Re: [Qemu-devel] [PATCH v4 09/24] ui/vnc: Use gcrypto_random_bytes for start_auth_vnc

[Richard Henderson]

On 5/7/19 3:49 AM, Laurent Vivier wrote:
>>     void start_auth_vnc(VncState *vs)
>>   {
>> -    make_challenge(vs);
>> +    Error *err = NULL;
>> +
>> +    if (qcrypto_random_bytes(vs->challenge, sizeof(vs->challenge), &err)) {
>> +        trace_vnc_auth_fail(vs, vs->auth, "cannot get random bytes",
>> +                            error_get_pretty(err));
>> +        error_free(err);
>> +        authentication_failed(vs);
>> +        return;
>> +    }
>> +
> 
> This part is weird for me: if auth fails we send "vnc_write_u32(vs, 1)" but if
> it succeeds we send the challenge. There is no success value to send (like
> "vnc_write_u32(vs, 0)") ?

There is, but this code is a mess of callbacks.  In this case it happens toward
the end of protocol_client_auth_vnc:

   2604         trace_vnc_auth_pass(vs, vs->auth);
   2605         vnc_write_u32(vs, 0); /* Accept auth */
   2606         vnc_flush(vs);


r~