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Auth plugin: fix early socket closure.

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My correspondent on the new authentication-plugin feature reports that
their plugin is not reliably receiving the final PLUGIN_AUTH_SUCCESS
message on Windows. I _think_ this is because the whole userauth layer
is being dismissed, leading to sk_close() of the Socket talking to the
plugin, before the data has actually been written to the outgoing
pipe.

This should fix it: track the Socket's backlog, and immediately after
sending that message, wait until we receive a notification that the
backlog has decreased to size 0. That stops us from terminating the
userauth layer until the message has left our process.
This commit is contained in:
Simon Tatham 2022-09-02 18:18:29 +01:00
parent fbb979aa98
commit 1d75ad4c93
1 changed files with 17 additions and 2 deletions
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19
ssh/userauth2-client.c
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@ -96,6 +96,7 @@ struct ssh2_userauth_state {
Plug authplugin_plug;
bufchain authplugin_bc;
strbuf *authplugin_incoming_msg;
size_t authplugin_backlog;
bool authplugin_eof;
bool authplugin_ki_active;
@ -335,11 +336,19 @@ static void authplugin_plug_receive(
queue_idempotent_callback(&s->ppl.ic_process_queue);
}
static void authplugin_plug_sent(Plug *plug, size_t bufsize)
{
struct ssh2_userauth_state *s = container_of(
plug, struct ssh2_userauth_state, authplugin_plug);
s->authplugin_backlog = bufsize;
queue_idempotent_callback(&s->ppl.ic_process_queue);
}
static const PlugVtable authplugin_plugvt = {
.log = authplugin_plug_log,
.closing = authplugin_plug_closing,
.receive = authplugin_plug_receive,
.sent = nullplug_sent,
.sent = authplugin_plug_sent,
};
static strbuf *authplugin_newmsg(uint8_t type)
@ -354,7 +363,7 @@ static void authplugin_send_free(struct ssh2_userauth_state *s, strbuf *amsg)
{
PUT_32BIT_MSB_FIRST(amsg->u, amsg->len - 4);
assert(s->authplugin);
sk_write(s->authplugin, amsg->u, amsg->len);
s->authplugin_backlog = sk_write(s->authplugin, amsg->u, amsg->len);
strbuf_free(amsg);
}
@ -1789,6 +1798,12 @@ static void ssh2_userauth_process_queue(PacketProtocolLayer *ppl)
if (plugin_msg >= 0) {
strbuf *amsg = authplugin_newmsg(plugin_msg);
authplugin_send_free(s, amsg);
/* Wait until we've actually sent it, in case
* we close the connection to the plugin
* before that outgoing message has left our
* own buffers */
crMaybeWaitUntilV(s->authplugin_backlog == 0);
}
}
} else if (s->can_passwd) {