Iam Access Analyzer Ai Policies: Verify AI-Generated Policies Before Attach

// scripts/iam-ai-gate.ts
import { IAMClient, SimulatePrincipalPolicyCommand } from "@aws-sdk/client-iam";
import { AccessAnalyzerClient, ValidatePolicyCommand } from "@aws-sdk/client-accessanalyzer";

export type AiPolicyDraft = {
  policyDocument: string;
  roleName: string;
  ticket: string;
};

const FORBIDDEN = [
  /"Action"\s*:\s*"\*"/,
  /"Action"\s*:\s*\[["']\*["']\]/,
  /"Resource"\s*:\s*"\*"/,
  /"NotAction"/,
];

export function assertNoWildcards(doc: string) {
  for (const re of FORBIDDEN) {
    if (re.test(doc)) throw new Error(`forbidden_iam_pattern:${re}`);
  }
}

export async function validateWithAnalyzer(doc: string) {
  const aa = new AccessAnalyzerClient({});
  const out = await aa.send(new ValidatePolicyCommand({
    policyDocument: doc,
    policyType: "IDENTITY_POLICY",
  }));
  const errors = (out.findings ?? []).filter((f) => f.findingType === "ERROR");
  if (errors.length) throw new Error(JSON.stringify(errors));
  return out.findings ?? [];
}

const iam = new IAMClient({});

export async function simulateMustAllow(roleArn: string, actions: string[], resources: string[]) {
  const r = await iam.send(new SimulatePrincipalPolicyCommand({
    PolicySourceArn: roleArn,
    ActionNames: actions,
    ResourceArns: resources,
  }));
  for (const e of r.EvaluationResults ?? []) {
    if (e.EvalDecision !== "allowed") {
      throw new Error(`expected_allow:${e.EvalActionName}:${e.EvalDecision}`);
    }
  }
}

export async function simulateMustDeny(roleArn: string, actions: string[], resources: string[]) {
  const r = await iam.send(new SimulatePrincipalPolicyCommand({
    PolicySourceArn: roleArn,
    ActionNames: actions,
    ResourceArns: resources,
  }));
  for (const e of r.EvaluationResults ?? []) {
    if (e.EvalDecision === "allowed") {
      throw new Error(`expected_deny_got_allow:${e.EvalActionName}`);
    }
  }
}

// Fixture: agent proposed s3:GetObject on payments bucket — must allow
// Same role must DENY s3:DeleteBucket on org-security bucket

# .github/workflows/iam-ai-gate.yml
name: iam-ai-gate
on:
  pull_request:
    paths: ["infra/iam/**", "**/iam-policies/**"]
jobs:
  analyze:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - run: pnpm tsx scripts/iam-ai-gate.ts --dir infra/iam
      - name: Fail on Access Analyzer ERROR findings
        run: test ! -s analyzer-errors.json

DENIED_PATTERNS:
- Action "*"
- Resource "*" on iam:*, kms:*, s3:*
- Missing aws:PrincipalOrgID on cross-account trusts