V3 file capabilities: alter behavior of cap_setpcap

[linux-2.6/x86.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>

#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(__le32 *caps, struct linux_binprm *bprm,
                                int size)
{
        __u32 magic_etc;

        if (size != XATTR_CAPS_SZ)
                return -EINVAL;

        magic_etc = le32_to_cpu(caps[0]);

        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[1]) );
                bprm->cap_inheritable = to_cap_t( le32_to_cpu(caps[2]) );
                return 0;
        default:
                return -EINVAL;
        }
}

/* Locate any VFS capabilities: */
static int get_file_caps(struct linux_binprm *bprm)
{
        struct dentry *dentry;
        int rc = 0;
        __le32 v1caps[XATTR_CAPS_SZ];
        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, &v1caps,
                                                        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(v1caps, 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_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;

        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);
}