[pkg-gnupg-maint] Bug#847206: workaround for sockets on long paths

[Antoine Beaupré]

After a little more testing and research, I have found a workaround for
failures to create socket paths larger than the predefined size.

It seems rather silly, but it turns out that the size is not based on
the absolute, canonical file path. This means a simple symlink in
another location works around the issue. I have unfortunately not been
able to instrument this in the test suite of the package I'm working on
right now.

But the idea is to pre-emptively start an agent for the affected process
(in my case, the test suite) under a directory with a shorter path,
symlinked to the normal GPGHOMEDIR, something like this:

    TMPDIR=$(mktemp -d gpghome)
    ln -s $PWD/testgpghome $TMPDIR/testgpghome
    gpg-agent --homedir $TMPDIR/testgpghome --daemon ...

Because it is a symlink, it does not suffer from the permission problems
other proposed solutions have. I create a temporary directory as a
parent to work around possible issues with GPG checking the parent
directories as well.

For some reason, this fails in my test setup:

# workaround bug in gpg-agent: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=847206
override_dh_auto_test:
	TMPDIR=`mktemp -d` && \
	ln -s $(CURDIR)/testdata/gpghome $$TMPDIR/testgpghome && \ 
	gpg-agent --homedir $$TMPDIR/testgpghome --daemon dh_auto_test && \
	rm -r $$TMPDIR

The already started agent gets ignored by the test suite, I don't know
why. Instead, I am using this detection code to skip the test suite in
case of an hostile environment:

SUN_PATH_LIMIT=108

# workaround bug in gpg-agent: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=847206
override_dh_auto_test:
	SOCKET_PATH="$${PWD}/testdata/gpghome/S.gpg-agent" ; \
	if [ $${#SOCKET_PATH} -gt $(SUN_PATH_LIMIT) ]; then \
	    echo "W: current path too long ($${#SOCKET_PATH} > 108), skipping tests: $$SOCKET_PATH" ; \
	else \
		echo "I: current path not too long, running tests ($${#SOCKET_PATH}): $$SOCKET_PATH"; dh_auto_test ;\
	fi

It's crap (because it just skips the tests), but at least it doesn't
crash the build. :/

A.

-- 
During the initial stage of the struggle, the oppressed, instead of
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their model of humanity.
                        - Paulo Freire, Pedagogy of the Oppressed