reskSecure

Per-user LLM firewall: unauthorized content becomes physically ungeneratable.

🔗 resk.fr/projects/resksecure — part of RESK Security

📚 Guides: Capability Bitmasks: Real RBAC for LLM Applications · Data Protection in AI

Installation

pip install resksecure

Requires Python ≥ 3.13, PyTorch ≥ 2.0, transformers ≥ 4.35, resklogits ≥ 0.1.0.

Usage rapide (30 seconds)

Define a policy (policy.yaml):

version: "1.0"
policies:
  - mask: 7
    name: contributor
    default: true
    rules:
      - { phrase: "DROP TABLE", mode: hard }
      - { phrase: "salaries",   mode: bias, penalty: -5.0 }
    tools:
      send_email: { required_bit: 1 }
      read_sql:   { required_bit: 2 }

Enforce it inside generation:

from resksecure import BitmaskLogitsProcessor, load_policy, verify_tool_action

policy = load_policy("policy.yaml")
processor = BitmaskLogitsProcessor(
    mask=7, model_name="mistralai/Mistral-7B-v0.1",
    tokenizer=tokenizer, policy_set=policy, device="cuda",
)
outputs = model.generate(**inputs, logits_processor=[processor])

# Defense-in-depth: verify tool calls against the bitmask
if not verify_tool_action("send_email", user_mask=7, policy_set=policy):
    raise PermissionError("Action not authorized")

Pourquoi reskSecure ?

Prompt filters are jailbreakable; post-generation moderation detects violations after the content is already emitted. reskSecure works at the logits level: every candidate token is checked against an Aho-Corasick automaton before sampling. If a user's capability bitmask doesn't allow it, the model cannot start generating the banned phrase or the disallowed tool call — no prompt engineering can change that.

	reskSecure	Prompt-based filters	Post-generation moderation	Generic policy engines (OPA…)
Where it acts	Inside the generation loop	On the prompt	On the finished output	App/API layer
Bypassable by prompt injection	❌	✅	❌	⚠️ if model emits
Forbidden content ever emitted	No	Yes	Yes — first	Yes
Per-user permissions	✅ capability bitmask	⚠️ prompt-level	❌ global policy	✅ but not generation
Tool-call gating at token level	✅ trigger phrases blocked per bit	❌	❌	⚠️ execution-time only
Policy hot-reload, no restart	✅ PolicyWatcher	—	—	✅
What it protects	LLM output itself	LLM input	Nothing retroactively	App resources

Documentation

• Policy reference (all fields) — below and in config/example_policy.yaml
• Examples — examples/
• Engine internals — resklogits

Policy reference

Field	Type	Description
mask	int	Capability bitmask identifying this policy
name	string	Human-readable policy name
strict	bool	Stop generation at the first banned prefix
default	bool	Used when no exact mask matches
rules	list	Phrase rules: phrase, mode (hard = -inf, bias = penalty), penalty
tools	dict	Tool name → required_bit + optional trigger_phrases

How it works

User request + bitmask (e.g. 7)
   → BitmaskLogitsProcessor intercepts each token prediction
   → Aho-Corasick automaton (resklogits, GPU-accelerated) checks if the token
     starts/completes a banned phrase
   → hard mode: logit = -inf · bias mode: logit += penalty
   → complete match ⇒ EOS forced, generation stops immediately

Tool calls are gated at the token level too: without the required bit, the first token of send_email( can never be generated.

Features: hard/bias severity modes · strict prefix mode · thread-safe (mask, model) automaton cache with TTL · YAML policies with hot-reload · post-generation verify_tool_action defense-in-depth · receives a raw integer bitmask (auth/JWT stays in your app).

Package structure

src/resksecure/
  policy_loader.py         YAML parsing, Policy/PolicySet models
  trie_factory.py          Builds VectorizedAhoCorasick from a Policy
  bitmask_processor.py     BitmaskLogitsProcessor
  tool_guard.py            Post-generation tool action verification
  cache.py                 Thread-safe TTL cache for automata
  policy_watcher.py        Hot-reload daemon

Ecosystem

Built on resklogits · pairs with Resk-LLM (input-time detection) and ReskPoints (action logging). The Resk full-stack app wires all three together.

License

RESK Software License — commercial use requires a paid license. See LICENSE or contact contact@resk.fr.