Annotation of src/usr.bin/doas/doas.c, Revision 1.46
1.46 ! tedu 1: /* $OpenBSD: doas.c,v 1.45 2015/10/24 19:23:48 miod 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: {
1.28 espie 40: fprintf(stderr, "usage: doas [-ns] [-C config] [-u user] command [args]\n");
1.1 tedu 41: exit(1);
42: }
43:
44: size_t
45: arraylen(const char **arr)
46: {
47: size_t cnt = 0;
1.9 tedu 48:
1.1 tedu 49: while (*arr) {
50: cnt++;
51: arr++;
52: }
53: return cnt;
54: }
55:
56: static int
57: parseuid(const char *s, uid_t *uid)
58: {
59: struct passwd *pw;
60: const char *errstr;
61:
62: if ((pw = getpwnam(s)) != NULL) {
63: *uid = pw->pw_uid;
64: return 0;
65: }
66: *uid = strtonum(s, 0, UID_MAX, &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:
1.33 tedu 84: static int
85: parsegid(const char *s, gid_t *gid)
1.1 tedu 86: {
87: struct group *gr;
88: const char *errstr;
89:
1.33 tedu 90: if ((gr = getgrnam(s)) != NULL) {
91: *gid = gr->gr_gid;
92: return 0;
93: }
94: *gid = strtonum(s, 0, GID_MAX, &errstr);
1.1 tedu 95: if (errstr)
96: return -1;
1.33 tedu 97: return 0;
1.1 tedu 98: }
99:
100: static int
101: match(uid_t uid, gid_t *groups, int ngroups, uid_t target, const char *cmd,
1.15 zhuk 102: const char **cmdargs, struct rule *r)
1.1 tedu 103: {
104: int i;
105:
106: if (r->ident[0] == ':') {
1.33 tedu 107: gid_t rgid;
108: if (parsegid(r->ident + 1, &rgid) == -1)
1.1 tedu 109: return 0;
110: for (i = 0; i < ngroups; i++) {
111: if (rgid == groups[i])
112: break;
113: }
114: if (i == ngroups)
115: return 0;
116: } else {
117: if (uidcheck(r->ident, uid) != 0)
118: return 0;
119: }
120: if (r->target && uidcheck(r->target, target) != 0)
121: return 0;
1.15 zhuk 122: if (r->cmd) {
123: if (strcmp(r->cmd, cmd))
124: return 0;
125: if (r->cmdargs) {
126: /* if arguments were given, they should match explicitly */
127: for (i = 0; r->cmdargs[i]; i++) {
128: if (!cmdargs[i])
129: return 0;
130: if (strcmp(r->cmdargs[i], cmdargs[i]))
131: return 0;
132: }
133: if (cmdargs[i])
134: return 0;
135: }
136: }
1.1 tedu 137: return 1;
138: }
139:
140: static int
141: permit(uid_t uid, gid_t *groups, int ngroups, struct rule **lastr,
1.15 zhuk 142: uid_t target, const char *cmd, const char **cmdargs)
1.1 tedu 143: {
144: int i;
145:
146: *lastr = NULL;
147: for (i = 0; i < nrules; i++) {
1.31 deraadt 148: if (match(uid, groups, ngroups, target, cmd,
149: cmdargs, rules[i]))
1.1 tedu 150: *lastr = rules[i];
151: }
152: if (!*lastr)
153: return 0;
154: return (*lastr)->action == PERMIT;
155: }
156:
157: static void
1.22 zhuk 158: parseconfig(const char *filename, int checkperms)
1.1 tedu 159: {
160: extern FILE *yyfp;
161: extern int yyparse(void);
1.6 nicm 162: struct stat sb;
1.1 tedu 163:
164: yyfp = fopen(filename, "r");
1.36 espie 165: if (!yyfp)
166: err(1, checkperms ? "doas is not enabled, %s" :
167: "could not open config file %s", filename);
1.6 nicm 168:
1.22 zhuk 169: if (checkperms) {
170: if (fstat(fileno(yyfp), &sb) != 0)
171: err(1, "fstat(\"%s\")", filename);
172: if ((sb.st_mode & (S_IWGRP|S_IWOTH)) != 0)
173: errx(1, "%s is writable by group or other", filename);
174: if (sb.st_uid != 0)
175: errx(1, "%s is not owned by root", filename);
176: }
1.6 nicm 177:
1.1 tedu 178: yyparse();
179: fclose(yyfp);
1.21 zhuk 180: if (parse_errors)
181: exit(1);
1.1 tedu 182: }
183:
1.30 zhuk 184: /*
1.32 tedu 185: * Copy the environment variables in safeset from oldenvp to envp.
