| 
                    1
                 | 
                                    
                                                     | 
                
                 | 
                <?php  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    2
                 | 
                                    
                                                     | 
                
                 | 
                 | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    3
                 | 
                                    
                                                     | 
                
                 | 
                /*  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    4
                 | 
                                    
                                                     | 
                
                 | 
                 * The MIT License (MIT)  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    5
                 | 
                                    
                                                     | 
                
                 | 
                 *  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    6
                 | 
                                    
                                                     | 
                
                 | 
                 * Copyright (c) 2014-2016 Spomky-Labs  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    7
                 | 
                                    
                                                     | 
                
                 | 
                 *  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    8
                 | 
                                    
                                                     | 
                
                 | 
                 * This software may be modified and distributed under the terms  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    9
                 | 
                                    
                                                     | 
                
                 | 
                 * of the MIT license.  See the LICENSE file for details.  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    10
                 | 
                                    
                                                     | 
                
                 | 
                 */  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    11
                 | 
                                    
                                                     | 
                
                 | 
                 | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    12
                 | 
                                    
                                                     | 
                
                 | 
                namespace Jose\Algorithm\Signature;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    13
                 | 
                                    
                                                     | 
                
                 | 
                 | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    14
                 | 
                                    
                                                     | 
                
                 | 
                use Assert\Assertion;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    15
                 | 
                                    
                                                     | 
                
                 | 
                use Jose\Algorithm\SignatureAlgorithmInterface;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    16
                 | 
                                    
                                                     | 
                
                 | 
                use Jose\KeyConverter\RSAKey;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    17
                 | 
                                    
                                                     | 
                
                 | 
                use Jose\Object\JWKInterface;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    18
                 | 
                                    
                                                     | 
                
                 | 
                use Jose\Util\RSA as JoseRSA;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    19
                 | 
                                    
                                                     | 
                
                 | 
                 | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    20
                 | 
                                    
                                                     | 
                
                 | 
                /**  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    21
                 | 
                                    
                                                     | 
                
                 | 
                 * Class RSA.  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    22
                 | 
                                    
                                                     | 
                
                 | 
                 */  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    23
                 | 
                                    
                                                     | 
                
                 | 
                abstract class RSA implements SignatureAlgorithmInterface  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    24
                 | 
                                    
                                                     | 
                
                 | 
                { | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    25
                 | 
                                    
                                                     | 
                
                 | 
                    /**  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    26
                 | 
                                    
                                                     | 
                
                 | 
                     * Probabilistic Signature Scheme.  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    27
                 | 
                                    
                                                     | 
                
                 | 
                     */  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    28
                 | 
                                    
                                                     | 
                
                 | 
                    const SIGNATURE_PSS = 1;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    29
                 | 
                                    
                                                     | 
                
                 | 
                 | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    30
                 | 
                                    
                                                     | 
                
                 | 
                    /**  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    31
                 | 
                                    
                                                     | 
                
                 | 
                     * Use the PKCS#1.  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    32
                 | 
                                    
                                                     | 
                
                 | 
                     */  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    33
                 | 
                                    
                                                     | 
                
                 | 
                    const SIGNATURE_PKCS1 = 2;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    34
                 | 
                                    
                                                     | 
                
                 | 
                 | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    35
                 | 
                                    
                                                     | 
                
                 | 
                    /**  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    36
                 | 
                                    
                                                     | 
                
                 | 
                     * @return mixed  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    37
                 | 
                                    
                                                     | 
                
                 | 
                     */  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    38
                 | 
                                    
                                                     | 
                
                 | 
                    abstract protected function getAlgorithm();  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    39
                 | 
                                    
                                                     | 
                
                 | 
                 | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    40
                 | 
                                    
                                                     | 
                
                 | 
                    /**  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    41
                 | 
                                    
                                                     | 
                
                 | 
                     * @return mixed  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    42
                 | 
                                    
                                                     | 
                
                 | 
                     */  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    43
                 | 
                                    
                                                     | 
                
                 | 
                    abstract protected function getSignatureMethod();  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    44
                 | 
                                    
                                                     | 
                
                 | 
                 | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    45
                 | 
                                    
                                                     | 
                
                 | 
                    /**  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    46
                 | 
                                    
                                                     | 
                
                 | 
                     * {@inheritdoc} | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    47
                 | 
                                    
                                                     | 
                
                 | 
                     */  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    48
                 | 
                                    
                                                     | 
                
                 | 
                    public function verify(JWKInterface $key, $input, $signature)  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    49
                 | 
                                    
                                                     | 
                
                 | 
                    { | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    50
                 | 
                                    
                                                     | 
                
                 | 
                        $this->checkKey($key);  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    51
                 | 
                                    
                                                     | 
                
                 | 
                 | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    52
                 | 
                                    
                                                     | 
                
                 | 
                        $pub = RSAKey::toPublic(new RSAKey($key));  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    53
                 | 
                                    
                                                     | 
                
                 | 
                 | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    54
                 | 
                                    
                                                     | 
                
                 | 
                        if ($this->getSignatureMethod() === self::SIGNATURE_PSS) { | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    55
                 | 
                                    
