Class: OStatus::Salmon

Inherits:
Object
  • Object
show all
Defined in:
lib/ostatus/salmon.rb

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(entry, signature = nil, plaintext = nil) ⇒ Salmon

Create a Salmon instance for a particular OStatus::Entry



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# File 'lib/ostatus/salmon.rb', line 10

def initialize entry, signature = nil, plaintext = nil
  @entry = entry
  @signature = signature
  @plaintext = plaintext
end

Instance Attribute Details

#entry ⇒ Object

Returns the value of attribute entry.



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# File 'lib/ostatus/salmon.rb', line 7

def entry
  @entry
end

Class Method Details

.from_follow(user_author, followed_author) ⇒ Object

Creates an entry for following a particular Author.



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# File 'lib/ostatus/salmon.rb', line 17

def Salmon.from_follow(user_author, followed_author)
  entry = OStatus::Entry.new(
    :author => user_author,
    :title => "Now following #{followed_author.name}",
    :content => Atom::Content::Html.new("Now following #{followed_author.name}")
  )

  entry.activity.verb = :follow
  entry.activity_object = followed_author

  OStatus::Salmon.new(entry)
end

.from_unfollow(user_author, followed_author) ⇒ Object

Creates an entry for unfollowing a particular Author.



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# File 'lib/ostatus/salmon.rb', line 31

def Salmon.from_unfollow(user_author, followed_author)
  entry = OStatus::Entry.new(
    :author => user_author,
    :title => "Stopped following #{followed_author.name}",
    :content => Atom::Content::Html.new("Stopped following #{followed_author.name}")
  )

  entry.activity_verb = "http://ostatus.org/schema/1.0/unfollow"
  entry.activity_object = followed_author

  OStatus::Salmon.new(entry)
end

.from_xml(source) ⇒ Object

Will pull a OStatus::Entry from a magic envelope described by the xml.



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# File 'lib/ostatus/salmon.rb', line 45

def Salmon.from_xml source
  if source.is_a?(String)
    source = XML::Document.string(source, 
                                  :options => XML::Parser::Options::NOENT)
  end

  # Retrieve the envelope
  envelope = source.find('/me:env', 
                      'me:http://salmon-protocol.org/ns/magic-env').first

  if envelope.nil?
    return nil
  end

  data = envelope.find('me:data', 
                       'me:http://salmon-protocol.org/ns/magic-env').first
  if data.nil?
    return nil
  end

  data_type = data.attributes["type"]
  if data_type.nil?
    data_type = 'application/atom+xml'
    armored_data_type = ''
  else
    armored_data_type = Base64::urlsafe_encode64(data_type)
  end

  encoding = envelope.find('me:encoding',
                           'me:http://salmon-protocol.org/ns/magic-env').first

  algorithm = envelope.find(
                      'me:alg',
                      'me:http://salmon-protocol.org/ns/magic-env').first

  signature = source.find('me:sig',
                       'me:http://salmon-protocol.org/ns/magic-env').first

  # Parse fields

  if signature.nil?
    # Well, if we cannot verify, we don't accept
    return nil
  else
    # XXX: Handle key_id attribute
    signature = signature.content
    signature = Base64::urlsafe_decode64(signature)
  end

  if encoding.nil?
    # When the encoding is omitted, use base64url
    # Cite: Magic Envelope Draft Spec Section 3.3
    armored_encoding = ''
    encoding = 'base64url'
  else
    armored_encoding = Base64::urlsafe_encode64(encoding.content)
    encoding = encoding.content.downcase
  end

  if algorithm.nil?
    # When algorithm is omitted, use 'RSA-SHA256'
    # Cite: Magic Envelope Draft Spec Section 3.3
    armored_algorithm = ''
    algorithm = 'rsa-sha256'
  else
    armored_algorithm = Base64::urlsafe_encode64(algorithm.content)
    algorithm = algorithm.content.downcase
  end

  # Retrieve and decode data payload

  data = data.content
  armored_data = data

  case encoding
  when 'base64url'
    data = Base64::urlsafe_decode64(data)
  else
    # Unsupported data encoding
    return nil
  end

