* lib/secrand.rb: new file for secure random interface.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@12475 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,3 +1,7 @@
+Fri Jun  8 14:26:18 2007  Tanaka Akira  <akr@fsij.org>
+
+	* lib/secrand.rb: new file for secure random interface.
+
 Fri Jun  8 12:44:37 2007  NAKAMURA Usaku  <usa@ruby-lang.org>
 
 	* {win32,wince}/Makefile.sub: add lex.c rule.

lib/secrand.rb

@@ -0,0 +1,66 @@
+begin
+  require 'openssl'
+rescue LoadError
+end
+
+module SecRand
+  def self.random_bytes(n=nil)
+    n ||= 16
+    if defined? OpenSSL::Random
+      return OpenSSL::Random.random_bytes(n)
+    end
+    if !defined?(@has_urandom) || @has_urandom
+      @has_urandom = false
+      flags = File::RDONLY
+      flags |= File::NONBLOCK if defined? File::NONBLOCK
+      flags |= File::NOCTTY if defined? File::NOCTTY
+      flags |= File::NOFOLLOW if defined? File::NOFOLLOW
+      begin
+        File.open("/dev/urandom", flags) {|f|
+          unless f.stat.chardev?
+            raise Errno::ENOENT
+          end
+          @has_urandom = true
+          ret = f.readpartial(n)
+          if ret.length != n
+            raise NotImplementedError, "Unexpected partial read from random device"
+          end
+          return ret
+        }
+      rescue Errno::ENOENT
+        raise NotImplementedError, "No random device"
+      end
+    end
+    raise NotImplementedError, "No random device"
+  end
+
+  def self.hex(n=nil)
+    random_bytes(n).unpack("H*")[0]
+  end
+
+  def self.base64(n=nil)
+    [random_bytes(n)].pack("m*").delete("\n")
+  end
+
+end
+
+def SecRand(n=0)
+  if 0 < n
+    hex = n.to_s(16)
+    hex = '0' + hex if (hex.length & 1) == 1
+    bin = [hex].pack("H*")
+    mask = bin[0].ord
+    mask |= mask >> 1
+    mask |= mask >> 2
+    mask |= mask >> 4
+    begin
+      rnd = SecRand.random_bytes(bin.length)
+      rnd[0] = (rnd[0].ord & mask).chr
+    end until rnd < bin
+    rnd.unpack("H*")[0].hex
+  else
+    # assumption: Float::MANT_DIG <= 64
+    i64 = SecRand.random_bytes(8).unpack("Q")[0]
+    Math.ldexp(i64 >> (64-Float::MANT_DIG), -Float::MANT_DIG)
+  end
+end