Commit d5280a38 authored by Ray Strode's avatar Ray Strode

daemon: introduce pam extension mechanism

This abuses PAM_BINARY_PROMPT for our own nefarious purposes.
The way it works is GDM advertises what "extensions" it supports
with the environment variable, GDM_SUPPORTED_PAM_EXTENSIONS (a space
separated list of reverse dns notation names). PAM services that
support this protocol, will read the environment variable, and
check for extension strings they support. They then know that sending
PAM_BINARY_PROMPT won't blow up, and know what format to use for the
binary data.  The type field of the structure is the index of the
string from the environment variable.

This commit is just foundation work. It doesn't actually add any
extensions.

https://bugzilla.gnome.org/show_bug.cgi?id=788851
parent 5683e5d5
......@@ -3,6 +3,7 @@ NULL =
SUBDIRS = \
data \
common \
pam-extensions \
daemon \
libgdm \
utils \
......
......@@ -539,6 +539,15 @@ if test "x$have_pam" = "xyes"; then
)],
[AC_MSG_RESULT(["not found - assume const, Linux-type PAM"])]
)
AC_CHECK_DECL(PAM_BINARY_PROMPT,
[supports_pam_extensions=yes],
[supports_pam_extensions=no],
#include <security/pam_appl.h>
)
fi
if test "x$supports_pam_extensions" = "xyes" ; then
AM_CONDITIONAL(SUPPORTS_PAM_EXTENSIONS, true)
AC_DEFINE(SUPPORTS_PAM_EXTENSIONS, 1, [Define if PAM supports GDMs custom extensions])
fi
AC_CHECK_LIB(keyutils, keyctl_read, [
......@@ -1548,6 +1557,8 @@ AC_DEFINE_UNQUOTED(X_XNEST_UNSCALED_FONTPATH,"$X_XNEST_UNSCALED_FONTPATH",[])
AC_CONFIG_FILES([
Makefile
pam-extensions/Makefile
pam-extensions/gdm-pam-extensions.pc
daemon/Makefile
docs/Makefile
chooser/Makefile
......
......@@ -4,6 +4,7 @@ AM_CPPFLAGS = \
-I. \
-I.. \
-I$(top_srcdir)/common \
-I$(top_srcdir)/pam-extensions \
-I$(top_builddir)/common \
-DBINDIR=\"$(bindir)\" \
-DDATADIR=\"$(datadir)\" \
......@@ -133,6 +134,10 @@ gdm_session_worker_SOURCES = \
gdm-dbus-util.h \
$(NULL)
if SUPPORTS_PAM_EXTENSIONS
gdm_session_worker_SOURCES += $(top_srcdir)/pam-extensions/gdm-pam-extensions.h
endif
nodist_gdm_session_worker_SOURCES = \
gdm-session-glue.h \
gdm-session-glue.c \
......
......@@ -61,6 +61,11 @@
#include "gdm-common.h"
#include "gdm-log.h"
#ifdef SUPPORTS_PAM_EXTENSIONS
#include "gdm-pam-extensions.h"
#endif
#include "gdm-session-worker.h"
#include "gdm-session-glue.h"
#include "gdm-session.h"
......@@ -149,6 +154,7 @@ struct GdmSessionWorkerPrivate
uid_t uid;
gid_t gid;
gboolean password_is_required;
char **extensions;
int cred_flags;
int login_vt;
......@@ -177,6 +183,15 @@ struct GdmSessionWorkerPrivate
GDBusMethodInvocation *pending_invocation;
};
#ifdef SUPPORTS_PAM_EXTENSIONS
static char gdm_pam_extension_environment_block[_POSIX_ARG_MAX];
static const char * const
gdm_supported_pam_extensions[] = {
NULL
};
#endif
enum {
PROP_0,
PROP_SERVER_ADDRESS,
......@@ -519,6 +534,32 @@ gdm_session_worker_report_problem (GdmSessionWorker *worker,
NULL);
}
#ifdef SUPPORTS_PAM_EXTENSIONS
static gboolean
gdm_session_worker_process_extended_pam_message (GdmSessionWorker *worker,
const struct pam_message *query,
char **response)
{
GdmPamExtensionMessage *extended_message;
gboolean res;
extended_message = GDM_PAM_EXTENSION_MESSAGE_FROM_PAM_MESSAGE (query);
if (GDM_PAM_EXTENSION_MESSAGE_TRUNCATED (extended_message)) {
g_warning ("PAM service requested binary response for truncated query");
return FALSE;
}
if (GDM_PAM_EXTENSION_MESSAGE_INVALID_TYPE (extended_message)) {
g_warning ("PAM service requested binary response for unadvertised query type");
return FALSE;
}
g_debug ("GdmSessionWorker: received extended pam message of unknown type %u", (unsigned int) extended_message->type);
