doas.c (9355B)
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 <readpassphrase.h> 24 #include <string.h> 25 #include <stdio.h> 26 #include <stdlib.h> 27 #include <err.h> 28 #include <unistd.h> 29 #include <pwd.h> 30 #include <grp.h> 31 #include <syslog.h> 32 #include <errno.h> 33 #include <fcntl.h> 34 #include <shadow.h> 35 36 #include "doas.h" 37 38 #ifndef UID_MAX 39 #define UID_MAX 65535 40 #endif 41 42 #ifndef GID_MAX 43 #define GID_MAX 65535 44 #endif 45 46 static void __dead 47 usage(void) 48 { 49 fprintf(stderr, "usage: doas [-Lns] [-C config] [-u user]" 50 " command [arg ...]\n"); 51 exit(1); 52 } 53 54 static int 55 parseuid(const char *s, uid_t *uid) 56 { 57 struct passwd *pw; 58 const char *errstr; 59 60 if ((pw = getpwnam(s)) != NULL) { 61 *uid = pw->pw_uid; 62 if (*uid == UID_MAX) 63 return -1; 64 return 0; 65 } 66 *uid = strtonum(s, 0, UID_MAX - 1, &errstr); 67 if (errstr) 68 return -1; 69 return 0; 70 } 71 72 static int 73 uidcheck(const char *s, uid_t desired) 74 { 75 uid_t uid; 76 77 if (parseuid(s, &uid) != 0) 78 return -1; 79 if (uid != desired) 80 return -1; 81 return 0; 82 } 83 84 static int 85 parsegid(const char *s, gid_t *gid) 86 { 87 struct group *gr; 88 const char *errstr; 89 90 if ((gr = getgrnam(s)) != NULL) { 91 *gid = gr->gr_gid; 92 if (*gid == GID_MAX) 93 return -1; 94 return 0; 95 } 96 *gid = strtonum(s, 0, GID_MAX - 1, &errstr); 97 if (errstr) 98 return -1; 99 return 0; 100 } 101 102 static int 103 match(uid_t uid, gid_t *groups, int ngroups, uid_t target, const char *cmd, 104 const char **cmdargs, struct rule *r) 105 { 106 int i; 107 108 if (r->ident[0] == ':') { 109 gid_t rgid; 110 if (parsegid(r->ident + 1, &rgid) == -1) 111 return 0; 112 for (i = 0; i < ngroups; i++) { 113 if (rgid == groups[i]) 114 break; 115 } 116 if (i == ngroups) 117 return 0; 118 } else { 119 if (uidcheck(r->ident, uid) != 0) 120 return 0; 121 } 122 if (r->target && uidcheck(r->target, target) != 0) 123 return 0; 124 if (r->cmd) { 125 if (strcmp(r->cmd, cmd)) 126 return 0; 127 if (r->cmdargs) { 128 /* if arguments were given, they should match explicitly */ 129 for (i = 0; r->cmdargs[i]; i++) { 130 if (!cmdargs[i]) 131 return 0; 132 if (strcmp(r->cmdargs[i], cmdargs[i])) 133 return 0; 134 } 135 if (cmdargs[i]) 136 return 0; 137 } 138 } 139 return 1; 140 } 141 142 static int 143 permit(uid_t uid, gid_t *groups, int ngroups, const struct rule **lastr, 144 uid_t target, const char *cmd, const char **cmdargs) 145 { 146 size_t i; 147 148 *lastr = NULL; 149 for (i = 0; i < nrules; i++) { 150 if (match(uid, groups, ngroups, target, cmd, 151 cmdargs, rules[i])) 152 *lastr = rules[i]; 153 } 154 if (!*lastr) 155 return -1; 156 if ((*lastr)->action == PERMIT) 157 return 0; 158 return -1; 159 } 160 161 static void 162 parseconfig(const char *filename, int checkperms) 163 { 164 extern FILE *yyfp; 165 extern int yyparse(void); 166 struct stat sb; 167 168 yyfp = fopen(filename, "r"); 169 if (!yyfp) 170 err(1, checkperms ? "doas is not enabled, %s" : 171 "could not open config file %s", filename); 172 173 if (checkperms) { 174 if (fstat(fileno(yyfp), &sb) != 0) 175 err(1, "fstat(\"%s\")", filename); 176 