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signature.go
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signature.go
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/*
Copyright 2024 Drewbernetes.
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
package sign
import (
"crypto/ecdsa"
"crypto/rand"
"crypto/sha256"
"crypto/x509"
"encoding/base64"
"encoding/pem"
"log"
)
func decodePrivateKey(privPEM []byte) *ecdsa.PrivateKey {
block, _ := pem.Decode(privPEM)
x509Encoded := block.Bytes
privateKey, err := x509.ParseECPrivateKey(x509Encoded)
if err != nil {
log.Fatal(err)
}
return privateKey
}
func decodePublicKey(pubPEM []byte) *ecdsa.PublicKey {
blockPub, _ := pem.Decode(pubPEM)
x509EncodedPub := blockPub.Bytes
genericPublicKey, err := x509.ParsePKIXPublicKey(x509EncodedPub)
if err != nil {
log.Fatal(err)
}
publicKey := genericPublicKey.(*ecdsa.PublicKey)
return publicKey
}
// EncodeKeys takes an ecdsa.PrivateKey and generates a PEM formatted public and private key
func EncodeKeys(pk *ecdsa.PrivateKey) ([]byte, []byte) {
priv, err := x509.MarshalECPrivateKey(pk)
if err != nil {
log.Fatal(err)
}
privPEM := pem.EncodeToMemory(&pem.Block{
Type: "PRIVATE KEY",
Bytes: priv,
})
pub, err := x509.MarshalPKIXPublicKey(&pk.PublicKey)
if err != nil {
log.Fatal(err)
}
pubPEM := pem.EncodeToMemory(&pem.Block{
Type: "PUBLIC KEY",
Bytes: pub,
})
return privPEM, pubPEM
}
// Sign creates a digest of an image by signing it with the private key
func Sign(imgID string, privKey []byte) (string, error) {
key := decodePrivateKey(privKey)
log.Println("generating digest and signing image")
hash := sha256.Sum256([]byte(imgID))
sign, err := ecdsa.SignASN1(rand.Reader, key, hash[:])
if err != nil {
return "", err
}
return base64.StdEncoding.EncodeToString(sign), nil
}
// Validate validates a digest using a public key
func Validate(imgID string, pubKey []byte, digest string) (bool, error) {
key := decodePublicKey(pubKey)
hash := sha256.Sum256([]byte(imgID))
bSign, err := base64.StdEncoding.DecodeString(digest)
if err != nil {
return false, err
}
return ecdsa.VerifyASN1(key, hash[:], bSign), nil
}