Merge commit '86cc97e55fe346502462284d2e636a2b3708163e' as 'Sources/OpenVPN3'

Sources/OpenVPN3/openvpn/openssl/crypto/api.hpp

@@ -0,0 +1,46 @@
+//    OpenVPN -- An application to securely tunnel IP networks
+//               over a single port, with support for SSL/TLS-based
+//               session authentication and key exchange,
+//               packet encryption, packet authentication, and
+//               packet compression.
+//
+//    Copyright (C) 2012-2017 OpenVPN Inc.
+//
+//    This program is free software: you can redistribute it and/or modify
+//    it under the terms of the GNU Affero General Public License Version 3
+//    as published by the Free Software Foundation.
+//
+//    This program is distributed in the hope that it will be useful,
+//    but WITHOUT ANY WARRANTY; without even the implied warranty of
+//    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+//    GNU Affero General Public License for more details.
+//
+//    You should have received a copy of the GNU Affero General Public License
+//    along with this program in the COPYING file.
+//    If not, see <http://www.gnu.org/licenses/>.
+
+#ifndef OPENVPN_OPENSSL_CRYPTO_API_H
+#define OPENVPN_OPENSSL_CRYPTO_API_H
+
+#include <openvpn/openssl/crypto/cipher.hpp>
+#include <openvpn/openssl/crypto/ciphergcm.hpp>
+#include <openvpn/openssl/crypto/digest.hpp>
+#include <openvpn/openssl/crypto/hmac.hpp>
+
+namespace openvpn {
+
+  // type container for OpenSSL Crypto-level API
+  struct OpenSSLCryptoAPI {
+    // cipher
+    typedef OpenSSLCrypto::CipherContext CipherContext;
+    typedef OpenSSLCrypto::CipherContextGCM CipherContextGCM;
+
+    // digest
+    typedef OpenSSLCrypto::DigestContext DigestContext;
+
+    // HMAC
+    typedef OpenSSLCrypto::HMACContext HMACContext;
+  };
+}
+
+#endif

Sources/OpenVPN3/openvpn/openssl/crypto/cipher.hpp

@@ -0,0 +1,200 @@
+//    OpenVPN -- An application to securely tunnel IP networks
+//               over a single port, with support for SSL/TLS-based
+//               session authentication and key exchange,
+//               packet encryption, packet authentication, and
+//               packet compression.
+//
+//    Copyright (C) 2012-2017 OpenVPN Inc.
+//
+//    This program is free software: you can redistribute it and/or modify
+//    it under the terms of the GNU Affero General Public License Version 3
+//    as published by the Free Software Foundation.
+//
+//    This program is distributed in the hope that it will be useful,
+//    but WITHOUT ANY WARRANTY; without even the implied warranty of
+//    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+//    GNU Affero General Public License for more details.
+//
+//    You should have received a copy of the GNU Affero General Public License
+//    along with this program in the COPYING file.
+//    If not, see <http://www.gnu.org/licenses/>.
+
+// Wrap the OpenSSL cipher API defined in <openssl/evp.h> so
+// that it can be used as part of the crypto layer of the OpenVPN core.
