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Developing Firefox Extensions with GNU/Linux

Posted by Zonk on from the extend-the-browser-extend-the-fun dept.

QT writes "Ars Technica has a lengthy but useful introduction to developing Firefox extensions with GNU/Linux. This guide comes hot on the heels of the RC for Beta 1 of Firefox. The article is a little more thorough than necessary, but I can't complain about anything that spurs Firefox development." From the article: "What can you do with a Firefox Extension? Firefox extensions can modify the Firefox user interface. This includes adding buttons to tool bars and menus; changing fonts, colors, and icons; capturing events in the client interface like page loads and clicks; and modifying web pages after the browser loads them and before the user sees them. All of this functionality comes with the aspect-oriented facility of overlays. Extensions also have as much access to the file system as the user running Firefox. Extensions can add protocol handlers, hooking actions to URLs like icq://, aim://, or stantz://. Extensions have UniversalXPConnect privileges, allowing them to harness any XPCOM component. Firefox comes with a rich library of XPCOM components that permit your extension to drive very low-level functionality like sockets from Javascript. You can also augment the XPCOM library with Firefox extensions by adding Javascript, linkable libraries, or XPIDL."

29 of 146 comments (clear)

  1. this reminds me... by QunaLop · · Score: 2, Insightful

    since these things have full access to the local machine, remind me why we love extensions and hate activex?

    1. Re:this reminds me... by jd142 · · Score: 4, Insightful

      They don't have full access to the local machine, they only have the user's access to the local machine. There's an important difference.

    2. Re:this reminds me... by moonbender · · Score: 4, Insightful

      Simple: ActiveX was and is often used by websites to extend website functionality. For instance, Microsoft uses it to implement the functionality of its Windows Update website. Trend Micro uses it to implement the functionality of its house call anti virus service. And so on. Of course there isn't anything inherently bad about it, both examples are very useful. It would be very insecure, though, to allow untrusted sites to extend their functionality this way, and it would have been very bad if ActiveX had been a standard repertoire of web design in the way that Flash is, for example.

      Firefox extensions are quite different. They typically extend the functionality of the browser, independent of the web sites you might use. I say typically because there are counterexamples, for instance extensions designed to make working with Wikipedia easier. But this is the exception, not the norm. Firefox extensions aren't "meant" to be used by a lot of different web site, and people would find it quite strange if they were required to install an extension for viewing just one web site.

      So maybe the technology is similar (I wouldn't know), the way they are typically used, and were designed and meant to be used are quite different.

      --
      Switch back to Slashdot's D1 system.
    3. Re:this reminds me... by NutscrapeSucks · · Score: 2, Insightful

      Because in theory, someone educated enough to run Firefox would also be educated enough to not allow it to run untrusted things.

      In theory, Firefox is a browser for the masses and is designed to supplant Internet Explorer. If Firefox has a userbase that's more technically sophisticated than other browsers, that only means that there's more work to do.

      So please quit blowing yourself by thinking Firefox is l33t d00d software -- it isn't. The whole goal is stripped down and simple for the ordinary IE user.

      Now it is true that Extentions are "elite", and they are generally only found on one or two sites. The questions is if the security model will hold up when Firefox gets more popular and users get used to instaling extentions from a varity of sources. I'm sure at some pont a signing mechanism like Authenicode will be deemed necessary.

      --
      Whenever I hear the word 'Innovation', I reach for my pistol.
    4. Re:this reminds me... by NutscrapeSucks · · Score: 3, Informative

      Or not so important, because Windows users generally run with administration privledges, and that's where the virus problem lies.

      --
      Whenever I hear the word 'Innovation', I reach for my pistol.
    5. Re:this reminds me... by baadger · · Score: 2, Insightful

      "I'm sure at some pont a signing mechanism like Authenicode will be deemed necessary."

      Just like signed ActiveX?

      Anyone can sign something. For signing to work you need a trusted registry/organisation to cryptographically sign things and use a whitelist system to reject untrusted signitures, just like SSL certificates. But we aren't talking about certificates we're talking about code. Anytime someone sticks an official stamp on something people start expecting the official stamper/supposed quality assurer to take responsibility when shit hits the fan.

      No, the best bet is to show a blatant warning when the user installs an extension and produce a centralised link to somewhere (like addons.mozilla.org) where users can discuss an extension and decide if they trust it for themselves. This would be the open source community bit. A blacklist of bad extensions/spyware might be a good idea too.

      Theres not much you can do to improve the way ActiveX components are installable except to educate users and provide easily accessable resources (as above). The security model underneath ActiveX apparently sucks (no personal experience)...but then firefox extensions can be a pain too.

