/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2011, David E. O'Brien.
 * Copyright (c) 2009-2011, Juniper Networks, Inc.
 * Copyright (c) 2015-2016, EMC Corp.
 * 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.
 *
 * THIS SOFTWARE IS PROVIDED BY JUNIPER NETWORKS 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 JUNIPER NETWORKS 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.
 */

#include <sys/cdefs.h>
#include <sys/eventhandler.h>
#include <sys/filedesc.h>
#include <sys/imgact.h>
#include <sys/priv.h>
#include <sys/stdarg.h>
#include <sys/sx.h>
#include <sys/sysent.h>
#include <sys/vnode.h>

static void filemon_output_event(struct filemon *filemon, const char *fmt, ...)
    __printflike(2, 3);

static eventhandler_tag filemon_exec_tag;
static eventhandler_tag filemon_exit_tag;
static eventhandler_tag filemon_fork_tag;

static void
filemon_output(struct filemon *filemon, char *msg, size_t len)
{
        struct uio auio;
        struct iovec aiov;
        int error;

        if (filemon->fp == NULL)
                return;

        aiov.iov_base = msg;
        aiov.iov_len = len;
        auio.uio_iov = &aiov;
        auio.uio_iovcnt = 1;
        auio.uio_resid = len;
        auio.uio_segflg = UIO_SYSSPACE;
        auio.uio_rw = UIO_WRITE;
        auio.uio_td = curthread;
        auio.uio_offset = (off_t) -1;

        if (filemon->fp->f_type == DTYPE_VNODE)
                bwillwrite();

        error = fo_write(filemon->fp, &auio, filemon->cred, 0, curthread);
        if (error != 0 && filemon->error == 0)
                filemon->error = error;
}

static void
filemon_output_event(struct filemon *filemon, const char *fmt, ...)
{
        va_list ap;
        size_t len;

        va_start(ap, fmt);
        len = vsnprintf(filemon->msgbufr, sizeof(filemon->msgbufr), fmt, ap);
        va_end(ap);
        /* The event is truncated but still worth logging. */
        if (len >= sizeof(filemon->msgbufr))
                len = sizeof(filemon->msgbufr) - 1;
        filemon_output(filemon, filemon->msgbufr, len);
}

static int
filemon_wrapper_chdir(struct thread *td, struct chdir_args *uap)
{
        int error, ret;
        struct filemon *filemon;

        if ((ret = sys_chdir(td, uap)) == 0) {
                if ((filemon = filemon_proc_get(curproc)) != NULL) {
                        if ((error = copyinstr(uap->path, filemon->fname1,
                            sizeof(filemon->fname1), NULL)) != 0) {
                                filemon->error = error;
                                goto copyfail;
                        }

                        filemon_output_event(filemon, "C %d %s\n",
                            curproc->p_pid, filemon->fname1);
copyfail:
                        filemon_drop(filemon);
                }
        }

        return (ret);
}

static void
filemon_event_process_exec(void *arg __unused, struct proc *p,
    struct image_params *imgp)
{
        struct filemon *filemon;

        if ((filemon = filemon_proc_get(p)) != NULL) {
                filemon_output_event(filemon, "E %d %s\n",
                    p->p_pid,
                    imgp->execpath != NULL ? imgp->execpath : "<unknown>");

                /* If the credentials changed then cease tracing. */
                if (imgp->newcred != NULL &&
                    imgp->credential_setid &&
                    priv_check_cred(filemon->cred, PRIV_DEBUG_DIFFCRED) != 0) {
                        /*
                         * It may have changed to NULL already, but
                         * will not be re-attached by anything else.
                         */
                        if (p->p_filemon != NULL) {
                                KASSERT(p->p_filemon == filemon,
                                    ("%s: proc %p didn't have expected"
                                    " filemon %p", __func__, p, filemon));
                                filemon_proc_drop(p);
                        }
                }


                filemon_drop(filemon);
        }
}

static void
_filemon_wrapper_openat(struct thread *td, const char *upath, int flags,
    int fd)
{
        int error;
        struct file *fp;
        struct filemon *filemon;
        char *atpath, *freepath;
        cap_rights_t rights;

