1/*
2 * SPDX-License-Identifier: BSD-2-Clause
3 *
4 * Copyright (c) 2019-2023, Juniper Networks, 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 AUTHOR ``AS IS'' AND ANY EXPRESS OR
17 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
18 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
19 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
21 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
22 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
23 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
24 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 */
28
29#include <sys/types.h>
30#include <sys/param.h>
31#include <sys/errno.h>
32#include <sys/mac.h>
33
34#include <unistd.h>
35#include <fcntl.h>
36#include <string.h>
37#include <syslog.h>
38
39#include <security/mac_grantbylabel/mac_grantbylabel.h>
40
41#include "libveriexec.h"
42
43static char *
44find_interpreter(const char *script)
45{
46	static const char ws[] = " \t\n\r";
47	static char buf[MAXPATHLEN+4];	/* allow space for #! etc */
48	char *cp;
49	int fd;
50	int n;
51
52	cp = NULL;
53	if ((fd = open(script, O_RDONLY)) >= 0) {
54		if ((n = read(fd, buf, sizeof(buf))) > 0) {
55			if (strncmp(buf, "#!", 2) == 0) {
56				buf[sizeof(buf) - 1] = '\0';
57				cp = &buf[2];
58				if ((n = strspn(cp, ws)) > 0)
59					cp += n;
60				if ((n = strcspn(cp, ws)) > 0) {
61					cp[n] = '\0';
62				} else {
63					cp = NULL;
64				}
65			}
66		}
67		close(fd);
68	}
69	return (cp);
70}
71
72/**
73 * @brief exec a python or similar script
74 *
75 * Python and similar scripts must normally be signed and
76 * run directly rather than fed to the interpreter which
77 * is not normally allowed to be run directly.
78 *
79 * If direct execv of script fails due to EAUTH
80 * and process has GBL_VERIEXEC syslog event and run via
81 * interpreter.
82 *
83 * If interpreter is NULL look at first block of script
84 * to find ``#!`` magic.
85 *
86 * @prarm[in] interpreter
87 *	if NULL, extract from script if necessary
88 *
89 * @prarm[in] argv
90 *	argv for execv(2)
91 *	argv[0] must be full path.
92 *	Python at least requires argv[1] to also be the script path.
93 *
94 * @return
95 * error on failure usually EPERM or EAUTH
96 */
97int
98execv_script(const char *interpreter, char * const *argv)
99{
100	const char *script;
101	int rc;
102
103	script = argv[0];
104	if (veriexec_check_path(script) == 0) {
105		rc = execv(script, argv);
106	}
107	/* still here? we might be allowed to run via interpreter */
108	if (gbl_check_pid(0) & GBL_VERIEXEC) {
109		if (!interpreter)
110			interpreter = find_interpreter(script);
111		if (interpreter) {
112			syslog(LOG_NOTICE, "running %s via %s",
113			    script, interpreter);
114			rc = execv(interpreter, argv);
115		}
116	}
117	return (rc);
118}
119
120#if defined(MAIN) || defined(UNIT_TEST)
121#include <sys/wait.h>
122#include <err.h>
123
124int
125main(int argc __unused, char *argv[])
126{
127	const char *interp;
128	int c;
129	int s;
130	pid_t child;
131
132	openlog("exec_script", LOG_PID|LOG_PERROR, LOG_DAEMON);
133
134	interp = NULL;
135	while ((c = getopt(argc, argv, "i:")) != -1) {
136		switch (c) {
137		case 'i':
138			interp = optarg;
139			break;
140		default:
141			errx(1, "unknown option: -%c", c);
142			break;
143		}
144	}
145	argc -= optind;
146	argv += optind;
147	/* we need a child */
148	child = fork();
149	if (child < 0)
150		err(2, "fork");
151	if (child == 0) {
152		c = execv_script(interp, argv);
153		err(2, "exec_script(%s,%s)", interp, argv[0]);
154	}
155	c = waitpid(child, &s, 0);
156	printf("%s: exit %d\n", argv[0], WEXITSTATUS(s));
157	return (0);
158}
159#endif
160