Re: [PATCH] PublicInbox::Import Extend add with a optional raw message parameter

[Eric Wong <e@80x24.org>]

"Eric W. Biederman" <ebiederm@xmission.com> wrote:
> Eric Wong <e@80x24.org> writes:
> 
> > "Eric W. Biederman" <ebiederm@xmission.com> wrote:
> >> 
> >> I don't trust the MIME type to not munge my email messages in horrible
> >> ways upon occasion.  Therefore  allow for passing in the raw message
> >> value instead of trusting the mime object to preserve it.
> >> 
> >> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
> >
> > I've had the same concern in the past about Email::MIME and
> > Email::Simple.  But after reading the code for Email::MIME,
> > Email::Simple and Email::{MIME,Simple}::Header, I don't think
> > the implementation of Email::MIME->as_string and all methods it
> > calls does anything unreasonable.
> >
> > The only notable munging they seem to do is make irrelevant
> > whitespace changes in headers and maybe fix quoting in headers.
> > No body changes AFAIK.
> 
> I was hoping I could skip the Email::MIME stuff entirely but the headers
> do need a bit of parsing to derive the git commit information.

Perhaps parsing git commit information can be skipped, entirely
(but it's still necessary for indexing, so I'm not sure if there's
 any gain, there).

> I will take a second look at the code.  I did not make it all of the
> way through last time.  I just know the bazillions of warnings I could
> not easily track down with old emails did not make me comfortable
> with that code base as anything other than a suggestion.

Ah, I added ce18b29d175ef5f01f05d59c95bcf8e0cd40e611
("index: warn with info about the message as context") exactly
for that.

> >> The context here is because the only copy of messages that I save
> >> I save in public-inbox I don't want to have to worry about losing
> >> information.  So I just pass the raw email_str to add.
> >> 
> >> I expect if I were to export these lists public I would want to do
> >> some more but for now I am just putting them in public-inbox
> >> so that I can read and archive the lists locally.
> >
> > I worry about public archives getting badly munged, too.
> >
> >>  lib/PublicInbox/Import.pm     | 10 +++++-----
> >>  lib/PublicInbox/V2Writable.pm |  8 ++++----
> >>  2 files changed, 9 insertions(+), 9 deletions(-)
> >
> > Did you have plans to modify -mda/-watch or another script to
> > use this?
> 
> I have been using this for a while with my own imap fetcher
> script.  As for the others I certain could.  I don't use -mda
> or -watch so they have not been a priority.

OK.  Tangent: which IMAP module(s) did you choose? (and why?)
I haven't gotten a chance to evaluate Perl IMAP client modules,
yet; but I want to extend -watch to support IMAP.

> >> diff --git a/lib/PublicInbox/Import.pm b/lib/PublicInbox/Import.pm
> >> index 81a38fb6987d..0a63784414f2 100644
> >> --- a/lib/PublicInbox/Import.pm
> >> +++ b/lib/PublicInbox/Import.pm
> >> @@ -359,7 +359,7 @@ sub clean_tree_v2 ($$$) {
> >>  # returns undef on duplicate
> >>  # returns the :MARK of the most recent commit
> >>  sub add {
> >> -	my ($self, $mime, $check_cb) = @_; # mime = Email::MIME
> >> +	my ($self, $mime, $check_cb, $email_str) = @_; # mime = Email::MIME
> >
> > I usually place callback args at the end of the arg list so
> > it's easy to write:
> >
> > 	$im->add($mime, sub {
> > 		# ...
> > 	});
> >
> > So having a parameter after the sub{} is a bit ugly...
> > If I had to support this, I think I'd accept $mime being
> > a plain hashref:
> >
> > 	if (ref($mime) eq 'HASH') {
> > 		$raw = $mime->{raw};
> > 		$mime = $mime->{mime};
> > 	} else {
> > 		$raw = $mime->as_string;
> > 	}
> >
> > But, I'm still on the fence about the idea...
> >
> > Side note: I'm also taking the opportunity to use "$raw" instead
> > of "$str", because I've been bitten by the difference header_raw
> > vs header_str in the Email::MIME API, so consistency with
> > that API would be good, here.
> 
> Yes the distinction about "$raw" is fair,
> and the placement in the argument list makes sense.
> 
> As for the hashref.  Perhaps what I should do is modify
> PublicInbox::MIME to at least conditionally keep the original raw email
> around.  Then the logic to get the raw email could be kept in
> PublicInbox::MIME as well.

Actually, since Perl "objects" are open-ended hashrefs with no
restrictions, we could set:

	$mime->{-public_inbox_raw} = $raw;
	$im->add($mime);

That would work for any code using Email::MIME, as well.  I
don't want the PublicInbox::MIME wrapper to be necessary forever
(it's only to workaround old bugs in Email::MIME).

And I doubt Email::* authors will start using "-public_inbox"
prefixes in their code to mess with us.

One caveat is we might need to modify our (Simple|MIME)->new callers:

-	::(Simple|MIME)->new(\$raw);
+	::(Simple|MIME)->new($raw);

since Email::Simple->new(\$raw) can clobber $raw in the
interest of memory savings, while the former preserves
the original.

> Which let's me think the general solution is to have a configuration
> option somewhere that says we want to archive the raw email.  We
> update PublicInbox::MIME to always keep the original raw email.
> 
> If add is not configured to drop any headers we use the raw original
> email str.  If add drops any headers we do what we do today.
> 
> I think perhaps we could move all of the scrubbing into
> PublicInbox::Filter::Base.pm::scrub.  Instead of having a hard coded
> drop_unwanted_headers in PublicInbox::Import.  That would make it very
> straight forward to just make this a knob that the user controls
> for how they want their email received/imported.

Not calling drop_unwanted_headers can have dangerous side-effects
(training loops, bugs in other consumers, private data exposure),
so I'm very hesitant to move it to Filter::Base

@PublicInbox::MDA::BAD_HEADERS is exposed via `our', so it could
remain stable-but-undocumented API if people really feel the
need to tweak it.  At most, we'd add a comment for that variable
asking potential hackers not to move/rename it.

> If that general idea sounds palatable I will investigate to see
> if I can move the caching of the raw email into PublicInbox::MIME,
> see about moving the dropping of headers into an appropriate config
> knob.

I think using $mime->{-public_inbox_raw} will be sufficient for
now.  Thanks.