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lwip/src/core/snmp/asn1_enc.c

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/**
* @file
* Abstract Syntax Notation One (ISO 8824, 8825) encoding
*
* @todo not optimised (yet), favor correctness over speed, favor speed over size
*/
/*
* Copyright (c) 2006 Axon Digital Design B.V., The Netherlands.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without modification,
* are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
* 3. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
* SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
* OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
* IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
* OF SUCH DAMAGE.
*
* Author: Christiaan Simons <christiaan.simons@axon.tv>
*/
#include "lwip/opt.h"
#if LWIP_SNMP /* don't build if not configured for use in lwipopts.h */
#include "lwip/snmp_asn1.h"
/**
* Returns octet count for length.
*
* @param length
* @param octets_needed points to the return value
*/
void
snmp_asn1_enc_length_cnt(u16_t length, u8_t *octets_needed)
{
if (length < 0x80U)
{
*octets_needed = 1;
}
else if (length < 0x100U)
{
*octets_needed = 2;
}
else
{
*octets_needed = 3;
}
}
/**
* Returns octet count for an u32_t.
*
* @param value
* @param octets_needed points to the return value
*
* @note ASN coded integers are _always_ signed. E.g. +0xFFFF is coded
* as 0x00,0xFF,0xFF. Note the leading sign octet. A positive value
* of 0xFFFFFFFF is preceded with 0x00 and the length is 5 octets!!
*/
void
snmp_asn1_enc_u32t_cnt(u32_t value, u16_t *octets_needed)
{
if (value < 0x80UL)
{
*octets_needed = 1;
}
else if (value < 0x8000UL)
{
*octets_needed = 2;
}
else if (value < 0x800000UL)
{
*octets_needed = 3;
}
else if (value < 0x80000000UL)
{
*octets_needed = 4;
}
else
{
*octets_needed = 5;
}
}
/**
* Returns octet count for an s32_t.
*
* @param value
* @param octets_needed points to the return value
*
* @note ASN coded integers are _always_ signed.
*/
void
snmp_asn1_enc_s32t_cnt(s32_t value, u16_t *octets_needed)
{
if (value < 0)
{
value = ~value;
}
if (value < 0x80L)
{
*octets_needed = 1;
}
else if (value < 0x8000L)
{
*octets_needed = 2;
}
else if (value < 0x800000L)
{
*octets_needed = 3;
}
else
{
*octets_needed = 4;
}
}
/**
* Returns octet count for an object identifier.
*
* @param ident_len object identifier array length
* @param ident points to object identifier array
* @param octets_needed points to the return value
*/
void
snmp_asn1_enc_oid_cnt(u8_t ident_len, s32_t *ident, u16_t *octets_needed)
{
s32_t sub_id;
u8_t cnt;
cnt = 0;
if (ident_len > 1)
{
/* compressed prefix in one octet */
cnt++;
ident_len -= 2;
ident += 2;
}
while(ident_len > 0)
{
ident_len--;
sub_id = *ident;
sub_id >>= 7;
cnt++;
while(sub_id > 0)
{
sub_id >>= 7;
cnt++;
}
ident++;
}
*octets_needed = cnt;
}
/**
* Encodes ASN type field into a pbuf chained ASN1 msg.
*
* @param p points to output pbuf to encode value into
* @param ofs points to the offset within the pbuf chain
* @param type input ASN1 type
* @return ERR_OK if successfull, ERR_ARG if we can't (or won't) encode
*/
err_t
snmp_asn1_enc_type(struct pbuf *p, u16_t ofs, u8_t type)
{
u16_t plen, base;
u8_t *msg_ptr;
plen = 0;
while (p != NULL)
{
base = plen;
plen += p->len;
if (ofs < plen)
{
msg_ptr = p->payload;
msg_ptr += ofs - base;
*msg_ptr = type;
return ERR_OK;
}
p = p->next;
}
/* p == NULL, ofs >= plen */
return ERR_ARG;
}
/**
* Encodes host order length field into a pbuf chained ASN1 msg.
