Adding upstream version 252.22.upstream/252.22

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1072 insertions, 0 deletions

diff --git a/src/home/pam_systemd_home.c b/src/home/pam_systemd_home.c
new file mode 100644
index 0000000..1eaa5de
--- /dev/null
+++ b/src/home/pam_systemd_home.c
@@ -0,0 +1,1072 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <security/pam_ext.h>
+#include <security/pam_modules.h>
+
+#include "sd-bus.h"
+
+#include "bus-common-errors.h"
+#include "bus-locator.h"
+#include "bus-util.h"
+#include "errno-util.h"
+#include "fd-util.h"
+#include "home-util.h"
+#include "memory-util.h"
+#include "pam-util.h"
+#include "parse-util.h"
+#include "strv.h"
+#include "user-record-util.h"
+#include "user-record.h"
+#include "user-util.h"
+
+static int parse_argv(
+                pam_handle_t *handle,
+                int argc, const char **argv,
+                bool *please_suspend,
+                bool *debug) {
+
+        assert(argc >= 0);
+        assert(argc == 0 || argv);
+
+        for (int i = 0; i < argc; i++) {
+                const char *v;
+
+                if ((v = startswith(argv[i], "suspend="))) {
+                        int k;
+
+                        k = parse_boolean(v);
+                        if (k < 0)
+                                pam_syslog(handle, LOG_WARNING, "Failed to parse suspend= argument, ignoring: %s", v);
+                        else if (please_suspend)
+                                *please_suspend = k;
+
+                } else if (streq(argv[i], "debug")) {
+                        if (debug)
+                                *debug = true;
+
+                } else if ((v = startswith(argv[i], "debug="))) {
+                        int k;
+                        k = parse_boolean(v);
+                        if (k < 0)
+                                pam_syslog(handle, LOG_WARNING, "Failed to parse debug= argument, ignoring: %s", v);
+                        else if (debug)
+                                *debug = k;
+
+                } else
+                        pam_syslog(handle, LOG_WARNING, "Unknown parameter '%s', ignoring", argv[i]);
+        }
+
+        return 0;
+}
+
+static int parse_env(
+                pam_handle_t *handle,
+                bool *please_suspend) {
+
+        const char *v;
+        int r;
+
+        /* Let's read the suspend setting from an env var in addition to the PAM command line. That makes it
+         * easy to declare the features of a display manager in code rather than configuration, and this is
+         * really a feature of code */
+
+        v = pam_getenv(handle, "SYSTEMD_HOME_SUSPEND");
+        if (!v) {
+                /* Also check the process env block, so that people can control this via an env var from the
+                 * outside of our process. */
+                v = secure_getenv("SYSTEMD_HOME_SUSPEND");
+                if (!v)
+                        return 0;
+        }
+
+        r = parse_boolean(v);
+        if (r < 0)
+                pam_syslog(handle, LOG_WARNING, "Failed to parse $SYSTEMD_HOME_SUSPEND argument, ignoring: %s", v);
+        else if (please_suspend)
+                *please_suspend = r;
+
+        return 0;
+}
+
+static int acquire_user_record(
+                pam_handle_t *handle,
+                const char *username,
+                bool debug,
+                UserRecord **ret_record) {
+
+        _cleanup_(sd_bus_message_unrefp) sd_bus_message *reply = NULL;
+        _cleanup_(json_variant_unrefp) JsonVariant *v = NULL;
+        _cleanup_(user_record_unrefp) UserRecord *ur = NULL;
+        _cleanup_(sd_bus_unrefp) sd_bus *bus = NULL;
+        _cleanup_free_ char *homed_field = NULL;
+        const char *json = NULL;
+        int r;
+
+        assert(handle);
+
+        if (!username) {
+                r = pam_get_user(handle, &username, NULL);
+                if (r != PAM_SUCCESS)
+                        return pam_syslog_pam_error(handle, LOG_ERR, r, "Failed to get user name: @PAMERR@");
+
+                if (isempty(username))
+                        return pam_syslog_pam_error(handle, LOG_ERR, PAM_SERVICE_ERR, "User name not set.");
+        }
+
+        /* Let's bypass all IPC complexity for the two user names we know for sure we don't manage, and for
+         * user names we don't consider valid. */
+        if (STR_IN_SET(username, "root", NOBODY_USER_NAME) || !valid_user_group_name(username, 0))
+                return PAM_USER_UNKNOWN;
+
+        /* We cache the user record in the PAM context. We use a field name that includes the username, since
+         * clients might change the user name associated with a PAM context underneath us. Notably, 'sudo'
+         * creates a single PAM context and first authenticates it with the user set to the originating user,
+         * then updates the user for the destination user and issues the session stack with the same PAM
+         * context. We thus must be prepared that the user record changes between calls and we keep any
+         * caching separate. */
+        homed_field = strjoin("systemd-home-user-record-", username);
+        if (!homed_field)
+                return pam_log_oom(handle);
+
+        /* Let's use the cache, so that we can share it between the session and the authentication hooks */
+        r = pam_get_data(handle, homed_field, (const void**) &json);
+        if (!IN_SET(r, PAM_SUCCESS, PAM_NO_MODULE_DATA))
+                return pam_syslog_pam_error(handle, LOG_ERR, r, "Failed to get PAM user record data: @PAMERR@");
+        if (r == PAM_SUCCESS && json) {
+                /* We determined earlier that this is not a homed user? Then exit early. (We use -1 as
+                 * negative cache indicator) */
+                if (json == POINTER_MAX)
+                        return PAM_USER_UNKNOWN;
+        } else {
+                _cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
