Home | History | Annotate | Line # | Download | only in paxctl
paxctl.c revision 1.2 
      1 /* $NetBSD: paxctl.c,v 1.2 2007/06/24 20:35:36 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 1.2 2007/06/24 20:35:36 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(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(u_long f)
    147 {
    148 	size_t i;
    149 
    150 	for (i = 0; i < __arraycount(flags); i++)
    151 		if (f & flags[i].bits)
    152 			(void)printf("  %c: %s\n",
    153 			    flags[i].mark, flags[i].name);
    154 }
    155 
    156 int
    157 main(int argc, char **argv)
    158 {
    159 	union {
    160 	    Elf32_Ehdr h32;
    161 	    Elf64_Ehdr h64;
    162 	} e;
    163 	union {
    164 	    Elf32_Phdr h32;
    165 	    Elf64_Phdr h64;
    166 	} p;
    167 	union {
    168 	    Elf32_Nhdr h32;
    169 	    Elf64_Nhdr h64;
    170 	} n;
    171 #define EH(field)	(size == 32 ? e.h32.field : e.h64.field)
    172 #define PH(field)	(size == 32 ? p.h32.field : p.h64.field)
    173 #define NH(field)	(size == 32 ? n.h32.field : n.h64.field)
    174 #define SPH(field, val)	do { \
    175     if (size == 32) \
    176 	    p.h32.field val; \
    177     else \
    178 	    p.h64.field val; \
    179 } while (/*CONSTCOND*/0)
    180 #define PHSIZE		(size == 32 ? sizeof(p.h32) : sizeof(p.h64))
    181 #define NHSIZE		(size == 32 ? sizeof(n.h32) : sizeof(n.h64))
    182 	struct {
    183 		char name[ELF_NOTE_PAX_NAMESZ];
    184 		uint32_t flags;
    185 	} pax_tag;
    186 
    187 	int size;
    188 	char *opt = NULL;
    189 	int fd, i, add_flags = 0, del_flags = 0, list = 0, ok = 0, flagged = 0;
    190 
    191 	if (argc < 2)
    192 		usage();
    193 
    194 	for (i = 1; i < argc; i++) {
    195 		opt = argv[i];
    196 
    197 		if (*opt == '-' || *opt == '+') {
    198 			int t;
    199 
    200 			t = pax_flag(opt + 1);
    201 			if (t == -1)
    202 				usage();
    203 
    204 			if (*opt == '-')
    205 				del_flags |= t;
    206 			else
    207 				add_flags |= t;
    208 
    209 			opt = NULL;
    210 		} else
    211 			break;
    212 	}
    213 
    214 	if (opt == NULL)
    215 		usage();
    216 
    217 	if (add_flags || del_flags) {
    218 		if (list)
    219 			usage();
    220 	} else
    221 		list = 1;
    222 
    223 	fd = open(opt, O_RDWR, 0);
    224 	if (fd == -1) {
    225 		if (!list || (fd = open(opt, O_RDONLY, 0))  == -1)
    226 			err(EXIT_FAILURE, "Can't open `%s'", opt);
    227 	}
    228 
    229 	if (read(fd, &e, sizeof(e)) != sizeof(e))
    230 		err(EXIT_FAILURE, "Can't read ELF header from `%s'", opt);
    231 
    232 	if (memcmp(e.h32.e_ident, ELFMAG, SELFMAG) != 0)
    233 		errx(EXIT_FAILURE,
    234 		    "Bad ELF magic from `%s' (maybe it's not an ELF?)", opt);
    235 
    236 	if (e.h32.e_ehsize == sizeof(e.h32))
    237 		size = 32;
    238 	else if (e.h64.e_ehsize == sizeof(e.h64))
    239 		size = 64;
    240 	else
    241 		errx(EXIT_FAILURE,
    242 		    "Bad ELF size %d from `%s' (maybe it's not an ELF?)",
    243 		    (int)e.h32.e_ehsize, opt);
    244 
    245 	for (i = 0; i < EH(e_phnum); i++) {
    246 		if (pread(fd, &p, PHSIZE,
    247 		    (off_t)EH(e_phoff) + i * PHSIZE) != PHSIZE)
    248 			err(EXIT_FAILURE, "Can't read program header data"
    249 			    " from `%s'", opt);
    250 
    251 		if (PH(p_type) != PT_NOTE)
    252 			continue;
    253 
    254 		if (pread(fd, &n, NHSIZE, (off_t)PH(p_offset)) != NHSIZE)
    255 			err(EXIT_FAILURE, "Can't read note header from `%s'",
    256 			    opt);
    257 		if (NH(n_type) != ELF_NOTE_TYPE_PAX_TAG ||
    258 		    NH(n_descsz) != ELF_NOTE_PAX_DESCSZ ||
    259 		    NH(n_namesz) != ELF_NOTE_PAX_NAMESZ)
    260 			continue;
    261 		if (pread(fd, &pax_tag, sizeof(pax_tag), PH(p_offset) + NHSIZE)
    262 		    != sizeof(pax_tag))
    263 			err(EXIT_FAILURE, "Can't read pax_tag from `%s'",
    264 			    opt);
    265 		if (memcmp(pax_tag.name, ELF_NOTE_PAX_NAME,
    266 		    sizeof(pax_tag.name)) != 0)
    267 			err(EXIT_FAILURE, "Unknown pax_tag name `%*.*s' from"
    268 			    " `%s'", ELF_NOTE_PAX_NAMESZ, ELF_NOTE_PAX_NAMESZ,
    269 			    pax_tag.name, opt);
    270 		ok = 1;
    271 
    272 		if (list) {
    273 			if (!pax_haveflags(pax_tag.flags))
    274 				break;
    275 
    276 			if (!pax_flags_sane(pax_tag.flags))
    277 				warnx("Current flags %x don't make sense",
    278 				    pax_tag.flags);
    279 
    280 			(void)printf("PaX flags:\n");
    281 
    282 			pax_printflags(pax_tag.flags);
    283 
    284 			flagged = 1;
    285 
    286 			break;
    287 		}
    288 
    289 		pax_tag.flags |= add_flags;
    290 		pax_tag.flags &= ~del_flags;
    291 
    292 		if (!pax_flags_sane(pax_tag.flags))
    293 			errx(EXIT_FAILURE, "New flags %x don't make sense",
    294 			    pax_tag.flags);
    295 
    296 		if (pwrite(fd, &pax_tag, sizeof(pax_tag),
    297 		    (off_t)PH(p_offset) + NHSIZE) != sizeof(pax_tag))
    298 			err(EXIT_FAILURE, "Can't modify flags on `%s'", opt);
    299 		break;
    300 	}
    301 
    302 	(void)close(fd);
    303 
    304 	if (!ok)
    305 		errx(EXIT_FAILURE,
    306 		    "Could not find an ELF PaX PT_NOTE section in `%s'", opt);
    307 
    308 	if (list && !flagged)
    309 		(void)printf("No PaX flags.\n");
    310 	return 0;
    311 }
    312