ethers.js/src.ts/crypto/signature.ts

import { ZeroHash } from "../constants/index.js";
import {
    concat, dataLength, getBigInt, getBytes, getNumber, getStore, hexlify,
    isHexString, setStore,
    assertArgument, assertPrivate
} from "../utils/index.js";

import type {
    BigNumberish, BytesLike, Freezable, Frozen
} from "../utils/index.js";


// Constants
const BN_0 = BigInt(0);
const BN_1 = BigInt(1);
const BN_2 = BigInt(2);
const BN_27 = BigInt(27);
const BN_28 = BigInt(28);
const BN_35 = BigInt(35);


const _guard = { };

// @TODO: Allow Uint8Array
export type SignatureLike = Signature | string | {
    r: string;
    s: string;
    v: BigNumberish;
    yParity?: 0 | 1;
    yParityAndS?: string;
} | {
    r: string;
    yParityAndS: string;
    yParity?: 0 | 1;
    s?: string;
    v?: number;
} | {
    r: string;
    s: string;
    yParity: 0 | 1;
    v?: BigNumberish;
    yParityAndS?: string;
};


export class Signature implements Freezable<Signature> {
    #props: { r: string, s: string, v: 27 | 28, networkV: null | bigint };

    get r(): string { return getStore(this.#props, "r"); }
    set r(value: BytesLike) {
        assertArgument(dataLength(value) === 32, "invalid r", "value", value);
        setStore(this.#props, "r", hexlify(value));
    }

    get s(): string { return getStore(this.#props, "s"); }
    set s(value: BytesLike) {
        assertArgument(dataLength(value) === 32, "invalid r", "value", value);
        assertArgument((getBytes(value)[0] & 0x80) === 0, "non-canonical s", "value", value);
        setStore(this.#props, "s", hexlify(value));
    }

    get v(): 27 | 28 { return getStore(this.#props, "v"); }
    set v(value: BigNumberish) {
        const v = getNumber(value, "value");
        assertArgument(v === 27 || v === 28, "invalid v", "v", value);
        setStore(this.#props, "v", v);
    }

    get networkV(): null | bigint { return getStore(this.#props, "networkV"); }
    get legacyChainId(): null | bigint {
        const v = this.networkV;
        if (v == null) { return null; }
        return Signature.getChainId(v);
    }

    get yParity(): 0 | 1 {
        return (this.v === 27) ? 0: 1;
    }

    get yParityAndS(): string {
        // The EIP-2098 compact representation
        const yParityAndS = getBytes(this.s);
        if (this.yParity) { yParityAndS[0] |= 0x80; }
        return hexlify(yParityAndS);
    }

    get compactSerialized(): string {
        return concat([ this.r, this.yParityAndS ]);
    }

    get serialized(): string {
        return concat([ this.r, this.s, (this.yParity ? "0x1c": "0x1b") ]);
    }

    constructor(guard: any, r: string, s: string, v: 27 | 28) {
        assertPrivate(guard, _guard, "Signature");
        this.#props = { r, s, v, networkV: null };
    }

    [Symbol.for('nodejs.util.inspect.custom')](): string {
        return `Signature { r: "${ this.r }", s: "${ this.s }", yParity: ${ this.yParity }, networkV: ${ this.networkV } }`;
    }

    clone(): Signature {
        const clone = new Signature(_guard, this.r, this.s, this.v);
        if (this.networkV) { setStore(clone.#props, "networkV", this.networkV); }
        return clone;
    }

    freeze(): Frozen<Signature> {
        Object.freeze(this.#props);
        return this;
    }

    isFrozen(): boolean {
        return Object.isFrozen(this.#props);
    }

    toJSON(): any {
        const networkV = this.networkV;
        return {
            _type: "signature",
            networkV: ((networkV != null) ? networkV.toString(): null),
            r: this.r, s: this.s, v: this.v,
        };
    }

    // Get the chain ID from an EIP-155 v
    static getChainId(v: BigNumberish): bigint {
        const bv = getBigInt(v, "v");

