![Serge E. Hallyn](/assets/img/avatar_default.png)
An unprivileged process must be able to kill a setuid root program started by the same user. This is legacy behavior needed for instance for xinit to kill X when the window manager exits. When an unprivileged user runs a setuid root program in !SECURE_NOROOT mode, fP, fI, and fE are set full on, so pP' and pE' are full on. Then cap_task_kill() prevents the user from signaling the setuid root task. This is a change in behavior compared to when !CONFIG_SECURITY_FILE_CAPABILITIES. This patch introduces a special check into cap_task_kill() just to check whether a non-root user is signaling a setuid root program started by the same user. If so, then signal is allowed. Signed-off-by: Serge E. Hallyn <serue@us.ibm.com> Cc: Andrew Morgan <morgan@kernel.org> Cc: Stephen Smalley <sds@epoch.ncsc.mil> Cc: Chris Wright <chrisw@sous-sol.org> Cc: James Morris <jmorris@namei.org> Cc: Casey Schaufler <casey@schaufler-ca.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
603 lines
15 KiB
C
603 lines
15 KiB
C
/* Common capabilities, needed by capability.o and root_plug.o
|
|
*
|
|
* This program is free software; you can redistribute it and/or modify
|
|
* it under the terms of the GNU General Public License as published by
|
|
* the Free Software Foundation; either version 2 of the License, or
|
|
* (at your option) any later version.
|
|
*
|
|
*/
|
|
|
|
#include <linux/capability.h>
|
|
#include <linux/module.h>
|
|
#include <linux/init.h>
|
|
#include <linux/kernel.h>
|
|
#include <linux/security.h>
|
|
#include <linux/file.h>
|
|
#include <linux/mm.h>
|
|
#include <linux/mman.h>
|
|
#include <linux/pagemap.h>
|
|
#include <linux/swap.h>
|
|
#include <linux/skbuff.h>
|
|
#include <linux/netlink.h>
|
|
#include <linux/ptrace.h>
|
|
#include <linux/xattr.h>
|
|
#include <linux/hugetlb.h>
|
|
#include <linux/mount.h>
|
|
#include <linux/sched.h>
|
|
|
|
#ifdef CONFIG_SECURITY_FILE_CAPABILITIES
|
|
/*
|
|
* Because of the reduced scope of CAP_SETPCAP when filesystem
|
|
* capabilities are in effect, it is safe to allow this capability to
|
|
* be available in the default configuration.
|
|
*/
|
|
# define CAP_INIT_BSET CAP_FULL_SET
|
|
#else /* ie. ndef CONFIG_SECURITY_FILE_CAPABILITIES */
|
|
# define CAP_INIT_BSET CAP_INIT_EFF_SET
|
|
#endif /* def CONFIG_SECURITY_FILE_CAPABILITIES */
|
|
|
|
kernel_cap_t cap_bset = CAP_INIT_BSET; /* systemwide capability bound */
|
|
EXPORT_SYMBOL(cap_bset);
|
|
|
|
/* Global security state */
|
|
|
|
unsigned securebits = SECUREBITS_DEFAULT; /* systemwide security settings */
|
|
EXPORT_SYMBOL(securebits);
|
|
|
|
int cap_netlink_send(struct sock *sk, struct sk_buff *skb)
|
|
{
|
|
NETLINK_CB(skb).eff_cap = current->cap_effective;
|
|
return 0;
|
|
}
|
|
|
|
int cap_netlink_recv(struct sk_buff *skb, int cap)
|
|
{
|
|
if (!cap_raised(NETLINK_CB(skb).eff_cap, cap))
|
|
return -EPERM;
|
|
return 0;
|
|
}
|
|
|
|
EXPORT_SYMBOL(cap_netlink_recv);
|
|
|
|
int cap_capable (struct task_struct *tsk, int cap)
