/* 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/audit.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>
#include <linux/prctl.h>
#include <linux/securebits.h>
int cap_netlink_send(struct sock *sk, struct sk_buff *skb)
{
NETLINK_CB(skb).eff_cap = current_cap();
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);
/*
* NOTE WELL: cap_capable() cannot be used like the kernel's capable()
* function. That is, it has the reverse semantics: cap_capable()
* returns 0 when a task has a capability, but the kernel's capable()
* returns 1 for this case.
*/
int cap_capable(struct task_struct *tsk, int cap, int audit)
{
__u32 cap_raised;
/* Derived from include/linux/sched.h:capable. */
rcu_read_lock();
cap_raised = cap_raised(__task_cred(tsk)->cap_effective, cap);
rcu_read_unlock();
return cap_raised ? 0 : -EPERM;
}
int cap_settime(struct timespec *ts, struct timezone *tz)
{
if (!capable(CAP_SYS_TIME))
return -EPERM;
return 0;
}
int cap_ptrace_may_access(struct task_struct *child, unsigned int mode)
{
int ret = 0;
rcu_read_lock();
if (!cap_issubset(__task_cred(child)->cap_permitted,
current_cred()->cap_permitted) &&
!capable(CAP_SYS_PTRACE))
ret = -EPERM;
rcu_read_unlock();
return ret;
}
int cap_ptrace_traceme(struct task_struct *parent)
{
int ret = 0;
rcu_read_lock();
if (!cap_issubset(current_cred()->cap_permitted,
__task_cred(parent)->cap_permitted) &&
!has_capability(parent, CAP_SYS_PTRACE))
ret = -EPERM;
rcu_read_unlock();
return ret;
}
int cap_capget (struct task_struct *target, kernel_cap_t *effective,
kernel_cap_t *inheritable, kernel_cap_t *permitted)
{
const struct cred *cred;
/* Derived from kernel/capability.c:sys_capget. */
rcu_read_lock();
cred = __task_cred(target);
*effective = cred->cap_effective;
*inheritable = cred->cap_inheritable;
*permitted = cred->cap_permitted;
rcu_read_unlock();
return 0;
}
#ifdef CONFIG_SECURITY_FILE_CAPABILITIES
static inline int cap_inh_is_capped(void)
{
/*
* Return 1 if changes to the inheritable set are limited
* to the old permitted set. That is, if the current task
* does *not* possess the CAP_SETPCAP capability.
*/
return cap_capable(current, CAP_SETPCAP, SECURITY_CAP_AUDIT) != 0;
}
static inline int cap_limit_ptraced_target(void) { return 1; }
#else /* ie., ndef CONFIG_SECURITY_FILE_CAPABILITIES */
static inline int cap_inh_is_capped(void) { return 1; }
static inline int cap_limit_ptraced_target(void)
{
return !capable(CAP_SETPCAP);
}
#endif /* def CONFIG_SECURITY_FILE_CAPABILITIES */
int cap_capset(struct cred *new,
const struct cred *old,
const kernel_cap_t *effective,
const kernel_cap_t *inheritable,
const kernel_cap_t *permitted)
{
if (cap_inh_is_capped() &&
!cap_issubset(*inheritable,
cap_combine(old->cap_inheritable,
old->cap_permitted)))
/* incapable of using this inheritable set */
return -EPERM;
if (!cap_issubset(*inheritable,
cap_combine(old->cap_inheritable,
old->cap_bset)))
/* no new pI capabilities outside bounding set */
return -EPERM;
/* verify restrictions on target's new Permitted set */
if (!cap_issubset(*permitted, old->cap_permitted))
return -EPERM;
/* verify the _new_Effective_ is a subset of the _new_Permitted_ */
if (!cap_issubset(*effective, *permitted))
return -EPERM;
new->cap_effective = *effective;
new->cap_inheritable = *inheritable;
new->cap_permitted = *permitted;
return 0;
}
static inline void bprm_clear_caps(struct linux_binprm *bprm)
{
cap_clear(bprm->cred->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 bprm_caps_from_vfs_caps(struct cpu_vfs_cap_data *caps,
struct linux_binprm *bprm,
bool *effective)
{
struct cred *new = bprm->cred;
unsigned i;
int ret = 0;
if (caps->magic_etc & VFS_CAP_FLAGS_EFFECTIVE)
*effective = true;
CAP_FOR_EACH_U32(i) {
__u32 permitted = caps->permitted.cap[i];
__u32 inheritable = caps->inheritable.cap[i];
/*
* pP' = (X & fP) | (pI & fI)
*/
new->cap_permitted.cap[i] =
(new->cap_bset.cap[i] & permitted) |
(new->cap_inheritable.cap[i] & inheritable);
if (permitted & ~new->cap_permitted.cap[i])
/* insufficient to execute correctly */
ret = -EPERM;
}
/*
* For legacy apps, with no internal support for recognizing they
* do not have enough capabilities, we return an error if they are
* missing some "forced" (aka file-permitted) capabilities.
