diff options
| -rw-r--r-- | usr.bin/ssh/readconf.c | 12 | ||||
| -rw-r--r-- | usr.bin/ssh/readconf.h | 3 | ||||
| -rw-r--r-- | usr.bin/ssh/ssh.1 | 7 | ||||
| -rw-r--r-- | usr.bin/ssh/ssh.c | 92 | ||||
| -rw-r--r-- | usr.bin/ssh/ssh_config.5 | 24 |
5 files changed, 106 insertions, 32 deletions
diff --git a/usr.bin/ssh/readconf.c b/usr.bin/ssh/readconf.c index cacfef567de..2492ac6c3ed 100644 --- a/usr.bin/ssh/readconf.c +++ b/usr.bin/ssh/readconf.c @@ -12,7 +12,7 @@ */ #include "includes.h" -RCSID("$OpenBSD: readconf.c,v 1.122 2003/10/08 15:21:24 markus Exp $"); +RCSID("$OpenBSD: readconf.c,v 1.123 2003/10/11 08:24:07 markus Exp $"); #include "ssh.h" #include "xmalloc.h" @@ -89,7 +89,7 @@ RCSID("$OpenBSD: readconf.c,v 1.122 2003/10/08 15:21:24 markus Exp $"); typedef enum { oBadOption, - oForwardAgent, oForwardX11, oGatewayPorts, + oForwardAgent, oForwardX11, oForwardX11Trusted, oGatewayPorts, oPasswordAuthentication, oRSAAuthentication, oChallengeResponseAuthentication, oXAuthLocation, oIdentityFile, oHostName, oPort, oCipher, oRemoteForward, oLocalForward, @@ -116,6 +116,7 @@ static struct { } keywords[] = { { "forwardagent", oForwardAgent }, { "forwardx11", oForwardX11 }, + { "forwardx11trusted", oForwardX11Trusted }, { "xauthlocation", oXAuthLocation }, { "gatewayports", oGatewayPorts }, { "useprivilegedport", oUsePrivilegedPort }, @@ -340,6 +341,10 @@ parse_flag: intptr = &options->forward_x11; goto parse_flag; + case oForwardX11Trusted: + intptr = &options->forward_x11_trusted; + goto parse_flag; + case oGatewayPorts: intptr = &options->gateway_ports; goto parse_flag; @@ -804,6 +809,7 @@ initialize_options(Options * options) memset(options, 'X', sizeof(*options)); options->forward_agent = -1; options->forward_x11 = -1; + options->forward_x11_trusted = -1; options->xauth_location = NULL; options->gateway_ports = -1; options->use_privileged_port = -1; @@ -870,6 +876,8 @@ fill_default_options(Options * options) options->forward_agent = 0; if (options->forward_x11 == -1) options->forward_x11 = 0; + if (options->forward_x11_trusted == -1) + options->forward_x11_trusted = 0; if (options->xauth_location == NULL) options->xauth_location = _PATH_XAUTH; if (options->gateway_ports == -1) diff --git a/usr.bin/ssh/readconf.h b/usr.bin/ssh/readconf.h index 60287f710c4..8aab2e6066f 100644 --- a/usr.bin/ssh/readconf.h +++ b/usr.bin/ssh/readconf.h @@ -1,4 +1,4 @@ -/* $OpenBSD: readconf.h,v 1.55 2003/09/01 18:15:50 markus Exp $ */ +/* $OpenBSD: readconf.h,v 1.56 2003/10/11 08:24:08 markus Exp $ */ /* * Author: Tatu Ylonen <ylo@cs.hut.fi> @@ -30,6 +30,7 @@ typedef struct { typedef struct { int forward_agent; /* Forward authentication agent. */ int forward_x11; /* Forward X11 display. */ + int forward_x11_trusted; /* Trust Forward X11 display. */ char *xauth_location; /* Location for xauth program */ int gateway_ports; /* Allow remote connects to forwarded ports. */ int use_privileged_port; /* Don't use privileged port if false. */ diff --git a/usr.bin/ssh/ssh.1 b/usr.bin/ssh/ssh.1 index 2ba7fa6fdbb..10784153383 100644 --- a/usr.bin/ssh/ssh.1 +++ b/usr.bin/ssh/ssh.1 @@ -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: ssh.1,v 1.177 2003/10/08 08:27:36 jmc Exp $ +.