# Class yii\base\Security

Inheritance | yii\base\Security » yii\base\Component » yii\base\BaseObject
Implements | yii\base\Configurable
Available since version | 2.0
Source Code | https://github.com/yiisoft/yii2/blob/master/framework/base/Security.php

Security provides a set of methods to handle common security-related tasks.

In particular, Security supports the following features:

- Encryption/decryption: encryptByKey(), decryptByKey(), encryptByPassword() and decryptByPassword()
- Key derivation using standard algorithms: pbkdf2() and hkdf()
- Data tampering prevention: hashData() and validateData()
- Password validation: generatePasswordHash() and validatePassword()

> Note: this class requires 'OpenSSL' PHP extension for random key/string generation on Windows and for encryption/decryption on all platforms. For the highest security level PHP version >= 5.5.0 is recommended.

For more details and usage information on Security, see the guide article on security.

## Public Properties

Hide inherited properties

Property | Type | Description | Defined By
--- | --- | --- | ---
$allowedCiphers | array[] | Look-up table of block sizes and key sizes for each supported OpenSSL cipher. | yii\base\Security
$authKeyInfo | string | HKDF info value for derivation of message authentication key. | yii\base\Security
$behaviors | yii\base\Behavior[] | List of behaviors attached to this component. This property is read-only. | yii\base\Component
$cipher | string | The cipher to use for encryption and decryption. | yii\base\Security
$derivationIterations | integer | Derivation iterations count. | yii\base\Security
$kdfHash | string | Hash algorithm for key derivation. | yii\base\Security
$macHash | string | Hash algorithm for message authentication. | yii\base\Security
$passwordHashCost | integer | Default cost used for password hashing. | yii\base\Security
$passwordHashStrategy | string | Strategy, which should be used to generate password hash. | yii\base\Security

## Public Methods

Hide inherited methods

Method | Description | Defined By
--- | --- | ---
__call() | Calls the named method which is not a class method. | yii\base\Component
__clone() | This method is called after the object is created by cloning an existing one. | yii\base\Component
__construct() | Constructor. | yii\base\BaseObject
__get() | Returns the value of a component property. | yii\base\Component
__isset() | Checks if a property is set, i.e. defined and not null. | yii\base\Component
__set() | Sets the value of a component property. | yii\base\Component
__unset() | Sets a component property to be null. | yii\base\Component
attachBehavior() | Attaches a behavior to this component. | yii\base\Component
attachBehaviors() | Attaches a list of behaviors to the component. | yii\base\Component
behaviors() | Returns a list of behaviors that this component should behave as. | yii\base\Component
canGetProperty() | Returns a value indicating whether a property can be read. | yii\base\Component
canSetProperty() | Returns a value indicating whether a property can be set. | yii\base\Component
className() | Returns the fully qualified name of this class. | yii\base\BaseObject
compareString() | Performs string comparison using timing attack resistant approach. | yii\base\Security
decryptByKey() | Verifies and decrypts data encrypted with encryptByKey(). | yii\base\Security
decryptByPassword() | Verifies and decrypts data encrypted with encryptByPassword(). | yii\base\Security
detachBehavior() | Detaches a behavior from the component. | yii\base\Component
detachBehaviors() | Detaches all behaviors from the component. | yii\base\Component
encryptByKey() | Encrypts data using a cryptographic key. | yii\base\Security
encryptByPassword() | Encrypts data using a password. | yii\base\Security
ensureBehaviors() | Makes sure that the behaviors declared in behaviors() are attached to this component. | yii\base\Component
generatePasswordHash() | Generates a secure hash from a password and a random salt. | yii\base\Security
generateRandomKey() | Generates specified number of random bytes. | yii\base\Security
generateRandomString() | Generates a random string of specified length. | yii\base\Security
getBehavior() | Returns the named behavior object. | yii\base\Component
getBehaviors() | Returns all behaviors attached to this component. | yii\base\Component
hasEventHandlers() | Returns a value indicating whether there is any handler attached to the named event. | yii\base\Component
hasMethod() | Returns a value indicating whether a method is defined. | yii\base\Component
hasProperty() | Returns a value indicating whether a property is defined for this component. | yii\base\Component
hashData() | Prefixes data with a keyed hash value so that it can later be detected if it is tampered. | yii\base\Security
hkdf() | Derives a key from the given input key using the standard HKDF algorithm. | yii\base\Security
init() | Initializes the object. | yii\base\BaseObject
maskToken() | Masks a token to make it uncompressible. | yii\base\Security
off() | Detaches an existing event handler from this component. | yii\base\Component
on() | Attaches an event handler to an event. | yii\base\Component
pbkdf2() | Derives a key from the given password using the standard PBKDF2 algorithm. | yii\base\Security
trigger() | Triggers an event. | yii\base\Component
unmaskToken() | Unmasks a token previously masked by `maskToken`. | yii\base\Security
validateData() | Validates if the given data is tampered. | yii\base\Security
validatePassword() | Verifies a password against a hash. | yii\base\Security

