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paxctl.c revision 1.4 
      1 /* $NetBSD: paxctl.c,v 1.4 2007/12/11 01:40:27 christos Exp $ */
      2 
      3 /*-
      4  * Copyright (c) 2006 Elad Efrat <elad (at) NetBSD.org>
      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  * 3. The name of the author may not be used to endorse or promote products
     16  *    derived from this software without specific prior written permission.
     17  *
     18  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
     19  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
     20  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
     21  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
     22  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
     23  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     24  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     25  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     26  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
     27  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     28  */
     29 #if HAVE_NBTOOL_CONFIG_H
     30 #include "nbtool_config.h"
     31 #endif
     32 
     33 #include <sys/cdefs.h>
     34 #ifndef lint
     35 #ifdef __RCSID
     36 __RCSID("$NetBSD: paxctl.c,v 1.4 2007/12/11 01:40:27 christos Exp $");
     37 #endif
     38 #endif /* not lint */
     39 
     40 #include <sys/types.h>
     41 #ifdef HAVE_NBTOOL_CONFIG_H
     42 #include "../../sys/sys/exec_elf.h"
     43 #else
     44 #include <elf.h>
     45 #endif
     46 #include <stdio.h>
     47 #include <err.h>
     48 #include <fcntl.h>
     49 #include <unistd.h>
     50 #include <stdlib.h>
     51 #include <string.h>
     52 
     53 static void usage(void) __attribute__((__noreturn__));
     54 static int pax_flag(const char *);
     55 static int pax_flags_sane(u_long);
     56 static int pax_haveflags(u_long);
     57 static void pax_printflags(const char *, int, u_long);
     58 
     59 #ifndef ELF_NOTE_TYPE_PAX_TAG
     60 /* NetBSD-specific note type: PaX.  There should be 1 NOTE per executable.
     61    section.  desc is a 32 bit bitmask */
     62 #define ELF_NOTE_TYPE_PAX_TAG		3
     63 #define	ELF_NOTE_PAX_MPROTECT		0x1	/* Force enable Mprotect */
     64 #define	ELF_NOTE_PAX_NOMPROTECT		0x2	/* Force disable Mprotect */
     65 #define	ELF_NOTE_PAX_GUARD		0x4	/* Force enable Segvguard */
     66 #define	ELF_NOTE_PAX_NOGUARD		0x8	/* Force disable Servguard */
     67 #define ELF_NOTE_PAX_NAMESZ		4
     68 #define ELF_NOTE_PAX_NAME		"PaX\0"
     69 #define ELF_NOTE_PAX_DESCSZ		4
     70 #endif
     71 #ifndef __arraycount
     72 #define __arraycount(a) (sizeof(a) / sizeof(a[0]))
     73 #endif
     74 
     75 
     76 static const struct paxflag {
     77 	char mark;
     78 	const char *name;
     79 	int bits;
     80 } flags[] = {
     81 	{ 'G', "Segvguard, explicit enable",
     82 	  ELF_NOTE_PAX_GUARD },
     83 	{ 'g', "Segvguard, explicit disable",
     84 	  ELF_NOTE_PAX_NOGUARD },
     85 	{ 'M', "mprotect(2) restrictions, explicit enable",
     86 	  ELF_NOTE_PAX_MPROTECT },
     87 	{ 'm', "mprotect(2) restrictions, explicit disable",
     88 	  ELF_NOTE_PAX_NOMPROTECT },
     89 };
     90 
     91 static void
     92 usage(void)
     93 {
     94 	(void)fprintf(stderr, "Usage: %s [ <-|+><G|g|M|m> ] <file> ...\n",
