CVE-2021-24116: 
NixOS vulnerability analysis and mitigation

In wolfSSL through 4.6.0, a side-channel vulnerability in base64 PEM file decoding allows system-level (administrator) attackers to obtain information about secret RSA keys via a controlled-channel and side-channel attack on software running in isolated environments that can be single stepped, especially Intel SGX (NVD, GitHub).

The vulnerability stems from a non-constant time implementation for base64 decoding in WolfSSL before version 4.6.0. The issue specifically involves the usage of a lookup table in decoding keys stored as PEM files, which allows an attacker to obtain key information by tracking the accessed cache lines during key decoding. This vulnerability was demonstrated particularly in Intel SGX environments (GitHub).

The vulnerability enables system-level attackers to extract sensitive information about RSA private keys through side-channel analysis. This is particularly concerning in secure enclave environments like Intel SGX, where the isolation of sensitive cryptographic operations is a critical security requirement (NVD).

The vulnerability requires system-level (administrator) access and the ability to perform controlled-channel and side-channel attacks in environments that can be single-stepped. The attack is particularly effective against software running in isolated environments such as Intel SGX (NVD).

The vulnerability was fixed in WolfSSL version 4.6.0. Users are recommended to upgrade to this version or later to address the side-channel vulnerability in base64 PEM file decoding (GitHub).