+
+#ifndef OPENVPN_OPENSSL_CRYPTO_CIPHER_H
+#define OPENVPN_OPENSSL_CRYPTO_CIPHER_H
+
+#include <string>
+
+#include <openssl/objects.h>
+#include <openssl/evp.h>
+
+#include <openvpn/common/size.hpp>
+#include <openvpn/common/exception.hpp>
+#include <openvpn/crypto/static_key.hpp>
+#include <openvpn/crypto/cryptoalgs.hpp>
+#include <openvpn/openssl/util/error.hpp>
+#include <openvpn/openssl/compat.hpp>
+
+namespace openvpn {
+  namespace OpenSSLCrypto {
+    class CipherContext
+    {
+      CipherContext(const CipherContext&) = delete;
+      CipherContext& operator=(const CipherContext&) = delete;
+
+    public:
+      OPENVPN_SIMPLE_EXCEPTION(openssl_cipher_mode_error);
+      OPENVPN_SIMPLE_EXCEPTION(openssl_cipher_uninitialized);
+      OPENVPN_EXCEPTION(openssl_cipher_error);
+
+      // mode parameter for constructor
+      enum {
+	MODE_UNDEF = -1,
+	ENCRYPT = 1,
+	DECRYPT = 0
+      };
+
+      // OpenSSL cipher constants
+      enum {
+	MAX_IV_LENGTH = EVP_MAX_IV_LENGTH,
+	CIPH_CBC_MODE = EVP_CIPH_CBC_MODE
+      };
+
+      CipherContext()
+	: initialized(false)
+      {
+      }
+
+      ~CipherContext() { erase() ; }
+
+      void init(const CryptoAlgs::Type alg, const unsigned char *key, const int mode)
+      {
+	// check that mode is valid
+	if (!(mode == ENCRYPT || mode == DECRYPT))
+	  throw openssl_cipher_mode_error();
+	erase();
+	ctx = EVP_CIPHER_CTX_new ();
+	EVP_CIPHER_CTX_reset (ctx);
+	if (!EVP_CipherInit_ex (ctx, cipher_type(alg), nullptr, key, nullptr, mode))
+	  {
+	    openssl_clear_error_stack();
+	    throw openssl_cipher_error("EVP_CipherInit_ex (init)");
+	  }
+	initialized = true;
+      }
+
+      void reset(const unsigned char *iv)
+      {
+	check_initialized();
+	if (!EVP_CipherInit_ex (ctx, nullptr, nullptr, nullptr, iv, -1))
+	  {
+	    openssl_clear_error_stack();
+	    throw openssl_cipher_error("EVP_CipherInit_ex (reset)");
+	  }
+      }
+
+      bool update(unsigned char *out, const size_t max_out_size,
+		  const unsigned char *in, const size_t in_size,
+		  size_t& out_acc)
+      {
+	check_initialized();
+	int outlen;
+	if (EVP_CipherUpdate (ctx, out, &outlen, in, int(in_size)))
+	  {
+	    out_acc += outlen;
+	    return true;
+	  }
+	else
+	  {
+	    openssl_clear_error_stack();
+	    return false;
+	  }
+      }
+
+      bool final(unsigned char *out, const size_t max_out_size, size_t& out_acc)
+      {
+	check_initialized();
+	int outlen;
+	if (EVP_CipherFinal_ex (ctx, out, &outlen))
+	  {
+	    out_acc += outlen;
+	    return true;
+	  }
+	else
+	  {
+	    openssl_clear_error_stack();
+	    return false;
+	  }
+      }
+
+      bool is_initialized() const { return initialized; }
+
+      size_t iv_length() const
+      {
+	check_initialized();
+	return EVP_CIPHER_CTX_iv_length (ctx);
+      }
+
+      size_t block_size() const
+      {
+	check_initialized();
+	return EVP_CIPHER_CTX_block_size (ctx);
+      }
+
+      // return cipher mode (such as CIPH_CBC_MODE, etc.)
