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require 'rack/utils'
require 'forwardable'
module Rack
# Rack::Lint validates your application and the requests and
# responses according to the Rack spec.
class Lint
def initialize(app)
@app = app
@content_length = nil
end
# :stopdoc:
class LintError < RuntimeError; end
module Assertion
def assert(message, &block)
unless block.call
raise LintError, message
end
end
end
include Assertion
## This specification aims to formalize the Rack protocol. You
## can (and should) use Rack::Lint to enforce it.
##
## When you develop middleware, be sure to add a Lint before and
## after to catch all mistakes.
## = Rack applications
## A Rack application is a Ruby object (not a class) that
## responds to +call+.
def call(env=nil)
dup._call(env)
end
def _call(env)
## It takes exactly one argument, the *environment*
assert("No env given") { env }
check_env env
env['rack.input'] = InputWrapper.new(env['rack.input'])
env['rack.errors'] = ErrorWrapper.new(env['rack.errors'])
## and returns an Array of exactly three values:
status, headers, @body = @app.call(env)
## The *status*,
check_status status
## the *headers*,
check_headers headers
check_hijack_response headers, env
## and the *body*.
check_content_type status, headers
check_content_length status, headers
@head_request = env[REQUEST_METHOD] == "HEAD"
[status, headers, self]
end
## == The Environment
def check_env(env)
