Update TLS certificate generation routines

Msf relies on Rex::Socket to create TLS certificates for services
hosted in the framework and used by some payloads. These certs are
flagged by NIDS - snort sid 1-34864 and such.

Now that Rex::Socket can accept a @@cert_provider from the Msf
namespace, a more robust generation routine can be used by all TLS
socket services, provided down from Msf to Rex, using dependencies
which Rex does not include.

This work adds the faker gem into runtime dependencies, creates an
Msf::Exploit::Remote::Ssl::CertProvider namespace, and provides
API compatible method invocations with the Rex version, but able
to generate higher entropy certs with more variables, options, etc.

This should reduce the hit rate against NIDS on the wire, reducing
pesky blue team interference until we slip up some other way. Also,
with the ability to generate different cert types, we may want to
look at extending this effort to probide a more comprehensive key
oracle to Framework and consumers.

Testing:
  None yet, internal tests pending.
  Travis should fail as this requires rex-socket #8.

lib/msf/core/exploit/ssl.rb

@@ -0,0 +1,99 @@
+module Msf
+  module Exploit::Remote::Ssl
+    require 'rex/socket/ssl'
+    require 'faker'
+    module CertProvider
+
+      def self.rand_vars(opts = {})
+        opts ||= {}
+        opts[:cc] ||= 'US'
+        opts[:st] ||= Faker::Address.state_abbr
+        opts[:loc] ||= Faker::Address.city
+        opts[:org] ||= Faker::Company.name
+        opts[:ou] ||= Faker::Hacker.send(%w{noun verb adjective}.sample.to_sym).gsub(/\W+/,'.')
+        opts[:cn] ||= opts[:org].downcase.gsub(/and/,'').gsub(/\W+/,'.') + '.' +  Faker::Internet.domain_suffix
+        opts[:email] ||= "#{opts[:ou]}@#{opts[:cn]}"
+        opts
+      end
+
+      def self.ssl_generate_subject(opts = {})
+        opts = self.rand_vars(opts)
+        subject = ""
+        subject << "/C=#{opts[:cc]}" if opts[:cc]
+        subject << "/ST=#{opts[:st]}" if opts[:st]
+        subject << "/O=#{opts[:org]}" if opts[:org]
+        subject << "/OU=#{opts[:ou]}" if opts[:ou]
+        subject << "/CN=#{opts[:cn]}" if opts[:cn]
+        subject << "/emailAddress=#{opts[:email]}" if opts[:email]
+        subject
+      end
+
+      # Not used, for API compatibility
+      def self.ssl_generate_issuer(
+        cc: 'US',
+        org: Faker::Company.name,
+        cn: Faker::Internet.domain_name
+      )
+        "#{cc}/O=#{org}/CN=#{cn}"
+      end
+
+      #
+      # Generate a realistic-looking but obstensibly fake SSL
+      # certificate. Use Faker gem to mimic other self-signed
+      # certificates on the web to reduce the chance of sig
+      # identification by NIDS and the like.
+      #
+      # @return [String, String, Array]
+      def self.ssl_generate_certificate(opts = {}, ksize = 2048)
+        yr      = 24*3600*365
+        vf      = opts[:not_before] || Time.at(Time.now.to_i - rand(yr * 3) - yr)
+        vt      = opts[:not_after]  || Time.at(vf.to_i + (rand(9)+1) * yr)
+        cvars   = opts[:cert_vars]  || self.rand_vars
+        subject = opts[:subject]    || ssl_generate_subject(cvars)
+        ctype   = opts[:cert_type]  || opts[:ca_cert].nil? ? :ca : :server
+        key     = opts[:key] || OpenSSL::PKey::RSA.new(ksize){ }
+        cert    = OpenSSL::X509::Certificate.new
+
+        cert.version    = opts[:version] || 2
+        cert.serial     = opts[:serial]  || (rand(0xFFFFFFFF) << 32) + rand(0xFFFFFFFF)
+        cert.subject    = OpenSSL::X509::Name.new([["C", subject]])
+        cert.issuer     = opts[:ca_cert] || cert.subject
+        cert.not_before = vf
+        cert.not_after  = vt
+        cert.public_key = key.public_key
+
+        bconst, kuse, ekuse = case ctype
+        when :ca
+          ['CA:TRUE', 'cRLSign,keyCertSign']
+        when :server
+          ['CA:FALSE', 'digitalSignature,keyEncipherment', 'serverAuth']
+        when :client
+          ['CA:FALSE', 'nonRepudiation,digitalSignature,keyEncipherment', 'clientAuth,emailProtection']
+        when :ocsp
+          ['CA:FALSE', 'nonRepudiation,digitalSignature', 'serverAuth,OCSPSigning']
+        when :tsca
+          ['CA:TRUE,pathlen:0', 'cRLSign,keyCertSign']
+        end
+
+        ef = OpenSSL::X509::ExtensionFactory.new
+        ef.subject_certificate = cert
+        ef.issuer_certificate = cert
+        cert.extensions = [
+          ef.create_extension("basicConstraints", bconst, true),
+          ef.create_extension("subjectKeyIdentifier", "hash")
+        ]
+        if kuse and !kuse.empty?
+          cert.extensions << ef.create_extension("keyUsage", kuse)
+        end
+
+        if ekuse and !ekuse.empty?
+          cert.extensions << ef.create_extension("extendedKeyUsage", ekuse)
+        end
+  
+        cert.sign(key, OpenSSL::Digest::SHA256.new)
+
+        [key, cert, nil]
+      end
+    end
+  end
+end

lib/msf/core/framework.rb

@@ -84,6 +84,9 @@ class Framework
     # Configure the thread factory
     Rex::ThreadFactory.provider = Metasploit::Framework::ThreadFactoryProvider.new(framework: self)
 
+    # Configure the SSL certificate generator
+    Rex::Socket::Ssl.cert_provider = Msf::Exploit::Remote::Ssl::CertProvider
+
     subscriber = FrameworkEventSubscriber.new(self)
     events.add_exploit_subscriber(subscriber)
     events.add_session_subscriber(subscriber)

metasploit-framework.gemspec

@@ -187,4 +187,6 @@ Gem::Specification.new do |spec|
   spec.add_runtime_dependency 'nexpose'
   # Needed for NDMP sockets
   spec.add_runtime_dependency 'xdr'
+  # Needed for ::Msf...CertProvider
+  spec.add_runtime_dependency 'faker'
 end