WIP Verify and respond to zap requests

app/controllers/lnurlpay_controller.rb

@@ -43,7 +43,7 @@ class LnurlpayController < ApplicationController
 
   # GET /lnurlpay/:username/invoice
   def invoice
-    amount = params[:amount].to_i / 1000 # msats
+    amount = params[:amount].to_i / 1000 # msats to sats
     comment = params[:comment] || ""
     address = @user.address
 
@@ -52,33 +52,19 @@ class LnurlpayController < ApplicationController
       return
     end
 
-    if !valid_comment?(comment)
-      render json: { status: "ERROR", reason: "Comment too long" }
-      return
+    if params[:nostr].present?
+      handle_zap_request amount, params[:nostr], params[:lnurl]
+    else
+      handle_pay_request address, amount, comment
     end
-
-    memo = "To #{address}"
-    memo = "#{memo}: \"#{comment}\"" if comment.present?
-
-    payment_request = @user.ln_create_invoice({
-      amount: amount, # we create invoices in sats
-      memo: memo,
-      description_hash: Digest::SHA2.hexdigest(metadata(address)),
-    })
-
-    render json: {
-      status: "OK",
-      successAction: {
-        tag: "message",
-        message: "Sats received. Thank you!"
-      },
-      routes: [],
-      pr: payment_request
-    }
   end
 
   private
 
+    def check_service_available
+      http_status :not_found unless Setting.lndhub_enabled?
+    end
+
     def find_user
       @user = User.where(cn: params[:username], ou: Setting.primary_domain).first
       http_status :not_found if @user.nil?
@@ -88,6 +74,10 @@ class LnurlpayController < ApplicationController
       "[[\"text/identifier\", \"#{address}\"], [\"text/plain\", \"Send sats, receive thanks.\"]]"
     end
 
+    def zap_metadata(event)
+      "[[\"application/json\", #{event.to_json}]]"
+    end
+
     def valid_amount?(amount_in_sats)
       amount_in_sats <= MAX_SATS && amount_in_sats >= MIN_SATS
     end
@@ -96,9 +86,63 @@ class LnurlpayController < ApplicationController
       comment.length <= MAX_COMMENT_CHARS
     end
 
-    private
+    def handle_pay_request(address, amount, comment)
+      if !valid_comment?(comment)
+        render json: { status: "ERROR", reason: "Comment too long" }
+        return
+      end
 
-    def check_service_available
-      http_status :not_found unless Setting.lndhub_enabled?
+      memo = "To #{address}"
+      memo = "#{memo}: \"#{comment}\"" if comment.present?
+
+      payment_request = @user.ln_create_invoice({
+        amount: amount, # sats
+        memo: memo,
+        description_hash: Digest::SHA2.hexdigest(metadata(address)),
+      })
+
+      render json: {
+        status: "OK",
+        successAction: {
+          tag: "message",
+          message: "Sats received. Thank you!"
+        },
+        routes: [],
+        pr: payment_request
+      }
+    end
+
+    def nostr_event_from_payload(nostr_param)
+      event_obj = JSON.parse(nostr_param).transform_keys(&:to_sym)
+      Nostr::Event.new(**event_obj)
+    rescue => e
+      return nil
+    end
+
+    def valid_zap_request?(amount, event, lnurl)
+      NostrManager::VerifyZapRequest.call(
+        amount: amount, event: event, lnurl: lnurl
+      )
+    end
+
+    def handle_zap_request(amount, nostr_param, lnurl_param)
+      event = nostr_event_from_payload(nostr_param)
+
+      unless event.present? && valid_zap_request?(amount*1000, event, lnurl_param)
+        render json: { status: "ERROR", reason: "Invalid zap request" }
+        return
+      end
+
+      # TODO
+      # raise zap_metadata(event).inspect
+
+      payment_request = @user.ln_create_invoice({
+        amount: amount, # sats
+        # TODO should be npub instead of address?
+        memo: "Zapped #{@user.address} on Nostr", # TODO include event ID if given
+        description_hash: Digest::SHA2.hexdigest(zap_metadata(event)),
+      })
+
+      render json: { status: "OK", pr: payment_request }
     end
 end