+      int cipher_mode() const
+      {
+	check_initialized();
+	return EVP_CIPHER_CTX_mode (ctx);
+      }
+
+    private:
+      static const EVP_CIPHER *cipher_type(const CryptoAlgs::Type alg)
+      {
+	switch (alg)
+	  {
+	  case CryptoAlgs::AES_128_CBC:
+	    return EVP_aes_128_cbc();
+	  case CryptoAlgs::AES_192_CBC:
+	    return EVP_aes_192_cbc();
+	  case CryptoAlgs::AES_256_CBC:
+	    return EVP_aes_256_cbc();
+	  case CryptoAlgs::AES_256_CTR:
+	    return EVP_aes_256_ctr();
+	  case CryptoAlgs::DES_CBC:
+	    return EVP_des_cbc();
+	  case CryptoAlgs::DES_EDE3_CBC:
+	    return EVP_des_ede3_cbc();
+	  case CryptoAlgs::BF_CBC:
+	    return EVP_bf_cbc();
+	  default:
+	    OPENVPN_THROW(openssl_cipher_error, CryptoAlgs::name(alg) << ": not usable");
+	  }
+      }
+
+      void erase()
+      {
+	if (initialized)
+	  {
+	    EVP_CIPHER_CTX_free (ctx);
+	    initialized = false;
+	  }
+      }
+
+      void check_initialized() const
+      {
+#ifdef OPENVPN_ENABLE_ASSERT
+	if (!initialized)
+	  throw openssl_cipher_uninitialized();
+#endif
+      }
+
+      bool initialized;
+      EVP_CIPHER_CTX* ctx;
+    };
+  }
+}
+
+#endif

Sources/OpenVPN3/openvpn/openssl/crypto/ciphergcm.hpp

@@ -0,0 +1,245 @@
+//    OpenVPN -- An application to securely tunnel IP networks
+//               over a single port, with support for SSL/TLS-based
+//               session authentication and key exchange,
+//               packet encryption, packet authentication, and
+//               packet compression.
+//
+//    Copyright (C) 2012-2017 OpenVPN Inc.
+//
+//    This program is free software: you can redistribute it and/or modify
+//    it under the terms of the GNU Affero General Public License Version 3
+//    as published by the Free Software Foundation.
+//
+//    This program is distributed in the hope that it will be useful,
+//    but WITHOUT ANY WARRANTY; without even the implied warranty of
+//    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+//    GNU Affero General Public License for more details.
+//
+//    You should have received a copy of the GNU Affero General Public License
+//    along with this program in the COPYING file.
+//    If not, see <http://www.gnu.org/licenses/>.
+
+// Wrap the OpenSSL GCM API.
+
+#ifndef OPENVPN_OPENSSL_CRYPTO_CIPHERGCM_H
+#define OPENVPN_OPENSSL_CRYPTO_CIPHERGCM_H
+
+#include <string>
+
+#include <openssl/objects.h>
+#include <openssl/evp.h>
+
+#include <openvpn/common/size.hpp>
+#include <openvpn/common/exception.hpp>
+#include <openvpn/common/likely.hpp>
+#include <openvpn/crypto/static_key.hpp>
+#include <openvpn/crypto/cryptoalgs.hpp>
+#include <openvpn/openssl/util/error.hpp>
+
+namespace openvpn {
+  namespace OpenSSLCrypto {
+    class CipherContextGCM
+    {
+      CipherContextGCM(const CipherContextGCM&) = delete;
+      CipherContextGCM& operator=(const CipherContextGCM&) = delete;
+
+    public:
+      OPENVPN_EXCEPTION(openssl_gcm_error);
+
+      // mode parameter for constructor
+      enum {
+	MODE_UNDEF = -1,
+	ENCRYPT = 1,
+	DECRYPT = 0
