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generator.go
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generator.go
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// Copyright © 2022 Ory Corp
// SPDX-License-Identifier: Apache-2.0
package jwksx
import (
"crypto"
"crypto/ecdsa"
"crypto/elliptic"
"crypto/rand"
"crypto/rsa"
"crypto/x509"
"io"
"github.com/pkg/errors"
"github.com/google/uuid"
"github.com/square/go-jose/v3"
"golang.org/x/crypto/ed25519"
)
// GenerateSigningKeys generates a JSON Web Key Set for signing.
func GenerateSigningKeys(id, alg string, bits int) (*jose.JSONWebKeySet, error) {
if id == "" {
id = uuid.New().String()
}
key, err := generate(jose.SignatureAlgorithm(alg), bits)
if err != nil {
return nil, err
}
return &jose.JSONWebKeySet{
Keys: []jose.JSONWebKey{
{
Algorithm: alg,
Use: "sig",
Key: key,
KeyID: id,
Certificates: []*x509.Certificate{},
},
},
}, nil
}
// GenerateSigningKeysAvailableAlgorithms lists available algorithms that are supported by GenerateSigningKeys.
func GenerateSigningKeysAvailableAlgorithms() []string {
return []string{
string(jose.HS256), string(jose.HS384), string(jose.HS512),
string(jose.ES256), string(jose.ES384), string(jose.ES512), string(jose.EdDSA),
string(jose.RS256), string(jose.RS384), string(jose.RS512), string(jose.PS256), string(jose.PS384), string(jose.PS512),
}
}
// generate generates keypair for corresponding SignatureAlgorithm.
func generate(alg jose.SignatureAlgorithm, bits int) (crypto.PrivateKey, error) {
switch alg {
case jose.ES256, jose.ES384, jose.ES512, jose.EdDSA:
keylen := map[jose.SignatureAlgorithm]int{
jose.ES256: 256,
jose.ES384: 384,
jose.ES512: 521, // sic!
jose.EdDSA: 256,
}
if bits != 0 && bits != keylen[alg] {
return nil, errors.Errorf(`jwksx: "%s" does not support arbitrary key length`, alg)
}
case jose.RS256, jose.RS384, jose.RS512, jose.PS256, jose.PS384, jose.PS512:
if bits == 0 {
bits = 2048
}
if bits < 2048 {
return nil, errors.Errorf(`jwksx: key size must be at least 2048 bit for algorithm "%s"`, alg)
}
case jose.HS256:
if bits == 0 {
bits = 256
}
if bits < 256 {
return nil, errors.Errorf(`jwksx: key size must be at least 256 bit for algorithm "%s"`, alg)
}
case jose.HS384:
if bits == 0 {
bits = 384
}
if bits < 384 {
return nil, errors.Errorf(`jwksx: key size must be at least 2038448 bit for algorithm "%s"`, alg)
}
case jose.HS512:
if bits == 0 {
bits = 1024
}
if bits < 512 {
return nil, errors.Errorf(`jwksx: key size must be at least 512 bit for algorithm "%s"`, alg)
}
}
switch alg {
case jose.ES256:
// The cryptographic operations are implemented using constant-time algorithms.
key, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
return key, errors.Wrapf(err, "jwks: unable to generate key")
case jose.ES384:
// NB: The cryptographic operations do not use constant-time algorithms.
key, err := ecdsa.GenerateKey(elliptic.P384(), rand.Reader)
return key, errors.Wrapf(err, "jwks: unable to generate key")
case jose.ES512:
// NB: The cryptographic operations do not use constant-time algorithms.
key, err := ecdsa.GenerateKey(elliptic.P521(), rand.Reader)
return key, errors.Wrapf(err, "jwks: unable to generate key")
case jose.EdDSA:
_, key, err := ed25519.GenerateKey(rand.Reader)
return key, errors.Wrapf(err, "jwks: unable to generate key")
case jose.RS256, jose.RS384, jose.RS512, jose.PS256, jose.PS384, jose.PS512:
key, err := rsa.GenerateKey(rand.Reader, bits)
return key, errors.Wrapf(err, "jwks: unable to generate key")
case jose.HS256, jose.HS384, jose.HS512:
if bits%8 != 0 {
return nil, errors.Errorf(`jwksx: key size must be a multiple of 8 for algorithm "%s" but got: %d`, alg, bits)
}
key := make([]byte, bits/8)
if _, err := io.ReadFull(rand.Reader, key); err != nil {
return nil, errors.Wrapf(err, "jwks: unable to generate key")
}
return key, nil
default:
return nil, errors.Errorf(`jwksx: available algorithms are "%+v" but unknown algorithm was requested: "%s"`, GenerateSigningKeysAvailableAlgorithms(), alg)
}
}