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pam-systemd: talk to logind via varlink

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This makes sure we now use Varlink per default as transport for
allocating sessions.

This reduces the time it takes to do one run0 cycle by roughly ~10% on my
completely synthetic test setup (assuming the target user's service
manager is already started)

The D-Bus codepaths are kept in place for two reasons:
* To make upgrades easy
* If the user actually sets resource properties on the PAM session we
  fall back to the D-Bus codepaths, as we currently have no way to
  encode the scope properties in JSON, this is only supported for D-Bus
  serialization.

The latter should be revisited once it is possible to allocate a scope
unit from PID1 via varlink.
This commit is contained in:
Lennart Poettering 2024-11-18 11:25:20 +01:00
parent f23262b53f
commit 5f5bd3941c
1 changed files with 230 additions and 81 deletions
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311
src/login/pam_systemd.c
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@ -18,6 +18,9 @@
#include <sys/types.h>
#include <unistd.h>
#include "sd-bus.h"
#include "sd-varlink.h"
#include "alloc-util.h"
#include "audit-util.h"
#include "bus-common-errors.h"
@ -35,6 +38,7 @@
#include "format-util.h"
#include "fs-util.h"
#include "hostname-util.h"
#include "json-util.h"
#include "locale-util.h"
#include "login-util.h"
#include "macro.h"
@ -1022,6 +1026,16 @@ static void session_context_mangle(
c->remote = !isempty(c->remote_host) && !is_localhost(c->remote_host);
}
static bool can_use_varlink(const SessionContext *c) {
/* Since PID 1 currently doesn't do Varlink right now, we cannot directly set properties for the
* scope, for now. */
return !c->memory_max &&
!c->runtime_max_sec &&
!c->tasks_max &&
!c->cpu_weight &&
!c->io_weight;
}
static int register_session(
pam_handle_t *handle,
SessionContext *c,
@ -1029,13 +1043,6 @@ static int register_session(
bool debug,
char **ret_seat) {
/* Let's release the D-Bus connection once this function exits, 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. */
_cleanup_(pam_bus_data_disconnectp) PamBusData *d = NULL;
_cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
_cleanup_(sd_bus_message_unrefp) sd_bus_message *m = NULL, *reply = NULL;
_cleanup_(sd_bus_flush_close_unrefp) sd_bus *bus = NULL;
int r;
assert(handle);
@ -1044,13 +1051,10 @@ static int register_session(
assert(ret_seat);
/* Make most of this a NOP on non-logind systems */
if (!logind_running())
goto skip;
/* Talk to logind over the message bus */
r = pam_acquire_bus_connection(handle, "pam-systemd", debug, &bus, &d);
if (r != PAM_SUCCESS)
return r;
if (!logind_running()) {
*ret_seat = NULL;
return PAM_SUCCESS;
}
pam_debug_syslog(handle, debug,
"Asking logind to create session: "
@ -1065,68 +1069,187 @@ static int register_session(
"memory_max=%s tasks_max=%s cpu_weight=%s io_weight=%s runtime_max_sec=%s",
strna(c->memory_max), strna(c->tasks_max), strna(c->cpu_weight), strna(c->io_weight), strna(c->runtime_max_sec));
r = create_session_message(
bus,
handle,
ur,
c,
/* avoid_pidfd = */ false,
&m);
if (r < 0)
return pam_bus_log_create_error(handle, r);
_cleanup_(sd_bus_message_unrefp) sd_bus_message *reply = NULL; /* the following variables point into this message, hence pin it for longer */
