Re: [exim] Debugging 'Invalid base64 data"

On 2006-03-02 at 15:23 +0100, Felix Brack wrote:
> I understand that exim gets the command "AUTH LOGIN" and then sends
> the prompt "Username:" ("VXNlcm5hbWU6" base64 encoded); this is fine
> and exactly what exim should do. The next thing exim does is send the
> message "501 Invalid base64 data". In between those two last
> statements in the log there should be the username sent from the
> client; is it possible to enable some debugging option that will show
> the username and password sent by the client?

As a generic answer: tcpdump(8)? And if you haven't tried it for
protocol analysis yet, the GUI program ethereal to dissect packets (as
long as you're careful to keep up with ethereal security holes).

Get a log:
tcpdump -s1500 -w filename.log -npi <interface> port 25
and feed it to ethereal (menus or as cmdline parameter).

> the username and password sent by the client? And: What is the message
> "501 Invalid base64 data" related to? To the username exim received
> from the client or to something else?

Yes, the client data. It means that Exim's auth_b64decode() routine
rejected the data, which means that it contained bad characters.

Looking at the decode routine, my suspicion is that the client data has
a trailing NUL character after the base64 string (not part of the data
wrapped by base64, but in the outside text stream, just after the base64
data). That's only suspicion, though.
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He is coddling tyrants.
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