[gtk-vnc] conn: Report error if vnc_connection_perform_auth_vnc fails

[Daniel P. Berrange <dberrange src gnome org>]

commit fa21beab5b44354c890699663a71b07d6ce18d40
Author: Christophe Fergeau <cfergeau redhat com>
Date:   Wed Jan 9 14:01:24 2019 +0100

    conn: Report error if vnc_connection_perform_auth_vnc fails
    
    At the moment, when the various crypto operations that
    vnc_connection_perform_auth_vnc performs fail, no error is reported to
    the client application. This commit adds the emission of a vnc-error
    signal when this happens. This is not reported as an auth failure as
    these errors are not something which is recoverable, they indicate
    system failures.
    
    Signed-off-by: Christophe Fergeau <cfergeau redhat com>

 src/vncconnection.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)
---
diff --git a/src/vncconnection.c b/src/vncconnection.c
index d8ecfd0..6805921 100644
--- a/src/vncconnection.c
+++ b/src/vncconnection.c
@@ -3638,33 +3638,38 @@ static gboolean vnc_connection_perform_auth_vnc(VncConnection *conn)
     error = gcry_cipher_open(&c, GCRY_CIPHER_DES, GCRY_CIPHER_MODE_ECB, 0);
     if (gcry_err_code (error) != GPG_ERR_NO_ERROR) {
         VNC_DEBUG("gcry_cipher_open error: %s\n", gcry_strerror(error));
-        return FALSE;
+        goto error;
     }
 
     error = gcry_cipher_setkey(c, key, 8);
     if (gcry_err_code (error) != GPG_ERR_NO_ERROR) {
         VNC_DEBUG("gcry_cipher_setkey error: %s\n", gcry_strerror(error));
         gcry_cipher_close(c);
-        return FALSE;
+        goto error;
     }
 
     error = gcry_cipher_encrypt(c, challenge, 8, challenge, 8);
     if (gcry_err_code (error) != GPG_ERR_NO_ERROR) {
         VNC_DEBUG("gcry_cipher_encrypt error: %s\n", gcry_strerror(error));
         gcry_cipher_close(c);
-        return FALSE;
+        goto error;
     }
     error = gcry_cipher_encrypt(c, challenge + 8, 8, challenge + 8, 8);
     if (gcry_err_code (error) != GPG_ERR_NO_ERROR) {
         VNC_DEBUG("gcry_cipher_encrypt error: %s\n", gcry_strerror(error));
         gcry_cipher_close(c);
-        return FALSE;
+        goto error;
     }
     gcry_cipher_close(c);
 
     vnc_connection_write(conn, challenge, 16);
     vnc_connection_flush(conn);
     return vnc_connection_check_auth_result(conn);
+
+error:
+    vnc_connection_set_error(conn, "%s: %s", "Unknown authentication failure: %s",
+                             gcry_strerror(error));
+    return FALSE;
 }
 
 /*