mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-08-23 01:10:04 +00:00
986 lines
27 KiB
C
986 lines
27 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/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>
|
|
|
|
/*
|
|
* If a non-root user executes a setuid-root binary in
|
|
* !secure(SECURE_NOROOT) mode, then we raise capabilities.
|
|
* However if fE is also set, then the intent is for only
|
|
* the file capabilities to be applied, and the setuid-root
|
|
* bit is left on either to change the uid (plausible) or
|
|
* to get full privilege on a kernel without file capabilities
|
|
* support. So in that case we do not raise capabilities.
|
|
*
|
|
* Warn if that happens, once per boot.
|
|
*/
|
|
static void warn_setuid_and_fcaps_mixed(char *fname)
|
|
{
|
|
static int warned;
|
|
if (!warned) {
|
|
printk(KERN_INFO "warning: `%s' has both setuid-root and"
|
|
" effective capabilities. Therefore not raising all"
|
|
" capabilities.\n", fname);
|
|
warned = 1;
|
|
}
|
|
}
|
|
|
|
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);
|
|
|
|
/**
|
|
* cap_capable - Determine whether a task has a particular effective capability
|
|
* @tsk: The task to query
|
|
* @cred: The credentials to use
|
|
* @cap: The capability to check for
|
|
* @audit: Whether to write an audit message or not
|
|
*
|
|
* Determine whether the nominated task has the specified capability amongst
|
|
* its effective set, returning 0 if it does, -ve if it does not.
|
|
*
|
|
* NOTE WELL: cap_has_capability() cannot be used like the kernel's capable()
|
|
* and has_capability() functions. That is, it has the reverse semantics:
|
|
* cap_has_capability() returns 0 when a task has a capability, but the
|
|
* kernel's capable() and has_capability() returns 1 for this case.
|
|
*/
|
|
int cap_capable(struct task_struct *tsk, const struct cred *cred, int cap,
|
|
int audit)
|
|
{
|
|
return cap_raised(cred->cap_effective, cap) ? 0 : -EPERM;
|
|
}
|
|
|
|
/**
|
|
* cap_settime - Determine whether the current process may set the system clock
|
|
* @ts: The time to set
|
|
* @tz: The timezone to set
|
|
*
|
|
* Determine whether the current process may set the system clock and timezone
|
|
* information, returning 0 if permission granted, -ve if denied.
|
|
*/
|
|
int cap_settime(struct timespec *ts, struct timezone *tz)
|
|
{
|
|
if (!capable(CAP_SYS_TIME))
|
|
return -EPERM;
|
|
return 0;
|
|
}
|
|
|
|
/**
|
|
* cap_ptrace_may_access - Determine whether the current process may access
|
|
* another
|
|
* @child: The process to be accessed
|
|
* @mode: The mode of attachment.
|
|
*
|
|
* Determine whether a process may access another, returning 0 if permission
|
|
* granted, -ve if denied.
|
|
*/
|
|
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;
|
|
}
|
|
|
|
/**
|
|
* cap_ptrace_traceme - Determine whether another process may trace the current
|
|
* @parent: The task proposed to be the tracer
|
|
*
|
|
* Determine whether the nominated task is permitted to trace the current
|
|
* process, returning 0 if permission is granted, -ve if denied.
|
|
*/
|
|
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;
|
|
}
|
|
|
|
/**
|
|
* cap_capget - Retrieve a task's capability sets
|
|
* @target: The task from which to retrieve the capability sets
|
|
* @effective: The place to record the effective set
|
|
* @inheritable: The place to record the inheritable set
|
|
* @permitted: The place to record the permitted set
|
|
*
|
|
* This function retrieves the capabilities of the nominated task and returns
|
|
* them to the caller.
|
|
*/
|
|
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;
|
|
}
|
|
|
|
/*
|
|
* Determine whether the inheritable capabilities are limited to the old
|
|
* permitted set. Returns 1 if they are limited, 0 if they are not.
