Add support for stream writer and reader (#26)

Co-authored-by: Knut Ahlers <knut@ahlers.me>

go.mod

@@ -1,5 +1,14 @@
 module github.com/Luzifer/go-openssl/v4
 
-go 1.14
+go 1.20
 
-require golang.org/x/crypto v0.0.0-20200604202706-70a84ac30bf9
+require (
+	github.com/stretchr/testify v1.8.4
+	golang.org/x/crypto v0.12.0
+)
+
+require (
+	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
+)

go.sum

@@ -0,0 +1,12 @@
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/stretchr/testify v1.8.4 h1:CcVxjf3Q8PM0mHUKJCdn+eZZtm5yQwehR5yeSVQQcUk=
+github.com/stretchr/testify v1.8.4/go.mod h1:sz/lmYIOXD/1dqDmKjjqLyZ2RngseejIcXlSw2iwfAo=
+golang.org/x/crypto v0.12.0 h1:tFM/ta59kqch6LlvYnPa0yx5a83cL2nHflFhYKvv9Yk=
+golang.org/x/crypto v0.12.0/go.mod h1:NF0Gs7EO5K4qLn+Ylc+fih8BSTeIjAP05siRnAh98yw=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
+gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

openssl.go

@@ -12,7 +12,7 @@ import (
 )
 
 // ErrInvalidSalt is returned when a salt with a length of != 8 byte is passed
-var ErrInvalidSalt = errors.New("Salt needs to have exactly 8 byte")
+var ErrInvalidSalt = errors.New("salt needs to have exactly 8 byte")
 
 // OpenSSL is a helper to generate OpenSSL compatible encryption
 // with autmatic IV derivation and storage. As long as the key is known all
@@ -68,7 +68,7 @@ func (o OpenSSL) DecryptBytes(passphrase string, encryptedBase64Data []byte, cg
 	data := make([]byte, base64.StdEncoding.DecodedLen(len(encryptedBase64Data)))
 	n, err := base64.StdEncoding.Decode(data, encryptedBase64Data)
 	if err != nil {
-		return nil, fmt.Errorf("Could not decode data: %s", err)
+		return nil, fmt.Errorf("could not decode data: %s", err)
 	}
 
 	// Truncate to real message length
@@ -89,11 +89,11 @@ func (o OpenSSL) DecryptBytes(passphrase string, encryptedBase64Data []byte, cg
 // condition and you will not be able to decrypt your data properly.
 func (o OpenSSL) DecryptBinaryBytes(passphrase string, encryptedData []byte, cg CredsGenerator) ([]byte, error) {
 	if len(encryptedData) < aes.BlockSize {
-		return nil, fmt.Errorf("Data is too short")
+		return nil, fmt.Errorf("data is too short")
 	}
 	saltHeader := encryptedData[:aes.BlockSize]
 	if string(saltHeader[:8]) != o.openSSLSaltHeader {
-		return nil, fmt.Errorf("Does not appear to have been encrypted with OpenSSL, salt header missing")
+		return nil, fmt.Errorf("does not appear to have been encrypted with OpenSSL, salt header missing")
 	}
 	salt := saltHeader[8:]
 

