/* $OpenBSD: ctr128.c,v 1.18 2025/05/18 09:05:59 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 "crypto_internal.h" #include "modes_local.h" /* NOTE: the IV/counter CTR mode is big-endian. The code itself * is endian-neutral. */ /* increment counter (128-bit int) by 1 */ static void ctr128_inc(unsigned char *counter) { uint32_t n = 16; uint8_t c; do { --n; c = counter[n]; ++c; counter[n] = c; if (c) return; } while (n); } static void ctr128_inc_aligned(unsigned char *counter) { #if BYTE_ORDER == LITTLE_ENDIAN ctr128_inc(counter); #else size_t *data, c, n; data = (size_t *)counter; n = 16 / sizeof(size_t); do { --n; c = data[n]; ++c; data[n] = c; if (c) return; } while (n); #endif } /* The input encrypted as though 128bit counter mode is being * used. The extra state information to record how much of the * 128bit block we have used is contained in *num, and the * encrypted counter is kept in ecount_buf. Both *num and * ecount_buf must be initialised with zeros before the first * call to CRYPTO_ctr128_encrypt(). * * This algorithm assumes that the counter is in the x lower bits * of the IV (ivec), and that the application has full control over * overflow and the rest of the IV. This implementation takes NO * responsibility for checking that the counter doesn't overflow * into the rest of the IV when incremented. */ void CRYPTO_ctr128_encrypt(const unsigned char *in, unsigned char *out, size_t len, const void *key, unsigned char ivec[16], unsigned char ecount_buf[16], unsigned int *num, block128_f block) { unsigned int n = *num; size_t l = 0; OPENSSL_assert(n < 16); if (16 % sizeof(size_t) == 0) do { /* always true actually */ while (n && len) { *(out++) = *(in++) ^ ecount_buf[n]; --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, ecount_buf, key); ctr128_inc_aligned(ivec); for (; n < 16; n += sizeof(size_t)) *(size_t *)(out + n) = *(size_t *)(in + n) ^ *(size_t *)(ecount_buf + n); len -= 16; out += 16; in += 16; n = 0; } if (len) { (*block)(ivec, ecount_buf, key); ctr128_inc_aligned(ivec); while (len--) { out[n] = in[n] ^ ecount_buf[n]; ++n; } } *num = n; return; } while (0); /* the rest would be commonly eliminated by x86* compiler */ while (l < len) { if (n == 0) { (*block)(ivec, ecount_buf, key); ctr128_inc(ivec); } out[l] = in[l] ^ ecount_buf[n]; ++l; n = (n + 1) % 16; } *num = n; } LCRYPTO_ALIAS(CRYPTO_ctr128_encrypt); /* increment upper 96 bits of 128-bit counter by 1 */ static void ctr96_inc(unsigned char *counter) { uint32_t n = 12; uint8_t c; do { --n; c = counter[n]; ++c; counter[n] = c; if (c) return; } while (n); } void CRYPTO_ctr128_encrypt_ctr32(const unsigned char *in, unsigned char *out, size_t len, const void *key, unsigned char ivec[16], unsigned char ecount_buf[16], unsigned int *num, ctr128_f func) { unsigned int n = *num; unsigned int ctr32; OPENSSL_assert(n < 16); while (n && len) { *(out++) = *(in++) ^ ecount_buf[n]; --len; n = (n + 1) % 16; } ctr32 = crypto_load_be32toh(&ivec[12]); while (len >= 16) { size_t blocks = len/16; /* * 1<<28 is just a not-so-small yet not-so-large number... * Below condition is practically never met, but it has to * be checked for code correctness. */ if (sizeof(size_t) > sizeof(unsigned int) && blocks > (1U << 28)) blocks = (1U << 28); /* * As (*func) operates on 32-bit counter, caller * has to handle overflow. 'if' below detects the * overflow, which is then handled by limiting the * amount of blocks to the exact overflow point... */ ctr32 += (uint32_t)blocks; if (ctr32 < blocks) { blocks -= ctr32; ctr32 = 0; } (*func)(in, out, blocks, key, ivec); /* (*ctr) does not update ivec, caller does: */ crypto_store_htobe32(&ivec[12], ctr32); /* ... overflow was detected, propagate carry. */ if (ctr32 == 0) ctr96_inc(ivec); blocks *= 16; len -= blocks; out += blocks; in += blocks; } if (len) { memset(ecount_buf, 0, 16); (*func)(ecount_buf, ecount_buf, 1, key, ivec); ++ctr32; crypto_store_htobe32(&ivec[12], ctr32); if (ctr32 == 0) ctr96_inc(ivec); while (len--) { out[n] = in[n] ^ ecount_buf[n]; ++n; } } *num = n; } LCRYPTO_ALIAS(CRYPTO_ctr128_encrypt_ctr32);