+      };
+
+      // OpenSSL cipher constants
+      enum {
+	IV_LEN = 12,
+	AUTH_TAG_LEN = 16,
+	SUPPORTS_IN_PLACE_ENCRYPT = 0,
+      };
+
+      CipherContextGCM()
+	: initialized(false)
+      {
+      }
+
+      ~CipherContextGCM() { erase() ; }
+
+      void init(const CryptoAlgs::Type alg,
+		const unsigned char *key,
+		const unsigned int keysize,
+		const int mode)
+      {
+	erase();
+	unsigned int ckeysz = 0;
+	const EVP_CIPHER *ciph = cipher_type(alg, ckeysz);
+	if (ckeysz > keysize)
+	  throw openssl_gcm_error("insufficient key material");
+	ctx = EVP_CIPHER_CTX_new();
+	EVP_CIPHER_CTX_reset(ctx);
+	switch (mode)
+	  {
+	  case ENCRYPT:
+	    if (!EVP_EncryptInit_ex(ctx, ciph, nullptr, key, nullptr))
+	      {
+		openssl_clear_error_stack();
+		throw openssl_gcm_error("EVP_EncryptInit_ex (init)");
+	      }
+	    break;
+	  case DECRYPT:
+	    if (!EVP_DecryptInit_ex(ctx, ciph, nullptr, key, nullptr))
+	      {
+		openssl_clear_error_stack();
+		throw openssl_gcm_error("EVP_DecryptInit_ex (init)");
+	      }
+	    break;
+	  default:
+	    throw openssl_gcm_error("bad mode");
+	  }
+	if (EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_GCM_SET_IVLEN, IV_LEN, nullptr) != 1)
+	  {
+	    openssl_clear_error_stack();
+	    throw openssl_gcm_error("EVP_CIPHER_CTX_ctrl set IV len");
+	  }
+	initialized = true;
+      }
+
+      void encrypt(const unsigned char *input,
+		   unsigned char *output,
+		   size_t length,
+		   const unsigned char *iv,
+		   unsigned char *tag,
+		   const unsigned char *ad,
+		   size_t ad_len)
+      {
+	int len;
+	int ciphertext_len;
+
+	check_initialized();
+	if (!EVP_EncryptInit_ex(ctx, nullptr, nullptr, nullptr, iv))
+	  {
+	    openssl_clear_error_stack();
+	    throw openssl_gcm_error("EVP_EncryptInit_ex (reset)");
+	  }
+	if (!EVP_EncryptUpdate(ctx, nullptr, &len, ad, int(ad_len)))
+	  {
+	    openssl_clear_error_stack();
+	    throw openssl_gcm_error("EVP_EncryptUpdate AD");
+	  }
+	if (!EVP_EncryptUpdate(ctx, output, &len, input, int(length)))
+	  {
+	    openssl_clear_error_stack();
+	    throw openssl_gcm_error("EVP_EncryptUpdate data");
+	  }
+	ciphertext_len = len;
+	if (!EVP_EncryptFinal_ex(ctx, output+len, &len))
+	  {
+	    openssl_clear_error_stack();
+	    throw openssl_gcm_error("EVP_EncryptFinal_ex");
+	  }
+	ciphertext_len += len;
+	if (ciphertext_len != length)
+	  {
+	    throw openssl_gcm_error("encrypt size inconsistency");
+	  }
+	if (!EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_GCM_GET_TAG, AUTH_TAG_LEN, tag))
+	  {
+	    openssl_clear_error_stack();
+	    throw openssl_gcm_error("EVP_CIPHER_CTX_ctrl get tag");
+	  }
+      }
+
+      bool decrypt(const unsigned char *input,
+		  unsigned char *output,
+		  size_t length,
+		  const unsigned char *iv,
+		  unsigned char *tag,
+		  const unsigned char *ad,
+		  size_t ad_len)
+      {
+	int len;
+	int plaintext_len;
+
+	check_initialized();
+	if (!EVP_DecryptInit_ex(ctx, nullptr, nullptr, nullptr, iv))
+	  {
+	    openssl_clear_error_stack();
