1 /* $OpenBSD: doas.c,v 1.99 2024/02/15 18:57:58 tedu 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 [arg ...]\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 size_t 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 -1; 149 if ((*lastr)->action == PERMIT) 150 return 0; 151 return -1; 152 } 153 154 static void 155 parseconfig(const char *filename, int checkperms) 156 { 157 extern FILE *yyfp; 158 extern int yyparse(void); 159 struct stat sb; 160 161 yyfp = fopen(filename, "r"); 162 if (!yyfp) 163 err(1, checkperms ? "doas is not enabled, %s" : 164 "could not open config file %s", filename); 165 166 if (checkperms) { 167 if (fstat(fileno(yyfp), &sb) != 0) 168 err(1, "fstat(\"%s\")", filename); 169 if ((sb.st_mode & (S_IWGRP|S_IWOTH)) != 0) 170 errx(1, "%s is writable by group or other", filename); 171 if (sb.st_uid != 0) 172 errx(1, "%s is not owned by root", filename); 173 } 174 175 yyparse(); 176 fclose(yyfp); 177 if (parse_error) 178 exit(1); 179 } 180 181 static void __dead 182 checkconfig(const char *confpath, int argc, char **argv, 183 uid_t uid, gid_t *groups, int ngroups, uid_t target) 184 { 185 const struct rule *rule; 186 int rv; 187 188 setresuid(uid, uid, uid); 189 if (pledge("stdio rpath getpw", NULL) == -1) 190 err(1, "pledge"); 191 parseconfig(confpath, 0); 192 if (!argc) 193 exit(0); 194 rv = permit(uid, groups, ngroups, &rule, target, argv[0], 195 (const char **)argv + 1); 196 if (rv == 0) { 197 printf("permit%s\n", (rule->options & NOPASS) ? " nopass" : ""); 198 exit(0); 199 } else { 200 printf("deny\n"); 201 exit(1); 202 } 203 } 204 205 static int 206 authuser_checkpass(char *myname, char *login_style) 207 { 208 char *challenge = NULL, *response, rbuf[1024], cbuf[128]; 209 auth_session_t *as; 210 211 if (!(as = auth_userchallenge(myname, login_style, "auth-doas", 212 &challenge))) { 213 warnx("Authentication failed"); 214 return AUTH_FAILED; 215 } 216 if (!challenge) { 217 char host[HOST_NAME_MAX + 1]; 218 219 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 warnx("Authentication failed"); 237 return AUTH_FAILED; 238 } 239 explicit_bzero(rbuf, sizeof(rbuf)); 240 return AUTH_OK; 241 } 242 243 static void 244 authuser(char *myname, char *login_style, int persist) 245 { 246 int i, fd = -1; 247 248 if (persist) 249 fd = open("/dev/tty", O_RDWR); 250 if (fd != -1) { 251 if (ioctl(fd, TIOCCHKVERAUTH) == 0) 252 goto good; 253 } 254 for (i = 0; i < AUTH_RETRIES; i++) { 255 if (authuser_checkpass(myname, login_style) == AUTH_OK) 256 goto good; 257 } 258 exit(1); 259 good: 260 if (fd != -1) { 261 int secs = 5 * 60; 262 ioctl(fd, TIOCSETVERAUTH, &secs); 263 close(fd); 264 } 265 } 266 267 int 268 unveilcommands(const char *ipath, const char *cmd) 269 { 270 char *path = NULL, *p; 271 int unveils = 0; 272 273 if (strchr(cmd, '/') != NULL) { 274 if (unveil(cmd, "x") != -1) 275 unveils++; 276 goto done; 277 } 278 279 if (!ipath) { 280 errno = ENOENT; 281 goto done; 282 } 283 path = strdup(ipath); 284 if (!path) { 285 errno = ENOENT; 286 goto done; 287 } 288 for (p = path; p && *p; ) { 289 char buf[PATH_MAX]; 290 char *cp = strsep(&p, ":"); 291 292 if (cp) { 293 int r = snprintf(buf, sizeof buf, "%s/%s", cp, cmd); 294 if (r >= 0 && r < sizeof buf) { 295 if (unveil(buf, "x") != -1) 296 unveils++; 297 } 298 } 299 } 300 done: 301 free(path); 302 return (unveils); 303 } 304 305 int 306 main(int argc, char **argv) 307 { 308 const char *safepath = "/bin:/sbin:/usr/bin:/usr/sbin:" 309 "/usr/local/bin:/usr/local/sbin"; 310 const char *confpath = NULL; 311 char *shargv[] = { NULL, NULL }; 312 char *sh; 313 const char *p; 314 const char *cmd; 315 char cmdline[LINE_MAX]; 316 char mypwbuf[_PW_BUF_LEN], targpwbuf[_PW_BUF_LEN]; 317 struct passwd mypwstore, targpwstore; 318 struct passwd *mypw, *targpw; 319 const struct rule *rule; 320 uid_t uid; 321 uid_t target = 0; 322 gid_t groups[NGROUPS_MAX + 1]; 323 int ngroups; 324 int i, ch, rv; 325 int sflag = 0; 326 int nflag = 0; 327 char cwdpath[PATH_MAX]; 328 const char *cwd; 329 char *login_style = NULL; 330 char **envp; 331 332 setprogname("doas"); 333 334 closefrom(STDERR_FILENO + 1); 335 336 uid = getuid(); 337 338 while ((ch = getopt(argc, argv, "a:C:Lnsu:")) != -1) { 339 switch (ch) { 