| diff -up openssh-7.4p1/channels.c.x11max openssh-7.4p1/channels.c |
| |
| |
| @@ -152,8 +152,8 @@ static int all_opens_permitted = 0; |
| #define FWD_PERMIT_ANY_HOST "*" |
| |
| /* -- X11 forwarding */ |
| -/* Maximum number of fake X11 displays to try. */ |
| -#define MAX_DISPLAYS 1000 |
| +/* Minimum port number for X11 forwarding */ |
| +#define X11_PORT_MIN 6000 |
| |
| /* Per-channel callback for pre/post select() actions */ |
| typedef void chan_fn(struct ssh *, Channel *c, |
| @@ -4228,7 +4228,7 @@ channel_send_window_changes(void) |
| */ |
| int |
| x11_create_display_inet(struct ssh *ssh, int x11_display_offset, |
| - int x11_use_localhost, int single_connection, |
| + int x11_use_localhost, int x11_max_displays, int single_connection, |
| u_int *display_numberp, int **chanids) |
| { |
| Channel *nc = NULL; |
| @@ -4240,10 +4241,15 @@ x11_create_display_inet(int x11_display_ |
| 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; |
| + port = X11_PORT_MIN + display_number; |
| + if (port < X11_PORT_MIN) /* overflow */ |
| + break; |
| memset(&hints, 0, sizeof(hints)); |
| hints.ai_family = ssh->chanctxt->IPv4or6; |
| hints.ai_flags = x11_use_localhost ? 0: AI_PASSIVE; |
| @@ -4295,7 +4301,7 @@ x11_create_display_inet(int x11_display_ |
| if (num_socks > 0) |
| break; |
| } |
| - if (display_number >= MAX_DISPLAYS) { |
| + if (display_number >= x11_max_displays || port < X11_PORT_MIN ) { |
| error("Failed to allocate internet-domain X11 display socket."); |
| return -1; |
| } |
| @@ -4441,7 +4447,7 @@ x11_connect_display(void) |
| memset(&hints, 0, sizeof(hints)); |
| hints.ai_family = ssh->chanctxt->IPv4or6; |
| hints.ai_socktype = SOCK_STREAM; |
| - snprintf(strport, sizeof strport, "%u", 6000 + display_number); |
| + snprintf(strport, sizeof strport, "%u", X11_PORT_MIN + display_number); |
| if ((gaierr = getaddrinfo(buf, strport, &hints, &aitop)) != 0) { |
| error("%.100s: unknown host. (%s)", buf, |
| ssh_gai_strerror(gaierr)); |
| @@ -4457,7 +4463,7 @@ x11_connect_display(void) |
| /* Connect it to the display. */ |
| if (connect(sock, ai->ai_addr, ai->ai_addrlen) == -1) { |
| debug2("connect %.100s port %u: %.100s", buf, |
| - 6000 + display_number, strerror(errno)); |
| + X11_PORT_MIN + display_number, strerror(errno)); |
| close(sock); |
| continue; |
| } |
| @@ -4466,8 +4472,8 @@ x11_connect_display(void) |
| } |
| freeaddrinfo(aitop); |
| if (!ai) { |
| - error("connect %.100s port %u: %.100s", buf, |
| - 6000 + display_number, strerror(errno)); |
| + error("connect %.100s port %u: %.100s", buf, |
| + X11_PORT_MIN + display_number, strerror(errno)); |
| return -1; |
| } |
| set_nodelay(sock); |
| diff -up openssh-7.4p1/channels.h.x11max openssh-7.4p1/channels.h |
| |
| |
| @@ -293,7 +293,7 @@ int permitopen_port(const char *); |
| |
| void channel_set_x11_refuse_time(struct ssh *, u_int); |
| int x11_connect_display(struct ssh *); |
| -int x11_create_display_inet(struct ssh *, int, int, int, u_int *, int **); |
| +int x11_create_display_inet(struct ssh *, int, int, int, int, u_int *, int **); |
| void x11_request_forwarding_with_spoofing(struct ssh *, int, |
| const char *, const char *, const char *, int); |
| |
| diff -up openssh-7.4p1/servconf.c.x11max openssh-7.4p1/servconf.c |
| |
| |
| @@ -95,6 +95,7 @@ initialize_server_options(ServerOptions |
| 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; |
| @@ -243,6 +244,8 @@ fill_default_server_options(ServerOption |
| 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) |
| @@ -419,7 +422,7 @@ typedef enum { |
| sPasswordAuthentication, sKbdInteractiveAuthentication, |
| sListenAddress, sAddressFamily, |
| sPrintMotd, sPrintLastLog, sIgnoreRhosts, |
| - sX11Forwarding, sX11DisplayOffset, sX11UseLocalhost, |
| + sX11Forwarding, sX11DisplayOffset, sX11MaxDisplays, sX11UseLocalhost, |
| sPermitTTY, sStrictModes, sEmptyPasswd, sTCPKeepAlive, |
| sPermitUserEnvironment, sAllowTcpForwarding, sCompression, |
| sRekeyLimit, sAllowUsers, sDenyUsers, sAllowGroups, sDenyGroups, |
| @@ -540,6 +543,7 @@ 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 }, |
| @@ -1316,6 +1320,10 @@ process_server_config_line(ServerOptions |
| *intptr = value; |
| break; |
| |
| + case sX11MaxDisplays: |
| + intptr = &options->x11_max_displays; |
| + goto parse_int; |
| + |
| case sX11UseLocalhost: |
| intptr = &options->x11_use_localhost; |
| goto parse_flag; |
| @@ -2063,6 +2071,7 @@ copy_set_server_options(ServerOptions *d |
| M_CP_INTOPT(fwd_opts.streamlocal_bind_unlink); |
| M_CP_INTOPT(x11_display_offset); |
| M_CP_INTOPT(x11_forwarding); |
| + M_CP_INTOPT(x11_max_displays); |
| M_CP_INTOPT(x11_use_localhost); |
| M_CP_INTOPT(permit_tty); |
| M_CP_INTOPT(permit_user_rc); |
| @@ -2315,6 +2324,7 @@ dump_config(ServerOptions *o) |
| #endif |
| dump_cfg_int(sLoginGraceTime, o->login_grace_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 -up openssh-7.4p1/servconf.h.x11max openssh-7.4p1/servconf.h |
| |
| |
| @@ -55,6 +55,7 @@ |
| |
| #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" |
| @@ -85,6 +86,7 @@ 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 -up openssh-7.4p1/session.c.x11max openssh-7.4p1/session.c |
| |
| |
| @@ -2518,8 +2518,9 @@ session_setup_x11fwd(Session *s) |
| return 0; |
| } |
| if (x11_create_display_inet(ssh, 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 -up openssh-7.4p1/sshd_config.5.x11max openssh-7.4p1/sshd_config.5 |
| |
| |
| @@ -1133,6 +1133,7 @@ Available keywords are |
| .Cm StreamLocalBindUnlink , |
| .Cm TrustedUserCAKeys , |
| .Cm X11DisplayOffset , |
| +.Cm X11MaxDisplays , |
| .Cm X11Forwarding |
| and |
| .Cm X11UseLocalhost . |
| @@ -1566,6 +1567,12 @@ Specifies the first display number avail |
| 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 |