1 /* $OpenBSD: doas.c,v 1.78 2019/06/17 19:51:23 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 [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 return 0; 56 } 57 *uid = strtonum(s, 0, UID_MAX, &errstr); 58 if (errstr) 59 return -1; 60 return 0; 61 } 62 63 static int 64 uidcheck(const char *s, uid_t desired) 65 { 66 uid_t uid; 67 68 if (parseuid(s, &uid) != 0) 69 return -1; 70 if (uid != desired) 71 return -1; 72 return 0; 73 } 74 75 static int 76 parsegid(const char *s, gid_t *gid) 77 { 78 struct group *gr; 79 const char *errstr; 80 81 if ((gr = getgrnam(s)) != NULL) { 82 *gid = gr->gr_gid; 83 return 0; 84 } 85 *gid = strtonum(s, 0, GID_MAX, &errstr); 86 if (errstr) 87 return -1; 88 return 0; 89 } 90 91 static int 92 match(uid_t uid, gid_t *groups, int ngroups, uid_t target, const char *cmd, 93 const char **cmdargs, struct rule *r) 94 { 95 int i; 96 97 if (r->ident[0] == ':') { 98 gid_t rgid; 99 if (parsegid(r->ident + 1, &rgid) == -1) 100 return 0; 101 for (i = 0; i < ngroups; i++) { 102 if (rgid == groups[i]) 103 break; 104 } 105 if (i == ngroups) 106 return 0; 107 } else { 108 if (uidcheck(r->ident, uid) != 0) 109 return 0; 110 } 111 if (r->target && uidcheck(r->target, target) != 0) 112 return 0; 113 if (r->cmd) { 114 if (strcmp(r->cmd, cmd)) 115 return 0; 116 if (r->cmdargs) { 117 /* if arguments were given, they should match explicitly */ 118 for (i = 0; r->cmdargs[i]; i++) { 119 if (!cmdargs[i]) 120 return 0; 121 if (strcmp(r->cmdargs[i], cmdargs[i])) 122 return 0; 123 } 124 if (cmdargs[i]) 125 return 0; 126 } 127 } 128 return 1; 129 } 130 131 static int 132 permit(uid_t uid, gid_t *groups, int ngroups, const struct rule **lastr, 133 uid_t target, const char *cmd, const char **cmdargs) 134 { 135 int i; 136 137 *lastr = NULL; 138 for (i = 0; i < nrules; i++) { 139 if (match(uid, groups, ngroups, target, cmd, 140 cmdargs, rules[i])) 141 *lastr = rules[i]; 142 } 143 if (!*lastr) 144 return 0; 145 return (*lastr)->action == PERMIT; 146 } 147 148 static void 149 parseconfig(const char *filename, int checkperms) 150 { 151 extern FILE *yyfp; 152 extern int yyparse(void); 153 struct stat sb; 154 155 yyfp = fopen(filename, "r"); 156 if (!yyfp) 157 err(1, checkperms ? "doas is not enabled, %s" : 158 "could not open config file %s", filename); 159 160 if (checkperms) { 161 if (fstat(fileno(yyfp), &sb) != 0) 162 err(1, "fstat(\"%s\")", filename); 163 if ((sb.st_mode & (S_IWGRP|S_IWOTH)) != 0) 164 errx(1, "%s is writable by group or other", filename); 165 if (sb.st_uid != 0) 166 errx(1, "%s is not owned by root", filename); 167 } 168 169 yyparse(); 170 fclose(yyfp); 171 if (parse_errors) 172 exit(1); 173 } 174 175 static void __dead 176 checkconfig(const char *confpath, int argc, char **argv, 177 uid_t uid, gid_t *groups, int ngroups, uid_t target) 178 { 179 const struct rule *rule; 180 181 setresuid(uid, uid, uid); 182 parseconfig(confpath, 0); 183 if (!argc) 184 exit(0); 185 186 if (permit(uid, groups, ngroups, &rule, target, argv[0], 187 (const char **)argv + 1)) { 188 printf("permit%s\n", (rule->options & NOPASS) ? " nopass" : ""); 189 exit(0); 190 } else { 191 printf("deny\n"); 192 exit(1); 193 } 194 } 195 196 static void 197 authuser(char *myname, char *login_style, int persist) 198 { 199 char *challenge = NULL, *response, rbuf[1024], cbuf[128]; 200 auth_session_t *as; 201 int fd = -1; 202 203 if (persist) 204 fd = open("/dev/tty", O_RDWR); 205 if (fd != -1) { 206 if (ioctl(fd, TIOCCHKVERAUTH) == 0) 207 goto good; 208 } 209 210 if (!