UAF TLV Decoder Example

UAFTLV.js

var chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_";

// Use a lookup table to find the index.
var lookup = new Uint8Array(256);
for (var i = 0; i < chars.length; i++) {
    lookup[chars.charCodeAt(i)] = i;
}

// stolen from:
// https://github.com/niklasvh/base64-arraybuffer/blob/master/lib/base64-arraybuffer.js
// modified to base64url by Yuriy :)
function decode(base64) {
    var bufferLength = base64.length * 0.75,
        len = base64.length,
        i, p = 0,
        encoded1, encoded2, encoded3, encoded4;

    if (base64[base64.length - 1] === "=") {
        bufferLength--;
        if (base64[base64.length - 2] === "=") {
            bufferLength--;
        }
    }

    var arraybuffer = new ArrayBuffer(bufferLength),
        bytes = new Uint8Array(arraybuffer);

    for (i = 0; i < len; i += 4) {
        encoded1 = lookup[base64.charCodeAt(i)];
        encoded2 = lookup[base64.charCodeAt(i + 1)];
        encoded3 = lookup[base64.charCodeAt(i + 2)];
        encoded4 = lookup[base64.charCodeAt(i + 3)];

        bytes[p++] = (encoded1 << 2) | (encoded2 >> 4);
        bytes[p++] = ((encoded2 & 15) << 4) | (encoded3 >> 2);
        bytes[p++] = ((encoded3 & 3) << 6) | (encoded4 & 63);
    }

    return arraybuffer;
}

function printHex(msg, buf) {
    // if the buffer was a TypedArray (e.g. Uint8Array), grab its buffer and use that
    if (ArrayBuffer.isView(buf) && buf.buffer instanceof ArrayBuffer) {
        buf = buf.buffer;
    }

    // check the arguments
    if ((typeof msg != "string") ||
        (typeof buf != "object")) {
        console.log("Bad args to printHex");
        return;
    }
    if (!(buf instanceof ArrayBuffer)) {
        console.log("Attempted printHex with non-ArrayBuffer:", buf);
        return;
    }
    // print the buffer as a 16 byte long hex string
    var arr = new Uint8Array(buf);
    var len = buf.byteLength;
    var i, str = "";
    console.log(msg);
    for (i = 0; i < len; i++) {
        var hexch = arr[i].toString(16);
        hexch = (hexch.length == 1) ? ("0" + hexch) : hexch;
        str += hexch.toUpperCase() + " ";
        if (i && !((i + 1) % 16)) {
            console.log(str);
            str = "";
        }
    }
    // print the remaining bytes
    if ((i) % 16) {
        console.log(str);
    }
}