        if ((filemon = filemon_proc_get(curproc)) != NULL) {
                atpath = "";
                freepath = NULL;
                fp = NULL;

                if ((error = copyinstr(upath, filemon->fname1,
                    sizeof(filemon->fname1), NULL)) != 0) {
                        filemon->error = error;
                        goto copyfail;
                }

                if (filemon->fname1[0] != '/' && fd != AT_FDCWD) {
                        /*
                         * rats - we cannot do too much about this.
                         * the trace should show a dir we read
                         * recently.. output an A record as a clue
                         * until we can do better.
                         * XXX: This may be able to come out with
                         * the namecache lookup now.
                         */
                        filemon_output_event(filemon, "A %d %s\n",
                            curproc->p_pid, filemon->fname1);
                        /*
                         * Try to resolve the path from the vnode using the
                         * namecache.  It may be inaccurate, but better
                         * than nothing.
                         */
                        if (getvnode(td, fd,
                            cap_rights_init_one(&rights, CAP_LOOKUP), &fp) == 0) {
                                vn_fullpath(fp->f_vnode, &atpath, &freepath);
                        }
                }
                if (flags & O_RDWR) {
                        /*
                         * We'll get the W record below, but need
                         * to also output an R to distinguish from
                         * O_WRONLY.
                         */
                        filemon_output_event(filemon, "R %d %s%s%s\n",
                            curproc->p_pid, atpath,
                            atpath[0] != '\0' ? "/" : "", filemon->fname1);
                }

                filemon_output_event(filemon, "%c %d %s%s%s\n",
                    (flags & O_ACCMODE) ? 'W':'R',
                    curproc->p_pid, atpath,
                    atpath[0] != '\0' ? "/" : "", filemon->fname1);
copyfail:
                filemon_drop(filemon);
                if (fp != NULL)
                        fdrop(fp, td);
                free(freepath, M_TEMP);
        }
}

static int
filemon_wrapper_open(struct thread *td, struct open_args *uap)
{
        int ret;

        if ((ret = sys_open(td, uap)) == 0)
                _filemon_wrapper_openat(td, uap->path, uap->flags, AT_FDCWD);

        return (ret);
}

static int
filemon_wrapper_openat(struct thread *td, struct openat_args *uap)
{
        int ret;

        if ((ret = sys_openat(td, uap)) == 0)
                _filemon_wrapper_openat(td, uap->path, uap->flag, uap->fd);

        return (ret);
}

static int
filemon_wrapper_rename(struct thread *td, struct rename_args *uap)
{
        int error, ret;
        struct filemon *filemon;

        if ((ret = sys_rename(td, uap)) == 0) {
                if ((filemon = filemon_proc_get(curproc)) != NULL) {
                        if (((error = copyinstr(uap->from, filemon->fname1,
                             sizeof(filemon->fname1), NULL)) != 0) ||
                            ((error = copyinstr(uap->to, filemon->fname2,
                             sizeof(filemon->fname2), NULL)) != 0)) {
                                filemon->error = error;
                                goto copyfail;
                        }

                        filemon_output_event(filemon, "M %d '%s' '%s'\n",
                            curproc->p_pid, filemon->fname1, filemon->fname2);
copyfail:
                        filemon_drop(filemon);
                }
        }

        return (ret);
}

static void
_filemon_wrapper_link(struct thread *td, const char *upath1,
    const char *upath2)
{
        struct filemon *filemon;
        int error;

        if ((filemon = filemon_proc_get(curproc)) != NULL) {
                if (((error = copyinstr(upath1, filemon->fname1,
                     sizeof(filemon->fname1), NULL)) != 0) ||
                    ((error = copyinstr(upath2, filemon->fname2,
                     sizeof(filemon->fname2), NULL)) != 0)) {
                        filemon->error = error;
                        goto copyfail;
                }