|
|
*/
|
|
static inline int cap_inh_is_capped(void)
|
|
{
|
|
#ifdef CONFIG_SECURITY_FILE_CAPABILITIES
|
|
|
|
/* they are so limited unless the current task has the CAP_SETPCAP
|
|
* capability
|
|
*/
|
|
if (cap_capable(current, current_cred(), CAP_SETPCAP,
|
|
SECURITY_CAP_AUDIT) == 0)
|
|
return 0;
|
|
#endif
|
|
return 1;
|
|
}
|
|
|
|
/**
|
|
* cap_capset - Validate and apply proposed changes to current's capabilities
|
|
* @new: The proposed new credentials; alterations should be made here
|
|
* @old: The current task's current credentials
|
|
* @effective: A pointer to the proposed new effective capabilities set
|
|
* @inheritable: A pointer to the proposed new inheritable capabilities set
|
|
* @permitted: A pointer to the proposed new permitted capabilities set
|
|
*
|
|
* This function validates and applies a proposed mass change to the current
|
|
* process's capability sets. The changes are made to the proposed new
|
|
* credentials, and assuming no error, will be committed by the caller of LSM.
|
|
*/
|
|
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;
|
|
}
|
|
|
|
/*
|
|
* Clear proposed capability sets for execve().
|
|
*/
|
|
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
|
|
|
|
/**
|
|
* cap_inode_need_killpriv - Determine if inode change affects privileges
|
|
* @dentry: The inode/dentry in being changed with change marked ATTR_KILL_PRIV
|
|
*
|
|
* Determine if an inode having a change applied that's marked ATTR_KILL_PRIV
|
|
* affects the security markings on that inode, and if it is, should
|
|
* inode_killpriv() be invoked or the change rejected?
|
|
*
|
|
* Returns 0 if granted; +ve if granted, but inode_killpriv() is required; and
|
|
* -ve to deny the change.
|
|
*/
|
|
int cap_inode_need_killpriv(struct dentry *dentry)
|
|
{
|
|
struct inode *inode = dentry->d_inode;
|
|
int error;
|
|
|
|
if (!inode->i_op->getxattr)
|
|
return 0;
|
|
|
|
error = inode->i_op->getxattr(dentry, XATTR_NAME_CAPS, NULL, 0);
|
|
if (error <= 0)
|
|
return 0;
|
|
return 1;
|
|
}
|
|
|
|
/**
|
|
* cap_inode_killpriv - Erase the security markings on an inode
|
|
* @dentry: The inode/dentry to alter
|
|
*
|
|
* Erase the privilege-enhancing security markings on an inode.
|
|
*
|
|
* Returns 0 if successful, -ve on error.
|
|
*/
|
|
int cap_inode_killpriv(struct dentry *dentry)
|
|
{
|
|
struct inode *inode = dentry->d_inode;
|
|
|
|
if (!inode->i_op->removexattr)
|
|
return 0;
|
|
|
|
return inode->i_op->removexattr(dentry, XATTR_NAME_CAPS);
|
|
}
|
|
|
|
/*
|
|
* Calculate the new process capability sets from the capability sets attached
|
|
* to a file.
|
|
*/
|
|
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;
|
|
}
|
|
|
|
/*
|
|
* Extract the on-exec-apply capability sets for an executable file.
|
|
*/
|
|
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->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;
|
|
}
|
|
|
|
/*
|
|
* Attempt to get the on-exec apply capability sets for an executable file from
|
|
* its xattrs and, if present, apply them to the proposed credentials being
|
|
* constructed by execve().
|
|
*/
|
|
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;
|
|
}
|
|
|
|
int get_vfs_caps_from_disk(const struct dentry *dentry, struct cpu_vfs_cap_data *cpu_caps)
|
|
{
|
|
memset(cpu_caps, 0, sizeof(struct cpu_vfs_cap_data));
|
|
return -ENODATA;
|
|
}
|
|
|
|
static inline int get_file_caps(struct linux_binprm *bprm, bool *effective)
|
|
{
|
|
bprm_clear_caps(bprm);
|
|
return 0;
|
|
}
|
|
#endif
|
|
|
|
/*
|
|
* Determine whether a exec'ing process's new permitted capabilities should be
|
|
* limited to just what it already has.
|
|
*
|
|
* This prevents processes that are being ptraced from gaining access to
|
|
* CAP_SETPCAP, unless the process they're tracing already has it, and the
|
|
* binary they're executing has filecaps that elevate it.
|
|
*
|
|
* Returns 1 if they should be limited, 0 if they are not.
