Tim MöhlmannGitHubLivio SpringCopilot Autofix powered by AIcopilot-swe-agent[bot] <[email protected]>muhlemmer# Which Problems Are Solved TOTP codes could be reused, violating [RFC 6238, section 5.2](https://datatracker.ietf.org/doc/html/rfc6238#section-5.2). # How the Problems Are Solved Transmitted codes are now recorded in each success event. As the codes amount to secrets, they are not stored verbatim but as a randomly salted HMAC-SHA256 (`crypto.HMACValue`). Each value gets a fresh random salt, so an equal code always produces a different stored value and two entries can never be recognized as being derived from the same code. This is deliberately not a replacement for proper secret storage: with the salt stored alongside the hash and a 6 digit payload, anyone with event access can brute-force the code in milliseconds. That is acceptable here because a code is worthless once its window has passed. The `HMACValue` doc comment states the same. TOTP codes are low-entropy (6 digits), pseudo random codes. Therefore it is possible for the same code to be generated more than once over the lifetime of a user. In order to prevent the (unlikely) case where users login with large time intervalls and a generated code may be equal to the one last used a long time ago, we only check for codes used within the recent period window. A simpler implementation would be simply storing the latest consumed step, but the TOTP library does not return this value. Because of the allowed skew there are always 3 steps within the validation window, so we can't calculate the current step based on time alone. The retained history spans one period more than the validation window: validity is decided by the app server's clock, while the stored events carry the database clock, and the extra period absorbs the drift between them. **Note:** a reused code pushes a distinct `user.human.mfa.otp.check.reused` event, not a failed check event. A replay therefore stays observable through the Events API without counting towards the lockout policy. Otherwise anyone who captured a code could replay it to lock the user out. # Additional Changes - Read only the latest events in recheck query # Additional Context - Closes https://github.com/zitadel/zitadel/issues/6452 --------- Co-authored-by: Livio Spring <[email protected]> Co-authored-by: Copilot Autofix powered by AI <[email protected]> Co-authored-by: copilot-swe-agent[bot] <[email protected]> Co-authored-by: muhlemmer <[email protected]>
The Identity Infrastructure for Developers
ZITADEL is an open-source identity and access management platform built for teams that need more than basic auth. Whether you're securing a SaaS product, building a B2B platform, or self-hosting a production IAM stack — ZITADEL gives you everything out of the box: SSO, MFA, Passkeys, OIDC, SAML, SCIM, and a battle-tested multi-tenancy model.
No vendor lock-in. No compromise on control. Just a robust, API-first identity platform you can own.
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Why ZITADEL
We built ZITADEL to handle the hardest IAM challenges at scale — starting with multi-tenancy.
| ZITADEL | FusionAuth | Keycloak | Auth0/Okta | |
|---|---|---|---|---|
| Open-source | ✅ | ❌ | ✅ | ❌ |
| Self-hostable | ✅ | ✅ | ✅ | ❌ |
| Infrastructure-level tenants | ✅ Instances (High scale) | ✅ Tenants | 🟡 Realms (Scaling limits) | ❌ (Multi-tenant = multi-account) |
| B2B Organizations | ✅ Native & Unlimited | 🟡 via Entity Management | ✅ (Recent addition) | 🟡 (Plan/Account dependent) |
| Full audit trail | ✅ Comprehensive Event Stream* | 🟡 Audit logs | 🟡 Audit logs | 🟡 Audit logs |
| Passkeys (FIDO2) | ✅ | ✅ | ✅ | ✅ |
| Actions / webhooks | ✅ | ✅ | 🟡 via SPI | ✅ |
| API-first (gRPC + REST) | ✅ | 🟡 REST only | 🟡 REST only | 🟡 REST only |
| SaaS + self-host parity | ✅ | ✅ | ➖ N/A | ➖ N/A |
ZITADEL Cloud and self-hosted ZITADEL run the same codebase.
Key differentiators for architects:
- Relational core, event-driven soul — every mutation is written as an immutable event for a complete, API-accessible audit trail. Unlike systems that log only select activities, ZITADEL provides a comprehensive event stream that can be audited or streamed to external systems via Webhooks.
- Strict multi-tenant hierarchy — Identity System → Organizations → Projects, with isolated data and policy scoping at multiple levels
- API-first design — every resource and action is available via connectRPC, gRPC, and HTTP/JSON APIs
- Zero-downtime updates and horizontal scalability without external session stores
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ZITADEL Self-Hosted
# Docker Compose — up and running in under 3 minutes
curl -LO https://raw.githubusercontent.com/zitadel/zitadel/main/deploy/compose/docker-compose.yml \
&& curl -LO https://raw.githubusercontent.com/zitadel/zitadel/main/deploy/compose/.env.example \
&& cp .env.example .env \
&& docker compose up -d --wait
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Integrate with the V2 API
ZITADEL exposes every capability over a typed API. Here's how to create a user with the V2 REST API:
curl -X POST https://$ZITADEL_DOMAIN/v2/users/human \
-H "Authorization: Bearer $ACCESS_TOKEN" \
-H "Content-Type: application/json" \
-d '{
"username": "[email protected]",
"profile": { "givenName": "Alice", "familyName": "Smith" },
"email": { "email": "[email protected]", "sendCode": {} }
}'
Explore the full API reference — including connectRPC and gRPC transports — or jump straight to quickstart examples.
Features
Authentication
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- Hosted Login V2
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- Identity brokering with pre-built IdP templates
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- PostgreSQL (≥ 14) · Zero-downtime updates · High scalability
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Showcase
Login V2
Our new, fully customizable login experience — documentation
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Used in production by organizations worldwide. See the full Adopters list — and add yours by submitting a pull request.
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Security policy: SECURITY.md
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