|
|
{
|
|
/* Derived from include/linux/sched.h:capable. */
|
|
if (cap_raised(tsk->cap_effective, cap))
|
|
return 0;
|
|
return -EPERM;
|
|
}
|
|
|
|
int cap_settime(struct timespec *ts, struct timezone *tz)
|
|
{
|
|
if (!capable(CAP_SYS_TIME))
|
|
return -EPERM;
|
|
return 0;
|
|
}
|
|
|
|
int cap_ptrace (struct task_struct *parent, struct task_struct *child)
|
|
{
|
|
/* Derived from arch/i386/kernel/ptrace.c:sys_ptrace. */
|
|
if (!cap_issubset(child->cap_permitted, parent->cap_permitted) &&
|
|
!__capable(parent, CAP_SYS_PTRACE))
|
|
return -EPERM;
|
|
return 0;
|
|
}
|
|
|
|
int cap_capget (struct task_struct *target, kernel_cap_t *effective,
|
|
kernel_cap_t *inheritable, kernel_cap_t *permitted)
|
|
{
|
|
/* Derived from kernel/capability.c:sys_capget. */
|
|
*effective = cap_t (target->cap_effective);
|
|
*inheritable = cap_t (target->cap_inheritable);
|
|
*permitted = cap_t (target->cap_permitted);
|
|
return 0;
|
|
}
|
|
|
|
#ifdef CONFIG_SECURITY_FILE_CAPABILITIES
|
|
|
|
static inline int cap_block_setpcap(struct task_struct *target)
|
|
{
|
|
/*
|
|
* No support for remote process capability manipulation with
|
|
* filesystem capability support.
|
|
*/
|
|
return (target != current);
|
|
}
|
|
|
|
static inline int cap_inh_is_capped(void)
|
|
{
|
|
/*
|
|
* return 1 if changes to the inheritable set are limited
|
|
* to the old permitted set.
|
|
*/
|
|
return !cap_capable(current, CAP_SETPCAP);
|
|
}
|
|
|
|
#else /* ie., ndef CONFIG_SECURITY_FILE_CAPABILITIES */
|
|
|
|
static inline int cap_block_setpcap(struct task_struct *t) { return 0; }
|
|
static inline int cap_inh_is_capped(void) { return 1; }
|
|
|
|
#endif /* def CONFIG_SECURITY_FILE_CAPABILITIES */
|
|
|
|
int cap_capset_check (struct task_struct *target, kernel_cap_t *effective,
|
|
kernel_cap_t *inheritable, kernel_cap_t *permitted)
|
|
{
|
|
if (cap_block_setpcap(target)) {
|
|
return -EPERM;
|
|
}
|
|
if (cap_inh_is_capped()
|
|
&& !cap_issubset(*inheritable,
|
|
cap_combine(target->cap_inheritable,
|
|
current->cap_permitted))) {
|
|
/* incapable of using this inheritable set */
|
|
return -EPERM;
|
|
}
|
|
|
|
/* verify restrictions on target's new Permitted set */
|
|
if (!cap_issubset (*permitted,
|
|
cap_combine (target->cap_permitted,
|
|
current->cap_permitted))) {
|
|
return -EPERM;
|
|
}
|
|
|
|
/* verify the _new_Effective_ is a subset of the _new_Permitted_ */
|
|
if (!cap_issubset (*effective, *permitted)) {
|
|
return -EPERM;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
void cap_capset_set (struct task_struct *target, kernel_cap_t *effective,
|
|
kernel_cap_t *inheritable, kernel_cap_t *permitted)
|
|
{
|
|
target->cap_effective = *effective;
|
|
target->cap_inheritable = *inheritable;
|
|
target->cap_permitted = *permitted;
|
|
}
|
|
|
|
static inline void bprm_clear_caps(struct linux_binprm *bprm)
|
|
{
|
|
cap_clear(bprm->cap_inheritable);
|
|
cap_clear(bprm->cap_permitted);
|
|
bprm->cap_effective = false;
|
|
}
|
|
|
|
