allow only one host header

lib/httpRequestBuilder.js

@@ -45,14 +45,21 @@ function requestBuilder (defaults) {
     const headers = reqData.headers
     const body = reqData.body
 
-    let host = getPropertyCaseInsensitive(reqData.headers, 'host') || reqData.host
+    const headersDefinedHost = getPropertyCaseInsensitive(reqData.headers, 'host')
+    let host = headersDefinedHost || reqData.host
 
     if (!host) {
       const hostname = reqData.hostname
       const port = reqData.port
       host = hostname + ':' + port
     }
-
+    const baseReq = [
+      `${method} ${path} HTTP/1.1`
+    ]
+    if (!headersDefinedHost) {
+      baseReq.push(`Host: ${host}`)
+    }
+    baseReq.push('Connection: keep-alive')
     if (reqData.auth) {
       const encodedAuth = Buffer.from(reqData.auth).toString('base64')
       headers.Authorization = `Basic ${encodedAuth}`
@@ -62,12 +69,6 @@ function requestBuilder (defaults) {
       throw new Error(`${method} HTTP method is not supported`)
     }
 
-    const baseReq = [
-      `${method} ${path} HTTP/1.1`,
-      `Host: ${host}`,
-      'Connection: keep-alive'
-    ]
-
     let bodyBuf
 
     if (typeof body === 'string') {

test/httpRequestBuilder.test.js

@@ -99,6 +99,23 @@ test('request builder should add a Content-Length header when the body buffer ex
     'request is okay')
 })
 
+test('request builder should add only one HOST header', (t) => {
+  t.plan(1)
+
+  const opts = server.address()
+  opts.method = 'POST'
+  opts.headers = {
+    Host: 'example.com'
+  }
+
+  const build = RequestBuilder(opts)
+
+  const result = build({ body: 'body' })
+  t.same(result,
+    Buffer.from('POST / HTTP/1.1\r\nConnection: keep-alive\r\nHost: example.com\r\nContent-Length: 4\r\n\r\nbody'),
+    'request is okay')
+})
+
 test('request builder should add a Content-Length header with correct calculated value when the body buffer exists and idReplacement is enabled as a default override', (t) => {
   t.plan(1)