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// +build go1.4
package jwt
import (
"crypto"
"crypto/rand"
"crypto/rsa"
)
// Implements the RSAPSS family of signing methods signing methods
type SigningMethodRSAPSS struct {
*SigningMethodRSA
Options *rsa.PSSOptions
}
// Specific instances for RS/PS and company
var (
SigningMethodPS256 *SigningMethodRSAPSS
SigningMethodPS384 *SigningMethodRSAPSS
SigningMethodPS512 *SigningMethodRSAPSS
)
func init() {
// PS256
SigningMethodPS256 = &SigningMethodRSAPSS{
&SigningMethodRSA{
Name: "PS256",
Hash: crypto.SHA256,
},
&rsa.PSSOptions{
SaltLength: rsa.PSSSaltLengthAuto,
Hash: crypto.SHA256,
},
}
RegisterSigningMethod(SigningMethodPS256.Alg(), func() SigningMethod {
return SigningMethodPS256
})
// PS384
SigningMethodPS384 = &SigningMethodRSAPSS{
&SigningMethodRSA{
Name: "PS384",
Hash: crypto.SHA384,
},
&rsa.PSSOptions{
SaltLength: rsa.PSSSaltLengthAuto,
Hash: crypto.SHA384,
},
}
RegisterSigningMethod(SigningMethodPS384.Alg(), func() SigningMethod {
return SigningMethodPS384
})
// PS512
SigningMethodPS512 = &SigningMethodRSAPSS{
&SigningMethodRSA{
Name: "PS512",
Hash: crypto.SHA512,
},
&rsa.PSSOptions{
SaltLength: rsa.PSSSaltLengthAuto,
Hash: crypto.SHA512,
},
}
RegisterSigningMethod(SigningMethodPS512.Alg(), func() SigningMethod {
return SigningMethodPS512
})
}
// Implements the Verify method from SigningMethod
// For this verify method, key must be an rsa.PublicKey struct
func (m *SigningMethodRSAPSS) 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
}
var rsaKey *rsa.PublicKey
switch k := key.(type) {
case *rsa.PublicKey:
rsaKey = k
default:
return ErrInvalidKey
}
// Create hasher
if !m.Hash.Available() {
return ErrHashUnavailable
}
hasher := m.Hash.New()
hasher.Write([]byte(signingString))
return rsa.VerifyPSS(rsaKey, m.Hash, hasher.Sum(nil), sig, m.Options)
}
// Implements the Sign method from SigningMethod
// For this signing method, key must be an rsa.PrivateKey struct
func (m *SigningMethodRSAPSS) Sign(signingString string, key interface{}) (string, error) {
var rsaKey *rsa.PrivateKey
switch k := key.(type) {
case *rsa.PrivateKey:
rsaKey = k
default:
return "", ErrInvalidKeyType
}
// Create the hasher
if !m.Hash.Available() {
return "", ErrHashUnavailable
}
hasher := m.Hash.New()
hasher.Write([]byte(signingString))
// Sign the string and return the encoded bytes
if sigBytes, err := rsa.SignPSS(rand.Reader, rsaKey, m.Hash, hasher.Sum(nil), m.Options); err == nil {
return EncodeSegment(sigBytes), nil
} else {
return "", err
}
}
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