101 lines
2.2 KiB
Go
101 lines
2.2 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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// Supports all nonce sizes
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type opensslGCM struct {
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key []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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// We support any nonce size
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return -1
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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. opensslGCM supports any nonce size.
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func (be opensslGCM) Seal(dst, nonce, plaintext, data []byte) []byte {
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// Preallocate output buffer
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var cipherBuf bytes.Buffer
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cipherBuf.Grow(len(dst) + len(plaintext) + AUTH_TAG_LEN)
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// Output will be appended to dst
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cipherBuf.Write(dst)
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ectx, err := openssl.NewGCMEncryptionCipherCtx(KEY_LEN*8, 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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err = ectx.ExtraData(data)
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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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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(KEY_LEN*8, 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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err = dctx.ExtraData(data)
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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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