Class: HTML::Pipeline::CamoFilter

Inherits:
Filter
  • Object
show all
Defined in:
lib/html/pipeline/camo_filter.rb

Overview

HTML Filter for replacing http image URLs with camo versions. See:

github.com/atmos/camo

All images provided in user content should be run through this filter so that http image sources do not cause mixed-content warnings in browser clients.

Context options:

:asset_proxy (required) - Base URL for constructed asset proxy URLs.
:asset_proxy_secret_key (required) - The shared secret used to encode URLs.

This filter does not write additional information to the context.

Instance Attribute Summary

Attributes inherited from Filter

#context, #result

Instance Method Summary collapse

Methods inherited from Filter

#base_url, call, #current_user, #doc, #has_ancestor?, #html, #initialize, #needs, #parse_html, #repository, to_document, to_html

Constructor Details

This class inherits a constructor from HTML::Pipeline::Filter

Instance Method Details

#asset_proxy_host ⇒ Object

Private: the hostname to use for generated asset proxied URLs.



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# File 'lib/html/pipeline/camo_filter.rb', line 55

def asset_proxy_host
  context[:asset_proxy]
end

#asset_proxy_secret_key ⇒ Object 



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# File 'lib/html/pipeline/camo_filter.rb', line 59

def asset_proxy_secret_key
  context[:asset_proxy_secret_key]
end

#asset_proxy_url(url) ⇒ Object

The camouflaged URL for a given image URL.



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# File 'lib/html/pipeline/camo_filter.rb', line 44

def asset_proxy_url(url)
  "#{asset_proxy_host}/#{asset_url_hash(url)}/#{hexencode(url)}"
end

#asset_url_hash(url) ⇒ Object

Private: calculate the HMAC digest for a image source URL.



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# File 'lib/html/pipeline/camo_filter.rb', line 49

def asset_url_hash(url)
  digest = OpenSSL::Digest::Digest.new('sha1')
  OpenSSL::HMAC.hexdigest(digest, asset_proxy_secret_key, url)
end

#call ⇒ Object

Hijacks images in the markup provided, replacing them with URLs that go through the github asset proxy.



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# File 'lib/html/pipeline/camo_filter.rb', line 21

def call
  doc.search("img").each do |element|
    next if element['src'].nil?
    src = element['src'].strip
    src = src.sub(%r!^http://github.com!, 'https://github.com')
    next if context[:disable_asset_proxy]

    if src =~ /^http:/ || src =~ /^https:\/\/img.skitch.com\//
      element['src'] = asset_proxy_url(src)
    else
      element['src'] = src
    end
  end
  doc
end

#hexencode(str) ⇒ Object

Private: helper to hexencode a string. Each byte ends up encoded into two characters, zero padded value in the range [0-9a-f].



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# File 'lib/html/pipeline/camo_filter.rb', line 65

def hexencode(str)
  str.to_enum(:each_byte).map { |byte| "%02x" % byte }.join
end

#validate ⇒ Object

Implementation of validate hook. Errors should raise exceptions or use an existing validator.



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# File 'lib/html/pipeline/camo_filter.rb', line 39

def validate
  needs :asset_proxy, :asset_proxy_secret_key
end