Re: [Bug-wget] [PATCH] Improve handling of SSL/TLS alerts with GnuTLS.

[Tim Ruehsen]

Hi,

thanks for your work to improve wget !

Are you shure, there are no other non-fatal return values ?
e.g. GNUTLS_E_REHANDSHAKE

AFAIK, a GnuTLS example that also uses a handshake loop, but relies completely 
on gnutls_error_is_fatal():

// simplified version without timeout handling
do {
        ret = gnutls_handshake(session);
} while (ret != 0 && !gnutls_error_is_fatal(ret));

Regards, Tim

Am Sunday 05 May 2013 schrieb mancha:
> Hello.
> 
> wget, built against GnuTLS, terminates SSL/TLS handshakes
> upon receiving any error alert (including non-fatal ones).
> 
> This creates a problem when connecting to servers that support
> TLS-SNI and reply with a warning-level unrecognized name alert
> (eg. due to misconfiguration).
> 
> My patch changes wget's behavior to ignore warning-level alerts
> during client/server hello and provides more detailed logging. The
> patch's compound conditional is not strictly necessary because
> GNUTLS_E_WARNING_ALERT_RECEIVED is non-fatal but a check on the
> latter is included as a fail-safe. It applies cleanly to
> address@hidden
> 
> Ignoring non-fatal alerts during handshake is consistent with
> Firefox and Chrome behavior.
> 
> I set up a server to replicate unrecognized_name alert conditions:
> 
> A. Current behavior:
> 
>    [warning-level alert]
>    $ wget https://localhost
>    --2013-05-05 08:18:35--  https://localhost/
>    Resolving localhost (localhost)... 127.0.0.1
>    Connecting to localhost (localhost)|127.0.0.1|:443... connected.
>    GnuTLS: A TLS warning alert has been received.
>    Unable to establish SSL connection.
> 
>    [fatal-level alert]
>    $ wget https://localhost
>    --2013-05-05 08:20:52--  https://localhost/
>    Resolving localhost (localhost)... 127.0.0.1
>    Connecting to localhost (localhost)|127.0.0.1|:443... connected.
>    GnuTLS: A TLS fatal alert has been received.
>    Unable to establish SSL connection.
> 
> B. Behavior after patch:
> 
>    [warning-level alert]
>    $ wget https://localhost
>    --2013-05-05 08:01:40--  https://localhost/
>    Resolving localhost (localhost)... 127.0.0.1
>    Connecting to localhost (localhost)|127.0.0.1|:443... connected.
>    GnuTLS: A TLS warning alert has been received.
>    GnuTLS: received alert [112]: The server name sent was not
> recognized
>    HTTP request sent, awaiting response... 200 OK
>    Length: unspecified [text/html]
>    Saving to: 'index.html'
> 
>    [fatal-level alert]
>    $ wget https://localhost
>    --2013-05-05 08:03:27--  https://localhost/
>    Resolving localhost (localhost)... 127.0.0.1
>    Connecting to localhost (localhost)|127.0.0.1|:443... connected.
>    GnuTLS: A TLS fatal alert has been received.
>    GnuTLS: received alert [112]: The server name sent was not
> recognized
>    Unable to establish SSL connection.
> 
> Cheers and thank you for wget!
> 
> --mancha