return FALSE;
}
#endif
static char *
convert_to_utf8 (const char *str)
{
......@@ -563,6 +604,11 @@ gdm_session_worker_process_pam_message (GdmSessionWorker *worker,
gdm_session_worker_update_username (worker);
#ifdef SUPPORTS_PAM_EXTENSIONS
if (query->msg_style == PAM_BINARY_PROMPT)
return gdm_session_worker_process_extended_pam_message (worker, query, response);
#endif
g_debug ("GdmSessionWorker: received pam message of type %u with payload '%s'",
query->msg_style, query->msg);
......@@ -991,16 +1037,17 @@ out:
}
static gboolean
gdm_session_worker_initialize_pam (GdmSessionWorker *worker,
const char *service,
const char *username,
const char *hostname,
gboolean display_is_local,
const char *x11_display_name,
const char *x11_authority_file,
const char *display_device,
const char *seat_id,
GError **error)
gdm_session_worker_initialize_pam (GdmSessionWorker *worker,
const char *service,
const char * const *extensions,
const char *username,
const char *hostname,
gboolean display_is_local,
const char *x11_display_name,
const char *x11_authority_file,
const char *display_device,
const char *seat_id,
GError **error)
{
struct pam_conv pam_conversation;
int error_code;
......@@ -1013,6 +1060,12 @@ gdm_session_worker_initialize_pam (GdmSessionWorker *worker,
username ? username : "(null)",
seat_id ? seat_id : "(null)");
#ifdef SUPPORTS_PAM_EXTENSIONS
if (extensions != NULL) {
GDM_PAM_EXTENSION_ADVERTISE_SUPPORTED_EXTENSIONS (gdm_pam_extension_environment_block, extensions);
}
#endif
pam_conversation.conv = (GdmSessionWorkerPamNewMessagesFunc) gdm_session_worker_pam_new_messages_handler;
pam_conversation.appdata_ptr = worker;
......@@ -2451,6 +2504,7 @@ do_setup (GdmSessionWorker *worker)
error = NULL;
res = gdm_session_worker_initialize_pam (worker,
worker->priv->service,
(const char **) worker->priv->extensions,
worker->priv->username,
worker->priv->hostname,
worker->priv->display_is_local,
......@@ -2817,6 +2871,32 @@ gdm_session_worker_handle_open (GdmDBusWorker *object,
return TRUE;
}
static char **
filter_extensions (const char * const *extensions)
{
size_t i, j;
GPtrArray *array = NULL;
char **filtered_extensions = NULL;
array = g_ptr_array_new ();
for (i = 0; extensions[i] != NULL; i++) {
for (j = 0; gdm_supported_pam_extensions[j] != NULL; j++) {
if (g_strcmp0 (extensions[i], gdm_supported_pam_extensions[j]) == 0) {
g_ptr_array_add (array, g_strdup (gdm_supported_pam_extensions[j]));
break;
}
}
}
g_ptr_array_add (array, NULL);
filtered_extensions = g_strdupv ((char **) array->pdata);
g_ptr_array_free (array, TRUE);
return filtered_extensions;
}
static gboolean
gdm_session_worker_handle_initialize (GdmDBusWorker *object,
GDBusMethodInvocation *invocation,
......@@ -2833,6 +2913,8 @@ gdm_session_worker_handle_initialize (GdmDBusWorker *object,
while (g_variant_iter_loop (&iter, "{sv}", &key, &value)) {
if (g_strcmp0 (key, "service") == 0) {
worker->priv->service = g_strdup (g_variant_get_string (value, NULL));
} else if (g_strcmp0 (key, "extensions") == 0) {
worker->priv->extensions = filter_extensions (g_variant_get_strv (value, NULL));
} else if (g_strcmp0 (key, "username") == 0) {
worker->priv->username = g_strdup (g_variant_get_string (value, NULL));
} else if (g_strcmp0 (key, "is-program-session") == 0) {
......@@ -3365,6 +3447,7 @@ gdm_session_worker_finalize (GObject *object)
g_free (worker->priv->username);
g_free (worker->priv->server_address);
g_strfreev (worker->priv->arguments);
g_strfreev (worker->priv->extensions);
g_hash_table_unref (worker->priv->reauthentication_requests);
......
