Class: MCollective::Security::Aes_security

Inherits:
Base
  • Object
show all
Defined in:
lib/mcollective/security/aes_security.rb

Overview

Impliments a security system that encrypts payloads using AES and secures the AES encrypted data using RSA public/private key encryption.

The design goals of this plugin are:

  • Each actor - clients and servers - can have their own set of public and private keys

  • All actors are uniquely and cryptographically identified

  • Requests are encrypted using the clients private key and anyone that has the public key can see the request. Thus an atacker may see the requests given access to network or machine due to the broadcast nature of mcollective

  • The message time and TTL of messages are cryptographically secured making the ensuring messages can not be replayed with fake TTLs or times

  • Replies are encrypted using the calling clients public key. Thus no-one but the caller can view the contents of replies.

  • Servers can all have their own RSA keys, or share one, or reuse keys created by other PKI using software like Puppet

  • Requests from servers - like registration data - can be secured even to external eaves droppers depending on the level of configuration you are prepared to do

  • Given a network where you can ensure third parties are not able to access the middleware public key distribution can happen automatically

Configuration Options:

Common Options:

# Enable this plugin
securityprovider = aes_security

# Use YAML as serializer
plugin.aes.serializer = yaml

# Send our public key with every request so servers can learn it
plugin.aes.send_pubkey = 1

Clients:

# The clients public and private keys
plugin.aes.client_private = /home/user/.mcollective.d/user-private.pem
plugin.aes.client_public = /home/user/.mcollective.d/user.pem

Servers:

# Where to cache client keys or find manually distributed ones
plugin.aes.client_cert_dir = /etc/mcollective/ssl/clients

# Cache public keys promiscuously from the network (this requires either a ca_cert to be set
  or insecure_learning to be enabled)
plugin.aes.learn_pubkeys = 1

# Do not check if client certificate can be verified by a CA
plugin.aes.insecure_learning = 1

# CA cert used to verify public keys when in learning mode
plugin.aes.ca_cert = /etc/mcollective/ssl/ca.cert

# Log but accept messages that may have been tampered with
plugin.aes.enforce_ttl = 0

# The servers public and private keys
plugin.aes.server_private = /etc/mcollective/ssl/server-private.pem
plugin.aes.server_public = /etc/mcollective/ssl/server-public.pem

Instance Attribute Summary

Attributes inherited from Base

#initiated_by, #stats

Instance Method Summary collapse

Methods inherited from Base

#create_reply, #create_request, inherited, #initialize, #should_process_msg?, #valid_callerid?, #validate_filter?, #validrequest?

Constructor Details

This class inherits a constructor from MCollective::Security::Base

Instance Method Details

#callerid ⇒ Object

sets the caller id to the md5 of the public key



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# File 'lib/mcollective/security/aes_security.rb', line 235

def callerid
  if @initiated_by == :client
    key = client_public_key
  else
    key = server_public_key
  end

  # First try and create a X509 certificate object. If that is possible,
  # we lift the callerid from the cert
  begin
    ssl_cert = OpenSSL::X509::Certificate.new(File.read(key))
    id = "cert=#{certname_from_certificate(ssl_cert)}"
  rescue
    # If the public key is not a certificate, use the file name as callerid
    id = "cert=#{File.basename(key).gsub(/\.pem$/, '')}"
  end

  return id
end

#certname_from_callerid(id) ⇒ Object

Takes our cert=foo callerids and return the foo bit else nil



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# File 'lib/mcollective/security/aes_security.rb', line 376

def certname_from_callerid(id)
  if id =~ /^cert=([\w\.\-]+)/
    return $1
  else
    raise("Received a callerid in an unexpected format: '#{id}', ignoring")
  end
end

#certname_from_certificate(cert) ⇒ Object 



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# File 'lib/mcollective/security/aes_security.rb', line 384

def certname_from_certificate(cert)
  id = cert.subject
  if id.to_s =~ /^\/CN=([\w\.\-]+)/
    return $1
  else
    raise("Received a callerid in an unexpected format in an SSL certificate: '#{id}', ignoring")
  end
end