*/
return *effective ? ret : 0;
}
int get_vfs_caps_from_disk(const struct dentry *dentry, struct cpu_vfs_cap_data *cpu_caps)
{
struct inode *inode = dentry->d_inode;
__u32 magic_etc;
unsigned tocopy, i;
int size;
struct vfs_cap_data caps;
memset(cpu_caps, 0, sizeof(struct cpu_vfs_cap_data));
if (!inode || !inode->i_op || !inode->i_op->getxattr)
return -ENODATA;
size = inode->i_op->getxattr((struct dentry *)dentry, XATTR_NAME_CAPS, &caps,
XATTR_CAPS_SZ);
if (size == -ENODATA || size == -EOPNOTSUPP)
/* no data, that's ok */
return -ENODATA;
if (size < 0)
return size;
if (size < sizeof(magic_etc))
return -EINVAL;
cpu_caps->magic_etc = magic_etc = le32_to_cpu(caps.magic_etc);
switch (magic_etc & VFS_CAP_REVISION_MASK) {
case VFS_CAP_REVISION_1:
if (size != XATTR_CAPS_SZ_1)
return -EINVAL;
tocopy = VFS_CAP_U32_1;
break;
case VFS_CAP_REVISION_2:
if (size != XATTR_CAPS_SZ_2)
return -EINVAL;
tocopy = VFS_CAP_U32_2;
break;
default:
return -EINVAL;
}
CAP_FOR_EACH_U32(i) {
if (i >= tocopy)
break;
cpu_caps->permitted.cap[i] = le32_to_cpu(caps.data[i].permitted);
cpu_caps->inheritable.cap[i] = le32_to_cpu(caps.data[i].inheritable);
}
return 0;
}
/* Locate any VFS capabilities: */
static int get_file_caps(struct linux_binprm *bprm, bool *effective)
{
struct dentry *dentry;
int rc = 0;
struct cpu_vfs_cap_data vcaps;
bprm_clear_caps(bprm);
if (!file_caps_enabled)
return 0;
if (bprm->file->f_vfsmnt->mnt_flags & MNT_NOSUID)
return 0;
dentry = dget(bprm->file->f_dentry);
rc = get_vfs_caps_from_disk(dentry, &vcaps);
if (rc < 0) {
if (rc == -EINVAL)
printk(KERN_NOTICE "%s: get_vfs_caps_from_disk returned %d for %s\n",
__func__, rc, bprm->filename);
else if (rc == -ENODATA)
rc = 0;
goto out;
}
rc = bprm_caps_from_vfs_caps(&vcaps, bprm, effective);
if (rc == -EINVAL)
printk(KERN_NOTICE "%s: cap_from_disk returned %d for %s\n",
__func__, 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, bool *effective)
{
bprm_clear_caps(bprm);
return 0;
}
#endif
/*
* set up the new credentials for an exec'd task
*/
int cap_bprm_set_creds(struct linux_binprm *bprm)
{
const struct cred *old = current_cred();
struct cred *new = bprm->cred;
bool effective;
int ret;
effective = false;
ret = get_file_caps(bprm, &effective);
if (ret < 0)
return ret;
if (!issecure(SECURE_NOROOT)) {
/*
* To support inheritance of root-permissions and suid-root
* executables under compatibility mode, we override the
* capability sets for the file.
