BUG: sendemail-validate hook is run too early

I'm trying to use the sendemail-validate hook to validate the recipients of the patch email, among other things. Turns out the hook gets run immediately on the input patches, *not* on the "e-mail to be sent" as claimed by githooks(5).

This means the recipients added by git send-email automatically or on the git send-email command-line, or any changes done by the user with --annotate will not be validated.

This is easy to demonstrate in a git repo with e.g.

$ ln -s /bin/cat .git/hooks/sendemail-validate $ git send-email --dry-run -1 --to bypass-validation@example.com

The file passed to the validate hook does not have the address.

If changing the location of the current validation hook seems too risky, as apparently it's been like this for more than a decade, I suggest adding another hook on the actual email to be sent.

BR, Jani.

Jani Nikula <jani.nikula@intel.com> writes:

I will make two suggestions, so please do not react before reading both ;-)

The purpose of the validate hook, at least as it was originally designed, was to vet the log message and patch contents, so what you reported is not at all surprising. After all, the sub that uses the hook is called "validate_patch" ;-).

A low-hanging documentation fix (this is one suggestion) is to phrase "e-mail to be sent" as "e-mail that has been submitted (to git-send-email)" to avoid the confusion.

You do not want to use the sendemail-validate hook for checking for the recipients, because the e-mail message is not a good source of that information.

When a recipient is added, two things happen:

 * The recipient is added to the (internal) list of recipients on
   the underlying sendmail command line arguments.  This is the list
   of addresses that actually matter where the piece of email goes.

 * The recipient is added to the text of the message being sent, if
   s/he is being added to either To: or Cc: (this is purely for
   human consumption and does not affect where the piece of email
   goes).  A blind-carbon-copy recipient would not be added for
   obvious reasons.

If you truly want to validate where the message goes, you'd need to vet the former list, not the latter one. Otherwise, you'll miss BCC recipients.

So the other suggestion is to have a separate hook to validate the list of recipients. This might be a bit more involved if we want to execute cleanly, but should not be rocket science.

The send_message() sub prepares @recipients list to form quite a bit of processing at the beginning, and the uses the resulting list to drive the sendmail by adding it to @sendmail_parameters(). The contents of this @recipients list is what you want to vet before the code talks to the sendmail program or daemon later in the function.

On Thu, 02 Jan 2020, Junio C Hamano <gitster@pobox.com> wrote:

Agreed; I think this should be done no matter what.

Understood.

One key point here is using the patch as input to the recipient validation. For example, requiring specific recipients when certain files are changed (a bit like get_maintainers.pl in Linux kernel). To make it easier for the hook writer, both the patch and the recipients should be passed to the hook at the same time.

I think one possible alternative to adding a completely new hook would be postponing the sendemail-validate hook, passing the same patch on the command-line as before (to ensure current users are unchanged), and additionally passing in the recipients. Perhaps write the recipient list in a temp file, and pass the filename on the command-line or via the environment to the hook.

Alas implementing this in perl *is* rocket science to me, so I'm pretty much dependent on the git community's help here.

BR, Jani.

On Fri, 03 Jan 2020, Jani Nikula <jani.nikula@intel.com> wrote:

I realize the validation is done on *all* patches in a series before any further processing, so the suggestion to postpone the current validation hook is a bad idea. We'd need a new hook. The other points about having both the patch contents and the recipients available to the hook remain.

BR, Jani.