stackoverflow/js/wgHelpers.js

import { getRandomValues } from "node:crypto";

const clamp = (z) => {
    z[31] = (z[31] & 127) | 64;
    z[0] &= 248;
};

const generatePublicKey = (() => {
    const gf = (init) => {
        const r = new Float64Array(16);
        if (init) {
            for (let i = 0; i < init.length; ++i) {
                r[i] = init[i];
            }
        }
        return r;
    };

    const carry = (o) => {
        for (let i = 0; i < 16; ++i) {
            o[(i + 1) % 16] += (i < 15 ? 1 : 38) * Math.floor(o[i] / 65536);
            o[i] &= 0xffff;
        }
    };

    const cswap = (p, q, b) => {
        let t;
        const c = ~(b - 1);
        for (let i = 0; i < 16; ++i) {
            t = c & (p[i] ^ q[i]);
            p[i] ^= t;
            q[i] ^= t;
        }
    };

    const pack = (o, n) => {
        let b;
        const m = gf();
        const t = gf();
        for (let i = 0; i < 16; ++i) {
            t[i] = n[i];
        }
        carry(t);
        carry(t);
        carry(t);
        for (let j = 0; j < 2; ++j) {
            m[0] = t[0] - 0xffed;
            for (let i = 1; i < 15; ++i) {
                m[i] = t[i] - 0xffff - ((m[i - 1] >> 16) & 1);
                m[i - 1] &= 0xffff;
            }
            m[15] = t[15] - 0x7fff - ((m[14] >> 16) & 1);
            b = (m[15] >> 16) & 1;
            m[14] &= 0xffff;
            cswap(t, m, 1 - b);
        }
        for (let i = 0; i < 16; ++i) {
            o[2 * i] = t[i] & 0xff;
            o[2 * i + 1] = t[i] >> 8;
        }
    };

    const add = (o, a, b) => {
        for (let i = 0; i < 16; ++i) {
            o[i] = (a[i] + b[i]) | 0;
        }
    };

    const subtract = (o, a, b) => {
        for (let i = 0; i < 16; ++i) {
            o[i] = (a[i] - b[i]) | 0;
        }
    };

    const multmod = (o, a, b) => {
        const t = new Float64Array(31);
        for (let i = 0; i < 16; ++i) {
            for (let j = 0; j < 16; ++j) {
                t[i + j] += a[i] * b[j];
            }
        }
        for (let i = 0; i < 15; ++i) {
            t[i] += 38 * t[i + 16];
        }
        for (let i = 0; i < 16; ++i) {
            o[i] = t[i];
        }
        carry(o);
        carry(o);
    };

    const invert = (o, i) => {
        const c = gf();
        for (let a = 0; a < 16; ++a) {
            c[a] = i[a];
        }
        for (let a = 253; a >= 0; --a) {
            multmod(c, c, c);
            if (a !== 2 && a !== 4) {
                multmod(c, c, i);
            }
        }
        for (let a = 0; a < 16; ++a) {
            o[a] = c[a];
        }
    };

    const generatePublicKey = (privateKey) => {
        let r;
        const z = new Uint8Array(32);
        const a = gf([1]);
        const b = gf([9]);
        const c = gf();
        const d = gf([1]);
        const e = gf();
        const f = gf();
        const _121665 = gf([0xdb41, 1]);
        const _9 = gf([9]);
        for (let i = 0; i < 32; ++i) {
            z[i] = privateKey[i];
        }
        clamp(z);
        for (let i = 254; i >= 0; --i) {
            r = (z[i >>> 3] >>> (i & 7)) & 1;
            cswap(a, b, r);
            cswap(c, d, r);
            add(e, a, c);
            subtract(a, a, c);
            add(c, b, d);
            subtract(b, b, d);
            multmod(d, e, e);
            multmod(f, a, a);
            multmod(a, c, a);
            multmod(c, b, e);
            add(e, a, c);
            subtract(a, a, c);
            multmod(b, a, a);
            subtract(c, d, f);
            multmod(a, c, _121665);
            add(a, a, d);
            multmod(c, c, a);
            multmod(a, d, f);
            multmod(d, b, _9);
            multmod(b, e, e);
            cswap(a, b, r);
            cswap(c, d, r);
        }
        invert(c, c);
        multmod(a, a, c);
        pack(z, a);
        return z;
    };
    return generatePublicKey;
})();
const generatePresharedKey = () => {
    const privateKey = new Uint8Array(32);
    getRandomValues(privateKey);
    return privateKey;
};

const generatePrivateKey = () => {
    const privateKey = generatePresharedKey();
    clamp(privateKey);
    return privateKey;
};

const keyToBase64 = (key) => Buffer.from(key).toString("base64");
const keyFromBase64 = (key) => Buffer.from(key, "base64");

const wireguard = {
    presharedKey: () => keyToBase64(generatePresharedKey()),
    privateKey: () => keyToBase64(generatePrivateKey()),
    publicKey: (privateKey) =>
        keyToBase64(generatePublicKey(keyFromBase64(privateKey))),
    generateKeypair: () => {
        const privateKey = generatePrivateKey();
        const publicKey = generatePublicKey(privateKey);
        return {
            publicKey: keyToBase64(publicKey),
            privateKey: keyToBase64(privateKey),
        };
    },
};
export { wireguard };