openssl: Generalize the GCM implementation a bit
This will allow us to use the implementation also for other algorithms.
This commit is contained in:
Tobias Brunner
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/*
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* Copyright (C) 2013-2019 Tobias Brunner
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* HSR Hochschule fuer Technik Rapperswil
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by the
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* Free Software Foundation; either version 2 of the License, or (at your
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* option) any later version. See <http://www.fsf.org/copyleft/gpl.txt>.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* for more details.
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*/
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#include <openssl/opensslv.h>
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#if OPENSSL_VERSION_NUMBER >= 0x1000100fL
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#include "openssl_aead.h"
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#include <openssl/evp.h>
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#include <crypto/iv/iv_gen_seq.h>
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/* the generic AEAD identifiers were added with 1.1.0 */
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#ifndef EVP_CTRL_AEAD_SET_IVLEN
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#define EVP_CTRL_AEAD_SET_IVLEN EVP_CTRL_GCM_SET_IVLEN
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#define EVP_CTRL_AEAD_SET_TAG EVP_CTRL_GCM_SET_TAG
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#define EVP_CTRL_AEAD_GET_TAG EVP_CTRL_GCM_GET_TAG
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#endif
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/** as defined in RFC 4106 */
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#define IV_LEN 8
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#define SALT_LEN 4
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#define NONCE_LEN (IV_LEN + SALT_LEN)
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typedef struct private_aead_t private_aead_t;
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/**
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* Private data of aead_t
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*/
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struct private_aead_t {
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/**
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* Public interface
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*/
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aead_t public;
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/**
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* The encryption key
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*/
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chunk_t key;
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/**
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* Salt value
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*/
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char salt[SALT_LEN];
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/**
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* Size of the integrity check value
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*/
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size_t icv_size;
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/**
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* IV generator
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*/
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iv_gen_t *iv_gen;
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/**
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* The cipher to use
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*/
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const EVP_CIPHER *cipher;
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};
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/**
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* Do the actual en/decryption in an EVP context
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*/
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static bool crypt(private_aead_t *this, chunk_t data, chunk_t assoc, chunk_t iv,
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u_char *out, int enc)
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{
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EVP_CIPHER_CTX *ctx;
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u_char nonce[NONCE_LEN];
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bool success = FALSE;
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int len;
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memcpy(nonce, this->salt, SALT_LEN);
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memcpy(nonce + SALT_LEN, iv.ptr, IV_LEN);
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ctx = EVP_CIPHER_CTX_new();
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EVP_CIPHER_CTX_set_padding(ctx, 0);
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if (!EVP_CipherInit_ex(ctx, this->cipher, NULL, NULL, NULL, enc) ||
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!EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_IVLEN, NONCE_LEN, NULL) ||
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!EVP_CipherInit_ex(ctx, NULL, NULL, this->key.ptr, nonce, enc))
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{
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goto done;
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}
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if (!enc && !EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_TAG, this->icv_size,
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data.ptr + data.len))
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{ /* set ICV for verification on decryption */
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goto done;
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}
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if (assoc.len && !EVP_CipherUpdate(ctx, NULL, &len, assoc.ptr, assoc.len))
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{ /* set AAD if specified */
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goto done;
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}
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if (!EVP_CipherUpdate(ctx, out, &len, data.ptr, data.len) ||
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!EVP_CipherFinal_ex(ctx, out + len, &len))
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{ /* EVP_CipherFinal_ex fails if ICV is incorrect on decryption */
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goto done;
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}
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if (enc && !EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_GET_TAG, this->icv_size,
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out + data.len))
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{ /* copy back the ICV when encrypting */
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goto done;
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}
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success = TRUE;
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done:
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EVP_CIPHER_CTX_free(ctx);
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return success;
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}
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METHOD(aead_t, encrypt, bool,
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private_aead_t *this, chunk_t plain, chunk_t assoc, chunk_t iv,
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chunk_t *encrypted)
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{
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u_char *out;
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out = plain.ptr;
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if (encrypted)
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{
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*encrypted = chunk_alloc(plain.len + this->icv_size);
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out = encrypted->ptr;
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}
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return crypt(this, plain, assoc, iv, out, 1);
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}
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METHOD(aead_t, decrypt, bool,
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private_aead_t *this, chunk_t encrypted, chunk_t assoc, chunk_t iv,
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chunk_t *plain)
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{
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u_char *out;
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if (encrypted.len < this->icv_size)
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{
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return FALSE;
