JA4 Fingerprint

src/core/config/Categories.json

@@ -231,6 +231,7 @@
             "VarInt Decode",
             "JA3 Fingerprint",
             "JA3S Fingerprint",
+            "JA4 Fingerprint",
             "HASSH Client Fingerprint",
             "HASSH Server Fingerprint",
             "Format MAC addresses",

src/core/lib/JA4.mjs

@@ -0,0 +1,166 @@
+/**
+ * JA4 resources.
+ *
+ * @author n1474335 [n1474335@gmail.com]
+ * @copyright Crown Copyright 2024
+ * @license Apache-2.0
+ *
+ * JA4 Copyright 2023 FoxIO, LLC.
+ * @license BSD-3-Clause
+ */
+
+import OperationError from "../errors/OperationError.mjs";
+import { parseTLSRecord, parseHighestSupportedVersion, parseFirstALPNValue } from "./TLS.mjs";
+import { toHexFast } from "./Hex.mjs";
+import { runHash } from "./Hash.mjs";
+import Utils from "../Utils.mjs";
+
+
+/**
+ * Calculate the JA4 from a given TLS Client Hello Stream
+ * @param {Uint8Array} bytes
+ * @returns {string}
+ */
+export function toJA4(bytes) {
+    let tlsr = {};
+    try {
+        tlsr = parseTLSRecord(bytes);
+    } catch (err) {
+        throw new OperationError("Data is not a valid TLS Client Hello. QUIC is not yet supported.\n" + err);
+    }
+
+    /* QUIC
+        “q” or “t”, which denotes whether the hello packet is for QUIC or TCP.
+        TODO: Implement QUIC
+    */
+    const ptype = "t";
+
+    /* TLS Version
+        TLS version is shown in 3 different places. If extension 0x002b exists (supported_versions), then the version
+        is the highest value in the extension. Remember to ignore GREASE values. If the extension doesn’t exist, then
+        the TLS version is the value of the Protocol Version. Handshake version (located at the top of the packet)
+        should be ignored.
+    */
+    let version = tlsr.version.value;
+    for (const ext of tlsr.handshake.value.extensions.value) {
+        if (ext.type.value === "supported_versions") {
+            version = parseHighestSupportedVersion(ext.value.data);
+            break;
+        }
+    }
+    switch (version) {
+        case 0x0304: version = "13"; break; // TLS 1.3
+        case 0x0303: version = "12"; break; // TLS 1.2
+        case 0x0302: version = "11"; break; // TLS 1.1
+        case 0x0301: version = "10"; break; // TLS 1.0
+        case 0x0300: version = "s3"; break; // SSL 3.0
+        case 0x0200: version = "s2"; break; // SSL 2.0
+        case 0x0100: version = "s1"; break; // SSL 1.0
+        default: version = "00"; // Unknown
+    }
+
+    /* SNI
+        If the SNI extension (0x0000) exists, then the destination of the connection is a domain, or “d” in the fingerprint.
+        If the SNI does not exist, then the destination is an IP address, or “i”.
+    */
+    let sni = "i";
+    for (const ext of tlsr.handshake.value.extensions.value) {
+        if (ext.type.value === "server_name") {
+            sni = "d";
+            break;
+        }
+    }
+
+    /* Number of Ciphers
+        2 character number of cipher suites, so if there’s 6 cipher suites in the hello packet, then the value should be “06”.
+        If there’s > 99, which there should never be, then output “99”. Remember, ignore GREASE values. They don’t count.
+    */
+    let cipherLen = 0;
+    for (const cs of tlsr.handshake.value.cipherSuites.value) {
+        if (cs.value !== "GREASE") cipherLen++;
+    }
+    cipherLen = cipherLen > 99 ? "99" : cipherLen.toString().padStart(2, "0");
+
+    /* Number of Extensions
+        Same as counting ciphers. Ignore GREASE. Include SNI and ALPN.
+    */
+    let extLen = 0;
+    for (const ext of tlsr.handshake.value.extensions.value) {
+        if (ext.type.value !== "GREASE") extLen++;
+    }
+    extLen = extLen > 99 ? "99" : extLen.toString().padStart(2, "0");
+
+    /* ALPN Extension Value
+        The first and last characters of the ALPN (Application-Layer Protocol Negotiation) first value.
+        If there are no ALPN values or no ALPN extension then we print “00” as the value in the fingerprint.
+    */
+    let alpn = "00";
+    for (const ext of tlsr.handshake.value.extensions.value) {
+        if (ext.type.value === "application_layer_protocol_negotiation") {
