Root/security/commoncap.c

1/* Common capabilities, needed by capability.o.
2 *
3 * This program is free software; you can redistribute it and/or modify
4 * it under the terms of the GNU General Public License as published by
5 * the Free Software Foundation; either version 2 of the License, or
6 * (at your option) any later version.
7 *
8 */
9
10#include <linux/capability.h>
11#include <linux/audit.h>
12#include <linux/module.h>
13#include <linux/init.h>
14#include <linux/kernel.h>
15#include <linux/security.h>
16#include <linux/file.h>
17#include <linux/mm.h>
18#include <linux/mman.h>
19#include <linux/pagemap.h>
20#include <linux/swap.h>
21#include <linux/skbuff.h>
22#include <linux/netlink.h>
23#include <linux/ptrace.h>
24#include <linux/xattr.h>
25#include <linux/hugetlb.h>
26#include <linux/mount.h>
27#include <linux/sched.h>
28#include <linux/prctl.h>
29#include <linux/securebits.h>
30#include <linux/user_namespace.h>
31#include <linux/binfmts.h>
32#include <linux/personality.h>
33
34/*
35 * If a non-root user executes a setuid-root binary in
36 * !secure(SECURE_NOROOT) mode, then we raise capabilities.
37 * However if fE is also set, then the intent is for only
38 * the file capabilities to be applied, and the setuid-root
39 * bit is left on either to change the uid (plausible) or
40 * to get full privilege on a kernel without file capabilities
41 * support. So in that case we do not raise capabilities.
42 *
43 * Warn if that happens, once per boot.
44 */
45static void warn_setuid_and_fcaps_mixed(const char *fname)
46{
47    static int warned;
48    if (!warned) {
49        printk(KERN_INFO "warning: `%s' has both setuid-root and"
50            " effective capabilities. Therefore not raising all"
51            " capabilities.\n", fname);
52        warned = 1;
53    }
54}
55
56int cap_netlink_send(struct sock *sk, struct sk_buff *skb)
57{
58    return 0;
59}
60
61/**
62 * cap_capable - Determine whether a task has a particular effective capability
63 * @cred: The credentials to use
64 * @ns: The user namespace in which we need the capability
65 * @cap: The capability to check for
66 * @audit: Whether to write an audit message or not
67 *
68 * Determine whether the nominated task has the specified capability amongst
69 * its effective set, returning 0 if it does, -ve if it does not.
70 *
71 * NOTE WELL: cap_has_capability() cannot be used like the kernel's capable()
72 * and has_capability() functions. That is, it has the reverse semantics:
73 * cap_has_capability() returns 0 when a task has a capability, but the
74 * kernel's capable() and has_capability() returns 1 for this case.
75 */
76int cap_capable(const struct cred *cred, struct user_namespace *targ_ns,
77        int cap, int audit)
78{
79    struct user_namespace *ns = targ_ns;
80
81    /* See if cred has the capability in the target user namespace
82     * by examining the target user namespace and all of the target
83     * user namespace's parents.
84     */
85    for (;;) {
86        /* Do we have the necessary capabilities? */
87        if (ns == cred->user_ns)
88            return cap_raised(cred->cap_effective, cap) ? 0 : -EPERM;
89
90        /* Have we tried all of the parent namespaces? */
91        if (ns == &init_user_ns)
92            return -EPERM;
93
94        /*
95         * The owner of the user namespace in the parent of the
96         * user namespace has all caps.
97         */
98        if ((ns->parent == cred->user_ns) && uid_eq(ns->owner, cred->euid))
99            return 0;
100
101        /*
102         * If you have a capability in a parent user ns, then you have
103         * it over all children user namespaces as well.
104         */
105        ns = ns->parent;
106    }
107
108    /* We never get here */
109}
110
111/**
112 * cap_settime - Determine whether the current process may set the system clock
113 * @ts: The time to set
114 * @tz: The timezone to set
115 *
116 * Determine whether the current process may set the system clock and timezone
117 * information, returning 0 if permission granted, -ve if denied.
118 */
119int cap_settime(const struct timespec *ts, const struct timezone *tz)
120{
121    if (!capable(CAP_SYS_TIME))
122        return -EPERM;
123    return 0;
124}
125
126/**
127 * cap_ptrace_access_check - Determine whether the current process may access
128 * another
129 * @child: The process to be accessed
130 * @mode: The mode of attachment.
131 *
132 * If we are in the same or an ancestor user_ns and have all the target
133 * task's capabilities, then ptrace access is allowed.
