/* $OpenBSD: cipher.c,v 1.119 2021/04/03 06:18:40 djm Exp $ */
/*
* Author: Tatu Ylonen <ylo@cs.hut.fi>
* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
* All rights reserved
*
* As far as I am concerned, the code I have written for this software
* can be used freely for any purpose. Any derived versions of this
* software must be clearly marked as such, and if the derived work is
* incompatible with the protocol description in the RFC file, it must be
* called by a name other than "ssh" or "Secure Shell".
*
*
* Copyright (c) 1999 Niels Provos. All rights reserved.
* Copyright (c) 1999, 2000 Markus Friedl. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "includes.h"
#include <sys/types.h>
#include <string.h>
#include <stdarg.h>
#include <stdio.h>
#include "cipher.h"
#include "misc.h"
#include "sshbuf.h"
#include "ssherr.h"
#include "digest.h"
#include "openbsd-compat/openssl-compat.h"
#ifndef WITH_OPENSSL
#define EVP_CIPHER_CTX void
#endif
struct sshcipher_ctx {
int plaintext;
int encrypt;
EVP_CIPHER_CTX *evp;
struct chachapoly_ctx *cp_ctx;
struct aesctr_ctx ac_ctx; /* XXX union with evp? */
const struct sshcipher *cipher;
};
struct sshcipher {
char *name;
u_int block_size;
u_int key_len;
u_int iv_len; /* defaults to block_size */
u_int auth_len;
u_int flags;
#define CFLAG_CBC (1<<0)
#define CFLAG_CHACHAPOLY (1<<1)
#define CFLAG_AESCTR (1<<2)
#define CFLAG_NONE (1<<3)
#define CFLAG_INTERNAL CFLAG_NONE /* Don't use "none" for packets */
#ifdef WITH_OPENSSL
const EVP_CIPHER *(*evptype)(void);
#else
void *ignored;
#endif
};
static const struct sshcipher ciphers[] = {
#ifdef WITH_OPENSSL
#ifndef OPENSSL_NO_DES
{ "3des-cbc", 8, 24, 0, 0, CFLAG_CBC, EVP_des_ede3_cbc },
#endif
{ "aes128-cbc", 16, 16, 0, 0, CFLAG_CBC, EVP_aes_128_cbc },
{ "aes192-cbc", 16, 24, 0, 0, CFLAG_CBC, EVP_aes_192_cbc },
{ "aes256-cbc", 16, 32, 0, 0, CFLAG_CBC, EVP_aes_256_cbc },
{ "aes128-ctr", 16, 16, 0, 0, 0, EVP_aes_128_ctr },
{ "aes192-ctr", 16, 24, 0, 0, 0, EVP_aes_192_ctr },
{ "aes256-ctr", 16, 32, 0, 0, 0, EVP_aes_256_ctr },
{ "aes128-gcm@openssh.com",
16, 16, 12, 16, 0, EVP_aes_128_gcm },
{ "aes256-gcm@openssh.com",
16, 32, 12, 16, 0, EVP_aes_256_gcm },
#else
{ "aes128-ctr", 16, 16, 0, 0, CFLAG_AESCTR, NULL },
{ "aes192-ctr", 16, 24, 0, 0, CFLAG_AESCTR, NULL },
{ "aes256-ctr", 16, 32, 0, 0, CFLAG_AESCTR, NULL },
#endif
{ "chacha20-poly1305@openssh.com",
8, 64, 0, 16, CFLAG_CHACHAPOLY, NULL },
{ "none", 8, 0, 0, 0, CFLAG_NONE, NULL },
{ NULL, 0, 0, 0, 0, 0, NULL }
};
/*--*/
/* Returns a comma-separated list of supported ciphers. */
char *
cipher_alg_list(char sep, int auth_only)
{
char *tmp, *ret = NULL;
size_t nlen, rlen = 0;
const struct sshcipher *c;
for (c = ciphers; c->name != NULL; c++) {
if ((c->flags & CFLAG_INTERNAL) != 0)
continue;
if (auth_only && c->auth_len == 0)
continue;
if (ret != NULL)
ret[rlen++] = sep;
nlen = strlen(c->name);
if ((tmp = realloc(ret, rlen + nlen + 2)) == NULL) {
free(ret);
return NULL;
}
ret = tmp;
memcpy(ret + rlen, c->name, nlen + 1);
rlen += nlen;
}
return ret;
}
const char *
compression_alg_list(int compression)
{
#ifdef WITH_ZLIB
return compression ? "zlib@openssh.com,zlib,none" :
"none,zlib@openssh.com,zlib";
#else
return "none";
#endif
}
u_int
cipher_blocksize(const struct sshcipher *c)
{
return (c->block_size);
}
u_int
cipher_keylen(const struct sshcipher *c)
{
return (c->key_len);
}
u_int
cipher_seclen(const struct sshcipher *c)
{
if (strcmp("3des-cbc", c->name) == 0)
return 14;
return cipher_keylen(c);
}
u_int
cipher_authlen(const struct sshcipher *c)
{
return (c->auth_len);
}
u_int
cipher_ivlen(const struct sshcipher *c)
{
/*
* Default is cipher block size, except for chacha20+poly1305 that
* needs no IV. XXX make iv_len == -1 default?