                filemon_output_event(filemon, "L %d '%s' '%s'\n",
                    curproc->p_pid, filemon->fname1, filemon->fname2);
copyfail:
                filemon_drop(filemon);
        }
}

static int
filemon_wrapper_link(struct thread *td, struct link_args *uap)
{
        int ret;

        if ((ret = sys_link(td, uap)) == 0)
                _filemon_wrapper_link(td, uap->path, uap->link);

        return (ret);
}

static int
filemon_wrapper_symlink(struct thread *td, struct symlink_args *uap)
{
        int ret;

        if ((ret = sys_symlink(td, uap)) == 0)
                _filemon_wrapper_link(td, uap->path, uap->link);

        return (ret);
}

static int
filemon_wrapper_linkat(struct thread *td, struct linkat_args *uap)
{
        int ret;

        if ((ret = sys_linkat(td, uap)) == 0)
                _filemon_wrapper_link(td, uap->path1, uap->path2);

        return (ret);
}

static void
filemon_event_process_exit(void *arg __unused, struct proc *p)
{
        struct filemon *filemon;

        if ((filemon = filemon_proc_get(p)) != NULL) {
                filemon_output_event(filemon, "X %d %d %d\n",
                    p->p_pid, p->p_xexit, p->p_xsig);

                /*
                 * filemon_untrack_processes() may have dropped this p_filemon
                 * already while in filemon_proc_get() before acquiring the
                 * filemon lock.
                 */
                KASSERT(p->p_filemon == NULL || p->p_filemon == filemon,
                    ("%s: p %p was attached while exiting, expected "
                    "filemon %p or NULL", __func__, p, filemon));
                if (p->p_filemon == filemon)
                        filemon_proc_drop(p);

                filemon_drop(filemon);
        }
}

static int
filemon_wrapper_unlink(struct thread *td, struct unlink_args *uap)
{
        int error, ret;
        struct filemon *filemon;

        if ((ret = sys_unlink(td, uap)) == 0) {
                if ((filemon = filemon_proc_get(curproc)) != NULL) {
                        if ((error = copyinstr(uap->path, filemon->fname1,
                            sizeof(filemon->fname1), NULL)) != 0) {
                                filemon->error = error;
                                goto copyfail;
                        }

                        filemon_output_event(filemon, "D %d %s\n",
                            curproc->p_pid, filemon->fname1);
copyfail:
                        filemon_drop(filemon);
                }
        }

        return (ret);
}

static void
filemon_event_process_fork(void *arg __unused, struct proc *p1,
    struct proc *p2, int flags __unused)
{
        struct filemon *filemon;

        if ((filemon = filemon_proc_get(p1)) != NULL) {
                filemon_output_event(filemon, "F %d %d\n",
                    p1->p_pid, p2->p_pid);

                /*
                 * filemon_untrack_processes() or
                 * filemon_ioctl(FILEMON_SET_PID) may have changed the parent's
                 * p_filemon while in filemon_proc_get() before acquiring the
                 * filemon lock.  Only inherit if the parent is still traced by
                 * this filemon.
                 */
                if (p1->p_filemon == filemon) {
                        PROC_LOCK(p2);
                        /*
                         * It may have been attached to already by a new
                         * filemon.
                         */
                        if (p2->p_filemon == NULL) {
                                p2->p_filemon = filemon_acquire(filemon);
                                ++filemon->proccnt;
                        }
                        PROC_UNLOCK(p2);
                }

                filemon_drop(filemon);
        }
}

static void
filemon_wrapper_install(void)
{

        sysent[SYS_chdir].sy_call = (sy_call_t *) filemon_wrapper_chdir;
        sysent[SYS_open].sy_call = (sy_call_t *) filemon_wrapper_open;
        sysent[SYS_openat].sy_call = (sy_call_t *) filemon_wrapper_openat;
        sysent[SYS_rename].sy_call = (sy_call_t *) filemon_wrapper_rename;
        sysent[SYS_unlink].sy_call = (sy_call_t *) filemon_wrapper_unlink;
        sysent[SYS_link].sy_call = (sy_call_t *) filemon_wrapper_link;
        sysent[SYS_symlink].sy_call = (sy_call_t *) filemon_wrapper_symlink;
        sysent[SYS_linkat].sy_call = (sy_call_t *) filemon_wrapper_linkat;

