/* $NetBSD: secmodel_securelevel.c,v 1.37 2020/12/05 17:33:53 thorpej Exp $ */
/*-
 * Copyright (c) 2006 Elad Efrat <elad@NetBSD.org>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/*
 * This file contains kauth(9) listeners needed to implement the traditional
 * NetBSD securelevel.
 *
 * The securelevel is a system-global indication on what operations are
 * allowed or not. It affects all users, including root.
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: secmodel_securelevel.c,v 1.37 2020/12/05 17:33:53 thorpej Exp $");

#ifdef _KERNEL_OPT
#include "opt_insecure.h"
#endif /* _KERNEL_OPT */

#include <sys/types.h>
#include <sys/param.h>
#include <sys/kauth.h>

#include <sys/conf.h>
#include <sys/mount.h>
#include <sys/sysctl.h>
#include <sys/vnode.h>
#include <sys/module.h>

#include <miscfs/specfs/specdev.h>

#include <secmodel/secmodel.h>
#include <secmodel/securelevel/securelevel.h>

MODULE(MODULE_CLASS_SECMODEL, securelevel, NULL);

static int securelevel;

static kauth_listener_t l_system, l_process, l_network, l_machdep, l_device,
    l_vnode;

static secmodel_t securelevel_sm;

/*
 * Sysctl helper routine for securelevel. Ensures that the value only rises
 * unless the caller is init.
 */
int
secmodel_securelevel_sysctl(SYSCTLFN_ARGS)
{
        int newsecurelevel, error;
        struct sysctlnode node;

        newsecurelevel = securelevel;
        node = *rnode;
        node.sysctl_data = &newsecurelevel;
        error = sysctl_lookup(SYSCTLFN_CALL(&node));
        if (error || newp == NULL)
                return (error);

        if ((newsecurelevel < securelevel) && (l->l_proc != initproc))
                return (EPERM);

        securelevel = newsecurelevel;

        return (error);
}

SYSCTL_SETUP(sysctl_security_securelevel_setup, "securelevel sysctl")
{
        const struct sysctlnode *rnode, *rnode2;

        sysctl_createv(clog, 0, NULL, &rnode,
                       CTLFLAG_PERMANENT,
                       CTLTYPE_NODE, "models", NULL,
                       NULL, 0, NULL, 0,
                       CTL_SECURITY, CTL_CREATE, CTL_EOL);

        /* Compatibility: security.models.bsd44 */
        rnode2 = rnode;
        sysctl_createv(clog, 0, &rnode2, &rnode2,
                       CTLFLAG_PERMANENT,
                       CTLTYPE_NODE, "bsd44", NULL,
                       NULL, 0, NULL, 0,
                       CTL_CREATE, CTL_EOL);

        /* Compatibility: security.models.bsd44.securelevel */
        sysctl_createv(clog, 0, &rnode2, NULL,
                       CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
                       CTLTYPE_INT, "securelevel",
                       SYSCTL_DESCR("System security level"),
                       secmodel_securelevel_sysctl, 0, NULL, 0,
                       CTL_CREATE, CTL_EOL);

        sysctl_createv(clog, 0, &rnode, &rnode,
                       CTLFLAG_PERMANENT,
                       CTLTYPE_NODE, "securelevel", NULL,
                       NULL, 0, NULL, 0,
                       CTL_CREATE, CTL_EOL);

        sysctl_createv(clog, 0, &rnode, NULL,
                       CTLFLAG_PERMANENT,
                       CTLTYPE_STRING, "name", NULL,
                       NULL, 0, __UNCONST(SECMODEL_SECURELEVEL_NAME), 0,
                       CTL_CREATE, CTL_EOL);

        sysctl_createv(clog, 0, &rnode, NULL,
                       CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
                       CTLTYPE_INT, "securelevel",
                       SYSCTL_DESCR("System security level"),
                       secmodel_securelevel_sysctl, 0, NULL, 0,
                       CTL_CREATE, CTL_EOL);