340 case 'a': 341 login_style = optarg; 342 break; 343 case 'C': 344 confpath = optarg; 345 break; 346 case 'L': 347 i = open("/dev/tty", O_RDWR); 348 if (i != -1) 349 ioctl(i, TIOCCLRVERAUTH); 350 exit(i == -1); 351 case 'u': 352 if (parseuid(optarg, &target) != 0) 353 errx(1, "unknown user"); 354 break; 355 case 'n': 356 nflag = 1; 357 break; 358 case 's': 359 sflag = 1; 360 break; 361 default: 362 usage(); 363 break; 364 } 365 } 366 argv += optind; 367 argc -= optind; 368 369 if (confpath) { 370 if (sflag) 371 usage(); 372 } else if ((!sflag && !argc) || (sflag && argc)) 373 usage(); 374 375 rv = getpwuid_r(uid, &mypwstore, mypwbuf, sizeof(mypwbuf), &mypw); 376 if (rv != 0) 377 err(1, "getpwuid_r failed"); 378 if (mypw == NULL) 379 errx(1, "no passwd entry for self"); 380 ngroups = getgroups(NGROUPS_MAX, groups); 381 if (ngroups == -1) 382 err(1, "can't get groups"); 383 groups[ngroups++] = getgid(); 384 385 if (sflag) { 386 sh = getenv("SHELL"); 387 if (sh == NULL || *sh == '\0') { 388 shargv[0] = mypw->pw_shell; 389 } else 390 shargv[0] = sh; 391 argv = shargv; 392 argc = 1; 393 } 394 395 if (confpath) { 396 if (pledge("stdio rpath getpw id", NULL) == -1) 397 err(1, "pledge"); 398 checkconfig(confpath, argc, argv, uid, groups, ngroups, 399 target); 400 exit(1); /* fail safe */ 401 } 402 403 if (geteuid()) 404 errx(1, "not installed setuid"); 405 406 parseconfig("/etc/doas.conf", 1); 407 408 /* cmdline is used only for logging, no need to abort on truncate */ 409 (void)strlcpy(cmdline, argv[0], sizeof(cmdline)); 410 for (i = 1; i < argc; i++) { 411 if (strlcat(cmdline, " ", sizeof(cmdline)) >= sizeof(cmdline)) 412 break; 413 if (strlcat(cmdline, argv[i], sizeof(cmdline)) >= sizeof(cmdline)) 414 break; 415 } 416 417 cmd = argv[0]; 418 rv = permit(uid, groups, ngroups, &rule, target, cmd, 419 (const char **)argv + 1); 420 if (rv != 0) { 421 syslog(LOG_AUTHPRIV | LOG_NOTICE, 422 "command not permitted for %s: %s", mypw->pw_name, cmdline); 423 errc(1, EPERM, NULL); 424 } 425 426 if (!(rule->options & NOPASS)) { 427 if (nflag) 428 errx(1, "Authentication required"); 429 430 authuser(mypw->pw_name, login_style, rule->options & PERSIST); 431 } 432 433 if ((p = getenv("PATH")) != NULL) 434 formerpath = strdup(p); 435 if (formerpath == NULL) 436 formerpath = ""; 437 438 if (unveil(_PATH_LOGIN_CONF, "r") == -1) 439 err(1, "unveil %s", _PATH_LOGIN_CONF); 440 if (unveil(_PATH_LOGIN_CONF ".db", "r") == -1) 441 err(1, "unveil %s.db", _PATH_LOGIN_CONF); 442 if (unveil(_PATH_LOGIN_CONF_D, "r") == -1) 443 err(1, "unveil %s", _PATH_LOGIN_CONF_D); 444 if (rule->cmd) { 445 if (setenv("PATH", safepath, 1) == -1) 446 err(1, "failed to set PATH '%s'", safepath); 447 } 448 if (unveilcommands(getenv("PATH"), cmd) == 0) 449 goto fail; 450 451 if (pledge("stdio rpath getpw exec id", NULL) == -1) 452 err(1, "pledge"); 453 454 rv = getpwuid_r(target, &targpwstore, targpwbuf, sizeof(targpwbuf), &targpw); 455 if (rv != 0) 456 err(1, "getpwuid_r failed"); 457 if (targpw == NULL) 458 errx(1, "no passwd entry for target"); 459 460 if (setusercontext(NULL, targpw, target, LOGIN_SETGROUP | 461 LOGIN_SETPATH | 462 LOGIN_SETPRIORITY | LOGIN_SETRESOURCES | LOGIN_SETUMASK | 463 LOGIN_SETUSER | LOGIN_SETENV | LOGIN_SETRTABLE) != 0) 464 errx(1, "failed to set user context for target"); 465 466 if (pledge("stdio rpath exec", NULL) == -1) 467 err(1, "pledge"); 468 469 if (getcwd(cwdpath, sizeof(cwdpath)) == NULL) 470 cwd = "(failed)"; 471 else 472 cwd = cwdpath; 473 474 if (pledge("stdio exec", NULL) == -1) 475 err(1, "pledge"); 476 477 if (!(rule->options & NOLOG)) { 478 syslog(LOG_AUTHPRIV | LOG_INFO, 479 "%s ran command %s as %s from %s", 480 mypw->pw_name, cmdline, targpw->pw_name, cwd); 481 } 482 483 envp = prepenv(rule, mypw, targpw); 484 485 /* setusercontext set path for the next process, so reset it for us */ 486 if (rule->cmd) { 487 if (setenv("PATH", safepath, 1) == -1) 488 err(1, "failed to set PATH '%s'", safepath); 489 } else { 490 if (setenv("PATH", formerpath, 1) == -1) 491 err(1, "failed to set PATH '%s'", formerpath); 492 } 493 execvpe(cmd, argv, envp); 494 fail: 495 if (errno == ENOENT) 496 errx(1, "%s: command not found", cmd); 497 err(1, "%s", cmd); 498 } 499