Close npm#804 Pass auth for tarball fetching

lib/utils/fetch.js

@@ -15,6 +15,7 @@ var http
   , mkdir = require("./mkdir-p")
   , consts = require("constants")
   , proxyify = require("./proxyify")
+  , regUrl = npm.cofig.get("registry")
 
 module.exports = fetch
 function fetch (remote, local, headers, cb) {
@@ -46,9 +47,21 @@ function fetch_ (remote, local, headers, cb) {
 function fetchAndWrite (remote, fstr, headers, maxRedirects, redirects) {
   if (!redirects) redirects = 0
   if (!maxRedirects) maxRedirects = 10
+
+  headers = headers || {}
   var remote = url.parse(remote)
-    , opts =
-      { headers: headers || {}
+  if (remote.host === regUrl && npm.config.get("always-auth")) {
+    var auth = npm.config.get("_auth")
+    if (!auth) return fstr.emit("error", new Error(
+      "Auth required and none provided. Please run 'npm adduser'"))
+    headers.authentication = "Basic "+auth
+  } else if (remote.auth) {
+    headers.authentication = "Basic "
+                           + (new Buffer(remote.auth).toString("base64"))
+  }
+
+  var opts =
+      { headers: headers
       , path: (remote.pathname||"/")+(remote.search||"")+(remote.hash||"")
       , host: remote.hostname
       , port: remote.port