Incorrect reliance on Trait memory layout in mopa
Critical severity
GitHub Reviewed
Published
Jan 6, 2022
to the GitHub Advisory Database
•
Updated Jun 13, 2023
Description
Published by the National Vulnerability Database
Dec 27, 2021
Reviewed
Jan 6, 2022
Published to the GitHub Advisory Database
Jan 6, 2022
Last updated
Jun 13, 2023
The mopa crate redefines the deprecated TraitObject struct from core::raw. This is done to then transmute a reference to a trait object (&dyn Trait for any trait Trait) into this struct and retrieve the data field for the purpose of downcasting. This is used to implement downcast_ref_unchecked(), in terms of which downcast_ref() is also implemented. Same goes for mutable reference downcasting and Box downcasting.
The Rust compiler explicitly reserves the right to change the memory layout of &dyn Trait for any trait Trait. The worst case scenario is that it swaps data and vtable, making an executable location breach and compromisation of ASLR possible, since reads from data would read vtable instead. Likewise, arbitrary code execution is also theoretically possible if reads of vtable generated by the compiler read data instead.
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