This commit replaces all those fiddly little linking modules
(be_all.c, be_none.c, be_ssh.c etc) with a single source file
controlled by ifdefs, and introduces a function be_list() in
setup.cmake that makes it easy to compile a version of it appropriate
to each application.
This is a net reduction in code according to 'git diff --stat', even
though I've introduced more comments. It also gets rid of another pile
of annoying little source files in the top-level directory that didn't
deserve to take up so much room in 'ls'.
More concretely, doing this has some maintenance advantages.
Centralisation means less to maintain (e.g. n_ui_backends is worked
out once in a way that makes sense everywhere), and also, 'appname'
can now be reliably set per program. Previously, some programs got the
wrong appname due to sharing the same linking module (e.g. Plink had
appname="PuTTY"), which was a latent bug that would have manifested if
I'd wanted to reuse the same string in another context.
One thing I've changed in this rework is that Windows pterm no longer
has the ConPTY backend in its backends[]: it now has an empty one. The
special be_conpty.c module shouldn't really have been there in the
first place: it was used in the very earliest uncommitted drafts of
the ConPTY work, where I was using another method of selecting that
backend, but now that Windows pterm has a dedicated
backend_vt_from_conf() that refers to conpty_backend by name, it has
no need to live in backends[] at all, just as it doesn't have to in
Unix pterm.
Passing an operating-system-specific error code to plug_closing(),
such as errno or GetLastError(), was always a bit weird, given that it
generally had to be handled by cross-platform receiving code in
backends. I had the platform.h implementations #define any error
values that the cross-platform code would have to handle specially,
but that's still not a great system, because it also doesn't leave
freedom to invent error representations of my own that don't
correspond to any OS code. (For example, the ones I just removed from
proxy.h.)
So now, the OS error code is gone from the plug_closing API, and in
its place is a custom enumeration of closure types: normal, error, and
the special case BROKEN_PIPE which is the only OS error code we have
so far needed to handle specially. (All others just mean 'abandon the
connection and print the textual message'.)
Having already centralised the handling of OS error codes in the
previous commit, we've now got a convenient place to add any further
type codes for errors needing special handling: each of Unix
plug_closing_errno(), Windows plug_closing_system_error(), and Windows
plug_closing_winsock_error() can easily grow extra special cases if
need be, and each one will only have to live in one place.
It was totally unused. No implementation of the 'closing' method in a
Plug vtable was checking it for any reason at all, except for
ProxySocket which captured it from its client in order to pass on to
its server (which, perhaps after further iterations of ProxySocket,
would have ended up ignoring it similarly). And every caller of
plug_closing set it to 0 (aka false), except for the one in sshproxy.c
which passed true (but it would have made no difference to anyone).
The comment in network.h refers to a FIXME comment which was in
try_send() when that code was written (see winnet.c in commit
7b0e082700). That FIXME is long gone, replaced by a use of a
toplevel callback. So I think the aim must have been to avoid
re-entrancy when sk_write called try_send which encountered a socket
error and called back to plug_closing - but that's long since fixed by
other means now.
Now you can turn various authentication methods on and off, so that
the server won't even offer (say) k-i or publickey at all.
This subsumes the previous -allow-none-auth option; there's now a
general -{allow,deny}-auth=foo option schema, so -allow-auth=none is
the new spelling of -allow-none-auth. The former spelling is kept for
backwards compatibility, just in case.
I've moved all the results of the command-line config options into a
small struct instead of having them be local variables of main(). We
maintain an array of those structs; most command-line options modify
the last element in the array; and we respond to the new special
option '--and' by appending a fresh struct to the end of the array and
initialising it to default values.
So now, if I want two or three SSH servers running on different ports
with separately configured host keys, banners, etc, I can do that with
a single command line along the lines of:
./uppity --listen 2222 --hostkey this.ppk --bannertext "this" \
--and --listen 2223 --hostkey that.ppk --bannertext "that"
There's a single number space of connections used in log messages, and
each new connection reports which of the servers it connects to.
This is only a marginally useful feature: there's not much it does
that couldn't have been done just as well by running multiple Uppitys
each in their own process. But when I do want several servers at once
(which I've been using recently to test the jump-host system), it's
quite nice to have them all producing a single combined stream of log
data and all conveniently killable with a single ^C.
In the case where these socket types are constructed because of a
local proxy command, we do actually have a SockAddr representing the
logical host we were trying to make a connection to. So we might as
well store it in the socket implementation, and then we can include it
in the PLUGLOG_CONNECT_SUCCESS call to make the log message more
informative.
This allows the 'no trivial auth' option introduced by the previous
commit to be tested. Uppity has grown three new options to make it
accept "none" authentication, keyboard-interactive involving no
prompts, and the perverse sending of USERAUTH_SUCCESS after a
signatureless public-key offer.
The first of those options also enables the analogue in SSH-1; the
other two have no SSH-1 analogues in the first place. (SSH-1 public
key authentication has a challenge-response structure that doesn't
contain any way to terminate the exchange early with success. And the
TIS and CryptoCard methods, which are its closest analogue of k-i,
have a fixed number of prompts, which is not 0.)
This gets rid of all those annoying 'win', 'ux' and 'gtk' prefixes
which made filenames annoying to type and to tab-complete. Also, as
with my other recent renaming sprees, I've taken the opportunity to
expand and clarify some of the names so that they're not such cryptic
abbreviations.