## The environment must be an instance of Hash that includes
## CGI-like headers. The application is free to modify the
## environment.
assert("env #{env.inspect} is not a Hash, but #{env.class}") {
env.kind_of? Hash
}
##
## The environment is required to include these variables
## (adopted from PEP333), except when they'd be empty, but see
## below.
## <tt>REQUEST_METHOD</tt>:: The HTTP request method, such as
## "GET" or "POST". This cannot ever
## be an empty string, and so is
## always required.
## <tt>SCRIPT_NAME</tt>:: The initial portion of the request
## URL's "path" that corresponds to the
## application object, so that the
## application knows its virtual
## "location". This may be an empty
## string, if the application corresponds
## to the "root" of the server.
## <tt>PATH_INFO</tt>:: The remainder of the request URL's
## "path", designating the virtual
## "location" of the request's target
## within the application. This may be an
## empty string, if the request URL targets
## the application root and does not have a
## trailing slash. This value may be
## percent-encoded when I originating from
## a URL.
## <tt>QUERY_STRING</tt>:: The portion of the request URL that
## follows the <tt>?</tt>, if any. May be
## empty, but is always required!
## <tt>SERVER_NAME</tt>, <tt>SERVER_PORT</tt>::
## When combined with <tt>SCRIPT_NAME</tt> and
## <tt>PATH_INFO</tt>, these variables can be
## used to complete the URL. Note, however,
## that <tt>HTTP_HOST</tt>, if present,
## should be used in preference to
## <tt>SERVER_NAME</tt> for reconstructing
## the request URL.
## <tt>SERVER_NAME</tt> and <tt>SERVER_PORT</tt>
## can never be empty strings, and so
## are always required.
## <tt>HTTP_</tt> Variables:: Variables corresponding to the
## client-supplied HTTP request
## headers (i.e., variables whose
## names begin with <tt>HTTP_</tt>). The
## presence or absence of these
## variables should correspond with
## the presence or absence of the
## appropriate HTTP header in the
## request. See
## <a href="https://tools.ietf.org/html/rfc3875#section-4.1.18">
## RFC3875 section 4.1.18</a> for
## specific behavior.
## In addition to this, the Rack environment must include these
## Rack-specific variables:
## <tt>rack.version</tt>:: The Array representing this version of Rack
## See Rack::VERSION, that corresponds to
## the version of this SPEC.
## <tt>rack.url_scheme</tt>:: +http+ or +https+, depending on the
## request URL.
## <tt>rack.input</tt>:: See below, the input stream.
## <tt>rack.errors</tt>:: See below, the error stream.
## <tt>rack.multithread</tt>:: true if the application object may be
## simultaneously invoked by another thread
## in the same process, false otherwise.
## <tt>rack.multiprocess</tt>:: true if an equivalent application object
## may be simultaneously invoked by another
## process, false otherwise.
## <tt>rack.run_once</tt>:: true if the server expects
## (but does not guarantee!) that the
## application will only be invoked this one
## time during the life of its containing
## process. Normally, this will only be true
## for a server based on CGI
## (or something similar).
## <tt>rack.hijack?</tt>:: present and true if the server supports
## connection hijacking. See below, hijacking.
## <tt>rack.hijack</tt>:: an object responding to #call that must be
## called at least once before using
## rack.hijack_io.
## It is recommended #call return rack.hijack_io
## as well as setting it in env if necessary.
## <tt>rack.hijack_io</tt>:: if rack.hijack? is true, and rack.hijack
## has received #call, this will contain
## an object resembling an IO. See hijacking.
## Additional environment specifications have approved to
## standardized middleware APIs. None of these are required to
## be implemented by the server.
## <tt>rack.session</tt>:: A hash like interface for storing
## request session data.
## The store must implement:
if session = env['rack.session']
## store(key, value) (aliased as []=);
assert("session #{session.inspect} must respond to store and []=") {
session.respond_to?(:store) && session.respond_to?(:[]=)
}
## fetch(key, default = nil) (aliased as []);
assert("session #{session.inspect} must respond to fetch and []") {
session.respond_to?(:fetch) && session.respond_to?(:[])
}
## delete(key);
assert("session #{session.inspect} must respond to delete") {
session.respond_to?(:delete)
}
## clear;
assert("session #{session.inspect} must respond to clear") {
session.respond_to?(:clear)
}
end
## <tt>rack.logger</tt>:: A common object interface for logging messages.
## The object must implement:
if logger = env['rack.logger']
## info(message, &block)
assert("logger #{logger.inspect} must respond to info") {
logger.respond_to?(:info)
}
## debug(message, &block)
assert("logger #{logger.inspect} must respond to debug") {
logger.respond_to?(:debug)
}
## warn(message, &block)
assert("logger #{logger.inspect} must respond to warn") {
logger.respond_to?(:warn)
}
## error(message, &block)
assert("logger #{logger.inspect} must respond to error") {
logger.respond_to?(:error)
}
## fatal(message, &block)
assert("logger #{logger.inspect} must respond to fatal") {
logger.respond_to?(:fatal)
}
end
## <tt>rack.multipart.buffer_size</tt>:: An Integer hint to the multipart parser as to what chunk size to use for reads and writes.
if bufsize = env['rack.multipart.buffer_size']
assert("rack.multipart.buffer_size must be an Integer > 0 if specified") {
bufsize.is_a?(Integer) && bufsize > 0
}
end
## <tt>rack.multipart.tempfile_factory</tt>:: An object responding to #call with two arguments, the filename and content_type given for the multipart form field, and returning an IO-like object that responds to #<< and optionally #rewind. This factory will be used to instantiate the tempfile for each multipart form file upload field, rather than the default class of Tempfile.
if tempfile_factory = env['rack.multipart.tempfile_factory']
assert("rack.multipart.tempfile_factory must respond to #call") { tempfile_factory.respond_to?(:call) }
env['rack.multipart.tempfile_factory'] = lambda do |filename, content_type|
io = tempfile_factory.call(filename, content_type)
assert("rack.multipart.tempfile_factory return value must respond to #<<") { io.respond_to?(:<<) }
