Auth: OIDC Code→Token Exchange Callback + Cookie-basiertes Login

app/main.py

@@ -291,16 +291,58 @@ async def auth_me(user=Depends(get_current_user)):
     return {"authenticated": False}
 
 
+@app.get("/api/auth/callback")
+async def auth_callback(request: Request, code: str = "", state: str = ""):
+    """OIDC Authorization Code → Access Token Exchange.
+
+    Keycloak redirects hierher nach Login mit ?code=... Parameter.
+    Wir tauschen den Code gegen ein Access Token und setzen es als Cookie.
+    """
+    if not _is_auth_enabled() or not code:
+        from fastapi.responses import RedirectResponse
+        return RedirectResponse("/")
+
+    from .auth import _keycloak_issuer
+    token_url = f"{_keycloak_issuer()}/protocol/openid-connect/token"
+
+    # Construct the same redirect_uri used for the auth request
+    base = str(request.base_url).rstrip("/").replace("http://", "https://")
+    redirect_uri = f"{base}/api/auth/callback"
+
+    async with httpx.AsyncClient(timeout=10) as client:
+        resp = await client.post(token_url, data={
+            "grant_type": "authorization_code",
+            "client_id": settings.keycloak_client_id,
+            "code": code,
+            "redirect_uri": redirect_uri,
+        })
+
+    if resp.status_code != 200:
+        logger.error("Token exchange failed: %s %s", resp.status_code, resp.text[:200])
+        raise HTTPException(status_code=401, detail="Login fehlgeschlagen")
+
+    tokens = resp.json()
+    access_token = tokens.get("access_token", "")
+
+    from fastapi.responses import RedirectResponse
+    response = RedirectResponse("/")
+    response.set_cookie(
+        "access_token", access_token,
+        httponly=True, secure=True, samesite="lax",
+        max_age=tokens.get("expires_in", 3600),
+    )
+    return response
+
+
 @app.get("/api/auth/login-url")
 async def auth_login_url(request: Request, redirect: str = "/"):
     """Keycloak-Login-URL für den Browser-Redirect."""
     if not _is_auth_enabled():
         return {"enabled": False, "url": ""}
-    # Construct absolute redirect URI. Traefik terminiert TLS, deshalb
+    # redirect_uri muss auf den Callback-Endpoint zeigen, nicht auf die
-    # sieht FastAPI http:// als base_url. Erzwinge https:// damit die
+    # Zielseite — der Callback tauscht den Code gegen ein Token.
-    # redirect_uri zum Keycloak-Client-Config passt.
     base = str(request.base_url).rstrip("/").replace("http://", "https://")
-    url = keycloak_login_url(f"{base}{redirect}")
+    url = keycloak_login_url(f"{base}/api/auth/callback")
     return {"enabled": True, "url": url}