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configuration.rb
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configuration.rb
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module SecureHeaders
class Configuration
DEFAULT_CONFIG = :default
NOOP_CONFIGURATION = "secure_headers_noop_config"
class NotYetConfiguredError < StandardError; end
class IllegalPolicyModificationError < StandardError; end
class << self
# Public: Set the global default configuration.
#
# Optionally supply a block to override the defaults set by this library.
#
# Returns the newly created config.
def default(&block)
config = new(&block)
add_noop_configuration
add_configuration(DEFAULT_CONFIG, config)
end
alias_method :configure, :default
# Public: create a named configuration that overrides the default config.
#
# name - use an idenfier for the override config.
# base - override another existing config, or override the default config
# if no value is supplied.
#
# Returns: the newly created config
def override(name, base = DEFAULT_CONFIG, &block)
unless get(base)
raise NotYetConfiguredError, "#{base} policy not yet supplied"
end
override = @configurations[base].dup
override.instance_eval &block if block_given?
add_configuration(name, override)
end
# Public: retrieve a global configuration object
#
# Returns the configuration with a given name or raises a
# NotYetConfiguredError if `default` has not been called.
def get(name = DEFAULT_CONFIG)
if @configurations.nil?
raise NotYetConfiguredError, "Default policy not yet supplied"
end
@configurations[name]
end
private
# Private: add a valid configuration to the global set of named configs.
#
# config - the config to store
# name - the lookup value for this config
#
# Raises errors if the config is invalid or if a config named `name`
# already exists.
#
# Returns the config, if valid
def add_configuration(name, config)
config.validate_config!
@configurations ||= {}
config.send(:cache_headers!)
config.freeze
@configurations[name] = config
end
# Private: Automatically add an "opt-out of everything" override.
#
# Returns the noop config
def add_noop_configuration
noop_config = new do |config|
ALL_HEADER_CLASSES.each do |klass|
config.send("#{klass::CONFIG_KEY}=", OPT_OUT)
end
config.dynamic_csp = OPT_OUT
end
add_configuration(NOOP_CONFIGURATION, noop_config)
end
# Public: perform a basic deep dup. The shallow copy provided by dup/clone
# can lead to modifying parent objects.
def deep_copy(config)
config.each_with_object({}) do |(key, value), hash|
hash[key] = if value.is_a?(Array)
value.dup
else
value
end
end
end
# Private: convenience method purely DRY things up. The value may not be a
# hash (e.g. OPT_OUT, nil)
def deep_copy_if_hash(value)
if value.is_a?(Hash)
deep_copy(value)
else
value
end
end
end
attr_writer :hsts, :x_frame_options, :x_content_type_options,
:x_xss_protection, :x_download_options, :x_permitted_cross_domain_policies,
:hpkp, :dynamic_csp, :secure_cookies
attr_reader :cached_headers, :csp, :dynamic_csp, :secure_cookies
def initialize(&block)
self.hpkp = OPT_OUT
self.csp = self.class.send(:deep_copy, CSP::DEFAULT_CONFIG)
instance_eval &block if block_given?
end
# Public: copy everything but the cached headers
#
# Returns a deep-dup'd copy of this configuration.
def dup
copy = self.class.new
copy.secure_cookies = @secure_cookies
copy.csp = self.class.send(:deep_copy_if_hash, @csp)
copy.dynamic_csp = self.class.send(:deep_copy_if_hash, @dynamic_csp)
copy.cached_headers = self.class.send(:deep_copy_if_hash, @cached_headers)
copy
end
def opt_out(header)
send("#{header}=", OPT_OUT)
if header == CSP::CONFIG_KEY
dynamic_csp = OPT_OUT
end
self.cached_headers.delete(header)
end
def update_x_frame_options(value)
self.cached_headers[XFrameOptions::CONFIG_KEY] = XFrameOptions.make_header(value)
end
# Public: generated cached headers for a specific user agent.
def rebuild_csp_header_cache!(user_agent)
self.cached_headers[CSP::CONFIG_KEY] = {}
unless current_csp == OPT_OUT
user_agent = UserAgent.parse(user_agent)
variation = CSP.ua_to_variation(user_agent)
self.cached_headers[CSP::CONFIG_KEY][variation] = CSP.make_header(current_csp, user_agent)
end
end
def current_csp
@dynamic_csp || @csp
end
# Public: validates all configurations values.
#
# Raises various configuration errors if any invalid config is detected.
#
# Returns nothing
def validate_config!
StrictTransportSecurity.validate_config!(@hsts)
ContentSecurityPolicy.validate_config!(@csp)
XFrameOptions.validate_config!(@x_frame_options)
XContentTypeOptions.validate_config!(@x_content_type_options)
XXssProtection.validate_config!(@x_xss_protection)
XDownloadOptions.validate_config!(@x_download_options)
XPermittedCrossDomainPolicies.validate_config!(@x_permitted_cross_domain_policies)
PublicKeyPins.validate_config!(@hpkp)
end
protected
def csp=(new_csp)
if self.dynamic_csp
raise IllegalPolicyModificationError, "You are attempting to modify CSP settings directly. Use dynamic_csp= isntead."
end
@csp = new_csp
end
def cached_headers=(headers)
@cached_headers = headers
end
private
# Public: Precompute the header names and values for this configuraiton.
# Ensures that headers generated at configure time, not on demand.
#
# Returns the cached headers
def cache_headers!
# generate defaults for the "easy" headers
headers = (ALL_HEADERS_BESIDES_CSP).each_with_object({}) do |klass, hash|
config = instance_variable_get("@#{klass::CONFIG_KEY}")
unless config == OPT_OUT
hash[klass::CONFIG_KEY] = klass.make_header(config).freeze
end
end
generate_csp_headers(headers)
headers.freeze
self.cached_headers = headers
end
# Private: adds CSP headers for each variation of CSP support.
#
# headers - generated headers are added to this hash namespaced by The
# different variations
#
# Returns nothing
def generate_csp_headers(headers)
unless @csp == OPT_OUT
headers[CSP::CONFIG_KEY] = {}
csp_config = self.current_csp
CSP::VARIATIONS.each do |name, _|
csp = CSP.make_header(csp_config, UserAgent.parse(name))
headers[CSP::CONFIG_KEY][name] = csp.freeze
end
end
end
end
end