mirror of
https://github.com/apache/nuttx-apps.git
synced 2026-08-01 20:29:00 +00:00
netutils/dropbear: back chacha20-poly1305 with NuttX /dev/crypto
Replace the bundled libtomcrypt chacha20-poly1305 implementation with an adapter that drives the NuttX crypto device: the SSH construction maps onto CRYPTO_CHACHA20_DJB (the original 64-bit counter/nonce ChaCha20 parameterization used by chacha20-poly1305@openssh.com) for the packet length and payload streams, and onto CRYPTO_POLY1305 for the authentication tag (plain MACs are driven in two steps through /dev/crypto: COP_FLAG_UPDATE feeds the data, a final call retrieves the tag). The NuttX crypto backend is a hard requirement of the port: NETUTILS_DROPBEAR selects CRYPTO_CRYPTODEV and its software backend, and the bundled chachapoly.c is unconditionally dropped from the build. Signed-off-by: Felipe Moura <moura.fmo@gmail.com>
This commit is contained in:
Felipe Moura
parent
1e490d3fbe
commit
26ae8d633e
4 changed files with 388 additions and 1 deletions
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@ -135,6 +135,11 @@ if(CONFIG_NETUTILS_DROPBEAR)
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file(GLOB_RECURSE LIBTOMCRYPT_SRCS CONFIGURE_DEPENDS
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"${CMAKE_CURRENT_SOURCE_DIR}/dropbear/libtomcrypt/src/*.c")
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list(FILTER LIBTOMCRYPT_SRCS EXCLUDE REGEX ".*/prngs/sober128tab\\.c$")
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# Replace the bundled chacha20-poly1305 with the /dev/crypto adapter.
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list(REMOVE_ITEM DROPBEAR_SRCS dropbear/src/chachapoly.c)
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list(APPEND DROPBEAR_SRCS port/dropbear_chachapoly.c)
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list(APPEND DROPBEAR_SRCS ${LIBTOMCRYPT_SRCS})
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if(CONFIG_NETUTILS_DROPBEAR_SCP)
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@ -19,13 +19,21 @@ menuconfig NETUTILS_DROPBEAR
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depends on DEV_URANDOM
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depends on LIBC_NETDB
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depends on LIBC_GAISTRERROR
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select CRYPTO
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depends on ALLOW_BSD_COMPONENTS
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depends on CRYPTO_CRYPTODEV
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depends on CRYPTO_CRYPTODEV_SOFTWARE_CRYPTO
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select CRYPTO_RANDOM_POOL
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---help---
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Enable a minimal Dropbear SSH server port for NuttX. This initial
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port is based on the ESP-IDF MCU test port and provides a single
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foreground SSH server process with SSH sessions backed by NSH.
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The port implements the chacha20-poly1305@openssh.com cipher
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through the NuttX crypto device (/dev/crypto), using the
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CRYPTO_CHACHA20_DJB and CRYPTO_POLY1305 algorithms instead of
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the bundled libtomcrypt implementation, which is dropped from
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the build.
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if NETUTILS_DROPBEAR
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config NETUTILS_DROPBEAR_STACKSIZE
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@ -119,6 +119,11 @@ CSRCS += \
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TOMMATH_SRCS = $(shell if [ -d "$(DROPBEAR_UNPACKNAME)/libtommath" ]; then find "$(DROPBEAR_UNPACKNAME)/libtommath" -name "*.c"; fi)
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TOMCRYPT_SRCS = $(shell if [ -d "$(DROPBEAR_UNPACKNAME)/libtomcrypt/src" ]; then find "$(DROPBEAR_UNPACKNAME)/libtomcrypt/src" -name "*.c" ! -name "sober128tab.c"; fi)
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# Replace the bundled chacha20-poly1305 with the /dev/crypto adapter.
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CSRCS := $(filter-out dropbear/src/chachapoly.c,$(CSRCS))
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CSRCS += port/dropbear_chachapoly.c
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CSRCS += $(TOMMATH_SRCS)
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CSRCS += $(TOMCRYPT_SRCS)
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369
netutils/dropbear/port/dropbear_chachapoly.c
Normal file
369
netutils/dropbear/port/dropbear_chachapoly.c
Normal file
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@ -0,0 +1,369 @@
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/****************************************************************************
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* apps/netutils/dropbear/port/dropbear_chachapoly.c
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*
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* SPDX-License-Identifier: Apache-2.0
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*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership. The
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* ASF licenses this file to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance with the
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* License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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*
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****************************************************************************/
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/* chacha20-poly1305@openssh.com backed by the NuttX crypto device.
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*
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* The SSH construction (see OpenSSH PROTOCOL.chacha20poly1305) uses the
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* original DJB ChaCha20 parameterization: a 64-bit block counter in state
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* words 12..13 and a 64-bit nonce (the packet sequence number, big endian)
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* in words 14..15. This maps to the kernel CRYPTO_CHACHA20_DJB transform,
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* whose 16-byte IV is loaded verbatim into words 12..15 as a 64-bit
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* little-endian counter followed by the 64-bit nonce. The Poly1305 tag is
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* computed with the kernel CRYPTO_POLY1305 transform, keyed with the first
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* keystream block (counter 0) of the main key, as the protocol requires.
