chapoly: Provide a generic ChaCha20/Poly1305 AEAD supporting driver backends
This commit is contained in:
Martin Willi
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/*
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* Copyright (C) 2015 Martin Willi
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* Copyright (C) 2015 revosec AG
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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 "chapoly_aead.h"
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#include "chapoly_drv.h"
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#include <crypto/iv/iv_gen_seq.h>
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/* maximum plain message size */
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#define P_MAX 247877906880
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typedef struct private_chapoly_aead_t private_chapoly_aead_t;
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/**
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* Private data of an chapoly_aead_t object.
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*/
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struct private_chapoly_aead_t {
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/**
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* Public chapoly_aead_t interface.
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*/
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chapoly_aead_t public;
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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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* Driver backend
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*/
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chapoly_drv_t *drv;
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};
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/**
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* Include a partial block to ICV by padding it with zero bytes
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*/
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static bool poly_update_padded(private_chapoly_aead_t *this,
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u_char *in, size_t len)
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{
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u_char b[POLY_BLOCK_SIZE];
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memset(b, 0, sizeof(b));
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memcpy(b, in, len);
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return this->drv->poly(this->drv, b, 1);
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}
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/**
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* Include associated data with padding to ICV
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*/
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static bool poly_head(private_chapoly_aead_t *this, u_char *assoc, size_t len)
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{
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u_int blocks, rem;
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blocks = len / POLY_BLOCK_SIZE;
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rem = len % POLY_BLOCK_SIZE;
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if (!this->drv->poly(this->drv, assoc, blocks))
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{
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return FALSE;
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}
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if (rem)
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{
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return poly_update_padded(this, assoc + blocks * POLY_BLOCK_SIZE, rem);
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}
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return TRUE;
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}
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/**
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* Include length fields to ICV
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*/
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static bool poly_tail(private_chapoly_aead_t *this, size_t alen, size_t clen)
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{
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struct {
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u_int64_t alen;
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u_int64_t clen;
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} b;
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b.alen = htole64(alen);
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b.clen = htole64(clen);
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return this->drv->poly(this->drv, (u_char*)&b, 1);
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}
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/**
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* Perform ChaCha20 encryption inline and generate an ICV tag
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*/
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static bool do_encrypt(private_chapoly_aead_t *this, size_t len, u_char *data,
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u_char *iv, size_t alen, u_char *assoc, u_char *icv)
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{
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u_int blocks, rem, prem;
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if (!this->drv->init(this->drv, iv) ||
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!poly_head(this, assoc, alen))
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{
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return FALSE;
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}
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blocks = len / CHACHA_BLOCK_SIZE;
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if (!this->drv->encrypt(this->drv, data, blocks))
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{
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return FALSE;
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}
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rem = len % CHACHA_BLOCK_SIZE;
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if (rem)
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{
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u_char stream[CHACHA_BLOCK_SIZE];
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data += blocks * CHACHA_BLOCK_SIZE;
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if (!this->drv->chacha(this->drv, stream))
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{
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return FALSE;
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}
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memxor(data, stream, rem);
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blocks = rem / POLY_BLOCK_SIZE;
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if (!this->drv->poly(this->drv, data, blocks))
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{
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return FALSE;
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}
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prem = rem % POLY_BLOCK_SIZE;
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if (prem)
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{
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poly_update_padded(this, data + blocks * POLY_BLOCK_SIZE, prem);
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}
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}
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return poly_tail(this, alen, len) &&
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this->drv->finish(this->drv, icv);
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}
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/**
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* Perform ChaCha20 decryption inline and generate an ICV tag
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*/
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static bool do_decrypt(private_chapoly_aead_t *this, size_t len, u_char *data,
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u_char *iv, size_t alen, u_char *assoc, u_char *icv)
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{
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u_int blocks, rem, prem;
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if (!this->drv->init(this->drv, iv) ||
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!poly_head(this, assoc, alen))
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{
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return FALSE;
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}
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blocks = len / CHACHA_BLOCK_SIZE;
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if (!this->drv->decrypt(this->drv, data, blocks))
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{
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return FALSE;
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}
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rem = len % CHACHA_BLOCK_SIZE;
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if (rem)
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{
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u_char stream[CHACHA_BLOCK_SIZE];
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data += blocks * CHACHA_BLOCK_SIZE;
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blocks = rem / POLY_BLOCK_SIZE;
