/*
 * linux/kernel/capability.c
 *
 * Copyright (C) 1997  Andrew Main <zefram@fysh.org>
 *
 * Integrated into 2.1.97+,  Andrew G. Morgan <morgan@kernel.org>
 * 30 May 2002: Cleanup, Robert M. Love <rml@tech9.net>
 */

#include <linux/capability.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/security.h>
#include <linux/syscalls.h>
#include <linux/pid_namespace.h>
#include <asm/uaccess.h>

/*
 * This lock protects task->cap_* for all tasks including current.
 * Locking rule: acquire this prior to tasklist_lock.
 */
static DEFINE_SPINLOCK(task_capability_lock);

/*
 * Leveraged for setting/resetting capabilities
 */

const kernel_cap_t __cap_empty_set = CAP_EMPTY_SET;
const kernel_cap_t __cap_full_set = CAP_FULL_SET;
const kernel_cap_t __cap_init_eff_set = CAP_INIT_EFF_SET;

EXPORT_SYMBOL(__cap_empty_set);
EXPORT_SYMBOL(__cap_full_set);
EXPORT_SYMBOL(__cap_init_eff_set);

/*
 * More recent versions of libcap are available from:
 *
 *   http://www.kernel.org/pub/linux/libs/security/linux-privs/
 */

static void warn_legacy_capability_use(void)
{
        static int warned;
        if (!warned) {
                char name[sizeof(current->comm)];

                printk(KERN_INFO "warning: `%s' uses 32-bit capabilities"
                       " (legacy support in use)\n",
                       get_task_comm(name, current));
                warned = 1;
        }
}

/*
 * Version 2 capabilities worked fine, but the linux/capability.h file
 * that accompanied their introduction encouraged their use without
 * the necessary user-space source code changes. As such, we have
 * created a version 3 with equivalent functionality to version 2, but
 * with a header change to protect legacy source code from using
 * version 2 when it wanted to use version 1. If your system has code
 * that trips the following warning, it is using version 2 specific
 * capabilities and may be doing so insecurely.
 *
 * The remedy is to either upgrade your version of libcap (to 2.10+,
 * if the application is linked against it), or recompile your
 * application with modern kernel headers and this warning will go
 * away.
 */

static void warn_deprecated_v2(void)
{
        static int warned;

        if (!warned) {
                char name[sizeof(current->comm)];

                printk(KERN_INFO "warning: `%s' uses deprecated v2"
                       " capabilities in a way that may be insecure.\n",
                       get_task_comm(name, current));
                warned = 1;
        }
}

/*
 * Version check. Return the number of u32s in each capability flag
 * array, or a negative value on error.
 */
static int cap_validate_magic(cap_user_header_t header, unsigned *tocopy)
{
        __u32 version;

        if (get_user(version, &header->version))
                return -EFAULT;

        switch (version) {
        case _LINUX_CAPABILITY_VERSION_1:
                warn_legacy_capability_use();
                *tocopy = _LINUX_CAPABILITY_U32S_1;
                break;
        case _LINUX_CAPABILITY_VERSION_2:
                warn_deprecated_v2();
                /*
                 * fall through - v3 is otherwise equivalent to v2.
                 */
        case _LINUX_CAPABILITY_VERSION_3:
                *tocopy = _LINUX_CAPABILITY_U32S_3;
                break;
        default:
                if (put_user((u32)_KERNEL_CAPABILITY_VERSION, &header->version))
                        return -EFAULT;
                return -EINVAL;
        }

        return 0;
}

#ifndef CONFIG_SECURITY_FILE_CAPABILITIES

/*
 * Without filesystem capability support, we nominally support one process
 * setting the capabilities of another
 */
static inline int cap_get_target_pid(pid_t pid, kernel_cap_t *pEp,
                                     kernel_cap_t *pIp, kernel_cap_t *pPp)
{
        struct task_struct *target;
        int ret;

        spin_lock(&task_capability_lock);
        read_lock(&tasklist_lock);

        if (pid && pid != task_pid_vnr(current)) {
                target = find_task_by_vpid(pid);
                if (!target) {
                        ret = -ESRCH;
                        goto out;
                }
        } else
                target = current;

        ret = security_capget(target, pEp, pIp, pPp);

out:
        read_unlock(&tasklist_lock);
        spin_unlock(&task_capability_lock);

        return ret;
}

/*
 * cap_set_pg - set capabilities for all processes in a given process
 * group.  We call this holding task_capability_lock and tasklist_lock.
 */
static inline int cap_set_pg(int pgrp_nr, kernel_cap_t *effective,
                             kernel_cap_t *inheritable,
                             kernel_cap_t *permitted)
{
        struct task_struct *g, *target;
        int ret = -EPERM;
        int found = 0;
        struct pid *pgrp;

        spin_lock(&task_capability_lock);
        read_lock(&tasklist_lock);

