Added authentication guidance and policy

2025-09-30 14:57:59 +02:00
parent 4554305f3a
commit 4ae6607c3d
2 changed files with 266 additions and 0 deletions
--- a/Security/authentication_guidance.md
+++ b/Security/authentication_guidance.md
@@ -0,0 +1,173 @@
+# Authentication Guidance & Hardening (Comprehensive, EU‑Aligned)
+
+**Document owner:** [Owner/Role]  
+**Approved by:** [Steering Committee / CISO]  
+**Effective date:** [YYYY-MM-DD]  
+**Review cadence:** [Annually]
+
+---
+
+## 1. Purpose & Scope
+This document provides practical guidance and examples for implementing the Authentication Policy across [Organization] systems.  
+It includes detailed examples for assurance levels, distinction of methods (passwords vs PINs vs biometrics), special cases (BitLocker, local admin accounts), out‑of‑band methods, central vs. local authentication, and reauthentication.
+
+---
+
+## 2. Method Identification Guide (What is it? Where does the secret live?)
+Use this section to classify any method you encounter.
+
+### 2.1 Memorized Secrets (Passwords)
+- **What it is:** A human‑chosen **password** sent to a **verifier** (server) that stores only a **hash**.  
+- **Where the secret lives:** In the **user’s memory**; verifier stores a **hashed verifier**.  
+- **Factor category:** **Something you know**.  
+- **Typical AAL:** **AAL1** alone; **AAL2** when combined with another factor.  
+- **Examples:** Account password for SSO, VPN, app logins.  
+- **Notes:** Allow paste/managers; use passphrases; blocklist screening; no composition rules; no periodic expiry.
+
+### 2.2 Activation Secrets (PINs that unlock local authenticators)
+- **What it is:** A **PIN** used to unlock a **local cryptographic key** (TPM, smart card, FIDO2). The PIN itself is **never transmitted** to a server.  
+- **Where the secret lives:** **On the device/token** only (e.g., TPM/smart‑card); verifier never sees it.  
+- **Factor category:** **Something you know** (used locally), combined with **something you have** (device/token).  
+- **Typical AAL:** Contributes to **AAL2** or **AAL3** depending on hardware and protocol.  
+- **Examples and distinctions:**  
+  - **Windows Hello PIN** → unlocks TPM‑bound private key on **that device only**; **not** the same as the account password.  
+  - **Smart‑card PIN** → unlocks card’s private key; used with certificate‑based login.  
+  - **FIDO2 PIN** → unlocks the authenticator to perform WebAuthn challenges.  
+  - **Mobile device screen PIN** → unlocks the phone; when used with a bound authenticator app, it protects the **OOB** channel.  
+  - **BitLocker pre‑boot PIN** → unlocks the disk key (see BitLocker section).  
+- **Minimums:** PIN **≥4**, **should be ≥6**; local throttling/lockout required.
+
+### 2.3 Biometrics (Local unlock only)
+- **What it is:** **Fingerprint/face/iris** used to unlock a **local key** (e.g., Windows Hello, phone biometric).  
+- **Where the secret lives:** Biometric template stays on the device/TPM/secure enclave.  
+- **Factor category:** **Something you are** (local unlock).  
+- **Typical AAL:** Part of **AAL2/AAL3** when combined with hardware key; **never** as sole factor.
+
+### 2.4 Out‑of‑Band (OOB) Methods
+- **What it is:** A second, **separate channel** (e.g., mobile app) to approve login.  
+- **Where the secret lives:** Bound to the **mobile device/app**; approvals sent over encrypted channel.  
+- **Factor category:** Typically **something you have** (the device), sometimes plus its **PIN/biometric** (something you know/are).  
+- **Typical AAL:** **AAL2** when **device‑bound and encrypted**.  
+- **Examples:** Push approvals; **QR‑code sign‑in** with Microsoft Authenticator.  
+- **Not permitted as primary:** SMS/voice/email (recovery only).
+
+---
+
+## 3. Assurance Levels – Examples & Guidance
+
+### 🔹 AAL1 (Single Factor)
+- **Examples:**  
+  - Password‑only login to low‑risk intranet site  
+  - Local Linux/Windows account with password  
+  - BitLocker with **PIN only** (no TPM)  
+  - Local admin password **without LAPS**  
+- **Risks:** Phishable/replayable; brute‑forceable.  
+- **Guidance:** Use only for low‑sensitivity or offline recovery; **not** for remote/external access; plan deprecation.