io
end
end
## The server or the application can store their own data in the
## environment, too. The keys must contain at least one dot,
## and should be prefixed uniquely. The prefix <tt>rack.</tt>
## is reserved for use with the Rack core distribution and other
## accepted specifications and must not be used otherwise.
##
%w[REQUEST_METHOD SERVER_NAME SERVER_PORT
QUERY_STRING
rack.version rack.input rack.errors
rack.multithread rack.multiprocess rack.run_once].each { |header|
assert("env missing required key #{header}") { env.include? header }
}
## The environment must not contain the keys
## <tt>HTTP_CONTENT_TYPE</tt> or <tt>HTTP_CONTENT_LENGTH</tt>
## (use the versions without <tt>HTTP_</tt>).
%w[HTTP_CONTENT_TYPE HTTP_CONTENT_LENGTH].each { |header|
assert("env contains #{header}, must use #{header[5,-1]}") {
not env.include? header
}
}
## The CGI keys (named without a period) must have String values.
env.each { |key, value|
next if key.include? "." # Skip extensions
assert("env variable #{key} has non-string value #{value.inspect}") {
value.kind_of? String
}
}
## There are the following restrictions:
## * <tt>rack.version</tt> must be an array of Integers.
assert("rack.version must be an Array, was #{env["rack.version"].class}") {
env["rack.version"].kind_of? Array
}
## * <tt>rack.url_scheme</tt> must either be +http+ or +https+.
assert("rack.url_scheme unknown: #{env["rack.url_scheme"].inspect}") {
%w[http https].include? env["rack.url_scheme"]
}
## * There must be a valid input stream in <tt>rack.input</tt>.
check_input env["rack.input"]
## * There must be a valid error stream in <tt>rack.errors</tt>.
check_error env["rack.errors"]
## * There may be a valid hijack stream in <tt>rack.hijack_io</tt>
check_hijack env
## * The <tt>REQUEST_METHOD</tt> must be a valid token.
assert("REQUEST_METHOD unknown: #{env[REQUEST_METHOD]}") {
env["REQUEST_METHOD"] =~ /\A[0-9A-Za-z!\#$%&'*+.^_`|~-]+\z/
}
## * The <tt>SCRIPT_NAME</tt>, if non-empty, must start with <tt>/</tt>
assert("SCRIPT_NAME must start with /") {
!env.include?("SCRIPT_NAME") ||
env["SCRIPT_NAME"] == "" ||
env["SCRIPT_NAME"] =~ /\A\//
}
## * The <tt>PATH_INFO</tt>, if non-empty, must start with <tt>/</tt>
assert("PATH_INFO must start with /") {
!env.include?("PATH_INFO") ||
env["PATH_INFO"] == "" ||
env["PATH_INFO"] =~ /\A\//
}
## * The <tt>CONTENT_LENGTH</tt>, if given, must consist of digits only.
assert("Invalid CONTENT_LENGTH: #{env["CONTENT_LENGTH"]}") {
!env.include?("CONTENT_LENGTH") || env["CONTENT_LENGTH"] =~ /\A\d+\z/
}
## * One of <tt>SCRIPT_NAME</tt> or <tt>PATH_INFO</tt> must be
## set. <tt>PATH_INFO</tt> should be <tt>/</tt> if
## <tt>SCRIPT_NAME</tt> is empty.
assert("One of SCRIPT_NAME or PATH_INFO must be set (make PATH_INFO '/' if SCRIPT_NAME is empty)") {
env["SCRIPT_NAME"] || env["PATH_INFO"]
}
## <tt>SCRIPT_NAME</tt> never should be <tt>/</tt>, but instead be empty.
assert("SCRIPT_NAME cannot be '/', make it '' and PATH_INFO '/'") {
env["SCRIPT_NAME"] != "/"
}
end
## === The Input Stream
##
## The input stream is an IO-like object which contains the raw HTTP
## POST data.
def check_input(input)
## When applicable, its external encoding must be "ASCII-8BIT" and it
## must be opened in binary mode, for Ruby 1.9 compatibility.
assert("rack.input #{input} does not have ASCII-8BIT as its external encoding") {
input.external_encoding.name == "ASCII-8BIT"
} if input.respond_to?(:external_encoding)
assert("rack.input #{input} is not opened in binary mode") {
input.binmode?
} if input.respond_to?(:binmode?)
