lwip_snmpv3.c

00001 /**
00002  * @file
00003  * Additional SNMPv3 functionality RFC3414 and RFC3826.
00004  */
00005 
00006 /*
00007  * Copyright (c) 2016 Elias Oenal.
00008  * All rights reserved.
00009  *
00010  * Redistribution and use in source and binary forms, with or without modification,
00011  * are permitted provided that the following conditions are met:
00012  *
00013  * 1. Redistributions of source code must retain the above copyright notice,
00014  *    this list of conditions and the following disclaimer.
00015  * 2. Redistributions in binary form must reproduce the above copyright notice,
00016  *    this list of conditions and the following disclaimer in the documentation
00017  *    and/or other materials provided with the distribution.
00018  * 3. The name of the author may not be used to endorse or promote products
00019  *    derived from this software without specific prior written permission.
00020  *
00021  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
00022  * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
00023  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
00024  * SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
00025  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
00026  * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
00027  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
00028  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
00029  * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
00030  * OF SUCH DAMAGE.
00031  *
00032  * Author: Elias Oenal <lwip@eliasoenal.com>
00033  */
00034 
00035 #include "snmpv3_priv.h"
00036 #include "lwip/apps/snmpv3.h"
00037 #include "lwip/sys.h"
00038 #include <string.h>
00039 
00040 #if LWIP_SNMP && LWIP_SNMP_V3
00041 
00042 #ifdef LWIP_SNMPV3_INCLUDE_ENGINE
00043 #include LWIP_SNMPV3_INCLUDE_ENGINE
00044 #endif
00045 
00046 #define SNMP_MAX_TIME_BOOT 2147483647UL
00047 
00048 /** Call this if engine has been changed. Has to reset boots, see below */
00049 void
00050 snmpv3_engine_id_changed(void)
00051 {
00052   snmpv3_set_engine_boots(0);
00053 }
00054 
00055 /** According to RFC3414 2.2.2.
00056  *
00057  * The number of times that the SNMP engine has
00058  * (re-)initialized itself since snmpEngineID
00059  * was last configured.
00060  */
00061 u32_t
00062 snmpv3_get_engine_boots_internal(void)
00063 {
00064   if (snmpv3_get_engine_boots() == 0 ||
00065       snmpv3_get_engine_boots() < SNMP_MAX_TIME_BOOT) {
00066     return snmpv3_get_engine_boots();
00067   }
00068 
00069   snmpv3_set_engine_boots(SNMP_MAX_TIME_BOOT);
00070   return snmpv3_get_engine_boots();
00071 }
00072 
00073 /** RFC3414 2.2.2.
00074  *
00075  * Once the timer reaches 2147483647 it gets reset to zero and the
00076  * engine boot ups get incremented.
00077  */
00078 u32_t
00079 snmpv3_get_engine_time_internal(void)
00080 {
00081   if (snmpv3_get_engine_time() >= SNMP_MAX_TIME_BOOT) {
00082     snmpv3_reset_engine_time();
00083 
00084     if (snmpv3_get_engine_boots() < SNMP_MAX_TIME_BOOT - 1) {
00085       snmpv3_set_engine_boots(snmpv3_get_engine_boots() + 1);
00086     } else {
00087       snmpv3_set_engine_boots(SNMP_MAX_TIME_BOOT);
00088     }
00089   }
00090 
00091   return snmpv3_get_engine_time();
00092 }
00093 
00094 #if LWIP_SNMP_V3_CRYPTO
00095 
00096 /* This function ignores the byte order suggestion in RFC3414
00097  * since it simply doesn't influence the effectiveness of an IV.
00098  *
00099  * Implementing RFC3826 priv param algorithm if LWIP_RAND is available.
00100  *
00101  * @todo: This is a potential thread safety issue.
00102  */
00103 err_t
00104 snmpv3_build_priv_param(u8_t* priv_param)
00105 {
00106 #ifdef LWIP_RAND /* Based on RFC3826 */
00107   static u8_t init;
00108   static u32_t priv1, priv2;
00109 
00110   /* Lazy initialisation */
00111   if (init == 0) {
00112     init = 1;
00113     priv1 = LWIP_RAND();
00114     priv2 = LWIP_RAND();
00115   }
00116 
00117   memcpy(&priv_param[0], &priv1, sizeof(priv1));
00118   memcpy(&priv_param[4], &priv2, sizeof(priv2));
00119 
00120   /* Emulate 64bit increment */
00121   priv1++;
00122   if (!priv1) { /* Overflow */
00123     priv2++;
00124   }
00125 #else /* Based on RFC3414 */
00126   static u32_t ctr;
00127   u32_t boots = LWIP_SNMPV3_GET_ENGINE_BOOTS();
00128   memcpy(&priv_param[0], &boots, 4);
00129   memcpy(&priv_param[4], &ctr, 4);
00130   ctr++;
00131 #endif
00132   return ERR_OK;
00133 }
00134 #endif /* LWIP_SNMP_V3_CRYPTO */
00135 
00136 #endif