        pgrp = find_vpid(pgrp_nr);
        do_each_pid_task(pgrp, PIDTYPE_PGID, g) {
                target = g;
                while_each_thread(g, target) {
                        if (!security_capset_check(target, effective,
                                                   inheritable, permitted)) {
                                security_capset_set(target, effective,
                                                    inheritable, permitted);
                                ret = 0;
                        }
                        found = 1;
                }
        } while_each_pid_task(pgrp, PIDTYPE_PGID, g);

        read_unlock(&tasklist_lock);
        spin_unlock(&task_capability_lock);

        if (!found)
                ret = 0;
        return ret;
}

/*
 * cap_set_all - set capabilities for all processes other than init
 * and self.  We call this holding task_capability_lock and tasklist_lock.
 */
static inline int cap_set_all(kernel_cap_t *effective,
                              kernel_cap_t *inheritable,
                              kernel_cap_t *permitted)
{
        struct task_struct *g, *target;
        int ret = -EPERM;
        int found = 0;

        spin_lock(&task_capability_lock);
        read_lock(&tasklist_lock);

        do_each_thread(g, target) {
                if (target == current
                    || is_container_init(target->group_leader))
                        continue;
                found = 1;
                if (security_capset_check(target, effective, inheritable,
                                          permitted))
                        continue;
                ret = 0;
                security_capset_set(target, effective, inheritable, permitted);
        } while_each_thread(g, target);

        read_unlock(&tasklist_lock);
        spin_unlock(&task_capability_lock);

        if (!found)
                ret = 0;

        return ret;
}

/*
 * Given the target pid does not refer to the current process we
 * need more elaborate support... (This support is not present when
 * filesystem capabilities are configured.)
 */
static inline int do_sys_capset_other_tasks(pid_t pid, kernel_cap_t *effective,
                                            kernel_cap_t *inheritable,
                                            kernel_cap_t *permitted)
{
        struct task_struct *target;
        int ret;

        if (!capable(CAP_SETPCAP))
                return -EPERM;

        if (pid == -1)            /* all procs other than current and init */
                return cap_set_all(effective, inheritable, permitted);

        else if (pid < 0)                    /* all procs in process group */
                return cap_set_pg(-pid, effective, inheritable, permitted);

        /* target != current */
        spin_lock(&task_capability_lock);
        read_lock(&tasklist_lock);

        target = find_task_by_vpid(pid);
        if (!target)
                ret = -ESRCH;
        else {
                ret = security_capset_check(target, effective, inheritable,
                                            permitted);

                /* having verified that the proposed changes are legal,
                   we now put them into effect. */
                if (!ret)
                        security_capset_set(target, effective, inheritable,
                                            permitted);
        }

        read_unlock(&tasklist_lock);
        spin_unlock(&task_capability_lock);

        return ret;
}

#else /* ie., def CONFIG_SECURITY_FILE_CAPABILITIES */

/*
 * If we have configured with filesystem capability support, then the
 * only thing that can change the capabilities of the current process
 * is the current process. As such, we can't be in this code at the
 * same time as we are in the process of setting capabilities in this
 * process. The net result is that we can limit our use of locks to
 * when we are reading the caps of another process.
 */
static inline int cap_get_target_pid(pid_t pid, kernel_cap_t *pEp,
                                     kernel_cap_t *pIp, kernel_cap_t *pPp)
{
        int ret;

        if (pid && (pid != task_pid_vnr(current))) {
                struct task_struct *target;

                spin_lock(&task_capability_lock);
                read_lock(&tasklist_lock);

                target = find_task_by_vpid(pid);
                if (!target)
                        ret = -ESRCH;
                else
                        ret = security_capget(target, pEp, pIp, pPp);

                read_unlock(&tasklist_lock);
                spin_unlock(&task_capability_lock);
        } else
                ret = security_capget(current, pEp, pIp, pPp);

        return ret;
}

/*
 * With filesystem capability support configured, the kernel does not
 * permit the changing of capabilities in one process by another
 * process. (CAP_SETPCAP has much less broad semantics when configured
 * this way.)
 */
static inline int do_sys_capset_other_tasks(pid_t pid,
                                            kernel_cap_t *effective,
                                            kernel_cap_t *inheritable,
                                            kernel_cap_t *permitted)
{
        return -EPERM;
}

#endif /* ie., ndef CONFIG_SECURITY_FILE_CAPABILITIES */

/*
 * Atomically modify the effective capabilities returning the original
 * value. No permission check is performed here - it is assumed that the
 * caller is permitted to set the desired effective capabilities.
 */
kernel_cap_t cap_set_effective(const kernel_cap_t pE_new)
{
        kernel_cap_t pE_old;

        spin_lock(&task_capability_lock);

        pE_old = current->cap_effective;
        current->cap_effective = pE_new;

        spin_unlock(&task_capability_lock);

        return pE_old;
}

EXPORT_SYMBOL(cap_set_effective);