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*/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include "includes.h"
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#include <sys/ioctl.h>
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#include <fcntl.h>
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#include <string.h>
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#include <unistd.h>
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#include <crypto/cryptodev.h>
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#include "algo.h"
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#include "dbutil.h"
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#include "chachapoly.h"
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/****************************************************************************
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* Pre-processor Definitions
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****************************************************************************/
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#define CHACHA20_KEY_LEN 32
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#define CHACHA20_BLOCKSIZE 8
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#define CHACHA20_IV_LEN 16
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#define POLY1305_KEY_LEN 32
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#define POLY1305_TAG_LEN 16
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/* The keystream comes from the NuttX crypto device, so each upstream
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* chacha_state is unused and its input[] buffer just stores the 32-byte key,
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* keeping the upstream header unpatched.
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*/
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#define KEY_MAIN(s) ((FAR unsigned char *)(s)->chacha.input)
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#define KEY_HEADER(s) ((FAR unsigned char *)(s)->header.input)
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/****************************************************************************
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* Private Data
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****************************************************************************/
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static const struct ltc_cipher_descriptor g_dropbear_chachapoly_dummy =
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{
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.name = NULL
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};
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static const struct dropbear_hash g_dropbear_chachapoly_mac =
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{
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NULL,
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POLY1305_KEY_LEN,
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POLY1305_TAG_LEN
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};
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static int g_dropbear_cryptofd = -1;
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/****************************************************************************
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* Public Data
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****************************************************************************/
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const struct dropbear_cipher dropbear_chachapoly =
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{
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&g_dropbear_chachapoly_dummy,
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CHACHA20_KEY_LEN * 2,
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CHACHA20_BLOCKSIZE
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};
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/****************************************************************************
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* Private Functions
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****************************************************************************/
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static int dropbear_cryptodev_fd(void)
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{
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int fd;
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int cfd;
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if (g_dropbear_cryptofd >= 0)
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{
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return g_dropbear_cryptofd;
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}
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fd = open("/dev/crypto", O_RDWR);
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if (fd < 0)
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{
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return -1;
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}
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if (ioctl(fd, CRIOGET, &cfd) < 0)
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{
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close(fd);
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return -1;
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}
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close(fd);
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g_dropbear_cryptofd = cfd;
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return g_dropbear_cryptofd;
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}
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/* One ChaCha20 (DJB layout) pass: encrypt/decrypt len bytes with the given
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* 64-bit block counter and the packet sequence number as nonce.
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*/
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static int dropbear_chacha(FAR const unsigned char *key, unsigned int seq,
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uint64_t counter, FAR const unsigned char *in,
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FAR unsigned char *out, size_t len)
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{
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struct session_op session;
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struct crypt_op cryp;
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unsigned char iv[CHACHA20_IV_LEN];
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int cfd;
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int ret = CRYPT_ERROR;
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int i;
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cfd = dropbear_cryptodev_fd();
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if (cfd < 0)
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{
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return CRYPT_ERROR;
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}
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/* IV = 64-bit little-endian block counter || 64-bit nonce. The nonce is
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* the packet sequence number stored big endian, as OpenSSH does.
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*/
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for (i = 0; i < 8; i++)
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{
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iv[i] = (unsigned char)(counter >> (8 * i));
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}
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STORE64H((uint64_t)seq, iv + 8);
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memset(&session, 0, sizeof(session));
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session.cipher = CRYPTO_CHACHA20_DJB;
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session.key = (caddr_t)key;
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session.keylen = CHACHA20_KEY_LEN;
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if (ioctl(cfd, CIOCGSESSION, &session) < 0)
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{
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return CRYPT_ERROR;
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}
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memset(&cryp, 0, sizeof(cryp));
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cryp.ses = session.ses;
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cryp.op = COP_ENCRYPT;
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cryp.len = len;
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cryp.src = (caddr_t)in;
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cryp.dst = (caddr_t)out;
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cryp.iv = (caddr_t)iv;
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cryp.ivlen = sizeof(iv);
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if (ioctl(cfd, CIOCCRYPT, &cryp) == 0)
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{
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ret = CRYPT_OK;
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}
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ioctl(cfd, CIOCFSESSION, &session.ses);
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return ret;
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}
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static int dropbear_poly1305(FAR const unsigned char *key,
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FAR const unsigned char *in, size_t len,
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FAR unsigned char *tag)
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{
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struct session_op session;
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struct crypt_op cryp;
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int cfd;
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int ret = CRYPT_ERROR;
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cfd = dropbear_cryptodev_fd();
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if (cfd < 0)
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{
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return CRYPT_ERROR;
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}
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memset(&session, 0, sizeof(session));
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session.mac = CRYPTO_POLY1305;
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session.mackey = (caddr_t)key;
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session.mackeylen = POLY1305_KEY_LEN;
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if (ioctl(cfd, CIOCGSESSION, &session) < 0)
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{
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return CRYPT_ERROR;
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}
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/* Plain (non-HMAC) MACs are driven in two steps through /dev/crypto:
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* COP_FLAG_UPDATE feeds the data, then a final call without the flag
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* writes out the tag.
