api/v2: bound every request body

huma gives RawBody no limit, and validates a whole body before
the handler runs. The token form is parsed before the secret check.

hscontrol/api/v2/acl.go

@@ -8,6 +8,7 @@ import (
 	"net/http"
 	"os"
 	"strings"
+	"time"
 
 	"github.com/danielgtaylor/huma/v2"
 	"github.com/juanfont/headscale/hscontrol/scope"
@@ -86,6 +87,10 @@ func registerACL(api huma.API, b Backend) {
 		// The body is an opaque HuJSON document captured raw; skip huma's
 		// schema validation (which would expect a base64 string).
 		SkipValidateBody: true,
+		// huma's own Body defaults, which it never applies to RawBody; also
+		// what v1 setPolicy accepts.
+		MaxBodyBytes:    1 << 20,
+		BodyReadTimeout: 5 * time.Second,
 		Errors: []int{
 			http.StatusBadRequest, http.StatusUnauthorized, http.StatusForbidden,
 			http.StatusNotFound, http.StatusPreconditionFailed, http.StatusInternalServerError,

hscontrol/api/v2/api.go

@@ -45,6 +45,11 @@ type Backend struct {
 // or as a Bearer token.
 var security = []map[string][]string{{"basicAuth": {}}, {"bearerAuth": {}}}
 
+// maxBodyBytes replaces huma's 1 MiB default on operations whose body huma
+// validates: validation records an error per bad element before the handler
+// runs, and a real body is a few names, tags or routes.
+const maxBodyBytes = 64 << 10
+
 // registrations is populated by each resource file's init(), so adding a
 // resource means adding a file rather than editing a shared list.
 var registrations []func(huma.API, Backend)

hscontrol/api/v2/devices.go

@@ -195,6 +195,7 @@ func registerDevices(api huma.API, b Backend) {
 		Tags:          deviceTags,
 		Security:      security,
 		DefaultStatus: http.StatusOK,
+		MaxBodyBytes:  maxBodyBytes,
 		Errors:        []int{http.StatusBadRequest, http.StatusUnauthorized, http.StatusForbidden, http.StatusNotFound},
 	}, scope.DevicesCore), func(ctx context.Context, in *setAuthorizedInput) (*emptyOutput, error) {
 		_, err := lookupNode(b, in.DeviceID)
@@ -222,6 +223,7 @@ func registerDevices(api huma.API, b Backend) {
 		Tags:          deviceTags,
 		Security:      security,
 		DefaultStatus: http.StatusOK,
+		MaxBodyBytes:  maxBodyBytes,
 		Errors:        []int{http.StatusBadRequest, http.StatusUnauthorized, http.StatusForbidden, http.StatusNotFound},
 	}, scope.DevicesCore), func(ctx context.Context, in *setNameInput) (*emptyOutput, error) {
 		node, err := lookupNode(b, in.DeviceID)
@@ -247,6 +249,7 @@ func registerDevices(api huma.API, b Backend) {
 		Tags:          deviceTags,
 		Security:      security,
 		DefaultStatus: http.StatusOK,
+		MaxBodyBytes:  maxBodyBytes,
 		Errors:        []int{http.StatusBadRequest, http.StatusUnauthorized, http.StatusForbidden, http.StatusNotFound},
 	}, scope.DevicesCore), func(ctx context.Context, in *setTagsInput) (*emptyOutput, error) {
 		node, err := lookupNode(b, in.DeviceID)
@@ -293,6 +296,7 @@ func registerDevices(api huma.API, b Backend) {
 		Tags:          deviceTags,
 		Security:      security,
 		DefaultStatus: http.StatusOK,
+		MaxBodyBytes:  maxBodyBytes,
 		Errors:        []int{http.StatusBadRequest, http.StatusUnauthorized, http.StatusForbidden, http.StatusNotFound},
 	}, scope.DevicesCore), func(ctx context.Context, in *setKeyInput) (*emptyOutput, error) {
 		node, err := lookupNode(b, in.DeviceID)
@@ -326,6 +330,7 @@ func registerDevices(api huma.API, b Backend) {
 		Tags:          deviceTags,
 		Security:      security,
 		DefaultStatus: http.StatusOK,
+		MaxBodyBytes:  maxBodyBytes,
 		Errors:        []int{http.StatusBadRequest, http.StatusUnauthorized, http.StatusForbidden, http.StatusNotFound},
 	}, scope.DevicesRoutes), func(ctx context.Context, in *setSubnetRoutesInput) (*deviceRoutesOutput, error) {
 		node, err := lookupNode(b, in.DeviceID)

hscontrol/api/v2/guard_test.go

@@ -47,6 +47,27 @@ func TestEveryAuthenticatedOperationDeclaresScope(t *testing.T) {
 	}
 }
 
