/**
* Checks and decodes incoming SNMP message header, logs header errors.
*
* @param p points to pbuf chain of SNMP message (UDP payload)
* @param ofs points to first octet of SNMP message
* @param pdu_len the length of the UDP payload
* @param ofs_ret returns the ofset of the variable bindings
* @param m_stat points to the current message request state return
* @return
* - ERR_OK SNMP header is sane and accepted
* - ERR_ARG SNMP header is either malformed or rejected
*/
static err_t
snmp_pdu_header_check(struct pbuf *p, u16_t ofs, u16_t pdu_len, u16_t *ofs_ret, struct snmp_msg_pstat *m_stat)
{
err_t derr;
u16_t len, ofs_base;
u8_t len_octets;
u8_t type;
s32_t version;
ofs_base = ofs;
snmp_asn1_dec_type(p, ofs, &type);
derr = snmp_asn1_dec_length(p, ofs+1, &len_octets, &len);
if ((derr != ERR_OK) ||
(pdu_len != (1 + len_octets + len)) ||
(type != (SNMP_ASN1_UNIV | SNMP_ASN1_CONSTR | SNMP_ASN1_SEQ))) {
snmp_inc_snmpinasnparseerrs();
return ERR_ARG;
}
ofs += (1 + len_octets);
snmp_asn1_dec_type(p, ofs, &type);
derr = snmp_asn1_dec_length(p, ofs+1, &len_octets, &len);
if ((derr != ERR_OK) || (type != (SNMP_ASN1_UNIV | SNMP_ASN1_PRIMIT | SNMP_ASN1_INTEG))) {
/* can't decode or no integer (version) */
snmp_inc_snmpinasnparseerrs();
return ERR_ARG;
}
derr = snmp_asn1_dec_s32t(p, ofs + 1 + len_octets, len, &version);
if (derr != ERR_OK) {
/* can't decode */
snmp_inc_snmpinasnparseerrs();
return ERR_ARG;
}
if (version != 0) {
/* not version 1 */
snmp_inc_snmpinbadversions();
return ERR_ARG;
}
ofs += (1 + len_octets + len);
snmp_asn1_dec_type(p, ofs, &type);
derr = snmp_asn1_dec_length(p, ofs+1, &len_octets, &len);
if ((derr != ERR_OK) || (type != (SNMP_ASN1_UNIV | SNMP_ASN1_PRIMIT | SNMP_ASN1_OC_STR))) {
/* can't decode or no octet string (community) */
snmp_inc_snmpinasnparseerrs();
return ERR_ARG;
}
derr = snmp_asn1_dec_raw(p, ofs + 1 + len_octets, len, SNMP_COMMUNITY_STR_LEN, m_stat->community);
if (derr != ERR_OK) {
snmp_inc_snmpinasnparseerrs();
return ERR_ARG;
}
/* add zero terminator */
len = ((len < (SNMP_COMMUNITY_STR_LEN))?(len):(SNMP_COMMUNITY_STR_LEN));
m_stat->community[len] = 0;
m_stat->com_strlen = (u8_t)len;
if (strncmp(snmp_publiccommunity, (const char*)m_stat->community, SNMP_COMMUNITY_STR_LEN) != 0) {
/** @todo: move this if we need to check more names */
snmp_inc_snmpinbadcommunitynames();
snmp_authfail_trap();
return ERR_ARG;
}
ofs += (1 + len_octets + len);
snmp_asn1_dec_type(p, ofs, &type);
derr = snmp_asn1_dec_length(p, ofs+1, &len_octets, &len);
if (derr != ERR_OK) {
snmp_inc_snmpinasnparseerrs();
return ERR_ARG;
}
switch(type) {
case (SNMP_ASN1_CONTXT | SNMP_ASN1_CONSTR | SNMP_ASN1_PDU_GET_REQ):
/* GetRequest PDU */
snmp_inc_snmpingetrequests();
derr = ERR_OK;
break;
case (SNMP_ASN1_CONTXT | SNMP_ASN1_CONSTR | SNMP_ASN1_PDU_GET_NEXT_REQ):
/* GetNextRequest PDU */
snmp_inc_snmpingetnexts();
