1 files changed, 113 insertions, 0 deletions
diff --git a/app/models/client_certificate.rb b/app/models/client_certificate.rb
new file mode 100644
index 0000000..76b07a2
--- /dev/null
+++ b/app/models/client_certificate.rb
@@ -0,0 +1,113 @@
+#
+# Model for certificates
+#
+# This file must be loaded after Config has been loaded.
+#
+require 'base64'
+require 'digest/md5'
+require 'openssl'
+require 'certificate_authority'
+require 'date'
+
+class ClientCertificate
+
+  attr_accessor :key                          # the client private RSA key
+  attr_accessor :cert                         # the client x509 certificate, signed by the CA
+
+  #
+  # generate the private key and client certificate
+  #
+  def initialize(options = {})
+    cert = CertificateAuthority::Certificate.new
+
+    # set subject
+    cert.subject.common_name = common_name(options[:prefix])
+
+    # set expiration
+    cert.not_before = yesterday
+    cert.not_after = months_from_yesterday(APP_CONFIG[:client_cert_lifespan])
+
+    # generate key
+    cert.serial_number.number = cert_serial_number
+    cert.key_material.generate_key(APP_CONFIG[:client_cert_bit_size])
+
+    # sign
+    cert.parent = ClientCertificate.root_ca
+    cert.sign! client_signing_profile
+
+    self.key = cert.key_material.private_key
+    self.cert = cert
+  end
+
+  def to_s
+    self.key.to_pem + self.cert.to_pem
+  end
+
+  private
+
+  def self.root_ca
+    @root_ca ||= begin
+                   crt = File.read(APP_CONFIG[:client_ca_cert])
+                   key = File.read(APP_CONFIG[:client_ca_key])
+                   openssl_cert = OpenSSL::X509::Certificate.new(crt)
+                   cert = CertificateAuthority::Certificate.from_openssl(openssl_cert)
+                   cert.key_material.private_key = OpenSSL::PKey::RSA.new(key, APP_CONFIG[:ca_key_password])
+                   cert
+                 end
+  end
+
+  #
+  # For cert serial numbers, we need a non-colliding number less than 160 bits.
+  # md5 will do nicely, since there is no need for a secure hash, just a short one.
+  # (md5 is 128 bits)
+  #
+  def cert_serial_number
+    Digest::MD5.hexdigest("#{rand(10**10)} -- #{Time.now}").to_i(16)
+  end
+
+  def common_name(prefix = nil)
+    [prefix, random_common_name].join
+  end
+
+  #
+  # for the random common name, we need a text string that will be unique across all certs.
+  # ruby 1.8 doesn't have a built-in uuid generator, or we would use SecureRandom.uuid
+  #
+  def random_common_name
+    cert_serial_number.to_s(36)
+  end
+
+  def client_signing_profile
+    {
+      "digest" => APP_CONFIG[:client_cert_hash],
+      "extensions" => {
+        "keyUsage" => {
+          "usage" => ["digitalSignature"]
+        },
+        "extendedKeyUsage" => {
+          "usage" => ["clientAuth"]
+        }
+      }
+    }
+  end
+
+  ##
+  ## TIME HELPERS
+  ##
+  ## note: we use 'yesterday' instead of 'today', because times are in UTC, and some people on the planet
+  ## are behind UTC.
+  ##
+
+  def yesterday
+    t = Time.now - 24*60*60
+    Time.utc t.year, t.month, t.day
+  end
+
+  def months_from_yesterday(num)
+    t = yesterday
+    date = Date.new t.year, t.month, t.day
+    date = date >> num # >> is months in the future operator
+    Time.utc date.year, date.month, date.day
+  end
+
+end