134 * If we have the ptrace capability to the target user_ns, then ptrace
135 * access is allowed.
136 * Else denied.
137 *
138 * Determine whether a process may access another, returning 0 if permission
139 * granted, -ve if denied.
140 */
141int cap_ptrace_access_check(struct task_struct *child, unsigned int mode)
142{
143    int ret = 0;
144    const struct cred *cred, *child_cred;
145
146    rcu_read_lock();
147    cred = current_cred();
148    child_cred = __task_cred(child);
149    if (cred->user_ns == child_cred->user_ns &&
150        cap_issubset(child_cred->cap_permitted, cred->cap_permitted))
151        goto out;
152    if (ns_capable(child_cred->user_ns, CAP_SYS_PTRACE))
153        goto out;
154    ret = -EPERM;
155out:
156    rcu_read_unlock();
157    return ret;
158}
159
160/**
161 * cap_ptrace_traceme - Determine whether another process may trace the current
162 * @parent: The task proposed to be the tracer
163 *
164 * If parent is in the same or an ancestor user_ns and has all current's
165 * capabilities, then ptrace access is allowed.
166 * If parent has the ptrace capability to current's user_ns, then ptrace
167 * access is allowed.
168 * Else denied.
169 *
170 * Determine whether the nominated task is permitted to trace the current
171 * process, returning 0 if permission is granted, -ve if denied.
172 */
173int cap_ptrace_traceme(struct task_struct *parent)
174{
175    int ret = 0;
176    const struct cred *cred, *child_cred;
177
178    rcu_read_lock();
179    cred = __task_cred(parent);
180    child_cred = current_cred();
181    if (cred->user_ns == child_cred->user_ns &&
182        cap_issubset(child_cred->cap_permitted, cred->cap_permitted))
183        goto out;
184    if (has_ns_capability(parent, child_cred->user_ns, CAP_SYS_PTRACE))
185        goto out;
186    ret = -EPERM;
187out:
188    rcu_read_unlock();
189    return ret;
190}
191
192/**
193 * cap_capget - Retrieve a task's capability sets
194 * @target: The task from which to retrieve the capability sets
195 * @effective: The place to record the effective set
196 * @inheritable: The place to record the inheritable set
197 * @permitted: The place to record the permitted set
198 *
199 * This function retrieves the capabilities of the nominated task and returns
200 * them to the caller.
201 */
202int cap_capget(struct task_struct *target, kernel_cap_t *effective,
203           kernel_cap_t *inheritable, kernel_cap_t *permitted)
204{
205    const struct cred *cred;
206
207    /* Derived from kernel/capability.c:sys_capget. */
208    rcu_read_lock();
209    cred = __task_cred(target);
210    *effective = cred->cap_effective;
211    *inheritable = cred->cap_inheritable;
212    *permitted = cred->cap_permitted;
213    rcu_read_unlock();
214    return 0;
215}
216
217/*
218 * Determine whether the inheritable capabilities are limited to the old
219 * permitted set. Returns 1 if they are limited, 0 if they are not.
220 */
221static inline int cap_inh_is_capped(void)
222{
223
224    /* they are so limited unless the current task has the CAP_SETPCAP
225     * capability
226     */
227    if (cap_capable(current_cred(), current_cred()->user_ns,
228            CAP_SETPCAP, SECURITY_CAP_AUDIT) == 0)
229        return 0;
230    return 1;
231}
232
233/**
234 * cap_capset - Validate and apply proposed changes to current's capabilities
235 * @new: The proposed new credentials; alterations should be made here
236 * @old: The current task's current credentials
237 * @effective: A pointer to the proposed new effective capabilities set
238 * @inheritable: A pointer to the proposed new inheritable capabilities set
239 * @permitted: A pointer to the proposed new permitted capabilities set
240 *
241 * This function validates and applies a proposed mass change to the current
242 * process's capability sets. The changes are made to the proposed new
243 * credentials, and assuming no error, will be committed by the caller of LSM.
