Ouroboros Soundess Issue (#1707)

crates/ouroboros/RUSTSEC-0000-0000.md

@@ -0,0 +1,51 @@
+```toml
+[advisory]
+id = "RUSTSEC-0000-0000"
+package = "ouroboros"
+date = "2023-06-11"
+url = "https://github.com/joshua-maros/ouroboros/issues/88"
+informational = "unsound"
+
+[versions]
+patched = []
+```
+
+# Ouroboros is Unsound
+
+## Summary
+
+Ouroboros has a soundness problem. A fix was attempted but 
+unsuccessful, leaving the crate unmaintained. Migrate code to use 
+[self_cell](https://github.com/Voultapher/self_cell) instead.
+
+## More details:
+
+Currently, Ouroboros works internally by creating a struct where all 
+uses of 'this are replaced by 'static. However, a recent addition to 
+Miri checks that references passed to functions are valid during the 
+entire execution of the function, even when those references are 
+passed inside a struct. This poses an issue for dropping 
+self-referencing values, as the reference becomes invalid during the 
+dropping process. Effectively, since self-referencing structs are 
+not allowed in vanilla Rust, there is no allowance for dropping data
+during a function that has also been given a reference to that data. 
+There's usually no way to pass a and &a to the same function.
+
+A fix was attempted, where the struct would be turned in to a raw 
+byte array and only transformed back into the underlying data type 
+inside each function. This is allowable as a reference can be 
+created and die over the body of a function, as long as the 
+reference was created inside the function. However, this is also 
+not sound if the original struct contains padding. There is no 
+way to initialize padding bytes to a known value that Miri will 
+accept, so when it is cast to an array some of the bytes contain 
+uninitialized values. This is not acceptable (despite the fact 
+that these bytes are never read) due to the potential for 
+optimizations that may read from the uninitialized bytes. Besides 
+which, this fix does not allow for template or constant parameters 
+as there is no way to check the size of a templated type without 
+giving specific, concrete values for the template parameters.
+
+The crate at this point is no longer maintained, and previous
+users should migrate their code to use 
+[self_cell](https://github.com/Voultapher/self_cell) instead.