#client_cert_dir ⇒ Object

Figures out where to get client public certs from the plugin.aes.client_cert_dir config option



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# File 'lib/mcollective/security/aes_security.rb', line 366

def client_cert_dir
  raise("No plugin.aes.client_cert_dir configuration option specified") unless @config.pluginconf.include?("aes.client_cert_dir")
  @config.pluginconf["aes.client_cert_dir"]
end

#client_private_key ⇒ Object

Figures out the client private key either from MCOLLECTIVE_AES_PRIVATE or the plugin.aes.client_private config option



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# File 'lib/mcollective/security/aes_security.rb', line 335

def client_private_key
  return ENV["MCOLLECTIVE_AES_PRIVATE"] if ENV.include?("MCOLLECTIVE_AES_PRIVATE")

  raise("No plugin.aes.client_private configuration option specified") unless @config.pluginconf.include?("aes.client_private")

  return @config.pluginconf["aes.client_private"]
end

#client_public_key ⇒ Object

Figures out the client public key either from MCOLLECTIVE_AES_PUBLIC or the plugin.aes.client_public config option



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# File 'lib/mcollective/security/aes_security.rb', line 345

def client_public_key
  return ENV["MCOLLECTIVE_AES_PUBLIC"] if ENV.include?("MCOLLECTIVE_AES_PUBLIC")

  raise("No plugin.aes.client_public configuration option specified") unless @config.pluginconf.include?("aes.client_public")

  return @config.pluginconf["aes.client_public"]
end

#decodemsg(msg) ⇒ Object 



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# File 'lib/mcollective/security/aes_security.rb', line 68

def decodemsg(msg)
  body = deserialize(msg.payload)

  should_process_msg?(msg, body[:requestid])
  # if we get a message that has a pubkey attached and we're set to learn
  # then add it to the client_cert_dir this should only happen on servers
  # since clients will get replies using their own pubkeys
  if Util.str_to_bool(@config.pluginconf.fetch("aes.learn_pubkeys", false)) && body.include?(:sslpubkey)
    certname = certname_from_callerid(body[:callerid])
    certfile = "#{client_cert_dir}/#{certname}.pem"
    if !File.exist?(certfile)
      if !Util.str_to_bool(@config.pluginconf.fetch("aes.insecure_learning", false))
        if !@config.pluginconf.fetch("aes.ca_cert", nil)
          raise "Cannot verify certificate for '#{certname}'. No CA certificate specified."
        end

        if !validate_certificate(body[:sslpubkey], certname)
          raise "Unable to validate certificate '#{certname}' against CA"
        end

        Log.debug("Verified certificate '#{certname}' against CA")
      else
        Log.warn("Insecure key learning is not a secure method of key distribution. Do NOT use this mode in sensitive environments.")
      end

      Log.debug("Caching client cert in #{certfile}")
      File.open(certfile, "w") {|f| f.print body[:sslpubkey]}
    else
      Log.debug("Not caching client cert. File #{certfile} already exists.")
    end
  end

  cryptdata = {:key => body[:sslkey], :data => body[:body]}

  if @initiated_by == :client
    body[:body] = deserialize(decrypt(cryptdata, nil))
  else
    certname = certname_from_callerid(body[:callerid])
    certfile = "#{client_cert_dir}/#{certname}.pem"
    # if aes.ca_cert is set every certificate is validated before we try and use it
    if @config.pluginconf.fetch("aes.ca_cert", nil) && !validate_certificate(File.read(certfile), certname)
      raise "Unable to validate certificate '#{certname}' against CA"
    end
    body[:body] = deserialize(decrypt(cryptdata, body[:callerid]))

