177 lines
4.1 KiB
C
177 lines
4.1 KiB
C
/*
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* Copyright (c) 2024 Stephen Heumann
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*
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* Permission to use, copy, modify, and distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*/
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#pragma noroot
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#pragma lint -1
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#pragma optimize -1
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#include <string.h>
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#include <stddef.h>
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#include "aes.h"
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extern void AES_ENCRYPT(void);
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static asm void aes_cmac_subkey_compute_step(struct aes_cmac_context *ctx) {
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tdc
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tay
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phb
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plx
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pla
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pld
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sta 1,s
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phx
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plb
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sep #0x20
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asl 15
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rol 14
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rol 13
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rol 12
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rol 11
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rol 10
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rol 9
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rol 8
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rol 7
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rol 6
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rol 5
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rol 4
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rol 3
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rol 2
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rol 1
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rol 0
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bcc done
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lda 15
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eor #0x87
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sta 15
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done: rep #0x20
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tya
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tcd
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rtl
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}
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/*
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* Initialize a context for AES-CMAC computation with a specified key.
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* This must be called before any calling aes_cmac_compute.
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*/
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void aes_cmac_init(struct aes_cmac_context *context,
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const unsigned char key[16])
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{
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memcpy(context->ctx.key, key, 16);
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aes128_expandkey(&context->ctx);
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memset(context->ctx.data, 0, 16);
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aes_encrypt(&context->ctx);
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aes_cmac_subkey_compute_step(context);
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memcpy(context->k1, context->ctx.data, 16);
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aes_cmac_subkey_compute_step(context);
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memcpy(context->k2, context->ctx.data, 16);
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}
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/*
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* Compute the AES-CMAC of a message as a single operation.
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* The result will be in context->ctx.data.
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* The context can be reused for multiple aes_cmac_compute operations.
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*/
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void aes_cmac_compute(struct aes_cmac_context *context,
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const unsigned char *message,
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unsigned long message_length)
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{
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unsigned i;
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memset(&context->ctx.data, 0, 16);
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while (message_length > 16) {
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asm {
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lda [message]
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eor [context]
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sta [context]
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ldy #2
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lda [message],y
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eor [context],y
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sta [context],y
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iny
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iny
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lda [message],y
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eor [context],y
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sta [context],y
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iny
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iny
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lda [message],y
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eor [context],y
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sta [context],y
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iny
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iny
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lda [message],y
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eor [context],y
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sta [context],y
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iny
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iny
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lda [message],y
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eor [context],y
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sta [context],y
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iny
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iny
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lda [message],y
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eor [context],y
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sta [context],y
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iny
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iny
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lda [message],y
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eor [context],y
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sta [context],y
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phd
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lda context
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tcd
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jsl AES_ENCRYPT
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pld
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}
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message_length -= 16;
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message += 16;
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}
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if (message_length == 16) {
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for (i = 0; i < 16; i++) {
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context->ctx.data[i] ^= message[i] ^ context->k1[i];
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}
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} else {
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for (i = 0; i < 16; i++) {
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if (i < message_length) {
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context->ctx.data[i] ^= message[i] ^ context->k2[i];
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} else if (i == message_length) {
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context->ctx.data[i] ^= 0x80 ^ context->k2[i];
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} else {
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context->ctx.data[i] ^= context->k2[i];
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}
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}
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}
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asm {
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phd
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lda context
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tcd
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jsl AES_ENCRYPT
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pld
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}
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}
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