CVE-2012-2140 (Ruby, published 2012-07-18T18:55Z)
Description: value: The Mail gem before 2.4.3 for Ruby allows remote attackers to execute arbitrary commands via shell metacharacters in a (1) sendmail or (2) exim delivery.
Severity: HIGH (CVSS v3 base score: )
Weakness: CWE-20 \u2014 Improper Input Validation
The product receives input or data, but it does
        not validate or incorrectly validates that the input has the
        properties that are required to process the data safely and
        correctly.
Repository: https://github.com/mikel/mail
Files changed:
lib/mail.rb
lib/mail/core_extensions/shell_escape.rb
lib/mail/network/delivery_methods/exim.rb
lib/mail/network/delivery_methods/sendmail.rb
spec/mail/network/delivery_methods/exim_spec.rb
spec/mail/network/delivery_methods/sendmail_spec.rb
Commit message: Fix security vulnerability allowing command line exploit when using exim or sendmail from the command line


Vulnerable code:
  require 'mail/core_extensions/shellwords' unless String.new.respond_to?(:shellescape)
# encoding: utf-8

# The following is imported from ruby 1.9.2 shellwords.rb
#
module Shellwords
  # Escapes a string so that it can be safely used in a Bourne shell
  # command line.
  #
  # Note that a resulted string should be used unquoted and is not
  # intended for use in double quotes nor in single quotes.
  #
  #   open("| grep #{Shellwords.escape(pattern)} file") { |pipe|
  #     # ...
  #   }
  #
  # +String#shellescape+ is a shorthand for this function.
  #
  #   open("| grep #{pattern.shellescape} file") { |pipe|
  #     # ...
  #   }
  #
  def shellescape(str)
    # An empty argument will be skipped, so return empty quotes.
    return "''" if str.empty?

    str = str.dup

    # Process as a single byte sequence because not all shell
    # implementations are multibyte aware.
    str.gsub!(/([^A-Za-z0-9_\-.,:\/@\n])/n, "\\\\\\1")

    # A LF cannot be escaped with a backslash because a backslash + LF
    # combo is regarded as line continuation and simply ignored.
    str.gsub!(/\n/, "'\n'")

    return str
  end

  module_function :shellescape

  class << self
    alias escape shellescape
  end

end

class String
  # call-seq:
  #   str.shellescape => string
  #
  # Escapes +str+ so that it can be safely used in a Bourne shell
  # command line.  See +Shellwords::shellescape+ for details.
  #
  def shellescape
    Shellwords.escape(self)
  end
end
    def deliver!(mail)
      envelope_from = mail.return_path || mail.sender || mail.from_addrs.first
      return_path = "-f \"#{envelope_from.to_s.shellescape}\"" if envelope_from
      arguments = [settings[:arguments], return_path].compact.join(" ")
      self.class.call(settings[:location], arguments, mail)
      return_path = "-f \"#{envelope_from.to_s.gsub('"', '\"')}\"" if envelope_from
      Sendmail.call(settings[:location], arguments, mail.destinations.collect(&:shellescape).join(" "), mail)
    def Sendmail.call(path, arguments, destinations, mail)


Fixed code:
  require 'mail/core_extensions/shell_escape'
# encoding: utf-8

# The following is an adaptation of ruby 1.9.2's shellwords.rb file,
# it is modified to include '+' in the allowed list to allow for
# sendmail to accept email addresses as the sender with a + in them
#
module Mail
  module ShellEscape
    # Escapes a string so that it can be safely used in a Bourne shell
    # command line.
    #
    # Note that a resulted string should be used unquoted and is not
    # intended for use in double quotes nor in single quotes.
    #
    #   open("| grep #{Shellwords.escape(pattern)} file") { |pipe|
    #     # ...
    #   }
    #
    # +String#shellescape+ is a shorthand for this function.
    #
    #   open("| grep #{pattern.shellescape} file") { |pipe|
    #     # ...
    #   }
    #
    def escape_for_shell(str)
      # An empty argument will be skipped, so return empty quotes.
      return "''" if str.empty?