    # If we got a hash it's possible that this is a message with secure
    # TTL and message time, attempt to decode that and transform into a
    # traditional message.
    #
    # If it's not a hash it might be a old style message like old discovery
    # ones that would just be a string so we allow that unaudited but only
    # if enforce_ttl is disabled.  This is primarly to allow a mixed old and
    # new plugin infrastructure to work
    if body[:body].is_a?(Hash)
      update_secure_property(body, :aes_ttl, :ttl, "TTL")
      update_secure_property(body, :aes_msgtime, :msgtime, "Message Time")

      body[:body] = body[:body][:aes_msg] if body[:body].include?(:aes_msg)
    else
      unless @config.pluginconf["aes.enforce_ttl"] == "0"
        raise "Message %s is in an unknown or older security protocol, ignoring" % [request_description(body)]
      end
    end
  end

  return body
rescue MsgDoesNotMatchRequestID
  raise

rescue OpenSSL::PKey::RSAError
  raise MsgDoesNotMatchRequestID, "Could not decrypt message using our key, possibly directed at another client"

rescue Exception => e
  Log.warn("Could not decrypt message from client: #{e.class}: #{e}")
  raise SecurityValidationFailed, "Could not decrypt message"
end

#decrypt(string, certid) ⇒ Object 



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# File 'lib/mcollective/security/aes_security.rb', line 278

def decrypt(string, certid)
  if @initiated_by == :client
    @ssl ||= SSL.new(client_public_key, client_private_key)

    Log.debug("Decrypting message using private key")
    return @ssl.decrypt_with_private(string)
  else
    Log.debug("Decrypting message using public key for #{certid}")
    ssl = SSL.new(public_key_path_for_client(certid))
    return ssl.decrypt_with_public(string)
  end
end

#deserialize(msg) ⇒ Object

De-Serializes a message using the configured encoder



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# File 'lib/mcollective/security/aes_security.rb', line 221

def deserialize(msg)
  serializer = @config.pluginconf["aes.serializer"] || "marshal"

  Log.debug("De-Serializing using #{serializer}")

  case serializer
  when "yaml"
    return YAML.load(msg)
  else
    return Marshal.load(msg)
  end
end

#encodereply(sender, msg, requestid, requestcallerid) ⇒ Object

Encodes a reply



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# File 'lib/mcollective/security/aes_security.rb', line 170

def encodereply(sender, msg, requestid, requestcallerid)
  crypted = encrypt(serialize(msg), requestcallerid)

  req = create_reply(requestid, sender, crypted[:data])
  req[:sslkey] = crypted[:key]

  serialize(req)
end

#encoderequest(sender, msg, requestid, filter, target_agent, target_collective, ttl = 60) ⇒ Object

Encodes a request msg



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# File 'lib/mcollective/security/aes_security.rb', line 180

def encoderequest(sender, msg, requestid, filter, target_agent, target_collective, ttl=60)
  req = create_request(requestid, filter, nil, @initiated_by, target_agent, target_collective, ttl)

  # embed the ttl and msgtime in the crypted data later we will use these in
  # the decoding of a message to set the message ones from secure sources. this
  # is to ensure messages are not tampered with to facility replay attacks etc
  aes_msg = {:aes_msg => msg,
    :aes_ttl => ttl,
    :aes_msgtime => req[:msgtime]}

  crypted = encrypt(serialize(aes_msg), callerid)

  req[:body] = crypted[:data]
  req[:sslkey] = crypted[:key]

  if @config.pluginconf.include?("aes.send_pubkey") && @config.pluginconf["aes.send_pubkey"] == "1"
    if @initiated_by == :client
      req[:sslpubkey] = File.read(client_public_key)
    else
      req[:sslpubkey] = File.read(server_public_key)
    end
  end

  serialize(req)
end

#encrypt(string, certid) ⇒ Object 



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# File 'lib/mcollective/security/aes_security.rb', line 255

def encrypt(string, certid)
  if @initiated_by == :client
    @ssl ||= SSL.new(client_public_key, client_private_key)

    Log.debug("Encrypting message using private key")
    return @ssl.encrypt_with_private(string)
  else
    # when the server is initating requests like for registration
    # then the certid will be our callerid
    if certid == callerid
      Log.debug("Encrypting message using private key #{server_private_key}")

      ssl = SSL.new(server_public_key, server_private_key)
      return ssl.encrypt_with_private(string)
    else
      Log.debug("Encrypting message using public key for #{certid}")

      ssl = SSL.new(public_key_path_for_client(certid))
      return ssl.encrypt_with_public(string)
    end
  end
end