+                _cleanup_free_ char *generic_field = NULL, *json_copy = NULL;
+
+                r = pam_acquire_bus_connection(handle, "pam-systemd-home", &bus);
+                if (r != PAM_SUCCESS)
+                        return r;
+
+                r = bus_call_method(bus, bus_home_mgr, "GetUserRecordByName", &error, &reply, "s", username);
+                if (r < 0) {
+                        if (bus_error_is_unknown_service(&error)) {
+                                if (debug)
+                                        pam_syslog(handle, LOG_DEBUG, "systemd-homed is not available: %s", bus_error_message(&error, r));
+                                goto user_unknown;
+                        }
+
+                        if (sd_bus_error_has_name(&error, BUS_ERROR_NO_SUCH_HOME)) {
+                                if (debug)
+                                        pam_syslog(handle, LOG_DEBUG, "Not a user managed by systemd-homed: %s", bus_error_message(&error, r));
+                                goto user_unknown;
+                        }
+
+                        pam_syslog(handle, LOG_ERR, "Failed to query user record: %s", bus_error_message(&error, r));
+                        return PAM_SERVICE_ERR;
+                }
+
+                r = sd_bus_message_read(reply, "sbo", &json, NULL, NULL);
+                if (r < 0)
+                        return pam_bus_log_parse_error(handle, r);
+
+                /* First copy: for the homed-specific data field, i.e. where we know the user record is from
+                 * homed */
+                json_copy = strdup(json);
+                if (!json_copy)
+                        return pam_log_oom(handle);
+
+                r = pam_set_data(handle, homed_field, json_copy, pam_cleanup_free);
+                if (r != PAM_SUCCESS)
+                        return pam_syslog_pam_error(handle, LOG_ERR, r,
+                                                    "Failed to set PAM user record data '%s': @PAMERR@", homed_field);
+
+                /* Take a second copy: for the generic data field, the one which we share with
+                 * pam_systemd. While we insist on only reusing homed records, pam_systemd is fine with homed
+                 * and non-homed user records. */
+                json_copy = strdup(json);
+                if (!json_copy)
+                        return pam_log_oom(handle);
+
+                generic_field = strjoin("systemd-user-record-", username);
+                if (!generic_field)
+                        return pam_log_oom(handle);
+
+                r = pam_set_data(handle, generic_field, json_copy, pam_cleanup_free);
+                if (r != PAM_SUCCESS)
+                        return pam_syslog_pam_error(handle, LOG_ERR, r,
+                                                    "Failed to set PAM user record data '%s': @PAMERR@", homed_field);
+
+                TAKE_PTR(json_copy);
+        }
+
+        r = json_parse(json, JSON_PARSE_SENSITIVE, &v, NULL, NULL);
+        if (r < 0)
+                return pam_syslog_errno(handle, LOG_ERR, r, "Failed to parse JSON user record: %m");
+
+        ur = user_record_new();
+        if (!ur)
+                return pam_log_oom(handle);
+
+        r = user_record_load(ur, v, USER_RECORD_LOAD_REFUSE_SECRET|USER_RECORD_PERMISSIVE);
+        if (r < 0)
+                return pam_syslog_errno(handle, LOG_ERR, r, "Failed to load user record: %m");
+
+        /* Safety check if cached record actually matches what we are looking for */
+        if (!streq_ptr(username, ur->user_name))
+                return pam_syslog_pam_error(handle, LOG_ERR, PAM_SERVICE_ERR,
+                                            "Acquired user record does not match user name.");
+
+        if (ret_record)
+                *ret_record = TAKE_PTR(ur);
+
+        return PAM_SUCCESS;
+
+user_unknown:
+        /* Cache this, so that we don't check again */
+        r = pam_set_data(handle, homed_field, POINTER_MAX, NULL);
+        if (r != PAM_SUCCESS)
+                pam_syslog_pam_error(handle, LOG_ERR, r,
+                                     "Failed to set PAM user record data '%s' to invalid, ignoring: @PAMERR@",
+                                     homed_field);
+
+        return PAM_USER_UNKNOWN;
+}
+
+static int release_user_record(pam_handle_t *handle, const char *username) {
+        _cleanup_free_ char *homed_field = NULL, *generic_field = NULL;
+        int r, k;
+
+        assert(handle);
+        assert(username);
+
+        homed_field = strjoin("systemd-home-user-record-", username);
+        if (!homed_field)
+                return pam_log_oom(handle);
+
+        r = pam_set_data(handle, homed_field, NULL, NULL);
+        if (r != PAM_SUCCESS)
+                pam_syslog_pam_error(handle, LOG_ERR, r,
+                                     "Failed to release PAM user record data '%s': @PAMERR@", homed_field);
+
+        generic_field = strjoin("systemd-user-record-", username);
+        if (!generic_field)
+                return pam_log_oom(handle);
+
+        k = pam_set_data(handle, generic_field, NULL, NULL);
+        if (k != PAM_SUCCESS)
+                pam_syslog_pam_error(handle, LOG_ERR, k,
+                                     "Failed to release PAM user record data '%s': @PAMERR@", generic_field);
+
+        return IN_SET(r, PAM_SUCCESS, PAM_NO_MODULE_DATA) ? k : r;
+}
+
+static void cleanup_home_fd(pam_handle_t *handle, void *data, int error_status) {
+        safe_close(PTR_TO_FD(data));
+}
+
+static int handle_generic_user_record_error(
+                pam_handle_t *handle,
+                const char *user_name,
+                UserRecord *secret,
+                int ret,
+                const sd_bus_error *error,
+                bool debug) {
+
+        assert(user_name);
+        assert(error);
+
+        int r;
+
+        /* Logs about all errors, except for PAM_CONV_ERR, i.e. when requesting more info failed. */
