refactor: fix soundness hole in Handle API
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CBenoit
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Aug 28, 2024
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| // Wraps a borrowed Windows [`HANDLE`]. | ||
| pub fn new_borrowed(handle: HANDLE) -> Self { | ||
| // SAFETY: It’s safe to wrap a non-owning Handle as we’ll not call `CloseHandle` on it. | ||
| unsafe { Self::new(handle, false) } | ||
| } |
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When we know that the handle is not owned in a static way, we can use the safe function new_borrowed which never causes any UB.
CBenoit
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Aug 28, 2024
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| pub fn new(handle: HANDLE, owned: bool) -> Self { | ||
| // Wraps a Windows [`HANDLE`]. | ||
| // | ||
| // # Safety | ||
| // | ||
| // When `owned` is `true`: | ||
| // | ||
| // - `handle` is a valid handle to an open object. | ||
| // - `handle` is not a pseudohandle. | ||
| // - The caller is actually responsible for freeing the `HANDLE` when the value goes out of scope. | ||
| // | ||
| // When `owned` is `false`: no outstanding precondition. | ||
| pub unsafe fn new(handle: HANDLE, owned: bool) -> Self { | ||
| Self { raw: handle, owned } | ||
| } | ||
|
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||
| // Wraps an owned Windows [`HANDLE`]. | ||
| // | ||
| // # Safety | ||
| // | ||
| // - `handle` is a valid handle to an open object. | ||
| // - `handle` is not a pseudohandle. | ||
| // - The caller is actually responsible for freeing the `HANDLE` when the value goes out of scope. | ||
| pub unsafe fn new_owned(handle: HANDLE) -> Self { | ||
| // SAFETY: Same preconditions as the called function. | ||
| unsafe { Self::new(handle, true) } |
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The Drop implementation is assuming we constructed the Handle object in a sane way to call CloseHandle, but there is no way for us to verify that the handle is actually owned outside of the callsite. Conceptually, calling Handle::new_owned(handle) or Handle::new(handle, true) is like calling the unsafe function CloseHandle and thus must inherits its safety preconditions.
pacmancoder
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Aug 28, 2024
CBenoit
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The API of
Handleinwin-api-wrappersis allowing UB without unsafe code. I adjusted the API to fix the hole.Note that this PR is not fixing any vulnerability or bug per se. It only fixes the unsound safe API that we are using correctly in this repository only.
cc @kbouchard-dev