## Protected Methods

Hide inherited methods

Method | Description | Defined By
--- | --- | ---
decrypt() | Decrypts data. | yii\base\Security
encrypt() | Encrypts data. | yii\base\Security
generateSalt() | Generates a salt that can be used to generate a password hash. | yii\base\Security
shouldUseLibreSSL() |  | yii\base\Security

## Property Details

$allowedCiphers public property

Look-up table of block sizes and key sizes for each supported OpenSSL cipher.

In each element, the key is one of the ciphers supported by OpenSSL (@see openssl_get_cipher_methods()). The value is an array of two integers, the first is the cipher's block size in bytes and the second is the key size in bytes.

> Warning: All OpenSSL ciphers that we recommend are in the default value, i.e. AES in CBC mode.

> Note: Yii's encryption protocol uses the same size for cipher key, HMAC signature key and key derivation salt.

public array[] $allowedCiphers = ['AES-128-CBC' => [16, 16], 'AES-192-CBC' => [16, 24], 'AES-256-CBC' => [16, 32]]
$authKeyInfo public property

HKDF info value for derivation of message authentication key.

See also hkdf().

public string $authKeyInfo = 'AuthorizationKey'
$cipher public property

The cipher to use for encryption and decryption.

public string $cipher = 'AES-128-CBC'
$derivationIterations public property

Derivation iterations count. Set as high as possible to hinder dictionary password attacks.

public integer $derivationIterations = 100000
$kdfHash public property

Hash algorithm for key derivation. Recommend sha256, sha384 or sha512.

See also hash_algos().

public string $kdfHash = 'sha256'
$macHash public property

Hash algorithm for message authentication. Recommend sha256, sha384 or sha512.

See also hash_algos().

public string $macHash = 'sha256'
$passwordHashCost public property (available since version 2.0.6)

Default cost used for password hashing. Allowed value is between 4 and 31.

See also generatePasswordHash().

public integer $passwordHashCost = 13
$passwordHashStrategy public property
Deprecated since version 2.0.7, generatePasswordHash() ignores $passwordHashStrategy and uses `password_hash()` when available or `crypt()` when not.

Strategy, which should be used to generate password hash. Available strategies:

- 'password_hash' - use of PHP `password_hash()` function with PASSWORD_DEFAULT algorithm. This option is recommended, but it requires PHP version >= 5.5.0
- 'crypt' - use PHP `crypt()` function.

public string $passwordHashStrategy = null

## Method Details

compareString() public method

Performs string comparison using timing attack resistant approach.

See also http://codereview.stackexchange.com/questions/13512.

public boolean compareString ( $expected, $actual )
$expected | string | String to compare.
$actual | string | User-supplied string.
return | boolean | Whether strings are equal.

decrypt() protected method

Decrypts data.

See also encrypt().

protected boolean|string decrypt ( $data, $passwordBased, $secret, $info )
$data | string | Encrypted data to be decrypted.
$passwordBased | boolean | Set true to use password-based key derivation
$secret | string | The decryption password or key
$info | string|null | Context/application specific information, @see encrypt()
return | boolean|string | The decrypted data or false on authentication failure
throws | yii\base\InvalidConfigException | on OpenSSL not loaded
throws | yii\base\Exception | on OpenSSL error

decryptByKey() public method

Verifies and decrypts data encrypted with encryptByKey().

See also encryptByKey().

public boolean|string decryptByKey ( $data, $inputKey, $info = null )
$data | string | The encrypted data to decrypt
$inputKey | string | The input to use for encryption and authentication
$info | string | Optional context and application specific information, see hkdf()
return | boolean|string | The decrypted data or false on authentication failure

decryptByPassword() public method

Verifies and decrypts data encrypted with encryptByPassword().

