HeapSafe: Securing Unprotected Heaps in RISC-V

Abstract

HeapSafe is a novel, lightweight hardware-assisted security scheme designed to mitigate critical memory corruption vulnerabilities, such as heap overflow and use-after-free, in bare-metal RISC-V systems. The approach utilizes a configurable coprocessor, decoupled from the main core, to validate heap accesses by tagging pointers with metadata indices and enforcing tag propagation. HeapSafe achieves superior security with a minimal 1.59% area overhead and only 1.5X performance overhead, proving 22% faster than corresponding software-based protections.

Report

Report: HeapSafe: Securing Unprotected Heaps in RISC-V

Key Highlights

• Innovation: HeapSafe is a lightweight, hardware-assisted scheme designed specifically for securing heap buffers in RISC-V Systems-on-Chip (SoC).
• Vulnerability Mitigation: It effectively mitigates dangerous memory corruption flaws, specifically heap overflow and use-after-free vulnerabilities.
• Implementation Architecture: The security mechanism is implemented as a configurable coprocessor, decoupled from the main RISC-V core.
• Performance Metrics (Baseline HeapSafe): It incurs a 1.5X performance overhead and a minimal 1.59% area overhead.
• Software Comparison: HeapSafe provides significant speed benefits, running 22% faster than comparable software-only protection methods.
• Optimized Design: An asynchronous version, HeapSafe-nb (non-blocking), further improves performance by 27% over the synchronous HeapSafe design.

Technical Details

• Target System: RISC-V architecture, specifically addressing bare-metal execution environments common in embedded systems where memory corruption risks are high.
• Core Mechanism (Tagging): The scheme secures pointers by tagging them with metadata indices. This metadata is associated with the allocated heap buffers.
• Security Enforcement: HeapSafe enforces tag propagation during pointer arithmetic and commonly used pointer operations to maintain security integrity.
• Validation Unit: The access validation logic resides within the decoupled, configurable coprocessor, allowing the main core to offload security checks.
• Design Variants: The study compares two distinct hardware designs: the synchronous HeapSafe and the asynchronous HeapSafe-nb, the latter utilizing non-blocking validation to reduce pipeline stalls.

Implications

• Elevating Security in RISC-V: HeapSafe provides a necessary, high-performance solution for fundamental memory safety issues that are critical for the adoption of RISC-V in security-sensitive or high-integrity domains.
• Suitability for Embedded Systems: Due to its lightweight nature (low area and modest performance overhead), this solution is highly viable for resource-constrained embedded systems and IoT devices where complex software protections are often impractical.
• Hardware-Software Co-Design: This work demonstrates the benefit of specialized hardware augmentation (the coprocessor model) to accelerate security tasks, potentially setting a standard for future hardware security features in open architectures.
• Addressing Bare-Metal Risks: By securing the heap without relying on a robust operating system layer, HeapSafe significantly improves the security posture of low-level, bare-metal RISC-V applications.