Re: [PATCH v2 3/3] t: add tests for safe.directory when running with sudo

[Phillip Wood <phillip.wood123@gmail.com>]

On 28/04/2022 17:55, Junio C Hamano wrote:
> Carlo Marcelo Arenas Belón  <carenas@gmail.com> writes:
> 
>> +test_description='verify safe.directory checks while running as root'
>> +
>> +. ./test-lib.sh
>> +
>> +if [ "$IKNOWWHATIAMDOING" != "YES" ]; then
> 
> Style.
> 
> 	if test "$IKNOWWHATIAMDOING" != "YES"
> 	then

Also naming - we normally prefix test environment variables with 
GIT_TEST_. IKNOWWHATIAMDOING does not tell us what we are allowing by 
setting the variable. Something like GIT_TEST_ALLOW_SUDO would tell us 
what we're letting ourselves in for by setting it.

>> +is_root() {
>> +	test -n "$1" && CMD="sudo -n"
>> +	test $($CMD id -u) = $(id -u root)
>> +}
> 
> Style.
> 
> 	is_root () {
> 		... body ..
> 
> But more importantly, why do we need this in the first place?
> SANITY prerequisite checks if the user is running as root or
> non-root---can't we use it here?
> 
> Or perhaps my reading is wrong?  I assumed from its name that it was
> just "see if we are running as user 'root' and return 0 or non-zero
> to answer", but if it does more than that, like priming "sudo", then
> probably it is misnamed.

I'm confused by this as well. Also if $1 is empty we run whatever 
happens to be in $CMD.

Best Wishes

Phillip

>> +test_lazy_prereq SUDO '
>> +	is_root sudo &&
>> +	! sudo grep -E '^[^#].*secure_path' /etc/sudoers
>> +'
> 
> OK.
> 
>> +test_lazy_prereq ROOT '
>> +	is_root
>> +'
>> +
>> +test_expect_success SUDO 'setup' '
>> +	sudo rm -rf root &&
>> +	mkdir -p root/r &&
>> +	sudo chown root root &&
>> +	(
>> +		cd root/r &&
>> +		git init
>> +	)
>> +'
> 
> We have a root-owned directory "root" with a subdirectory "r" owned
> by us.  We want to be able to use our "root/r" directory as a
> repository.  OK.
> 
> The prerequisite allows this test to be started as root, but I do
> not quite see the point.  It may pass when started as root, but it
> is not testing what this test is designed to check (i.e. an ordinary
> user who has repository at root/r can do things there).
> 
>> +test_expect_success SUDO 'sudo git status as original owner' '
>> +	(
>> +		cd root/r &&
>> +		git status &&
>> +		sudo git status
>> +	)
>> +'
> 
> And the directory can be used by the user under "sudo", too.  Good.
> 
> The same "this is allowed to run as root, but why?" question
> applies.  If this was started by 'root', root, root/r and
> root/r/.git all are owned by 'root' and we are checking if 'root'
> can run 'git status' as 'root' (or 'root' via sudo) there.  Such a
> test may well pass, but it is not catching a future regression on
> the code you wrote for this series.
> 
>> +test_expect_success SUDO 'setup root owned repository' '
>> +	sudo mkdir -p root/p &&
>> +	sudo git init root/p
>> +'
> 
> Now we go on to create root owned repository at root/p
> 
>> +test_expect_success SUDO,!ROOT 'can access if owned by root' '
>> +	(
>> +		cd root/p &&
>> +		test_must_fail git status
>> +	)
>> +'
> 
> And as an ordinary user, we fail to access a repository that is
> owned by a wrong person (i.e. root).  !ROOT (or SANITY) prereq
> should be there NOT because the test written here would fail if run
> by root, but because running it as root, even if passed, is totally
> pointless, because we are *not* testing "person A has a repository,
> person B cannot access it" combination.
> 
> The other side of the same coin is that the lack of !ROOT (or
> SANITY) prereq in earlier tests I pointed out above misses the point
> of why we have prerequisite mechanism in the first place.  It is not
> to mark a test that fails when the precondition is not met.  It is
> to avoid running code that would NOT test what we want to test.
> 
> The difference is that a test that passes for a wrong reason
> (e.g. we wanted to see of person A can access a repository of their
> own even when the user identity is tentatively switched to 'root'
> via 'sudo'---if person A is 'root', the access will be granted even
> if the special code to handle 'sudo' situation we have is broken)
> should also be excluded with prerequisite.
> 
>> +test_expect_success SUDO,!ROOT 'can access with sudo' '
>> +	# fail to access using sudo
>> +	(
>> +		# TODO: test_must_fail missing functionality
> 
> Care to explain a bit in the log message or in this comment the
> reason why we do not use test_must_fail but use ! here?  Are we
> over-eager to reject anything non "git" be fed, or something?
> 
>> +		cd root/p &&
>> +		! sudo git status
>> +	)
>> +'
> 
> The repository is owned by 'root', but because of the 'sudo'
> "support", you cannot access the repository with "sudo git".
> 
> The test title needs updating.  We expect that the repository cannot
> be accessed under sudo.
> 
>> +test_expect_success SUDO 'can access with workaround' '
> 
> "workarounds", I think.
> 
>> +	# provide explicit GIT_DIR
>> +	(
>> +		cd root/p &&
>> +		sudo sh -c "
>> +			GIT_DIR=.git GIT_WORK_TREE=. git status
>> +		"
>> +	) &&
>> +	# discard SUDO_UID
>> +	(
>> +		cd root/p &&
>> +		sudo sh -c "
>> +			unset SUDO_UID &&
>> +			git status
>> +		"
>> +	)
>> +'
> 
> Again, this lack !ROOT (or SANITY) because tests pass for a wrong
> reason.
> 
> Overall, I like the simplicity and clarity of "do not start this
> test as 'root'" in the previous round much better.
> 
> But other than that, the test coverage given by this patch looks
> quite sensible.
> 
> Thanks.
> 
>> +
>> +test_expect_success SUDO 'cleanup' '
>> +	sudo rm -rf root
>> +'
>> +
>> +test_done