## The input stream must respond to +gets+, +each+, +read+ and +rewind+.
[:gets, :each, :read, :rewind].each { |method|
assert("rack.input #{input} does not respond to ##{method}") {
input.respond_to? method
}
}
end
class InputWrapper
include Assertion
def initialize(input)
@input = input
end
## * +gets+ must be called without arguments and return a string,
## or +nil+ on EOF.
def gets(*args)
assert("rack.input#gets called with arguments") { args.size == 0 }
v = @input.gets
assert("rack.input#gets didn't return a String") {
v.nil? or v.kind_of? String
}
v
end
## * +read+ behaves like IO#read.
## Its signature is <tt>read([length, [buffer]])</tt>.
##
## If given, +length+ must be a non-negative Integer (>= 0) or +nil+,
## and +buffer+ must be a String and may not be nil.
##
## If +length+ is given and not nil, then this method reads at most
## +length+ bytes from the input stream.
##
## If +length+ is not given or nil, then this method reads
## all data until EOF.
##
## When EOF is reached, this method returns nil if +length+ is given
## and not nil, or "" if +length+ is not given or is nil.
##
## If +buffer+ is given, then the read data will be placed
## into +buffer+ instead of a newly created String object.
def read(*args)
assert("rack.input#read called with too many arguments") {
args.size <= 2
}
if args.size >= 1
assert("rack.input#read called with non-integer and non-nil length") {
args.first.kind_of?(Integer) || args.first.nil?
}
assert("rack.input#read called with a negative length") {
args.first.nil? || args.first >= 0
}
end
if args.size >= 2
assert("rack.input#read called with non-String buffer") {
args[1].kind_of?(String)
}
end
v = @input.read(*args)
assert("rack.input#read didn't return nil or a String") {
v.nil? or v.kind_of? String
}
if args[0].nil?
assert("rack.input#read(nil) returned nil on EOF") {
!v.nil?
}
end
v
end
## * +each+ must be called without arguments and only yield Strings.
def each(*args)
assert("rack.input#each called with arguments") { args.size == 0 }
@input.each { |line|
assert("rack.input#each didn't yield a String") {
line.kind_of? String
}
yield line
}
end
## * +rewind+ must be called without arguments. It rewinds the input
## stream back to the beginning. It must not raise Errno::ESPIPE:
## that is, it may not be a pipe or a socket. Therefore, handler
## developers must buffer the input data into some rewindable object
## if the underlying input stream is not rewindable.
def rewind(*args)
assert("rack.input#rewind called with arguments") { args.size == 0 }
assert("rack.input#rewind raised Errno::ESPIPE") {
begin
@input.rewind
true
rescue Errno::ESPIPE
false
end
}
end
## * +close+ must never be called on the input stream.
def close(*args)
assert("rack.input#close must not be called") { false }
end
end
## === The Error Stream
def check_error(error)
## The error stream must respond to +puts+, +write+ and +flush+.
[:puts, :write, :flush].each { |method|
assert("rack.error #{error} does not respond to ##{method}") {
error.respond_to? method
}
}
end
class ErrorWrapper
include Assertion
def initialize(error)
@error = error
end
## * +puts+ must be called with a single argument that responds to +to_s+.
def puts(str)
@error.puts str
end
## * +write+ must be called with a single argument that is a String.
def write(str)
assert("rack.errors#write not called with a String") { str.kind_of? String }
@error.write str
end
## * +flush+ must be called without arguments and must be called
## in order to make the error appear for sure.
def flush
@error.flush
end
## * +close+ must never be called on the error stream.
def close(*args)
assert("rack.errors#close must not be called") { false }
end
end
class HijackWrapper
include Assertion
extend Forwardable
REQUIRED_METHODS = [
:read, :write, :read_nonblock, :write_nonblock, :flush, :close,
:close_read, :close_write, :closed?
]
def_delegators :@io, *REQUIRED_METHODS
def initialize(io)
@io = io
REQUIRED_METHODS.each do |meth|
assert("rack.hijack_io must respond to #{meth}") { io.respond_to? meth }
end
end
end
## === Hijacking
#
# AUTHORS: n.b. The trailing whitespace between paragraphs is important and
# should not be removed. The whitespace creates paragraphs in the RDoc
# output.
#
## ==== Request (before status)
def check_hijack(env)
if env['rack.hijack?']
