[netwatch.git] / lwip / src / core / snmp / asn1_dec.c

/**
 * @file
 * Abstract Syntax Notation One (ISO 8824, 8825) decoding
 *
 * @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"

/**
 * Retrieves type field from incoming pbuf chain.
 *
 * @param p points to a pbuf holding an ASN1 coded type field
 * @param ofs points to the offset within the pbuf chain of the ASN1 coded type field
 * @param type return ASN1 type
 * @return ERR_OK if successfull, ERR_ARG if we can't (or won't) decode
 */
err_t
snmp_asn1_dec_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;
      *type = *msg_ptr;
      return ERR_OK;
    }
    p = p->next;
  }
  /* p == NULL, ofs >= plen */
  return ERR_ARG;
}

/**
 * Decodes length field from incoming pbuf chain into host length.
 *
 * @param p points to a pbuf holding an ASN1 coded length
 * @param ofs points to the offset within the pbuf chain of the ASN1 coded length
 * @param octets_used returns number of octets used by the length code
 * @param length return host order length, upto 64k
 * @return ERR_OK if successfull, ERR_ARG if we can't (or won't) decode
 */
err_t
snmp_asn1_dec_length(struct pbuf *p, u16_t ofs, u8_t *octets_used, 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 (*msg_ptr < 0x80)
      {
        /* primitive definite length format */
        *octets_used = 1;
        *length = *msg_ptr;
        return ERR_OK;
      }
      else if (*msg_ptr == 0x80)
      {
        /* constructed indefinite length format, termination with two zero octets */
        u8_t zeros;
        u8_t i;

        *length = 0;
        zeros = 0;
        while (zeros != 2)
        {
          i = 2;
          while (i > 0)
          {
            i--;
            (*length) += 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++;
            }
            if (*msg_ptr == 0)
            {
              zeros++;
              if (zeros == 2)
              {
                /* stop while (i > 0) */
                i = 0;
              }
            }
            else
            {
              zeros = 0;
            }
          }
        }
        *octets_used = 1;
        return ERR_OK;
      }
      else if (*msg_ptr == 0x81)
      {
        /* constructed definite length format, one octet */
        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++;
        }
        *length = *msg_ptr;
        *octets_used = 2;
        return ERR_OK;
      }
      else if (*msg_ptr == 0x82)
      {
        u8_t i;

        /* constructed definite length format, two octets */
        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 */
            *length |= *msg_ptr;
          }
          else
          {
            /* most significant length octet */
            *length = (*msg_ptr) << 8;
          }
        }
        *octets_used = 3;
        return ERR_OK;
      }
      else
      {
        /* constructed definite length format 3..127 octets, this is too big (>64k) */
        /**  @todo: do we need to accept inefficient codings with many leading zero's? */
        *octets_used = 1 + ((*msg_ptr) & 0x7f);
        return ERR_ARG;
      }
    }
    p = p->next;
  }

  /* p == NULL, ofs >= plen */
  return ERR_ARG;
}

/**
 * Decodes positive integer (counter, gauge, timeticks) into u32_t.
 *
 * @param p points to a pbuf holding an ASN1 coded integer
 * @param ofs points to the offset within the pbuf chain of the ASN1 coded integer
 * @param len length of the coded integer field
 * @param value return host order integer
 * @return ERR_OK if successfull, ERR_ARG if we can't (or won't) decode
 *
 * @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!!
 */
err_t
snmp_asn1_dec_u32t(struct pbuf *p, u16_t ofs, u16_t len, 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 ((len > 0) && (len < 6))
      {
        /* start from zero */
        *value = 0;
        if (*msg_ptr & 0x80)
        {
          /* negative, expecting zero sign bit! */
          return ERR_ARG;
        }
        else
        {
          /* positive */
          if ((len > 1) && (*msg_ptr == 0))
          {
            /* skip leading "sign byte" octet 0x00 */
            len--;
            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++;
            }
          }
        }
        /* OR octets with value */
        while (len > 1)
        {
          len--;
          *value |= *msg_ptr;
          *value <<= 8;
          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++;
          }
        }
        *value |= *msg_ptr;
        return ERR_OK;
      }
      else
      {
        return ERR_ARG;
      }
    }
    p = p->next;
  }
  /* p == NULL, ofs >= plen */
  return ERR_ARG;
}

