Annotation of src/usr.bin/su/su.c, Revision 1.62
1.62 ! sobrado 1: /* $OpenBSD: su.c,v 1.61 2010/12/09 16:02:42 sobrado 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/param.h>
33: #include <sys/time.h>
34: #include <sys/resource.h>
1.8 millert 35:
36: #include <err.h>
37: #include <errno.h>
38: #include <grp.h>
1.33 millert 39: #include <login_cap.h>
1.8 millert 40: #include <paths.h>
41: #include <pwd.h>
1.1 deraadt 42: #include <stdio.h>
43: #include <stdlib.h>
44: #include <string.h>
1.8 millert 45: #include <syslog.h>
1.1 deraadt 46: #include <unistd.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;
1.59 millert 64: int altshell = 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;
68: char avshellbuf[MAXPATHLEN];
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:
1.59 millert 76: while ((ch = getopt(argc, argv, "a:c:fKLlms:-")) != -1)
1.45 deraadt 77: switch (ch) {
1.36 millert 78: case 'a':
79: if (style)
80: usage();
81: style = optarg;
1.1 deraadt 82: break;
1.33 millert 83: case 'c':
1.36 millert 84: if (class)
85: usage();
1.33 millert 86: class = optarg;
87: break;
1.1 deraadt 88: case 'f':
89: fastlogin = 1;
90: break;
1.36 millert 91: case 'K':
92: if (style)
93: usage();
94: style = "passwd";
95: break;
1.47 millert 96: case 'L':
97: emlogin = 1;
98: break;
99: case 'l':
1.1 deraadt 100: case '-':
101: asme = 0;
102: asthem = 1;
103: break;
104: case 'm':
105: asme = 1;
106: asthem = 0;
107: break;
1.59 millert 108: case 's':
109: altshell = 1;
110: shell = optarg;
111: break;
1.1 deraadt 112: default:
1.36 millert 113: usage();
1.1 deraadt 114: }
115: argv += optind;
116:
117: errno = 0;
118: prio = getpriority(PRIO_PROCESS, 0);
119: if (errno)
120: prio = 0;
121: (void)setpriority(PRIO_PROCESS, 0, -2);
122: openlog("su", LOG_CONS, 0);
123:
1.36 millert 124: if ((as = auth_open()) == NULL) {
125: syslog(LOG_ERR, "auth_open: %m");
1.39 millert 126: err(1, "unable to initialize BSD authentication");
1.36 millert 127: }
1.39 millert 128: auth_setoption(as, "login", "yes");
1.36 millert 129:
1.1 deraadt 130: /* get current login name and shell */
131: ruid = getuid();
132: username = getlogin();
1.40 hin 133:
1.47 millert 134: if (ruid && class)
135: auth_errx(as, 1, "only the superuser may specify a login class");
136:
1.59 millert 137: if (ruid && altshell)
138: auth_errx(as, 1, "only the superuser may specify a login shell");
139:
1.41 millert 140: if (username != NULL)
1.40 hin 141: auth_setoption(as, "invokinguser", username);
142:
1.1 deraadt 143: if (username == NULL || (pwd = getpwnam(username)) == NULL ||
144: pwd->pw_uid != ruid)
145: pwd = getpwuid(ruid);
1.8 millert 146: if (pwd == NULL)
1.36 millert 147: auth_errx(as, 1, "who are you?");
1.9 millert 148: if ((username = strdup(pwd->pw_name)) == NULL)
1.41 millert 149: auth_errx(as, 1, "can't allocate memory");
1.59 millert 150: if (asme && !altshell) {
1.10 millert 151: if (pwd->pw_shell && *pwd->pw_shell) {
1.42 millert 152: if ((shell = strdup(pwd->pw_shell)) == NULL)
153: auth_errx(as, 1, "can't allocate memory");
1.10 millert 154: } else {
1.1 deraadt 155: shell = _PATH_BSHELL;
156: iscsh = NO;
157: }
1.31 art 158: }
1.1 deraadt 159:
1.47 millert 160: for (;;) {
161: /* get target user, default to root unless in -L mode */
162: if (*argv) {
163: user = *argv;
164: } else if (emlogin) {
165: if ((user = getloginname()) == NULL) {
166: auth_close(as);
167: exit(1);
168: }
169: } else {
170: user = "root";
171: }
172: /* style may be specified as part of the username */
173: if ((p = strchr(user, ':')) != NULL) {
174: *p++ = '\0';
1.49 millert 175: style = p; /* XXX overrides -a flag */
176: }
1.47 millert 177:
1.36 millert 178: /*
1.47 millert 179: * Clean and setup our current authentication session.
