{"id":18023,"date":"2014-11-06T10:12:39","date_gmt":"2014-11-06T15:12:39","guid":{"rendered":"https:\/\/nuxx.net\/blog\/?p=18023"},"modified":"2014-11-06T10:15:57","modified_gmt":"2014-11-06T15:15:57","slug":"fiddler-for-chained-proxy-authentication","status":"publish","type":"post","link":"https:\/\/nuxx.net\/blog\/2014\/11\/06\/fiddler-for-chained-proxy-authentication\/","title":{"rendered":"Fiddler for Chained Proxy Authentication"},"content":{"rendered":"

\"\"<\/p>\n

I recently had an\u00a0issue where an application which supports proxies but doesn’t prompt for credentials needed to\u00a0use a proxy server\u00a0to communicate with the\u00a0internet. The solution? Use Fiddler<\/a> and its built in scripting language<\/a> as a secondary proxy chained to the primary, forcibly sending a valid\u00a0authentication header to the proxies.<\/p>\n

How does one\u00a0this? Here’s how, which is a bit more detailed writeup than what’s found here at Stack Overflow<\/a>. Note that this presumes basic familiarity with Fiddler:<\/p>\n

    \n
  1. Use Fiddler to watch a session that uses Basic authentication<\/a> to the proxy. Look at one of the requests headers after successful authentication and find the line which\u00a0contains Proxy-Authorization: Basic<\/code>. Copy this value\u00a0to the clipboard. (Example line:\u00a0Proxy-Authorization: Basic dXNlcm5hbWU6cGFzc3dvcmQxMg==<\/code>)<\/li>\n
  2. In Fiddler, click Rules<\/em>\u00a0\u2192\u00a0Customize Rules<\/em> to open CustomRules.js<\/code> in an editor.<\/li>\n
  3. Locate the function OnBeforeRequst<\/code>. The line beginning this will read something like\u00a0static function OnBeforeRequest(oSession: Session)<\/code>\u00a0and is line 159 in the rulset that ships with Fiddler v4.4.9.2 (latest as of November 6, 2014).<\/li>\n
  4. Below this, add a line as follows, with the secondary part being the string that was copied in step 1. In this example the bolded portion is what we’ve added:
    \n[...]<\/code>
    \nstatic function OnBeforeRequest(oSession: Session) {<\/code>
    \n \/\/ Inject a Basic\u00a0authentication header<\/code><\/strong>
    \n oSession.oRequest[\"Proxy-Authorization\"] = \"Basic Yno5eWw1Oldyb25nLmdvLldheSsyNDA=\";<\/code><\/strong>
    \n\/\/ Sample noRule: Color ASPX requests in RED<\/code>
    \n \/\/ if (oSession.uriContains(\".aspx\")) { oSession[\"ui-color\"] = \"red\"; }<\/code>
    \n[...]<\/code><\/li>\n
  5. Save and close CustomRules.js<\/code>. Fiddler will now begin using this modified ruleset. You can observe that this header is now included with every request.<\/li>\n
  6. Ensure that your application using Fiddler as its proxy. If the application is local to the computer on which Fiddler is running and uses\u00a0WinINET<\/a>\u00a0then this is likely automatic.\u00a0If not, it will need to be manually pointed to the\u00a0local proxy. Fiddler can also\u00a0accept connections from computers elsewhere on a network (Tools<\/em>\u00a0\u2192 Fiddler Options…<\/em>\u00a0\u2192 Connections<\/em>), but configuration of this is beyond the scope of this article. See the Fiddler documentation for more information.<\/li>\n<\/ol>\n","protected":false},"excerpt":{"rendered":"

    I recently had an\u00a0issue where an application which supports proxies but doesn’t prompt for credentials needed to\u00a0use a proxy server\u00a0to communicate with the\u00a0internet. The solution?…<\/p>\n

    Continue readingFiddler for Chained Proxy Authentication<\/span><\/a><\/div>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[13],"tags":[],"class_list":["post-18023","post","type-post","status-publish","format-standard","hentry","category-computers","entry"],"amp_enabled":true,"_links":{"self":[{"href":"https:\/\/nuxx.net\/blog\/wp-json\/wp\/v2\/posts\/18023","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/nuxx.net\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/nuxx.net\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/nuxx.net\/blog\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/nuxx.net\/blog\/wp-json\/wp\/v2\/comments?post=18023"}],"version-history":[{"count":6,"href":"https:\/\/nuxx.net\/blog\/wp-json\/wp\/v2\/posts\/18023\/revisions"}],"predecessor-version":[{"id":18029,"href":"https:\/\/nuxx.net\/blog\/wp-json\/wp\/v2\/posts\/18023\/revisions\/18029"}],"wp:attachment":[{"href":"https:\/\/nuxx.net\/blog\/wp-json\/wp\/v2\/media?parent=18023"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/nuxx.net\/blog\/wp-json\/wp\/v2\/categories?post=18023"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/nuxx.net\/blog\/wp-json\/wp\/v2\/tags?post=18023"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}