/**
 * sys_capget - get the capabilities of a given process.
 * @header: pointer to struct that contains capability version and
 *      target pid data
 * @dataptr: pointer to struct that contains the effective, permitted,
 *      and inheritable capabilities that are returned
 *
 * Returns 0 on success and < 0 on error.
 */
SYSCALL_DEFINE2(capget, cap_user_header_t, header, cap_user_data_t, dataptr)
{
        int ret = 0;
        pid_t pid;
        unsigned tocopy;
        kernel_cap_t pE, pI, pP;

        ret = cap_validate_magic(header, &tocopy);
        if (ret != 0)
                return ret;

        if (get_user(pid, &header->pid))
                return -EFAULT;

        if (pid < 0)
                return -EINVAL;

        ret = cap_get_target_pid(pid, &pE, &pI, &pP);

        if (!ret) {
                struct __user_cap_data_struct kdata[_KERNEL_CAPABILITY_U32S];
                unsigned i;

                for (i = 0; i < tocopy; i++) {
                        kdata[i].effective = pE.cap[i];
                        kdata[i].permitted = pP.cap[i];
                        kdata[i].inheritable = pI.cap[i];
                }

                /*
                 * Note, in the case, tocopy < _KERNEL_CAPABILITY_U32S,
                 * we silently drop the upper capabilities here. This
                 * has the effect of making older libcap
                 * implementations implicitly drop upper capability
                 * bits when they perform a: capget/modify/capset
                 * sequence.
                 *
                 * This behavior is considered fail-safe
                 * behavior. Upgrading the application to a newer
                 * version of libcap will enable access to the newer
                 * capabilities.
                 *
                 * An alternative would be to return an error here
                 * (-ERANGE), but that causes legacy applications to
                 * unexpectidly fail; the capget/modify/capset aborts
                 * before modification is attempted and the application
                 * fails.
                 */
                if (copy_to_user(dataptr, kdata, tocopy
                                 * sizeof(struct __user_cap_data_struct))) {
                        return -EFAULT;
                }
        }

        return ret;
}

/**
 * sys_capset - set capabilities for a process or (*) a group of processes
 * @header: pointer to struct that contains capability version and
 *      target pid data
 * @data: pointer to struct that contains the effective, permitted,
 *      and inheritable capabilities
 *
 * Set capabilities for a given process, all processes, or all
 * processes in a given process group.
 *
 * The restrictions on setting capabilities are specified as:
 *
 * [pid is for the 'target' task.  'current' is the calling task.]
 *
 * I: any raised capabilities must be a subset of the (old current) permitted
 * P: any raised capabilities must be a subset of the (old current) permitted
 * E: must be set to a subset of (new target) permitted
 *
 * Returns 0 on success and < 0 on error.
 */
SYSCALL_DEFINE2(capset, cap_user_header_t, header, const cap_user_data_t, data)
{
        struct __user_cap_data_struct kdata[_KERNEL_CAPABILITY_U32S];
        unsigned i, tocopy;
        kernel_cap_t inheritable, permitted, effective;
        int ret;
        pid_t pid;

        ret = cap_validate_magic(header, &tocopy);
        if (ret != 0)
                return ret;

        if (get_user(pid, &header->pid))
                return -EFAULT;

        if (copy_from_user(&kdata, data, tocopy
                           * sizeof(struct __user_cap_data_struct))) {
                return -EFAULT;
        }

        for (i = 0; i < tocopy; i++) {
                effective.cap[i] = kdata[i].effective;
                permitted.cap[i] = kdata[i].permitted;
                inheritable.cap[i] = kdata[i].inheritable;
        }
        while (i < _KERNEL_CAPABILITY_U32S) {
                effective.cap[i] = 0;
                permitted.cap[i] = 0;
                inheritable.cap[i] = 0;
                i++;
        }

        if (pid && (pid != task_pid_vnr(current)))
                ret = do_sys_capset_other_tasks(pid, &effective, &inheritable,
                                                &permitted);
        else {
                /*
                 * This lock is required even when filesystem
                 * capability support is configured - it protects the
                 * sys_capget() call from returning incorrect data in
                 * the case that the targeted process is not the
                 * current one.
                 */
                spin_lock(&task_capability_lock);

                ret = security_capset_check(current, &effective, &inheritable,
                                            &permitted);
                /*
                 * Having verified that the proposed changes are
                 * legal, we now put them into effect.
                 */
                if (!ret)
                        security_capset_set(current, &effective, &inheritable,
                                            &permitted);
                spin_unlock(&task_capability_lock);
        }


        return ret;
}

/**
 * capable - Determine if the current task has a superior capability in effect
 * @cap: The capability to be tested for
 *
 * Return true if the current task has the given superior capability currently
 * available for use, false if not.
 *
 * This sets PF_SUPERPRIV on the task if the capability is available on the
 * assumption that it's about to be used.
 */
int capable(int cap)
{
        if (has_capability(current, cap)) {
                current->flags |= PF_SUPERPRIV;
                return 1;
        }
        return 0;
}
EXPORT_SYMBOL(capable);