var uafThingy = [{
    "assertions": [{
        "assertionScheme": "UAFV1TLV",
        "assertion": "AT4TBAM-ywALLgkAODA4NiM1MDE2Di4HAAABAQIAAQEKLiAAyhcSKymHB0XKDW24w-JwL6Bi5VhIeXAaxwLsnKspLI8JLiAA6_Iy-fYu6ZGzXPMcrNUcAGQPQVrljGsgi0aTNvNFGNUNLggADAAAAA8AAAAMLlsAMFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAEbe5AVrIzVoXZnEv9xfc_O-SiyA3qIoepR98IWImcpSCAhELgIMf9Td3H_uQFgAjsAHGGMSIXzp5DnhtCqKrk7Qc-QAMGLkcAMEUCIQDbmSd3w1smcsOnShtl-ygCWbfwogkuT_ExoEMDpSD4kwIgelhGj9Vzmk-G8G7Yy2wizbclirt5uy_KdwAXV0oopUgFLvECMIIC7TCCAdWgAwIBAgICENQwDQYJKoZIhvcNAQELBQAwVDELMAkGA1UEBhMCVVMxEzARBgNVBAgMCkNhbGlmb3JuaWExDjAMBgNVBAoMBUludGVsMSAwHgYDVQQDDBdQYXltZW50IFByb2plY3QgVGVzdCBDQTAeFw0xNjAyMDgxNzQ3MjVaFw0xODAyMDcxNzQ3MjVaMGwxCzAJBgNVBAYTAlVTMQswCQYDVQQIDAJDQTEUMBIGA1UEBwwLU2FudGEgQ2xhcmExDjAMBgNVBAoMBUludGVsMQwwCgYDVQQLDANTU0cxHDAaBgNVBAMME0FBRSBUZXN0IEVDRFNBIENlcnQwWTATBgcqhkjOPQIBBggqhkjOPQMBBwNCAAT0mupJAfo2ZB6GEppbhllAvn-f4g2wWc8ujNOUyayMyEBDSP-iGUZGFIgYfISwCC1JxilXN509S7O0cX95TzCeo3wwejAJBgNVHRMEAjAAMB0GA1UdDgQWBBTO6UVCsHHm_3cewtekuatVFM38rjAfBgNVHSMEGDAWgBSKY1RPVFVXtk3d8JjvFGkeN8KL7jAOBgNVHQ8BAf8EBAMCBeAwHQYDVR0lBBYwFAYIKwYBBQUHAwIGCCsGAQUFBwMEMA0GCSqGSIb3DQEBCwUAA4IBAQAwfGfyW2EQ1xGHbXln_PYNKiR9UMikMJ_NEiM_D3dNFv7wOxWbryHT5AVnOKqis_HSMBf2aROWE5NgZpPT3r8RAaxhbWkHmJG50iQZBpj9L3m6XHzmXy-tDPBABuQw8q6x6VnoEFuGljRgRN0Jt6Cx0sSYXnjY1D5GJ0neQXelFUdB6FA58S-jig_kUXI4kAJ0kXFpfU7pVV6l84SHfaBfMcYsp9rxxsk3_MEVa8OyJeIQJQ3r02np4DXhVsih0alzYhkSAliOSifJCpjkTukzi5SiWCY-7xuY9WznbuT6zwAQS8MZaEzzqiGxTz1ZHEZyxDAXhEZwaf7i-tMjM6JL"
    }],
    "header": {
        "upv": {
            "major": 1,
            "minor": 0
        },
        "op": "Reg",
        "appID": "https://192.168.1.103:8080"
    },
    "fcParams": "eyJhcHBJRCI6Imh0dHBzOi8vMTkyLjE2OC4xLjEwMzo4MDgwIiwiY2hhbGxlbmdlIjoiSVI5Y2VsT29VdjFCdUVzVGhkd05WUXYiLCJmYWNldElEIjoiaHR0cHM6Ly8xOTIuMTY4LjEuMTAzOjgwODAiLCJjaGFubmVsQmluZGluZyI6e319"
}];

// var thing2 = [{
//     "assertions": [{
//         "assertion": "AT5IAQM-_AALLgkARDQwOSMwOTAxDi4HAAEAAQEAAAEKLiAA-PuqiaEkPiZYMWltcBEaQjJ2sn5ozCfoHNnzlZRAvngJLiQARDYxMkE5QjYtQjU5OS00MzUzLTg5QzItRjMwMjQzOTUzRDhFDS4IAAAAAAAAAAAADC5BAATOEmN5XMKnxzyZ9pe4QwMAdHHp9TnTqeDgvsWDakirV5PEttcN5UGycBDv9ZbLApElgRPktVV6r_jfkmTseLwfEj5DABMuGwBjb20uZGFvbi5zZGsuZXh0ZW5zaW9uc0hhc2gULiAAbjQLnP-zepicpUTmu3gKLHiQHT-zNzh2hRGjBhevoB0IPkQABi5AAIW9Tw-vcb8vau8i0Zd1HTQ-CcghdY73DJQ9jQCzceuTe8IXyOjBZeyEhrOLkFPZ9OhEZbJRmUy-4kZ4cH31Vb0=",
//         "assertionScheme": "UAFV1TLV"
//     }],
//     "header": {
//         "op": "Reg",
//         "appID": "https://api-rp.identityx-cloud.com/jbtest2/facets",
//         "upv": {
//             "major": 1,
//             "minor": 0
//         }
//     },
//     "fcParams": "eyJmYWNldElEIjoiaW9zOmJ1bmRsZS1pZDpjb20uZGFvbi5EYW9uRmlkb1NhbXBsZVJwQXBwIiwiY2hhbm5lbEJpbmRpbmciOnt9LCJhcHBJRCI6Imh0dHBzOi8vYXBpLXJwLmlkZW50aXR5eC1jbG91ZC5jb20vamJ0ZXN0Mi9mYWNldHMiLCJjaGFsbGVuZ2UiOiJJaVNtYVAybFJqOWtKeVphNVFzMFh3In0="
// }];