244 */
245int cap_capset(struct cred *new,
246           const struct cred *old,
247           const kernel_cap_t *effective,
248           const kernel_cap_t *inheritable,
249           const kernel_cap_t *permitted)
250{
251    if (cap_inh_is_capped() &&
252        !cap_issubset(*inheritable,
253              cap_combine(old->cap_inheritable,
254                      old->cap_permitted)))
255        /* incapable of using this inheritable set */
256        return -EPERM;
257
258    if (!cap_issubset(*inheritable,
259              cap_combine(old->cap_inheritable,
260                      old->cap_bset)))
261        /* no new pI capabilities outside bounding set */
262        return -EPERM;
263
264    /* verify restrictions on target's new Permitted set */
265    if (!cap_issubset(*permitted, old->cap_permitted))
266        return -EPERM;
267
268    /* verify the _new_Effective_ is a subset of the _new_Permitted_ */
269    if (!cap_issubset(*effective, *permitted))
270        return -EPERM;
271
272    new->cap_effective = *effective;
273    new->cap_inheritable = *inheritable;
274    new->cap_permitted = *permitted;
275    return 0;
276}
277
278/*
279 * Clear proposed capability sets for execve().
280 */
281static inline void bprm_clear_caps(struct linux_binprm *bprm)
282{
283    cap_clear(bprm->cred->cap_permitted);
284    bprm->cap_effective = false;
285}
286
287/**
288 * cap_inode_need_killpriv - Determine if inode change affects privileges
289 * @dentry: The inode/dentry in being changed with change marked ATTR_KILL_PRIV
290 *
291 * Determine if an inode having a change applied that's marked ATTR_KILL_PRIV
292 * affects the security markings on that inode, and if it is, should
293 * inode_killpriv() be invoked or the change rejected?
294 *
295 * Returns 0 if granted; +ve if granted, but inode_killpriv() is required; and
296 * -ve to deny the change.
297 */
298int cap_inode_need_killpriv(struct dentry *dentry)
299{
300    struct inode *inode = dentry->d_inode;
301    int error;
302
303    if (!inode->i_op->getxattr)
304           return 0;
305
306    error = inode->i_op->getxattr(dentry, XATTR_NAME_CAPS, NULL, 0);
307    if (error <= 0)
308        return 0;
309    return 1;
310}
311
312/**
313 * cap_inode_killpriv - Erase the security markings on an inode
314 * @dentry: The inode/dentry to alter
315 *
316 * Erase the privilege-enhancing security markings on an inode.
317 *
318 * Returns 0 if successful, -ve on error.
319 */
320int cap_inode_killpriv(struct dentry *dentry)
321{
322    struct inode *inode = dentry->d_inode;
323
324    if (!inode->i_op->removexattr)
325           return 0;
326
327    return inode->i_op->removexattr(dentry, XATTR_NAME_CAPS);
328}
329
330/*
331 * Calculate the new process capability sets from the capability sets attached
332 * to a file.
333 */
334static inline int bprm_caps_from_vfs_caps(struct cpu_vfs_cap_data *caps,
335                      struct linux_binprm *bprm,
336                      bool *effective,
337                      bool *has_cap)
338{
339    struct cred *new = bprm->cred;
340    unsigned i;
341    int ret = 0;
342
343    if (caps->magic_etc & VFS_CAP_FLAGS_EFFECTIVE)
344        *effective = true;
345
346    if (caps->magic_etc & VFS_CAP_REVISION_MASK)
347        *has_cap = true;
348
349    CAP_FOR_EACH_U32(i) {
350        __u32 permitted = caps->permitted.cap[i];
351        __u32 inheritable = caps->inheritable.cap[i];
352
353        /*
354         * pP' = (X & fP) | (pI & fI)
355         */
356        new->cap_permitted.cap[i] =
357            (new->cap_bset.cap[i] & permitted) |
358            (new->cap_inheritable.cap[i] & inheritable);
359
360        if (permitted & ~new->cap_permitted.cap[i])
361            /* insufficient to execute correctly */
362            ret = -EPERM;
363    }
364
365    /*
366     * For legacy apps, with no internal support for recognizing they
367     * do not have enough capabilities, we return an error if they are
368     * missing some "forced" (aka file-permitted) capabilities.
369     */
370    return *effective ? ret : 0;
371}
372
373/*
374 * Extract the on-exec-apply capability sets for an executable file.
