class ActiveSupport::MessageVerifier

verifier.rotate old_secret, digest: “SHA256”, serializer: Marshal
Though the above would most likely be combined into one rotation:
verifier.rotate serializer: Marshal # Fallback to an old serializer instead of JSON.
verifier.rotate digest: “SHA256” # Fallback to an old digest instead of SHA512.
verifier.rotate old_secret # Fallback to an old secret instead of @secret.
generated with the old values will then work until the rotation is removed.
Then gradually rotate the old values out by adding them as fallbacks. Any message
verifier = ActiveSupport::MessageVerifier.new(@secret, digest: “SHA512”, serializer: JSON)
You’d give your verifier the new defaults:
verifier unless specified otherwise.
By default any rotated verifiers use the values of the primary
either verified or verify will also try verifying with the fallback.
back to a stack of verifiers. Call rotate to build and add a verifier so
MessageVerifier also supports rotating out old configurations by falling
=== Rotating keys
ActiveSupport::MessageVerifier::InvalidSignature.
Thereafter, the verified method returns nil while verify raises
Then the messages can be verified and returned up to the expire time.
@verifier.generate(“doowad”, expires_at: Time.now.end_of_year)
@verifier.generate(“parcel”, expires_in: 1.month)
time with :expires_in or :expires_at.
return the original value. But messages can be set to expire at a given
By default messages last forever and verifying one year from now will still
=== Making messages expire
@verifier.verify(token) # => “the conversation is lively”
@verifier.verify(token, purpose: :scare_tactics) # => ActiveSupport::MessageVerifier::InvalidSignature
@verifier.verified(token) # => “the conversation is lively”
@verifier.verified(token, purpose: :scare_tactics) # => nil
token = @verifier.generate(“the conversation is lively”)
a specific purpose.
Likewise, if a message has no purpose it won’t be returned when verifying with
@verifier.verify(token) # => ActiveSupport::MessageVerifier::InvalidSignature
@verifier.verify(token, purpose: :shipping) # => ActiveSupport::MessageVerifier::InvalidSignature
@verifier.verify(token, purpose: :login) # => “this is the chair”
@verifier.verified(token) # => nil
@verifier.verified(token, purpose: :shipping) # => nil
@verifier.verified(token, purpose: :login) # => “this is the chair”
Then that same purpose must be passed when verifying to get the data back out:
token = @verifier.generate(“this is the chair”, purpose: :login)
confined to a specific :purpose.
By default any message can be used throughout your app. But they can also be
=== Confining messages to a specific purpose
@verifier = ActiveSupport::MessageVerifier.new(‘s3Krit’, digest: ‘SHA256’)
:digest key as an option while initializing the verifier:
If you want to use a different hash algorithm, you can change it by providing
MessageVerifier creates HMAC signatures using SHA1 hash algorithm by default.
@verifier = ActiveSupport::MessageVerifier.new(‘s3Krit’, serializer: YAML)
hash upon initialization:
another serialization method, you can set the serializer in the options
By default it uses Marshal to serialize the message. If you want to use
end
self.current_user = User.find(id)
if Time.now < time
id, time = @verifier.verify(cookies)
In the authentication filter:<br><br>cookies = @verifier.generate([@user.id, 2.weeks.from_now])
Remember Me:
where the session store isn’t suitable or available.
This is useful for cases like remember-me tokens and auto-unsubscribe links
signed to prevent tampering.
MessageVerifier makes it easy to generate and verify messages which are

def decode(data) 

def decode(data)
  ::Base64.strict_decode64(data)
end

def digest_length_in_hex 

def digest_length_in_hex
  # In hexadecimal (AKA base16) it takes 4 bits to represent a character,
  # hence we multiply the digest's length (in bytes) by 8 to get it in
  # bits and divide by 4 to get its number of characters it hex. Well, 8
  # divided by 4 is 2.
  @digest_length_in_hex ||= OpenSSL::Digest.new(@digest).digest_length * 2
end

def digest_matches_data?(digest, data) 

def digest_matches_data?(digest, data)
  data.present? && digest.present? && ActiveSupport::SecurityUtils.secure_compare(digest, generate_digest(data))
end

def encode(data) 

def encode(data)
  ::Base64.strict_encode64(data)
end

def generate(value, expires_at: nil, expires_in: nil, purpose: nil)

verifier.generate 'a private message' # => "BAhJIhRwcml2YXRlLW1lc3NhZ2UGOgZFVA==--e2d724331ebdee96a10fb99b089508d1c72bd772"
verifier = ActiveSupport::MessageVerifier.new 's3Krit'

Returns Base64-encoded message joined with the generated signature.
The message is signed with the +MessageVerifier+'s secret.

