Re: [Qemu-devel] Make 9pfs buildable for Windows

[Michael Fritscher]

> On 29/09/2017 16:14, Michael Fritscher wrote:
>>> Yes, that's pretty much the only way to do it; it's not the easiest
>>> thing because you have to use NT kernel APIs (NtCreateFile) rather than
>>> e.g. CreateFile.  Likewise for NtQueryAttributesFile,
>>> NtQueryDirectoryObject, etc. NtOpenDirectoryObject. :(
>>>
>>> Paolo
>>>
>> Hi,
>>
>> why do I need the NT* functions instead of the "normal" ones from
>> kernel32? And it was working even with the posix functions some time ago
>> (Which I'll port to current qemu atm)
>
> openat lets you create a file from a directory handle and relative path.
>  CreateFile doesn't let you do that, only the ntdll functions can.
>
> Paolo
>

Hi,

dumb question: what is the advantage of openat vs. open - only the thing
that someone doesn't need to build the path together by hand?

If I understand the man page of openat correctly, it does _not_ prevent
someone to break out of the jail by using e.g. ../../../blah .
If this assumption is correctly perhaps it is better to avoid using the
*at function family (as it was some time ago) and sanitize the path (by
somehow canonizing it and than check if the beginning is ok).

Then I could use the "normal" posix function again and avoid using the NT*
Functions directly which is not soooo nice for various reasons.

Best regards,
Michael Fritscher