Merge pull request #122 from lnbits/lnurl-auth

lnbits/core/models.py

@@ -1,4 +1,7 @@
 import json
+import hmac
+import hashlib
+from ecdsa import SECP256k1, SigningKey  # type: ignore
 from typing import List, NamedTuple, Optional, Dict
 from sqlite3 import Row
 
@@ -33,6 +36,16 @@ class Wallet(NamedTuple):
     def balance(self) -> int:
         return self.balance_msat // 1000
 
+    def lnurlauth_key(self, domain: str) -> SigningKey:
+        hashing_key = hashlib.sha256(self.id.encode("utf-8")).digest()
+        linking_key = hmac.digest(hashing_key, domain.encode("utf-8"), "sha256")
+
+        return SigningKey.from_string(
+            linking_key,
+            curve=SECP256k1,
+            hashfunc=hashlib.sha256,
+        )
+
     def get_payment(self, payment_hash: str) -> Optional["Payment"]:
         from .crud import get_wallet_payment
 

lnbits/core/services.py

@@ -1,8 +1,12 @@
 import trio  # type: ignore
+import json
 import httpx
+from io import BytesIO
+from binascii import unhexlify
 from typing import Optional, Tuple, Dict
+from urllib.parse import urlparse, parse_qs
 from quart import g
-from lnurl import LnurlWithdrawResponse  # type: ignore
+from lnurl import LnurlErrorResponse, LnurlWithdrawResponse  # type: ignore
 
 try:
     from typing import TypedDict  # type: ignore
@@ -155,6 +159,77 @@ async def redeem_lnurl_withdraw(wallet_id: str, res: LnurlWithdrawResponse, memo
         )
 
 
+async def perform_lnurlauth(callback: str) -> Optional[LnurlErrorResponse]:
+    cb = urlparse(callback)
+
+    k1 = unhexlify(parse_qs(cb.query)["k1"][0])
+    key = g.wallet.lnurlauth_key(cb.netloc)
+
+    def int_to_bytes_suitable_der(x: int) -> bytes:
+        """for strict DER we need to encode the integer with some quirks"""
+        b = x.to_bytes((x.bit_length() + 7) // 8, "big")
+
+        if len(b) == 0:
+            # ensure there's at least one byte when the int is zero
+            return bytes([0])
+
+        if b[0] & 0x80 != 0:
+            # ensure it doesn't start with a 0x80 and so it isn't
+            # interpreted as a negative number
+            return bytes([0]) + b
+
+        return b
+
+    def encode_strict_der(r_int, s_int, order):
+        # if s > order/2 verification will fail sometimes
+        # so we must fix it here (see https://github.com/indutny/elliptic/blob/e71b2d9359c5fe9437fbf46f1f05096de447de57/lib/elliptic/ec/index.js#L146-L147)
+        if s_int > order // 2:
+            s_int = order - s_int
+
+        # now we do the strict DER encoding copied from
+        # https://github.com/KiriKiri/bip66 (without any checks)
+        r = int_to_bytes_suitable_der(r_int)
+        s = int_to_bytes_suitable_der(s_int)
+
+        r_len = len(r)
+        s_len = len(s)
+        sign_len = 6 + r_len + s_len
+
+        signature = BytesIO()
+        signature.write(0x30 .to_bytes(1, "big", signed=False))
+        signature.write((sign_len - 2).to_bytes(1, "big", signed=False))
+        signature.write(0x02 .to_bytes(1, "big", signed=False))
+        signature.write(r_len.to_bytes(1, "big", signed=False))
+        signature.write(r)
+        signature.write(0x02 .to_bytes(1, "big", signed=False))
+        signature.write(s_len.to_bytes(1, "big", signed=False))
+        signature.write(s)
+
+        return signature.getvalue()
+
+    sig = key.sign_digest_deterministic(k1, sigencode=encode_strict_der)
+
+    async with httpx.AsyncClient() as client:
+        r = await client.get(
+            callback,
+            params={
+                "k1": k1.hex(),
+                "key": key.verifying_key.to_string("compressed").hex(),
+                "sig": sig.hex(),
+            },
+        )
+        try:
+            resp = json.loads(r.text)
+            if resp["status"] == "OK":
+                return None
+
+            return LnurlErrorResponse(reason=resp["reason"])
+        except (KeyError, json.decoder.JSONDecodeError):
+            return LnurlErrorResponse(
+                reason=r.text[:200] + "..." if len(r.text) > 200 else r.text,
+            )
+
+
 def check_invoice_status(wallet_id: str, payment_hash: str) -> PaymentStatus:
     payment = get_wallet_payment(wallet_id, payment_hash)
     if not payment:

lnbits/core/static/js/wallet.js

@@ -128,6 +128,7 @@ new Vue({
         show: false,
         invoice: null,
         lnurlpay: null,
+        lnurlauth: null,
         data: {
           request: '',
           amount: 0,
@@ -237,6 +238,7 @@ new Vue({
       this.parse.show = true
       this.parse.invoice = null
       this.parse.lnurlpay = null
+      this.parse.lnurlauth = null
       this.parse.data.request = ''
       this.parse.data.comment = ''
       this.parse.data.paymentChecker = null
@@ -342,7 +344,7 @@ new Vue({
           .request(
             'GET',
             '/api/v1/lnurlscan/' + this.parse.data.request,
-            this.g.user.wallets[0].adminkey
+            this.g.wallet.adminkey
           )
           .catch(err => {
             LNbits.utils.notifyApiError(err)
@@ -363,6 +365,8 @@ new Vue({
             if (data.kind === 'pay') {
               this.parse.lnurlpay = Object.freeze(data)
               this.parse.data.amount = data.minSendable / 1000
+            } else if (data.kind === 'auth') {
+              this.parse.lnurlauth = Object.freeze(data)
             } else if (data.kind === 'withdraw') {
               this.parse.show = false
               this.receive.show = true
@@ -542,6 +546,37 @@ new Vue({
           LNbits.utils.notifyApiError(err)
         })
     },
+    authLnurl: function () {
+      let dismissAuthMsg = this.$q.notify({
+        timeout: 10,
+        message: 'Performing authentication...'
+      })
+
+      LNbits.api
+        .authLnurl(this.g.wallet, this.parse.lnurlauth.callback)
+        .then(response => {
+          dismissAuthMsg()
+          this.$q.notify({
+            message: `Authentication successful.`,
+            type: 'positive',
+            timeout: 3500
+          })
+          this.parse.show = false
+        })
+        .catch(err => {
+          dismissAuthMsg()
+          if (err.response.data.reason) {
+            this.$q.notify({
+              message: `Authentication failed. ${this.parse.lnurlauth.domain} says:`,
+              caption: err.response.data.reason,
+              type: 'warning',
+              timeout: 5000
+            })
+          } else {
+            LNbits.utils.notifyApiError(err)
+          }
+        })
+    },
     deleteWallet: function (walletId, user) {
       LNbits.utils
         .confirmDialog('Are you sure you want to delete this wallet?')

lnbits/core/templates/core/wallet.html

@@ -329,7 +329,7 @@
       {% raw %}
       <h6 class="q-my-none">{{ parse.invoice.fsat }} sat</h6>
       <q-separator class="q-my-sm"></q-separator>
-      <p style="word-break: break-all">
+      <p class="text-wrap">
         <strong>Description:</strong> {{ parse.invoice.description }}<br />
         <strong>Expire date:</strong> {{ parse.invoice.expireDate }}<br />
         <strong>Hash:</strong> {{ parse.invoice.hash }}
@@ -346,6 +346,32 @@
         <q-btn v-close-popup flat color="grey" class="q-ml-auto">Cancel</q-btn>
       </div>
     </div>
+    <div v-else-if="parse.lnurlauth">
+      {% raw %}
+      <q-form @submit="authLnurl" class="q-gutter-md">
+        <p class="q-my-none text-h6">
+          Authenticate with <b>{{ parse.lnurlauth.domain }}</b> from wallet <em>{{ g.wallet.name }}</em>?
+        </p>
+        <q-separator class="q-my-sm"></q-separator>
+        <p>
+          For every website and for every LNbits wallet, a new keypair will be
+          deterministically generated so your identity can't be tied to your
+          LNbits wallet or linked across websites. No other data will be shared
+          with {{ parse.lnurlauth.domain }}.
+        </p>
+        <p>Your public key for <b>{{ parse.lnurlauth.domain }}</b> is:</p>
+        <p class="q-mx-xl">
+          <code class="text-wrap"> {{ parse.lnurlauth.pubkey }} </code>
+        </p>
+        <div class="row q-mt-lg">
+          <q-btn unelevated color="deep-purple" type="submit">Login</q-btn>
+          <q-btn v-close-popup flat color="grey" class="q-ml-auto"
+            >Cancel</q-btn
+          >
+        </div>
+      </q-form>
+      {% endraw %}
+    </div>
     <div v-else-if="parse.lnurlpay">
       {% raw %}
       <q-form @submit="payLnurl" class="q-gutter-md">

lnbits/core/views/api.py

@@ -13,7 +13,7 @@ from lnbits import bolt11
 from lnbits.decorators import api_check_wallet_key, api_validate_post_request
 
 from .. import core_app
-from ..services import create_invoice, pay_invoice
+from ..services import create_invoice, pay_invoice, perform_lnurlauth
 from ..crud import delete_expired_invoices
 from ..tasks import sse_listeners
 