derr = ERR_OK;
break;
case (SNMP_ASN1_CONTXT | SNMP_ASN1_CONSTR | SNMP_ASN1_PDU_GET_RESP):
/* GetResponse PDU */
snmp_inc_snmpingetresponses();
derr = ERR_ARG;
break;
case (SNMP_ASN1_CONTXT | SNMP_ASN1_CONSTR | SNMP_ASN1_PDU_SET_REQ):
/* SetRequest PDU */
snmp_inc_snmpinsetrequests();
derr = ERR_OK;
break;
case (SNMP_ASN1_CONTXT | SNMP_ASN1_CONSTR | SNMP_ASN1_PDU_TRAP):
/* Trap PDU */
snmp_inc_snmpintraps();
derr = ERR_ARG;
break;
default:
snmp_inc_snmpinasnparseerrs();
derr = ERR_ARG;
break;
}
if (derr != ERR_OK) {
/* unsupported input PDU for this agent (no parse error) */
return ERR_ARG;
}
m_stat->rt = type & 0x1F;
ofs += (1 + len_octets);
if (len != (pdu_len - (ofs - ofs_base))) {
/* decoded PDU length does not equal actual payload length */
snmp_inc_snmpinasnparseerrs();
return ERR_ARG;
}
snmp_asn1_dec_type(p, ofs, &type);
derr = snmp_asn1_dec_length(p, ofs+1, &len_octets, &len);
if ((derr != ERR_OK) || (type != (SNMP_ASN1_UNIV | SNMP_ASN1_PRIMIT | SNMP_ASN1_INTEG))) {
/* can't decode or no integer (request ID) */
snmp_inc_snmpinasnparseerrs();
return ERR_ARG;
}
derr = snmp_asn1_dec_s32t(p, ofs + 1 + len_octets, len, &m_stat->rid);
if (derr != ERR_OK) {
/* can't decode */
snmp_inc_snmpinasnparseerrs();
return ERR_ARG;
}
ofs += (1 + len_octets + len);
snmp_asn1_dec_type(p, ofs, &type);
derr = snmp_asn1_dec_length(p, ofs+1, &len_octets, &len);
if ((derr != ERR_OK) || (type != (SNMP_ASN1_UNIV | SNMP_ASN1_PRIMIT | SNMP_ASN1_INTEG))) {
/* can't decode or no integer (error-status) */
snmp_inc_snmpinasnparseerrs();
return ERR_ARG;
}
/* must be noError (0) for incoming requests.
log errors for mib-2 completeness and for debug purposes */
derr = snmp_asn1_dec_s32t(p, ofs + 1 + len_octets, len, &m_stat->error_status);
if (derr != ERR_OK) {
/* can't decode */
snmp_inc_snmpinasnparseerrs();
return ERR_ARG;
}
switch (m_stat->error_status) {
case SNMP_ES_TOOBIG:
snmp_inc_snmpintoobigs();
break;
case SNMP_ES_NOSUCHNAME:
snmp_inc_snmpinnosuchnames();
break;
case SNMP_ES_BADVALUE:
snmp_inc_snmpinbadvalues();
break;
case SNMP_ES_READONLY:
snmp_inc_snmpinreadonlys();
break;
case SNMP_ES_GENERROR:
snmp_inc_snmpingenerrs();
break;
}
ofs += (1 + len_octets + len);
snmp_asn1_dec_type(p, ofs, &type);
derr = snmp_asn1_dec_length(p, ofs+1, &len_octets, &len);
if ((derr != ERR_OK) || (type != (SNMP_ASN1_UNIV | SNMP_ASN1_PRIMIT | SNMP_ASN1_INTEG))) {
/* can't decode or no integer (error-index) */
snmp_inc_snmpinasnparseerrs();
return ERR_ARG;
}
/* must be 0 for incoming requests.
decode anyway to catch bad integers (and dirty tricks) */
derr = snmp_asn1_dec_s32t(p, ofs + 1 + len_octets, len, &m_stat->error_index);
if (derr != ERR_OK) {
/* can't decode */
snmp_inc_snmpinasnparseerrs();
return ERR_ARG;
}
ofs += (1 + len_octets + len);
*ofs_ret = ofs;
return ERR_OK;
}
/**
* Checks and decodes incoming SNMP message header, logs header errors.