#if defined(COMPAT_FREEBSD32)
        freebsd32_sysent[FREEBSD32_SYS_chdir].sy_call = (sy_call_t *) filemon_wrapper_chdir;
        freebsd32_sysent[FREEBSD32_SYS_open].sy_call = (sy_call_t *) filemon_wrapper_open;
        freebsd32_sysent[FREEBSD32_SYS_openat].sy_call = (sy_call_t *) filemon_wrapper_openat;
        freebsd32_sysent[FREEBSD32_SYS_rename].sy_call = (sy_call_t *) filemon_wrapper_rename;
        freebsd32_sysent[FREEBSD32_SYS_unlink].sy_call = (sy_call_t *) filemon_wrapper_unlink;
        freebsd32_sysent[FREEBSD32_SYS_link].sy_call = (sy_call_t *) filemon_wrapper_link;
        freebsd32_sysent[FREEBSD32_SYS_symlink].sy_call = (sy_call_t *) filemon_wrapper_symlink;
        freebsd32_sysent[FREEBSD32_SYS_linkat].sy_call = (sy_call_t *) filemon_wrapper_linkat;
#endif  /* COMPAT_FREEBSD32 */

        filemon_exec_tag = EVENTHANDLER_REGISTER(process_exec,
            filemon_event_process_exec, NULL, EVENTHANDLER_PRI_LAST);
        filemon_exit_tag = EVENTHANDLER_REGISTER(process_exit,
            filemon_event_process_exit, NULL, EVENTHANDLER_PRI_LAST);
        filemon_fork_tag = EVENTHANDLER_REGISTER(process_fork,
            filemon_event_process_fork, NULL, EVENTHANDLER_PRI_LAST);
}

static void
filemon_wrapper_deinstall(void)
{

        sysent[SYS_chdir].sy_call = (sy_call_t *)sys_chdir;
        sysent[SYS_open].sy_call = (sy_call_t *)sys_open;
        sysent[SYS_openat].sy_call = (sy_call_t *)sys_openat;
        sysent[SYS_rename].sy_call = (sy_call_t *)sys_rename;
        sysent[SYS_unlink].sy_call = (sy_call_t *)sys_unlink;
        sysent[SYS_link].sy_call = (sy_call_t *)sys_link;
        sysent[SYS_symlink].sy_call = (sy_call_t *)sys_symlink;
        sysent[SYS_linkat].sy_call = (sy_call_t *)sys_linkat;

#if defined(COMPAT_FREEBSD32)
        freebsd32_sysent[FREEBSD32_SYS_chdir].sy_call = (sy_call_t *)sys_chdir;
        freebsd32_sysent[FREEBSD32_SYS_open].sy_call = (sy_call_t *)sys_open;
        freebsd32_sysent[FREEBSD32_SYS_openat].sy_call = (sy_call_t *)sys_openat;
        freebsd32_sysent[FREEBSD32_SYS_rename].sy_call = (sy_call_t *)sys_rename;
        freebsd32_sysent[FREEBSD32_SYS_unlink].sy_call = (sy_call_t *)sys_unlink;
        freebsd32_sysent[FREEBSD32_SYS_link].sy_call = (sy_call_t *)sys_link;
        freebsd32_sysent[FREEBSD32_SYS_symlink].sy_call = (sy_call_t *)sys_symlink;
        freebsd32_sysent[FREEBSD32_SYS_linkat].sy_call = (sy_call_t *)sys_linkat;
#endif  /* COMPAT_FREEBSD32 */

        EVENTHANDLER_DEREGISTER(process_exec, filemon_exec_tag);
        EVENTHANDLER_DEREGISTER(process_exit, filemon_exit_tag);
        EVENTHANDLER_DEREGISTER(process_fork, filemon_fork_tag);
}