+
+### 🔹 AAL2 (Standard MFA)
+- **Examples:**  
+  - Password + **TOTP** authenticator app  
+  - Password + **push** approval on a bound device  
+  - Password + **QR‑code** sign‑in with Microsoft Authenticator  
+  - **Smart‑card + PIN**  
+  - **Windows Hello** (TPM‑backed key) + PIN/biometric  
+  - **BitLocker: TPM + PIN**  
+  - Local admin password **with LAPS** (unique per device, rotated) for offline recovery scenarios  
+- **Risks:** Still phishable (push/QR can be proxied).  
+- **Guidance:** Default for SaaS, VPN, employee desktops; allow push/QR only when **device‑bound** and **rate‑limited**; enroll **≥2 MFA methods** per user.
+
+### 🔹 AAL3 (High Assurance)
+- **Examples:**  
+  - **FIDO2/WebAuthn hardware** security key  
+  - **PIV/smart‑card** login with crypto challenge + PIN  
+  - **Windows Hello** with biometric unlocking a **TPM‑bound** key used for hardware‑backed auth  
+  - **BitLocker: TPM + PIN + post‑boot FIDO2** login  
+- **Risks:** Strong phishing and verifier‑impersonation resistance.  
+- **Guidance:** Required for admins, production, regulated systems; **no OOB**; keys must be **non‑exportable** and hardware‑protected; biometrics only unlock keys.
+
+---
+
+## 4. Central vs. Local Authentication
+- **Central (preferred):** IdP/SSO (SAML/OIDC/RADIUS) with consistent policy, logging, and conditional access.  
+- **Local (supporting/offline):** BitLocker pre‑boot PIN, Windows Hello PIN, Linux root password.  
+- **Guidance:** Local methods **must** follow length/blocklist rules for memorized secrets and enforce local throttling; prefer TPM/smart‑card integration for higher assurance.
+
+---
+
+## 5. BitLocker Pre‑Boot Authentication (Deep‑dive)
+- **TPM only:** Disk key released automatically → **AAL1**. Not acceptable for sensitive data.  
+- **PIN only (no TPM):** PIN protects disk key → **AAL1**. Use only with compensating **post‑boot MFA** and limited roles.  
+- **TPM + PIN:** PIN unlocks TPM which releases disk key → **AAL2**. Enterprise baseline for laptops.  
+- **TPM + PIN + post‑boot FIDO2/smart‑card:** Meets **AAL3** for privileged/regulated systems.  
+- **Operational requirements:** PIN length **≥6** recommended; enforce lockout/anti‑hammering; maintain recovery key hygiene; test pre‑boot accessibility for users with assistive tech.
+
+---
+
+## 6. Local Administrator Accounts
+- **Without LAPS:** Shared/static password → **AAL1 (high risk)**; prohibited except as break‑glass in a vault with approvals and audit.  
+- **With LAPS:** Unique random password per device, rotated automatically → **AAL1 (mitigated)**; acceptable for offline recovery; retrieval must be logged.  
+- **Preferred daily admin:** Central privileged accounts with **MFA** (**AAL2/AAL3**).
+
+---
+
+## 7. Reauthentication & Session Management
+- **AAL1:** Reauth **≤ 30 days**.  
+- **AAL2:** Reauth **≤ 24 hours**, inactivity **≤ 1 hour**.  
+- **AAL3:** Reauth **≤ 12 hours**, inactivity **≤ 15 minutes**.  
+- **Tips:** Warn prior to expiry; support seamless reauth with device‑bound authenticators.
+
+---
+
+## 8. Password Creation & User Education (Quick Guide)
+- Prefer **passphrases** (multiple unrelated words with spaces).  
+- Avoid personal info, service names, or keyboard patterns.  
+- Use a **password manager**; unique secret per site/system.  
+- Expect **blocklist rejection** for weak/compromised choices.  
+- Do **not** write down passwords in plain sight; if written, store securely.
