Return to cipher-ctr.c CVS log

Up to [local] / src / usr.bin / ssh

Annotation of src/usr.bin/ssh/cipher-ctr.c, Revision 1.5

1.1       markus      1: /*
1.2       markus      2:  * Copyright (c) 2003 Markus Friedl <markus@openbsd.org>
1.1       markus      3:  *
1.2       markus      4:  * Permission to use, copy, modify, and distribute this software for any
                      5:  * purpose with or without fee is hereby granted, provided that the above
                      6:  * copyright notice and this permission notice appear in all copies.
1.1       markus      7:  *
1.2       markus      8:  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
                      9:  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
                     10:  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
                     11:  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
                     12:  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
                     13:  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
                     14:  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
1.1       markus     15:  */
                     16: #include "includes.h"
1.5     ! djm        17: RCSID("$OpenBSD: cipher-ctr.c,v 1.4 2004/02/06 23:41:13 dtucker Exp $");
1.1       markus     18:
                     19: #include <openssl/evp.h>
1.5     ! djm        20: #include <openssl/aes.h>
1.1       markus     21:
                     22: #include "log.h"
                     23: #include "xmalloc.h"
                     24:
                     25: const EVP_CIPHER *evp_aes_128_ctr(void);
                     26: void ssh_aes_ctr_iv(EVP_CIPHER_CTX *, int, u_char *, u_int);
                     27:
                     28: struct ssh_aes_ctr_ctx
                     29: {
                     30:        AES_KEY         aes_ctx;
                     31:        u_char          aes_counter[AES_BLOCK_SIZE];
                     32: };
                     33:
                     34: /*
                     35:  * increment counter 'ctr',
                     36:  * the counter is of size 'len' bytes and stored in network-byte-order.
                     37:  * (LSB at ctr[len-1], MSB at ctr[0])
                     38:  */
                     39: static void
                     40: ssh_ctr_inc(u_char *ctr, u_int len)
                     41: {
                     42:        int i;
                     43:
                     44:        for (i = len - 1; i >= 0; i--)
                     45:                if (++ctr[i])   /* continue on overflow */
                     46:                        return;
                     47: }
                     48:
                     49: static int
                     50: ssh_aes_ctr(EVP_CIPHER_CTX *ctx, u_char *dest, const u_char *src,
                     51:     u_int len)
                     52: {
                     53:        struct ssh_aes_ctr_ctx *c;
                     54:        u_int n = 0;
                     55:        u_char buf[AES_BLOCK_SIZE];
                     56:
                     57:        if (len == 0)
                     58:                return (1);
                     59:        if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) == NULL)
                     60:                return (0);
                     61:
                     62:        while ((len--) > 0) {
                     63:                if (n == 0) {
                     64:                        AES_encrypt(c->aes_counter, buf, &c->aes_ctx);
                     65:                        ssh_ctr_inc(c->aes_counter, AES_BLOCK_SIZE);
                     66:                }
                     67:                *(dest++) = *(src++) ^ buf[n];
                     68:                n = (n + 1) % AES_BLOCK_SIZE;
                     69:        }
                     70:        return (1);
                     71: }
                     72:
                     73: static int
                     74: ssh_aes_ctr_init(EVP_CIPHER_CTX *ctx, const u_char *key, const u_char *iv,
                     75:     int enc)
                     76: {
                     77:        struct ssh_aes_ctr_ctx *c;
                     78:
                     79:        if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) == NULL) {
                     80:                c = xmalloc(sizeof(*c));
                     81:                EVP_CIPHER_CTX_set_app_data(ctx, c);
                     82:        }
                     83:        if (key != NULL)
1.4       dtucker    84:                AES_set_encrypt_key(key, EVP_CIPHER_CTX_key_length(ctx) * 8,
                     85:                     &c->aes_ctx);
1.1       markus     86:        if (iv != NULL)
                     87:                memcpy(c->aes_counter, iv, AES_BLOCK_SIZE);
                     88:        return (1);
                     89: }
                     90:
                     91: static int
                     92: ssh_aes_ctr_cleanup(EVP_CIPHER_CTX *ctx)
                     93: {
                     94:        struct ssh_aes_ctr_ctx *c;
                     95:
                     96:        if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) != NULL) {
                     97:                memset(c, 0, sizeof(*c));
                     98:                xfree(c);
                     99:                EVP_CIPHER_CTX_set_app_data(ctx, NULL);
                    100:        }
                    101:        return (1);
                    102: }
                    103:
                    104: void
                    105: ssh_aes_ctr_iv(EVP_CIPHER_CTX *evp, int doset, u_char * iv, u_int len)
                    106: {
                    107:        struct ssh_aes_ctr_ctx *c;
                    108:
                    109:        if ((c = EVP_CIPHER_CTX_get_app_data(evp)) == NULL)
                    110:                fatal("ssh_aes_ctr_iv: no context");
                    111:        if (doset)
                    112:                memcpy(c->aes_counter, iv, len);
                    113:        else
                    114:                memcpy(iv, c->aes_counter, len);
                    115: }
                    116:
                    117: const EVP_CIPHER *
                    118: evp_aes_128_ctr(void)
                    119: {
                    120:        static EVP_CIPHER aes_ctr;
                    121:
                    122:        memset(&aes_ctr, 0, sizeof(EVP_CIPHER));
                    123:        aes_ctr.nid = NID_undef;
                    124:        aes_ctr.block_size = AES_BLOCK_SIZE;
                    125:        aes_ctr.iv_len = AES_BLOCK_SIZE;
                    126:        aes_ctr.key_len = 16;
                    127:        aes_ctr.init = ssh_aes_ctr_init;
                    128:        aes_ctr.cleanup = ssh_aes_ctr_cleanup;
                    129:        aes_ctr.do_cipher = ssh_aes_ctr;
                    130:        aes_ctr.flags = EVP_CIPH_CBC_MODE | EVP_CIPH_VARIABLE_LENGTH |
                    131:            EVP_CIPH_ALWAYS_CALL_INIT | EVP_CIPH_CUSTOM_IV;
                    132:        return (&aes_ctr);
                    133: }