94 lines
2.1 KiB
Go
94 lines
2.1 KiB
Go
package cryptfs
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// Implements cipher.AEAD with OpenSSL backend
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import (
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"bytes"
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"github.com/spacemonkeygo/openssl"
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)
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type opensslGCM struct {
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key [16]byte
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}
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func (be opensslGCM) Overhead() int {
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return AUTH_TAG_LEN
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}
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func (be opensslGCM) NonceSize() int {
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return NONCE_LEN
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}
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// Seal encrypts and authenticates plaintext, authenticates the
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// additional data and appends the result to dst, returning the updated
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// slice. The nonce must be NonceSize() bytes long and unique for all
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// time, for a given key.
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//
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// The plaintext and dst may alias exactly or not at all.
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func (be opensslGCM) Seal(dst, nonce, plaintext, data []byte) []byte {
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cipherBuf := bytes.NewBuffer(dst)
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ectx, err := openssl.NewGCMEncryptionCipherCtx(128, nil, be.key[:], nonce[:])
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if err != nil {
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panic(err)
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}
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part, err := ectx.EncryptUpdate(plaintext)
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if err != nil {
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panic(err)
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}
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cipherBuf.Write(part)
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part, err = ectx.EncryptFinal()
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if err != nil {
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panic(err)
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}
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cipherBuf.Write(part)
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part, err = ectx.GetTag()
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if err != nil {
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panic(err)
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}
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cipherBuf.Write(part)
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return cipherBuf.Bytes()
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}
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// Open decrypts and authenticates ciphertext, authenticates the
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// additional data and, if successful, appends the resulting plaintext
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// to dst, returning the updated slice. The nonce must be NonceSize()
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// bytes long and both it and the additional data must match the
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// value passed to Seal.
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//
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// The ciphertext and dst may alias exactly or not at all.
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func (be opensslGCM) Open(dst, nonce, ciphertext, data []byte) ([]byte, error) {
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if len(data) > 0 {
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panic("Extra data is not supported")
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}
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l := len(ciphertext)
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tag := ciphertext[l-AUTH_TAG_LEN:l]
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ciphertext = ciphertext[0:l-AUTH_TAG_LEN]
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plainBuf := bytes.NewBuffer(dst)
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dctx, err := openssl.NewGCMDecryptionCipherCtx(128, nil, be.key[:], nonce[:])
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if err != nil {
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return nil, err
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}
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part, err := dctx.DecryptUpdate(ciphertext)
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if err != nil {
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return nil, err
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}
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plainBuf.Write(part)
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err = dctx.SetTag(tag)
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if err != nil {
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return nil, err
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}
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part, err = dctx.DecryptFinal()
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if err != nil {
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return nil, err
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}
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plainBuf.Write(part)
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return plainBuf.Bytes(), nil
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}
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