*
* @param p points to pbuf chain of SNMP message (UDP payload)
* @param ofs points to first octet of SNMP message
* @param pdu_len the length of the UDP payload
* @param ofs_ret returns the ofset of the variable bindings
* @param m_stat points to the current message request state return
* @return
* - ERR_OK SNMP header is sane and accepted
* - ERR_ARG SNMP header is either malformed or rejected
*/
static err_t
snmp_pdu_header_check(struct pbuf *p, u16_t ofs, u16_t pdu_len, u16_t *ofs_ret, struct snmp_msg_pstat *m_stat)
{
err_t derr;
u16_t len, ofs_base;
u8_t len_octets;
u8_t type;
s32_t version;
ofs_base = ofs;
snmp_asn1_dec_type(p, ofs, &type);
derr = snmp_asn1_dec_length(p, ofs+1, &len_octets, &len);
if ((derr != ERR_OK) ||
(pdu_len != (1 + len_octets + len)) ||
(type != (SNMP_ASN1_UNIV | SNMP_ASN1_CONSTR | SNMP_ASN1_SEQ)))
{
snmp_inc_snmpinasnparseerrs();
return ERR_ARG;
}
ofs += (1 + len_octets);
snmp_asn1_dec_type(p, ofs, &type);
derr = snmp_asn1_dec_length(p, ofs+1, &len_octets, &len);
if ((derr != ERR_OK) || (type != (SNMP_ASN1_UNIV | SNMP_ASN1_PRIMIT | SNMP_ASN1_INTEG)))
{
/* can't decode or no integer (version) */
snmp_inc_snmpinasnparseerrs();
return ERR_ARG;
}
derr = snmp_asn1_dec_s32t(p, ofs + 1 + len_octets, len, &version);
if (derr != ERR_OK)
{
/* can't decode */
snmp_inc_snmpinasnparseerrs();
return ERR_ARG;
}
if (version != 0)
{
/* not version 1 */
snmp_inc_snmpinbadversions();
return ERR_ARG;
}
ofs += (1 + len_octets + len);
snmp_asn1_dec_type(p, ofs, &type);
derr = snmp_asn1_dec_length(p, ofs+1, &len_octets, &len);
if ((derr != ERR_OK) || (type != (SNMP_ASN1_UNIV | SNMP_ASN1_PRIMIT | SNMP_ASN1_OC_STR)))
{
/* can't decode or no octet string (community) */
snmp_inc_snmpinasnparseerrs();
return ERR_ARG;
}
derr = snmp_asn1_dec_raw(p, ofs + 1 + len_octets, len, SNMP_COMMUNITY_STR_LEN, m_stat->community);
if (derr != ERR_OK)
{
snmp_inc_snmpinasnparseerrs();
return ERR_ARG;
}
/* add zero terminator */
len = ((len < (SNMP_COMMUNITY_STR_LEN))?(len):(SNMP_COMMUNITY_STR_LEN));
m_stat->community[len] = 0;
m_stat->com_strlen = (u8_t)len;
ofs += (1 + len_octets + len);
snmp_asn1_dec_type(p, ofs, &type);
#if SNMP_COMMUNITY_EXT
if (strncmp(snmp_community_write, (const char*)m_stat->community, SNMP_COMMUNITY_STR_LEN) != 0)
{
/* community does not match the write-access community, check if this is a SetRequest */
if (type == (SNMP_ASN1_CONTXT | SNMP_ASN1_CONSTR | SNMP_ASN1_PDU_SET_REQ))
{
/* wrong community for SetRequest PDU */
snmp_inc_snmpinbadcommunitynames();
snmp_authfail_trap();
return ERR_ARG;
}
#else /* SNMP_COMMUNITY_EXT */
{
#endif /* SNMP_COMMUNITY_EXT */
if (strncmp(snmp_community, (const char*)m_stat->community, SNMP_COMMUNITY_STR_LEN) != 0)
{
snmp_inc_snmpinbadcommunitynames();
snmp_authfail_trap();
return ERR_ARG;
}
}
derr = snmp_asn1_dec_length(p, ofs+1, &len_octets, &len);
if (derr != ERR_OK)
{
snmp_inc_snmpinasnparseerrs();
return ERR_ARG;
}
switch(type)
{
