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- djm@cvs.openbsd.org 2010/09/20 07:19:27

Browse Source 
[mux.c]
     "atomically" create the listening mux socket by binding it on a temorary
     name and then linking it into position after listen() has succeeded.
     this allows the mux clients to determine that the server socket is
     either ready or stale without races. stale server sockets are now
     automatically removed
     ok deraadt
This commit is contained in:
Damien Miller 2010-09-24 22:07:55 +10:00
parent 18e1cab1a1
commit 603134e077
2 changed files with 54 additions and 4 deletions
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8
ChangeLog
View File

@ -23,6 +23,14 @@
- djm@cvs.openbsd.org 2010/09/20 04:54:07
[jpake.c]
missing #include
- djm@cvs.openbsd.org 2010/09/20 07:19:27
[mux.c]
"atomically" create the listening mux socket by binding it on a temorary
name and then linking it into position after listen() has succeeded.
this allows the mux clients to determine that the server socket is
either ready or stale without races. stale server sockets are now
automatically removed
ok deraadt
20100910
- (dtucker) [openbsd-compat/port-linux.c] Check is_selinux_enabled for exact

50
mux.c
View File

@ -1,4 +1,4 @@
/* $OpenBSD: mux.c,v 1.21 2010/06/25 23:15:36 djm Exp $ */
/* $OpenBSD: mux.c,v 1.22 2010/09/20 07:19:27 djm Exp $ */
/*
* Copyright (c) 2002-2008 Damien Miller <djm@openbsd.org>
*
@ -1026,6 +1026,9 @@ muxserver_listen(void)
struct sockaddr_un addr;
socklen_t sun_len;
mode_t old_umask;
char *orig_control_path = options.control_path;
char rbuf[16+1];
u_int i, r;
if (options.control_path == NULL ||
options.control_master == SSHCTL_MASTER_NO)
@ -1033,6 +1036,23 @@ muxserver_listen(void)
debug("setting up multiplex master socket");
/*
* Use a temporary path before listen so we can pseudo-atomically
* establish the listening socket in its final location to avoid
* other processes racing in between bind() and listen() and hitting
* an unready socket.
*/
for (i = 0; i < sizeof(rbuf) - 1; i++) {
r = arc4random_uniform(26+26+10);
rbuf[i] = (r < 26) ? 'a' + r :
(r < 26*2) ? 'A' + r - 26 :
'0' + r - 26 - 26;
}
rbuf[sizeof(rbuf) - 1] = '\0';
options.control_path = NULL;
xasprintf(&options.control_path, "%s.%s", orig_control_path, rbuf);
debug3("%s: temporary control path %s", __func__, options.control_path);
memset(&addr, '\0', sizeof(addr));
addr.sun_family = AF_UNIX;
sun_len = offsetof(struct sockaddr_un, sun_path) +
@ -1051,6 +1071,7 @@ muxserver_listen(void)
if (errno == EINVAL || errno == EADDRINUSE) {
error("ControlSocket %s already exists, "
"disabling multiplexing", options.control_path);
disable_mux_master:
close(muxserver_sock);
muxserver_sock = -1;
xfree(options.control_path);
@ -1065,12 +1086,29 @@ muxserver_listen(void)
if (listen(muxserver_sock, 64) == -1)
fatal("%s listen(): %s", __func__, strerror(errno));
/* Now atomically "move" the mux socket into position */
if (link(options.control_path, orig_control_path) != 0) {
if (errno != EEXIST) {
fatal("%s: link mux listener %s => %s: %s", __func__,
options.control_path, orig_control_path,
strerror(errno));
}
error("ControlSocket %s already exists, disabling multiplexing",
orig_control_path);
xfree(orig_control_path);
unlink(options.control_path);
goto disable_mux_master;
}
unlink(options.control_path);
xfree(options.control_path);
options.control_path = orig_control_path;
set_nonblock(muxserver_sock);
mux_listener_channel = channel_new("mux listener",
SSH_CHANNEL_MUX_LISTENER, muxserver_sock, muxserver_sock, -1,
CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT,
0, addr.sun_path, 1);
0, options.control_path, 1);
mux_listener_channel->mux_rcb = mux_master_read_cb;
debug3("%s: mux listener channel %d fd %d", __func__,
mux_listener_channel->self, mux_listener_channel->sock);
@ -1823,9 +1861,13 @@ muxclient(const char *path)
fatal("Control socket connect(%.100s): %s", path,
strerror(errno));
}
if (errno == ENOENT)
if (errno == ECONNREFUSED &&
options.control_master != SSHCTL_MASTER_NO) {
debug("Stale control socket %.100s, unlinking", path);
unlink(path);
} else if (errno == ENOENT) {
debug("Control socket \"%.100s\" does not exist", path);
else {
} else {
error("Control socket connect(%.100s): %s", path,
strerror(errno));
}