/**
 * Decodes integer into s32_t.
 *
 * @param p points to a pbuf holding an ASN1 coded integer
 * @param ofs points to the offset within the pbuf chain of the ASN1 coded integer
 * @param len length of the coded integer field
 * @param value return host order integer
 * @return ERR_OK if successfull, ERR_ARG if we can't (or won't) decode
 *
 * @note ASN coded integers are _always_ signed!
 */
err_t
snmp_asn1_dec_s32t(struct pbuf *p, u16_t ofs, u16_t len, s32_t *value)
{
  u16_t plen, base;
  u8_t *msg_ptr;
#if BYTE_ORDER == LITTLE_ENDIAN
  u8_t *lsb_ptr = (u8_t*)value;
#endif
#if BYTE_ORDER == BIG_ENDIAN
  u8_t *lsb_ptr = (u8_t*)value + sizeof(s32_t) - 1;
#endif
  u8_t sign;

  plen = 0;
  while (p != NULL)
  {
    base = plen;
    plen += p->len;
    if (ofs < plen)
    {
      msg_ptr = p->payload;
      msg_ptr += ofs - base;
      if ((len > 0) && (len < 5))
      {
        if (*msg_ptr & 0x80)
        {
          /* negative, start from -1 */
          *value = -1;
          sign = 1;
        }
        else
        {
          /* positive, start from 0 */
          *value = 0;
          sign = 0;
        }
        /* OR/AND octets with value */
        while (len > 1)
        {
          len--;
          if (sign)
          {
            *lsb_ptr &= *msg_ptr;
            *value <<= 8;
            *lsb_ptr |= 255;
          }
          else
          {
            *lsb_ptr |= *msg_ptr;
            *value <<= 8;
          }
          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 (sign)
        {
          *lsb_ptr &= *msg_ptr;
        }
        else
        {
          *lsb_ptr |= *msg_ptr;
        }
        return ERR_OK;
      }
      else
      {
        return ERR_ARG;
      }
    }
    p = p->next;
  }
  /* p == NULL, ofs >= plen */
  return ERR_ARG;
}

/**
 * Decodes object identifier from incoming message into array of s32_t.
 *
 * @param p points to a pbuf holding an ASN1 coded object identifier
 * @param ofs points to the offset within the pbuf chain of the ASN1 coded object identifier
 * @param len length of the coded object identifier
 * @param oid return object identifier struct
 * @return ERR_OK if successfull, ERR_ARG if we can't (or won't) decode
 */
err_t
snmp_asn1_dec_oid(struct pbuf *p, u16_t ofs, u16_t len, struct snmp_obj_id *oid)
{
  u16_t plen, base;
  u8_t *msg_ptr;
  s32_t *oid_ptr;

  plen = 0;
  while (p != NULL)
  {
    base = plen;
    plen += p->len;
    if (ofs < plen)
    {
      msg_ptr = p->payload;
      msg_ptr += ofs - base;

      oid->len = 0;
      oid_ptr = &oid->id[0];
      if (len > 0)
      {
        /* first compressed octet */
        if (*msg_ptr == 0x2B)
        {
          /* (most) common case 1.3 (iso.org) */
          *oid_ptr = 1;
          oid_ptr++;
          *oid_ptr = 3;
          oid_ptr++;
        }
        else if (*msg_ptr < 40)
        {
          *oid_ptr = 0;
          oid_ptr++;
          *oid_ptr = *msg_ptr;
          oid_ptr++;
        }
        else if (*msg_ptr < 80)
        {
          *oid_ptr = 1;
          oid_ptr++;
          *oid_ptr = (*msg_ptr) - 40;
          oid_ptr++;
        }
        else
        {
          *oid_ptr = 2;
          oid_ptr++;
          *oid_ptr = (*msg_ptr) - 80;
          oid_ptr++;
        }
        oid->len = 2;
      }
      else
      {
        /* accepting zero length identifiers e.g. for
           getnext operation. uncommon but valid */
        return ERR_OK;
      }
      len--;
      if (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++;
        }
      }
      while ((len > 0) && (oid->len < LWIP_SNMP_OBJ_ID_LEN))
      {
        /* sub-identifier uses multiple octets */
        if (*msg_ptr & 0x80)
        {
          s32_t sub_id = 0;