case (SNMP_ASN1_CONTXT | SNMP_ASN1_CONSTR | SNMP_ASN1_PDU_GET_REQ):
/* GetRequest PDU */
snmp_inc_snmpingetrequests();
derr = ERR_OK;
break;
case (SNMP_ASN1_CONTXT | SNMP_ASN1_CONSTR | SNMP_ASN1_PDU_GET_NEXT_REQ):
/* GetNextRequest PDU */
snmp_inc_snmpingetnexts();
derr = ERR_OK;
break;
case (SNMP_ASN1_CONTXT | SNMP_ASN1_CONSTR | SNMP_ASN1_PDU_GET_RESP):
/* GetResponse PDU */
snmp_inc_snmpingetresponses();
derr = ERR_ARG;
break;
case (SNMP_ASN1_CONTXT | SNMP_ASN1_CONSTR | SNMP_ASN1_PDU_SET_REQ):
/* SetRequest PDU */
snmp_inc_snmpinsetrequests();
derr = ERR_OK;
break;
case (SNMP_ASN1_CONTXT | SNMP_ASN1_CONSTR | SNMP_ASN1_PDU_TRAP):
/* Trap PDU */
snmp_inc_snmpintraps();
derr = ERR_ARG;
break;
default:
snmp_inc_snmpinasnparseerrs();
derr = ERR_ARG;
break;
}
if (derr != ERR_OK)
{
/* unsupported input PDU for this agent (no parse error) */
return ERR_ARG;
}
m_stat->rt = type & 0x1F;
ofs += (1 + len_octets);
if (len != (pdu_len - (ofs - ofs_base)))
{
/* decoded PDU length does not equal actual payload length */
snmp_inc_snmpinasnparseerrs();
return ERR_ARG;
}
snmp_asn1_dec_type(p, ofs, &type);
derr = snmp_asn1_dec_length(p, ofs+1, &len_octets, &len);
if ((derr != ERR_OK) || (type != (SNMP_ASN1_UNIV | SNMP_ASN1_PRIMIT | SNMP_ASN1_INTEG)))
{
/* can't decode or no integer (request ID) */
snmp_inc_snmpinasnparseerrs();
return ERR_ARG;
}
derr = snmp_asn1_dec_s32t(p, ofs + 1 + len_octets, len, &m_stat->rid);
if (derr != ERR_OK)
{
/* can't decode */
snmp_inc_snmpinasnparseerrs();
return ERR_ARG;
}
ofs += (1 + len_octets + len);
snmp_asn1_dec_type(p, ofs, &type);
derr = snmp_asn1_dec_length(p, ofs+1, &len_octets, &len);
if ((derr != ERR_OK) || (type != (SNMP_ASN1_UNIV | SNMP_ASN1_PRIMIT | SNMP_ASN1_INTEG)))
{
/* can't decode or no integer (error-status) */
snmp_inc_snmpinasnparseerrs();
return ERR_ARG;
}
/* must be noError (0) for incoming requests.
log errors for mib-2 completeness and for debug purposes */
derr = snmp_asn1_dec_s32t(p, ofs + 1 + len_octets, len, &m_stat->error_status);
if (derr != ERR_OK)
{
/* can't decode */
snmp_inc_snmpinasnparseerrs();
return ERR_ARG;
}
switch (m_stat->error_status)
{
case SNMP_ES_NOERROR:
/* nothing to do */
break;
case SNMP_ES_TOOBIG:
snmp_inc_snmpintoobigs();
break;
case SNMP_ES_NOSUCHNAME:
snmp_inc_snmpinnosuchnames();
break;
case SNMP_ES_BADVALUE:
snmp_inc_snmpinbadvalues();
break;
case SNMP_ES_READONLY:
snmp_inc_snmpinreadonlys();
break;
case SNMP_ES_GENERROR:
snmp_inc_snmpingenerrs();
break;
default:
LWIP_DEBUGF(SNMP_MSG_DEBUG, ("snmp_pdu_header_check(): unknown error_status: %d\n", (int)m_stat->error_status));
break;
}
ofs += (1 + len_octets + len);
snmp_asn1_dec_type(p, ofs, &type);
derr = snmp_asn1_dec_length(p, ofs+1, &len_octets, &len);
if ((derr != ERR_OK) || (type != (SNMP_ASN1_UNIV | SNMP_ASN1_PRIMIT | SNMP_ASN1_INTEG)))
{
/* can't decode or no integer (error-index) */
snmp_inc_snmpinasnparseerrs();
return ERR_ARG;
}
/* must be 0 for incoming requests.
