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Diffstat (limited to 'cipher.c')
| -rw-r--r-- | cipher.c | 526 |
1 files changed, 526 insertions, 0 deletions
diff --git a/cipher.c b/cipher.c new file mode 100644 index 0000000..02aea40 --- /dev/null +++ b/cipher.c @@ -0,0 +1,526 @@ +/* $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; +} |