1 /* $OpenBSD: doas.c,v 1.84 2020/10/09 07:43:38 kn Exp $ */ 2 /* 3 * Copyright (c) 2015 Ted Unangst <tedu@openbsd.org> 4 * 5 * Permission to use, copy, modify, and distribute this software for any 6 * purpose with or without fee is hereby granted, provided that the above 7 * copyright notice and this permission notice appear in all copies. 8 * 9 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES 10 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 11 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR 12 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 13 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN 14 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF 15 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. 16 */ 17 18 #include <sys/types.h> 19 #include <sys/stat.h> 20 #include <sys/ioctl.h> 21 22 #include <limits.h> 23 #include <login_cap.h> 24 #include <bsd_auth.h> 25 #include <readpassphrase.h> 26 #include <string.h> 27 #include <stdio.h> 28 #include <stdlib.h> 29 #include <err.h> 30 #include <unistd.h> 31 #include <pwd.h> 32 #include <grp.h> 33 #include <syslog.h> 34 #include <errno.h> 35 #include <fcntl.h> 36 37 #include "doas.h" 38 39 static void __dead 40 usage(void) 41 { 42 fprintf(stderr, "usage: doas [-Lns] [-a style] [-C config] [-u user]" 43 " command [args]\n"); 44 exit(1); 45 } 46 47 static int 48 parseuid(const char *s, uid_t *uid) 49 { 50 struct passwd *pw; 51 const char *errstr; 52 53 if ((pw = getpwnam(s)) != NULL) { 54 *uid = pw->pw_uid; 55 if (*uid == UID_MAX) 56 return -1; 57 return 0; 58 } 59 *uid = strtonum(s, 0, UID_MAX - 1, &errstr); 60 if (errstr) 61 return -1; 62 return 0; 63 } 64 65 static int 66 uidcheck(const char *s, uid_t desired) 67 { 68 uid_t uid; 69 70 if (parseuid(s, &uid) != 0) 71 return -1; 72 if (uid != desired) 73 return -1; 74 return 0; 75 } 76 77 static int 78 parsegid(const char *s, gid_t *gid) 79 { 80 struct group *gr; 81 const char *errstr; 82 83 if ((gr = getgrnam(s)) != NULL) { 84 *gid = gr->gr_gid; 85 if (*gid == GID_MAX) 86 return -1; 87 return 0; 88 } 89 *gid = strtonum(s, 0, GID_MAX - 1, &errstr); 90 if (errstr) 91 return -1; 92 return 0; 93 } 94 95 static int 96 match(uid_t uid, gid_t *groups, int ngroups, uid_t target, const char *cmd, 97 const char **cmdargs, struct rule *r) 98 { 99 int i; 100 101 if (r->ident[0] == ':') { 102 gid_t rgid; 103 if (parsegid(r->ident + 1, &rgid) == -1) 104 return 0; 105 for (i = 0; i < ngroups; i++) { 106 if (rgid == groups[i]) 107 break; 108 } 109 if (i == ngroups) 110 return 0; 111 } else { 112 if (uidcheck(r->ident, uid) != 0) 113 return 0; 114 } 115 if (r->target && uidcheck(r->target, target) != 0) 116 return 0; 117 if (r->cmd) { 118 if (strcmp(r->cmd, cmd)) 119 return 0; 120 if (r->cmdargs) { 121 /* if arguments were given, they should match explicitly */ 122 for (i = 0; r->cmdargs[i]; i++) { 123 if (!cmdargs[i]) 124 return 0; 125 if (strcmp(r->cmdargs[i], cmdargs[i])) 126 return 0; 127 } 128 if (cmdargs[i]) 129 return 0; 130 } 131 } 132 return 1; 133 } 134 135 static int 136 permit(uid_t uid, gid_t *groups, int ngroups, const struct rule **lastr, 137 uid_t target, const char *cmd, const char **cmdargs) 138 { 139 int i; 140 141 *lastr = NULL; 142 for (i = 0; i < nrules; i++) { 143 if (match(uid, groups, ngroups, target, cmd, 144 cmdargs, rules[i])) 145 *lastr = rules[i]; 146 } 147 if (!