The Security Liability of Memory Allocation in TEEs: A Design Decision Log

Memory allocation is not a feature — it is a security liability. In high-assurance Trusted Execution Environments (TEEs), you cannot afford the jitter or the fragmentation of a probabilistic global heap. When building the sakshi-core attestation loop for the Sovereign Spine architecture, the requirement was absolute: determinism. Standard heap allocation introduces non-deterministic paths, memory fragmentation, and significantly increases the complexity of the Trusted Computing Base (TCB). For our enclave, that is unacceptable. The Problem: Why GlobalAlloc Fails the TEE Test In a standard Rust environment, we lean on the global allocator. In a TEE, however, the global allocator is a massive attack surface. Jitter: Allocation time varies based on heap state, leaking metadata through timing side-channels. Fragmentation: Heap fragmentation can lead to unpredictable exhaustion, a vector for Denial of Service (DoS) within the enclave. TCB Bloat: The allocator logic itself adds thousands of lines of code to your audit surface. The Solution: Session-Scoped Bump Buffer To enforce architectural certainty, I stripped away the dependency on standard heap allocation in the enclave. Instead, I implemented a session-scoped bump buffer . This is a contract-based memory model: Constant-time execution: Allocation is a pointer increment operation, taking 1-2 CPU cycles. Zero-fragmentation: Memory is allocated linearly and cleared atomically at the session boundary. Simplified TCB: By removing GlobalAlloc , the enclave memory logic is reduced to a handful of lines of verifiable code. Implementation Concept The core logic relies on a pre-allocated static region. We do not ask the system for memory; we own a dedicated slab of silicon-backed memory and manage it strictly within the request lifecycle. // Conceptual implementation of the session-scoped buffer pub struct BumpBuffer { buffer : & 'static mut [ u8 ], offset : usize , } impl BumpBuffer { pub fn alloc ( & mut self , size : usize