          while ((*msg_ptr & 0x80) && (len > 1))
          {
            len--;
            sub_id = (sub_id << 7) + (*msg_ptr & ~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++;
            }
          }
          if (!(*msg_ptr & 0x80) && (len > 0))
          {
            /* last octet sub-identifier */
            len--;
            sub_id = (sub_id << 7) + *msg_ptr;
            *oid_ptr = sub_id;
          }
        }
        else
        {
          /* !(*msg_ptr & 0x80) sub-identifier uses single octet */
          len--;
          *oid_ptr = *msg_ptr;
        }
        if (len > 0)
        {
          /* remaining oid bytes available ... */
          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++;
          }
        }
        oid_ptr++;
        oid->len++;
      }
      if (len == 0)
      {
        /* len == 0, end of oid */
        return ERR_OK;
      }
      else
      {
        /* len > 0, oid->len == LWIP_SNMP_OBJ_ID_LEN or malformed encoding */
        return ERR_ARG;
      }

    }
    p = p->next;
  }
  /* p == NULL, ofs >= plen */
  return ERR_ARG;
}

/**
 * Decodes (copies) raw data (ip-addresses, octet strings, opaque encoding)
 * from incoming message into array.
 *
 * @param p points to a pbuf holding an ASN1 coded raw data
 * @param ofs points to the offset within the pbuf chain of the ASN1 coded raw data
 * @param len length of the coded raw data (zero is valid, e.g. empty string!)
 * @param raw_len length of the raw return value
 * @param raw return raw bytes
 * @return ERR_OK if successfull, ERR_ARG if we can't (or won't) decode
 */
err_t
snmp_asn1_dec_raw(struct pbuf *p, u16_t ofs, u16_t len, u16_t raw_len, u8_t *raw)
{
  u16_t plen, base;
  u8_t *msg_ptr;

  if (len > 0)
  {
    plen = 0;
    while (p != NULL)
    {
      base = plen;
      plen += p->len;
      if (ofs < plen)
      {
        msg_ptr = p->payload;
        msg_ptr += ofs - base;
        if (raw_len >= len)
        {
          while (len > 1)
          {
            /* copy len - 1 octets */
            len--;
            *raw = *msg_ptr;
            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++;
            }
          }
          /* copy last octet */
          *raw = *msg_ptr;
          return ERR_OK;
        }
        else
        {
          /* raw_len < len, not enough dst space */
          return ERR_ARG;
        }
      }
      p = p->next;
    }
    /* p == NULL, ofs >= plen */
    return ERR_ARG;
  }
  else
  {
    /* len == 0, empty string */
    return ERR_OK;
  }
}