                                                     | 
                
                 | 
                 | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    56
                 | 
                                    
                                                     | 
                
                 | 
                            return JoseRSA::verify($pub, $input, $signature, $this->getAlgorithm());  | 
            
                            
                    | 
                        
                     | 
                     | 
                     | 
                    
                                                                                                    
                        
                         
                                                                                        
                                                                                     
                     | 
                
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    57
                 | 
                                    
                                                     | 
                
                 | 
                        } else { | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    58
                 | 
                                    
                                                     | 
                
                 | 
                 | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    59
                 | 
                                    
                                                     | 
                
                 | 
                            return 1 === openssl_verify($input, $signature, $pub->toPEM(), $this->getAlgorithm());  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    60
                 | 
                                    
                                                     | 
                
                 | 
                        }  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    61
                 | 
                                    
                                                     | 
                
                 | 
                    }  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    62
                 | 
                                    
                                                     | 
                
                 | 
                 | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    63
                 | 
                                    
                                                     | 
                
                 | 
                    /**  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    64
                 | 
                                    
                                                     | 
                
                 | 
                     * {@inheritdoc} | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    65
                 | 
                                    
                                                     | 
                
                 | 
                     */  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    66
                 | 
                                    
                                                     | 
                
                 | 
                    public function sign(JWKInterface $key, $input)  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    67
                 | 
                                    
                                                     | 
                
                 | 
                    { | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    68
                 | 
                                    
                                                     | 
                
                 | 
                        $this->checkKey($key);  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    69
                 | 
                                    
                                                     | 
                
                 | 
                        Assertion::true($key->has('d'), 'The key is not a private key'); | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    70
                 | 
                                    
                                                     | 
                
                 | 
                 | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    71
                 | 
                                    
                                                     | 
                
                 | 
                        $priv = new RSAKey($key);  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    72
                 | 
                                    
                                                     | 
                
                 | 
                 | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    73
                 | 
                                    
                                                     | 
                
                 | 
                        if ($this->getSignatureMethod() === self::SIGNATURE_PSS) { | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    74
                 | 
                                    
                                                     | 
                
                 | 
                            $result = JoseRSA::sign($priv, $input, $this->getAlgorithm());  | 
            
                            
                    | 
                        
                     | 
                     | 
                     | 
                    
                                                                                                    
                        
                         
                                                                                        
                                                                                     
                     | 
                
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    75
                 | 
                                    
                                                     | 
                
                 | 
                            Assertion::string($result, 'An error occurred during the creation of the signature');  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    76
                 | 
                                    
                                                     | 
                
                 | 
                 | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    77
                 | 
                                    
                                                     | 
                
                 | 
                            return $result;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    78
                 | 
                                    
                                                     | 
                
                 | 
                        } else { | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    79
                 | 
                                    
                                                     | 
                
                 | 
                            $result = openssl_sign($input, $signature, $priv->toPEM(), $this->getAlgorithm());  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    80
                 | 
                                    
                                                     | 
                
                 | 
                            Assertion::true($result, 'Unable to sign');  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    81
                 | 
                                    
                                                     | 
                
                 | 
                 | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    82
                 | 
                                    
                                                     | 
                
                 | 
                            return $signature;  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    83
                 | 
                                    
                                                     | 
                
                 | 
                        }  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    84
                 | 
                                    
                                                     | 
                
                 | 
                    }  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    85
                 | 
                                    
                                                     | 
                
                 | 
                 | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    86
                 | 
                                    
                                                     | 
                
                 | 
                    /**  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    87
                 | 
                                    
                                                     | 
                
                 | 
                     * @param JWKInterface $key  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    88
                 | 
                                    
                                                     | 
                
                 | 
                     */  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    89
                 | 
                                    
                                                     | 
                
                 | 
                    private function checkKey(JWKInterface $key)  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    90
                 | 
                                    
                                                     | 
                
                 | 
                    { | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    91
                 | 
                                    
                                                     | 
                
                 | 
                        Assertion::eq($key->get('kty'), 'RSA', 'Wrong key type.'); | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    92
                 | 
                                    
                                                     | 
                
                 | 
                    }  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    93
                 | 
                                    
                                                     | 
                
                 | 
                }  | 
            
            
                                                                                                            
                            
            
                                    
            
            
                | 
                    94
                 | 
                                    
                                                     | 
                
                 | 
                 | 
            
            
                        
If you return a value from a function or method, it should be a sub-type of the type that is given by the parent type f.e. an interface, or abstract method. This is more formally defined by the Lizkov substitution principle, and guarantees that classes that depend on the parent type can use any instance of a child type interchangably. This principle also belongs to the SOLID principles for object oriented design.
Let’s take a look at an example:
Our function
my_functionexpects aPostobject, and outputs the author of the post. The base classPostreturns a simple string and outputting a simple string will work just fine. However, the child classBlogPostwhich is a sub-type ofPostinstead decided to return anobject, and is therefore violating the SOLID principles. If aBlogPostwere passed tomy_function, PHP would not complain, but ultimately fail when executing thestrtouppercall in its body.