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6fa15ff3f6
CPU IDs may contain very little entropy. Often only a single byte may change between two CPUs. To mitigate this use a somewhat 'proper' hash algorithm (I chose DJB2 hash simply because it's small) and 'extend' it to the required output size. For 50 STM32 CPU IDs from the grenoble site, this produces a much more random LUID output.
137 lines
2.7 KiB
C
137 lines
2.7 KiB
C
/*
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* Copyright (C) 2017 Freie Universität Berlin
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*
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* This file is subject to the terms and conditions of the GNU Lesser
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* General Public License v2.1. See the file LICENSE in the top level
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* directory for more details.
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*/
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/**
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* @ingroup sys_luid
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* @{
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*
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* @file
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* @brief LUID module implementation
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*
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* @author Hauke Petersen <hauke.petersen@fu-berlin.de>
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*
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* @}
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*/
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#include <stdint.h>
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#include <string.h>
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#include "assert.h"
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#include "periph/cpuid.h"
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#include "luid.h"
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#if CPUID_LEN
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/* based on DJB2 Hash */
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static void _luid_round(const uint8_t *in, size_t in_len, uint8_t *out, size_t out_len)
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{
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uint32_t hash = 5381;
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for (size_t i = 0; i < in_len; i++) {
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hash = hash * 33 + in[i];
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out[i % out_len] ^= hash;
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}
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}
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#endif
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void __attribute__((weak)) luid_base(void *buf, size_t len)
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{
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memset(buf, LUID_BACKUP_SEED, len);
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#if CPUID_LEN
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uint8_t cid[CPUID_LEN];
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cpuid_get(cid);
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_luid_round(cid, sizeof(cid), buf, len);
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_luid_round(buf, len, buf, len);
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#endif
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}
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static uint8_t lastused;
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void luid_get(void *buf, size_t len)
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{
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luid_base(buf, len);
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((uint8_t *)buf)[0] ^= lastused++;
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}
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void luid_get_lb(void *buf, size_t len)
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{
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luid_base(buf, len);
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((uint8_t *)buf)[len - 1] ^= lastused++;
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}
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void luid_custom(void *buf, size_t len, int gen)
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{
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luid_base(buf, len);
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for (size_t i = 0; i < sizeof(gen); i++) {
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((uint8_t *)buf)[i % len] ^= ((gen >> (i * 8)) & 0xff);
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}
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}
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void luid_get_short(network_uint16_t *addr)
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{
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luid_base(addr, sizeof(*addr));
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addr->u8[1] ^= lastused++;
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/* https://tools.ietf.org/html/rfc4944#section-12 requires the first bit to
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* 0 for unicast addresses */
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addr->u8[0] &= 0x7F;
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}
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void luid_get_eui48(eui48_t *addr)
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{
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luid_base(addr, sizeof(*addr));
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addr->uint8[5] ^= lastused++;
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eui48_set_local(addr);
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eui48_clear_group(addr);
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}
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void luid_netdev_get_eui48(const netdev_t *netdev, eui48_t *addr)
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{
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luid_base(addr, sizeof(*addr));
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#ifdef MODULE_NETDEV_REGISTER
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addr->uint8[4] ^= netdev->type;
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addr->uint8[5] ^= netdev->index;
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#else
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/* we should only get here with gnrc_netif_single */
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(void)netdev;
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#endif
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eui48_set_local(addr);
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eui48_clear_group(addr);
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}
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void luid_get_eui64(eui64_t *addr)
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{
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luid_base(addr, sizeof(*addr));
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addr->uint8[7] ^= lastused++;
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eui64_set_local(addr);
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eui64_clear_group(addr);
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}
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void luid_netdev_get_eui64(const netdev_t *netdev, eui64_t *addr)
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{
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luid_base(addr, sizeof(*addr));
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#ifdef MODULE_NETDEV_REGISTER
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addr->uint8[6] ^= netdev->type;
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addr->uint8[7] ^= netdev->index;
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#else
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/* we should only get here with gnrc_netif_single */
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(void)netdev;
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#endif
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eui64_set_local(addr);
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eui64_clear_group(addr);
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}
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