identity: client-credentials grant (RFC 6749 §4.4, +9 tests)

oauth.sx now owns a client registry (loop/6) with register_client and the
client_credentials grant. A confidential client authenticates and gets a
token acting on its own behalf (subject = the client), no refresh token
(§4.4.3). A public client is unauthorized_client; any auth failure (unknown
client or wrong secret) is invalid_client — no client-existence oracle
(§5.2). identity-load-oauth! now pulls its deps. New tests/grants.sx.
158/158.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

lib/identity/conformance.sh

@@ -40,6 +40,7 @@ SUITES=(
   "federation|id-fed-test-pass|id-fed-test-count"
   "expiry|id-expiry-test-pass|id-expiry-test-count"
   "clients|id-clients-test-pass|id-clients-test-count"
+  "grants|id-grants-test-pass|id-grants-test-count"
 )
 
 cat > "$TMPFILE" << 'EPOCHS'
@@ -73,6 +74,7 @@ cat > "$TMPFILE" << 'EPOCHS'
 (load "lib/identity/tests/federation.sx")
 (load "lib/identity/tests/expiry.sx")
 (load "lib/identity/tests/clients.sx")
+(load "lib/identity/tests/grants.sx")
 (epoch 100)
 (eval "(list id-session-test-pass id-session-test-count)")
 (epoch 101)
@@ -97,6 +99,8 @@ cat > "$TMPFILE" << 'EPOCHS'
 (eval "(list id-expiry-test-pass id-expiry-test-count)")
 (epoch 111)
 (eval "(list id-clients-test-pass id-clients-test-count)")
+(epoch 112)
+(eval "(list id-grants-test-pass id-grants-test-count)")
 EPOCHS
 
 timeout 600 "$SX_SERVER" < "$TMPFILE" > "$OUTFILE" 2>&1

lib/identity/scoreboard.json

@@ -1,7 +1,7 @@
 {
   "language": "identity",
-  "total_pass": 149,
-  "total": 149,
+  "total_pass": 158,
+  "total": 158,
   "suites": [
     {"name":"session","pass":11,"total":11,"status":"ok"},
     {"name":"token","pass":24,"total":24,"status":"ok"},
@@ -14,6 +14,7 @@
     {"name":"audit","pass":11,"total":11,"status":"ok"},
     {"name":"federation","pass":12,"total":12,"status":"ok"},
     {"name":"expiry","pass":8,"total":8,"status":"ok"},
-    {"name":"clients","pass":11,"total":11,"status":"ok"}
+    {"name":"clients","pass":11,"total":11,"status":"ok"},
+    {"name":"grants","pass":9,"total":9,"status":"ok"}
   ]
 }

lib/identity/scoreboard.md

@@ -1,6 +1,6 @@
 # identity-on-sx Scoreboard
 
-**Total: 149 / 149 tests passing**
+**Total: 158 / 158 tests passing**
 
 |  | Suite | Pass | Total |
 |---|---|---|---|
@@ -16,6 +16,7 @@
 | ✅ | federation | 12 | 12 |
 | ✅ | expiry | 8 | 8 |
 | ✅ | clients | 11 | 11 |
+| ✅ | grants | 9 | 9 |
 
 
 Generated by `lib/identity/conformance.sh`.

