--- /dev/null
+/**
+ * @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 */
