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- dtucker@cvs.openbsd.org 2006/07/17 12:06:00 

[channels.c channels.h servconf.c sshd_config.5]
     Add PermitOpen directive to sshd_config which is equivalent to the
     "permitopen" key option.  Allows server admin to allow TCP port
     forwarding only two specific host/port pairs.  Useful when combined
     with Match.
     If permitopen is used in both sshd_config and a key option, both
     must allow a given connection before it will be permitted.
     Note that users can still use external forwarders such as netcat,
     so to be those must be controlled too for the limits to be effective.
     Feedback & ok djm@, man page corrections & ok jmc@.
This commit is contained in:
Damien Miller 2006-07-24 14:04:00 +10:00
parent 98299261eb
commit 9b439df18a
5 changed files with 121 additions and 13 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
ChangeLog
View File

@ -26,6 +26,17 @@
- dtucker@cvs.openbsd.org 2006/07/17 12:02:24
[auth-options.c]
Use '\0' rather than 0 to terminates strings; ok djm@
- dtucker@cvs.openbsd.org 2006/07/17 12:06:00
[channels.c channels.h servconf.c sshd_config.5]
Add PermitOpen directive to sshd_config which is equivalent to the
"permitopen" key option. Allows server admin to allow TCP port
forwarding only two specific host/port pairs. Useful when combined
with Match.
If permitopen is used in both sshd_config and a key option, both
must allow a given connection before it will be permitted.
Note that users can still use external forwarders such as netcat,
so to be those must be controlled too for the limits to be effective.
Feedback & ok djm@, man page corrections & ok jmc@.
20060713
- (dtucker) [auth-krb5.c auth-pam.c] Still more errno.h
@ -4944,4 +4955,4 @@
- (djm) Trim deprecated options from INSTALL. Mention UsePAM
- (djm) Fix quote handling in sftp; Patch from admorten AT umich.edu
$Id: ChangeLog,v 1.4414 2006/07/24 04:01:43 djm Exp $
$Id: ChangeLog,v 1.4415 2006/07/24 04:04:00 djm Exp $

52
channels.c
View File

@ -1,4 +1,4 @@
/* $OpenBSD: channels.c,v 1.256 2006/07/17 01:31:09 stevesk Exp $ */
/* $OpenBSD: channels.c,v 1.257 2006/07/17 12:06:00 dtucker Exp $ */
/*
* Author: Tatu Ylonen <ylo@cs.hut.fi>
* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@ -106,11 +106,18 @@ typedef struct {
u_short listen_port; /* Remote side should listen port number. */
} ForwardPermission;
/* List of all permitted host/port pairs to connect. */
/* List of all permitted host/port pairs to connect by the user. */
static ForwardPermission permitted_opens[SSH_MAX_FORWARDS_PER_DIRECTION];
/* Number of permitted host/port pairs in the array. */
/* List of all permitted host/port pairs to connect by the admin. */
static ForwardPermission permitted_adm_opens[SSH_MAX_FORWARDS_PER_DIRECTION];
/* Number of permitted host/port pairs in the array permitted by the user. */
static int num_permitted_opens = 0;
/* Number of permitted host/port pair in the array permitted by the admin. */
static int num_adm_permitted_opens = 0;
/*
* If this is true, all opens are permitted. This is the case on the server
* on which we have to trust the client anyway, and the user could do
@ -2646,6 +2653,19 @@ channel_add_permitted_opens(char *host, int port)
all_opens_permitted = 0;
}
void
channel_add_adm_permitted_opens(char *host, int port)
{
if (num_adm_permitted_opens >= SSH_MAX_FORWARDS_PER_DIRECTION)
fatal("channel_add_adm_permitted_opens: too many forwards");
debug("allow port forwarding to host %s port %d", host, port);
permitted_adm_opens[num_adm_permitted_opens].host_to_connect
= xstrdup(host);
permitted_adm_opens[num_adm_permitted_opens].port_to_connect = port;
num_adm_permitted_opens++;
}
void
channel_clear_permitted_opens(void)
{
@ -2655,7 +2675,17 @@ channel_clear_permitted_opens(void)
if (permitted_opens[i].host_to_connect != NULL)
xfree(permitted_opens[i].host_to_connect);
num_permitted_opens = 0;
}
void
channel_clear_adm_permitted_opens(void)
{
int i;
for (i = 0; i < num_adm_permitted_opens; i++)
if (permitted_adm_opens[i].host_to_connect != NULL)
xfree(permitted_adm_opens[i].host_to_connect);
num_adm_permitted_opens = 0;
}
/* return socket to remote host, port */
@ -2734,7 +2764,7 @@ channel_connect_by_listen_address(u_short listen_port)
int
channel_connect_to(const char *host, u_short port)
{
int i, permit;
int i, permit, permit_adm = 1;
permit = all_opens_permitted;
if (!permit) {
@ -2743,9 +2773,19 @@ channel_connect_to(const char *host, u_short port)
permitted_opens[i].port_to_connect == port &&
strcmp(permitted_opens[i].host_to_connect, host) == 0)
permit = 1;
}
if (!permit) {
if (num_adm_permitted_opens > 0) {
permit_adm = 0;
for (i = 0; i < num_adm_permitted_opens; i++)
if (permitted_adm_opens[i].host_to_connect != NULL &&
permitted_adm_opens[i].port_to_connect == port &&
strcmp(permitted_adm_opens[i].host_to_connect, host)
== 0)
permit_adm = 1;
}
if (!permit || !permit_adm) {
logit("Received request to connect to host %.100s port %d, "
"but the request was denied.", host, port);
return -1;

