xref: /freebsd/usr.bin/brandelf/brandelf.c (revision 2ff63af9b88c7413b7d71715b5532625752a248e)
1 /*-
2  * SPDX-License-Identifier: BSD-3-Clause
3  *
4  * Copyright (c) 2000, 2001 David O'Brien
5  * Copyright (c) 1996 Søren Schmidt
6  * All rights reserved.
7  *
8  * Redistribution and use in source and binary forms, with or without
9  * modification, are permitted provided that the following conditions
10  * are met:
11  * 1. Redistributions of source code must retain the above copyright
12  *    notice, this list of conditions and the following disclaimer
13  *    in this position and unchanged.
14  * 2. Redistributions in binary form must reproduce the above copyright
15  *    notice, this list of conditions and the following disclaimer in the
16  *    documentation and/or other materials provided with the distribution.
17  * 3. The name of the author may not be used to endorse or promote products
18  *    derived from this software without specific prior written permission
19  *
20  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
21  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
22  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
23  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
24  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
25  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
26  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
27  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
28  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
29  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
30  */
31 
32 #include <sys/cdefs.h>
33 __FBSDID("$FreeBSD$");
34 
35 #include <sys/param.h>
36 #include <sys/capsicum.h>
37 #include <sys/elf_common.h>
38 #include <sys/errno.h>
39 
40 #include <capsicum_helpers.h>
41 #include <err.h>
42 #include <fcntl.h>
43 #include <stdbool.h>
44 #include <stdio.h>
45 #include <stdlib.h>
46 #include <string.h>
47 #include <unistd.h>
48 
49 #include <libcasper.h>
50 #include <casper/cap_fileargs.h>
51 
52 static int elftype(const char *);
53 static const char *iselftype(int);
54 static void printelftypes(void);
55 static void usage(void) __dead2;
56 
57 struct ELFtypes {
58 	const char *str;
59 	int value;
60 };
61 /* XXX - any more types? */
62 static struct ELFtypes elftypes[] = {
63 	{ "FreeBSD",	ELFOSABI_FREEBSD },
64 	{ "Linux",	ELFOSABI_LINUX },
65 	{ "Solaris",	ELFOSABI_SOLARIS },
66 	{ "SVR4",	ELFOSABI_SYSV }
67 };
68 
69 int
70 main(int argc, char **argv)
71 {
72 
73 	const char *strtype = "FreeBSD";
74 	int ch, flags, retval, type;
75 	bool change, force, listed;
76 	fileargs_t *fa;
77 	cap_rights_t rights;
78 
79 	type = ELFOSABI_FREEBSD;
80 	retval = 0;
81 	change = false;
82 	force = false;
83 	listed = false;
84 
85 	while ((ch = getopt(argc, argv, "f:lt:v")) != -1)
86 		switch (ch) {
87 		case 'f':
88 			if (change)
89 				errx(1, "f option incompatible with t option");
90 			force = true;
91 			type = atoi(optarg);
92 			if (errno == ERANGE || type < 0 || type > 255) {
93 				warnx("invalid argument to option f: %s",
94 				    optarg);
95 				usage();
96 			}
97 			break;
98 		case 'l':
99 			printelftypes();
100 			listed = true;
101 			break;
102 		case 'v':
103 			/* does nothing */
104 			break;
105 		case 't':
106 			if (force)
107 				errx(1, "t option incompatible with f option");
108 			change = true;
109 			strtype = optarg;
110 			break;
111 		default:
112 			usage();
113 	}
114 	argc -= optind;
115 	argv += optind;
116 	if (argc == 0) {
117 		if (listed)
118 			exit(0);
119 		else {
120 			warnx("no file(s) specified");
121 			usage();
122 		}
123 	}
124 
125 	if (!force && (type = elftype(strtype)) == -1) {
126 		warnx("invalid ELF type '%s'", strtype);
127 		printelftypes();
128 		usage();
129 	}
130 
131 	flags = change || force ? O_RDWR : O_RDONLY;
132 	cap_rights_init(&rights, CAP_READ, CAP_SEEK);
133 	if (flags == O_RDWR)
134 		cap_rights_set(&rights, CAP_WRITE);
135 
136 	fa = fileargs_init(argc, argv, flags, 0, &rights, FA_OPEN);
137 	if (fa == NULL)
138 		err(1, "unable to init casper");
139 
140 	caph_cache_catpages();
141 	if (caph_limit_stdio() < 0 || caph_enter_casper() < 0)
142 		err(1, "unable to enter capability mode");
143 
144 	while (argc != 0) {
145 		int fd;
146 		char buffer[EI_NIDENT];
147 
148 		if ((fd = fileargs_open(fa, argv[0])) < 0) {
149 			warn("error opening file %s", argv[0]);
150 			retval = 1;
151 			goto fail;
152 		}
153 		if (read(fd, buffer, EI_NIDENT) < EI_NIDENT) {
154 			warnx("file '%s' too short", argv[0]);
155 			retval = 1;
156 			goto fail;
157 		}
158 		if (buffer[0] != ELFMAG0 || buffer[1] != ELFMAG1 ||
159 		    buffer[2] != ELFMAG2 || buffer[3] != ELFMAG3) {
160 			warnx("file '%s' is not ELF format", argv[0]);
161 			retval = 1;
162 			goto fail;
163 		}
164 		if (!change && !force) {
165 			fprintf(stdout,
166 				"File '%s' is of brand '%s' (%u).\n",
167 				argv[0], iselftype(buffer[EI_OSABI]),
168 				buffer[EI_OSABI]);
169 			if (!iselftype(type)) {
170 				warnx("ELF ABI Brand '%u' is unknown",
171 				      type);
172 				printelftypes();
173 			}
174 		}
175 		else {
176 			buffer[EI_OSABI] = type;
177 			lseek(fd, 0, SEEK_SET);
178 			if (write(fd, buffer, EI_NIDENT) != EI_NIDENT) {
179 				warn("error writing %s %d", argv[0], fd);
180 				retval = 1;
181 				goto fail;
182 			}
183 		}
184 fail:
185 		close(fd);
186 		argc--;
187 		argv++;
188 	}
189 
190 	fileargs_free(fa);
191 	return (retval);
192 }
193 
194 static void
195 usage(void)
196 {
197 	(void)fprintf(stderr,
198 	    "usage: brandelf [-lv] [-f ELF_ABI_number] [-t string] file ...\n");
199 	exit(1);
200 }
201 
202 static const char *
203 iselftype(int etype)
204 {
205 	size_t elfwalk;
206 
207 	for (elfwalk = 0; elfwalk < nitems(elftypes); elfwalk++)
208 		if (etype == elftypes[elfwalk].value)
209 			return (elftypes[elfwalk].str);
210 	return (0);
211 }
212 
213 static int
214 elftype(const char *elfstrtype)
215 {
216 	size_t elfwalk;
217 
218 	for (elfwalk = 0; elfwalk < nitems(elftypes); elfwalk++)
219 		if (strcasecmp(elfstrtype, elftypes[elfwalk].str) == 0)
220 			return (elftypes[elfwalk].value);
221 	return (-1);
222 }
223 
224 static void
225 printelftypes(void)
226 {
227 	size_t elfwalk;
228 
229 	fprintf(stderr, "known ELF types are: ");
230 	for (elfwalk = 0; elfwalk < nitems(elftypes); elfwalk++)
231 		fprintf(stderr, "%s(%u) ", elftypes[elfwalk].str,
232 		    elftypes[elfwalk].value);
233 	fprintf(stderr, "\n");
234 }
235