tls: Separate TLS protection to abstracted AEAD modes

To better separate the code path for different TLS versions and modes of
operation, we introduce a TLS AEAD abstraction. We provide three implementations
using traditional transforms, and get prepared for TLS AEAD modes.

src/libtls/tls_aead_expl.c

@@ -0,0 +1,223 @@
+/*
+ * 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;
+
+	/**
+	 * traditional crypter
+	 */
+	crypter_t *crypter;
+
+	/**
+	 * traditional signer
+	 */
+	signer_t *signer;
+
+	/**
+	 * IV generator
+	 */
+	iv_gen_t *iv_gen;
+};
+
+/**
+ * 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, mac, padding, iv;
+	u_int8_t bs, padlen;
+	sigheader_t hdr;
+
+	hdr.type = type;
+	htoun64(&hdr.seq, seq);
+	htoun16(&hdr.version, version);
+	htoun16(&hdr.length, data->len);
+
+	assoc = chunk_from_thing(hdr);
+	if (!this->signer->get_signature(this->signer, assoc, NULL) ||
+		!this->signer->allocate_signature(this->signer, *data, &mac))
+	{
+		return FALSE;
+	}
+	bs = this->crypter->get_block_size(this->crypter);
+	padlen = pad_len(data->len + mac.len + 1, bs);
+
+	padding = chunk_alloca(padlen);
+	memset(padding.ptr, padlen, padding.len);
+
+	/* TLSv1.1 uses random IVs, prepended to record */
+	iv.len = this->crypter->get_iv_size(this->crypter);
+	iv = chunk_alloca(iv.len);
+	if (!this->iv_gen->get_iv(this->iv_gen, seq, iv.len, iv.ptr))
+	{
+		return FALSE;
+	}
+	*data = chunk_cat("mmcc", *data, mac, padding, chunk_from_thing(padlen));
+	/* encrypt inline */
+	if (!this->crypter->encrypt(this->crypter, *data, iv, NULL))
+	{
+		free(data->ptr);
+		return FALSE;
+	}
+	/* prepend IV */
+	*data = chunk_cat("cm", iv, *data);
+	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, mac, iv;
+	u_int8_t bs, padlen;
+	sigheader_t hdr;
+
+	iv.len = this->crypter->get_iv_size(this->crypter);
+	if (data->len < iv.len)
+	{
+		return FALSE;
+	}
+	iv.ptr = data->ptr;
+	*data = chunk_skip(*data, iv.len);
+	bs = this->crypter->get_block_size(this->crypter);
+	if (data->len < bs || data->len % bs)
+	{
+		return FALSE;
+	}
+	if (!this->crypter->decrypt(this->crypter, *data, iv, NULL))
+	{
+		return FALSE;
+	}
+	padlen = data->ptr[data->len - 1];
+	if (padlen < data->len)
+	{	/* If padding looks valid, remove it */
+		data->len -= padlen + 1;
+	}
+
+	bs = this->signer->get_block_size(this->signer);
+	if (data->len < bs)
+	{
+		return FALSE;
+	}
+	mac = chunk_skip(*data, data->len - bs);
+	data->len -= bs;
+
+	hdr.type = type;
+	htoun64(&hdr.seq, seq);
+	htoun16(&hdr.version, version);
+	htoun16(&hdr.length, data->len);
+
+	assoc = chunk_from_thing(hdr);
+	if (!this->signer->get_signature(this->signer, assoc, NULL) ||
+		!this->signer->verify_signature(this->signer, *data, mac))
+	{
+		return FALSE;
+	}
+	return TRUE;
+}
+
+METHOD(tls_aead_t, get_mac_key_size, size_t,
+	private_tls_aead_t *this)
+{
+	return this->signer->get_key_size(this->signer);
+}
+
+METHOD(tls_aead_t, get_encr_key_size, size_t,
+	private_tls_aead_t *this)
+{
+	return this->crypter->get_key_size(this->crypter);
+}
+
+METHOD(tls_aead_t, get_iv_size, size_t,
+	private_tls_aead_t *this)
+{
+	return 0;
+}
+
+METHOD(tls_aead_t, set_keys, bool,
+	private_tls_aead_t *this, chunk_t mac, chunk_t encr, chunk_t iv)
+{
+	if (iv.len)
+	{
+		return FALSE;
+	}
+	return this->signer->set_key(this->signer, mac) &&
+		   this->crypter->set_key(this->crypter, encr);
+}
+
+METHOD(tls_aead_t, destroy, void,
+	private_tls_aead_t *this)
+{
+	this->iv_gen->destroy(this->iv_gen);
+	DESTROY_IF(this->crypter);
+	DESTROY_IF(this->signer);
+	free(this);
+}
+
+/**
+ * See header
+ */
+tls_aead_t *tls_aead_create_explicit(integrity_algorithm_t mac,
+								encryption_algorithm_t encr, size_t encr_size)
+{
+	private_tls_aead_t *this;
+
+	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,
+		},
+		.crypter = lib->crypto->create_crypter(lib->crypto, encr, encr_size),
+		.signer = lib->crypto->create_signer(lib->crypto, mac),
+		.iv_gen = iv_gen_rand_create(),
+	);
+
+	if (!this->crypter || !this->signer)
+	{
+		destroy(this);
+		return NULL;
+	}
+
+	return &this->public;
+}