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mauricelambertmauricelambert
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Fix: Calling convention non volatile registers
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‎rc4.asm

+196-192
Original file line numberDiff line numberDiff line change
@@ -1,192 +1,196 @@
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; This file implements RC4 in ASM.
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; Copyright (C) 2023 Maurice Lambert
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; This program is free software: you can redistribute it and/or modify
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; it under the terms of the GNU General Public License as published by
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; the Free Software Foundation, either version 3 of the License, or
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; (at your option) any later version.
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; This program is distributed in the hope that it will be useful,
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; but WITHOUT ANY WARRANTY; without even the implied warranty of
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; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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; GNU General Public License for more details.
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; You should have received a copy of the GNU General Public License
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; along with this program. If not, see <https://www.gnu.org/licenses/>.
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; arc4_null_byte([IN/OUT] char *data) -> NULL
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; arc4([IN/OUT] char *data, [IN] unsigned long long length) -> NULL
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; generate_iv() -> NULL
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; xor_key_iv() -> NULL
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; generate_key(char *key) -> NULL
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; reset_key() -> NULL
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; get_iv() -> char[256] // null byte terminate string
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; set_iv([IN] char iv[256]) -> NULL
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; encrypt([IN] char *key, [IN/OUT] char *data, [IN] unsigned long long length) -> NULL // if length is 0 call arc4_null_byte
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; decrypt([IN] char *key, [IN] char iv[256], [IN/OUT] char *data, [IN] unsigned long long length) -> NULL // there is no way to decrypt string terminating by null byte because encrypted data can contains null byte
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global arc4, generate_iv, generate_key, xor_key_iv, reset_key, get_iv, set_iv, encrypt, decrypt, arc4_null_byte
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default rel
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section .text
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arc4:
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mov r10, rsi ; length
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xor rdx, rdx ; dl = index1 = 0
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xor rcx, rcx ; cl = index2 = 0
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xor rax, rax
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xor rbx, rbx
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lea rsi, [key]
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._4: test r10, r10 ; if length == 0: return;
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jne ._3
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ret
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._3: mov al, byte [rdi]
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sub r10, 1 ; length -= 1;
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add dl, 1
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add cl, byte [rsi + rdx]
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mov al, byte [rsi + rdx]
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mov bl, byte [rsi + rcx]
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mov byte [rsi + rdx], bl
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mov byte [rsi + rcx], al ; value1, value2 = value2, value1
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add al, bl
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mov al, byte [rsi + rax]
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xor byte [rdi], al
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add rdi, 1 ; next character
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jmp ._4
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arc4_null_byte:
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xor rdx, rdx ; dl = index1 = 0
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xor rcx, rcx ; cl = index2 = 0
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xor rax, rax
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xor rbx, rbx
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lea rsi, [key]
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._11: mov al, byte [rdi]
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test al, al
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jne ._10 ; if character == 0 (end of string) return else crypt character
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ret
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._10: add dl, 1
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add cl, byte [rsi + rdx]
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mov al, byte [rsi + rdx]
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mov bl, byte [rsi + rcx]
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mov byte [rsi + rdx], bl
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mov byte [rsi + rcx], al ; value1, value2 = value2, value1
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add al, bl
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mov al, byte [rsi + rax]
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xor byte [rdi], al
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add rdi, 1 ; next character
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jmp ._11
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generate_iv:
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mov rax, 228 ; syscall 228 == sys_clock_gettime
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xor rdi, rdi ; 0 == CLOCK_REALTIME
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lea rsi, [iv]
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syscall
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mov rcx, 64
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mov rax, qword [rsi + 8] ; Nanosecond (pseudo random start number)
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._5: mov rbx, rax
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shl rax, 13
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xor rax, rbx
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mov rbx, rax
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shr rax, 7
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xor rax, rbx
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mov rbx, rax
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shl rax, 17
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xor rax, rbx
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mov [rsi + rcx * 4 - 4], rax
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sub rcx, 1
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test rcx, rcx
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jne ._5
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mov byte [rsi + 256], 0 ; end with null byte (257 characters = 256 characters + null byte)
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ret
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xor_key_iv:
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xor rax, rax
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lea rdi, [key]
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lea rsi, [iv]
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._6: mov rbx, [rsi + rax] ; 256 / 4 == 64, faster way (using 64 bit register) to xor all the key with iv than character (8 bit register) by character
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xor [rdi + rax], rbx
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add al, 8
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test al, al
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jne ._6
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ret
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generate_key:
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mov rsi, rdi ; save first argument (string) address
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xor rdx, rdx ; dl = index1 = 0
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xor rax, rax ; al = i = 0
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xor rbx, rbx
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lea rcx, [key]
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._2: add dl, byte [rcx + rax]
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mov bl, byte [rdi]
