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Annotation of src/usr.bin/ssh/cipher-ctr.c, Revision 1.10

1.10    ! deraadt     1: /* $OpenBSD: cipher-ctr.c,v 1.9 2006/07/22 20:48:22 stevesk Exp $ */
1.1       markus      2: /*
1.2       markus      3:  * Copyright (c) 2003 Markus Friedl <markus@openbsd.org>
1.1       markus      4:  *
1.2       markus      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.
1.1       markus      8:  *
1.2       markus      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.
1.1       markus     16:  */
1.10    ! deraadt    17:
        !            18: #include <sys/types.h>
1.9       stevesk    19:
                     20: #include <string.h>
1.1       markus     21:
                     22: #include <openssl/evp.h>
1.5       djm        23: #include <openssl/aes.h>
1.1       markus     24:
1.10    ! deraadt    25: #include "xmalloc.h"
1.1       markus     26: #include "log.h"
                     27:
                     28: const EVP_CIPHER *evp_aes_128_ctr(void);
                     29: void ssh_aes_ctr_iv(EVP_CIPHER_CTX *, int, u_char *, u_int);
                     30:
                     31: struct ssh_aes_ctr_ctx
                     32: {
                     33:        AES_KEY         aes_ctx;
                     34:        u_char          aes_counter[AES_BLOCK_SIZE];
                     35: };
                     36:
                     37: /*
                     38:  * increment counter 'ctr',
                     39:  * the counter is of size 'len' bytes and stored in network-byte-order.
                     40:  * (LSB at ctr[len-1], MSB at ctr[0])
                     41:  */
                     42: static void
                     43: ssh_ctr_inc(u_char *ctr, u_int len)
                     44: {
                     45:        int i;
                     46:
                     47:        for (i = len - 1; i >= 0; i--)
                     48:                if (++ctr[i])   /* continue on overflow */
                     49:                        return;
                     50: }
                     51:
                     52: static int
                     53: ssh_aes_ctr(EVP_CIPHER_CTX *ctx, u_char *dest, const u_char *src,
                     54:     u_int len)
                     55: {
                     56:        struct ssh_aes_ctr_ctx *c;
                     57:        u_int n = 0;
                     58:        u_char buf[AES_BLOCK_SIZE];
                     59:
                     60:        if (len == 0)
                     61:                return (1);
                     62:        if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) == NULL)
                     63:                return (0);
                     64:
                     65:        while ((len--) > 0) {
                     66:                if (n == 0) {
                     67:                        AES_encrypt(c->aes_counter, buf, &c->aes_ctx);
                     68:                        ssh_ctr_inc(c->aes_counter, AES_BLOCK_SIZE);
                     69:                }
                     70:                *(dest++) = *(src++) ^ buf[n];
                     71:                n = (n + 1) % AES_BLOCK_SIZE;
                     72:        }
                     73:        return (1);
                     74: }
                     75:
                     76: static int
                     77: ssh_aes_ctr_init(EVP_CIPHER_CTX *ctx, const u_char *key, const u_char *iv,
                     78:     int enc)
                     79: {
                     80:        struct ssh_aes_ctr_ctx *c;
                     81:
                     82:        if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) == NULL) {
                     83:                c = xmalloc(sizeof(*c));
                     84:                EVP_CIPHER_CTX_set_app_data(ctx, c);
                     85:        }
                     86:        if (key != NULL)
1.4       dtucker    87:                AES_set_encrypt_key(key, EVP_CIPHER_CTX_key_length(ctx) * 8,
1.6       djm        88:                    &c->aes_ctx);
1.1       markus     89:        if (iv != NULL)
                     90:                memcpy(c->aes_counter, iv, AES_BLOCK_SIZE);
                     91:        return (1);
                     92: }
                     93:
                     94: static int
                     95: ssh_aes_ctr_cleanup(EVP_CIPHER_CTX *ctx)
                     96: {
                     97:        struct ssh_aes_ctr_ctx *c;
                     98:
                     99:        if ((c = EVP_CIPHER_CTX_get_app_data(ctx)) != NULL) {
                    100:                memset(c, 0, sizeof(*c));
                    101:                xfree(c);
                    102:                EVP_CIPHER_CTX_set_app_data(ctx, NULL);
                    103:        }
                    104:        return (1);
                    105: }
                    106:
                    107: void
                    108: ssh_aes_ctr_iv(EVP_CIPHER_CTX *evp, int doset, u_char * iv, u_int len)
                    109: {
                    110:        struct ssh_aes_ctr_ctx *c;
                    111:
                    112:        if ((c = EVP_CIPHER_CTX_get_app_data(evp)) == NULL)
                    113:                fatal("ssh_aes_ctr_iv: no context");
                    114:        if (doset)
                    115:                memcpy(c->aes_counter, iv, len);
                    116:        else
                    117:                memcpy(iv, c->aes_counter, len);
                    118: }
                    119:
                    120: const EVP_CIPHER *
                    121: evp_aes_128_ctr(void)
                    122: {
                    123:        static EVP_CIPHER aes_ctr;
                    124:
                    125:        memset(&aes_ctr, 0, sizeof(EVP_CIPHER));
                    126:        aes_ctr.nid = NID_undef;
                    127:        aes_ctr.block_size = AES_BLOCK_SIZE;
                    128:        aes_ctr.iv_len = AES_BLOCK_SIZE;
                    129:        aes_ctr.key_len = 16;
                    130:        aes_ctr.init = ssh_aes_ctr_init;
                    131:        aes_ctr.cleanup = ssh_aes_ctr_cleanup;
                    132:        aes_ctr.do_cipher = ssh_aes_ctr;
                    133:        aes_ctr.flags = EVP_CIPH_CBC_MODE | EVP_CIPH_VARIABLE_LENGTH |
                    134:            EVP_CIPH_ALWAYS_CALL_INIT | EVP_CIPH_CUSTOM_IV;
                    135:        return (&aes_ctr);
                    136: }