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Uppity: add a stunt mode --close-after-banner.

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A user reported yesterday that PuTTY can fail to print a userauth
banner message if the server sends one and then immediately slams the
connection shut. The first step to fixing this is making a convenient
way to reproduce that server behaviour.

(Apparently the real use case has to do with account expiry - the
server in question presumably doesn't have enough layer violations to
be able to put the text "Your account has expired" into an
SSH_MSG_DISCONNECT, so instead it does the next best thing and sends
it as a userauth banner immediately before disconnection.)
This commit is contained in:
Simon Tatham 2023-04-29 11:34:08 +01:00
parent 62b69a4f16
commit fe63b5d57e
4 changed files with 24 additions and 0 deletions
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1
ssh/server.c
View File

@ -502,6 +502,7 @@ void ssh_sw_abort(Ssh *ssh, const char *fmt, ...)
void ssh_user_close(Ssh *ssh, const char *fmt, ...)
{
server *srv = container_of(ssh, server, ssh);
ssh_bpp_handle_output(srv->bpp);
LOG_FORMATTED_MSG(srv->logctx, fmt);
queue_toplevel_callback(ssh_server_free_callback, srv);
}

1
ssh/server.h
View File

@ -23,6 +23,7 @@ struct SshServerConfig {
bool stunt_open_unconditional_agent_socket;
bool stunt_allow_trivial_ki_auth;
bool stunt_return_success_to_pubkey_offer;
bool stunt_close_after_banner;
};
Plug *ssh_server_plug(

20
ssh/userauth2-server.c
View File

@ -113,6 +113,21 @@ static void ssh2_userauth_server_add_session_id(
}
}
static void ssh2_userauth_server_close_after_banner(void *vctx)
{
struct ssh2_userauth_server_state *s =
(struct ssh2_userauth_server_state *)vctx;
if (pq_peek(s->ppl.out_pq)) {
/* Don't close the connection until we've passed on our final banner
* packet to the lower layer */
queue_toplevel_callback(ssh2_userauth_server_close_after_banner, s);
} else {
ssh_user_close(s->ppl.ssh, "Closing connection on request due to "
"--close-after-banner");
}
}
static void ssh2_userauth_server_process_queue(PacketProtocolLayer *ppl)
{
struct ssh2_userauth_server_state *s =
@ -131,6 +146,11 @@ static void ssh2_userauth_server_process_queue(PacketProtocolLayer *ppl)
pq_push(s->ppl.out_pq, pktout);
}
if (s->ssc->stunt_close_after_banner) {
queue_toplevel_callback(ssh2_userauth_server_close_after_banner, s);
crReturnV;
}
while (1) {
crMaybeWaitUntilV((pktin = ssh2_userauth_server_pop(s)) != NULL);
if (pktin->type != SSH2_MSG_USERAUTH_REQUEST) {

2
unix/uppity.c
View File

@ -924,6 +924,8 @@ int main(int argc, char **argv)
ci->ssc.stunt_allow_trivial_ki_auth = true;
} else if (!strcmp(arg, "--return-success-to-pubkey-offer")) {
ci->ssc.stunt_return_success_to_pubkey_offer = true;
} else if (!strcmp(arg, "--close-after-banner")) {
ci->ssc.stunt_close_after_banner = true;
} else {
fprintf(stderr, "%s: unrecognised option '%s'\n", appname, arg);
exit(1);