decode anyway to catch bad integers (and dirty tricks) */
derr = snmp_asn1_dec_s32t(p, ofs + 1 + len_octets, len, &m_stat->error_index);
if (derr != ERR_OK)
{
/* can't decode */
snmp_inc_snmpinasnparseerrs();
return ERR_ARG;
}
ofs += (1 + len_octets + len);
*ofs_ret = ofs;
return ERR_OK;
}
static err_t
snmp_pdu_dec_varbindlist(struct pbuf *p, u16_t ofs, u16_t *ofs_ret, struct snmp_msg_pstat *m_stat)
{
err_t derr;
u16_t len, vb_len;
u8_t len_octets;
u8_t type;
/* variable binding list */
snmp_asn1_dec_type(p, ofs, &type);
derr = snmp_asn1_dec_length(p, ofs+1, &len_octets, &vb_len);
if ((derr != ERR_OK) ||
(type != (SNMP_ASN1_UNIV | SNMP_ASN1_CONSTR | SNMP_ASN1_SEQ)))
{
snmp_inc_snmpinasnparseerrs();
return ERR_ARG;
}
ofs += (1 + len_octets);
/* start with empty list */
m_stat->invb.count = 0;
m_stat->invb.head = NULL;
m_stat->invb.tail = NULL;
while (vb_len > 0)
{
struct snmp_obj_id oid, oid_value;
struct snmp_varbind *vb;
snmp_asn1_dec_type(p, ofs, &type);
derr = snmp_asn1_dec_length(p, ofs+1, &len_octets, &len);
if ((derr != ERR_OK) ||
(type != (SNMP_ASN1_UNIV | SNMP_ASN1_CONSTR | SNMP_ASN1_SEQ)) ||
(len == 0) || (len > vb_len))
{
snmp_inc_snmpinasnparseerrs();
/* free varbinds (if available) */
snmp_varbind_list_free(&m_stat->invb);
return ERR_ARG;
}
ofs += (1 + len_octets);
vb_len -= (1 + len_octets);
snmp_asn1_dec_type(p, ofs, &type);
derr = snmp_asn1_dec_length(p, ofs+1, &len_octets, &len);
if ((derr != ERR_OK) || (type != (SNMP_ASN1_UNIV | SNMP_ASN1_PRIMIT | SNMP_ASN1_OBJ_ID)))
{
/* can't decode object name length */
snmp_inc_snmpinasnparseerrs();
/* free varbinds (if available) */
snmp_varbind_list_free(&m_stat->invb);
return ERR_ARG;
}
derr = snmp_asn1_dec_oid(p, ofs + 1 + len_octets, len, &oid);
if (derr != ERR_OK)
{
/* can't decode object name */
snmp_inc_snmpinasnparseerrs();
/* free varbinds (if available) */
snmp_varbind_list_free(&m_stat->invb);
return ERR_ARG;
}
ofs += (1 + len_octets + len);
vb_len -= (1 + len_octets + len);
snmp_asn1_dec_type(p, ofs, &type);
derr = snmp_asn1_dec_length(p, ofs+1, &len_octets, &len);
if (derr != ERR_OK)
{
/* can't decode object value length */
snmp_inc_snmpinasnparseerrs();
/* free varbinds (if available) */
snmp_varbind_list_free(&m_stat->invb);
return ERR_ARG;
}
switch (type)
{
case (SNMP_ASN1_UNIV | SNMP_ASN1_PRIMIT | SNMP_ASN1_INTEG):
vb = snmp_varbind_alloc(&oid, type, sizeof(s32_t));
if (vb != NULL)
{
s32_t *vptr = (s32_t*)vb->value;