## If rack.hijack? is true then rack.hijack must respond to #call.
original_hijack = env['rack.hijack']
assert("rack.hijack must respond to call") { original_hijack.respond_to?(:call) }
env['rack.hijack'] = proc do
## rack.hijack must return the io that will also be assigned (or is
## already present, in rack.hijack_io.
io = original_hijack.call
HijackWrapper.new(io)
##
## rack.hijack_io must respond to:
## <tt>read, write, read_nonblock, write_nonblock, flush, close,
## close_read, close_write, closed?</tt>
##
## The semantics of these IO methods must be a best effort match to
## those of a normal ruby IO or Socket object, using standard
## arguments and raising standard exceptions. Servers are encouraged
## to simply pass on real IO objects, although it is recognized that
## this approach is not directly compatible with SPDY and HTTP 2.0.
##
## IO provided in rack.hijack_io should preference the
## IO::WaitReadable and IO::WaitWritable APIs wherever supported.
##
## There is a deliberate lack of full specification around
## rack.hijack_io, as semantics will change from server to server.
## Users are encouraged to utilize this API with a knowledge of their
## server choice, and servers may extend the functionality of
## hijack_io to provide additional features to users. The purpose of
## rack.hijack is for Rack to "get out of the way", as such, Rack only
## provides the minimum of specification and support.
env['rack.hijack_io'] = HijackWrapper.new(env['rack.hijack_io'])
io
end
else
##
## If rack.hijack? is false, then rack.hijack should not be set.
assert("rack.hijack? is false, but rack.hijack is present") { env['rack.hijack'].nil? }
##
## If rack.hijack? is false, then rack.hijack_io should not be set.
assert("rack.hijack? is false, but rack.hijack_io is present") { env['rack.hijack_io'].nil? }
end
end
## ==== Response (after headers)
## It is also possible to hijack a response after the status and headers
## have been sent.
def check_hijack_response(headers, env)
# this check uses headers like a hash, but the spec only requires
# headers respond to #each
headers = Rack::Utils::HeaderHash.new(headers)
## In order to do this, an application may set the special header
## <tt>rack.hijack</tt> to an object that responds to <tt>call</tt>
## accepting an argument that conforms to the <tt>rack.hijack_io</tt>
## protocol.
##
## After the headers have been sent, and this hijack callback has been
## called, the application is now responsible for the remaining lifecycle
## of the IO. The application is also responsible for maintaining HTTP
## semantics. Of specific note, in almost all cases in the current SPEC,
## applications will have wanted to specify the header Connection:close in
## HTTP/1.1, and not Connection:keep-alive, as there is no protocol for
## returning hijacked sockets to the web server. For that purpose, use the
## body streaming API instead (progressively yielding strings via each).
##
## Servers must ignore the <tt>body</tt> part of the response tuple when
## the <tt>rack.hijack</tt> response API is in use.
if env['rack.hijack?'] && headers['rack.hijack']
assert('rack.hijack header must respond to #call') {
headers['rack.hijack'].respond_to? :call
}
original_hijack = headers['rack.hijack']
headers['rack.hijack'] = proc do |io|
original_hijack.call HijackWrapper.new(io)
end
else
##
## The special response header <tt>rack.hijack</tt> must only be set
## if the request env has <tt>rack.hijack?</tt> <tt>true</tt>.
assert('rack.hijack header must not be present if server does not support hijacking') {
headers['rack.hijack'].nil?