     95 #if HAVE_NBTOOL_CONFIG_H
     96 	    "paxctl"
     97 #else
     98 	    getprogname()
     99 #endif
    100 	);
    101 	exit(1);
    102 }
    103 
    104 static int
    105 pax_flag(const char *s)
    106 {
    107 	size_t i;
    108 
    109 	if (s[0] == '\0' || s[1] != '\0')
    110 		return -1;
    111 
    112 	for (i = 0; i < __arraycount(flags); i++)
    113 		if (*s == flags[i].mark)
    114 			return flags[i].bits;
    115 
    116 	return -1;
    117 }
    118 
    119 static int
    120 pax_flags_sane(u_long f)
    121 {
    122 	size_t i;
    123 
    124 	for (i = 0; i < __arraycount(flags) - 1; i += 2) {
    125 		int g = flags[i].bits | flags[i+1].bits;
    126 		if ((f & g) == g)
    127 			return 0;
    128 	}
    129 
    130 	return 1;
    131 }
    132 
    133 static int
    134 pax_haveflags(u_long f)
    135 {
    136 	size_t i;
    137 
    138 	for (i = 0; i < __arraycount(flags); i++)
    139 		if (f & flags[i].bits)
    140 			return (1);
    141 
    142 	return (0);
    143 }
    144 
    145 static void
    146 pax_printflags(const char *name, int many, u_long f)
    147 {
    148 	size_t i;
    149 
    150 	for (i = 0; i < __arraycount(flags); i++)
    151 		if (f & flags[i].bits) {
    152 			if (many)
    153 				(void)printf("%s: ", name);
    154 			(void)printf("  %c: %s\n",
    155 			    flags[i].mark, flags[i].name);
    156 		}
    157 }
    158 
    159 static int
    160 process_one(const char *name, int add_flags, int del_flags, int list, int many)
    161 {
    162 	union {
    163 	    Elf32_Ehdr h32;
    164 	    Elf64_Ehdr h64;
    165 	} e;
    166 	union {
    167 	    Elf32_Phdr h32;
    168 	    Elf64_Phdr h64;
    169 	} p;
    170 	union {
    171 	    Elf32_Nhdr h32;
    172 	    Elf64_Nhdr h64;
    173 	} n;
    174 #define EH(field)	(size == 32 ? e.h32.field : e.h64.field)
    175 #define PH(field)	(size == 32 ? p.h32.field : p.h64.field)
    176 #define NH(field)	(size == 32 ? n.h32.field : n.h64.field)
    177 #define SPH(field, val)	do { \
    178     if (size == 32) \
    179 	    p.h32.field val; \
    180     else \
    181 	    p.h64.field val; \
    182 } while (/*CONSTCOND*/0)
    183 #define PHSIZE		(size == 32 ? sizeof(p.h32) : sizeof(p.h64))
    184 #define NHSIZE		(size == 32 ? sizeof(n.h32) : sizeof(n.h64))
    185 	struct {
    186 		char name[ELF_NOTE_PAX_NAMESZ];
    187 		uint32_t flags;
    188 	} pax_tag;
    189 	int i, fd, size, ok = 0, flagged = 0;
    190 
    191 	fd = open(name, list ? O_RDONLY: O_RDWR, 0);
    192 	if (fd == -1) {
    193 		warn("Can't open `%s'", name);
    194 		return 1;
    195 	}
    196 
    197 	if (read(fd, &e, sizeof(e)) != sizeof(e)) {
    198 		warn("Can't read ELF header from `%s'", name);
    199 		return 1;
    200 	}
    201 
    202 	if (memcmp(e.h32.e_ident, ELFMAG, SELFMAG) != 0) {
    203 		warn("Bad ELF magic from `%s' (maybe it's not an ELF?)", name);
    204 		return 1;
    205 	}
    206 
    207 	if (e.h32.e_ehsize == sizeof(e.h32))
    208 		size = 32;
    209 	else if (e.h64.e_ehsize == sizeof(e.h64))
    210 		size = 64;
    211 	else {
    212 		warn("Bad ELF size %d from `%s' (maybe it's not an ELF?)",
    213 		    (int)e.h32.e_ehsize, name);
    214 		return 1;
    215 	}
    216 
    217 	for (i = 0; i < EH(e_phnum); i++) {