      You shouldn't worry too much about anything beyond personal assessment and a warning IMHO. It's a definate slippery slope to spyware removal tools for Firefox. It's gonna happen unless someone makes a revelation.

    6. Re:this reminds me... by FST777 · · Score: 2, Insightful

      Exactly what I was thinking. Asume Firefox has 90% market share. One gets an (spam-)mail in, asking it to visit stated link. The link gives the user a request to install a certain Firefox extension. The user thinks it is save, because that is the sole reason he/she installed Firefox in the first place (with the upcoming IE 7 there really aren't any more standing reasons yet). And there you go, a fully open browser, with access to the filesystem, throwing all the information needed for anything nasty, right trough our beloved extension system.

      This wouldn't be an exploit if the parent's parent of this post is right: "Firefox users should be the most intelligent people on the earth". But that is not the goal of Firefox at all (at least, AFAIK). If it is, it would be the very same additude which kills Open Source in many situations (yes, *** is complicated, but hey, if you don't understand it, it's just not made for you!)

      And to think that I talked so many people into Firefox, just to prove that Open Source could be for them too... (and apart from this additude, the update-system proved me wrong... good to hear that they are tackling that one!)

      --
      Free beer is never free as in speech. Free speech is always free as in beer.
    7. Re:this reminds me... by NutscrapeSucks · · Score: 2, Insightful

      No, I don't think signing is a cure-all, but it does minimize one social exploit. Whatever you think about ActiveX, I've never heard about an evil control that pretends to be Windows Update or Macromedia Flash.

      If firefox become popular, it's possible there would be a ton of fake "Ad Block" and "Tab Browser" extentions, and signing is pretty much the only way to stop it.

      If you want to see an example of this in action, search Google for "eMule", the opensource filesharing client. About 90% of the links go to fake sites which are probably spyware-laden clients. Too bad the official Emule installer doesn't use Authenicode -- I would defiantly check it.

      Now it would be nice if code-signing was extended so that things could be "Certified by So-N-So to be Spyware-Free!". But even then, if it's an open system, fake certifiers will come about.

      --
      Whenever I hear the word 'Innovation', I reach for my pistol.
    8. Re:this reminds me... by Bogtha · · Score: 2, Informative

      With ActiveX the code is loaded when I visit the page, for the average user there is no choice if the code will run; since the default settings typically aren't changed.

      What you say simply isn't true. I just booted up XP to check. The default settings are to prompt the user for signed controls and to ignore unsigned controls altogether.

      --
      Bogtha Bogtha Bogtha
    9. Re:this reminds me... by baadger · · Score: 2, Interesting
      "Whatever you think about ActiveX, I've never heard about an evil control that pretends to be Windows Update or Macromedia Flash."

      Very very true. The problems with ActiveX all stem from uninformed users clicking yes to that XXX Toolbar popup.

      I definately think it'd be a good idea for Mozilla to implement a community page for every extension any firefox browser anywhere tries to install from a remote location. Something much like the current extension directory, but inclusive of extensions not even hosted there (even any commercial extensions that may arise in the future). It could work something like this:

      1. The browser hashes the extension code minus any fuzziness, whitespace etc (or better yet hash the bytecode) to try and ensure malicious authors don't try to scatter negative feedback.
      2. Offer the user a friendly details link to http://extensions.mozilla.org/?lookup=hash on the warning screen when they try to install the extension
      3. The user can read other peoples warnings, doubts, or happy reviews see the extension rating, how many people have installed it, etc and can then decide for themselves whether it's trustable enough to install.
      4. The hash links could be redirected to proper extension pages with names, descriptions and version #'s etc once the extension is well established and rated to be 'safe' by the community.
      5. For users too lazy to 'waste' time checking the feedback pages thoroughly, the warning dialog could show any immediate threat or trust rating and whether the code for this extension has been peer reviewed.


      Problems:
      • Successfully identification of extensions could be tricky if a malicious author tries to dodge the system.
      • The trust ratings and user comments need to be safe from poisoning and therefore moderated
    10. Re:this reminds me... by NutscrapeSucks · · Score: 2, Insightful

      The trust ratings and user comments need to be safe from poisoning and therefore moderated

      Keep in mind that Kazaa was the run-away most popular filesharing client for years, despite all of the well-known spyware it came with.

      If you want to moderate all of the "wrong" opinons or just plain spam on this proposed BBS, you might as well just skip a step and put the Cabal directly in charge. (Whether that would be mozilla.org is unlikely, I think.)

