/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
/***
This file is part of systemd.
Copyright 2010 Lennart Poettering
Copyright 2013 Daniel Mack
Copyright 2014 Kay Sievers
Copyright 2014 David Herrmann
systemd 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.
systemd is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with systemd; If not, see .
***/
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include "log.h"
#include "util.h"
#include "socket-util.h"
#include "sd-daemon.h"
#include "sd-bus.h"
#include "bus-internal.h"
#include "bus-message.h"
#include "bus-util.h"
#include "build.h"
#include "strv.h"
#include "def.h"
#include "capability.h"
#include "bus-control.h"
#include "smack-util.h"
#include "set.h"
#include "bus-xml-policy.h"
#include "driver.h"
#include "proxy.h"
#include "synthesize.h"
static int proxy_create_dest(Proxy *p, const char *dest, const char *local_sec, bool negotiate_fds) {
_cleanup_bus_close_unref_ sd_bus *b = NULL;
int r;
r = sd_bus_new(&b);
if (r < 0)
return log_error_errno(r, "Failed to allocate bus: %m");
r = sd_bus_set_description(b, "sd-proxy");
if (r < 0)
return log_error_errno(r, "Failed to set bus name: %m");
r = sd_bus_set_address(b, dest);
if (r < 0)
return log_error_errno(r, "Failed to set address to connect to: %m");
r = sd_bus_negotiate_fds(b, negotiate_fds);
if (r < 0)
return log_error_errno(r, "Failed to set FD negotiation: %m");
r = sd_bus_negotiate_creds(b, true, SD_BUS_CREDS_EUID|SD_BUS_CREDS_PID|SD_BUS_CREDS_EGID|SD_BUS_CREDS_SELINUX_CONTEXT);
if (r < 0)
return log_error_errno(r, "Failed to set credential negotiation: %m");
if (p->local_creds.pid > 0) {
b->fake_pids.pid = p->local_creds.pid;
b->fake_pids_valid = true;
b->fake_creds.uid = p->local_creds.uid;
b->fake_creds.euid = p->local_creds.uid;
b->fake_creds.suid = p->local_creds.uid;
b->fake_creds.fsuid = p->local_creds.uid;
b->fake_creds.gid = p->local_creds.gid;
b->fake_creds.egid = p->local_creds.gid;
b->fake_creds.sgid = p->local_creds.gid;
b->fake_creds.fsgid = p->local_creds.gid;
b->fake_creds_valid = true;
}
if (local_sec) {
b->fake_label = strdup(local_sec);
if (!b->fake_label)
return log_oom();
}
b->manual_peer_interface = true;
r = sd_bus_start(b);
if (r < 0)
return log_error_errno(r, "Failed to start bus client: %m");
p->dest_bus = b;
b = NULL;
return 0;
}
static int proxy_create_local(Proxy *p, int in_fd, int out_fd, bool negotiate_fds) {
_cleanup_bus_close_unref_ sd_bus *b = NULL;
sd_id128_t server_id;
int r;
r = sd_bus_new(&b);
if (r < 0)
return log_error_errno(r, "Failed to allocate bus: %m");
r = sd_bus_set_fd(b, in_fd, out_fd);
if (r < 0)
return log_error_errno(r, "Failed to set fds: %m");
r = sd_bus_get_bus_id(p->dest_bus, &server_id);
if (r < 0)
return log_error_errno(r, "Failed to get server ID: %m");
r = sd_bus_set_server(b, 1, server_id);
if (r < 0)
return log_error_errno(r, "Failed to set server mode: %m");
r = sd_bus_negotiate_fds(b, negotiate_fds);
if (r < 0)
return log_error_errno(r, "Failed to set FD negotiation: %m");
r = sd_bus_negotiate_creds(b, true, SD_BUS_CREDS_EUID|SD_BUS_CREDS_PID|SD_BUS_CREDS_EGID|SD_BUS_CREDS_SELINUX_CONTEXT);
if (r < 0)