#endif /* LWIP_SNMP */
Commit	Line	Data
6e6d4a8b JP	1	/**
	2	* @file
	3	* Abstract Syntax Notation One (ISO 8824, 8825) decoding
	4	*
	5	* @todo not optimised (yet), favor correctness over speed, favor speed over size
	6	*/
	7
	8	/*
	9	* Copyright (c) 2006 Axon Digital Design B.V., The Netherlands.
	10	* All rights reserved.
	11	*
	12	* Redistribution and use in source and binary forms, with or without modification,
	13	* are permitted provided that the following conditions are met:
	14	*
	15	* 1. Redistributions of source code must retain the above copyright notice,
	16	* this list of conditions and the following disclaimer.
	17	* 2. Redistributions in binary form must reproduce the above copyright notice,
	18	* this list of conditions and the following disclaimer in the documentation
	19	* and/or other materials provided with the distribution.
	20	* 3. The name of the author may not be used to endorse or promote products
	21	* derived from this software without specific prior written permission.
	22	*
	23	* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
	24	* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
	25	* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
	26	* SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
	27	* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
	28	* OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
	29	* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
	30	* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
	31	* IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
	32	* OF SUCH DAMAGE.
	33	*
	34	* Author: Christiaan Simons <christiaan.simons@axon.tv>
	35	*/
	36
	37	#include "lwip/opt.h"
	38
	39	#if LWIP_SNMP /* don't build if not configured for use in lwipopts.h */
	40
	41	#include "lwip/snmp_asn1.h"
	42
	43	/**
	44	* Retrieves type field from incoming pbuf chain.
	45	*
	46	* @param p points to a pbuf holding an ASN1 coded type field
	47	* @param ofs points to the offset within the pbuf chain of the ASN1 coded type field
	48	* @param type return ASN1 type
	49	* @return ERR_OK if successfull, ERR_ARG if we can't (or won't) decode
	50	*/
	51	err_t
	52	snmp_asn1_dec_type(struct pbuf p, u16_t ofs, u8_t type)
	53	{
	54	u16_t plen, base;
	55	u8_t *msg_ptr;
	56
	57	plen = 0;
	58	while (p != NULL)
	59	{
	60	base = plen;
	61	plen += p->len;
	62	if (ofs < plen)
	63	{
	64	msg_ptr = p->payload;
65	msg_ptr += ofs - base;
66	type = msg_ptr;
67	return ERR_OK;
68	}
69	p = p->next;
70	}
71	/* p == NULL, ofs >= plen */
72	return ERR_ARG;
73	}
74
75	/**
76	* Decodes length field from incoming pbuf chain into host length.
77	*
78	* @param p points to a pbuf holding an ASN1 coded length
79	* @param ofs points to the offset within the pbuf chain of the ASN1 coded length
80	* @param octets_used returns number of octets used by the length code
81	* @param length return host order length, upto 64k
82	* @return ERR_OK if successfull, ERR_ARG if we can't (or won't) decode
83	*/
84	err_t
85	snmp_asn1_dec_length(struct pbuf p, u16_t ofs, u8_t octets_used, u16_t *length)
86	{
87	u16_t plen, base;
88	u8_t *msg_ptr;
89
90	plen = 0;
91	while (p != NULL)
92	{
93	base = plen;
94	plen += p->len;
95	if (ofs < plen)
96	{
97	msg_ptr = p->payload;
98	msg_ptr += ofs - base;
99
100	if (*msg_ptr < 0x80)
101	{
102	/* primitive definite length format */
103	*octets_used = 1;
104	length = msg_ptr;
105	return ERR_OK;
106	}
107	else if (*msg_ptr == 0x80)
108	{
109	/* constructed indefinite length format, termination with two zero octets */
110	u8_t zeros;
111	u8_t i;
112
113	*length = 0;
114	zeros = 0;
