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paxctl.c revision 1.12 
      1 /* $NetBSD: paxctl.c,v 1.12 2009/10/27 16:27:47 christos Exp $ */
      2 
      3 /*-
      4  * Copyright (c) 2006 Elad Efrat <elad (at) NetBSD.org>
      5  * Copyright (c) 2008 Christos Zoulas <christos (at) NetBSD.org>
      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  * 2. Redistributions in binary form must reproduce the above copyright
     14  *    notice, this list of conditions and the following disclaimer in the
     15  *    documentation and/or other materials provided with the distribution.
     16  * 3. The name of the author may not be used to endorse or promote products
     17  *    derived from this software without specific prior written permission.
     18  *
     19  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
     20  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
     21  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
     22  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
     23  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
     24  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     25  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     26  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     27  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
     28  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     29  */
     30 #if HAVE_NBTOOL_CONFIG_H
     31 #include "nbtool_config.h"
     32 #endif
     33 
     34 #include <sys/cdefs.h>
     35 #ifndef lint
     36 #ifdef __RCSID
     37 __RCSID("$NetBSD: paxctl.c,v 1.12 2009/10/27 16:27:47 christos Exp $");
     38 #endif
     39 #endif /* not lint */
     40 
     41 #include <sys/types.h>
     42 #ifdef HAVE_NBTOOL_CONFIG_H
     43 #include "../../sys/sys/exec_elf.h"
     44 #else
     45 #include <elf.h>
     46 #endif
     47 #include <stdio.h>
     48 #include <err.h>
     49 #include <fcntl.h>
     50 #include <unistd.h>
     51 #include <stdlib.h>
     52 #include <string.h>
     53 
     54 static void usage(void) __dead;
     55 static uint32_t pax_flag(char);
     56 static int pax_flags_sane(uint32_t);
     57 static int pax_haveflags(uint32_t);
     58 static void pax_printflags(const char *, int, uint32_t);
     59 
     60 #ifndef ELF_NOTE_TYPE_PAX_TAG
     61 /* NetBSD-specific note type: PaX.  There should be 1 NOTE per executable.
     62    section.  desc is a 32 bit bitmask */
     63 #define ELF_NOTE_TYPE_PAX_TAG		3
     64 #define	ELF_NOTE_PAX_MPROTECT		0x01	/* Force enable MPROTECT */
     65 #define	ELF_NOTE_PAX_NOMPROTECT		0x02	/* Force disable MPROTECT */
     66 #define	ELF_NOTE_PAX_GUARD		0x04	/* Force enable Segvguard */
     67 #define	ELF_NOTE_PAX_NOGUARD		0x08	/* Force disable Segvguard */
     68 #define	ELF_NOTE_PAX_ASLR		0x10	/* Force enable ASLR */
     69 #define	ELF_NOTE_PAX_NOASLR		0x20	/* Force disable ASLR */
     70 #define ELF_NOTE_PAX_NAMESZ		4
     71 #define ELF_NOTE_PAX_NAME		"PaX\0"
     72 #define ELF_NOTE_PAX_DESCSZ		4
     73 #endif
     74 #ifndef __arraycount
     75 #define __arraycount(a) (sizeof(a) / sizeof(a[0]))
     76 #endif
     77 
     78 
     79 static const struct paxflag {
     80 	char mark;
     81 	const char *name;
     82 	uint32_t bits;
     83 } flags[] = {
     84 	{ 'A', "ASLR, explicit enable",
     85 	  ELF_NOTE_PAX_ASLR },
     86 	{ 'a', "ASLR, explicit disable",
     87 	  ELF_NOTE_PAX_NOASLR },
     88 	{ 'G', "Segvguard, explicit enable",
     89 	  ELF_NOTE_PAX_GUARD },
     90 	{ 'g', "Segvguard, explicit disable",
     91 	  ELF_NOTE_PAX_NOGUARD },
     92 	{ 'M', "mprotect(2) restrictions, explicit enable",
     93 	  ELF_NOTE_PAX_MPROTECT },
     94 	{ 'm', "mprotect(2) restrictions, explicit disable",
     95 	  ELF_NOTE_PAX_NOMPROTECT },
     96 };
     97 
     98 static void
     99 usage(void)
    100 {
