libpathrs v0.1.1 -- "頒布と聞いたら蛇に睨まれた蛙になるよ"

This is the first patch release of the 0.1.z branch of libpathrs. The
primary fixes are related to packaging the Python libpathrs bindings for
distributions.

• procfs: add support for operating on files in the /proc root (or other
  processes) with ProcfsBase::ProcRoot.

  While the cached file descriptor shouldn't leak into containers (container
  runtimes know to set PR_SET_DUMPABLE, and our cached file descriptor is
  O_CLOEXEC), I felt a little uncomfortable about having a global unmasked
  procfs handle sitting around in libpathrs. So, in order to avoid making a
  file descriptor leak by a libpathrs user catastrophic, libpathrs will
  always try to use a "limited" procfs handle as the global cached handle
  (which is much safer to leak into a container) and for operations on
  ProcfsBase::ProcRoot, a temporary new "unrestricted" procfs handle is
  created just for that operartion. This is more expensive, but it avoids a
  potential leak turning into a breakout or other nightmare scenario.

• python bindings: The cffi build script is now a little easier to use for
  distributions that want to build the python bindings at the same time as the
  main library. After compiling the library, set the PATHRS_SRC_ROOT
  environment variable to the root of the libpathrs source directory. This
  will instruct the cffi build script (when called from setup.py or
  python3 -m build) to link against the library built in the source directory
  rather than using system libraries. As long as you install the same library
  later, this should cause no issues.

  Standard wheel builds still work the same way, so users that want to link
  against the system libraries don't need to make any changes.

• Root::mkdir_all no longer does strict verification that directories craeted
  by mkdir_all "look right" after opening each component. These checks didn't
  protect against any practical attack (since an attacker could just get us to
  use a directory by creating it before Root::mkdir_all and we would happily
  use it) and just resulted in spurious errors when dealing with complicated
  filesystem configurations (POSIX ACLs, weird filesystem-specific mount
  options). (#71)

• capi: Passing invalid pathrs_proc_base_t values to pathrs_proc_* will now
  return an error rather than resulting in Undefined Behaviour™.

Thanks to the following people who made this release possible:

• Aleksa Sarai [email protected]
• Ayose [email protected]

Signed-off-by: Aleksa Sarai [email protected]