Annotation of src/usr.bin/su/su.c, Revision 1.84
1.84 ! beck 1: /* $OpenBSD: su.c,v 1.83 2020/10/30 16:23:57 millert Exp $ */
1.4 deraadt 2:
1.1 deraadt 3: /*
4: * Copyright (c) 1988 The Regents of the University of California.
5: * All rights reserved.
6: *
7: * Redistribution and use in source and binary forms, with or without
8: * modification, are permitted provided that the following conditions
9: * are met:
10: * 1. Redistributions of source code must retain the above copyright
11: * notice, this list of conditions and the following disclaimer.
12: * 2. Redistributions in binary form must reproduce the above copyright
13: * notice, this list of conditions and the following disclaimer in the
14: * documentation and/or other materials provided with the distribution.
1.52 millert 15: * 3. Neither the name of the University nor the names of its contributors
1.1 deraadt 16: * may be used to endorse or promote products derived from this software
17: * without specific prior written permission.
18: *
19: * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
20: * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21: * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22: * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
23: * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24: * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
25: * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
26: * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
27: * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
28: * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29: * SUCH DAMAGE.
30: */
31:
32: #include <sys/time.h>
33: #include <sys/resource.h>
1.8 millert 34:
35: #include <err.h>
36: #include <errno.h>
37: #include <grp.h>
1.33 millert 38: #include <login_cap.h>
1.8 millert 39: #include <paths.h>
40: #include <pwd.h>
1.1 deraadt 41: #include <stdio.h>
42: #include <stdlib.h>
43: #include <string.h>
1.8 millert 44: #include <syslog.h>
1.1 deraadt 45: #include <unistd.h>
1.66 deraadt 46: #include <limits.h>
1.47 millert 47: #include <utmp.h>
1.36 millert 48: #include <stdarg.h>
49: #include <bsd_auth.h>
50:
1.47 millert 51: char *getloginname(void);
1.43 millert 52: char *ontty(void);
1.53 millert 53: int chshell(const char *);
1.47 millert 54: int verify_user(char *, struct passwd *, char *, login_cap_t *,
55: auth_session_t *);
1.43 millert 56: void usage(void);
57: void auth_err(auth_session_t *, int, const char *, ...);
58: void auth_errx(auth_session_t *, int, const char *, ...);
1.1 deraadt 59:
60: int
1.47 millert 61: main(int argc, char **argv)
1.1 deraadt 62: {
1.54 deraadt 63: int asme = 0, asthem = 0, ch, fastlogin = 0, emlogin = 0, prio;
1.65 robert 64: int altshell = 0, homeless = 0;
1.45 deraadt 65: char *user, *shell = NULL, *avshell, *username, **np;
1.47 millert 66: char *class = NULL, *style = NULL, *p;
1.45 deraadt 67: enum { UNSET, YES, NO } iscsh = UNSET;
1.66 deraadt 68: char avshellbuf[PATH_MAX];
1.1 deraadt 69: extern char **environ;
1.45 deraadt 70: auth_session_t *as;
1.36 millert 71: struct passwd *pwd;
1.45 deraadt 72: login_cap_t *lc;
1.9 millert 73: uid_t ruid;
1.54 deraadt 74: u_int flags;
1.1 deraadt 75:
1.71 deraadt 76: if (pledge("stdio unveil rpath getpw proc exec id", NULL) == -1)
1.68 deraadt 77: err(1, "pledge");
78:
1.59 millert 79: while ((ch = getopt(argc, argv, "a:c:fKLlms:-")) != -1)
1.45 deraadt 80: switch (ch) {
1.36 millert 81: case 'a':
82: if (style)
83: usage();
84: style = optarg;
1.1 deraadt 85: break;
1.33 millert 86: case 'c':