+// TestEveryRequestBodyIsBounded fails an operation whose body has no size or
+// read-time limit, or a validated body above maxBodyBytes. huma sets its
+// defaults only for a Body input, never for RawBody.
+func TestEveryRequestBodyIsBounded(t *testing.T) {
+	api := NewAPI(chi.NewMux(), Backend{})
+
+	for path, item := range api.OpenAPI().Paths {
+		for method, op := range humaOperations(item) {
+			if op == nil || op.RequestBody == nil {
+				continue
+			}
+
+			if op.MaxBodyBytes <= 0 || op.BodyReadTimeout <= 0 ||
+				(!op.SkipValidateBody && op.MaxBodyBytes > maxBodyBytes) {
+				t.Errorf("%s %s: MaxBodyBytes=%d BodyReadTimeout=%s",
+					method, path, op.MaxBodyBytes, op.BodyReadTimeout)
+			}
+		}
+	}
+}
+
 func humaOperations(item *huma.PathItem) map[string]*huma.Operation {
 	return map[string]*huma.Operation{
 		"GET":    item.Get,

hscontrol/api/v2/keys.go

@@ -126,13 +126,14 @@ func registerKeys(api huma.API, b Backend) {
 	keysTags := []string{"Keys", "Tailscale compat"}
 
 	huma.Register(api, huma.Operation{
-		OperationID: "createKey",
-		Method:      http.MethodPost,
-		Path:        "/api/v2/tailnet/{tailnet}/keys",
-		Summary:     "Create an auth key or OAuth client",
-		Description: "Requires the `auth_keys` scope for an auth key, or `oauth_keys` for an OAuth client (an admin API key is all-access).",
-		Tags:        keysTags,
-		Security:    security,
+		OperationID:  "createKey",
+		Method:       http.MethodPost,
+		Path:         "/api/v2/tailnet/{tailnet}/keys",
+		Summary:      "Create an auth key or OAuth client",
+		Description:  "Requires the `auth_keys` scope for an auth key, or `oauth_keys` for an OAuth client (an admin API key is all-access).",
+		Tags:         keysTags,
+		Security:     security,
+		MaxBodyBytes: maxBodyBytes,
 		Errors: []int{
 			http.StatusBadRequest,
 			http.StatusUnauthorized,

hscontrol/api/v2/oauth.go

@@ -16,6 +16,10 @@ import (
 // Tailscale's non-configurable one hour.
 const accessTokenTTL = time.Hour
 
+// maxTokenRequestBytes caps the token request form, which is read before the
+// secret is checked and whose scope and tag lists are stored on the token.
+const maxTokenRequestBytes = 16 << 10
+
 // registerOAuthToken mounts POST /api/v2/oauth/token on the router. It is a plain
 // handler, not a Huma operation: it consumes application/x-www-form-urlencoded
 // and emits RFC 6749 OAuth2 error bodies ({"error","error_description"}), neither
@@ -38,6 +42,8 @@ type tokenResponse struct {
 // short-lived bearer token.
 func oauthTokenHandler(b Backend) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
+		r.Body = http.MaxBytesReader(w, r.Body, maxTokenRequestBytes)
+
 		err := r.ParseForm()
 		if err != nil {
 			writeOAuthError(w, http.StatusBadRequest, "invalid_request", "could not parse request body")

hscontrol/apiv2_acl_test.go

@@ -10,6 +10,7 @@ import (
 	"net/http/httptest"
 	"os"
 	"path/filepath"
+	"strings"
 	"testing"
 
 	"github.com/danielgtaylor/huma/v2/humatest"
@@ -128,6 +129,17 @@ func TestAPIv2ACLSetHuJSONWithComments(t *testing.T) {
 	assert.Equal(t, policyETagOf(policy), raw.Header().Get("Etag"))
 }
 
+// TestAPIv2ACLSetBodyLimited: huma gives a RawBody input no size limit of its
+// own, so setACL must declare one.
+func TestAPIv2ACLSetBodyLimited(t *testing.T) {
+	app := createTestApp(t)
+	api := registerAPIV2(t, app)
+
+	set := setACL(t, api, allowAllPolicy+strings.Repeat(" ", 1<<20), "application/json")
+	assert.Equal(t, http.StatusRequestEntityTooLarge, set.Code)
+	assert.Empty(t, storedPolicy(t, app))
+}
+
 func TestAPIv2ACLETagChangesOnChangeStableOnNoop(t *testing.T) {
 	app := createTestApp(t)
 	api := registerAPIV2(t, app)

hscontrol/apiv2_oauth_test.go

@@ -13,6 +13,7 @@ import (
 	"testing"
 
 	apiv2 "github.com/juanfont/headscale/hscontrol/api/v2"
+	"github.com/juanfont/headscale/hscontrol/scope"
 	"github.com/juanfont/headscale/hscontrol/types/testcapture"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
@@ -222,6 +223,23 @@ func TestAPIv2OAuth_TokenEndpoint(t *testing.T) {
 	assert.Equal(t, "no-store", resp.Header.Get("Cache-Control"))
 }
 
+// TestAPIv2OAuth_RequestBodiesBounded: the token form is parsed before the
+// secret is checked, and huma validates a whole body before the handler runs.
+func TestAPIv2OAuth_RequestBodiesBounded(t *testing.T) {
+	_, baseURL, admin := newOAuthTestServer(t)
+	_, secret := createClient(t, baseURL, admin, []string{"users:read"}, nil)
+
+	scopes := strings.TrimSpace(strings.Repeat("users:read ", 2000))
+	status, m := mintToken(t, baseURL, "", secret, scopes, false)
+	assert.Equalf(t, http.StatusBadRequest, status, "%v", m)
+	assert.Equal(t, "invalid_request", m["error"])
+
+	tok := mintScopedToken(t, baseURL, admin, scope.AuthKeys)
+	status, _ = apiReq(t, http.MethodPost, baseURL+"/api/v2/tailnet/-/keys", tok,
+		map[string]any{"tags": make([]int, 40000)})
+	assert.Equal(t, http.StatusRequestEntityTooLarge, status)
+}
+
 func TestAPIv2OAuth_ScopeEnforcement(t *testing.T) {
 	_, baseURL, admin := newOAuthTestServer(t)