source: branches/2.2.9/mindi-busybox/loginutils/login.c @ 2142

Last change on this file since 2142 was 1765, checked in by bruno, 12 years ago

Update to busybox 1.7.2

File size: 12.2 KB
Line 
1/* vi: set sw=4 ts=4: */
2/*
3 * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
4 */
5
6#include "libbb.h"
7#include <utmp.h>
8#include <sys/resource.h>
9#include <syslog.h>
10
11#if ENABLE_SELINUX
12#include <selinux/selinux.h>  /* for is_selinux_enabled()  */
13#include <selinux/get_context_list.h> /* for get_default_context() */
14#include <selinux/flask.h> /* for security class definitions  */
15#endif
16
17#if ENABLE_PAM
18/* PAM may include <locale.h>. We may need to undefine bbox's stub define: */
19#undef setlocale
20/* For some obscure reason, PAM is not in pam/xxx, but in security/xxx.
21 * Apparently they like to confuse people. */
22#include <security/pam_appl.h>
23#include <security/pam_misc.h>
24static const struct pam_conv conv = {
25    misc_conv,
26    NULL
27};
28#endif
29
30enum {
31    TIMEOUT = 60,
32    EMPTY_USERNAME_COUNT = 10,
33    USERNAME_SIZE = 32,
34    TTYNAME_SIZE = 32,
35};
36
37static char* short_tty;
38
39#if ENABLE_FEATURE_UTMP
40/* vv  Taken from tinylogin utmp.c  vv */
41/*
42 * read_or_build_utent - see if utmp file is correct for this process
43 *
44 *  System V is very picky about the contents of the utmp file
45 *  and requires that a slot for the current process exist.
46 *  The utmp file is scanned for an entry with the same process
47 *  ID.  If no entry exists the process exits with a message.
48 *
49 *  The "picky" flag is for network and other logins that may
50 *  use special flags.  It allows the pid checks to be overridden.
51 *  This means that getty should never invoke login with any
52 *  command line flags.
53 */
54
55static void read_or_build_utent(struct utmp *utptr, int picky)
56{
57    struct utmp *ut;
58    pid_t pid = getpid();
59
60    setutent();
61
62    /* First, try to find a valid utmp entry for this process.  */
63    while ((ut = getutent()))
64        if (ut->ut_pid == pid && ut->ut_line[0] && ut->ut_id[0] &&
65        (ut->ut_type == LOGIN_PROCESS || ut->ut_type == USER_PROCESS))
66            break;
67
68    /* If there is one, just use it, otherwise create a new one.  */
69    if (ut) {
70        *utptr = *ut;
71    } else {
72        if (picky)
73            bb_error_msg_and_die("no utmp entry found");
74
75        memset(utptr, 0, sizeof(*utptr));
76        utptr->ut_type = LOGIN_PROCESS;
77        utptr->ut_pid = pid;
78        strncpy(utptr->ut_line, short_tty, sizeof(utptr->ut_line));
79        /* This one is only 4 chars wide. Try to fit something
80         * remotely meaningful by skipping "tty"... */
81        strncpy(utptr->ut_id, short_tty + 3, sizeof(utptr->ut_id));
82        strncpy(utptr->ut_user, "LOGIN", sizeof(utptr->ut_user));
83        utptr->ut_time = time(NULL);
84    }
85    if (!picky) /* root login */
86        memset(utptr->ut_host, 0, sizeof(utptr->ut_host));
87}
88
89/*
90 * write_utent - put a USER_PROCESS entry in the utmp file
91 *
92 *  write_utent changes the type of the current utmp entry to
93 *  USER_PROCESS.  the wtmp file will be updated as well.
