fix: add padding to bigints whose byte-length is expected

fixes #283

src/__tests__/VerifierAlgorithm.test.ts

@@ -211,8 +211,8 @@ const publicKeyBase58 = bytesToBase58(publicKeyBytes)
 const publicKeyJwk = {
   crv: 'secp256k1',
   kty: 'EC',
-  x: bytesToBase64url(bigintToBytes(publicKeyPoint.x)),
-  y: bytesToBase64url(bigintToBytes(publicKeyPoint.y)),
+  x: bytesToBase64url(bigintToBytes(publicKeyPoint.x, 32)),
+  y: bytesToBase64url(bigintToBytes(publicKeyPoint.y, 32)),
 }
 const publicKeyMultibase = bytesToMultibase(publicKeyBytes, 'base58btc')
 const eip155 = toEthereumAddress(publicKeyHex)

src/__tests__/util.test.ts

@@ -0,0 +1,65 @@
+import { bigintToBytes, hexToBytes } from '../util'
+
+describe('bigintToBytes', () => {
+  it('should convert a bigint to bytes', () => {
+    const bn = BigInt(65535)
+    const bytes = bigintToBytes(bn)
+    expect(bytes).toEqual(new Uint8Array([255, 255]))
+  })
+
+  it('should convert a bigint to bytes given a minimum length', () => {
+    const bn = BigInt(65535)
+    const bytes = bigintToBytes(bn, 32)
+    expect(bytes).toEqual(
+      new Uint8Array([
+        0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 255, 255,
+      ])
+    )
+  })
+
+  it('should convert a bigint to bytes given a minimum length less than the number', () => {
+    const bn = BigInt('0x112233445566778899')
+    const bytes = bigintToBytes(bn, 5)
+    expect(bytes).toEqual(new Uint8Array([17, 34, 51, 68, 85, 102, 119, 136, 153]))
+  })
+
+  it('should convert a bigint to bytes given an odd number of bytes', () => {
+    const bn = BigInt('0x101010101010101')
+    const bytes = bigintToBytes(bn)
+    expect(bytes).toEqual(new Uint8Array([1, 1, 1, 1, 1, 1, 1, 1]))
+  })
+})
+
+describe('hexToBytes', () => {
+  it('should convert a hex string to bytes', () => {
+    const bn = '0101'
+    const bytes = hexToBytes(bn)
+    expect(bytes).toEqual(new Uint8Array([1, 1]))
+  })
+
+  it('should convert a hex string with a prefix to bytes', () => {
+    const bn = '0x0101'
+    const bytes = hexToBytes(bn)
+    expect(bytes).toEqual(new Uint8Array([1, 1]))
+  })
+
+  it('should convert a hex string to bytes given a minimum length', () => {
+    const bn = '0101'
+    const bytes = hexToBytes(bn, 32)
+    expect(bytes).toEqual(
+      new Uint8Array([0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1])
+    )
+  })
+
+  it('should convert a hex string to bytes given a minimum length less than the number', () => {
+    const bn = '0x112233445566778899'
+    const bytes = hexToBytes(bn, 5)
+    expect(bytes).toEqual(new Uint8Array([17, 34, 51, 68, 85, 102, 119, 136, 153]))
+  })
+
+  it('should convert a hexString to bytes given an odd number of bytes', () => {
+    const bn = '0x101010101010101'
+    const bytes = hexToBytes(bn)
+    expect(bytes).toEqual(new Uint8Array([1, 1, 1, 1, 1, 1, 1, 1]))
+  })
+})

src/util.ts

@@ -56,8 +56,18 @@ export function bytesToMultibase(b: Uint8Array, base: keyof typeof bases): strin
   return bases[base].encode(b)
 }
 
-export function hexToBytes(s: string): Uint8Array {
-  const input = s.startsWith('0x') ? s.substring(2) : s
+export function hexToBytes(s: string, minLength?: number): Uint8Array {
+  let input = s.startsWith('0x') ? s.substring(2) : s
+
+  if (input.length % 2 !== 0) {
+    input = `0${input}`
+  }
+
+  if (minLength) {
+    const paddedLength = Math.max(input.length, minLength * 2)
+    input = input.padStart(paddedLength, '00')
+  }
+
   return u8a.fromString(input.toLowerCase(), 'base16')
 }
 
@@ -77,8 +87,8 @@ export function bytesToBigInt(b: Uint8Array): bigint {
   return BigInt(`0x` + u8a.toString(b, 'base16'))
 }
 
-export function bigintToBytes(n: bigint): Uint8Array {
-  return u8a.fromString(n.toString(16), 'base16')
+export function bigintToBytes(n: bigint, minLength?: number): Uint8Array {
+  return hexToBytes(n.toString(16), minLength)
 }
 
 export function stringToBytes(s: string): Uint8Array {