      str = str.dup

      # Process as a single byte sequence because not all shell
      # implementations are multibyte aware.
      str.gsub!(/([^A-Za-z0-9_\s\+\-.,:\/@\n])/n, "\\\\\\1")

      # A LF cannot be escaped with a backslash because a backslash + LF
      # combo is regarded as line continuation and simply ignored.
      str.gsub!(/\n/, "'\n'")

      return str
    end

    module_function :escape_for_shell
  end
end

class String
  # call-seq:
  #   str.shellescape => string
  #
  # Escapes +str+ so that it can be safely used in a Bourne shell
  # command line.  See +Shellwords::shellescape+ for details.
  #
  def escape_for_shell
    Mail::ShellEscape.escape_for_shell(self)
  end
end
  # A delivery method implementation which sends via exim.
  #
  # To use this, first find out where the exim binary is on your computer,
  # if you are on a mac or unix box, it is usually in /usr/sbin/exim, this will
  # be your exim location.
  #
  #   Mail.defaults do
  #     delivery_method :exim
  #   end
  #
  # Or if your exim binary is not at '/usr/sbin/exim'
  #
  #   Mail.defaults do
  #     delivery_method :exim, :location => '/absolute/path/to/your/exim'
  #   end
  #
  # Then just deliver the email as normal:
  #
  #   Mail.deliver do
  #     to 'mikel@test.lindsaar.net'
  #     from 'ada@test.lindsaar.net'
  #     subject 'testing exim'
  #     body 'testing exim'
  #   end
  #
  # Or by calling deliver on a Mail message
  #
  #   mail = Mail.new do
  #     to 'mikel@test.lindsaar.net'
  #     from 'ada@test.lindsaar.net'
  #     subject 'testing exim'
  #     body 'testing exim'
  #   end
  #
  #   mail.deliver!
    def initialize(values)
      self.settings = { :location       => '/usr/sbin/exim',
                        :arguments      => '-i -t' }.merge(values)
      return_path = "-f " + '"' + envelope_from.escape_for_shell + '"' if envelope_from
      self.class.call(settings[:location], arguments, mail.destinations.collect(&:shellescape).join(" "), mail)
    def self.call(path, arguments, destinations, mail)
# encoding: utf-8
require 'spec_helper'

describe "exim delivery agent" do
  
  before(:each) do
    # Reset all defaults back to original state
    Mail.defaults do
      delivery_method :smtp, { :address              => "localhost",
                               :port                 => 25,
                               :domain               => 'localhost.localdomain',
                               :user_name            => nil,
                               :password             => nil,
                               :authentication       => nil,
                               :enable_starttls_auto => true  }
    end
  end

  it "should send an email using exim" do
    Mail.defaults do
      delivery_method :exim
    end
    
    mail = Mail.new do
      from    'roger@test.lindsaar.net'
      to      'marcel@test.lindsaar.net, bob@test.lindsaar.net'
      subject 'invalid RFC2822'
    end
    
    Mail::Exim.should_receive(:call).with('/usr/sbin/exim', 
                                          '-i -t -f "roger@test.lindsaar.net"', 
                                          'marcel@test.lindsaar.net bob@test.lindsaar.net', 
                                          mail)
    mail.deliver!
  end

  describe "return path" do

    it "should send an email with a return-path using exim" do
      Mail.defaults do
        delivery_method :exim
      end

      mail = Mail.new do
        to "to@test.lindsaar.net"
        from "from@test.lindsaar.net"
        sender "sender@test.lindsaar.net"
        subject "Can't set the return-path"
        return_path "return@test.lindsaar.net"
        message_id "<1234@test.lindsaar.net>"
        body "body"
      end
      