115	while (zeros != 2)
116	{
117	i = 2;
118	while (i > 0)
119	{
120	i--;
121	(*length) += 1;
122	ofs += 1;
123	if (ofs >= plen)
124	{
125	/* next octet in next pbuf */
126	p = p->next;
127	if (p == NULL) { return ERR_ARG; }
128	msg_ptr = p->payload;
129	plen += p->len;
130	}
131	else
132	{
133	/* next octet in same pbuf */
134	msg_ptr++;
135	}
136	if (*msg_ptr == 0)
137	{
138	zeros++;
139	if (zeros == 2)
140	{
141	/* stop while (i > 0) */
142	i = 0;
143	}
144	}
145	else
146	{
147	zeros = 0;
148	}
149	}
150	}
151	*octets_used = 1;
152	return ERR_OK;
153	}
154	else if (*msg_ptr == 0x81)
155	{
156	/* constructed definite length format, one octet */
157	ofs += 1;
158	if (ofs >= plen)
159	{
160	/* next octet in next pbuf */
161	p = p->next;
162	if (p == NULL) { return ERR_ARG; }
163	msg_ptr = p->payload;
164	}
165	else
166	{
167	/* next octet in same pbuf */
168	msg_ptr++;
169	}
170	length = msg_ptr;
171	*octets_used = 2;
172	return ERR_OK;
173	}
174	else if (*msg_ptr == 0x82)
175	{
176	u8_t i;
177
178	/* constructed definite length format, two octets */
179	i = 2;
180	while (i > 0)
181	{
182	i--;
183	ofs += 1;
184	if (ofs >= plen)
185	{
186	/* next octet in next pbuf */
187	p = p->next;
188	if (p == NULL) { return ERR_ARG; }
189	msg_ptr = p->payload;
190	plen += p->len;
191	}
192	else
193	{
194	/* next octet in same pbuf */
195	msg_ptr++;
196	}
197	if (i == 0)
198	{
199	/* least significant length octet */
200	length \|= msg_ptr;
201	}
202	else
203	{
204	/* most significant length octet */
205	length = (msg_ptr) << 8;
206	}
207	}
208	*octets_used = 3;
209	return ERR_OK;
210	}
211	else
212	{
213	/* constructed definite length format 3..127 octets, this is too big (>64k) */
214	/** @todo: do we need to accept inefficient codings with many leading zero's? */
215	octets_used = 1 + ((msg_ptr) & 0x7f);
216	return ERR_ARG;
217	}
218	}
219	p = p->next;
220	}
221
222	/* p == NULL, ofs >= plen */
223	return ERR_ARG;
224	}
225
226	/**
227	* Decodes positive integer (counter, gauge, timeticks) into u32_t.
228	*
229	* @param p points to a pbuf holding an ASN1 coded integer
230	* @param ofs points to the offset within the pbuf chain of the ASN1 coded integer
231	* @param len length of the coded integer field
232	* @param value return host order integer
233	* @return ERR_OK if successfull, ERR_ARG if we can't (or won't) decode
234	*
235	* @note ASN coded integers are _always_ signed. E.g. +0xFFFF is coded
236	* as 0x00,0xFF,0xFF. Note the leading sign octet. A positive value
237	* of 0xFFFFFFFF is preceded with 0x00 and the length is 5 octets!!
238	*/
239	err_t
240	snmp_asn1_dec_u32t(struct pbuf p, u16_t ofs, u16_t len, u32_t value)
241	{
242	u16_t plen, base;
243	u8_t *msg_ptr;
244
245	plen = 0;
246	while (p != NULL)
247	{
248	base = plen;
249	plen += p->len;
250	if (ofs < plen)
251	{
252	msg_ptr = p->payload;
253	msg_ptr += ofs - base;
254	if ((len > 0) && (len < 6))
255	{
256	/* start from zero */
257	*value = 0;
258	if (*msg_ptr & 0x80)
259	{
260	/* negative, expecting zero sign bit! */
261	return ERR_ARG;
262	}
263	else
264	{
265	/* positive */
266	if ((len > 1) && (*msg_ptr == 0))
267	{
268	/* skip leading "sign byte" octet 0x00 */
269	len--;
270	ofs += 1;
271	if (ofs >= plen)
272	{
273	/* next octet in next pbuf */
274	p = p->next;
275	if (p == NULL) { return ERR_ARG; }
276	msg_ptr = p->payload;
277	plen += p->len;
278	}
279	else
280	{
281	/* next octet in same pbuf */
282	msg_ptr++;
283	}
284	}
285	}
286	/* OR octets with value */
287	while (len > 1)
288	{
289	len--;
290	value \|= msg_ptr;
291	*value <<= 8;
292	ofs += 1;
