Attachment 2825 Details for Bug 2580 – Updated X11MaxDisplays patch w/documentation and fixed whitespace

[patch] Updated X11MaxDisplays patch w/documentation and fixed whitespace

x11maxdisplays-20160604-final.patch (text/plain), 7.72 KB, created by AG on 2016-06-05 09:22:34 AEST

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Creator: AG

Created: 2016-06-05 09:22:34 AEST

Size: 7.72 KB

patch

obsolete

>From c04c96537871188bd44666bb93b36db010f540ef Mon Sep 17 00:00:00 2001
>From: Adam Greene <agreene5@bloomberg.net>
>Date: Sat, 4 Jun 2016 19:11:48 -0400
>Subject: [PATCH] Removed MAX_DISPLAYS Added X11MaxDisplays option
>
>This option allows sshd_config to override the hardcoded limit on
>X11 forwards. This value was previously set at 1000. It will now
>stay at 1000 by default, but can be set by the user if they need
>more than 1000 active displays. This is useful on gateway/jump boxes
>where a system acts as a chokepoint and provides X11 to a large
>amount of users.
>---
> channels.c    | 15 +++++++++------
> channels.h    |  2 +-
> servconf.c    | 12 +++++++++++-
> servconf.h    |  2 ++
> session.c     |  5 +++--
> sshd_config.5 |  7 +++++++
> 6 files changed, 33 insertions(+), 10 deletions(-)
>
>diff --git a/channels.c b/channels.c
>index 7ee1f98..b883de2 100644
>--- a/channels.c
>+++ b/channels.c
>@@ -148,9 +148,6 @@ static int all_opens_permitted = 0;
> 
> /* -- X11 forwarding */
> 
>-/* Maximum number of fake X11 displays to try. */
>-#define MAX_DISPLAYS  1000
>-
> /* Saved X11 local (client) display. */
> static char *x11_saved_display = NULL;
> 
>@@ -3890,7 +3887,8 @@ channel_send_window_changes(void)
>  */
> int
> x11_create_display_inet(int x11_display_offset, int x11_use_localhost,
>-    int single_connection, u_int *display_numberp, int **chanids)
>+	int x11_max_displays, int single_connection, u_int *display_numberp,
>+	int **chanids)
> {
> 	Channel *nc = NULL;
> 	int display_number, sock;
>@@ -3902,10 +3900,15 @@ x11_create_display_inet(int x11_display_offset, int x11_use_localhost,
> 	if (chanids == NULL)
> 		return -1;
> 
>+	/* Try to bind ports starting at 6000+X11DisplayOffset */
>+	x11_max_displays = x11_max_displays + x11_display_offset;
>+
> 	for (display_number = x11_display_offset;
>-	    display_number < MAX_DISPLAYS;
>+	    display_number < x11_max_displays;
> 	    display_number++) {
> 		port = 6000 + display_number;
>+		if (port < 6000) /* overflow */
>+			break;
> 		memset(&hints, 0, sizeof(hints));
> 		hints.ai_family = IPv4or6;
> 		hints.ai_flags = x11_use_localhost ? 0: AI_PASSIVE;
>@@ -3957,7 +3960,7 @@ x11_create_display_inet(int x11_display_offset, int x11_use_localhost,
> 		if (num_socks > 0)
> 			break;
> 	}
>-	if (display_number >= MAX_DISPLAYS) {
>+	if (display_number >= x11_max_displays || port < 6000 ) {
> 		error("Failed to allocate internet-domain X11 display socket.");
> 		return -1;
> 	}
>diff --git a/channels.h b/channels.h
>index 9d76c9d..338a082 100644
>--- a/channels.h
>+++ b/channels.h
>@@ -286,7 +286,7 @@ int	 permitopen_port(const char *);
> 
> void	 channel_set_x11_refuse_time(u_int);
> int	 x11_connect_display(void);
>-int	 x11_create_display_inet(int, int, int, u_int *, int **);
>+int	 x11_create_display_inet(int, int, int, int, u_int *, int **);
> int      x11_input_open(int, u_int32_t, void *);
> void	 x11_request_forwarding_with_spoofing(int, const char *, const char *,
> 	     const char *, int);
>diff --git a/servconf.c b/servconf.c
>index 1cb45f5..0fbbfef 100644
>--- a/servconf.c
>+++ b/servconf.c
>@@ -96,6 +96,7 @@ initialize_server_options(ServerOptions *options)
> 	options->print_lastlog = -1;
> 	options->x11_forwarding = -1;
> 	options->x11_display_offset = -1;
>+	options->x11_max_displays = -1;
> 	options->x11_use_localhost = -1;
> 	options->permit_tty = -1;
> 	options->permit_user_rc = -1;
>@@ -251,6 +252,8 @@ fill_default_server_options(ServerOptions *options)
> 		options->x11_forwarding = 0;
> 	if (options->x11_display_offset == -1)
> 		options->x11_display_offset = 10;
>+	if (options->x11_max_displays == -1)
>+		options->x11_max_displays = DEFAULT_MAX_DISPLAYS;
> 	if (options->x11_use_localhost == -1)
> 		options->x11_use_localhost = 1;
> 	if (options->xauth_location == NULL)
>@@ -407,7 +410,7 @@ typedef enum {
