ActiveSupport::MessageEncryptor

ActiveSupport::MessageEncryptor
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Ruby on Rails 8.1.3
Class
ActiveSupport::MessageEncryptor

Messages::Codec
activesupport/lib/active_support/message_encryptor.rb
v8.1.3
Active Support Message Encryptor
MessageEncryptor
is a simple way to encrypt values which get stored somewhere you don’t trust.
The cipher text and initialization vector are base64 encoded and returned to you.
This can be used in situations similar to the
MessageVerifier
, but where you don’t want users to be able to determine the value of the payload.
len
ActiveSupport
::
MessageEncryptor
key_len
salt
SecureRandom
random_bytes
len
key
ActiveSupport
::
KeyGenerator
new
'password'
).
generate_key
salt
len
# => "\x89\xE0\x156\xAC..."
crypt
ActiveSupport
::
MessageEncryptor
new
key
# => #
encrypted_data
crypt
encrypt_and_sign
'my secret data'
# => "NlFBTTMwOUV5UlA1QlNEN2xkY2d6eThYWWh..."
crypt
decrypt_and_verify
encrypted_data
# => "my secret data"
The
decrypt_and_verify
method will raise an
ActiveSupport::MessageEncryptor::InvalidMessage
exception if the data provided cannot be decrypted or verified.
crypt
decrypt_and_verify
'not encrypted data'
# => ActiveSupport::MessageEncryptor::InvalidMessage
Confining messages to a specific purpose
By default any message can be used throughout your app. But they can also be confined to a specific
:purpose
token
crypt
encrypt_and_sign
"this is the chair"
purpose:
:login
Then that same purpose must be passed when verifying to get the data back out:
crypt
decrypt_and_verify
token
purpose:
:login
# => "this is the chair"
crypt
decrypt_and_verify
token
purpose:
:shipping
# => nil
crypt
decrypt_and_verify
token
# => nil
Likewise, if a message has no purpose it won’t be returned when verifying with a specific purpose.
token
crypt
encrypt_and_sign
"the conversation is lively"
crypt
decrypt_and_verify
token
purpose:
:scare_tactics
# => nil
crypt
decrypt_and_verify
token
# => "the conversation is lively"
Making messages expire
By default messages last forever and verifying one year from now will still return the original value. But messages can be set to expire at a given time with
:expires_in
or
:expires_at
crypt
encrypt_and_sign
parcel
expires_in:
month
crypt
encrypt_and_sign
doowad
expires_at:
Time
now
end_of_year
Then the messages can be verified and returned up to the expire time. Thereafter, verifying returns
nil
Rotating keys
MessageEncryptor
also supports rotating out old configurations by falling back to a stack of encryptors. Call
rotate
to build and add an encryptor so
decrypt_and_verify
will also try the fallback.
By default any rotated encryptors use the values of the primary encryptor unless specified otherwise.
You’d give your encryptor the new defaults:
crypt
ActiveSupport
::
MessageEncryptor
new
@secret
cipher:
"aes-256-gcm"
Then gradually rotate the old values out by adding them as fallbacks. Any message generated with the old values will then work until the rotation is removed.
crypt
rotate
old_secret
# Fallback to an old secret instead of @secret.
crypt
rotate
cipher:
"aes-256-cbc"
# Fallback to an old cipher instead of aes-256-gcm.
Though if both the secret and the cipher was changed at the same time, the above should be combined into:
crypt
rotate
old_secret
cipher:
"aes-256-cbc"
Namespace
CLASS
ActiveSupport::MessageEncryptor::InvalidMessage
Methods
decrypt_and_verify
encrypt_and_sign
key_len
new
Constants
OpenSSLCipherError
OpenSSL::Cipher::CipherError
Class Public methods
key_len
(cipher = default_cipher)
Link
Given a cipher, returns the key length of the cipher to help generate the key of desired size
Source:
show
on GitHub
# File activesupport/lib/active_support/message_encryptor.rb, line 252
def
self
key_len
cipher
default_cipher
OpenSSL
::
Cipher
new
cipher
).
key_len
end
new
(secret, sign_secret = nil, **options)
Link
Initialize a new
MessageEncryptor
secret
must be at least as long as the cipher key size. For the default ‘aes-256-gcm’ cipher, this is 256 bits. If you are using a user-entered secret, you can generate a suitable key by using
ActiveSupport::KeyGenerator
or a similar key derivation function.
The first additional parameter is used as the signature key for
MessageVerifier
. This allows you to specify keys to encrypt and sign data. Ignored when using an AEAD cipher like ‘aes-256-gcm’.
