Plug.Crypto (Plug.Crypto v1.2.2) View Source
Namespace and module for crypto-related functionality.
For low-level functionality, see Plug.Crypto.KeyGenerator
,
Plug.Crypto.MessageEncryptor
, and Plug.Crypto.MessageVerifier
.
Link to this section Summary
Functions
Decrypts the original data from the token and verifies its integrity.
Encodes, encrypts, and signs data into a token you can send to clients.
Masks the token on the left with the token on the right.
Compares the two binaries (one being masked) in constant-time to avoid timing attacks.
A restricted version of :erlang.binary_to_term/2
that forbids
executable terms, such as anonymous functions.
Prunes the stacktrace to remove any argument trace.
Compares the two binaries in constant-time to avoid timing attacks.
Encodes and signs data into a token you can send to clients.
Decodes the original data from the token and verifies its integrity.
Link to this section Functions
Decrypts the original data from the token and verifies its integrity.
Options
:max_age
- verifies the token only if it has been generated "max age" ago in seconds. A reasonable value is 1 day (86400 seconds):key_iterations
- option passed toPlug.Crypto.KeyGenerator
when generating the encryption and signing keys. Defaults to 1000:key_length
- option passed toPlug.Crypto.KeyGenerator
when generating the encryption and signing keys. Defaults to 32:key_digest
- option passed toPlug.Crypto.KeyGenerator
when generating the encryption and signing keys. Defaults to:sha256
Encodes, encrypts, and signs data into a token you can send to clients.
Options
:key_iterations
- option passed toPlug.Crypto.KeyGenerator
when generating the encryption and signing keys. Defaults to 1000:key_length
- option passed toPlug.Crypto.KeyGenerator
when generating the encryption and signing keys. Defaults to 32:key_digest
- option passed toPlug.Crypto.KeyGenerator
when generating the encryption and signing keys. Defaults to:sha256
:signed_at
- set the timestamp of the token in seconds. Defaults toSystem.system_time(:second)
:max_age
- the default maximum age of the token. Defaults to86400
seconds (1 day) and it may be overridden ondecrypt/4
.
Specs
Masks the token on the left with the token on the right.
Both tokens are required to have the same size.
Specs
Compares the two binaries (one being masked) in constant-time to avoid timing attacks.
It is assumed the right token is masked according to the given mask.
Specs
A restricted version of :erlang.binary_to_term/2
that forbids
executable terms, such as anonymous functions.
The opts
are given to the underlying :erlang.binary_to_term/2
call, with an empty list as a default.
By default this function does not restrict atoms, as an atom interned in one node may not yet have been interned on another (except for releases, which preload all code).
If you want to avoid atoms from being created, then you can pass
[:safe]
as options, as that will also enable the safety mechanisms
from :erlang.binary_to_term/2
itself.
Specs
prune_args_from_stacktrace(Exception.stacktrace()) :: Exception.stacktrace()
Prunes the stacktrace to remove any argument trace.
This is useful when working with functions that receives secrets and we want to make sure those secrets do not leak on error messages.
Specs
Compares the two binaries in constant-time to avoid timing attacks.
Encodes and signs data into a token you can send to clients.
Plug.Crypto.sign(conn.secret_key_base, "user-secret", {:elixir, :terms})
Options
:key_iterations
- option passed toPlug.Crypto.KeyGenerator
when generating the encryption and signing keys. Defaults to 1000:key_length
- option passed toPlug.Crypto.KeyGenerator
when generating the encryption and signing keys. Defaults to 32:key_digest
- option passed toPlug.Crypto.KeyGenerator
when generating the encryption and signing keys. Defaults to:sha256
:signed_at
- set the timestamp of the token in seconds. Defaults toSystem.system_time(:second)
:max_age
- the default maximum age of the token. Defaults to86400
seconds (1 day) and it may be overridden onverify/4
.
Decodes the original data from the token and verifies its integrity.
Examples
In this scenario we will create a token, sign it, then provide it to a client
application. The client will then use this token to authenticate requests for
resources from the server. See Plug.Crypto
summary for more info about
creating tokens.
iex> user_id = 99
iex> secret = "kjoy3o1zeidquwy1398juxzldjlksahdk3"
iex> user_salt = "user salt"
iex> token = Plug.Crypto.sign(secret, user_salt, user_id)
The mechanism for passing the token to the client is typically through a cookie, a JSON response body, or HTTP header. For now, assume the client has received a token it can use to validate requests for protected resources.
When the server receives a request, it can use verify/4
to determine if it
should provide the requested resources to the client:
iex> Plug.Crypto.verify(secret, user_salt, token, max_age: 86400)
{:ok, 99}
In this example, we know the client sent a valid token because verify/4
returned a tuple of type {:ok, user_id}
. The server can now proceed with
the request.
However, if the client had sent an expired or otherwise invalid token
verify/4
would have returned an error instead:
iex> Plug.Crypto.verify(secret, user_salt, expired, max_age: 86400)
{:error, :expired}
iex> Plug.Crypto.verify(secret, user_salt, invalid, max_age: 86400)
{:error, :invalid}
Options
:max_age
- verifies the token only if it has been generated "max age" ago in seconds. Defaults to the max age signed in the token (86400):key_iterations
- option passed toPlug.Crypto.KeyGenerator
when generating the encryption and signing keys. Defaults to 1000:key_length
- option passed toPlug.Crypto.KeyGenerator
when generating the encryption and signing keys. Defaults to 32:key_digest
- option passed toPlug.Crypto.KeyGenerator
when generating the encryption and signing keys. Defaults to:sha256