Annotation of src/usr.bin/doas/doas.c, Revision 1.50
1.50 ! tedu 1: /* $OpenBSD: doas.c,v 1.49 2016/01/24 13:19:21 gsoares Exp $ */
1.1 tedu 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: */
1.6 nicm 17:
1.1 tedu 18: #include <sys/types.h>
1.6 nicm 19: #include <sys/stat.h>
1.1 tedu 20:
21: #include <limits.h>
22: #include <login_cap.h>
23: #include <bsd_auth.h>
1.46 tedu 24: #include <readpassphrase.h>
1.1 tedu 25: #include <string.h>
26: #include <stdio.h>
27: #include <stdlib.h>
28: #include <err.h>
29: #include <unistd.h>
30: #include <pwd.h>
31: #include <grp.h>
32: #include <syslog.h>
1.10 tedu 33: #include <errno.h>
1.1 tedu 34:
35: #include "doas.h"
36:
37: static void __dead
38: usage(void)
39: {
1.47 sthen 40: fprintf(stderr, "usage: doas [-ns] [-a style] [-C config] [-u user]"
41: " command [args]\n");
1.1 tedu 42: exit(1);
43: }
44:
45: size_t
46: arraylen(const char **arr)
47: {
48: size_t cnt = 0;
1.9 tedu 49:
1.1 tedu 50: while (*arr) {
51: cnt++;
52: arr++;
53: }
54: return cnt;
55: }
56:
57: static int
58: parseuid(const char *s, uid_t *uid)
59: {
60: struct passwd *pw;
61: const char *errstr;
62:
63: if ((pw = getpwnam(s)) != NULL) {
64: *uid = pw->pw_uid;
65: return 0;
66: }
67: *uid = strtonum(s, 0, UID_MAX, &errstr);
68: if (errstr)
69: return -1;
70: return 0;
71: }
72:
73: static int
74: uidcheck(const char *s, uid_t desired)
75: {
76: uid_t uid;
77:
78: if (parseuid(s, &uid) != 0)
79: return -1;
80: if (uid != desired)
81: return -1;
82: return 0;
83: }
84:
1.33 tedu 85: static int
86: parsegid(const char *s, gid_t *gid)
1.1 tedu 87: {
88: struct group *gr;
89: const char *errstr;
90:
1.33 tedu 91: if ((gr = getgrnam(s)) != NULL) {
92: *gid = gr->gr_gid;
93: return 0;
94: }
95: *gid = strtonum(s, 0, GID_MAX, &errstr);
1.1 tedu 96: if (errstr)
97: return -1;
1.33 tedu 98: return 0;
1.1 tedu 99: }
100:
101: static int
102: match(uid_t uid, gid_t *groups, int ngroups, uid_t target, const char *cmd,
1.15 zhuk 103: const char **cmdargs, struct rule *r)
1.1 tedu 104: {
105: int i;
106:
107: if (r->ident[0] == ':') {
1.33 tedu 108: gid_t rgid;
109: if (parsegid(r->ident + 1, &rgid) == -1)
1.1 tedu 110: return 0;
111: for (i = 0; i < ngroups; i++) {
112: if (rgid == groups[i])
113: break;
114: }
115: if (i == ngroups)
116: return 0;
117: } else {
118: if (uidcheck(r->ident, uid) != 0)
119: return 0;
120: }
121: if (r->target && uidcheck(r->target, target) != 0)
122: return 0;
1.15 zhuk 123: if (r->cmd) {
124: if (strcmp(r->cmd, cmd))
125: return 0;
126: if (r->cmdargs) {
127: /* if arguments were given, they should match explicitly */
128: for (i = 0; r->cmdargs[i]; i++) {
129: if (!cmdargs[i])
130: return 0;
131: if (strcmp(r->cmdargs[i], cmdargs[i]))
132: return 0;
133: }
134: if (cmdargs[i])
135: return 0;
136: }
137: }
1.1 tedu 138: return 1;
139: }
140:
141: static int
142: permit(uid_t uid, gid_t *groups, int ngroups, struct rule **lastr,
1.15 zhuk 143: uid_t target, const char *cmd, const char **cmdargs)
1.1 tedu 144: {
145: int i;
146:
147: *lastr = NULL;
148: for (i = 0; i < nrules; i++) {
1.31 deraadt 149: if (match(uid, groups, ngroups, target, cmd,
150: cmdargs, rules[i]))
1.1 tedu 151: *lastr = rules[i];
152: }
153: if (!*lastr)
154: return 0;
155: return (*lastr)->action == PERMIT;
156: }
157:
158: static void
1.22 zhuk 159: parseconfig(const char *filename, int checkperms)
1.1 tedu 160: {
161: extern FILE *yyfp;
162: extern int yyparse(void);
1.6 nicm 163: struct stat sb;
1.1 tedu 164:
165: yyfp = fopen(filename, "r");
1.36 espie 166: if (!yyfp)
167: err(1, checkperms ? "doas is not enabled, %s" :
168: "could not open config file %s", filename);
1.6 nicm 169:
1.22 zhuk 170: if (checkperms) {
171: if (fstat(fileno(yyfp), &sb) != 0)
172: err(1, "fstat(\"%s\")", filename);
173: if ((sb.st_mode & (S_IWGRP|S_IWOTH)) != 0)
174: errx(1, "%s is writable by group or other", filename);
175: if (sb.st_uid != 0)
176: errx(1, "%s is not owned by root", filename);
177: }
1.6 nicm 178:
1.1 tedu 179: yyparse();
180: fclose(yyfp);
1.21 zhuk 181: if (parse_errors)
182: exit(1);
1.1 tedu 183: }
184:
1.30 zhuk 185: /*
1.32 tedu 186: * Copy the environment variables in safeset from oldenvp to envp.