app/services/nostr_manager/verify_zap_request.rb

@@ -0,0 +1,51 @@
+module NostrManager
+  class VerifyZapRequest < NostrManagerService
+    def initialize(amount:, event:, lnurl: nil)
+      @amount, @event, @lnurl = amount, event, lnurl
+    end
+
+    # https://github.com/nostr-protocol/nips/blob/27fef638e2460139cc9078427a0aec0ce4470517/57.md#appendix-d-lnurl-server-zap-request-validation
+    def call
+      tags = parse_tags(@event.tags)
+
+      @event.verify_signature &&
+      @event.kind == 9734 &&
+      tags.present? &&
+      valid_p_tag?(tags[:p]) &&
+      valid_e_tag?(tags[:e]) &&
+      valid_a_tag?(tags[:a]) &&
+      valid_amount_tag?(tags[:amount]) &&
+      valid_lnurl_tag?(tags[:lnurl])
+    end
+
+    def valid_p_tag?(tag)
+      return false unless tag.present? && tag.length == 1
+      key = Nostr::PublicKey.new(tag.first) rescue nil
+      key.present?
+    end
+
+    def valid_e_tag?(tag)
+      return true unless tag.present?
+      # TODO validate format of event ID properly
+      tag.length == 1 && tag.first.is_a?(String)
+    end
+
+    def valid_a_tag?(tag)
+      return true unless tag.present?
+      # TODO validate format of event coordinate properly
+      tag.length == 1 && tag.first.is_a?(String)
+    end
+
+    def valid_amount_tag?(tag)
+      return true unless tag.present?
+      amount = tag.first
+      amount.is_a?(String) && amount.to_i == @amount
+    end
+
+    def valid_lnurl_tag?(tag)
+      return true unless tag.present?
+      # TODO validate lnurl matching recipient's lnurlp
+      tag.first.is_a?(String)
+    end
+  end
+end

spec/fixtures/nostr/zap_request_event.json

@@ -0,0 +1,22 @@
+{
+  "kind": 9734,
+  "created_at": 1712066899,
+  "content": "",
+  "tags": [
+    ["p", "3bf0c63fcb93463407af97a5e5ee64fa883d107ef9e558472c4eb9aaaefa459d"],
+    ["amount", "21000"],
+    [
+      "relays",
+      "wss://relay.primal.net",
+      "wss://relay.snort.social",
+      "wss://nostr.wine",
+      "wss://relay.damus.io",
+      "wss://eden.nostr.land",
+      "wss://atlas.nostr.land",
+      "wss://nostr.bitcoiner.social",
+      "wss://relay.mostr.pub",
+      "wss://relay.mostr.pub/",
+      "wss://nostr-01.bolt.observer"
+    ]
+  ]
+}

spec/requests/lnurlpay_spec.rb

@@ -1,9 +1,8 @@
 require 'rails_helper'
 
 RSpec.describe "/lnurlpay", type: :request do
-
   context "Non-existent user" do
-    describe "GET /.well-known/lnurlpay/:username" do
+    describe "GET /.well-known/lnurlp/:username" do
       it "returns a 404" do
         get lightning_address_path(username: "csw")
         expect(response).to have_http_status(:not_found)
@@ -32,7 +31,7 @@ RSpec.describe "/lnurlpay", type: :request do
       login_as user, :scope => :user
     end
 
-    describe "GET /.well-known/lnurlpay/:username" do
+    describe "GET /.well-known/lnurlp/:username" do
       it "returns a formatted Lightning Address response" do
         get lightning_address_path(username: "satoshi")
 
@@ -67,29 +66,83 @@ RSpec.describe "/lnurlpay", type: :request do
         expect(res["pr"]).to eq("lnbc50u1p3lwgknpp52g78gqya5euvzjc53fc6hkmlm2rfjhcd305tcmc0g9gaestav48sdq4gdhkven9v5sx6mmwv4ujzcqzpgxqyz5vqsp5skkz4jlqr6tkvv2g9739ygrjupc4rkqd94mc7dfpj3pgx3f6w7qs9qyyssq7mf3fzcuxlmkr9nqatcch3u8uf4gjyawe052tejz8e9fqxu4pncqk3qklt8g6ylpshg09xyjquyrgtc72vcw5cp0dzcf406apyua7dgpnfn7an")
       end
 
