1 /* 2 * Copyright (c) 2013 Damien Miller <djm@mindrot.org> 3 * 4 * Permission to use, copy, modify, and distribute this software for any 5 * purpose with or without fee is hereby granted, provided that the above 6 * copyright notice and this permission notice appear in all copies. 7 * 8 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES 9 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 10 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR 11 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 12 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN 13 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF 14 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. 15 */ 16 17 /* $OpenBSD: cipher-chachapoly-libcrypto.c,v 1.1 2020/04/03 04:32:21 djm Exp $ */ 18 19 #include "includes.h" 20 #ifdef WITH_OPENSSL 21 #include "openbsd-compat/openssl-compat.h" 22 #endif 23 24 #if defined(HAVE_EVP_CHACHA20) && !defined(HAVE_BROKEN_CHACHA20) 25 26 #include <sys/types.h> 27 #include <stdarg.h> /* needed for log.h */ 28 #include <string.h> 29 #include <stdio.h> /* needed for misc.h */ 30 31 #include <openssl/evp.h> 32 33 #include "log.h" 34 #include "sshbuf.h" 35 #include "ssherr.h" 36 #include "cipher-chachapoly.h" 37 38 struct chachapoly_ctx { 39 EVP_CIPHER_CTX *main_evp, *header_evp; 40 }; 41 42 struct chachapoly_ctx * 43 chachapoly_new(const u_char *key, u_int keylen) 44 { 45 struct chachapoly_ctx *ctx; 46 47 if (keylen != (32 + 32)) /* 2 x 256 bit keys */ 48 return NULL; 49 if ((ctx = calloc(1, sizeof(*ctx))) == NULL) 50 return NULL; 51 if ((ctx->main_evp = EVP_CIPHER_CTX_new()) == NULL || 52 (ctx->header_evp = EVP_CIPHER_CTX_new()) == NULL) 53 goto fail; 54 if (!EVP_CipherInit(ctx->main_evp, EVP_chacha20(), key, NULL, 1)) 55 goto fail; 56 if (!EVP_CipherInit(ctx->header_evp, EVP_chacha20(), key + 32, NULL, 1)) 57 goto fail; 58 if (EVP_CIPHER_CTX_iv_length(ctx->header_evp) != 16) 59 goto fail; 60 return ctx; 61 fail: 62 chachapoly_free(ctx); 63 return NULL; 64 } 65 66 void 67 chachapoly_free(struct chachapoly_ctx *cpctx) 68 { 69 if (cpctx == NULL) 70 return; 71 EVP_CIPHER_CTX_free(cpctx->main_evp); 72 EVP_CIPHER_CTX_free(cpctx->header_evp); 73 freezero(cpctx, sizeof(*cpctx)); 74 } 75 76 /* 77 * chachapoly_crypt() operates as following: 78 * En/decrypt with header key 'aadlen' bytes from 'src', storing result 79 * to 'dest'. The ciphertext here is treated as additional authenticated 80 * data for MAC calculation. 81 * En/decrypt 'len' bytes at offset 'aadlen' from 'src' to 'dest'. Use 82 * POLY1305_TAGLEN bytes at offset 'len'+'aadlen' as the authentication 83 * tag. This tag is written on encryption and verified on decryption. 84 */ 85 int 86 chachapoly_crypt(struct chachapoly_ctx *ctx, u_int seqnr, u_char *dest, 87 const u_char *src, u_int len, u_int aadlen, u_int authlen, int do_encrypt) 88 { 89 u_char seqbuf[16]; /* layout: u64 counter || u64 seqno */ 90 int r = SSH_ERR_INTERNAL_ERROR; 91 u_char expected_tag[POLY1305_TAGLEN], poly_key[POLY1305_KEYLEN]; 92 93 /* 94 * Run ChaCha20 once to generate the Poly1305 key. The IV is the 95 * packet sequence number. 96 */ 97 memset(seqbuf, 0, sizeof(seqbuf)); 98 POKE_U64(seqbuf + 8, seqnr); 99 memset(poly_key, 0, sizeof(poly_key)); 100 if (!EVP_CipherInit(ctx->main_evp, NULL, NULL, seqbuf, 1) || 101 EVP_Cipher(ctx->main_evp, poly_key, 102 poly_key, sizeof(poly_key)) < 0) { 103 r = SSH_ERR_LIBCRYPTO_ERROR; 104 goto out; 105 } 106 107 /* If decrypting, check tag before anything else */ 108 if (!do_encrypt) { 109 const u_char *tag = src + aadlen + len; 110 111 poly1305_auth(expected_tag, src, aadlen + len, poly_key); 112 if (timingsafe_bcmp(expected_tag, tag, POLY1305_TAGLEN) != 0) { 113 r = SSH_ERR_MAC_INVALID; 114 goto out; 115 } 116 } 117 118 /* Crypt additional data */ 119 if (aadlen) { 120 if (!EVP_CipherInit(ctx->header_evp, NULL, NULL, seqbuf, 1) || 121 EVP_Cipher(ctx->header_evp, dest, src, aadlen) < 0) { 122 r = SSH_ERR_LIBCRYPTO_ERROR; 123 goto out; 124 } 125 } 126 127 /* Set Chacha's block counter to 1 */ 128 seqbuf[0] = 1; 129 if (!EVP_CipherInit(ctx->main_evp, NULL, NULL, seqbuf, 1) || 130 EVP_Cipher(ctx->main_evp, dest + aadlen, src + aadlen, len) < 0) { 131 r = SSH_ERR_LIBCRYPTO_ERROR; 132 goto out; 133 } 134 135 /* If encrypting, calculate and append tag */ 136 if (do_encrypt) { 137 poly1305_auth(dest + aadlen + len, dest, aadlen + len, 138 poly_key); 139 } 140 r = 0; 141 out: 142 explicit_bzero(expected_tag, sizeof(expected_tag)); 143 explicit_bzero(seqbuf, sizeof(seqbuf)); 144 explicit_bzero(poly_key, sizeof(poly_key)); 145 return r; 146 } 147 148 /* Decrypt and extract the encrypted packet length */ 149 int 150 chachapoly_get_length(struct chachapoly_ctx *ctx, 151 u_int *plenp, u_int seqnr, const u_char *cp, u_int len) 152 { 153 u_char buf[4], seqbuf[16]; 154 155 if (len < 4) 156 return SSH_ERR_MESSAGE_INCOMPLETE; 157 memset(seqbuf, 0, sizeof(seqbuf)); 158 POKE_U64(seqbuf + 8, seqnr); 159 if (!EVP_CipherInit(ctx->header_evp, NULL, NULL, seqbuf, 0)) 160 return SSH_ERR_LIBCRYPTO_ERROR; 161 if (EVP_Cipher(ctx->header_evp, buf, (u_char *)cp, sizeof(buf)) < 0) 162 return SSH_ERR_LIBCRYPTO_ERROR; 163 *plenp = PEEK_U32(buf); 164 return 0; 165 } 166 #endif /* defined(HAVE_EVP_CHACHA20) && !defined(HAVE_BROKEN_CHACHA20) */ 167