+
+        if (sd_bus_error_has_name(error, BUS_ERROR_HOME_ABSENT)) {
+                (void) pam_prompt(handle, PAM_ERROR_MSG, NULL,
+                                  "Home of user %s is currently absent, please plug in the necessary storage device or backing file system.", user_name);
+                return pam_syslog_pam_error(handle, LOG_ERR, PAM_PERM_DENIED,
+                                            "Failed to acquire home for user %s: %s", user_name, bus_error_message(error, ret));
+
+        } else if (sd_bus_error_has_name(error, BUS_ERROR_AUTHENTICATION_LIMIT_HIT)) {
+                (void) pam_prompt(handle, PAM_ERROR_MSG, NULL, "Too frequent login attempts for user %s, try again later.", user_name);
+                return pam_syslog_pam_error(handle, LOG_ERR, PAM_MAXTRIES,
+                                            "Failed to acquire home for user %s: %s", user_name, bus_error_message(error, ret));
+
+        } else if (sd_bus_error_has_name(error, BUS_ERROR_BAD_PASSWORD)) {
+                _cleanup_(erase_and_freep) char *newp = NULL;
+
+                assert(secret);
+
+                /* This didn't work? Ask for an (additional?) password */
+
+                if (strv_isempty(secret->password))
+                        r = pam_prompt(handle, PAM_PROMPT_ECHO_OFF, &newp, "Password: ");
+                else {
+                        (void) pam_prompt(handle, PAM_ERROR_MSG, NULL, "Password incorrect or not sufficient for authentication of user %s.", user_name);
+                        r = pam_prompt(handle, PAM_PROMPT_ECHO_OFF, &newp, "Sorry, try again: ");
+                }
+                if (r != PAM_SUCCESS)
+                        return PAM_CONV_ERR; /* no logging here */
+
+                if (isempty(newp)) {
+                        if (debug)
+                                pam_syslog(handle, LOG_DEBUG, "Password request aborted.");
+                        return PAM_AUTHTOK_ERR;
+                }
+
+                r = user_record_set_password(secret, STRV_MAKE(newp), true);
+                if (r < 0)
+                        return pam_syslog_errno(handle, LOG_ERR, r, "Failed to store password: %m");
+
+        } else if (sd_bus_error_has_name(error, BUS_ERROR_BAD_RECOVERY_KEY)) {
+                _cleanup_(erase_and_freep) char *newp = NULL;
+
+                assert(secret);
+
+                /* Hmm, homed asks for recovery key (because no regular password is defined maybe)? Provide it. */
+
+                if (strv_isempty(secret->password))
+                        r = pam_prompt(handle, PAM_PROMPT_ECHO_OFF, &newp, "Recovery key: ");
+                else {
+                        (void) pam_prompt(handle, PAM_ERROR_MSG, NULL, "Password/recovery key incorrect or not sufficient for authentication of user %s.", user_name);
+                        r = pam_prompt(handle, PAM_PROMPT_ECHO_OFF, &newp, "Sorry, reenter recovery key: ");
+                }
+                if (r != PAM_SUCCESS)
+                        return PAM_CONV_ERR; /* no logging here */
+
+                if (isempty(newp)) {
+                        if (debug)
+                                pam_syslog(handle, LOG_DEBUG, "Recovery key request aborted.");
+                        return PAM_AUTHTOK_ERR;
+                }
+
+                r = user_record_set_password(secret, STRV_MAKE(newp), true);
+                if (r < 0)
+                        return pam_syslog_errno(handle, LOG_ERR, r, "Failed to store recovery key: %m");
+
+        } else if (sd_bus_error_has_name(error, BUS_ERROR_BAD_PASSWORD_AND_NO_TOKEN)) {
+                _cleanup_(erase_and_freep) char *newp = NULL;
+
+                assert(secret);
+
+                if (strv_isempty(secret->password)) {
+                        (void) pam_prompt(handle, PAM_ERROR_MSG, NULL, "Security token of user %s not inserted.", user_name);
+                        r = pam_prompt(handle, PAM_PROMPT_ECHO_OFF, &newp, "Try again with password: ");
+                } else {
+                        (void) pam_prompt(handle, PAM_ERROR_MSG, NULL, "Password incorrect or not sufficient, and configured security token of user %s not inserted.", user_name);
+                        r = pam_prompt(handle, PAM_PROMPT_ECHO_OFF, &newp, "Try again with password: ");
+                }
+                if (r != PAM_SUCCESS)
+                        return PAM_CONV_ERR; /* no logging here */
+
+                if (isempty(newp)) {
+                        if (debug)
+                                pam_syslog(handle, LOG_DEBUG, "Password request aborted.");
+                        return PAM_AUTHTOK_ERR;
+                }
+
+
+                r = user_record_set_password(secret, STRV_MAKE(newp), true);
+                if (r < 0)
+                        return pam_syslog_errno(handle, LOG_ERR, r, "Failed to store password: %m");
+
+        } else if (sd_bus_error_has_name(error, BUS_ERROR_TOKEN_PIN_NEEDED)) {
+                _cleanup_(erase_and_freep) char *newp = NULL;
+
+                assert(secret);
+
+                r = pam_prompt(handle, PAM_PROMPT_ECHO_OFF, &newp, "Security token PIN: ");
+                if (r != PAM_SUCCESS)
+                        return PAM_CONV_ERR; /* no logging here */
+
+                if (isempty(newp)) {
+                        if (debug)
+                                pam_syslog(handle, LOG_DEBUG, "PIN request aborted.");
+                        return PAM_AUTHTOK_ERR;
+                }
+
+                r = user_record_set_token_pin(secret, STRV_MAKE(newp), false);
+                if (r < 0)
+                        return pam_syslog_errno(handle, LOG_ERR, r, "Failed to store PIN: %m");
+
+        } else if (sd_bus_error_has_name(error, BUS_ERROR_TOKEN_PROTECTED_AUTHENTICATION_PATH_NEEDED)) {
+
+                assert(secret);
+