-      context "amount too low" do
+      describe "amount too low" do
         it "returns an error" do
           get lnurlpay_invoice_path(username: "satoshi", params: {
             amount: 5000, comment: "Coffee time!"
           })
+
           expect(response).to have_http_status(:ok)
+
           res = JSON.parse(response.body)
           expect(res["status"]).to eq('ERROR')
           expect(res["reason"]).to eq('Invalid amount')
         end
       end
 
-      context "comment too long" do
+      describe "comment too long" do
         it "returns an error" do
           get lnurlpay_invoice_path(username: "satoshi", params: {
             amount: 5000000, comment: "Coffee time is the best time, so here's some money for you to get some. May I suggest to sample some Pacamara beans from El Salvador?"
           })
+
           expect(response).to have_http_status(:ok)
+
           res = JSON.parse(response.body)
           expect(res["status"]).to eq('ERROR')
           expect(res["reason"]).to eq('Comment too long')
         end
       end
+
+      context "zap request" do
+        describe "with invalid request event" do
+          it "returns an error" do
+            get lnurlpay_invoice_path(username: "satoshi", params: {
+              amount: 2100000, nostr: { foo: "bar" }.to_json
+            })
+
+            res = JSON.parse(response.body)
+            expect(res["status"]).to eq('ERROR')
+            expect(res["reason"]).to eq('Invalid zap request')
+          end
+        end
+
+        describe "with valid request event" do
+          let(:event) {
+            {
+              id: "3cf02d7f0ccd9711c25098fc50b3a7ab880326e4e51cc8c7a7b59f147cff4fff",
+              pubkey: "730b43e6f62c2ab22710b046e481802c8ac1108ed2cb9c21dff808d57ba24b6c",
+              created_at: 1712487443,
+              kind: 9734,
+              tags: [
+                ["relays", "wss://nostr.kosmos.org", "wss://relay.example.com"],
+                ["p", "07e188a1ff87ce171d517b8ed2bb7a31b1d3453a0db3b15379ec07b724d232f3"]],
+              content: "",
+              sig: "e9e9bb2bac4267a107ab5c3368f504b4f11b8e3b5ae875a1d63c74d6934138d2521dc35815b6f534fc5d803cbf633736d871886368bb8f92c4ad3837a68a06f2"
+            }
+          }
+
+          it "returns an invoice" do
+            expect_any_instance_of(User).to receive(:ln_create_invoice)
+              .with(
+                amount: 2100,
+                memo: "Zapped satoshi@kosmos.org on Nostr",
+                description_hash: "540279cd9da15279c8299d6d9ff1ab2a79eb259ee218adf3de393e1abe723077"
+            )
+              .and_return("lnbc50u1p3lwgknpp52g78gqya5euvzjc53fc6hkmlm2rfjhcd305tcmc0g9gaestav48sdq4gdhkven9v5sx6mmwv4ujzcqzpgxqyz5vqsp5skkz4jlqr6tkvv2g9739ygrjupc4rkqd94mc7dfpj3pgx3f6w7qs9qyyssq7mf3fzcuxlmkr9nqatcch3u8uf4gjyawe052tejz8e9fqxu4pncqk3qklt8g6ylpshg09xyjquyrgtc72vcw5cp0dzcf406apyua7dgpnfn7an")
+
+            get lnurlpay_invoice_path(username: "satoshi", params: {
+              amount: 2100000, nostr: event.to_json
+            })
+
+            expect(response).to have_http_status(:ok)
+
+            res = JSON.parse(response.body)
+            expect(res["status"]).to eq('OK')
+            expect(res["pr"]).to match(/^lnbc/)
+          end
+        end
+      end
     end
 