293	if (ofs >= plen)
294	{
295	/* next octet in next pbuf */
296	p = p->next;
297	if (p == NULL) { return ERR_ARG; }
298	msg_ptr = p->payload;
299	plen += p->len;
300	}
301	else
302	{
303	/* next octet in same pbuf */
304	msg_ptr++;
305	}
306	}
307	value \|= msg_ptr;
308	return ERR_OK;
309	}
310	else
311	{
312	return ERR_ARG;
313	}
314	}
315	p = p->next;
316	}
317	/* p == NULL, ofs >= plen */
318	return ERR_ARG;
319	}
320
321	/**
322	* Decodes integer into s32_t.
323	*
324	* @param p points to a pbuf holding an ASN1 coded integer
325	* @param ofs points to the offset within the pbuf chain of the ASN1 coded integer
326	* @param len length of the coded integer field
327	* @param value return host order integer
328	* @return ERR_OK if successfull, ERR_ARG if we can't (or won't) decode
329	*
330	* @note ASN coded integers are _always_ signed!
331	*/
332	err_t
333	snmp_asn1_dec_s32t(struct pbuf p, u16_t ofs, u16_t len, s32_t value)
334	{
335	u16_t plen, base;
336	u8_t *msg_ptr;
337	#if BYTE_ORDER == LITTLE_ENDIAN
338	u8_t lsb_ptr = (u8_t)value;
339	#endif
340	#if BYTE_ORDER == BIG_ENDIAN
341	u8_t lsb_ptr = (u8_t)value + sizeof(s32_t) - 1;
342	#endif
343	u8_t sign;
344
345	plen = 0;
346	while (p != NULL)
347	{
348	base = plen;
349	plen += p->len;
350	if (ofs < plen)
351	{
352	msg_ptr = p->payload;
353	msg_ptr += ofs - base;
354	if ((len > 0) && (len < 5))
355	{
356	if (*msg_ptr & 0x80)
357	{
358	/* negative, start from -1 */
359	*value = -1;
360	sign = 1;
361	}
362	else
363	{
364	/* positive, start from 0 */
365	*value = 0;
366	sign = 0;
367	}
368	/* OR/AND octets with value */
369	while (len > 1)
370	{
371	len--;
372	if (sign)
373	{
374	lsb_ptr &= msg_ptr;
375	*value <<= 8;
376	*lsb_ptr \|= 255;
377	}
378	else
379	{
380	lsb_ptr \|= msg_ptr;
381	*value <<= 8;
382	}
383	ofs += 1;
384	if (ofs >= plen)
385	{
386	/* next octet in next pbuf */
387	p = p->next;
388	if (p == NULL) { return ERR_ARG; }
389	msg_ptr = p->payload;
390	plen += p->len;
391	}
392	else
393	{
394	/* next octet in same pbuf */
395	msg_ptr++;
396	}
397	}
398	if (sign)
399	{
400	lsb_ptr &= msg_ptr;
401	}
402	else
403	{
404	lsb_ptr \|= msg_ptr;
405	}
406	return ERR_OK;
407	}
408	else
409	{
410	return ERR_ARG;
411	}
412	}
413	p = p->next;
414	}
415	/* p == NULL, ofs >= plen */
416	return ERR_ARG;
417	}
418
419	/**
420	* Decodes object identifier from incoming message into array of s32_t.
421	*
422	* @param p points to a pbuf holding an ASN1 coded object identifier
423	* @param ofs points to the offset within the pbuf chain of the ASN1 coded object identifier
424	* @param len length of the coded object identifier
425	* @param oid return object identifier struct
426	* @return ERR_OK if successfull, ERR_ARG if we can't (or won't) decode
427	*/
428	err_t
429	snmp_asn1_dec_oid(struct pbuf p, u16_t ofs, u16_t len, struct snmp_obj_id oid)
430	{
431	u16_t plen, base;
432	u8_t *msg_ptr;
433	s32_t *oid_ptr;
434
435	plen = 0;
436	while (p != NULL)
437	{
438	base = plen;
439	plen += p->len;
440	if (ofs < plen)
441	{
442	msg_ptr = p->payload;
443	msg_ptr += ofs - base;
444
445	oid->len = 0;
446	oid_ptr = &oid->id[0];
447	if (len > 0)
448	{
449	/* first compressed octet */
450	if (*msg_ptr == 0x2B)
451	{
452	/* (most) common case 1.3 (iso.org) */
453	*oid_ptr = 1;
454	oid_ptr++;
455	*oid_ptr = 3;
456	oid_ptr++;
457	}
458	else if (*msg_ptr < 40)
459	{
460	*oid_ptr = 0;
461	oid_ptr++;
462	oid_ptr = msg_ptr;
463	oid_ptr++;
464	}
465	else if (*msg_ptr < 80)
466	{
467	*oid_ptr = 1;
468	oid_ptr++;
469	oid_ptr = (msg_ptr) - 40;
470	oid_ptr++;
471	}
472	else
473	{
474	*oid_ptr = 2;