    101 	(void)fprintf(stderr, "Usage: %s [ <-|+><A|a|G|g|M|m> ] <file> ...\n",
    102 #if HAVE_NBTOOL_CONFIG_H
    103 	    "paxctl"
    104 #else
    105 	    getprogname()
    106 #endif
    107 	);
    108 	exit(1);
    109 }
    110 
    111 static uint32_t
    112 pax_flag(char s)
    113 {
    114 	size_t i;
    115 
    116 	if (s == '\0')
    117 		return (uint32_t)-1;
    118 
    119 	for (i = 0; i < __arraycount(flags); i++)
    120 		if (s == flags[i].mark)
    121 			return flags[i].bits;
    122 
    123 	return (uint32_t)-1;
    124 }
    125 
    126 static int
    127 pax_flags_sane(uint32_t f)
    128 {
    129 	size_t i;
    130 
    131 	for (i = 0; i < __arraycount(flags) - 1; i += 2) {
    132 		uint32_t g = flags[i].bits | flags[i+1].bits;
    133 		if ((f & g) == g)
    134 			return 0;
    135 	}
    136 
    137 	return 1;
    138 }
    139 
    140 static int
    141 pax_haveflags(uint32_t f)
    142 {
    143 	size_t i;
    144 
    145 	for (i = 0; i < __arraycount(flags); i++)
    146 		if (f & flags[i].bits)
    147 			return (1);
    148 
    149 	return (0);
    150 }
    151 
    152 static void
    153 pax_printflags(const char *name, int many, uint32_t f)
    154 {
    155 	size_t i;
    156 
    157 	for (i = 0; i < __arraycount(flags); i++)
    158 		if (f & flags[i].bits) {
    159 			if (many)
    160 				(void)printf("%s: ", name);
    161 			(void)printf("  %c: %s\n",
    162 			    flags[i].mark, flags[i].name);
    163 		}
    164 }
    165 
    166 static int
    167 process_one(const char *name, uint32_t add_flags, uint32_t del_flags,
    168     int list, int many)
    169 {
    170 	union {
    171 	    Elf32_Ehdr h32;
    172 	    Elf64_Ehdr h64;
    173 	} e;
    174 	union {
    175 	    Elf32_Shdr h32;
    176 	    Elf64_Shdr h64;
    177 	} s;
    178 	union {
    179 	    Elf32_Nhdr h32;
    180 	    Elf64_Nhdr h64;
    181 	} n;
    182 #define SWAP(a)	(swap == 0 ? (a) : \
    183     /*LINTED*/(sizeof(a) == 1 ? (a) : \
    184     /*LINTED*/(sizeof(a) == 2 ? bswap16(a) : \
    185     /*LINTED*/(sizeof(a) == 4 ? bswap32(a) : \
    186     /*LINTED*/(sizeof(a) == 8 ? bswap64(a) : (abort(), (a)))))))
    187 #define EH(field)	(size == 32 ? SWAP(e.h32.field) : SWAP(e.h64.field))
    188 #define SH(field)	(size == 32 ? SWAP(s.h32.field) : SWAP(s.h64.field))
    189 #define NH(field)	(size == 32 ? SWAP(n.h32.field) : SWAP(n.h64.field))
    190 #define SHSIZE		(size == 32 ? sizeof(s.h32) : sizeof(s.h64))
    191 #define NHSIZE		(size == 32 ? sizeof(n.h32) : sizeof(n.h64))
    192 	struct {
    193 		char name[ELF_NOTE_PAX_NAMESZ];
    194 		uint32_t flags;
    195 	} pax_tag;
    196 	int fd, size, ok = 0, flagged = 0, swap, error = 1;
    197 	size_t i;
    198 
    199 	fd = open(name, list ? O_RDONLY: O_RDWR, 0);
    200 	if (fd == -1) {
    201 		warn("Can't open `%s'", name);
    202 		return error;
    203 	}
    204 
    205 	if (read(fd, &e, sizeof(e)) != sizeof(e)) {
    206 		warn("Can't read ELF header from `%s'", name);
    207 		goto out;
    208 	}
    209 
    210 	if (memcmp(e.h32.e_ident, ELFMAG, SELFMAG) != 0) {
    211 		warnx("Bad ELF magic from `%s' (maybe it's not an ELF?)", name);
    212 		goto out;
    213 	}
    214 
    215 	if (e.h32.e_ehsize == sizeof(e.h32)) {
    216 		size = 32;
    217 		swap = 0;
    218 	} else if (e.h64.e_ehsize == sizeof(e.h64)) {
    219 		size = 64;
    220 		swap = 0;
    221 	} else if (bswap16(e.h32.e_ehsize) == sizeof(e.h32)) {
    222 		size = 32;
    223 		swap = 1;
    224 	} else if (bswap16(e.h64.e_ehsize) == sizeof(e.h64)) {
    225 		size = 64;
    226 		swap = 1;
    227 	} else {
    228 		warnx("Bad ELF size %d from `%s' (maybe it's not an ELF?)",
    229 		    (int)e.h32.e_ehsize, name);
    230 		goto out;
    231 	}
    232 
    233 	for (i = 0; i < EH(e_shnum); i++) {
    234 		if ((size_t)pread(fd, &s, SHSIZE,
