fix(browser): remote tunnel matches Chromium for IPv6 bypass rules and <-loopback> (#32665)

src/main/browser/browser-network-tunnel-proxy-selection.ts

@@ -30,12 +30,7 @@ export function selectBrowserNetworkTunnelProxy(
   const bypassRules = fromSettings
     ? normalizeProxyBypassRules(settings?.httpProxyBypassRules)
     : getProxyBypassRulesFromEnvironment(env)
-  if (
-    // Match browser sessions' default loopback bypass.
-    isEligibleLocalCertificateHost(target.host) ||
-    isLoopbackAddress(target.host) ||
-    matchesProxyBypassRules(target, bypassRules, fromSettings ? 'chromium' : 'no-proxy')
-  ) {
+  if (matchesProxyBypassRules(target, bypassRules, fromSettings ? 'chromium' : 'no-proxy')) {
     return { kind: 'direct' }
   }
   const url = new URL(proxyUrl)
@@ -48,16 +43,20 @@ export function selectBrowserNetworkTunnelProxy(
   return { kind: 'unsupported', protocol: url.protocol }
 }
 
-// BlockList also recognizes expanded IPv6 loopback addresses from the SOCKS front end.
-const LOOPBACK_ADDRESSES = new BlockList()
-LOOPBACK_ADDRESSES.addSubnet('127.0.0.0', 8, 'ipv4')
-LOOPBACK_ADDRESSES.addAddress('::1', 'ipv6')
-LOOPBACK_ADDRESSES.addSubnet('::ffff:127.0.0.0', 104, 'ipv6')
+// BlockList also recognizes expanded IPv6 addresses from the SOCKS front end.
+const IMPLICIT_BYPASS_ADDRESSES = new BlockList()
+IMPLICIT_BYPASS_ADDRESSES.addSubnet('127.0.0.0', 8, 'ipv4')
+IMPLICIT_BYPASS_ADDRESSES.addAddress('::1', 'ipv6')
+IMPLICIT_BYPASS_ADDRESSES.addSubnet('::ffff:127.0.0.0', 104, 'ipv6')
+IMPLICIT_BYPASS_ADDRESSES.addSubnet('169.254.0.0', 16, 'ipv4')
+IMPLICIT_BYPASS_ADDRESSES.addSubnet('fe80::', 10, 'ipv6')
 
-function isLoopbackAddress(host: string): boolean {
-  const address = normalizeHost(host)
-  const family = isIP(address)
-  return family !== 0 && LOOPBACK_ADDRESSES.check(address, family === 4 ? 'ipv4' : 'ipv6')
+// Chromium never proxies localhost, loopback or link-local unless `<-loopback>` subtracts them.
+function matchesImplicitBypassRules(host: string): boolean {
+  const family = isIP(host)
+  return family === 0
+    ? isEligibleLocalCertificateHost(host)
+    : IMPLICIT_BYPASS_ADDRESSES.check(host, family === 4 ? 'ipv4' : 'ipv6')
 }
 
 function normalizeHost(host: string): string {
@@ -66,17 +65,22 @@ function normalizeHost(host: string): string {
 }
 
 // Bare hosts match exactly in Chromium rules and include subdomains in NO_PROXY.
+// As in Chromium, the last matching rule wins (`<-loopback>` subtracts), then implicit rules apply.
 export function matchesProxyBypassRules(
   target: Pick<BrowserNetworkTunnelOpen, 'host' | 'port'>,
   rules: string,
   style: 'chromium' | 'no-proxy'
 ): boolean {
   const host = normalizeHost(target.host)
-  return rules
+  const implicit = matchesImplicitBypassRules(host)
+  const decisive = rules
     .split(';')
     .map((rule) => rule.trim().toLowerCase())
     .filter(Boolean)
-    .some((rule) => matchesBypassRule(host, target.port, rule, style))
+    .findLast((rule) =>
+      rule === '<-loopback>' ? implicit : matchesBypassRule(host, target.port, rule, style)
+    )
+  return decisive === undefined ? implicit : decisive !== '<-loopback>'
 }
 
 const SCHEME_PORTS: Record<string, string> = { http: '80', ws: '80', https: '443', wss: '443' }
@@ -110,6 +114,10 @@ function matchesBypassRule(
   if (rulePort !== undefined && Number(rulePort) !== port) {
     return false
   }
+  const ruleFamily = isIP(ruleHost)
+  if (ruleFamily !== 0) {
+    return matchesCidr(host, ruleHost, ruleFamily === 4 ? 32 : 128)
+  }
   const pattern = stripTrailingDot(ruleHost.startsWith('.') ? `*${ruleHost}` : ruleHost)
   if (pattern.includes('*')) {
     // NO_PROXY also reads `.corp` and `*.corp` as the domain itself; Chromium does not.

src/main/browser/browser-network-tunnel-proxy.test.ts

@@ -191,6 +191,8 @@ describe('proxy bypass rules', () => {
     ['10.0.0.0/8', '10.20.30.40', 443, true, true],
     ['10.0.0.0/8', '11.0.0.1', 443, false, false],
     ['[fd00::1]', 'fd00::1', 443, true, true],
+    ['[fd00::1]', 'fd00:0:0:0:0:0:0:1', 443, true, true],
+    ['fd00:0::1', '[FD00::1]', 443, true, true],
     ['https://corp.test', 'corp.test', 443, true, true],
     ['https://corp.test', 'corp.test', 80, false, false],
     ['ftp://corp.test', 'corp.test', 21, false, false],
@@ -199,9 +201,20 @@ describe('proxy bypass rules', () => {
     ['192.168.*', '192.168.4.20', 443, true, true],
     ['api.*.corp.test', 'api.eu.corp.test', 443, true, true],
     ['api.*.corp.test', 'web.eu.corp.test', 443, false, false],
-    ['corp.test', 'corp.test.', 443, true, true]
+    ['corp.test', 'corp.test.', 443, true, true],
+    ['', '169.254.169.254', 80, true, true],
+    ['<-loopback>', 'localhost', 3000, false, false],
+    ['<-loopback>;<local>', 'localhost', 3000, true, true],
+    ['<local>;<-loopback>', 'localhost', 3000, false, false],
+    ['<local>;<-loopback>', 'intranet', 80, true, true]
   ])('%s against %s:%d (NO_PROXY %s, Chromium %s)', (rule, host, port, noProxy, chromium) => {
     expect(matchesProxyBypassRules({ host, port }, rule, 'no-proxy')).toBe(noProxy)
     expect(matchesProxyBypassRules({ host, port }, rule, 'chromium')).toBe(chromium)
   })
+
+  it('proxies loopback destinations when the bypass list subtracts them', () => {
+    const settings = { httpProxyUrl: 'http://proxy.test:8080', httpProxyBypassRules: '<-loopback>' }
+    const target = { host: '127.0.0.1', port: 3000 }
+    expect(selectBrowserNetworkTunnelProxy(target, settings, {})).toMatchObject({ kind: 'http' })
+  })
 })