pam: implement systemd PAM module and generelize cgroup API for that a bit

1 files changed, 466 insertions, 0 deletions

diff --git a/src/pam-module.c b/src/pam-module.c
new file mode 100644
index 0000000000..5157897a71
--- /dev/null
+++ b/src/pam-module.c
@@ -0,0 +1,466 @@
+/*-*- Mode: C; c-basic-offset: 8 -*-*/
+
+/***
+  This file is part of systemd.
+
+  Copyright 2010 Lennart Poettering
+
+  systemd is free software; you can redistribute it and/or modify it
+  under the terms of the GNU General Public License as published by
+  the Free Software Foundation; either version 2 of the License, or
+  (at your option) any later version.
+
+  systemd is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+  General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include <errno.h>
+#include <fcntl.h>
+#include <sys/file.h>
+#include <pwd.h>
+
+#include <security/pam_modules.h>
+#include <security/_pam_macros.h>
+#include <security/pam_modutil.h>
+#include <security/pam_ext.h>
+#include <security/pam_misc.h>
+
+#include <libcgroup.h>
+
+#include "util.h"
+#include "cgroup-util.h"
+#include "macro.h"
+#include "sd-daemon.h"
+
+static int parse_argv(pam_handle_t *handle,
+                      int argc, const char **argv,
+                      bool *create_session,
+                      bool *kill_session,
+                      bool *kill_user) {
+
+        unsigned i;
+
+        assert(argc >= 0);
+        assert(argc == 0 || argv);
+
+        for (i = 0; i < (unsigned) argc; i++) {
+                int k;
+
+                if (startswith(argv[i], "create-session=")) {
+                        if ((k = parse_boolean(argv[i] + 15)) < 0) {
+                                pam_syslog(handle, LOG_ERR, "Failed to parse create-session= argument.");
+                                return k;
+                        }
+
+                        if (create_session)
+                                *create_session = k;
+                } else if (startswith(argv[i], "kill-session=")) {
+                        if ((k = parse_boolean(argv[i] + 13)) < 0) {
+                                pam_syslog(handle, LOG_ERR, "Failed to parse kill-session= argument.");
+                                return k;
+                        }
+
+                        if (kill_session)
+                                *kill_session = k;
+
+                } else if (startswith(argv[i], "kill-user=")) {
+                        if ((k = parse_boolean(argv[i] + 10)) < 0) {
+                                pam_syslog(handle, LOG_ERR, "Failed to parse kill-user= argument.");
+                                return k;
+                        }
+
+                        if (kill_user)
+                                *kill_user = k;
+                } else {
+                        pam_syslog(handle, LOG_ERR, "Unknown parameter '%s'.", argv[i]);
+                        return -EINVAL;
+                }
+        }
+
+        if (kill_session && *kill_session && kill_user)
+                *kill_user = true;
+
+        return 0;
+}
+
+static int open_file_and_lock(const char *fn) {
+        int fd;
+
+        assert(fn);
+
+        if ((fd = open(fn, O_RDWR|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW|O_CREAT, 0600)) < 0)
+                return -errno;
+
+        if (flock(fd, LOCK_EX) < 0)
+                return -errno;
+
+        return fd;
+}
+
+static uint32_t combine32(unsigned long long u) {
+        uint32_t r = 0;
+        unsigned i;
+
+        for (i = 0; i < sizeof(u)/4; i ++)
+                r ^= (uint32_t) ((u >> (i*32)) & 0xFFFFFFFFULL);
+
+        return r;
+}
+
+static char *generate_session_cookie(void) {
+        char *machine;
+        char *cookie;
+        unsigned long long r;
+        usec_t u;
+        int k;
+
+        if (getmachineid_malloc(&machine) < 0)
+                if (!(machine = gethostname_malloc()))
+                        return NULL;