     describe "GET /.well-known/keysend/:username/" do

spec/services/nostr_manager/verify_zap_request_spec.rb

@@ -0,0 +1,206 @@
+require 'rails_helper'
+
+RSpec.describe NostrManager::VerifyZapRequest, type: :model do
+  describe "Signature invalid" do
+    let(:event) {
+      Nostr::Event.new(
+        id: "3cf02d7f0ccd9711c25098fc50b3a7ab880326e4e51cc8c7a7b59f147cff4fff",
+        pubkey: "730b43e6f62c2ab22710b046e481802c8ac1108ed2cb9c21dff808d57ba24b6c",
+        created_at: 1712487443,
+        kind: 9734,
+        tags: [
+          ["relays", "wss://nostr.kosmos.org", "wss://relay.example.com"],
+          ["p", "07e188a1ff87ce171d517b8ed2bb7a31b1d3453a0db3b15379ec07b724d232f3"]],
+        content: "",
+        sig: "1234562bac4267a107ab5c3368f504b4f11b8e3b5ae875a1d63c74d6934138d2521dc35815b6f534fc5d803cbf633736d871886368bb8f92c4ad3837a68a06f2"
+      )
+    }
+
+    subject {
+      NostrManager::VerifyZapRequest.call(amount: 100000, event: event, lnurl: nil)
+    }
+
+    it "returns false" do
+      expect(subject).to be(false)
+    end
+  end
+
+  describe "p tag missing" do
+    let(:event) {
+      Nostr::Event.new(
+        id: "eb53c5e728b625831e318c7ab09373502dd4a41ed11c17f80f32fd1c3fe1252b",
+        pubkey: "730b43e6f62c2ab22710b046e481802c8ac1108ed2cb9c21dff808d57ba24b6c",
+        created_at: 1712580669,
+        kind: 9734,
+        tags: [["relays", "wss://nostr.kosmos.org","wss://relay.example.com"]],
+        content: "",
+        sig: "8e22dcb3e91d080c9549ea0808b018194cc352dde3056a4911796d6f0239de7e1955f287c7e6769909e59ab0ffa09e307178c32128dc451823fb00102ed7e80a"
+      )
+    }
+
+    subject {
+      NostrManager::VerifyZapRequest.call(amount: 100000, event: event, lnurl: nil)
+    }
+
+    it "returns false" do
+      expect(subject).to be(false)
+    end
+  end
+
+  describe "p tag not a valid pubkey" do
+    let(:event) {
+      Nostr::Event.new(
+        id: "f2c23f038cf4d0307147d40ddceb87e34ee94acf632f5a67217a55a0b41c5d95",
+        pubkey: "730b43e6f62c2ab22710b046e481802c8ac1108ed2cb9c21dff808d57ba24b6c",
+        created_at: 1712581702,
+        kind: 9734,
+        tags: [
+          ["relays", "wss://nostr.kosmos.org","wss://relay.example.com"],
+          ["p","123456abcdef"]
+        ],
+        content: "",
+        sig: "b33e6b231273d38629f5efb86325ce3b4e02a7d84dfa1f37167ca2de8392cea654ae34000fc365ddfc6e21dc8ce2365fcb000ccb9064fbbcd54c7ea4a943955b"
+      )
+    }
+
+    subject {
+      NostrManager::VerifyZapRequest.call(amount: 100000, event: event, lnurl: nil)
+    }
+
+    it "returns false" do
+      expect(subject).to be(false)
+    end
+  end
+
+  describe "Minimum valid request" do
+    let(:event) {
+      Nostr::Event.new(
+        id: "3cf02d7f0ccd9711c25098fc50b3a7ab880326e4e51cc8c7a7b59f147cff4fff",
+        pubkey: "730b43e6f62c2ab22710b046e481802c8ac1108ed2cb9c21dff808d57ba24b6c",
+        created_at: 1712487443,
+        kind: 9734,
+        tags: [
+          ["relays", "wss://nostr.kosmos.org", "wss://relay.example.com"],
+          ["p", "07e188a1ff87ce171d517b8ed2bb7a31b1d3453a0db3b15379ec07b724d232f3"]],
+        content: "",
+        sig: "e9e9bb2bac4267a107ab5c3368f504b4f11b8e3b5ae875a1d63c74d6934138d2521dc35815b6f534fc5d803cbf633736d871886368bb8f92c4ad3837a68a06f2"
+      )
+    }
+
+    subject {
+      NostrManager::VerifyZapRequest.call(amount: 100000, event: event, lnurl: nil)
+    }
+
+    it "returns true" do
+      expect(subject).to be(true)
+    end
+  end
+
+  describe "Optional amount property" do
+    describe "does not match given amount" do
+      let(:event) {
+        Nostr::Event.new(
+          id: "be3d3ba15a257546f6fbba849d4717641fd4ea9f21ae6e9278a045f31d212c5e",
