| // SPDX-License-Identifier: GPL-2.0 OR MIT |
| /* |
| * Copyright (C) 2015-2020 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved. |
| * |
| * This is a specialized constant-time base64/hex implementation that resists side-channel attacks. |
| */ |
| |
| #include <string.h> |
| #include "encoding.h" |
| |
| static inline void encode_base64(char dest[static 4], const uint8_t src[static 3]) |
| { |
| const uint8_t input[] = { (src[0] >> 2) & 63, ((src[0] << 4) | (src[1] >> 4)) & 63, ((src[1] << 2) | (src[2] >> 6)) & 63, src[2] & 63 }; |
| |
| for (unsigned int i = 0; i < 4; ++i) |
| dest[i] = input[i] + 'A' |
| + (((25 - input[i]) >> 8) & 6) |
| - (((51 - input[i]) >> 8) & 75) |
| - (((61 - input[i]) >> 8) & 15) |
| + (((62 - input[i]) >> 8) & 3); |
| |
| } |
| |
| void key_to_base64(char base64[static WG_KEY_LEN_BASE64], const uint8_t key[static WG_KEY_LEN]) |
| { |
| unsigned int i; |
| |
| for (i = 0; i < WG_KEY_LEN / 3; ++i) |
| encode_base64(&base64[i * 4], &key[i * 3]); |
| encode_base64(&base64[i * 4], (const uint8_t[]){ key[i * 3 + 0], key[i * 3 + 1], 0 }); |
| base64[WG_KEY_LEN_BASE64 - 2] = '='; |
| base64[WG_KEY_LEN_BASE64 - 1] = '\0'; |
| } |
| |
| static inline int decode_base64(const char src[static 4]) |
| { |
| int val = 0; |
| |
| for (unsigned int i = 0; i < 4; ++i) |
| val |= (-1 |
| + ((((('A' - 1) - src[i]) & (src[i] - ('Z' + 1))) >> 8) & (src[i] - 64)) |
| + ((((('a' - 1) - src[i]) & (src[i] - ('z' + 1))) >> 8) & (src[i] - 70)) |
| + ((((('0' - 1) - src[i]) & (src[i] - ('9' + 1))) >> 8) & (src[i] + 5)) |
| + ((((('+' - 1) - src[i]) & (src[i] - ('+' + 1))) >> 8) & 63) |
| + ((((('/' - 1) - src[i]) & (src[i] - ('/' + 1))) >> 8) & 64) |
| ) << (18 - 6 * i); |
| return val; |
| } |
| |
| bool key_from_base64(uint8_t key[static WG_KEY_LEN], const char *base64) |
| { |
| unsigned int i; |
| volatile uint8_t ret = 0; |
| int val; |
| |
| if (strlen(base64) != WG_KEY_LEN_BASE64 - 1 || base64[WG_KEY_LEN_BASE64 - 2] != '=') |
| return false; |
| |
| for (i = 0; i < WG_KEY_LEN / 3; ++i) { |
| val = decode_base64(&base64[i * 4]); |
| ret |= (uint32_t)val >> 31; |
| key[i * 3 + 0] = (val >> 16) & 0xff; |
| key[i * 3 + 1] = (val >> 8) & 0xff; |
| key[i * 3 + 2] = val & 0xff; |
| } |
| val = decode_base64((const char[]){ base64[i * 4 + 0], base64[i * 4 + 1], base64[i * 4 + 2], 'A' }); |
| ret |= ((uint32_t)val >> 31) | (val & 0xff); |
| key[i * 3 + 0] = (val >> 16) & 0xff; |
| key[i * 3 + 1] = (val >> 8) & 0xff; |
| |
| return 1 & ((ret - 1) >> 8); |
| } |
| |
| void key_to_hex(char hex[static WG_KEY_LEN_HEX], const uint8_t key[static WG_KEY_LEN]) |
| { |
| unsigned int i; |
| |
| for (i = 0; i < WG_KEY_LEN; ++i) { |
| hex[i * 2] = 87U + (key[i] >> 4) + ((((key[i] >> 4) - 10U) >> 8) & ~38U); |
| hex[i * 2 + 1] = 87U + (key[i] & 0xf) + ((((key[i] & 0xf) - 10U) >> 8) & ~38U); |
| } |
| hex[i * 2] = '\0'; |
| } |
| |
| bool key_from_hex(uint8_t key[static WG_KEY_LEN], const char *hex) |
| { |
| uint8_t c, c_acc, c_alpha0, c_alpha, c_num0, c_num, c_val; |
| volatile uint8_t ret = 0; |
| |
| if (strlen(hex) != WG_KEY_LEN_HEX - 1) |
| return false; |
| |
| for (unsigned int i = 0; i < WG_KEY_LEN_HEX - 1; i += 2) { |
| c = (uint8_t)hex[i]; |
| c_num = c ^ 48U; |
| c_num0 = (c_num - 10U) >> 8; |
| c_alpha = (c & ~32U) - 55U; |
| c_alpha0 = ((c_alpha - 10U) ^ (c_alpha - 16U)) >> 8; |
| ret |= ((c_num0 | c_alpha0) - 1) >> 8; |
| c_val = (c_num0 & c_num) | (c_alpha0 & c_alpha); |
| c_acc = c_val * 16U; |
| |
| c = (uint8_t)hex[i + 1]; |
| c_num = c ^ 48U; |
| c_num0 = (c_num - 10U) >> 8; |
| c_alpha = (c & ~32U) - 55U; |
| c_alpha0 = ((c_alpha - 10U) ^ (c_alpha - 16U)) >> 8; |
| ret |= ((c_num0 | c_alpha0) - 1) >> 8; |
| c_val = (c_num0 & c_num) | (c_alpha0 & c_alpha); |
| key[i / 2] = c_acc | c_val; |
| } |
| |
| return 1 & ((ret - 1) >> 8); |
| } |
| |
| bool key_is_zero(const uint8_t key[static WG_KEY_LEN]) |
| { |
| volatile uint8_t acc = 0; |
| |
| for (unsigned int i = 0; i < WG_KEY_LEN; ++i) { |
| acc |= key[i]; |
| asm volatile("" : "=r"(acc) : "0"(acc)); |
| } |
| return 1 & ((acc - 1) >> 8); |
| } |