Re: [PATCH v1] send-email: provide whitelist of SMTP AUTH mechanisms

Eric Sunshine [off-list ref] writes:

What I was really asking was whether this sort of checking really
belongs in git-send-email or if it is better left to Net::SMTP (and
Authen::SASL) to do so since they are in better positions to know what
is valid and what is not. If the Perl module(s) generate suitable
diagnostics for bad input, then it makes sense to leave the checking
to them. If not, then I can understand your motivation for
git-send-email doing the checking instead in order to emit
user-friendly diagnostics.

So, that's what I meant when I asked 'What are the consequences of not
limiting the input to this "approved" list?'.

The other reason I asked was that it increases maintenance costs for
us to maintain a list of "approved" mechanisms, since the list needs
to be updated when new ones are implemented (and, as brian pointed
out, some may already exist which are not in your list).

Both are very good points.  I do not think we should be limiting the
user input; instead, we (1) either let the Perl module emit proper
diagnosis (e.g. it may say "There is no valid auth method in the
list you gave me, which was 'PLIAN LOGIN CROM-MD5'") and do nothing,
or (2) catch the error from the Perl module and then guess what
happened after the fact (e.g. the module may say in its die() message
something that is understandable by the program but not by the user,
and "eval { ... module call ... }; if ($@) { ... HERE ... }" would
massage what it can learn in HERE from $@ into what the end user
would understand.  It may be that it is sufficient to have something
as simple as this:

	my $msg = "$@"
	if ($smtp_auth is used to customize) {
		$msg .= "\nYour customized <$smtp_auth> might be misspelt?"
	}
	die $msg;

in "HERE" above.

...
Maybe. This leads back to my original question of whether it's really
git-send-email's responsibility to do validation or if that can be
left to Net::SMTP/Authen::SASL. If the Perl module(s) emit suitable
diagnostics for bad input, then validation can be omitted from
git-send-email.

Yes, exactly.  What happens if we go the route of doing nothing
here?  What are the horrible diagnostic message the end user would
not understand?