+
+        r = random_ull();
+        u = now(CLOCK_REALTIME);
+
+        k = asprintf(&cookie, "%s-%lu-%lu",
+                     machine,
+                     (unsigned long) combine32(r),
+                     (unsigned long) combine32((unsigned long long) u));
+        free(machine);
+
+        return k < 0 ? NULL : cookie;
+}
+
+static int get_user_data(
+                pam_handle_t *handle,
+                const char **ret_username,
+                struct passwd **ret_pw) {
+
+        const char *username;
+        struct passwd *pw;
+        int r;
+
+        assert(handle);
+        assert(ret_username);
+        assert(ret_pw);
+
+        if ((r = pam_get_user(handle, &username, NULL)) != PAM_SUCCESS) {
+                pam_syslog(handle, LOG_ERR, "Failed to get user name.");
+                return r;
+        }
+
+        if (!username || !*username) {
+                pam_syslog(handle, LOG_ERR, "User name not valid.");
+                return PAM_AUTH_ERR;
+        }
+
+        if (!(pw = pam_modutil_getpwnam(handle, username))) {
+                pam_syslog(handle, LOG_ERR, "Failed to get user data.");
+                return PAM_USER_UNKNOWN;
+        }
+
+        *ret_pw = pw;
+        *ret_username = username;
+
+        return PAM_SUCCESS;
+}
+
+static int create_user_group(pam_handle_t *handle, const char *group, struct passwd *pw, bool attach) {
+        int r;
+
+        assert(handle);
+        assert(group);
+
+        if (attach)
+                r = cg_create_and_attach("name=systemd", group, 0);
+        else
+                r = cg_create("name=systemd", group);
+
+        if (r < 0) {
+                pam_syslog(handle, LOG_ERR, "Failed to create cgroup: %s", strerror(-r));
+                return PAM_SESSION_ERR;
+        }
+
+        if ((r = cg_set_task_access("name=systemd", group, 0755, pw->pw_uid, pw->pw_gid)) < 0 ||
+            (r = cg_set_group_access("name=systemd", group, 0755, pw->pw_uid, pw->pw_gid)) < 0) {
+                pam_syslog(handle, LOG_ERR, "Failed to change access modes: %s", strerror(-r));
+                return PAM_SESSION_ERR;
+        }
+
+        return PAM_SUCCESS;
+}
+
+_public_ PAM_EXTERN int pam_sm_open_session(
+                pam_handle_t *handle,
+                int flags,
+                int argc, const char **argv) {
+
+        const char *username = NULL;
+        struct passwd *pw;
+        int r;
+        char *buf = NULL;
+        int lock_fd = -1;
+        bool create_session = true;
+
+        assert(handle);
+
+        pam_syslog(handle, LOG_INFO, "pam-systemd initializing");
+
+        if (parse_argv(handle, argc, argv, &create_session, NULL, NULL) < 0)
+                return PAM_SESSION_ERR;
+
+        /* Make this a NOP on non-systemd systems */
+        if (sd_booted() <= 0)
+                return PAM_SUCCESS;
+
+        if ((r = cgroup_init()) != 0) {
+                pam_syslog(handle, LOG_ERR, "libcgroup initialization failed: %s", cgroup_strerror(r));
+                r = PAM_SESSION_ERR;
+                goto finish;
+        }
+
+        if ((r = get_user_data(handle, &username, &pw)) != PAM_SUCCESS)
+                goto finish;
+
+        if (safe_mkdir(RUNTIME_DIR "/user", 0755, 0, 0) < 0) {
+                pam_syslog(handle, LOG_ERR, "Failed to create runtime directory: %m");
+                r = PAM_SYSTEM_ERR;
+                goto finish;
+        }
+
+        if ((lock_fd = open_file_and_lock(RUNTIME_DIR "/user/.pam-systemd-lock")) < 0) {
+                pam_syslog(handle, LOG_ERR, "Failed to lock runtime directory: %m");
+                r = PAM_SYSTEM_ERR;
+                goto finish;
+        }
+
+        /* Create /var/run/$USER */
+        free(buf);
+        if (asprintf(&buf, RUNTIME_DIR "/user/%s", username) < 0) {
+                r = PAM_BUF_ERR;
+                goto finish;
+        }
+
+        if (safe_mkdir(buf, 0700, pw->pw_uid, pw->pw_gid) < 0) {
