void gseDecodePDU(unsigned char *buf) {
unsigned char tag = 0;
CTYPE_INT16U lengthFieldSize = 0;
CTYPE_INT16U lengthValue = 0;
CTYPE_INT16U offsetForSequence = 0;
CTYPE_INT16U offsetForNonSequence = 0;
unsigned char *gocbRef = NULL;
CTYPE_INT16U gocbRefLength = 0;
CTYPE_INT32U timeAllowedToLive = 0;
CTYPE_TIMESTAMP T = 0;
CTYPE_INT32U sqNum = 0;
CTYPE_INT32U stNum = 0;
while (1) {
tag = (unsigned char) buf[0]; // assumes only one byte is used
lengthFieldSize = getLengthFieldSize((unsigned char) buf[1]);
lengthValue = decodeLength((unsigned char *) &buf[1]);
offsetForSequence = 1 + lengthFieldSize;
offsetForNonSequence = 1 + lengthFieldSize + lengthValue;
switch (tag) {
case GSE_TAG_GOCBREF:
// save pointer to gocbRef name
gocbRef = &buf[offsetForSequence];
gocbRefLength = lengthValue;
buf = &buf[offsetForNonSequence];
break;
case GSE_TAG_TIME_ALLOWED_TO_LIVE:
ber_decode_integer(&buf[offsetForSequence], lengthValue, &timeAllowedToLive, SV_GET_LENGTH_INT32U);
buf = &buf[offsetForNonSequence];
break;
case ASN1_TAG_SEQUENCE:
buf = &buf[offsetForSequence];
break;
case GSE_TAG_DATSET:
buf = &buf[offsetForNonSequence];
break;
case GSE_TAG_T:
memcpy(&T, &buf[offsetForSequence], BER_GET_LENGTH_CTYPE_TIMESTAMP(&T));
buf = &buf[offsetForNonSequence];
break;
case GSE_TAG_STNUM:
ber_decode_integer(&buf[offsetForSequence], lengthValue, &stNum, SV_GET_LENGTH_INT32U);
buf = &buf[offsetForNonSequence];
break;
case GSE_TAG_SQNUM:
ber_decode_integer(&buf[offsetForSequence], lengthValue, &sqNum, SV_GET_LENGTH_INT32U);
buf = &buf[offsetForNonSequence];
break;
case GSE_TAG_ALLDATA:
gseDecodeDataset(&buf[offsetForSequence], lengthValue, gocbRef, gocbRefLength, timeAllowedToLive, T, stNum, sqNum);
return;
default:
buf = &buf[offsetForNonSequence];
break;
}
}
}
int BER_DECODE_CTYPE_ENUM(unsigned char *buf, CTYPE_ENUM *value) { // assuming enum is an int - allows any enum type to be used
CTYPE_INT16U offset = 0;
CTYPE_INT16U len = 0;
if (buf[offset++] == ASN1_TAG_UNSIGNED) {
len += decodeLength(&buf[offset]);
offset += getLengthFieldSize(buf[offset]);
#if GOOSE_FIXED_SIZE == 1
ber_decode_integer(&buf[offset], len, value, SV_GET_LENGTH_INT8);
#else
ber_decode_integer(&buf[offset], len, value, SV_GET_LENGTH_INT32U);
#endif
}
return offset + len;
}
int BER_DECODE_CTYPE_INT32U(unsigned char *buf, CTYPE_INT32U *value) {
CTYPE_INT16U offset = 0;
CTYPE_INT16U len = 0;
if (buf[offset++] == ASN1_TAG_UNSIGNED) {
len += decodeLength(&buf[offset]);
offset += getLengthFieldSize(buf[offset]);
ber_decode_integer(&buf[offset], len, value, SV_GET_LENGTH_INT32U);
}
return offset + len;
}
static s8t decode_USM_parameters(u8t* const input, const u16t input_len, u16t* pos, message_v3_t* request)
{
u8t type;
u16t length;
/* encoded as a string value */
TRY(ber_decode_type_length(input, input_len, pos, &type, &length));
if (type != BER_TYPE_OCTET_STRING) {
snmp_log("bad type, expected string: type %02X length %d\n", type, length);
return FAILURE;
}
/* sequence */
TRY(ber_decode_sequence_length(input, input_len, pos, &length));
/* msgAuthoritativeEngineID */
TRY(ber_decode_string((u8t*)input, input_len, pos, &request->msgAuthoritativeEngineID.ptr, &request->msgAuthoritativeEngineID.len));
/* msgAuthoritativeEngineBoots */
TRY(ber_decode_integer(input, input_len, pos, (s32t*)&request->msgAuthoritativeEngineBoots));
/* msgAuthoritativeEngineTime */
TRY(ber_decode_integer(input, input_len, pos, (s32t*)&request->msgAuthoritativeEngineTime));
/* msgUserName */
TRY(ber_decode_string((u8t*)input, input_len, pos, &request->msgUserName.ptr, &request->msgUserName.len));
/* msgAuthenticationParameters */
TRY(ber_decode_string((u8t*)input, input_len, pos, &request->msgAuthenticationParameters.ptr, &request->msgAuthenticationParameters.len));
/* msgPrivacyParameters */
TRY(ber_decode_string((u8t*)input, input_len, pos, &request->msgPrivacyParameters.ptr, &request->msgPrivacyParameters.len));
if (request->msgFlags & FLAG_PRIV) {
TRY(ber_decode_type_length((u8t*)input, input_len, pos, &type, &length));
if (type != BER_TYPE_OCTET_STRING || length != input_len - *pos) {
return FAILURE;
}
}
return 0;
}
s8t prepareDataElements_v3(u8t* const input, const u16t input_len, u16t* pos, message_v3_t* request)
