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'chmod' equivalent in snapshot preview1? #33

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titzer opened this issue Jul 28, 2021 · 4 comments
Open

'chmod' equivalent in snapshot preview1? #33

titzer opened this issue Jul 28, 2021 · 4 comments
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enhancement New feature or request

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@titzer
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titzer commented Jul 28, 2021

It appears that snapshot preview 1 does not have a way to change file permissions. This is important functionality for one of my use cases (a compiler that generates executables). This functionality does appear to be planned for the next version of wasi.

Is snapshot preview1 being updated? Is there interest in adding a chmod-like capability?

If so, I would propose a simple fs_chmod(fd: i32, mode: i32) function.
@sunfishcode sunfishcode transferred this issue from WebAssembly/WASI Jul 28, 2021
@sunfishcode
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We've have a permissions_set function in the latest proposal, though it's not yet in a published shapshot. It's currently limited to just read/write/execute, as well as a private flag, rather than exposing the Unix user/group/other bits individually. But the upside is that it should be implementable on Windows. Do you think that would be enough for your usecase, or do you need more fine-grained control?

Adding a full chmod is also an option, though it might need to be designed in a way that would allow it to fail if the underlying filesystem doesn't use Unix-style user/group/other.

@titzer
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titzer commented Jul 28, 2021

For my use case, just u+x would be enough to limp along, but that feels like it wouldn't be general enough. Designating permission categories user/group/other and failing if one of the categories does not exist would allow an app to at least try setting permissions. Keep in mind there is also the setuid bit, which is esoteric, but useful in some situations.

@sunfishcode
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setuid is tricky (even ignoring its long troubled security history), because setuid allows programs to effectively grant the full host-process authority to other programs, and WASI programs may be considered less privileged than the host-process user. There are ways we could model it, such as passing programs an extra handle to represent a "host-process authority" that they'd have to pass into the API to set a setuid bit. But before we start designing something, it'd be good to have specific motivating use cases.

@titzer
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titzer commented Jul 28, 2021

I'm happy to leave setuid out of functionality for chmod, as I don't have a use case for it. I just mentioned it for completeness.

sunfishcode added a commit to sunfishcode/wasi-filesystem that referenced this issue Nov 22, 2021
@sunfishcode
Port the wasi-filesystem API to the new wai format.
c0a9a5d 
This makes a number of changes, to make use of interface-types features such
as `expected`, variant types, and resources. The change to use resources in
particular means that filesystem functions are now methods of the `descriptor`
resource. Since this means renaming everything, take this opportunity to
introduce a new naming conventions, with `_at` being used for functions that
take dirfd+path arguments.

This also eliminates the `rights` concept what was present in earlier versions
of WASI, has has discussed in WebAssembly#31. This required adding new flags to `open_at`,
so while here, this also adds basic `chmod`-like support, as discussed in WebAssembly#33.

And, this removes support for readdir seeking (seekdir/telldir), as discussed
in WebAssembly#7.

And it adds a fifo file type and a more general socket type, as discussed in
sunfishcode added a commit to sunfishcode/wasi-filesystem that referenced this issue Nov 22, 2021
@sunfishcode
Port the wasi-filesystem API to the new wai format.
1e12701 
This makes a number of changes, to make use of interface-types features such
as `expected`, variant types, and resources. The change to use resources in
particular means that filesystem functions are now methods of the `descriptor`
resource. Since this means renaming everything, take this opportunity to
introduce a new naming conventions, with `_at` being used for functions that
take dirfd+path arguments.

This also eliminates the `rights` concept what was present in earlier versions
of WASI, has has discussed in WebAssembly#31. This required adding new flags to `open_at`,
so while here, this also adds basic `chmod`-like support, as discussed in WebAssembly#33.

And, this removes support for readdir seeking (seekdir/telldir), as discussed
in WebAssembly#7.

And it adds a fifo file type and a more general socket type, as discussed in
@sunfishcode sunfishcode mentioned this issue Nov 22, 2021
Closed
sunfishcode added a commit to sunfishcode/wasi-filesystem that referenced this issue Nov 22, 2021
@sunfishcode
Port the wasi-filesystem API to the new wai format.
7661609 
This makes a number of changes, to make use of interface-types features such
as `expected`, variant types, and resources. The change to use resources in
particular means that filesystem functions are now methods of the `descriptor`
resource. Since this means renaming everything, take this opportunity to
introduce a new naming conventions, with `_at` being used for functions that
take dirfd+path arguments.

This also eliminates the `rights` concept what was present in earlier versions
of WASI, has has discussed in WebAssembly#31. This required adding new flags to `open_at`,
so while here, this also adds basic `chmod`-like support, as discussed in WebAssembly#33.

And, this removes support for readdir seeking (seekdir/telldir), as discussed
in WebAssembly#7.

And it adds a fifo file type and a more general socket type, as discussed in
sunfishcode added a commit to sunfishcode/wasi-filesystem that referenced this issue Nov 22, 2021
@sunfishcode
Port the wasi-filesystem API to the new wai format. WebAssembly#35
41621d1 
This makes a number of changes, to make use of interface-types features such
as expected, variant types, and resources. The change to use resources in
particular means that filesystem functions are now methods of the descriptor
resource. Since this means renaming everything, take this opportunity to
introduce a new naming conventions, with _at being used for functions that
take dirfd+path arguments.

This also eliminates the rights concept what was present in earlier versions
of WASI, has has discussed in WebAssembly#31. This required adding new flags to open_at,
so while here, this also adds basic chmod-like support, as discussed in WebAssembly#33.

And, this removes support for readdir seeking (seekdir/telldir), as discussed
in WebAssembly#7.

And it adds a fifo file type and a more general socket type, as discussed in WebAssembly#4.
@sunfishcode sunfishcode mentioned this issue Nov 22, 2021
Merged
sunfishcode added a commit that referenced this issue Dec 15, 2021
@sunfishcode
Port the wasi-filesystem API to the new wai format. #35
54203de 
This makes a number of changes, to make use of interface-types features such
as expected, variant types, and resources. The change to use resources in
particular means that filesystem functions are now methods of the descriptor
resource. Since this means renaming everything, take this opportunity to
introduce a new naming conventions, with _at being used for functions that
take dirfd+path arguments.

This also eliminates the rights concept what was present in earlier versions
of WASI, has has discussed in #31. This required adding new flags to open_at,
so while here, this also adds basic chmod-like support, as discussed in #33.

And, this removes support for readdir seeking (seekdir/telldir), as discussed
in #7.

And it adds a fifo file type and a more general socket type, as discussed in #4.
@sunfishcode sunfishcode added the enhancement New feature or request label Jul 20, 2022
@Puellaquae Puellaquae mentioned this issue Sep 27, 2022
Open
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@sunfishcode sunfishcode mentioned this issue Dec 22, 2022
Open
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