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(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.
This is the README for PuTTY, a free Windows and Unix Telnet and SSH
client.
PuTTY is built using CMake <https://cmake.org/>. To compile in the
simplest way (on any of Linux, Windows or Mac), run these commands in
the source directory:
cmake .
cmake --build .
Documentation (in various formats including Windows Help and Unix
`man' pages) is built from the Halibut (`.but') files in the `doc'
subdirectory using `doc/Makefile'. If you aren't using one of our
source snapshots, you'll need to do this yourself. Halibut can be
found at <https://www.chiark.greenend.org.uk/~sgtatham/halibut/>.
The PuTTY home web site is
https://www.chiark.greenend.org.uk/~sgtatham/putty/
If you want to send bug reports or feature requests, please read the
Feedback section of the web site before doing so. Sending one-line
reports saying `it doesn't work' will waste your time as much as
ours.
See the file LICENCE for the licence conditions.