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Portal dev auth: replace mkcert CA install with leaf-only localhost trust

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
48/100
Issue type
Feature
Clarity
Mostly clear
Activity status
Quiet
Tech stack
docker, docker-compose, shell
Domain
authentication, devops, security

Research direction

Start with scripts/ensure-dev-certs.sh and the entra-local and entra-local-certs-init services in docker-compose.yml, tracing the existing certificate generation, trust installation, and DEV_CERT_DIR handling. Verify direct leaf trust and the one-command entra-local flow on the target platform(s), including the browser/MSAL TLS handshake. Done means the leaf is localhost-scoped and trusted without the root-CA installation path, with the shared certificate directory and validity requirements covered.

Written by the indexing model from the issue text.

Description

Original author: @manekinekko

Follow-up from PR #1243 review (finding 🟡, by @cedricvidal_microsoft).

Context

The one-command local dev auth flow (entra-local served over HTTPS) currently uses mkcert -install, which adds a root CA to the OS/browser trust store. That CA can sign a cert for any hostname and forces a one-time admin/sudo prompt. For a dev emulator that only ever needs to be trusted for localhost, this is a heavier trust grant than the feature requires.

Proposal

Drop mkcert -install and trust only the leaf cert (already CA:FALSE, SAN-scoped to localhost / 127.0.0.1 / ::1). Trusting the leaf directly (e.g. security add-trusted-cert -r trustAsRoot into the login keychain on macOS, no sudo) caps the trust blast radius to localhost and can't vouch for any other domain. MSAL only needs the TLS handshake to https://localhost:<port> to succeed.

Scope / considerations

  • Cross-platform trust plumbing is the main cost: mkcert -install hides the macOS/Linux/Windows trust stores behind one command; leaf-only means doing it per-OS ourselves (security add-trusted-cert on macOS, plus Linux and Windows equivalents). Landing macOS first and staging Linux/Windows as follow-ups may be acceptable.
  • Validity cap: directly-trusted leaves can hit the browser 398-day server-cert cap (mkcert's leaf is ~823 days). Mint a =398-day leaf to sidestep it.
  • Shared cert dir: parameterize the compose mount to ${DEV_CERT_DIR:-./.certs}:/certs-src:ro (the script already honors DEV_CERT_DIR) so a dev can set DEV_CERT_DIR=$HOME/.scope-dev-certs once and share a single leaf + a single trust action across all worktrees and ports.
  • Verify before committing: confirm browsers/MSAL accept a directly-trusted leaf on each target platform (untested as of the PR review).

Not in scope

The rootless/UID-remapped container permission issue (finding F1) was already fixed in PR #1243 (f886e348) independently, without loosening the key, via an ownership-fixing init service. If we adopt leaf-only later, the in-volume key handling can be revisited then.

Relevant files: scripts/ensure-dev-certs.sh, docker-compose.yml (the entra-local / entra-local-certs-init services).

Dominant language
TypeScript
Stars
7
Forks
13
Avg merge
3d 5h
Merged PRs (30d)
26

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