*/
return (c->iv_len != 0 || (c->flags & CFLAG_CHACHAPOLY) != 0) ?
c->iv_len : c->block_size;
}
u_int
cipher_is_cbc(const struct sshcipher *c)
{
return (c->flags & CFLAG_CBC) != 0;
}
u_int
cipher_ctx_is_plaintext(struct sshcipher_ctx *cc)
{
return cc->plaintext;
}
const struct sshcipher *
cipher_by_name(const char *name)
{
const struct sshcipher *c;
for (c = ciphers; c->name != NULL; c++)
if (strcmp(c->name, name) == 0)
return c;
return NULL;
}
#define CIPHER_SEP ","
int
ciphers_valid(const char *names)
{
const struct sshcipher *c;
char *cipher_list, *cp;
char *p;
if (names == NULL || strcmp(names, "") == 0)
return 0;
if ((cipher_list = cp = strdup(names)) == NULL)
return 0;
for ((p = strsep(&cp, CIPHER_SEP)); p && *p != '\0';
(p = strsep(&cp, CIPHER_SEP))) {
c = cipher_by_name(p);
if (c == NULL || (c->flags & CFLAG_INTERNAL) != 0) {
free(cipher_list);
return 0;
}
}
free(cipher_list);
return 1;
}
const char *
cipher_warning_message(const struct sshcipher_ctx *cc)
{
if (cc == NULL || cc->cipher == NULL)
return NULL;
/* XXX repurpose for CBC warning */
return NULL;
}
int
cipher_init(struct sshcipher_ctx **ccp, const struct sshcipher *cipher,
const u_char *key, u_int keylen, const u_char *iv, u_int ivlen,
int do_encrypt)
{
struct sshcipher_ctx *cc = NULL;
int ret = SSH_ERR_INTERNAL_ERROR;
#ifdef WITH_OPENSSL
const EVP_CIPHER *type;
int klen;
#endif
*ccp = NULL;
if ((cc = calloc(sizeof(*cc), 1)) == NULL)
return SSH_ERR_ALLOC_FAIL;
cc->plaintext = (cipher->flags & CFLAG_NONE) != 0;
cc->encrypt = do_encrypt;
if (keylen < cipher->key_len ||
(iv != NULL && ivlen < cipher_ivlen(cipher))) {
ret = SSH_ERR_INVALID_ARGUMENT;
goto out;
}
cc->cipher = cipher;
if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) {
cc->cp_ctx = chachapoly_new(key, keylen);
ret = cc->cp_ctx != NULL ? 0 : SSH_ERR_INVALID_ARGUMENT;
goto out;
}
if ((cc->cipher->flags & CFLAG_NONE) != 0) {
ret = 0;
goto out;
}
#ifndef WITH_OPENSSL
if ((cc->cipher->flags & CFLAG_AESCTR) != 0) {
aesctr_keysetup(&cc->ac_ctx, key, 8 * keylen, 8 * ivlen);
aesctr_ivsetup(&cc->ac_ctx, iv);
ret = 0;
goto out;
}
ret = SSH_ERR_INVALID_ARGUMENT;
goto out;
#else /* WITH_OPENSSL */
type = (*cipher->evptype)();
if ((cc->evp = EVP_CIPHER_CTX_new()) == NULL) {
ret = SSH_ERR_ALLOC_FAIL;
goto out;
}
if (EVP_CipherInit(cc->evp, type, NULL, (u_char *)iv,
(do_encrypt == CIPHER_ENCRYPT)) == 0) {
ret = SSH_ERR_LIBCRYPTO_ERROR;
goto out;
}
if (cipher_authlen(cipher) &&
!EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_SET_IV_FIXED,
-1, (u_char *)iv)) {