#ifdef CONFIG_SECURITY_FILE_CAPABILITIES
|
|
|
|
int cap_inode_need_killpriv(struct dentry *dentry)
|
|
{
|
|
struct inode *inode = dentry->d_inode;
|
|
int error;
|
|
|
|
if (!inode->i_op || !inode->i_op->getxattr)
|
|
return 0;
|
|
|
|
error = inode->i_op->getxattr(dentry, XATTR_NAME_CAPS, NULL, 0);
|
|
if (error <= 0)
|
|
return 0;
|
|
return 1;
|
|
}
|
|
|
|
int cap_inode_killpriv(struct dentry *dentry)
|
|
{
|
|
struct inode *inode = dentry->d_inode;
|
|
|
|
if (!inode->i_op || !inode->i_op->removexattr)
|
|
return 0;
|
|
|
|
return inode->i_op->removexattr(dentry, XATTR_NAME_CAPS);
|
|
}
|
|
|
|
static inline int cap_from_disk(struct vfs_cap_data *caps,
|
|
struct linux_binprm *bprm,
|
|
int size)
|
|
{
|
|
__u32 magic_etc;
|
|
|
|
if (size != XATTR_CAPS_SZ)
|
|
return -EINVAL;
|
|
|
|
magic_etc = le32_to_cpu(caps->magic_etc);
|
|
|
|
switch ((magic_etc & VFS_CAP_REVISION_MASK)) {
|
|
case VFS_CAP_REVISION:
|
|
if (magic_etc & VFS_CAP_FLAGS_EFFECTIVE)
|
|
bprm->cap_effective = true;
|
|
else
|
|
bprm->cap_effective = false;
|
|
bprm->cap_permitted = to_cap_t(le32_to_cpu(caps->permitted));
|
|
bprm->cap_inheritable = to_cap_t(le32_to_cpu(caps->inheritable));
|
|
return 0;
|
|
default:
|
|
return -EINVAL;
|
|
}
|
|
}
|
|
|
|
/* Locate any VFS capabilities: */
|
|
static int get_file_caps(struct linux_binprm *bprm)
|
|
{
|
|
struct dentry *dentry;
|
|
int rc = 0;
|
|
struct vfs_cap_data incaps;
|
|
struct inode *inode;
|
|
|
|
if (bprm->file->f_vfsmnt->mnt_flags & MNT_NOSUID) {
|
|
bprm_clear_caps(bprm);
|
|
return 0;
|
|
}
|
|
|
|
dentry = dget(bprm->file->f_dentry);
|
|
inode = dentry->d_inode;
|
|
if (!inode->i_op || !inode->i_op->getxattr)
|
|
goto out;
|
|
|
|
rc = inode->i_op->getxattr(dentry, XATTR_NAME_CAPS, NULL, 0);
|
|
if (rc > 0) {
|
|
if (rc == XATTR_CAPS_SZ)
|
|
rc = inode->i_op->getxattr(dentry, XATTR_NAME_CAPS,
|
|
&incaps, XATTR_CAPS_SZ);
|
|
else
|
|
rc = -EINVAL;
|
|
}
|
|
if (rc == -ENODATA || rc == -EOPNOTSUPP) {
|
|
/* no data, that's ok */
|
|
rc = 0;
|
|
goto out;
|
|
}
|
|
if (rc < 0)
|
|
goto out;
|
|
|
|
rc = cap_from_disk(&incaps, bprm, rc);
|
|
if (rc)
|
|
printk(KERN_NOTICE "%s: cap_from_disk returned %d for %s\n",
|
|
__FUNCTION__, rc, bprm->filename);
|
|
|
|
out:
|
|
dput(dentry);
|
|
if (rc)
|
|
bprm_clear_caps(bprm);
|
|
|
|
return rc;
|
|
}
|
|
|
|
#else
|
|
int cap_inode_need_killpriv(struct dentry *dentry)
|
|
{
|
|
return 0;
|
|
}
|
|
|
|
int cap_inode_killpriv(struct dentry *dentry)
|
|
{
|
|
return 0;
|
|
}
|
|
|
|
static inline int get_file_caps(struct linux_binprm *bprm)
|
|
{
|
|
bprm_clear_caps(bprm);
|
|
return 0;
|
|
}
|
|
#endif
|
|
|
|
int cap_bprm_set_security (struct linux_binprm *bprm)
|
|
{
|
|
int ret;
|
|
|
|
ret = get_file_caps(bprm);
|
|
if (ret)
|
|
printk(KERN_NOTICE "%s: get_file_caps returned %d for %s\n",
|
|
__FUNCTION__, ret, bprm->filename);
|
|
|
|
/* To support inheritance of root-permissions and suid-root
|
|
* executables under compatibility mode, we raise all three
|
|
* capability sets for the file.