375 */
376int get_vfs_caps_from_disk(const struct dentry *dentry, struct cpu_vfs_cap_data *cpu_caps)
377{
378    struct inode *inode = dentry->d_inode;
379    __u32 magic_etc;
380    unsigned tocopy, i;
381    int size;
382    struct vfs_cap_data caps;
383
384    memset(cpu_caps, 0, sizeof(struct cpu_vfs_cap_data));
385
386    if (!inode || !inode->i_op->getxattr)
387        return -ENODATA;
388
389    size = inode->i_op->getxattr((struct dentry *)dentry, XATTR_NAME_CAPS, &caps,
390                   XATTR_CAPS_SZ);
391    if (size == -ENODATA || size == -EOPNOTSUPP)
392        /* no data, that's ok */
393        return -ENODATA;
394    if (size < 0)
395        return size;
396
397    if (size < sizeof(magic_etc))
398        return -EINVAL;
399
400    cpu_caps->magic_etc = magic_etc = le32_to_cpu(caps.magic_etc);
401
402    switch (magic_etc & VFS_CAP_REVISION_MASK) {
403    case VFS_CAP_REVISION_1:
404        if (size != XATTR_CAPS_SZ_1)
405            return -EINVAL;
406        tocopy = VFS_CAP_U32_1;
407        break;
408    case VFS_CAP_REVISION_2:
409        if (size != XATTR_CAPS_SZ_2)
410            return -EINVAL;
411        tocopy = VFS_CAP_U32_2;
412        break;
413    default:
414        return -EINVAL;
415    }
416
417    CAP_FOR_EACH_U32(i) {
418        if (i >= tocopy)
419            break;
420        cpu_caps->permitted.cap[i] = le32_to_cpu(caps.data[i].permitted);
421        cpu_caps->inheritable.cap[i] = le32_to_cpu(caps.data[i].inheritable);
422    }
423
424    return 0;
425}
426
427/*
428 * Attempt to get the on-exec apply capability sets for an executable file from
429 * its xattrs and, if present, apply them to the proposed credentials being
430 * constructed by execve().
431 */
432static int get_file_caps(struct linux_binprm *bprm, bool *effective, bool *has_cap)
433{
434    struct dentry *dentry;
435    int rc = 0;
436    struct cpu_vfs_cap_data vcaps;
437
438    bprm_clear_caps(bprm);
439
440    if (!file_caps_enabled)
441        return 0;
442
443    if (bprm->file->f_path.mnt->mnt_flags & MNT_NOSUID)
444        return 0;
445
446    dentry = dget(bprm->file->f_dentry);
447
448    rc = get_vfs_caps_from_disk(dentry, &vcaps);
449    if (rc < 0) {
450        if (rc == -EINVAL)
451            printk(KERN_NOTICE "%s: get_vfs_caps_from_disk returned %d for %s\n",
452                __func__, rc, bprm->filename);
453        else if (rc == -ENODATA)
454            rc = 0;
455        goto out;
456    }
457
458    rc = bprm_caps_from_vfs_caps(&vcaps, bprm, effective, has_cap);
459    if (rc == -EINVAL)
460        printk(KERN_NOTICE "%s: cap_from_disk returned %d for %s\n",
461               __func__, rc, bprm->filename);
462
463out:
464    dput(dentry);
465    if (rc)
466        bprm_clear_caps(bprm);
467
468    return rc;
469}
470
471/**
472 * cap_bprm_set_creds - Set up the proposed credentials for execve().
473 * @bprm: The execution parameters, including the proposed creds
474 *
475 * Set up the proposed credentials for a new execution context being
476 * constructed by execve(). The proposed creds in @bprm->cred is altered,
477 * which won't take effect immediately. Returns 0 if successful, -ve on error.
478 */
479int cap_bprm_set_creds(struct linux_binprm *bprm)
480{
481    const struct cred *old = current_cred();
482    struct cred *new = bprm->cred;
483    bool effective, has_cap = false;
484    int ret;
485    kuid_t root_uid;
486
487    effective = false;
488    ret = get_file_caps(bprm, &effective, &has_cap);
489    if (ret < 0)
490        return ret;
491
492    root_uid = make_kuid(new->user_ns, 0);
493
494    if (!issecure(SECURE_NOROOT)) {
495        /*
496         * If the legacy file capability is set, then don't set privs
497         * for a setuid root binary run by a non-root user. Do set it
498         * for a root user just to cause least surprise to an admin.
499         */
500        if (has_cap && !uid_eq(new->uid, root_uid) && uid_eq(new->euid, root_uid)) {
501            warn_setuid_and_fcaps_mixed(bprm->filename);
502            goto skip;
503        }
504        /*
505         * To support inheritance of root-permissions and suid-root
506         * executables under compatibility mode, we override the
507         * capability sets for the file.
508         *
509         * If only the real uid is 0, we do not set the effective bit.
