## Why
ArgoCD SSO fails with `failed to query provider "https://identity.unkin.net/application/o/argocd/": tls: failed to verify certificate: x509: certificate signed by unknown authority`. argocd-server does OIDC discovery to identity.unkin.net over TLS served by the internal `unkin.net` CA. Unlike argocd-repo-server (which mounts `vault-ca-cert`), argocd-server has no internal CA in its trust store and no `rootCA` in `oidc.config`, so it never trusted the issuer.
## Change
- argocd-cm `oidc.config`: add `rootCA` (inline PEM) = the internal `unkin.net` root CA. argocd-server hot-reloads argocd-cm, so no rollout restart is required.
## Why the root, not the cluster vault-ca-cert bundle
The `unkin.net Intermediate Authority` was recently **re-keyed** (same serial, new key: bundle SHA1 `C4:48:78…` vs served `F1:DD:34…`). The cluster `vault-ca-cert` bundle still carries the **stale** intermediate and fails `openssl verify` against the currently-served identity cert. identity.unkin.net presents its current intermediate in the handshake, so anchoring on the long-lived, stable `unkin.net` root (valid to 2034, matches the host trust anchor) is both correct and rotation-proof. Verified: `openssl verify -CAfile <root> -untrusted <served-intermediate> <served-leaf>` = OK; the embedded PEM round-trips through the YAML patch and validates the served leaf.
## Verify after merge
argocd-server picks up argocd-cm live; retest SSO login. (Separately, the cluster `vault-ca-cert` reflected secret carries a stale intermediate and should be refreshed, but that is out of scope here.)
https://claude.ai/code/session_015ur3i7D2azsMAWTSVABApv
Reviewed-on: #303
Co-authored-by: Ben Vincent <ben@unkin.net>
Co-committed-by: Ben Vincent <ben@unkin.net>
unkinben
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