  # Signature plaintext
  plaintext = "#{armored_data}.#{armored_data_type}.#{armored_encoding}.#{armored_algorithm}"

  # Interpret data payload
  payload = XML::Reader.string(data)
  Salmon.new OStatus::Entry.new(payload), signature, plaintext
end

Instance Method Details

#sign(message, key) ⇒ Object 



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# File 'lib/ostatus/salmon.rb', line 193

def sign message, key
  @plaintext = message 

  modulus_byte_count = key.private_key.modulus.size

  @signature = signature(modulus_byte_count)
  @signature = key.decrypt(@signature)
end

#signature(modulus_byte_length) ⇒ Object

Return the EMSA string for this Salmon instance given the size of the public key modulus.



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# File 'lib/ostatus/salmon.rb', line 179

def signature modulus_byte_length
  plaintext = Digest::SHA2.new(256).digest(@plaintext)

  prefix = "\x30\x31\x30\x0d\x06\x09\x60\x86\x48\x01\x65\x03\x04\x02\x01\x05\x00\x04\x20"
  padding_count = modulus_byte_length - prefix.bytes.count - plaintext.bytes.count - 3

  padding = ""
  padding_count.times do 
    padding = padding + "\xff"
  end

  "\x00\x01#{padding}\x00#{prefix}#{plaintext}"
end

#to_xml(key) ⇒ Object

Generate the xml for this Salmon notice and sign with the given private key.



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# File 'lib/ostatus/salmon.rb', line 137

def to_xml key
  # Generate magic envelope
  magic_envelope = XML::Document.new

  magic_envelope.root = XML::Node.new 'env'

  me_ns = XML::Namespace.new(magic_envelope.root, 
               'me', 'http://salmon-protocol.org/ns/magic-env')

  magic_envelope.root.namespaces.namespace = me_ns

  # Armored Data <me:data>
  data = @entry.to_xml
  @plaintext = data
  data_armored = Base64::urlsafe_encode64(data)
  elem = XML::Node.new 'data', data_armored, me_ns
  elem.attributes['type'] = 'application/atom+xml'
  data_type_armored = 'YXBwbGljYXRpb24vYXRvbSt4bWw='
  magic_envelope.root << elem

  # Encoding <me:encoding>
  magic_envelope.root << XML::Node.new('encoding', 'base64url', me_ns)
  encoding_armored = 'YmFzZTY0dXJs'

  # Signing Algorithm <me:alg>
  magic_envelope.root << XML::Node.new('alg', 'RSA-SHA256', me_ns)
  algorithm_armored = 'UlNBLVNIQTI1Ng=='

  # Signature <me:sig>
  plaintext = "#{data_armored}.#{data_type_armored}.#{encoding_armored}.#{algorithm_armored}"
  
  # Assign @signature to the signature generated from the plaintext
  sign(plaintext, key)

  signature_armored = Base64::urlsafe_encode64(@signature)
  magic_envelope.root << XML::Node.new('sig', signature_armored, me_ns)
  
  magic_envelope.to_s :indent => true, :encoding => XML::Encoding::UTF_8
end

#verified?(key) ⇒ Boolean

Use RSA to verify the signature key - RSA::KeyPair with the public key to use

Returns:

  • (Boolean) 


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# File 'lib/ostatus/salmon.rb', line 204

def verified? key
  # RSA encryption is needed to compare the signatures

  # Get signature to check
  emsa = self.signature key.public_key.modulus.size

  # Get signature in payload
  emsa_signature = key.encrypt(@signature)

  # RSA gem drops leading 0s since it does math upon an Integer
  # As a workaround, I check for what I expect the second byte to be (\x01)
  # This workaround will also handle seeing a \x00 first if the RSA gem is
  # fixed.
  if emsa_signature.getbyte(0) == 1
    emsa_signature = "\x00#{emsa_signature}"
  end

  # Does the signature match?
  # Return the result.
  emsa_signature == emsa
end