_cleanup_(sd_varlink_unrefp) sd_varlink *vl = NULL; /* similar */
const char *id = NULL, *object_path = NULL, *runtime_path = NULL, *real_seat = NULL;
int session_fd = -EBADF, existing = false;
uint32_t original_uid = UID_INVALID, real_vtnr = 0;
r = sd_bus_call(bus, m, LOGIN_SLOW_BUS_CALL_TIMEOUT_USEC, &error, &reply);
if (r < 0 && sd_bus_error_has_name(&error, SD_BUS_ERROR_UNKNOWN_METHOD)) {
sd_bus_error_free(&error);
pam_debug_syslog(handle, debug,
"CreateSessionWithPIDFD() API is not available, retrying with CreateSession().");
bool done = false;
if (can_use_varlink(c)) {
m = sd_bus_message_unref(m);
r = create_session_message(bus,
handle,
ur,
c,
/* avoid_pidfd = */ true,
&m);
r = sd_varlink_connect_address(&vl, "/run/systemd/io.systemd.Login");
if (r < 0)
log_debug_errno(r, "Failed to connect to logind via Varlink, falling back to D-Bus: %m");
else {
r = sd_varlink_set_allow_fd_passing_input(vl, true);
if (r < 0)
return pam_syslog_errno(handle, LOG_ERR, r, "Failed to enable input fd passing on Varlink socket: %m");
r = sd_varlink_set_allow_fd_passing_output(vl, true);
if (r < 0)
return pam_syslog_errno(handle, LOG_ERR, r, "Failed to enable output fd passing on Varlink socket: %m");
r = sd_varlink_set_relative_timeout(vl, LOGIN_SLOW_BUS_CALL_TIMEOUT_USEC);
if (r < 0)
return pam_syslog_errno(handle, LOG_ERR, r, "Failed to set relative timeout on Varlink socket: %m");
_cleanup_(pidref_done) PidRef pidref = PIDREF_NULL;
r = pidref_set_self(&pidref);
if (r < 0)
return pam_syslog_errno(handle, LOG_ERR, r, "Failed to acquire PID reference on ourselves: %m");
sd_json_variant *vreply = NULL;
const char *error_id = NULL;
r = sd_varlink_callbo(
vl,
"io.systemd.Login.CreateSession",
&vreply,
&error_id,
SD_JSON_BUILD_PAIR_UNSIGNED("UID", ur->uid),
JSON_BUILD_PAIR_PIDREF("PID", &pidref),
JSON_BUILD_PAIR_STRING_NON_EMPTY("Service", c->service),
SD_JSON_BUILD_PAIR("Type", JSON_BUILD_STRING_UNDERSCORIFY(c->type)),
SD_JSON_BUILD_PAIR("Class", JSON_BUILD_STRING_UNDERSCORIFY(c->class)),
JSON_BUILD_PAIR_STRING_NON_EMPTY("Desktop", c->desktop),
JSON_BUILD_PAIR_STRING_NON_EMPTY("Seat", c->seat),
SD_JSON_BUILD_PAIR_CONDITION(c->vtnr > 0, "VTNr", SD_JSON_BUILD_UNSIGNED(c->vtnr)),
JSON_BUILD_PAIR_STRING_NON_EMPTY("TTY", c->tty),
JSON_BUILD_PAIR_STRING_NON_EMPTY("Display", c->display),
SD_JSON_BUILD_PAIR_BOOLEAN("Remote", c->remote),
JSON_BUILD_PAIR_STRING_NON_EMPTY("RemoteUser", c->remote_user),
JSON_BUILD_PAIR_STRING_NON_EMPTY("RemoteHost", c->remote_host));
if (r < 0)
return pam_syslog_errno(handle, LOG_ERR, r,
"Failed to register session: %s", error_id);
if (streq_ptr(error_id, "io.systemd.Login.AlreadySessionMember")) {
/* We are already in a session, don't do anything */
pam_debug_syslog(handle, debug, "Not creating session: %s", error_id);
*ret_seat = NULL;
return PAM_SUCCESS;
}
if (error_id)
return pam_syslog_errno(handle, LOG_ERR, sd_varlink_error_to_errno(error_id, vreply),
"Failed to issue CreateSession() varlink call: %s", error_id);
struct {
const char *id;
const char *runtime_path;
unsigned session_fd_idx;
uid_t uid;
const char *seat;
unsigned vtnr;
bool existing;
} p = {
.session_fd_idx = UINT_MAX,
.uid = UID_INVALID,
};
static const sd_json_dispatch_field dispatch_table[] = {
{ "Id", SD_JSON_VARIANT_STRING, sd_json_dispatch_const_string, voffsetof(p, id), SD_JSON_MANDATORY },