*
* @param p points to output pbuf to encode length into
* @param ofs points to the offset within the pbuf chain
* @param length is the host order length to be encoded
* @return ERR_OK if successfull, ERR_ARG if we can't (or won't) encode
*/
err_t
snmp_asn1_enc_length(struct pbuf *p, u16_t ofs, u16_t length)
{
u16_t plen, base;
u8_t *msg_ptr;
plen = 0;
while (p != NULL)
{
base = plen;
plen += p->len;
if (ofs < plen)
{
msg_ptr = p->payload;
msg_ptr += ofs - base;
if (length < 0x80)
{
*msg_ptr = length;
return ERR_OK;
}
else if (length < 0x100)
{
*msg_ptr = 0x81;
ofs += 1;
if (ofs >= plen)
{
/* next octet in next pbuf */
p = p->next;
if (p == NULL) { return ERR_ARG; }
msg_ptr = p->payload;
}
else
{
/* next octet in same pbuf */
msg_ptr++;
}
*msg_ptr = length;
return ERR_OK;
}
else
{
u8_t i;
/* length >= 0x100 && length <= 0xFFFF */
*msg_ptr = 0x82;
i = 2;
while (i > 0)
{
i--;
ofs += 1;
if (ofs >= plen)
{
/* next octet in next pbuf */
p = p->next;
if (p == NULL) { return ERR_ARG; }
msg_ptr = p->payload;
plen += p->len;
}
else
{
/* next octet in same pbuf */
msg_ptr++;
}
if (i == 0)
{
/* least significant length octet */
*msg_ptr = length;
}
else
{
/* most significant length octet */
*msg_ptr = length >> 8;
}
}
return ERR_OK;
}
}
p = p->next;
}
/* p == NULL, ofs >= plen */
return ERR_ARG;
}
/**
* Encodes u32_t (counter, gauge, timeticks) into a pbuf chained ASN1 msg.
*
* @param p points to output pbuf to encode value into
* @param ofs points to the offset within the pbuf chain
* @param octets_needed encoding length (from snmp_asn1_enc_u32t_cnt())
* @param value is the host order u32_t value to be encoded
* @return ERR_OK if successfull, ERR_ARG if we can't (or won't) encode
*
* @see snmp_asn1_enc_u32t_cnt()
*/
err_t
snmp_asn1_enc_u32t(struct pbuf *p, u16_t ofs, u8_t octets_needed, u32_t value)
{
u16_t plen, base;
u8_t *msg_ptr;
plen = 0;
while (p != NULL)
{
base = plen;
plen += p->len;
if (ofs < plen)
{
msg_ptr = p->payload;
msg_ptr += ofs - base;
if (octets_needed == 5)
{
/* not enough bits in 'value' add leading 0x00 */
octets_needed--;
*msg_ptr = 0x00;
ofs += 1;
if (ofs >= plen)
{
/* next octet in next pbuf */
p = p->next;
if (p == NULL) { return ERR_ARG; }
msg_ptr = p->payload;
plen += p->len;
}
else
{
/* next octet in same pbuf */
msg_ptr++;
}
}
while (octets_needed > 1)
{
octets_needed--;
*msg_ptr = value >> (octets_needed << 3);
ofs += 1;
if (ofs >= plen)
{
/* next octet in next pbuf */
p = p->next;
if (p == NULL) { return ERR_ARG; }
msg_ptr = p->payload;
plen += p->len;
}
else
{
/* next octet in same pbuf */
msg_ptr++;
}
}
/* (only) one least significant octet */
*msg_ptr = value;
return ERR_OK;
}
p = p->next;
}
/* p == NULL, ofs >= plen */
return ERR_ARG;
}
/**
* Encodes s32_t integer into a pbuf chained ASN1 msg.
*
* @param p points to output pbuf to encode value into
* @param ofs points to the offset within the pbuf chain
* @param octets_needed encoding length (from snmp_asn1_enc_s32t_cnt())
* @param value is the host order s32_t value to be encoded
* @return ERR_OK if successfull, ERR_ARG if we can't (or won't) encode
*
* @see snmp_asn1_enc_s32t_cnt()
*/
err_t
snmp_asn1_enc_s32t(struct pbuf *p, u16_t ofs, u8_t octets_needed, s32_t value)
{
u16_t plen, base;
u8_t *msg_ptr;
plen = 0;
while (p != NULL)
{
base = plen;
plen += p->len;
if (ofs < plen)
{
msg_ptr = p->payload;
msg_ptr += ofs - base;
while (octets_needed > 1)
{
octets_needed--;
*msg_ptr = value >> (octets_needed << 3);
ofs += 1;
if (ofs >= plen)
{
/* next octet in next pbuf */
p = p->next;
if (p == NULL) { return ERR_ARG; }
msg_ptr = p->payload;
plen += p->len;
}
else
{
/* next octet in same pbuf */
msg_ptr++;
}
}
/* (only) one least significant octet */
*msg_ptr = value;
return ERR_OK;
}
p = p->next;
}
/* p == NULL, ofs >= plen */
return ERR_ARG;
}
/**
* Encodes object identifier into a pbuf chained ASN1 msg.