return log_error_errno(r, "Failed to set credential negotiation: %m");
r = sd_bus_set_anonymous(b, true);
if (r < 0)
return log_error_errno(r, "Failed to set anonymous authentication: %m");
b->manual_peer_interface = true;
r = sd_bus_start(b);
if (r < 0)
return log_error_errno(r, "Failed to start bus client: %m");
p->local_bus = b;
b = NULL;
return 0;
}
static int proxy_prepare_matches(Proxy *p) {
_cleanup_free_ char *match = NULL;
const char *unique;
int r;
if (!p->dest_bus->is_kernel)
return 0;
r = sd_bus_get_unique_name(p->dest_bus, &unique);
if (r < 0)
return log_error_errno(r, "Failed to get unique name: %m");
match = strjoin("type='signal',"
"sender='org.freedesktop.DBus',"
"path='/org/freedesktop/DBus',"
"interface='org.freedesktop.DBus',"
"member='NameOwnerChanged',"
"arg1='",
unique,
"'",
NULL);
if (!match)
return log_oom();
r = sd_bus_add_match(p->dest_bus, NULL, match, NULL, NULL);
if (r < 0)
return log_error_errno(r, "Failed to add match for NameLost: %m");
free(match);
match = strjoin("type='signal',"
"sender='org.freedesktop.DBus',"
"path='/org/freedesktop/DBus',"
"interface='org.freedesktop.DBus',"
"member='NameOwnerChanged',"
"arg2='",
unique,
"'",
NULL);
if (!match)
return log_oom();
r = sd_bus_add_match(p->dest_bus, NULL, match, NULL, NULL);
if (r < 0)
return log_error_errno(r, "Failed to add match for NameAcquired: %m");
return 0;
}
int proxy_new(Proxy **out, int in_fd, int out_fd, const char *dest) {
_cleanup_(proxy_freep) Proxy *p = NULL;
_cleanup_free_ char *local_sec = NULL;
bool is_unix;
int r;
p = new0(Proxy, 1);
if (!p)
return log_oom();
p->local_in = in_fd;
p->local_out = out_fd;
p->owned_names = set_new(&string_hash_ops);
if (!p->owned_names)
return log_oom();
is_unix = sd_is_socket(in_fd, AF_UNIX, 0, 0) > 0 &&
sd_is_socket(out_fd, AF_UNIX, 0, 0) > 0;
if (is_unix) {
(void) getpeercred(in_fd, &p->local_creds);
(void) getpeersec(in_fd, &local_sec);
}
r = proxy_create_dest(p, dest, local_sec, is_unix);
if (r < 0)
return r;
r = proxy_create_local(p, in_fd, out_fd, is_unix);
if (r < 0)
return r;
r = proxy_prepare_matches(p);
if (r < 0)
return r;
*out = p;
p = NULL;
return 0;
}
Proxy *proxy_free(Proxy *p) {
if (!p)
return NULL;
sd_bus_close_unrefp(&p->local_bus);
sd_bus_close_unrefp(&p->dest_bus);
set_free_free(p->owned_names);
free(p);
return NULL;
}
int proxy_set_policy(Proxy *p, SharedPolicy *sp, char **configuration) {
_cleanup_strv_free_ char **strv = NULL;
Policy *policy;
int r;
assert(p);
assert(sp);
/* no need to load legacy policy if destination is not kdbus */
if (!p->dest_bus->is_kernel)
return 0;
p->policy = sp;
policy = shared_policy_acquire(sp);
if (policy) {
/* policy already pre-loaded */
shared_policy_release(sp, policy);
return 0;
}
if (!configuration) {
const char *scope;
r = sd_bus_get_scope(p->dest_bus, &scope);
if (r < 0)
return log_error_errno(r, "Couldn't determine bus scope: %m");
if (streq(scope, "system"))
strv = strv_new("/etc/dbus-1/system.conf",
"/etc/dbus-1/system.d/",
"/etc/dbus-1/system-local.conf",
NULL);
else if (streq(scope, "user"))
strv = strv_new("/etc/dbus-1/session.conf",
"/etc/dbus-1/session.d/",
"/etc/dbus-1/session-local.conf",
NULL);
else