|
|
*/
|
|
static inline int cap_limit_ptraced_target(void)
|
|
{
|
|
#ifndef CONFIG_SECURITY_FILE_CAPABILITIES
|
|
if (capable(CAP_SETPCAP))
|
|
return 0;
|
|
#endif
|
|
return 1;
|
|
}
|
|
|
|
/**
|
|
* cap_bprm_set_creds - Set up the proposed credentials for execve().
|
|
* @bprm: The execution parameters, including the proposed creds
|
|
*
|
|
* Set up the proposed credentials for a new execution context being
|
|
* constructed by execve(). The proposed creds in @bprm->cred is altered,
|
|
* which won't take effect immediately. Returns 0 if successful, -ve on error.
|
|
*/
|
|
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)) {
|
|
/*
|
|
* If the legacy file capability is set, then don't set privs
|
|
* for a setuid root binary run by a non-root user. Do set it
|
|
* for a root user just to cause least surprise to an admin.
|
|
*/
|
|
if (effective && new->uid != 0 && new->euid == 0) {
|
|
warn_setuid_and_fcaps_mixed(bprm->filename);
|
|
goto skip;
|
|
}
|
|
/*
|
|
* 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;
|
|
}
|
|
skip:
|
|
|
|
/* 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;
|
|
}
|
|
|
|
/**
|
|
* cap_bprm_secureexec - Determine whether a secure execution is required
|
|
* @bprm: The execution parameters
|
|
*
|
|
* Determine whether a secure execution is required, return 1 if it is, and 0
|
|
* if it is not.
|
|
*
|
|
* The credentials have been committed by this point, and so are no longer
|
|
* available through @bprm->cred.
|
|
*/
|
|
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);
|
|
}
|
|
|
|
/**
|
|
* cap_inode_setxattr - Determine whether an xattr may be altered
|
|
* @dentry: The inode/dentry being altered
|
|
* @name: The name of the xattr to be changed
|
|
* @value: The value that the xattr will be changed to
|
|
* @size: The size of value
|
|
* @flags: The replacement flag
|
|
*
|
|
* Determine whether an xattr may be altered or set on an inode, returning 0 if
|
|
* permission is granted, -ve if denied.
|
|
*
|
|
* This is used to make sure security xattrs don't get updated or set by those
|
|
* who aren't privileged to do so.
|
|
*/
|
|
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;
|
|
}
|
|
|
|
if (!strncmp(name, XATTR_SECURITY_PREFIX,
|
|
sizeof(XATTR_SECURITY_PREFIX) - 1) &&
|
|
!capable(CAP_SYS_ADMIN))
|
|
return -EPERM;
|
|
return 0;
|
|
}
|
|
|
|
/**
|
|
* cap_inode_removexattr - Determine whether an xattr may be removed
|
|
* @dentry: The inode/dentry being altered
|
|
* @name: The name of the xattr to be changed
|
|
*
|
|
* Determine whether an xattr may be removed from an inode, returning 0 if
|
|
* permission is granted, -ve if denied.
|
|
*
|
|
* This is used to make sure security xattrs don't get removed by those who
|
|
* aren't privileged to remove them.
|
|
*/
|
|
int cap_inode_removexattr(struct dentry *dentry, const char *name)
|
|
{
|
|
if (!strcmp(name, XATTR_NAME_CAPS)) {
|
|
if (!capable(CAP_SETFCAP))
|
|
return -EPERM;
|
|
return 0;
|
|
}
|
|
|
|
if (!strncmp(name, XATTR_SECURITY_PREFIX,
|
|
sizeof(XATTR_SECURITY_PREFIX) - 1) &&
|
|
!capable(CAP_SYS_ADMIN))
|
|
return -EPERM;
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* 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;
|
|
}
|
|
|
|
/**
|
|
* cap_task_fix_setuid - Fix up the results of setuid() call
|
|
* @new: The proposed credentials
|
|
* @old: The current task's current credentials
|
|
* @flags: Indications of what has changed
|
|
*
|
|
* Fix up the results of setuid() call before the credential changes are
|
|
* actually applied, returning 0 to grant the changes, -ve to deny them.
