putty-source/nosshproxy.c

/*
 * nosshproxy.c: stub implementation of sshproxy_new_connection().
 */

#include "putty.h"
#include "network.h"

const bool ssh_proxy_supported = false;

Socket *sshproxy_new_connection(SockAddr *addr, const char *hostname,
                                int port, bool privport,
                                bool oobinline, bool nodelay, bool keepalive,
                                Plug *plug, Conf *conf,
                                LogPolicy *clientlp, Seat **clientseat)
{
    return NULL;
}
Initial support for in-process proxy SSH connections. This introduces a new entry to the radio-button list of proxy types, in which the 'Proxy host' box is taken to be the name of an SSH server or saved session. We make an entire subsidiary SSH connection to that host, open a direct-tcpip channel through it, and use that as the connection over which to run the primary network connection. The result is basically the same as if you used a local proxy subprocess, with a command along the lines of 'plink -batch %proxyhost -nc %host:%port'. But it's all done in-process, by having an SshProxy object implement the Socket trait to talk to the main connection, and implement Seat and LogPolicy to talk to its subsidiary SSH backend. All the refactoring in recent years has got us to the point where we can do that without both SSH instances fighting over some global variable or unique piece of infrastructure. From an end user perspective, doing SSH proxying in-process like this is a little bit easier to set up: it doesn't require you to bake the full pathname of Plink into your saved session (or to have it on the system PATH), and the SshProxy setup function automatically turns off SSH features that would be inappropriate in this context, such as additional port forwardings, or acting as a connection-sharing upstream. And it has minor advantages like getting the Event Log for the subsidiary connection interleaved in the main Event Log, as if it were stderr output from a proxy subcommand, without having to deliberately configure the subsidiary Plink into verbose mode. However, this is an initial implementation only, and it doesn't yet support the _big_ payoff for doing this in-process, which (I hope) will be the ability to handle interactive prompts from the subsidiary SSH connection via the same user interface as the primary one. For example, you might need to answer two password prompts in succession, or (the first time you use a session configured this way) confirm the host keys for both proxy and destination SSH servers. Comments in the new source file discuss some design thoughts on filling in this gap. For the moment, if the proxy SSH connection encounters any situation where an interactive prompt is needed, it will make the safe assumption, the same way 'plink -batch' would do. So it's at least no _worse_ than the existing technique of putting the proxy connection in a subprocess. 2021-05-22 11:51:23 +00:00			`/*`
			`* nosshproxy.c: stub implementation of sshproxy_new_connection().`
			`*/`

			`#include "putty.h"`
			`#include "network.h"`

			`const bool ssh_proxy_supported = false;`

			`Socket sshproxy_new_connection(SockAddr addr, const char *hostname,`
			`int port, bool privport,`
			`bool oobinline, bool nodelay, bool keepalive,`
sshproxy: share the caller's LogPolicy. Now new_connection() takes an optional LogPolicy * argument, and passes it on to the SshProxy setup. This means that SshProxy's implementation of the LogPolicy trait can answer queries like askappend() and logging_error() by passing them on to the same LogPolicy used by the main backend. Not all callers of new_connection have a LogPolicy, so we still have to fall back to the previous conservative default behaviour if SshProxy doesn't have a LogPolicy it can ask. The main backend implementations didn't _quite_ have access to a LogPolicy already, but they do have a LogContext, which has a LogPolicy vtable pointer inside it; so I've added a query function log_get_policy() which allows them to extract that pointer to pass to new_connection. This is the first step of fixing the non-interactivity limitations of SshProxy. But it's also the easiest step: the next ones will be more involved. 2021-09-13 16:17:20 +00:00			`Plug plug, Conf conf,`
sshproxy: borrow a Seat for host key and crypto dialogs. This puts the previous commit's framework to practical use. Now the main new_connection() passes its Seat ** through to the SshProxy setup function, which (if the stars align) will actually use it: stash it, return a TempSeat wrapper on it for the main backend to use in the interim, and pass through the GUI dialog prompts for host key confirmation and weak-crypto warnings. This is unfinished at the UI end: those dialog prompts will now need to be much clearer about which SSH server they're talking to (since now there could be two involved), and I haven't made that change yet. I haven't attempted to deal with get_userpass_input yet, though. That's much harder, and I'm still working on it. 2021-09-13 15:30:59 +00:00			`LogPolicy clientlp, Seat *clientseat)`
Initial support for in-process proxy SSH connections. This introduces a new entry to the radio-button list of proxy types, in which the 'Proxy host' box is taken to be the name of an SSH server or saved session. We make an entire subsidiary SSH connection to that host, open a direct-tcpip channel through it, and use that as the connection over which to run the primary network connection. The result is basically the same as if you used a local proxy subprocess, with a command along the lines of 'plink -batch %proxyhost -nc %host:%port'. But it's all done in-process, by having an SshProxy object implement the Socket trait to talk to the main connection, and implement Seat and LogPolicy to talk to its subsidiary SSH backend. All the refactoring in recent years has got us to the point where we can do that without both SSH instances fighting over some global variable or unique piece of infrastructure. From an end user perspective, doing SSH proxying in-process like this is a little bit easier to set up: it doesn't require you to bake the full pathname of Plink into your saved session (or to have it on the system PATH), and the SshProxy setup function automatically turns off SSH features that would be inappropriate in this context, such as additional port forwardings, or acting as a connection-sharing upstream. And it has minor advantages like getting the Event Log for the subsidiary connection interleaved in the main Event Log, as if it were stderr output from a proxy subcommand, without having to deliberately configure the subsidiary Plink into verbose mode. However, this is an initial implementation only, and it doesn't yet support the _big_ payoff for doing this in-process, which (I hope) will be the ability to handle interactive prompts from the subsidiary SSH connection via the same user interface as the primary one. For example, you might need to answer two password prompts in succession, or (the first time you use a session configured this way) confirm the host keys for both proxy and destination SSH servers. Comments in the new source file discuss some design thoughts on filling in this gap. For the moment, if the proxy SSH connection encounters any situation where an interactive prompt is needed, it will make the safe assumption, the same way 'plink -batch' would do. So it's at least no _worse_ than the existing technique of putting the proxy connection in a subprocess. 2021-05-22 11:51:23 +00:00			`{`
			`return NULL;`
			`}`