PhilippTheServer

security

Hardening, boundaries, and being honest about what a control actually protects.

  1. Running a Self-Hosted Tailscale Control Server Behind a Reverse Proxy

    Headscale behind Traefik: tls.options=no-h2@file with alpnProtocols http/1.1, because the Tailscale noise handshake breaks when ALPN negotiates h2.

    networking dns security docker

  2. One Local Endpoint for Every Agent Session

    OPENAI_BASE_URL=http://localhost:8080/v1 for every AI tool: one local FastAPI proxy that logs each request and refuses internal-only projects.

    llm security python

  3. Treating Issue Bodies as Untrusted Input

    Prompt injection via GitHub issue bodies: fence untrusted text and accept model output only as a fixed JSON action schema, tested without a model.

    security agents llm

  4. From a Large Allowlist to Three Denials: Permissions for a Coding Agent

    bwrap --unshare-net --cap-drop ALL instead of a command allowlist: sandboxing a coding agent's shell so rm -rf and curl cannot leave the workspace.

    agents security linux

  5. Self-Hosted LLM Inference: Serving, Benchmarking and Agent Guardrails

    Ollama OpenAI-compatible /v1/chat/completions: a repeatable benchmark on your own tasks and a dry-run plus --approve guardrail for infrastructure agents.

    llm agents testing security

  6. The Label as Contract: Consent and Priority as the Whole Queue

    agent-ready label as the only consent gate for a coding agent: FIFO order by label time and a re-read-then-swap claim so two runs never share an issue.

    agents security

  7. Self-Hosted Identity with Keycloak: Central Offboarding and Forward Auth

    Keycloak "invalid_grant" "Account disabled": one admin API call disables a user for every OIDC client, plus oauth2-proxy forward auth for apps without login.

    identity security architecture

  8. Forward Auth: Putting Real Authentication in Front of Software That Has None

    Traefik forwardAuth with X-Auth-Request-User: strip the header first or clients can spoof it. oauth2-proxy and Keycloak in front of apps with no login.

    identity networking security

  9. Enforcing Client Identity Alongside Realm Roles

    Keycloak azp claim: a realm role does not show which client the token was issued to. Enforcing azp next to role checks in a FastAPI dependency.

    identity security fastapi

  10. OIDC Client Shapes: A Token-Validating API Is Not a Login Client

    Keycloak directAccessGrantsEnabled on a token-validating API lets it mint tokens. bearerOnly client, oidc-audience-mapper and a PyJWT aud check.

    identity security api-design

  11. Realm-as-Code: Reconciling Clients and Roles But Never Users or Signing Keys

    kc.sh import with --override=true recreates the realm, dropping users and signing keys. Reconciling only clients and roles via the Keycloak Admin REST API.

    identity gitops security

  12. External Secrets with Offline JWT Validation When Vault Cannot Reach the Cluster

    Vault kubernetes auth "failed to validate token" tokenreviews i/o timeout: jwt auth with jwt_validation_pubkeys from sa.pub for External Secrets.

    kubernetes vault secrets-management security

  13. Overlay Mesh Networking with NetBird: Peer Addressing and the Public DNS Fallthrough

    NetBird mesh hostnames resolve to the public host via a zone wildcard when the mesh resolver is down. Fix: a *.mesh blackhole record and accept-new.

    networking dns security linux

  14. Rootless BuildKit: What fuse-overlayfs Costs on a Cold Cache

    Rootless BuildKit with --oci-worker-snapshotter=fuse-overlayfs needs no --privileged, but cold-cache builds pay a FUSE round-trip per file. Measuring it.

    docker security performance

  15. Trusting an Internal and a Public Certificate Authority in One Process

    curl: (60) SSL certificate problem after SSL_CERT_FILE points at an internal CA: it replaces the trust store. Append with update-ca-certificates instead.

    tls security

  16. A Confidential OIDC Client That Exists Only to Introspect Tokens

    invalid_client "Parameter client_secret is missing" on Keycloak token introspection for a public SPA client: add a confidential introspection-only client.

    identity security

  17. Auto-Unsealing Vault Without Cloud KMS or a TPM, Using Tang and Clevis

    clevis encrypt sss with Tang pins to auto-unseal Vault without cloud KMS or a TPM: binding Shamir key shares, a systemd unit, and the t threshold.

    vault security linux

  18. Runtime Secret Injection with a Vault Agent Sidecar and a Wrapped AppRole

    secret_id_response_wrapping_path in Vault Agent approle auto_auth: a sidecar that bootstraps from a single-use wrapped secret_id and renders secrets to a file.

    vault secrets-management security docker

  19. Vault KV-v2: Why put Silently Wipes Every Sibling Field

    vault kv put wipes sibling fields and -cas fails with "check-and-set parameter did not match the current version": why, and how patch avoids it.

    vault secrets-management security

  20. Replacing Distributed SSH Keys with a Vault Certificate Authority

    TrustedUserCAKeys with the Vault ssh secrets engine: short-lived SSH user certificates limited by allowed_users and ttl instead of authorized_keys.

    vault security tls

  21. Reasserting Kernel Sysctls That Docker Silently Reverts

    net.ipv4.ip_forward = 1 although sysctl.d says 0: dockerd rewrites it at start. A oneshot unit After=docker.service reruns sysctl --system.

    linux docker security

  22. Migrating the SSH Port Mid-Playbook Without Locking Ansible Out

    Ansible meta: reset_connection after changing the sshd Port: validate with sshd -t, flush_handlers, and ping before closing the old port.

    ansible security linux infrastructure-as-code

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