Add a Seat vtable method to get a stripctrl.

If centralised code like the SSH implementation wants to sanitise
escape sequences out of a piece of server-provided text, it will need
to do it by making a locale-based StripCtrlChars if it's running in a
console context, or a Terminal-based one if it's in a GUI terminal-
window application.

All the other changes of behaviour needed between those two contexts
are handled by providing reconfigurable methods in the Seat vtable;
this one is no different. So now there's a new method in the Seat
vtable that will construct a StripCtrlChars appropriate to that kind
of seat. Terminal-window seats (gtkwin.c, window.c) implement it by
calling the new stripctrl_new_term(), and console ones use the locale-
based stripctrl_new().

misc.c

@@ -333,6 +333,8 @@ const char *nullseat_get_x_display(Seat *seat) { return NULL; }
 bool nullseat_get_windowid(Seat *seat, long *id_out) { return false; }
 bool nullseat_get_window_pixel_size(
     Seat *seat, int *width, int *height) { return false; }
+StripCtrlChars *nullseat_stripctrl_new(
+    Seat *seat, BinarySink *bs, bool cr, wchar_t sub) { return NULL; }
 
 void sk_free_peer_info(SocketPeerInfo *pi)
 {

pscp.c

@@ -80,6 +80,7 @@ static const SeatVtable pscp_seat_vt = {
     nullseat_get_x_display,
     nullseat_get_windowid,
     nullseat_get_window_pixel_size,
+    console_stripctrl_new,
 };
 static Seat pscp_seat[1] = {{ &pscp_seat_vt }};
 

psftp.c

@@ -61,6 +61,7 @@ static const SeatVtable psftp_seat_vt = {
     nullseat_get_x_display,
     nullseat_get_windowid,
     nullseat_get_window_pixel_size,
+    console_stripctrl_new,
 };
 static Seat psftp_seat[1] = {{ &psftp_seat_vt }};
 

putty.h

@@ -930,6 +930,15 @@ struct SeatVtable {
      * true.
      */
     bool (*get_window_pixel_size)(Seat *seat, int *width, int *height);
+
+    /*
+     * Return a StripCtrlChars appropriate for sanitising untrusted
+     * terminal data (e.g. SSH banners, prompts) being sent to the
+     * user of this seat. May return NULL if no sanitisation is
+     * needed.
+     */
+    StripCtrlChars *(*stripctrl_new)(Seat *seat, BinarySink *bs_out,
+                                     bool permit_cr, wchar_t substitution);
 };
 
 static inline size_t seat_output(
@@ -970,6 +979,9 @@ static inline bool seat_get_windowid(Seat *seat, long *id_out)
 { return seat->vt->get_windowid(seat, id_out); }
 static inline bool seat_get_window_pixel_size(Seat *seat, int *w, int *h)
 { return seat->vt->get_window_pixel_size(seat, w, h); }
+static inline StripCtrlChars *seat_stripctrl_new(
+    Seat *seat, BinarySink *bs, bool cr, wchar_t sub)
+{ return seat->vt->stripctrl_new(seat, bs, cr, sub); }
 
 /* Unlike the seat's actual method, the public entry point
  * seat_connection_fatal is a wrapper function with a printf-like API,
@@ -1014,6 +1026,8 @@ void nullseat_echoedit_update(Seat *seat, bool echoing, bool editing);
 const char *nullseat_get_x_display(Seat *seat);
 bool nullseat_get_windowid(Seat *seat, long *id_out);
 bool nullseat_get_window_pixel_size(Seat *seat, int *width, int *height);
+StripCtrlChars *nullseat_stripctrl_new(Seat *seat, BinarySink *bs_out,
+                                       bool permit_cr, wchar_t substitution);
 
 /*
  * Seat functions provided by the platform's console-application
@@ -1031,6 +1045,8 @@ int console_confirm_weak_crypto_primitive(
 int console_confirm_weak_cached_hostkey(
     Seat *seat, const char *algname, const char *betteralgs,
     void (*callback)(void *ctx, int result), void *ctx);
+StripCtrlChars *console_stripctrl_new(Seat *seat, BinarySink *bs_out,
+                                      bool permit_cr, wchar_t substitution);
 
 /*
  * Other centralised seat functions.

