/
cryptoprovider.go
204 lines (168 loc) · 4.75 KB
/
cryptoprovider.go
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package zcrypto
import (
"io"
"os"
"github.com/pkg/errors"
"github.com/stormentt/zpass-lib/util/slices"
)
// CryptoProvider provides encryption, integrity, and authentication using symmetric keys for encryption and public/private keys for authentication.
type CryptoProvider struct {
encryptionKey EncryptionKey
integrityKey IntegrityKey
authPair AuthPair
raw []byte
}
// NewCryptoProvider generates a new CryptoProvider with random keys
func NewCryptoProvider() (*CryptoProvider, error) {
var err error
encKey, err := NewEncryptionKey()
if err != nil {
return nil, err
}
intKey, err := NewIntegrityKey()
if err != nil {
return nil, err
}
authPair, err := NewAuthPair()
if err != nil {
return nil, err
}
provider := CryptoProvider{
encryptionKey: encKey,
integrityKey: intKey,
authPair: authPair,
raw: slices.Combine(encKey, intKey, authPair.Bytes()),
}
return &provider, nil
}
// CryptoProviderFromBytes creates a CryptoProvider from a byte slice
//
// b must be EncKeySize+IntKeySize+AuthFullSize in length
func CryptoProviderFromBytes(b []byte) (*CryptoProvider, error) {
provider := new(CryptoProvider)
provider.raw = make([]byte, len(b))
copy(provider.raw, b)
if len(b) == EncKeySize+IntKeySize+AuthFullSize {
provider.encryptionKey = provider.raw[:EncKeySize]
provider.integrityKey = provider.raw[EncKeySize:IntKeySize]
authPair, _ := AuthPairFromBytes(provider.raw[EncKeySize+IntKeySize:])
provider.authPair = authPair
} else {
return nil, CryptoProviderBadSizeError{len(b)}
}
return provider, nil
}
// Encrypt encrypts a byte slice & generates a MAC
//
// The MAC is prepended to the encrypted slice. This is to encourage MAC validation before decryption.
func (c *CryptoProvider) Encrypt(msg []byte) ([]byte, error) {
ciphertext, err := c.encryptionKey.Encrypt(msg)
if err != nil {
return nil, err
}
mac, err := c.integrityKey.Sign(ciphertext)
if err != nil {
return nil, err
}
return slices.Combine(mac, ciphertext), nil
}
// Decrypt decrypts an encrypted byte slice
//
// If the message's MAC is invalid decryption will return a nil & an error
func (c *CryptoProvider) Decrypt(msg []byte) ([]byte, error) {
if len(msg) < MsgOverhead {
return nil, MsgTooShortError{wanted: MsgOverhead, size: len(msg)}
}
sig := msg[:IntHashSize]
ciphertext := msg[IntHashSize:]
valid, err := c.integrityKey.Verify(ciphertext, sig)
if err != nil {
return nil, err
} else if !valid {
return nil, InvalidSignatureError{sig}
}
plaintext, err := c.encryptionKey.Decrypt(msg)
return plaintext, err
}
// EncryptFile encrypts a file & generates a MAC
//
// The MAC is prepended to the encrypted file. This is to encourage MAC validation before decryption.
func (c *CryptoProvider) EncryptFile(inPath, outPath string) error {
in, err := os.Open(inPath)
if err != nil {
return errors.WithStack(err)
}
out, err := os.Open(outPath)
if err != nil {
return errors.WithStack(err)
}
sw, err := NewSalsaWriter(c.encryptionKey, c.integrityKey, out)
if err != nil {
return errors.WithStack(err)
}
_, err = io.Copy(sw, in)
if err != nil {
return errors.WithStack(err)
}
err = sw.Close()
if err != nil {
return errors.WithStack(err)
}
_ = in.Close()
err = out.Close()
if err != nil {
return errors.WithStack(err)
}
return nil
}
// DecryptFile decrypts a file
//
// If the file's MAC is invalid decryption will return an error
func (c *CryptoProvider) DecryptFile(inPath, outPath string) error {
in, err := os.Open(inPath)
if err != nil {
return errors.WithStack(err)
}
out, err := os.Open(outPath)
if err != nil {
return errors.WithStack(err)
}
sr, err := NewSalsaReader(c.encryptionKey, c.integrityKey, in)
if err != nil {
return errors.WithStack(err)
}
_, err = io.Copy(out, sr)
if err != nil {
return errors.WithStack(err)
}
_ = in.Close()
err = out.Close()
if err != nil {
return errors.WithStack(err)
}
return nil
}
// Sign signs a message
//
// Sign will fail if the CryptoProvider does not have a private auth key.
func (c *CryptoProvider) Sign(msg []byte) ([]byte, error) {
return c.authPair.Sign(msg)
}
// SignFile signs a file
//
// SignFile will fail if the CryptoProvider does not have a private auth key.
func (c *CryptoProvider) SignFile(path string) ([]byte, error) {
return c.authPair.SignFile(path)
}
// Verify checks the signature of a message
//
// Verify will fail if the CryptoProvider does not have a public auth key.
func (c *CryptoProvider) Verify(msg, sig []byte) bool {
return c.authPair.Verify(msg, sig)
}
// VerifyFile checks the signature of a file
//
// VerifyFile will fail if the CryptoProvider does not have a public auth key.
func (c *CryptoProvider) VerifyFile(path string, sig []byte) (bool, error) {
return c.authPair.VerifyFile(path, sig)
}