/*-
 * Copyright (c) 1999-2002, 2007 Robert N. M. Watson
 * Copyright (c) 2001-2002 Networks Associates Technology, Inc.
 * Copyright (c) 2006 SPARTA, Inc.
 * All rights reserved.
 *
 * This software was developed by Robert Watson for the TrustedBSD Project.
 *
 * This software was developed for the FreeBSD Project in part by Network
 * Associates Laboratories, the Security Research Division of Network
 * Associates, Inc. under DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"),
 * as part of the DARPA CHATS research program.
 *
 * This software was enhanced by SPARTA ISSO under SPAWAR contract
 * N66001-04-C-6019 ("SEFOS").
 *
 * 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``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 OR CONTRIBUTORS 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.
 */

/*
 * Developed by the TrustedBSD Project.
 *
 * Prevent processes owned by a particular uid from seeing various transient
 * kernel objects associated with other uids.
 */

#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/module.h>
#include <sys/priv.h>
#include <sys/proc.h>
#include <sys/rmlock.h>
#include <sys/systm.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <sys/sysctl.h>

#include <net/route.h>
#include <netinet/in.h>
#include <netinet/in_pcb.h>

#include <security/mac/mac_policy.h>

static MALLOC_DEFINE(M_SEEOTHERUIDS, "mac_seeotheruids",
    "mac_seeotheruids(4) security module");

static SYSCTL_NODE(_security_mac, OID_AUTO, seeotheruids,
    CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
    "TrustedBSD mac_seeotheruids policy controls");

static int      seeotheruids_enabled = 1;
SYSCTL_INT(_security_mac_seeotheruids, OID_AUTO, enabled, CTLFLAG_RW,
    &seeotheruids_enabled, 0, "Enforce seeotheruids policy");

/*
 * Exception: allow credentials to be aware of other credentials with the
 * same primary gid.
 */
static int      primarygroup_enabled = 0;
SYSCTL_INT(_security_mac_seeotheruids, OID_AUTO, primarygroup_enabled,
    CTLFLAG_RW, &primarygroup_enabled, 0, "Make an exception for credentials "
    "with the same real primary group id");

/*
 * Exception: allow the root user to be aware of other credentials by virtue
 * of privilege.
 */
static int      suser_privileged = 1;
SYSCTL_INT(_security_mac_seeotheruids, OID_AUTO, suser_privileged,
    CTLFLAG_RW, &suser_privileged, 0, "Make an exception for superuser");

/*
 * Exception: allow processes with a specific gid to be exempt from the
 * policy.  One sysctl enables this functionality; the other sets the
 * exempt gid.
 */
static int      specificgid_enabled = 0;
SYSCTL_INT(_security_mac_seeotheruids, OID_AUTO, specificgid_enabled,
    CTLFLAG_RW, &specificgid_enabled, 0, "Make an exception for credentials "
    "with a specific gid as their real primary group id or group set");

static struct rmlock seeotheruids_rmlock;
RM_SYSINIT_FLAGS(mac_seeotheruids_lock, &seeotheruids_rmlock,
    "mac_seeotheruids_lock", RM_SLEEPABLE);

static gid_t    *specificgids;
static size_t    specificgidcnt;

static int
gidp_cmp(const void *p1, const void *p2)
{
        const gid_t g1 = *(const gid_t *)p1;
        const gid_t g2 = *(const gid_t *)p2;

        return ((g1 > g2) - (g1 < g2));
}

static void
specificgid_normalize(gid_t *gidlist, size_t *ngidp)
{
        int ins_idx;
        gid_t prev_g;

        if (*ngidp < 2)
                return;

        qsort(gidlist, *ngidp, sizeof(*gidlist), gidp_cmp);

        prev_g = gidlist[0];
        ins_idx = 1;
        for (int i = ins_idx; i < *ngidp; ++i) {
                const gid_t g = gidlist[i];

                if (g != prev_g) {
                        if (i != ins_idx)
                                gidlist[ins_idx] = g;
                        ++ins_idx;
                        prev_g = g;
                }
        }

        *ngidp = ins_idx;
}

static int
specificgid_sysctl(SYSCTL_HANDLER_ARGS)
{
        gid_t *newgids = NULL;
        size_t ingidcnt, newgidcnt = 0;
        int error;

        /* Allocate our new gid array before we take our non-sleepable lock. */
        if (req->newptr != NULL) {
                if (req->newlen % sizeof(gid_t) != 0)
                        return (EINVAL);
                ingidcnt = newgidcnt = howmany(req->newlen, sizeof(gid_t));
                newgids = mallocarray(newgidcnt, sizeof(*newgids),
                    M_SEEOTHERUIDS, M_WAITOK);

                error = SYSCTL_IN(req, newgids, newgidcnt * sizeof(*newgids));
                if (error != 0) {
                        free(newgids, M_SEEOTHERUIDS);
                        return (error);
                }

                specificgid_normalize(newgids, &newgidcnt);