+                (void) pam_prompt(handle, PAM_ERROR_MSG, NULL, "Please authenticate physically on security token of user %s.", user_name);
+
+                r = user_record_set_pkcs11_protected_authentication_path_permitted(secret, true);
+                if (r < 0)
+                        return pam_syslog_errno(handle, LOG_ERR, r,
+                                                "Failed to set PKCS#11 protected authentication path permitted flag: %m");
+
+        } else if (sd_bus_error_has_name(error, BUS_ERROR_TOKEN_USER_PRESENCE_NEEDED)) {
+
+                assert(secret);
+
+                (void) pam_prompt(handle, PAM_ERROR_MSG, NULL, "Please confirm presence on security token of user %s.", user_name);
+
+                r = user_record_set_fido2_user_presence_permitted(secret, true);
+                if (r < 0)
+                        return pam_syslog_errno(handle, LOG_ERR, r,
+                                                "Failed to set FIDO2 user presence permitted flag: %m");
+
+        } else if (sd_bus_error_has_name(error, BUS_ERROR_TOKEN_USER_VERIFICATION_NEEDED)) {
+
+                assert(secret);
+
+                (void) pam_prompt(handle, PAM_ERROR_MSG, NULL, "Please verify user on security token of user %s.", user_name);
+
+                r = user_record_set_fido2_user_verification_permitted(secret, true);
+                if (r < 0)
+                        return pam_syslog_errno(handle, LOG_ERR, r,
+                                                "Failed to set FIDO2 user verification permitted flag: %m");
+
+        } else if (sd_bus_error_has_name(error, BUS_ERROR_TOKEN_PIN_LOCKED)) {
+
+                (void) pam_prompt(handle, PAM_ERROR_MSG, NULL, "Security token PIN is locked, please unlock it first. (Hint: Removal and re-insertion might suffice.)");
+                return PAM_SERVICE_ERR;
+
+        } else if (sd_bus_error_has_name(error, BUS_ERROR_TOKEN_BAD_PIN)) {
+                _cleanup_(erase_and_freep) char *newp = NULL;
+
+                assert(secret);
+
+                (void) pam_prompt(handle, PAM_ERROR_MSG, NULL, "Security token PIN incorrect for user %s.", user_name);
+                r = pam_prompt(handle, PAM_PROMPT_ECHO_OFF, &newp, "Sorry, retry security token PIN: ");
+                if (r != PAM_SUCCESS)
+                        return PAM_CONV_ERR; /* no logging here */
+
+                if (isempty(newp)) {
+                        if (debug)
+                                pam_syslog(handle, LOG_DEBUG, "PIN request aborted.");
+                        return PAM_AUTHTOK_ERR;
+                }
+
+                r = user_record_set_token_pin(secret, STRV_MAKE(newp), false);
+                if (r < 0)
+                        return pam_syslog_errno(handle, LOG_ERR, r, "Failed to store PIN: %m");
+
+        } else if (sd_bus_error_has_name(error, BUS_ERROR_TOKEN_BAD_PIN_FEW_TRIES_LEFT)) {
+                _cleanup_(erase_and_freep) char *newp = NULL;
+
+                assert(secret);
+
+                (void) pam_prompt(handle, PAM_ERROR_MSG, NULL, "Security token PIN of user %s incorrect (only a few tries left!)", user_name);
+                r = pam_prompt(handle, PAM_PROMPT_ECHO_OFF, &newp, "Sorry, retry security token PIN: ");
+                if (r != PAM_SUCCESS)
+                        return PAM_CONV_ERR; /* no logging here */
+
+                if (isempty(newp)) {
+                        if (debug)
+                                pam_syslog(handle, LOG_DEBUG, "PIN request aborted.");
+                        return PAM_AUTHTOK_ERR;
+                }
+
+                r = user_record_set_token_pin(secret, STRV_MAKE(newp), false);
+                if (r < 0)
+                        return pam_syslog_errno(handle, LOG_ERR, r, "Failed to store PIN: %m");
+
+        } else if (sd_bus_error_has_name(error, BUS_ERROR_TOKEN_BAD_PIN_ONE_TRY_LEFT)) {
+                _cleanup_(erase_and_freep) char *newp = NULL;
+
+                assert(secret);
+
+                (void) pam_prompt(handle, PAM_ERROR_MSG, NULL, "Security token PIN of user %s incorrect (only one try left!)", user_name);
+                r = pam_prompt(handle, PAM_PROMPT_ECHO_OFF, &newp, "Sorry, retry security token PIN: ");
+                if (r != PAM_SUCCESS)
+                        return PAM_CONV_ERR; /* no logging here */
+
+                if (isempty(newp)) {
+                        if (debug)
+                                pam_syslog(handle, LOG_DEBUG, "PIN request aborted.");
+                        return PAM_AUTHTOK_ERR;
+                }
+
+                r = user_record_set_token_pin(secret, STRV_MAKE(newp), false);
+                if (r < 0)
+                        return pam_syslog_errno(handle, LOG_ERR, r, "Failed to store PIN: %m");
+
+        } else
+                return pam_syslog_pam_error(handle, LOG_ERR, PAM_SERVICE_ERR,
+                                            "Failed to acquire home for user %s: %s", user_name, bus_error_message(error, ret));
+
+        return PAM_SUCCESS;
+}
+
+static int acquire_home(
+                pam_handle_t *handle,
+                bool please_authenticate,
+                bool please_suspend,
+                bool debug) {
+
+        _cleanup_(user_record_unrefp) UserRecord *ur = NULL, *secret = NULL;
+        bool do_auth = please_authenticate, home_not_active = false, home_locked = false;
+        _cleanup_(sd_bus_unrefp) sd_bus *bus = NULL;
+        _cleanup_close_ int acquired_fd = -1;
+        _cleanup_free_ char *fd_field = NULL;
+        const void *home_fd_ptr = NULL;
+        const char *username = NULL;
+        unsigned n_attempts = 0;
+        int r;
+
+        assert(handle);
+
+        /* This acquires a reference to a home directory in one of two ways: if please_authenticate is true,
+         * then we'll call AcquireHome() after asking the user for a password. Otherwise it tries to call
+         * RefHome() and if that fails queries the user for a password and uses AcquireHome().