Generates a signed message for the provided value. 
def generate(value, expires_at: nil, expires_in: nil, purpose: nil)
  data = encode(Messages::Metadata.wrap(@serializer.dump(value), expires_at: expires_at, expires_in: expires_in, purpose: purpose))
  "#{data}#{SEPARATOR}#{generate_digest(data)}"
end

def generate_digest(data) 

def generate_digest(data)
  OpenSSL::HMAC.hexdigest(@digest, @secret, data)
end

def get_data_and_digest_from(signed_message) 

def get_data_and_digest_from(signed_message)
  return if signed_message.nil? || !signed_message.valid_encoding? || signed_message.empty?
  separator_index = separator_index_for(signed_message)
  return if separator_index.nil?
  data = signed_message[0...separator_index]
  digest = signed_message[separator_index + SEPARATOR_LENGTH..-1]
  [data, digest]
end

def initialize(secret, digest: nil, serializer: nil) 

def initialize(secret, digest: nil, serializer: nil)
  raise ArgumentError, "Secret should not be nil." unless secret
  @secret = secret
  @digest = digest&.to_s || "SHA1"
  @serializer = serializer || Marshal
end

def separator_index_for(signed_message) 

def separator_index_for(signed_message)
  index = signed_message.length - digest_length_in_hex - SEPARATOR_LENGTH
  return if index.negative? || signed_message[index, SEPARATOR_LENGTH] != SEPARATOR
  index
end

def valid_message?(signed_message)

verifier.valid_message?(tampered_message) # => false
tampered_message = signed_message.chop # editing the message invalidates the signature

verifier.valid_message?(signed_message) # => true
signed_message = verifier.generate 'a private message'
verifier = ActiveSupport::MessageVerifier.new 's3Krit'

with the +MessageVerifier+'s secret.
Checks if a signed message could have been generated by signing an object 
def valid_message?(signed_message)
  data, digest = get_data_and_digest_from(signed_message)
  digest_matches_data?(digest, data)
end

def verified(signed_message, purpose: nil, **)

verifier.verified(incompatible_message) # => TypeError: incompatible marshal file format
incompatible_message = "test--dad7b06c94abba8d46a15fafaef56c327665d5ff"

Raises any error raised while decoding the signed message.

verifier.verified(invalid_message) # => nil
invalid_message = "f--46a0120593880c733a53b6dad75b42ddc1c8996d"

Returns +nil+ if the message is not Base64-encoded.

other_verifier.verified(signed_message) # => nil
other_verifier = ActiveSupport::MessageVerifier.new 'd1ff3r3nt-s3Krit'

Returns +nil+ if the message was not signed with the same secret.

verifier.verified(signed_message) # => 'a private message'
signed_message = verifier.generate 'a private message'

verifier = ActiveSupport::MessageVerifier.new 's3Krit'

Decodes the signed message using the +MessageVerifier+'s secret. 
def verified(signed_message, purpose: nil, **)
  data, digest = get_data_and_digest_from(signed_message)
  if digest_matches_data?(digest, data)
    begin
      message = Messages::Metadata.verify(decode(data), purpose)
      @serializer.load(message) if message
    rescue ArgumentError => argument_error
      return if argument_error.message.include?("invalid base64")
      raise
    end
  end
end

def verify(*args, **options)

other_verifier.verify(signed_message) # => ActiveSupport::MessageVerifier::InvalidSignature
other_verifier = ActiveSupport::MessageVerifier.new 'd1ff3r3nt-s3Krit'

secret or was not Base64-encoded.
Raises +InvalidSignature+ if the message was not signed with the same

verifier.verify(signed_message) # => 'a private message'

signed_message = verifier.generate 'a private message'
verifier = ActiveSupport::MessageVerifier.new 's3Krit'

Decodes the signed message using the +MessageVerifier+'s secret. 
def verify(*args, **options)
  verified(*args, **options) || raise(InvalidSignature)
end