        // The v is not an EIP-155 v, so it is the unspecified chain ID
        if ((bv == BN_27) || (bv == BN_28)) { return BN_0; }

        // Bad value for an EIP-155 v
        assertArgument(bv >= BN_35, "invalid EIP-155 v", "v", v);

        return (bv - BN_35) / BN_2;
    }

    // Get the EIP-155 v transformed for a given chainId
    static getChainIdV(chainId: BigNumberish, v: 27 | 28): bigint {
        return (getBigInt(chainId) * BN_2) + BigInt(35 + v - 27);
    }

    // Convert an EIP-155 v into a normalized v
    static getNormalizedV(v: BigNumberish): 27 | 28 {
        const bv = getBigInt(v);

        if (bv == BN_0) { return 27; }
        if (bv == BN_1) { return 28; }

        // Otherwise, EIP-155 v means odd is 27 and even is 28
        return (bv & BN_1) ? 27: 28;
    }

    static from(sig?: SignatureLike): Signature {
        function assertError(check: unknown, message: string): asserts check {
            assertArgument(check, message, "signature", sig);
        };

        if (sig == null) {
            return new Signature(_guard, ZeroHash, ZeroHash, 27);
        }

        if (typeof(sig) === "string") {
            const bytes = getBytes(sig, "signature");
            if (bytes.length === 64) {
                const r = hexlify(bytes.slice(0, 32));
                const s = bytes.slice(32, 64);
                const v = (s[0] & 0x80) ? 28: 27;
                s[0] &= 0x7f;
                return new Signature(_guard, r, hexlify(s), v);
            }

            if (bytes.length === 65) {
                const r = hexlify(bytes.slice(0, 32));
                const s = bytes.slice(32, 64);
                assertError((s[0] & 0x80) === 0, "non-canonical s");
                const v = Signature.getNormalizedV(bytes[64]);
                return new Signature(_guard, r, hexlify(s), v);
            }

            assertError(false, "invlaid raw signature length");
        }

        if (sig instanceof Signature) { return sig.clone(); }

        // Get r
        const r = sig.r;
        assertError(r != null, "missing r");
        assertError(isHexString(r, 32), "invalid r");

        // Get s; by any means necessary (we check consistency below)
        const s = (function(s?: string, yParityAndS?: string) {
            if (s != null) {
                assertError(isHexString(s, 32), "invalid s");
                return s;
            }

            if (yParityAndS != null) {
                assertError(isHexString(yParityAndS, 32), "invalid yParityAndS");
                const bytes = getBytes(yParityAndS);
                bytes[0] &= 0x7f;
                return hexlify(bytes);
            }

            assertError(false, "missing s");
        })(sig.s, sig.yParityAndS);
        assertError((getBytes(s)[0] & 0x80) == 0, "non-canonical s");

        // Get v; by any means necessary (we check consistency below)
        const { networkV, v } = (function(_v?: BigNumberish, yParityAndS?: string, yParity?: number): { networkV?: bigint, v: 27 | 28 } {
            if (_v != null) {
                const v = getBigInt(_v);
                return {
                    networkV: ((v >= BN_35) ? v: undefined),
                    v: Signature.getNormalizedV(v)
                };
            }

            if (yParityAndS != null) {
                assertError(isHexString(yParityAndS, 32), "invalid yParityAndS");
                return { v: ((getBytes(yParityAndS)[0] & 0x80) ? 28: 27) };
            }

            if (yParity != null) {
                switch (yParity) {
                    case 0: return { v: 27 };
                    case 1: return { v: 28 };
                }
                assertError(false, "invalid yParity");
            }

            assertError(false, "missing v");
        })(sig.v, sig.yParityAndS, sig.yParity);

        const result = new Signature(_guard, r, s, v);
        if (networkV) { setStore(result.#props, "networkV", networkV); }

        // If multiple of v, yParity, yParityAndS we given, check they match
        assertError(!("yParity" in sig && sig.yParity !== result.yParity), "yParity mismatch");
        assertError(!("yParityAndS" in sig && sig.yParityAndS !== result.yParityAndS), "yParityAndS mismatch");

        return result;
    }
}