var authAlgList = new Map([
    [0x01, 'UAF_ALG_SIGN_SECP256R1_ECDSA_SHA256_RAW'],
    [0x02, 'UAF_ALG_SIGN_SECP256R1_ECDSA_SHA256_DER'],
    [0x03, 'UAF_ALG_SIGN_RSASSA_PSS_SHA256_RAW'],
    [0x04, 'UAF_ALG_SIGN_RSASSA_PSS_SHA256_DER'],
    [0x05, 'UAF_ALG_SIGN_SECP256K1_ECDSA_SHA256_RAW'],
    [0x06, 'UAF_ALG_SIGN_SECP256K1_ECDSA_SHA256_DER'],
]);

var pkFormatList = new Map([
    [0x100, 'UAF_ALG_KEY_ECC_X962_RAW'],
    [0x101, 'UAF_ALG_KEY_ECC_X962_DER'],
    [0x102, 'UAF_ALG_KEY_RSA_2048_PSS_RAW'],
    [0x103, 'UAF_ALG_KEY_RSA_2048_PSS_DER'],
]);

// Tag values are defined at:
// https://fidoalliance.org/specs/fido-uaf-v1.0-ps-20141208/fido-uaf-reg-v1.0-ps-20141208.html#predefined-tags
var tagList = new Map([
    [0x3E01, "TAG_UAFV1_REG_ASSERTION"],
    [0x3E02, "TAG_UAFV1_AUTH_ASSERTION"],
    [0x3E03, "TAG_UAFV1_KRD"],
    [0x3E04, "TAG_UAFV1_SIGNED_DATA"],
    [0x2E05, "TAG_ATTESTATION_CERT"],
    [0x2E06, "TAG_SIGNATURE"],
    [0x3E07, "TAG_ATTESTATION_BASIC_FULL"],
    [0x3E08, "TAG_ATTESTATION_BASIC_SURROGATE"],
    [0x2E09, "TAG_KEYID"],
    [0x2E0A, "TAG_FINAL_CHALLENGE"],
    [0x2E0B, "TAG_AAID"],
    [0x2E0C, "TAG_PUB_KEY"],
    [0x2E0D, "TAG_COUNTERS"],
    [0x2E0E, "TAG_ASSERTION_INFO"],
    [0x2E0F, "TAG_AUTHENTICATOR_NONCE"],
    [0x2E10, "TAG_TRANSACTION_CONTENT_HASH"],
    [0x3E11, "TAG_EXTENSION1"],
    [0x3E12, "TAG_EXTENSION2"],
    [0x2E13, "TAG_EXTENSION_ID"],
    [0x2E14, "TAG_EXTENSION_DATA"],

    ["TAG_UAFV1_REG_ASSERTION", 0x3E01],
    ["TAG_UAFV1_AUTH_ASSERTION", 0x3E02],
    ["TAG_UAFV1_KRD", 0x3E03],
    ["TAG_UAFV1_SIGNED_DATA", 0x3E04],
    ["TAG_ATTESTATION_CERT", 0x2E05],
    ["TAG_SIGNATURE", 0x2E06],
    ["TAG_ATTESTATION_BASIC_FULL", 0x3E07],
    ["TAG_ATTESTATION_BASIC_SURROGATE", 0x3E08],
    ["TAG_KEYID", 0x2E09],
    ["TAG_FINAL_CHALLENGE", 0x2E0A],
    ["TAG_AAID", 0x2E0B],
    ["TAG_PUB_KEY", 0x2E0C],
    ["TAG_COUNTERS", 0x2E0D],
    ["TAG_ASSERTION_INFO", 0x2E0E],
    ["TAG_AUTHENTICATOR_NONCE", 0x2E0F],
    ["TAG_TRANSACTION_CONTENT_HASH", 0x2E10],
    ["TAG_EXTENSION1", 0x3E11],
    ["TAG_EXTENSION2", 0x3E12],
    ["TAG_EXTENSION_ID", 0x2E13],
    ["TAG_EXTENSION_DATA", 0x2E14],
]);

function tagToString(tag) {
    return tagList.get(tag);
}

function printTag(msg, tag) {
    console.log(`${msg}: 0x${tag.toString(16).toUpperCase()} (${tagToString (tag)})`);
}