if ((sb.st_mode & (S_IWGRP|S_IWOTH)) != 0) 177 errx(1, "%s is writable by group or other", filename); 178 if (sb.st_uid != 0) 179 errx(1, "%s is not owned by root", filename); 180 } 181 182 yyparse(); 183 fclose(yyfp); 184 if (parse_error) 185 exit(1); 186 } 187 188 static void __dead 189 checkconfig(const char *confpath, int argc, char **argv, 190 uid_t uid, gid_t *groups, int ngroups, uid_t target) 191 { 192 const struct rule *rule; 193 int rv; 194 195 setresuid(uid, uid, uid); 196 if (pledge("stdio rpath getpw", NULL) == -1) 197 err(1, "pledge"); 198 parseconfig(confpath, 0); 199 if (!argc) 200 exit(0); 201 rv = permit(uid, groups, ngroups, &rule, target, argv[0], (const char **)argv + 1); 202 if (rv == 0) { 203 printf("permit%s\n", (rule->options & NOPASS) ? " nopass" : ""); 204 exit(0); 205 } else { 206 printf("deny\n"); 207 exit(1); 208 } 209 } 210 211 static int 212 verifypasswd(const char *user, const char *pass) 213 { 214 struct spwd *sp; 215 char *p1, *p2; 216 217 sp = getspnam(user); 218 if (!sp) 219 return 0; 220 p1 = sp->sp_pwdp; 221 if (p1[0] == '!' || p1[0] == '*') 222 return 0; 223 p2 = crypt(pass, p1); 224 if (!p2) 225 return 0; 226 return strcmp(p1, p2) == 0; 227 } 228 229 static int 230 authuser_checkpass(char *myname) 231 { 232 char *challenge = NULL, *response, rbuf[1024], cbuf[128]; 233 234 if (!challenge) { 235 char host[HOST_NAME_MAX + 1]; 236 237 if (gethostname(host, sizeof(host))) 238 snprintf(host, sizeof(host), "?"); 239 snprintf(cbuf, sizeof(cbuf), 240 "\rdoas (%.32s@%.32s) password: ", myname, host); 241 challenge = cbuf; 242 } 243 response = readpassphrase(challenge, rbuf, sizeof(rbuf), 244 RPP_REQUIRE_TTY); 245 if (response == NULL && errno == ENOTTY) { 246 syslog(LOG_NOTICE, "tty required for %s", myname); 247 errx(1, "a tty is required"); 248 } 249 if (!verifypasswd(myname, response)) { 250 explicit_bzero(rbuf, sizeof(rbuf)); 251 syslog(LOG_NOTICE, "failed auth for %s", myname); 252 warnx("Authentication failed"); 253 return AUTH_FAILED; 254 } 255 explicit_bzero(rbuf, sizeof(rbuf)); 256 return AUTH_OK; 257 } 258 259 static void 260 authuser(char *myname, int persist) 261 { 262 int i, fd = -1, valid = 0; 263 264 if (persist) { 265 fd = openpersist(&valid); 266 if (valid) 267 goto good; 268 } 269 for (i = 0; i < AUTH_RETRIES; i++) { 270 if (authuser_checkpass(myname) == AUTH_OK) 271 goto good; 272 } 273 exit(1); 274 good: 275 if (fd != -1) { 276 setpersist(fd); 277 close(fd); 278 } 279 } 280 281 int 282 main(int argc, char **argv) 283 { 284 const char *confpath = NULL; 285 char *shargv[] = { NULL, NULL }; 286 char *sh; 287 const char *cmd; 288 char cmdline[LINE_MAX]; 289 char mypwbuf[1024], targpwbuf[1024]; 290 struct passwd mypwstore, targpwstore; 291 struct passwd *mypw, *targpw; 292 const struct rule *rule; 293 uid_t uid; 294 uid_t target = 0; 295 gid_t groups[NGROUPS_MAX + 1]; 296 int ngroups; 297 int i, ch, rv; 298 int sflag = 0; 299 int nflag = 0; 300 char cwdpath[PATH_MAX]; 301 const char *cwd; 302 char **envp; 303 304 setprogname("doas"); 305 openlog("doas", 0, LOG_AUTHPRIV); 306 307 uid = getuid(); 308 309 while ((ch = getopt(argc, argv, "C:Lnsu:")) != -1) { 