Golang EVP_EncryptFinal_ex Examples

Example #1

File: ciphers.go Project: Machyne/mongo

func (ctx *encryptionCipherCtx) EncryptFinal() ([]byte, error) {
	outbuf := make([]byte, ctx.BlockSize())
	var outlen C.int
	if 1 != C.EVP_EncryptFinal_ex(ctx.ctx, (*C.uchar)(&outbuf[0]), &outlen) {
		return nil, errors.New("encryption failed")
	}
	return outbuf[:outlen], nil
}

Example #2

File: stupidgcm.go Project: rfjakob/gocryptfs

// Seal encrypts "in" using "iv" and "authData" and append the result to "dst"
func (g stupidGCM) Seal(dst, iv, in, authData []byte) []byte {
	if len(iv) != ivLen {
		log.Panicf("Only %d-byte IVs are supported", ivLen)
	}
	if len(in) == 0 {
		log.Panic("Zero-length input data is not supported")
	}
	buf := make([]byte, len(in)+tagLen)

	// https://wiki.openssl.org/index.php/EVP_Authenticated_Encryption_and_Decryption#Authenticated_Encryption_using_GCM_mode

	// Create scratch space "context"
	ctx := C.EVP_CIPHER_CTX_new()
	if ctx == nil {
		log.Panic("EVP_CIPHER_CTX_new failed")
	}

	// Set cipher to AES-256
	if C.EVP_EncryptInit_ex(ctx, C.EVP_aes_256_gcm(), nil, nil, nil) != 1 {
		log.Panic("EVP_EncryptInit_ex I failed")
	}

	// Use 16-byte IV
	if C.EVP_CIPHER_CTX_ctrl(ctx, C.EVP_CTRL_GCM_SET_IVLEN, ivLen, nil) != 1 {
		log.Panic("EVP_CIPHER_CTX_ctrl EVP_CTRL_GCM_SET_IVLEN failed")
	}

	// Set key and IV
	if C.EVP_EncryptInit_ex(ctx, nil, nil, (*C.uchar)(&g.key[0]), (*C.uchar)(&iv[0])) != 1 {
		log.Panic("EVP_EncryptInit_ex II failed")
	}

	// Provide authentication data
	var resultLen C.int
	if C.EVP_EncryptUpdate(ctx, nil, &resultLen, (*C.uchar)(&authData[0]), C.int(len(authData))) != 1 {
		log.Panic("EVP_EncryptUpdate authData failed")
	}
	if int(resultLen) != len(authData) {
		log.Panicf("Unexpected length %d", resultLen)
	}

	// Encrypt "in" into "buf"
	if C.EVP_EncryptUpdate(ctx, (*C.uchar)(&buf[0]), &resultLen, (*C.uchar)(&in[0]), C.int(len(in))) != 1 {
		log.Panic("EVP_EncryptUpdate failed")
	}
	if int(resultLen) != len(in) {
		log.Panicf("Unexpected length %d", resultLen)
	}

	// Finalise encryption
	// Because GCM is a stream encryption, this will not write out any data.
	dummy := make([]byte, 16)
	if C.EVP_EncryptFinal_ex(ctx, (*C.uchar)(&dummy[0]), &resultLen) != 1 {
		log.Panic("EVP_EncryptFinal_ex failed")
	}
	if resultLen != 0 {
		log.Panicf("Unexpected length %d", resultLen)
	}

	// Get GMAC tag and append it to the ciphertext in "buf"
	if C.EVP_CIPHER_CTX_ctrl(ctx, C.EVP_CTRL_GCM_GET_TAG, tagLen, (unsafe.Pointer)(&buf[len(in)])) != 1 {
		log.Panic("EVP_CIPHER_CTX_ctrl EVP_CTRL_GCM_GET_TAG failed")
	}

	// Free scratch space
	C.EVP_CIPHER_CTX_free(ctx)

	return append(dst, buf...)
}