/* 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/config.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/smp_lock.h>
#include <linux/skbuff.h>
#include <linux/netlink.h>
#include <linux/ptrace.h>
#include <linux/xattr.h>
#include <linux/hugetlb.h>

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;
        else
                return -EPERM;
}

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, current->cap_permitted) &&
            !capable (CAP_SYS_PTRACE))
                return -EPERM;
        else
                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;
}

int cap_capset_check (struct task_struct *target, kernel_cap_t *effective,
                      kernel_cap_t *inheritable, kernel_cap_t *permitted)
{
        /* Derived from kernel/capability.c:sys_capset. */
        /* verify restrictions on target's new Inheritable set */
        if (!cap_issubset (*inheritable,
                           cap_combine (target->cap_inheritable,
                                        current->cap_permitted))) {
                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;
}

int cap_bprm_set_security (struct linux_binprm *bprm)
{
        /* Copied from fs/exec.c:prepare_binprm. */

        /* We don't have VFS support for capabilities yet */
        cap_clear (bprm->cap_inheritable);
        cap_clear (bprm->cap_permitted);
        cap_clear (bprm->cap_effective);

        /*  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)
                        cap_set_full (bprm->cap_effective);
        }
        return 0;
}

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)) {
                current->mm->dumpable = suid_dumpable;

                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 (current->pid != 1) {
                current->cap_permitted = new_permitted;
                current->cap_effective =
                    cap_intersect (new_permitted, bprm->cap_effective);
        }

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

        current->keep_capabilities = 0;
}

int cap_bprm_secureexec (struct linux_binprm *bprm)
{
        /* If/when this module is enhanced to incorporate capability
           bits on files, the test below should be extended to also perform a 
           test between the old and new capability sets.  For now,
           it simply preserves the legacy decision algorithm used by
           the old userland. */
        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 (!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 (!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;
}

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;
}

/*
 * Check that a process has enough memory to allocate a new virtual
 * mapping. 0 means there is enough memory for the allocation to
 * succeed and -ENOMEM implies there is not.
 *
 * We currently support three overcommit policies, which are set via the
 * vm.overcommit_memory sysctl.  See Documentation/vm/overcommit-accounting
 *
 * Strict overcommit modes added 2002 Feb 26 by Alan Cox.
 * Additional code 2002 Jul 20 by Robert Love.
 */
int cap_vm_enough_memory(long pages)
{
        unsigned long free, allowed;

        vm_acct_memory(pages);

        /*
         * Sometimes we want to use more memory than we have
         */
        if (sysctl_overcommit_memory == OVERCOMMIT_ALWAYS)
                return 0;

        if (sysctl_overcommit_memory == OVERCOMMIT_GUESS) {
                unsigned long n;

                free = get_page_cache_size();
                free += nr_swap_pages;

                /*
                 * Any slabs which are created with the
                 * SLAB_RECLAIM_ACCOUNT flag claim to have contents
                 * which are reclaimable, under pressure.  The dentry
                 * cache and most inode caches should fall into this
                 */
                free += atomic_read(&slab_reclaim_pages);

                /*
                 * Leave the last 3% for root
                 */
                if (!capable(CAP_SYS_ADMIN))
                        free -= free / 32;

                if (free > pages)
                        return 0;

                /*
                 * nr_free_pages() is very expensive on large systems,
                 * only call if we're about to fail.
                 */
                n = nr_free_pages();
                if (!capable(CAP_SYS_ADMIN))
                        n -= n / 32;
                free += n;

                if (free > pages)
                        return 0;
                vm_unacct_memory(pages);
                return -ENOMEM;
        }

        allowed = (totalram_pages - hugetlb_total_pages())
                * sysctl_overcommit_ratio / 100;
        /*
         * Leave the last 3% for root
         */
        if (!capable(CAP_SYS_ADMIN))
                allowed -= allowed / 32;
        allowed += total_swap_pages;

        if (atomic_read(&vm_committed_space) < (long)allowed)
                return 0;

        vm_unacct_memory(pages);

        return -ENOMEM;
}

EXPORT_SYMBOL(cap_capable);
EXPORT_SYMBOL(cap_ptrace);
EXPORT_SYMBOL(cap_capget);
EXPORT_SYMBOL(cap_capset_check);
EXPORT_SYMBOL(cap_capset_set);
EXPORT_SYMBOL(cap_bprm_set_security);
EXPORT_SYMBOL(cap_bprm_apply_creds);
EXPORT_SYMBOL(cap_bprm_secureexec);
EXPORT_SYMBOL(cap_inode_setxattr);
EXPORT_SYMBOL(cap_inode_removexattr);
EXPORT_SYMBOL(cap_task_post_setuid);
EXPORT_SYMBOL(cap_task_reparent_to_init);
EXPORT_SYMBOL(cap_syslog);
EXPORT_SYMBOL(cap_vm_enough_memory);

MODULE_DESCRIPTION("Standard Linux Common Capabilities Security Module");
MODULE_LICENSE("GPL");