+         *
+         * The idea is that the PAM authentication hook sets please_authenticate and thus always
+         * authenticates, while the other PAM hooks unset it so that they can a ref of their own without
+         * authentication if possible, but with authentication if necessary. */
+
+        r = pam_get_user(handle, &username, NULL);
+        if (r != PAM_SUCCESS)
+                return pam_syslog_pam_error(handle, LOG_ERR, r, "Failed to get user name: @PAMERR@");
+
+        if (isempty(username))
+                return pam_syslog_pam_error(handle, LOG_ERR, PAM_SERVICE_ERR, "User name not set.");
+
+        /* If we already have acquired the fd, let's shortcut this */
+        fd_field = strjoin("systemd-home-fd-", username);
+        if (!fd_field)
+                return pam_log_oom(handle);
+
+        r = pam_get_data(handle, fd_field, &home_fd_ptr);
+        if (!IN_SET(r, PAM_SUCCESS, PAM_NO_MODULE_DATA))
+                return pam_syslog_pam_error(handle, LOG_ERR, r,
+                                            "Failed to retrieve PAM home reference fd: @PAMERR@");
+        if (r == PAM_SUCCESS && PTR_TO_FD(home_fd_ptr) >= 0)
+                return PAM_SUCCESS;
+
+        r = pam_acquire_bus_connection(handle, "pam-systemd-home", &bus);
+        if (r != PAM_SUCCESS)
+                return r;
+
+        r = acquire_user_record(handle, username, debug, &ur);
+        if (r != PAM_SUCCESS)
+                return r;
+
+        /* Implement our own retry loop here instead of relying on the PAM client's one. That's because it
+         * might happen that the record we stored on the host does not match the encryption password of
+         * the LUKS image in case the image was used in a different system where the password was
+         * changed. In that case it will happen that the LUKS password and the host password are
+         * different, and we handle that by collecting and passing multiple passwords in that case. Hence we
+         * treat bad passwords as a request to collect one more password and pass the new all all previously
+         * used passwords again. */
+
+        for (;;) {
+                _cleanup_(sd_bus_message_unrefp) sd_bus_message *m = NULL, *reply = NULL;
+                _cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
+
+                if (do_auth && !secret) {
+                        const char *cached_password = NULL;
+
+                        secret = user_record_new();
+                        if (!secret)
+                                return pam_log_oom(handle);
+
+                        /* If there's already a cached password, use it. But if not let's authenticate
+                         * without anything, maybe some other authentication mechanism systemd-homed
+                         * implements (such as PKCS#11) allows us to authenticate without anything else. */
+                        r = pam_get_item(handle, PAM_AUTHTOK, (const void**) &cached_password);
+                        if (!IN_SET(r, PAM_BAD_ITEM, PAM_SUCCESS))
+                                return pam_syslog_pam_error(handle, LOG_ERR, r,
+                                                            "Failed to get cached password: @PAMERR@");
+
+                        if (!isempty(cached_password)) {
+                                r = user_record_set_password(secret, STRV_MAKE(cached_password), true);
+                                if (r < 0)
+                                        return pam_syslog_errno(handle, LOG_ERR, r, "Failed to store password: %m");
+                        }
+                }
+
+                r = bus_message_new_method_call(bus, &m, bus_home_mgr, do_auth ? "AcquireHome" : "RefHome");
+                if (r < 0)
+                        return pam_bus_log_create_error(handle, r);
+
+                r = sd_bus_message_append(m, "s", ur->user_name);
+                if (r < 0)
+                        return pam_bus_log_create_error(handle, r);
+
+                if (do_auth) {
+                        r = bus_message_append_secret(m, secret);
+                        if (r < 0)
+                                return pam_bus_log_create_error(handle, r);
+                }
+
+                r = sd_bus_message_append(m, "b", please_suspend);
+                if (r < 0)
+                        return pam_bus_log_create_error(handle, r);
+
+                r = sd_bus_call(bus, m, HOME_SLOW_BUS_CALL_TIMEOUT_USEC, &error, &reply);
+                if (r < 0) {
+
+                        if (sd_bus_error_has_name(&error, BUS_ERROR_HOME_NOT_ACTIVE))
+                                /* Only on RefHome(): We can't access the home directory currently, unless
+                                 * it's unlocked with a password. Hence, let's try this again, this time with
+                                 * authentication. */
+                                home_not_active = true;
+                        else if (sd_bus_error_has_name(&error, BUS_ERROR_HOME_LOCKED))
+                                home_locked = true; /* Similar */
+                        else {
+                                r = handle_generic_user_record_error(handle, ur->user_name, secret, r, &error, debug);
+                                if (r == PAM_CONV_ERR) {
+                                        /* Password/PIN prompts will fail in certain environments, for example when
+                                         * we are called from OpenSSH's account or session hooks, or in systemd's
+                                         * per-service PAM logic. In that case, print a friendly message and accept
+                                         * failure. */
+
+                                        if (home_not_active)
+                                                (void) pam_prompt(handle, PAM_ERROR_MSG, NULL, "Home of user %s is currently not active, please log in locally first.", ur->user_name);
+                                        if (home_locked)
+                                                (void) pam_prompt(handle, PAM_ERROR_MSG, NULL, "Home of user %s is currently locked, please unlock locally first.", ur->user_name);
+
+                                        if (please_authenticate || debug)