+                pam_syslog(handle, LOG_WARNING, "Failed to create runtime directory: %m");
+                r = PAM_SYSTEM_ERR;
+                goto finish;
+        } else if ((r = pam_misc_setenv(handle, "XDG_RUNTIME_DIR", buf, 0)) != PAM_SUCCESS) {
+                pam_syslog(handle, LOG_ERR, "Failed to set runtime dir.");
+                goto finish;
+        }
+
+        free(buf);
+        buf = NULL;
+
+        if (create_session) {
+                const char *cookie;
+
+                /* Reuse or create XDG session ID */
+                if (!(cookie = pam_getenv(handle, "XDG_SESSION_COOKIE"))) {
+                        if (!(buf = generate_session_cookie())) {
+                                r = PAM_BUF_ERR;
+                                goto finish;
+                        }
+
+                        if ((r = pam_misc_setenv(handle, "XDG_SESSION_COOKIE", buf, 0)) != PAM_SUCCESS) {
+                                pam_syslog(handle, LOG_ERR, "Failed to set cookie.");
+                                goto finish;
+                        }
+
+                        if (!(cookie = pam_getenv(handle, "XDG_SESSION_COOKIE"))) {
+                                pam_syslog(handle, LOG_ERR, "Failed to get cookie.");
+                                r = PAM_SESSION_ERR;
+                                goto finish;
+                        }
+                }
+
+                r = asprintf(&buf, "/user/%s/%s", username, cookie);
+        } else
+                r = asprintf(&buf, "/user/%s/no-session", username);
+
+        if (r < 0) {
+                r = PAM_BUF_ERR;
+                goto finish;
+        }
+
+        if ((r = create_user_group(handle, buf, pw, true)) != PAM_SUCCESS)
+                goto finish;
+
+        r = PAM_SUCCESS;
+
+finish:
+        free(buf);
+
+        if (lock_fd >= 0)
+                close_nointr_nofail(lock_fd);
+
+        return r;
+}
+
+static int session_remains(pam_handle_t *handle, const char *user_path) {
+        struct cgroup_file_info info;
+        int level = 0, r;
+        void *iterator = NULL;
+        bool remains = false;
+
+        zero(info);
+
+        r = cgroup_walk_tree_begin("name=systemd", user_path, 0, &iterator, &info, &level);
+        while (r == 0) {
+
+                if (info.type != CGROUP_FILE_TYPE_DIR)
+                        goto next;
+
+                if (streq(info.path, ""))
+                        goto next;
+
+                if (streq(info.path, "no-session"))
+                        goto next;
+
+                remains = true;
+                break;
+
+        next:
+
+                r = cgroup_walk_tree_next(0, &iterator, &info, level);
+        }
+
+
+        if (remains)
+                r = 1;
+        else if (r == 0 || r == ECGEOF)
+                r = 0;
+        else
+                r = cg_translate_error(r, errno);
+
+        assert_se(cgroup_walk_tree_end(&iterator) == 0);
+
+        return r;
+}
+
+_public_ PAM_EXTERN int pam_sm_close_session(
+                pam_handle_t *handle,
+                int flags,
+                int argc, const char **argv) {
+
+        const char *username = NULL;
+        bool kill_session = false;
+        bool kill_user = false;
+        int lock_fd = -1, r;
+        char *session_path = NULL, *nosession_path = NULL, *user_path = NULL;
+        const char *cookie;
+        struct passwd *pw;
+
+        assert(handle);
+
+        if (parse_argv(handle, argc, argv, NULL, &kill_session, &kill_user) < 0)
+                return PAM_SESSION_ERR;
+
+        /* Make this a NOP on non-systemd systems */
+        if (sd_booted() <= 0)
+                return PAM_SUCCESS;
+
+        if ((r = get_user_data(handle, &username, &pw)) != PAM_SUCCESS)
+                goto finish;
+
+        if ((lock_fd = open_file_and_lock(RUNTIME_DIR "/user/.pam-systemd-lock")) < 0) {