return log_error("Unknown scope %s, don't know which policy to load. Refusing.", scope);
if (!strv)
return log_oom();
configuration = strv;
}
return shared_policy_preload(sp, configuration);
}
int proxy_hello_policy(Proxy *p, uid_t original_uid) {
Policy *policy;
int r = 0;
assert(p);
if (!p->policy)
return 0;
policy = shared_policy_acquire(p->policy);
if (p->local_creds.uid == original_uid)
log_debug("Permitting access, since bus owner matches bus client.");
else if (policy_check_hello(policy, p->local_creds.uid, p->local_creds.gid))
log_debug("Permitting access due to XML policy.");
else
r = log_error_errno(EPERM, "Policy denied connection.");
shared_policy_release(p->policy, policy);
return r;
}
static int proxy_wait(Proxy *p) {
uint64_t timeout_dest, timeout_local, t;
int events_dest, events_local, fd;
struct timespec _ts, *ts;
struct pollfd *pollfd;
int r;
assert(p);
fd = sd_bus_get_fd(p->dest_bus);
if (fd < 0)
return log_error_errno(fd, "Failed to get fd: %m");
events_dest = sd_bus_get_events(p->dest_bus);
if (events_dest < 0)
return log_error_errno(events_dest, "Failed to get events mask: %m");
r = sd_bus_get_timeout(p->dest_bus, &timeout_dest);
if (r < 0)
return log_error_errno(r, "Failed to get timeout: %m");
events_local = sd_bus_get_events(p->local_bus);
if (events_local < 0)
return log_error_errno(events_local, "Failed to get events mask: %m");
r = sd_bus_get_timeout(p->local_bus, &timeout_local);
if (r < 0)
return log_error_errno(r, "Failed to get timeout: %m");
t = timeout_dest;
if (t == (uint64_t) -1 || (timeout_local != (uint64_t) -1 && timeout_local < timeout_dest))
t = timeout_local;
if (t == (uint64_t) -1)
ts = NULL;
else {
usec_t nw;
nw = now(CLOCK_MONOTONIC);
if (t > nw)
t -= nw;
else
t = 0;
ts = timespec_store(&_ts, t);
}
pollfd = (struct pollfd[3]) {
{ .fd = fd, .events = events_dest, },
{ .fd = p->local_in, .events = events_local & POLLIN, },
{ .fd = p->local_out, .events = events_local & POLLOUT, },
};
r = ppoll(pollfd, 3, ts, NULL);
if (r < 0)
return log_error_errno(errno, "ppoll() failed: %m");
return 0;
}
static int handle_policy_error(sd_bus_message *m, int r) {
if (r == -ESRCH || r == -ENXIO)
return synthetic_reply_method_errorf(m, SD_BUS_ERROR_NAME_HAS_NO_OWNER, "Name %s is currently not owned by anyone.", m->destination);
return r;
}
static int process_policy_unlocked(sd_bus *from, sd_bus *to, sd_bus_message *m, Policy *policy, const struct ucred *our_ucred, Set *owned_names) {
int r;
assert(from);
assert(to);
assert(m);
if (!policy)
return 0;
/*
* dbus-1 distinguishes expected and non-expected replies by tracking
* method-calls and timeouts. By default, DENY rules are *NEVER* applied
* on expected replies, unless explicitly specified. But we dont track
* method-calls, thus, we cannot know whether a reply is expected.
* Fortunately, the kdbus forbids non-expected replies, so we can safely
* ignore any policy on those and let the kernel deal with it.
*
* TODO: To be correct, we should only ignore policy-tags that are
* applied on non-expected replies. However, so far we don't parse those
* tags so we let everything pass. I haven't seen a DENY policy tag on
* expected-replies, ever, so don't bother..