1.30 zhuk 186: */
1.1 tedu 187: static int
1.4 deraadt 188: copyenvhelper(const char **oldenvp, const char **safeset, int nsafe,
189: char **envp, int ei)
1.1 tedu 190: {
191: int i;
1.9 tedu 192:
1.1 tedu 193: for (i = 0; i < nsafe; i++) {
194: const char **oe = oldenvp;
195: while (*oe) {
196: size_t len = strlen(safeset[i]);
197: if (strncmp(*oe, safeset[i], len) == 0 &&
198: (*oe)[len] == '=') {
199: if (!(envp[ei++] = strdup(*oe)))
200: err(1, "strdup");
201: break;
202: }
203: oe++;
204: }
205: }
206: return ei;
207: }
208:
209: static char **
210: copyenv(const char **oldenvp, struct rule *rule)
211: {
212: const char *safeset[] = {
1.14 tedu 213: "DISPLAY", "HOME", "LOGNAME", "MAIL",
1.1 tedu 214: "PATH", "TERM", "USER", "USERNAME",
1.11 tedu 215: NULL
216: };
217: const char *badset[] = {
218: "ENV",
219: NULL
1.1 tedu 220: };
221: char **envp;
222: const char **extra;
223: int ei;
1.11 tedu 224: int nsafe, nbad;
1.9 tedu 225: int nextras = 0;
1.20 zhuk 226:
1.30 zhuk 227: /* if there was no envvar whitelist, pass all except badset ones */
1.11 tedu 228: nbad = arraylen(badset);
1.1 tedu 229: if ((rule->options & KEEPENV) && !rule->envlist) {
1.30 zhuk 230: size_t iold, inew;
1.12 tedu 231: size_t oldlen = arraylen(oldenvp);
232: envp = reallocarray(NULL, oldlen + 1, sizeof(char *));
1.5 nicm 233: if (!envp)
234: err(1, "reallocarray");
1.30 zhuk 235: for (inew = iold = 0; iold < oldlen; iold++) {
236: size_t ibad;
237: for (ibad = 0; ibad < nbad; ibad++) {
238: size_t len = strlen(badset[ibad]);
239: if (strncmp(oldenvp[iold], badset[ibad], len) == 0 &&
240: oldenvp[iold][len] == '=') {
1.11 tedu 241: break;
242: }
243: }
1.30 zhuk 244: if (ibad == nbad) {
245: if (!(envp[inew] = strdup(oldenvp[iold])))
1.11 tedu 246: err(1, "strdup");
1.30 zhuk 247: inew++;
1.11 tedu 248: }
1.1 tedu 249: }
1.30 zhuk 250: envp[inew] = NULL;
1.1 tedu 251: return envp;
252: }
253:
254: nsafe = arraylen(safeset);
255: if ((extra = rule->envlist)) {
1.30 zhuk 256: size_t isafe;
1.1 tedu 257: nextras = arraylen(extra);
1.30 zhuk 258: for (isafe = 0; isafe < nsafe; isafe++) {
259: size_t iextras;
260: for (iextras = 0; iextras < nextras; iextras++) {
261: if (strcmp(extra[iextras], safeset[isafe]) == 0) {
1.29 zhuk 262: nextras--;
1.30 zhuk 263: extra[iextras] = extra[nextras];
1.1 tedu 264: extra[nextras] = NULL;
1.30 zhuk 265: iextras--;
1.1 tedu 266: }
267: }
268: }
269: }
270:
271: envp = reallocarray(NULL, nsafe + nextras + 1, sizeof(char *));
272: if (!envp)
273: err(1, "can't allocate new environment");
274:
275: ei = 0;
276: ei = copyenvhelper(oldenvp, safeset, nsafe, envp, ei);
277: ei = copyenvhelper(oldenvp, rule->envlist, nextras, envp, ei);
278: envp[ei] = NULL;
279:
280: return envp;
281: }
282:
283: static void __dead
1.22 zhuk 284: checkconfig(const char *confpath, int argc, char **argv,
