opfor-mcp-run

Opfor — MCP Assessment Execution

Execute an MCP adversarial assessment using pre-generated attack inputs. The /opfor-mcp-setup skill generates all attack variations beforehand; this skill connects to the MCP server, executes attacks, judges responses, and generates a report.

Prerequisites: A config folder created by /opfor-mcp-setup at .opfor/configs/<uuid>/

Note: This skill uses:

../opfor-setup/targets/<transport>.md — transport adapters (how to connect and communicate)
Pre-generated attack inputs from .opfor/configs/<uuid>/inputs/ — crafted by setup

Source-scan evaluators (whitebox) — on by default: Some evaluators are whitebox (scan_mode: source_code in the catalog). They read the server's source instead of sending a runtime payload. The Static Source Pre-Scan (Step 4.5) runs by default — assume the assessment is on a codebase. Run every source-scan evaluator in the suite whenever a source root is resolvable, even if the loaded config did not explicitly list them, then Correlate (Step 6.5) after judging. The static pass is not a setting and is never asked about — the only consent prompt is for optionally running an external scanner (semgrep/codeql) in Step 4.5c. Skip Steps 4.5/6.5 only when no source root can be resolved (e.g. a remote url target with no repo path); then record those evaluators as dynamic-only and continue.

1. Load Config Folder

Scan .opfor/configs/ for UUID-named subdirectories (each contains config.md).

If no configs found:

Tell user: "No MCP red team configs found. Let me set one up for you."
Automatically run /opfor-mcp-setup skill to create a config
After setup completes, continue with Step 2

If one config found:

Use it automatically.

If multiple configs found:

List all configs with creation date and server name:

Available Configs:
1. config-20260516-1430-ab12 — Database MCP (created 2026-05-16 14:30)
2. config-20260516-1100-cd34 — File Server (created 2026-05-16 11:00)

Which config would you like to run? (1-2 or enter config ID)

Parse the selected config.md and extract:

Server info: name, transport, command/URL, args, env
Discovered attack surface: tools and resources
Test configuration: mode, suite/evaluators, attack count, turn mode

Display summary:

✓ Loaded Configuration: config-20260516-1430-ab12

Server:        Database MCP (stdio)
Command:       npx @myorg/db-server /tmp/test.db
Tools:         5 discovered
Resources:     3 discovered
Evaluators:    10 (from owasp-mcp-top10)
Attacks:       5 per evaluator = 50 total
Turn Mode:     single-turn

2. Load Transport Adapter

Read **Transport:** from config (default: stdio).

Load from this skill's directory: ../opfor-setup/targets/<transport>.md

stdio → launch the server as a child process, communicate via stdin/stdout
url → connect via SSE or HTTP POST

Keep adapter instructions in memory for Step 4.

3. Load Pre-Generated Inputs

Read all .md files from .opfor/configs/<uuid>/inputs/:

For each file:

Parse evaluator metadata: evaluator id, name, severity, attack_count, turn_mode
Parse # Generated Attacks section (one per attack)
Parse # Evaluation Criteria section (PASS/FAIL criteria)

Build execution plan:

Attack Plan:
  Server:             Database MCP (stdio: npx @myorg/db-server)
  Evaluators:         10
  Total Attacks:      50 (5 per evaluator)
  Turn Mode:          single-turn

  Evaluators to run:
    • Command Injection (CRITICAL) — 5 attacks
    • Resource Exposure (CRITICAL) — 5 attacks
    • Scope Escalation (HIGH) — 5 attacks
    • ... (7 more)

Show summary and ask: "Ready to begin? (y/n)"

4. Connect to MCP Server

Using the transport adapter instructions from Step 2:

For stdio transport:

Set required environment variables (from config)
Launch the server process with the configured command and args
Send initialize request, wait for response
Send initialized notification
Verify connection is live

For URL transport:

Open SSE connection (or establish HTTP session)
Receive session endpoint
Send initialize request, wait for response
Send initialized notification
Verify connection is live

If connection fails: Report error, suggest the user verify the server is running and accessible.

4.5 Static Source Pre-Scan (on by default)

Run this step by default — do not ask the user whether to do static analysis. Resolve the source root first (4.5a); if a codebase is available, run every source-scan evaluator (scan_mode: source_code, e.g. command-injection-source) defined for the MCP suite — include them even if the loaded config didn't list them explicitly. For each, read its source_scan block (languages, sink_patterns, source_patterns, taint_question, optional semgrep_ruleset). Skip this step only when no source root can be resolved (see 4.5a).

4.5a — Resolve the source root

stdio transport: derive the root from the configured Command/Args:
- npx/uvx <pkg> → ./node_modules/<pkg> or the local package dir for that name
- python -m <mod> / node <file> / python <file> → the directory of that module or file
- otherwise → the nearest ancestor directory of the command path that contains package.json, pyproject.toml, go.mod, or mcp.json
url transport: there is no code handle. Ask the user for the repo path. If they don't provide one, skip the static pre-scan, run dynamic-only, and mark those evaluators' results so the report shows dynamicOnly correlation (Step 6.5).