> 	sPasswordAuthentication, sKbdInteractiveAuthentication,
> 	sListenAddress, sAddressFamily,
> 	sPrintMotd, sPrintLastLog, sIgnoreRhosts,
>-	sX11Forwarding, sX11DisplayOffset, sX11UseLocalhost,
>+	sX11Forwarding, sX11DisplayOffset, sX11MaxDisplays, sX11UseLocalhost,
> 	sPermitTTY, sStrictModes, sEmptyPasswd, sTCPKeepAlive,
> 	sPermitUserEnvironment, sUseLogin, sAllowTcpForwarding, sCompression,
> 	sRekeyLimit, sAllowUsers, sDenyUsers, sAllowGroups, sDenyGroups,
>@@ -515,6 +518,7 @@ static struct {
> 	{ "ignoreuserknownhosts", sIgnoreUserKnownHosts, SSHCFG_GLOBAL },
> 	{ "x11forwarding", sX11Forwarding, SSHCFG_ALL },
> 	{ "x11displayoffset", sX11DisplayOffset, SSHCFG_ALL },
>+	{ "x11maxdisplays", sX11MaxDisplays, SSHCFG_ALL },
> 	{ "x11uselocalhost", sX11UseLocalhost, SSHCFG_ALL },
> 	{ "xauthlocation", sXAuthLocation, SSHCFG_GLOBAL },
> 	{ "strictmodes", sStrictModes, SSHCFG_GLOBAL },
>@@ -1279,6 +1283,10 @@ process_server_config_line(ServerOptions *options, char *line,
> 		intptr = &options->x11_display_offset;
> 		goto parse_int;
> 
>+	case sX11MaxDisplays:
>+		intptr = &options->x11_max_displays;
>+		goto parse_int;
>+
> 	case sX11UseLocalhost:
> 		intptr = &options->x11_use_localhost;
> 		goto parse_flag;
>@@ -1996,6 +2004,7 @@ copy_set_server_options(ServerOptions *dst, ServerOptions *src, int preauth)
> 	M_CP_INTOPT(fwd_opts.gateway_ports);
> 	M_CP_INTOPT(fwd_opts.streamlocal_bind_unlink);
> 	M_CP_INTOPT(x11_display_offset);
>+	M_CP_INTOPT(x11_max_displays);
> 	M_CP_INTOPT(x11_forwarding);
> 	M_CP_INTOPT(x11_use_localhost);
> 	M_CP_INTOPT(permit_tty);
>@@ -2252,6 +2261,7 @@ dump_config(ServerOptions *o)
> 	dump_cfg_int(sLoginGraceTime, o->login_grace_time);
> 	dump_cfg_int(sKeyRegenerationTime, o->key_regeneration_time);
> 	dump_cfg_int(sX11DisplayOffset, o->x11_display_offset);
>+	dump_cfg_int(sX11MaxDisplays, o->x11_max_displays);
> 	dump_cfg_int(sMaxAuthTries, o->max_authtries);
> 	dump_cfg_int(sMaxSessions, o->max_sessions);
> 	dump_cfg_int(sClientAliveInterval, o->client_alive_interval);
>diff --git a/servconf.h b/servconf.h
>index f4137af..8362e81 100644
>--- a/servconf.h
>+++ b/servconf.h
>@@ -50,6 +50,7 @@
> 
> #define DEFAULT_AUTH_FAIL_MAX	6	/* Default for MaxAuthTries */
> #define DEFAULT_SESSIONS_MAX	10	/* Default for MaxSessions */
>+#define DEFAULT_MAX_DISPLAYS	1000 /* Maximum number of fake X11 displays to try. */
> 
> /* Magic name for internal sftp-server */
> #define INTERNAL_SFTP_NAME	"internal-sftp"
>@@ -82,6 +83,7 @@ typedef struct {
> 	int     x11_forwarding;	/* If true, permit inet (spoofing) X11 fwd. */
> 	int     x11_display_offset;	/* What DISPLAY number to start
> 					 * searching at */
>+	int 	x11_max_displays; /* Number of displays to search */
> 	int     x11_use_localhost;	/* If true, use localhost for fake X11 server. */
> 	char   *xauth_location;	/* Location of xauth program */
> 	int	permit_tty;	/* If false, deny pty allocation */
>diff --git a/session.c b/session.c
>index 4653b09..e6f7daa 100644
>--- a/session.c
>+++ b/session.c
>@@ -2701,8 +2701,9 @@ session_setup_x11fwd(Session *s)
> 		return 0;
> 	}
> 	if (x11_create_display_inet(options.x11_display_offset,
>-	    options.x11_use_localhost, s->single_connection,
>-	    &s->display_number, &s->x11_chanids) == -1) {
>+	    options.x11_use_localhost, options.x11_max_displays,
>+	    s->single_connection, &s->display_number, 
>+	    &s->x11_chanids) == -1) {
> 		debug("x11_create_display_inet failed.");
> 		return 0;
> 	}
>diff --git a/sshd_config.5 b/sshd_config.5
>index 479fa38..fefcc24 100644
>--- a/sshd_config.5
>+++ b/sshd_config.5
>@@ -1128,6 +1128,7 @@ Available keywords are
> .Cm StreamLocalBindUnlink ,
> .Cm TrustedUserCAKeys ,
> .Cm X11DisplayOffset ,
>+.Cm X11MaxDisplays ,
> .Cm X11Forwarding
> and
> .Cm X11UseLocalHost .
>@@ -1621,6 +1622,12 @@ Specifies the first display number available for
> X11 forwarding.
> This prevents sshd from interfering with real X11 servers.
> The default is 10.
>+.It Cm X11MaxDisplays
>+Specifies the maximum number of displays available for
>+.Xr sshd 8 Ns 's
>+X11 forwarding.
>+This prevents sshd from exhausting local ports.
>+The default is 1000.
> .It Cm X11Forwarding
> Specifies whether X11 forwarding is permitted.
> The argument must be
>-- 
>2.1.4
>

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