1.24 tedu 285: uid_t uid, gid_t *groups, int ngroups, uid_t target)
286: {
1.22 zhuk 287: struct rule *rule;
288:
289: setresuid(uid, uid, uid);
290: parseconfig(confpath, 0);
291: if (!argc)
292: exit(0);
293:
294: if (permit(uid, groups, ngroups, &rule, target, argv[0],
295: (const char **)argv + 1)) {
296: printf("permit%s\n", (rule->options & NOPASS) ? " nopass" : "");
1.24 tedu 297: exit(0);
1.22 zhuk 298: } else {
299: printf("deny\n");
1.24 tedu 300: exit(1);
1.22 zhuk 301: }
302: }
303:
1.1 tedu 304: int
305: main(int argc, char **argv, char **envp)
306: {
1.9 tedu 307: const char *safepath = "/bin:/sbin:/usr/bin:/usr/sbin:"
308: "/usr/local/bin:/usr/local/sbin";
1.22 zhuk 309: const char *confpath = NULL;
1.9 tedu 310: char *shargv[] = { NULL, NULL };
311: char *sh;
312: const char *cmd;
1.7 doug 313: char cmdline[LINE_MAX];
314: char myname[_PW_NAME_LEN + 1];
1.9 tedu 315: struct passwd *pw;
316: struct rule *rule;
317: uid_t uid;
318: uid_t target = 0;
1.1 tedu 319: gid_t groups[NGROUPS_MAX + 1];
320: int ngroups;
321: int i, ch;
1.8 nicm 322: int sflag = 0;
1.26 espie 323: int nflag = 0;
1.38 doug 324: char cwdpath[PATH_MAX];
325: const char *cwd;
1.42 tedu 326:
1.46 ! tedu 327: if (pledge("stdio rpath getpw tty proc exec id", NULL) == -1)
1.43 deraadt 328: err(1, "pledge");
329:
1.42 tedu 330: closefrom(STDERR_FILENO + 1);
1.1 tedu 331:
1.26 espie 332: uid = getuid();
1.34 tedu 333:
1.26 espie 334: while ((ch = getopt(argc, argv, "C:nsu:")) != -1) {
1.1 tedu 335: switch (ch) {
1.16 tedu 336: case 'C':
1.22 zhuk 337: confpath = optarg;
338: break;
1.1 tedu 339: case 'u':
340: if (parseuid(optarg, &target) != 0)
341: errx(1, "unknown user");
342: break;
1.26 espie 343: case 'n':
344: nflag = 1;
345: break;
1.8 nicm 346: case 's':
347: sflag = 1;
348: break;
1.1 tedu 349: default:
350: usage();
351: break;
352: }
353: }
354: argv += optind;
355: argc -= optind;
356:
1.22 zhuk 357: if (confpath) {
358: if (sflag)
359: usage();
360: } else if ((!sflag && !argc) || (sflag && argc))
1.1 tedu 361: usage();
1.16 tedu 362:
1.1 tedu 363: pw = getpwuid(uid);
364: if (!pw)
365: err(1, "getpwuid failed");
1.7 doug 366: if (strlcpy(myname, pw->pw_name, sizeof(myname)) >= sizeof(myname))
367: errx(1, "pw_name too long");
1.1 tedu 368: ngroups = getgroups(NGROUPS_MAX, groups);
369: if (ngroups == -1)
370: err(1, "can't get groups");
371: groups[ngroups++] = getgid();
1.8 nicm 372:
373: if (sflag) {
374: sh = getenv("SHELL");
375: if (sh == NULL || *sh == '\0')
376: shargv[0] = pw->pw_shell;
377: else
378: shargv[0] = sh;
379: argv = shargv;
380: argc = 1;
381: }
1.22 zhuk 382:
1.24 tedu 383: if (confpath) {
384: checkconfig(confpath, argc, argv, uid, groups, ngroups,
385: target);
386: exit(1); /* fail safe */
387: }
388:
1.22 zhuk 389: parseconfig("/etc/doas.conf", 1);
1.8 nicm 390:
1.23 zhuk 391: /* cmdline is used only for logging, no need to abort on truncate */
1.25 zhuk 392: (void) strlcpy(cmdline, argv[0], sizeof(cmdline));
1.8 nicm 393: for (i = 1; i < argc; i++) {
394: if (strlcat(cmdline, " ", sizeof(cmdline)) >= sizeof(cmdline))
1.23 zhuk 395: break;
1.8 nicm 396: if (strlcat(cmdline, argv[i], sizeof(cmdline)) >= sizeof(cmdline))
1.23 zhuk 397: break;
1.8 nicm 398: }
1.1 tedu 399:
1.23 zhuk 400: cmd = argv[0];
1.15 zhuk 401: if (!permit(uid, groups, ngroups, &rule, target, cmd,
402: (const char**)argv + 1)) {
1.4 deraadt 403: syslog(LOG_AUTHPRIV | LOG_NOTICE,
404: "failed command for %s: %s", myname, cmdline);
1.41 tedu 405: errc(1, EPERM, NULL);
1.1 tedu 406: }
407:
408: if (!(rule->options & NOPASS)) {
1.46 ! tedu 409: char *challenge = NULL, *response, rbuf[1024], cbuf[128];
! 410: auth_session_t *as;
! 411:
1.26 espie 412: if (nflag)
413: errx(1, "Authorization required");
1.46 ! tedu 414:
! 415: if (!(as = auth_userchallenge(myname, NULL, "auth-doas",
! 416: &challenge)))
! 417: err(1, "auth challenge failed");
! 418: if (!challenge) {
! 419: char host[HOST_NAME_MAX + 1];
! 420: if (gethostname(host, sizeof(host)))
! 421: snprintf(host, sizeof(host), "?");
! 422: snprintf(cbuf, sizeof(cbuf),
! 423: "doas (%.32s@%.32s) password: ", myname, host);
! 424: challenge = cbuf;
! 425: }
! 426: response = readpassphrase(challenge, rbuf, sizeof(rbuf), 0);
! 427: if (!auth_userresponse(as, response, 0)) {
1.4 deraadt 428: syslog(LOG_AUTHPRIV | LOG_NOTICE,
1.46 ! tedu 429: "failed auth for %s", myname);
1.41 tedu 430: errc(1, EPERM, NULL);
1.1 tedu 431: }
432: }
1.43 deraadt 433:
434: if (pledge("stdio rpath getpw exec id", NULL) == -1)
435: err(1, "pledge");
436:
1.1 tedu 437: pw = getpwuid(target);
438: if (!pw)
439: errx(1, "no passwd entry for target");
1.43 deraadt 440:
1.1 tedu 441: if (setusercontext(NULL, pw, target, LOGIN_SETGROUP |
442: LOGIN_SETPRIORITY | LOGIN_SETRESOURCES | LOGIN_SETUMASK |
443: LOGIN_SETUSER) != 0)
444: errx(1, "failed to set user context for target");
445:
1.43 deraadt 446: if (pledge("stdio rpath exec", NULL) == -1)
447: err(1, "pledge");
448:
1.38 doug 449: if (getcwd(cwdpath, sizeof(cwdpath)) == NULL)
450: cwd = "(failed)";
451: else
452: cwd = cwdpath;
1.43 deraadt 453:
454: if (pledge("stdio exec", NULL) == -1)
455: err(1, "pledge");
1.38 doug 456:
457: syslog(LOG_AUTHPRIV | LOG_INFO, "%s ran command %s as %s from %s",
458: myname, cmdline, pw->pw_name, cwd);
1.44 tedu 459:
460: envp = copyenv((const char **)envp, rule);
1.38 doug 461:
1.40 tedu 462: if (rule->cmd) {
463: if (setenv("PATH", safepath, 1) == -1)
464: err(1, "failed to set PATH '%s'", safepath);
465: }
1.1 tedu 466: execvpe(cmd, argv, envp);
1.10 tedu 467: if (errno == ENOENT)
468: errx(1, "%s: command not found", cmd);
1.1 tedu 469: err(1, "%s", cmd);
470: }
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