    235 		    (off_t)EH(e_shoff) + i * SHSIZE) != SHSIZE) {
    236 			warn("Can't read section header data from `%s'", name);
    237 			goto out;
    238 		}
    239 
    240 		if (SH(sh_type) != SHT_NOTE)
    241 			continue;
    242 
    243 		if (pread(fd, &n, NHSIZE, (off_t)SH(sh_offset)) != NHSIZE) {
    244 			warn("Can't read note header from `%s'", name);
    245 			goto out;
    246 		}
    247 		if (NH(n_type) != ELF_NOTE_TYPE_PAX_TAG ||
    248 		    NH(n_descsz) != ELF_NOTE_PAX_DESCSZ ||
    249 		    NH(n_namesz) != ELF_NOTE_PAX_NAMESZ)
    250 			continue;
    251 		if (pread(fd, &pax_tag, sizeof(pax_tag), SH(sh_offset) + NHSIZE)
    252 		    != sizeof(pax_tag)) {
    253 			warn("Can't read pax_tag from `%s'", name);
    254 			goto out;
    255 		}
    256 		if (memcmp(pax_tag.name, ELF_NOTE_PAX_NAME,
    257 		    sizeof(pax_tag.name)) != 0) {
    258 			warn("Unknown pax_tag name `%*.*s' from `%s'",
    259 			    ELF_NOTE_PAX_NAMESZ, ELF_NOTE_PAX_NAMESZ,
    260 			    pax_tag.name, name);
    261 			goto out;
    262 		}
    263 		ok = 1;
    264 
    265 		if (list) {
    266 			if (!pax_haveflags(SWAP(pax_tag.flags)))
    267 				break;
    268 
    269 			if (!pax_flags_sane(SWAP(pax_tag.flags)))
    270 				warnx("Current flags 0x%x don't make sense",
    271 				    (uint32_t)SWAP(pax_tag.flags));
    272 
    273 			if (many)
    274 				(void)printf("%s: ", name);
    275 			(void)printf("PaX flags:\n");
    276 
    277 			pax_printflags(name, many, SWAP(pax_tag.flags));
    278 			flagged = 1;
    279 			break;
    280 		}
    281 
    282 		pax_tag.flags |= SWAP(add_flags);
    283 		pax_tag.flags &= SWAP(~del_flags);
    284 
    285 		if (!pax_flags_sane(SWAP(pax_tag.flags))) {
    286 			warnx("New flags 0x%x don't make sense",
    287 			    (uint32_t)SWAP(pax_tag.flags));
    288 			goto out;
    289 		}
    290 
    291 		if (pwrite(fd, &pax_tag, sizeof(pax_tag),
    292 		    (off_t)SH(sh_offset) + NHSIZE) != sizeof(pax_tag))
    293 			warn("Can't modify flags on `%s'", name);
    294 		break;
    295 	}
    296 
    297 	if (!ok) {
    298 		warnx("Could not find an ELF PaX SHT_NOTE section in `%s'",
    299 		    name);
    300 		goto out;
    301 	}
    302 
    303 	error = 0;
    304 	if (list && !flagged) {
    305 		if (many)
    306 			(void)printf("%s: ", name);
    307 		(void)printf("No PaX flags.\n");
    308 	}
    309 out:
    310 	(void)close(fd);
    311 	return error;
    312 }
    313 
    314 int
    315 main(int argc, char **argv)
    316 {
    317 	char *opt;
    318 	int i, list = 0, bad = 0, many, minus;
    319 	uint32_t add_flags = 0, del_flags = 0;
    320 
    321 	setprogname(argv[0]);
    322 
    323 	if (argc < 2)
    324 		usage();
    325 
    326 	for (i = 1; i < argc; i++) {
    327 		opt = argv[i];
    328 
    329 		if (*opt == '-' || *opt == '+') {
    330 			uint32_t t;
    331 			minus = 0;
    332 
    333 			while (*opt) {
    334 				switch (*opt) {
    335 				case '+':
    336 					minus = 0;
    337 					opt++;
    338 					break;
    339 				case '-':
    340 					minus = 1;
    341 					opt++;
    342 					break;
    343 				case ',':
    344 					opt++;
    345 					break;
    346 				default:
    347 					t = pax_flag(*opt++);
    348 					if (t == (uint32_t)-1)
    349 						usage();
    350 					if (minus)
    351 						del_flags |= t;
    352 					else
    353 						add_flags |= t;
    354 					break;
    355 				}
    356 			}
    357 		} else
    358 			break;
    359 	}
    360 
    361 	if (i == argc)
    362 		usage();
    363 
    364 	if (add_flags || del_flags) {
    365 		if (list)
    366 			usage();
    367 	} else
    368 		list = 1;
    369 
    370 	many = i != argc - 1;
    371 	for (; i < argc; i++)
    372 		bad |= process_one(argv[i], add_flags, del_flags, list, many);
    373 
    374 	return bad ? EXIT_FAILURE : 0;
    375 }
    376