510         */
511        if (uid_eq(new->euid, root_uid) || uid_eq(new->uid, root_uid)) {
512            /* pP' = (cap_bset & ~0) | (pI & ~0) */
513            new->cap_permitted = cap_combine(old->cap_bset,
514                             old->cap_inheritable);
515        }
516        if (uid_eq(new->euid, root_uid))
517            effective = true;
518    }
519skip:
520
521    /* if we have fs caps, clear dangerous personality flags */
522    if (!cap_issubset(new->cap_permitted, old->cap_permitted))
523        bprm->per_clear |= PER_CLEAR_ON_SETID;
524
525
526    /* Don't let someone trace a set[ug]id/setpcap binary with the revised
527     * credentials unless they have the appropriate permit.
528     *
529     * In addition, if NO_NEW_PRIVS, then ensure we get no new privs.
530     */
531    if ((!uid_eq(new->euid, old->uid) ||
532         !gid_eq(new->egid, old->gid) ||
533         !cap_issubset(new->cap_permitted, old->cap_permitted)) &&
534        bprm->unsafe & ~LSM_UNSAFE_PTRACE_CAP) {
535        /* downgrade; they get no more than they had, and maybe less */
536        if (!capable(CAP_SETUID) ||
537            (bprm->unsafe & LSM_UNSAFE_NO_NEW_PRIVS)) {
538            new->euid = new->uid;
539            new->egid = new->gid;
540        }
541        new->cap_permitted = cap_intersect(new->cap_permitted,
542                           old->cap_permitted);
543    }
544
545    new->suid = new->fsuid = new->euid;
546    new->sgid = new->fsgid = new->egid;
547
548    if (effective)
549        new->cap_effective = new->cap_permitted;
550    else
551        cap_clear(new->cap_effective);
552    bprm->cap_effective = effective;
553
554    /*
555     * Audit candidate if current->cap_effective is set
556     *
557     * We do not bother to audit if 3 things are true:
558     * 1) cap_effective has all caps
559     * 2) we are root
560     * 3) root is supposed to have all caps (SECURE_NOROOT)
561     * Since this is just a normal root execing a process.
562     *
563     * Number 1 above might fail if you don't have a full bset, but I think
564     * that is interesting information to audit.
565     */
566    if (!cap_isclear(new->cap_effective)) {
567        if (!cap_issubset(CAP_FULL_SET, new->cap_effective) ||
568            !uid_eq(new->euid, root_uid) || !uid_eq(new->uid, root_uid) ||
569            issecure(SECURE_NOROOT)) {
570            ret = audit_log_bprm_fcaps(bprm, new, old);
571            if (ret < 0)
572                return ret;
573        }
574    }
575
576    new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
577    return 0;
578}
579
580/**
581 * cap_bprm_secureexec - Determine whether a secure execution is required
582 * @bprm: The execution parameters
583 *
584 * Determine whether a secure execution is required, return 1 if it is, and 0
585 * if it is not.
586 *
587 * The credentials have been committed by this point, and so are no longer
588 * available through @bprm->cred.
589 */
590int cap_bprm_secureexec(struct linux_binprm *bprm)
591{
592    const struct cred *cred = current_cred();
593    kuid_t root_uid = make_kuid(cred->user_ns, 0);
594
595    if (!uid_eq(cred->uid, root_uid)) {
596        if (bprm->cap_effective)
597            return 1;
598        if (!cap_isclear(cred->cap_permitted))
599            return 1;
600    }
601
602    return (!uid_eq(cred->euid, cred->uid) ||
603        !gid_eq(cred->egid, cred->gid));
604}
605
606/**
607 * cap_inode_setxattr - Determine whether an xattr may be altered
608 * @dentry: The inode/dentry being altered
609 * @name: The name of the xattr to be changed
610 * @value: The value that the xattr will be changed to
611 * @size: The size of value
612 * @flags: The replacement flag
613 *
614 * Determine whether an xattr may be altered or set on an inode, returning 0 if
615 * permission is granted, -ve if denied.
616 *
617 * This is used to make sure security xattrs don't get updated or set by those
618 * who aren't privileged to do so.
619 */
620int cap_inode_setxattr(struct dentry *dentry, const char *name,
621               const void *value, size_t size, int flags)
622{
623    if (!strcmp(name, XATTR_NAME_CAPS)) {
624        if (!capable(CAP_SETFCAP))
625            return -EPERM;
626        return 0;
627    }
628
629    if (!strncmp(name, XATTR_SECURITY_PREFIX,
630             sizeof(XATTR_SECURITY_PREFIX) - 1) &&
631        !capable(CAP_SYS_ADMIN))
632        return -EPERM;
633    return 0;
634}
635
636/**
637 * cap_inode_removexattr - Determine whether an xattr may be removed
638 * @dentry: The inode/dentry being altered
639 * @name: The name of the xattr to be changed
640 *
641 * Determine whether an xattr may be removed from an inode, returning 0 if
642 * permission is granted, -ve if denied.