1.30 zhuk 187: */
1.1 tedu 188: static int
1.4 deraadt 189: copyenvhelper(const char **oldenvp, const char **safeset, int nsafe,
190: char **envp, int ei)
1.1 tedu 191: {
192: int i;
1.9 tedu 193:
1.1 tedu 194: for (i = 0; i < nsafe; i++) {
195: const char **oe = oldenvp;
196: while (*oe) {
197: size_t len = strlen(safeset[i]);
198: if (strncmp(*oe, safeset[i], len) == 0 &&
199: (*oe)[len] == '=') {
200: if (!(envp[ei++] = strdup(*oe)))
201: err(1, "strdup");
202: break;
203: }
204: oe++;
205: }
206: }
207: return ei;
208: }
209:
210: static char **
211: copyenv(const char **oldenvp, struct rule *rule)
212: {
213: const char *safeset[] = {
1.14 tedu 214: "DISPLAY", "HOME", "LOGNAME", "MAIL",
1.1 tedu 215: "PATH", "TERM", "USER", "USERNAME",
1.11 tedu 216: NULL
217: };
218: const char *badset[] = {
219: "ENV",
220: NULL
1.1 tedu 221: };
222: char **envp;
223: const char **extra;
224: int ei;
1.11 tedu 225: int nsafe, nbad;
1.9 tedu 226: int nextras = 0;
1.20 zhuk 227:
1.30 zhuk 228: /* if there was no envvar whitelist, pass all except badset ones */
1.11 tedu 229: nbad = arraylen(badset);
1.1 tedu 230: if ((rule->options & KEEPENV) && !rule->envlist) {
1.30 zhuk 231: size_t iold, inew;
1.12 tedu 232: size_t oldlen = arraylen(oldenvp);
233: envp = reallocarray(NULL, oldlen + 1, sizeof(char *));
1.5 nicm 234: if (!envp)
235: err(1, "reallocarray");
1.30 zhuk 236: for (inew = iold = 0; iold < oldlen; iold++) {
237: size_t ibad;
238: for (ibad = 0; ibad < nbad; ibad++) {
239: size_t len = strlen(badset[ibad]);
240: if (strncmp(oldenvp[iold], badset[ibad], len) == 0 &&
241: oldenvp[iold][len] == '=') {
1.11 tedu 242: break;
243: }
244: }
1.30 zhuk 245: if (ibad == nbad) {
246: if (!(envp[inew] = strdup(oldenvp[iold])))
1.11 tedu 247: err(1, "strdup");
1.30 zhuk 248: inew++;
1.11 tedu 249: }
1.1 tedu 250: }
1.30 zhuk 251: envp[inew] = NULL;
1.1 tedu 252: return envp;
253: }
254:
255: nsafe = arraylen(safeset);
256: if ((extra = rule->envlist)) {
1.30 zhuk 257: size_t isafe;
1.1 tedu 258: nextras = arraylen(extra);
1.30 zhuk 259: for (isafe = 0; isafe < nsafe; isafe++) {
260: size_t iextras;
261: for (iextras = 0; iextras < nextras; iextras++) {
262: if (strcmp(extra[iextras], safeset[isafe]) == 0) {
1.29 zhuk 263: nextras--;
1.30 zhuk 264: extra[iextras] = extra[nextras];
1.1 tedu 265: extra[nextras] = NULL;
1.30 zhuk 266: iextras--;
1.1 tedu 267: }
268: }
269: }
270: }
271:
272: envp = reallocarray(NULL, nsafe + nextras + 1, sizeof(char *));
273: if (!envp)
274: err(1, "can't allocate new environment");
275:
276: ei = 0;
277: ei = copyenvhelper(oldenvp, safeset, nsafe, envp, ei);
278: ei = copyenvhelper(oldenvp, rule->envlist, nextras, envp, ei);
279: envp[ei] = NULL;
280:
281: return envp;
282: }
283:
284: static void __dead
1.22 zhuk 285: checkconfig(const char *confpath, int argc, char **argv,
1.24 tedu 286: uid_t uid, gid_t *groups, int ngroups, uid_t target)
287: {
1.22 zhuk 288: struct rule *rule;
289:
290: setresuid(uid, uid, uid);