*/
if (m->reply_cookie > 0)
return 0;
if (from->is_kernel) {
uid_t sender_uid = UID_INVALID;
gid_t sender_gid = GID_INVALID;
char **sender_names = NULL;
/* Driver messages are always OK */
if (streq_ptr(m->sender, "org.freedesktop.DBus"))
return 0;
/* The message came from the kernel, and is sent to our legacy client. */
sd_bus_creds_get_well_known_names(&m->creds, &sender_names);
(void) sd_bus_creds_get_euid(&m->creds, &sender_uid);
(void) sd_bus_creds_get_egid(&m->creds, &sender_gid);
if (sender_uid == UID_INVALID || sender_gid == GID_INVALID) {
_cleanup_bus_creds_unref_ sd_bus_creds *sender_creds = NULL;
/* If the message came from another legacy
* client, then the message creds will be
* missing, simply because on legacy clients
* per-message creds were unknown. In this
* case, query the creds of the peer
* instead. */
r = bus_get_name_creds_kdbus(from, m->sender, SD_BUS_CREDS_EUID|SD_BUS_CREDS_EGID, true, &sender_creds);
if (r < 0)
return handle_policy_error(m, r);
(void) sd_bus_creds_get_euid(sender_creds, &sender_uid);
(void) sd_bus_creds_get_egid(sender_creds, &sender_gid);
}
/* First check whether the sender can send the message to our name */
if (policy_check_send(policy, sender_uid, sender_gid, m->header->type, owned_names, NULL, m->path, m->interface, m->member, false, NULL) &&
policy_check_recv(policy, our_ucred->uid, our_ucred->gid, m->header->type, NULL, sender_names, m->path, m->interface, m->member, false))
return 0;
/* Return an error back to the caller */
if (m->header->type == SD_BUS_MESSAGE_METHOD_CALL)
return synthetic_reply_method_errorf(m, SD_BUS_ERROR_ACCESS_DENIED, "Access prohibited by XML receiver policy.");
/* Return 1, indicating that the message shall not be processed any further */
return 1;
}
if (to->is_kernel) {
_cleanup_bus_creds_unref_ sd_bus_creds *destination_creds = NULL;
uid_t destination_uid = UID_INVALID;
gid_t destination_gid = GID_INVALID;
const char *destination_unique = NULL;
char **destination_names = NULL;
char *n;
/* Driver messages are always OK */
if (streq_ptr(m->destination, "org.freedesktop.DBus"))
return 0;
/* The message came from the legacy client, and is sent to kdbus. */
if (m->destination) {
r = bus_get_name_creds_kdbus(to, m->destination,
SD_BUS_CREDS_WELL_KNOWN_NAMES|SD_BUS_CREDS_UNIQUE_NAME|
SD_BUS_CREDS_EUID|SD_BUS_CREDS_EGID|SD_BUS_CREDS_PID,
true, &destination_creds);
if (r < 0)
return handle_policy_error(m, r);
r = sd_bus_creds_get_unique_name(destination_creds, &destination_unique);
if (r < 0)
return handle_policy_error(m, r);
sd_bus_creds_get_well_known_names(destination_creds, &destination_names);
(void) sd_bus_creds_get_euid(destination_creds, &destination_uid);
(void) sd_bus_creds_get_egid(destination_creds, &destination_gid);
}
/* First check if we (the sender) can send to this name */
if (policy_check_send(policy, our_ucred->uid, our_ucred->gid, m->header->type, NULL, destination_names, m->path, m->interface, m->member, true, &n)) {
if (n) {
/* If we made a receiver decision, then remember which
* name's policy we used, and to which unique ID it
* mapped when we made the decision. Then, let's pass
* this to the kernel when sending the message, so that
* it refuses the operation should the name and unique
* ID not map to each other anymore. */
r = free_and_strdup(&m->destination_ptr, n);
if (r < 0)
return r;
r = bus_kernel_parse_unique_name(destination_unique, &m->verify_destination_id);
if (r < 0)
return r;
}
if (sd_bus_message_is_signal(m, NULL, NULL)) {
/* If we forward a signal from dbus-1 to kdbus,
* we have no idea who the recipient is.