94 */
95static void write_utent(struct utmp *utptr, const char *username)
96{
97    utptr->ut_type = USER_PROCESS;
98    strncpy(utptr->ut_user, username, sizeof(utptr->ut_user));
99    utptr->ut_time = time(NULL);
100    /* other fields already filled in by read_or_build_utent above */
101    setutent();
102    pututline(utptr);
103    endutent();
104#if ENABLE_FEATURE_WTMP
105    if (access(bb_path_wtmp_file, R_OK|W_OK) == -1) {
106        close(creat(bb_path_wtmp_file, 0664));
107    }
108    updwtmp(bb_path_wtmp_file, utptr);
109#endif
110}
111#else /* !ENABLE_FEATURE_UTMP */
112#define read_or_build_utent(utptr, picky) ((void)0)
113#define write_utent(utptr, username) ((void)0)
114#endif /* !ENABLE_FEATURE_UTMP */
115
116#if ENABLE_FEATURE_NOLOGIN
117static void die_if_nologin_and_non_root(int amroot)
118{
119    FILE *fp;
120    int c;
121
122    if (access("/etc/nologin", F_OK))
123        return;
124
125    fp = fopen("/etc/nologin", "r");
126    if (fp) {
127        while ((c = getc(fp)) != EOF)
128            putchar((c=='\n') ? '\r' : c);
129        fflush(stdout);
130        fclose(fp);
131    } else
132        puts("\r\nSystem closed for routine maintenance\r");
133    if (!amroot)
134        exit(1);
135    puts("\r\n[Disconnect bypassed -- root login allowed]\r");
136}
137#else
138static ALWAYS_INLINE void die_if_nologin_and_non_root(int amroot) {}
139#endif
140
141#if ENABLE_FEATURE_SECURETTY && !ENABLE_PAM
142static int check_securetty(void)
143{
144    FILE *fp;
145    int i;
146    char buf[256];
147
148    fp = fopen("/etc/securetty", "r");
149    if (!fp) {
150        /* A missing securetty file is not an error. */
151        return 1;
152    }
153    while (fgets(buf, sizeof(buf)-1, fp)) {
154        for (i = strlen(buf)-1; i >= 0; --i) {
155            if (!isspace(buf[i]))
156                break;
157        }
158        buf[++i] = '\0';
159        if (!buf[0] || (buf[0] == '#'))
160            continue;
161        if (strcmp(buf, short_tty) == 0) {
162            fclose(fp);
163            return 1;
164        }
165    }
166    fclose(fp);
167    return 0;
168}
169#else
170static ALWAYS_INLINE int check_securetty(void) { return 1; }
171#endif
172
173static void get_username_or_die(char *buf, int size_buf)
174{
175    int c, cntdown;
176
177    cntdown = EMPTY_USERNAME_COUNT;
178 prompt:
179    print_login_prompt();
180    /* skip whitespace */
181    do {
182        c = getchar();
183        if (c == EOF) exit(1);
184        if (c == '\n') {
185            if (!--cntdown) exit(1);
186            goto prompt;
187        }
188    } while (isspace(c));
189
190    *buf++ = c;
191    if (!fgets(buf, size_buf-2, stdin))
192        exit(1);
193    if (!strchr(buf, '\n'))
194        exit(1);
195    while (isgraph(*buf)) buf++;
196    *buf = '\0';
197}
198
199static void motd(void)
200{
201    int fd;
202
203    fd = open(bb_path_motd_file, O_RDONLY);
204    if (fd) {
205        fflush(stdout);
206        bb_copyfd_eof(fd, STDOUT_FILENO);
207        close(fd);
208    }
209}
210
211static void alarm_handler(int sig ATTRIBUTE_UNUSED)
212{
213    /* This is the escape hatch!  Poor serial line users and the like
214     * arrive here when their connection is broken.
215     * We don't want to block here */
216    ndelay_on(1);
217    ndelay_on(2);
218    printf("\r\nLogin timed out after %d seconds\r\n", TIMEOUT);
219    exit(EXIT_SUCCESS);
220}
221
222int login_main(int argc, char **argv);
223int login_main(int argc, char **argv)
224{
225    enum {
226        LOGIN_OPT_f = (1<<0),
227        LOGIN_OPT_h = (1<<1),
228        LOGIN_OPT_p = (1<<2),
229    };
230    char *fromhost;
231    char username[USERNAME_SIZE];
232    const char *tmp;
233    int amroot;
234    unsigned opt;
235    int count = 0;
236    struct passwd *pw;
237    char *opt_host = NULL;
238    char *opt_user = NULL;
239    char full_tty[TTYNAME_SIZE];
240    USE_SELINUX(security_context_t user_sid = NULL;)
241    USE_FEATURE_UTMP(struct utmp utent;)
242    USE_PAM(pam_handle_t *pamh;)
243    USE_PAM(int pamret;)
244    USE_PAM(const char *failed_msg;)
245
246    short_tty = full_tty;
247    username[0] = '\0';
248    amroot = (getuid() == 0);
249    signal(SIGALRM, alarm_handler);
250    alarm(TIMEOUT);
251
252    /* Mandatory paranoia for suid applet:
253     * ensure that fd# 0,1,2 are opened (at least to /dev/null)
254     * and any extra open fd's are closed.
