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
|
# frozen_string_literal: true
require "base64"
require "active_support/core_ext/object/blank"
require "active_support/security_utils"
module ActiveSupport
# +MessageVerifier+ makes it easy to generate and verify messages which are
# signed to prevent tampering.
#
# This is useful for cases like remember-me tokens and auto-unsubscribe links
# where the session store isn't suitable or available.
#
# Remember Me:
# cookies[:remember_me] = @verifier.generate([@user.id, 2.weeks.from_now])
#
# In the authentication filter:
#
# id, time = @verifier.verify(cookies[:remember_me])
# if Time.now < time
# self.current_user = User.find(id)
# end
#
# By default it uses Marshal to serialize the message. If you want to use
# another serialization method, you can set the serializer in the options
# hash upon initialization:
#
# @verifier = ActiveSupport::MessageVerifier.new('s3Krit', serializer: YAML)
#
# +MessageVerifier+ creates HMAC signatures using SHA1 hash algorithm by default.
# If you want to use a different hash algorithm, you can change it by providing
# `:digest` key as an option while initializing the verifier:
#
# @verifier = ActiveSupport::MessageVerifier.new('s3Krit', digest: 'SHA256')
class MessageVerifier
class InvalidSignature < StandardError; end
def initialize(secret, options = {})
raise ArgumentError, "Secret should not be nil." unless secret
@secret = secret
@digest = options[:digest] || "SHA1"
@serializer = options[:serializer] || Marshal
end
# Checks if a signed message could have been generated by signing an object
# with the +MessageVerifier+'s secret.
#
# verifier = ActiveSupport::MessageVerifier.new 's3Krit'
# signed_message = verifier.generate 'a private message'
# verifier.valid_message?(signed_message) # => true
#
# tampered_message = signed_message.chop # editing the message invalidates the signature
# verifier.valid_message?(tampered_message) # => false
def valid_message?(signed_message)
return if signed_message.nil? || !signed_message.valid_encoding? || signed_message.blank?
data, digest = signed_message.split("--".freeze)
data.present? && digest.present? && ActiveSupport::SecurityUtils.secure_compare(digest, generate_digest(data))
end
# Decodes the signed message using the +MessageVerifier+'s secret.
#
# verifier = ActiveSupport::MessageVerifier.new 's3Krit'
#
# signed_message = verifier.generate 'a private message'
# verifier.verified(signed_message) # => 'a private message'
#
# Returns +nil+ if the message was not signed with the same secret.
#
# other_verifier = ActiveSupport::MessageVerifier.new 'd1ff3r3nt-s3Krit'
# other_verifier.verified(signed_message) # => nil
#
# Returns +nil+ if the message is not Base64-encoded.
#
# invalid_message = "f--46a0120593880c733a53b6dad75b42ddc1c8996d"
# verifier.verified(invalid_message) # => nil
#
# Raises any error raised while decoding the signed message.
#
# incompatible_message = "test--dad7b06c94abba8d46a15fafaef56c327665d5ff"
# verifier.verified(incompatible_message) # => TypeError: incompatible marshal file format
def verified(signed_message)
if valid_message?(signed_message)
begin
data = signed_message.split("--".freeze)[0]
@serializer.load(decode(data))
rescue ArgumentError => argument_error
return if argument_error.message.include?("invalid base64")
raise
end
end
end
# Decodes the signed message using the +MessageVerifier+'s secret.
#
# verifier = ActiveSupport::MessageVerifier.new 's3Krit'
# signed_message = verifier.generate 'a private message'
#
# verifier.verify(signed_message) # => 'a private message'
#
# Raises +InvalidSignature+ if the message was not signed with the same
# secret or was not Base64-encoded.
#
# other_verifier = ActiveSupport::MessageVerifier.new 'd1ff3r3nt-s3Krit'
# other_verifier.verify(signed_message) # => ActiveSupport::MessageVerifier::InvalidSignature
def verify(signed_message)
verified(signed_message) || raise(InvalidSignature)
end
# Generates a signed message for the provided value.
#
# The message is signed with the +MessageVerifier+'s secret. Without knowing
# the secret, the original value cannot be extracted from the message.
#
# verifier = ActiveSupport::MessageVerifier.new 's3Krit'
# verifier.generate 'a private message' # => "BAhJIhRwcml2YXRlLW1lc3NhZ2UGOgZFVA==--e2d724331ebdee96a10fb99b089508d1c72bd772"
def generate(value)
data = encode(@serializer.dump(value))
"#{data}--#{generate_digest(data)}"
end
private
def encode(data)
::Base64.strict_encode64(data)
end
def decode(data)
::Base64.strict_decode64(data)
end
def generate_digest(data)
require "openssl" unless defined?(OpenSSL)
OpenSSL::HMAC.hexdigest(OpenSSL::Digest.const_get(@digest).new, @secret, data)
end
end
end
|
