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214 lines
8.6 KiB
214 lines
8.6 KiB
2 years ago
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diff -up openssh-7.4p1/channels.c.x11max openssh-7.4p1/channels.c
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--- openssh-7.4p1/channels.c.x11max 2016-12-23 15:46:32.071506625 +0100
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+++ openssh-7.4p1/channels.c 2016-12-23 15:46:32.139506636 +0100
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@@ -152,8 +152,8 @@ static int all_opens_permitted = 0;
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#define FWD_PERMIT_ANY_HOST "*"
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/* -- X11 forwarding */
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-/* Maximum number of fake X11 displays to try. */
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-#define MAX_DISPLAYS 1000
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+/* Minimum port number for X11 forwarding */
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+#define X11_PORT_MIN 6000
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/* Per-channel callback for pre/post select() actions */
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typedef void chan_fn(struct ssh *, Channel *c,
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@@ -4228,7 +4228,7 @@ channel_send_window_changes(void)
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*/
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int
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x11_create_display_inet(struct ssh *ssh, int x11_display_offset,
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- int x11_use_localhost, int single_connection,
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+ int x11_use_localhost, int x11_max_displays, int single_connection,
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u_int *display_numberp, int **chanids)
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{
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Channel *nc = NULL;
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@@ -4240,10 +4241,15 @@ x11_create_display_inet(int x11_display_
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if (chanids == NULL)
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return -1;
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+ /* Try to bind ports starting at 6000+X11DisplayOffset */
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+ x11_max_displays = x11_max_displays + x11_display_offset;
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+
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for (display_number = x11_display_offset;
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- display_number < MAX_DISPLAYS;
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+ display_number < x11_max_displays;
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display_number++) {
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- port = 6000 + display_number;
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+ port = X11_PORT_MIN + display_number;
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+ if (port < X11_PORT_MIN) /* overflow */
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+ break;
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memset(&hints, 0, sizeof(hints));
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hints.ai_family = ssh->chanctxt->IPv4or6;
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hints.ai_flags = x11_use_localhost ? 0: AI_PASSIVE;
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@@ -4295,7 +4301,7 @@ x11_create_display_inet(int x11_display_
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if (num_socks > 0)
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break;
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}
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- if (display_number >= MAX_DISPLAYS) {
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+ if (display_number >= x11_max_displays || port < X11_PORT_MIN ) {
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error("Failed to allocate internet-domain X11 display socket.");
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return -1;
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}
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@@ -4441,7 +4447,7 @@ x11_connect_display(void)
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memset(&hints, 0, sizeof(hints));
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hints.ai_family = ssh->chanctxt->IPv4or6;
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hints.ai_socktype = SOCK_STREAM;
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- snprintf(strport, sizeof strport, "%u", 6000 + display_number);
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+ snprintf(strport, sizeof strport, "%u", X11_PORT_MIN + display_number);
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if ((gaierr = getaddrinfo(buf, strport, &hints, &aitop)) != 0) {
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error("%.100s: unknown host. (%s)", buf,
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ssh_gai_strerror(gaierr));
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@@ -4457,7 +4463,7 @@ x11_connect_display(void)
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/* Connect it to the display. */
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if (connect(sock, ai->ai_addr, ai->ai_addrlen) == -1) {
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debug2("connect %.100s port %u: %.100s", buf,
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- 6000 + display_number, strerror(errno));
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+ X11_PORT_MIN + display_number, strerror(errno));
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close(sock);
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continue;
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}
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@@ -4466,8 +4472,8 @@ x11_connect_display(void)
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}
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freeaddrinfo(aitop);
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if (!ai) {
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- error("connect %.100s port %u: %.100s", buf,
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- 6000 + display_number, strerror(errno));