+
+---
+
+## 9. Quick Comparison Tables
+
+### 9.1 Method Classification
+| Method | What it is | Secret location | Factor(s) | Typical AAL | Notes |
+|---|---|---|---|---|---|
+| Account **password** | Memorized secret sent to verifier | User memory / verifier stores hash | Know | AAL1 (alone) | Needs blocklist; no composition; no expiry |
+| **Windows Hello PIN** | Local PIN to unlock TPM key | Device TPM | Know + Have (device) | AAL2–AAL3* | Device‑specific; not account password |
+| **Smart‑card PIN** | Local PIN to unlock card key | Smart‑card | Know + Have | AAL2–AAL3 | Cert‑based login |
+| **FIDO2 PIN** | Local PIN to unlock FIDO key | Hardware key | Know + Have | AAL3 | Phishing‑resistant |
+| **Biometric** | Local unlock (face/fingerprint) | Device enclave | Are (+ Have) | AAL2–AAL3 | Unlock only; not sole factor |
+| **TOTP app** | One‑time code generator | Mobile device | Have (+ Know if app PIN) | AAL2 | Bind device; protect seed |
+| **Push/QR OOB** | Encrypted approval channel | Mobile device | Have (+ Know/Are) | AAL2 | Device‑bound & rate‑limited |
+| **SMS/voice/email OTP** | Code over PSTN/email | Network/mail | Have? (weak) | Recovery only | Not primary MFA |
+
+\*Depends on deployment: with hardware‑bound non‑exportable keys and phishing‑resistant protocol usage, Windows Hello deployments can reach AAL3.
+
+### 9.2 BitLocker Summary
+| Mode | AAL | Use Case | Notes |
+|---|---|---|---|
+| TPM only | AAL1 | Low‑risk fleets | Not for sensitive data |
+| PIN only (no TPM) | AAL1 | Legacy/no‑TPM | Must pair with post‑boot MFA |
+| TPM + PIN | AAL2 | Enterprise baseline | Enforce ≥6 PIN, anti‑hammering |
+| TPM + PIN + post‑boot FIDO2 | AAL3 | Admin/regulated | Strongest posture |
+
+---
+
+## 10. Hardening Checklist
+✅ Map systems to **AAL1–AAL3**  
+✅ Enforce **password** rules (length, 64‑char support, Unicode, blocklist, no composition)  
+✅ Enroll **≥2 MFA methods** per user (primary + backup)  
+✅ Prefer **FIDO2/smart‑card** for AAL3; ban **OOB** at AAL3  
+✅ Permit only **device‑bound encrypted** push/QR; **ban SMS/email/voice** as primary  
+✅ Enforce **LAPS** on all Windows endpoints; ban shared local admin passwords  
+✅ Configure **rate‑limiting** for online guesses; local anti‑hammering for PINs  
+✅ Implement **session timeouts** per AAL; warn users pre‑expiry  
+✅ Audit **MFA resets**, **local admin retrievals**, and **failed logins**  
+
+---
+
+## 11. References
+- NIST SP 800‑63B (Digital Identity Guidelines, 2023 update)  
+- CIS Controls v8.1 (Controls 5 & 6)  
+- ENISA Guidelines on Identity and Access Management  
+- OWASP Authentication Cheat Sheet  
--- a/Security/authentication_policy.md
+++ b/Security/authentication_policy.md
@@ -0,0 +1,93 @@
+# Authentication Policy (Comprehensive, EU‑Aligned)
+
+**Document owner:** [Owner/Role]  
+**Approved by:** [Steering Committee / CISO]  
+**Effective date:** [YYYY-MM-DD]  
+**Review cadence:** [Annually]
+
+---
+
+## 1. Purpose & Scope
+This policy establishes mandatory requirements for authentication across [Organization] systems, including:  
+- Passwords and memorized secrets  
+- Multi‑factor authentication (MFA)  
+- Authenticator Assurance Levels (AALs)  
+- Out‑of‑band (OOB) authentication  
+- Central vs. local authentication  
+- Special cases (BitLocker, local admin accounts, device/smart‑card/mobile PINs)  
+- Session management and reauthentication  
+
+It is aligned with **NIST SP 800‑63B** (as best practice), **CIS Controls v8.1**, and **ENISA guidance**.  
+It applies to all employees, contractors, vendors, and service accounts.  
+This policy supports GDPR principles of **data protection by design** and **accountability**.
+
+---
+
+## 2. Policy Statements
+
+### 2.1 Assurance Levels
+- [Organization] **shall** align with Authenticator Assurance Levels (AALs):  
+  - **AAL1:** Single‑factor authentication. Permitted only for low‑sensitivity internal apps or offline scenarios.  
+  - **AAL2:** Multi‑factor authentication combining two categories (e.g., password + OTP app, push, QR code OOB). Required for employee logins, SaaS, and external‑facing systems.  
+  - **AAL3:** High‑assurance, hardware‑backed MFA (e.g., FIDO2, smartcards). Required for privileged/admin access, production, and regulated data systems.  
+
+### 2.2 Memorized Secrets (Passwords)
+- **Length:**  
+  - **15+ characters** when used as a single factor.  