+                                                pam_syslog(handle, please_authenticate ? LOG_ERR : LOG_DEBUG, "Failed to prompt for password/prompt.");
+
+                                        return home_not_active || home_locked ? PAM_PERM_DENIED : PAM_CONV_ERR;
+                                }
+                                if (r != PAM_SUCCESS)
+                                        return r;
+                        }
+
+                } else {
+                        int fd;
+
+                        r = sd_bus_message_read(reply, "h", &fd);
+                        if (r < 0)
+                                return pam_bus_log_parse_error(handle, r);
+
+                        acquired_fd = fcntl(fd, F_DUPFD_CLOEXEC, 3);
+                        if (acquired_fd < 0)
+                                return pam_syslog_errno(handle, LOG_ERR, errno,
+                                                        "Failed to duplicate acquired fd: %m");
+                        break;
+                }
+
+                if (++n_attempts >= 5) {
+                        (void) pam_prompt(handle, PAM_ERROR_MSG, NULL,
+                                          "Too many unsuccessful login attempts for user %s, refusing.", ur->user_name);
+                        return pam_syslog_pam_error(handle, LOG_ERR, PAM_MAXTRIES,
+                                                    "Failed to acquire home for user %s: %s", ur->user_name, bus_error_message(&error, r));
+                }
+
+                /* Try again, this time with authentication if we didn't do that before. */
+                do_auth = true;
+        }
+
+        /* Later PAM modules may need the auth token, but only during pam_authenticate. */
+        if (please_authenticate && !strv_isempty(secret->password)) {
+                r = pam_set_item(handle, PAM_AUTHTOK, *secret->password);
+                if (r != PAM_SUCCESS)
+                        return pam_syslog_pam_error(handle, LOG_ERR, r, "Failed to set PAM auth token: @PAMERR@");
+        }
+
+        r = pam_set_data(handle, fd_field, FD_TO_PTR(acquired_fd), cleanup_home_fd);
+        if (r != PAM_SUCCESS)
+                return pam_syslog_pam_error(handle, LOG_ERR, r, "Failed to set PAM bus data: @PAMERR@");
+        TAKE_FD(acquired_fd);
+
+        if (do_auth) {
+                /* We likely just activated the home directory, let's flush out the user record, since a
+                 * newer embedded user record might have been acquired from the activation. */
+
+                r = release_user_record(handle, ur->user_name);
+                if (!IN_SET(r, PAM_SUCCESS, PAM_NO_MODULE_DATA))
+                        return r;
+        }
+
+        pam_syslog(handle, LOG_NOTICE, "Home for user %s successfully acquired.", ur->user_name);
+        return PAM_SUCCESS;
+}
+
+static int release_home_fd(pam_handle_t *handle, const char *username) {
+        _cleanup_free_ char *fd_field = NULL;
+        const void *home_fd_ptr = NULL;
+        int r;
+
+        assert(handle);
+        assert(username);
+
+        fd_field = strjoin("systemd-home-fd-", username);
+        if (!fd_field)
+                return pam_log_oom(handle);
+
+        r = pam_get_data(handle, fd_field, &home_fd_ptr);
+        if (r == PAM_NO_MODULE_DATA || (r == PAM_SUCCESS && PTR_TO_FD(home_fd_ptr) < 0))
+                return PAM_NO_MODULE_DATA;
+        if (r != PAM_SUCCESS)
+                return pam_syslog_pam_error(handle, LOG_ERR, r, "Failed to retrieve PAM home reference fd: @PAMERR@");
+
+        r = pam_set_data(handle, fd_field, NULL, NULL);
+        if (r != PAM_SUCCESS)
+                return pam_syslog_pam_error(handle, LOG_ERR, r, "Failed to release PAM home reference fd: @PAMERR@");
+
+        return PAM_SUCCESS;
+}
+
+_public_ PAM_EXTERN int pam_sm_authenticate(
+                pam_handle_t *handle,
+                int flags,
+                int argc, const char **argv) {
+
+        bool debug = false, suspend_please = false;
+
+        if (parse_env(handle, &suspend_please) < 0)
+                return PAM_AUTH_ERR;
+
+        if (parse_argv(handle,
+                       argc, argv,
+                       &suspend_please,
+                       &debug) < 0)
+                return PAM_AUTH_ERR;
+
+        if (debug)
+                pam_syslog(handle, LOG_DEBUG, "pam-systemd-homed authenticating");
+
+        return acquire_home(handle, /* please_authenticate= */ true, suspend_please, debug);
+}
+
+_public_ PAM_EXTERN int pam_sm_setcred(pam_handle_t *pamh, int flags, int argc, const char **argv) {
+        return PAM_SUCCESS;
+}
+
+_public_ PAM_EXTERN int pam_sm_open_session(
+                pam_handle_t *handle,
+                int flags,
+                int argc, const char **argv) {
+
+        bool debug = false, suspend_please = false;
+        int r;
+
+        if (parse_env(handle, &suspend_please) < 0)
+                return PAM_SESSION_ERR;
+
+        if (parse_argv(handle,
+                       argc, argv,
+                       &suspend_please,
+                       &debug) < 0)
+                return PAM_SESSION_ERR;
+
+        if (debug)
+                pam_syslog(handle, LOG_DEBUG, "pam-systemd-homed session start");
+
+        r = acquire_home(handle, /* please_authenticate = */ false, suspend_please, debug);
+        if (r == PAM_USER_UNKNOWN) /* Not managed by us? Don't complain. */
+                goto success; /* Need to free the bus resource, as acquire_home() takes a reference. */
+        if (r != PAM_SUCCESS)
+                return r;
+
+        r = pam_putenv(handle, "SYSTEMD_HOME=1");
+        if (r != PAM_SUCCESS)
+                return pam_syslog_pam_error(handle, LOG_ERR, r,
+                                            "Failed to set PAM environment variable $SYSTEMD_HOME: @PAMERR@");
+
+        r = pam_putenv(handle, suspend_please ? "SYSTEMD_HOME_SUSPEND=1" : "SYSTEMD_HOME_SUSPEND=0");
+        if (r != PAM_SUCCESS)
+                return pam_syslog_pam_error(handle, LOG_ERR, r,
+                                            "Failed to set PAM environment variable $SYSTEMD_HOME_SUSPEND: @PAMERR@");
+
+success:
+        /* Let's release the D-Bus connection, after all the session might live quite a long time, and we are