      And since your proposal relies on hashes, browser support, and some sort of authority, you might as well accept that you've just proposed code signing and you agree with me :)

      --
      Whenever I hear the word 'Innovation', I reach for my pistol.
  2. Where's my bittorrent:// ? by Anonymous Coward · · Score: 3, Insightful

    Where's my bittorrent:// protocol??!?!

    I would love to simply do a bittorrent from firefox. I think that'd spur alot more users and make it easier to... um... *LEGAL* download torrents... (like knoppix, fedora, etc.)

    Bring on the torrents!!!

    1. Re:Where's my bittorrent:// ? by brsmith4 · · Score: 5, Informative

      http://firepuddle.mozdev.org/ might help sometime soon...

    2. Re:Where's my bittorrent:// ? by MSch · · Score: 2, Informative

      Opera 8.10 has integrated bittorrent support.

    3. Re:Where's my bittorrent:// ? by drsquare · · Score: 2, Funny

      Well, Opera usually seems to be a few years ahead of Firefox when it comes to functionality, speed and ease of use, so we should see integrated bittorrent support for Firefox somewhere around 2009.

  3. In other words... by nmb3000 · · Score: 4, Insightful

    Firefox extensions are are useful and powerful tools when used correctly, yet have the ability to easily become malicious and destructive if the user doesn't pay attention.

    Hmmm, sounds a lot like ActiveX. While the main intent for the two is a little different (browser tweaking vs. client-side scripting & server interaction), both require users to make informed decisions. People going on about how Firefox is so much safer because it doesn't support ActiveX might need to consider dropping that argument. As Firefox's market share grows, so will the number of websites that advertise Firefox plugins, and unaware users will be just as susceptible to malware and viruses as they were with IE.

    --
    "What do you despise? By this are you truly known." --Princess Irulan, Manual of Muad'Dib
    /)
    1. Re:In other words... by Unordained · · Score: 3, Informative

      It seems like it'd be nice if apps like Firefox were routinely (!) run as a user with fewer privs than the actual user sitting at the terminal. I know it needs -some- disk access for cache, etc. and some access to the user's files (when uploading or downloading specific files) but on the whole it'd be nice to have some sort of mechanism in place to keep apps from accessing things when they shouldn't. The view that an app should only have access to the current user's files is okay, but not ideal -- users still don't want their own setup trashed by some tricky extension, even if the rest of the host computer is fine. In a multi-user environment, that's not so easy ... creating a new user, for every app/user combination, that provides exactly the access required by the app and no more. Lots of maintenance.

      I'm not sure that users would be very accepting of an environment in which they were asked each time an app requested a new file handle -- "would you like to allow Firefox to access /home/unordained/file1.txt in read-only mode?" ... "would you like to allow p2p-app-1 to open a socket to ip xxx.xxx.xxx.xxx?" ... "would you like to allow some-app-2 to change the following registry keys?" ... but that is, (without the annoyance) what I'd like. Our computing environments are just far too unsafe for the average user.

      Suggestions? Existing (partial) solutions? (This is your opportunity to go on at length about your preferred, overly-safe-for-you operating system, and for others to trash it on grounds of any remaining work-arounds.)

    2. Re:In other words... by Leffe · · Score: 2, Interesting

      How is "download virus.xpi here idiot" any different from "download virus.exe here idiot"?

      Stupid people are stupid, they make the Internet and the world a worse place for all of us. It's too bad I don't have the time to spend to revoke all of their life certificates.

    3. Re:In other words... by cortana · · Score: 2, Informative

      You are describing SELinux. :)

  4. Danger Will Robinson! by Elrac · · Score: 5, Insightful
    All of this functionality comes with the aspect-oriented facility of overlays. Extensions also have as much access to the file system as the user running Firefox.
    But... but... isn't it just this extreme flexibility that represents the biggest Achilles heal (sic) of Outlook and IE? Isn't this what Mozilla proudly avoids?

    I realize that there are some differences, such as the fact that the red carpet is only rolled out for extensions the user trusts, but... when you advertise Firefox to dummies, your trusting users will BE dummies!
    --
    When one person suffers from a delusion, it is called insanity. When many people suffer from a delusion it is called Rel
  5. Re:HORRIBLE idea..(and my inability to close tags) by radish · · Score: 2, Informative

    Speaking as someone currently undergoing such a "borrowing" - it sucks.

    Please for the love of god people, don't bounce messages back saying "My spam filter has blocked your message". I didn't send it, I don't care. Leave me alone!!!!!