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test bl, bl ; test character is not 0 (end of string)
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jne ._1
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mov rdi, rsi ; if character is 0 (end of string) got to the first character of the string
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._1: add dl, byte [rdi]
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add rdi, 1 ; next character
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mov bl, byte [rcx + rdx]
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mov bh, byte [rcx + rax]
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mov [rcx + rax], bl
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mov [rcx + rdx], bh ; value1, value2 = value2, value1
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add al, 1
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test al, al
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jne ._2 ; loop 256 times
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ret
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reset_key:
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xor rax, rax
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lea rdi, [key]
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._7: mov byte [rdi + rax], al
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add rax, 1
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test al, al
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jne ._7
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ret
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get_iv:
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lea rax, [iv]
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ret
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set_iv:
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lea rsi, [iv]
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xor rax, rax
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._8: mov rbx, [rdi + rax]
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mov [rsi + rax], rbx
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add rax, 4
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test al, al
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jne ._8
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mov byte [rsi + 256], al ; end with null byte (257 characters = 256 characters + null byte)
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ret
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encrypt:
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push rdx ; syscall in generate_iv use registers like r11
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push rsi
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call generate_key
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call generate_iv
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call xor_key_iv
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pop rdi
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pop rsi
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test rsi, rsi
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jne ._12
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call arc4_null_byte
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ret
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._12: call arc4
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ret
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decrypt:
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mov r11, rcx
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mov r8, rsi
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mov r9, rdx
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call generate_key
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mov rdi, r8
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call set_iv
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call xor_key_iv
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mov rdi, r9
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mov rsi, r11
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call arc4
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ret
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section .data
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key db 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138, 139, 140, 141, 142, 143, 144, 145, 146, 147, 148, 149, 150, 151, 152, 153, 154, 155, 156, 157, 158, 159, 160, 161, 162, 163, 164, 165, 166, 167, 168, 169, 170, 171, 172, 173, 174, 175, 176, 177, 178, 179, 180, 181, 182, 183, 184, 185, 186, 187, 188, 189, 190, 191, 192, 193, 194, 195, 196, 197, 198, 199, 200, 201, 202, 203, 204, 205, 206, 207, 208, 209, 210, 211, 212, 213, 214, 215, 216, 217, 218, 219, 220, 221, 222, 223, 224, 225, 226, 227, 228, 229, 230, 231, 232, 233, 234, 235, 236, 237, 238, 239, 240, 241, 242, 243, 244, 245, 246, 247, 248, 249, 250, 251, 252, 253, 254, 255, 0
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section .bss
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iv resb 257
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; This file implements RC4 in ASM.
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; Copyright (C) 2023, 2024 Maurice Lambert
3+
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; This program is free software: you can redistribute it and/or modify
5+
; it under the terms of the GNU General Public License as published by
6+
; the Free Software Foundation, either version 3 of the License, or
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; (at your option) any later version.
8+
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; This program is distributed in the hope that it will be useful,
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; but WITHOUT ANY WARRANTY; without even the implied warranty of
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; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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; GNU General Public License for more details.
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; You should have received a copy of the GNU General Public License
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; along with this program. If not, see <https://www.gnu.org/licenses/>.
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; nasm -f elf64 rc4.asm
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; gcc XXXXXXX.c rc4.o
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; gcc -shared rc4.o -o librc4.so
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; arc4_null_byte([IN/OUT] char *data) -> NULL
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; arc4([IN/OUT] char *data, [IN] unsigned long long length) -> NULL
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; generate_iv() -> NULL
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; xor_key_iv() -> NULL
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; generate_key(char *key) -> NULL
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; reset_key() -> NULL
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; get_iv() -> char[256] // null byte terminate string
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; set_iv([IN] char iv[256]) -> NULL
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; encrypt([IN] char *key, [IN/OUT] char *data, [IN] unsigned long long length) -> NULL // if length is 0 call arc4_null_byte
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; decrypt([IN] char *key, [IN] char iv[256], [IN/OUT] char *data, [IN] unsigned long long length) -> NULL // there is no way to decrypt string terminating by null byte because encrypted data can contains null byte
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global arc4, generate_iv, generate_key, xor_key_iv, reset_key, get_iv, set_iv, encrypt, decrypt, arc4_null_byte
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default rel
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section .text
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arc4:
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mov r10, rsi ; length
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xor rdx, rdx ; dl = index1 = 0
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xor rcx, rcx ; cl = index2 = 0
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xor rax, rax
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xor r11, r11
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lea rsi, [key]
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._4: test r10, r10 ; if length == 0: return;
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jne ._3
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ret
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._3: mov al, byte [rdi]
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dec r10 ; length -= 1;
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inc dl
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add cl, byte [rsi + rdx]
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mov al, byte [rsi + rdx]
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mov r11b, byte [rsi + rcx]
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mov byte [rsi + rdx], r11b
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mov byte [rsi + rcx], al ; value1, value2 = value2, value1