* Therefore, we cannot apply any dbus-1
* receiver policies that match on receiver
* credentials. We know sd-bus always sets
* KDBUS_MSG_SIGNAL, so the kernel applies
* receiver policies to the message. Therefore,
* skip policy checks in this case. */
return 0;
} else if (policy_check_recv(policy, destination_uid, destination_gid, m->header->type, owned_names, NULL, m->path, m->interface, m->member, true)) {
return 0;
}
}
/* Return an error back to the caller */
if (m->header->type == SD_BUS_MESSAGE_METHOD_CALL)
return synthetic_reply_method_errorf(m, SD_BUS_ERROR_ACCESS_DENIED, "Access prohibited by XML sender policy.");
/* Return 1, indicating that the message shall not be processed any further */
return 1;
}
return 0;
}
static int process_policy(sd_bus *from, sd_bus *to, sd_bus_message *m, SharedPolicy *sp, const struct ucred *our_ucred, Set *owned_names) {
Policy *policy;
int r;
assert(sp);
policy = shared_policy_acquire(sp);
r = process_policy_unlocked(from, to, m, policy, our_ucred, owned_names);
shared_policy_release(sp, policy);
return r;
}
static int process_hello(Proxy *p, sd_bus_message *m) {
_cleanup_bus_message_unref_ sd_bus_message *n = NULL;
bool is_hello;
int r;
assert(p);
assert(m);
/* As reaction to hello we need to respond with two messages:
* the callback reply and the NameAcquired for the unique
* name, since hello is otherwise obsolete on kdbus. */
is_hello =
sd_bus_message_is_method_call(m, "org.freedesktop.DBus", "Hello") &&
streq_ptr(m->destination, "org.freedesktop.DBus");
if (!is_hello) {
if (p->got_hello)
return 0;
return log_error_errno(-EIO, "First packet isn't hello (it's %s.%s), aborting.", m->interface, m->member);
}
if (p->got_hello)
return log_error_errno(-EIO, "Got duplicate hello, aborting.");
p->got_hello = true;
if (!p->dest_bus->is_kernel)
return 0;
r = sd_bus_message_new_method_return(m, &n);
if (r < 0)
return log_error_errno(r, "Failed to generate HELLO reply: %m");
r = sd_bus_message_append(n, "s", p->dest_bus->unique_name);
if (r < 0)
return log_error_errno(r, "Failed to append unique name to HELLO reply: %m");
r = bus_message_append_sender(n, "org.freedesktop.DBus");
if (r < 0)
return log_error_errno(r, "Failed to append sender to HELLO reply: %m");
r = bus_seal_synthetic_message(p->local_bus, n);
if (r < 0)
return log_error_errno(r, "Failed to seal HELLO reply: %m");
r = sd_bus_send(p->local_bus, n, NULL);
if (r < 0)
return log_error_errno(r, "Failed to send HELLO reply: %m");
n = sd_bus_message_unref(n);
r = sd_bus_message_new_signal(
p->local_bus,
&n,
"/org/freedesktop/DBus",
"org.freedesktop.DBus",
"NameAcquired");
if (r < 0)
return log_error_errno(r, "Failed to allocate initial NameAcquired message: %m");
r = sd_bus_message_append(n, "s", p->dest_bus->unique_name);
if (r < 0)
return log_error_errno(r, "Failed to append unique name to NameAcquired message: %m");
r = bus_message_append_sender(n, "org.freedesktop.DBus");
if (r < 0)
return log_error_errno(r, "Failed to append sender to NameAcquired message: %m");
r = bus_seal_synthetic_message(p->local_bus, n);
if (r < 0)
return log_error_errno(r, "Failed to seal NameAcquired message: %m");
r = sd_bus_send(p->local_bus, n, NULL);
if (r < 0)
return log_error_errno(r, "Failed to send NameAcquired message: %m");
return 1;
}
static int patch_sender(sd_bus *a, sd_bus_message *m) {
char **well_known = NULL;
sd_bus_creds *c;
int r;
assert(a);
assert(m);
if (!a->is_kernel)
return 0;
/* We will change the sender of messages from the bus driver
* so that they originate from the bus driver. This is a
* speciality originating from dbus1, where the bus driver did
* not have a unique id, but only the well-known name. */
c = sd_bus_message_get_creds(m);
if (!c)
return 0;
r = sd_bus_creds_get_well_known_names(c, &well_known);
if (r < 0)
return r;