*
* If only the real uid is 0, we do not set the effective bit.
*/
if (new->euid == 0 || new->uid == 0) {
/* pP' = (cap_bset & ~0) | (pI & ~0) */
new->cap_permitted = cap_combine(old->cap_bset,
old->cap_inheritable);
}
if (new->euid == 0)
effective = true;
}
/* Don't let someone trace a set[ug]id/setpcap binary with the revised
* credentials unless they have the appropriate permit
*/
if ((new->euid != old->uid ||
new->egid != old->gid ||
!cap_issubset(new->cap_permitted, old->cap_permitted)) &&
bprm->unsafe & ~LSM_UNSAFE_PTRACE_CAP) {
/* downgrade; they get no more than they had, and maybe less */
if (!capable(CAP_SETUID)) {
new->euid = new->uid;
new->egid = new->gid;
}
if (cap_limit_ptraced_target())
new->cap_permitted = cap_intersect(new->cap_permitted,
old->cap_permitted);
}
new->suid = new->fsuid = new->euid;
new->sgid = new->fsgid = new->egid;
/* For init, we want to retain the capabilities set in the initial
* task. Thus we skip the usual capability rules
*/
if (!is_global_init(current)) {
if (effective)
new->cap_effective = new->cap_permitted;
else
cap_clear(new->cap_effective);
}
bprm->cap_effective = effective;
/*
* Audit candidate if current->cap_effective is set
*
* We do not bother to audit if 3 things are true:
* 1) cap_effective has all caps
* 2) we are root
* 3) root is supposed to have all caps (SECURE_NOROOT)
* Since this is just a normal root execing a process.
*
* Number 1 above might fail if you don't have a full bset, but I think
* that is interesting information to audit.
*/
if (!cap_isclear(new->cap_effective)) {
if (!cap_issubset(CAP_FULL_SET, new->cap_effective) ||
new->euid != 0 || new->uid != 0 ||
issecure(SECURE_NOROOT)) {
ret = audit_log_bprm_fcaps(bprm, new, old);
if (ret < 0)
return ret;
}
}
new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
return 0;
}
/*
* determine whether a secure execution is required
* - the creds have been committed at this point, and are no longer available
* through bprm
*/
int cap_bprm_secureexec(struct linux_binprm *bprm)
{
const struct cred *cred = current_cred();
if (cred->uid != 0) {
if (bprm->cap_effective)
return 1;
if (!cap_isclear(cred->cap_permitted))
return 1;
}
return (cred->euid != cred->uid ||
cred->egid != cred->gid);
}
int cap_inode_setxattr(struct dentry *dentry, const char *name,
const 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, const 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(struct cred *new, const struct cred *old)
{
if ((old->uid == 0 || old->euid == 0 || old->suid == 0) &&
(new->uid != 0 && new->euid != 0 && new->suid != 0) &&
!issecure(SECURE_KEEP_CAPS)) {
cap_clear(new->cap_permitted);
cap_clear(new->cap_effective);
}
if (old->euid == 0 && new->euid != 0)
cap_clear(new->cap_effective);
if (old->euid != 0 && new->euid == 0)
new->cap_effective = new->cap_permitted;
}
int cap_task_fix_setuid(struct cred *new, const struct cred *old, 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(new, old);
break;
case LSM_SETID_FS:
/* 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 && new->fsuid != 0) {
new->cap_effective =
cap_drop_fs_set(new->cap_effective);
}
if (old->fsuid != 0 && new->fsuid == 0) {
new->cap_effective =
cap_raise_fs_set(new->cap_effective,
new->cap_permitted);
}
}
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 int cap_safe_nice(struct task_struct *p)
{
int is_subset;
rcu_read_lock();
is_subset = cap_issubset(__task_cred(p)->cap_permitted,
current_cred()->cap_permitted);
rcu_read_unlock();
if (!is_subset && !capable(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);
}
/*
* called from kernel/sys.c for prctl(PR_CABSET_DROP)
* done without task_capability_lock() because it introduces
* no new races - i.e. only another task doing capget() on
* this task could get inconsistent info. There can be no
* racing writer bc a task can only change its own caps.
