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mirror of https://git.tartarus.org/simon/putty.git synced 2025-01-10 01:48:00 +00:00
putty-source/utils/nullseat.c
Simon Tatham 7eb7d5e2e9 New Seat query, has_mixed_input_stream().
(TL;DR: to suppress redundant 'Press Return to begin session' prompts
in between hops of a jump-host configuration, in Plink.)

This new query method directly asks the Seat the question: is the same
stream of input used to provide responses to interactive login
prompts, and the session input provided after login concludes?

It's used to suppress the last-ditch anti-spoofing defence in Plink of
interactively asking 'Access granted. Press Return to begin session',
on the basis that any such spoofing attack works by confusing the user
about what's a legit login prompt before the session begins and what's
sent by the server after the main session begins - so if those two
things take input from different places, the user can't be confused.

This doesn't change the existing behaviour of Plink, which was already
suppressing the antispoof prompt in cases where its standard input was
redirected from something other than a terminal. But previously it was
doing it within the can_set_trust_status() seat query, and I've now
moved it out into a separate query function.

The reason why these need to be separate is for SshProxy, which needs
to give an unusual combination of answers when run inside Plink. For
can_set_trust_status(), it needs to return whatever the parent Seat
returns, so that all the login prompts for a string of proxy
connections in session will be antispoofed the same way. But you only
want that final 'Access granted' prompt to happen _once_, after all
the proxy connection setup phases are done, because up until then
you're still in the safe hands of PuTTY itself presenting an unbroken
sequence of legit login prompts (even if they come from a succession
of different servers). Hence, SshProxy unconditionally returns 'no' to
the query of whether it has a single mixed input stream, because
indeed, it never does - for purposes of session input it behaves like
an always-redirected Plink, no matter what kind of real Seat it ends
up sending its pre-session login prompts to.
2021-11-06 14:48:26 +00:00

51 lines
2.7 KiB
C

/*
* Stub methods usable by Seat implementations.
*/
#include "putty.h"
size_t nullseat_output(
Seat *seat, SeatOutputType type, const void *data, size_t len) {return 0;}
bool nullseat_eof(Seat *seat) { return true; }
void nullseat_sent(Seat *seat, size_t bufsize) {}
size_t nullseat_banner(Seat *seat, const void *data, size_t len) {return 0;}
size_t nullseat_banner_to_stderr(Seat *seat, const void *data, size_t len)
{ return seat_output(seat, SEAT_OUTPUT_STDERR, data, len); }
int nullseat_get_userpass_input(Seat *seat, prompts_t *p) { return 0; }
void nullseat_notify_session_started(Seat *seat) {}
void nullseat_notify_remote_exit(Seat *seat) {}
void nullseat_notify_remote_disconnect(Seat *seat) {}
void nullseat_connection_fatal(Seat *seat, const char *message) {}
void nullseat_update_specials_menu(Seat *seat) {}
char *nullseat_get_ttymode(Seat *seat, const char *mode) { return NULL; }
void nullseat_set_busy_status(Seat *seat, BusyStatus status) {}
int nullseat_confirm_ssh_host_key(
Seat *seat, const char *host, int port, const char *keytype,
char *keystr, const char *keydisp, char **key_fingerprints, bool mismatch,
void (*callback)(void *ctx, int result), void *ctx) { return 0; }
int nullseat_confirm_weak_crypto_primitive(
Seat *seat, const char *algtype, const char *algname,
void (*callback)(void *ctx, int result), void *ctx) { return 0; }
int nullseat_confirm_weak_cached_hostkey(
Seat *seat, const char *algname, const char *betteralgs,
void (*callback)(void *ctx, int result), void *ctx) { return 0; }
bool nullseat_is_never_utf8(Seat *seat) { return false; }
bool nullseat_is_always_utf8(Seat *seat) { return true; }
void nullseat_echoedit_update(Seat *seat, bool echoing, bool editing) {}
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_out, SeatInteractionContext sic) {return NULL;}
void nullseat_set_trust_status(Seat *seat, bool trusted) {}
bool nullseat_can_set_trust_status_yes(Seat *seat) { return true; }
bool nullseat_can_set_trust_status_no(Seat *seat) { return false; }
bool nullseat_has_mixed_input_stream_yes(Seat *seat) { return true; }
bool nullseat_has_mixed_input_stream_no(Seat *seat) { return false; }
bool nullseat_verbose_no(Seat *seat) { return false; }
bool nullseat_verbose_yes(Seat *seat) { return true; }
bool nullseat_interactive_no(Seat *seat) { return false; }
bool nullseat_interactive_yes(Seat *seat) { return true; }
bool nullseat_get_cursor_position(Seat *seat, int *x, int *y) { return false; }