问net-snmp没有正确地更改auth和priv协议。

EN

int main(int argc, char** argv) {
struct snmp_session session, session1, *ss, *ss1;
struct snmp_pdu *pdu, *pdu1;
struct snmp_pdu *response, *response1;

oid anOID[MAX_OID_LEN];
size_t anOID_len = MAX_OID_LEN;

struct variable_list *vars;
int status, status1;

init_snmp("snmpapp");

const char* user = "md5";
string authpw = "123123123";
string privpw = "";
string ipString = "192.168.15.32";

char ip[16];
memset(&ip, 0, sizeof (ip));
ipString.copy(ip, sizeof (ip) - 1, 0);

/*
 * First request: AuthProto is MD5, no PrivProto is used. The snmp-get
 * request is successful
 */
snmp_sess_init(&session); /* set up defaults */
session.peername = ip;
session.version = SNMP_VERSION_3;

/* set the SNMPv3 user name */
session.securityName = strdup(user);
session.securityNameLen = strlen(session.securityName);

// set the authentication method to MD5     
session.securityLevel = SNMP_SEC_LEVEL_AUTHNOPRIV;

session.securityAuthProto = usmHMACMD5AuthProtocol;
session.securityAuthProtoLen = USM_AUTH_PROTO_MD5_LEN;
session.securityAuthKeyLen = USM_AUTH_KU_LEN;;

if (generate_Ku(session.securityAuthProto,
        session.securityAuthProtoLen,
        (u_char *) authpw.c_str(), strlen(authpw.c_str()),
        session.securityAuthKey,
        &session.securityAuthKeyLen) != SNMPERR_SUCCESS) {
    //if code reaches here, the creation of the security key was not successful

}

cout << "SecurityAuthProto - session: " << session.securityAuthProto[9] << " / SecurityAuthKey - session: " << session.securityAuthKey << endl;

ss = snmp_open(&session); /* establish the session */

if (!ss) {
    cout << "Couldn't open session1 correctly";
    exit(2);
}

cout << "SecurityAuthProto - ss: " << ss->securityAuthProto[9] << " / SecurityAuthKey - ss: " << ss->securityAuthKey << endl;

//send message
pdu = snmp_pdu_create(SNMP_MSG_GET);
read_objid(".1.3.6.1.2.1.1.1.0", anOID, &anOID_len);
snmp_add_null_var(pdu, anOID, anOID_len);
status = snmp_synch_response(ss, pdu, &response);

/*
 * Process the response.
 */
if (status == STAT_SUCCESS && response->errstat == SNMP_ERR_NOERROR) {
    cout << "SNMP-read success" << endl;
} else {
    cout << "SNMP-read fail" << endl;
}

if (response)
    snmp_free_pdu(response);
if (!snmp_close(ss))
    cout << "Snmp closing failed" << endl;

/*
 * Second request: Only the authProto is changed from MD5 to SHA1. I expect,
 * that the snmp-get fails, but it still succeeds.
 */

snmp_sess_init(&session1);
session1.peername = ip;
session1.version = SNMP_VERSION_3;

/* set the SNMPv3 user name */
session1.securityName = strdup(user);
session1.securityNameLen = strlen(session1.securityName);

// set the authentication method to SHA1 
session1.securityLevel = SNMP_SEC_LEVEL_AUTHNOPRIV;

session1.securityAuthProto = usmHMACSHA1AuthProtocol;
session1.securityAuthProtoLen = USM_AUTH_PROTO_SHA_LEN;
session1.securityAuthKeyLen = USM_AUTH_KU_LEN;

if (generate_Ku(session1.securityAuthProto,
        session1.securityAuthProtoLen,
        (u_char *) authpw.c_str(), strlen(authpw.c_str()),
        session1.securityAuthKey,
        &session1.securityAuthKeyLen) != SNMPERR_SUCCESS) {
    //if code reaches here, the creation of the security key was not successful
}

cout << "SecurityAuthProto - session1: " << session1.securityAuthProto[9] << " / SecurityAuthKey - session1: " << session1.securityAuthKey << endl;

ss1 = snmp_open(&session1); /* establish the session */

if (!ss1) {
    cout << "Couldn't open session1 correctly";
    exit(2);
}

cout << "SecurityAuthProto - ss1: " << ss1->securityAuthProto[9] << " / SecurityAuthKey - ss1: " << ss1->securityAuthKey << endl;

//send message
pdu1 = snmp_pdu_create(SNMP_MSG_GET);
read_objid(".1.3.6.1.2.1.1.1.0", anOID, &anOID_len);
snmp_add_null_var(pdu1, anOID, anOID_len);
status1 = snmp_synch_response(ss1, pdu1, &response1);

/*
 * Process the response.
 */
if (status1 == STAT_SUCCESS && response1->errstat == SNMP_ERR_NOERROR) {
    cout << "SNMP-read success" << endl;
} else {
    cout << "SNMP-read fail" << endl;
}

if (response1)
    snmp_free_pdu(response1);
snmp_close(ss1);

return 0;