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glib/gio/gdbusauthmechanismexternal.c
Giuseppe Scrivano b51e3ab09e GDBusServer: Accept empty authorization identity for EXTERNAL mechanism 
RFC 4422 appendix A defines the empty authorization identity to mean
the identity that the server associated with its authentication
credentials. In this case, this means whatever uid is in the
GCredentials object.

In particular, this means that clients in a different Linux user
namespace can authenticate against our server and will be authorized
as the version of their uid that is visible in the server's namespace,
even if the corresponding numeric uid returned by geteuid() in the
client's namespace was different. systemd's sd-bus has relied on this
since commit
1ed4723d38.

[Originally part of a larger commit; commit message added by smcv]

Signed-off-by: Simon McVittie <smcv@collabora.com>
2022-07-18 17:53:32 +01:00

446 lines
16 KiB
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/* GDBus - GLib D-Bus Library
*
* Copyright (C) 2008-2010 Red Hat, Inc.
*
* SPDX-License-Identifier: LGPL-2.1-or-later
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General
* Public License along with this library; if not, see <http://www.gnu.org/licenses/>.
*
* Author: David Zeuthen <davidz@redhat.com>
*/
#include "config.h"
#include <string.h>
#include "gdbusauthmechanismexternal.h"
#include "gcredentials.h"
#include "gdbuserror.h"
#include "gioenumtypes.h"
#include "glibintl.h"
#ifdef G_OS_WIN32
#include "gwin32sid.h"
#endif
struct _GDBusAuthMechanismExternalPrivate
{
gboolean is_client;
gboolean is_server;
GDBusAuthMechanismState state;
gboolean empty_data_sent;
};
static gint mechanism_get_priority (void);
static const gchar *mechanism_get_name (void);
static gboolean mechanism_is_supported (GDBusAuthMechanism *mechanism);
static gchar *mechanism_encode_data (GDBusAuthMechanism *mechanism,
const gchar *data,
gsize data_len,
gsize *out_data_len);
static gchar *mechanism_decode_data (GDBusAuthMechanism *mechanism,
const gchar *data,
gsize data_len,
gsize *out_data_len);
static GDBusAuthMechanismState mechanism_server_get_state (GDBusAuthMechanism *mechanism);
static void mechanism_server_initiate (GDBusAuthMechanism *mechanism,
const gchar *initial_response,
gsize initial_response_len);
static void mechanism_server_data_receive (GDBusAuthMechanism *mechanism,
const gchar *data,
gsize data_len);
static gchar *mechanism_server_data_send (GDBusAuthMechanism *mechanism,
gsize *out_data_len);
static gchar *mechanism_server_get_reject_reason (GDBusAuthMechanism *mechanism);
static void mechanism_server_shutdown (GDBusAuthMechanism *mechanism);
static GDBusAuthMechanismState mechanism_client_get_state (GDBusAuthMechanism *mechanism);
static gchar *mechanism_client_initiate (GDBusAuthMechanism *mechanism,
gsize *out_initial_response_len);
static void mechanism_client_data_receive (GDBusAuthMechanism *mechanism,
const gchar *data,
gsize data_len);
static gchar *mechanism_client_data_send (GDBusAuthMechanism *mechanism,
gsize *out_data_len);
static void mechanism_client_shutdown (GDBusAuthMechanism *mechanism);
/* ---------------------------------------------------------------------------------------------------- */
G_DEFINE_TYPE_WITH_PRIVATE (GDBusAuthMechanismExternal, _g_dbus_auth_mechanism_external, G_TYPE_DBUS_AUTH_MECHANISM)
/* ---------------------------------------------------------------------------------------------------- */
static void
