summaryrefslogtreecommitdiffstats
path: root/src/shared/utmp-wtmp.c
blob: cfeabbdfb5c84d21ba53f35dcbe2517fa7c98dc7 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
/* SPDX-License-Identifier: LGPL-2.1-or-later */

#include <errno.h>
#include <fcntl.h>
#include <poll.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/time.h>
#include <sys/utsname.h>
#include <unistd.h>
#include <utmpx.h>

#include "alloc-util.h"
#include "fd-util.h"
#include "hostname-util.h"
#include "io-util.h"
#include "macro.h"
#include "memory-util.h"
#include "path-util.h"
#include "string-util.h"
#include "terminal-util.h"
#include "time-util.h"
#include "user-util.h"
#include "utmp-wtmp.h"

int utmp_get_runlevel(int *runlevel, int *previous) {
        _unused_ _cleanup_(utxent_cleanup) bool utmpx = false;
        struct utmpx *found, lookup = { .ut_type = RUN_LVL };
        const char *e;

        assert(runlevel);

        /* If these values are set in the environment this takes
         * precedence. Presumably, sysvinit does this to work around a
         * race condition that would otherwise exist where we'd always
         * go to disk and hence might read runlevel data that might be
         * very new and not apply to the current script being executed. */

        e = getenv("RUNLEVEL");
        if (!isempty(e)) {
                *runlevel = e[0];
                if (previous)
                        *previous = 0;

                return 0;
        }

        if (utmpxname(_PATH_UTMPX) < 0)
                return -errno;

        utmpx = utxent_start();

        found = getutxid(&lookup);
        if (!found)
                return -errno;

        *runlevel = found->ut_pid & 0xFF;
        if (previous)
                *previous = (found->ut_pid >> 8) & 0xFF;

        return 0;
}

static void init_timestamp(struct utmpx *store, usec_t t) {
        assert(store);

        if (t <= 0)
                t = now(CLOCK_REALTIME);

        store->ut_tv.tv_sec = t / USEC_PER_SEC;
        store->ut_tv.tv_usec = t % USEC_PER_SEC;
}

static void init_entry(struct utmpx *store, usec_t t) {
        struct utsname uts = {};

        assert(store);

        init_timestamp(store, t);

        if (uname(&uts) >= 0)
                strncpy(store->ut_host, uts.release, sizeof(store->ut_host));

        strncpy(store->ut_line, "~", sizeof(store->ut_line));  /* or ~~ ? */
        strncpy(store->ut_id, "~~", sizeof(store->ut_id));
}

static int write_entry_utmp(const struct utmpx *store) {
        _unused_ _cleanup_(utxent_cleanup) bool utmpx = false;

        assert(store);

        /* utmp is similar to wtmp, but there is only one entry for
         * each entry type resp. user; i.e. basically a key/value
         * table. */

        if (utmpxname(_PATH_UTMPX) < 0)
                return -errno;

        utmpx = utxent_start();

        if (pututxline(store))
                return 0;
        if (errno == ENOENT) {
                /* If utmp/wtmp have been disabled, that's a good thing, hence ignore the error. */
                log_debug_errno(errno, "Not writing utmp: %m");
                return 0;
        }
        return -errno;
}

static int write_entry_wtmp(const struct utmpx *store) {
        assert(store);

        /* wtmp is a simple append-only file where each entry is
         * simply appended to the end; i.e. basically a log. */

        errno = 0;
        updwtmpx(_PATH_WTMPX, store);
        if (errno == ENOENT) {
                /* If utmp/wtmp have been disabled, that's a good thing, hence ignore the error. */
                log_debug_errno(errno, "Not writing wtmp: %m");
                return 0;
        }
        if (errno == EROFS) {
                log_warning_errno(errno, "Failed to write wtmp record, ignoring: %m");
                return 0;
        }
        return -errno;
}

static int write_utmp_wtmp(const struct utmpx *store_utmp, const struct utmpx *store_wtmp) {
        int r, s;

        r = write_entry_utmp(store_utmp);
        s = write_entry_wtmp(store_wtmp);
        return r < 0 ? r : s;
}

static int write_entry_both(const struct utmpx *store) {
        return write_utmp_wtmp(store, store);
}

int utmp_put_shutdown(void) {
        struct utmpx store = {};

        init_entry(&store, 0);

        store.ut_type = RUN_LVL;
        strncpy(store.ut_user, "shutdown", sizeof(store.ut_user));

        return write_entry_both(&store);
}

int utmp_put_reboot(usec_t t) {
        struct utmpx store = {};

        init_entry(&store, t);

        store.ut_type = BOOT_TIME;
        strncpy(store.ut_user, "reboot", sizeof(store.ut_user));

        return write_entry_both(&store);
}

static void copy_suffix(char *buf, size_t buf_size, const char *src) {
        size_t l;

        l = strlen(src);
        if (l < buf_size)
                strncpy(buf, src, buf_size);
        else
                memcpy(buf, src + l - buf_size, buf_size);
}

int utmp_put_init_process(const char *id, pid_t pid, pid_t sid, const char *line, int ut_type, const char *user) {
        struct utmpx store = {
                .ut_type = INIT_PROCESS,
                .ut_pid = pid,
                .ut_session = sid,
        };
        int r;

        assert(id);

        init_timestamp(&store, 0);

