1 files changed, 107 insertions, 0 deletions
diff --git a/File-decryption/webapp/main.js b/File-decryption/webapp/main.js
new file mode 100644
index 0000000..792eb3d
--- /dev/null
+++ b/File-decryption/webapp/main.js
@@ -0,0 +1,107 @@
+// as seen in /usr/lib/libzc.so / SetupKeys
+const MASTER_KEY = new Uint8Array([
+    0x13, 0x27, 0x3f, 0x42,
+    0xa5, 0xb6, 0x79, 0xe8,
+    0x20, 0x31, 0xc4, 0xf5,
+    0x16, 0x17, 0x88, 0x2f,
+    0x43, 0xa4, 0x55, 0x69,
+    0x77, 0xb8, 0xe2, 0x83,
+    0x04, 0x05, 0x60, 0x70,
+    0x80, 0x02, 0x03, 0x04,
+    0x50, 0x6a, 0x7c, 0x8a,
+    0x02, 0x30, 0x40, 0x51,
+    0x6a, 0x7d, 0x8d, 0x22,
+    0x33, 0x44, 0x59, 0x66,
+    0x71, 0x08, 0x02, 0x03,
+    0x43, 0x05, 0x67, 0x7a,
+    0x8f]);
+
+function hex(byteArray) {
+    return Array.prototype.map.call(byteArray, function (byte) {
+        return ('0' + (byte & 0xFF).toString(16)).slice(-2);
+    }).join('');
+}
+
+// ported from EVP_BytesToKey 
+// https://github.com/openssl/openssl/blob/c04e78f0c69201226430fed14c291c281da47f2d/crypto/evp/evp_key.c#L78
+function deriveKeyAndIV(password, iterations = 10) {
+    var keyLen = 16;
+    var ivLen = 16;
+    var addmd = 0;
+
+    var key = new Uint8Array(keyLen);
+    var iv = new Uint8Array(ivLen);
+    var tmp = new Uint8Array();
+    var i, key_i = 0, iv_i = 0;
+
+    for (; keyLen > 0 || ivLen > 0;) {
+        if (addmd++) {
+            block = new Uint8Array([...tmp, ...password]);
+        } else {
+            block = password;
+        }
+
+        tmp = new Uint8Array(sha1.array(block));
+        for (i = 1; i < iterations; i++) {
+            tmp = sha1.array(tmp);
+        }
+
+        i = 0;
+        while (keyLen && i != tmp.length) {
+            key[key_i++] = tmp[i];
+            keyLen--;
+            i++;
+        }
+
+        while (ivLen != 0 && i != tmp.length) {
+            iv[iv_i++] = tmp[i];
+            ivLen--;
+            i++;
+        }
+    }
+
+    return { key: key, iv: iv };
+}
+
+function processFileInput(e) {
+    const fileName = e.target.fileName;
+    const serial = document.getElementById('serial-input').value;
+    let main_key = null;
+    if (serial.length > 0) {
+        // local decryption, use master key + serial
+        main_key = new Uint8Array([...MASTER_KEY, ...new TextEncoder("utf-8").encode(serial)]);
+    } else {
+        // global decryption, use master key only
+        main_key = MASTER_KEY;
+    }
+
+    // derive key and iv with our EVP_BytesToKey port
+    const derived = deriveKeyAndIV(main_key);
+    // encrypted file contents
+    const ciphertext = e.target.result;
+    // import the raw key
+    window.crypto.subtle.importKey("raw", derived.key, "AES-CTR", true, ["encrypt", "decrypt"]).then(function (key) {
+        // decrypt using aes-128-ctr
+        window.crypto.subtle.decrypt({ name: "AES-CTR", counter: derived.iv, length: 128 }, key, ciphertext).then(function (cleartext) {
+            var blob = new Blob([cleartext], { type: "application/octet-stream" });
+            const link = document.createElement('a');
+            link.href = window.URL.createObjectURL(blob);
+            link.download = fileName + '.dec';
+            link.click();
+        });
+    });
+}
+
+document.addEventListener("DOMContentLoaded", function () {
+    // handle file uploads
+    let fileInput = document.getElementById('file-input')
+    fileInput.onchange = () => {
+        const reader = new FileReader()
+        reader.onload = processFileInput;
+        for (let file of fileInput.files) {
+            // https://stackoverflow.com/questions/24245105/how-to-get-the-filename-from-the-javascript-filereader
+            reader.fileName = file.name;
+            reader.readAsArrayBuffer(file);
+        }
+    };
+});
+\ No newline at end of file