_g_dbus_auth_mechanism_external_finalize (GObject *object)
{
//GDBusAuthMechanismExternal *mechanism = G_DBUS_AUTH_MECHANISM_EXTERNAL (object);
if (G_OBJECT_CLASS (_g_dbus_auth_mechanism_external_parent_class)->finalize != NULL)
G_OBJECT_CLASS (_g_dbus_auth_mechanism_external_parent_class)->finalize (object);
}
static void
_g_dbus_auth_mechanism_external_class_init (GDBusAuthMechanismExternalClass *klass)
{
GObjectClass *gobject_class;
GDBusAuthMechanismClass *mechanism_class;
gobject_class = G_OBJECT_CLASS (klass);
gobject_class->finalize = _g_dbus_auth_mechanism_external_finalize;
mechanism_class = G_DBUS_AUTH_MECHANISM_CLASS (klass);
mechanism_class->get_name = mechanism_get_name;
mechanism_class->get_priority = mechanism_get_priority;
mechanism_class->is_supported = mechanism_is_supported;
mechanism_class->encode_data = mechanism_encode_data;
mechanism_class->decode_data = mechanism_decode_data;
mechanism_class->server_get_state = mechanism_server_get_state;
mechanism_class->server_initiate = mechanism_server_initiate;
mechanism_class->server_data_receive = mechanism_server_data_receive;
mechanism_class->server_data_send = mechanism_server_data_send;
mechanism_class->server_get_reject_reason = mechanism_server_get_reject_reason;
mechanism_class->server_shutdown = mechanism_server_shutdown;
mechanism_class->client_get_state = mechanism_client_get_state;
mechanism_class->client_initiate = mechanism_client_initiate;
mechanism_class->client_data_receive = mechanism_client_data_receive;
mechanism_class->client_data_send = mechanism_client_data_send;
mechanism_class->client_shutdown = mechanism_client_shutdown;
}
static void
_g_dbus_auth_mechanism_external_init (GDBusAuthMechanismExternal *mechanism)
{
mechanism->priv = _g_dbus_auth_mechanism_external_get_instance_private (mechanism);
}
/* ---------------------------------------------------------------------------------------------------- */
static gboolean
mechanism_is_supported (GDBusAuthMechanism *mechanism)
{
g_return_val_if_fail (G_IS_DBUS_AUTH_MECHANISM_EXTERNAL (mechanism), FALSE);
#if defined(G_OS_WIN32)
/* all that is required is current process SID */
return TRUE;
#else
/* This mechanism is only available if credentials has been exchanged */
if (_g_dbus_auth_mechanism_get_credentials (mechanism) != NULL)
return TRUE;
else
return FALSE;
#endif
}
static gint
mechanism_get_priority (void)
{
/* We prefer EXTERNAL to most other mechanism (DBUS_COOKIE_SHA1 and ANONYMOUS) */
return 100;
}
static const gchar *
mechanism_get_name (void)
{
return "EXTERNAL";
}
static gchar *
mechanism_encode_data (GDBusAuthMechanism *mechanism,
const gchar *data,
gsize data_len,
gsize *out_data_len)
{
return NULL;
}
static gchar *
mechanism_decode_data (GDBusAuthMechanism *mechanism,
const gchar *data,
gsize data_len,
gsize *out_data_len)
{
return NULL;
}
/* ---------------------------------------------------------------------------------------------------- */
static GDBusAuthMechanismState
mechanism_server_get_state (GDBusAuthMechanism *mechanism)
{
GDBusAuthMechanismExternal *m = G_DBUS_AUTH_MECHANISM_EXTERNAL (mechanism);
g_return_val_if_fail (G_IS_DBUS_AUTH_MECHANISM_EXTERNAL (mechanism), G_DBUS_AUTH_MECHANISM_STATE_INVALID);
g_return_val_if_fail (m->priv->is_server && !m->priv->is_client, G_DBUS_AUTH_MECHANISM_STATE_INVALID);
return m->priv->state;
}
static gboolean
data_matches_credentials (const gchar *data,
gsize data_len,
GCredentials *credentials)
{
gboolean match;
match = FALSE;
if (credentials == NULL)
goto out;
