Diff: core/snmp/asn1_enc.c

Revision:

0:51ac1d130fd4

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/core/snmp/asn1_enc.c	Fri Jun 22 09:25:39 2012 +0000
@@ -0,0 +1,611 @@
+/**
+ * @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 = (u8_t*)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 = (u8_t*)p->payload;
+      msg_ptr += ofs - base;
+
+      if (length < 0x80)
+      {
+        *msg_ptr = (u8_t)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 = (u8_t*)p->payload;
+        }
+        else
+        {
+          /* next octet in same pbuf */
+          msg_ptr++;
+        }
+        *msg_ptr = (u8_t)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 = (u8_t*)p->payload;
+            plen += p->len;
+          }
+          else
+          {
+            /* next octet in same pbuf */
+            msg_ptr++;
+          }
+          if (i == 0)
+          {
+            /* least significant length octet */
+            *msg_ptr = (u8_t)length;
+          }
+          else
+          {
+            /* most significant length octet */
+            *msg_ptr = (u8_t)(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, u16_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 = (u8_t*)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 = (u8_t*)p->payload;
+          plen += p->len;
+        }
+        else
+        {
+          /* next octet in same pbuf */
+          msg_ptr++;
+        }
+      }
+      while (octets_needed > 1)
+      {
+        octets_needed--;
+        *msg_ptr = (u8_t)(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 = (u8_t*)p->payload;
+          plen += p->len;
+        }
+        else
+        {
+          /* next octet in same pbuf */
+          msg_ptr++;
+        }
+      }
+      /* (only) one least significant octet */
+      *msg_ptr = (u8_t)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, u16_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 = (u8_t*)p->payload;
+      msg_ptr += ofs - base;
+
+      while (octets_needed > 1)
+      {
+        octets_needed--;
+        *msg_ptr = (u8_t)(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 = (u8_t*)p->payload;
+          plen += p->len;
+        }
+        else
+        {
+          /* next octet in same pbuf */
+          msg_ptr++;
+        }
+      }
+      /* (only) one least significant octet */
+      *msg_ptr = (u8_t)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 = (u8_t*)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 = (u8_t)((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 = (u8_t*)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 = (u8_t)(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 = (u8_t*)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 = (u8_t*)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, u16_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 = (u8_t*)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 = (u8_t*)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 */