+	    throw openssl_gcm_error("EVP_DecryptInit_ex (reset)");
+	  }
+	if (!EVP_DecryptUpdate(ctx, nullptr, &len, ad, int(ad_len)))
+	  {
+	    openssl_clear_error_stack();
+	    throw openssl_gcm_error("EVP_DecryptUpdate AD");
+	  }
+	if (!EVP_DecryptUpdate(ctx, output, &len, input, int(length)))
+	  {
+	    openssl_clear_error_stack();
+	    throw openssl_gcm_error("EVP_DecryptUpdate data");
+	  }
+	plaintext_len = len;
+	if (!EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_GCM_SET_TAG, AUTH_TAG_LEN, tag))
+	  {
+	    openssl_clear_error_stack();
+	    throw openssl_gcm_error("EVP_CIPHER_CTX_ctrl set tag");
+	  }
+	if (!EVP_DecryptFinal_ex(ctx, output+len, &len))
+	  {
+	    openssl_clear_error_stack();
+	    return false;
+	  }
+	plaintext_len += len;
+	if (plaintext_len != length)
+	  {
+	    throw openssl_gcm_error("decrypt size inconsistency");
+	  }
+	return true;
+      }
+
+      bool is_initialized() const { return initialized; }
+
+    private:
+      static const EVP_CIPHER *cipher_type(const CryptoAlgs::Type alg,
+					   unsigned int& keysize)
+      {
+	switch (alg)
+	  {
+	  case CryptoAlgs::AES_128_GCM:
+	    keysize = 16;
+	    return EVP_aes_128_gcm();
+	  case CryptoAlgs::AES_192_GCM:
+	    keysize = 24;
+	    return EVP_aes_192_gcm();
+	  case CryptoAlgs::AES_256_GCM:
+	    keysize = 32;
+	    return EVP_aes_256_gcm();
+	  default:
+	    OPENVPN_THROW(openssl_gcm_error, CryptoAlgs::name(alg) << ": not usable");
+	  }
+      }
+
+      void erase()
+      {
+	if (initialized)
+	  {
+	    EVP_CIPHER_CTX_free(ctx);
+	    initialized = false;
+	  }
+      }
+
+      void check_initialized() const
+      {
+#ifdef OPENVPN_ENABLE_ASSERT
+	if (unlikely(!initialized))
+	  throw openssl_gcm_error("uninitialized");
+#endif
+      }
+
+      bool initialized;
+      EVP_CIPHER_CTX *ctx;
+    };
+  }
+}
+
+#endif

Sources/OpenVPN3/openvpn/openssl/crypto/digest.hpp

@@ -0,0 +1,168 @@
+//    OpenVPN -- An application to securely tunnel IP networks
+//               over a single port, with support for SSL/TLS-based
+//               session authentication and key exchange,
+//               packet encryption, packet authentication, and
+//               packet compression.
+//
+//    Copyright (C) 2012-2017 OpenVPN Inc.
+//
+//    This program is free software: you can redistribute it and/or modify
+//    it under the terms of the GNU Affero General Public License Version 3
+//    as published by the Free Software Foundation.
+//
+//    This program is distributed in the hope that it will be useful,
+//    but WITHOUT ANY WARRANTY; without even the implied warranty of
+//    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+//    GNU Affero General Public License for more details.
+//
+//    You should have received a copy of the GNU Affero General Public License
+//    along with this program in the COPYING file.
+//    If not, see <http://www.gnu.org/licenses/>.
+
+// Wrap the OpenSSL digest API defined in <openssl/evp.h>
+// so that it can be used as part of the crypto layer of the OpenVPN core.
