Bump version to 0.1.5

There is a regular expression denial of service (ReDoS) vulnerability in
the parser we use to process the `Sec-WebSocket-Extensions` header. It
can be exploited by sending an opening WebSocket handshake to a server
containing a header of the form:

    Sec-WebSocket-Extensions: a;b="\c\c\c\c\c\c\c\c\c\c ...

i.e. a header containing an unclosed string parameter value whose
content is a repeating two-byte sequence of a backslash and some other
character. The parser takes exponential time to reject this header as
invalid, and this can be used to exhaust the server's capacity to
process requests.

This vulnerability has been assigned the identifier CVE-2020-7663.

We believe this flaw stems from the grammar specified for this header.
[RFC 6455][1] defines the grammar for the header as:

    Sec-WebSocket-Extensions = extension-list

    extension-list    = 1#extension
    extension         = extension-token *( ";" extension-param )
    extension-token   = registered-token
    registered-token  = token
    extension-param   = token [ "=" (token | quoted-string) ]

It refers to [RFC 2616][2] for the definitions of `token` and
`quoted-string`, which are:

    token          = 1*<any CHAR except CTLs or separators>
    separators     = "(" | ")" | "<" | ">" | "@"
                   | "," | ";" | ":" | "\" | <">
                   | "/" | "[" | "]" | "?" | "="
                   | "{" | "}" | SP | HT

    quoted-string  = ( <"> *(qdtext | quoted-pair ) <"> )
    qdtext         = <any TEXT except <">>
    quoted-pair    = "\" CHAR

These rely on the `CHAR`, `CTL` and `TEXT` grammars, which are:

    CHAR           = <any US-ASCII character (octets 0 - 127)>
    CTL            = <any US-ASCII control character (octets 0 - 31) and DEL (127)>
    TEXT           = <any OCTET except CTLs, but including LWS>

Other relevant definitions to support these:

    OCTET          = <any 8-bit sequence of data>
    LWS            = [CRLF] 1*( SP | HT )
    CRLF           = CR LF

    HT             = <US-ASCII HT, horizontal-tab (9)>
    LF             = <US-ASCII LF, linefeed (10)>
    CR             = <US-ASCII CR, carriage return (13)>
    SP             = <US-ASCII SP, space (32)>

To expand some of these terms out and write them as regular expressions:

    OCTET         = [\x00-\xFF]
    CHAR          = [\x00-\x7F]
    TEXT          = [\t \x21-\x7E\x80-\xFF]

The allowable bytes for `token` are [\x00-\x7F], except [\x00-\x1F\x7F]
(leaving [\x20-\x7E]) and `separators`, which leaves the following set
of allowed chars:

    ! # $ % & ' * + - . ^ _ ` | ~ [0-9] [A-Z] [a-z]

`quoted-string` contains a repeated pattern of either `qdtext` or
`quoted-pair`. `qdtext` is any `TEXT` byte except <">, and the <">
character is ASCII 34, or 0x22. The <!> character is 0x21. So `qdtext`
can be written either positively as:

    qdtext        = [\t !\x23-\x7E\x80-\xFF]

or negatively, as:

    qdtext        = [^\x00-\x08\x0A-\x1F\x7F"]

We use the negative definition here. The other alternative in the
`quoted-string` pattern is:

    quoted-pair   = \\[\x00-\x7F]

The problem is that the set of bytes matched by `qdtext` includes <\>,
and intersects with the second element of `quoted-pair`. That means the
sequence \c can be matched as either two `qdtext` bytes, or as a single
`quoted-pair`. When the regex engine fails to find a trailing <"> to
close the string, it back-tracks and tries every alternate parse for the
string, which doubles with each pair of bytes in the input.

To fix the ReDoS flaw we need to rewrite the repeating pattern so that
none of its alternate branches can match the same text. For example, we
could try dividing the set of bytes [\x00-\xFF] into those that must not
follow a <\>, those that may follow a <\>, and those that must be
preceded by <\>, and thereby construct a pattern of the form:

    (A|\?B|\C)*

where A, B and C have no characters in common. In our case the three
branch patterns would be:

    A   =   qdtext - CHAR   =   [\x80-\xFF]
    B   =   qdtext & CHAR   =   [\t !\x23-\x7E]
    C   =   CHAR - qdtext   =   [\x00-\x08\x0A-\x1F\x7F"]

These sets do not intersect, and notice <"> appears in set C so must be
preceded by <\>. But we still have a problem: <\> (0x5C) and all the
alphabetic characters are in set B, so the pattern \?B can match all
these:

    c
    \
    \c

So the sequence \c\c\c... still produces exponential back-tracking. It
also fails to parse input like this correctly:

    Sec-WebSocket-Extensions: a; b="c\", d"

Because the grammar allows a single backslash to appear by itself, this
is arguably a syntax error where the parameter `b` has value `c\` and
then a new extension `d` begins with a <"> appearing where it should
not.

