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Support interactive password prompts in Telnet proxy.

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The Telnet proxy system is not a proper network protocol - we have no
reliable way to receive communication from the proxy telling us
whether a password is even required. However, we _do_ know (a) whether
the keywords '%user' or '%pass' appeared in the format string stored
in the Conf, and (b) whether we actually had a username or a password
to substitute into them. So that's how we know whether to ask for a
username or a password: if the format string asks for them and the
Conf doesn't provide them, we prompt for them at startup.

This involved turning TelnetProxyNegotiator into a coroutine (matching
all the other proxy types, but previously, it was the only one simple
enough not to need to be one), so that it can wait until a response
arrives to that prompt. (And also, as it turned out, so that it can
wait until setup is finished before even presenting the prompt!)

It also involves having format_telnet_command grow an extra output
parameter, in the form of 'unsigned *flags', with which it can
communicate back to the caller that a username or password was wanted
but not found. The other clients of that function (the local proxy
implementations) don't use those flags, but if necessary, they could.
This commit is contained in:
Simon Tatham
2021-11-19 16:03:22 +00:00
parent 445bcd7030
commit a864f7bb57
4 changed files with 165 additions and 30 deletions
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4
unix/local-proxy.c
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@ -29,7 +29,7 @@ Socket *platform_new_connection(SockAddr *addr, const char *hostname,
return NULL;
if (proxytype == PROXY_CMD) {
cmd = format_telnet_command(addr, port, conf);
cmd = format_telnet_command(addr, port, conf, NULL);
{
char *logmsg = dupprintf("Starting local proxy command: %s", cmd);
@ -79,7 +79,7 @@ Socket *platform_new_connection(SockAddr *addr, const char *hostname,
infd = from_cmd_pipe[0];
inerrfd = cmd_err_pipe[0];
} else {
cmd = format_telnet_command(addr, port, conf);
cmd = format_telnet_command(addr, port, conf, NULL);
outfd = open("/dev/null", O_WRONLY);
if (outfd == -1) {
sfree(cmd);