feat: Add HTTP Schnorr signature authentication (Phase 1)

Add request-level authentication via BIP-340 Schnorr signatures using the NIP-98 HTTP Auth scheme (Authorization: Nostr <base64>). Verified identities resolve to did:nostr:<pubkey> URIs that work with existing Solid ACL rules as acl:agent values — no changes needed to the ACL layer. Tested against all 10 official http-schnorr-auth spec test vectors and verified live with read + write operations against a running NSS instance. Refs: #1845
melvincarvalho · Mar 1, 2026 · Mar 1, 2026 · 3d64b63feb48b8acd205ee3e26d9a438b1078410
commit 3d64b63feb48b8acd205ee3e26d9a438b1078410
diff --git a/lib/api/authn/index.mjs b/lib/api/authn/index.mjs
@@ -1,8 +1,9 @@
 import oidc from './webid-oidc.mjs'
 import tls from './webid-tls.mjs'
 import forceUser from './force-user.mjs'
+import nostr from './webid-nostr.mjs'
 
-export { oidc, tls, forceUser }
+export { oidc, tls, forceUser, nostr }
 
 // Provide a default export so callers can `import Auth from './lib/api/authn/index.mjs'`
-export default { oidc, tls, forceUser }
+export default { oidc, tls, forceUser, nostr }
diff --git a/lib/api/authn/webid-nostr.mjs b/lib/api/authn/webid-nostr.mjs
@@ -0,0 +1,118 @@
+'use strict'
+
+import { schnorr } from '@noble/curves/secp256k1'
+import { sha256 } from '@noble/hashes/sha256'
+import { bytesToHex } from '@noble/hashes/utils'
+import Debug from 'debug'
+
+const debug = Debug('solid:authn:nostr')
+
+/**
+ * Verifies a NIP-98 HTTP Auth event from the Authorization header.
+ *
+ * @see https://nostrcg.github.io/http-schnorr-auth/
+ * @see https://github.com/nostr-protocol/nips/blob/master/98.md
+ *
+ * @param {object} req - Express request object
+ * @param {object} [options] - Options for testing
+ * @param {number} [options.now] - Override current time (unix seconds)
+ * @returns {string|null} `did:nostr:<pubkey>` on success, null on failure
+ */
+export async function verifyNostrAuth (req, options = {}) {
+  const authHeader = req.get('Authorization')
+  if (!authHeader || !authHeader.startsWith('Nostr ')) {
+    return null
+  }
+
+  debug('Processing Nostr auth...')
+
+  try {
+    const base64Event = authHeader.slice(6)
+    const eventJson = Buffer.from(base64Event, 'base64').toString('utf-8')
+    const event = JSON.parse(eventJson)
+
+    // Validate required fields
+    if (!event.pubkey || !event.sig || !event.id || !event.tags) {
+      debug('Invalid event structure')
+      return null
+    }
+
+    // Kind must be 27235 (NIP-98 HTTP Auth)
+    if (event.kind !== 27235) {
+      debug(`Wrong event kind: ${event.kind}`)
+      return null
+    }
+
+    // Timestamp within 60 seconds
+    const now = options.now || Math.floor(Date.now() / 1000)
+    if (Math.abs(now - event.created_at) > 60) {
+      debug('Event timestamp out of range')
+      return null
+    }
+
+    // Required tags
+    const urlTag = event.tags.find(t => t[0] === 'u')
+    if (!urlTag) {
+      debug('Missing URL tag')
+      return null
+    }
+
+    // Validate URL matches the request
+    const requestUrl = req.absoluteUrl ||
+      (req.protocol + '://' + req.get('host') + req.originalUrl)
+    if (urlTag[1] !== requestUrl) {
+      debug(`URL mismatch: ${urlTag[1]} vs ${requestUrl}`)
+      return null
+    }
+
+    const methodTag = event.tags.find(t => t[0] === 'method')
+    if (!methodTag) {
+      debug('Missing method tag')
+      return null
+    }
+
+    if (methodTag[1].toUpperCase() !== req.method.toUpperCase()) {
+      debug(`Method mismatch: ${methodTag[1]} vs ${req.method}`)
+      return null
+    }
+
+    // Verify event ID is SHA-256 of serialized event (NIP-01)
+    const serialized = JSON.stringify([
+      0, event.pubkey, event.created_at, event.kind, event.tags, event.content
+    ])
+    const expectedId = bytesToHex(sha256(new TextEncoder().encode(serialized)))
+    if (event.id !== expectedId) {
+      debug('Event ID mismatch')
+      return null
+    }
+
+    // Verify BIP-340 Schnorr signature
+    const valid = schnorr.verify(event.sig, event.id, event.pubkey)
+    if (!valid) {
+      debug('Invalid Schnorr signature')
+      return null
+    }
+
+    // Optional: verify payload hash for requests with bodies
+    const payloadTag = event.tags.find(t => t[0] === 'payload')
+    if (payloadTag && req.body) {
+      const bodyBytes = typeof req.body === 'string'
+        ? new TextEncoder().encode(req.body)
+        : req.body
+      const bodyHash = bytesToHex(sha256(bodyBytes))
+      if (payloadTag[1] !== bodyHash) {
+        debug('Payload hash mismatch')
+        return null
+      }
+    }
+
+    const webId = `did:nostr:${event.pubkey}`
+    debug(`Authenticated: ${webId}`)
+    return webId
+  } catch (err) {
+    debug(`Auth error: ${err.message}`)
+    return null
+  }
+}
+
+export default { verifyNostrAuth }
diff --git a/lib/api/authn/webid-oidc.mjs b/lib/api/authn/webid-oidc.mjs
@@ -40,6 +40,12 @@ export function initialize (app, argv) {
 
   // Perform the actual authentication
   app.use('/', async (req, res, next) => {
+    // Skip OIDC auth for Nostr-authenticated requests (handled by allow.mjs)
+    const authHeader = req.get('Authorization')
+    if (authHeader && authHeader.startsWith('Nostr ')) {
+      return next()
+    }
+
     oidc.rs.authenticate({ tokenTypesSupported: argv.tokenTypesSupported })(req, res, (err) => {
       // Error handling should be deferred to the ldp in case a user with a bad token is trying
       // to access a public resource

diff --git a/lib/handlers/allow.mjs b/lib/handlers/allow.mjs
@@ -1,4 +1,5 @@
 import ACL from '../acl-checker.mjs'
+import { verifyNostrAuth } from '../api/authn/webid-nostr.mjs'
 // import debug from '../debug.mjs'
 
 export default function allow (mode) {
@@ -38,7 +39,13 @@ export default function allow (mode) {
     // Obtain and store the ACL of the requested resource
     const resourceUrl = rootUrl + resourcePath
     // Ensure the user has the required permission
-    const userId = req.session.userId
+    let userId = req.session?.userId
+    if (!userId) {
+      userId = await verifyNostrAuth(req)
+      if (userId) {
+        res.set('User', userId)
+      }
+    }
     try {
       req.acl = ACL.createFromLDPAndRequest(resourceUrl, ldp, req)