+  - **8+ characters** when used only in combination with MFA.  
+  - Systems **must** allow at least **64 characters**, accept **spaces/Unicode**, and **must not truncate** entered secrets.  
+- **Composition:** No mandatory composition rules (no required mixes of upper/lower/digit/symbol).  
+- **Screening:** New/changed passwords **must** be screened against **blocklists** of commonly used, expected, or **compromised** passwords (including organization‑specific terms).  
+- **Expiration:** **No periodic expiration**. Change **only** upon suspected compromise or policy breach.  
+- **Usability:** **Allow paste/autofill** and provide a **“show password”** option. **No password hints** and **no knowledge‑based questions (KBA)**.  
+- **Reuse:** Password **must not** match the user’s current or any **of the last 5** passwords (where technically supported).  
+- **Rate limiting:** Verifiers **must** throttle online guessing (progressive delays; avoid permanent lockout DoS).  
+- **Storage:** Store only **salted, hashed** verifiers using **Argon2id (preferred)**, **bcrypt**, or **PBKDF2** with strong parameters; per‑credential unique salt; optional server‑side **pepper** protected separately.  
+- **Transport:** Collect and transmit passwords only over **authenticated, encrypted channels** (TLS 1.2+).  
+- **Managers:** Users **should** use an approved **password manager** to generate/store unique passwords.  
+
+### 2.3 Activation Secrets (Local Unlock PINs/Biometrics)
+- **Definition:** An **activation secret** (e.g., device PIN, Windows Hello PIN, smart‑card PIN, FIDO2 PIN) is used **only to unlock a local authenticator/TPM/smart‑card**. It is **not transmitted** to a server and is **not** a password.  
+- **Requirements:** Activation secrets **shall** remain on the device/token; **shall be ≥4 characters** and **should be ≥6**; online guesses **shall** be throttled/limited locally.  
+- **Biometrics:** May be used **only** to unlock a device‑bound key and **must not** be the sole authenticator.  
+
+### 2.4 Acceptable Authenticators
+- **Allowed:** FIDO2/WebAuthn keys; smartcards with PIN; authenticator apps (TOTP, push, **QR‑code sign‑in**); device‑bound biometrics (unlock only).  
+- **Fallback only:** SMS/voice OTPs.  
+- **Prohibited:** Email OTP; KBA/security questions.  
+
+### 2.5 Out‑of‑Band (OOB) Methods
+- OOB authenticators **must** use **encrypted, device‑bound** channels (e.g., push or QR‑code flows) and **must** implement rate‑limiting.  
+- **SMS/voice/email** **must not** be used as **primary** MFA. SMS/voice may be used **only** as recovery with risk acceptance.  
+
+### 2.6 Central vs. Local Authentication
+- **Central IdP/SSO** **must** be the default for enterprise access.  
+- **Local authentication** (device‑only) may be used for **pre‑boot**, **offline**, or **recovery**, but **must** meet the applicable AAL and other requirements in this policy.  
+
+### 2.7 BitLocker Pre‑Boot Authentication
+- **TPM only:** AAL1; not acceptable for sensitive systems.  
+- **PIN only (no TPM):** AAL1; acceptable only with compensating controls.  
+- **TPM + PIN:** AAL2; recommended baseline for enterprise laptops.  
+- **TPM + PIN + post‑boot FIDO2/smart‑card MFA:** Meets AAL3 for administrative systems.  
+
+### 2.8 Local Administrator Accounts
+- Local admin accounts **must not** share passwords across devices.  
+- **LAPS or equivalent** **must** randomize and rotate local admin passwords.  
+- Local admin accounts **must not** be used for daily administration; use **central privileged accounts with MFA** (AAL2/AAL3).  
+
+### 2.9 Reauthentication & Session Management
+- **AAL1:** Reauthentication **≤ 30 days**.  
+- **AAL2:** Reauthentication **≤ 24 hours**, inactivity timeout **≤ 1 hour**.  
+- **AAL3:** Reauthentication **≤ 12 hours**, inactivity timeout **≤ 15 minutes**.  
+
+### 2.10 Enforcement
+- Violations **may** result in disciplinary action or revocation of access.  
+- Non‑compliant systems **must** be remediated or formally excepted with CISO approval.  
+
+---
+
+## 3. References
+- NIST SP 800‑63B (Digital Identity Guidelines, 2023 update)  
+- CIS Controls v8.1 (Controls 5 & 6)  
+- ENISA Guidelines on Identity and Access Management  
+- OWASP Authentication Cheat Sheet