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cors.rb
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cors.rb
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require 'logger'
module Rack
class Cors
ENV_KEY = 'X_RACK_CORS'.freeze
ORIGIN_HEADER_KEY = 'HTTP_ORIGIN'.freeze
PATH_INFO_HEADER_KEY = 'PATH_INFO'.freeze
def initialize(app, opts={}, &block)
@app = app
@debug_mode = !!opts[:debug]
if logger = opts[:logger]
if logger.respond_to? :call
@logger_proc = opts[:logger]
else
@logger = logger
end
end
if block_given?
if block.arity == 1
block.call(self)
else
instance_eval(&block)
end
end
end
def debug?
@debug_mode
end
def allow(&block)
all_resources << (resources = Resources.new)
if block.arity == 1
block.call(resources)
else
resources.instance_eval(&block)
end
end
def call(env)
env[ORIGIN_HEADER_KEY] ||= env['HTTP_X_ORIGIN']
add_headers = nil
if env[ORIGIN_HEADER_KEY]
debug(env) do
[ 'Incoming Headers:',
" Origin: #{env[ORIGIN_HEADER_KEY]}",
" Access-Control-Request-Method: #{env['HTTP_ACCESS_CONTROL_REQUEST_METHOD']}",
" Access-Control-Request-Headers: #{env['HTTP_ACCESS_CONTROL_REQUEST_HEADERS']}"
].join("\n")
end
if env['REQUEST_METHOD'] == 'OPTIONS' and env['HTTP_ACCESS_CONTROL_REQUEST_METHOD']
if headers = process_preflight(env)
debug(env) do
"Preflight Headers:\n" +
headers.collect{|kv| " #{kv.join(': ')}"}.join("\n")
end
return [200, headers, []]
end
else
add_headers = process_cors(env)
end
else
Result.miss(env, Result::MISS_NO_ORIGIN)
end
status, headers, body = @app.call env
if add_headers
headers = headers.merge(add_headers)
# http://www.w3.org/TR/cors/#resource-implementation
unless headers['Access-Control-Allow-Origin'] == '*'
vary = headers['Vary']
headers['Vary'] = ((vary ? vary.split(/,\s*/) : []) + ['Origin']).uniq.join(', ')
end
end
if debug? && result = env[ENV_KEY]
result.append_header(headers)
end
[status, headers, body]
end
protected
def debug(env, message = nil, &block)
(@logger || select_logger(env)).debug(message, &block) if debug?
end
def select_logger(env)
@logger = if @logger_proc
logger_proc = @logger_proc
@logger_proc = nil
logger_proc.call
elsif defined?(Rails) && Rails.logger
Rails.logger
elsif env['rack.logger']
env['rack.logger']
else
::Logger.new(STDOUT).tap { |logger| logger.level = ::Logger::Severity::DEBUG }
end
end
def all_resources
@all_resources ||= []
end
def process_preflight(env)
resource, error = find_resource(env)
if resource
Result.preflight_hit(env)
preflight = resource.process_preflight(env)
preflight
else
Result.preflight_miss(env, error)
nil
end
end
def process_cors(env)
resource, error = find_resource(env)
if resource
Result.hit(env)
cors = resource.to_headers(env)
cors
else
Result.miss(env, error)
nil
end
end
def find_resource(env)
path = env[PATH_INFO_HEADER_KEY]
origin = env[ORIGIN_HEADER_KEY]
origin_matched = false
all_resources.each do |r|
if r.allow_origin?(origin, env)
origin_matched = true
if found = r.find_resource(path)
return [found, nil]
end
end
end
[nil, origin_matched ? Result::MISS_NO_PATH : Result::MISS_NO_ORIGIN]
end
class Result
HEADER_KEY = 'X-Rack-CORS'.freeze
MISS_NO_ORIGIN = 'no-origin'.freeze
MISS_NO_PATH = 'no-path'.freeze
attr_accessor :preflight, :hit, :miss_reason
def hit?
!!hit
end
def preflight?