// decode the TLV assertion to an ArrayBuffer
var bufThing = decode(uafThingy[0].assertions[0].assertion);
console.log(`Got assertion, ${bufThing.byteLength} bytes`);
// printHex ("decoded", buf);

// Decoding registration assertion, based on:
// https://fidoalliance.org/specs/fido-uaf-v1.0-ps-20141208/fido-uaf-authnr-cmds-v1.0-ps-20141208.html#tag_uafv1_reg_assertion
parseRegAssn (bufThing);
function parseRegAssn(buf) {
    var view = new DataView(buf);
    var offset = 0;

    // assertion type = TAG_UAFV1_REG_ASSERTION (2)
    var assnType = view.getUint16(offset, true);
    printTag("Assertion Type", assnType);
    offset += 2;

    // Length of the structure (2)
    var assnLen = view.getUint16(offset, true);
    console.log("Assertion Length:", assnLen);
    offset += 2;

    // TAG_UAFV1_KRD (2)
    var krd = view.getUint16(offset, true);
    printTag("KRD", krd);
    offset += 2;

    // Length of AAID (2)
    var krdLen = view.getUint16(offset, true);
    console.log("KRD Length:", krdLen);
    offset += 2;

    // TAG_AAID (2)
    var aaidTag = view.getUint16(offset, true);
    printTag("AAID Tag", aaidTag);
    offset += 2;

    // AAID len (2)
    var aaidLen = view.getUint16(offset, true);
    console.log("AAID Length:", aaidLen);
    offset += 2;

    // AAID (n)
    var aaid = view.buffer.slice (offset, offset + aaidLen);
    printHex ("AAID:", aaid);
    offset += aaidLen;

    // TAG_ASSERTION_INFO (2)
    var assnInfo = view.getUint16(offset, true);
    printTag("Assertion Info", assnInfo);
    offset += 2;

    // Length of Assertion Information (2)
    var assnInfoLen = view.getUint16(offset, true);
    console.log("Assn Info Length:", assnInfoLen);
    offset += 2;

    // Vendor assigned authenticator version (2)
    var vendorAuthnVersion = view.getUint16(offset, true);
    console.log("Authenticator Version: 0x" + vendorAuthnVersion.toString(16).toUpperCase());
    offset += 2;

    // For Registration this must be 0x01 indicating that the user has explicitly verified the action (1)
    var verifiedAction = view.getUint8(offset);
    console.log("Verified Action: 0x" + verifiedAction.toString(16).toUpperCase());
    offset += 1;

    // Signature Algorithm and Encoding of the attestation signature (2)
    var sigAlg = view.getUint16(offset, true);
    console.log(`Signature Algorithm: 0x${sigAlg.toString(16).toUpperCase()} (${authAlgList.get(sigAlg)})`); // TODO: translate
    offset += 2;

    // Public Key algorithm and encoding of the newly generated UAuth.pub key (2)
    var pkAlg = view.getUint16(offset, true);
    console.log(`Public Key Algorithm: 0x${pkAlg.toString(16).toUpperCase()} (${pkFormatList.get(pkAlg)})`); // TODO: translate
    offset += 2;

    // TAG_FINAL_CHALLENGE (2)
    var fcTag = view.getUint16(offset, true);
    printTag("Final Challenge", fcTag);
    offset += 2;

    // Final Challenge length (2)
    var fcLen = view.getUint16(offset, true);
    console.log("Final Challenge Length:", fcLen);
    offset += 2;

    // (binary value of) Final Challenge provided in the Command (n)
    var fc = view.buffer.slice (offset, offset + fcLen);
    printHex ("Final Challenge:", fc);
    offset += fcLen;

    // TAG_KEYID (2)
    var keyidTag = view.getUint16(offset, true);
    printTag("Key ID Tag", keyidTag);
    offset += 2;

    // Length of KeyID (2)
    var keyidLen = view.getUint16(offset, true);
    console.log("Key ID Length:", keyidLen);
    offset += 2;

    // (binary value of) KeyID generated by Authenticator (n)
    var keyid = view.buffer.slice (offset, offset + keyidLen);
    printHex ("Key ID:", keyid);
    offset += keyidLen;