1.36 millert 87: if (class)
88: usage();
1.33 millert 89: class = optarg;
90: break;
1.1 deraadt 91: case 'f':
92: fastlogin = 1;
93: break;
1.36 millert 94: case 'K':
95: if (style)
96: usage();
97: style = "passwd";
98: break;
1.47 millert 99: case 'L':
100: emlogin = 1;
101: break;
102: case 'l':
1.1 deraadt 103: case '-':
104: asme = 0;
105: asthem = 1;
106: break;
107: case 'm':
108: asme = 1;
109: asthem = 0;
110: break;
1.59 millert 111: case 's':
112: altshell = 1;
113: shell = optarg;
114: break;
1.1 deraadt 115: default:
1.36 millert 116: usage();
1.1 deraadt 117: }
118: argv += optind;
119:
120: errno = 0;
121: prio = getpriority(PRIO_PROCESS, 0);
122: if (errno)
123: prio = 0;
1.67 deraadt 124: setpriority(PRIO_PROCESS, 0, -2);
1.1 deraadt 125: openlog("su", LOG_CONS, 0);
126:
1.36 millert 127: if ((as = auth_open()) == NULL) {
128: syslog(LOG_ERR, "auth_open: %m");
1.39 millert 129: err(1, "unable to initialize BSD authentication");
1.36 millert 130: }
1.39 millert 131: auth_setoption(as, "login", "yes");
1.36 millert 132:
1.1 deraadt 133: /* get current login name and shell */
134: ruid = getuid();
135: username = getlogin();
1.40 hin 136:
1.47 millert 137: if (ruid && class)
138: auth_errx(as, 1, "only the superuser may specify a login class");
139:
1.59 millert 140: if (ruid && altshell)
141: auth_errx(as, 1, "only the superuser may specify a login shell");
142:
1.41 millert 143: if (username != NULL)
1.40 hin 144: auth_setoption(as, "invokinguser", username);
145:
1.1 deraadt 146: if (username == NULL || (pwd = getpwnam(username)) == NULL ||
147: pwd->pw_uid != ruid)
148: pwd = getpwuid(ruid);
1.8 millert 149: if (pwd == NULL)
1.36 millert 150: auth_errx(as, 1, "who are you?");
1.9 millert 151: if ((username = strdup(pwd->pw_name)) == NULL)
1.78 deraadt 152: auth_err(as, 1, NULL);
1.59 millert 153: if (asme && !altshell) {
1.10 millert 154: if (pwd->pw_shell && *pwd->pw_shell) {
1.42 millert 155: if ((shell = strdup(pwd->pw_shell)) == NULL)
1.78 deraadt 156: auth_err(as, 1, NULL);
1.10 millert 157: } else {
1.1 deraadt 158: shell = _PATH_BSHELL;
159: iscsh = NO;
160: }
1.31 art 161: }
1.1 deraadt 162:
1.71 deraadt 163: if (unveil(_PATH_LOGIN_CONF, "r") == -1)
1.84 ! beck 164: err(1, "unveil %s", _PATH_LOGIN_CONF);
1.77 semarie 165: if (unveil(_PATH_LOGIN_CONF ".db", "r") == -1)
1.84 ! beck 166: err(1, "unveil %s.db", _PATH_LOGIN_CONF);
1.71 deraadt 167: if (unveil(_PATH_AUTHPROGDIR, "x") == -1)
1.84 ! beck 168: err(1, "unveil %s", _PATH_AUTHPROGDIR);
1.72 deraadt 169: if (unveil(_PATH_SHELLS, "r") == -1)
1.84 ! beck 170: err(1, "unveil %s", _PATH_SHELLS);
1.73 deraadt 171: if (unveil(_PATH_DEVDB, "r") == -1)
1.84 ! beck 172: err(1, "unveil %s", _PATH_DEVDB);
1.82 semarie 173: if (unveil(_PATH_NOLOGIN, "r") == -1)
1.84 ! beck 174: err(1, "unveil %s", _PATH_NOLOGIN);
1.71 deraadt 175:
1.47 millert 176: for (;;) {
1.79 millert 177: char *pw_class = class;
178:
1.47 millert 179: /* get target user, default to root unless in -L mode */
180: if (*argv) {
181: user = *argv;
182: } else if (emlogin) {
183: if ((user = getloginname()) == NULL) {
184: auth_close(as);
185: exit(1);
186: }
187: } else {
188: user = "root";
189: }
190: /* style may be specified as part of the username */
191: if ((p = strchr(user, ':')) != NULL) {
192: *p++ = '\0';
1.49 millert 193: style = p; /* XXX overrides -a flag */
194: }
1.65 robert 195:
1.36 millert 196: /*
1.47 millert 197: * Clean and setup our current authentication session.
198: * Note that options *are* not cleared.