!!preflight
end
def self.hit(env)
r = Result.new
r.preflight = false
r.hit = true
env[ENV_KEY] = r
end
def self.miss(env, reason)
r = Result.new
r.preflight = false
r.hit = false
r.miss_reason = reason
env[ENV_KEY] = r
end
def self.preflight_hit(env)
r = Result.new
r.preflight = true
r.hit = true
env[ENV_KEY] = r
end
def self.preflight_miss(env, reason)
r = Result.new
r.preflight = true
r.hit = false
r.miss_reason = reason
env[ENV_KEY] = r
end
def append_header(headers)
headers[HEADER_KEY] = if hit?
preflight? ? 'preflight-hit' : 'hit'
else
[
(preflight? ? 'preflight-miss' : 'preflight-hit'),
miss_reason
].join('; ')
end
end
end
class Resources
def initialize
@origins = []
@resources = []
@public_resources = false
end
def origins(*args, &blk)
@origins = args.flatten.collect do |n|
case n
when Regexp,
/^https?:\/\//,
'file://' then n
when '*' then @public_resources = true; n
else Regexp.compile("^[a-z][a-z0-9.+-]*:\\\/\\\/#{Regexp.quote(n)}")
end
end.flatten
@origins.push(blk) if blk
end
def resource(path, opts={})
@resources << Resource.new(public_resources?, path, opts)
end
def public_resources?
@public_resources
end
def allow_origin?(source,env = {})
return true if public_resources?
effective_source = (source == 'null' ? 'file://' : source)
return !! @origins.detect do |origin|
if origin.is_a?(Proc)
origin.call(source,env)
else
origin === effective_source
end
end
end
def find_resource(path)
@resources.detect{|r| r.match?(path)}
end
end
class Resource
attr_accessor :path, :methods, :headers, :expose, :max_age, :credentials, :pattern
def initialize(public_resource, path, opts={})
self.path = path
self.methods = prepare_and_validate_methods_option(opts[:methods]) || [:get]
self.credentials = opts[:credentials].nil? ? true : opts[:credentials]
self.max_age = opts[:max_age] || 1728000
self.pattern = compile(path)
@public_resource = public_resource
self.headers = case opts[:headers]
when :any then :any
when nil then nil
else
[opts[:headers]].flatten.collect{|h| h.downcase}
end
self.expose = opts[:expose] ? [opts[:expose]].flatten : nil
end
def match?(path)
pattern =~ path
end
def process_preflight(env)
return nil if invalid_method_request?(env) || invalid_headers_request?(env)
{'Content-Type' => 'text/plain'}.merge(to_preflight_headers(env))
end
def to_headers(env)
x_origin = env['HTTP_ACCESS_CONTROL_REQUEST_HEADERS']
h = {
'Access-Control-Allow-Origin' => origin_for_response_header(env[ORIGIN_HEADER_KEY]),
'Access-Control-Allow-Methods' => methods.collect{|m| m.to_s.upcase}.join(', '),
'Access-Control-Expose-Headers' => expose.nil? ? '' : expose.join(', '),
'Access-Control-Max-Age' => max_age.to_s }
h['Access-Control-Allow-Credentials'] = 'true' if credentials
h
end
protected
def public_resource?
@public_resource
end
def origin_for_response_header(origin)
return '*' if public_resource? && !credentials
origin
end
def to_preflight_headers(env)
h = to_headers(env)
if env['HTTP_ACCESS_CONTROL_REQUEST_HEADERS']
h.merge!('Access-Control-Allow-Headers' => env['HTTP_ACCESS_CONTROL_REQUEST_HEADERS'])
end
h
end
def invalid_method_request?(env)
request_method = env['HTTP_ACCESS_CONTROL_REQUEST_METHOD']
request_method.nil? || !methods.include?(request_method.downcase.to_sym)
end
def invalid_headers_request?(env)
request_headers = env['HTTP_ACCESS_CONTROL_REQUEST_HEADERS']
request_headers && !allow_headers?(request_headers)
end
def allow_headers?(request_headers)
return false if headers.nil?
headers == :any || begin
request_headers = request_headers.split(/,\s*/) if request_headers.kind_of?(String)
request_headers.all?{|h| headers.include?(h.downcase)}
end
end
def prepare_and_validate_methods_option setting
raise ArgumentError.new("rack-cors methods must be an single HTTP verb, or an array of verbs") if setting && setting == :any
ensure_enum setting
end
def ensure_enum(v)
return nil if v.nil?
[v].flatten
end
def compile(path)
if path.respond_to? :to_str
special_chars = %w{. + ( )}
pattern =
path.to_str.gsub(/((:\w+)|[\*#{special_chars.join}])/) do |match|
case match
when "*"
"(.*?)"
when *special_chars
Regexp.escape(match)
else
"([^/?&#]+)"
end
end
/^#{pattern}$/
elsif path.respond_to? :match
path
else
raise TypeError, path
end
end
end
end
end