lib/identity/tests/grants.sx

@@ -0,0 +1,96 @@
+;; identity/tests/grants.sx — the client-credentials grant (RFC 6749
+;; §4.4): a confidential client authenticates and gets a token acting on
+;; its own behalf — no end-user, no refresh token (§4.4.3). Public clients
+;; cannot use it.
+
+(define id-grants-test-count 0)
+(define id-grants-test-pass 0)
+(define id-grants-test-fails (list))
+
+(define
+  id-grants-test
+  (fn
+    (name actual expected)
+    (set! id-grants-test-count (+ id-grants-test-count 1))
+    (if
+      (= actual expected)
+      (set! id-grants-test-pass (+ id-grants-test-pass 1))
+      (append! id-grants-test-fails {:name name :expected expected :actual actual}))))
+
+(define idg-ev erlang-eval-ast)
+(define idgnm (fn (v) (get v :name)))
+
+(identity-load-oauth!)
+
+;; ── confidential client-credentials happy path ───────────────────
+
+(id-grants-test
+  "a confidential client obtains a working token"
+  (idgnm
+    (idg-ev
+      "O = identity_oauth:start(),\n       identity_oauth:register_client(O, svc, confidential, sk, [uri1]),\n       {ok, T} = identity_oauth:client_credentials(O, svc, sk, batch),\n       case identity_oauth:introspect(O, T) of\n         {active, _, _, _} -> active;\n         {inactive} -> inactive\n       end"))
+  "active")
+
+(id-grants-test
+  "the client-credentials token's subject is the client itself"
+  (idgnm
+    (idg-ev
+      "O = identity_oauth:start(),\n       identity_oauth:register_client(O, svc, confidential, sk, [uri1]),\n       {ok, T} = identity_oauth:client_credentials(O, svc, sk, batch),\n       case identity_oauth:introspect(O, T) of\n         {active, Subject, _, _} -> Subject\n       end"))
+  "svc")
+
+(id-grants-test
+  "the client-credentials token carries the requested scope"
+  (idgnm
+    (idg-ev
+      "O = identity_oauth:start(),\n       identity_oauth:register_client(O, svc, confidential, sk, [uri1]),\n       {ok, T} = identity_oauth:client_credentials(O, svc, sk, reports),\n       case identity_oauth:introspect(O, T) of\n         {active, _, _, Scope} -> Scope\n       end"))
+  "reports")
+
+(id-grants-test
+  "client-credentials issues no refresh token (single value)"
+  (idgnm
+    (idg-ev
+      "O = identity_oauth:start(),\n       identity_oauth:register_client(O, svc, confidential, sk, [uri1]),\n       case identity_oauth:client_credentials(O, svc, sk, batch) of\n         {ok, _, _} -> pair;\n         {ok, _} -> single;\n         {error, W} -> W\n       end"))
+  "single")
+
+;; ── authentication failures ──────────────────────────────────────
+
+(id-grants-test
+  "a wrong client secret is invalid_client"
+  (idgnm
+    (idg-ev
+      "O = identity_oauth:start(),\n       identity_oauth:register_client(O, svc, confidential, sk, [uri1]),\n       case identity_oauth:client_credentials(O, svc, wrong, batch) of\n         {ok, _} -> issued;\n         {error, W} -> W\n       end"))
+  "invalid_client")
+
+(id-grants-test
+  "a public client cannot use client-credentials"
+  (idgnm
+    (idg-ev
+      "O = identity_oauth:start(),\n       identity_oauth:register_client(O, spa, public, none, [uri1]),\n       case identity_oauth:client_credentials(O, spa, none, batch) of\n         {ok, _} -> issued;\n         {error, W} -> W\n       end"))
+  "unauthorized_client")
+
+(id-grants-test
+  "an unregistered client cannot use client-credentials"
+  (idgnm
+    (idg-ev
+      "O = identity_oauth:start(),\n       case identity_oauth:client_credentials(O, ghost, x, batch) of\n         {ok, _} -> issued;\n         {error, W} -> W\n       end"))
+  "invalid_client")
+
+;; ── independence + real revocation for client tokens ─────────────
+
+(id-grants-test
+  "two confidential clients get independent tokens"
+  (idgnm
+    (idg-ev
+      "O = identity_oauth:start(),\n       identity_oauth:register_client(O, svc1, confidential, k1, [uri1]),\n       identity_oauth:register_client(O, svc2, confidential, k2, [uri1]),\n       {ok, _T1} = identity_oauth:client_credentials(O, svc1, k1, batch),\n       {ok, T2} = identity_oauth:client_credentials(O, svc2, k2, batch),\n       case identity_oauth:introspect(O, T2) of\n         {active, Subject, _, _} -> Subject\n       end"))
+  "svc2")
+
+(id-grants-test
+  "a client-credentials token can be revoked"
+  (idgnm
+    (idg-ev
+      "O = identity_oauth:start(),\n       identity_oauth:register_client(O, svc, confidential, sk, [uri1]),\n       {ok, T} = identity_oauth:client_credentials(O, svc, sk, batch),\n       identity_oauth:revoke(O, T),\n       case identity_oauth:introspect(O, T) of\n         {active, _, _, _} -> still_valid;\n         {inactive} -> inactive\n       end"))
+  "inactive")
+
+(define
+  id-grants-test-summary
+  (str "grants " id-grants-test-pass "/" id-grants-test-count))