file capabilities: add no_file_caps switch (v4)

[linux-2.6/libata-dev.git] / security / commoncap.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>
#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_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);

/*
 * 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)
{
        /* 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_may_access(struct task_struct *child, unsigned int mode)
{
        /* Derived from arch/i386/kernel/ptrace.c:sys_ptrace. */
        if (cap_issubset(child->cap_permitted, current->cap_permitted))
                return 0;
        if (capable(CAP_SYS_PTRACE))
                return 0;
        return -EPERM;
}

int cap_ptrace_traceme(struct task_struct *parent)
{
        /* Derived from arch/i386/kernel/ptrace.c:sys_ptrace. */
        if (cap_issubset(current->cap_permitted, parent->cap_permitted))
                return 0;
        if (has_capability(parent, CAP_SYS_PTRACE))
                return 0;
        return -EPERM;
}

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 = target->cap_effective;
        *inheritable = target->cap_inheritable;
        *permitted = 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. That is, if the current task
         * does *not* possess the CAP_SETPCAP capability.
         */
        return (cap_capable(current, CAP_SETPCAP) != 0);
}

static inline int cap_limit_ptraced_target(void) { return 1; }

#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; }
static inline int cap_limit_ptraced_target(void)
{
        return !capable(CAP_SETPCAP);
}

#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;
        }
        if (!cap_issubset(*inheritable,
                           cap_combine(target->cap_inheritable,
                                       current->cap_bset))) {
                /* no new pI capabilities outside bounding 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_post_exec_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, unsigned size)
{
        __u32 magic_etc;
        unsigned tocopy, i;
        int ret;

        if (size < sizeof(magic_etc))
                return -EINVAL;

        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;
        }

        if (magic_etc & VFS_CAP_FLAGS_EFFECTIVE) {
                bprm->cap_effective = true;
        } else {
                bprm->cap_effective = false;
        }

        ret = 0;

        CAP_FOR_EACH_U32(i) {
                __u32 value_cpu;

                if (i >= tocopy) {
                        /*
                         * Legacy capability sets have no upper bits
                         */
                        bprm->cap_post_exec_permitted.cap[i] = 0;
                        continue;
                }
                /*
                 * pP' = (X & fP) | (pI & fI)
                 */
                value_cpu = le32_to_cpu(caps->data[i].permitted);
                bprm->cap_post_exec_permitted.cap[i] =
                        (current->cap_bset.cap[i] & value_cpu) |
                        (current->cap_inheritable.cap[i] &
                                le32_to_cpu(caps->data[i].inheritable));
                if (value_cpu & ~bprm->cap_post_exec_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 bprm->cap_effective ? ret : 0;
}

/* Locate any VFS capabilities: */
static int get_file_caps(struct linux_binprm *bprm)
{
        struct dentry *dentry;
        int rc = 0;
        struct vfs_cap_data vcaps;
        struct inode *inode;

        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);
        inode = dentry->d_inode;
        if (!inode->i_op || !inode->i_op->getxattr)
                goto out;

        rc = inode->i_op->getxattr(dentry, XATTR_NAME_CAPS, &vcaps,
                                   XATTR_CAPS_SZ);
        if (rc == -ENODATA || rc == -EOPNOTSUPP) {
                /* no data, that's ok */
                rc = 0;
                goto out;
        }
        if (rc < 0)
                goto out;

        rc = cap_from_disk(&vcaps, bprm, rc);
        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)
{
        bprm_clear_caps(bprm);
        return 0;
}
#endif

int cap_bprm_set_security (struct linux_binprm *bprm)
{
        int ret;

        ret = get_file_caps(bprm);

