ASN1: #to_der in pure ruby

lib/openssl/asn1.rb

@@ -10,6 +10,20 @@
 
 module OpenSSL
   module ASN1
+    INT_MAX = begin
+      n_bytes = [42].pack('i').size
+      n_bits = n_bytes * 16
+      2 ** (n_bits - 2) - 1
+    end
+
+    V_ASN1_UNIVERSAL= 0x00
+    V_ASN1_APPLICATION = 0x40
+    V_ASN1_CONTEXT_SPECIFIC = 0x80
+    V_ASN1_PRIVATE = 0xc0
+    V_ASN1_CONSTRUCTED = 0x20
+    V_ASN1_PRIMITIVE_TAG = 0x1f
+
+
     class ASN1Data
       #
       # Carries the value of a ASN.1 type.
@@ -71,6 +85,101 @@ def initialize(value, tag, tag_class)
         @tag_class = tag_class
         @indefinite_length = false
       end
+
+      def to_der
+        if @value.is_a?(Array)
+          cons_to_der
+        elsif @indefinite_length
+          raise ASN1Error, "indefinite length form cannot be used " \
+		        "with primitive encoding"
+        else
+          prim_to_der
+        end
+      end
+
+      private
+
+      def cons_to_der
+        ary = @value.to_a
+        str = "".b
+
+        @value.each_with_index do |item, idx|
+          if @indefinite_length && item.is_a?(EndOfContent)
+            if idx != ary.size - 1
+              raise ASN1Error, "illegal EOC octets in value"
+            end
+
+            break
+          end
+
+          item = item.to_der if item.respond_to?(:to_der)
+
+          str << item
+        end
+
+        to_der_internal(str, true)
+      end
+
+      def prim_to_der
+        return to_der_internal(@value) unless ASN1.take_default_tag(self.class)
+
+        # TODO: how to translate this?
+        asn1 = ossl_asn1_get_asn1type(self)
+        alllen = i2d_ASN1_TYPE(asn1, NULL)
+
+        if (alllen < 0)
+          ASN1_TYPE_free(asn1)
+          raise ASN1Error, "i2d_ASN1_TYPE"
+        end
+
+        str = String.new(capacity: alllen)
+
+        p0 = p1 = str;
+        if (i2d_ASN1_TYPE(asn1, &p0) < 0)
+            ASN1_TYPE_free(asn1);
+            ossl_raise(eASN1Error, "i2d_ASN1_TYPE");
+        end
+        ASN1_TYPE_free(asn1);
+        ossl_str_adjust(str, p0);
+
+        j = ASN1_get_object(p1, bodylen, tag, tc, alllen)
+        if j & 0x80
+	        ossl_raise(eASN1Error, "ASN1_get_object"); # should not happen
+        end
+
+        to_der_internal(str[(alllen - bodylen)..-1])
+      end
+
+      def to_der_internal(body, constructed = false)
+        default_tag = ASN1.take_default_tag(self.class)
+        body_len = body.size
+
+        if @tagging == :EXPLICIT
+          raise ASN1Error, "explicit tagging of unknown tag" unless default_tag
+
+          inner_len = ASN1.object_size(constructed && @indefinite_length, body_len, default_tag)
+          total_len = ASN1.object_size(@indefinite_length, inner_len, @tag)
+
+          # Put explicit tag
+          str = ASN1.put_object(constructed, @indefinite_length, inner_len, @tag, @tag_class) <<
+                # Append inner object
+                ASN1.put_object(constructed, @indefinite_length, body_len, default_tag, :UNIVERSAL)
+
+          str << body
+          if @indefinite_length
+            str << "\x00\x00\x00\x00"
+          end
+        else
+          total_length = ASN1.object_size(constructed && @indefinite_length, body_len, @tag)
+          str = ASN1.put_object(constructed, @indefinite_length, body_len, @tag, @tag_class)
+          str << body
+          if @indefinite_length
+            str << "\x00\x00"
+          end
+        end
+
+        str
+      end
     end
 
     module TaggedASN1Data
@@ -172,8 +281,110 @@ def initialize
       end
     end
 
+    module_function
+
+    # ruby port of ASN1_object_size
+    def object_size(indefinite_length, length, tag)
+      ret = 1
+
+      return -1 if length < 0
+
+      if tag >= 31
+        while tag > 0
+          tag >>= 7
+          ret += 1
+        end
+      end
+      if indefinite_length
+        ret += 3
+      else
+        ret += 1
+        if length > 127
+          tmplen = length
+          while tmplen > 0
+            tmplen >>= 8
+            ret+=1
+          end
+        end
+      end
+
+      return -1 if (ret >= INT_MAX - length)
+
+
+      ret + length
+    end
+
+    # ruby port of openssl ASN1_put_object
+    def put_object(constructed, indefinite_length, length, tag, tag_class)
+      str = "".b
+      xclass = take_asn1_tag_class(tag_class)
+
+      i = constructed ? V_ASN1_CONSTRUCTED : 0
+      i |= (xclass & V_ASN1_PRIVATE)
+
+      if tag < 31
+        str << (i | (tag & V_ASN1_PRIMITIVE_TAG)).chr
+
+      else
+        str << (i | V_ASN1_PRIMITIVE_TAG).chr
+
+        i = 0
+        ttag = tag
+
+        while ttag > 0
+          i += 1
+          ttag >>= 7
+        end
+
+        ttag = i
+
+        while i > 0
+          i -= 1
+          tag_str = tag & 0x7f
+          if (i != (ttag - 1))
+            tag_str |= 0x80
+          end
+          str.insert(1, tag_str.chr)
+          tag >>= 7
+        end
+      end
+
+      if constructed && indefinite_length
+        str << 0x80.chr
+      else
+        str << put_length(length)
+      end
+      str
+    end
+
+
+    def put_length(length)
+      raise ASN1Error, "invalid length" if length < 0
+
+      if length < 0x80
+        length.chr
+      else
+        i = length
+
+        if i >= 0
+          done = 0
+        else
+          done = -1
+        end
+
+        octets = "".b
+        begin
+          octets = (i & 0xff).chr << octets
+          i = i >> 8
+        end until i == done
+        octets
+
+        (octets.size | 0x80).chr << octets
+      end
+    end
+
     # :nodoc:
-    def self.take_default_tag(klass)
+    def take_default_tag(klass)
       tag = CLASS_TAG_MAP[klass]
 
       return tag if tag
@@ -184,5 +395,17 @@ def self.take_default_tag(klass)
 
       take_default_tag(sklass)
     end
+
+    # from ossl_asn1.c : ossl_asn1_tag_class
+    def take_asn1_tag_class(tag_class)
+      case tag_class
+      when :UNIVERSAL, nil then V_ASN1_UNIVERSAL
+      when :APPLICATION then V_ASN1_APPLICATION
+      when :CONTEXT_SPECIFIC then V_ASN1_CONTEXT_SPECIFIC
+      when :PRIVATE then V_ASN1_PRIVATE
+      else
+        raise ASN1Error,  "invalid tag class"
+      end
+    end
   end
 end