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