A small library to make management of crypto stuff easier in go.
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package pki
import (
"crypto"
"crypto/ecdsa"
"crypto/elliptic"
"crypto/rand"
"crypto/x509"
"encoding/asn1"
"encoding/pem"
"errors"
"io"
"math/big"
)
// This label is used as the type in the pem encoding of ECDSA private keys.
const PemLabelEcdsa = "EC PRIVATE KEY"
type (
// This type handles the function calls to the ecdsa private key by
// implementing the interface.
EcdsaPrivateKey struct {
private_key *ecdsa.PrivateKey
}
// EcdsaPublicKey is the specific public key type for ecdsa. It implements the
// the PublicKey interface.
EcdsaPublicKey struct {
public_key *ecdsa.PublicKey
}
// This struct is used to marshal and parse the ecdsa signature.
signatureEcdsa struct {
R, S *big.Int
}
)
// Create a new ECDSA private key using the specified curve.
// For available curves, please take a look at the crypto/elliptic package.
func NewPrivateKeyEcdsa(curve elliptic.Curve) (*EcdsaPrivateKey, error) {
key, err := ecdsa.GenerateKey(curve, rand.Reader)
if err != nil {
return nil, err
}
return &EcdsaPrivateKey{key}, nil
}
// Load the private key from the asn1 representation.
func LoadPrivateKeyEcdsa(raw []byte) (*EcdsaPrivateKey, error) {
key, err := x509.ParseECPrivateKey(raw)
if err != nil {
return nil, err
}
return &EcdsaPrivateKey{key}, nil
}
// Create a new public key from the private key.
func (pr EcdsaPrivateKey) Public() PublicKey {
return &EcdsaPublicKey{pr.private_key.Public().(*ecdsa.PublicKey)}
}
// Sign a message using the private key and the provided hash function.
func (pr EcdsaPrivateKey) Sign(message []byte, hash crypto.Hash) ([]byte, error) {
empty := make([]byte, 0)
if !hash.Available() {
return empty, errors.New("Hash method is not available!")
}
hashed_message := hash.New()
hashed_message.Write(message)
return pr.private_key.Sign(rand.Reader, hashed_message.Sum(nil), hash)
}
// This function returns the crypto.PrivateKey structure of the ECDSA key.
func (pr EcdsaPrivateKey) PrivateKey() crypto.PrivateKey {
return pr.private_key
}
// This function implements the Pemmer interface to marshal the private key
// into a pem block.
func (pr EcdsaPrivateKey) MarshalPem() (io.WriterTo, error) {
pem_block, err := pr.ToPem()
if err != nil {
return nil, err
}
return marshalledPemBlock(pem.EncodeToMemory(&pem_block)), nil
}
// This function implements ToPem to return the raw pem block.
func (pr EcdsaPrivateKey) ToPem() (pem.Block, error) {
asn1, err := x509.MarshalECPrivateKey(pr.private_key)
if err != nil {
return pem.Block{}, err
}
return pem.Block{Type: PemLabelEcdsa, Bytes: asn1}, nil
}
// This functoin loads an ecdsa public key from the asn.1 representation.
func LoadPublicKeyEcdsa(raw []byte) (*EcdsaPublicKey, error) {
raw_pub, err := x509.ParsePKIXPublicKey(raw)
if err != nil {
return nil, err
}
pub, ok := raw_pub.(*ecdsa.PublicKey)
if !ok {
return nil, errors.New("Not an ecdsa key!")
}
return &EcdsaPublicKey{pub}, nil
}
// ToPem returns the pem block of the public key.
func (pu *EcdsaPublicKey) ToPem() (pem.Block, error) {
asn1, err := x509.MarshalPKIXPublicKey(pu.public_key)
if err != nil {
return pem.Block{}, err
}
return pem.Block{Type: PemLabelPublic, Bytes: asn1}, nil
}
// This function implements the Pemmer interface to marshal the public key into
// a pem block.
func (pu *EcdsaPublicKey) MarshalPem() (io.WriterTo, error) {
if block, err := pu.ToPem(); err != nil {
return nil, err
} else {
return marshalledPemBlock(pem.EncodeToMemory(&block)), nil
}
}
// This function verifies a message using the public key, signature and hash
// function.
// The hash function must be the same as was used to create the signature.
func (pu *EcdsaPublicKey) Verify(message []byte, signature_raw []byte, hash crypto.Hash) (bool, error) {
var sig signatureEcdsa
_, err := asn1.Unmarshal(signature_raw, &sig)
if err != nil {
return false, err
}
hashed_message := hash.New()
hashed_message.Write(message)
return ecdsa.Verify(pu.public_key, hashed_message.Sum(nil), sig.R, sig.S), nil
}