Class: GlobalSession::Session::V3

Inherits:
Abstract
  • Object
show all
Defined in:
lib/global_session/session/v3.rb

Overview

Global session V3 uses JSON serialization, no compression, and a detached signature that is excluded from the JSON structure for efficiency reasons.

The binary structure of a V3 session looks like this:

<utf8_json><0x00><binary_signature>

Its JSON structure is an Array with the following format:

[<version_integer>,
 <uuid_string>,
 <signing_authority_string>,
 <creation_timestamp_integer>,
 <expiration_timestamp_integer>,
 {<signed_data_hash>},
 {<unsigned_data_hash>}]

The design goal of V3 is to ensure broad compatibility across various programming languages and cryptographic libraries, and to create a serialization format that can be reused for future versions. To this end, it sacrifices space efficiency by switching back to JSON encoding (instead of msgpack), and uses the undocumented OpenSSL::PKey#sign and #verify operations which rely on the PKCS7-compliant OpenSSL EVP API.

Constant Summary collapse

HEADER =

Pattern that matches strings that are probably a V3 session cookie.

/^WzM/
STRING_ENCODING = 
!!(RUBY_VERSION !~ /1.8/)

Instance Attribute Summary

Attributes inherited from Abstract

#authority, #created_at, #directory, #expired_at, #id, #insecure, #signed

Class Method Summary collapse

Instance Method Summary collapse

Methods inherited from Abstract

#[], #[]=, #delete, #dirty?, #each_pair, #has_key?, #initialize, #inspect, #invalidate!, #keys, #new_record?, #renew!, #supports_key?, #to_h, #valid?, #values

Constructor Details

This class inherits a constructor from GlobalSession::Session::Abstract

Class Method Details

Utility method to decode a cookie; good for console debugging. This performs no validation or security check of any sort.

Parameters

cookie(String)

well-formed global session cookie



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# File 'lib/global_session/session/v3.rb', line 60

def self.decode_cookie(cookie)
  bin = GlobalSession::Encoding::Base64Cookie.load(cookie)
  json, sig = split_body(bin)
  return GlobalSession::Encoding::JSON.load(json), sig
end

.join_body(json, signature) ⇒ String

Join a UTF-8 JSON document and an ASCII-8bit binary string.

This is an implementation helper for GlobalSession serialization and not useful for the public at large. It’s left public as an aid for those who want to hack sessions.

Parameters:

  • json (String) —

    a UTF-8 JSON document (encoding will be forced to UTF_8!)

  • signature (String) —

    a binary signautre (encoding will be forced to ASCII_8BIT!)

Returns:

  • (String) —

    a binary concatenation of the two inputs, separated by 0x00



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# File 'lib/global_session/session/v3.rb', line 102

def self.join_body(json, signature)
  result = ""
  if STRING_ENCODING
    result.force_encoding(Encoding::ASCII_8BIT)
    json.force_encoding(Encoding::ASCII_8BIT)
    signature.force_encoding(Encoding::ASCII_8BIT)
  end

  result << json
  result << "\x00"
  result << signature
  result
end

.split_body(input) ⇒ Array

Split an ASCII-8bit input string into two constituent parts: a UTF-8 JSON document and an ASCII-8bit binary string. A null (0x00) separator character is presumed to separate the two parts of the input string.

This is an implementation helper for GlobalSession serialization and not useful for the public at large. It’s left public as an aid for those who want to hack sessions.

Parameters:

  • input (String) —

    a binary string (encoding will be forced to ASCII_8BIT!)

Returns:

  • (Array) —

    returns a 2-element Array of String: json document, plus binary signature

Raises:

  • (ArgumentError) —

    if the null separator is missing



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# File 'lib/global_session/session/v3.rb', line 76

def self.split_body(input)
  input.force_encoding(Encoding::ASCII_8BIT) if STRING_ENCODING
  null_at = input.index("\x00")

  if null_at
    json = input[0...null_at]
    sig = input[null_at+1..-1]
    if STRING_ENCODING
      json.force_encoding(Encoding::UTF_8)
      sig.force_encoding(Encoding::ASCII_8BIT)
    end

    return json, sig
  else
    raise ArgumentError, "Malformed input string does not contain 0x00 byte"
  end
end

Instance Method Details

#signature_digest ⇒ Object

Return the SHA1 hash of the most recently-computed RSA signature of this session. This isn’t really intended for the end user; it exists so the Web framework integration code can optimize request speed by caching the most recently verified signature in the local session and avoid re-verifying it on every request.

Return

digest(String)

SHA1 hex-digest of most-recently-computed signature



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# File 'lib/global_session/session/v3.rb', line 169

def signature_digest
  @signature ? digest(@signature) : nil
end

#to_s ⇒ String

Serialize the session to a form suitable for use with HTTP cookies. If any secure attributes have changed since the session was instantiated, compute a fresh RSA signature.

Returns:

  • (String) —

    a B64cookie-encoded JSON-serialized global session

Raises:



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# File 'lib/global_session/session/v3.rb', line 122

def to_s
  if @cookie && !dirty?
    #use cached cookie if nothing has changed
    return @cookie
  end

  unless serializable?(@signed) && serializable?(@insecure)
    raise GlobalSession::UnserializableType,
          "Attributes hash contains non-String keys, cannot be cleanly marshalled"
  end

  hash = {'v' => 3,
          'id' => @id, 'a' => @authority,
          'tc' => @created_at.to_i, 'te' => @expired_at.to_i,
          'ds' => @signed}

  if @signature && !(@dirty_timestamps || @dirty_secure)
    #use cached signature unless we've changed secure state
    authority = @authority
  else
    authority_check
    authority = @directory.local_authority_name
    hash['a'] = authority
    signed_hash = RightSupport::Crypto::SignedHash.new(
      hash,
      @directory.private_key,
      envelope: true,
      encoding: GlobalSession::Encoding::JSON)
    @signature = signed_hash.sign(@expired_at)
  end

  hash['dx'] = @insecure
  hash['a'] = authority

  array = attribute_hash_to_array(hash)
  json = GlobalSession::Encoding::JSON.dump(array)
  bin = self.class.join_body(json, @signature)
  return GlobalSession::Encoding::Base64Cookie.dump(bin)
end