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// cryptopasta - basic cryptography examples
//
// Written in 2015 by George Tankersley <george.tankersley@gmail.com>
//
// To the extent possible under law, the author(s) have dedicated all copyright
// and related and neighboring rights to this software to the public domain
// worldwide. This software is distributed without any warranty.
//
// You should have received a copy of the CC0 Public Domain Dedication along
// with this software. If not, see // <http://creativecommons.org/publicdomain/zero/1.0/>.
// Provides encoding and decoding routines for various cryptographic structures.
package cryptopasta
import (
"crypto/ecdsa"
"crypto/x509"
"encoding/base64"
"encoding/pem"
"errors"
"fmt"
)
// DecodePublicKey decodes a PEM-encoded ECDSA public key.
func DecodePublicKey(encodedKey []byte) (*ecdsa.PublicKey, error) {
block, _ := pem.Decode(encodedKey)
if block == nil || block.Type != "PUBLIC KEY" {
return nil, fmt.Errorf("marshal: could not decode PEM block type %s", block.Type)
}
pub, err := x509.ParsePKIXPublicKey(block.Bytes)
if err != nil {
return nil, err
}
ecdsaPub, ok := pub.(*ecdsa.PublicKey)
if !ok {
return nil, errors.New("marshal: data was not an ECDSA public key")
}
return ecdsaPub, nil
}
// EncodePublicKey encodes an ECDSA public key to PEM format.
func EncodePublicKey(key *ecdsa.PublicKey) ([]byte, error) {
derBytes, err := x509.MarshalPKIXPublicKey(key)
if err != nil {
return nil, err
}
block := &pem.Block{
Type: "PUBLIC KEY",
Bytes: derBytes,
}
return pem.EncodeToMemory(block), nil
}
// DecodePrivateKey decodes a PEM-encoded ECDSA private key.
func DecodePrivateKey(encodedKey []byte) (*ecdsa.PrivateKey, error) {
var skippedTypes []string
var block *pem.Block
for {
block, encodedKey = pem.Decode(encodedKey)
if block == nil {
return nil, fmt.Errorf("failed to find EC PRIVATE KEY in PEM data after skipping types %v", skippedTypes)
}
if block.Type == "EC PRIVATE KEY" {
break
} else {
skippedTypes = append(skippedTypes, block.Type)
continue
}
}
privKey, err := x509.ParseECPrivateKey(block.Bytes)
if err != nil {
return nil, err
}
return privKey, nil
}
// EncodePrivateKey encodes an ECDSA private key to PEM format.
func EncodePrivateKey(key *ecdsa.PrivateKey) ([]byte, error) {
derKey, err := x509.MarshalECPrivateKey(key)
if err != nil {
return nil, err
}
keyBlock := &pem.Block{
Type: "EC PRIVATE KEY",
Bytes: derKey,
}
return pem.EncodeToMemory(keyBlock), nil
}
// Encodes an ECDSA signature according to
// https://tools.ietf.org/html/rfc7515#appendix-A.3.1
func EncodeSignatureJWT(sig []byte) string {
return base64.RawURLEncoding.EncodeToString(sig)
}
// Decodes an ECDSA signature according to
// https://tools.ietf.org/html/rfc7515#appendix-A.3.1
func DecodeSignatureJWT(b64sig string) ([]byte, error) {
return base64.RawURLEncoding.DecodeString(b64sig)
}
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