291: parseconfig(confpath, 0);
292: if (!argc)
293: exit(0);
294:
295: if (permit(uid, groups, ngroups, &rule, target, argv[0],
296: (const char **)argv + 1)) {
297: printf("permit%s\n", (rule->options & NOPASS) ? " nopass" : "");
1.24 tedu 298: exit(0);
1.22 zhuk 299: } else {
300: printf("deny\n");
1.24 tedu 301: exit(1);
1.22 zhuk 302: }
303: }
304:
1.1 tedu 305: int
306: main(int argc, char **argv, char **envp)
307: {
1.9 tedu 308: const char *safepath = "/bin:/sbin:/usr/bin:/usr/sbin:"
309: "/usr/local/bin:/usr/local/sbin";
1.22 zhuk 310: const char *confpath = NULL;
1.9 tedu 311: char *shargv[] = { NULL, NULL };
312: char *sh;
313: const char *cmd;
1.7 doug 314: char cmdline[LINE_MAX];
315: char myname[_PW_NAME_LEN + 1];
1.9 tedu 316: struct passwd *pw;
317: struct rule *rule;
318: uid_t uid;
319: uid_t target = 0;
1.1 tedu 320: gid_t groups[NGROUPS_MAX + 1];
321: int ngroups;
322: int i, ch;
1.8 nicm 323: int sflag = 0;
1.26 espie 324: int nflag = 0;
1.38 doug 325: char cwdpath[PATH_MAX];
326: const char *cwd;
1.47 sthen 327: char *login_style = NULL;
1.42 tedu 328:
1.46 tedu 329: if (pledge("stdio rpath getpw tty proc exec id", NULL) == -1)
1.43 deraadt 330: err(1, "pledge");
331:
1.42 tedu 332: closefrom(STDERR_FILENO + 1);
1.1 tedu 333:
1.26 espie 334: uid = getuid();
1.34 tedu 335:
1.47 sthen 336: while ((ch = getopt(argc, argv, "a:C:nsu:")) != -1) {
1.1 tedu 337: switch (ch) {
1.47 sthen 338: case 'a':
339: login_style = optarg;
340: break;
1.16 tedu 341: case 'C':
1.22 zhuk 342: confpath = optarg;
343: break;
1.1 tedu 344: case 'u':
345: if (parseuid(optarg, &target) != 0)
346: errx(1, "unknown user");
347: break;
1.26 espie 348: case 'n':
349: nflag = 1;
350: break;
1.8 nicm 351: case 's':
352: sflag = 1;
353: break;
1.1 tedu 354: default:
355: usage();
356: break;
357: }
358: }
359: argv += optind;
360: argc -= optind;
361:
1.22 zhuk 362: if (confpath) {
363: if (sflag)
364: usage();
365: } else if ((!sflag && !argc) || (sflag && argc))
1.1 tedu 366: usage();
1.16 tedu 367:
1.1 tedu 368: pw = getpwuid(uid);
369: if (!pw)
370: err(1, "getpwuid failed");
1.7 doug 371: if (strlcpy(myname, pw->pw_name, sizeof(myname)) >= sizeof(myname))
372: errx(1, "pw_name too long");
1.1 tedu 373: ngroups = getgroups(NGROUPS_MAX, groups);
374: if (ngroups == -1)
375: err(1, "can't get groups");
376: groups[ngroups++] = getgid();
1.8 nicm 377:
378: if (sflag) {
379: sh = getenv("SHELL");
380: if (sh == NULL || *sh == '\0')
381: shargv[0] = pw->pw_shell;
382: else
383: shargv[0] = sh;
384: argv = shargv;
385: argc = 1;
386: }
1.22 zhuk 387:
1.24 tedu 388: if (confpath) {
389: checkconfig(confpath, argc, argv, uid, groups, ngroups,
390: target);
391: exit(1); /* fail safe */
392: }
393:
1.22 zhuk 394: parseconfig("/etc/doas.conf", 1);
1.8 nicm 395:
1.23 zhuk 396: /* cmdline is used only for logging, no need to abort on truncate */
1.25 zhuk 397: (void) strlcpy(cmdline, argv[0], sizeof(cmdline));
1.8 nicm 398: for (i = 1; i < argc; i++) {