        /* Compatibility: kern.securelevel */

        sysctl_createv(clog, 0, NULL, NULL,
                       CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
                       CTLTYPE_INT, "securelevel",
                       SYSCTL_DESCR("System security level"),
                       secmodel_securelevel_sysctl, 0, NULL, 0,
                       CTL_KERN, KERN_SECURELVL, CTL_EOL);
}

void
secmodel_securelevel_init(void)
{
#ifdef INSECURE
        securelevel = -1;
#else
        securelevel = 0;
#endif /* INSECURE */
}

void
secmodel_securelevel_start(void)
{
        l_system = kauth_listen_scope(KAUTH_SCOPE_SYSTEM,
            secmodel_securelevel_system_cb, NULL);
        l_process = kauth_listen_scope(KAUTH_SCOPE_PROCESS,
            secmodel_securelevel_process_cb, NULL);
        l_network = kauth_listen_scope(KAUTH_SCOPE_NETWORK,
            secmodel_securelevel_network_cb, NULL);
        l_machdep = kauth_listen_scope(KAUTH_SCOPE_MACHDEP,
            secmodel_securelevel_machdep_cb, NULL);
        l_device = kauth_listen_scope(KAUTH_SCOPE_DEVICE,
            secmodel_securelevel_device_cb, NULL);
        l_vnode = kauth_listen_scope(KAUTH_SCOPE_VNODE,
            secmodel_securelevel_vnode_cb, NULL);
}

void
secmodel_securelevel_stop(void)
{
        kauth_unlisten_scope(l_system);
        kauth_unlisten_scope(l_process);
        kauth_unlisten_scope(l_network);
        kauth_unlisten_scope(l_machdep);
        kauth_unlisten_scope(l_device);
        kauth_unlisten_scope(l_vnode);
}

static int
securelevel_eval(const char *what, void *arg, void *ret)
{
        int error = 0;

        if (strcasecmp(what, "is-securelevel-above") == 0) {
                int level = (int)(uintptr_t)arg;
                bool *bp = ret;

                *bp = (securelevel > level);
        } else {
                error = ENOENT;
        }

        return error;
}

static int
securelevel_modcmd(modcmd_t cmd, void *arg)
{
        int error = 0;

        switch (cmd) {
        case MODULE_CMD_INIT:
                secmodel_securelevel_init();
                error = secmodel_register(&securelevel_sm,
                    SECMODEL_SECURELEVEL_ID, SECMODEL_SECURELEVEL_NAME,
                    NULL, securelevel_eval, NULL);
                if (error != 0)
                        printf("securelevel_modcmd::init: secmodel_register "
                            "returned %d\n", error);

                secmodel_securelevel_start();
                break;

        case MODULE_CMD_FINI:
                secmodel_securelevel_stop();

                error = secmodel_deregister(securelevel_sm);
                if (error != 0)
                        printf("securelevel_modcmd::fini: secmodel_deregister "
                            "returned %d\n", error);

                break;

        case MODULE_CMD_AUTOUNLOAD:
                error = EPERM;
                break;

        default:
                error = ENOTTY;
                break;
        }

        return (error);
}

/*
 * kauth(9) listener
 *
 * Security model: Traditional NetBSD
 * Scope: System
 * Responsibility: Securelevel
 */
int
secmodel_securelevel_system_cb(kauth_cred_t cred, kauth_action_t action,
    void *cookie, void *arg0, void *arg1, void *arg2, void *arg3)
{
        int result;
        enum kauth_system_req req;

        result = KAUTH_RESULT_DEFER;
        req = (enum kauth_system_req)(uintptr_t)arg0;

        switch (action) {
        case KAUTH_SYSTEM_CHSYSFLAGS:
                /* Deprecated. */
                if (securelevel > 0)
                        result = KAUTH_RESULT_DENY;
                break;

        case KAUTH_SYSTEM_TIME:
                switch (req) {
                case KAUTH_REQ_SYSTEM_TIME_RTCOFFSET:
                        if (securelevel > 0)
                                result = KAUTH_RESULT_DENY;
                        break;

                case KAUTH_REQ_SYSTEM_TIME_SYSTEM: {
                        struct timespec *ts = arg1;
                        struct timespec *delta = arg2;

                        if (securelevel > 1 && time_wraps(ts, delta))
                                result = KAUTH_RESULT_DENY;