+            alpn = parseFirstALPNValue(ext.value.data);
+            alpn = alpn.charAt(0) + alpn.charAt(alpn.length - 1);
+            break;
+        }
+    }
+
+    /* Cipher hash
+        A 12 character truncated sha256 hash of the list of ciphers sorted in hex order, first 12 characters.
+        The list is created using the 4 character hex values of the ciphers, lower case, comma delimited, ignoring GREASE.
+    */
+    const originalCiphersList = [];
+    for (const cs of tlsr.handshake.value.cipherSuites.value) {
+        if (cs.value !== "GREASE") {
+            originalCiphersList.push(toHexFast(cs.data));
+        }
+    }
+    const sortedCiphersList = [...originalCiphersList].sort();
+    const sortedCiphersRaw = sortedCiphersList.join(",");
+    const originalCiphersRaw = originalCiphersList.join(",");
+    const sortedCiphers = runHash(
+        "sha256",
+        Utils.strToArrayBuffer(sortedCiphersRaw)
+    ).substring(0, 12);
+    const originalCiphers = runHash(
+        "sha256",
+        Utils.strToArrayBuffer(originalCiphersRaw)
+    ).substring(0, 12);
+
+    /* Extension hash
+        A 12 character truncated sha256 hash of the list of extensions, sorted by hex value, followed by the list of signature
+        algorithms, in the order that they appear (not sorted).
+        The extension list is created using the 4 character hex values of the extensions, lower case, comma delimited, sorted
+        (not in the order they appear). Ignore the SNI extension (0000) and the ALPN extension (0010) as we’ve already captured
+        them in the a section of the fingerprint. These values are omitted so that the same application would have the same b
+        section of the fingerprint regardless of if it were going to a domain, IP, or changing ALPNs.
+    */
+    const originalExtensionsList = [];
+    let signatureAlgorithms = "";
+    for (const ext of tlsr.handshake.value.extensions.value) {
+        if (ext.type.value !== "GREASE") {
+            originalExtensionsList.push(toHexFast(ext.type.data));
+        }
+        if (ext.type.value === "signature_algorithms") {
+            signatureAlgorithms = toHexFast(ext.value.data.slice(2));
+            signatureAlgorithms = signatureAlgorithms.replace(/(.{4})/g, "$1,");
+            signatureAlgorithms = signatureAlgorithms.substring(0, signatureAlgorithms.length - 1);
+        }
+    }
+    const sortedExtensionsList = [...originalExtensionsList].filter(e => e !== "0000" && e !== "0010").sort();
+    const sortedExtensionsRaw = sortedExtensionsList.join(",") + "_" + signatureAlgorithms;
+    const originalExtensionsRaw = originalExtensionsList.join(",") + "_" + signatureAlgorithms;
+    const sortedExtensions = runHash(
+        "sha256",
+        Utils.strToArrayBuffer(sortedExtensionsRaw)
+    ).substring(0, 12);
+    const originalExtensions = runHash(
+        "sha256",
+        Utils.strToArrayBuffer(originalExtensionsRaw)
+    ).substring(0, 12);
+
+    return {
+        "JA4":    `${ptype}${version}${sni}${cipherLen}${extLen}${alpn}_${sortedCiphers}_${sortedExtensions}`,
+        "JA4_o":  `${ptype}${version}${sni}${cipherLen}${extLen}${alpn}_${originalCiphers}_${originalExtensions}`,
+        "JA4_r":  `${ptype}${version}${sni}${cipherLen}${extLen}${alpn}_${sortedCiphersRaw}_${sortedExtensionsRaw}`,
+        "JA4_ro": `${ptype}${version}${sni}${cipherLen}${extLen}${alpn}_${originalCiphersRaw}_${originalExtensionsRaw}`,
+    };
+}

src/core/lib/Stream.mjs

@@ -18,12 +18,23 @@ export default class Stream {
      * Stream constructor.
      *
      * @param {Uint8Array} input
+     * @param {number} pos
+     * @param {number} bitPos
      */
-    constructor(input) {
+    constructor(input, pos=0, bitPos=0) {
         this.bytes = input;
         this.length = this.bytes.length;
-        this.position = 0;
-        this.bitPos = 0;
+        this.position = pos;
+        this.bitPos = bitPos;
+    }
+
+    /**
+     * Clone this Stream returning a new identical Stream.
+     *
+     * @returns {Stream}
+     */
+    clone() {
+        return new Stream(this.bytes, this.position, this.bitPos);
     }
 
     /**