255     * (The name of the function is misleading. Not daemonizing here.) */
256    bb_daemonize_or_rexec(DAEMON_ONLY_SANITIZE | DAEMON_CLOSE_EXTRA_FDS, NULL);
257
258    opt = getopt32(argv, "f:h:p", &opt_user, &opt_host);
259    if (opt & LOGIN_OPT_f) {
260        if (!amroot)
261            bb_error_msg_and_die("-f is for root only");
262        safe_strncpy(username, opt_user, sizeof(username));
263    }
264    if (optind < argc) /* user from command line (getty) */
265        safe_strncpy(username, argv[optind], sizeof(username));
266
267    /* Let's find out and memorize our tty */
268    if (!isatty(0) || !isatty(1) || !isatty(2))
269        return EXIT_FAILURE;        /* Must be a terminal */
270    safe_strncpy(full_tty, "UNKNOWN", sizeof(full_tty));
271    tmp = ttyname(0);
272    if (tmp) {
273        safe_strncpy(full_tty, tmp, sizeof(full_tty));
274        if (strncmp(full_tty, "/dev/", 5) == 0)
275            short_tty = full_tty + 5;
276    }
277
278    read_or_build_utent(&utent, !amroot);
279
280    if (opt_host) {
281        USE_FEATURE_UTMP(
282            safe_strncpy(utent.ut_host, opt_host, sizeof(utent.ut_host));
283        )
284        fromhost = xasprintf(" on '%s' from '%s'", short_tty, opt_host);
285    } else
286        fromhost = xasprintf(" on '%s'", short_tty);
287
288    /* Was breaking "login <username>" from shell command line: */
289    /*bb_setpgrp();*/
290
291    openlog(applet_name, LOG_PID | LOG_CONS | LOG_NOWAIT, LOG_AUTH);
292
293    while (1) {
294        if (!username[0])
295            get_username_or_die(username, sizeof(username));
296
297#if ENABLE_PAM
298        pamret = pam_start("login", username, &conv, &pamh);
299        if (pamret != PAM_SUCCESS) {
300            failed_msg = "pam_start";
301            goto pam_auth_failed;
302        }
303        /* set TTY (so things like securetty work) */
304        pamret = pam_set_item(pamh, PAM_TTY, short_tty);
305        if (pamret != PAM_SUCCESS) {
306            failed_msg = "pam_set_item(TTY)";
307            goto pam_auth_failed;
308        }
309        pamret = pam_authenticate(pamh, 0);
310        if (pamret != PAM_SUCCESS) {
311            failed_msg = "pam_authenticate";
312            goto pam_auth_failed;
313            /* TODO: or just "goto auth_failed"
314             * since user seems to enter wrong password
315             * (in this case pamret == 7)
316             */
317        }
318        /* check that the account is healthy */
319        pamret = pam_acct_mgmt(pamh, 0);
320        if (pamret != PAM_SUCCESS) {
321            failed_msg = "account setup";
322            goto pam_auth_failed;
323        }
324        /* read user back */
325        {
326            const char *pamuser;
327            /* gcc: "dereferencing type-punned pointer breaks aliasing rules..."
