Re: OT: Re: Less is more

On Wed, 5 May 2004 06:02, Keith Moore wrote:
> the job of the submission agent is to authenticate the source (for some
> meaning of "authenticate", to reject or fix invalid messages (and
> provide feedback to the user that his MUA is broken) and submit
> valid messages to the email transport system.

My earlier point still holds. Regardless of whether or not a client is acting 
in the "submission" role or the "relay" role, it may or may not be violating 
protocol somewhere in the transaction. If a server performs strict protocol 
checks at every stage of the dialogue, then it will reject such violations; 
if it assumes that the client observes protocol correctly, then it will 
propagate violations.

To put it another way, it's the client's job to pass on data only in a way 
that observes protocol, but can the server assume the client is doing its 
job? This seems to be largely a question of implementation. An implementation 
should consider the consequences of passing on data from a client 
uncritically, doubly so if the client might be actively malicious in its 
crafting of data. The safer path is to perform strict validation in all 
cases.