1 /* $OpenBSD: doas.c,v 1.65 2016/09/15 00:58:23 deraadt 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 size_t 48 arraylen(const char **arr) 49 { 50 size_t cnt = 0; 51 52 while (*arr) { 53 cnt++; 54 arr++; 55 } 56 return cnt; 57 } 58 59 static int 60 parseuid(const char *s, uid_t *uid) 61 { 62 struct passwd *pw; 63 const char *errstr; 64 65 if ((pw = getpwnam(s)) != NULL) { 66 *uid = pw->pw_uid; 67 return 0; 68 } 69 *uid = strtonum(s, 0, UID_MAX, &errstr); 70 if (errstr) 71 return -1; 72 return 0; 73 } 74 75 static int 76 uidcheck(const char *s, uid_t desired) 77 { 78 uid_t uid; 79 80 if (parseuid(s, &uid) != 0) 81 return -1; 82 if (uid != desired) 83 return -1; 84 return 0; 85 } 86 87 static int 88 parsegid(const char *s, gid_t *gid) 89 { 90 struct group *gr; 91 const char *errstr; 92 93 if ((gr = getgrnam(s)) != NULL) { 94 *gid = gr->gr_gid; 95 return 0; 96 } 97 *gid = strtonum(s, 0, GID_MAX, &errstr); 98 if (errstr) 99 return -1; 100 return 0; 101 } 102 103 static int 104 match(uid_t uid, gid_t *groups, int ngroups, uid_t target, const char *cmd, 105 const char **cmdargs, struct rule *r) 106 { 107 int i; 108 109 if (r->ident[0] == ':') { 110 gid_t rgid; 111 if (parsegid(r->ident + 1, &rgid) == -1) 112 return 0; 113 for (i = 0; i < ngroups; i++) { 114 if (rgid == groups[i]) 115 break; 116 } 117 if (i == ngroups) 118 return 0; 119 } else { 120 if (uidcheck(r->ident, uid) != 0) 121 return 0; 122 } 123 if (r->target && uidcheck(r->target, target) != 0) 124 return 0; 125 if (r->cmd) { 126 if (strcmp(r->cmd, cmd)) 127 return 0; 128 if (r->cmdargs) { 129 /* if arguments were given, they should match explicitly */ 130 for (i = 0; r->cmdargs[i]; i++) { 131 if (!cmdargs[i]) 132 return 0; 133 if (strcmp(r->cmdargs[i], cmdargs[i])) 134 return 0; 135 } 136 if (cmdargs[i]) 137 return 0; 138 } 139 } 140 return 1; 141 } 142 143 static int 144 permit(uid_t uid, gid_t *groups, int ngroups, struct rule **lastr, 145 uid_t target, const char *cmd, const char **cmdargs) 146 { 147 int i; 148 149 *lastr = NULL; 150 for (i = 0; i < nrules; i++) { 151 if (match(uid, groups, ngroups, target, cmd, 152 cmdargs, rules[i])) 153 *lastr = rules[i]; 154 } 155 if (!*lastr) 156 return 0; 157 return (*lastr)->action == PERMIT; 158 } 159 160 static void 161 parseconfig(const char *filename, int checkperms) 162 { 163 extern FILE *yyfp; 164 struct stat sb; 165 166 yyfp = fopen(filename, "r"); 167 if (!yyfp) 168 err(1, checkperms ? "doas is not enabled, %s" : 169 "could not open config file %s", filename); 170 171 if (checkperms) { 172 if (fstat(fileno(yyfp), &sb) != 0) 173 err(1, "fstat(\"%s\")", filename); 174 if ((sb.st_mode & (S_IWGRP|S_IWOTH)) != 0) 175 errx(1, "%s is writable by group or other", filename); 176 if (sb.st_uid != 0) 177 errx(1, "%s is not owned by root", filename); 178 } 179 180 yyparse(); 