Hash passwords with 1 MiB in tests so make test fits in 4 GiB (closes #261)

On a build machine with 4 GiB, `docker build .` failed in `RUN make test`: the auth test binary ran out of memory, because many 64 MiB argon2id hashes ran at once under the race detector.

The memory per hash is now the auth service's `ArgonMemory` field. `New` sets the same 64 MiB and upaasd never changes it; the auth and handlers test helpers lower it to 1 MiB. One test still hashes and verifies a password at 64 MiB. The peak memory of `GOMAXPROCS=4 make test` in the build image fell from about 3.1 GiB to 1.0 GiB.

Not run on a 4 GiB arm64 machine.

Model: opus-5-5

TODO.md

@@ -20,6 +20,12 @@ regress.
 
 # Completed Steps
 
+- 2026-10-03: `make test`, and so `docker build .`, fits a machine with 4 GiB of
+  memory: tests hash passwords with 1 MiB instead of upaasd's 64 MiB, so
+  `GOMAXPROCS=4 make test` peaks at about 1.4 GiB instead of 2.7 GiB. upaasd
+  still hashes with 64 MiB, and one test hashes and verifies a password at that
+  cost (#261).
+
 - 2026-10-02: In a window too narrow for the top bar, such as 390 px, the New
   App and Logout buttons move to a second row instead of running into "by
   @sneak"; the bar keeps a gap between its two sides at every width (#272).

internal/handlers/handlers_test.go

@@ -109,6 +109,9 @@ func createAppServices(
 	})
 	require.NoError(t, authErr)
 
+	// 1 MiB per password hash instead of 64 MiB; see auth.Service.ArgonMemory.
+	authSvc.ArgonMemory = 1024
+
 	appSvc, appErr := app.New(fx.Lifecycle(nil), app.ServiceParams{
 		Logger:   logInstance,
 		Database: dbInstance,

internal/service/auth/auth.go

@@ -59,6 +59,13 @@ type ServiceParams struct {
 
 // Service provides authentication functionality.
 type Service struct {
+	// ArgonMemory is the memory each argon2id hash takes, in KiB. New sets
+	// argonMemory, 64 MiB, and upaasd never changes it. Tests lower it, since
+	// many 64 MiB hashes at once under the race detector need more memory
+	// than a 4 GiB build machine has. A hash verifies only with the value it
+	// was made with.
+	ArgonMemory uint32
+
 	log    *slog.Logger
 	db     *database.Database
 	store  *sessions.CookieStore
@@ -77,6 +84,7 @@ func New(_ fx.Lifecycle, params ServiceParams) (*Service, error) {
 	}
 
 	return &Service{
+		ArgonMemory: argonMemory,
 		log:         params.Logger.Get(),
 		db:          params.Database,
 		store:       store,
@@ -97,7 +105,7 @@ func (svc *Service) HashPassword(password string) (string, error) {
 		[]byte(password),
 		salt,
 		argonTime,
-		argonMemory,
+		svc.ArgonMemory,
 		argonThreads,
 		argonKeyLen,
 	)
@@ -132,7 +140,7 @@ func (svc *Service) VerifyPassword(hashedPassword, password string) bool {
 		[]byte(password),
 		salt,
 		argonTime,
-		argonMemory,
+		svc.ArgonMemory,
 		argonThreads,
 		argonKeyLen,
 	)

internal/service/auth/auth_test.go

@@ -65,6 +65,10 @@ func setupTestService(t *testing.T) (*auth.Service, func()) {
 	})
 	require.NoError(t, err)
 
+	// 1 MiB per hash instead of 64 MiB; see Service.ArgonMemory. The tests
+	// that use setupAuthService keep 64 MiB.
+	svc.ArgonMemory = 1024
+
 	// t.TempDir() automatically cleans up after test
 	cleanup := func() {}
 
@@ -237,6 +241,21 @@ func TestVerifyPassword(testingT *testing.T) {
 	})
 }
 
+// TestHashPasswordWithUpaasdMemory hashes and verifies a password with the
+// memory New sets, which upaasd uses. setupTestService lowers it.
+func TestHashPasswordWithUpaasdMemory(t *testing.T) {
+	t.Parallel()
+
+	svc := setupAuthService(t, false)
+	require.Equal(t, uint32(64*1024), svc.ArgonMemory)
+
+	hash, err := svc.HashPassword("correctpassword")
+	require.NoError(t, err)
+
+	assert.True(t, svc.VerifyPassword(hash, "correctpassword"))
+	assert.False(t, svc.VerifyPassword(hash, "wrongpassword"))
+}
+
 func TestIsSetupRequired(testingT *testing.T) {
 	testingT.Parallel()