643 *
644 * This is used to make sure security xattrs don't get removed by those who
645 * aren't privileged to remove them.
646 */
647int cap_inode_removexattr(struct dentry *dentry, const char *name)
648{
649    if (!strcmp(name, XATTR_NAME_CAPS)) {
650        if (!capable(CAP_SETFCAP))
651            return -EPERM;
652        return 0;
653    }
654
655    if (!strncmp(name, XATTR_SECURITY_PREFIX,
656             sizeof(XATTR_SECURITY_PREFIX) - 1) &&
657        !capable(CAP_SYS_ADMIN))
658        return -EPERM;
659    return 0;
660}
661
662/*
663 * cap_emulate_setxuid() fixes the effective / permitted capabilities of
664 * a process after a call to setuid, setreuid, or setresuid.
665 *
666 * 1) When set*uiding _from_ one of {r,e,s}uid == 0 _to_ all of
667 * {r,e,s}uid != 0, the permitted and effective capabilities are
668 * cleared.
669 *
670 * 2) When set*uiding _from_ euid == 0 _to_ euid != 0, the effective
671 * capabilities of the process are cleared.
672 *
673 * 3) When set*uiding _from_ euid != 0 _to_ euid == 0, the effective
674 * capabilities are set to the permitted capabilities.
675 *
676 * fsuid is handled elsewhere. fsuid == 0 and {r,e,s}uid!= 0 should
677 * never happen.
678 *
679 * -astor
680 *
681 * cevans - New behaviour, Oct '99
682 * A process may, via prctl(), elect to keep its capabilities when it
683 * calls setuid() and switches away from uid==0. Both permitted and
684 * effective sets will be retained.
685 * Without this change, it was impossible for a daemon to drop only some
686 * of its privilege. The call to setuid(!=0) would drop all privileges!
687 * Keeping uid 0 is not an option because uid 0 owns too many vital
688 * files..
689 * Thanks to Olaf Kirch and Peter Benie for spotting this.
690 */
691static inline void cap_emulate_setxuid(struct cred *new, const struct cred *old)
692{
693    kuid_t root_uid = make_kuid(old->user_ns, 0);
694
695    if ((uid_eq(old->uid, root_uid) ||
696         uid_eq(old->euid, root_uid) ||
697         uid_eq(old->suid, root_uid)) &&
698        (!uid_eq(new->uid, root_uid) &&
699         !uid_eq(new->euid, root_uid) &&
700         !uid_eq(new->suid, root_uid)) &&
701        !issecure(SECURE_KEEP_CAPS)) {
702        cap_clear(new->cap_permitted);
703        cap_clear(new->cap_effective);
704    }
705    if (uid_eq(old->euid, root_uid) && !uid_eq(new->euid, root_uid))
706        cap_clear(new->cap_effective);
707    if (!uid_eq(old->euid, root_uid) && uid_eq(new->euid, root_uid))
708        new->cap_effective = new->cap_permitted;
709}
710
711/**
712 * cap_task_fix_setuid - Fix up the results of setuid() call
713 * @new: The proposed credentials
714 * @old: The current task's current credentials
715 * @flags: Indications of what has changed
716 *
717 * Fix up the results of setuid() call before the credential changes are
718 * actually applied, returning 0 to grant the changes, -ve to deny them.
719 */
720int cap_task_fix_setuid(struct cred *new, const struct cred *old, int flags)
721{
722    switch (flags) {
723    case LSM_SETID_RE:
724    case LSM_SETID_ID:
725    case LSM_SETID_RES:
726        /* juggle the capabilities to follow [RES]UID changes unless
727         * otherwise suppressed */
728        if (!issecure(SECURE_NO_SETUID_FIXUP))
729            cap_emulate_setxuid(new, old);
730        break;
731
732    case LSM_SETID_FS:
733        /* juggle the capabilties to follow FSUID changes, unless
734         * otherwise suppressed
735         *
736         * FIXME - is fsuser used for all CAP_FS_MASK capabilities?
737         * if not, we might be a bit too harsh here.
