mcpnuke-add-patterns

name	mcpnuke-add-patterns
description	Add new regex detection patterns to mcpnuke's pattern libraries with test coverage. Use when adding new patterns to rules.py or probes.py, or when extending detection for a vulnerability class.

Add mcpnuke Patterns

Pattern Files

File	Purpose	Used By
mcpnuke/patterns/rules.py	Static regex for metadata analysis	Static checks (injection, permissions, theft, etc.)
mcpnuke/patterns/probes.py	Probe payloads and response analysis	Behavioral checks (tool_probes, resource_poisoning)

Adding Static Patterns

1. Define the pattern list in rules.py

YOUR_PATTERNS = [
    r"pattern_one",
    r"pattern_two",
]

Pattern guidelines:

• Use raw strings (r"...")
• Case-insensitive matching is done by the caller (re.IGNORECASE)
• Use \s+ for whitespace, \b for word boundaries
• Use .{0,30} for bounded wildcards (not .*)
• Test each pattern against both positive and negative examples

2. Add tests in tests/test_patterns.py

def test_your_patterns_match():
    text = "String that should match"
    matches = [p for p in YOUR_PATTERNS if re.search(p, text, re.IGNORECASE)]
    assert len(matches) >= 1


def test_your_patterns_no_false_positive():
    text = "Normal safe string"
    matches = [p for p in YOUR_PATTERNS if re.search(p, text, re.IGNORECASE)]
    assert len(matches) == 0

3. Run tests (TDD: write tests FIRST, then patterns)

Follow superpowers test-driven-development: write the test assertions before adding patterns to rules.py. Watch them fail (RED), then add patterns (GREEN).

uv run pytest tests/test_patterns.py -v

Adding Probe Payloads

In probes.py

Injection probes (sent to tools):

YOUR_PROBES = [
    f"payload_with_{CANARY}",
    "payload_two",
]

Response analysis patterns (checked in tool output):

YOUR_RESPONSE_PATTERNS = [
    r"pattern_to_find_in_responses",
]

Rules:

• Probes should be safe — they test for vuln without causing damage
• Use the CANARY string (MCP_PROBE_8f4c2a) to detect reflection
• Response patterns use the same regex conventions as rules.py

Existing Pattern Sets (reference)

Name	Count	Purpose
INJECTION_PATTERNS	19	Prompt injection in metadata
POISON_PATTERNS	11	Hidden instructions, exfil hints
DANGEROUS_TOOL_PATTERNS	8 categories	Dangerous capabilities
TOKEN_THEFT_PATTERNS	10	Credential exfiltration
CODE_EXEC_PATTERNS	9	Code execution indicators
RATE_LIMIT_PATTERNS	5	Missing rate limiting
PROMPT_LEAKAGE_PATTERNS	8	Prompt exposure
SUPPLY_CHAIN_PATTERNS	9	Dynamic package install
RAC_PATTERNS	6 categories	Remote access
RESPONSE_INJECTION_PATTERNS	11	Injection in tool responses
ERROR_LEAKAGE_PATTERNS	9	Info disclosure in errors
CREDENTIAL_CONTENT_PATTERNS	11	Actual secrets in content