derr = snmp_asn1_dec_s32t(p, ofs + 1 + len_octets, len, vptr);
snmp_varbind_tail_add(&m_stat->invb, vb);
}
else
{
derr = ERR_ARG;
}
break;
case (SNMP_ASN1_APPLIC | SNMP_ASN1_PRIMIT | SNMP_ASN1_COUNTER):
case (SNMP_ASN1_APPLIC | SNMP_ASN1_PRIMIT | SNMP_ASN1_GAUGE):
case (SNMP_ASN1_APPLIC | SNMP_ASN1_PRIMIT | SNMP_ASN1_TIMETICKS):
vb = snmp_varbind_alloc(&oid, type, sizeof(u32_t));
if (vb != NULL)
{
u32_t *vptr = (u32_t*)vb->value;
derr = snmp_asn1_dec_u32t(p, ofs + 1 + len_octets, len, vptr);
snmp_varbind_tail_add(&m_stat->invb, vb);
}
else
{
derr = ERR_ARG;
}
break;
case (SNMP_ASN1_UNIV | SNMP_ASN1_PRIMIT | SNMP_ASN1_OC_STR):
case (SNMP_ASN1_APPLIC | SNMP_ASN1_PRIMIT | SNMP_ASN1_OPAQUE):
LWIP_ASSERT("invalid length", len <= 0xff);
vb = snmp_varbind_alloc(&oid, type, (u8_t)len);
if (vb != NULL)
{
derr = snmp_asn1_dec_raw(p, ofs + 1 + len_octets, len, vb->value_len, (u8_t*)vb->value);
snmp_varbind_tail_add(&m_stat->invb, vb);
}
else
{
derr = ERR_ARG;
}
break;
case (SNMP_ASN1_UNIV | SNMP_ASN1_PRIMIT | SNMP_ASN1_NUL):
vb = snmp_varbind_alloc(&oid, type, 0);
if (vb != NULL)
{
snmp_varbind_tail_add(&m_stat->invb, vb);
derr = ERR_OK;
}
else
{
derr = ERR_ARG;
}
break;
case (SNMP_ASN1_UNIV | SNMP_ASN1_PRIMIT | SNMP_ASN1_OBJ_ID):
derr = snmp_asn1_dec_oid(p, ofs + 1 + len_octets, len, &oid_value);
if (derr == ERR_OK)
{
vb = snmp_varbind_alloc(&oid, type, oid_value.len * sizeof(s32_t));
if (vb != NULL)
{
u8_t i = oid_value.len;
s32_t *vptr = (s32_t*)vb->value;
while(i > 0)
{
i--;
vptr[i] = oid_value.id[i];
}
snmp_varbind_tail_add(&m_stat->invb, vb);
derr = ERR_OK;
}
else
{
derr = ERR_ARG;
}
}
break;
case (SNMP_ASN1_APPLIC | SNMP_ASN1_PRIMIT | SNMP_ASN1_IPADDR):
if (len == 4)
{
/* must be exactly 4 octets! */
vb = snmp_varbind_alloc(&oid, type, 4);
if (vb != NULL)
{
derr = snmp_asn1_dec_raw(p, ofs + 1 + len_octets, len, vb->value_len, (u8_t*)vb->value);
snmp_varbind_tail_add(&m_stat->invb, vb);
}
else
{
derr = ERR_ARG;
}
}
else
{
derr = ERR_ARG;
}
break;
default:
derr = ERR_ARG;
break;
}
if (derr != ERR_OK)
{
snmp_inc_snmpinasnparseerrs();
/* free varbinds (if available) */
snmp_varbind_list_free(&m_stat->invb);
return ERR_ARG;
}
ofs += (1 + len_octets + len);
vb_len -= (1 + len_octets + len);
}
if (m_stat->rt == SNMP_ASN1_PDU_SET_REQ)
{
snmp_add_snmpintotalsetvars(m_stat->invb.count);
}
else
{
snmp_add_snmpintotalreqvars(m_stat->invb.count);
}
*ofs_ret = ofs;
return ERR_OK;
}