                /*
                 * It might be debatable whether shrinking the allocation is
                 * worth it, but we'll do it in the off-chance that someone is
                 * generating specificgid entries from various configuration
                 * sources that won't de-duplicate.
                 */
                if (newgidcnt < ingidcnt) {
                        newgids = realloc(newgids, newgidcnt * sizeof(*newgids),
                            M_SEEOTHERUIDS, M_WAITOK);
                }
        }

        rm_wlock(&seeotheruids_rmlock);

        error = SYSCTL_OUT(req, specificgids,
            specificgidcnt * sizeof(*specificgids));
        if (error == 0 && req->newptr != NULL) {
                free(specificgids, M_SEEOTHERUIDS);

                specificgids = newgids;
                specificgidcnt = newgidcnt;
        } else if (error != 0) {
                free(newgids, M_SEEOTHERUIDS);
        }

        rm_wunlock(&seeotheruids_rmlock);
        return (error);
}
SYSCTL_PROC(_security_mac_seeotheruids, OID_AUTO, specificgid,
    CTLFLAG_RW | CTLTYPE_UINT | CTLFLAG_MPSAFE, 0, 0,
    &specificgid_sysctl, "I",
    "Specific gid(s) to be exempt from seeotheruids policy");

static void
seeotheruids_destroy(struct mac_policy_conf *mpc __unused)
{
        free(specificgids, M_SEEOTHERUIDS);
}

static int
seeotheruids_check(struct ucred *cr1, struct ucred *cr2)
{
        struct rm_priotracker tracker;
        int error = ESRCH;

        if (!seeotheruids_enabled)
                return (0);

        if (primarygroup_enabled) {
                if (cr1->cr_rgid == cr2->cr_rgid)
                        return (0);
        }

        if (cr1->cr_ruid == cr2->cr_ruid)
                return (0);

        if (suser_privileged) {
                if (priv_check_cred(cr1, PRIV_SEEOTHERUIDS) == 0)
                        return (0);
        }

        rm_rlock(&seeotheruids_rmlock, &tracker);
        if (specificgid_enabled && specificgids != NULL) {
                const gid_t *suppgroups = cr1->cr_groups;
                size_t nsupp = cr1->cr_ngroups;

#if __FreeBSD_version < 1500056
                /*
                 * FreeBSD 15.0 changed the cr_groups layout: earlier versions
                 * used cr_groups[0] for the effective GID, but that's somewhat
                 * error-prone when propagated throughout the various parts of
                 * the system (e.g., setgroups/getgroups).  In older versions,
                 * we want to hop over the egid.
                 */
                suppgroups++;
                nsupp--;
#endif

                for (size_t i = 0, s = 0; i < specificgidcnt; i++) {
                        gid_t cgid;

                        cgid = specificgids[i];
                        if (cgid == cr1->cr_rgid) {
                                error = 0;
                                break;
                        }

                        /*
                         * specificgids and suppgroups are both sorted
                         * ascending, so advance past all of the supplemental
                         * groups that are lower than the specificgid we're
                         * currently at.
                         */
                        while (s < nsupp && cgid > suppgroups[s])
                                s++;

                        /*
                         * Out of supplementary groups, but we'll keep checking
                         * for rgid matches.
                         */
                        if (s == nsupp)
                                continue;

                        if (cgid == suppgroups[s]) {
                                error = 0;
                                break;
                        }
                }
        }

        rm_runlock(&seeotheruids_rmlock, &tracker);
        return (error);
}

static int
seeotheruids_proc_check_debug(struct ucred *cred, struct proc *p)
{

        return (seeotheruids_check(cred, p->p_ucred));
}

static int
seeotheruids_proc_check_sched(struct ucred *cred, struct proc *p)
{

        return (seeotheruids_check(cred, p->p_ucred));
}

static int
seeotheruids_proc_check_signal(struct ucred *cred, struct proc *p,
    int signum)
{

        return (seeotheruids_check(cred, p->p_ucred));
}

static int
seeotheruids_cred_check_visible(struct ucred *cr1, struct ucred *cr2)
{

        return (seeotheruids_check(cr1, cr2));
}

static int
seeotheruids_inpcb_check_visible(struct ucred *cred, struct inpcb *inp,
    struct label *inplabel)
{

        return (seeotheruids_check(cred, inp->inp_cred));
}

static int
seeotheruids_socket_check_visible(struct ucred *cred, struct socket *so,
    struct label *solabel)
{

        return (seeotheruids_check(cred, so->so_cred));
}

static struct mac_policy_ops seeotheruids_ops =
{
        .mpo_destroy = seeotheruids_destroy,
        .mpo_proc_check_debug = seeotheruids_proc_check_debug,
        .mpo_proc_check_sched = seeotheruids_proc_check_sched,
        .mpo_proc_check_signal = seeotheruids_proc_check_signal,
        .mpo_cred_check_visible = seeotheruids_cred_check_visible,
        .mpo_inpcb_check_visible = seeotheruids_inpcb_check_visible,
        .mpo_socket_check_visible = seeotheruids_socket_check_visible,
};

MAC_POLICY_SET(&seeotheruids_ops, mac_seeotheruids,
    "TrustedBSD MAC/seeotheruids", MPC_LOADTIME_FLAG_UNLOADOK, NULL);