0.2.1: client address from the edge's hop, not the client's

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@profullstack/x402-gateway",
-  "version": "0.2.0",
+  "version": "0.2.1",
   "type": "module",
   "description": "Sell crawl access to AI training crawlers by the day over x402, settled by CoinPay. One middleware: 402 with an offer, a sales page with CLI instructions, signed passes, and a robots.txt that keeps search crawlers welcome.",
   "keywords": [

src/edge.js

@@ -59,16 +59,25 @@ export function inCidrs(ip, compiled) {
 /**
  * The caller's address, as the edge reported it.
  *
- * `x-forwarded-for` is a list the client can seed; the LAST hop appended by
- * our own edge is trustworthy and the first is not, but every platform in
- * front of these sites (Railway, a bare droplet behind nginx) puts the real
- * client first and nothing else, so first is what is used. `x-real-ip` is the
- * nginx spelling of the same thing.
+ * `x-forwarded-for` is a list the client can seed, and a denylist read from
+ * its first entry is a denylist any client can step around by sending one.
+ * The entry our own edge appends is the LAST, on every platform in front of
+ * these sites (Railway's proxy, nginx with `$proxy_add_x_forwarded_for`), so
+ * last is what is used. `x-real-ip` is nginx's spelling of the same hop and
+ * is preferred when present, because nginx sets it from the socket and
+ * nothing a client sends survives into it.
+ *
+ * A CDN in front of the edge would make the last hop the CDN's; put its
+ * ranges nowhere near `denyCidrs` and this still fails safe: nothing is
+ * refused, nothing is charged, by this check.
  */
 export function clientIp(request) {
+  const real = request.headers.get('x-real-ip')?.trim();
+  if (real) return real;
   const xff = request.headers.get('x-forwarded-for');
-  if (xff) return xff.split(',')[0].trim();
-  return request.headers.get('x-real-ip')?.trim() ?? '';
+  if (!xff) return '';
+  const hops = xff.split(',').map((h) => h.trim()).filter(Boolean);
+  return hops[hops.length - 1] ?? '';
 }
 
 /* -------------------------------------------------------------- spoofing -- */

test/gateway.test.js

@@ -347,7 +347,7 @@ describe('the gate', () => {
 describe('crawlers that do not say who they are', () => {
   const OVH = ['51.38.0.0/16', '54.38.0.0/16', '141.94.0.0/16'];
   const from = (ip, extra = {}) =>
-    req('/topics/x', { ua: CHROME, ...extra, headers: { 'x-forwarded-for': `${ip}, 10.0.0.1`, ...(extra.headers ?? {}) } });
+    req('/topics/x', { ua: CHROME, ...extra, headers: { 'x-forwarded-for': `10.0.0.1, ${ip}`, ...(extra.headers ?? {}) } });
 
   it('parses CIDRs and matches addresses, and drops what it cannot read', () => {
     const c = compileCidrs([...OVH, 'garbage', '1.2.3.4', '300.1.1.1/8', '10.0.0.0/33']);
@@ -362,9 +362,12 @@ describe('crawlers that do not say who they are', () => {
     assert.equal(inCidrs('9.9.9.9', compileCidrs(['0.0.0.0/0'])), true);
   });
 
-  it('reads the client address the way the edge writes it', () => {
-    assert.equal(clientIp(req('/', { headers: { 'x-forwarded-for': '203.0.113.9, 10.1.1.1' } })), '203.0.113.9');
-    assert.equal(clientIp(req('/', { headers: { 'x-real-ip': '203.0.113.10' } })), '203.0.113.10');
+  it('reads the client address from the hop our own edge appended, never one the client seeded', () => {
+    // A client that sends its own X-Forwarded-For puts a lie first; the edge appends the truth.
+    assert.equal(clientIp(req('/', { headers: { 'x-forwarded-for': '1.1.1.1, 203.0.113.9' } })), '203.0.113.9');
+    assert.equal(clientIp(req('/', { headers: { 'x-forwarded-for': '203.0.113.9' } })), '203.0.113.9');
+    assert.equal(clientIp(req('/', { headers: { 'x-real-ip': '203.0.113.10', 'x-forwarded-for': '1.1.1.1, 5.5.5.5' } })), '203.0.113.10');
+    assert.equal(clientIp(req('/', { headers: { 'x-forwarded-for': ' , ' } })), '');
     assert.equal(clientIp(req('/')), '');
   });