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}
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encrypted.len -= this->icv_size;
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out = encrypted.ptr;
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if (plain)
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{
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*plain = chunk_alloc(encrypted.len);
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out = plain->ptr;
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}
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return crypt(this, encrypted, assoc, iv, out, 0);
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}
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METHOD(aead_t, get_block_size, size_t,
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private_aead_t *this)
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{
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return EVP_CIPHER_block_size(this->cipher);
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}
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METHOD(aead_t, get_icv_size, size_t,
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private_aead_t *this)
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{
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return this->icv_size;
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}
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METHOD(aead_t, get_iv_size, size_t,
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private_aead_t *this)
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{
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return IV_LEN;
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}
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METHOD(aead_t, get_iv_gen, iv_gen_t*,
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private_aead_t *this)
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{
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return this->iv_gen;
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}
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METHOD(aead_t, get_key_size, size_t,
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private_aead_t *this)
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{
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return this->key.len + SALT_LEN;
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}
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METHOD(aead_t, set_key, bool,
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private_aead_t *this, chunk_t key)
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{
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if (key.len != get_key_size(this))
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{
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return FALSE;
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}
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memcpy(this->salt, key.ptr + key.len - SALT_LEN, SALT_LEN);
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memcpy(this->key.ptr, key.ptr, this->key.len);
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return TRUE;
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}
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METHOD(aead_t, destroy, void,
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private_aead_t *this)
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{
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chunk_clear(&this->key);
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this->iv_gen->destroy(this->iv_gen);
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free(this);
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}
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/*
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* Described in header
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*/
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aead_t *openssl_aead_create(encryption_algorithm_t algo,
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size_t key_size, size_t salt_size)
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{
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private_aead_t *this;
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INIT(this,
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.public = {
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.encrypt = _encrypt,
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.decrypt = _decrypt,
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.get_block_size = _get_block_size,
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.get_icv_size = _get_icv_size,
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.get_iv_size = _get_iv_size,
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.get_iv_gen = _get_iv_gen,
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.get_key_size = _get_key_size,
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.set_key = _set_key,
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.destroy = _destroy,
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},
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);
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switch (algo)
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{
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case ENCR_AES_GCM_ICV8:
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this->icv_size = 8;
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break;
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case ENCR_AES_GCM_ICV12:
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this->icv_size = 12;
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break;
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case ENCR_AES_GCM_ICV16:
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this->icv_size = 16;
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break;
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default:
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free(this);
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return NULL;
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}
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if (salt_size && salt_size != SALT_LEN)
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{
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/* currently not supported */
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free(this);
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return NULL;
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}
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switch (algo)
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{
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case ENCR_AES_GCM_ICV8:
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case ENCR_AES_GCM_ICV12:
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case ENCR_AES_GCM_ICV16:
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switch (key_size)
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{
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case 0:
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key_size = 16;
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/* FALL */
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case 16:
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this->cipher = EVP_aes_128_gcm();
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break;
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case 24:
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this->cipher = EVP_aes_192_gcm();
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break;
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case 32:
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this->cipher = EVP_aes_256_gcm();
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break;
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default:
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free(this);
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return NULL;
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}
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break;
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default:
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free(this);
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return NULL;
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}
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if (!this->cipher)
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{
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free(this);
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return NULL;
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}
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this->key = chunk_alloc(key_size);
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this->iv_gen = iv_gen_seq_create();
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return &this->public;
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}
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#endif /* OPENSSL_VERSION_NUMBER */
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