    // TAG_COUNTERS (2)
    var countersTag = view.getUint16(offset, true);
    printTag("Counters Tag", countersTag);
    offset += 2;

    // Length of Counters (2)
    var countersLen = view.getUint16(offset, true);
    console.log("Counters Length:", countersLen);
    offset += 2;

    // Signature Counter (4)
    var sigCounter = view.getUint32(offset, true);
    console.log("Signature Counter: 0x" + sigCounter.toString(16).toUpperCase());
    offset += 4;

    // Registration Counter (4)
    var regCounter = view.getUint32(offset, true);
    console.log("Registration Counter: 0x" + regCounter.toString(16).toUpperCase());
    offset += 4;

    // TAG_PUB_KEY (2)
    var pkTag = view.getUint16(offset, true);
    printTag("Public Key Tag", pkTag);
    offset += 2;

    // Length of UAuth.pub (2)
    var pkLen = view.getUint16(offset, true);
    console.log("Public Key Length:", pkLen);
    offset += 2;

    // User authentication public key (UAuth.pub) newly generated by authenticator (n)
    var pk = view.buffer.slice (offset, offset + pkLen);
    printHex ("Key ID:", pk);
    offset += pkLen;

    // TAG_ATTESTATION_BASIC_FULL (2) (choice 1)
    var attestationTag = view.getUint16(offset, true);
    printTag("Attestation Tag", attestationTag);
    offset += 2;

    // Length of structure (2)
    var attestationLen = view.getUint16(offset, true);
    console.log("Attestation Length:", attestationLen);
    offset += 2;

    var attestation = view.buffer.slice (offset, offset + attestationLen);
    if (attestationTag === tagList.get("TAG_ATTESTATION_BASIC_FULL")) {
        parseBasicFullAttestation (attestation);
    } else if (attestationTag === tagList.get("TAG_ATTESTATION_BASIC_SURROGATE")) {
        parseSurrogateAttestation (attestation);
    }
}

function parseBasicFullAttestation (buf) {
    var view = new DataView(buf);
    var offset = 0;
    // TAG_ATTESTATION_BASIC_FULL (2) (choice 1) -- PARSED ABOVE
    // Length of structure (2) -- PARSED ABOVE
    // TAG_SIGNATURE (2)
    var sigTag = view.getUint16(offset, true);
    printTag("Signature Tag", sigTag);
    offset += 2;

    // Length of signature (2)
    var sigLen = view.getUint16(offset, true);
    console.log("Signature Length:", sigLen);
    offset += 2;

    // Signature calculated with Basic Attestation Private Key over TAG_UAFV1_KRD content (n)
    var signature = view.buffer.slice (offset, offset + sigLen);
    printHex ("Signature:", signature);
    offset += sigLen;

    // TAG_ATTESTATION_CERT (multiple occurrences possible) (2)
    var attestationCertTag = view.getUint16(offset, true);
    printTag("Attestation Certificate Tag", attestationCertTag);
    offset += 2;

    // Length of Attestation Cert (2)
    var attCertLen = view.getUint16(offset, true);
    console.log("Attestation Certificate Length:", attCertLen);
    offset += 2;

    // Single X.509 DER-encoded [ITU-X690-2008] Attestation Certificate or a single certificate from the attestation certificate chain (n)
    var cert = view.buffer.slice (offset, offset + attCertLen);
    printHex ("Cert:", cert);
    offset += attCertLen;
}

function parseSurrogateAttestation (buf) {
    var view = new DataView(buf);
    var offset = 0;
    throw new TypeError ("parseSurrogateAttestation not tested -- remove this at your own peril");
    // TAG_ATTESTATION_BASIC_SURROGATE (2) (choice 2) -- PARSED ABOVE
    // Length of structure (2) -- PARSED ABOVE
    // TAG_SIGNATURE (2)
    var sigTag = view.getUint16(offset, true);
    printTag("Signature Tag", sigTag);
    offset += 2;

    // Length of signature (2)
    var sigLen = view.getUint16(offset, true);
    console.log("Signature Length:", sigLen);
    offset += 2;

    // Signature calculated with newly generated UAuth.priv key over TAG_UAFV1_KRD content (n)
    var signature = view.buffer.slice (offset, offset + sigLen);
    printHex ("Signature:", signature);
    offset += sigLen;
}