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add al, r11b
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mov al, byte [rsi + rax]
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xor byte [rdi], al
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inc rdi ; next character
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jmp ._4
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arc4_null_byte:
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xor rdx, rdx ; dl = index1 = 0
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xor rcx, rcx ; cl = index2 = 0
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xor rax, rax
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xor r11, r11
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lea rsi, [key]
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._11: mov al, byte [rdi]
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test al, al
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jne ._10 ; if character == 0 (end of string) return else crypt character
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ret
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._10: inc dl
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add cl, byte [rsi + rdx]
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mov al, byte [rsi + rdx]
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mov r11b, byte [rsi + rcx]
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mov byte [rsi + rdx], r11b
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mov byte [rsi + rcx], al ; value1, value2 = value2, value1
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add al, r11b
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mov al, byte [rsi + rax]
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xor byte [rdi], al
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inc rdi ; next character
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jmp ._11
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generate_iv:
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mov rax, 228 ; syscall 228 == sys_clock_gettime
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xor rdi, rdi ; 0 == CLOCK_REALTIME
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lea rsi, [iv]
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syscall
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mov rcx, 64
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mov rax, qword [rsi + 8] ; Nanosecond (pseudo random start number)
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._5: mov r11, rax
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shl rax, 13
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xor rax, r11
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mov r11, rax
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shr rax, 7
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xor rax, r11
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mov r11, rax
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shl rax, 17
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xor rax, r11
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mov [rsi + rcx * 4 - 4], rax
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dec rcx
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test rcx, rcx
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jne ._5
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mov byte [rsi + 256], 0 ; end with null byte (257 characters = 256 characters + null byte)
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ret
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xor_key_iv:
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xor rax, rax
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lea rdi, [key]
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lea rsi, [iv]
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._6: mov r11, [rsi + rax] ; 256 / 4 == 64, faster way (using 64 bit register) to xor all the key with iv than character (8 bit register) by character
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xor [rdi + rax], r11
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add al, 8
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test al, al
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jne ._6
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ret
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generate_key:
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mov r11, rdi ; save first argument (string) address
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xor rdx, rdx ; dl = index1 = 0
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xor rax, rax ; al = i = 0
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xor rcx, rcx
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lea rsi, [key]
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._2: add dl, byte [rsi + rax]
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mov cl, byte [rdi]
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test cl, cl ; test character is not 0 (end of string)
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jne ._1
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mov rdi, r11 ; if character is 0 (end of string) got to the first character of the string
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._1: add dl, byte [rdi]
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inc rdi ; next character
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mov cl, byte [rsi + rdx]
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mov ch, byte [rsi + rax]
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mov byte [rsi + rax], cl
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mov byte [rsi + rdx], ch ; value1, value2 = value2, value1
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inc al
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test al, al
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jne ._2 ; loop 256 times
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ret
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reset_key:
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xor rax, rax
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lea rdi, [key]
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._7: mov byte [rdi + rax], al
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inc rax
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test al, al
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jne ._7
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ret
148+
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get_iv:
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lea rax, [iv]
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ret
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set_iv:
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lea rsi, [iv]
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xor rax, rax
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._8: mov r11, [rdi + rax]
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mov [rsi + rax], r11
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add rax, 4
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test al, al
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jne ._8
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mov byte [rsi + 256], al ; end with null byte (257 characters = 256 characters + null byte)
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ret
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encrypt:
165+
push rdx
166+
push rsi
167+
call generate_key
168+
call generate_iv
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call xor_key_iv
170+
pop rdi
171+
pop rsi
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test rsi, rsi
173+
jne ._12
174+
call arc4_null_byte
175+
ret
176+
._12: call arc4
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ret
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decrypt:
180+
mov r10, rcx
181+
mov r8, rsi
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mov r9, rdx
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call generate_key
184+
mov rdi, r8
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call set_iv
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call xor_key_iv
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mov rdi, r9
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mov rsi, r10
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call arc4
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ret
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section .data
193+
key db 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138, 139, 140, 141, 142, 143, 144, 145, 146, 147, 148, 149, 150, 151, 152, 153, 154, 155, 156, 157, 158, 159, 160, 161, 162, 163, 164, 165, 166, 167, 168, 169, 170, 171, 172, 173, 174, 175, 176, 177, 178, 179, 180, 181, 182, 183, 184, 185, 186, 187, 188, 189, 190, 191, 192, 193, 194, 195, 196, 197, 198, 199, 200, 201, 202, 203, 204, 205, 206, 207, 208, 209, 210, 211, 212, 213, 214, 215, 216, 217, 218, 219, 220, 221, 222, 223, 224, 225, 226, 227, 228, 229, 230, 231, 232, 233, 234, 235, 236, 237, 238, 239, 240, 241, 242, 243, 244, 245, 246, 247, 248, 249, 250, 251, 252, 253, 254, 255, 0
194+
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section .bss
196+
iv resb 257

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