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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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20
ssh/userauth2-server.c
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@ -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) {