ActiveSupport
::
MessageEncryptor
new
'secret'
'signature_secret'
Options
:cipher
Cipher to use. Can be any cipher returned by
OpenSSL::Cipher.ciphers
. Default is ‘aes-256-gcm’.
:digest
Digest
used for signing. Ignored when using an AEAD cipher like ‘aes-256-gcm’.
:serializer
The serializer used to serialize message data. You can specify any object that responds to
dump
and
load
, or you can choose from several preconfigured serializers:
:marshal
:json_allow_marshal
:json
:message_pack_allow_marshal
:message_pack
The preconfigured serializers include a fallback mechanism to support multiple deserialization formats. For example, the
:marshal
serializer will serialize using
Marshal
, but can deserialize using
Marshal
ActiveSupport::JSON
, or
ActiveSupport::MessagePack
. This makes it easy to migrate between serializers.
The
:marshal
:json_allow_marshal
, and
:message_pack_allow_marshal
serializers support deserializing using
Marshal
, but the others do not. Beware that
Marshal
is a potential vector for deserialization attacks in cases where a message signing secret has been leaked.
If possible, choose a serializer that does not support
Marshal
The
:message_pack
and
:message_pack_allow_marshal
serializers use
ActiveSupport::MessagePack
, which can roundtrip some Ruby types that are not supported by
JSON
, and may provide improved performance. However, these require the
msgpack
gem.
When using Rails, the default depends on
config.active_support.message_serializer
. Otherwise, the default is
:marshal
:url_safe
By default,
MessageEncryptor
generates RFC 4648 compliant strings which are not URL-safe. In other words, they can contain “+” and “/”. If you want to generate URL-safe strings (in compliance with “Base 64 Encoding with URL and Filename Safe Alphabet” in RFC 4648), you can pass
true
:force_legacy_metadata_serializer
Whether to use the legacy metadata serializer, which serializes the message first, then wraps it in an envelope which is also serialized. This was the default in Rails 7.0 and below.
If you don’t pass a truthy value, the default is set using
config.active_support.use_message_serializer_for_metadata
Source:
show
on GitHub
# File activesupport/lib/active_support/message_encryptor.rb, line 183
def
initialize
secret
sign_secret
nil
**
options
super
**
options
@secret
secret
@cipher
options
:cipher
||
self
class
default_cipher
@aead_mode
new_cipher
authenticated?
@verifier
if
@aead_mode
MessageVerifier
new
sign_secret
||
secret
**
options
serializer:
NullSerializer
end
end
Instance Public methods
decrypt_and_verify
(message, **options)
Link
Decrypt and verify a message. We need to verify the message in order to avoid padding attacks. Reference:
www.limited-entropy.com/padding-oracle-attacks
/.
Options
:purpose
The purpose that the message was generated with. If the purpose does not match,
decrypt_and_verify
will return
nil
message
encryptor
encrypt_and_sign
"hello"
purpose:
"greeting"
encryptor
decrypt_and_verify
message
purpose:
"greeting"
# => "hello"
encryptor
decrypt_and_verify
message
# => nil
message
encryptor
encrypt_and_sign
"bye"
encryptor
decrypt_and_verify
message
# => "bye"
encryptor
decrypt_and_verify
message
purpose:
"greeting"
# => nil
Source:
show
on GitHub
# File activesupport/lib/active_support/message_encryptor.rb, line 241
def
decrypt_and_verify
message
**
options
catch_and_raise
:invalid_message_format
as:
InvalidMessage
do
catch_and_raise
:invalid_message_serialization
as:
InvalidMessage
do
catch_and_ignore
:invalid_message_content
do
read_message
message
**
options
end
end
end
end
encrypt_and_sign
(value, **options)
Link
Encrypt and sign a message. We need to sign the message in order to avoid padding attacks. Reference:
www.limited-entropy.com/padding-oracle-attacks
/.
Options
:expires_at
The datetime at which the message expires. After this datetime, verification of the message will fail.
message
encryptor
encrypt_and_sign
"hello"
expires_at:
Time
now
tomorrow
encryptor
decrypt_and_verify
message
# => "hello"
# 24 hours later...
encryptor
decrypt_and_verify
message
# => nil
:expires_in
The duration for which the message is valid. After this duration has elapsed, verification of the message will fail.
message
encryptor
encrypt_and_sign
"hello"
expires_in:
24
hours
encryptor
decrypt_and_verify
message
# => "hello"
# 24 hours later...
encryptor
decrypt_and_verify
message
# => nil
:purpose
The purpose of the message. If specified, the same purpose must be specified when verifying the message; otherwise, verification will fail. (See
decrypt_and_verify
.)
Source:
show
on GitHub
# File activesupport/lib/active_support/message_encryptor.rb, line 220
def
encrypt_and_sign
value
**
options
create_message
value
**
options
end