So the core problem is with the grammar itself: `qdtext` matches a
single backslash <\>, and `quoted-pair` matches a pair <\\>. So given a
sequence of backslashes there's no canonical parse and the grammar is
ambiguous.

[RFC 7230][3] remedies this problem and makes the grammar clearer.
First, it defines `token` explicitly rather than implicitly:

    token          = 1*tchar

    tchar          = "!" / "#" / "$" / "%" / "&" / "'" / "*"
                   / "+" / "-" / "." / "^" / "_" / "`" / "|" / "~"
                   / DIGIT / ALPHA

And second, it defines `quoted-string` so that backslashes cannot appear
on their own:

     quoted-string  = DQUOTE *( qdtext / quoted-pair ) DQUOTE
     qdtext         = HTAB / SP /%x21 / %x23-5B / %x5D-7E / obs-text
     obs-text       = %x80-FF
     quoted-pair    = "\" ( HTAB / SP / VCHAR / obs-text )

where VCHAR is any printing ASCII character 0x21-0x7E. Notice `qdtext`
is just our previous definition but with 5C excluded, so it cannot
accept a single backslash.

This commit makes this modification to our matching patterns, and
thereby removes the ReDoS vector. Technically this means it does not
match the grammar of RFC 6455, but we expect this to have little or no
practical impact, especially since the one main protocol extension,
`permessage-deflate` ([RFC 7692][4]), does not have any string-valued
parameters.

[1]: https://tools.ietf.org/html/rfc6455#section-9.1
[2]: https://tools.ietf.org/html/rfc2616#section-2.2
[3]: https://tools.ietf.org/html/rfc7230#section-3.2.6
[4]: https://tools.ietf.org/html/rfc7692

.travis.yml

@@ -1,10 +1,23 @@
+sudo: false
 language: ruby
 
 rvm:
   - 1.9.3
   - 2.0.0
-  - 2.1.3
+  - 2.1.10
+  - 2.2.10
+  - 2.3.8
+  - 2.4.10
+  - 2.5.8
+  - 2.6.6
+  - 2.7.1
   - jruby-19mode
-  - rbx-2.2
+  - jruby-9.0
+  - jruby-9.1
+  - jruby-9.2
 
-script: bundle exec rspec -c spec/
+before_install:
+  - '[[ "$(ruby --version)" != *"1.9.3"* ]] || gem update --system 2.4.8'
+
+script:
+  - bundle exec rspec

CHANGELOG.md

@@ -0,0 +1,24 @@
+### 0.1.5 / 2020-06-02
+
+- Remove a ReDoS vulnerability in the header parser (CVE-2020-7663)
+
+### 0.1.4 / 2019-06-10
+
+- Fix a deprecation warning for using the `=~` operator on `true`
+- Change license from MIT to Apache 2.0
+
+### 0.1.3 / 2017-11-11
+
+- Accept extension names and parameters including uppercase letters
+
+### 0.1.2 / 2015-02-19
+
+- Make it safe to call `Extensions#close` if the handshake is not complete
+
+### 0.1.1 / 2014-12-14
+
+- Explicitly require `strscan` which is not loaded in a vanilla Ruby environment
+
+### 0.1.0 / 2014-12-13
+
+- Initial release

CODE_OF_CONDUCT.md

@@ -0,0 +1,4 @@
+# Code of Conduct
+
+All projects under the [Faye](https://github.com/faye) umbrella are covered by
+the [Code of Conduct](https://github.com/faye/code-of-conduct).

LICENSE.md

@@ -0,0 +1,12 @@
+Copyright 2014-2020 James Coglan
+
+Licensed under the Apache License, Version 2.0 (the "License"); you may not use
+this file except in compliance with the License. You may obtain a copy of the
+License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software distributed
+under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
+CONDITIONS OF ANY KIND, either express or implied. See the License for the
+specific language governing permissions and limitations under the License.

