summaryrefslogtreecommitdiffstats
path: root/lib/securerandom.rb
blob: 0de118cb44d4f1e418caaf853f2cb594c605739b (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
# = Secure random number generator interface.
#
# This library is an interface for secure random number generator which is
# suitable for generating session key in HTTP cookies, etc.
#
# It supports following secure random number generators.
#
# * openssl
# * /dev/urandom
# * Win32
#
# == Example
#
# # random hexadecimal string.
# p SecureRandom.hex(10) #=> "52750b30ffbc7de3b362"
# p SecureRandom.hex(10) #=> "92b15d6c8dc4beb5f559"
# p SecureRandom.hex(11) #=> "6aca1b5c58e4863e6b81b8"
# p SecureRandom.hex(12) #=> "94b2fff3e7fd9b9c391a2306"
# p SecureRandom.hex(13) #=> "39b290146bea6ce975c37cfc23"
# ...
#
# # random base64 string.
# p SecureRandom.base64(10) #=> "EcmTPZwWRAozdA=="
# p SecureRandom.base64(10) #=> "9b0nsevdwNuM/w=="
# p SecureRandom.base64(10) #=> "KO1nIU+p9DKxGg=="
# p SecureRandom.base64(11) #=> "l7XEiFja+8EKEtY="
# p SecureRandom.base64(12) #=> "7kJSM/MzBJI+75j8"
# p SecureRandom.base64(13) #=> "vKLJ0tXBHqQOuIcSIg=="
# ...
#
# # random binary string.
# p SecureRandom.random_bytes(10) #=> "\016\t{\370g\310pbr\301"
# p SecureRandom.random_bytes(10) #=> "\323U\030TO\234\357\020\a\337"
# ...

begin
  require 'openssl'
rescue LoadError
end

module SecureRandom
  # SecureRandom.random_bytes generates a random binary string.
  #
  # The argument n specifies the length of the result string.
  #
  # If n is not specified, 16 is assumed.
  # It may be larger in future.
  #
  # If secure random number generator is not available,
  # NotImplementedError is raised.
  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
      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
        @has_urandom = false
      end
    end

    if !defined?(@has_win32)
      begin
        require 'Win32API'

        crypt_acquire_context = Win32API.new("advapi32", "CryptAcquireContext", 'PPPII', 'L')
        @crypt_gen_random = Win32API.new("advapi32", "CryptGenRandom", 'LIP', 'L')

        hProvStr = " " * 4
        prov_rsa_full = 1
        crypt_verifycontext = 0xF0000000

        if crypt_acquire_context.call(hProvStr, nil, nil, prov_rsa_full, crypt_verifycontext) == 0
          raise SystemCallError, "CryptAcquireContext failed: #{lastWin32ErrorMessage}"
        end
        @hProv, = hProvStr.unpack('L')

        @has_win32 = true
      rescue LoadError
        @has_win32 = false
      end
    end
    if @has_win32
      bytes = " " * n
      if @crypt_gen_random.call(@hProv, bytes.size, bytes) == 0
        raise SystemCallError, "CryptGenRandom failed: #{lastWin32ErrorMessage}"
      end
      return bytes
    end

    raise NotImplementedError, "No random device"
  end

  # SecureRandom.hex generates a random hex string.
  #
  # The argument n specifies the length of the random length.
  # The length of the result string is twice of n.
  #
  # If n is not specified, 16 is assumed.
  # It may be larger in future.
  #
  # If secure random number generator is not available,
  # NotImplementedError is raised.
  def self.hex(n=nil)
    random_bytes(n).unpack("H*")[0]
  end

  # SecureRandom.base64 generates a random base64 string.
  #
  # The argument n specifies the length of the random length.
  # The length of the result string is about 4/3 of n.
  #
  # If n is not specified, 16 is assumed.
  # It may be larger in future.
  #
  # If secure random number generator is not available,
  # NotImplementedError is raised.
  def self.base64(n=nil)
    [random_bytes(n)].pack("m*").delete("\n")
  end

  # SecureRandom.random_number generates a random number.
  #
  # If an positive integer is given as n,
  # SecureRandom.random_number returns an integer:
  # 0 <= SecureRandom.random_number(n) < n.
  #
  # If 0 is given or an argument is not given,
  # SecureRandom.random_number returns an float:
  # 0.0 <= SecureRandom.random_number() < 1.0.
  def self.random_number(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 = SecureRandom.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 = SecureRandom.random_bytes(8).unpack("Q")[0]
      Math.ldexp(i64 >> (64-Float::MANT_DIG), -Float::MANT_DIG)
    end
  end

  # Following code is based on David Garamond's GUID library for Ruby.
  def self.lastWin32ErrorMessage # :nodoc:
    get_last_error = Win32API.new("kernel32", "GetLastError", '', 'L')
    format_message = Win32API.new("kernel32", "FormatMessageA", 'LPLLPLPPPPPPPP', 'L')
    format_message_ignore_inserts = 0x00000200
    format_message_from_system    = 0x00001000

    code = get_last_error.call
    msg = "\0" * 1024
    len = format_message.call(format_message_ignore_inserts + format_message_from_system, 0, code, 0, msg, 1024, nil, nil, nil, nil, nil, nil, nil, nil)
    msg[0, len].tr("\r", '').chomp
  end
end