CVE-2022-39294

conduit-hyper integrates a conduit application with the hyper server. Prior to version 0.4.2, conduit-hyper did not check any limit on a requests length before calling hyper::body::to_bytes. An attacker could send a malicious request with an abnormally large Content-Length, which could lead to a panic if memory allocation failed for that request. In version 0.4.2, conduit-hyper sets an internal limit of 128 MiB per request, otherwise returning status 400 (Bad Request). This crate is part of the implementation of Rusts crates.io, but that service is not affected due to its existing cloud infrastructure, which already drops such malicious requests. Even with the new limit in place, conduit-hyper is not recommended for production use, nor to directly serve the public Internet.

Weakness

The product receives input that is expected to specify a quantity (such as size or length), but it does not validate or incorrectly validates that the quantity has the required properties.

Affected Software

Extended Description

Specified quantities include size, length, frequency, price, rate, number of operations, time, and others. Code may rely on specified quantities to allocate resources, perform calculations, control iteration, etc. When the quantity is not properly validated, then attackers can specify malicious quantities to cause excessive resource allocation, trigger unexpected failures, enable buffer overflows, etc.

Potential Mitigations

• Assume all input is malicious. Use an “accept known good” input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
• When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, “boat” may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as “red” or “blue.”
• Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code’s environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.

References

• https://github.com/conduit-rust/conduit-hyper/security/advisories/GHSA-9398-5ghf-7pr6