sesschan.c

@@ -193,6 +193,7 @@ static const SeatVtable sesschan_seat_vt = {
     nullseat_get_x_display,
     nullseat_get_windowid,
     sesschan_get_window_pixel_size,
+    nullseat_stripctrl_new,
 };
 
 Channel *sesschan_new(SshChannel *c, LogContext *logctx,

sshserver.c

@@ -113,6 +113,7 @@ static const SeatVtable server_seat_vt = {
     nullseat_get_x_display,
     nullseat_get_windowid,
     nullseat_get_window_pixel_size,
+    nullseat_stripctrl_new,
 };
 
 static void server_socket_log(Plug *plug, int type, SockAddr *addr, int port,

unix/gtkwin.c

@@ -351,6 +351,13 @@ static bool gtk_seat_get_window_pixel_size(Seat *seat, int *w, int *h)
     return true;
 }
 
+StripCtrlChars *gtk_seat_stripctrl_new(Seat *seat, BinarySink *bs_out,
+                                       bool permit_cr, wchar_t substitution)
+{
+    GtkFrontend *inst = container_of(seat, GtkFrontend, seat);
+    return stripctrl_new_term(bs_out, permit_cr, substitution, inst->term);
+}
+
 static void gtk_seat_notify_remote_exit(Seat *seat);
 static void gtk_seat_update_specials_menu(Seat *seat);
 static void gtk_seat_set_busy_status(Seat *seat, BusyStatus status);
@@ -380,6 +387,7 @@ static const SeatVtable gtk_seat_vt = {
     gtk_seat_get_windowid,
 #endif
     gtk_seat_get_window_pixel_size,
+    gtk_seat_stripctrl_new,
 };
 
 static void gtk_eventlog(LogPolicy *lp, const char *string)

unix/uxcons.c

@@ -465,6 +465,12 @@ static void console_eventlog(LogPolicy *lp, const char *string)
         console_logging_error(lp, string);
 }
 
+StripCtrlChars *console_stripctrl_new(Seat *seat, BinarySink *bs_out,
+                                      bool permit_cr, wchar_t substitution)
+{
+    return stripctrl_new(bs_out, permit_cr, substitution);
+}
+
 /*
  * Special functions to read and print to the console for password
  * prompts and the like. Uses /dev/tty or stdin/stderr, in that order

unix/uxplink.c

@@ -403,6 +403,7 @@ static const SeatVtable plink_seat_vt = {
     nullseat_get_x_display,
     nullseat_get_windowid,
     nullseat_get_window_pixel_size,
+    console_stripctrl_new,
 };
 static Seat plink_seat[1] = {{ &plink_seat_vt }};
 

windows/wincons.c

@@ -388,6 +388,12 @@ static void console_eventlog(LogPolicy *lp, const char *string)
         console_logging_error(lp, string);
 }
 
+StripCtrlChars *console_stripctrl_new(Seat *seat, BinarySink *bs_out,
+                                      bool permit_cr, wchar_t substitution)
+{
+    return stripctrl_new(bs_out, permit_cr, substitution);
+}
+
 static void console_data_untrusted(HANDLE hout, const char *data, size_t len)
 {
     DWORD dummy;

windows/window.c

@@ -320,6 +320,12 @@ bool win_seat_get_window_pixel_size(Seat *seat, int *x, int *y)
     return true;
 }
 
+StripCtrlChars *win_seat_stripctrl_new(Seat *seat, BinarySink *bs_out,
+                                       bool permit_cr, wchar_t substitution)
+{
+    return stripctrl_new_term(bs_out, permit_cr, substitution, term);
+}
+
 static size_t win_seat_output(
     Seat *seat, bool is_stderr, const void *, size_t);
 static bool win_seat_eof(Seat *seat);
@@ -347,6 +353,7 @@ static const SeatVtable win_seat_vt = {
     nullseat_get_x_display,
     nullseat_get_windowid,
     win_seat_get_window_pixel_size,
+    win_seat_stripctrl_new,
 };
 static Seat win_seat_impl = { &win_seat_vt };
 Seat *const win_seat = &win_seat_impl;

windows/winplink.c

@@ -105,6 +105,7 @@ static const SeatVtable plink_seat_vt = {
     nullseat_get_x_display,
     nullseat_get_windowid,
     nullseat_get_window_pixel_size,
+    console_stripctrl_new,
 };
 static Seat plink_seat[1] = {{ &plink_seat_vt }};