*
* @param p points to output pbuf to encode oid into
* @param ofs points to the offset within the pbuf chain
* @param ident_len object identifier array length
* @param ident points to object identifier array
* @return ERR_OK if successfull, ERR_ARG if we can't (or won't) encode
*/
err_t
snmp_asn1_enc_oid(struct pbuf *p, u16_t ofs, u8_t ident_len, s32_t *ident)
{
u16_t plen, base;
u8_t *msg_ptr;
plen = 0;
while (p != NULL)
{
base = plen;
plen += p->len;
if (ofs < plen)
{
msg_ptr = p->payload;
msg_ptr += ofs - base;
if (ident_len > 1)
{
if ((ident[0] == 1) && (ident[1] == 3))
{
/* compressed (most common) prefix .iso.org */
*msg_ptr = 0x2b;
}
else
{
/* calculate prefix */
*msg_ptr = (ident[0] * 40) + ident[1];
}
ofs += 1;
if (ofs >= plen)
{
/* next octet in next pbuf */
p = p->next;
if (p == NULL) { return ERR_ARG; }
msg_ptr = p->payload;
plen += p->len;
}
else
{
/* next octet in same pbuf */
msg_ptr++;
}
ident_len -= 2;
ident += 2;
}
else
{
/* @bug: allow empty varbinds for symmetry (we must decode them for getnext), allow partial compression?? */
/* ident_len <= 1, at least we need zeroDotZero (0.0) (ident_len == 2) */
return ERR_ARG;
}
while (ident_len > 0)
{
s32_t sub_id;
u8_t shift, tail;
ident_len--;
sub_id = *ident;
tail = 0;
shift = 28;
while(shift > 0)
{
u8_t code;
code = sub_id >> shift;
if ((code != 0) || (tail != 0))
{
tail = 1;
*msg_ptr = code | 0x80;
ofs += 1;
if (ofs >= plen)
{
/* next octet in next pbuf */
p = p->next;
if (p == NULL) { return ERR_ARG; }
msg_ptr = p->payload;
plen += p->len;
}
else
{
/* next octet in same pbuf */
msg_ptr++;
}
}
shift -= 7;
}
*msg_ptr = (u8_t)sub_id & 0x7F;
if (ident_len > 0)
{
ofs += 1;
if (ofs >= plen)
{
/* next octet in next pbuf */
p = p->next;
if (p == NULL) { return ERR_ARG; }
msg_ptr = p->payload;
plen += p->len;
}
else
{
/* next octet in same pbuf */
msg_ptr++;
}
}
/* proceed to next sub-identifier */
ident++;
}
return ERR_OK;
}
p = p->next;
}
/* p == NULL, ofs >= plen */
return ERR_ARG;
}
/**
* Encodes raw data (octet string, opaque) into a pbuf chained ASN1 msg.
*
* @param p points to output pbuf to encode raw data into
* @param ofs points to the offset within the pbuf chain
* @param raw_len raw data length
* @param raw points raw data
* @return ERR_OK if successfull, ERR_ARG if we can't (or won't) encode
*/
err_t
snmp_asn1_enc_raw(struct pbuf *p, u16_t ofs, u8_t raw_len, u8_t *raw)
{
u16_t plen, base;
u8_t *msg_ptr;
plen = 0;
while (p != NULL)
{
base = plen;
plen += p->len;
if (ofs < plen)
{
msg_ptr = p->payload;
msg_ptr += ofs - base;
while (raw_len > 1)
{
/* copy raw_len - 1 octets */
raw_len--;
*msg_ptr = *raw;
raw++;
ofs += 1;
if (ofs >= plen)
{
/* next octet in next pbuf */
p = p->next;
if (p == NULL) { return ERR_ARG; }
msg_ptr = p->payload;
plen += p->len;
}
else
{
/* next octet in same pbuf */
msg_ptr++;
}
}
if (raw_len > 0)
{
/* copy last or single octet */
*msg_ptr = *raw;
}
return ERR_OK;
}
p = p->next;
}
/* p == NULL, ofs >= plen */
return ERR_ARG;
}
#endif /* LWIP_SNMP */
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