    --

    ---- Den ene knappen er powerknapp, den andre er Bender voice knapp "Bite My Shiny Metal Ass"

  6. Re:HORRIBLE idea..(and my inability to close tags) by Noksagt · · Score: 2, Insightful

    The problem is he probably ISN'T a spambot. The FROM header is very easily spoofed. His machine need not be the sender for the message to claim it came from him.

  7. Re:HORRIBLE idea..(and my inability to close tags) by radish · · Score: 2, Insightful

    I'm not a spambot you moron. Go read up on SMTP and some back when you know what you're talking about. The FROM and REPLY-TO headers are spoofed (trivially easy) and the spamees aren't checking my domain's SPF records. Nothing to do with me whatsoever, other than getting me flooded with bounce messages.

    --

    ---- Den ene knappen er powerknapp, den andre er Bender voice knapp "Bite My Shiny Metal Ass"

  8. More Resources by stoolpigeon · · Score: 4, Informative

    These are a few sites that I found helpful. Some are a little old but I got something out of all of them.

    http://www.xulplanet.com/
    http://kb.mozillazine.org/Dev_:_Extensions
    http://roachfiend.com/archives/2004/12/08/how-to-c reate-firefox-extensions/
    http://businesslogs.com/technology/firefox_extensi on_tutorial.php
    http://www.bengoodger.com/software/mb/extensions/p ackaging/extensions.html
    http://mozilla-firefox-extension-dev.blogspot.com/
    http://books.mozdev.org/index.html
    http://www.mozilla.org/xpfe/gettingstarted.html

    Of course another good way to learn about extensions is to download a few and look at the code. That has probably been the biggest help to me once the tutorials, etc. gave me the basic idea of what is going on.

    --
    It's hard to believe that's how Micronians are made. Why don't we see it right now by having you both kiss one another?
  9. Talk about appropriate... by null+etc. · · Score: 3, Funny
    The article is a little more thorough than necessary

    ...followed by a 146-word "excerpt" from the article.

  10. Re:But what if... by protocol420 · · Score: 2, Funny

    good luck finding a compiler built into the kernel

    --
    www.gaian-mind.org - eco-punk/crust coop and collective | www.anarchistfederation.org - so cal anarchist federation
  11. My thinking on the subject by TheSpoom · · Score: 4, Insightful

    When should you use a Firefox extension?

    Only when you're EXTENDING FIREFOX.

    If your website requires an extension (or, for that matter, ActiveX) to work, you're simply coding it incorrectly.

    Possible exceptions includes Windows Update, but even then, Microsoft coded that as part of the OS in XP, so the web portal really isn't necessary.

    --
    It's better to vote for what you want and not get it than to vote for what you don't want and get it.
    - E. Debs
  12. Common misconceptions about XPCOM and ActiveX by SimHacker · · Score: 4, Informative
    Noksagt, you are wrong, and spreading some common misconceptions, which you should stop repeating.

    XPCOM extensions for Firefox are compiled binary machine language files, which have just as much access to your system as ActiveX controls do. Firefox XPCOM extensions are no more secure than ActiveX controls. Binary ActiveX and XPCOM controls are useful for situations where you need to do things that JavaScript doesn't support, like shaping the window of a pie menu (an open source ActiveX component, that you can download the source code if you like).

    Internet Explorer has something similar to the way you can write Firefox extensions in JavaScript and UIL. But that's a totally different thing than binary ActiveX controls and behaviors, and it severly restricts what you can do.

    You can script trustable ActiveX controls for Internet Explorer called "Dynamic HTML Behavior Components", using JavaScript (or any other ActiveX compatible scripting languages), XML and DHTML.

    For example, user interface components like JavaScript Pie Menus for Internet Explorer or the Run On Sentence dynamic text animation style run with the same restrictions as JavaScript in the browser, so they can't access files or shape popup windows. (Also open source).

    -Don

    --
    Take a look and feel free: http://www.PieMenu.com
  13. Re:anti-ActiveX by Noksagt · · Score: 3, Interesting
    They are better sandboxed than IE ActiveX controls used to be.
    Here, I made a (rightly well-criticized) mistatement. I'm wrong. Both XPCOM and ActiveX can execute with full user-priviledges.

    As I said, though: webpages could tell IE (at least used to) where to download an ActiveX control. If the control was not already installed, IE would automatically download and install the control from the specified source. In firefox, the page must me whitelisted before extensions could be downloaded. Can someone tell me if IE has changed to the whitelist model yet? Last I heard, they were even maintaining a list of malicious ActiveX controls. This seemed inance to me, as there is most likely more malicious junk out there than truly useful controls.