310 switch (ch) { 311 case 'C': 312 confpath = optarg; 313 break; 314 case 'L': 315 exit(clearpersist() != 0); 316 case 'u': 317 if (parseuid(optarg, &target) != 0) 318 errx(1, "unknown user"); 319 break; 320 case 'n': 321 nflag = 1; 322 break; 323 case 's': 324 sflag = 1; 325 break; 326 default: 327 usage(); 328 break; 329 } 330 } 331 argv += optind; 332 argc -= optind; 333 334 if (confpath) { 335 if (sflag) 336 usage(); 337 } else if ((!sflag && !argc) || (sflag && argc)) 338 usage(); 339 340 rv = getpwuid_r(uid, &mypwstore, mypwbuf, sizeof(mypwbuf), &mypw); 341 if (rv != 0) 342 err(1, "getpwuid_r failed"); 343 if (mypw == NULL) 344 errx(1, "no passwd entry for self"); 345 ngroups = getgroups(NGROUPS_MAX, groups); 346 if (ngroups == -1) 347 err(1, "can't get groups"); 348 groups[ngroups++] = getgid(); 349 350 if (sflag) { 351 sh = getenv("SHELL"); 352 if (sh == NULL || *sh == '\0') { 353 shargv[0] = mypw->pw_shell; 354 } else 355 shargv[0] = sh; 356 argv = shargv; 357 argc = 1; 358 } 359 360 if (confpath) { 361 if (pledge("stdio rpath getpw id", NULL) == -1) 362 err(1, "pledge"); 363 checkconfig(confpath, argc, argv, uid, groups, ngroups, 364 target); 365 exit(1); /* fail safe */ 366 } 367 368 if (geteuid()) 369 errx(1, "not installed setuid"); 370 371 parseconfig("/etc/doas.conf", 1); 372 373 /* cmdline is used only for logging, no need to abort on truncate */ 374 (void)strlcpy(cmdline, argv[0], sizeof(cmdline)); 375 for (i = 1; i < argc; i++) { 376 if (strlcat(cmdline, " ", sizeof(cmdline)) >= sizeof(cmdline)) 377 break; 378 if (strlcat(cmdline, argv[i], sizeof(cmdline)) >= sizeof(cmdline)) 379 break; 380 } 381 382 cmd = argv[0]; 383 rv = permit(uid, groups, ngroups, &rule, target, cmd, (const char **)argv + 1); 384 if (rv != 0) { 385 syslog(LOG_NOTICE, "command not permitted for %s: %s", mypw->pw_name, cmdline); 386 errno = EPERM; 387 err(1, NULL); 388 } 389 390 if (!(rule->options & NOPASS)) { 391 if (nflag) 392 errx(1, "Authentication required"); 393 394 authuser(mypw->pw_name, rule->options & PERSIST); 395 } 396 397 rv = getpwuid_r(target, &targpwstore, targpwbuf, sizeof(targpwbuf), &targpw); 398 if (rv != 0) 399 err(1, "getpwuid_r failed"); 400 if (targpw == NULL) 401 errx(1, "no passwd entry for target"); 402 403 if (initgroups(targpw->pw_name, targpw->pw_gid) == -1) 404 err(1, "initgroups"); 405 if (setgid(targpw->pw_gid) == -1) 406 err(1, "setgid"); 407 if (setuid(targpw->pw_uid) == -1) 408 err(1, "setuid"); 409 410 if (pledge("stdio rpath exec", NULL) == -1) 411 err(1, "pledge"); 412 413 if (getcwd(cwdpath, sizeof(cwdpath)) == NULL) 414 cwd = "(failed)"; 415 else 416 cwd = cwdpath; 417 418 if (pledge("stdio exec", NULL) == -1) 419 err(1, "pledge"); 420 421 if (!(rule->options & NOLOG)) { 422 syslog(LOG_INFO, "%s ran command %s as %s from %s", 423 mypw->pw_name, cmdline, targpw->pw_name, cwd); 424 } 425 426 envp = prepenv(rule, mypw, targpw); 427 428 if (rule->cmd) { 429 if (setenv("PATH", safepath, 1) == -1) 430 err(1, "failed to set PATH '%s'", safepath); 431 } 432 execvpe(cmd, argv, envp); 433 if (errno == ENOENT) 434 errx(1, "%s: command not found", cmd); 435 err(1, "%s", cmd); 436 }