475	oid_ptr++;
476	oid_ptr = (msg_ptr) - 80;
477	oid_ptr++;
478	}
479	oid->len = 2;
480	}
481	else
482	{
483	/* accepting zero length identifiers e.g. for
484	getnext operation. uncommon but valid */
485	return ERR_OK;
486	}
487	len--;
488	if (len > 0)
489	{
490	ofs += 1;
491	if (ofs >= plen)
492	{
493	/* next octet in next pbuf */
494	p = p->next;
495	if (p == NULL) { return ERR_ARG; }
496	msg_ptr = p->payload;
497	plen += p->len;
498	}
499	else
500	{
501	/* next octet in same pbuf */
502	msg_ptr++;
503	}
504	}
505	while ((len > 0) && (oid->len < LWIP_SNMP_OBJ_ID_LEN))
506	{
507	/* sub-identifier uses multiple octets */
508	if (*msg_ptr & 0x80)
509	{
510	s32_t sub_id = 0;
511
512	while ((*msg_ptr & 0x80) && (len > 1))
513	{
514	len--;
515	sub_id = (sub_id << 7) + (*msg_ptr & ~0x80);
516	ofs += 1;
517	if (ofs >= plen)
518	{
519	/* next octet in next pbuf */
520	p = p->next;
521	if (p == NULL) { return ERR_ARG; }
522	msg_ptr = p->payload;
523	plen += p->len;
524	}
525	else
526	{
527	/* next octet in same pbuf */
528	msg_ptr++;
529	}
530	}
531	if (!(*msg_ptr & 0x80) && (len > 0))
532	{
533	/* last octet sub-identifier */
534	len--;
535	sub_id = (sub_id << 7) + *msg_ptr;
536	*oid_ptr = sub_id;
537	}
538	}
539	else
540	{
541	/* !(msg_ptr & 0x80) sub-identifier uses single octet /
542	len--;
543	oid_ptr = msg_ptr;
544	}
545	if (len > 0)
546	{
547	/* remaining oid bytes available ... */
548	ofs += 1;
549	if (ofs >= plen)
550	{
551	/* next octet in next pbuf */
552	p = p->next;
553	if (p == NULL) { return ERR_ARG; }
554	msg_ptr = p->payload;
555	plen += p->len;
556	}
557	else
558	{
559	/* next octet in same pbuf */
560	msg_ptr++;
561	}
562	}
563	oid_ptr++;
564	oid->len++;
565	}
566	if (len == 0)
567	{
568	/* len == 0, end of oid */
569	return ERR_OK;
570	}
571	else
572	{
573	/* len > 0, oid->len == LWIP_SNMP_OBJ_ID_LEN or malformed encoding */
574	return ERR_ARG;
575	}
576
577	}
578	p = p->next;
579	}
580	/* p == NULL, ofs >= plen */
581	return ERR_ARG;
582	}
583
584	/**
585	* Decodes (copies) raw data (ip-addresses, octet strings, opaque encoding)
586	* from incoming message into array.
587	*
588	* @param p points to a pbuf holding an ASN1 coded raw data
589	* @param ofs points to the offset within the pbuf chain of the ASN1 coded raw data
590	* @param len length of the coded raw data (zero is valid, e.g. empty string!)
591	* @param raw_len length of the raw return value
592	* @param raw return raw bytes
593	* @return ERR_OK if successfull, ERR_ARG if we can't (or won't) decode
594	*/
595	err_t
596	snmp_asn1_dec_raw(struct pbuf p, u16_t ofs, u16_t len, u16_t raw_len, u8_t raw)
597	{
598	u16_t plen, base;
599	u8_t *msg_ptr;
600
601	if (len > 0)
602	{
603	plen = 0;
604	while (p != NULL)
605	{
606	base = plen;
607	plen += p->len;
608	if (ofs < plen)
609	{
610	msg_ptr = p->payload;
611	msg_ptr += ofs - base;
612	if (raw_len >= len)
613	{
614	while (len > 1)
615	{
616	/* copy len - 1 octets */
617	len--;
618	raw = msg_ptr;
619	raw++;
620	ofs += 1;
621	if (ofs >= plen)
622	{
623	/* next octet in next pbuf */
624	p = p->next;
625	if (p == NULL) { return ERR_ARG; }
626	msg_ptr = p->payload;
627	plen += p->len;
628	}
629	else
630	{
631	/* next octet in same pbuf */
632	msg_ptr++;
633	}
634	}
635	/* copy last octet */
636	raw = msg_ptr;
637	return ERR_OK;
638	}
639	else
640	{
641	/* raw_len < len, not enough dst space */
642	return ERR_ARG;
643	}
644	}
645	p = p->next;
646	}
647	/* p == NULL, ofs >= plen */
648	return ERR_ARG;
649	}
650	else
651	{
652	/* len == 0, empty string */
653	return ERR_OK;
654	}
655	}
656
657	#endif /* LWIP_SNMP */