                        break;
                }

                default:
                        break;
                }
                break;

        case KAUTH_SYSTEM_MAP_VA_ZERO:
                if (securelevel > 0)
                        result = KAUTH_RESULT_DENY;
                break;

        case KAUTH_SYSTEM_MODULE:
                if (securelevel > 0)
                        result = KAUTH_RESULT_DENY;
                break;

        case KAUTH_SYSTEM_MOUNT:
                switch (req) {
                case KAUTH_REQ_SYSTEM_MOUNT_NEW:
                        if (securelevel > 1)
                                result = KAUTH_RESULT_DENY;

                        break;

                case KAUTH_REQ_SYSTEM_MOUNT_UPDATE:
                        if (securelevel > 1) {
                                struct mount *mp = arg1;
                                u_long flags = (u_long)arg2;

                                /* Can only degrade from read/write to read-only. */
                                if (flags != (mp->mnt_flag | MNT_RDONLY | MNT_RELOAD |
                                    MNT_FORCE | MNT_UPDATE))
                                        result = KAUTH_RESULT_DENY;
                        }

                        break;

                default:
                        break;
                }

                break;

        case KAUTH_SYSTEM_SYSCTL:
                switch (req) {
                case KAUTH_REQ_SYSTEM_SYSCTL_ADD:
                case KAUTH_REQ_SYSTEM_SYSCTL_DELETE:
                case KAUTH_REQ_SYSTEM_SYSCTL_DESC:
                        if (securelevel > 0)
                                result = KAUTH_RESULT_DENY;
                        break;

                default:
                        break;
                }
                break;

        case KAUTH_SYSTEM_SETIDCORE:
                if (securelevel > 0)
                        result = KAUTH_RESULT_DENY;
                break;

        case KAUTH_SYSTEM_DEBUG:
        default:
                break;
        }

        return (result);
}

/*
 * kauth(9) listener
 *
 * Security model: Traditional NetBSD
 * Scope: Process
 * Responsibility: Securelevel
 */
int
secmodel_securelevel_process_cb(kauth_cred_t cred, kauth_action_t action,
    void *cookie, void *arg0, void *arg1, void *arg2, void *arg3)
{
        struct proc *p;
        int result;

        result = KAUTH_RESULT_DEFER;
        p = arg0;

        switch (action) {
        case KAUTH_PROCESS_PROCFS: {
                enum kauth_process_req req;

                req = (enum kauth_process_req)(uintptr_t)arg2;
                switch (req) {
                case KAUTH_REQ_PROCESS_PROCFS_READ:
                        break;

                case KAUTH_REQ_PROCESS_PROCFS_RW:
                case KAUTH_REQ_PROCESS_PROCFS_WRITE:
                        if ((p == initproc) && (securelevel > -1))
                                result = KAUTH_RESULT_DENY;

                        break;

                default:
                        break;
                }

                break;
                }

        case KAUTH_PROCESS_PTRACE:
                if ((p == initproc) && (securelevel > -1))
                        result = KAUTH_RESULT_DENY;

                break;

        case KAUTH_PROCESS_CORENAME:
                if (securelevel > 1)
                        result = KAUTH_RESULT_DENY;
                break;

        default:
                break;
        }

        return (result);
}

/*
 * kauth(9) listener
 *
 * Security model: Traditional NetBSD
 * Scope: Network
 * Responsibility: Securelevel
 */
int
secmodel_securelevel_network_cb(kauth_cred_t cred, kauth_action_t action,
    void *cookie, void *arg0, void *arg1, void *arg2, void *arg3)
{
        int result;
        enum kauth_network_req req;

        result = KAUTH_RESULT_DEFER;
        req = (enum kauth_network_req)(uintptr_t)arg0;

        switch (action) {
        case KAUTH_NETWORK_FIREWALL:
                switch (req) {
                case KAUTH_REQ_NETWORK_FIREWALL_FW:
                case KAUTH_REQ_NETWORK_FIREWALL_NAT:
                        if (securelevel > 1)
                                result = KAUTH_RESULT_DENY;
                        break;

                default:
                        break;
                }
                break;

        case KAUTH_NETWORK_FORWSRCRT:
                if (securelevel > 0)
                        result = KAUTH_RESULT_DENY;
                break;

        default:
                break;
        }

        return (result);
}

/*
 * kauth(9) listener
 *
 * Security model: Traditional NetBSD
 * Scope: Machdep
 * Responsibility: Securelevel
 */
int
secmodel_securelevel_machdep_cb(kauth_cred_t cred, kauth_action_t action,
    void *cookie, void *arg0, void *arg1, void *arg2, void *arg3)
{
        int result;