+          pubkey: "730b43e6f62c2ab22710b046e481802c8ac1108ed2cb9c21dff808d57ba24b6c",
+          created_at: 1712579812,
+          kind: 9734,
+          tags: [
+            ["relays", "wss://nostr.kosmos.org","wss://relay.example.com"],
+            ["p", "07e188a1ff87ce171d517b8ed2bb7a31b1d3453a0db3b15379ec07b724d232f3"],
+            ["amount", "21000"]
+          ],
+          content: "",
+          sig: "2ca9cfd0fdaf43dd8a50ab586e83da4bd9d592def8ed198536f5e3e7aad3537818687e42d98eb61d60e33dbd848c1eecf72b68fd98376bbabdab7e029e810869"
+        )
+      }
+
+      subject {
+        NostrManager::VerifyZapRequest.call(amount: 100000, event: event, lnurl: nil)
+      }
+
+      it "returns false" do
+        expect(subject).to be(false)
+      end
+    end
+
+    describe "matches given amount" do
+      let(:event) {
+        Nostr::Event.new(
+          id: "be3d3ba15a257546f6fbba849d4717641fd4ea9f21ae6e9278a045f31d212c5e",
+          pubkey: "730b43e6f62c2ab22710b046e481802c8ac1108ed2cb9c21dff808d57ba24b6c",
+          created_at: 1712579812,
+          kind: 9734,
+          tags: [
+            ["relays", "wss://nostr.kosmos.org","wss://relay.example.com"],
+            ["p", "07e188a1ff87ce171d517b8ed2bb7a31b1d3453a0db3b15379ec07b724d232f3"],
+            ["amount", "21000"]
+          ],
+          content: "",
+          sig: "2ca9cfd0fdaf43dd8a50ab586e83da4bd9d592def8ed198536f5e3e7aad3537818687e42d98eb61d60e33dbd848c1eecf72b68fd98376bbabdab7e029e810869"
+        )
+      }
+
+      subject {
+        NostrManager::VerifyZapRequest.call(amount: 21000, event: event, lnurl: nil)
+      }
+
+      it "returns true" do
+        expect(subject).to be(true)
+      end
+    end
+  end
+
+  describe "Optional amount property" do
+    describe "does not match given amount" do
+      let(:event) {
+        Nostr::Event.new(
+          id: "be3d3ba15a257546f6fbba849d4717641fd4ea9f21ae6e9278a045f31d212c5e",
+          pubkey: "730b43e6f62c2ab22710b046e481802c8ac1108ed2cb9c21dff808d57ba24b6c",
+          created_at: 1712579812,
+          kind: 9734,
+          tags: [
+            ["relays", "wss://nostr.kosmos.org","wss://relay.example.com"],
+            ["p", "07e188a1ff87ce171d517b8ed2bb7a31b1d3453a0db3b15379ec07b724d232f3"],
+            ["amount", "21000"]
+          ],
+          content: "",
+          sig: "2ca9cfd0fdaf43dd8a50ab586e83da4bd9d592def8ed198536f5e3e7aad3537818687e42d98eb61d60e33dbd848c1eecf72b68fd98376bbabdab7e029e810869"
+        )
+      }
+
+      subject {
+        NostrManager::VerifyZapRequest.call(amount: 100000, event: event, lnurl: nil)
+      }
+
+      it "returns false" do
+        expect(subject).to be(false)
+      end
+    end
+
+    describe "matches given amount" do
+      let(:event) {
+        Nostr::Event.new(
+          id: "be3d3ba15a257546f6fbba849d4717641fd4ea9f21ae6e9278a045f31d212c5e",
+          pubkey: "730b43e6f62c2ab22710b046e481802c8ac1108ed2cb9c21dff808d57ba24b6c",
+          created_at: 1712579812,
+          kind: 9734,
+          tags: [
+            ["relays", "wss://nostr.kosmos.org","wss://relay.example.com"],
+            ["p", "07e188a1ff87ce171d517b8ed2bb7a31b1d3453a0db3b15379ec07b724d232f3"],
+            ["amount", "21000"]
+          ],
+          content: "",
+          sig: "2ca9cfd0fdaf43dd8a50ab586e83da4bd9d592def8ed198536f5e3e7aad3537818687e42d98eb61d60e33dbd848c1eecf72b68fd98376bbabdab7e029e810869"
+        )
+      }
+
+      subject {
+        NostrManager::VerifyZapRequest.call(amount: 21000, event: event, lnurl: nil)
+      }
+
+      it "returns true" do
+        expect(subject).to be(true)
+      end
+    end
+  end
+end