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Diffstat (limited to 'src/crypto/modes/ctr.c')
-rw-r--r-- | src/crypto/modes/ctr.c | 219 |
1 files changed, 219 insertions, 0 deletions
diff --git a/src/crypto/modes/ctr.c b/src/crypto/modes/ctr.c new file mode 100644 index 0000000..61832ba --- /dev/null +++ b/src/crypto/modes/ctr.c @@ -0,0 +1,219 @@ +/* ==================================================================== + * 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 <openssl/modes.h> + +#include <assert.h> +#include <string.h> + +#include "internal.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(uint8_t *counter) { + uint32_t n = 16; + uint8_t c; + + do { + --n; + c = counter[n]; + ++c; + counter[n] = c; + if (c) { + return; + } + } while (n); +} + +/* 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 uint8_t *in, uint8_t *out, size_t len, + const void *key, uint8_t ivec[16], + uint8_t ecount_buf[16], unsigned int *num, + block128_f block) { + unsigned int n; + + assert(in && out && key && ecount_buf && num); + assert(*num < 16); + assert((16 % sizeof(size_t)) == 0); + + n = *num; + + while (n && len) { + *(out++) = *(in++) ^ ecount_buf[n]; + --len; + n = (n + 1) % 16; + } + +#if STRICT_ALIGNMENT + if (((size_t)in | (size_t)out | (size_t)ivec) % sizeof(size_t) != 0) { + size_t l = 0; + 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; + return; + } +#endif + + while (len >= 16) { + (*block)(ivec, ecount_buf, key); + ctr128_inc(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(ivec); + while (len--) { + out[n] = in[n] ^ ecount_buf[n]; + ++n; + } + } + *num = n; +} + +/* increment upper 96 bits of 128-bit counter by 1 */ +static void ctr96_inc(uint8_t *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 uint8_t *in, uint8_t *out, + size_t len, const void *key, + uint8_t ivec[16], + uint8_t ecount_buf[16], + unsigned int *num, ctr128_f func) { + unsigned int n, ctr32; + + assert(in && out && key && ecount_buf && num); + assert(*num < 16); + + n = *num; + + while (n && len) { + *(out++) = *(in++) ^ ecount_buf[n]; + --len; + n = (n + 1) % 16; + } + + ctr32 = GETU32(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); + /* (*func) does not update ivec, caller does: */ + PUTU32(ivec + 12, ctr32); + /* ... overflow was detected, propogate 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; + PUTU32(ivec + 12, ctr32); + if (ctr32 == 0) { + ctr96_inc(ivec); + } + while (len--) { + out[n] = in[n] ^ ecount_buf[n]; + ++n; + } + } + + *num = n; +} |