|
|
*/
|
|
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:
|
|
/* juggle the capabilities to follow [RES]UID changes unless
|
|
* otherwise suppressed */
|
|
if (!issecure(SECURE_NO_SETUID_FIXUP))
|
|
cap_emulate_setxuid(new, old);
|
|
break;
|
|
|
|
case LSM_SETID_FS:
|
|
/* juggle the capabilties to follow FSUID changes, unless
|
|
* otherwise suppressed
|
|
*
|
|
* 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;
|
|
}
|
|
|
|
/**
|
|
* cap_task_setscheduler - Detemine if scheduler policy change is permitted
|
|
* @p: The task to affect
|
|
* @policy: The policy to effect
|
|
* @lp: The parameters to the scheduling policy
|
|
*
|
|
* Detemine if the requested scheduler policy change is permitted for the
|
|
* specified task, returning 0 if permission is granted, -ve if denied.
|
|
*/
|
|
int cap_task_setscheduler(struct task_struct *p, int policy,
|
|
struct sched_param *lp)
|
|
{
|
|
return cap_safe_nice(p);
|
|
}
|
|
|
|
/**
|
|
* cap_task_ioprio - Detemine if I/O priority change is permitted
|
|
* @p: The task to affect
|
|
* @ioprio: The I/O priority to set
|
|
*
|
|
* Detemine if the requested I/O priority change is permitted for the specified
|
|
* task, returning 0 if permission is granted, -ve if denied.
|
|
*/
|
|
int cap_task_setioprio(struct task_struct *p, int ioprio)
|
|
{
|
|
return cap_safe_nice(p);
|
|
}
|
|
|
|
/**
|
|
* cap_task_ioprio - Detemine if task priority change is permitted
|
|
* @p: The task to affect
|
|
* @nice: The nice value to set
|
|
*
|
|
* Detemine if the requested task priority change is permitted for the
|
|
* specified task, returning 0 if permission is granted, -ve if denied.
|
|
*/
|
|
int cap_task_setnice(struct task_struct *p, int nice)
|
|
{
|
|
return cap_safe_nice(p);
|
|
}
|
|
|
|
/*
|
|
* Implement PR_CAPBSET_DROP. Attempt to remove the specified capability from
|
|
* the current task's bounding set. Returns 0 on success, -ve on error.
|
|
*/
|
|
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
|
|
|
|
/**
|
|
* cap_task_prctl - Implement process control functions for this security module
|
|
* @option: The process control function requested
|
|
* @arg2, @arg3, @arg4, @arg5: The argument data for this function
|
|
*
|
|
* Allow process control functions (sys_prctl()) to alter capabilities; may
|
|
* also deny access to other functions not otherwise implemented here.
|
|
*
|
|
* Returns 0 or +ve on success, -ENOSYS if this function is not implemented
|
|
* here, other -ve on error. If -ENOSYS is returned, sys_prctl() and other LSM
|
|
* modules will consider performing the function.
|
|
*/
|
|
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, current_cred(), 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:
|
|
abort_creds(new);
|
|
return error;
|
|
}
|
|
|
|
/**
|
|
* cap_syslog - Determine whether syslog function is permitted
|
|
* @type: Function requested
|
|
*
|
|
* Determine whether the current process is permitted to use a particular
|
|
* syslog function, returning 0 if permission is granted, -ve if not.
|
|
*/
|
|
int cap_syslog(int type)
|
|
{
|
|
if ((type != 3 && type != 10) && !capable(CAP_SYS_ADMIN))
|
|
return -EPERM;
|
|
return 0;
|
|
}
|
|
|
|
/**
|
|
* cap_vm_enough_memory - Determine whether a new virtual mapping is permitted
|
|
* @mm: The VM space in which the new mapping is to be made
|
|
* @pages: The size of the mapping
|
|
*
|
|
* Determine whether the allocation of a new virtual mapping by the current
|
|
* task is permitted, returning 0 if permission is granted, -ve if not.
|
|
*/
|
|
int cap_vm_enough_memory(struct mm_struct *mm, long pages)
|
|
{
|
|
int cap_sys_admin = 0;
|
|
|
|
if (cap_capable(current, current_cred(), CAP_SYS_ADMIN,
|
|
SECURITY_CAP_NOAUDIT) == 0)
|
|
cap_sys_admin = 1;
|
|
return __vm_enough_memory(mm, pages, cap_sys_admin);
|
|
}
|