        /* Copy the whole string if it fits, or just the suffix without the terminating NUL. */
        copy_suffix(store.ut_id, sizeof(store.ut_id), id);

        if (line)
                strncpy_exact(store.ut_line, line, sizeof(store.ut_line));

        r = write_entry_both(&store);
        if (r < 0)
                return r;

        if (IN_SET(ut_type, LOGIN_PROCESS, USER_PROCESS)) {
                store.ut_type = LOGIN_PROCESS;
                r = write_entry_both(&store);
                if (r < 0)
                        return r;
        }

        if (ut_type == USER_PROCESS) {
                store.ut_type = USER_PROCESS;
                strncpy(store.ut_user, user, sizeof(store.ut_user)-1);
                r = write_entry_both(&store);
                if (r < 0)
                        return r;
        }

        return 0;
}

int utmp_put_dead_process(const char *id, pid_t pid, int code, int status) {
        _unused_ _cleanup_(utxent_cleanup) bool utmpx = false;
        struct utmpx lookup = {
                .ut_type = INIT_PROCESS /* looks for DEAD_PROCESS, LOGIN_PROCESS, USER_PROCESS, too */
        }, store, store_wtmp, *found;

        assert(id);

        utmpx = utxent_start();

        /* Copy the whole string if it fits, or just the suffix without the terminating NUL. */
        copy_suffix(lookup.ut_id, sizeof(lookup.ut_id), id);

        found = getutxid(&lookup);
        if (!found)
                return 0;

        if (found->ut_pid != pid)
                return 0;

        memcpy(&store, found, sizeof(store));
        store.ut_type = DEAD_PROCESS;
        store.ut_exit.e_termination = code;
        store.ut_exit.e_exit = status;

        zero(store.ut_user);
        zero(store.ut_host);
        zero(store.ut_tv);

        memcpy(&store_wtmp, &store, sizeof(store_wtmp));
        /* wtmp wants the current time */
        init_timestamp(&store_wtmp, 0);

        return write_utmp_wtmp(&store, &store_wtmp);
}

int utmp_put_runlevel(int runlevel, int previous) {
        struct utmpx store = {};
        int r;

        assert(runlevel > 0);

        if (previous <= 0) {
                /* Find the old runlevel automatically */

                r = utmp_get_runlevel(&previous, NULL);
                if (r < 0) {
                        if (r != -ESRCH)
                                return r;

                        previous = 0;
                }
        }

        if (previous == runlevel)
                return 0;

        init_entry(&store, 0);

        store.ut_type = RUN_LVL;
        store.ut_pid = (runlevel & 0xFF) | ((previous & 0xFF) << 8);
        strncpy(store.ut_user, "runlevel", sizeof(store.ut_user));

        return write_entry_both(&store);
}

#define TIMEOUT_USEC (50 * USEC_PER_MSEC)

static int write_to_terminal(const char *tty, const char *message) {
        _cleanup_close_ int fd = -1;
        const char *p;
        size_t left;
        usec_t end;

        assert(tty);
        assert(message);

        fd = open(tty, O_WRONLY|O_NONBLOCK|O_NOCTTY|O_CLOEXEC);
        if (fd < 0 || !isatty(fd))
                return -errno;

        p = message;
        left = strlen(message);

        end = now(CLOCK_MONOTONIC) + TIMEOUT_USEC;

        while (left > 0) {
                ssize_t n;
                usec_t t;
                int k;

                t = now(CLOCK_MONOTONIC);

                if (t >= end)
                        return -ETIME;

                k = fd_wait_for_event(fd, POLLOUT, end - t);
                if (k < 0)
                        return k;
                if (k == 0)
                        return -ETIME;

                n = write(fd, p, left);
                if (n < 0) {
                        if (errno == EAGAIN)
                                continue;

                        return -errno;
                }

                assert((size_t) n <= left);

                p += n;
                left -= n;
        }

        return 0;
}

int utmp_wall(
        const char *message,
        const char *username,
        const char *origin_tty,
        bool (*match_tty)(const char *tty, bool is_local, void *userdata),
        void *userdata) {

        _unused_ _cleanup_(utxent_cleanup) bool utmpx = false;
        _cleanup_free_ char *text = NULL, *hn = NULL, *un = NULL, *stdin_tty = NULL;
        struct utmpx *u;
        int r;

        hn = gethostname_malloc();
        if (!hn)
                return -ENOMEM;
        if (!username) {
                un = getlogname_malloc();
                if (!un)
                        return -ENOMEM;
        }

        if (!origin_tty) {
                getttyname_harder(STDIN_FILENO, &stdin_tty);
                origin_tty = stdin_tty;
        }

        if (asprintf(&text,
                     "\r\n"
                     "Broadcast message from %s@%s%s%s (%s):\r\n\r\n"
                     "%s\r\n\r\n",
                     un ?: username, hn,
                     origin_tty ? " on " : "", strempty(origin_tty),
                     FORMAT_TIMESTAMP(now(CLOCK_REALTIME)),
                     message) < 0)
                return -ENOMEM;

        utmpx = utxent_start();

        r = 0;

        while ((u = getutxent())) {
                _cleanup_free_ char *buf = NULL;
                const char *path;
                int q;

                if (u->ut_type != USER_PROCESS || u->ut_user[0] == 0)
                        continue;

                /* This access is fine, because strlen("/dev/") < 32 (UT_LINESIZE) */
                if (path_startswith(u->ut_line, "/dev/"))
                        path = u->ut_line;
                else {
                        if (asprintf(&buf, "/dev/%.*s", (int) sizeof(u->ut_line), u->ut_line) < 0)
                                return -ENOMEM;
                        path = buf;
                }

                /* It seems that the address field is always set for remote logins.
                 * For local logins and other local entries, we get [0,0,0,0]. */
                bool is_local = memeqzero(u->ut_addr_v6, sizeof(u->ut_addr_v6));

                if (!match_tty || match_tty(path, is_local, userdata)) {
                        q = write_to_terminal(path, text);
                        if (q < 0)
                                r = q;
                }
        }

        return r;
}