|
|
*
|
|
* If only the real uid is 0, we only raise the inheritable
|
|
* and permitted sets of the executable file.
|
|
*/
|
|
|
|
if (!issecure (SECURE_NOROOT)) {
|
|
if (bprm->e_uid == 0 || current->uid == 0) {
|
|
cap_set_full (bprm->cap_inheritable);
|
|
cap_set_full (bprm->cap_permitted);
|
|
}
|
|
if (bprm->e_uid == 0)
|
|
bprm->cap_effective = true;
|
|
}
|
|
|
|
return ret;
|
|
}
|
|
|
|
void cap_bprm_apply_creds (struct linux_binprm *bprm, int unsafe)
|
|
{
|
|
/* Derived from fs/exec.c:compute_creds. */
|
|
kernel_cap_t new_permitted, working;
|
|
|
|
new_permitted = cap_intersect (bprm->cap_permitted, cap_bset);
|
|
working = cap_intersect (bprm->cap_inheritable,
|
|
current->cap_inheritable);
|
|
new_permitted = cap_combine (new_permitted, working);
|
|
|
|
if (bprm->e_uid != current->uid || bprm->e_gid != current->gid ||
|
|
!cap_issubset (new_permitted, current->cap_permitted)) {
|
|
set_dumpable(current->mm, suid_dumpable);
|
|
current->pdeath_signal = 0;
|
|
|
|
if (unsafe & ~LSM_UNSAFE_PTRACE_CAP) {
|
|
if (!capable(CAP_SETUID)) {
|
|
bprm->e_uid = current->uid;
|
|
bprm->e_gid = current->gid;
|
|
}
|
|
if (!capable (CAP_SETPCAP)) {
|
|
new_permitted = cap_intersect (new_permitted,
|
|
current->cap_permitted);
|
|
}
|
|
}
|
|
}
|
|
|
|
current->suid = current->euid = current->fsuid = bprm->e_uid;
|
|
current->sgid = current->egid = current->fsgid = bprm->e_gid;
|
|
|
|
/* For init, we want to retain the capabilities set
|
|
* in the init_task struct. Thus we skip the usual
|
|
* capability rules */
|
|
if (!is_global_init(current)) {
|
|
current->cap_permitted = new_permitted;
|
|
current->cap_effective = bprm->cap_effective ?
|
|
new_permitted : 0;
|
|
}
|
|
|
|
/* AUD: Audit candidate if current->cap_effective is set */
|
|
|
|
current->keep_capabilities = 0;
|
|
}
|
|
|
|
int cap_bprm_secureexec (struct linux_binprm *bprm)
|
|
{
|
|
if (current->uid != 0) {
|
|
if (bprm->cap_effective)
|
|
return 1;
|
|
if (!cap_isclear(bprm->cap_permitted))
|
|
return 1;
|
|
if (!cap_isclear(bprm->cap_inheritable))
|
|
return 1;
|
|
}
|
|
|
|
return (current->euid != current->uid ||
|
|
current->egid != current->gid);
|
|
}
|
|
|
|
int cap_inode_setxattr(struct dentry *dentry, char *name, void *value,
|
|
size_t size, int flags)
|
|
{
|
|
if (!strcmp(name, XATTR_NAME_CAPS)) {
|
|
if (!capable(CAP_SETFCAP))
|
|
return -EPERM;
|
|
return 0;
|
|
} else if (!strncmp(name, XATTR_SECURITY_PREFIX,
|
|
sizeof(XATTR_SECURITY_PREFIX) - 1) &&
|
|
!capable(CAP_SYS_ADMIN))
|
|
return -EPERM;
|
|
return 0;
|
|
}
|
|
|
|
int cap_inode_removexattr(struct dentry *dentry, char *name)
|
|
{
|
|
if (!strcmp(name, XATTR_NAME_CAPS)) {
|
|
if (!capable(CAP_SETFCAP))
|
|
return -EPERM;
|
|
return 0;
|
|
} else if (!strncmp(name, XATTR_SECURITY_PREFIX,
|
|
sizeof(XATTR_SECURITY_PREFIX) - 1) &&
|
|
!capable(CAP_SYS_ADMIN))
|
|
return -EPERM;
|
|
return 0;
|
|
}
|
|
|
|
/* moved from kernel/sys.c. */
|
|
/*
|
|
* cap_emulate_setxuid() fixes the effective / permitted capabilities of
|
|
* a process after a call to setuid, setreuid, or setresuid.