      Mail::Exim.should_receive(:call).with('/usr/sbin/exim',
                                                '-i -t -f "return@test.lindsaar.net"', 
                                                'to@test.lindsaar.net', 
                                                mail)
                                                
      mail.deliver

    end

    it "should use the sender address is no return path is specified" do
      Mail.defaults do
        delivery_method :exim
      end

      mail = Mail.new do
        to "to@test.lindsaar.net"
        from "from@test.lindsaar.net"
        sender "sender@test.lindsaar.net"
        subject "Can't set the return-path"
        message_id "<1234@test.lindsaar.net>"
        body "body"
      end

      Mail::Exim.should_receive(:call).with('/usr/sbin/exim',
                                                '-i -t -f "sender@test.lindsaar.net"', 
                                                'to@test.lindsaar.net', 
                                                mail)

      mail.deliver
    end
    
    it "should use the from address is no return path or sender are specified" do
      Mail.defaults do
        delivery_method :exim
      end

      mail = Mail.new do
        to "to@test.lindsaar.net"
        from "from@test.lindsaar.net"
        subject "Can't set the return-path"
        message_id "<1234@test.lindsaar.net>"
        body "body"
      end

      Mail::Exim.should_receive(:call).with('/usr/sbin/exim',
                                                '-i -t -f "from@test.lindsaar.net"', 
                                                'to@test.lindsaar.net', 
                                                mail)
      mail.deliver
    end

    it "should escape the return path address" do
      Mail.defaults do
        delivery_method :exim
      end

      mail = Mail.new do
        to 'to@test.lindsaar.net'
        from '"from+suffix test"@test.lindsaar.net'
        subject 'Can\'t set the return-path'
        message_id '<1234@test.lindsaar.net>'
        body 'body'
      end

      Mail::Exim.should_receive(:call).with('/usr/sbin/exim',
                                                '-i -t -f "\"from+suffix test\"@test.lindsaar.net"',
                                                'to@test.lindsaar.net',
                                                mail)
      mail.deliver
    end
  end

  it "should still send an email if the settings have been set to nil" do
    Mail.defaults do
      delivery_method :exim, :arguments => nil
    end
    
    mail = Mail.new do
      from    'from@test.lindsaar.net'
      to      'marcel@test.lindsaar.net, bob@test.lindsaar.net'
      subject 'invalid RFC2822'
    end
    
    Mail::Exim.should_receive(:call).with('/usr/sbin/exim', 
                                              '-f "from@test.lindsaar.net"', 
                                              'marcel@test.lindsaar.net bob@test.lindsaar.net', 
                                              mail)
    mail.deliver!
  end

  it "should escape evil haxxor attemptes" do
    Mail.defaults do
      delivery_method :exim, :arguments => nil
    end
    
    mail = Mail.new do
      from    '"foo\";touch /tmp/PWNED;\""@blah.com'
      to      'marcel@test.lindsaar.net'
      subject 'invalid RFC2822'
    end
    
    Mail::Exim.should_receive(:call).with('/usr/sbin/exim', 
                                              "-f \"\\\"foo\\\\\\\"\\;touch /tmp/PWNED\\;\\\\\\\"\\\"@blah.com\"", 
                                              'marcel@test.lindsaar.net', 
                                              mail)
    mail.deliver!
  end
end

  it "should escape evil haxxor attemptes" do
    Mail.defaults do
      delivery_method :sendmail, :arguments => nil
    end
    
    mail = Mail.new do
      from    '"foo\";touch /tmp/PWNED;\""@blah.com'
      to      'marcel@test.lindsaar.net'
      subject 'invalid RFC2822'
    end
    
    Mail::Sendmail.should_receive(:call).with('/usr/sbin/sendmail', 
                                              "-f \"\\\"foo\\\\\\\"\\;touch /tmp/PWNED\\;\\\\\\\"\\\"@blah.com\"", 
                                              'marcel@test.lindsaar.net', 
                                              mail)
    mail.deliver!
  end