See also encryptByPassword().

public boolean|string decryptByPassword ( $data, $password )
$data | string | The encrypted data to decrypt
$password | string | The password to use for decryption
return | boolean|string | The decrypted data or false on authentication failure

encrypt() protected method

Encrypts data.

See also decrypt().

protected string encrypt ( $data, $passwordBased, $secret, $info )
$data | string | Data to be encrypted
$passwordBased | boolean | Set true to use password-based key derivation
$secret | string | The encryption password or key
$info | string|null | Context/application specific information, e.g. a user ID See RFC 5869 Section 3.2 for more details.
return | string | The encrypted data as byte string
throws | yii\base\InvalidConfigException | on OpenSSL not loaded
throws | yii\base\Exception | on OpenSSL error

encryptByKey() public method

Encrypts data using a cryptographic key.

Derives keys for encryption and authentication from the input key using HKDF and a random salt, which is very fast relative to encryptByPassword(). The input key must be properly random -- use generateRandomKey() to generate keys. The encrypted data includes a keyed message authentication code (MAC) so there is no need to hash input or output data.

See also:

- decryptByKey()
- encryptByPassword()

public string encryptByKey ( $data, $inputKey, $info = null )
$data | string | The data to encrypt
$inputKey | string | The input to use for encryption and authentication
$info | string | Optional context and application specific information, see hkdf()
return | string | The encrypted data as byte string

encryptByPassword() public method

Encrypts data using a password.

Derives keys for encryption and authentication from the password using PBKDF2 and a random salt, which is deliberately slow to protect against dictionary attacks. Use encryptByKey() to encrypt fast using a cryptographic key rather than a password. Key derivation time is determined by $derivationIterations, which should be set as high as possible. The encrypted data includes a keyed message authentication code (MAC) so there is no need to hash input or output data. > Note: Avoid encrypting with passwords wherever possible. Nothing can protect against poor-quality or compromised passwords.

See also:

- decryptByPassword()
- encryptByKey()

public string encryptByPassword ( $data, $password )
$data | string | The data to encrypt
$password | string | The password to use for encryption
return | string | The encrypted data as byte string

generatePasswordHash() public method

Generates a secure hash from a password and a random salt.

The generated hash can be stored in database. Later when a password needs to be validated, the hash can be fetched and passed to validatePassword(). For example,

    // generates the hash (usually done during user registration or when the password is changed)
    $hash = Yii::$app->getSecurity()->generatePasswordHash($password);
    // ...save $hash in database...

    // during login, validate if the password entered is correct using $hash fetched from database
    if (Yii::$app->getSecurity()->validatePassword($password, $hash)) {
        // password is good
    } else {
        // password is bad
    }

See also validatePassword().

public string generatePasswordHash ( $password, $cost = null )
$password | string | The password to be hashed.
$cost | integer | Cost parameter used by the Blowfish hash algorithm. The higher the value of cost, the longer it takes to generate the hash and to verify a password against it. Higher cost therefore slows down a brute-force attack. For best protection against brute-force attacks, set it to the highest value that is tolerable on production servers. The time taken to compute the hash doubles for every increment by one of $cost.
return | string | The password hash string. When $passwordHashStrategy is set to 'crypt', the output is always 60 ASCII characters, when set to 'password_hash' the output length might increase in future versions of PHP (https://secure.php.net/manual/en/function.password-hash.php)
throws | yii\base\Exception | on bad password parameter or cost parameter.

generateRandomKey() public method

Generates specified number of random bytes.

Note that output may not be ASCII.

See also generateRandomString() if you need a string.

public string generateRandomKey ( $length = 32 )
$length | integer | The number of bytes to generate
return | string | The generated random bytes
throws | yii\base\InvalidArgumentException | if wrong length is specified
throws | yii\base\Exception | on failure.

generateRandomString() public method

Generates a random string of specified length.

The string generated matches [A-Za-z0-9_-]+ and is transparent to URL-encoding.

public string generateRandomString ( $length = 32 )
$length | integer | The length of the key in characters
return | string | The generated random key
throws | yii\base\Exception | on failure.

generateSalt() protected method

Generates a salt that can be used to generate a password hash.