+         * not going to process the bus connection in that time, so let's better close before the daemon
+         * kicks us off because we are not processing anything. */
+        (void) pam_release_bus_connection(handle, "pam-systemd-home");
+        return PAM_SUCCESS;
+}
+
+_public_ PAM_EXTERN int pam_sm_close_session(
+                pam_handle_t *handle,
+                int flags,
+                int argc, const char **argv) {
+
+        _cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
+        _cleanup_(sd_bus_message_unrefp) sd_bus_message *m = NULL;
+        _cleanup_(sd_bus_unrefp) sd_bus *bus = NULL;
+        const char *username = NULL;
+        bool debug = false;
+        int r;
+
+        if (parse_argv(handle,
+                       argc, argv,
+                       NULL,
+                       &debug) < 0)
+                return PAM_SESSION_ERR;
+
+        if (debug)
+                pam_syslog(handle, LOG_DEBUG, "pam-systemd-homed session end");
+
+        r = pam_get_user(handle, &username, NULL);
+        if (r != PAM_SUCCESS)
+                return pam_syslog_pam_error(handle, LOG_ERR, r, "Failed to get user name: @PAMERR@");
+
+        if (isempty(username))
+                return pam_syslog_pam_error(handle, LOG_ERR, PAM_SERVICE_ERR, "User name not set.");
+
+        /* Let's explicitly drop the reference to the homed session, so that the subsequent ReleaseHome()
+         * call will be able to do its thing. */
+        r = release_home_fd(handle, username);
+        if (r == PAM_NO_MODULE_DATA) /* Nothing to do, we never acquired an fd */
+                return PAM_SUCCESS;
+        if (r != PAM_SUCCESS)
+                return r;
+
+        r = pam_acquire_bus_connection(handle, "pam-systemd-home", &bus);
+        if (r != PAM_SUCCESS)
+                return r;
+
+        r = bus_message_new_method_call(bus, &m, bus_home_mgr, "ReleaseHome");
+        if (r < 0)
+                return pam_bus_log_create_error(handle, r);
+
+        r = sd_bus_message_append(m, "s", username);
+        if (r < 0)
+                return pam_bus_log_create_error(handle, r);
+
+        r = sd_bus_call(bus, m, HOME_SLOW_BUS_CALL_TIMEOUT_USEC, &error, NULL);
+        if (r < 0) {
+                if (sd_bus_error_has_name(&error, BUS_ERROR_HOME_BUSY))
+                        pam_syslog(handle, LOG_NOTICE, "Not deactivating home directory of %s, as it is still used.", username);
+                else
+                        return pam_syslog_pam_error(handle, LOG_ERR, PAM_SESSION_ERR,
+                                                    "Failed to release user home: %s", bus_error_message(&error, r));
+        }
+
+        return PAM_SUCCESS;
+}
+
+_public_ PAM_EXTERN int pam_sm_acct_mgmt(
+                pam_handle_t *handle,
+                int flags,
+                int argc,
+                const char **argv) {
+
+        _cleanup_(user_record_unrefp) UserRecord *ur = NULL;
+        bool debug = false, please_suspend = false;
+        usec_t t;
+        int r;
+
+        if (parse_env(handle, &please_suspend) < 0)
+                return PAM_AUTH_ERR;
+
+        if (parse_argv(handle,
+                       argc, argv,
+                       &please_suspend,
+                       &debug) < 0)
+                return PAM_AUTH_ERR;
+
+        if (debug)
+                pam_syslog(handle, LOG_DEBUG, "pam-systemd-homed account management");
+
+        r = acquire_home(handle, /* please_authenticate = */ false, please_suspend, debug);
+        if (r != PAM_SUCCESS)
+                return r;
+
+        r = acquire_user_record(handle, NULL, debug, &ur);
+        if (r != PAM_SUCCESS)
+                return r;
+
+        r = user_record_test_blocked(ur);
+        switch (r) {
+
+        case -ESTALE:
+                pam_syslog(handle, LOG_WARNING, "User record for '%s' is newer than current system time, assuming incorrect system clock, allowing access.", ur->user_name);
+                break;
+
+        case -ENOLCK:
+                (void) pam_prompt(handle, PAM_ERROR_MSG, NULL, "User record is blocked, prohibiting access.");
+                return PAM_ACCT_EXPIRED;
+
+        case -EL2HLT:
+                (void) pam_prompt(handle, PAM_ERROR_MSG, NULL, "User record is not valid yet, prohibiting access.");
+                return PAM_ACCT_EXPIRED;
+
+        case -EL3HLT:
+                (void) pam_prompt(handle, PAM_ERROR_MSG, NULL, "User record is not valid anymore, prohibiting access.");
+                return PAM_ACCT_EXPIRED;
+
+        default:
+                if (r < 0) {
+                        (void) pam_prompt(handle, PAM_ERROR_MSG, NULL, "User record not valid, prohibiting access.");
+                        return PAM_ACCT_EXPIRED;
+                }
+
+                break;
+        }
+
+        t = user_record_ratelimit_next_try(ur);
+        if (t != USEC_INFINITY) {
+                usec_t n = now(CLOCK_REALTIME);
+
+                if (t > n) {
+                        (void) pam_prompt(handle, PAM_ERROR_MSG, NULL, "Too many logins, try again in %s.",
+                                          FORMAT_TIMESPAN(t - n, USEC_PER_SEC));
+
+                        return PAM_MAXTRIES;
+                }
+        }
+
+        r = user_record_test_password_change_required(ur);
+        switch (r) {
+
+        case -EKEYREVOKED:
+                (void) pam_prompt(handle, PAM_ERROR_MSG, NULL, "Password change required.");
+                return PAM_NEW_AUTHTOK_REQD;
+
+        case -EOWNERDEAD:
+                (void) pam_prompt(handle, PAM_ERROR_MSG, NULL, "Password expired, change required.");
+                return PAM_NEW_AUTHTOK_REQD;
+
+        case -EKEYREJECTED:
+                /* Strictly speaking this is only about password expiration, and we might want to allow
+                 * authentication via PKCS#11 or so, but let's ignore this fine distinction for now. */
+                (void) pam_prompt(handle, PAM_ERROR_MSG, NULL, "Password is expired, but can't change, refusing login.");
+                return PAM_AUTHTOK_EXPIRED;
+
+        case -EKEYEXPIRED:
+                (void) pam_prompt(handle, PAM_ERROR_MSG, NULL, "Password will expire soon, please change.");
+                break;
+
+        case -ESTALE:
+                /* If the system clock is wrong, let's log but continue */
