implement nip26 delegation.

README.md

@@ -202,6 +202,41 @@ sub.on('event', (event) => {
 })
 ```
 
+### Performing and checking for delegation
+
+```js
+import {nip26, getPublicKey, generatePrivateKey} from 'nostr-tools'
+
+// delegator
+let sk1 = generatePrivateKey()
+let pk1 = getPublicKey(sk1)
+
+// delegatee
+let sk2 = generatePrivateKey()
+let pk2 = getPublicKey(sk2)
+
+// generate delegation
+let delegation = nip26.createDelegation(sk1, {
+  pubkey: pk2,
+  kind: 1,
+  since: Math.round(Date.now() / 1000),
+  until: Math.round(Date.now() / 1000) + 60 * 60 * 24 * 30 /* 30 days */
+})
+
+// the delegatee uses the delegation when building an event
+let event = {
+  pubkey: pk2,
+  kind: 1,
+  created_at: Math.round(Date.now() / 1000),
+  content: 'hello from a delegated key',
+  tags: [['delegation', delegation.from, delegation.cond, delegation.sig]]
+}
+
+// finally any receiver of this event can check for the presence of a valid delegation tag
+let delegator = nip26.getDelegator(event)
+assert(delegator === pk1) // will be null if there is no delegation tag or if it is invalid
+```
+
 Please consult the tests or [the source code](https://github.com/fiatjaf/nostr-tools) for more information that isn't available here.
 
 ### Using from the browser (if you don't want to use a bundler)

index.ts

@@ -7,3 +7,13 @@ export * as nip04 from './nip04'
 export * as nip05 from './nip05'
 export * as nip06 from './nip06'
 export * as nip19 from './nip19'
+export * as nip26 from './nip26'
+
+// monkey patch secp256k1
+import * as secp256k1 from '@noble/secp256k1'
+import {hmac} from '@noble/hashes/hmac'
+import {sha256} from '@noble/hashes/sha256'
+secp256k1.utils.hmacSha256Sync = (key, ...msgs) =>
+  hmac(sha256, key, secp256k1.utils.concatBytes(...msgs))
+secp256k1.utils.sha256Sync = (...msgs) =>
+  sha256(secp256k1.utils.concatBytes(...msgs))

nip26.test.js

@@ -0,0 +1,105 @@
+/* eslint-env jest */
+
+const {nip26, getPublicKey, generatePrivateKey} = require('./lib/nostr.cjs')
+
+test('parse good delegation from NIP', async () => {
+  expect(
+    nip26.getDelegator({
+      id: 'a080fd288b60ac2225ff2e2d815291bd730911e583e177302cc949a15dc2b2dc',
+      pubkey:
+        '62903b1ff41559daf9ee98ef1ae67cc52f301bb5ce26d14baba3052f649c3f49',
+      created_at: 1660896109,
+      kind: 1,
+      tags: [
+        [
+          'delegation',
+          '86f0689bd48dcd19c67a19d994f938ee34f251d8c39976290955ff585f2db42e',
+          'kind=1&created_at>1640995200',
+          'c33c88ba78ec3c760e49db591ac5f7b129e3887c8af7729795e85a0588007e5ac89b46549232d8f918eefd73e726cb450135314bfda419c030d0b6affe401ec1'
+        ]
+      ],
+      content: 'Hello world',
+      sig: 'cd4a3cd20dc61dcbc98324de561a07fd23b3d9702115920c0814b5fb822cc5b7c5bcdaf3fa326d24ed50c5b9c8214d66c75bae34e3a84c25e4d122afccb66eb6'
+    })
+  ).toEqual('86f0689bd48dcd19c67a19d994f938ee34f251d8c39976290955ff585f2db42e')
+})
+
+test('parse bad delegations', async () => {
+  expect(
+    nip26.getDelegator({
+      id: 'a080fd288b60ac2225ff2e2d815291bd730911e583e177302cc949a15dc2b2dc',
+      pubkey:
+        '62903b1ff41559daf9ee98ef1ae67cc52f301bb5ce26d14baba3052f649c3f49',
+      created_at: 1660896109,
+      kind: 1,
+      tags: [
+        [
+          'delegation',
+          '86f0689bd48dcd19c67a19d994f938ee34f251d8c39976290955ff585f2db42f',
+          'kind=1&created_at>1640995200',
+          'c33c88ba78ec3c760e49db591ac5f7b129e3887c8af7729795e85a0588007e5ac89b46549232d8f918eefd73e726cb450135314bfda419c030d0b6affe401ec1'
+        ]
+      ],
+      content: 'Hello world',
+      sig: 'cd4a3cd20dc61dcbc98324de561a07fd23b3d9702115920c0814b5fb822cc5b7c5bcdaf3fa326d24ed50c5b9c8214d66c75bae34e3a84c25e4d122afccb66eb6'
+    })
+  ).toEqual(null)
+
+  expect(
+    nip26.getDelegator({
+      id: 'a080fd288b60ac2225ff2e2d815291bd730911e583e177302cc949a15dc2b2dc',
+      pubkey:
+        '62903b1ff41559daf9ee98ef1ae67cc52f301bb5ce26d14baba3052f649c3f49',
+      created_at: 1660896109,
+      kind: 1,
+      tags: [
+        [
+          'delegation',
+          '86f0689bd48dcd19c67a19d994f938ee34f251d8c39976290955ff585f2db42e',
+          'kind=1&created_at>1740995200',
+          'c33c88ba78ec3c760e49db591ac5f7b129e3887c8af7729795e85a0588007e5ac89b46549232d8f918eefd73e726cb450135314bfda419c030d0b6affe401ec1'