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*/
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memset(&cryp, 0, sizeof(cryp));
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cryp.ses = session.ses;
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cryp.op = COP_ENCRYPT;
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cryp.flags = COP_FLAG_UPDATE;
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cryp.len = len;
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cryp.src = (caddr_t)in;
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if (ioctl(cfd, CIOCCRYPT, &cryp) == 0)
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{
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cryp.flags = 0;
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cryp.len = 0;
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cryp.src = NULL;
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cryp.mac = (caddr_t)tag;
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if (ioctl(cfd, CIOCCRYPT, &cryp) == 0)
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{
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ret = CRYPT_OK;
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}
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}
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ioctl(cfd, CIOCFSESSION, &session.ses);
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return ret;
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}
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static int dropbear_chachapoly_start(int cipher,
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FAR const unsigned char *iv,
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FAR const unsigned char *key,
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int keylen, int num_rounds,
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FAR void *cipher_state)
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{
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FAR dropbear_chachapoly_state *state = cipher_state;
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UNUSED(cipher);
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UNUSED(iv);
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if (keylen != CHACHA20_KEY_LEN * 2 || num_rounds != 0)
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{
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return CRYPT_ERROR;
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}
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if (dropbear_cryptodev_fd() < 0)
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{
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return CRYPT_ERROR;
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}
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memcpy(KEY_MAIN(state), key, CHACHA20_KEY_LEN);
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memcpy(KEY_HEADER(state), key + CHACHA20_KEY_LEN, CHACHA20_KEY_LEN);
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return CRYPT_OK;
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}
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static int dropbear_chachapoly_crypt(unsigned int seq,
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FAR const unsigned char *in,
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FAR unsigned char *out,
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unsigned long len, unsigned long taglen,
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FAR void *cipher_state,
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int direction)
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{
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FAR dropbear_chachapoly_state *state = cipher_state;
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unsigned char key[POLY1305_KEY_LEN];
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unsigned char tag[POLY1305_TAG_LEN];
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unsigned char zero[POLY1305_KEY_LEN];
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int ret = CRYPT_ERROR;
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if (len < 4 || taglen != POLY1305_TAG_LEN)
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{
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return CRYPT_ERROR;
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}
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/* Poly1305 key = first keystream block of the main key at counter 0 */
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memset(zero, 0, sizeof(zero));
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if (dropbear_chacha(KEY_MAIN(state), seq, 0, zero, key,
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sizeof(key)) != CRYPT_OK)
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{
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goto out;
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}
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if (direction == LTC_DECRYPT)
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{
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if (dropbear_poly1305(key, in, len, tag) != CRYPT_OK)
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{
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goto out;
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}
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if (constant_time_memcmp(in + len, tag, sizeof(tag)) != 0)
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{
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goto out;
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}
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}
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/* Packet length: header key, counter 0. Payload: main key, counter 1. */
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if (dropbear_chacha(KEY_HEADER(state), seq, 0, in, out, 4) != CRYPT_OK)
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{
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goto out;
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}
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if (dropbear_chacha(KEY_MAIN(state), seq, 1, in + 4, out + 4,
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len - 4) != CRYPT_OK)
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{
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goto out;
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}
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if (direction == LTC_ENCRYPT)
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{
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if (dropbear_poly1305(key, out, len, out + len) != CRYPT_OK)
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{
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goto out;
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}
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}
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ret = CRYPT_OK;
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out:
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zeromem(key, sizeof(key));
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zeromem(tag, sizeof(tag));
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return ret;
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}
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static int
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dropbear_chachapoly_getlength(unsigned int seq, FAR const unsigned char *in,
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FAR unsigned int *outlen, unsigned long len,
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FAR void *cipher_state)
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{
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FAR dropbear_chachapoly_state *state = cipher_state;
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unsigned char buf[4];
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if (len < sizeof(buf))
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{
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return CRYPT_ERROR;
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}
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if (dropbear_chacha(KEY_HEADER(state), seq, 0, in, buf,
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sizeof(buf)) != CRYPT_OK)
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{
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return CRYPT_ERROR;
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}
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LOAD32H(*outlen, buf);
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return CRYPT_OK;
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}
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/****************************************************************************
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* Public Data
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****************************************************************************/
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const struct dropbear_cipher_mode dropbear_mode_chachapoly =
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{
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dropbear_chachapoly_start,
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NULL,
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NULL,
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dropbear_chachapoly_crypt,
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dropbear_chachapoly_getlength,
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&g_dropbear_chachapoly_mac
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};
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