ed25519.go

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

     1  package jwt
     2  
     3  import (
     4  	"crypto"
     5  	"crypto/ed25519"
     6  	"crypto/rand"
     7  	"errors"
     8  )
     9  
    10  var (
    11  	ErrEd25519Verification = errors.New("ed25519: verification error")
    12  )
    13  
    14  // SigningMethodEd25519 implements the EdDSA family.
    15  // Expects ed25519.PrivateKey for signing and ed25519.PublicKey for verification
    16  type SigningMethodEd25519 struct{}
    17  
    18  // Specific instance for EdDSA
    19  var (
    20  	SigningMethodEdDSA *SigningMethodEd25519
    21  )
    22  
    23  func init() {
    24  	SigningMethodEdDSA = &SigningMethodEd25519{}
    25  	RegisterSigningMethod(SigningMethodEdDSA.Alg(), func() SigningMethod {
    26  		return SigningMethodEdDSA
    27  	})
    28  }
    29  
    30  func (m *SigningMethodEd25519) Alg() string {
    31  	return "EdDSA"
    32  }
    33  
    34  // Verify implements token verification for the SigningMethod.
    35  // For this verify method, key must be an ed25519.PublicKey
    36  func (m *SigningMethodEd25519) Verify(signingString string, sig []byte, key interface{}) error {
    37  	var ed25519Key ed25519.PublicKey
    38  	var ok bool
    39  
    40  	if ed25519Key, ok = key.(ed25519.PublicKey); !ok {
    41  		return newError("Ed25519 verify expects ed25519.PublicKey", ErrInvalidKeyType)
    42  	}
    43  
    44  	if len(ed25519Key) != ed25519.PublicKeySize {
    45  		return ErrInvalidKey
    46  	}
    47  
    48  	// Verify the signature
    49  	if !ed25519.Verify(ed25519Key, []byte(signingString), sig) {
    50  		return ErrEd25519Verification
    51  	}
    52  
    53  	return nil
    54  }
    55  
    56  // Sign implements token signing for the SigningMethod.
    57  // For this signing method, key must be an ed25519.PrivateKey
    58  func (m *SigningMethodEd25519) Sign(signingString string, key interface{}) ([]byte, error) {
    59  	var ed25519Key crypto.Signer
    60  	var ok bool
    61  
    62  	if ed25519Key, ok = key.(crypto.Signer); !ok {
    63  		return nil, newError("Ed25519 sign expects crypto.Signer", ErrInvalidKeyType)
    64  	}
    65  
    66  	if _, ok := ed25519Key.Public().(ed25519.PublicKey); !ok {
    67  		return nil, ErrInvalidKey
    68  	}
    69  
    70  	// Sign the string and return the result. ed25519 performs a two-pass hash
    71  	// as part of its algorithm. Therefore, we need to pass a non-prehashed
    72  	// message into the Sign function, as indicated by crypto.Hash(0)
    73  	sig, err := ed25519Key.Sign(rand.Reader, []byte(signingString), crypto.Hash(0))
    74  	if err != nil {
    75  		return nil, err
    76  	}
    77  
    78  	return sig, nil
    79  }
    80
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