1.36 millert 199: */
1.47 millert 200: auth_clean(as);
201: if (auth_setitem(as, AUTHV_INTERACTIVE, "True") != 0 ||
202: auth_setitem(as, AUTHV_NAME, user) != 0)
1.78 deraadt 203: auth_err(as, 1, NULL);
1.47 millert 204: if ((user = auth_getitem(as, AUTHV_NAME)) == NULL)
205: auth_errx(as, 1, "internal error");
206: if (auth_setpwd(as, NULL) || (pwd = auth_getpwd(as)) == NULL) {
207: if (emlogin)
208: pwd = NULL;
209: else
210: auth_errx(as, 1, "unknown login %s", user);
1.1 deraadt 211: }
1.36 millert 212:
1.47 millert 213: /* If the user specified a login class, use it */
1.79 millert 214: if (pw_class == NULL && pwd != NULL)
215: pw_class = pwd->pw_class;
216: if ((lc = login_getclass(pw_class)) == NULL)
1.47 millert 217: auth_errx(as, 1, "no such login class: %s",
1.79 millert 218: pw_class ? pw_class : LOGIN_DEFCLASS);
1.47 millert 219:
220: if ((ruid == 0 && !emlogin) ||
221: verify_user(username, pwd, style, lc, as) == 0)
222: break;
223: syslog(LOG_AUTH|LOG_WARNING, "BAD SU %s to %s%s",
224: username, user, ontty());
225: if (!emlogin) {
1.36 millert 226: fprintf(stderr, "Sorry\n");
227: auth_close(as);
228: exit(1);
1.1 deraadt 229: }
1.47 millert 230: fprintf(stderr, "Login incorrect\n");
1.1 deraadt 231: }
1.78 deraadt 232: if (pwd == NULL)
233: auth_errx(as, 1, "internal error");
1.1 deraadt 234:
1.71 deraadt 235: if (pledge("stdio unveil rpath getpw exec id", NULL) == -1)
1.70 miod 236: err(1, "pledge");
237:
1.59 millert 238: if (!altshell) {
239: if (asme) {
1.74 millert 240: /* must be root to override non-std target shell */
241: if (ruid && !chshell(pwd->pw_shell))
1.59 millert 242: auth_errx(as, 1, "permission denied (shell).");
243: } else if (pwd->pw_shell && *pwd->pw_shell) {
244: if ((shell = strdup(pwd->pw_shell)) == NULL)
1.78 deraadt 245: auth_err(as, 1, NULL);
1.59 millert 246: iscsh = UNSET;
247: } else {
248: shell = _PATH_BSHELL;
249: iscsh = NO;
250: }
1.1 deraadt 251: }
252:
1.71 deraadt 253: if (unveil(shell, "x") == -1)
1.84 ! beck 254: err(1, "unveil %s", shell);
1.71 deraadt 255: if (unveil(pwd->pw_dir, "r") == -1)
1.84 ! beck 256: err(1, "unveil %s", pwd->pw_dir);
1.71 deraadt 257:
1.30 deraadt 258: if ((p = strrchr(shell, '/')))
1.1 deraadt 259: avshell = p+1;
260: else
261: avshell = shell;
262:
263: /* if we're forking a csh, we want to slightly muck the args */
264: if (iscsh == UNSET)
265: iscsh = strcmp(avshell, "csh") ? NO : YES;
266:
267: if (!asme) {
268: if (asthem) {
269: p = getenv("TERM");
1.23 deraadt 270: if ((environ = calloc(1, sizeof (char *))) == NULL)
1.36 millert 271: auth_errx(as, 1, "calloc");
1.33 millert 272: if (setusercontext(lc, pwd, pwd->pw_uid, LOGIN_SETPATH))
1.36 millert 273: auth_err(as, 1, "unable to set user context");
274: if (p && setenv("TERM", p, 1) == -1)
275: auth_err(as, 1, "unable to set environment");
1.5 deraadt 276:
1.57 deraadt 277: setegid(pwd->pw_gid);
1.5 deraadt 278: seteuid(pwd->pw_uid);
1.65 robert 279:
280: homeless = chdir(pwd->pw_dir);
1.76 deraadt 281: if (homeless == -1) {
1.65 robert 282: if (login_getcapbool(lc, "requirehome", 0)) {
283: auth_err(as, 1, "%s", pwd->pw_dir);
284: } else {
1.71 deraadt 285: if (unveil("/", "r") == -1)
1.84 ! beck 286: err(1, "unveil /");
1.67 deraadt 287: printf("No home directory %s!\n", pwd->pw_dir);
288: printf("Logging in with home = \"/\".\n");
1.76 deraadt 289: if (chdir("/") == -1)
1.65 robert 290: auth_err(as, 1, "/");
291: }
292: }
1.57 deraadt 293: setegid(0); /* XXX use a saved gid instead? */
