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Work around a race with password-less logins and double clicks #1

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17 changes: 17 additions & 0 deletions src/greeter.c
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Original file line number Diff line number Diff line change
Expand Up @@ -75,6 +75,14 @@ typedef struct
/* TRUE if logging into guest session */
gboolean guest_account_authenticated;

/* Avoid a race where we already sent SERVER_MESSAGE_END_AUTHENTICATION to the greeter,
* but before it digests it, it handles more X11 events, sending us a GREETER_MESSAGE_CONTINUE_AUTHENTICATION
* (before the GREETER_MESSAGE_START_SESSION) which will confuse handle_continue_authentication(),
* calling session_respond_error(), which then sends a PAM_CONV_ERR to the session child,
* which will confuse that because it's expecting the (length of the) session error file name.
*/
gboolean have_sent_end_authentication;

/* Communication channels to communicate with */
int to_greeter_input;
int from_greeter_output;
Expand Down Expand Up @@ -410,11 +418,13 @@ send_end_authentication (Greeter *greeter, guint32 sequence_number, const gchar
{
guint8 message[MAX_MESSAGE_LENGTH];
gsize offset = 0;
GreeterPrivate *priv = greeter_get_instance_private (greeter);
write_header (message, MAX_MESSAGE_LENGTH, SERVER_MESSAGE_END_AUTHENTICATION, int_length () + string_length (username) + int_length (), &offset);
write_int (message, MAX_MESSAGE_LENGTH, sequence_number, &offset);
write_string (message, MAX_MESSAGE_LENGTH, username, &offset);
write_int (message, MAX_MESSAGE_LENGTH, result, &offset);
write_message (greeter, message, offset);
priv->have_sent_end_authentication = TRUE;
}

void
Expand Down Expand Up @@ -489,6 +499,7 @@ reset_session (Greeter *greeter)
}

priv->guest_account_authenticated = FALSE;
priv->have_sent_end_authentication = FALSE;
}

static void
Expand Down Expand Up @@ -648,6 +659,12 @@ handle_continue_authentication (Greeter *greeter, gchar **secrets)
int messages_length = session_get_messages_length (priv->authentication_session);
const struct pam_message *messages = session_get_messages (priv->authentication_session);

/* We may have already sent SERVER_MESSAGE_END_AUTHENTICATION, but the greeter may not have digested it yet. */
if (priv->have_sent_end_authentication) {
g_debug ("Ignoring continue authentication");
return;
}

/* Check correct number of responses */
int n_prompts = 0;
for (int i = 0; i < messages_length; i++)
Expand Down