{
u8t type;
u16t length;
s32t int_value;
/* msgGlobalData sequence */
TRY(ber_decode_sequence_length(input, input_len, pos, &length));
/* msgId */
TRY(ber_decode_integer(input, input_len, pos, &int_value));
request->msgId = int_value;
snmp_log("msgId: %d\n", request->msgId);
/* msgMaxSize */
TRY(ber_decode_integer(input, input_len, pos, &int_value));
snmp_log("msgMaxSize: %d\n", int_value);
/* msgFlags */
TRY(ber_decode_type_length(input, input_len, pos, &type, &length));
if (type != BER_TYPE_OCTET_STRING || length != 1) {
return FAILURE;
}
request->msgFlags = input[*pos];
*pos = *pos + 1;
snmp_log("msgFlags: %d\n", request->msgFlags);
if (!(request->msgFlags & FLAG_AUTH) && (request->msgFlags & FLAG_PRIV)) {
/* If the authFlag is not set and privFlag is set, then the message is discarded without further processing */
return FAILURE;
}
/* msgSecurityModel */
TRY(ber_decode_integer(input, input_len, pos, &int_value));
snmp_log("msgSecurityModel: %d\n", int_value);
/* treat Security Model */
s8t ret;
switch (int_value) {
case USM_SECURITY_MODEL:
/* Authentication & Privacy validations */
ret = processIncomingMsg_USM(input, input_len, pos, request);
if (ret == FAILURE) {
return FAILURE;
} else if (ret == ERR_USM) {
/* stop processing this message, a report will be sent */
return 0;
}
break;
default:
snmp_log("unsupported security model [%d]\n", request->msgSecurityModel);
return FAILURE;
}
/* ScopedPduData sequence */
TRY(ber_decode_sequence_length(input, input_len, pos, &length));
/* contextEngineID */
TRY(ber_decode_string((u8t*)input, input_len, pos, &request->contextEngineID.ptr, &request->contextEngineID.len));
/* contextName */
TRY(ber_decode_string((u8t*)input, input_len, pos, &request->contextName.ptr, &request->contextName.len));
/* decode PDU */
ber_decode_pdu(input, input_len, pos, &request->pdu);
return 0;
}
/*
* Handle an SNMP request
*/
s8t dispatch(u8t* const input, const u16t input_len, u8t* output, u16t* output_len, const u16t max_output_len)
{
snmpInPkts++;
snmp_log("---------------------------------\n");
/* too big incoming message */
if (input_len > MAX_BUF_SIZE) {
snmp_log("discard the message, its size [%d] is too big\n", input_len);
return FAILURE;
}
u16t pos = 0;
s32t tmp;
/* decode sequence & version */
if ((ber_decode_sequence(input, input_len, &pos)) != ERR_NO_ERROR ||
ber_decode_integer(input, input_len, &pos, &tmp) != ERR_NO_ERROR) {
snmpInASNParseErrs++;
return FAILURE;
}
/* create the right message_t data structure */
message_t* msg_ptr;
switch (tmp) {
#if ENABLE_SNMPv1
case SNMP_VERSION_1:
msg_ptr = malloc(sizeof(message_t));
memset(msg_ptr, 0, sizeof(message_t));
break;
#endif
#if ENABLE_SNMPv3
case SNMP_VERSION_3:
msg_ptr = malloc(sizeof(message_v3_t));
memset(msg_ptr, 0, sizeof(message_v3_t));
break;
#endif
default:
/* If the version is not supported, it discards the datagram and performs no further actions. */
snmpInBadVersions++;
snmp_log("unsupported SNMP version %d\n", tmp);
return ERR_UNSUPPORTED_VERSION;
}
msg_ptr->version = (u8t)tmp;
snmp_log("snmp version: %d\n", msg_ptr->version);
/* dispatch processing to the version-specific Message Processing Model */
switch (msg_ptr->version) {
#if ENABLE_SNMPv1
case SNMP_VERSION_1:
tmp = prepareDataElements_v1(input, input_len, &pos, (message_t*)msg_ptr);
break;
#endif
#if ENABLE_SNMPv3
case SNMP_VERSION_3:
tmp = prepareDataElements_v3(input, input_len, &pos, (message_v3_t*)msg_ptr);
break;
#endif
}
if (tmp != ERR_NO_ERROR) {
snmpInASNParseErrs++;
free_message(msg_ptr);
return FAILURE;
}
/* delegate request processing to the Command Responder */
handle(msg_ptr);
/* dispatch preparing the response to the version-specific Message Processing Model */
switch (msg_ptr->version) {
#if ENABLE_SNMPv1
case SNMP_VERSION_1:
tmp = prepareResponseMessage_v1((message_t*)msg_ptr, output, output_len, input, input_len, max_output_len);
break;
#endif
#if ENABLE_SNMPv3
case SNMP_VERSION_3:
tmp = prepareResponseMessage_v3((message_v3_t*)msg_ptr, output, output_len, input, input_len, max_output_len);
break;
#endif
}
free_message(msg_ptr);
if (tmp != ERR_NO_ERROR) {
return FAILURE;
}
return 0;
}