+                pam_syslog(handle, LOG_WARNING, "Couldn't check if password change is required, last change is in the future, system clock likely wrong.");
+                break;
+
+        case -EROFS:
+                /* All good, just means the password if we wanted to change we couldn't, but we don't need to */
+                break;
+
+        default:
+                if (r < 0) {
+                        (void) pam_prompt(handle, PAM_ERROR_MSG, NULL, "User record not valid, prohibiting access.");
+                        return PAM_AUTHTOK_EXPIRED;
+                }
+
+                break;
+        }
+
+        return PAM_SUCCESS;
+}
+
+_public_ PAM_EXTERN int pam_sm_chauthtok(
+                pam_handle_t *handle,
+                int flags,
+                int argc,
+                const char **argv) {
+
+        _cleanup_(user_record_unrefp) UserRecord *ur = NULL, *old_secret = NULL, *new_secret = NULL;
+        const char *old_password = NULL, *new_password = NULL;
+        _cleanup_(sd_bus_unrefp) sd_bus *bus = NULL;
+        unsigned n_attempts = 0;
+        bool debug = false;
+        int r;
+
+        if (parse_argv(handle,
+                       argc, argv,
+                       NULL,
+                       &debug) < 0)
+                return PAM_AUTH_ERR;
+
+        if (debug)
+                pam_syslog(handle, LOG_DEBUG, "pam-systemd-homed account management");
+
+        r = pam_acquire_bus_connection(handle, "pam-systemd-home", &bus);
+        if (r != PAM_SUCCESS)
+                return r;
+
+        r = acquire_user_record(handle, NULL, debug, &ur);
+        if (r != PAM_SUCCESS)
+                return r;
+
+        /* Start with cached credentials */
+        r = pam_get_item(handle, PAM_OLDAUTHTOK, (const void**) &old_password);
+        if (!IN_SET(r, PAM_BAD_ITEM, PAM_SUCCESS))
+                return pam_syslog_pam_error(handle, LOG_ERR, r, "Failed to get old password: @PAMERR@");
+
+        r = pam_get_item(handle, PAM_AUTHTOK, (const void**) &new_password);
+        if (!IN_SET(r, PAM_BAD_ITEM, PAM_SUCCESS))
+                return pam_syslog_pam_error(handle, LOG_ERR, r, "Failed to get cached password: @PAMERR@");
+
+        if (isempty(new_password)) {
+                /* No, it's not cached, then let's ask for the password and its verification, and cache
+                 * it. */
+
+                r = pam_get_authtok_noverify(handle, &new_password, "New password: ");
+                if (r != PAM_SUCCESS)
+                        return pam_syslog_pam_error(handle, LOG_ERR, r, "Failed to get new password: @PAMERR@");
+
+                if (isempty(new_password)) {
+                        if (debug)
+                                pam_syslog(handle, LOG_DEBUG, "Password request aborted.");
+                        return PAM_AUTHTOK_ERR;
+                }
+
+                r = pam_get_authtok_verify(handle, &new_password, "new password: "); /* Lower case, since PAM prefixes 'Repeat' */
+                if (r != PAM_SUCCESS)
+                        return pam_syslog_pam_error(handle, LOG_ERR, r, "Failed to get password again: @PAMERR@");
+
+                // FIXME: pam_pwquality will ask for the password a third time. It really shouldn't do
+                // that, and instead assume the password was already verified once when it is found to be
+                // cached already. needs to be fixed in pam_pwquality
+        }
+
+        /* Now everything is cached and checked, let's exit from the preliminary check */
+        if (FLAGS_SET(flags, PAM_PRELIM_CHECK))
+                return PAM_SUCCESS;
+
+        old_secret = user_record_new();
+        if (!old_secret)
+                return pam_log_oom(handle);
+
+        if (!isempty(old_password)) {
+                r = user_record_set_password(old_secret, STRV_MAKE(old_password), true);
+                if (r < 0)
+                        return pam_syslog_errno(handle, LOG_ERR, r, "Failed to store old password: %m");
+        }
+
+        new_secret = user_record_new();
+        if (!new_secret)
+                return pam_log_oom(handle);
+
+        r = user_record_set_password(new_secret, STRV_MAKE(new_password), true);
+        if (r < 0)
+                return pam_syslog_errno(handle, LOG_ERR, r, "Failed to store new password: %m");
+
+        for (;;) {
+                _cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
+                _cleanup_(sd_bus_message_unrefp) sd_bus_message *m = NULL;
+
+                r = bus_message_new_method_call(bus, &m, bus_home_mgr, "ChangePasswordHome");
+                if (r < 0)
+                        return pam_bus_log_create_error(handle, r);
+
+                r = sd_bus_message_append(m, "s", ur->user_name);
+                if (r < 0)
+                        return pam_bus_log_create_error(handle, r);
+
+                r = bus_message_append_secret(m, new_secret);
+                if (r < 0)
+                        return pam_bus_log_create_error(handle, r);
+
+                r = bus_message_append_secret(m, old_secret);
+                if (r < 0)
+                        return pam_bus_log_create_error(handle, r);
+
+                r = sd_bus_call(bus, m, HOME_SLOW_BUS_CALL_TIMEOUT_USEC, &error, NULL);
+                if (r < 0) {
+                        r = handle_generic_user_record_error(handle, ur->user_name, old_secret, r, &error, debug);
+                        if (r == PAM_CONV_ERR)
+                                return pam_syslog_pam_error(handle, LOG_ERR, r,
+                                                            "Failed to prompt for password/prompt.");
+                        if (r != PAM_SUCCESS)
+                                return r;
+                } else
+                        return pam_syslog_pam_error(handle, LOG_NOTICE, PAM_SUCCESS,
+                                                    "Successfully changed password for user %s.", ur->user_name);
+
+                if (++n_attempts >= 5)
+                        break;
+
+                /* Try again */
+        };
+
+        return pam_syslog_pam_error(handle, LOG_NOTICE, PAM_MAXTRIES,
+                                    "Failed to change password for user %s: @PAMERR@", ur->user_name);
+}