328             * thus we cast to (void*) */
329            if (pam_get_item(pamh, PAM_USER, (void*)&pamuser) != PAM_SUCCESS) {
330                failed_msg = "pam_get_item(USER)";
331                goto pam_auth_failed;
332            }
333            safe_strncpy(username, pamuser, sizeof(username));
334        }
335        /* If we get here, the user was authenticated, and is
336         * granted access. */
337        pw = getpwnam(username);
338        if (pw)
339            break;
340        goto auth_failed;
341 pam_auth_failed:
342        bb_error_msg("%s failed: %s (%d)", failed_msg, pam_strerror(pamh, pamret), pamret);
343        safe_strncpy(username, "UNKNOWN", sizeof(username));
344#else /* not PAM */
345        pw = getpwnam(username);
346        if (!pw) {
347            strcpy(username, "UNKNOWN");
348            goto fake_it;
349        }
350
351        if (pw->pw_passwd[0] == '!' || pw->pw_passwd[0] == '*')
352            goto auth_failed;
353
354        if (opt & LOGIN_OPT_f)
355            break; /* -f USER: success without asking passwd */
356
357        if (pw->pw_uid == 0 && !check_securetty())
358            goto auth_failed;
359
360        /* Don't check the password if password entry is empty (!) */
361        if (!pw->pw_passwd[0])
362            break;
363 fake_it:
364        /* authorization takes place here */
365        if (correct_password(pw))
366            break;
367#endif /* ENABLE_PAM */
368 auth_failed:
369        opt &= ~LOGIN_OPT_f;
370        bb_do_delay(FAIL_DELAY);
371        /* TODO: doesn't sound like correct English phrase to me */
372        puts("Login incorrect");
373        if (++count == 3) {
374            syslog(LOG_WARNING, "invalid password for '%s'%s",
375                        username, fromhost);
376            return EXIT_FAILURE;
377        }
378        username[0] = '\0';
379    }
380
381    alarm(0);
382    die_if_nologin_and_non_root(pw->pw_uid == 0);
383
384    write_utent(&utent, username);
385
386#if ENABLE_SELINUX
387    if (is_selinux_enabled()) {
388        security_context_t old_tty_sid, new_tty_sid;
389
390        if (get_default_context(username, NULL, &user_sid)) {
391            bb_error_msg_and_die("cannot get SID for %s",
392                    username);
393        }
394        if (getfilecon(full_tty, &old_tty_sid) < 0) {
395            bb_perror_msg_and_die("getfilecon(%s) failed",
396                    full_tty);
397        }
398        if (security_compute_relabel(user_sid, old_tty_sid,
399                    SECCLASS_CHR_FILE, &new_tty_sid) != 0) {
400            bb_perror_msg_and_die("security_change_sid(%s) failed",
401                    full_tty);
402        }
403        if (setfilecon(full_tty, new_tty_sid) != 0) {
404            bb_perror_msg_and_die("chsid(%s, %s) failed",
405                    full_tty, new_tty_sid);
406        }
407    }
408#endif
409    /* Try these, but don't complain if they fail.
410     * _f_chown is safe wrt race t=ttyname(0);...;chown(t); */
411    fchown(0, pw->pw_uid, pw->pw_gid);
412    fchmod(0, 0600);
413
414    if (ENABLE_LOGIN_SCRIPTS) {
415        char *t_argv[2];
416
417        t_argv[0] = getenv("LOGIN_PRE_SUID_SCRIPT");
418        if (t_argv[0]) {
419            t_argv[1] = NULL;
420            xsetenv("LOGIN_TTY", full_tty);
421            xsetenv("LOGIN_USER", pw->pw_name);
422            xsetenv("LOGIN_UID", utoa(pw->pw_uid));
423            xsetenv("LOGIN_GID", utoa(pw->pw_gid));
424            xsetenv("LOGIN_SHELL", pw->pw_shell);
425            xspawn(t_argv); /* NOMMU-friendly */
426            /* All variables are unset by setup_environment */
427            wait(NULL);
428        }
429    }
430
431    change_identity(pw);
432    tmp = pw->pw_shell;
433    if (!tmp || !*tmp)
434        tmp = DEFAULT_SHELL;
435    /* setup_environment params: shell, loginshell, changeenv, pw */
436    setup_environment(tmp, 1, !(opt & LOGIN_OPT_p), pw);
437    /* FIXME: login shell = 1 -> 3rd parameter is ignored! */
438
439    motd();
440
441    if (pw->pw_uid == 0)
442        syslog(LOG_INFO, "root login%s", fromhost);
443#if ENABLE_SELINUX
444    /* well, a simple setexeccon() here would do the job as well,
445     * but let's play the game for now */
446    set_current_security_context(user_sid);
447#endif
448
449    // util-linux login also does:
450    // /* start new session */
451    // setsid();
452    // /* TIOCSCTTY: steal tty from other process group */
453    // if (ioctl(0, TIOCSCTTY, 1)) error_msg...
454    // BBox login used to do this (see above):
455    // bb_setpgrp();
456    // If this stuff is really needed, add it and explain why!
457
458    /* set signals to defaults */
459    signal(SIGALRM, SIG_DFL);
460    /* Is this correct? This way user can ctrl-c out of /etc/profile,
461     * potentially creating security breach (tested with bash 3.0).
462     * But without this, bash 3.0 will not enable ctrl-c either.
463     * Maybe bash is buggy?
464     * Need to find out what standards say about /bin/login -
465     * should it leave SIGINT etc enabled or disabled? */
466    signal(SIGINT, SIG_DFL);
467
468    /* Exec login shell with no additional parameters */
469    run_shell(tmp, 1, NULL, NULL);
470
471    /* return EXIT_FAILURE; - not reached */
472}
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