Re Angr

MCP server for angr (UC Santa Barbara, BSD) — symbolic execution + CFG + reaching-definitions. The "I have a heavy constraint problem and want a second opinion" tool.

Why

The other RE-AI MCP servers handle most RE tasks well. But there are two cases where angr's approach is materially different from re-triton's:

• CFG construction. angr's CFG is built statically (no execution, no emulation) and is one of the most accurate in the open-source world. re-rizin.analyze_function is faster but uses different heuristics; cross-validating with angr catches edge cases.
• Reaching definitions. angr's dataflow analysis is what makes re-mba-deobfuscate reliable. An MBA identity like x + y == (x & y) + (x | y) looks like real arithmetic, but the reaching-defs graph reveals that (x & y) and (x | y) were defined from the same source — the identity is a no-op substitution.

re-angr exposes both, and re-triton for the same constraint problem. The two together give the analyst a much stronger signal than either alone.

Architecture

The Python MCP server is a thin wrapper around an angr-cli Python helper installed by install.sh:

Claude Code (MCP stdio)
  │
  ▼
re-angr server (Python, this directory)
  │  subprocess.run(...)
  ▼
angr-cli (small Python script, wraps the angr API)
  │
  └─ angr>=9.2 (pip-installed, the actual binary analysis platform)

The subprocess boundary is intentional: angr keeps long-lived AngrProject objects, which don't survive across JSON-RPC calls cleanly. The helper spawns a fresh Python process per call, which matches the per-tool-call model the MCP server uses.

Tools

Tool	What it does
check_angr	Health check — return angr + cle versions
build_cfg	Build a control-flow graph of a binary (or one function)
symbolic_exec	Run angr symbolic execution starting at an address
reaching_definitions	Compute the def-use graph for a function

Install

./install.sh installs angr>=9.2 from PyPI.

To install standalone:

pip install 're-angr[core]'

Requirements

• Python 3.11+
• angr>=9.2 (BSD, on PyPI)
• No system dependencies

Degraded mode

If angr-cli is not installed, every tool returns {"status": "WARN", "error": "angr-cli not installed; run install.sh", ...}. The Python MCP server itself always loads so Claude Code can surface the install hint.

Pairing with re-triton

re-triton is the fast first-call symbolic executor (Triton 1.0 with Quarkslab's bindings). re-angr is the cross-validation pass:

• Use re-triton.solve_constraint for "what input reaches this branch?" (fast, in-process).
• Use re-angr.symbolic_exec for "does another symbolic executor agree?" (slower, but independent).
• Use re-angr.reaching_definitions for "where was this variable defined?" (Triton doesn't compute this — it's a static dataflow analysis).

For MBA-obfuscated arithmetic: re-triton.solve_constraint solves the symbolic equation; re-angr.reaching_definitions shows the variable is a no-op substitution. Both together is a strong "this is a known identity" signal.

For CFG construction: re-rizin.analyze_function is the fast first call; re-angr.build_cfg is the cross-validation pass. Discrepancies (e.g. angr sees an indirect call that rizin doesn't) are worth investigating.