|
|
*
|
|
* 1) When set*uiding _from_ one of {r,e,s}uid == 0 _to_ all of
|
|
* {r,e,s}uid != 0, the permitted and effective capabilities are
|
|
* cleared.
|
|
*
|
|
* 2) When set*uiding _from_ euid == 0 _to_ euid != 0, the effective
|
|
* capabilities of the process are cleared.
|
|
*
|
|
* 3) When set*uiding _from_ euid != 0 _to_ euid == 0, the effective
|
|
* capabilities are set to the permitted capabilities.
|
|
*
|
|
* fsuid is handled elsewhere. fsuid == 0 and {r,e,s}uid!= 0 should
|
|
* never happen.
|
|
*
|
|
* -astor
|
|
*
|
|
* cevans - New behaviour, Oct '99
|
|
* A process may, via prctl(), elect to keep its capabilities when it
|
|
* calls setuid() and switches away from uid==0. Both permitted and
|
|
* effective sets will be retained.
|
|
* Without this change, it was impossible for a daemon to drop only some
|
|
* of its privilege. The call to setuid(!=0) would drop all privileges!
|
|
* Keeping uid 0 is not an option because uid 0 owns too many vital
|
|
* files..
|
|
* Thanks to Olaf Kirch and Peter Benie for spotting this.
|
|
*/
|
|
static inline void cap_emulate_setxuid (int old_ruid, int old_euid,
|
|
int old_suid)
|
|
{
|
|
if ((old_ruid == 0 || old_euid == 0 || old_suid == 0) &&
|
|
(current->uid != 0 && current->euid != 0 && current->suid != 0) &&
|
|
!current->keep_capabilities) {
|
|
cap_clear (current->cap_permitted);
|
|
cap_clear (current->cap_effective);
|
|
}
|
|
if (old_euid == 0 && current->euid != 0) {
|
|
cap_clear (current->cap_effective);
|
|
}
|
|
if (old_euid != 0 && current->euid == 0) {
|
|
current->cap_effective = current->cap_permitted;
|
|
}
|
|
}
|
|
|
|
int cap_task_post_setuid (uid_t old_ruid, uid_t old_euid, uid_t old_suid,
|
|
int flags)
|
|
{
|
|
switch (flags) {
|
|
case LSM_SETID_RE:
|
|
case LSM_SETID_ID:
|
|
case LSM_SETID_RES:
|
|
/* Copied from kernel/sys.c:setreuid/setuid/setresuid. */
|
|
if (!issecure (SECURE_NO_SETUID_FIXUP)) {
|
|
cap_emulate_setxuid (old_ruid, old_euid, old_suid);
|
|
}
|
|
break;
|
|
case LSM_SETID_FS:
|
|
{
|
|
uid_t old_fsuid = old_ruid;
|
|
|
|
/* Copied from kernel/sys.c:setfsuid. */
|
|
|
|
/*
|
|
* FIXME - is fsuser used for all CAP_FS_MASK capabilities?
|
|
* if not, we might be a bit too harsh here.
|
|
*/
|
|
|
|
if (!issecure (SECURE_NO_SETUID_FIXUP)) {
|
|
if (old_fsuid == 0 && current->fsuid != 0) {
|
|
cap_t (current->cap_effective) &=
|
|
~CAP_FS_MASK;
|
|
}
|
|
if (old_fsuid != 0 && current->fsuid == 0) {
|
|
cap_t (current->cap_effective) |=
|
|
(cap_t (current->cap_permitted) &
|
|
CAP_FS_MASK);
|
|
}
|
|
}
|
|
break;
|
|
}
|
|
default:
|
|
return -EINVAL;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
#ifdef CONFIG_SECURITY_FILE_CAPABILITIES
|
|
/*
|
|
* Rationale: code calling task_setscheduler, task_setioprio, and
|
|
* task_setnice, assumes that
|
|
* . if capable(cap_sys_nice), then those actions should be allowed
|
|
* . if not capable(cap_sys_nice), but acting on your own processes,
|
|
* then those actions should be allowed
|
|
* This is insufficient now since you can call code without suid, but
|
|
* yet with increased caps.
