useradd: implemented useradd -K/--key KEY=VALUE (override /etc/login.defs defaults)

src/shadow-core/src/login_defs.rs

@@ -72,6 +72,24 @@ impl LoginDefs {
     pub fn get_i64(&self, key: &str) -> Option<i64> {
         self.entries.get(key).and_then(|v| v.parse().ok())
     }
+
+    /// Insert or replace a configuration value for later `get` / `get_i64` calls.
+    ///
+    /// Used when a tool accepts runtime overrides of login.defs defaults
+    /// (for example `useradd -K KEY=VALUE`).
+    pub fn set(&mut self, key: impl Into<String>, value: impl Into<String>) {
+        self.entries.insert(key.into(), value.into());
+    }
+
+    /// Apply several `KEY=VALUE` overrides; later entries win on duplicate keys.
+    pub fn apply_overrides<'a, I>(&mut self, overrides: I)
+    where
+        I: IntoIterator<Item = (&'a str, &'a str)>,
+    {
+        for (key, value) in overrides {
+            self.set(key, value);
+        }
+    }
 }
 
 #[cfg(test)]
@@ -138,6 +156,32 @@ mod tests {
         assert_eq!(defs.get_i64("ENCRYPT_METHOD"), None);
     }
 
+    #[test]
+    fn test_set_overrides_existing_and_inserts_new() {
+        let dir = tempfile::tempdir().unwrap();
+        let path = write_login_defs(dir.path(), "UID_MIN 1000\n");
+        let mut defs = LoginDefs::load(&path).unwrap();
+        assert_eq!(defs.get_i64("UID_MIN"), Some(1000));
+
+        defs.set("UID_MIN", "9100");
+        defs.set("PASS_MAX_DAYS", "-1");
+        assert_eq!(defs.get_i64("UID_MIN"), Some(9100));
+        assert_eq!(defs.get("PASS_MAX_DAYS"), Some("-1"));
+    }
+
+    #[test]
+    fn test_apply_overrides() {
+        let mut defs = LoginDefs::load(Path::new("/nonexistent")).unwrap();
+        defs.apply_overrides([
+            ("UID_MIN", "2000"),
+            ("UID_MAX", "2000"),
+            ("UID_MIN", "3000"),
+        ]);
+        // Later duplicate wins.
+        assert_eq!(defs.get("UID_MIN"), Some("3000"));
+        assert_eq!(defs.get("UID_MAX"), Some("2000"));
+    }
+
     // -------------------------------------------------------------------
     // Issue #16: parser edge case tests
     // -------------------------------------------------------------------