#public_key_path_for_client(clientid) ⇒ Object

On servers this will look in the aes.client_cert_dir for public keys matching the clientid, clientid is expected to be in the format set by callerid



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# File 'lib/mcollective/security/aes_security.rb', line 325

def public_key_path_for_client(clientid)
  raise "Unknown callerid format in '#{clientid}'" unless clientid.match(/^cert=(.+)$/)

  clientid = $1

  client_cert_dir + "/#{clientid}.pem"
end

#request_description(msg) ⇒ Object 



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# File 'lib/mcollective/security/aes_security.rb', line 371

def request_description(msg)
  "%s from %s@%s" % [msg[:requestid], msg[:callerid], msg[:senderid]]
end

#serialize(msg) ⇒ Object

Serializes a message using the configured encoder



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# File 'lib/mcollective/security/aes_security.rb', line 207

def serialize(msg)
  serializer = @config.pluginconf["aes.serializer"] || "marshal"

  Log.debug("Serializing using #{serializer}")

  case serializer
  when "yaml"
    return YAML.dump(msg)
  else
    return Marshal.dump(msg)
  end
end

#server_private_key ⇒ Object

Figures out the server private key from the plugin.aes.server_private config option



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# File 'lib/mcollective/security/aes_security.rb', line 360

def server_private_key
  raise("No plugin.aes.server_private configuration option specified") unless @config.pluginconf.include?("aes.server_private")
  @config.pluginconf["aes.server_private"]
end

#server_public_key ⇒ Object

Figures out the server public key from the plugin.aes.server_public config option



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# File 'lib/mcollective/security/aes_security.rb', line 354

def server_public_key
  raise("No aes.server_public configuration option specified") unless @config.pluginconf.include?("aes.server_public")
  return @config.pluginconf["aes.server_public"]
end

#update_secure_property(msg, secure_property, property, description) ⇒ Object

To avoid tampering we turn the origin body into a hash and copy some of the protocol keys like :ttl and :msg_time into the hash before encrypting it.

This function compares and updates the unencrypted ones based on the encrypted ones. By default it enforces matching and presense by raising exceptions, if aes.enforce_ttl is set to 0 it will only log warnings about violations



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# File 'lib/mcollective/security/aes_security.rb', line 151

def update_secure_property(msg, secure_property, property, description)
  req = request_description(msg)

  unless @config.pluginconf["aes.enforce_ttl"] == "0"
    raise "Request #{req} does not have a secure #{description}" unless msg[:body].include?(secure_property)
    raise "Request #{req} #{description} does not match encrypted #{description} - possible tampering"  unless msg[:body][secure_property] == msg[property]
  else
    if msg[:body].include?(secure_property)
      Log.warn("Request #{req} #{description} does not match encrypted #{description} - possible tampering") unless msg[:body][secure_property] == msg[property]
    else
      Log.warn("Request #{req} does not have a secure #{description}") unless msg[:body].include?(secure_property)
    end
  end

  msg[property] = msg[:body][secure_property] if msg[:body].include?(secure_property)
  msg[:body].delete(secure_property)
end

#validate_certificate(client_cert, certid) ⇒ Object 



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# File 'lib/mcollective/security/aes_security.rb', line 291

def validate_certificate(client_cert, certid)
  cert_file = @config.pluginconf.fetch("aes.ca_cert", nil)

  begin
    ssl_cert = OpenSSL::X509::Certificate.new(client_cert)
  rescue OpenSSL::X509::CertificateError
    Log.warn("Received public key that is not a X509 certficate")
    return false
  end

  ssl_certname = certname_from_certificate(ssl_cert)

  if certid != ssl_certname
    Log.warn("certname '#{certid}' doesn't match certificate '#{ssl_certname}'")
    return false
  end

  Log.debug("Loading CA Cert for verification")
  ca_cert = OpenSSL::X509::Store.new
  ca_cert.add_file cert_file

  if ca_cert.verify(ssl_cert)
    Log.debug("Verified certificate '#{ssl_certname}' against CA")
  else
    # TODO add cert id
    Log.warn("Unable to validate certificate '#{ssl_certname}'' against CA")
    return false
  end
  return true
end