#if defined(G_OS_UNIX)
{
gint64 alleged_uid;
gchar *endp;
/* If we were unable to find out the uid, then nothing
* can possibly match it. */
if (g_credentials_get_unix_user (credentials, NULL) == (uid_t) -1)
goto out;
/* An empty authorization identity means we want to be
* whatever identity the out-of-band credentials say we have
* (RFC 4422 appendix A.1). This effectively matches any uid. */
if (data == NULL || data_len == 0)
{
match = TRUE;
goto out;
}
/* on UNIX, this is the uid as a string in base 10 */
alleged_uid = g_ascii_strtoll (data, &endp, 10);
if (*endp == '\0')
{
if (g_credentials_get_unix_user (credentials, NULL) == alleged_uid)
{
match = TRUE;
}
}
}
#else
/* TODO: Dont know how to compare credentials on this OS. Please implement. */
#endif
out:
return match;
}
static void
mechanism_server_initiate (GDBusAuthMechanism *mechanism,
const gchar *initial_response,
gsize initial_response_len)
{
GDBusAuthMechanismExternal *m = G_DBUS_AUTH_MECHANISM_EXTERNAL (mechanism);
g_return_if_fail (G_IS_DBUS_AUTH_MECHANISM_EXTERNAL (mechanism));
g_return_if_fail (!m->priv->is_server && !m->priv->is_client);
m->priv->is_server = TRUE;
if (initial_response != NULL)
{
if (data_matches_credentials (initial_response,
initial_response_len,
_g_dbus_auth_mechanism_get_credentials (mechanism)))
{
m->priv->state = G_DBUS_AUTH_MECHANISM_STATE_ACCEPTED;
}
else
{
m->priv->state = G_DBUS_AUTH_MECHANISM_STATE_REJECTED;
}
}
else
{
/* The initial-response optimization was not used, so we need to
* send an empty challenge to prompt the client to respond. */
m->priv->state = G_DBUS_AUTH_MECHANISM_STATE_HAVE_DATA_TO_SEND;
}
}
static void
mechanism_server_data_receive (GDBusAuthMechanism *mechanism,
const gchar *data,
gsize data_len)
{
GDBusAuthMechanismExternal *m = G_DBUS_AUTH_MECHANISM_EXTERNAL (mechanism);
g_return_if_fail (G_IS_DBUS_AUTH_MECHANISM_EXTERNAL (mechanism));
g_return_if_fail (m->priv->is_server && !m->priv->is_client);
g_return_if_fail (m->priv->state == G_DBUS_AUTH_MECHANISM_STATE_WAITING_FOR_DATA);
if (data_matches_credentials (data,
data_len,
_g_dbus_auth_mechanism_get_credentials (mechanism)))
{
m->priv->state = G_DBUS_AUTH_MECHANISM_STATE_ACCEPTED;
}
else
{
m->priv->state = G_DBUS_AUTH_MECHANISM_STATE_REJECTED;
}
}
static gchar *
mechanism_server_data_send (GDBusAuthMechanism *mechanism,
gsize *out_data_len)
{
GDBusAuthMechanismExternal *m = G_DBUS_AUTH_MECHANISM_EXTERNAL (mechanism);
g_return_val_if_fail (G_IS_DBUS_AUTH_MECHANISM_EXTERNAL (mechanism), NULL);
g_return_val_if_fail (m->priv->is_server && !m->priv->is_client, NULL);
if (out_data_len)
*out_data_len = 0;
if (m->priv->empty_data_sent)
{
/* We have already sent an empty data response.
Reject the connection. */
m->priv->state = G_DBUS_AUTH_MECHANISM_STATE_REJECTED;
return NULL;
}
m->priv->state = G_DBUS_AUTH_MECHANISM_STATE_WAITING_FOR_DATA;
m->priv->empty_data_sent = TRUE;
return g_strdup ("");
}
static gchar *
mechanism_server_get_reject_reason (GDBusAuthMechanism *mechanism)
{
GDBusAuthMechanismExternal *m = G_DBUS_AUTH_MECHANISM_EXTERNAL (mechanism);
g_return_val_if_fail (G_IS_DBUS_AUTH_MECHANISM_EXTERNAL (mechanism), NULL);
g_return_val_if_fail (m->priv->is_server && !m->priv->is_client, NULL);
g_return_val_if_fail (m->priv->state == G_DBUS_AUTH_MECHANISM_STATE_REJECTED, NULL);
/* can never end up here because we are never in the REJECTED state */
g_assert_not_reached ();
return NULL;
}
static void
mechanism_server_shutdown (GDBusAuthMechanism *mechanism)
{
