xref: /openbsd-src/libexec/login_yubikey/yubikey.c (revision 6cc4e57d498809f6ec364f1c10349bb4b55a87d8)

/* $OpenBSD: yubikey.c,v 1.6 2017/09/16 08:07:15 anton Exp $ */

/*
 * Written by Simon Josefsson <simon@josefsson.org>.
 * Copyright (c) 2006, 2007, 2008, 2009 Yubico AB
 * Copyright (c) 2010 Daniel Hartmeier <daniel@benzedrine.cx>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 * * Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 *
 * * Redistributions in binary form must reproduce the above
 *   copyright notice, this list of conditions and the following
 *   disclaimer in the documentation and/or other materials provided
 *   with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 */

#include <ctype.h>
#include <stdlib.h>
#include <wchar.h>
#include <locale.h>
#include <errno.h>

#include "yubikey.h"
#include "keymaps.h"

static const uint8_t RC[] = {
	0x1, 0x2, 0x4, 0x8, 0x10, 0x20, 0x40, 0x80, 0x1B, 0x36
};

static const uint8_t rijndael_sbox[] = {
	0x63, 0x7C, 0x77, 0x7B, 0xF2, 0x6B, 0x6F, 0xC5,
	0x30, 0x01, 0x67, 0x2B, 0xFE, 0xD7, 0xAB, 0x76,
	0xCA, 0x82, 0xC9, 0x7D, 0xFA, 0x59, 0x47, 0xF0,
	0xAD, 0xD4, 0xA2, 0xAF, 0x9C, 0xA4, 0x72, 0xC0,
	0xB7, 0xFD, 0x93, 0x26, 0x36, 0x3F, 0xF7, 0xCC,
	0x34, 0xA5, 0xE5, 0xF1, 0x71, 0xD8, 0x31, 0x15,
	0x04, 0xC7, 0x23, 0xC3, 0x18, 0x96, 0x05, 0x9A,
	0x07, 0x12, 0x80, 0xE2, 0xEB, 0x27, 0xB2, 0x75,
	0x09, 0x83, 0x2C, 0x1A, 0x1B, 0x6E, 0x5A, 0xA0,
	0x52, 0x3B, 0xD6, 0xB3, 0x29, 0xE3, 0x2F, 0x84,
	0x53, 0xD1, 0x00, 0xED, 0x20, 0xFC, 0xB1, 0x5B,
	0x6A, 0xCB, 0xBE, 0x39, 0x4A, 0x4C, 0x58, 0xCF,
	0xD0, 0xEF, 0xAA, 0xFB, 0x43, 0x4D, 0x33, 0x85,
	0x45, 0xF9, 0x02, 0x7F, 0x50, 0x3C, 0x9F, 0xA8,
	0x51, 0xA3, 0x40, 0x8F, 0x92, 0x9D, 0x38, 0xF5,
	0xBC, 0xB6, 0xDA, 0x21, 0x10, 0xFF, 0xF3, 0xD2,
	0xCD, 0x0C, 0x13, 0xEC, 0x5F, 0x97, 0x44, 0x17,
	0xC4, 0xA7, 0x7E, 0x3D, 0x64, 0x5D, 0x19, 0x73,
	0x60, 0x81, 0x4F, 0xDC, 0x22, 0x2A, 0x90, 0x88,
	0x46, 0xEE, 0xB8, 0x14, 0xDE, 0x5E, 0x0B, 0xDB,
	0xE0, 0x32, 0x3A, 0x0A, 0x49, 0x06, 0x24, 0x5C,
	0xC2, 0xD3, 0xAC, 0x62, 0x91, 0x95, 0xE4, 0x79,
	0xE7, 0xC8, 0x37, 0x6D, 0x8D, 0xD5, 0x4E, 0xA9,
	0x6C, 0x56, 0xF4, 0xEA, 0x65, 0x7A, 0xAE, 0x08,
	0xBA, 0x78, 0x25, 0x2E, 0x1C, 0xA6, 0xB4, 0xC6,
	0xE8, 0xDD, 0x74, 0x1F, 0x4B, 0xBD, 0x8B, 0x8A,
	0x70, 0x3E, 0xB5, 0x66, 0x48, 0x03, 0xF6, 0x0E,
	0x61, 0x35, 0x57, 0xB9, 0x86, 0xC1, 0x1D, 0x9E,
	0xE1, 0xF8, 0x98, 0x11, 0x69, 0xD9, 0x8E, 0x94,
	0x9B, 0x1E, 0x87, 0xE9, 0xCE, 0x55, 0x28, 0xDF,
	0x8C, 0xA1, 0x89, 0x0D, 0xBF, 0xE6, 0x42, 0x68,
	0x41, 0x99, 0x2D, 0x0F, 0xB0, 0x54, 0xBB, 0x16
};