\" $OpenBSD: ssh.1,v 1.178 2003/10/11 08:24:08 markus Exp $ .Dd September 25, 1999 .Dt SSH 1 .Os @@ -43,7 +43,7 @@ .Nd OpenSSH SSH client (remote login program) .Sh SYNOPSIS .Nm ssh -.Op Fl 1246AaCfgkNnqsTtVvXx +.Op Fl 1246AaCfgkNnqsTtVvXxY .Op Fl b Ar bind_address .Op Fl c Ar cipher_spec .Op Fl D Ar port @@ -624,6 +624,7 @@ For full details of the options listed below, and their possible values, see .It EscapeChar .It ForwardAgent .It ForwardX11 +.It ForwardX11Trusted .It GatewayPorts .It GlobalKnownHostsFile .It GSSAPIAuthentication @@ -732,6 +733,8 @@ can access the local X11 display through the forwarded connection. An attacker may then be able to perform activities such as keystroke monitoring. .It Fl x Disables X11 forwarding. +.It Fl Y +Enables trusted X11 forwarding. .El .Sh CONFIGURATION FILES .Nm diff --git a/usr.bin/ssh/ssh.c b/usr.bin/ssh/ssh.c index 941c0ae18ec..29729c60b69 100644 --- a/usr.bin/ssh/ssh.c +++ b/usr.bin/ssh/ssh.c @@ -13,7 +13,7 @@ * called by a name other than "ssh" or "Secure Shell". * * Copyright (c) 1999 Niels Provos. All rights reserved. - * Copyright (c) 2000, 2001, 2002 Markus Friedl. All rights reserved. + * Copyright (c) 2000, 2001, 2002, 2003 Markus Friedl. All rights reserved. * * Modified to work with SSL by Niels Provos <provos@citi.umich.edu> * in Canada (German citizen). @@ -40,7 +40,7 @@ */ #include "includes.h" -RCSID("$OpenBSD: ssh.c,v 1.201 2003/09/01 18:15:50 markus Exp $"); +RCSID("$OpenBSD: ssh.c,v 1.202 2003/10/11 08:24:08 markus Exp $"); #include <openssl/evp.h> #include <openssl/err.h> @@ -151,6 +151,7 @@ usage(void) fprintf(stderr, " -A Enable authentication agent forwarding.\n"); fprintf(stderr, " -a Disable authentication agent forwarding (default).\n"); fprintf(stderr, " -X Enable X11 connection forwarding.\n"); + fprintf(stderr, " -Y Enable trusted X11 connection forwarding.\n"); fprintf(stderr, " -x Disable X11 connection forwarding (default).\n"); fprintf(stderr, " -i file Identity for public key authentication " "(default: ~/.ssh/identity)\n"); @@ -255,7 +256,7 @@ main(int ac, char **av) again: while ((opt = getopt(ac, av, - "1246ab:c:e:fgi:kl:m:no:p:qstvxACD:F:I:L:NPR:TVX")) != -1) { + "1246ab:c:e:fgi:kl:m:no:p:qstvxACD:F:I:L:NPR:TVXY")) != -1) { switch (opt) { case '1': options.protocol = SSH_PROTO_1; @@ -282,6 +283,10 @@ again: case 'X': options.forward_x11 = 1; break; + case 'Y': + options.forward_x11 = 1; + options.forward_x11_trusted = 1; + break; case 'g': options.gateway_ports = 1; break; @@ -706,19 +711,25 @@ again: return exit_status; } +#define SSH_X11_PROTO "MIT-MAGIC-COOKIE-1" + static void x11_get_proto(char **_proto, char **_data) { + char cmd[1024]; char line[512]; + char xdisplay[512]; static char proto[512], data[512]; FILE *f; - int got_data = 0, i; - char *display; + int got_data = 0, generated = 0, do_unlink = 0, i; + char *display, *xauthdir, *xauthfile; struct stat st; + xauthdir = xauthfile = NULL; *_proto = proto; *_data = data; proto[0] = data[0] = '\0'; + if (!options.xauth_location || (stat(options.xauth_location, &st) == -1)) { debug("No xauth program."); @@ -727,28 +738,59 @@ x11_get_proto(char **_proto, char **_data) debug("x11_get_proto: DISPLAY not set"); return; } - /* Try to get Xauthority information for the display. */ - if (strncmp(display, "localhost:", 10) == 0) - /* - * Handle FamilyLocal case where $DISPLAY does - * not match an authorization entry. For this we - * just try "xauth list unix:displaynum.screennum". - * XXX: "localhost" match to determine FamilyLocal - * is not perfect. - */ - snprintf(line, sizeof line, "%s list unix:%s 2>" - _PATH_DEVNULL, options.xauth_location, display+10); - else - snprintf(line, sizeof line, "%s list %.200s 2>" - _PATH_DEVNULL, options.xauth_location, display); - debug2("x11_get_proto: %s", line); - f = popen(line, "r"); + /* + * Handle FamilyLocal case where $DISPLAY does + * not match an authorization entry. For this we + * just try "xauth list unix:displaynum.screennum". + * XXX: "localhost" match to determine FamilyLocal + * is not perfect. + */ + if (strncmp(display, "localhost:", 10) == 0) { + snprintf(xdisplay, sizeof(xdisplay), "unix:%s", + display + 10); + display = xdisplay; + } + if (options.forward_x11_trusted == 0) { + xauthdir = xmalloc(MAXPATHLEN); + xauthfile = xmalloc(MAXPATHLEN); + strlcpy(xauthdir, "/tmp/ssh-XXXXXXXXXX", MAXPATHLEN); + if (mkdtemp(xauthdir) != NULL) { + do_unlink = 1; + snprintf(xauthfile, MAXPATHLEN, "%s/xauthfile", + xauthdir); + snprintf(cmd, sizeof(cmd), + "%s -f %s generate %s " SSH_X11_PROTO + " untrusted timeout 120 2>" _PATH_DEVNULL, + options.xauth_location, xauthfile, display); + debug2("x11_get_proto: %s", cmd); + if (system(cmd) == 0) + generated = 1; + } + } + snprintf(cmd, sizeof(cmd), + "%s %s%s list %s . 2>" _PATH_DEVNULL, + options.xauth_location, + generated ? "-f " : "" , + generated ? xauthfile : "", + display); + debug2("x11_get_proto: %s", cmd); + f = popen(cmd, "r"); if (f && fgets(line, sizeof(line), f) && sscanf(line, "%*s %511s %511s", proto, data) == 2) got_data = 1; if (f) pclose(f); } + + if (do_unlink) { + unlink(xauthfile); + rmdir(xauthdir); + } + if (xauthdir) + xfree(xauthdir); + if (xauthfile) + xfree(xauthfile); + /* * If we didn't get authentication data, just make up some * data. The forwarding code will check the validity of the @@ -760,12 +802,14 @@ x11_get_proto(char **_proto, char **_data) if (!got_data) { u_int32_t rand = 0; - logit("Warning: No xauth data; using fake authentication data for X11 forwarding."); - strlcpy(proto, "MIT-MAGIC-COOKIE-1", sizeof proto); + logit("Warning: No xauth data; " + "using fake authentication data for X11 forwarding."); + strlcpy(proto, SSH_X11_PROTO, sizeof proto); for (i = 0; i < 16; i++) { if (i % 4 == 0) rand = arc4random(); - snprintf(data + 2 * i, sizeof data - 2 * i, "%02x", rand & 0xff); + snprintf(data + 2 * i, sizeof data - 2 * i, "%02x", + rand & 0xff); rand >>= 8; } } diff --git a/usr.bin/ssh/ssh_config.5 b/usr.bin/ssh/ssh_config.5 index da162499b85..7f3c7064a15 100644 --- a/usr.bin/ssh/ssh_config.5 +++ b/usr.bin/ssh/ssh_config.5 @@ -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: ssh_config.5,v 1.21 2003/10/08 15:21:24 markus Exp $ +.\" $OpenBSD: ssh_config.5,v 1.22 2003/10/11 08:24:08 markus Exp $ .Dd September 25, 1999 .Dt SSH_CONFIG 5 .Os @@ -306,9 +306,27 @@ The default is .Pp X11 forwarding should be enabled with caution. Users with the ability to bypass file permissions on the remote host -(for the user's X authorization database) +(for the user's X11 authorization database) can access the local X11 display through the forwarded connection. -An attacker may then be able to perform activities such as keystroke monitoring. +An attacker may then be able to perform activities such as keystroke monitoring +if the +.Cm ForwardX11Trusted +option is also enabled. +.It Cm ForwardX11Trusted +If the this option is set to +.Dq yes +then remote X11 clients will have full access to the original X11 display. +If this option is set to +.Dq no +then remote X11 clients will be considered untrusted and prevented +from stealing or tampering with data belonging to trusted X11 +clients. +.Pp +The default is +.Dq no . +.Pp +See the X11 SECURITY extension specification for full details on +the restrictions imposed on untrusted clients. .It Cm GatewayPorts Specifies whether remote hosts are allowed to connect to local forwarded ports. |