keygen-html: add zip file example

A little bit more JavaScript for easy copy&pasting.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

contrib/keygen-html/keygen.html

@@ -7,7 +7,9 @@
 
 function sendPubkeyToServer(pubkey, username, password)
 {
-	alert("Sending " + username + ":" + password + " to server for new pubkey " + pubkey + "...");
+	var node = document.createElement("li");
+	node.innerText = "Sending " + username + ":" + password + " to server for new pubkey " + pubkey + "...";
+	document.body.appendChild(node);
 
 	// send info to server
 
@@ -38,8 +40,12 @@ function downloadNewConfiguration()
 	config.push("AllowedIPs = " + serverResponse.allowedIPs.join(", "));
 	config.push("Endpoint = " + serverResponse.endpoint);
 	config.push("");
-	config = config.join("\n");
+	return config.join("\n");
+}
 
+function giveOneConfigurationToUser()
+{
+	var config = downloadNewConfiguration();
 	var blob = new Blob([config], { type: "text/plain" });
 	var a = document.createElement("a");
 	a.download = "demo0.conf";
@@ -49,6 +55,124 @@ function downloadNewConfiguration()
 	a.click();
 	document.body.removeChild(a);
 }
+
+function putU32(b, n)
+{
+	b.push(n & 0xff, (n >>> 8) & 0xff, (n >>> 16) & 0xff, (n >>> 24) & 0xff);
+}
+
+function putU16(b, n)
+{
+	b.push(n & 0xff, (n >>> 8) & 0xff);
+}
+
+function putBytes(b, a)
+{
+	for (var i = 0; i < a.length; ++i)
+		b.push(a[i] & 0xff);
+}
+
+function encodeString(s)
+{
+	var utf8 = unescape(encodeURIComponent(s));
+	var b = new Uint8Array(utf8.length);
+	for (var i = 0; i < utf8.length; ++i)
+		b[i] = utf8.charCodeAt(i);
+	return b;
+}
+
+function crc32(b)
+{
+	if (!crc32.table) {
+		crc32.table = [];
+		for (var c = 0, n = 0; n < 256; c = ++n) {
+			for (var k = 0; k < 8; ++k)
+				c = ((c & 1) ? (0xedb88320 ^ (c >>> 1)) : (c >>> 1));
+			crc32.table[n] = c;
+		}
+	}
+	var crc = -1;
+	for (var i = 0; i < b.length; ++i)
+		crc = (crc >>> 8) ^ crc32.table[(crc ^ b[i]) & 0xff];
+	return (crc ^ (-1)) >>> 0;
+}
+
+function createZipFile(files)
+{
+	var b = [];
+	var cd = [];
+	var offset = 0;
+
+	for (var i = 0; i < files.length; ++i) {
+		var name = encodeString(files[i].name);
+		var contents = encodeString(files[i].contents);
+		var crc = crc32(contents);
+
+		putU32(b, 0x04034b50); /* signature */
+		putU16(b, 20); /* version needed */
+		putU16(b, 0); /* flags */
+		putU16(b, 0); /* compression method */
+		putU16(b, 0); /* mtime */
+		putU16(b, 0); /* mdate */
+		putU32(b, crc); /* crc32 */
+		putU32(b, contents.length); /* compressed size */
+		putU32(b, contents.length); /* uncompressed size */
+		putU16(b, name.length); /* file name length */
+		putU16(b, 0); /* extra field length */
+		putBytes(b, name);
+		putBytes(b, contents);
+
+		putU32(cd, 0x02014b50); /* signature */
+		putU16(cd, 0); /* version made */
+		putU16(cd, 20); /* version needed */
+		putU16(cd, 0); /* flags */
+		putU16(cd, 0); /* compression method */
+		putU16(cd, 0); /* mtime */
+		putU16(cd, 0); /* mdate */
+		putU32(cd, crc); /* crc32 */
+		putU32(cd, contents.length); /* compressed size */
+		putU32(cd, contents.length); /* uncompressed size */
+		putU16(cd, name.length); /* file name length */
+		putU16(cd, 0); /* extra field length */
+		putU16(cd, 0); /* file comment length */
+		putU16(cd, 0); /* disk number start */
+		putU16(cd, 0); /* internal file attributes */
+		putU32(cd, 32); /* external file attributes - 'archive' bit set (32) */
+		putU32(cd, offset); /* relative offset of local header */
+		putBytes(cd, name); /* file name */
+
+		offset += 30 + contents.length + name.length
+	}
+	putBytes(b, cd); /* central directory */
+	putU32(b, 0x06054b50); /* end of central directory signature */
+	putU16(b, 0); /* number of this disk */
+	putU16(b, 0); /* number of disk with central directory start */
+	putU16(b, files.length); /* number of entries on disk */
+	putU16(b, files.length); /* number of entries */
+	putU32(b, cd.length); /* length of central directory */
+	putU32(b, offset); /* offset to start of central directory */
+	putU16(b, 0); /* zip comment size */
+	return Uint8Array.from(b);
+}
+
+function giveMultipleConfigurationsToUser()
+{
+	var zipFile = createZipFile([
+		{ name: "demo0.conf", contents: downloadNewConfiguration() },
+		{ name: "demo1.conf", contents: downloadNewConfiguration() },
+		{ name: "demo2.conf", contents: downloadNewConfiguration() }
+	]);
+	var blob = new Blob([zipFile], { type: "application/zip" });
+	var a = document.createElement("a");
+	a.download = "demo-configs.zip";
+	a.href = URL.createObjectURL(blob);
+	a.style.display = "none";
+	document.body.appendChild(a);
+	a.click();
+	document.body.removeChild(a);
+}
+
 </script>
 
-<a href="javascript:downloadNewConfiguration()">Download a WireGuard configuration file</a>
+<p><a href="javascript:giveOneConfigurationToUser()">Download a WireGuard configuration file</a></p>
+<p><a href="javascript:giveMultipleConfigurationsToUser()">Download several WireGuard configuration files</a></p>