static const uint8_t rijndael_inv_sbox[] = {
	0x52, 0x09, 0x6A, 0xD5, 0x30, 0x36, 0xA5, 0x38,
	0xBF, 0x40, 0xA3, 0x9E, 0x81, 0xF3, 0xD7, 0xFB,
	0x7C, 0xE3, 0x39, 0x82, 0x9B, 0x2F, 0xFF, 0x87,
	0x34, 0x8E, 0x43, 0x44, 0xC4, 0xDE, 0xE9, 0xCB,
	0x54, 0x7B, 0x94, 0x32, 0xA6, 0xC2, 0x23, 0x3D,
	0xEE, 0x4C, 0x95, 0x0B, 0x42, 0xFA, 0xC3, 0x4E,
	0x08, 0x2E, 0xA1, 0x66, 0x28, 0xD9, 0x24, 0xB2,
	0x76, 0x5B, 0xA2, 0x49, 0x6D, 0x8B, 0xD1, 0x25,
	0x72, 0xF8, 0xF6, 0x64, 0x86, 0x68, 0x98, 0x16,
	0xD4, 0xA4, 0x5C, 0xCC, 0x5D, 0x65, 0xB6, 0x92,
	0x6C, 0x70, 0x48, 0x50, 0xFD, 0xED, 0xB9, 0xDA,
	0x5E, 0x15, 0x46, 0x57, 0xA7, 0x8D, 0x9D, 0x84,
	0x90, 0xD8, 0xAB, 0x00, 0x8C, 0xBC, 0xD3, 0x0A,
	0xF7, 0xE4, 0x58, 0x05, 0xB8, 0xB3, 0x45, 0x06,
	0xD0, 0x2C, 0x1E, 0x8F, 0xCA, 0x3F, 0x0F, 0x02,
	0xC1, 0xAF, 0xBD, 0x03, 0x01, 0x13, 0x8A, 0x6B,
	0x3A, 0x91, 0x11, 0x41, 0x4F, 0x67, 0xDC, 0xEA,
	0x97, 0xF2, 0xCF, 0xCE, 0xF0, 0xB4, 0xE6, 0x73,
	0x96, 0xAC, 0x74, 0x22, 0xE7, 0xAD, 0x35, 0x85,
	0xE2, 0xF9, 0x37, 0xE8, 0x1C, 0x75, 0xDF, 0x6E,
	0x47, 0xF1, 0x1A, 0x71, 0x1D, 0x29, 0xC5, 0x89,
	0x6F, 0xB7, 0x62, 0x0E, 0xAA, 0x18, 0xBE, 0x1B,
	0xFC, 0x56, 0x3E, 0x4B, 0xC6, 0xD2, 0x79, 0x20,
	0x9A, 0xDB, 0xC0, 0xFE, 0x78, 0xCD, 0x5A, 0xF4,
	0x1F, 0xDD, 0xA8, 0x33, 0x88, 0x07, 0xC7, 0x31,
	0xB1, 0x12, 0x10, 0x59, 0x27, 0x80, 0xEC, 0x5F,
	0x60, 0x51, 0x7F, 0xA9, 0x19, 0xB5, 0x4A, 0x0D,
	0x2D, 0xE5, 0x7A, 0x9F, 0x93, 0xC9, 0x9C, 0xEF,
	0xA0, 0xE0, 0x3B, 0x4D, 0xAE, 0x2A, 0xF5, 0xB0,
	0xC8, 0xEB, 0xBB, 0x3C, 0x83, 0x53, 0x99, 0x61,
	0x17, 0x2B, 0x04, 0x7E, 0xBA, 0x77, 0xD6, 0x26,
	0xE1, 0x69, 0x14, 0x63, 0x55, 0x21, 0x0C, 0x7D
};

static inline uint8_t
xtime(uint8_t b)
{
	return (b & 0x80) ? ((b << 1) ^ 0x1b) : (b << 1);
}