180: * Note that options *are* not cleared.
1.36 millert 181: */
1.47 millert 182: auth_clean(as);
183: if (auth_setitem(as, AUTHV_INTERACTIVE, "True") != 0 ||
184: auth_setitem(as, AUTHV_NAME, user) != 0)
185: auth_errx(as, 1, "can't allocate memory");
186: if ((user = auth_getitem(as, AUTHV_NAME)) == NULL)
187: auth_errx(as, 1, "internal error");
188: if (auth_setpwd(as, NULL) || (pwd = auth_getpwd(as)) == NULL) {
189: if (emlogin)
190: pwd = NULL;
191: else
192: auth_errx(as, 1, "unknown login %s", user);
1.1 deraadt 193: }
1.36 millert 194:
1.47 millert 195: /* If the user specified a login class, use it */
196: if (!class && pwd && pwd->pw_class && pwd->pw_class[0] != '\0')
197: class = pwd->pw_class;
198: if ((lc = login_getclass(class)) == NULL)
199: auth_errx(as, 1, "no such login class: %s",
200: class ? class : LOGIN_DEFCLASS);
201:
202: if ((ruid == 0 && !emlogin) ||
203: verify_user(username, pwd, style, lc, as) == 0)
204: break;
205: syslog(LOG_AUTH|LOG_WARNING, "BAD SU %s to %s%s",
206: username, user, ontty());
207: if (!emlogin) {
1.36 millert 208: fprintf(stderr, "Sorry\n");
209: auth_close(as);
210: exit(1);
1.1 deraadt 211: }
1.47 millert 212: fprintf(stderr, "Login incorrect\n");
1.1 deraadt 213: }
214:
1.59 millert 215: if (!altshell) {
216: if (asme) {
217: /* if asme and non-std target shell, must be root */
218: if (ruid && !chshell(shell))
219: auth_errx(as, 1, "permission denied (shell).");
220: } else if (pwd->pw_shell && *pwd->pw_shell) {
221: if ((shell = strdup(pwd->pw_shell)) == NULL)
222: auth_errx(as, 1, "can't allocate memory");
223: iscsh = UNSET;
224: } else {
225: shell = _PATH_BSHELL;
226: iscsh = NO;
227: }
1.1 deraadt 228: }
229:
1.30 deraadt 230: if ((p = strrchr(shell, '/')))
1.1 deraadt 231: avshell = p+1;
232: else
233: avshell = shell;
234:
235: /* if we're forking a csh, we want to slightly muck the args */
236: if (iscsh == UNSET)
237: iscsh = strcmp(avshell, "csh") ? NO : YES;
238:
239: if (!asme) {
240: if (asthem) {
241: p = getenv("TERM");
1.23 deraadt 242: if ((environ = calloc(1, sizeof (char *))) == NULL)
1.36 millert 243: auth_errx(as, 1, "calloc");
1.33 millert 244: if (setusercontext(lc, pwd, pwd->pw_uid, LOGIN_SETPATH))
1.36 millert 245: auth_err(as, 1, "unable to set user context");
246: if (p && setenv("TERM", p, 1) == -1)
247: auth_err(as, 1, "unable to set environment");
1.5 deraadt 248:
1.57 deraadt 249: setegid(pwd->pw_gid);
1.5 deraadt 250: seteuid(pwd->pw_uid);
1.8 millert 251: if (chdir(pwd->pw_dir) < 0)
1.36 millert 252: auth_err(as, 1, "%s", pwd->pw_dir);
1.57 deraadt 253: setegid(0); /* XXX use a saved gid instead? */
1.5 deraadt 254: seteuid(0);
1.33 millert 255: } else if (pwd->pw_uid == 0) {
256: if (setusercontext(lc,
257: pwd, pwd->pw_uid, LOGIN_SETPATH|LOGIN_SETUMASK))
1.36 millert 258: auth_err(as, 1, "unable to set user context");
1.1 deraadt 259: }
1.15 millert 260: if (asthem || pwd->pw_uid) {
1.34 deraadt 261: if (setenv("LOGNAME", pwd->pw_name, 1) == -1 ||
262: setenv("USER", pwd->pw_name, 1) == -1)
