Commit 511d1d80 authored by Kathleen Brade's avatar Kathleen Brade Committed by Georg Koppen
Browse files

Bug 26146: Spoof HTTP User-Agent header for desktop platforms 

In Tor Browser 8.0, the OS was revealed in both the HTTP User-Agent
header and to JavaScript code via navigator.userAgent. To avoid
leaking the OS inside each HTTP request (which many web servers
log), always use the Windows 7 OS value in the desktop User-Agent
header. We continue to allow access to the actual OS via JavaScript,
since doing so improves compatibility with web applications such
as GitHub and Google Docs.
parent 15ee4460

browser/app/profile/000-tor-browser.js

+0 −1
Original line number Diff line number Diff line
@@ -122,7 +122,6 @@ pref("general.appname.override", "Netscape"); 
pref("general.appversion.override", "5.0 (Windows)");

pref("general.oscpu.override", "Windows NT 6.1");

pref("general.platform.override", "Win32");

pref("general.useragent.override", "Mozilla/5.0 (Windows NT 6.1; rv:60.0) Gecko/20100101 Firefox/60.0");

pref("general.productSub.override", "20100101");

pref("general.buildID.override", "20100101");

pref("browser.startup.homepage_override.buildID", "20100101");

dom/base/Navigator.cpp

+13 −0
Original line number Diff line number Diff line
@@ -1772,6 +1772,19 @@ Navigator::GetUserAgent(nsPIDOMWindowInner* aWindow, 
    }

  }



  // When the caller is content and 'privacy.resistFingerprinting' is true,

  // return a spoofed userAgent which reveals the platform but not the

  // specific OS version, etc.

  if (!aIsCallerChrome && nsContentUtils::ShouldResistFingerprinting()) {

    nsAutoCString spoofedUA;

    nsresult rv = nsRFPService::GetSpoofedUserAgent(spoofedUA, false);

    if (NS_WARN_IF(NS_FAILED(rv))) {

      return rv;

    }

    CopyASCIItoUTF16(spoofedUA, aUserAgent);

    return NS_OK;

  }



  nsresult rv;

  nsCOMPtr<nsIHttpProtocolHandler>

    service(do_GetService(NS_NETWORK_PROTOCOL_CONTRACTID_PREFIX "http", &rv));

netwerk/protocol/http/nsHttpHandler.cpp

+1 −1
Original line number Diff line number Diff line
@@ -491,7 +491,7 @@ nsHttpHandler::Init() 
    }



    // Generating the spoofed User Agent for fingerprinting resistance.

    rv = nsRFPService::GetSpoofedUserAgent(mSpoofedUserAgent);

    rv = nsRFPService::GetSpoofedUserAgent(mSpoofedUserAgent, true);

    if (NS_FAILED(rv)) {

      // Empty mSpoofedUserAgent to make sure the unsuccessful spoofed UA string

      // will not be used anywhere.

toolkit/components/resistfingerprinting/nsRFPService.cpp

+3 −2
Original line number Diff line number Diff line
@@ -666,7 +666,7 @@ nsRFPService::GetSpoofedPresentedFrames(double aTime, uint32_t aWidth, uint32_t 


/* static */

nsresult

nsRFPService::GetSpoofedUserAgent(nsACString &userAgent)

nsRFPService::GetSpoofedUserAgent(nsACString &userAgent, bool isForHTTPHeader)

{

  // This function generates the spoofed value of User Agent.

  // We spoof the values of the platform and Firefox version, which could be
@@ -703,9 +703,10 @@ nsRFPService::GetSpoofedUserAgent(nsACString &userAgent) 
  // Except we used 60 as an ESR instead of 59.

  // We infer the last and closest ESR version based on this rule.

  uint32_t spoofedVersion = firefoxVersion - ((firefoxVersion - 4) % 7);

  const char *spoofedOS = isForHTTPHeader ? SPOOFED_HTTP_UA_OS : SPOOFED_UA_OS;

  userAgent.Assign(nsPrintfCString(

    "Mozilla/5.0 (%s; rv:%d.0) Gecko/%s Firefox/%d.0",

    SPOOFED_UA_OS, spoofedVersion, LEGACY_BUILD_ID, spoofedVersion));

    spoofedOS, spoofedVersion, LEGACY_BUILD_ID, spoofedVersion));



  return rv;

}

toolkit/components/resistfingerprinting/nsRFPService.h

+9 −1
Original line number Diff line number Diff line
@@ -48,6 +48,14 @@ 
#define SPOOFED_APPNAME    "Netscape"

#define LEGACY_BUILD_ID    "20100101"



// For the HTTP User-Agent header, we use a simpler set of spoofed values

// that do not reveal the specific desktop platform.

#if defined(MOZ_WIDGET_ANDROID)

#define SPOOFED_HTTP_UA_OS      "Android 6.0; Mobile"

#else

#define SPOOFED_HTTP_UA_OS      "Windows NT 6.1"

#endif



// Forward declare LRUCache, defined in nsRFPService.cpp

class LRUCache;
@@ -212,7 +220,7 @@ public: 
  static uint32_t GetSpoofedPresentedFrames(double aTime, uint32_t aWidth, uint32_t aHeight);



  // This method generates the spoofed value of User Agent.

  static nsresult GetSpoofedUserAgent(nsACString &userAgent);

  static nsresult GetSpoofedUserAgent(nsACString &userAgent, bool isForHTTPHeader);



  /**

   * This method for getting spoofed modifier states for the given keyboard event.