|
|
* So we check for increased caps on the target process.
|
|
*/
|
|
static inline int cap_safe_nice(struct task_struct *p)
|
|
{
|
|
if (!cap_issubset(p->cap_permitted, current->cap_permitted) &&
|
|
!__capable(current, CAP_SYS_NICE))
|
|
return -EPERM;
|
|
return 0;
|
|
}
|
|
|
|
int cap_task_setscheduler (struct task_struct *p, int policy,
|
|
struct sched_param *lp)
|
|
{
|
|
return cap_safe_nice(p);
|
|
}
|
|
|
|
int cap_task_setioprio (struct task_struct *p, int ioprio)
|
|
{
|
|
return cap_safe_nice(p);
|
|
}
|
|
|
|
int cap_task_setnice (struct task_struct *p, int nice)
|
|
{
|
|
return cap_safe_nice(p);
|
|
}
|
|
|
|
int cap_task_kill(struct task_struct *p, struct siginfo *info,
|
|
int sig, u32 secid)
|
|
{
|
|
if (info != SEND_SIG_NOINFO && (is_si_special(info) || SI_FROMKERNEL(info)))
|
|
return 0;
|
|
|
|
/*
|
|
* Running a setuid root program raises your capabilities.
|
|
* Killing your own setuid root processes was previously
|
|
* allowed.
|
|
* We must preserve legacy signal behavior in this case.
|
|
*/
|
|
if (p->euid == 0 && p->uid == current->uid)
|
|
return 0;
|
|
|
|
/* sigcont is permitted within same session */
|
|
if (sig == SIGCONT && (task_session_nr(current) == task_session_nr(p)))
|
|
return 0;
|
|
|
|
if (secid)
|
|
/*
|
|
* Signal sent as a particular user.
|
|
* Capabilities are ignored. May be wrong, but it's the
|
|
* only thing we can do at the moment.
|
|
* Used only by usb drivers?
|
|
*/
|
|
return 0;
|
|
if (cap_issubset(p->cap_permitted, current->cap_permitted))
|
|
return 0;
|
|
if (capable(CAP_KILL))
|
|
return 0;
|
|
|
|
return -EPERM;
|
|
}
|
|
#else
|
|
int cap_task_setscheduler (struct task_struct *p, int policy,
|
|
struct sched_param *lp)
|
|
{
|
|
return 0;
|
|
}
|
|
int cap_task_setioprio (struct task_struct *p, int ioprio)
|
|
{
|
|
return 0;
|
|
}
|
|
int cap_task_setnice (struct task_struct *p, int nice)
|
|
{
|
|
return 0;
|
|
}
|
|
int cap_task_kill(struct task_struct *p, struct siginfo *info,
|
|
int sig, u32 secid)
|
|
{
|
|
return 0;
|
|
}
|
|
#endif
|
|
|
|
void cap_task_reparent_to_init (struct task_struct *p)
|
|
{
|
|
p->cap_effective = CAP_INIT_EFF_SET;
|
|
p->cap_inheritable = CAP_INIT_INH_SET;
|
|
p->cap_permitted = CAP_FULL_SET;
|
|
p->keep_capabilities = 0;
|
|
return;
|
|
}
|
|
|
|
int cap_syslog (int type)
|
|
{
|
|
if ((type != 3 && type != 10) && !capable(CAP_SYS_ADMIN))
|
|
return -EPERM;
|
|
return 0;
|
|
}
|
|
|
|
int cap_vm_enough_memory(struct mm_struct *mm, long pages)
|
|
{
|
|
int cap_sys_admin = 0;
|
|
|
|
if (cap_capable(current, CAP_SYS_ADMIN) == 0)
|
|
cap_sys_admin = 1;
|
|
return __vm_enough_memory(mm, pages, cap_sys_admin);
|
|
}
|
|
|