{ "RuntimePath", SD_JSON_VARIANT_STRING, json_dispatch_const_path, voffsetof(p, runtime_path), SD_JSON_MANDATORY },
{ "SessionFileDescriptor", _SD_JSON_VARIANT_TYPE_INVALID, sd_json_dispatch_uint64, voffsetof(p, session_fd_idx), SD_JSON_MANDATORY },
{ "UID", _SD_JSON_VARIANT_TYPE_INVALID, sd_json_dispatch_uid_gid, voffsetof(p, uid), SD_JSON_MANDATORY },
{ "Seat", SD_JSON_VARIANT_STRING, sd_json_dispatch_const_string, voffsetof(p, seat), 0 },
{ "VTNr", _SD_JSON_VARIANT_TYPE_INVALID, sd_json_dispatch_uint, voffsetof(p, vtnr), 0 },
{}
};
r = sd_json_dispatch(vreply, dispatch_table, SD_JSON_ALLOW_EXTENSIONS, &p);
if (r < 0)
return pam_syslog_errno(handle, LOG_ERR, r, "Failed to parse CreateSession() reply: %m");
session_fd = sd_varlink_peek_fd(vl, p.session_fd_idx);
if (session_fd < 0)
return pam_syslog_errno(handle, LOG_ERR, session_fd, "Failed to extract session fd from CreateSession() reply: %m");
id = p.id;
runtime_path = p.runtime_path;
original_uid = p.uid;
real_seat = p.seat;
real_vtnr = p.vtnr;
existing = false; /* Even on D-Bus logind only returns false these days */
done = true;
}
}
if (!done) {
/* Let's release the D-Bus connection once we are done here, 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. */
_cleanup_(pam_bus_data_disconnectp) PamBusData *d = NULL;
_cleanup_(sd_bus_flush_close_unrefp) sd_bus *bus = NULL;
/* Talk to logind over the message bus */
r = pam_acquire_bus_connection(handle, "pam-systemd", debug, &bus, &d);
if (r != PAM_SUCCESS)
return r;
_cleanup_(sd_bus_message_unrefp) sd_bus_message *m = NULL;
r = create_session_message(
bus,
handle,
ur,
c,
/* avoid_pidfd = */ false,
&m);
if (r < 0)
return pam_bus_log_create_error(handle, r);
_cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
r = sd_bus_call(bus, m, LOGIN_SLOW_BUS_CALL_TIMEOUT_USEC, &error, &reply);
}
if (r < 0) {
if (sd_bus_error_has_name(&error, BUS_ERROR_SESSION_BUSY)) {
/* We are already in a session, don't do anything */
if (r < 0 && sd_bus_error_has_name(&error, SD_BUS_ERROR_UNKNOWN_METHOD)) {
sd_bus_error_free(&error);
pam_debug_syslog(handle, debug,
"Not creating session: %s", bus_error_message(&error, r));
goto skip;
"CreateSessionWithPIDFD() API is not available, retrying with CreateSession().");
m = sd_bus_message_unref(m);
r = create_session_message(bus,
handle,
ur,
c,
/* avoid_pidfd = */ true,
&m);
if (r < 0)
return pam_bus_log_create_error(handle, r);
r = sd_bus_call(bus, m, LOGIN_SLOW_BUS_CALL_TIMEOUT_USEC, &error, &reply);
}
if (r < 0) {
if (sd_bus_error_has_name(&error, BUS_ERROR_SESSION_BUSY)) {
/* We are already in a session, don't do anything */
pam_debug_syslog(handle, debug,
"Not creating session: %s", bus_error_message(&error, r));
*ret_seat = NULL;
return PAM_SUCCESS;
}
pam_syslog(handle, LOG_ERR,
"Failed to create session: %s", bus_error_message(&error, r));
return PAM_SESSION_ERR;
}
pam_syslog(handle, LOG_ERR,
"Failed to create session: %s", bus_error_message(&error, r));
return PAM_SESSION_ERR;
r = sd_bus_message_read(
reply,
"soshusub",
&id,
&object_path,
&runtime_path,
&session_fd,
&original_uid,
&real_seat,
&real_vtnr,
&existing);
if (r < 0)
return pam_bus_log_parse_error(handle, r);
}
const char *id, *object_path, *runtime_path, *real_seat;
int session_fd = -EBADF, existing;
uint32_t original_uid, real_vtnr;
r = sd_bus_message_read(
reply,
"soshusub",
&id,
&object_path,
&runtime_path,
&session_fd,
