fix: validate machine rename input

CHANGELOG.md

@@ -13,6 +13,7 @@
 - The machine actions backend has been reworked to better handle errors and provide more information to the user (closes [#185](https://github.com/tale/headplane/issues/185)).
 - Machine tags now show states when waiting for subnet or exit node approval and when expiry is disabled.
 - Expiry status on the UI was incorrectly showing as never due to changes in the Headscale API.
+- Added validation for machine renaming to prevent invalid submissions (closes [#192](https://github.com/tale/headplane/issues/192)).
 
 ### 0.5.10 (April 4, 2025)
 - Fix an issue where other preferences to skip onboarding affected every user.

app/components/Input.tsx

@@ -71,14 +71,14 @@ export default function Input(props: InputProps) {
 					{props.description}
 				</div>
 			)}
-			{isInvalid && (
+			{isInvalid ? (
 				<div
 					{...errorMessageProps}
 					className={cn('text-xs px-3 mt-1', 'text-red-500 dark:text-red-400')}
 				>
 					{validationErrors.join(' ')}
 				</div>
-			)}
+			) : null}
 		</div>
 	);
 }

app/routes/machines/dialogs/rename.tsx

@@ -30,11 +30,42 @@ export default function Rename({
 				<input type="hidden" name="action_id" value="rename" />
 				<input type="hidden" name="node_id" value={machine.id} />
 				<Input
+					isRequired
 					label="Machine name"
 					placeholder="Machine name"
+					validationBehavior="native"
 					name="name"
 					defaultValue={machine.givenName}
 					onChange={setName}
+					validate={(value) => {
+						if (value.length === 0) {
+							return 'Cannot be empty';
+						}
+
+						// DNS hostname validation
+						if (value.toLowerCase() !== value) {
+							return 'Cannot contain uppercase letters';
+						}
+
+						if (value.length > 63) {
+							return 'DNS hostnames cannot be 64+ characters';
+						}
+
+						// Test for invalid characters
+						if (!/^[a-z0-9-]+$/.test(value)) {
+							return 'Cannot contain special characters';
+						}
+
+						// Test for leading/trailing hyphens
+						if (value.startsWith('-') || value.endsWith('-')) {
+							return 'Cannot start or end with a hyphen';
+						}
+
+						// Test for consecutive hyphens
+						if (value.includes('--')) {
+							return 'Cannot contain consecutive hyphens';
+						}
+					}}
 				/>
 				{magic ? (
 					name.length > 0 && name !== machine.givenName ? (