1 files changed, 405 insertions, 0 deletions
diff --git a/src/shared/utmp-wtmp.c b/src/shared/utmp-wtmp.c
new file mode 100644
index 0000000..cfeabbd
--- /dev/null
+++ b/src/shared/utmp-wtmp.c
@@ -0,0 +1,405 @@
+/* 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;
+}