(as = auth_userchallenge(myname, login_style, "auth-doas", 211 &challenge))) 212 errx(1, "Authorization failed"); 213 if (!challenge) { 214 char host[HOST_NAME_MAX + 1]; 215 if (gethostname(host, sizeof(host))) 216 snprintf(host, sizeof(host), "?"); 217 snprintf(cbuf, sizeof(cbuf), 218 "\rdoas (%.32s@%.32s) password: ", myname, host); 219 challenge = cbuf; 220 } 221 response = readpassphrase(challenge, rbuf, sizeof(rbuf), 222 RPP_REQUIRE_TTY); 223 if (response == NULL && errno == ENOTTY) { 224 syslog(LOG_AUTHPRIV | LOG_NOTICE, 225 "tty required for %s", myname); 226 errx(1, "a tty is required"); 227 } 228 if (!auth_userresponse(as, response, 0)) { 229 explicit_bzero(rbuf, sizeof(rbuf)); 230 syslog(LOG_AUTHPRIV | LOG_NOTICE, 231 "failed auth for %s", myname); 232 errx(1, "Authorization failed"); 233 } 234 explicit_bzero(rbuf, sizeof(rbuf)); 235 good: 236 if (fd != -1) { 237 int secs = 5 * 60; 238 ioctl(fd, TIOCSETVERAUTH, &secs); 239 close(fd); 240 } 241 } 242 243 int 244 unveilcommands(const char *ipath, const char *cmd) 245 { 246 char *path = NULL, *p; 247 int unveils = 0; 248 249 if (strchr(cmd, '/') != NULL) { 250 if (unveil(cmd, "x") != -1) 251 unveils++; 252 goto done; 253 } 254 255 if (!ipath) { 256 errno = ENOENT; 257 goto done; 258 } 259 path = strdup(ipath); 260 if (!path) { 261 errno = ENOENT; 262 goto done; 263 } 264 for (p = path; p && *p; ) { 265 char buf[PATH_MAX]; 266 char *cp = strsep(&p, ":"); 267 268 if (cp) { 269 int r = snprintf(buf, sizeof buf, "%s/%s", cp, cmd); 270 if (r != -1 && r < sizeof buf) { 271 if (unveil(buf, "x") != -1) 272 unveils++; 273 } 274 } 275 } 276 done: 277 free(path); 278 return (unveils); 279 } 280 281 int 282 main(int argc, char **argv) 283 { 284 const char *safepath = "/bin:/sbin:/usr/bin:/usr/sbin:" 285 "/usr/local/bin:/usr/local/sbin"; 286 const char *confpath = NULL; 287 char *shargv[] = { NULL, NULL }; 288 char *sh; 289 const char *p; 290 const char *cmd; 291 char cmdline[LINE_MAX]; 292 char mypwbuf[_PW_BUF_LEN], targpwbuf[_PW_BUF_LEN]; 293 struct passwd mypwstore, targpwstore; 294 struct passwd *mypw, *targpw; 295 const struct rule *rule; 296 uid_t uid; 297 uid_t target = 0; 298 gid_t groups[NGROUPS_MAX + 1]; 299 int ngroups; 300 int i, ch, rv; 301 int sflag = 0; 302 int nflag = 0; 303 char cwdpath[PATH_MAX]; 304 const char *cwd; 305 char *login_style = NULL; 306 char **envp; 307 308 setprogname("doas"); 309 310 closefrom(STDERR_FILENO + 1); 311 312 uid = getuid(); 313 314 while ((ch = getopt(argc, argv, "a:C:Lnsu:")) != -1) { 315 switch (ch) { 316 case 'a': 317 login_style = optarg; 318 break; 319 case 'C': 320 confpath = optarg; 321 break; 322 case 'L': 323 i = open("/dev/tty", O_RDWR); 324 if (i != -1) 325 ioctl(i, TIOCCLRVERAUTH); 326 exit(i == -1); 327 case 'u': 328 if (parseuid(optarg, &target) != 0) 329 errx(1, "unknown user"); 330 break; 331 case 'n': 332 nflag = 1; 333 break; 334 case 's': 335 sflag = 1; 336 break; 337 default: 338 usage(); 339 break; 340 } 341 } 342 argv += optind; 343 argc -= optind; 344 345 if (confpath) { 346 if (sflag) 347 usage(); 348 } else if ((!sflag && !argc) || (sflag && argc)) 349 usage(); 350 351 rv = getpwuid_r(uid, &mypwstore, mypwbuf, sizeof(mypwbuf), &mypw); 352 if (rv != 0) 353 err(1, "getpwuid_r failed"); 354 if (mypw == NULL) 355 errx(1, "no passwd entry for self"); 356 ngroups = getgroups(NGROUPS_MAX, groups); 357 if (ngroups == -1) 358 err(1, "can't get groups"); 359 groups[ngroups++] = getgid(); 360 361 if (sflag) { 362 sh = getenv("SHELL"); 363 if (sh == NULL || *sh == '\0') { 364 shargv[0] = mypw->pw_shell; 365 } else 366 shargv[0] = sh; 367 argv = shargv; 368 argc = 1; 369 } 370 371 if (confpath) { 372 checkconfig(confpath, argc, argv, uid, groups, ngroups, 373 target); 374 exit(1); /* fail safe */ 375 } 376 377 if (geteuid()) 378 errx(1, "not installed setuid"); 379 380 parseconfig("/etc/doas.conf", 1); 381 382 /* cmdline is used only for logging, no need to abort on truncate */ 383 (void)strlcpy(cmdline, argv[0], sizeof(cmdline)); 384 for (i = 1; i < argc; i++) { 385 if (strlcat(cmdline, " ", sizeof(cmdline)) >= sizeof(cmdline)) 386 break; 387 if (strlcat(cmdline, argv[i], sizeof(cmdline)) >= sizeof(cmdline)) 388 break; 389 } 390 391 cmd = argv[0]; 392 if (!permit(uid, groups, ngroups, &rule, target, cmd, 393 (const char **)argv + 1)) { 394 syslog(LOG_AUTHPRIV | LOG_NOTICE, 395 "failed command for %s: %s", mypw->pw_name, cmdline); 396 errc(1, EPERM, NULL); 397 } 398 399 if (!(rule->options & NOPASS)) { 400 if (nflag) 401 errx(1, "Authorization required"); 402 403 authuser(mypw->pw_name, login_style, rule->options & PERSIST); 404 } 405 406 if ((p = getenv("PATH")) != NULL) 407 formerpath = strdup(p); 408 if (formerpath == NULL) 409 formerpath = ""; 410 411 if (unveil(_PATH_LOGIN_CONF, "r") == -1) 412 err(1, "unveil"); 413 if (rule->cmd) { 414 if (setenv("PATH", safepath, 1) == -1) 415 err(1, "failed to set PATH '%s'", safepath); 416 } 417 if (unveilcommands(getenv("PATH"), cmd) == 0) 418 goto fail; 419 420 if (pledge("stdio rpath getpw exec id", NULL) == -1) 421 err(1, "pledge"); 422 423 rv = getpwuid_r(target, &targpwstore, targpwbuf, sizeof(targpwbuf), &targpw); 424 if (rv != 0) 425 err(1, "getpwuid_r failed"); 426 if (targpw == NULL) 427 errx(1, "no passwd entry for target"); 428 429 if (setusercontext(NULL, targpw, target, LOGIN_SETGROUP | 430 LOGIN_SETPATH | 431 LOGIN_SETPRIORITY | LOGIN_SETRESOURCES | LOGIN_SETUMASK | 432 LOGIN_SETUSER) != 0) 433 errx(1, "failed to set user context for target"); 434 435 if (pledge("stdio rpath exec", NULL) == -1) 436 err(1, "pledge"); 437 438 if (getcwd(cwdpath, sizeof(cwdpath)) == NULL) 439 cwd = "(failed)"; 440 else 441 cwd = cwdpath; 442 443 if (pledge("stdio exec", NULL) == -1) 444 err(1, "pledge"); 445 446 syslog(LOG_AUTHPRIV | LOG_INFO, "%s ran command %s as %s from %s", 447 mypw->pw_name, cmdline, targpw->pw_name, cwd); 448 449 envp = prepenv(rule, mypw, targpw); 450 451 if (rule->cmd) { 452 /* do this again after setusercontext reset it */ 453 if (setenv("PATH", safepath, 1) == -1) 454 err(1, "failed to set PATH '%s'", safepath); 455 } 456 execvpe(cmd, argv, envp); 457 fail: 458 if (errno == ENOENT) 459 errx(1, "%s: command not found", cmd); 460 err(1, "%s", cmd); 461 } 462