+
+#ifndef OPENVPN_OPENSSL_CRYPTO_DIGEST_H
+#define OPENVPN_OPENSSL_CRYPTO_DIGEST_H
+
+#include <string>
+
+#include <openssl/objects.h>
+#include <openssl/evp.h>
+#include <openssl/md4.h>
+#include <openssl/md5.h>
+#include <openssl/sha.h>
+#include <openssl/hmac.h>
+
+#include <openvpn/common/size.hpp>
+#include <openvpn/common/exception.hpp>
+#include <openvpn/crypto/cryptoalgs.hpp>
+#include <openvpn/openssl/util/error.hpp>
+
+#include <openvpn/openssl/compat.hpp>
+
+namespace openvpn {
+  namespace OpenSSLCrypto {
+    class HMACContext;
+
+    class DigestContext
+    {
+      DigestContext(const DigestContext&) = delete;
+      DigestContext& operator=(const DigestContext&) = delete;
+
+    public:
+      friend class HMACContext;
+
+      OPENVPN_SIMPLE_EXCEPTION(openssl_digest_uninitialized);
+      OPENVPN_EXCEPTION(openssl_digest_error);
+
+      enum {
+	MAX_DIGEST_SIZE = EVP_MAX_MD_SIZE
+      };
+
+      DigestContext()
+	: initialized(false)
+      {
+      }
+
+      DigestContext(const CryptoAlgs::Type alg)
+	: initialized(false)
+      {
+	init(alg);
+      }
+
+      ~DigestContext() { erase() ; }
+
+      void init(const CryptoAlgs::Type alg)
+      {
+	erase();
+	ctx=EVP_MD_CTX_new ();
+	if (!EVP_DigestInit(ctx, digest_type(alg)))
+	  {
+	    openssl_clear_error_stack();
+	    throw openssl_digest_error("EVP_DigestInit");
+	  }
+	initialized = true;
+      }
+
+      void update(const unsigned char *in, const size_t size)
+      {
+	check_initialized();
+	if (!EVP_DigestUpdate(ctx, in, int(size)))
+	  {
+	    openssl_clear_error_stack();
+	    throw openssl_digest_error("EVP_DigestUpdate");
+	  }
+      }
+
+      size_t final(unsigned char *out)
+      {
+	check_initialized();
+	unsigned int outlen;
+	if (!EVP_DigestFinal(ctx, out, &outlen))
+	  {
+	    openssl_clear_error_stack();
+	    throw openssl_digest_error("EVP_DigestFinal");
+	  }
+	return outlen;
+      }
+
+      size_t size() const
+      {
+	check_initialized();
+	return EVP_MD_CTX_size(ctx);
+      }
+
+      bool is_initialized() const { return initialized; }
+
+    private:
+      static const EVP_MD *digest_type(const CryptoAlgs::Type alg)
+      {
+	switch (alg)
+	  {
+	  case CryptoAlgs::MD4:
+	    return EVP_md4();
+	  case CryptoAlgs::MD5:
+	    return EVP_md5();
+	  case CryptoAlgs::SHA1:
+	    return EVP_sha1();
+	  case CryptoAlgs::SHA224:
+	    return EVP_sha224();
+	  case CryptoAlgs::SHA256:
+	    return EVP_sha256();
+	  case CryptoAlgs::SHA384:
+	    return EVP_sha384();
+	  case CryptoAlgs::SHA512:
+	    return EVP_sha512();
+	  default:
+	    OPENVPN_THROW(openssl_digest_error, CryptoAlgs::name(alg) << ": not usable");
+	  }
+      }
+
+      void erase()
+      {
+	if (initialized)
+	  {
+#if OPENSSL_VERSION_NUMBER < 0x10100000L
+	    EVP_MD_CTX_cleanup(ctx);
+#endif
+	    EVP_MD_CTX_free(ctx);
+	    initialized = false;
+	  }
+      }
+
+      void check_initialized() const
+      {
+#ifdef OPENVPN_ENABLE_ASSERT
+	if (!initialized)
+	  throw openssl_digest_uninitialized();
+#endif
+      }
+
+      bool initialized;
+      EVP_MD_CTX *ctx;
+    };
+  }
+}
+
+#endif

Sources/OpenVPN3/openvpn/openssl/crypto/hmac.hpp

@@ -0,0 +1,148 @@
+//    OpenVPN -- An application to securely tunnel IP networks
+//               over a single port, with support for SSL/TLS-based
+//               session authentication and key exchange,
+//               packet encryption, packet authentication, and
+//               packet compression.
+//
+//    Copyright (C) 2012-2017 OpenVPN Inc.
+//
+//    This program is free software: you can redistribute it and/or modify
+//    it under the terms of the GNU Affero General Public License Version 3
+//    as published by the Free Software Foundation.