}
end
end
## ==== Conventions
## * Middleware should not use hijack unless it is handling the whole
## response.
## * Middleware may wrap the IO object for the response pattern.
## * Middleware should not wrap the IO object for the request pattern. The
## request pattern is intended to provide the hijacker with "raw tcp".
## == The Response
## === The Status
def check_status(status)
## This is an HTTP status. When parsed as integer (+to_i+), it must be
## greater than or equal to 100.
assert("Status must be >=100 seen as integer") { status.to_i >= 100 }
end
## === The Headers
def check_headers(header)
## The header must respond to +each+, and yield values of key and value.
assert("headers object should respond to #each, but doesn't (got #{header.class} as headers)") {
header.respond_to? :each
}
header.each { |key, value|
## Special headers starting "rack." are for communicating with the
## server, and must not be sent back to the client.
next if key =~ /^rack\..+$/
## The header keys must be Strings.
assert("header key must be a string, was #{key.class}") {
key.kind_of? String
}
## The header must not contain a +Status+ key.
assert("header must not contain Status") { key.downcase != "status" }
## The header must conform to RFC7230 token specification, i.e. cannot
## contain non-printable ASCII, DQUOTE or "(),/:;<=>?@[\]{}".
assert("invalid header name: #{key}") { key !~ /[\(\),\/:;<=>\?@\[\\\]{}[:cntrl:]]/ }
## The values of the header must be Strings,
assert("a header value must be a String, but the value of " +
"'#{key}' is a #{value.class}") { value.kind_of? String }
## consisting of lines (for multiple header values, e.g. multiple
## <tt>Set-Cookie</tt> values) separated by "\\n".
value.split("\n").each { |item|
## The lines must not contain characters below 037.
assert("invalid header value #{key}: #{item.inspect}") {
item !~ /[\000-\037]/
}
}
}
end
## === The Content-Type
def check_content_type(status, headers)
headers.each { |key, value|
## There must not be a <tt>Content-Type</tt>, when the +Status+ is 1xx,
## 204, 205 or 304.
if key.downcase == "content-type"
assert("Content-Type header found in #{status} response, not allowed") {
not Rack::Utils::STATUS_WITH_NO_ENTITY_BODY.include? status.to_i
}
return
end
}
end
## === The Content-Length
def check_content_length(status, headers)
headers.each { |key, value|
if key.downcase == 'content-length'
## There must not be a <tt>Content-Length</tt> header when the
## +Status+ is 1xx, 204, 205 or 304.
assert("Content-Length header found in #{status} response, not allowed") {
not Rack::Utils::STATUS_WITH_NO_ENTITY_BODY.include? status.to_i
}
@content_length = value
end
}
end
def verify_content_length(bytes)
if @head_request
assert("Response body was given for HEAD request, but should be empty") {
bytes == 0
}
elsif @content_length
assert("Content-Length header was #{@content_length}, but should be #{bytes}") {
@content_length == bytes.to_s
}
end
end
## === The Body
def each
@closed = false
bytes = 0
## The Body must respond to +each+
assert("Response body must respond to each") do
@body.respond_to?(:each)
end
@body.each { |part|
## and must only yield String values.
assert("Body yielded non-string value #{part.inspect}") {
part.kind_of? String
}
bytes += Rack::Utils.bytesize(part)
yield part
}
verify_content_length(bytes)
##
## The Body itself should not be an instance of String, as this will
## break in Ruby 1.9.
##
## If the Body responds to +close+, it will be called after iteration. If
## the body is replaced by a middleware after action, the original body
## must be closed first, if it responds to close.
# XXX howto: assert("Body has not been closed") { @closed }
##
## If the Body responds to +to_path+, it must return a String
## identifying the location of a file whose contents are identical
## to that produced by calling +each+; this may be used by the
## server as an alternative, possibly more efficient way to
## transport the response.
if @body.respond_to?(:to_path)
assert("The file identified by body.to_path does not exist") {
::File.exist? @body.to_path
}
end
##
## The Body commonly is an Array of Strings, the application
## instance itself, or a File-like object.
end
def close
@closed = true
@body.close if @body.respond_to?(:close)
end
# :startdoc:
end
end
## == Thanks
## Some parts of this specification are adopted from PEP333: Python
## Web Server Gateway Interface
## v1.0 (http://www.python.org/dev/peps/pep-0333/). I'd like to thank
## everyone involved in that effort.