1.5 deraadt 294: seteuid(0);
1.33 millert 295: } else if (pwd->pw_uid == 0) {
296: if (setusercontext(lc,
297: pwd, pwd->pw_uid, LOGIN_SETPATH|LOGIN_SETUMASK))
1.36 millert 298: auth_err(as, 1, "unable to set user context");
1.1 deraadt 299: }
1.15 millert 300: if (asthem || pwd->pw_uid) {
1.34 deraadt 301: if (setenv("LOGNAME", pwd->pw_name, 1) == -1 ||
302: setenv("USER", pwd->pw_name, 1) == -1)
1.36 millert 303: auth_err(as, 1, "unable to set environment");
1.15 millert 304: }
1.65 robert 305: if (setenv("HOME", homeless ? "/" : pwd->pw_dir, 1) == -1 ||
1.34 deraadt 306: setenv("SHELL", shell, 1) == -1)
1.59 millert 307: auth_err(as, 1, "unable to set environment");
308: } else if (altshell) {
309: if (setenv("SHELL", shell, 1) == -1)
1.36 millert 310: auth_err(as, 1, "unable to set environment");
1.34 deraadt 311: }
1.71 deraadt 312: if (pledge("stdio rpath getpw exec id", NULL) == -1)
313: err(1, "pledge");
1.28 deraadt 314:
1.47 millert 315: np = *argv ? argv : argv - 1;
1.81 jca 316:
1.1 deraadt 317: if (iscsh == YES) {
318: if (fastlogin)
319: *np-- = "-f";
320: if (asme)
321: *np-- = "-m";
322:
1.81 jca 323: if (asthem)
1.80 jca 324: avshellbuf[0] = '-';
1.81 jca 325: else {
326: /* csh strips the first character... */
327: avshellbuf[0] = '_';
1.80 jca 328: }
1.81 jca 329: strlcpy(avshellbuf+1, avshell, sizeof(avshellbuf) - 1);
330: avshell = avshellbuf;
331: } else if (asthem && !fastlogin) {
332: avshellbuf[0] = '-';
1.36 millert 333: strlcpy(avshellbuf+1, avshell, sizeof(avshellbuf) - 1);
1.1 deraadt 334: avshell = avshellbuf;
335: }
1.45 deraadt 336:
1.1 deraadt 337: *np = avshell;
338:
339: if (ruid != 0)
340: syslog(LOG_NOTICE|LOG_AUTH, "%s to %s%s",
341: username, user, ontty());
342:
1.67 deraadt 343: setpriority(PRIO_PROCESS, 0, prio);
1.51 millert 344: if (emlogin) {
1.48 millert 345: flags = LOGIN_SETALL & ~LOGIN_SETPATH;
1.51 millert 346: /*
1.55 miod 347: * Only call setlogin() if this process is a session leader.
1.51 millert 348: * In practice, this means the login name will be set only if
349: * we are exec'd by a shell. This is important because
350: * otherwise the parent shell's login name would change too.
351: */
352: if (getsid(0) != getpid())
353: flags &= ~LOGIN_SETLOGIN;
1.64 millert 354: } else {
355: flags = LOGIN_SETRESOURCES|LOGIN_SETGROUP|LOGIN_SETUSER;
356: if (asthem)
357: flags |= LOGIN_SETENV|LOGIN_SETPRIORITY|LOGIN_SETUMASK;
358: }
1.48 millert 359: if (setusercontext(lc, pwd, pwd->pw_uid, flags) != 0)
1.36 millert 360: auth_err(as, 1, "unable to set user context");
1.68 deraadt 361:
362: if (pledge("stdio rpath exec", NULL) == -1)
363: err(1, "pledge");
364:
1.75 deraadt 365: if (pwd->pw_uid && auth_approval(as, lc, pwd->pw_name, "su") == 0)
1.83 millert 366: auth_errx(as, 1, "approval failure");
1.36 millert 367: auth_close(as);
1.1 deraadt 368:
369: execv(shell, np);
1.32 millert 370: err(1, "%s", shell);
1.1 deraadt 371: }
372:
373: int
1.47 millert 374: verify_user(char *from, struct passwd *pwd, char *style,
375: login_cap_t *lc, auth_session_t *as)
376: {
377: struct group *gr;
378: char **g, *cp;
379: int authok;
380:
381: /*
382: * If we are trying to become root and the default style
383: * is being used, don't bother to look it up (we might be
384: * be su'ing up to fix /etc/login.conf)
385: */
386: if ((pwd == NULL || pwd->pw_uid != 0 || style == NULL ||
387: strcmp(style, LOGIN_DEFSTYLE) != 0) &&
