AWSCRT

Problem

Software components sometimes need to interact with higher privilege parts of the operating system, often requiring administrative access to accomplish a task. System certificate stores are databases that define the chain of trust for a machine. These databases control the list of websites the machine can securely connect to, and the list of applications that the operating system implicitly trusts. For that reason, attackers often abuse system certificate stores to ensure their malicious code executes without being detected by security solutions. While the presence of code that tampers with system certificate stores does not necessarily imply malicious intent, all of its uses in a software package should be documented and approved. Only select applications should consider using functions that interact with system certificate stores. One example of acceptable use for such functions is adding publisher certificates to the system trust store during software installation.

Problem

Control Flow Guard (CFG/CFI) protects the code flow integrity by ensuring that dynamic calls are made only to vetted functions. Trusted execution paths rely on the ability of the operating system to build a list of valid function targets. Certain functions can intentionally be disallowed to prevent malicious code from deactivating vulnerability mitigation features. A list of such invalid function targets can include publicly exported symbols. Applications that enhance control flow integrity through export suppression rely on libraries to mark their publicly visible symbols as suppressed. This is done for all symbols that are considered to be sensitive functions, and to which access should be restricted. It is considered dangerous to mix applications that perform export suppression with libraries that do not.

Problem

Control Flow Guard (CFG/CFI) protects the code flow integrity by ensuring that indirect calls are made only to vetted functions. This mitigation protects dynamically resolved function targets by instrumenting the code responsible for transferring execution control. Higher-level programming languages implement structured exception handling by managing their own code flow execution paths. As such, they are subject to code flow hijacking during runtime. Language-specific exception handling mitigation enforces execution integrity by instrumenting calls to manage execution context switching. Any deviation from the known and trusted code flow paths will cause the application to terminate. This makes malicious code less likely to execute.

Problem

On Linux, external symbols are resolved via the procedure linkage table (PLT) and the global offset table (GOT). Without any protection, both are writable at runtime and thus leave the executable vulnerable to pointer hijacking - an attack where the function address is overwritten with an address of a malicious function. Pointer hijacking can be mitigated by using full read-only relocations, which instruct the compiler to unify global offset tables into a single read-only table. This requires that all external function symbols are resolved at load-time instead of during execution, and may increase loading time for large programs.

Problem

Digital signatures are applied to applications, packages and documents as a cryptographically secured authenticity record. Signatures verify the origin and the integrity of the object they apply to. The integrity validation relies on the cryptographic strength of the encryption and the hash verification algorithm. If either of the two is considered weak by current standards, there is a chance the signed object could be maliciously modified, without triggering the integrity failure check.