if (strv_contains(well_known, "org.freedesktop.DBus"))
m->sender = "org.freedesktop.DBus";
return 0;
}
static int proxy_process_dest_to_local(Proxy *p) {
_cleanup_bus_message_unref_ sd_bus_message *m = NULL;
int r;
assert(p);
r = sd_bus_process(p->dest_bus, &m);
if (r < 0) {
/* treat 'connection reset by peer' as clean exit condition */
if (r != -ECONNRESET)
log_error_errno(r, "Failed to process destination bus: %m");
return r;
}
if (r == 0)
return 0;
if (!m)
return 1;
/* We officially got EOF, let's quit */
if (sd_bus_message_is_signal(m, "org.freedesktop.DBus.Local", "Disconnected"))
return -ECONNRESET;
r = synthesize_name_acquired(p->dest_bus, p->local_bus, m);
if (r < 0)
return log_error_errno(r, "Failed to synthesize message: %m");
patch_sender(p->dest_bus, m);
if (p->policy) {
r = process_policy(p->dest_bus, p->local_bus, m, p->policy, &p->local_creds, p->owned_names);
if (r < 0)
return log_error_errno(r, "Failed to process policy: %m");
else if (r > 0)
return 1;
}
r = sd_bus_send(p->local_bus, m, NULL);
if (r < 0) {
if (r == -EPERM && m->reply_cookie > 0) {
/* If the peer tries to send a reply and it is rejected with EPERM
* by the kernel, we ignore the error. This catches cases where the
* original method-call didn't had EXPECT_REPLY set, but the proxy-peer
* still sends a reply. This is allowed in dbus1, but not in kdbus. We
* don't want to track reply-windows in the proxy, so we simply ignore
* EPERM for all replies. The only downside is, that callers are no
* longer notified if their replies are dropped. However, this is
* equivalent to the caller's timeout to expire, so this should be
* acceptable. Nobody sane sends replies without a matching method-call,
* so nobody should care. */
return 1;
} else {
if (r != -ECONNRESET)
log_error_errno(r, "Failed to send message to client: %m");
return r;
}
}
return 1;
}
static int proxy_process_local_to_dest(Proxy *p) {
_cleanup_bus_message_unref_ sd_bus_message *m = NULL;
int r;
assert(p);
r = sd_bus_process(p->local_bus, &m);
if (r < 0) {
/* treat 'connection reset by peer' as clean exit condition */
if (r != -ECONNRESET)
log_error_errno(r, "Failed to process local bus: %m");
return r;
}
if (r == 0)
return 0;
if (!m)
return 1;
/* We officially got EOF, let's quit */
if (sd_bus_message_is_signal(m, "org.freedesktop.DBus.Local", "Disconnected"))
return -ECONNRESET;
r = process_hello(p, m);
if (r < 0)
return log_error_errno(r, "Failed to process HELLO: %m");
else if (r > 0)
return 1;
r = bus_proxy_process_driver(p->dest_bus, p->local_bus, m, p->policy, &p->local_creds, p->owned_names);
if (r < 0)
return log_error_errno(r, "Failed to process driver calls: %m");
else if (r > 0)
return 1;
for (;;) {
if (p->policy) {
r = process_policy(p->local_bus, p->dest_bus, m, p->policy, &p->local_creds, p->owned_names);
if (r < 0)
return log_error_errno(r, "Failed to process policy: %m");
else if (r > 0)
return 1;
}
r = sd_bus_send(p->dest_bus, m, NULL);
if (r < 0) {
if (r == -EREMCHG) {
/* The name database changed since the policy check, hence let's check again */
continue;
} else if (r == -EPERM && m->reply_cookie > 0) {
/* see above why EPERM is ignored for replies */
return 1;
} else {
if (r != -ECONNRESET)
log_error_errno(r, "Failed to send message to bus: %m");
return r;
}
}
break;
}
return 1;
}
int proxy_run(Proxy *p) {
int r;
assert(p);
for (;;) {
bool busy = false;
if (p->got_hello) {
/* Read messages from bus, to pass them on to our client */
r = proxy_process_dest_to_local(p);
if (r == -ECONNRESET)
return 0;
else if (r < 0)
return r;
else if (r > 0)
busy = true;
}
/* Read messages from our client, to pass them on to the bus */
r = proxy_process_local_to_dest(p);
if (r == -ECONNRESET)
return 0;
else if (r < 0)
return r;
else if (r > 0)
busy = true;
if (!busy) {
r = proxy_wait(p);
if (r < 0)
return r;
}
}
return 0;
}