1.36 millert 263: auth_err(as, 1, "unable to set environment");
1.15 millert 264: }
1.34 deraadt 265: if (setenv("HOME", pwd->pw_dir, 1) == -1 ||
266: setenv("SHELL", shell, 1) == -1)
1.59 millert 267: auth_err(as, 1, "unable to set environment");
268: } else if (altshell) {
269: if (setenv("SHELL", shell, 1) == -1)
1.36 millert 270: auth_err(as, 1, "unable to set environment");
1.34 deraadt 271: }
1.28 deraadt 272:
1.47 millert 273: np = *argv ? argv : argv - 1;
1.1 deraadt 274: if (iscsh == YES) {
275: if (fastlogin)
276: *np-- = "-f";
277: if (asme)
278: *np-- = "-m";
279: }
280:
281: if (asthem) {
282: avshellbuf[0] = '-';
1.36 millert 283: strlcpy(avshellbuf+1, avshell, sizeof(avshellbuf) - 1);
1.1 deraadt 284: avshell = avshellbuf;
285: } else if (iscsh == YES) {
286: /* csh strips the first character... */
287: avshellbuf[0] = '_';
1.36 millert 288: strlcpy(avshellbuf+1, avshell, sizeof(avshellbuf) - 1);
1.1 deraadt 289: avshell = avshellbuf;
290: }
1.45 deraadt 291:
1.1 deraadt 292: *np = avshell;
293:
294: if (ruid != 0)
295: syslog(LOG_NOTICE|LOG_AUTH, "%s to %s%s",
296: username, user, ontty());
297:
298: (void)setpriority(PRIO_PROCESS, 0, prio);
1.51 millert 299: if (emlogin) {
1.48 millert 300: flags = LOGIN_SETALL & ~LOGIN_SETPATH;
1.51 millert 301: /*
1.55 miod 302: * Only call setlogin() if this process is a session leader.
1.51 millert 303: * In practice, this means the login name will be set only if
304: * we are exec'd by a shell. This is important because
305: * otherwise the parent shell's login name would change too.
306: */
307: if (getsid(0) != getpid())
308: flags &= ~LOGIN_SETLOGIN;
309: } else
1.48 millert 310: flags = (asthem ? (LOGIN_SETPRIORITY | LOGIN_SETUMASK) : 0) |
311: LOGIN_SETRESOURCES | LOGIN_SETGROUP | LOGIN_SETUSER;
312: if (setusercontext(lc, pwd, pwd->pw_uid, flags) != 0)
1.36 millert 313: auth_err(as, 1, "unable to set user context");
314: if (pwd->pw_uid && auth_approval(as, lc, pwd->pw_name, "su") <= 0)
315: auth_err(as, 1, "approval failure");
316: auth_close(as);
1.1 deraadt 317:
318: execv(shell, np);
1.32 millert 319: err(1, "%s", shell);
1.1 deraadt 320: }
321:
322: int
1.47 millert 323: verify_user(char *from, struct passwd *pwd, char *style,
324: login_cap_t *lc, auth_session_t *as)
325: {
326: struct group *gr;
327: char **g, *cp;
328: int authok;
329:
330: /*
331: * If we are trying to become root and the default style
332: * is being used, don't bother to look it up (we might be
333: * be su'ing up to fix /etc/login.conf)
334: */
335: if ((pwd == NULL || pwd->pw_uid != 0 || style == NULL ||
336: strcmp(style, LOGIN_DEFSTYLE) != 0) &&
337: (style = login_getstyle(lc, style, "auth-su")) == NULL)
338: auth_errx(as, 1, "invalid authentication type");
339:
340: /*
341: * Let the authentication program know whether they are
342: * in group wheel or not (if trying to become super user)
343: */
344: if (pwd != NULL && pwd->pw_uid == 0 && (gr = getgrgid(0)) != NULL &&
345: gr->gr_mem != NULL && *(gr->gr_mem) != NULL) {