@@ -300,30 +300,42 @@ async def api_lnurlscan(code: str):
     try:
         url = lnurl.Lnurl(code)
     except ValueError:
-        return jsonify({"error": "invalid lnurl"}), HTTPStatus.BAD_REQUEST
+        return jsonify({"message": "invalid lnurl"}), HTTPStatus.BAD_REQUEST
 
     domain = urlparse(url.url).netloc
-    if url.is_login:
-        return jsonify({"domain": domain, "kind": "auth", "error": "unsupported"}), HTTPStatus.BAD_REQUEST
 
+    # params is what will be returned to the client
+    params: Dict = {"domain": domain}
+
+    if url.is_login:
+        params.update(kind="auth")
+        params.update(callback=url.url)  # with k1 already in it
+
+        lnurlauth_key = g.wallet.lnurlauth_key(domain)
+        params.update(pubkey=lnurlauth_key.verifying_key.to_string("compressed").hex())
+    else:
         async with httpx.AsyncClient() as client:
             r = await client.get(url.url, timeout=40)
             if r.is_error:
-            return jsonify({"domain": domain, "error": "failed to get parameters"}), HTTPStatus.SERVICE_UNAVAILABLE
+                return (
+                    jsonify({"domain": domain, "message": "failed to get parameters"}),
+                    HTTPStatus.SERVICE_UNAVAILABLE,
+                )
 
         try:
             jdata = json.loads(r.text)
             data: lnurl.LnurlResponseModel = lnurl.LnurlResponse.from_dict(jdata)
         except (json.decoder.JSONDecodeError, lnurl.exceptions.LnurlResponseException):
             return (
-            jsonify({"domain": domain, "error": f"got invalid response '{r.text[:200]}'"}),
+                jsonify({"domain": domain, "message": f"got invalid response '{r.text[:200]}'"}),
                 HTTPStatus.SERVICE_UNAVAILABLE,
             )
 
         if type(data) is lnurl.LnurlChannelResponse:
-        return jsonify({"domain": domain, "kind": "channel", "error": "unsupported"}), HTTPStatus.BAD_REQUEST
+            return jsonify({"domain": domain, "kind": "channel", "message": "unsupported"}), HTTPStatus.BAD_REQUEST
+
+        params.update(**data.dict())
 
-    params: Dict = data.dict()
         if type(data) is lnurl.LnurlWithdrawResponse:
             params.update(kind="withdraw")
             params.update(fixed=data.min_withdrawable == data.max_withdrawable)
@@ -346,5 +358,18 @@ async def api_lnurlscan(code: str):
                 params.update(image=data_uri)
             params.update(commentAllowed=jdata.get("commentAllowed", 0))
 
-    params.update(domain=domain)
     return jsonify(params)
+
+
+@core_app.route("/api/v1/lnurlauth", methods=["POST"])
+@api_check_wallet_key("admin")
+@api_validate_post_request(
+    schema={
+        "callback": {"type": "string", "required": True},
+    }
+)
+async def api_perform_lnurlauth():
+    err = await perform_lnurlauth(g.data["callback"])
+    if err:
+        return jsonify({"reason": err.reason}), HTTPStatus.SERVICE_UNAVAILABLE
+    return "", HTTPStatus.OK

lnbits/extensions/usermanager/views_api.py

@@ -69,7 +69,7 @@ async def api_usermanager_users_delete(user_id):
 async def api_usermanager_activate_extension():
     user = get_user(g.data["userid"])
     if not user:
-        return jsonify({"error": "no such user"}), HTTPStatus.NO_CONTENT
+        return jsonify({"message": "no such user"}), HTTPStatus.NOT_FOUND
     update_user_extension(user_id=g.data["userid"], extension=g.data["extension"], active=g.data["active"])
     return jsonify({"extension": "updated"}), HTTPStatus.CREATED
 

lnbits/static/js/base.js

@@ -44,6 +44,11 @@ window.LNbits = {
         description
       })
     },
+    authLnurl: function (wallet, callback) {
+      return this.request('post', '/api/v1/lnurlauth', wallet.adminkey, {
+        callback
+      })
+    },
     getWallet: function (wallet) {
       return this.request('get', '/api/v1/wallet', wallet.inkey)
     },