    218 		if (pread(fd, &p, PHSIZE, (off_t)EH(e_phoff) + i * PHSIZE) !=
    219 		    PHSIZE) {
    220 			warn("Can't read program header data from `%s'", name);
    221 			return 1;
    222 		}
    223 
    224 		if (PH(p_type) != PT_NOTE)
    225 			continue;
    226 
    227 		if (pread(fd, &n, NHSIZE, (off_t)PH(p_offset)) != NHSIZE) {
    228 			warn("Can't read note header from `%s'", name);
    229 			return 1;
    230 		}
    231 		if (NH(n_type) != ELF_NOTE_TYPE_PAX_TAG ||
    232 		    NH(n_descsz) != ELF_NOTE_PAX_DESCSZ ||
    233 		    NH(n_namesz) != ELF_NOTE_PAX_NAMESZ)
    234 			continue;
    235 		if (pread(fd, &pax_tag, sizeof(pax_tag), PH(p_offset) + NHSIZE)
    236 		    != sizeof(pax_tag)) {
    237 			warn("Can't read pax_tag from `%s'", name);
    238 			return 1;
    239 		}
    240 		if (memcmp(pax_tag.name, ELF_NOTE_PAX_NAME,
    241 		    sizeof(pax_tag.name)) != 0) {
    242 			warn("Unknown pax_tag name `%*.*s' from `%s'",
    243 			    ELF_NOTE_PAX_NAMESZ, ELF_NOTE_PAX_NAMESZ,
    244 			    pax_tag.name, name);
    245 			return 1;
    246 		}
    247 		ok = 1;
    248 
    249 		if (list) {
    250 			if (!pax_haveflags(pax_tag.flags))
    251 				break;
    252 
    253 			if (!pax_flags_sane(pax_tag.flags))
    254 				warnx("Current flags %x don't make sense",
    255 				    pax_tag.flags);
    256 
    257 			if (many)
    258 				(void)printf("%s: ", name);
    259 			(void)printf("PaX flags:\n");
    260 
    261 			pax_printflags(name, many, pax_tag.flags);
    262 
    263 			flagged = 1;
    264 
    265 			break;
    266 		}
    267 
    268 		pax_tag.flags |= add_flags;
    269 		pax_tag.flags &= ~del_flags;
    270 
    271 		if (!pax_flags_sane(pax_tag.flags)) {
    272 			warn("New flags %x don't make sense", pax_tag.flags);
    273 			return 1;
    274 		}
    275 
    276 		if (pwrite(fd, &pax_tag, sizeof(pax_tag),
    277 		    (off_t)PH(p_offset) + NHSIZE) != sizeof(pax_tag))
    278 			warn("Can't modify flags on `%s'", name);
    279 		break;
    280 	}
    281 
    282 	(void)close(fd);
    283 
    284 	if (!ok) {
    285 		warn("Could not find an ELF PaX PT_NOTE section in `%s'", name);
    286 		return 1;
    287 	}
    288 
    289 	if (list && !flagged) {
    290 		if (many)
    291 			(void)printf("%s: ", name);
    292 		(void)printf("No PaX flags.\n");
    293 	}
    294 	return 0;
    295 }
    296 
    297 int
    298 main(int argc, char **argv)
    299 {
    300 	char *opt;
    301 	int i, add_flags = 0, del_flags = 0, list = 0, bad = 0, many;
    302 
    303 	if (argc < 2)
    304 		usage();
    305 
    306 	for (i = 1; i < argc; i++) {
    307 		opt = argv[i];
    308 
    309 		if (*opt == '-' || *opt == '+') {
    310 			int t;
    311 
    312 			t = pax_flag(opt + 1);
    313 			if (t == -1)
    314 				usage();
    315 
    316 			if (*opt == '-')
    317 				del_flags |= t;
    318 			else
    319 				add_flags |= t;
    320 
    321 			opt = NULL;
    322 		} else
    323 			break;
    324 	}
    325 
    326 	if (i == argc)
    327 		usage();
    328 
    329 	if (add_flags || del_flags) {
    330 		if (list)
    331 			usage();
    332 	} else
    333 		list = 1;
    334 
    335 	many = i != argc - 1;
    336 	for (; i < argc; i++)
    337 		bad |= process_one(argv[i], add_flags, del_flags, list, many);
    338 
    339 	return bad ? EXIT_FAILURE : 0;
    340 }
    341