181 fclose(yyfp); 182 if (parse_errors) 183 exit(1); 184 } 185 186 static void __dead 187 checkconfig(const char *confpath, int argc, char **argv, 188 uid_t uid, gid_t *groups, int ngroups, uid_t target) 189 { 190 struct rule *rule; 191 192 setresuid(uid, uid, uid); 193 parseconfig(confpath, 0); 194 if (!argc) 195 exit(0); 196 197 if (permit(uid, groups, ngroups, &rule, target, argv[0], 198 (const char **)argv + 1)) { 199 printf("permit%s\n", (rule->options & NOPASS) ? " nopass" : ""); 200 exit(0); 201 } else { 202 printf("deny\n"); 203 exit(1); 204 } 205 } 206 207 static void 208 authuser(char *myname, char *login_style, int persist) 209 { 210 char *challenge = NULL, *response, rbuf[1024], cbuf[128]; 211 auth_session_t *as; 212 int fd = -1; 213 214 if (persist) 215 fd = open("/dev/tty", O_RDWR); 216 if (fd != -1) { 217 if (ioctl(fd, TIOCCHKVERAUTH) == 0) 218 goto good; 219 } 220 221 if (!(as = auth_userchallenge(myname, login_style, "auth-doas", 222 &challenge))) 223 errx(1, "Authorization failed"); 224 if (!challenge) { 225 char host[HOST_NAME_MAX + 1]; 226 if (gethostname(host, sizeof(host))) 227 snprintf(host, sizeof(host), "?"); 228 snprintf(cbuf, sizeof(cbuf), 229 "\rdoas (%.32s@%.32s) password: ", myname, host); 230 challenge = cbuf; 231 } 232 response = readpassphrase(challenge, rbuf, sizeof(rbuf), 233 RPP_REQUIRE_TTY); 234 if (response == NULL && errno == ENOTTY) { 235 syslog(LOG_AUTHPRIV | LOG_NOTICE, 236 "tty required for %s", myname); 237 errx(1, "a tty is required"); 238 } 239 if (!auth_userresponse(as, response, 0)) { 240 syslog(LOG_AUTHPRIV | LOG_NOTICE, 241 "failed auth for %s", myname); 242 errc(1, EPERM, NULL); 243 } 244 explicit_bzero(rbuf, sizeof(rbuf)); 245 good: 246 if (fd != -1) { 247 int secs = 5 * 60; 248 ioctl(fd, TIOCSETVERAUTH, &secs); 249 close(fd); 250 } 251 } 252 253 int 254 main(int argc, char **argv) 255 { 256 const char *safepath = "/bin:/sbin:/usr/bin:/usr/sbin:" 257 "/usr/local/bin:/usr/local/sbin"; 258 const char *confpath = NULL; 259 char *shargv[] = { NULL, NULL }; 260 char *sh; 261 const char *cmd; 262 char cmdline[LINE_MAX]; 263 char myname[_PW_NAME_LEN + 1]; 264 struct passwd *pw; 265 struct rule *rule; 266 uid_t uid; 267 uid_t target = 0; 268 gid_t groups[NGROUPS_MAX + 1]; 269 int ngroups; 270 int i, ch; 271 int sflag = 0; 272 int nflag = 0; 273 char cwdpath[PATH_MAX]; 274 const char *cwd; 275 char *login_style = NULL; 276 char **envp; 277 278 setprogname("doas"); 279 280 closefrom(STDERR_FILENO + 1); 281 282 uid = getuid(); 283 284 while ((ch = getopt(argc, argv, "a:C:Lnsu:")) != -1) { 285 switch (ch) { 286 case 'a': 287 login_style = optarg; 288 break; 289 case 'C': 290 confpath = optarg; 291 break; 292 case 'L': 293 i = open("/dev/tty", O_RDWR); 294 if (i != -1) 295 ioctl(i, TIOCCLRVERAUTH); 296 exit(i != -1); 297 case 'u': 298 if (parseuid(optarg, &target) != 0) 299 errx(1, "unknown user"); 300 break; 301 case 'n': 302 nflag = 1; 303 break; 304 case 's': 305 sflag = 1; 306 break; 307 default: 308 usage(); 309 break; 310 } 311 } 312 argv += optind; 313 argc -= optind; 314 315 if (confpath) { 316 if (sflag) 317 usage(); 318 } else if ((!sflag && !argc) || (sflag && argc)) 319 usage(); 320 321 pw = getpwuid(uid); 322 if (!pw) 323 err(1, "getpwuid failed"); 324 if (strlcpy(myname, pw->pw_name, sizeof(myname)) >= sizeof(myname)) 325 errx(1, "pw_name too long"); 326 ngroups = getgroups(NGROUPS_MAX, groups); 327 if (ngroups == -1) 328 err(1, "can't get groups"); 329 groups[ngroups++] = getgid(); 330 331 if (sflag) { 332 sh = getenv("SHELL"); 333 if (sh == NULL || *sh == '\0') { 334 shargv[0] = strdup(pw->pw_shell); 335 if (shargv[0] == NULL) 336 err(1, NULL); 337 } else 338 shargv[0] = sh; 339 argv = shargv; 340 argc = 1; 341 } 342 343 if (confpath) { 344 checkconfig(confpath, argc, argv, uid, groups, ngroups, 345 target); 346 exit(1); /* fail safe */ 347 } 348 349 parseconfig("/etc/doas.conf", 1); 350 351 /* cmdline is used only for logging, no need to abort on truncate */ 352 (void)strlcpy(cmdline, argv[0], sizeof(cmdline)); 353 for (i = 1; i < argc; i++) { 354 if (strlcat(cmdline, " ", sizeof(cmdline)) >= sizeof(cmdline)) 355 break; 356 if (strlcat(cmdline, argv[i], sizeof(cmdline)) >= sizeof(cmdline)) 357 break; 358 } 359 360 cmd = argv[0]; 361 if (!permit(uid, groups, ngroups, &rule, target, cmd, 362 (const char **)argv + 1)) { 363 syslog(LOG_AUTHPRIV | LOG_NOTICE, 364 "failed command for %s: %s", myname, cmdline); 365 errc(1, EPERM, NULL); 366 } 367 368 if (!(rule->options & NOPASS)) { 369 if (nflag) 370 errx(1, "Authorization required"); 371 372 authuser(myname, login_style, rule->options & PERSIST); 373 } 374 375 if (pledge("stdio rpath getpw exec id", NULL) == -1) 376 err(1, "pledge"); 377 378 pw = getpwuid(target); 379 if (!pw) 380 errx(1, "no passwd entry for target"); 381 382 if (setusercontext(NULL, pw, target, LOGIN_SETGROUP | 383 LOGIN_SETPRIORITY | LOGIN_SETRESOURCES | LOGIN_SETUMASK | 384 LOGIN_SETUSER) != 0) 385 errx(1, "failed to set user context for target"); 386 387 if (pledge("stdio rpath exec", NULL) == -1) 388 err(1, "pledge"); 389 390 if (getcwd(cwdpath, sizeof(cwdpath)) == NULL) 391 cwd = "(failed)"; 392 else 393 cwd = cwdpath; 394 395 if (pledge("stdio exec", NULL) == -1) 396 err(1, "pledge"); 397 398 syslog(LOG_AUTHPRIV | LOG_INFO, "%s ran command %s as %s from %s", 399 myname, cmdline, pw->pw_name, cwd); 400 401 envp = prepenv(rule); 402 403 if (rule->cmd) { 404 if (setenv("PATH", safepath, 1) == -1) 405 err(1, "failed to set PATH '%s'", safepath); 406 } 407 execvpe(cmd, argv, envp); 408 if (errno == ENOENT) 409 errx(1, "%s: command not found", cmd); 410 err(1, "%s", cmd); 411 } 412