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defmodule WalletAuth.Jwks.KeySet do |
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@moduledoc """ |
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JWKS key set management and key rotation baseline. |
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Per ADR 0006: |
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- Keys identified by `kid` (key ID). |
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- Rotation: new key introduced before old key is retired. |
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- Overlap window ensures validation continuity during rotation. |
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- Key lifecycle events are audited. |
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Algorithm support: |
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- HS256 (HMAC-SHA256) — default for development/test. |
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- RS256 (RSA-SHA256) — production target; swap signer module via config. |
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In production, key material is sourced from the secret provider, never from |
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static config. Key IDs and versions are stored here; raw key bytes come from |
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WalletAuth.Secrets.SecretProvider. |
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""" |
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alias WalletAuth.Secrets.SecretProvider |
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@type key_id :: String.t() |
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@type algorithm :: :HS256 | :RS256 |
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@type key_entry :: %{ |
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kid: key_id(), |
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algorithm: algorithm(), |
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status: :active | :retiring | :revoked, |
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activated_at: DateTime.t() |
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} |
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@doc """ |
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Returns the current active signing key ID and its raw key material. |
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The key material is fetched from the secret provider on each call to |
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avoid caching stale values. |
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Returns `{kid, key_bytes}`. |
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""" |
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@spec current_signing_key() :: {key_id(), binary()} |
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def current_signing_key do |
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kid = Application.get_env(:wallet_auth, :active_kid, "key_v1") |
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secret_name = "jwt_signing_key_#{kid}" |
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key_bytes = SecretProvider.get!(secret_name) |
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{kid, key_bytes} |
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end |
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@doc """ |
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Returns all configured key IDs and their metadata (excludes raw key bytes). |
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Used for JWKS endpoint publication. |
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""" |
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@spec all_key_metadata() :: [key_entry()] |
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def all_key_metadata do |
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Application.get_env(:wallet_auth, :jwks_keys, [ |
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%{ |
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kid: "key_v1", |
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algorithm: :HS256, |
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status: :active, |
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activated_at: ~U[2026-03-11 00:00:00Z] |
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} |
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]) |
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end |
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@doc """ |
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Finds key material for validation by kid. |
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Supports overlap window: retiring keys can still validate tokens until revoked. |
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Returns `{:ok, key_bytes}` or `{:error, :kid_not_found | :key_revoked}`. |
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""" |
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@spec find_validation_key(key_id()) :: |
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{:ok, binary()} | {:error, :kid_not_found | :key_revoked} |
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def find_validation_key(kid) do |
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keys = all_key_metadata() |
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case Enum.find(keys, &(&1.kid == kid)) do |
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nil -> |
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{:error, :kid_not_found} |
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:-( |
%{status: :revoked} -> |
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{:error, :key_revoked} |
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%{status: status} when status in [:active, :retiring] -> |
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secret_name = "jwt_signing_key_#{kid}" |
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case SecretProvider.get(secret_name) do |
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{:ok, key_bytes} -> {:ok, key_bytes} |
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{:error, _} -> {:error, :kid_not_found} |
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end |
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end |
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end |
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@doc """ |
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Rotates the active key by updating application config. |
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This is a runtime operation that should be followed by publishing the new JWKS. |
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In production, this triggers: |
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1. New kid becomes active. |
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2. Old kid enters :retiring status (validation still works). |
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3. After overlap window, old kid is revoked. |
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Returns `:ok`. |
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""" |
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@spec rotate_to(key_id()) :: :ok |
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def rotate_to(new_kid) do |
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Application.put_env(:wallet_auth, :active_kid, new_kid) |
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:ok |
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end |
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end |