#define NUMBER_OF_ROUNDS 10

void
yubikey_aes_decrypt(uint8_t *state, const uint8_t *key)
{
	uint8_t i, j, round_key[0x10];
	uint8_t a02x, a13x;
	uint8_t a02xx, a13xx;
	uint8_t k1, k2;

	memcpy(round_key, key, sizeof(round_key));
	for (i = 0; i < NUMBER_OF_ROUNDS; i++) {
		round_key[0] ^= RC[i];

		round_key[0] ^= rijndael_sbox[round_key[13]];
		round_key[1] ^= rijndael_sbox[round_key[14]];
		round_key[2] ^= rijndael_sbox[round_key[15]];
		round_key[3] ^= rijndael_sbox[round_key[12]];

		for (j = 4; j < 16; j++)
			round_key[j] ^= round_key[j - 4];
	}
	for (i = 0; i < 0x10; i++)
		state[i] ^= round_key[i];

	for (i = 1; i <= NUMBER_OF_ROUNDS; i++) {
		/* inv_byte_sub_shift_row(); */

		/* First row: 0 shift, 0 4 8 12 */
		state[0] = rijndael_inv_sbox[state[0]];
		state[4] = rijndael_inv_sbox[state[4]];
		state[8] = rijndael_inv_sbox[state[8]];
		state[12] = rijndael_inv_sbox[state[12]];

		/* Second row: -1 shift, 1 5 9 13 */
		j = state[13];
		state[13] = rijndael_inv_sbox[state[9]];
		state[9] = rijndael_inv_sbox[state[5]];
		state[5] = rijndael_inv_sbox[state[1]];
		state[1] = rijndael_inv_sbox[j];

		/* Third row: -2 shift, 2 6 10 14 */
		j = state[2];
		state[2] = rijndael_inv_sbox[state[10]];
		state[10] = rijndael_inv_sbox[j];
		j = state[6];
		state[6] = rijndael_inv_sbox[state[14]];
		state[14] = rijndael_inv_sbox[j];

		/* Fourth row: -3 shift, 3 7 11 15 */
		j = state[3];
		state[3] = rijndael_inv_sbox[state[7]];
		state[7] = rijndael_inv_sbox[state[11]];
		state[11] = rijndael_inv_sbox[state[15]];
		state[15] = rijndael_inv_sbox[j];

		/* get_inv_round_key(i); */

		for (j = 15; j > 3; j--)
			round_key[j] ^= round_key[j - 4];

		round_key[0] ^= (RC[NUMBER_OF_ROUNDS - i] ^
		    rijndael_sbox[round_key[13]]);

		round_key[1] ^= rijndael_sbox[round_key[14]];
		round_key[2] ^= rijndael_sbox[round_key[15]];
		round_key[3] ^= rijndael_sbox[round_key[12]];

		for (j = 0; j < 16; j++)
			state[j] ^= round_key[j];
		if (i != NUMBER_OF_ROUNDS) {
			/* inv_mix_column(); */

			for (j = 0; j < 16; j += 4) {
				k1 = state[j] ^ state[j + 2];
				a02x = xtime(k1);
				k2 = state[j + 1] ^ state[j + 3];
				a13x = xtime(k2);

				k1 ^= (k2 ^ xtime(state[j + 1] ^ state[j + 2]));
				k2 = k1;

				a02xx = xtime(a02x);
				a13xx = xtime(a13x);


				k1 ^= (xtime(a02xx ^ a13xx) ^ a02xx);
				k2 ^= (xtime(a02xx ^ a13xx) ^ a13xx);

				state[j] ^= (k1 ^ a02x);
				state[j + 1] ^= k2;
				state[j + 2] ^= (k1 ^ a13x);
				state[j + 3] ^= (k2 ^ a02x ^ a13x);
			}
		}

