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rust-secp256k1-unsafe-fast
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context: introduce unsafe `PreallocatedContext` trait 

Fixes unsoundness in `preallocated_gen_new` which previously did not
properly constrain the lifetime of the buffer used to back the context
object. We introduce an unsafe marker trait, and impl it for our
existing preallocated-context markers.

Annoyingly the trait has to be public even though it should never be
used directly, and is only used alongside the sealed `Context` trait,
so it is de-facto sealed itself.

Fixes #543
This commit is contained in:
Andrew Poelstra 2022-12-02 12:58:32 +00:00
parent 525613902c
commit f961497e69
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1 changed files with 9 additions and 1 deletions
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src/context.rs
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@ -318,7 +318,15 @@ unsafe impl<'buf> Context for AllPreallocated<'buf> {
} }
} }
impl<'buf, C: Context + 'buf> Secp256k1<C> { /// Trait marking that a particular context object internally points to
/// memory that must outlive `'a`
pub unsafe trait PreallocatedContext<'a> {}
unsafe impl<'buf> PreallocatedContext<'buf> for AllPreallocated<'buf> {}
unsafe impl<'buf> PreallocatedContext<'buf> for SignOnlyPreallocated<'buf> {}
unsafe impl<'buf> PreallocatedContext<'buf> for VerifyOnlyPreallocated<'buf> {}
impl<'buf, C: Context + PreallocatedContext<'buf>> Secp256k1<C> {
/// Lets you create a context with a preallocated buffer in a generic manner (sign/verify/all). /// Lets you create a context with a preallocated buffer in a generic manner (sign/verify/all).
pub fn preallocated_gen_new(buf: &'buf mut [AlignedType]) -> Result<Secp256k1<C>, Error> { pub fn preallocated_gen_new(buf: &'buf mut [AlignedType]) -> Result<Secp256k1<C>, Error> {
#[cfg(target_arch = "wasm32")] #[cfg(target_arch = "wasm32")]