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41 results

port.c

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  • aes-decrypt-internal.asm 3.96 KiB
    C x86/aes-decrypt-internal.asm
    
    ifelse(<
       Copyright (C) 2001, 2002, 2005, Rafael R. Sevilla, Niels Möller
       Copyright (C) 2008, 2013 Niels Möller
    
       This file is part of GNU Nettle.
    
       GNU Nettle is free software: you can redistribute it and/or
       modify it under the terms of either:
    
         * the GNU Lesser General Public License as published by the Free
           Software Foundation; either version 3 of the License, or (at your
           option) any later version.
    
       or
    
         * the GNU General Public License as published by the Free
           Software Foundation; either version 2 of the License, or (at your
           option) any later version.
    
       or both in parallel, as here.
    
       GNU Nettle is distributed in the hope that it will be useful,
       but WITHOUT ANY WARRANTY; without even the implied warranty of
       MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
       General Public License for more details.
    
       You should have received copies of the GNU General Public License and
       the GNU Lesser General Public License along with this program.  If
       not, see http://www.gnu.org/licenses/.
    >)
    
    include_src(<x86/aes.m4>)
    
    C Register usage:
    
    C AES state
    define(<SA>,<%eax>)
    define(<SB>,<%ebx>)
    define(<SC>,<%ecx>)
    define(<SD>,<%edx>)
    
    C Primary use of these registers. They're also used temporarily for other things.
    define(<T>,<%ebp>)
    define(<TMP>,<%edi>)
    define(<KEY>,<%esi>)
    
    define(<PARAM_ROUNDS>,	<40(%esp)>)
    define(<PARAM_KEYS>,	<44(%esp)>)
    define(<PARAM_TABLE>,	<48(%esp)>)
    define(<PARAM_LENGTH>,	<52(%esp)>)
    define(<PARAM_DST>,	<56(%esp)>)
    define(<PARAM_SRC>,	<60(%esp)>)
    
    define(<FRAME_KEY>,	<16(%esp)>)
    define(<FRAME_COUNT>,	<12(%esp)>)
    define(<TA>,		<8(%esp)>)
    define(<TB>,		<4(%esp)>)
    define(<TC>,		<(%esp)>)
    
    C The aes state is kept in %eax, %ebx, %ecx and %edx
    C
    C %esi is used as temporary, to point to the input, and to the
    C subkeys, etc.
    C
    C %ebp is used as the round counter, and as a temporary in the final round.
    C
    C %edi is a temporary, often used as an accumulator.
    
    	.file "aes-decrypt-internal.asm"
    	
    	C _aes_decrypt(unsigned rounds, const uint32_t *keys,
    	C	       const struct aes_table *T,
    	C	       size_t length, uint8_t *dst,
    	C	       uint8_t *src)
    	.text
    	ALIGN(16)
    PROLOGUE(_nettle_aes_decrypt)
    	C save all registers that need to be saved
    	pushl	%ebx		C  20(%esp)
    	pushl	%ebp		C  16(%esp)
    	pushl	%esi		C  12(%esp)
    	pushl	%edi		C  8(%esp)
    
    	subl	$20, %esp	C  loop counter and save area for the key pointer
    
    	movl	PARAM_LENGTH, %ebp
    	testl	%ebp,%ebp
    	jz	.Lend
    
    	shrl	$4, PARAM_LENGTH
    	subl	$1, PARAM_ROUNDS
    .Lblock_loop:
    	movl	PARAM_KEYS, KEY	C  address of subkeys
    	
    	movl	PARAM_SRC, TMP	C  address of plaintext
    	AES_LOAD(SA, SB, SC, SD, TMP, KEY)
    	addl	$16, PARAM_SRC	C Increment src pointer
    	movl	PARAM_TABLE, T
    
    	movl	PARAM_ROUNDS, TMP
    	C Loop counter on stack
    	movl	TMP, FRAME_COUNT
    
    	addl	$16,KEY		C  point to next key
    	movl	KEY,FRAME_KEY
    	ALIGN(16)
    .Lround_loop:
    	AES_ROUND(T, SA,SD,SC,SB, TMP, KEY)
    	movl	TMP, TA
    
    	AES_ROUND(T, SB,SA,SD,SC, TMP, KEY)
    	movl	TMP, TB
    
    	AES_ROUND(T, SC,SB,SA,SD, TMP, KEY)
    	movl	TMP, TC
    
    	AES_ROUND(T, SD,SC,SB,SA, SD, KEY)
    	
    	movl	TA, SA
    	movl	TB, SB
    	movl	TC, SC
    	
    	movl	FRAME_KEY, KEY
    
    	xorl	(KEY),SA	C  add current session key to plaintext
    	xorl	4(KEY),SB
    	xorl	8(KEY),SC
    	xorl	12(KEY),SD
    	addl	$16,FRAME_KEY	C  point to next key
    	decl	FRAME_COUNT
    	jnz	.Lround_loop
    
    	C last round
    
    	AES_FINAL_ROUND(SA,SD,SC,SB,T, TMP, KEY)
    	movl	TMP, TA
    
    	AES_FINAL_ROUND(SB,SA,SD,SC,T, TMP, KEY)
    	movl	TMP, TB
    
    	AES_FINAL_ROUND(SC,SB,SA,SD,T, TMP, KEY)
    	movl	TMP, TC
    
    	AES_FINAL_ROUND(SD,SC,SB,SA,T, SD, KEY)
    
    	movl	TA, SA
    	movl	TB, SB
    	movl	TC, SC
    
    	C Inverse S-box substitution
    	mov	$3,TMP
    .Lsubst:
    	AES_SUBST_BYTE(SA,SB,SC,SD, T, KEY)
    
    	decl	TMP
    	jnz	.Lsubst
    
    	C Add last subkey, and store decrypted data
    	movl	PARAM_DST,TMP
    	movl	FRAME_KEY, KEY
    	AES_STORE(SA,SB,SC,SD, KEY, TMP)
    	
    	addl	$16, PARAM_DST		C Increment destination pointer
    	decl	PARAM_LENGTH
    
    	jnz	.Lblock_loop
    
    .Lend:
    	addl	$20, %esp
    	popl	%edi
    	popl	%esi
    	popl	%ebp
    	popl	%ebx
    	ret
    EPILOGUE(_nettle_aes_decrypt)