The PHP crypt() built-in function requires, for the Blowfish hash algorithm, a salt string in a specific format: "$2a$", "$2x$" or "$2y$", a two digit cost parameter, "$", and 22 characters from the alphabet "./0-9A-Za-z".

protected string generateSalt ( $cost = 13 )
$cost | integer | The cost parameter
return | string | The random salt value.
throws | yii\base\InvalidArgumentException | if the cost parameter is out of the range of 4 to 31.

hashData() public method

Prefixes data with a keyed hash value so that it can later be detected if it is tampered.

There is no need to hash inputs or outputs of encryptByKey() or encryptByPassword() as those methods perform the task.

See also:

- validateData()
- generateRandomKey()
- hkdf()
- pbkdf2()

public string hashData ( $data, $key, $rawHash = false )
$data | string | The data to be protected
$key | string | The secret key to be used for generating hash. Should be a secure cryptographic key.
$rawHash | boolean | Whether the generated hash value is in raw binary format. If false, lowercase hex digits will be generated.
return | string | The data prefixed with the keyed hash
throws | yii\base\InvalidConfigException | when HMAC generation fails.

hkdf() public method

Derives a key from the given input key using the standard HKDF algorithm.

Implements HKDF specified in RFC 5869. Recommend use one of the SHA-2 hash algorithms: sha224, sha256, sha384 or sha512.

public string hkdf ( $algo, $inputKey, $salt = null, $info = null, $length = 0 )
$algo | string | A hash algorithm supported by `hash_hmac()`, e.g. 'SHA-256'
$inputKey | string | The source key
$salt | string | The random salt
$info | string | Optional info to bind the derived key material to application- and context-specific information, e.g. a user ID or API version, see RFC 5869
$length | integer | Length of the output key in bytes. If 0, the output key is the length of the hash algorithm output.
return | string | The derived key
throws | yii\base\InvalidArgumentException | when HMAC generation fails.

maskToken() public method (available since version 2.0.12)

Masks a token to make it uncompressible.

Applies a random mask to the token and prepends the mask used to the result making the string always unique. Used to mitigate BREACH attack by randomizing how token is outputted on each request.

public string maskToken ( $token )
$token | string | An unmasked token.
return | string | A masked token.

pbkdf2() public method

Derives a key from the given password using the standard PBKDF2 algorithm.

Implements HKDF2 specified in RFC 2898 Recommend use one of the SHA-2 hash algorithms: sha224, sha256, sha384 or sha512.

public string pbkdf2 ( $algo, $password, $salt, $iterations, $length = 0 )
$algo | string | A hash algorithm supported by `hash_hmac()`, e.g. 'SHA-256'
$password | string | The source password
$salt | string | The random salt
$iterations | integer | The number of iterations of the hash algorithm. Set as high as possible to hinder dictionary password attacks.
$length | integer | Length of the output key in bytes. If 0, the output key is the length of the hash algorithm output.
return | string | The derived key
throws | yii\base\InvalidArgumentException | when hash generation fails due to invalid params given.

shouldUseLibreSSL() protected method (available since version 2.0.36)

protected boolean shouldUseLibreSSL ( )
return | boolean | If LibreSSL should be used Use version is 2.1.5 or higher.

unmaskToken() public method (available since version 2.0.12)

Unmasks a token previously masked by `maskToken`.

public string unmaskToken ( $maskedToken )
$maskedToken | string | A masked token.
return | string | An unmasked token, or an empty string in case of token format is invalid.

validateData() public method

Validates if the given data is tampered.

See also hashData().

public string|false validateData ( $data, $key, $rawHash = false )
$data | string | The data to be validated. The data must be previously generated by hashData().
$key | string | The secret key that was previously used to generate the hash for the data in hashData(). function to see the supported hashing algorithms on your system. This must be the same as the value passed to hashData() when generating the hash for the data.
$rawHash | boolean | This should take the same value as when you generate the data using hashData(). It indicates whether the hash value in the data is in binary format. If false, it means the hash value consists of lowercase hex digits only. hex digits will be generated.
return | string|false | The real data with the hash stripped off. False if the data is tampered.
throws | yii\base\InvalidConfigException | when HMAC generation fails.

validatePassword() public method

Verifies a password against a hash.

See also generatePasswordHash().

public boolean validatePassword ( $password, $hash )
$password | string | The password to verify.
$hash | string | The hash to verify the password against.
return | boolean | Whether the password is correct.
throws | yii\base\InvalidArgumentException | on bad password/hash parameters or if crypt() with Blowfish hash is not available.