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Annotation of src/usr.bin/ssh/cipher-aesctr.c, Revision 1.1

1.1     ! markus      1: /* $OpenBSD: cipher-ctr.c,v 1.11 2010/10/01 23:05:32 djm Exp $ */
        !             2: /*
        !             3:  * Copyright (c) 2003 Markus Friedl <markus@openbsd.org>
        !             4:  *
        !             5:  * Permission to use, copy, modify, and distribute this software for any
        !             6:  * purpose with or without fee is hereby granted, provided that the above
        !             7:  * copyright notice and this permission notice appear in all copies.
        !             8:  *
        !             9:  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
        !            10:  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
        !            11:  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
        !            12:  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
        !            13:  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
        !            14:  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
        !            15:  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
        !            16:  */
        !            17:
        !            18: #include <sys/types.h>
        !            19: #include <string.h>
        !            20:
        !            21: #include "cipher-aesctr.h"
        !            22:
        !            23: /*
        !            24:  * increment counter 'ctr',
        !            25:  * the counter is of size 'len' bytes and stored in network-byte-order.
        !            26:  * (LSB at ctr[len-1], MSB at ctr[0])
        !            27:  */
        !            28: static __inline__ void
        !            29: aesctr_inc(u8 *ctr, u32 len)
        !            30: {
        !            31:        ssize_t i;
        !            32:
        !            33: #ifndef CONSTANT_TIME_INCREMENT
        !            34:        for (i = len - 1; i >= 0; i--)
        !            35:                if (++ctr[i])   /* continue on overflow */
        !            36:                        return;
        !            37: #else
        !            38:        u8 x, add = 1;
        !            39:
        !            40:        for (i = len - 1; i >= 0; i--) {
        !            41:                ctr[i] += add;
        !            42:                /* constant time for: x = ctr[i] ? 1 : 0 */
        !            43:                x = ctr[i];
        !            44:                x = (x | (x >> 4)) & 0xf;
        !            45:                x = (x | (x >> 2)) & 0x3;
        !            46:                x = (x | (x >> 1)) & 0x1;
        !            47:                add *= (x^1);
        !            48:        }
        !            49: #endif
        !            50: }
        !            51:
        !            52: void
        !            53: aesctr_keysetup(aesctr_ctx *x,const u8 *k,u32 kbits,u32 ivbits)
        !            54: {
        !            55:        x->rounds = rijndaelKeySetupEnc(x->ek, k, kbits);
        !            56: }
        !            57:
        !            58: void
        !            59: aesctr_ivsetup(aesctr_ctx *x,const u8 *iv)
        !            60: {
        !            61:        memcpy(x->ctr, iv, AES_BLOCK_SIZE);
        !            62: }
        !            63:
        !            64: void
        !            65: aesctr_encrypt_bytes(aesctr_ctx *x,const u8 *m,u8 *c,u32 bytes)
        !            66: {
        !            67:        u32 n = 0;
        !            68:        u8 buf[AES_BLOCK_SIZE];
        !            69:
        !            70:        while ((bytes--) > 0) {
        !            71:                if (n == 0) {
        !            72:                        rijndaelEncrypt(x->ek, x->rounds, x->ctr, buf);
        !            73:                        aesctr_inc(x->ctr, AES_BLOCK_SIZE);
        !            74:                }
        !            75:                *(c++) = *(m++) ^ buf[n];
        !            76:                n = (n + 1) % AES_BLOCK_SIZE;
        !            77:        }
        !            78: }