/* $NetBSD: cipher-chachapoly-libcrypto.c,v 1.3.2.2 2023/12/25 12:31:03 martin Exp $ */ /* $OpenBSD: cipher-chachapoly-libcrypto.c,v 1.2 2023/07/17 05:26:38 djm Exp $ */ /* * Copyright (c) 2013 Damien Miller * * Permission to use, copy, modify, and distribute this software for any * purpose with or without fee is hereby granted, provided that the above * copyright notice and this permission notice appear in all copies. * * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */ #include "includes.h" __RCSID("$NetBSD: cipher-chachapoly-libcrypto.c,v 1.3.2.2 2023/12/25 12:31:03 martin Exp $"); #include #include /* needed for log.h */ #include #include /* needed for misc.h */ #include #include "log.h" #include "sshbuf.h" #include "ssherr.h" #include "cipher-chachapoly.h" struct chachapoly_ctx { EVP_CIPHER_CTX *main_evp, *header_evp; }; struct chachapoly_ctx * chachapoly_new(const u_char *key, u_int keylen) { struct chachapoly_ctx *ctx; if (keylen != (32 + 32)) /* 2 x 256 bit keys */ return NULL; if ((ctx = calloc(1, sizeof(*ctx))) == NULL) return NULL; if ((ctx->main_evp = EVP_CIPHER_CTX_new()) == NULL || (ctx->header_evp = EVP_CIPHER_CTX_new()) == NULL) goto fail; if (!EVP_CipherInit(ctx->main_evp, EVP_chacha20(), key, NULL, 1)) goto fail; if (!EVP_CipherInit(ctx->header_evp, EVP_chacha20(), key + 32, NULL, 1)) goto fail; if (EVP_CIPHER_CTX_iv_length(ctx->header_evp) != 16) goto fail; return ctx; fail: chachapoly_free(ctx); return NULL; } void chachapoly_free(struct chachapoly_ctx *cpctx) { if (cpctx == NULL) return; EVP_CIPHER_CTX_free(cpctx->main_evp); EVP_CIPHER_CTX_free(cpctx->header_evp); freezero(cpctx, sizeof(*cpctx)); } /* * chachapoly_crypt() operates as following: * En/decrypt with header key 'aadlen' bytes from 'src', storing result * to 'dest'. The ciphertext here is treated as additional authenticated * data for MAC calculation. * En/decrypt 'len' bytes at offset 'aadlen' from 'src' to 'dest'. Use * POLY1305_TAGLEN bytes at offset 'len'+'aadlen' as the authentication * tag. This tag is written on encryption and verified on decryption. */ int chachapoly_crypt(struct chachapoly_ctx *ctx, u_int seqnr, u_char *dest, const u_char *src, u_int len, u_int aadlen, u_int authlen, int do_encrypt) { u_char seqbuf[16]; /* layout: u64 counter || u64 seqno */ int r = SSH_ERR_INTERNAL_ERROR; u_char expected_tag[POLY1305_TAGLEN], poly_key[POLY1305_KEYLEN]; /* * Run ChaCha20 once to generate the Poly1305 key. The IV is the * packet sequence number. */ memset(seqbuf, 0, sizeof(seqbuf)); POKE_U64(seqbuf + 8, seqnr); memset(poly_key, 0, sizeof(poly_key)); if (!EVP_CipherInit(ctx->main_evp, NULL, NULL, seqbuf, 1) || EVP_Cipher(ctx->main_evp, poly_key, poly_key, sizeof(poly_key)) < 0) { r = SSH_ERR_LIBCRYPTO_ERROR; goto out; } /* If decrypting, check tag before anything else */ if (!do_encrypt) { const u_char *tag = src + aadlen + len; poly1305_auth(expected_tag, src, aadlen + len, poly_key); if (timingsafe_bcmp(expected_tag, tag, POLY1305_TAGLEN) != 0) { r = SSH_ERR_MAC_INVALID; goto out; } } /* Crypt additional data */ if (aadlen) { if (!EVP_CipherInit(ctx->header_evp, NULL, NULL, seqbuf, 1) || EVP_Cipher(ctx->header_evp, dest, src, aadlen) < 0) { r = SSH_ERR_LIBCRYPTO_ERROR; goto out; } } /* Set Chacha's block counter to 1 */ seqbuf[0] = 1; if (!EVP_CipherInit(ctx->main_evp, NULL, NULL, seqbuf, 1) || EVP_Cipher(ctx->main_evp, dest + aadlen, src + aadlen, len) < 0) { r = SSH_ERR_LIBCRYPTO_ERROR; goto out; } /* If encrypting, calculate and append tag */ if (do_encrypt) { poly1305_auth(dest + aadlen + len, dest, aadlen + len, poly_key); } r = 0; out: explicit_bzero(expected_tag, sizeof(expected_tag)); explicit_bzero(seqbuf, sizeof(seqbuf)); explicit_bzero(poly_key, sizeof(poly_key)); return r; } /* Decrypt and extract the encrypted packet length */ int chachapoly_get_length(struct chachapoly_ctx *ctx, u_int *plenp, u_int seqnr, const u_char *cp, u_int len) { u_char buf[4], seqbuf[16]; if (len < 4) return SSH_ERR_MESSAGE_INCOMPLETE; memset(seqbuf, 0, sizeof(seqbuf)); POKE_U64(seqbuf + 8, seqnr); if (!EVP_CipherInit(ctx->header_evp, NULL, NULL, seqbuf, 0)) return SSH_ERR_LIBCRYPTO_ERROR; if (EVP_Cipher(ctx->header_evp, buf, (u_char *)cp, sizeof(buf)) < 0) return SSH_ERR_LIBCRYPTO_ERROR; *plenp = PEEK_U32(buf); return 0; }