......@@ -52,7 +52,5 @@ GType gdm_session_worker_get_type (void);
GdmSessionWorker * gdm_session_worker_new (const char *server_address,
gboolean is_for_reauth) G_GNUC_MALLOC;
G_END_DECLS
#endif /* GDM_SESSION_WORKER_H */
......@@ -101,6 +101,7 @@ struct _GdmSessionPrivate
char **conversation_environment;
GdmDBusUserVerifier *user_verifier_interface;
GHashTable *user_verifier_extensions;
GdmDBusGreeter *greeter_interface;
GdmDBusRemoteGreeter *remote_greeter_interface;
GdmDBusChooser *chooser_interface;
......@@ -1218,6 +1219,20 @@ begin_verification_conversation (GdmSession *self,
return conversation;
}
static gboolean
gdm_session_handle_client_enable_extensions (GdmDBusUserVerifier *user_verifier_interface,
GDBusMethodInvocation *invocation,
const char * const * extensions,
GDBusConnection *connection)
{
GdmSession *self = g_object_get_data (G_OBJECT (connection), "gdm-session");
g_hash_table_remove_all (self->priv->user_verifier_extensions);
gdm_dbus_user_verifier_complete_enable_extensions (user_verifier_interface, invocation);
return TRUE;
}
static gboolean
gdm_session_handle_client_begin_verification (GdmDBusUserVerifier *user_verifier_interface,
GDBusMethodInvocation *invocation,
......@@ -1372,6 +1387,13 @@ export_user_verifier_interface (GdmSession *self,
{
GdmDBusUserVerifier *user_verifier_interface;
user_verifier_interface = GDM_DBUS_USER_VERIFIER (gdm_dbus_user_verifier_skeleton_new ());
g_object_set_data (G_OBJECT (connection), "gdm-session", self);
g_signal_connect (user_verifier_interface,
"handle-enable-extensions",
G_CALLBACK (gdm_session_handle_client_enable_extensions),
connection);
g_signal_connect (user_verifier_interface,
"handle-begin-verification",
G_CALLBACK (gdm_session_handle_client_begin_verification),
......@@ -1810,6 +1832,15 @@ next_line:
g_free (contents);
}
static void
unexport_and_free_user_verifier_extension (GDBusInterfaceSkeleton *interface)
{
g_dbus_interface_skeleton_unexport (interface);
g_object_run_dispose (G_OBJECT (interface));
g_object_unref (interface);
}
static void
gdm_session_init (GdmSession *self)
{
......@@ -1826,6 +1857,11 @@ gdm_session_init (GdmSession *self)
g_str_equal,
(GDestroyNotify) g_free,
(GDestroyNotify) g_free);
self->priv->user_verifier_extensions = g_hash_table_new_full (g_str_hash,
g_str_equal,
NULL,
(GDestroyNotify)
unexport_and_free_user_verifier_extension);
load_lang_config_file (self);
setup_worker_server (self);
......@@ -2099,14 +2135,19 @@ initialize (GdmSession *self,
const char *username,
const char *log_file)
{
GVariantBuilder details;
GdmSessionConversation *conversation;
GVariantBuilder details;
const char **extensions;
GdmSessionConversation *conversation;
g_assert (service_name != NULL);
g_variant_builder_init (&details, G_VARIANT_TYPE ("a{sv}"));
g_variant_builder_add_parsed (&details, "{'service', <%s>}", service_name);
extensions = (const char **) g_hash_table_get_keys_as_array (self->priv->user_verifier_extensions, NULL);
g_variant_builder_add_parsed (&details, "{'extensions', <%^as>}", extensions);
if (username != NULL)
g_variant_builder_add_parsed (&details, "{'username', <%s>}", username);
......@@ -2148,6 +2189,8 @@ initialize (GdmSession *self,
(GAsyncReadyCallback) on_initialization_complete_cb,
conversation);
}
g_free (extensions);
}
void
......@@ -3294,6 +3337,8 @@ gdm_session_dispose (GObject *object)
g_hash_table_unref);
g_clear_object (&self->priv->user_verifier_interface);
g_clear_pointer (&self->priv->user_verifier_extensions,
g_hash_table_unref);
g_clear_object (&self->priv->greeter_interface);
g_clear_object (&self->priv->chooser_interface);
......
......@@ -24,6 +24,9 @@
</method>
</interface>
<interface name="org.gnome.DisplayManager.UserVerifier">
<method name="EnableExtensions">
<arg name="extensions" direction="in" type="as"/>
</method>
<method name="BeginVerification">
<arg name="service_name" direction="in" type="s"/>
</method>
......
NULL =
AM_CPPFLAGS = \
-I$(srcdir) \
-I$(builddir) \
-I$(top_srcdir) \
-I$(top_builddir) \
-DG_LOG_DOMAIN=\"Gdm\" \
-DDMCONFDIR=\""$(dmconfdir)"\" \
-DDATADIR=\""$(datadir)"\" \
$(NULL)
if SUPPORTS_PAM_EXTENSIONS
pkgconfigdir = $(libdir)/pkgconfig
pkgconfig_DATA = gdm-pam-extensions.pc
pam_extensions_includedir = $(includedir)/gdm
pam_extensions_include_HEADERS = gdm-pam-extensions.h
endif
EXTRA_DIST = \
gdm-pam-extensions.pc \
$(NULL)
/* -*- Mode: C; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 8 -*-
*
* Copyright (C) 2017 Red Hat, Inc.