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+ error("connect %.100s port %u: %.100s", buf,
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+ X11_PORT_MIN + display_number, strerror(errno));
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return -1;
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}
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set_nodelay(sock);
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diff -up openssh-7.4p1/channels.h.x11max openssh-7.4p1/channels.h
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--- openssh-7.4p1/channels.h.x11max 2016-12-19 05:59:41.000000000 +0100
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+++ openssh-7.4p1/channels.h 2016-12-23 15:46:32.139506636 +0100
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@@ -293,7 +293,7 @@ int permitopen_port(const char *);
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void channel_set_x11_refuse_time(struct ssh *, u_int);
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int x11_connect_display(struct ssh *);
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-int x11_create_display_inet(struct ssh *, int, int, int, u_int *, int **);
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+int x11_create_display_inet(struct ssh *, int, int, int, int, u_int *, int **);
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void x11_request_forwarding_with_spoofing(struct ssh *, int,
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const char *, const char *, const char *, int);
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diff -up openssh-7.4p1/servconf.c.x11max openssh-7.4p1/servconf.c
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--- openssh-7.4p1/servconf.c.x11max 2016-12-23 15:46:32.133506635 +0100
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+++ openssh-7.4p1/servconf.c 2016-12-23 15:47:27.320519121 +0100
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@@ -95,6 +95,7 @@ initialize_server_options(ServerOptions
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options->print_lastlog = -1;
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options->x11_forwarding = -1;
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options->x11_display_offset = -1;
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+ options->x11_max_displays = -1;
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options->x11_use_localhost = -1;
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options->permit_tty = -1;
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options->permit_user_rc = -1;
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@@ -243,6 +244,8 @@ fill_default_server_options(ServerOption
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options->x11_forwarding = 0;
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if (options->x11_display_offset == -1)
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options->x11_display_offset = 10;
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+ if (options->x11_max_displays == -1)
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+ options->x11_max_displays = DEFAULT_MAX_DISPLAYS;
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if (options->x11_use_localhost == -1)
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options->x11_use_localhost = 1;
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if (options->xauth_location == NULL)
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@@ -419,7 +422,7 @@ typedef enum {
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sPasswordAuthentication, sKbdInteractiveAuthentication,
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sListenAddress, sAddressFamily,
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sPrintMotd, sPrintLastLog, sIgnoreRhosts,
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- sX11Forwarding, sX11DisplayOffset, sX11UseLocalhost,
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+ sX11Forwarding, sX11DisplayOffset, sX11MaxDisplays, sX11UseLocalhost,
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sPermitTTY, sStrictModes, sEmptyPasswd, sTCPKeepAlive,
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sPermitUserEnvironment, sAllowTcpForwarding, sCompression,
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sRekeyLimit, sAllowUsers, sDenyUsers, sAllowGroups, sDenyGroups,
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@@ -540,6 +543,7 @@ static struct {
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{ "ignoreuserknownhosts", sIgnoreUserKnownHosts, SSHCFG_GLOBAL },
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{ "x11forwarding", sX11Forwarding, SSHCFG_ALL },
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{ "x11displayoffset", sX11DisplayOffset, SSHCFG_ALL },
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+ { "x11maxdisplays", sX11MaxDisplays, SSHCFG_ALL },
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{ "x11uselocalhost", sX11UseLocalhost, SSHCFG_ALL },
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{ "xauthlocation", sXAuthLocation, SSHCFG_GLOBAL },
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{ "strictmodes", sStrictModes, SSHCFG_GLOBAL },
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@@ -1316,6 +1320,10 @@ process_server_config_line(ServerOptions
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*intptr = value;
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break;
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+ case sX11MaxDisplays:
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+ intptr = &options->x11_max_displays;
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+ goto parse_int;
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+
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case sX11UseLocalhost:
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intptr = &options->x11_use_localhost;
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goto parse_flag;
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@@ -2063,6 +2071,7 @@ copy_set_server_options(ServerOptions *d
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M_CP_INTOPT(fwd_opts.streamlocal_bind_unlink);
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M_CP_INTOPT(x11_display_offset);
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M_CP_INTOPT(x11_forwarding);
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+ M_CP_INTOPT(x11_max_displays);