*lastr) 148 return 0; 149 return (*lastr)->action == PERMIT; 150 } 151 152 static void 153 parseconfig(const char *filename, int checkperms) 154 { 155 extern FILE *yyfp; 156 extern int yyparse(void); 157 struct stat sb; 158 159 yyfp = fopen(filename, "r"); 160 if (!yyfp) 161 err(1, checkperms ? "doas is not enabled, %s" : 162 "could not open config file %s", filename); 163 164 if (checkperms) { 165 if (fstat(fileno(yyfp), &sb) != 0) 166 err(1, "fstat(\"%s\")", filename); 167 if ((sb.st_mode & (S_IWGRP|S_IWOTH)) != 0) 168 errx(1, "%s is writable by group or other", filename); 169 if (sb.st_uid != 0) 170 errx(1, "%s is not owned by root", filename); 171 } 172 173 yyparse(); 174 fclose(yyfp); 175 if (parse_errors) 176 exit(1); 177 } 178 179 static void __dead 180 checkconfig(const char *confpath, int argc, char **argv, 181 uid_t uid, gid_t *groups, int ngroups, uid_t target) 182 { 183 const struct rule *rule; 184 185 setresuid(uid, uid, uid); 186 parseconfig(confpath, 0); 187 if (!argc) 188 exit(0); 189 190 if (permit(uid, groups, ngroups, &rule, target, argv[0], 191 (const char **)argv + 1)) { 192 printf("permit%s\n", (rule->options & NOPASS) ? " nopass" : ""); 193 exit(0); 194 } else { 195 printf("deny\n"); 196 exit(1); 197 } 198 } 199 200 static void 201 authuser(char *myname, char *login_style, int persist) 202 { 203 char *challenge = NULL, *response, rbuf[1024], cbuf[128]; 204 auth_session_t *as; 205 int fd = -1; 206 207 if (persist) 208 fd = open("/dev/tty", O_RDWR); 209 if (fd != -1) { 210 if (ioctl(fd, TIOCCHKVERAUTH) == 0) 211 goto good; 212 } 213 214 if (!(as = auth_userchallenge(myname, login_style, "auth-doas", 215 &challenge))) 216 errx(1, "Authorization failed"); 217 if (!challenge) { 218 char host[HOST_NAME_MAX + 1]; 219 if (gethostname(host, sizeof(host))) 220 snprintf(host, sizeof(host), "?"); 221 snprintf(cbuf, sizeof(cbuf), 222 "\rdoas (%.32s@%.32s) password: ", myname, host); 223 challenge = cbuf; 224 } 225 response = readpassphrase(challenge, rbuf, sizeof(rbuf), 226 RPP_REQUIRE_TTY); 227 if (response == NULL && errno == ENOTTY) { 228 syslog(LOG_AUTHPRIV | LOG_NOTICE, 229 "tty required for %s", myname); 230 errx(1, "a tty is required"); 231 } 232 if (!auth_userresponse(as, response, 0)) { 233 explicit_bzero(rbuf, sizeof(rbuf)); 234 syslog(LOG_AUTHPRIV | LOG_NOTICE, 235 "failed auth for %s", myname); 236 errx(1, "Authorization failed"); 237 } 238 explicit_bzero(rbuf, sizeof(rbuf)); 239 good: 240 if (fd != -1) { 241 int secs = 5 * 60; 242 ioctl(fd, TIOCSETVERAUTH, &secs); 243 close(fd); 244 } 245 } 246 247 int 248 unveilcommands(const char *ipath, const char *cmd) 249 { 250 char *path = NULL, *p; 251 int unveils = 0; 252 253 if (strchr(cmd, '/') != NULL) { 254 if (unveil(cmd, "x") != -1) 255 unveils++; 256 goto done; 257 } 258 259 if (!ipath) { 260 errno = ENOENT; 261 goto done; 262 } 263 path = strdup(ipath); 264 if (!path) { 265 errno = ENOENT; 266 goto done; 267 } 268 for (p = path; p && *p; ) { 269 char buf[PATH_MAX]; 270 char *cp = strsep(&p, ":"); 271 272 if (cp) { 273 int r = snprintf(buf, sizeof buf, "%s/%s", cp, cmd); 274 if (r >= 0 && r < sizeof buf) { 275 if (unveil(buf, "x") != -1) 276 unveils++; 277 } 278 } 279 } 280 done: 281 free(path); 282 return (unveils); 283 } 284 285 int 286 main(int argc, char **argv) 287 { 288 const char *safepath = "/bin:/sbin:/usr/bin:/usr/sbin:" 289 "/usr/local/bin:/usr/local/sbin"; 290 const char *confpath = NULL; 291 char *shargv[] = { NULL, NULL }; 292 char *sh; 293 const char *p; 294 const char *cmd; 295 char cmdline[LINE_MAX]; 296 char mypwbuf[_PW_BUF_LEN], targpwbuf[_PW_BUF_LEN]; 297 struct passwd mypwstore, targpwstore; 298 struct passwd *mypw, *targpw; 299 const struct rule *rule; 300 uid_t uid; 301 uid_t target = 0; 302 gid_t groups[NGROUPS_MAX + 1]; 303 int ngroups; 304 int i, ch, rv; 305 int sflag = 0; 306 int nflag = 0; 307 char cwdpath[PATH_MAX]; 308 const char *cwd; 309 char *login_style = NULL; 310 char **envp; 311 312 setprogname("doas"); 313 314 closefrom(STDERR_FILENO + 1); 315 316 uid = getuid(); 317 318 while ((ch = getopt(argc, argv, "a:C:Lnsu:")) != -1) { 319 switch (ch) { 320 case 'a': 321 login_style = optarg; 322 break; 323 case 'C': 324 confpath = optarg; 325 break; 326 case 'L': 327 i = open("/dev/tty", O_RDWR); 328 if (i != -1) 329 ioctl(i, TIOCCLRVERAUTH); 330 exit(i == -1); 331 case 'u': 332 if (parseuid(optarg, &target) != 0) 333 errx(1, "unknown user"); 334 break; 335 case 'n': 336 nflag = 1; 337 break; 338 case 's': 339 sflag = 1; 340 break; 341 default: 342 usage(); 343 break; 344 } 345 } 346 argv += optind; 347 argc -= optind; 348 349 if (confpath) { 350 if (sflag) 351 usage(); 352 } else if ((!sflag && !argc) || (sflag && argc)) 353 usage(); 354 355 rv = getpwuid_r(uid, &mypwstore, mypwbuf, sizeof(mypwbuf), &mypw); 356 if (rv != 0) 357 err(1, "getpwuid_r failed"); 358 if (mypw == NULL) 359 errx(1, "no passwd entry for self"); 360 ngroups = getgroups(NGROUPS_MAX, groups); 361 if (ngroups == -1) 362 err(1, "can't get groups"); 363 groups[ngroups++] = getgid(); 364 365 if (sflag) { 366 sh = getenv("SHELL"); 367 if (sh == NULL || *sh == '\0') { 368 shargv[0] = mypw->pw_shell; 369 } else 370 shargv[0] = sh; 371 argv = shargv; 372 argc = 1; 373 } 374 375 if (confpath) { 376 checkconfig(confpath, argc, argv, uid, groups, ngroups, 377 target); 378 exit(1); /* fail safe */ 379 } 380 381 if (geteuid()) 382 errx(1, "not installed setuid"); 383 384 parseconfig("/etc/doas.conf", 1); 385 386 /* cmdline is used only for logging, no need to abort on truncate */ 387 (void)strlcpy(cmdline, argv[0], sizeof(cmdline)); 388 for (i = 1; i < argc; i++) { 389 if (strlcat(cmdline, " ", sizeof(cmdline)) >= sizeof(cmdline)) 390 break; 391 if (strlcat(cmdline, argv[i], sizeof(cmdline)) >= sizeof(cmdline)) 392 break; 393 } 394 395 cmd = argv[0]; 396 if (!permit(uid, groups, ngroups, &rule, target, cmd, 397 (const char **)argv + 1)) { 398 syslog(LOG_AUTHPRIV | LOG_NOTICE, 399 "command not permitted for %s: %s", mypw->pw_name, cmdline); 400 errc(1, EPERM, NULL); 401 } 402 403 if (!(rule->options & NOPASS)) { 404 if (nflag) 405 errx(1, "Authorization required"); 406 407 authuser(mypw->pw_name, login_style, rule->options & PERSIST); 408 } 409 410 if ((p = getenv("PATH")) != NULL) 411 formerpath = strdup(p); 412 if (formerpath == NULL) 413 formerpath = ""; 414 415 if (unveil(_PATH_LOGIN_CONF, "r") == -1 || 416 unveil(_PATH_LOGIN_CONF ".db", "r") == -1) 417 err(1, "unveil"); 418 if (rule->cmd) { 419 if (setenv("PATH", safepath, 1) == -1) 420 err(1, "failed to set PATH '%s'", safepath); 421 } 422 if (unveilcommands(getenv("PATH"), cmd) == 0) 423 goto fail; 424 425 if (pledge("stdio rpath getpw exec id", NULL) == -1) 426 err(1, "pledge"); 427 428 rv = getpwuid_r(target, &targpwstore, targpwbuf, sizeof(targpwbuf), &targpw); 429 if (rv != 0) 430 err(1, "getpwuid_r failed"); 431 if (targpw == NULL) 432 errx(1, "no passwd entry for target"); 433 434 if (setusercontext(NULL, targpw, target, LOGIN_SETGROUP | 435 LOGIN_SETPATH | 436 LOGIN_SETPRIORITY | LOGIN_SETRESOURCES | LOGIN_SETUMASK | 437 LOGIN_SETUSER) != 0) 438 errx(1, "failed to set user context for target"); 439 440 if (pledge("stdio rpath exec", NULL) == -1) 441 err(1, "pledge"); 442 443 if (getcwd(cwdpath, sizeof(cwdpath)) == NULL) 444 cwd = "(failed)"; 445 else 446 cwd = cwdpath; 447 448 if (pledge("stdio exec", NULL) == -1) 449 err(1, "pledge"); 450 451 if (!(rule->options & NOLOG)) { 452 syslog(LOG_AUTHPRIV | LOG_INFO, 453 "%s ran command %s as %s from %s", 454 mypw->pw_name, cmdline, targpw->pw_name, cwd); 455 } 456 457 envp = prepenv(rule, mypw, targpw); 458 459 /* setusercontext set path for the next process, so reset it for us */ 460 if (rule->cmd) { 461 if (setenv("PATH", safepath, 1) == -1) 462 err(1, "failed to set PATH '%s'", safepath); 463 } else { 464 if (setenv("PATH", formerpath, 1) == -1) 465 err(1, "failed to set PATH '%s'", formerpath); 466 } 467 execvpe(cmd, argv, envp); 468 fail: 469 if (errno == ENOENT) 470 errx(1, "%s: command not found", cmd); 471 err(1, "%s", cmd); 472 } 473