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Date: Wed, 25 Nov 2020 22:40:00 +0300
From: Alexey Izbyshev <izbyshev@...ras.ru>
To: musl@...ts.openwall.com
Subject: Re: realpath without procfs -- should be ready for inclusion

On 2020-11-25 18:02, Rich Felker wrote:
> On Tue, Nov 24, 2020 at 12:21:36PM +0300, Alexey Izbyshev wrote:
>> On 2020-11-24 09:30, Rich Felker wrote:
>> >I think before this goes upstream we should have a good set of
>> >testcases that can be contributed to libc-test. Do you have ideas for
>> >coverage? Some that come to mind:
>> >
>> Added some more ideas.
>> 
>> >- Absolute argument starting with /, //, and ///
>> - Absolute argument equal to one of /, //, and ///
>> >- Absolute symlink target starting with /, //, and ///
>> - Absolute symlink target equal to one of /, //, and ///, with the
>> link separated from the following component with /, //
>> >- Final / after symlink-to-dir, dir, symlink-to-nondir, nondir
>> - Intermediate / after symlink-to-nondir, nondir
>> >- Final / in link contents after [the above]
>> - Multiple / after ., .., normal component
>> >- Initial .. in argument, cwd root or non-root
>> >- Initial .. in symlink target, symlink in root or non-root
>> >- Initial ...
>> >- .. following symlink-to-dir, dir, symlink-to-nondir, nondir
>> - . following symlink-to-dir, dir, symlink-to-nondir, nondir
>> >- More .. than path depth
>> >- Null argument
>> >- Empty string argument
>> - Argument consisting of a single ., ..
>> >- Empty string link contents (testable only with seccomp hack)
>> >- Argument valid abs path exact length PATH_MAX-1
>> >- Argument valid rel path exact length PATH_MAX-1 to short abs path
>> - Argument with PATH_MAX length (ENAMETOOLONG)
>> - A relative symlink in the argument such that the length of the
>> result is PATH_MAX-1 (valid path), PATH_MAX (ENAMETOOLONG)
>> - An absolute symlink in the argument similar to the above
>> - A relative argument with the current directory similar to the above
>> - An argument consisting of a single (relative, absolute) symlink
>> with the target having length PATH_MAX-1
>> - An argument ending with a relative symlink with the target having
>> length PATH_MAX-1 (ENAMETOOLONG)
>> - An argument ending with an absolute symlink with the target having
>> length PATH_MAX-1 (valid path)
> 
> OK, here are my WIP testcases. They only cover static cases, not
> anything that depends on implementation-defined value of PATH_MAX or
> how the working directory combines with tests to reach PATH_MAX.
> 
> The way you run the tests is by running ../setup.sh then ../checker.sh
> from a scratch subdir of the dir containing the test files (realpath.c
> also needs to be compiled and linked against the realpath impl you
> want to test)
> 
> Format of the testcase file is one test per line, input and expected
> output separated by whitespace. . and .. in expected output are
> translated based on working dir. Error names are treated as output
> since they don't fall in same namespace (no initial /).
> 
> All tests are currently passing for me.
> 
Tests pass for me too. For the previous procfs-based impl and for glibc 
realpath(), the set of failing tests is exactly the same (all tests for 
//):

// -> / (expected //)
//.. -> / (expected //)
alt1 -> / (expected //)
alt1/ -> / (expected //)
alt1/. -> / (expected //)
alt2 -> / (expected //)
alt2/ -> / (expected //)
alt2/. -> / (expected //)

> If you have ideas for additional static tests that fit the form and
> are easy to add, please suggest.
> 
A test for ELOOP is easy to add.

Some of the skipped tests of the initially proposed list also fall 
within "static tests" limitations, e.g.:

* trailing . (could be added in the form of <normal, ENOTDIR, ENOENT> 
triples as existing tests for trailing / and ..)

* initial .. (or .) in a symlink target

* multiple / in the middle of the argument before a component that is 
not going to be removed

Alexey




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