src/hero.mjs: Add validateUpgrade(), computeHash() and their helper functions

1 files changed, 99 insertions, 0 deletions

diff --git a/src/hero.mjs b/src/hero.mjs
index 859d86f..6df57ea 100644
--- a/src/hero.mjs
+++ b/src/hero.mjs
@@ -38,6 +38,105 @@ export const makeLogger = (writerFn = console.error) => ({
 
 export const log = makeLogger();
 
+export const isValidMethod = method =>
+	method === "GET";
+
+export const isValidUpgrade = val =>
+	val.toLowerCase() === "websocket";
+
+export const isValidKey = key =>
+	/^[0-9a-zA-Z+/]{22}==$/.test(key);
+
+export const isValidVersion = n =>
+	n === 13;
+
+export const validateUpgrade = (method, headers) => {
+	const upgrade    = headers["upgrade"];
+	const key        = headers["sec-websocket-key"];
+	const versionStr = headers["sec-websocket-version"];
+	const version    = parseInt(versionStr);
+
+	if (!isValidMethod(method)) {
+		return {
+			isValid: false,
+			response: {
+				status: 405,
+			},
+		};
+	}
+
+	if (!upgrade) {
+		return {
+			isValid: false,
+			response: {
+				status: 400,
+				body: 'Missing "Upgrade" header\n',
+			},
+		};
+	}
+
+	if (!isValidUpgrade(upgrade)) {
+		return {
+			isValid: false,
+			response: {
+				status: 400,
+				body: 'Invalid "Upgrade" value\n',
+			},
+		};
+	}
+
+	if (!key) {
+		return {
+			isValid: false,
+			response: {
+				status: 400,
+				body: 'Missing "Sec-WebSocket-Key" header\n',
+			},
+		};
+	}
+
+	if (!isValidKey(key)) {
+		return {
+			isValid: false,
+			response: {
+				status: 400,
+				body: 'Invalid "Sec-WebSocket-Key" value\n',
+			},
+		};
+	}
+
+	if (!version) {
+		return {
+			isValid: false,
+			response: {
+				status: 400,
+				body: 'Missing "Sec-WebSocket-Version" header\n',
+			},
+		};
+	}
+
+	if (!isValidVersion(version)) {
+		return {
+			isValid: false,
+			response: {
+				status: 400,
+				body: 'Invalid "Sec-WebSocket-Version" value\n',
+			},
+		};
+	}
+
+	return {
+		isValid: true,
+	};
+};
+
+const GUID_MAGIC_NUMBER = "258EAFA5-E914-47DA-95CA-C5AB0DC85B11";
+export const computeHash = key =>
+	crypto
+		.createHash("SHA1")
+		.update(key + GUID_MAGIC_NUMBER)
+		.digest("base64");
+
 export const interceptorsFn = ({
 	uuidFn = crypto.randomUUID,
 	logger = log,