738         */
739        if (!issecure(SECURE_NO_SETUID_FIXUP)) {
740            kuid_t root_uid = make_kuid(old->user_ns, 0);
741            if (uid_eq(old->fsuid, root_uid) && !uid_eq(new->fsuid, root_uid))
742                new->cap_effective =
743                    cap_drop_fs_set(new->cap_effective);
744
745            if (!uid_eq(old->fsuid, root_uid) && uid_eq(new->fsuid, root_uid))
746                new->cap_effective =
747                    cap_raise_fs_set(new->cap_effective,
748                             new->cap_permitted);
749        }
750        break;
751
752    default:
753        return -EINVAL;
754    }
755
756    return 0;
757}
758
759/*
760 * Rationale: code calling task_setscheduler, task_setioprio, and
761 * task_setnice, assumes that
762 * . if capable(cap_sys_nice), then those actions should be allowed
763 * . if not capable(cap_sys_nice), but acting on your own processes,
764 * then those actions should be allowed
765 * This is insufficient now since you can call code without suid, but
766 * yet with increased caps.
767 * So we check for increased caps on the target process.
768 */
769static int cap_safe_nice(struct task_struct *p)
770{
771    int is_subset, ret = 0;
772
773    rcu_read_lock();
774    is_subset = cap_issubset(__task_cred(p)->cap_permitted,
775                 current_cred()->cap_permitted);
776    if (!is_subset && !ns_capable(__task_cred(p)->user_ns, CAP_SYS_NICE))
777        ret = -EPERM;
778    rcu_read_unlock();
779
780    return ret;
781}
782
783/**
784 * cap_task_setscheduler - Detemine if scheduler policy change is permitted
785 * @p: The task to affect
786 *
787 * Detemine if the requested scheduler policy change is permitted for the
788 * specified task, returning 0 if permission is granted, -ve if denied.
789 */
790int cap_task_setscheduler(struct task_struct *p)
791{
792    return cap_safe_nice(p);
793}
794
795/**
796 * cap_task_ioprio - Detemine if I/O priority change is permitted
797 * @p: The task to affect
798 * @ioprio: The I/O priority to set
799 *
800 * Detemine if the requested I/O priority change is permitted for the specified
801 * task, returning 0 if permission is granted, -ve if denied.
802 */
803int cap_task_setioprio(struct task_struct *p, int ioprio)
804{
805    return cap_safe_nice(p);
806}
807
808/**
809 * cap_task_ioprio - Detemine if task priority change is permitted
810 * @p: The task to affect
811 * @nice: The nice value to set
812 *
813 * Detemine if the requested task priority change is permitted for the
814 * specified task, returning 0 if permission is granted, -ve if denied.
815 */
816int cap_task_setnice(struct task_struct *p, int nice)
817{
818    return cap_safe_nice(p);
819}
820
821/*
822 * Implement PR_CAPBSET_DROP. Attempt to remove the specified capability from
823 * the current task's bounding set. Returns 0 on success, -ve on error.
824 */
825static long cap_prctl_drop(struct cred *new, unsigned long cap)
826{
827    if (!ns_capable(current_user_ns(), CAP_SETPCAP))
828        return -EPERM;
829    if (!cap_valid(cap))
830        return -EINVAL;
831
832    cap_lower(new->cap_bset, cap);
833    return 0;
834}
835
836/**
837 * cap_task_prctl - Implement process control functions for this security module
838 * @option: The process control function requested
839 * @arg2, @arg3, @arg4, @arg5: The argument data for this function
840 *
841 * Allow process control functions (sys_prctl()) to alter capabilities; may
842 * also deny access to other functions not otherwise implemented here.
843 *
844 * Returns 0 or +ve on success, -ENOSYS if this function is not implemented
845 * here, other -ve on error. If -ENOSYS is returned, sys_prctl() and other LSM
846 * modules will consider performing the function.
847 */
848int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3,
849           unsigned long arg4, unsigned long arg5)
850{
851    struct cred *new;
852    long error = 0;
853
854    new = prepare_creds();
855    if (!new)
856        return -ENOMEM;
857
858    switch (option) {
859    case PR_CAPBSET_READ:
860        error = -EINVAL;
861        if (!cap_valid(arg2))
862            goto error;
863        error = !!cap_raised(new->cap_bset, arg2);
864        goto no_change;
865
866    case PR_CAPBSET_DROP:
867        error = cap_prctl_drop(new, arg2);
868        if (error < 0)
869            goto error;
870        goto changed;
871
872    /*
873     * The next four prctl's remain to assist with transitioning a
874     * system from legacy UID=0 based privilege (when filesystem
875     * capabilities are not in use) to a system using filesystem
876     * capabilities only - as the POSIX.1e draft intended.
