3 files changed, 207 insertions, 0 deletions

diff --git a/plugins/check_users.d/config.h b/plugins/check_users.d/config.h
new file mode 100644
index 00000000..26d3ee70
--- /dev/null
+++ b/plugins/check_users.d/config.h
@@ -0,0 +1,20 @@
+#pragma once
+
+#include "output.h"
+#include "thresholds.h"
+
+typedef struct check_users_config {
+        mp_thresholds thresholds;
+
+        bool output_format_is_set;
+        mp_output_format output_format;
+} check_users_config;
+
+check_users_config check_users_config_init() {
+        check_users_config tmp = {
+                .thresholds = mp_thresholds_init(),
+
+                .output_format_is_set = false,
+        };
+        return tmp;
+}
diff --git a/plugins/check_users.d/users.c b/plugins/check_users.d/users.c
new file mode 100644
index 00000000..a08f79c5
--- /dev/null
+++ b/plugins/check_users.d/users.c
@@ -0,0 +1,169 @@
+#include "./users.h"
+
+#ifdef _WIN32
+#       ifdef HAVE_WTSAPI32_H
+#               include <windows.h>
+#               include <wtsapi32.h>
+#               undef ERROR
+#               define ERROR -1
+
+get_num_of_users_wrapper get_num_of_users_windows() {
+        WTS_SESSION_INFO *wtsinfo;
+        DWORD wtscount;
+
+        get_num_of_users_wrapper result = {};
+
+        if (!WTSEnumerateSessions(WTS_CURRENT_SERVER_HANDLE, 0, 1, &wtsinfo, &wtscount)) {
+                // printf(_("Could not enumerate RD sessions: %d\n"), GetLastError());
+                result.error = WINDOWS_COULD_NOT_ENUMERATE_SESSIONS;
+                return result;
+        }
+
+        for (DWORD index = 0; index < wtscount; index++) {
+                LPTSTR username;
+                DWORD size;
+
+                if (!WTSQuerySessionInformation(WTS_CURRENT_SERVER_HANDLE, wtsinfo[index].SessionId,
+                                                                                WTSUserName, &username, &size)) {
+                        continue;
+                }
+
+                int len = lstrlen(username);
+
+                WTSFreeMemory(username);
+
+                if (len == 0) {
+                        continue;
+                }
+
+                if (wtsinfo[index].State == WTSActive || wtsinfo[index].State == WTSDisconnected) {
+                        result.users++;
+                }
+        }
+
+        WTSFreeMemory(wtsinfo);
+        return result;
+}
+#       else // HAVE_WTSAPI32_H
+#               error On windows but without the WTSAPI32 lib
+#       endif // HAVE_WTSAPI32_H
+
+#else // _WIN32
+
+#       include "../../config.h"
+#       include <stddef.h>
+
+#       ifdef HAVE_LIBSYSTEMD
+#               include <systemd/sd-daemon.h>
+#               include <systemd/sd-login.h>
+
+get_num_of_users_wrapper get_num_of_users_systemd() {
+        get_num_of_users_wrapper result = {};
+
+        // Test whether we booted with systemd
+        if (sd_booted() > 0) {
+                int users = sd_get_uids(NULL);
+                if (users >= 0) {
+                        // Success
+                        result.users = users;
+                        return result;
+                }
+
+                // Failure! return the error code
+                result.errorcode = users;
+                return result;
+        }
+
+        // Looks like we are not running systemd,
+        // return with error here
+        result.errorcode = NO_SYSTEMD_ERROR;
+        return result;
+}
+#       endif
+
+#       ifdef HAVE_UTMPX_H
+#               include <utmpx.h>
+
+get_num_of_users_wrapper get_num_of_users_utmp() {
+        int users = 0;
+
+        /* get currently logged users from utmpx */
+        setutxent();
+
+        struct utmpx *putmpx;
+        while ((putmpx = getutxent()) != NULL) {
+                if (putmpx->ut_type == USER_PROCESS) {
+                        users++;
+                }
+        }
+
+        endutxent();
+
+        get_num_of_users_wrapper result = {
+                .errorcode = 0,
+                .users = users,
+        };
+
+        return result;
+}
+#       endif
+
+#       ifndef HAVE_WTSAPI32_H
+#               ifndef HAVE_LIBSYSTEMD
+#                       ifndef HAVE_UTMPX_H
+//  Fall back option here for the others (probably still not on windows)
+
+#                               include "../common.h"
+#                               include "../popen.h"
+#                               include "../utils.h"
+
+get_num_of_users_wrapper get_num_of_users_who_command() {
+        /* run the command */
+        child_process = spopen(WHO_COMMAND);
+        if (child_process == NULL) {
+                // printf(_("Could not open pipe: %s\n"), WHO_COMMAND);
+                get_num_of_users_wrapper result = {
+                        .errorcode = COULD_NOT_OPEN_PIPE,
+                };
+                return result;
+        }
+
+        child_stderr = fdopen(child_stderr_array[fileno(child_process)], "r");
+        if (child_stderr == NULL) {
+                // printf(_("Could not open stderr for %s\n"), WHO_COMMAND);
+                //  TODO this error should probably be reported
+        }
+
+        get_num_of_users_wrapper result = {};
+        char input_buffer[MAX_INPUT_BUFFER];
+        while (fgets(input_buffer, MAX_INPUT_BUFFER - 1, child_process)) {
+                /* increment 'users' on all lines except total user count */
+                if (input_buffer[0] != '#') {
+                        result.users++;
+                        continue;
+                }
+
+                /* get total logged in users */
+                if (sscanf(input_buffer, _("# users=%d"), &result.users) == 1) {
+                        break;
+                }
+        }
+
+        /* check STDERR */
+        if (fgets(input_buffer, MAX_INPUT_BUFFER - 1, child_stderr)) {
+                // if this fails, something broke and the result can not be relied upon or so is the theorie
+                // here
+                result.errorcode = STDERR_COULD_NOT_BE_READ;
+        }
+        (void)fclose(child_stderr);
+
+        /* close the pipe */
+        spclose(child_process);
+
+        return result;
+}
+
+#                       endif
+#               endif
+#       endif
+#endif
diff --git a/plugins/check_users.d/users.h b/plugins/check_users.d/users.h
new file mode 100644
index 00000000..aacba775
--- /dev/null
+++ b/plugins/check_users.d/users.h
@@ -0,0 +1,18 @@
+#pragma once
+
+typedef struct get_num_of_users_wrapper {
+        int errorcode;
+        int users;
+} get_num_of_users_wrapper;
+
+enum {
+        NO_SYSTEMD_ERROR = 64,
+        WINDOWS_COULD_NOT_ENUMERATE_SESSIONS,
+        COULD_NOT_OPEN_PIPE,
+        STDERR_COULD_NOT_BE_READ,
+};
+
+get_num_of_users_wrapper get_num_of_users_systemd();
+get_num_of_users_wrapper get_num_of_users_utmp();
+get_num_of_users_wrapper get_num_of_users_windows();
+get_num_of_users_wrapper get_num_of_users_who_command();