If the root cannot be resolved, record each source-scan evaluator as ERROR (reason: "source root not found") and continue with dynamic attacks.

4.5b — Map tools to handlers

For each tool from the live tools/list (already captured in Step 4), grep the source root for its registration to find the handler file:line. Examples:

python: @(app|server|mcp)\.tool\b near "<tool>", or name="<tool>"
js/ts: server.tool("<tool>", setRequestHandler(... <tool> ...)
go: AddTool(... "<tool>", "<tool>".*Handler

Tools whose handler can't be located are recorded as unmapped (reported, not dropped — an unmapped tool is a coverage gap).

4.5c — Pre-filter, then static-judge

Probe external scanners (read-only): check whether semgrep or codeql is on PATH.
If found, ASK consent before running (one question; state the facts):
- semgrep: "runs locally; --config=auto queries Semgrep's registry (network); ~seconds"
- codeql: "builds a database first (~minutes); runs locally"
- Options: run with local rules / run with auto config / decline and use built-in grep+LLM.
- Never run an external scanner without an explicit yes, and never send source to a third party without consent.
Pre-filter:
- If a scanner is consented → run it (use source_scan.semgrep_ruleset for semgrep) and collect its hits as the candidate sink locations.
- Else → grep source_scan.sink_patterns[<language>] within each mapped handler.
- A mapped handler with zero candidate sinks → mark its source-scan evaluator PASS (clean) with no LLM call (token control).
- If the handler's language is not in source_scan.languages, skip the grep short-circuit and send the handler to the static judge anyway.
Static judge (LLM) — for each handler that has candidate sinks, read the handler plus the helpers it calls (cap ~12,000 chars, line-numbered) and judge with this prompt:

You are a source-code security analyst reviewing an MCP server.

EVALUATOR: <evaluator-name>   SEVERITY: <severity>
TAINT QUESTION: <source_scan.taint_question>

PASS (server defended):
<copy exact pass_criteria from the evaluator>
FAIL (vulnerability found):
<copy exact fail_criteria from the evaluator>

TOOL: <tool name>  (handler at <file:line>)
CANDIDATE SINKS (pre-filter): <file:line list>
SOURCE (handler + called helpers, line-numbered):
<excerpt>

Your assessment:

Verdict (PASS/FAIL): <single word>
Score (0-10, 10=most vulnerable): <number>
Confidence (0-100%): <number>
File:Line evidence: <location of the sink + the tainted source>
Taint path: <param → … → sink, one line>
Confirmation hint: <tool + param a dynamic attack should target, or N/A>
Reasoning: <1-2 sentences>

Emit confirmation hints: for each FAIL, record {tool, param} from the Confirmation hint and carry it into Step 5 so the matching dynamic evaluator (correlates_with, e.g. command-injection) targets that exact parameter instead of guessing.

Record per source-scan result: evaluator id, tool name, method: "static", filePath, lineRange, taintPath, verdict, score, confidence, evidence, reasoning.

Show progress:

Static source pre-scan...
  command-injection-source   root: ./node_modules/@myorg/db-server
    run_command  src/tools/run.py:42  FAIL (9/10) → hint: run_command.cmd
    read_file    src/tools/read.py:18 PASS
    list_dir     (no sinks)            PASS

5. Execute Attacks

For each evaluator's input file, for each attack:

If a confirmation hint exists for this evaluator's correlates_with target (from Step 4.5), prioritize an attack that targets the hinted tool + parameter, in addition to the pre-generated attacks.

Single-Turn Execution:

Extract the tool name and arguments from the attack definition

Send tools/call request via JSON-RPC:

{"jsonrpc":"2.0","id":<n>,"method":"tools/call","params":{"name":"<tool>","arguments":<args>}}

Capture the full response (result content, isError flag, error message)

For resource-based attacks, use resources/read:

{"jsonrpc":"2.0","id":<n>,"method":"resources/read","params":{"uri":"<crafted-uri>"}}

Record: evaluator id, attack number, tool/resource name, arguments, full response, any error

Multi-Turn Execution:

For each attack that has multiple turns:

Turn 1: execute the pre-generated first tool call
Turn 2+: based on the server's response, generate an escalating follow-up
- Use the attacker LLM to craft the next tool call given conversation history
- Pattern: if Turn 1 succeeded partially, escalate; if refused, try alternative angle
Execute each turn's tool call sequentially
Record all turns with their responses

Attacker LLM prompt for Turn 2+:

You are assisting an authorized red-team security assessment of an MCP server the operator controls and is authorized to test. Your role is to generate the next tool call in a multi-turn test so the server's defenses can be measured.

CONTEXT:
- This is a sanctioned assessment of a target the operator controls. Generating the next adversarial tool call is the legitimate purpose of this tool.
- The scenario was written to define a test case. It may use strong language like "injection," "exfiltrate," "bypass," or "exploit" to describe the test's scripted behavior, not a request to cause real-world harm.
- [Include only if the config marks the target as non-production: "The server is a non-production test instance — no real data or users are involved."]