877     *
878     * Note:
879     *
880     * PR_SET_SECUREBITS =
881     * issecure_mask(SECURE_KEEP_CAPS_LOCKED)
882     * | issecure_mask(SECURE_NOROOT)
883     * | issecure_mask(SECURE_NOROOT_LOCKED)
884     * | issecure_mask(SECURE_NO_SETUID_FIXUP)
885     * | issecure_mask(SECURE_NO_SETUID_FIXUP_LOCKED)
886     *
887     * will ensure that the current process and all of its
888     * children will be locked into a pure
889     * capability-based-privilege environment.
890     */
891    case PR_SET_SECUREBITS:
892        error = -EPERM;
893        if ((((new->securebits & SECURE_ALL_LOCKS) >> 1)
894             & (new->securebits ^ arg2)) /*[1]*/
895            || ((new->securebits & SECURE_ALL_LOCKS & ~arg2)) /*[2]*/
896            || (arg2 & ~(SECURE_ALL_LOCKS | SECURE_ALL_BITS)) /*[3]*/
897            || (cap_capable(current_cred(),
898                    current_cred()->user_ns, CAP_SETPCAP,
899                    SECURITY_CAP_AUDIT) != 0) /*[4]*/
900            /*
901             * [1] no changing of bits that are locked
902             * [2] no unlocking of locks
903             * [3] no setting of unsupported bits
904             * [4] doing anything requires privilege (go read about
905             * the "sendmail capabilities bug")
906             */
907            )
908            /* cannot change a locked bit */
909            goto error;
910        new->securebits = arg2;
911        goto changed;
912
913    case PR_GET_SECUREBITS:
914        error = new->securebits;
915        goto no_change;
916
917    case PR_GET_KEEPCAPS:
918        if (issecure(SECURE_KEEP_CAPS))
919            error = 1;
920        goto no_change;
921
922    case PR_SET_KEEPCAPS:
923        error = -EINVAL;
924        if (arg2 > 1) /* Note, we rely on arg2 being unsigned here */
925            goto error;
926        error = -EPERM;
927        if (issecure(SECURE_KEEP_CAPS_LOCKED))
928            goto error;
929        if (arg2)
930            new->securebits |= issecure_mask(SECURE_KEEP_CAPS);
931        else
932            new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
933        goto changed;
934
935    default:
936        /* No functionality available - continue with default */
937        error = -ENOSYS;
938        goto error;
939    }
940
941    /* Functionality provided */
942changed:
943    return commit_creds(new);
944
945no_change:
946error:
947    abort_creds(new);
948    return error;
949}
950
951/**
952 * cap_vm_enough_memory - Determine whether a new virtual mapping is permitted
953 * @mm: The VM space in which the new mapping is to be made
954 * @pages: The size of the mapping
955 *
956 * Determine whether the allocation of a new virtual mapping by the current
957 * task is permitted, returning 0 if permission is granted, -ve if not.
958 */
959int cap_vm_enough_memory(struct mm_struct *mm, long pages)
960{
961    int cap_sys_admin = 0;
962
963    if (cap_capable(current_cred(), &init_user_ns, CAP_SYS_ADMIN,
964            SECURITY_CAP_NOAUDIT) == 0)
965        cap_sys_admin = 1;
966    return __vm_enough_memory(mm, pages, cap_sys_admin);
967}
968
969/*
970 * cap_mmap_addr - check if able to map given addr
971 * @addr: address attempting to be mapped
972 *
973 * If the process is attempting to map memory below dac_mmap_min_addr they need
974 * CAP_SYS_RAWIO. The other parameters to this function are unused by the
975 * capability security module. Returns 0 if this mapping should be allowed
976 * -EPERM if not.
977 */
978int cap_mmap_addr(unsigned long addr)
979{
980    int ret = 0;
981
982    if (addr < dac_mmap_min_addr) {
983        ret = cap_capable(current_cred(), &init_user_ns, CAP_SYS_RAWIO,
984                  SECURITY_CAP_AUDIT);
985        /* set PF_SUPERPRIV if it turns out we allow the low mmap */
986        if (ret == 0)
987            current->flags |= PF_SUPERPRIV;
988    }
989    return ret;
990}
991
992int cap_mmap_file(struct file *file, unsigned long reqprot,
993          unsigned long prot, unsigned long flags)
994{
995    return 0;
996}
997

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