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      1 /*	$NetBSD: subr_exec_fd.c,v 1.12 2021/06/29 22:40:53 dholland Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 2008 The NetBSD Foundation, Inc.
      5  * All rights reserved.
      6  *
      7  * Redistribution and use in source and binary forms, with or without
      8  * modification, are permitted provided that the following conditions
      9  * are met:
     10  * 1. Redistributions of source code must retain the above copyright
     11  *    notice, this list of conditions and the following disclaimer.
     12  * 2. Redistributions in binary form must reproduce the above copyright
     13  *    notice, this list of conditions and the following disclaimer in the
     14  *    documentation and/or other materials provided with the distribution.
     15  *
     16  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     17  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     18  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     19  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     20  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     21  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     22  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     23  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     24  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     25  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     26  * POSSIBILITY OF SUCH DAMAGE.
     27  */
     28 
     29 #include <sys/cdefs.h>
     30 __KERNEL_RCSID(0, "$NetBSD: subr_exec_fd.c,v 1.12 2021/06/29 22:40:53 dholland Exp $");
     31 
     32 #include <sys/param.h>
     33 #include <sys/atomic.h>
     34 #include <sys/file.h>
     35 #include <sys/filedesc.h>
     36 #include <sys/mutex.h>
     37 #include <sys/namei.h>
     38 #include <sys/syslog.h>
     39 #include <sys/vnode.h>
     40 #include <sys/ktrace.h>
     41 
     42 void
     43 fd_ktrexecfd(void)
     44 {
     45 	proc_t *p;
     46 	filedesc_t *fdp;
     47 	fdfile_t *ff;
     48 	lwp_t *l;
     49 	fdtab_t *dt;
     50 	file_t *fp;
     51 	int fd;
     52 
     53 	l = curlwp;
     54 	p = l->l_proc;
     55 	fdp = p->p_fd;
     56 	dt = atomic_load_consume(&fdp->fd_dt);
     57 
     58 	for (fd = 0; fd <= fdp->fd_lastfile; fd++) {
     59 		if ((ff = dt->dt_ff[fd]) == NULL) {
     60 			KASSERT(fd >= NDFDFILE);
     61 			continue;
     62 		}
     63 		KASSERT(fd >= NDFDFILE ||
     64 		    ff == (fdfile_t *)fdp->fd_dfdfile[fd]);
     65 		if ((fp = atomic_load_consume(&ff->ff_file)) == NULL)
     66 			continue;
     67 		ktr_execfd(fd, fp->f_type);
     68 	}
     69 }
     70 
     71 /*
     72  * It is unsafe for set[ug]id processes to be started with file
     73  * descriptors 0..2 closed, as these descriptors are given implicit
     74  * significance in the Standard C library.  fd_checkstd() will create a
     75  * descriptor referencing /dev/null for each of stdin, stdout, and
     76  * stderr that is not already open.
     77  */
     78 #define CHECK_UPTO 3
     79 int
     80 fd_checkstd(void)
     81 {
     82 	struct proc *p;
     83 	struct pathbuf *pb;
     84 	struct vnode *vp;
     85 	filedesc_t *fdp;
     86 	file_t *fp;
     87 	fdtab_t *dt;
     88 	struct proc *pp;
     89 	int fd, i, error, flags = FREAD|FWRITE;
     90 	char closed[CHECK_UPTO * 3 + 1], which[3 + 1];
     91 
     92 	p = curproc;
     93 	closed[0] = '\0';
     94 	if ((fdp = p->p_fd) == NULL)
     95 		return (0);
     96 	dt = atomic_load_consume(&fdp->fd_dt);
     97 	for (i = 0; i < CHECK_UPTO; i++) {
     98 		KASSERT(i >= NDFDFILE ||
     99 		    dt->dt_ff[i] == (fdfile_t *)fdp->fd_dfdfile[i]);
    100 		if (dt->dt_ff[i]->ff_file != NULL)
    101 			continue;
    102 		snprintf(which, sizeof(which), ",%d", i);
    103 		strlcat(closed, which, sizeof(closed));
    104 		if ((error = fd_allocfile(&fp, &fd)) != 0)
    105 			return (error);
    106 		KASSERT(fd < CHECK_UPTO);
    107 		pb = pathbuf_create("/dev/null");
    108 		if (pb == NULL) {
    109 			return ENOMEM;
    110 		}
    111 		error = vn_open(NULL, pb, 0, flags, 0, &vp, NULL, NULL);
    112 		if (error != 0) {
    113 			pathbuf_destroy(pb);
    114 			fd_abort(p, fp, fd);
    115 			return (error);
    116 		}
    117 		fp->f_type = DTYPE_VNODE;
    118 		fp->f_vnode = vp;
    119 		fp->f_flag = flags;
    120 		fp->f_ops = &vnops;
    121 		VOP_UNLOCK(vp);
    122 		fd_affix(p, fp, fd);
    123 		pathbuf_destroy(pb);
    124 	}
    125 	if (closed[0] != '\0') {
    126 		mutex_enter(&proc_lock);
    127 		pp = p->p_pptr;
    128 		mutex_enter(pp->p_lock);
    129 		log(LOG_WARNING, "set{u,g}id pid %d (%s) "
    130 		    "was invoked by uid %d ppid %d (%s) "
    131 		    "with fd %s closed\n",
    132 		    p->p_pid, p->p_comm, kauth_cred_geteuid(pp->p_cred),
    133 		    pp->p_pid, pp->p_comm, &closed[1]);
    134 		mutex_exit(pp->p_lock);
    135 		mutex_exit(&proc_lock);
    136 	}
    137 	return (0);
    138 }
    139 #undef CHECK_UPTO
    140