feat: support acl capabilities check

app/routes/acls/acl-action.ts

@@ -0,0 +1,113 @@
+import { ActionFunctionArgs, data } from 'react-router';
+import { LoadContext } from '~/server';
+import ResponseError from '~/server/headscale/api-error';
+import { Capabilities } from '~/server/web/roles';
+import { data400, data403 } from '~/utils/res';
+
+// We only check capabilities here and assume it is writable
+// If it isn't, it'll gracefully error anyways, since this means some
+// fishy client manipulation is happening.
+export async function aclAction({
+	request,
+	context,
+}: ActionFunctionArgs<LoadContext>) {
+	const session = await context.sessions.auth(request);
+	const check = await context.sessions.check(
+		request,
+		Capabilities.write_policy,
+	);
+	if (!check) {
+		throw data403('You do not have permission to write to the ACL policy');
+	}
+
+	// Try to write to the ACL policy via the API or via config file (TODO).
+	const formData = await request.formData();
+	const policyData = formData.get('policy')?.toString();
+	if (!policyData) {
+		throw data400('Missing `policy` in the form data.');
+	}
+
+	try {
+		const { policy, updatedAt } = await context.client.put<{
+			policy: string;
+			updatedAt: string;
+		}>('v1/policy', session.get('api_key')!, {
+			policy: policyData,
+		});
+
+		return data({
+			success: true,
+			error: undefined,
+			policy,
+			updatedAt,
+		});
+	} catch (error) {
+		// This means Headscale returned a protobuf error to us
+		// It also means we 100% know this is in database mode
+		if (error instanceof ResponseError && error.responseObject?.message) {
+			const message = error.responseObject.message as string;
+			// This is stupid, refer to the link
+			// https://github.com/juanfont/headscale/blob/main/hscontrol/types/policy.go
+			if (message.includes('update is disabled')) {
+				// This means the policy is not writable
+				throw data403('Policy is not writable');
+			}
+
+			// https://github.com/juanfont/headscale/blob/main/hscontrol/policy/v1/acls.go#L81
+			if (message.includes('parsing hujson')) {
+				// This means the policy was invalid, return a 400
+				// with the actual error message from Headscale
+				const cutIndex = message.indexOf('err: hujson:');
+				const trimmed =
+					cutIndex > -1
+						? `Syntax error: ${message.slice(cutIndex + 12)}`
+						: message;
+
+				return data(
+					{
+						success: false,
+						error: trimmed,
+						policy: undefined,
+						updatedAt: undefined,
+					},
+					400,
+				);
+			}
+
+			if (message.includes('unmarshalling policy')) {
+				// This means the policy was invalid, return a 400
+				// with the actual error message from Headscale
+				const cutIndex = message.indexOf('err:');
+				const trimmed =
+					cutIndex > -1
+						? `Syntax error: ${message.slice(cutIndex + 5)}`
+						: message;
+
+				return data(
+					{
+						success: false,
+						error: trimmed,
+						policy: undefined,
+						updatedAt: undefined,
+					},
+					400,
+				);
+			}
+
+			if (message.includes('empty policy')) {
+				return data(
+					{
+						success: false,
+						error: 'Policy error: Supplied policy was empty',
+						policy: undefined,
+						updatedAt: undefined,
+					},
+					400,
+				);
+			}
+		}
+
+		// Otherwise, this is a Headscale error that we can just propagate.
+		throw error;
+	}
+}