*/
static long cap_prctl_drop(struct cred *new, unsigned long cap)
{
if (!capable(CAP_SETPCAP))
return -EPERM;
if (!cap_valid(cap))
return -EINVAL;
cap_lower(new->cap_bset, cap);
return 0;
}
#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;
}
#endif
int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3,
unsigned long arg4, unsigned long arg5)
{
struct cred *new;
long error = 0;
new = prepare_creds();
if (!new)
return -ENOMEM;
switch (option) {
case PR_CAPBSET_READ:
error = -EINVAL;
if (!cap_valid(arg2))
goto error;
error = !!cap_raised(new->cap_bset, arg2);
goto no_change;
#ifdef CONFIG_SECURITY_FILE_CAPABILITIES
case PR_CAPBSET_DROP:
error = cap_prctl_drop(new, arg2);
if (error < 0)
goto error;
goto changed;
/*
* The next four prctl's remain to assist with transitioning a
* system from legacy UID=0 based privilege (when filesystem
* capabilities are not in use) to a system using filesystem
* capabilities only - as the POSIX.1e draft intended.
*
* Note:
*
* PR_SET_SECUREBITS =
* issecure_mask(SECURE_KEEP_CAPS_LOCKED)
* | issecure_mask(SECURE_NOROOT)
* | issecure_mask(SECURE_NOROOT_LOCKED)
* | issecure_mask(SECURE_NO_SETUID_FIXUP)
* | issecure_mask(SECURE_NO_SETUID_FIXUP_LOCKED)
*
* will ensure that the current process and all of its
* children will be locked into a pure
* capability-based-privilege environment.
*/
case PR_SET_SECUREBITS:
error = -EPERM;
if ((((new->securebits & SECURE_ALL_LOCKS) >> 1)
& (new->securebits ^ arg2)) /*[1]*/
|| ((new->securebits & SECURE_ALL_LOCKS & ~arg2)) /*[2]*/
|| (arg2 & ~(SECURE_ALL_LOCKS | SECURE_ALL_BITS)) /*[3]*/
|| (cap_capable(current, CAP_SETPCAP, SECURITY_CAP_AUDIT) != 0) /*[4]*/
/*
* [1] no changing of bits that are locked
* [2] no unlocking of locks
* [3] no setting of unsupported bits
* [4] doing anything requires privilege (go read about
* the "sendmail capabilities bug")
*/
)
/* cannot change a locked bit */
goto error;
new->securebits = arg2;
goto changed;
case PR_GET_SECUREBITS:
error = new->securebits;
goto no_change;
#endif /* def CONFIG_SECURITY_FILE_CAPABILITIES */
case PR_GET_KEEPCAPS:
if (issecure(SECURE_KEEP_CAPS))
error = 1;
goto no_change;
case PR_SET_KEEPCAPS:
error = -EINVAL;
if (arg2 > 1) /* Note, we rely on arg2 being unsigned here */
goto error;
error = -EPERM;
if (issecure(SECURE_KEEP_CAPS_LOCKED))
goto error;
if (arg2)
new->securebits |= issecure_mask(SECURE_KEEP_CAPS);
else
new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
goto changed;
default:
/* No functionality available - continue with default */
error = -ENOSYS;
goto error;
}
/* Functionality provided */
changed:
return commit_creds(new);
no_change:
error = 0;
error:
abort_creds(new);
return error;
}
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, SECURITY_CAP_NOAUDIT) == 0)
cap_sys_admin = 1;
return __vm_enough_memory(mm, pages, cap_sys_admin);
}