GDBusAuthMechanismExternal *m = G_DBUS_AUTH_MECHANISM_EXTERNAL (mechanism);
g_return_if_fail (G_IS_DBUS_AUTH_MECHANISM_EXTERNAL (mechanism));
g_return_if_fail (m->priv->is_server && !m->priv->is_client);
m->priv->is_server = FALSE;
}
/* ---------------------------------------------------------------------------------------------------- */
static GDBusAuthMechanismState
mechanism_client_get_state (GDBusAuthMechanism *mechanism)
{
GDBusAuthMechanismExternal *m = G_DBUS_AUTH_MECHANISM_EXTERNAL (mechanism);
g_return_val_if_fail (G_IS_DBUS_AUTH_MECHANISM_EXTERNAL (mechanism), G_DBUS_AUTH_MECHANISM_STATE_INVALID);
g_return_val_if_fail (m->priv->is_client && !m->priv->is_server, G_DBUS_AUTH_MECHANISM_STATE_INVALID);
return m->priv->state;
}
static gchar *
mechanism_client_initiate (GDBusAuthMechanism *mechanism,
gsize *out_initial_response_len)
{
GDBusAuthMechanismExternal *m = G_DBUS_AUTH_MECHANISM_EXTERNAL (mechanism);
gchar *initial_response = NULL;
#if defined(G_OS_UNIX)
GCredentials *credentials;
#endif
g_return_val_if_fail (G_IS_DBUS_AUTH_MECHANISM_EXTERNAL (mechanism), NULL);
g_return_val_if_fail (!m->priv->is_server && !m->priv->is_client, NULL);
m->priv->is_client = TRUE;
m->priv->state = G_DBUS_AUTH_MECHANISM_STATE_REJECTED;
*out_initial_response_len = 0;
/* return the uid */
#if defined(G_OS_UNIX)
credentials = _g_dbus_auth_mechanism_get_credentials (mechanism);
g_assert (credentials != NULL);
initial_response = g_strdup_printf ("%" G_GINT64_FORMAT, (gint64) g_credentials_get_unix_user (credentials, NULL));
#elif defined(G_OS_WIN32)
initial_response = _g_win32_current_process_sid_string (NULL);
#else
#ifdef __GNUC__
#pragma GCC diagnostic push
#pragma GCC diagnostic warning "-Wcpp"
#warning Dont know how to send credentials on this OS. The EXTERNAL D-Bus authentication mechanism will not work.
#pragma GCC diagnostic pop
#endif
#endif
if (initial_response)
{
m->priv->state = G_DBUS_AUTH_MECHANISM_STATE_ACCEPTED;
*out_initial_response_len = strlen (initial_response);
}
return initial_response;
}
static void
mechanism_client_data_receive (GDBusAuthMechanism *mechanism,
const gchar *data,
gsize data_len)
{
GDBusAuthMechanismExternal *m = G_DBUS_AUTH_MECHANISM_EXTERNAL (mechanism);
g_return_if_fail (G_IS_DBUS_AUTH_MECHANISM_EXTERNAL (mechanism));
g_return_if_fail (m->priv->is_client && !m->priv->is_server);
g_return_if_fail (m->priv->state == G_DBUS_AUTH_MECHANISM_STATE_WAITING_FOR_DATA);
/* can never end up here because we are never in the WAITING_FOR_DATA state */
g_assert_not_reached ();
}
static gchar *
mechanism_client_data_send (GDBusAuthMechanism *mechanism,
gsize *out_data_len)
{
GDBusAuthMechanismExternal *m = G_DBUS_AUTH_MECHANISM_EXTERNAL (mechanism);
g_return_val_if_fail (G_IS_DBUS_AUTH_MECHANISM_EXTERNAL (mechanism), NULL);
g_return_val_if_fail (m->priv->is_client && !m->priv->is_server, NULL);
g_return_val_if_fail (m->priv->state == G_DBUS_AUTH_MECHANISM_STATE_HAVE_DATA_TO_SEND, NULL);
/* can never end up here because we are never in the HAVE_DATA_TO_SEND state */
g_assert_not_reached ();
return NULL;
}
static void
mechanism_client_shutdown (GDBusAuthMechanism *mechanism)
{
GDBusAuthMechanismExternal *m = G_DBUS_AUTH_MECHANISM_EXTERNAL (mechanism);
g_return_if_fail (G_IS_DBUS_AUTH_MECHANISM_EXTERNAL (mechanism));
g_return_if_fail (m->priv->is_client && !m->priv->is_server);
m->priv->is_client = FALSE;
}
/* ---------------------------------------------------------------------------------------------------- */
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