From dd0bb0a39104a54c26015df807c1eb113331c242 Mon Sep 17 00:00:00 2001
From: Ophestra <cat@gensokyo.uk>
Date: Fri, 3 Oct 2025 16:42:42 +0900
Subject: [PATCH] internal/app: check username validation

This stuff should be hardcoded in libc, but check it anyway.

Signed-off-by: Ophestra <cat@gensokyo.uk>
---
 internal/app/sysconf_test.go  | 15 +++++++++++++++
 internal/app/username_test.go | 26 ++++++++++++++++++++++++++
 2 files changed, 41 insertions(+)
 create mode 100644 internal/app/sysconf_test.go
 create mode 100644 internal/app/username_test.go

diff --git a/internal/app/sysconf_test.go b/internal/app/sysconf_test.go
new file mode 100644
index 0000000..b73f2d0
--- /dev/null
+++ b/internal/app/sysconf_test.go
@@ -0,0 +1,15 @@
+package app
+
+import "testing"
+
+const (
+	_POSIX_LOGIN_NAME_MAX = 9
+)
+
+func TestSysconf(t *testing.T) {
+	t.Run("LOGIN_NAME_MAX", func(t *testing.T) {
+		if got := sysconf(_SC_LOGIN_NAME_MAX); got < _POSIX_LOGIN_NAME_MAX {
+			t.Errorf("sysconf(_SC_LOGIN_NAME_MAX): %d < _POSIX_LOGIN_NAME_MAX", got)
+		}
+	})
+}
diff --git a/internal/app/username_test.go b/internal/app/username_test.go
new file mode 100644
index 0000000..15f15a4
--- /dev/null
+++ b/internal/app/username_test.go
@@ -0,0 +1,26 @@
+package app
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestIsValidUsername(t *testing.T) {
+	t.Run("long", func(t *testing.T) {
+		if isValidUsername(strings.Repeat("a", sysconf(_SC_LOGIN_NAME_MAX))) {
+			t.Errorf("isValidUsername unexpected true")
+		}
+	})
+
+	t.Run("regexp", func(t *testing.T) {
+		if isValidUsername("0") {
+			t.Errorf("isValidUsername unexpected true")
+		}
+	})
+
+	t.Run("valid", func(t *testing.T) {
+		if !isValidUsername("alice") {
+			t.Errorf("isValidUsername unexpected false")
+		}
+	})
+}