dream: auth — pure-SX base64 + HTTP Basic + Bearer-token middleware + 23 tests

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
2026-06-07 15:16:29 +00:00
parent 7fb833f54c
commit 85aea61f3c
4 changed files with 290 additions and 0 deletions
--- a/lib/dream/auth.sx
+++ b/lib/dream/auth.sx
@@ -0,0 +1,172 @@
+;; lib/dream/auth.sx — Dream-on-SX authentication helpers.
+;; HTTP Basic auth (with a pure-SX base64 codec) and Bearer-token guards.
+;; Depends on types.sx.
+
+;; ── base64 (pure SX; arithmetic, no bitwise) ───────────────────────
+(define
+  dr/b64-alpha
+  "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/")
+(define dr/b64-char (fn (n) (char-at dr/b64-alpha n)))
+(define dr/b64-index (fn (c) (index-of dr/b64-alpha c)))
+
+(define
+  dr/b64-encode-loop
+  (fn
+    (s i n acc)
+    (if
+      (>= i n)
+      acc
+      (let
+        ((b0 (char-code (char-at s i))) (rem (- n i)))
+        (cond
+          ((>= rem 3)
+            (let
+              ((triple (+ (* b0 65536) (* (char-code (char-at s (+ i 1))) 256) (char-code (char-at s (+ i 2))))))
+              (dr/b64-encode-loop
+                s
+                (+ i 3)
+                n
+                (str
+                  acc
+                  (dr/b64-char (mod (quotient triple 262144) 64))
+                  (dr/b64-char (mod (quotient triple 4096) 64))
+                  (dr/b64-char (mod (quotient triple 64) 64))
+                  (dr/b64-char (mod triple 64))))))
+          ((= rem 2)
+            (let
+              ((triple (+ (* b0 65536) (* (char-code (char-at s (+ i 1))) 256))))
+              (str
+                acc
+                (dr/b64-char (mod (quotient triple 262144) 64))
+                (dr/b64-char (mod (quotient triple 4096) 64))
+                (dr/b64-char (mod (quotient triple 64) 64))
+                "=")))
+          (else
+            (let
+              ((triple (* b0 65536)))
+              (str
+                acc
+                (dr/b64-char (mod (quotient triple 262144) 64))
+                (dr/b64-char (mod (quotient triple 4096) 64))
+                "=="))))))))
+
+(define
+  dream-base64-encode
+  (fn (s) (dr/b64-encode-loop s 0 (string-length s) "")))
+
+(define
+  dr/b64-decode-loop
+  (fn
+    (s i n acc)
+    (if
+      (>= i n)
+      acc
+      (let
+        ((p2 (char-at s (+ i 2)))
+          (p3 (char-at s (+ i 3))))
+        (let
+          ((c0 (dr/b64-index (char-at s i)))
+            (c1 (dr/b64-index (char-at s (+ i 1))))
+            (c2 (if (= p2 "=") 0 (dr/b64-index p2)))
+            (c3 (if (= p3 "=") 0 (dr/b64-index p3))))
+          (let
+            ((triple (+ (* c0 262144) (* c1 4096) (* c2 64) c3)))
+            (dr/b64-decode-loop
+              s
+              (+ i 4)
+              n
+              (str
+                acc
+                (char-from-code
+                  (mod (quotient triple 65536) 256))
+                (if
+                  (= p2 "=")
+                  ""
+                  (char-from-code
+                    (mod (quotient triple 256) 256)))
+                (if (= p3 "=") "" (char-from-code (mod triple 256)))))))))))
+
+(define
+  dream-base64-decode
+  (fn
+    (s)
+    (if (= s "") "" (dr/b64-decode-loop s 0 (string-length s) ""))))
+
+;; ── Authorization header parsing ───────────────────────────────────
+(define dream-authorization (fn (req) (dream-header req "authorization")))
+
+(define
+  dream-bearer-token
+  (fn
+    (req)
+    (let
+      ((a (dream-authorization req)))
+      (if (and a (starts-with? a "Bearer ")) (substr a 7) nil))))
+
+(define
+  dream-basic-credentials
+  (fn
+    (req)
+    (let
+      ((a (dream-authorization req)))
+      (if
+        (and a (starts-with? a "Basic "))
+        (let
+          ((decoded (dream-base64-decode (substr a 6))))
+          (let
+            ((colon (index-of decoded ":")))
+            (if (< colon 0) nil {:pass (substr decoded (+ colon 1)) :user (substr decoded 0 colon)})))
+        nil))))
+
+;; ── Basic auth middleware ──────────────────────────────────────────
+;; check is (fn (user pass) -> bool). On success the request gains :dream-user.
+(define
+  dr/www-authenticate
+  (fn
+    (realm)
+    (dream-add-header
+      (dream-response 401 {:content-type "text/plain; charset=utf-8"} "Unauthorized")
+      "www-authenticate"
+      (str "Basic realm=\"" realm "\""))))
+
+(define
+  dream-basic-auth
+  (fn
+    (realm check)
+    (fn
+      (next)
+      (fn
+        (req)
+        (let
+          ((creds (dream-basic-credentials req)))
+          (if
+            (and creds (check (get creds :user) (get creds :pass)))
+            (next (assoc req :dream-user (get creds :user)))
+            (dr/www-authenticate realm)))))))
+
+(define dream-user (fn (req) (get req :dream-user)))
+
+;; ── Bearer-token middleware ────────────────────────────────────────
+;; check is (fn (token) -> principal | nil). On success the request gains
+;; :dream-principal. Missing/invalid -> 401.
+(define
+  dream-require-bearer
+  (fn
+    (check)
+    (fn
+      (next)
+      (fn
+        (req)
+        (let
+          ((tok (dream-bearer-token req)))
+          (let
+            ((principal (if tok (check tok) nil)))
+            (if
+              (nil? principal)
+              (dream-add-header
+                (dream-response 401 {:content-type "text/plain; charset=utf-8"} "Unauthorized")
+                "www-authenticate"
+                "Bearer")
+              (next (assoc req :dream-principal principal)))))))))
+
+(define dream-principal (fn (req) (get req :dream-principal)))