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M_CP_INTOPT(x11_use_localhost);
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M_CP_INTOPT(permit_tty);
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M_CP_INTOPT(permit_user_rc);
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@@ -2315,6 +2324,7 @@ dump_config(ServerOptions *o)
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#endif
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dump_cfg_int(sLoginGraceTime, o->login_grace_time);
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dump_cfg_int(sX11DisplayOffset, o->x11_display_offset);
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+ dump_cfg_int(sX11MaxDisplays, o->x11_max_displays);
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dump_cfg_int(sMaxAuthTries, o->max_authtries);
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dump_cfg_int(sMaxSessions, o->max_sessions);
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dump_cfg_int(sClientAliveInterval, o->client_alive_interval);
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diff -up openssh-7.4p1/servconf.h.x11max openssh-7.4p1/servconf.h
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--- openssh-7.4p1/servconf.h.x11max 2016-12-23 15:46:32.133506635 +0100
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+++ openssh-7.4p1/servconf.h 2016-12-23 15:46:32.140506636 +0100
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@@ -55,6 +55,7 @@
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#define DEFAULT_AUTH_FAIL_MAX 6 /* Default for MaxAuthTries */
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#define DEFAULT_SESSIONS_MAX 10 /* Default for MaxSessions */
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+#define DEFAULT_MAX_DISPLAYS 1000 /* Maximum number of fake X11 displays to try. */
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/* Magic name for internal sftp-server */
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#define INTERNAL_SFTP_NAME "internal-sftp"
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@@ -85,6 +86,7 @@ typedef struct {
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int x11_forwarding; /* If true, permit inet (spoofing) X11 fwd. */
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int x11_display_offset; /* What DISPLAY number to start
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* searching at */
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+ int x11_max_displays; /* Number of displays to search */
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int x11_use_localhost; /* If true, use localhost for fake X11 server. */
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char *xauth_location; /* Location of xauth program */
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int permit_tty; /* If false, deny pty allocation */
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diff -up openssh-7.4p1/session.c.x11max openssh-7.4p1/session.c
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--- openssh-7.4p1/session.c.x11max 2016-12-23 15:46:32.136506636 +0100
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+++ openssh-7.4p1/session.c 2016-12-23 15:46:32.141506636 +0100
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@@ -2518,8 +2518,9 @@ session_setup_x11fwd(Session *s)
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return 0;
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}
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if (x11_create_display_inet(ssh, options.x11_display_offset,
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- options.x11_use_localhost, s->single_connection,
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- &s->display_number, &s->x11_chanids) == -1) {
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+ options.x11_use_localhost, options.x11_max_displays,
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+ s->single_connection, &s->display_number,
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+ &s->x11_chanids) == -1) {
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debug("x11_create_display_inet failed.");
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return 0;
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}
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diff -up openssh-7.4p1/sshd_config.5.x11max openssh-7.4p1/sshd_config.5
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--- openssh-7.4p1/sshd_config.5.x11max 2016-12-23 15:46:32.134506635 +0100
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+++ openssh-7.4p1/sshd_config.5 2016-12-23 15:46:32.141506636 +0100
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@@ -1133,6 +1133,7 @@ Available keywords are
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.Cm StreamLocalBindUnlink ,
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.Cm TrustedUserCAKeys ,
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.Cm X11DisplayOffset ,
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+.Cm X11MaxDisplays ,
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.Cm X11Forwarding
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and
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.Cm X11UseLocalhost .
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@@ -1566,6 +1567,12 @@ Specifies the first display number avail
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X11 forwarding.
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This prevents sshd from interfering with real X11 servers.
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The default is 10.
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+.It Cm X11MaxDisplays
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+Specifies the maximum number of displays available for
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+.Xr sshd 8 Ns 's
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+X11 forwarding.
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+This prevents sshd from exhausting local ports.
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+The default is 1000.
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.It Cm X11Forwarding
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Specifies whether X11 forwarding is permitted.
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The argument must be
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