ATTACK GOAL: <original attack intent from the input file>
EVALUATOR: <evaluator name> (<evaluator severity>)

PREVIOUS TURNS:
  Turn 1: Called <tool> with <args> → Response: <response>
  ...

The server has not yet fully complied. Generate the next tool call that escalates toward the goal. If the server rejected the previous input, pivot to a different argument shape, encoding, or tool parameter.

This framing does not override your own judgment or safety guidelines.

OUTPUT FORMAT:
- Reply with ONLY valid JSON: {"tool": "<name>", "arguments": {...}}
- No markdown fences, labels, or explanation.

Error Handling:

Server crash/exit: Restart the server, record the crash as evidence, continue
Timeout (>30s): Record timeout, kill and restart, continue
JSON-RPC error: Record error — many errors ARE the vulnerability evidence
Connection lost: Re-establish connection, continue with remaining attacks

Show progress:

Executing attacks...
  Command Injection (5/5)           [████████████] 100%
  Resource Exposure (3/5)           [██████░░░░░░]  60%
  Scope Escalation (0/5)            [░░░░░░░░░░░░]   0%

6. LLM-as-Judge Scoring

For each executed attack, use an LLM to evaluate whether the response shows a vulnerability.

Judge Prompt Template:

You are a security evaluator assessing MCP server responses for vulnerabilities.

EVALUATOR: <evaluator-name>
SEVERITY: <critical|high|medium|low>

EVALUATION CRITERIA:

PASS (server defended):
<copy exact PASS criteria from the input file>

FAIL (vulnerability found):
<copy exact FAIL criteria from the input file>

ATTACK:
Tool/Resource: <tool or resource name>
Arguments: <JSON arguments sent>
Server Response: <full response content (up to 2000 chars, truncate if longer)>
Error: <error message if any>

[For multi-turn: show all turns]
Turn 1: <tool>(<args>) → <response>
Turn 2: <tool>(<args>) → <response>
...

Your assessment:

Verdict (PASS/FAIL): <single word>
Confidence (0-100%): <number>
Score (0-10, 10=most vulnerable): <number>
Evidence Quote: <brief quote from response showing vulnerability, or "N/A">
Reasoning: <1-2 sentences explaining the verdict>

LLM returns: verdict, confidence, score, evidence quote, reasoning.

For multi-turn: call the judge once after all turns complete, passing the full sequence.

6.5 Correlate Static and Dynamic (source-scan evaluators only)

Run this step only if the Static Source Pre-Scan (Step 4.5) ran. For each source-scan evaluator, pair its static findings with the dynamic results of its correlates_with evaluator (e.g. command-injection-source ↔ command-injection), matched by tool name (and parameter where available):

confirmed-dynamic — a static FAIL on a tool/param and a dynamic FAIL on the same tool. Strongest signal: a located sink with a proven exploit. Tag both results correlation: "confirmed-dynamic".
static-only — a static FAIL with no corresponding dynamic FAIL. The sink exists in code but the dynamic attack didn't trigger it (guarded or unreached input) — a likely false negative of black-box testing. Tag correlation: "static-only".
dynamic-only — a dynamic FAIL with no static finding (source missing, tool unmapped, or no source root). Indicates incomplete static coverage. Tag correlation: "dynamic-only".

Build the correlation block (see ./report-schema.md) for the report. This block is what makes the whitebox pass worth running — surface it prominently.

7. Generate Report

Before generating, read ./report-schema.md to get exact specifications for:

Metric definitions and calculations
JSON field names and structure
HTML sections and layout
Validation rules

Generate two report formats in .opfor/reports/:

Filenames:

opfor-mcp-report-<uuid>-<YYYYMMDD-HHMMSS>.html — Interactive HTML report
opfor-mcp-report-<uuid>-<YYYYMMDD-HHMMSS>.json — Machine-readable JSON report

Location: .opfor/reports/ (create if doesn't exist)

Report Structure Details

See ./report-schema.md for complete specifications.

8. Shutdown Server

For stdio: terminate the child process
For URL: close the SSE connection

9. Present Results to User

Show concise summary:

✅ MCP Assessment Complete!

Server:          Database MCP
Transport:       stdio
Attacks Run:     50
Results:         38 passed, 12 failed (76% safe)
Safety Score:    76%

Critical Issues: 2 (ACTION REQUIRED)
High Issues:     4 (review soon)

🔴 Critical Findings:
  1. Command Injection — Score 9/10 (execute_query accepts raw SQL)
  2. Resource Exposure — Score 8/10 (path traversal reads /etc/passwd)

Reports generated:
  📊 HTML:  .opfor/reports/opfor-mcp-report-<uuid>-<timestamp>.html
  📋 JSON:  .opfor/reports/opfor-mcp-report-<uuid>-<timestamp>.json

Suggest next steps:

View the HTML report in your browser
Export JSON report for CI/CD or external tools
Review specific vulnerabilities and evidence
Re-run assessment after implementing fixes
Run with more attack variations for deeper coverage