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  #1  
Old December 29th, 2005, 04:58 PM
mdaoust mdaoust is offline
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Simple Ruby Question

Don't really know where to go with this one, but I gotta know...

What is the difference between the two following pieces of code?

Code:
<%= h(truncate(product.description, 80)) %>


and

Code:
<%= truncate(product.description, 80) %>


This question could also be asked by asking what h() does.

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  #2  
Old January 8th, 2006, 02:54 PM
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h is a user defined function, clearly since it looks like nothing in the ruby library.

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  #3  
Old January 8th, 2006, 02:55 PM
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and a bad choice of function name at that, as it's in no way meaningful to anyone but the original author (assuming of course that it isn't a core Ruby function)
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Old January 8th, 2006, 02:59 PM
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Ruby doesn't have any core functions, they're all in classes.

eg. File access = `File` class.

myfile = new File("myfilename"){|z| print z}

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  #5  
Old January 8th, 2006, 07:32 PM
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  #6  
Old January 12th, 2006, 10:36 AM
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My Agile Web Development with Rails just arrived yesterday night. I opened the book this morning and by strange coincidence, I opened it on page 345 which had the exact answer.

h() is short for html_escape() in the rails framework. You can use either h() or html_escape(), but most rails programmers use h() by convention, because it saves them some typing. Basically, you can use this method to html_escape any data. Why should you do this? What if your product description has a & in it. To output an & into your browser, the HTML should have & instead of &. Similarly, you should have < and > instead of < and > in your code. Using h() will convert & to & and < and > to < and > and other such conversions.

There are more security implications too. Consider the following rails code:
Code:
Name is <%= params[:name] %>

where name is entered by the user from a form. Normally, you would expect users to just enter their name (say "Joe Schmoe") and it would show the page like this:
Code:
Name is Joe Schmoe

Now, what if the user enters their name like this:
%3Ch1%3EJoe Schmoe%3C/h1%3E
The funky stuff is URL encoded HTML for <h1>Joe Schmoe</h1> and thus our page will show the text in big font, when we didn't mean it to. Of course, the person could do something a lot worse instead by entering some javascript instead and execute a cross side scripting attack.

To prevent this, it is a good idea to html escape the output. You can use:
Code:
Name is <%= h(params[:name]) %>

and it will HTML encode the output safely, so it can't be exploited.

Incidentally, rails also provides the sanitize() method. The sanitize method takes a string and cleans up any dangerous HTML elements. <form>, <script> are escaped, any on= attribs (onclick=, onselect= etc.) and links with javascript: tags are removed.
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Last edited by Scorpions4ever : January 12th, 2006 at 10:44 AM.

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  #7  
Old February 7th, 2006, 03:50 AM
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  #8  
Old February 17th, 2006, 11:11 PM
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and, not to suggest anyone look elsewhere for help....

the rails community has amazing support: http://rubyonrails.com/community

i prefer #rubyonrails on IRC or the mailing list

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Old February 18th, 2006, 06:00 AM
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Quote:
Originally Posted by eriksays
and, not to suggest anyone look elsewhere for help....

the rails community has amazing support: http://rubyonrails.com/community

i prefer #rubyonrails on IRC or the mailing list
#rubyonrails on freenode can be a good place, yes, but they can be twats as well, merely telling you to google, even if you spent an hour doing so already

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