feat: add serializeSignature + parseSignature

wevm · Jul 1, 2024 · ffc1b57 · ffc1b57
1 parent 1e90195
commit ffc1b57
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diff --git a/src/README.md b/src/README.md
@@ -301,7 +301,7 @@ Serializes a public key into a hex string or bytes.
 #### Usage
 
 ```ts
-import { parsePublicKey } from 'webauthn-p256'
+import { serializePublicKey } from 'webauthn-p256'
 
 const publicKey = serializePublicKey({
   x: 12341...,
@@ -319,7 +319,52 @@ console.log(publicKey)
 | `publicKey` | P256 Credential public key. | `PublicKey` |
 | returns     | Serialized public key.      | `string`    |
 
+### `parseSignature`
+
+Parses a serialized signature into r and s coordinates.
+
+#### Usage
+
+```ts
+import { parseSignature } from 'webauthn-p256'
+
+const signature = parseSignature('0x...')
+
+console.log(signature)
+// { r: 1231..., s: 12412... }
+```
+
+#### API
+
+| Name        | Description                            | Type          |
+| ----------- | -------------------------------------- | ------------- |
+| `signature` | Serialized P256 signature. | `0x${string}` |
+| returns     | Parsed P256 signature.                     | `Signature`   |
+
+### `serializeSignature`
 
+Serializes a signature into a hex string or bytes.
+
+#### Usage
+
+```ts
+import { serializeSignature } from 'webauthn-p256'
+
+const signature = serializeSignature({
+  r: 12341...,
+  s: 12341...,
+})
+
+console.log(signature)
+// '0x...'
+```
+
+#### API
+
+| Name        | Description                 | Type        |
+| ----------- | --------------------------- | ----------- |
+| `signature` | P256 signature. | `Signature` |
+| returns     | Serialized signature.      | `string`    |
 
 ## Authors
 

diff --git a/src/sign.test.ts b/src/sign.test.ts
@@ -2,6 +2,8 @@ import { describe, expect, test } from 'vitest'
 import {
   getCredentialSignRequestOptions,
   parseAsn1Signature,
+  parseSignature,
+  serializeSignature,
   sign,
 } from './sign.js'
 
@@ -307,3 +309,128 @@ describe('parseAsn1Signature', async () => {
     `)
   })
 })
+
+describe('parseSignature', () => {
+  test('default', () => {
+    const signature =
+      '0x16d6f4bd3231c71c5e58927b9cf2ee701df03b52e3db71efc03d1139122f854f67f32a4fcb17b07ab9b7755b61e999b99139074fc8e1aa6d33d25beccbb2fbd4'
+    expect(parseSignature(signature)).toMatchInlineSnapshot(
+      `
+      {
+        "r": 10330677067519063752777069525326520293658884904426299601620960859195372963151n,
+        "s": 47017859265388077754498411591757867926785106410894171160067329762716841868244n,
+      }
+    `,
+    )
+    expect(serializeSignature(parseSignature(signature))).toEqual(signature)
+  })
+
+  test('bytes', () => {
+    const signature = new Uint8Array([
+      22, 214, 244, 189, 50, 49, 199, 28, 94, 88, 146, 123, 156, 242, 238, 112,
+      29, 240, 59, 82, 227, 219, 113, 239, 192, 61, 17, 57, 18, 47, 133, 79,
+      103, 243, 42, 79, 203, 23, 176, 122, 185, 183, 117, 91, 97, 233, 153, 185,
+      145, 57, 7, 79, 200, 225, 170, 109, 51, 210, 91, 236, 203, 178, 251, 212,
+    ])
+    expect(parseSignature(signature)).toMatchInlineSnapshot(
+      `
+      {
+        "r": 10330677067519063752777069525326520293658884904426299601620960859195372963151n,
+        "s": 47017859265388077754498411591757867926785106410894171160067329762716841868244n,
+      }
+    `,
+    )
+  })
+})
+
+describe('serializeSignature', () => {
+  test('default', () => {
+    const signature = {
+      r: 10330677067519063752777069525326520293658884904426299601620960859195372963151n,
+      s: 47017859265388077754498411591757867926785106410894171160067329762716841868244n,
+    } as const
+    expect(serializeSignature(signature)).toMatchInlineSnapshot(
+      `"0x16d6f4bd3231c71c5e58927b9cf2ee701df03b52e3db71efc03d1139122f854f67f32a4fcb17b07ab9b7755b61e999b99139074fc8e1aa6d33d25beccbb2fbd4"`,
+    )
+    expect(parseSignature(serializeSignature(signature))).toEqual(signature)
+  })
+
+  test('bytes', () => {
+    const signature = {
+      r: 10330677067519063752777069525326520293658884904426299601620960859195372963151n,
+      s: 47017859265388077754498411591757867926785106410894171160067329762716841868244n,
+    } as const
+    expect(
+      serializeSignature(signature, { to: 'bytes' }),
+    ).toMatchInlineSnapshot(
+      `
+      Uint8Array [
+        22,
+        214,
+        244,
+        189,
+        50,
+        49,
+        199,
+        28,
+        94,
+        88,
+        146,
+        123,
+        156,
+        242,
+        238,
+        112,
+        29,
+        240,
+        59,
+        82,
+        227,
+        219,
+        113,
+        239,
+        192,
+        61,
+        17,
+        57,
+        18,
+        47,
+        133,
+        79,
+        103,
+        243,
+        42,
+        79,
+        203,
+        23,
+        176,
+        122,
+        185,
+        183,
+        117,
+        91,
+        97,
+        233,
+        153,
+        185,
+        145,
+        57,
+        7,
+        79,
+        200,
+        225,
+        170,
+        109,
+        51,
+        210,
+        91,
+        236,
+        203,
+        178,
+        251,
+        212,
+      ]
+    `,
+    )
+  })
+})
diff --git a/src/sign.ts b/src/sign.ts
@@ -1,3 +1,4 @@
+import { numberToBytesBE } from '@noble/curves/abstract/utils'
 import { p256 } from '@noble/curves/p256'
 import type { Credential, Hex, Signature, WebAuthnData } from './types.js'
 import {
@@ -142,3 +143,36 @@ export function parseAsn1Signature(bytes: Uint8Array) {
     s: s > n / 2n ? n - s : s,
   }
 }
+
+/**
+ * Parses a serialized signature into r and s values.
+ */
+export function parseSignature(signature: Hex | Uint8Array): Signature {
+  const bytes =
+    typeof signature === 'string' ? hexToBytes(signature) : signature
+  const r = bytes.slice(0, 32)
+  const s = bytes.slice(32, 64)
+  return {
+    r: BigInt(bytesToHex(r)),
+    s: BigInt(bytesToHex(s)),
+  }
+}
+
+export type SerializeSignatureOptions<to extends 'hex' | 'bytes' = 'hex'> = {
+  to?: to | 'bytes' | 'hex' | undefined
+}
+
+/**
+ * Serializes a signature into a hex string or bytes.
+ */
+export function serializeSignature<to extends 'hex' | 'bytes' = 'hex'>(
+  signature: Signature,
+  options: SerializeSignatureOptions<to> = {},
+): to extends 'hex' ? Hex : Uint8Array {
+  const { to = 'hex' } = options
+  const result = new Uint8Array([
+    ...numberToBytesBE(signature.r, 32),
+    ...numberToBytesBE(signature.s, 32),
+  ])
+  return (to === 'hex' ? bytesToHex(result) : result) as any
+}