README.md

@@ -227,8 +227,8 @@ then the `permessage-deflate` extension will receive the call:
 
 ```rb
 ext.create_server_session([
-  {'server_no_context_takeover' => true, 'server_max_window_bits' => 8},
-  {'server_max_window_bits' => 15}
+  { 'server_no_context_takeover' => true, 'server_max_window_bits' => 8 },
+  { 'server_max_window_bits' => 15 }
 ])
 ```
 
@@ -244,8 +244,8 @@ implement the following methods, as well as the *Session* API listed below.
 ```rb
 client_session.generate_offer
 # e.g.  -> [
-#            {'server_no_context_takeover' => true, 'server_max_window_bits' => 8},
-#            {'server_max_window_bits' => 15}
+#            { 'server_no_context_takeover' => true, 'server_max_window_bits' => 8 },
+#            { 'server_max_window_bits' => 15 }
 #          ]
 ```
 
@@ -270,7 +270,7 @@ must implement the following methods, as well as the *Session* API listed below.
 
 ```rb
 server_session.generate_response
-# e.g.  -> {'server_max_window_bits' => 8}
+# e.g.  -> { 'server_max_window_bits' => 8 }
 ```
 
 This returns the set of parameters the server session wants to send in its
@@ -309,29 +309,5 @@ the session to release any resources it's using.
 
 ## Examples
 
-* Consumer: [websocket-driver](https://github.com/faye/websocket-driver-ruby)
-* Provider: [permessage-deflate](https://github.com/faye/permessage-deflate-ruby)
-
-## License
-
-(The MIT License)
-
-Copyright (c) 2014 James Coglan
-
-Permission is hereby granted, free of charge, to any person obtaining a copy of
-this software and associated documentation files (the 'Software'), to deal in
-the Software without restriction, including without limitation the rights to
-use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
-of the Software, and to permit persons to whom the Software is furnished to do
-so, subject to the following conditions:
-
-The above copyright notice and this permission notice shall be included in all
-copies or substantial portions of the Software.
-
-THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
-AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
-SOFTWARE.
+- Consumer: [websocket-driver](https://github.com/faye/websocket-driver-ruby)
+- Provider: [permessage-deflate](https://github.com/faye/permessage-deflate-ruby)

lib/websocket/extensions.rb

@@ -38,7 +38,7 @@ module WebSocket
       end
 
       if @by_name.has_key?(ext.name)
-        raise TypeError, %Q{An extension with name "#{ext.name}" is already registered}
+        raise TypeError, %Q{An extension with name "#{ ext.name }" is already registered}
       end
 
       @by_name[ext.name] = ext
@@ -78,18 +78,18 @@ module WebSocket
 
       responses.each_offer do |name, params|
         unless record = @index[name]
-          raise ExtensionError, %Q{Server sent am extension response for unknown extension "#{name}"}
+          raise ExtensionError, %Q{Server sent am extension response for unknown extension "#{ name } }
         end
 
         ext, session = *record
 
         if reserved = reserved?(ext)
-          raise ExtensionError, %Q{Server sent two extension responses that use the RSV#{reserved[0]} } +
-                               %Q{ bit: "#{reserved[1]}" and "#{ext.name}"}
+          raise ExtensionError, %Q{Server sent two extension responses that use the RSV#{ reserved[0] }} +
+                                %Q{bit: "#{ reserved[1] }" and "#{ ext.name }"}
         end
 
         unless session.activate(params) == true
-          raise ExtensionError, %Q{Server send unacceptable extension parameters: #{Parser.serialize_params(name, params)}}
+          raise ExtensionError, %Q{Server send unacceptable extension parameters: #{ Parser.serialize_params(name, params) }}
         end
 
         reserve(ext)
@@ -98,9 +98,9 @@ module WebSocket
     end
 
     def generate_response(header)
-      offers   = Parser.parse_header(header)
       sessions = []
       response = []
+      offers   = Parser.parse_header(header)
 
       @in_order.each do |ext|
         offer = offers.by_name(ext.name)
@@ -118,7 +118,7 @@ module WebSocket
     end
 
     def valid_frame_rsv(frame)
-      allowed = {:rsv1 => false, :rsv2 => false, :rsv3 => false}
+      allowed = { :rsv1 => false, :rsv2 => false, :rsv3 => false }
 
       if MESSAGE_OPCODES.include?(frame.opcode)
         @sessions.each do |ext, session|
@@ -155,6 +155,8 @@ module WebSocket
     end
 
     def close
+      return unless @sessions
+
       @sessions.each do |ext, session|
         session.close rescue nil
       end