stream.go

@@ -0,0 +1,212 @@
+package openssl
+
+import (
+	"bufio"
+	"bytes"
+	"crypto/aes"
+	"crypto/cipher"
+	"crypto/rand"
+	"errors"
+	"fmt"
+	"io"
+)
+
+// DecryptReader represents an io.Reader for OpenSSL encrypted data
+type DecryptReader struct {
+	r          *bufio.Reader
+	mode       cipher.BlockMode
+	cg         CredsGenerator
+	passphrase []byte
+}
+
+// NewReader creates a new OpenSSL stream reader with underlying reader,
+// passphrase and CredsGenerator
+func NewReader(r io.Reader, passphrase string, cg CredsGenerator) *DecryptReader {
+	return &DecryptReader{
+		r:          bufio.NewReader(r),
+		cg:         cg,
+		passphrase: []byte(passphrase),
+	}
+}
+
+// Read implements the io.Reader interface to read from an encrypted
+// datastream
+func (d *DecryptReader) Read(b []byte) (int, error) {
+	if d.mode == nil {
+		if err := d.initMode(); err != nil {
+			return 0, fmt.Errorf("init failed: %w", err)
+		}
+	}
+
+	size := (len(b) / aes.BlockSize) * aes.BlockSize
+
+	if size == 0 {
+		return 0, nil
+	}
+
+	n, err := d.r.Read(b[:size])
+	if err != nil {
+		if errors.Is(err, io.EOF) {
+			return n, io.EOF
+		}
+		return n, fmt.Errorf("reading from underlying reader: %w", err)
+	}
+
+	d.mode.CryptBlocks(b[:n], b[:n])
+
+	// AS OpenSSL enforces the encrypted data to have a length of a
+	// multpliple of the AES BlockSize we will always read full blocks.
+	// Therefore we can check whether the next block exists or yields
+	// an io.EOF error. If it does we need to remove the PKCS7 padding.
+	if _, err = d.r.Peek(aes.BlockSize); errors.Is(err, io.EOF) {
+		n -= int(b[n-1])
+	}
+
+	return n, nil
+}
+
+func (d *DecryptReader) initMode() error {
+	if d.mode != nil {
+		return nil
+	}
+
+	saltHeader := make([]byte, aes.BlockSize)
+	if _, err := io.ReadFull(d.r, saltHeader); err != nil {
+		return fmt.Errorf("read salt header failed: %w", err)
+	}
+
+	if string(saltHeader[:8]) != "Salted__" {
+		return fmt.Errorf("does not appear to have been encrypted with OpenSSL, salt header missing")
+	}
+
+	salt := saltHeader[8:]
+
+	creds, err := d.cg(d.passphrase, salt)
+	if err != nil {
+		return err
+	}
+
+	c, err := aes.NewCipher(creds.Key)
+	if err != nil {
+		return fmt.Errorf("new aes cipher failed: %w", err)
+	}
+	d.mode = cipher.NewCBCDecrypter(c, creds.IV)
+	return nil
+}
+
+// EncryptWriter represents an io.WriteCloser info OpenSSL encrypted data
+type EncryptWriter struct {
+	mode       cipher.BlockMode
+	w          io.Writer
+	cg         CredsGenerator
+	passphrase []byte
+	buf        []byte
+}
+
+// NewWriter create new openssl stream writer with underlying writer,
+// passphrase and CredsGenerator.
+//
+// Make sure close the writer after writing all data, to ensure the
+// remaining data is padded and written to the underlying writer.
+func NewWriter(w io.Writer, passphrase string, cg CredsGenerator) *EncryptWriter {
+	return &EncryptWriter{
+		w:          w,
+		cg:         cg,
+		passphrase: []byte(passphrase),
+	}
+}
+
+// Write implements io.WriteCloser to write encrypted data into the
+// underlying writer. The Write call may keep data in the buffer and
+// needs to flush them through the Close function.
+func (e *EncryptWriter) Write(b []byte) (int, error) {
+	if e.mode == nil {
+		if err := e.initMode(); err != nil {
+			return 0, err
+		}
+	}
+
+	originSize := len(b)
+
+	buf := bytes.NewBuffer(nil)
+
+	if e.buf != nil {
+		if _, err := buf.Write(e.buf); err != nil {
+			return 0, fmt.Errorf("write last remain data to buf failed: %w", err)
+		}
+		e.buf = nil
+	}
+
+	if _, err := buf.Write(b); err != nil {
+		return 0, fmt.Errorf("write current data to buf failed: %w", err)
+	}
+
+	size := (buf.Len() / aes.BlockSize) * aes.BlockSize
+
+	if remain := buf.Len() - size; remain > 0 {
+		e.buf = buf.Bytes()[size:]
+	}
+
+	if size == 0 {
+		return originSize, nil
+	}
+
+	e.mode.CryptBlocks(buf.Bytes()[:size], buf.Bytes()[:size])
+
+	n, err := e.w.Write(buf.Bytes()[:size])
+	if err != nil {
+		return n, fmt.Errorf("write encrypted data to underlying writer failed: %w", err)
+	}
+
+	return originSize, nil
+}
+
+// Close writes any buffered data to the underlying io.Writer.
+// Make sure close the writer after write all data.
+func (e *EncryptWriter) Close() error {
+	padlen := 1
+	for ((len(e.buf) + padlen) % aes.BlockSize) != 0 {
+		padlen++
+	}
+
+	pad := bytes.Repeat([]byte{byte(padlen)}, padlen)
+	pad = append(e.buf, pad...)
+
+	e.buf = nil
+	e.mode.CryptBlocks(pad, pad)
+
+	if _, err := e.w.Write(pad); err != nil {
+		return fmt.Errorf("write padding to underlying writer failed: %w", err)
+	}
+
+	return nil
+}
+
+func (e *EncryptWriter) initMode() error {
+	if e.mode != nil {
+		return nil
+	}
+
+	salt := make([]byte, 8) // Generate an 8 byte salt
+	_, err := io.ReadFull(rand.Reader, salt)
+	if err != nil {
+		return fmt.Errorf("read salt failed: %w", err)
+	}
+
+	_, err = e.w.Write(append([]byte("Salted__"), salt...))
+	if err != nil {
+		return fmt.Errorf("write salt to underlying writer failed: %w", err)
+	}
+
+	creds, err := e.cg(e.passphrase, salt)
+	if err != nil {
+		return err
+	}
+
+	c, err := aes.NewCipher(creds.Key)
+	if err != nil {
+		return fmt.Errorf("new aes cipher failed: %w", err)
+	}
+	e.mode = cipher.NewCBCEncrypter(c, creds.IV)
+	return nil
+}

stream_test.go

@@ -0,0 +1,43 @@
+package openssl
+
+import (
+	"bytes"
+	"io"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestReader(t *testing.T) {
+	o := New()
+
+	pass := "abcd"
+	plaintext := []byte("123abc,./vvvczcekdewfeojdosndsdlsndlncnepcnodcnviorf409eofnvkdfvjfvdsoijvo")
+
+	data, err := o.EncryptBinaryBytes(pass, plaintext, BytesToKeyMD5)
+	require.NoError(t, err)
+
+	buf := bytes.NewBuffer(nil)
+	_, err = io.Copy(buf, NewReader(bytes.NewReader(data), pass, BytesToKeyMD5))
+	require.NoError(t, err)
+	require.Equal(t, buf.Bytes(), plaintext)
+}
+
+func TestWriter(t *testing.T) {
+	o := New()
+
+	pass := "abcd"
+	plaintext := []byte("123abc,./vvvczcekdewfeojzaasdsddsdosnd432pdneonkefnoescndisbcisfheosfbdk vsdovsdn]sdlsndlncnepcnodcnviorf409eofnvkdfvjfvdsoijvo")
+
+	buf := bytes.NewBuffer(nil)
+	es := NewWriter(buf, pass, BytesToKeyMD5)
+
+	_, err := es.Write(plaintext)
+	require.NoError(t, err)
+	require.NoError(t, es.Close())
+
+	da, err := o.DecryptBinaryBytes(pass, buf.Bytes(), BytesToKeyMD5)
+	require.NoError(t, err)
+
+	require.Equal(t, da, plaintext)
+}