+//
+//    This program is distributed in the hope that it will be useful,
+//    but WITHOUT ANY WARRANTY; without even the implied warranty of
+//    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+//    GNU Affero General Public License for more details.
+//
+//    You should have received a copy of the GNU Affero General Public License
+//    along with this program in the COPYING file.
+//    If not, see <http://www.gnu.org/licenses/>.
+
+// Wrap the OpenSSL HMAC API defined in <openssl/hmac.h> so
+// that it can be used as part of the crypto layer of the OpenVPN core.
+
+#ifndef OPENVPN_OPENSSL_CRYPTO_HMAC_H
+#define OPENVPN_OPENSSL_CRYPTO_HMAC_H
+
+#include <string>
+
+#include <openvpn/common/size.hpp>
+#include <openvpn/common/exception.hpp>
+#include <openvpn/openssl/crypto/digest.hpp>
+
+#include <openvpn/openssl/compat.hpp>
+
+namespace openvpn {
+  namespace OpenSSLCrypto {
+    class HMACContext
+    {
+      HMACContext(const HMACContext&) = delete;
+      HMACContext& operator=(const HMACContext&) = delete;
+
+    public:
+      OPENVPN_SIMPLE_EXCEPTION(openssl_hmac_uninitialized);
+      OPENVPN_EXCEPTION(openssl_hmac_error);
+
+      enum {
+	MAX_HMAC_SIZE = EVP_MAX_MD_SIZE
+      };
+
+      HMACContext()
+	: initialized(false)
+      {
+      }
+
+      HMACContext(const CryptoAlgs::Type digest, const unsigned char *key, const size_t key_size)
+	: initialized(false)
+      {
+	init(digest, key, key_size);
+      }
+
+      ~HMACContext() { erase() ; }
+
+      void init(const CryptoAlgs::Type digest, const unsigned char *key, const size_t key_size)
+      {
+	erase();
+	ctx = HMAC_CTX_new ();
+	if (!HMAC_Init_ex (ctx, key, int(key_size), DigestContext::digest_type(digest), nullptr))
+	  {
+	    openssl_clear_error_stack();
+	    throw openssl_hmac_error("HMAC_Init_ex (init)");
+	  }
+	initialized = true;
+      }
+
+      void reset()
+      {
+	check_initialized();
+	if (!HMAC_Init_ex (ctx, nullptr, 0, nullptr, nullptr))
+	  {
+	    openssl_clear_error_stack();
+	    throw openssl_hmac_error("HMAC_Init_ex (reset)");
+	  }
+      }
+
+      void update(const unsigned char *in, const size_t size)
+      {
+	check_initialized();
+
+	if (!HMAC_Update(ctx, in, int(size)))
+	  {
+	    openssl_clear_error_stack();
+	    throw openssl_hmac_error("HMAC_Update");
+	  }
+      }
+
+      size_t final(unsigned char *out)
+      {
+	check_initialized();
+	unsigned int outlen;
+	if (!HMAC_Final(ctx, out, &outlen))
+	  {
+	    openssl_clear_error_stack();
+	    throw openssl_hmac_error("HMAC_Final");
+	  }
+	return outlen;
+      }
+
+      size_t size() const
+      {
+	check_initialized();
+	return size_();
+      }
+
+      bool is_initialized() const { return initialized; }
+
+    private:
+      void erase()
+      {
+	if (initialized)
+	  {
+#if OPENSSL_VERSION_NUMBER < 0x10100000L
+#endif
+	    HMAC_CTX_free(ctx);
+	    initialized = false;
+	  }
+      }
+
+      size_t size_() const
+      {
+	return HMAC_size(ctx);
+      }
+
+      void check_initialized() const
+      {
+#ifdef OPENVPN_ENABLE_ASSERT
+	if (!initialized)
+	  throw openssl_hmac_uninitialized();
+#endif
+      }
+
+      bool initialized;
+      HMAC_CTX* ctx;
+    };
+  }
+}
+
+#endif