+        ]
+      ],
+      content: 'Hello world',
+      sig: 'cd4a3cd20dc61dcbc98324de561a07fd23b3d9702115920c0814b5fb822cc5b7c5bcdaf3fa326d24ed50c5b9c8214d66c75bae34e3a84c25e4d122afccb66eb6'
+    })
+  ).toEqual(null)
+
+  expect(
+    nip26.getDelegator({
+      id: 'a080fd288b60ac2225ff2e2d815291bd730911e583e177302cc949a15dc2b2dc',
+      pubkey:
+        '62903b1ff41559daf9ee98ef1ae67c152f301bb5ce26d14baba3052f649c3f49',
+      created_at: 1660896109,
+      kind: 1,
+      tags: [
+        [
+          'delegation',
+          '86f0689bd48dcd19c67a19d994f938ee34f251d8c39976290955ff585f2db42e',
+          'kind=1&created_at>1640995200',
+          'c33c88ba78ec3c760e49db591ac5f7b129e3887c8af7729795e85a0588007e5ac89b46549232d8f918eefd73e726cb450135314bfda419c030d0b6affe401ec1'
+        ]
+      ],
+      content: 'Hello world',
+      sig: 'cd4a3cd20dc61dcbc98324de561a07fd23b3d9702115920c0814b5fb822cc5b7c5bcdaf3fa326d24ed50c5b9c8214d66c75bae34e3a84c25e4d122afccb66eb6'
+    })
+  ).toEqual(null)
+})
+
+test('create and verify delegation', async () => {
+  let sk1 = generatePrivateKey()
+  let pk1 = getPublicKey(sk1)
+  let sk2 = generatePrivateKey()
+  let pk2 = getPublicKey(sk2)
+  let delegation = nip26.createDelegation(sk1, {pubkey: pk2, kind: 1})
+  expect(delegation).toHaveProperty('from', pk1)
+  expect(delegation).toHaveProperty('to', pk2)
+  expect(delegation).toHaveProperty('cond', 'kind=1')
+
+  let event = {
+    kind: 1,
+    tags: [['delegation', delegation.from, delegation.cond, delegation.sig]],
+    pubkey: pk2
+  }
+  expect(nip26.getDelegator(event)).toEqual(pk1)
+})

nip26.ts

@@ -0,0 +1,90 @@
+import * as secp256k1 from '@noble/secp256k1'
+import {sha256} from '@noble/hashes/sha256'
+
+import {Event} from './event'
+import {utf8Encoder} from './utils'
+import {getPublicKey} from './keys'
+
+export type Parameters = {
+  pubkey: string // the key to whom the delegation will be given
+  kind: number | undefined
+  until: number | undefined // delegation will only be valid until this date
+  since: number | undefined // delegation will be valid from this date on
+}
+
+export type Delegation = {
+  from: string // the pubkey who signed the delegation
+  to: string // the pubkey that is allowed to use the delegation
+  cond: string // the string of conditions as they should be included in the event tag
+  sig: string
+}
+
+export function createDelegation(
+  privateKey: string,
+  parameters: Parameters
+): Delegation {
+  let conditions = []
+  if ((parameters.kind || -1) >= 0) conditions.push(`kind=${parameters.kind}`)
+  if (parameters.until) conditions.push(`created_at<${parameters.until}`)
+  if (parameters.since) conditions.push(`created_at>${parameters.since}`)
+  let cond = conditions.join('&')
+
+  if (cond === '')
+    throw new Error('refusing to create a delegation without any conditions')
+
+  let sighash = sha256(
+    utf8Encoder.encode(`nostr:delegation:${parameters.pubkey}:${cond}`)
+  )
+
+  let sig = secp256k1.utils.bytesToHex(
+    secp256k1.schnorr.signSync(sighash, privateKey)
+  )
+
+  return {
+    from: getPublicKey(privateKey),
+    to: parameters.pubkey,
+    cond,
+    sig
+  }
+}
+
+export function getDelegator(event: Event): string | null {
+  // find delegation tag
+  let tag = event.tags.find(tag => tag[0] === 'delegation' && tag.length >= 4)
+  if (!tag) return null
+
+  let pubkey = tag[1]
+  let cond = tag[2]
+  let sig = tag[3]
+
+  // check conditions
+  let conditions = cond.split('&')
+  for (let i = 0; i < conditions.length; i++) {
+    let [key, operator, value] = conditions[i].split(/\b/)
+
+    // the supported conditions are just 'kind' and 'created_at' for now
+    if (key === 'kind' && operator === '=' && event.kind === parseInt(value))
+      continue
+    else if (
+      key === 'created_at' &&
+      operator === '<' &&
+      event.created_at < parseInt(value)
+    )
+      continue
+    else if (
+      key === 'created_at' &&
+      operator === '>' &&
+      event.created_at > parseInt(value)
+    )
+      continue
+    else return null // invalid condition
+  }
+
+  // check signature
+  let sighash = sha256(
+    utf8Encoder.encode(`nostr:delegation:${event.pubkey}:${cond}`)
+  )
+  if (!secp256k1.schnorr.verifySync(sig, sighash, pubkey)) return null
+
+  return pubkey
+}