/* $OpenBSD: cfb128.c,v 1.10 2025/04/23 10:09:08 jsing Exp $ */ /* ==================================================================== * Copyright (c) 2008 The OpenSSL Project. 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. * * 3. All advertising materials mentioning features or use of this * software must display the following acknowledgment: * "This product includes software developed by the OpenSSL Project * for use in the OpenSSL Toolkit. (http://www.openssl.org/)" * * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to * endorse or promote products derived from this software without * prior written permission. For written permission, please contact * openssl-core@openssl.org. * * 5. Products derived from this software may not be called "OpenSSL" * nor may "OpenSSL" appear in their names without prior written * permission of the OpenSSL Project. * * 6. Redistributions of any form whatsoever must retain the following * acknowledgment: * "This product includes software developed by the OpenSSL Project * for use in the OpenSSL Toolkit (http://www.openssl.org/)" * * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY * EXPRESSED 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 OpenSSL PROJECT OR * ITS CONTRIBUTORS 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 <string.h> #include <openssl/crypto.h> #include "modes_local.h" /* The input and output encrypted as though 128bit cfb mode is being * used. The extra state information to record how much of the * 128bit block we have used is contained in *num; */ void CRYPTO_cfb128_encrypt(const unsigned char *in, unsigned char *out, size_t len, const void *key, unsigned char ivec[16], int *num, int enc, block128_f block) { unsigned int n; size_t l = 0; n = *num; if (enc) { if (16 % sizeof(size_t) == 0) do { /* always true actually */ while (n && len) { *(out++) = ivec[n] ^= *(in++); --len; n = (n + 1) % 16; } #ifdef __STRICT_ALIGNMENT if (((size_t)in|(size_t)out|(size_t)ivec) % sizeof(size_t) != 0) break; #endif while (len >= 16) { (*block)(ivec, ivec, key); for (; n < 16; n += sizeof(size_t)) { *(size_t *)(out + n) = *(size_t *)(ivec + n) ^= *(size_t *)(in + n); } len -= 16; out += 16; in += 16; n = 0; } if (len) { (*block)(ivec, ivec, key); while (len--) { out[n] = ivec[n] ^= in[n]; ++n; } } *num = n; return; } while (0); /* the rest would be commonly eliminated by x86* compiler */ while (l < len) { if (n == 0) { (*block)(ivec, ivec, key); } out[l] = ivec[n] ^= in[l]; ++l; n = (n + 1) % 16; } *num = n; } else { if (16 % sizeof(size_t) == 0) do { /* always true actually */ while (n && len) { unsigned char c; *(out++) = ivec[n] ^ (c = *(in++)); ivec[n] = c; --len; n = (n + 1) % 16; } #ifdef __STRICT_ALIGNMENT if (((size_t)in|(size_t)out|(size_t)ivec) % sizeof(size_t) != 0) break; #endif while (len >= 16) { (*block)(ivec, ivec, key); for (; n < 16; n += sizeof(size_t)) { size_t t = *(size_t *)(in + n); *(size_t *)(out + n) = *(size_t *)(ivec + n) ^ t; *(size_t *)(ivec + n) = t; } len -= 16; out += 16; in += 16; n = 0; } if (len) { (*block)(ivec, ivec, key); while (len--) { unsigned char c; out[n] = ivec[n] ^ (c = in[n]); ivec[n] = c; ++n; } } *num = n; return; } while (0); /* the rest would be commonly eliminated by x86* compiler */ while (l < len) { unsigned char c; if (n == 0) { (*block)(ivec, ivec, key); } out[l] = ivec[n] ^ (c = in[l]); ivec[n] = c; ++l; n = (n + 1) % 16; } *num = n; } } LCRYPTO_ALIAS(CRYPTO_cfb128_encrypt); /* This expects a single block of size nbits for both in and out. Note that it corrupts any extra bits in the last byte of out */ static void cfbr_encrypt_block(const unsigned char *in, unsigned char *out, int nbits, const void *key, unsigned char ivec[16], int enc, block128_f block) { int n, rem, num; unsigned char ovec[16*2 + 1]; /* +1 because we dererefence (but don't use) one byte off the end */ if (nbits <= 0 || nbits > 128) return; /* fill in the first half of the new IV with the current IV */ memcpy(ovec, ivec, 16); /* construct the new IV */ (*block)(ivec, ivec, key); num = (nbits + 7)/8; if (enc) /* encrypt the input */ for (n = 0; n < num; ++n) out[n] = (ovec[16 + n] = in[n] ^ ivec[n]); else /* decrypt the input */ for (n = 0; n < num; ++n) out[n] = (ovec[16 + n] = in[n]) ^ ivec[n]; /* shift ovec left... */ rem = nbits % 8; num = nbits/8; if (rem == 0) memcpy(ivec, ovec + num, 16); else for (n = 0; n < 16; ++n) ivec[n] = ovec[n + num] << rem | ovec[n + num + 1] >> (8 - rem); /* it is not necessary to cleanse ovec, since the IV is not secret */ } /* N.B. This expects the input to be packed, MS bit first */ void CRYPTO_cfb128_1_encrypt(const unsigned char *in, unsigned char *out, size_t bits, const void *key, unsigned char ivec[16], int *num, int enc, block128_f block) { size_t n; unsigned char c[1], d[1]; for (n = 0; n < bits; ++n) { c[0] = (in[n/8] & (1 << (7 - n % 8))) ? 0x80 : 0; cfbr_encrypt_block(c, d, 1, key, ivec, enc, block); out[n/8] = (out[n/8] & ~(1 << (unsigned int)(7 - n % 8))) | ((d[0] & 0x80) >> (unsigned int)(n % 8)); } } LCRYPTO_ALIAS(CRYPTO_cfb128_1_encrypt); void CRYPTO_cfb128_8_encrypt(const unsigned char *in, unsigned char *out, size_t length, const void *key, unsigned char ivec[16], int *num, int enc, block128_f block) { size_t n; for (n = 0; n < length; ++n) cfbr_encrypt_block(&in[n], &out[n], 8, key, ivec, enc, block); } LCRYPTO_ALIAS(CRYPTO_cfb128_8_encrypt);