	}
}

uint16_t
yubikey_crc16(const uint8_t *buf, size_t buf_size)
{
	uint16_t m_crc = 0xffff;

	while (buf_size--) {
		int i, j;

		m_crc ^= (uint8_t)*buf++ & 0xFF;
		for (i = 0; i < 8; i++) {
			j = m_crc & 1;
			m_crc >>= 1;
			if (j)
				m_crc ^= 0x8408;
		}
	}
	return m_crc;
}

static const char hex_trans[] = "0123456789abcdef";

void
yubikey_hex_encode(char *dst, const char *src, size_t srcSize)
{
	while (srcSize--) {
		*dst++ = hex_trans[(*src >> 4) & 0xf];
		*dst++ = hex_trans[*src++ & 0xf];
	}
	*dst = '\0';
}

void
yubikey_hex_decode(char *dst, const char *src, size_t dstSize)
{
	char b;
	int flag = 0;
	char *p1;

	for (; *src && dstSize > 0; src++) {
		p1 = strchr(hex_trans, tolower((unsigned char)*src));
		if (p1 == NULL)
			b = 0;
		else
			b = (char)(p1 - hex_trans);
		if ((flag = !flag))
			*dst = b;
		else {
			*dst = (*dst << 4) | b;
			dst++;
			dstSize--;
		}
	}
	while (dstSize--)
		*dst++ = 0;
}

static const char modhex_trans[] = "cbdefghijklnrtuv";

void
yubikey_modhex_decode(char *dst, const char *src, size_t dstSize)
{
	char b;
	int flag = 0;
	char *p1;

	for (; *src && dstSize > 0; src++) {
		p1 = strchr(modhex_trans, tolower((unsigned char)*src));
		if (p1 == NULL)
			b = 0;
		else
			b = (char)(p1 - modhex_trans);

		if ((flag = !flag))
			*dst = b;
		else {
			*dst = (*dst << 4) | b;
			dst++;
			dstSize--;
		}
	}
	while (dstSize--)
		*dst++ = 0;
}

uint8_t
yubikey_keymap_decode(wchar_t *wpassword, char *token, int index)
{
	int c, j, found;
	for (j=0; j<YUBIKEY_TOKEN_SIZE; j++) {
		found = 0;
		for (c=0; c<16; c++) {
			if (wpassword[j] == keymaps[index][c]) {
				token[j] = modhex_trans[c];
				found++;
				break;
			}
		}
		if (found == 0)
			return 1;
	}
	return 0;
}

int
yubikey_parse(const uint8_t *password, const uint8_t key[YUBIKEY_KEY_SIZE],
    yubikey_token_t out, int index)
{
	wchar_t *wpassword, *pp;
	char token[YUBIKEY_TOKEN_SIZE + 1], *lc_ctype;
	size_t len;
	int rc = 0;

	if (index < 0 || index >= YUBIKEY_KEYMAP_COUNT)
		return -1;

	len = strlen(password);
	pp = wpassword = reallocarray(NULL, len + 1, sizeof(wchar_t));
	if (pp == NULL)
		return ENOMEM;

	memset(out, 0, sizeof(*out));
	memset(token, 0, YUBIKEY_TOKEN_SIZE + 1);

	lc_ctype = getenv("LC_CTYPE");
	setlocale(LC_CTYPE, lc_ctype ? lc_ctype : "C.UTF-8");
	len = mbstowcs(wpassword, password, len);
	if (len == (size_t)-1) {
		rc = errno;
		goto ret;
	}
	setlocale(LC_CTYPE, "C");

	if (len > YUBIKEY_TOKEN_SIZE)
		pp = pp + len - YUBIKEY_TOKEN_SIZE;
	if (len < YUBIKEY_TOKEN_SIZE) {
		rc = EMSGSIZE;
		goto ret;
	}

	if (yubikey_keymap_decode(pp, token, index)) {
		rc = EINVAL;
		goto ret;
	}
	yubikey_modhex_decode((void *)out, token, sizeof(*out));
	yubikey_aes_decrypt((void *)out, key);

ret:
	freezero(wpassword, (len + 1) * sizeof(wchar_t));
	return rc;
}