&original_uid,
&real_seat,
&real_vtnr,
&existing);
if (r < 0)
return pam_bus_log_parse_error(handle, r);
pam_debug_syslog(handle, debug,
"Reply from logind: "
"id=%s object_path=%s runtime_path=%s session_fd=%d seat=%s vtnr=%u original_uid=%u",
id, object_path, runtime_path, session_fd, real_seat, real_vtnr, original_uid);
id, strna(object_path), runtime_path, session_fd, real_seat, real_vtnr, original_uid);
/* Please update manager_default_environment() in core/manager.c accordingly if more session envvars
* shall be added. */
@ -1191,18 +1314,17 @@ static int register_session(
/* Everything worked, hence let's patch in the data we learned. Since 'real_set' points into the
* D-Bus message, let's copy it and return it as a buffer */
char *rs = strdup(real_seat);
if (!rs)
return pam_log_oom(handle);
char *rs = NULL;
if (real_seat) {
rs = strdup(real_seat);
if (!rs)
return pam_log_oom(handle);
}
c->seat = *ret_seat = rs;
c->vtnr = real_vtnr;
return PAM_SUCCESS;
skip:
*ret_seat = NULL;
return PAM_SUCCESS;
}
static int import_shell_credentials(pam_handle_t *handle) {
@ -1337,20 +1459,47 @@ _public_ PAM_EXTERN int pam_sm_close_session(
id = pam_getenv(handle, "XDG_SESSION_ID");
if (id && !existing) {
_cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
_cleanup_(sd_bus_flush_close_unrefp) sd_bus *bus = NULL;
_cleanup_(sd_varlink_unrefp) sd_varlink *vl = NULL;
bool done = false;
/* Before we go and close the FIFO we need to tell logind that this is a clean session
* shutdown, so that it doesn't just go and slaughter us immediately after closing the fd */
r = pam_acquire_bus_connection(handle, "pam-systemd", debug, &bus, NULL);
if (r != PAM_SUCCESS)
return r;
r = bus_call_method(bus, bus_login_mgr, "ReleaseSession", &error, NULL, "s", id);
r = sd_varlink_connect_address(&vl, "/run/systemd/io.systemd.Login");
if (r < 0)
return pam_syslog_pam_error(handle, LOG_ERR, PAM_SESSION_ERR,
"Failed to release session: %s", bus_error_message(&error, r));
log_debug_errno(r, "Failed to connect to logind via Varlink, falling back to D-Bus: %m");
else {
_cleanup_(sd_json_variant_unrefp) sd_json_variant *vreply = NULL;
const char *error_id = NULL;
r = sd_varlink_callbo(
vl,
"io.systemd.Login.ReleaseSession",
/* ret_reply= */ NULL,
&error_id,
SD_JSON_BUILD_PAIR_STRING("Id", id));
if (r < 0)
return pam_syslog_errno(handle, LOG_ERR, r, "Failed to register session: %s", error_id);
if (error_id)
return pam_syslog_errno(handle, LOG_ERR, sd_varlink_error_to_errno(error_id, vreply),
"Failed to issue ReleaseSession() varlink call: %s", error_id);
done = true;
}
if (!done) {
_cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
_cleanup_(pam_bus_data_disconnectp) PamBusData *d = NULL;
_cleanup_(sd_bus_flush_close_unrefp) sd_bus *bus = NULL;
/* Before we go and close the FIFO we need to tell logind that this is a clean session
* shutdown, so that it doesn't just go and slaughter us immediately after closing the fd */
r = pam_acquire_bus_connection(handle, "pam-systemd", debug, &bus, &d);
if (r != PAM_SUCCESS)
return r;
r = bus_call_method(bus, bus_login_mgr, "ReleaseSession", &error, NULL, "s", id);
if (r < 0)
return pam_syslog_pam_error(handle, LOG_ERR, PAM_SESSION_ERR,
"Failed to release session: %s", bus_error_message(&error, r));
}
}
/* Note that we are knowingly leaking the FIFO fd here. This way, logind can watch us die. If we