ret = SSH_ERR_LIBCRYPTO_ERROR;
goto out;
}
klen = EVP_CIPHER_CTX_key_length(cc->evp);
if (klen > 0 && keylen != (u_int)klen) {
if (EVP_CIPHER_CTX_set_key_length(cc->evp, keylen) == 0) {
ret = SSH_ERR_LIBCRYPTO_ERROR;
goto out;
}
}
if (EVP_CipherInit(cc->evp, NULL, (u_char *)key, NULL, -1) == 0) {
ret = SSH_ERR_LIBCRYPTO_ERROR;
goto out;
}
ret = 0;
#endif /* WITH_OPENSSL */
out:
if (ret == 0) {
/* success */
*ccp = cc;
} else {
if (cc != NULL) {
#ifdef WITH_OPENSSL
EVP_CIPHER_CTX_free(cc->evp);
#endif /* WITH_OPENSSL */
freezero(cc, sizeof(*cc));
}
}
return ret;
}
/*
* cipher_crypt() operates as following:
* Copy 'aadlen' bytes (without en/decryption) from 'src' to 'dest'.
* These bytes are treated as additional authenticated data for
* authenticated encryption modes.
* En/Decrypt 'len' bytes at offset 'aadlen' from 'src' to 'dest'.
* Use 'authlen' bytes at offset 'len'+'aadlen' as the authentication tag.
* This tag is written on encryption and verified on decryption.
* Both 'aadlen' and 'authlen' can be set to 0.
*/
int
cipher_crypt(struct sshcipher_ctx *cc, u_int seqnr, u_char *dest,
const u_char *src, u_int len, u_int aadlen, u_int authlen)
{
if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) {
return chachapoly_crypt(cc->cp_ctx, seqnr, dest, src,
len, aadlen, authlen, cc->encrypt);
}
if ((cc->cipher->flags & CFLAG_NONE) != 0) {
memcpy(dest, src, aadlen + len);
return 0;
}
#ifndef WITH_OPENSSL
if ((cc->cipher->flags & CFLAG_AESCTR) != 0) {
if (aadlen)
memcpy(dest, src, aadlen);
aesctr_encrypt_bytes(&cc->ac_ctx, src + aadlen,
dest + aadlen, len);
return 0;
}
return SSH_ERR_INVALID_ARGUMENT;
#else
if (authlen) {
u_char lastiv[1];
if (authlen != cipher_authlen(cc->cipher))
return SSH_ERR_INVALID_ARGUMENT;
/* increment IV */
if (!EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_IV_GEN,
1, lastiv))
return SSH_ERR_LIBCRYPTO_ERROR;
/* set tag on decyption */
if (!cc->encrypt &&
!EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_SET_TAG,
authlen, (u_char *)src + aadlen + len))
return SSH_ERR_LIBCRYPTO_ERROR;
}
if (aadlen) {
if (authlen &&
EVP_Cipher(cc->evp, NULL, (u_char *)src, aadlen) < 0)
return SSH_ERR_LIBCRYPTO_ERROR;
memcpy(dest, src, aadlen);
}
if (len % cc->cipher->block_size)
return SSH_ERR_INVALID_ARGUMENT;
if (EVP_Cipher(cc->evp, dest + aadlen, (u_char *)src + aadlen,
len) < 0)
return SSH_ERR_LIBCRYPTO_ERROR;
if (authlen) {
/* compute tag (on encrypt) or verify tag (on decrypt) */
if (EVP_Cipher(cc->evp, NULL, NULL, 0) < 0)
return cc->encrypt ?