        result = KAUTH_RESULT_DEFER;

        switch (action) {
        case KAUTH_MACHDEP_IOPERM_SET:
        case KAUTH_MACHDEP_IOPL:
                if (securelevel > 0)
                        result = KAUTH_RESULT_DENY;
                break;

        case KAUTH_MACHDEP_UNMANAGEDMEM:
                if (securelevel > 0)
                        result = KAUTH_RESULT_DENY;
                break;

        case KAUTH_MACHDEP_SVS_DISABLE:
                /* Deprecated. */
                if (securelevel > 0)
                        result = KAUTH_RESULT_DENY;
                break;

        case KAUTH_MACHDEP_CPU_UCODE_APPLY:
                if (securelevel > 1)
                        result = KAUTH_RESULT_DENY;
                break;

        default:
                break;
        }

        return (result);
}

/*
 * kauth(9) listener
 *
 * Security model: Traditional NetBSD
 * Scope: Device
 * Responsibility: Securelevel
 */
int
secmodel_securelevel_device_cb(kauth_cred_t cred, kauth_action_t action,
    void *cookie, void *arg0, void *arg1, void *arg2, void *arg3)
{
        int result;

        result = KAUTH_RESULT_DEFER;

        switch (action) {
        case KAUTH_DEVICE_RAWIO_SPEC: {
                struct vnode *vp;
                enum kauth_device_req req;

                req = (enum kauth_device_req)(uintptr_t)arg0;
                vp = arg1;

                KASSERT(vp != NULL);

                /* Handle /dev/mem and /dev/kmem. */
                if (iskmemvp(vp)) {
                        switch (req) {
                        case KAUTH_REQ_DEVICE_RAWIO_SPEC_READ:
                                break;

                        case KAUTH_REQ_DEVICE_RAWIO_SPEC_WRITE:
                        case KAUTH_REQ_DEVICE_RAWIO_SPEC_RW:
                                if (securelevel > 0)
                                        result = KAUTH_RESULT_DENY;

                                break;

                        default:
                                break;
                        }

                        break;
                }

                switch (req) {
                case KAUTH_REQ_DEVICE_RAWIO_SPEC_READ:
                        break;

                case KAUTH_REQ_DEVICE_RAWIO_SPEC_WRITE:
                case KAUTH_REQ_DEVICE_RAWIO_SPEC_RW: {
                        int error;

                        error = rawdev_mounted(vp, NULL);

                        /* Not a disk. */
                        if (error == EINVAL)
                                break;

                        if (error && securelevel > 0)
                                result = KAUTH_RESULT_DENY;

                        if (securelevel > 1)
                                result = KAUTH_RESULT_DENY;

                        break;
                        }

                default:
                        break;
                }

                break;
                }

        case KAUTH_DEVICE_RAWIO_PASSTHRU:
                if (securelevel > 0) {
                        u_long bits;

                        bits = (u_long)arg0;

                        KASSERT(bits != 0);
                        KASSERT((bits & ~KAUTH_REQ_DEVICE_RAWIO_PASSTHRU_ALL) == 0);

                        if (bits & ~KAUTH_REQ_DEVICE_RAWIO_PASSTHRU_READCONF)
                                result = KAUTH_RESULT_DENY;
                }

                break;

        case KAUTH_DEVICE_GPIO_PINSET:
                if (securelevel > 0)
                        result = KAUTH_RESULT_DENY;
                break;

        case KAUTH_DEVICE_RND_ADDDATA_ESTIMATE:
                if (securelevel > 1)
                        result = KAUTH_RESULT_DENY;
                break;

        default:
                break;
        }

        return (result);
}

int
secmodel_securelevel_vnode_cb(kauth_cred_t cred, kauth_action_t action,
    void *cookie, void *arg0, void *arg1, void *arg2, void *arg3)
{
        int result;

        result = KAUTH_RESULT_DEFER;

        if ((action & KAUTH_VNODE_WRITE_SYSFLAGS) &&
            (action & KAUTH_VNODE_HAS_SYSFLAGS)) {
                if (securelevel > 0)
                        result = KAUTH_RESULT_DENY;
        }

        return (result);
}