_memory),
1468};
1469
Kees Cookd117a152018-09-14 15:40:45 -07001470static int __init capability_init(void)
Casey Schauflerb1d9e6b2015-05-02 15:11:42 -07001471{
Casey Schauflerd69dece52017-01-18 17:09:05 -08001472 security_add_hooks(capability_hooks, ARRAY_SIZE(capability_hooks),
1473 "capability");
Kees Cookd117a152018-09-14 15:40:45 -07001474 return 0;
Casey Schauflerb1d9e6b2015-05-02 15:11:42 -07001475}
1476
Kees Cookd117a152018-09-14 15:40:45 -07001477DEFINE_LSM(capability) = {
1478 .name = "capability",
1479 .order = LSM_ORDER_FIRST,
1480 .init = capability_init,
1481};
1482
Casey Schauflerb1d9e6b2015-05-02 15:11:42 -07001483#endif /* CONFIG_SECURITY */