        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 (bprm->e_uid == 0 || current->uid == 0) {
                        /* pP' = (cap_bset & ~0) | (pI & ~0) */
                        bprm->cap_post_exec_permitted = cap_combine(
                                current->cap_bset, current->cap_inheritable
                                );
                        bprm->cap_effective = (bprm->e_uid == 0);
                        ret = 0;
                }
        }

        return ret;
}

void cap_bprm_apply_creds (struct linux_binprm *bprm, int unsafe)
{
        if (bprm->e_uid != current->uid || bprm->e_gid != current->gid ||
            !cap_issubset(bprm->cap_post_exec_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 (cap_limit_ptraced_target()) {
                                bprm->cap_post_exec_permitted = cap_intersect(
                                        bprm->cap_post_exec_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 = bprm->cap_post_exec_permitted;
                if (bprm->cap_effective)
                        current->cap_effective = bprm->cap_post_exec_permitted;
                else
                        cap_clear(current->cap_effective);
        }

        /* AUD: Audit candidate if current->cap_effective is set */

        current->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
}

int cap_bprm_secureexec (struct linux_binprm *bprm)
{
        if (current->uid != 0) {
                if (bprm->cap_effective)
                        return 1;
                if (!cap_isclear(bprm->cap_post_exec_permitted))
                        return 1;
        }

        return (current->euid != current->uid ||
                current->egid != current->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 (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) &&
            !issecure(SECURE_KEEP_CAPS)) {
                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) {
                                        current->cap_effective =
                                                cap_drop_fs_set(
                                                    current->cap_effective);
                                }
                                if (old_fsuid != 0 && current->fsuid == 0) {
                                        current->cap_effective =
                                                cap_raise_fs_set(
                                                    current->cap_effective,
                                                    current->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)
{
        if (!cap_issubset(p->cap_permitted, current->cap_permitted) &&
            !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(unsigned long cap)
{
        if (!capable(CAP_SETPCAP))
                return -EPERM;
        if (!cap_valid(cap))
                return -EINVAL;
        cap_lower(current->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, long *rc_p)
{
        long error = 0;

        switch (option) {
        case PR_CAPBSET_READ:
                if (!cap_valid(arg2))
                        error = -EINVAL;
                else
                        error = !!cap_raised(current->cap_bset, arg2);
                break;
#ifdef CONFIG_SECURITY_FILE_CAPABILITIES
        case PR_CAPBSET_DROP:
                error = cap_prctl_drop(arg2);
                break;

        /*
         * 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:
                if ((((current->securebits & SECURE_ALL_LOCKS) >> 1)
                     & (current->securebits ^ arg2))                  /*[1]*/
                    || ((current->securebits & SECURE_ALL_LOCKS
                         & ~arg2))                                    /*[2]*/
                    || (arg2 & ~(SECURE_ALL_LOCKS | SECURE_ALL_BITS)) /*[3]*/
                    || (cap_capable(current, CAP_SETPCAP) != 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")
                         */
                        error = -EPERM;  /* cannot change a locked bit */
                } else {
                        current->securebits = arg2;
                }
                break;
        case PR_GET_SECUREBITS:
                error = current->securebits;
                break;

#endif /* def CONFIG_SECURITY_FILE_CAPABILITIES */

        case PR_GET_KEEPCAPS:
                if (issecure(SECURE_KEEP_CAPS))
                        error = 1;
                break;
        case PR_SET_KEEPCAPS:
                if (arg2 > 1) /* Note, we rely on arg2 being unsigned here */
                        error = -EINVAL;
                else if (issecure(SECURE_KEEP_CAPS_LOCKED))
                        error = -EPERM;
                else if (arg2)
                        current->securebits |= issecure_mask(SECURE_KEEP_CAPS);
                else
                        current->securebits &=
                                ~issecure_mask(SECURE_KEEP_CAPS);
                break;

        default:
                /* No functionality available - continue with default */
                return 0;
        }

        /* Functionality provided */
        *rc_p = error;
        return 1;
}

void cap_task_reparent_to_init (struct task_struct *p)
{
        cap_set_init_eff(p->cap_effective);
        cap_clear(p->cap_inheritable);
        cap_set_full(p->cap_permitted);
        p->securebits = SECUREBITS_DEFAULT;
        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);
}