399: if (strlcat(cmdline, " ", sizeof(cmdline)) >= sizeof(cmdline))
1.23 zhuk 400: break;
1.8 nicm 401: if (strlcat(cmdline, argv[i], sizeof(cmdline)) >= sizeof(cmdline))
1.23 zhuk 402: break;
1.8 nicm 403: }
1.1 tedu 404:
1.23 zhuk 405: cmd = argv[0];
1.15 zhuk 406: if (!permit(uid, groups, ngroups, &rule, target, cmd,
407: (const char**)argv + 1)) {
1.4 deraadt 408: syslog(LOG_AUTHPRIV | LOG_NOTICE,
409: "failed command for %s: %s", myname, cmdline);
1.41 tedu 410: errc(1, EPERM, NULL);
1.1 tedu 411: }
412:
413: if (!(rule->options & NOPASS)) {
1.46 tedu 414: char *challenge = NULL, *response, rbuf[1024], cbuf[128];
415: auth_session_t *as;
416:
1.26 espie 417: if (nflag)
418: errx(1, "Authorization required");
1.46 tedu 419:
1.47 sthen 420: if (!(as = auth_userchallenge(myname, login_style, "auth-doas",
1.46 tedu 421: &challenge)))
1.48 tedu 422: errx(1, "Authorization failed");
1.46 tedu 423: if (!challenge) {
424: char host[HOST_NAME_MAX + 1];
425: if (gethostname(host, sizeof(host)))
426: snprintf(host, sizeof(host), "?");
427: snprintf(cbuf, sizeof(cbuf),
428: "doas (%.32s@%.32s) password: ", myname, host);
429: challenge = cbuf;
430: }
1.50 ! tedu 431: response = readpassphrase(challenge, rbuf, sizeof(rbuf),
! 432: RPP_REQUIRE_TTY);
! 433: if (response == NULL && errno == ENOTTY) {
! 434: syslog(LOG_AUTHPRIV | LOG_NOTICE,
! 435: "tty required for %s", myname);
! 436: errx(1, "a tty is required");
! 437: }
1.46 tedu 438: if (!auth_userresponse(as, response, 0)) {
1.4 deraadt 439: syslog(LOG_AUTHPRIV | LOG_NOTICE,
1.46 tedu 440: "failed auth for %s", myname);
1.41 tedu 441: errc(1, EPERM, NULL);
1.1 tedu 442: }
1.49 gsoares 443: explicit_bzero(rbuf, sizeof(rbuf));
1.1 tedu 444: }
1.43 deraadt 445:
446: if (pledge("stdio rpath getpw exec id", NULL) == -1)
447: err(1, "pledge");
448:
1.1 tedu 449: pw = getpwuid(target);
450: if (!pw)
451: errx(1, "no passwd entry for target");
1.43 deraadt 452:
1.1 tedu 453: if (setusercontext(NULL, pw, target, LOGIN_SETGROUP |
454: LOGIN_SETPRIORITY | LOGIN_SETRESOURCES | LOGIN_SETUMASK |
455: LOGIN_SETUSER) != 0)
456: errx(1, "failed to set user context for target");
457:
1.43 deraadt 458: if (pledge("stdio rpath exec", NULL) == -1)
459: err(1, "pledge");
460:
1.38 doug 461: if (getcwd(cwdpath, sizeof(cwdpath)) == NULL)
462: cwd = "(failed)";
463: else
464: cwd = cwdpath;
1.43 deraadt 465:
466: if (pledge("stdio exec", NULL) == -1)
467: err(1, "pledge");
1.38 doug 468:
469: syslog(LOG_AUTHPRIV | LOG_INFO, "%s ran command %s as %s from %s",
470: myname, cmdline, pw->pw_name, cwd);
1.44 tedu 471:
472: envp = copyenv((const char **)envp, rule);
1.38 doug 473:
1.40 tedu 474: if (rule->cmd) {
475: if (setenv("PATH", safepath, 1) == -1)
476: err(1, "failed to set PATH '%s'", safepath);
477: }
1.1 tedu 478: execvpe(cmd, argv, envp);
1.10 tedu 479: if (errno == ENOENT)
480: errx(1, "%s: command not found", cmd);
1.1 tedu 481: err(1, "%s", cmd);
482: }
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