+                pam_syslog(handle, LOG_ERR, "Failed to lock runtime directory: %m");
+                r = PAM_SYSTEM_ERR;
+                goto finish;
+        }
+
+        if (asprintf(&user_path, "/user/%s", username) < 0) {
+                r = PAM_BUF_ERR;
+                goto finish;
+        }
+
+        if ((cookie = pam_getenv(handle, "XDG_SESSION_COOKIE"))) {
+
+                if (asprintf(&session_path, "/user/%s/%s", username, cookie) < 0 ||
+                    asprintf(&nosession_path, "/user/%s/no-session", username) < 0) {
+                        r = PAM_BUF_ERR;
+                        goto finish;
+                }
+
+                if (kill_session)  {
+                        pam_syslog(handle, LOG_INFO, "KILLING ENTER");
+
+                        /* Kill processes in session cgroup */
+                        if ((r = cg_kill_recursive_and_wait("name=systemd", session_path)) < 0)
+                                pam_syslog(handle, LOG_ERR, "Failed to kill session cgroup: %s", strerror(-r));
+
+                        pam_syslog(handle, LOG_INFO, "KILLING EXIT");
+
+                } else  {
+                        /* Migrate processes from session to
+                         * no-session cgroup. First, try to create the
+                         * no-session group in case it doesn't exist
+                         * yet. */
+                        create_user_group(handle, nosession_path, pw, 0);
+
+                        if ((r = cg_migrate_recursive("name=systemd", session_path, nosession_path, false)) < 0)
+                                pam_syslog(handle, LOG_ERR, "Failed to migrate session cgroup: %s", strerror(-r));
+                }
+
+                /* Delete session cgroup */
+                if (r < 0)
+                        pam_syslog(handle, LOG_INFO, "Couldn't empty session cgroup, not deleting.");
+                else {
+                        if ((r = cg_delete("name=systemd", session_path)) < 0)
+                                pam_syslog(handle, LOG_ERR, "Failed to delete session cgroup: %s", strerror(-r));
+                }
+        }
+
+        /* GC user tree */
+        cg_trim("name=systemd", user_path, false);
+
+        if ((r = session_remains(handle, user_path)) < 0)
+                pam_syslog(handle, LOG_ERR, "Failed to determine whether a session remains: %s", strerror(-r));
+
+        /* Kill user processes not attached to any session */
+        if (kill_user && r == 0) {
+
+                /* Kill no-session cgroup */
+                if ((r = cg_kill_recursive_and_wait("name=systemd", user_path)) < 0)
+                        pam_syslog(handle, LOG_ERR, "Failed to kill user cgroup: %s", strerror(-r));
+        } else {
+
+                if ((r = cg_is_empty_recursive("name=systemd", user_path, true)) < 0)
+                        pam_syslog(handle, LOG_ERR, "Failed to check user cgroup: %s", strerror(-r));
+
+                /* If we managed to kill somebody, don't cleanup the cgroup. */
+                if (r == 0)
+                        r = -EBUSY;
+        }
+
+        if (r >= 0) {
+                const char *runtime_dir;
+
+                /* Remove user cgroup */
+                if ((r = cg_delete("name=systemd", user_path)) < 0)
+                        pam_syslog(handle, LOG_ERR, "Failed to delete user cgroup: %s", strerror(-r));
+
+                /* This will migrate us to the /user cgroup. */
+
+                if ((runtime_dir = pam_getenv(handle, "XDG_RUNTIME_DIR")))
+                        if ((r = rm_rf(runtime_dir, false, true)) < 0)
+                                pam_syslog(handle, LOG_ERR, "Failed to remove runtime directory: %s", strerror(-r));
+        }
+
+        r = PAM_SUCCESS;
+
+finish:
+        if (lock_fd >= 0)
+                close_nointr_nofail(lock_fd);
+
+        free(session_path);
+        free(nosession_path);
+        free(user_path);
+
+        return r;
+}