1 /**
2  * @file
3  * Additional SNMPv3 functionality RFC3414 and RFC3826.
4  */
5 
6 /*
7  * Copyright (c) 2016 Elias Oenal.
8  * All rights reserved.
9  *
10  * Redistribution and use in source and binary forms, with or without modification,
11  * are permitted provided that the following conditions are met:
12  *
13  * 1. Redistributions of source code must retain the above copyright notice,
14  *    this list of conditions and the following disclaimer.
15  * 2. Redistributions in binary form must reproduce the above copyright notice,
16  *    this list of conditions and the following disclaimer in the documentation
17  *    and/or other materials provided with the distribution.
18  * 3. The name of the author may not be used to endorse or promote products
19  *    derived from this software without specific prior written permission.
20  *
21  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
22  * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
23  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
24  * SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
25  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
26  * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
27  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
28  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
29  * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
30  * OF SUCH DAMAGE.
31  *
32  * Author: Elias Oenal <lwip@eliasoenal.com>
33  */
34 
35 #include "snmpv3_priv.h"
36 #include "lwip/apps/snmpv3.h"
37 #include "lwip/sys.h"
38 #include <string.h>
39 
40 #if LWIP_SNMP && LWIP_SNMP_V3
41 
42 #ifdef LWIP_SNMPV3_INCLUDE_ENGINE
43 #include LWIP_SNMPV3_INCLUDE_ENGINE
44 #endif
45 
46 #define SNMP_MAX_TIME_BOOT 2147483647UL
47 
48 /** Call this if engine has been changed. Has to reset boots, see below */
49 void
50 snmpv3_engine_id_changed(void)
51 {
52   snmpv3_set_engine_boots(0);
53 }
54 
55 /** According to RFC3414 2.2.2.
56  *
57  * The number of times that the SNMP engine has
58  * (re-)initialized itself since snmpEngineID
59  * was last configured.
60  */
61 s32_t
62 snmpv3_get_engine_boots_internal(void)
63 {
64   if (snmpv3_get_engine_boots() == 0 ||
65       snmpv3_get_engine_boots() < SNMP_MAX_TIME_BOOT) {
66     return snmpv3_get_engine_boots();
67   }
68 
69   snmpv3_set_engine_boots(SNMP_MAX_TIME_BOOT);
70   return snmpv3_get_engine_boots();
71 }
72 
73 /** RFC3414 2.2.2.
74  *
75  * Once the timer reaches 2147483647 it gets reset to zero and the
76  * engine boot ups get incremented.
77  */
78 s32_t
79 snmpv3_get_engine_time_internal(void)
80 {
81   if (snmpv3_get_engine_time() >= SNMP_MAX_TIME_BOOT) {
82     snmpv3_reset_engine_time();
83 
84     if (snmpv3_get_engine_boots() < SNMP_MAX_TIME_BOOT - 1) {
85       snmpv3_set_engine_boots(snmpv3_get_engine_boots() + 1);
86     } else {
87       snmpv3_set_engine_boots(SNMP_MAX_TIME_BOOT);
88     }
89   }
90 
91   return snmpv3_get_engine_time();
92 }
93 
94 #if LWIP_SNMP_V3_CRYPTO
95 
96 /* This function ignores the byte order suggestion in RFC3414
97  * since it simply doesn't influence the effectiveness of an IV.
98  *
99  * Implementing RFC3826 priv param algorithm if LWIP_RAND is available.
100  *
101  * @todo: This is a potential thread safety issue.
102  */
103 err_t
104 snmpv3_build_priv_param(u8_t *priv_param)
105 {
106 #ifdef LWIP_RAND /* Based on RFC3826 */
107   static u8_t init;
108   static u32_t priv1, priv2;
109 
110   /* Lazy initialisation */
111   if (init == 0) {
112     init = 1;
113     priv1 = LWIP_RAND();
114     priv2 = LWIP_RAND();
115   }
116 
117   SMEMCPY(&priv_param[0], &priv1, sizeof(priv1));
118   SMEMCPY(&priv_param[4], &priv2, sizeof(priv2));
119 
120   /* Emulate 64bit increment */
121   priv1++;
122   if (!priv1) { /* Overflow */
123     priv2++;
124   }
125 #else /* Based on RFC3414 */
126   static u32_t ctr;
127   u32_t boots = snmpv3_get_engine_boots_internal();
128   SMEMCPY(&priv_param[0], &boots, 4);
129   SMEMCPY(&priv_param[4], &ctr, 4);
130   ctr++;
131 #endif
132   return ERR_OK;
133 }
134 #endif /* LWIP_SNMP_V3_CRYPTO */
135 
136 #endif
137