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Annotation of src/usr.bin/ssh/cipher-ctr.c, Revision 1.7

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