ueno / ruby-gpgme / 173

89%

master: 89%

Pull #135

travis-ci

ctx: do not autoclose in `path_function`

The default callback for writing a password to GPGME takes a file
descriptor and needs to write the given password to it. By creating a
new `IO` object directly on the file descriptor, the object will take
ownership of it. This is a problem because the file descriptor passed to
this callback will be explicitly closed by GPGME, and eventually, the
`IO` allocated in `self.pass_function` will be garbage collected,
closing the file descriptor again.

Usually, closing a file descriptor that has already been closed results
in a silent `EBADFD`, but a serious race condition can happen if the
Kernel allocates the same file descriptor (e.g. through another `open`
call in another part of your Ruby program): when GC triggers, the
FD will be closed unexpectedly.

To prevent this, simply set `IO#autoclose = false` on the `IO` object:
the garbage collector will no longer close the file descriptor on
cleanup, so the descriptor will only be closed once (in the explicit
close call performed by us).

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