jiami

js/page-unlock.js

@@ -0,0 +1,78 @@
+(function () {
+    const encoder = new TextEncoder();
+    const decoder = new TextDecoder();
+    const form = document.getElementById('unlockForm');
+    const passwordInput = document.getElementById('letterPassword');
+    const statusEl = document.getElementById('unlockStatus');
+    const payloadEl = document.getElementById('encryptedPayload');
+
+    function fromBase64(value) {
+        const binary = atob(value);
+        const bytes = new Uint8Array(binary.length);
+        for (let i = 0; i < binary.length; i += 1) {
+            bytes[i] = binary.charCodeAt(i);
+        }
+        return bytes;
+    }
+
+    async function deriveKey(password, salt, iterations) {
+        const baseKey = await crypto.subtle.importKey(
+            'raw',
+            encoder.encode(password),
+            'PBKDF2',
+            false,
+            ['deriveKey']
+        );
+
+        return crypto.subtle.deriveKey(
+            {
+                name: 'PBKDF2',
+                salt,
+                iterations,
+                hash: 'SHA-256'
+            },
+            baseKey,
+            { name: 'AES-GCM', length: 256 },
+            false,
+            ['decrypt']
+        );
+    }
+
+    async function unlock(password) {
+        const payload = JSON.parse(payloadEl.textContent);
+        const salt = fromBase64(payload.salt);
+        const iv = fromBase64(payload.iv);
+        const ciphertext = fromBase64(payload.ciphertext);
+        const key = await deriveKey(password, salt, payload.iterations);
+        const plaintext = await crypto.subtle.decrypt(
+            { name: 'AES-GCM', iv },
+            key,
+            ciphertext
+        );
+
+        return decoder.decode(plaintext);
+    }
+
+    form.addEventListener('submit', async event => {
+        event.preventDefault();
+        const password = passwordInput.value;
+        if (!password) {
+            statusEl.textContent = '请输入密码。';
+            return;
+        }
+
+        statusEl.textContent = '正在解锁...';
+        form.querySelector('button').disabled = true;
+
+        try {
+            const html = await unlock(password);
+            document.open();
+            document.write(html);
+            document.close();
+        } catch (error) {
+            statusEl.textContent = '密码不正确，或页面密文已损坏。';
+            form.querySelector('button').disabled = false;
+            passwordInput.select();
+        }
+    });
+}());