346: for (g = gr->gr_mem; *g; ++g) {
347: if (strcmp(from, *g) == 0) {
348: auth_setoption(as, "wheel", "yes");
349: break;
350: }
351: }
352: if (!*g)
353: auth_setoption(as, "wheel", "no");
354: }
355:
356: auth_verify(as, style, NULL, lc->lc_class, (char *)NULL);
357: authok = auth_getstate(as);
358: if ((authok & AUTH_ALLOW) == 0) {
359: if ((cp = auth_getvalue(as, "errormsg")) != NULL)
360: fprintf(stderr, "%s\n", cp);
361: return(1);
362: }
363: return(0);
364: }
365:
366: int
1.53 millert 367: chshell(const char *sh)
1.1 deraadt 368: {
1.36 millert 369: char *cp;
1.53 millert 370: int found = 0;
1.1 deraadt 371:
1.53 millert 372: setusershell();
373: while ((cp = getusershell()) != NULL) {
374: if (strcmp(cp, sh) == 0) {
375: found = 1;
376: break;
377: }
378: }
379: endusershell();
380: return (found);
1.1 deraadt 381: }
382:
383: char *
1.47 millert 384: ontty(void)
1.1 deraadt 385: {
386: static char buf[MAXPATHLEN + 4];
1.36 millert 387: char *p;
1.1 deraadt 388:
389: buf[0] = 0;
1.30 deraadt 390: if ((p = ttyname(STDERR_FILENO)))
1.8 millert 391: snprintf(buf, sizeof(buf), " on %s", p);
1.1 deraadt 392: return (buf);
393: }
394:
1.47 millert 395: /*
396: * Allow for a '.' and 16 characters for any instance as well as
1.56 otto 397: * space for a ':' and 16 characters defining the authentication type.
1.47 millert 398: */
399: #define NBUFSIZ (UT_NAMESIZE + 1 + 16 + 1 + 16)
400:
401: char *
402: getloginname(void)
403: {
404: static char nbuf[NBUFSIZ], *p;
405: int ch;
406:
407: for (;;) {
408: (void)printf("login: ");
409: for (p = nbuf; (ch = getchar()) != '\n'; ) {
410: if (ch == EOF)
411: return (NULL);
412: if (p < nbuf + (NBUFSIZ - 1))
413: *p++ = ch;
414: }
415: if (p > nbuf) {
416: if (nbuf[0] == '-') {
417: (void)fprintf(stderr,
418: "login names may not start with '-'.\n");
419: } else {
420: *p = '\0';
421: break;
422: }
423: }
424: }
425: return (nbuf);
426: }
427:
1.36 millert 428: void
1.47 millert 429: usage(void)
1.1 deraadt 430: {
1.36 millert 431: extern char *__progname;
1.1 deraadt 432:
1.47 millert 433: fprintf(stderr, "usage: %s [-fKLlm] [-a auth-type] [-c login-class] "
1.61 sobrado 434: "[-s login-shell]\n"
435: "%-*s[login [shell arguments]]\n", __progname,
1.62 ! sobrado 436: (int)strlen(__progname) + 8, "");
1.36 millert 437: exit(1);
1.1 deraadt 438: }
439:
1.36 millert 440: void
441: auth_err(auth_session_t *as, int eval, const char *fmt, ...)
1.1 deraadt 442: {
1.36 millert 443: va_list ap;
1.46 millert 444:
1.36 millert 445: va_start(ap, fmt);
1.46 millert 446: vwarn(fmt, ap);
447: va_end(ap);
1.36 millert 448: auth_close(as);
1.46 millert 449: exit(eval);
1.28 deraadt 450: }
451:
1.36 millert 452: void
453: auth_errx(auth_session_t *as, int eval, const char *fmt, ...)
1.28 deraadt 454: {
1.36 millert 455: va_list ap;
1.46 millert 456:
1.36 millert 457: va_start(ap, fmt);
1.46 millert 458: vwarnx(fmt, ap);
459: va_end(ap);
1.36 millert 460: auth_close(as);
1.46 millert 461: exit(eval);
1.1 deraadt 462: }
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