*
* This program 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.
*
* This program 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 this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*
*/
#ifndef GDM_PAM_EXTENSIONS_H
#define GDM_PAM_EXTENSIONS_H
#include <alloca.h>
#include <endian.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
#include <limits.h>
#include <security/pam_appl.h>
typedef struct {
uint32_t length;
unsigned char type;
unsigned char data[];
} GdmPamExtensionMessage;
#define GDM_PAM_EXTENSION_MESSAGE_FROM_PAM_MESSAGE(query) (GdmPamExtensionMessage *) (void *) query->msg
#define GDM_PAM_EXTENSION_MESSAGE_TO_PAM_REPLY(msg) (char *) (void *) msg
#define GDM_PAM_EXTENSION_MESSAGE_TO_BINARY_PROMPT_MESSAGE(extended_message, binary_message) \
{ \
(binary_message)->msg_style = PAM_BINARY_PROMPT; \
(binary_message)->msg = (void *) extended_message; \
}
#define GDM_PAM_EXTENSION_MESSAGE_TRUNCATED(msg) be32toh(msg->length) < sizeof (GdmPamExtensionMessage)
#define GDM_PAM_EXTENSION_MESSAGE_INVALID_TYPE(msg) \
({ \
bool _invalid = true; \
int _n = -1; \
const char *_supported_extensions; \
_supported_extensions = getenv ("GDM_SUPPORTED_PAM_EXTENSIONS"); \
if (_supported_extensions != NULL) { \
const char *_p = _supported_extensions; \
while (*_p != '\0' && _n < UCHAR_MAX) { \
size_t _length; \
_length = strcspn (_p, " "); \
if (_length > 0) \
_n++; \
_p += _length; \
_length = strspn (_p, " "); \
_p += _length; \
} \
if (_n >= msg->type) \
_invalid = false; \
} \
_invalid; \
})
#define GDM_PAM_EXTENSION_MESSAGE_MATCH(msg, supported_extensions, name) (strcmp (supported_extensions[msg->type], name) == 0)
/* environment block should be a statically allocated chunk of memory. This is important because
* putenv() will leak otherwise (and setenv isn't thread safe)
*/
#define GDM_PAM_EXTENSION_ADVERTISE_SUPPORTED_EXTENSIONS(environment_block, supported_extensions) \
{ \
size_t _size = 0; \
unsigned char _t, _num_chunks; \
char *_p; \
_p = environment_block; \
_p = stpncpy (_p, "GDM_SUPPORTED_PAM_EXTENSIONS", sizeof(environment_block)); \
*_p = '\0'; \
_size += strlen (_p); \
for (_t = 0; supported_extensions[_t] != NULL && _t < UCHAR_MAX; _t++) {\
size_t _next_chunk = strlen (supported_extensions[_t]) + strlen (" "); \
if (_size + _next_chunk >= sizeof (environment_block)) \
break; \
_size += _next_chunk; \
}\
_num_chunks = _t; \
if (_t != 0) { \
_p = stpcpy (_p, "="); \
for (_t = 0; _t < _num_chunks; _t++) { \
if (_t != 0) \
_p = stpcpy (_p, " "); \
_p = stpcpy (_p, supported_extensions[_t]); \
} \
*_p = '\0'; \
putenv (environment_block); \
} \
}
#define GDM_PAM_EXTENSION_LOOK_UP_TYPE(name, extension_type) \
({ \
bool _supported = false; \
unsigned char _t = 0; \
const char *_supported_extensions; \
_supported_extensions = getenv ("GDM_SUPPORTED_PAM_EXTENSIONS"); \
if (_supported_extensions != NULL) { \
const char *_p = _supported_extensions; \
while (*_p != '\0') { \
size_t _length; \
_length = strcspn (_p, " "); \
if (strncmp (_p, name, _length) == 0) { \
_supported = true; \
break; \
} \
_p += _length; \
_length = strspn (_p, " "); \
_p += _length; \
if (_t >= UCHAR_MAX) { \
break; \
} \
_t++; \
} \
if (_supported && extension_type != NULL) \
*extension_type = _t; \
} \
_supported; \
})
#define GDM_PAM_EXTENSION_SUPPORTED(name) GDM_PAM_EXTENSION_LOOK_UP_TYPE(name, (unsigned char *) NULL)
#endif
prefix=@prefix@
exec_prefix=@exec_prefix@
libdir=@libdir@
includedir=@includedir@
Name: GDM PAM Extensions
Description: Macros for custom protocols over PAM
Version: @VERSION@
Cflags: -I${includedir}/gdm
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