4
channels.h
View File

@ -1,4 +1,4 @@
/* $OpenBSD: channels.h,v 1.85 2006/07/11 18:50:47 markus Exp $ */
/* $OpenBSD: channels.h,v 1.86 2006/07/17 12:06:00 dtucker Exp $ */
/*
* Author: Tatu Ylonen <ylo@cs.hut.fi>
@ -207,7 +207,9 @@ int channel_find_open(void);
void channel_set_af(int af);
void channel_permit_all_opens(void);
void channel_add_permitted_opens(char *, int);
void channel_add_adm_permitted_opens(char *, int);
void channel_clear_permitted_opens(void);
void channel_clear_adm_permitted_opens(void);
int channel_input_port_forward_request(int, int);
int channel_connect_to(const char *, u_short);
int channel_connect_by_listen_address(u_short);

29
servconf.c
View File

@ -1,4 +1,4 @@
/* $OpenBSD: servconf.c,v 1.155 2006/07/17 01:31:09 stevesk Exp $ */
/* $OpenBSD: servconf.c,v 1.156 2006/07/17 12:06:00 dtucker Exp $ */
/*
* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
* All rights reserved
@ -31,6 +31,7 @@
#include "kex.h"
#include "mac.h"
#include "match.h"
#include "channels.h"
static void add_listen_addr(ServerOptions *, char *, u_short);
static void add_one_listen_addr(ServerOptions *, char *, u_short);
@ -281,7 +282,7 @@ typedef enum {
sHostbasedUsesNameFromPacketOnly, sClientAliveInterval,
sClientAliveCountMax, sAuthorizedKeysFile, sAuthorizedKeysFile2,
sGssAuthentication, sGssCleanupCreds, sAcceptEnv, sPermitTunnel,
sMatch,
sMatch, sPermitOpen,
sUsePrivilegeSeparation,
sDeprecated, sUnsupported
} ServerOpCodes;
@ -390,6 +391,8 @@ static struct {
{ "useprivilegeseparation", sUsePrivilegeSeparation, SSHCFG_GLOBAL },
{ "acceptenv", sAcceptEnv, SSHCFG_GLOBAL },
{ "permittunnel", sPermitTunnel, SSHCFG_GLOBAL },
{ "match", sMatch, SSHCFG_ALL },
{ "permitopen", sPermitOpen, SSHCFG_ALL },
{ NULL, sBadOption, 0 }
};
@ -1148,6 +1151,28 @@ parse_flag:
*activep = value;
break;
case sPermitOpen:
arg = strdelim(&cp);
if (!arg || *arg == '\0')
fatal("%s line %d: missing PermitOpen specification",
filename, linenum);
if (strcmp(arg, "any") == 0) {
if (*activep)
channel_clear_adm_permitted_opens();
break;
}
p = hpdelim(&arg);
if (p == NULL)
fatal("%s line %d: missing host in PermitOpen",
filename, linenum);
p = cleanhostname(p);
if (arg == NULL || (port = a2port(arg)) == 0)
fatal("%s line %d: bad port number in PermitOpen",
filename, linenum);
if (*activep)
channel_add_adm_permitted_opens(p, port);
break;
case sDeprecated:
logit("%s line %d: Deprecated option %s",
filename, linenum, arg);

36
sshd_config.5
View File

@ -34,7 +34,7 @@
.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
.\"
.\" $OpenBSD: sshd_config.5,v 1.61 2006/07/12 13:39:55 jmc Exp $
.\" $OpenBSD: sshd_config.5,v 1.62 2006/07/17 12:06:00 dtucker Exp $
.Dd September 25, 1999
.Dt SSHD_CONFIG 5
.Os
@ -482,9 +482,10 @@ Only a subset of keywords may be used on the lines following a
.Cm Match
keyword.
Available keywords are
.Cm AllowTcpForwarding
.Cm AllowTcpForwarding ,
.Cm GatewayPorts ,
and
.Cm GatewayPorts .
.Cm PermitOpen .
.It Cm MaxAuthTries
Specifies the maximum number of authentication attempts permitted per
connection.
@ -524,6 +525,35 @@ When password authentication is allowed, it specifies whether the
server allows login to accounts with empty password strings.
The default is
.Dq no .
.It Cm PermitOpen
Specifies the destinations to which TCP port forwarding is permitted.
The forwarding specification must be one of the following forms:
.Pp
.Bl -item -offset indent -compact
.It
.Cm PermitOpen
.Sm off
.Ar host : port
.Sm on
.It
.Cm PermitOpen
.Sm off
.Ar IPv4_addr : port
.Sm on
.It
.Cm PermitOpen
.Sm off
.Ar \&[ IPv6_addr \&] : port
.Sm on
.El
.Pp
Multiple instances of
.Cm PermitOpen
are permitted.
An argument of
.Dq any
can be used to remove all restrictions and permit any forwarding requests.
By default all port forward requests are permitted.
.It Cm PermitRootLogin
Specifies whether root can log in using
.Xr ssh 1 .