tls: Implement the TLS AEAD abstraction for real AEAD modes

src/libtls/tls_aead.c

@@ -0,0 +1,218 @@
+/*
+ * Copyright (C) 2014 Martin Willi
+ * Copyright (C) 2014 revosec AG
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation; either version 2 of the License, or (at your
+ * option) any later version.  See <http://www.fsf.org/copyleft/gpl.txt>.
+ *
+ * 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 General Public License
+ * for more details.
+ */
+
+#include "tls_aead.h"
+
+#include <crypto/iv/iv_gen_rand.h>
+
+typedef struct private_tls_aead_t private_tls_aead_t;
+
+/**
+ * Private data of an tls_aead_t object.
+ */
+struct private_tls_aead_t {
+
+	/**
+	 * Public tls_aead_t interface.
+	 */
+	tls_aead_t public;
+
+	/**
+	 * AEAD transform
+	 */
+	aead_t *aead;
+
+	/**
+	 * Size of salt, the implicit nonce
+	 */
+	size_t salt;
+};
+
+/**
+ * Associated header data to create signature over
+ */
+typedef struct __attribute__((__packed__)) {
+	u_int64_t seq;
+	u_int8_t type;
+	u_int16_t version;
+	u_int16_t length;
+} sigheader_t;
+
+METHOD(tls_aead_t, encrypt, bool,
+	private_tls_aead_t *this, tls_version_t version, tls_content_type_t type,
+	u_int64_t seq, chunk_t *data)
+{
+	chunk_t assoc, encrypted, iv, plain;
+	u_int8_t icvlen;
+	sigheader_t hdr;
+	iv_gen_t *gen;
+
+	gen = this->aead->get_iv_gen(this->aead);
+	iv.len = this->aead->get_iv_size(this->aead);
+	icvlen = this->aead->get_icv_size(this->aead);
+
+	encrypted = chunk_alloc(iv.len + data->len + icvlen);
+	iv.ptr = encrypted.ptr;
+	if (!gen->get_iv(gen, seq, iv.len, iv.ptr))
+	{
+		chunk_free(&encrypted);
+		return FALSE;
+	}
+	memcpy(encrypted.ptr + iv.len, data->ptr, data->len);
+	plain = chunk_skip(encrypted, iv.len);
+	plain.len -= icvlen;
+
+	hdr.type = type;
+	htoun64(&hdr.seq, seq);
+	htoun16(&hdr.version, version);
+	htoun16(&hdr.length, plain.len);
+
+	assoc = chunk_from_thing(hdr);
+	if (!this->aead->encrypt(this->aead, plain, assoc, iv, NULL))
+	{
+		return FALSE;
+	}
+	chunk_free(data);
+	*data = encrypted;
+	return TRUE;
+}
+
+METHOD(tls_aead_t, decrypt, bool,
+	private_tls_aead_t *this, tls_version_t version, tls_content_type_t type,
+	u_int64_t seq, chunk_t *data)
+{
+	chunk_t assoc, iv;
+	u_int8_t icvlen;
+	sigheader_t hdr;
+
+	iv.len = this->aead->get_iv_size(this->aead);
+	if (data->len < iv.len)
+	{
+		return FALSE;
+	}
+	iv.ptr = data->ptr;
+	*data = chunk_skip(*data, iv.len);
+	icvlen = this->aead->get_icv_size(this->aead);
+	if (data->len < icvlen)
+	{
+		return FALSE;
+	}
+
+	hdr.type = type;
+	htoun64(&hdr.seq, seq);
+	htoun16(&hdr.version, version);
+	htoun16(&hdr.length, data->len - icvlen);
+
+	assoc = chunk_from_thing(hdr);
+	if (!this->aead->decrypt(this->aead, *data, assoc, iv, NULL))
+	{
+		return FALSE;
+	}
+	data->len -= icvlen;
+	return TRUE;
+}
+
+METHOD(tls_aead_t, get_mac_key_size, size_t,
+	private_tls_aead_t *this)
+{
+	return 0;
+}
+
+METHOD(tls_aead_t, get_encr_key_size, size_t,
+	private_tls_aead_t *this)
+{
+	return this->aead->get_key_size(this->aead) - this->salt;
+}
+
+METHOD(tls_aead_t, get_iv_size, size_t,
+	private_tls_aead_t *this)
+{
+	return this->salt;
+}
+
+METHOD(tls_aead_t, set_keys, bool,
+	private_tls_aead_t *this, chunk_t mac, chunk_t encr, chunk_t iv)
+{
+	chunk_t key;
+
+	if (mac.len)
+	{
+		return FALSE;
+	}
+	key = chunk_cata("cc", encr, iv);
+	return this->aead->set_key(this->aead, key);
+}
+
+METHOD(tls_aead_t, destroy, void,
+	private_tls_aead_t *this)
+{
+	this->aead->destroy(this->aead);
+	free(this);
+}
+
+/**
+ * See header
+ */
+tls_aead_t *tls_aead_create_aead(encryption_algorithm_t encr, size_t encr_size)
+{
+	private_tls_aead_t *this;
+	size_t salt;
+
+	switch (encr)
+	{
+		case ENCR_AES_GCM_ICV8:
+		case ENCR_AES_GCM_ICV12:
+		case ENCR_AES_GCM_ICV16:
+		case ENCR_AES_CCM_ICV8:
+		case ENCR_AES_CCM_ICV12:
+		case ENCR_AES_CCM_ICV16:
+		case ENCR_CAMELLIA_CCM_ICV8:
+		case ENCR_CAMELLIA_CCM_ICV12:
+		case ENCR_CAMELLIA_CCM_ICV16:
+			salt = 4;
+			break;
+		default:
+			return NULL;
+	}
+
+	INIT(this,
+		.public = {
+			.encrypt = _encrypt,
+			.decrypt = _decrypt,
+			.get_iv_size = _get_iv_size,
+			.get_mac_key_size = _get_mac_key_size,
+			.get_encr_key_size = _get_encr_key_size,
+			.get_iv_size = _get_iv_size,
+			.set_keys = _set_keys,
+			.destroy = _destroy,
+		},
+		.aead = lib->crypto->create_aead(lib->crypto, encr, encr_size, salt),
+		.salt = salt,
+	);
+
+	if (!this->aead)
+	{
+		free(this);
+		return NULL;
+	}
+
+	if (this->aead->get_block_size(this->aead) != 1)
+	{	/* TLS does not define any padding scheme for AEAD */
+		destroy(this);
+		return NULL;
+	}
+
+	return &this->public;
+}