Closes the caller side of FLEX-WP-0015. FlexAuthHTTPAdapter reads the audience-scoped projected ServiceAccount token from a file on every decision, so hourly rotation needs no restart, and runtime configuration now requires USER_ENGINE_FLEX_AUTH_TOKEN_FILE. A missing, empty, or unreadable token file fails closed as a denial without reaching flex-auth: OSError joins the caught set and an empty read raises. Coverage proves all three unusable-token cases deny before any request is made, and that neither the deny reason nor the decision repr carries the token value. Tenant-authority reads now identify user-engine as actor `user-engine` under the protected tenant.read action, keeping tenant ids opaque and URL-encoded. Contract: docs/flex-auth-caller-identity.md. Full suite: 148 tests, 3 provider-gated skips. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
28 lines
1.4 KiB
Markdown
28 lines
1.4 KiB
Markdown
# flex-auth caller identity contract
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Status: source implemented; production promotion pending.
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user-engine calls `flex-auth-user-engine` with a projected Kubernetes
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ServiceAccount token whose audience is exactly `flex-auth`. The adapter reads
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the token file for every decision so hourly projection rotation requires no
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restart. A missing, empty or unreadable file fails closed as an authorization
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denial; the token value is never logged.
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flex-auth binds protected system `user-engine` to principal
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`system:serviceaccount:user-engine:user-engine`. The token authenticates the
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calling workload only. It does not replace the IAM actor/tenant/assurance facts
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inside the authorization request and grants no Kubernetes API permission to
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user-engine.
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Runtime configuration requires `USER_ENGINE_FLEX_AUTH_TOKEN_FILE`. Local
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construction keeps the adapter argument optional so unit tests and explicit
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non-production adapters remain usable.
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The tenant authority seam is distinct: user-engine identifies itself as actor
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`user-engine` on tenant lifecycle reads and writes; tenant-engine performs its
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own flex-auth decision before store access. Tenant ids remain opaque and are
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URL-encoded. No client may infer existence from an unauthorized read.
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The current deployed image predates this file-based caller token. Promote only
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with the matching flex-auth A2 image and bindings; otherwise enforcing flex-auth
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will correctly return 401 to the old caller.
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