SSH_ERR_LIBCRYPTO_ERROR : SSH_ERR_MAC_INVALID;
if (cc->encrypt &&
!EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_GET_TAG,
authlen, dest + aadlen + len))
return SSH_ERR_LIBCRYPTO_ERROR;
}
return 0;
#endif
}
/* Extract the packet length, including any decryption necessary beforehand */
int
cipher_get_length(struct sshcipher_ctx *cc, u_int *plenp, u_int seqnr,
const u_char *cp, u_int len)
{
if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0)
return chachapoly_get_length(cc->cp_ctx, plenp, seqnr,
cp, len);
if (len < 4)
return SSH_ERR_MESSAGE_INCOMPLETE;
*plenp = PEEK_U32(cp);
return 0;
}
void
cipher_free(struct sshcipher_ctx *cc)
{
if (cc == NULL)
return;
if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) {
chachapoly_free(cc->cp_ctx);
cc->cp_ctx = NULL;
} else if ((cc->cipher->flags & CFLAG_AESCTR) != 0)
explicit_bzero(&cc->ac_ctx, sizeof(cc->ac_ctx));
#ifdef WITH_OPENSSL
EVP_CIPHER_CTX_free(cc->evp);
cc->evp = NULL;
#endif
freezero(cc, sizeof(*cc));
}
/*
* Exports an IV from the sshcipher_ctx required to export the key
* state back from the unprivileged child to the privileged parent
* process.
*/
int
cipher_get_keyiv_len(const struct sshcipher_ctx *cc)
{
const struct sshcipher *c = cc->cipher;
if ((c->flags & CFLAG_CHACHAPOLY) != 0)
return 0;
else if ((c->flags & CFLAG_AESCTR) != 0)
return sizeof(cc->ac_ctx.ctr);
#ifdef WITH_OPENSSL
return EVP_CIPHER_CTX_iv_length(cc->evp);
#else
return 0;
#endif
}
int
cipher_get_keyiv(struct sshcipher_ctx *cc, u_char *iv, size_t len)
{
#ifdef WITH_OPENSSL
const struct sshcipher *c = cc->cipher;
int evplen;
#endif
if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0) {
if (len != 0)
return SSH_ERR_INVALID_ARGUMENT;
return 0;
}
if ((cc->cipher->flags & CFLAG_AESCTR) != 0) {
if (len != sizeof(cc->ac_ctx.ctr))
return SSH_ERR_INVALID_ARGUMENT;
memcpy(iv, cc->ac_ctx.ctr, len);
return 0;
}
if ((cc->cipher->flags & CFLAG_NONE) != 0)
return 0;
#ifdef WITH_OPENSSL
evplen = EVP_CIPHER_CTX_iv_length(cc->evp);
if (evplen == 0)
return 0;
else if (evplen < 0)
return SSH_ERR_LIBCRYPTO_ERROR;
if ((size_t)evplen != len)
return SSH_ERR_INVALID_ARGUMENT;
if (cipher_authlen(c)) {
if (!EVP_CIPHER_CTX_ctrl(cc->evp, EVP_CTRL_GCM_IV_GEN,
len, iv))
return SSH_ERR_LIBCRYPTO_ERROR;
} else if (!EVP_CIPHER_CTX_get_iv(cc->evp, iv, len))
return SSH_ERR_LIBCRYPTO_ERROR;
#endif
return 0;
}
int
cipher_set_keyiv(struct sshcipher_ctx *cc, const u_char *iv, size_t len)
{
#ifdef WITH_OPENSSL
const struct sshcipher *c = cc->cipher;
int evplen = 0;
#endif
if ((cc->cipher->flags & CFLAG_CHACHAPOLY) != 0)
return 0;
if ((cc->cipher->flags & CFLAG_NONE) != 0)
return 0;
#ifdef WITH_OPENSSL
evplen = EVP_CIPHER_CTX_iv_length(cc->evp);
if (evplen <= 0)
return SSH_ERR_LIBCRYPTO_ERROR;
if ((size_t)evplen != len)
return SSH_ERR_INVALID_ARGUMENT;
if (cipher_authlen(c)) {
/* XXX iv arg is const, but EVP_CIPHER_CTX_ctrl isn't */
if (!EVP_CIPHER_CTX_ctrl(cc->evp,
EVP_CTRL_GCM_SET_IV_FIXED, -1, (void *)iv))
return SSH_ERR_LIBCRYPTO_ERROR;
} else if (!EVP_CIPHER_CTX_set_iv(cc->evp, iv, evplen))
return SSH_ERR_LIBCRYPTO_ERROR;
#endif
return 0;
}