lib/websocket/extensions/parser.rb

@@ -1,13 +1,15 @@
+require 'strscan'
+
 module WebSocket
   class Extensions
 
     class Parser
-      TOKEN    = /([!#\$%&'\*\+\-\.\^_`\|~0-9a-z]+)/
-      NOTOKEN  = /([^!#\$%&'\*\+\-\.\^_`\|~0-9a-z])/
-      QUOTED   = /"((?:\\[\x00-\x7f]|[^\x00-\x08\x0a-\x1f\x7f"])*)"/
-      PARAM    = %r{#{TOKEN.source}(?:=(?:#{TOKEN.source}|#{QUOTED.source}))?}
-      EXT      = %r{#{TOKEN.source}(?: *; *#{PARAM.source})*}
-      EXT_LIST = %r{^#{EXT.source}(?: *, *#{EXT.source})*$}
+      TOKEN    = /([!#\$%&'\*\+\-\.\^_`\|~0-9A-Za-z]+)/
+      NOTOKEN  = /([^!#\$%&'\*\+\-\.\^_`\|~0-9A-Za-z])/
+      QUOTED   = /"((?:\\[\x00-\x7f]|[^\x00-\x08\x0a-\x1f\x7f"\\])*)"/
+      PARAM    = %r{#{ TOKEN.source }(?:=(?:#{ TOKEN.source }|#{ QUOTED.source }))?}
+      EXT      = %r{#{ TOKEN.source }(?: *; *#{ PARAM.source })*}
+      EXT_LIST = %r{^#{ EXT.source }(?: *, *#{ EXT.source })*$}
       NUMBER   = /^-?(0|[1-9][0-9]*)(\.[0-9]+)?$/
 
       ParseError = Class.new(ArgumentError)
@@ -17,7 +19,7 @@ module WebSocket
         return offers if header == '' or header.nil?
 
         unless header =~ EXT_LIST
-          raise ParseError, "Invalid Sec-WebSocket-Extensions header: #{header}"
+          raise ParseError, "Invalid Sec-WebSocket-Extensions header: #{ header }"
         end
 
         scanner = StringScanner.new(header)
@@ -36,7 +38,7 @@ module WebSocket
             else
               data = true
             end
-            if data =~ NUMBER
+            if data != true and data =~ NUMBER
               data = data =~ /\./ ? data.to_f : data.to_i(10)
             end
 

spec/websocket/extensions/parser_spec.rb

@@ -20,62 +20,68 @@ describe WebSocket::Extensions::Parser do
 
     it "parses one offer with no params" do
       expect(parse 'a').to eq [
-        {:name => "a", :params => {}}
+        { :name => "a", :params => {} }
       ]
     end
 
     it "parses two offers with no params" do
       expect(parse 'a, b').to eq [
-        {:name => "a", :params => {}}, {:name => "b", :params => {}}
+        { :name => "a", :params => {} }, { :name => "b", :params => {} }
       ]
     end
 
     it "parses a duplicate offer name" do
       expect(parse 'a, a').to eq [
-        {:name => "a", :params => {}},
-        {:name => "a", :params => {}}
+        { :name => "a", :params => {} },
+        { :name => "a", :params => {} }
       ]
     end
 
     it "parses a flag" do
       expect(parse 'a; b').to eq [
-        {:name => "a", :params => {"b" => true}}
+        { :name => "a", :params => { "b" => true } }
       ]
     end
 
     it "parses an unquoted param" do
       expect(parse 'a; b=1').to eq [
-        {:name => "a", :params => {"b" => 1}}
+        { :name => "a", :params => { "b" => 1 } }
       ]
     end
 
     it "parses a quoted param" do
       expect(parse 'a; b="hi, \"there"').to eq [
-        {:name => "a", :params => {"b" => 'hi, "there'}}
+        { :name => "a", :params => { "b" => 'hi, "there' } }
       ]
     end
 
     it "parses multiple params" do
       expect(parse 'a; b; c=1; d="hi"').to eq [
-        {:name => "a", :params => {"b" => true, "c" => 1, "d" => "hi"}}
+        { :name => "a", :params => { "b" => true, "c" => 1, "d" => "hi" } }
       ]
     end
 
     it "parses duplicate params" do
       expect(parse 'a; b; c=1; b="hi"').to eq [
-        {:name => "a", :params => {"b" => [true, "hi"], "c" => 1}}
+        { :name => "a", :params => { "b" => [true, "hi"], "c" => 1 } }
       ]
     end
 