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if (!this->drv->poly(this->drv, data, blocks))
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{
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return FALSE;
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}
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prem = rem % POLY_BLOCK_SIZE;
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if (prem)
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{
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poly_update_padded(this, data + blocks * POLY_BLOCK_SIZE, prem);
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}
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if (!this->drv->chacha(this->drv, stream))
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{
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return FALSE;
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}
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memxor(data, stream, rem);
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}
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return poly_tail(this, alen, len) &&
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this->drv->finish(this->drv, icv);
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}
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METHOD(aead_t, encrypt, bool,
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private_chapoly_aead_t *this, chunk_t plain, chunk_t assoc, chunk_t iv,
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chunk_t *encr)
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{
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u_char *out;
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if (sizeof(plain.len) > sizeof(u_int32_t) && plain.len > P_MAX)
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{
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return FALSE;
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}
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if (iv.len != CHACHA_IV_SIZE)
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{
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return FALSE;
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}
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out = plain.ptr;
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if (encr)
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{
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*encr = chunk_alloc(plain.len + POLY_ICV_SIZE);
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out = encr->ptr;
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memcpy(out, plain.ptr, plain.len);
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}
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do_encrypt(this, plain.len, out, iv.ptr, assoc.len, assoc.ptr,
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out + plain.len);
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return TRUE;
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}
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METHOD(aead_t, decrypt, bool,
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private_chapoly_aead_t *this, chunk_t encr, chunk_t assoc, chunk_t iv,
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chunk_t *plain)
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{
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u_char *out, icv[POLY_ICV_SIZE];
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if (iv.len != CHACHA_IV_SIZE || encr.len < POLY_ICV_SIZE)
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{
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return FALSE;
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}
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encr.len -= POLY_ICV_SIZE;
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if (sizeof(encr.len) > sizeof(u_int32_t) && encr.len > P_MAX)
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{
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return FALSE;
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}
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out = encr.ptr;
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if (plain)
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{
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*plain = chunk_alloc(encr.len);
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out = plain->ptr;
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memcpy(out, encr.ptr, encr.len);
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}
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do_decrypt(this, encr.len, out, iv.ptr, assoc.len, assoc.ptr, icv);
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return memeq_const(icv, encr.ptr + encr.len, POLY_ICV_SIZE);
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}
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METHOD(aead_t, get_block_size, size_t,
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private_chapoly_aead_t *this)
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{
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return 1;
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}
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METHOD(aead_t, get_icv_size, size_t,
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private_chapoly_aead_t *this)
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{
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return POLY_ICV_SIZE;
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}
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METHOD(aead_t, get_iv_size, size_t,
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private_chapoly_aead_t *this)
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{
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return CHACHA_IV_SIZE;
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}
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METHOD(aead_t, get_iv_gen, iv_gen_t*,
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private_chapoly_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_chapoly_aead_t *this)
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{
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return CHACHA_KEY_SIZE + CHACHA_SALT_SIZE;
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}
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METHOD(aead_t, set_key, bool,
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private_chapoly_aead_t *this, chunk_t key)
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{
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if (key.len != CHACHA_KEY_SIZE + CHACHA_SALT_SIZE)
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{
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return FALSE;
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}
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return this->drv->set_key(this->drv, "expand 32-byte k",
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key.ptr, key.ptr + CHACHA_KEY_SIZE);
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}
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METHOD(aead_t, destroy, void,
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private_chapoly_aead_t *this)
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{
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this->drv->destroy(this->drv);
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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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* See header
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*/
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chapoly_aead_t *chapoly_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_chapoly_aead_t *this;
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chapoly_drv_t *drv;
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if (algo != ENCR_CHACHA20_POLY1305)
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{
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return NULL;
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}
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if (key_size && key_size != CHACHA_KEY_SIZE)
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{
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return NULL;
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}
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if (salt_size && salt_size != CHACHA_SALT_SIZE)
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{
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return NULL;
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}
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drv = chapoly_drv_probe();
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if (!drv)
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{
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return NULL;
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}
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INIT(this,
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.public = {
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.aead = {
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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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.iv_gen = iv_gen_seq_create(),
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.drv = drv,
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);
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return &this->public;
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}
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