rsa.go

Documentation: github.com/golang-jwt/jwt/v5

     1  package jwt
     2  
     3  import (
     4  	"crypto"
     5  	"crypto/rand"
     6  	"crypto/rsa"
     7  )
     8  
     9  // SigningMethodRSA implements the RSA family of signing methods.
    10  // Expects *rsa.PrivateKey for signing and *rsa.PublicKey for validation
    11  type SigningMethodRSA struct {
    12  	Name string
    13  	Hash crypto.Hash
    14  }
    15  
    16  // Specific instances for RS256 and company
    17  var (
    18  	SigningMethodRS256 *SigningMethodRSA
    19  	SigningMethodRS384 *SigningMethodRSA
    20  	SigningMethodRS512 *SigningMethodRSA
    21  )
    22  
    23  func init() {
    24  	// RS256
    25  	SigningMethodRS256 = &SigningMethodRSA{"RS256", crypto.SHA256}
    26  	RegisterSigningMethod(SigningMethodRS256.Alg(), func() SigningMethod {
    27  		return SigningMethodRS256
    28  	})
    29  
    30  	// RS384
    31  	SigningMethodRS384 = &SigningMethodRSA{"RS384", crypto.SHA384}
    32  	RegisterSigningMethod(SigningMethodRS384.Alg(), func() SigningMethod {
    33  		return SigningMethodRS384
    34  	})
    35  
    36  	// RS512
    37  	SigningMethodRS512 = &SigningMethodRSA{"RS512", crypto.SHA512}
    38  	RegisterSigningMethod(SigningMethodRS512.Alg(), func() SigningMethod {
    39  		return SigningMethodRS512
    40  	})
    41  }
    42  
    43  func (m *SigningMethodRSA) Alg() string {
    44  	return m.Name
    45  }
    46  
    47  // Verify implements token verification for the SigningMethod
    48  // For this signing method, must be an *rsa.PublicKey structure.
    49  func (m *SigningMethodRSA) Verify(signingString string, sig []byte, key interface{}) error {
    50  	var rsaKey *rsa.PublicKey
    51  	var ok bool
    52  
    53  	if rsaKey, ok = key.(*rsa.PublicKey); !ok {
    54  		return newError("RSA verify expects *rsa.PublicKey", ErrInvalidKeyType)
    55  	}
    56  
    57  	// Create hasher
    58  	if !m.Hash.Available() {
    59  		return ErrHashUnavailable
    60  	}
    61  	hasher := m.Hash.New()
    62  	hasher.Write([]byte(signingString))
    63  
    64  	// Verify the signature
    65  	return rsa.VerifyPKCS1v15(rsaKey, m.Hash, hasher.Sum(nil), sig)
    66  }
    67  
    68  // Sign implements token signing for the SigningMethod
    69  // For this signing method, must be an *rsa.PrivateKey structure.
    70  func (m *SigningMethodRSA) Sign(signingString string, key interface{}) ([]byte, error) {
    71  	var rsaKey *rsa.PrivateKey
    72  	var ok bool
    73  
    74  	// Validate type of key
    75  	if rsaKey, ok = key.(*rsa.PrivateKey); !ok {
    76  		return nil, newError("RSA sign expects *rsa.PrivateKey", ErrInvalidKeyType)
    77  	}
    78  
    79  	// Create the hasher
    80  	if !m.Hash.Available() {
    81  		return nil, ErrHashUnavailable
    82  	}
    83  
    84  	hasher := m.Hash.New()
    85  	hasher.Write([]byte(signingString))
    86  
    87  	// Sign the string and return the encoded bytes
    88  	if sigBytes, err := rsa.SignPKCS1v15(rand.Reader, rsaKey, m.Hash, hasher.Sum(nil)); err == nil {
    89  		return sigBytes, nil
    90  	} else {
    91  		return nil, err
    92  	}
    93  }
    94
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