woodpecker/vendor/github.com/dgrijalva/jwt-go/ecdsa.go
2015-09-29 17:34:44 -07:00

136 lines
3 KiB
Go

package jwt
import (
"crypto"
"crypto/ecdsa"
"crypto/rand"
"encoding/asn1"
"errors"
"math/big"
)
var (
// Sadly this is missing from crypto/ecdsa compared to crypto/rsa
ErrECDSAVerification = errors.New("crypto/ecdsa: verification error")
)
// Implements the ECDSA family of signing methods signing methods
type SigningMethodECDSA struct {
Name string
Hash crypto.Hash
}
// Marshalling structure for r, s EC point
type ECPoint struct {
R *big.Int
S *big.Int
}
// Specific instances for EC256 and company
var (
SigningMethodES256 *SigningMethodECDSA
SigningMethodES384 *SigningMethodECDSA
SigningMethodES512 *SigningMethodECDSA
)
func init() {
// ES256
SigningMethodES256 = &SigningMethodECDSA{"ES256", crypto.SHA256}
RegisterSigningMethod(SigningMethodES256.Alg(), func() SigningMethod {
return SigningMethodES256
})
// ES384
SigningMethodES384 = &SigningMethodECDSA{"ES384", crypto.SHA384}
RegisterSigningMethod(SigningMethodES384.Alg(), func() SigningMethod {
return SigningMethodES384
})
// ES512
SigningMethodES512 = &SigningMethodECDSA{"ES512", crypto.SHA512}
RegisterSigningMethod(SigningMethodES512.Alg(), func() SigningMethod {
return SigningMethodES512
})
}
func (m *SigningMethodECDSA) Alg() string {
return m.Name
}
// Implements the Verify method from SigningMethod
// For this verify method, key must be an ecdsa.PublicKey struct
func (m *SigningMethodECDSA) Verify(signingString, signature string, key interface{}) error {
var err error
// Decode the signature
var sig []byte
if sig, err = DecodeSegment(signature); err != nil {
return err
}
// Get the key
var ecdsaKey *ecdsa.PublicKey
switch k := key.(type) {
case *ecdsa.PublicKey:
ecdsaKey = k
default:
return ErrInvalidKey
}
// Unmarshal asn1 ECPoint
var ecpoint = new(ECPoint)
if _, err := asn1.Unmarshal(sig, ecpoint); err != nil {
return err
}
// Create hasher
if !m.Hash.Available() {
return ErrHashUnavailable
}
hasher := m.Hash.New()
hasher.Write([]byte(signingString))
// Verify the signature
if verifystatus := ecdsa.Verify(ecdsaKey, hasher.Sum(nil), ecpoint.R, ecpoint.S); verifystatus == true {
return nil
} else {
return ErrECDSAVerification
}
}
// Implements the Sign method from SigningMethod
// For this signing method, key must be an ecdsa.PrivateKey struct
func (m *SigningMethodECDSA) Sign(signingString string, key interface{}) (string, error) {
// Get the key
var ecdsaKey *ecdsa.PrivateKey
switch k := key.(type) {
case *ecdsa.PrivateKey:
ecdsaKey = k
default:
return "", ErrInvalidKey
}
// Create the hasher
if !m.Hash.Available() {
return "", ErrHashUnavailable
}
hasher := m.Hash.New()
hasher.Write([]byte(signingString))
// Sign the string and return r, s
if r, s, err := ecdsa.Sign(rand.Reader, ecdsaKey, hasher.Sum(nil)); err == nil {
// asn1 marhsal r, s using ecPoint as the structure
var ecpoint = new(ECPoint)
ecpoint.R = r
ecpoint.S = s
if signature, err := asn1.Marshal(*ecpoint); err != nil {
return "", err
} else {
return EncodeSegment(signature), nil
}
} else {
return "", err
}
}