388: (style = login_getstyle(lc, style, "auth-su")) == NULL)
389: auth_errx(as, 1, "invalid authentication type");
390:
391: /*
392: * Let the authentication program know whether they are
393: * in group wheel or not (if trying to become super user)
394: */
395: if (pwd != NULL && pwd->pw_uid == 0 && (gr = getgrgid(0)) != NULL &&
396: gr->gr_mem != NULL && *(gr->gr_mem) != NULL) {
397: for (g = gr->gr_mem; *g; ++g) {
398: if (strcmp(from, *g) == 0) {
399: auth_setoption(as, "wheel", "yes");
400: break;
401: }
402: }
403: if (!*g)
404: auth_setoption(as, "wheel", "no");
405: }
406:
407: auth_verify(as, style, NULL, lc->lc_class, (char *)NULL);
408: authok = auth_getstate(as);
409: if ((authok & AUTH_ALLOW) == 0) {
410: if ((cp = auth_getvalue(as, "errormsg")) != NULL)
411: fprintf(stderr, "%s\n", cp);
412: return(1);
413: }
414: return(0);
415: }
416:
417: int
1.53 millert 418: chshell(const char *sh)
1.1 deraadt 419: {
1.36 millert 420: char *cp;
1.53 millert 421: int found = 0;
1.1 deraadt 422:
1.53 millert 423: setusershell();
424: while ((cp = getusershell()) != NULL) {
425: if (strcmp(cp, sh) == 0) {
426: found = 1;
427: break;
428: }
429: }
430: endusershell();
431: return (found);
1.1 deraadt 432: }
433:
434: char *
1.47 millert 435: ontty(void)
1.1 deraadt 436: {
1.66 deraadt 437: static char buf[PATH_MAX + 4];
1.36 millert 438: char *p;
1.1 deraadt 439:
440: buf[0] = 0;
1.30 deraadt 441: if ((p = ttyname(STDERR_FILENO)))
1.8 millert 442: snprintf(buf, sizeof(buf), " on %s", p);
1.1 deraadt 443: return (buf);
444: }
445:
1.47 millert 446: /*
447: * Allow for a '.' and 16 characters for any instance as well as
1.56 otto 448: * space for a ':' and 16 characters defining the authentication type.
1.47 millert 449: */
450: #define NBUFSIZ (UT_NAMESIZE + 1 + 16 + 1 + 16)
451:
452: char *
453: getloginname(void)
454: {
455: static char nbuf[NBUFSIZ], *p;
456: int ch;
457:
458: for (;;) {
1.67 deraadt 459: printf("login: ");
1.47 millert 460: for (p = nbuf; (ch = getchar()) != '\n'; ) {
461: if (ch == EOF)
462: return (NULL);
463: if (p < nbuf + (NBUFSIZ - 1))
464: *p++ = ch;
465: }
466: if (p > nbuf) {
467: if (nbuf[0] == '-') {
1.67 deraadt 468: fprintf(stderr,
1.47 millert 469: "login names may not start with '-'.\n");
470: } else {
471: *p = '\0';
472: break;
473: }
474: }
475: }
476: return (nbuf);
477: }
478:
1.36 millert 479: void
1.47 millert 480: usage(void)
1.1 deraadt 481: {
1.36 millert 482: extern char *__progname;
1.1 deraadt 483:
1.47 millert 484: fprintf(stderr, "usage: %s [-fKLlm] [-a auth-type] [-c login-class] "
1.61 sobrado 485: "[-s login-shell]\n"
486: "%-*s[login [shell arguments]]\n", __progname,
1.62 sobrado 487: (int)strlen(__progname) + 8, "");
1.36 millert 488: exit(1);
1.1 deraadt 489: }
490:
1.36 millert 491: void
492: auth_err(auth_session_t *as, int eval, const char *fmt, ...)
1.1 deraadt 493: {
1.36 millert 494: va_list ap;
1.46 millert 495:
1.36 millert 496: va_start(ap, fmt);
1.46 millert 497: vwarn(fmt, ap);
498: va_end(ap);
1.36 millert 499: auth_close(as);
1.46 millert 500: exit(eval);
1.28 deraadt 501: }
502:
1.36 millert 503: void
504: auth_errx(auth_session_t *as, int eval, const char *fmt, ...)
1.28 deraadt 505: {
1.36 millert 506: va_list ap;
1.46 millert 507:
1.36 millert 508: va_start(ap, fmt);
1.46 millert 509: vwarnx(fmt, ap);
510: va_end(ap);
1.36 millert 511: auth_close(as);
1.46 millert 512: exit(eval);
1.1 deraadt 513: }
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