Corrected object identifier codec for object ids not starting with .iso.dod (e.g. zeroDotZero (0.0)).

src/core/snmp/asn1_dec.c

@@ -420,6 +420,7 @@ 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)
@@ -431,13 +432,52 @@ snmp_asn1_dec_oid(struct pbuf *p, u16_t ofs, u16_t len, struct snmp_obj_id *oid)
       msg_ptr = p->payload;
       msg_ptr += ofs - base;
 
-      if ((len > 1) && (*msg_ptr == 0x2B))
+      oid->len = 0;
+      oid_ptr = &oid->id[0];
+      if (len > 0)
       {
-        s32_t *oid_ptr;
+        /* first compressed octet */
-
+        if (*msg_ptr == 0x2B)
-        /* we have compressed 1.3 (iso.org) Z = (X * 40) + Y */
+        {
+          /* (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
+      {
+        /* length == 0, zero length (empty list) isn't allowed here.
+           ISO 8825 (BER) isn't clear about this, but some seem to accept it (why?).
+           zeroDotZero (0.0) must be at least 06 01 00  */
+        return ERR_ARG;
+      }
       len--;
-        /* proceed to .dod */
+      if (len > 0)
+      {
         ofs += 1;
         if (ofs >= plen)
         {
@@ -452,8 +492,7 @@ snmp_asn1_dec_oid(struct pbuf *p, u16_t ofs, u16_t len, struct snmp_obj_id *oid)
           /* next octet in same pbuf */
           msg_ptr++;
         }
-        oid->len = 0;
+      }
-        oid_ptr = &oid->id[0];
       while ((len > 0) && (oid->len < LWIP_SNMP_OBJ_ID_LEN))
       {
         /* sub-identifier uses multiple octets */
@@ -525,12 +564,7 @@ snmp_asn1_dec_oid(struct pbuf *p, u16_t ofs, u16_t len, struct snmp_obj_id *oid)
         /* len > 0, oid->len == LWIP_SNMP_OBJ_ID_LEN or malformed encoding */
         return ERR_ARG;
       }
-      }
+
-      else
-      {
-        /* length <= 1 OR prefix not 1.3 (iso.org) */
-        return ERR_ARG;
-      }
     }
     p = p->next;
   }

src/core/snmp/asn1_enc.c

@@ -143,6 +143,13 @@ snmp_asn1_enc_oid_cnt(u8_t ident_len, s32_t *ident, u16_t *octets_needed)
   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--;
@@ -157,8 +164,6 @@ snmp_asn1_enc_oid_cnt(u8_t ident_len, s32_t *ident, u16_t *octets_needed)
     }
     ident++;
   }
-  /* one extra for compressed iso.dod. prefix */
-  cnt++;
   *octets_needed = cnt;
 }
 
@@ -445,8 +450,19 @@ snmp_asn1_enc_oid(struct pbuf *p, u16_t ofs, u8_t ident_len, s32_t *ident)
     {      
       msg_ptr = p->payload;
       msg_ptr += ofs - base;
-      /* add compressed prefix .iso.dod */ 
+      
+      if (ident_len > 1)
+      {
+        if ((ident[0] == 1) && (ident[1] == 3))
+        {
+          /* compressed (most common) prefix .iso.dod */ 
           *msg_ptr = 0x2b;
+        }
+        else
+        {
+          /* calculate prefix */
+          *msg_ptr = (ident[0] * 40) + ident[1];
+        }
         ofs += 1;
         if (ofs >= plen)
         {
@@ -461,6 +477,14 @@ snmp_asn1_enc_oid(struct pbuf *p, u16_t ofs, u8_t ident_len, s32_t *ident)
           /* next octet in same pbuf */
           msg_ptr++;
         }
+        ident_len -= 2;
+        ident += 2;
+      }
+      else
+      {
+        /* ident_len <= 1, at least we need zeroDotZero (0.0) (ident_len == 2) */
+        return ERR_ARG;
+      }
       while (ident_len > 0)
       {
         s32_t sub_id;