     it "parses multiple complex offers" do
       expect(parse 'a; b=1, c, b; d, c; e="hi, there"; e, a; b').to eq [
-        {:name => "a", :params => {"b" => 1}},
-        {:name => "c", :params => {}},
-        {:name => "b", :params => {"d" => true}},
-        {:name => "c", :params => {"e" => ['hi, there', true]}},
-        {:name => "a", :params => {"b" => true}}
+        { :name => "a", :params => { "b" => 1 } },
+        { :name => "c", :params => {} },
+        { :name => "b", :params => { "d" => true } },
+        { :name => "c", :params => { "e" => ['hi, there', true] } },
+        { :name => "a", :params => { "b" => true } }
       ]
     end
+
+    it "rejects a string missing its closing quote" do
+      expect {
+        parse "foo; bar=\"fooa\\a\\a\\a\\a\\a\\a\\a\\a\\a\\a\\a\\a\\a\\a\\a\\a\\a\\a\\a\\a\\a\\a\\a\\a\\a\\a\\a\\a\\a\\a"
+      }.to raise_error(WebSocket::Extensions::Parser::ParseError)
+    end
   end
 
   describe :serialize_params do

spec/websocket/extensions_spec.rb

@@ -39,7 +39,7 @@ describe WebSocket::Extensions do
 
   describe "client sessions" do
     before do
-      @offer = {"mode" => "compress"}
+      @offer = { "mode" => "compress" }
       allow(@ext).to receive(:create_client_session).and_return(@session)
       allow(@session).to receive(:generate_offer).and_return(@offer)
       @extensions.add(@ext)
@@ -248,7 +248,7 @@ describe WebSocket::Extensions do
 
   describe "server sessions" do
     before do
-      @response = {"mode" => "compress"}
+      @response = { "mode" => "compress" }
       allow(@ext).to receive(:create_server_session).and_return(@session)
       allow(@session).to receive(:generate_response).and_return(@response)
 
@@ -269,12 +269,12 @@ describe WebSocket::Extensions do
 
     describe :generate_response do
       it "asks the extension for a server session with the offer" do
-        expect(@ext).to receive(:create_server_session).with([{"flag" => true}]).exactly(1).and_return(@session)
+        expect(@ext).to receive(:create_server_session).with([{ "flag" => true }]).exactly(1).and_return(@session)
         @extensions.generate_response("deflate; flag")
       end
 
       it "asks the extension for a server session with multiple offers" do
-        expect(@ext).to receive(:create_server_session).with([{"a" => true}, {"b" => true}]).exactly(1).and_return(@session)
+        expect(@ext).to receive(:create_server_session).with([{ "a" => true }, { "b" => true }]).exactly(1).and_return(@session)
         @extensions.generate_response("deflate; a, deflate; b")
       end
 
@@ -325,11 +325,14 @@ describe WebSocket::Extensions do
         expect(@extensions.generate_response("deflate, tar")).to eq "deflate; mode=compress"
       end
 
-      it "returns a response for potentially conflicting extensions if their preceeding extensions don't build a session" do
+      it "raises an error if the header is invalid" do
+        expect { @extensions.generate_response("x-webkit- -frame") }.to raise_error(WebSocket::Extensions::Parser::ParseError)
+      end
+
+      it "returns a response for potentially conflicting extensions if their preceding extensions don't build a session" do
         allow(@ext).to receive(:create_server_session).and_return(nil)
         expect(@extensions.generate_response("deflate, tar")).to eq "tar; gzip"
       end
-
     end
   end
 end

websocket-extensions.gemspec

@@ -1,17 +1,17 @@
 Gem::Specification.new do |s|
-  s.name              = 'websocket-extensions'
-  s.version           = '0.1.0'
-  s.summary           = 'Generic extension manager for WebSocket connections'
-  s.author            = 'James Coglan'
-  s.email             = 'jcoglan@gmail.com'
-  s.homepage          = 'http://github.com/faye/websocket-extensions-ruby'
-  s.license           = 'MIT'
+  s.name     = 'websocket-extensions'
+  s.version  = '0.1.5'
+  s.summary  = 'Generic extension manager for WebSocket connections'
+  s.author   = 'James Coglan'
+  s.email    = 'jcoglan@gmail.com'
+  s.homepage = 'https://github.com/faye/websocket-extensions-ruby'
+  s.license  = 'Apache-2.0'
 
-  s.extra_rdoc_files  = %w[README.md]
-  s.rdoc_options      = %w[--main README.md --markup markdown]
-  s.require_paths     = %w[lib]
+  s.extra_rdoc_files = %w[README.md]
+  s.rdoc_options     = %w[--main README.md --markup markdown]
+  s.require_paths    = %w[lib]
 
-  s.files = %w[README.md] + Dir.glob('lib/**/*.rb')
+  s.files = %w[CHANGELOG.md LICENSE.md README.md] + Dir.glob('lib/**/*.rb')
 
   s.add_development_dependency 'rspec'
 end