/*
 * SNMP PDU Encoding
 *
 * Complies with:
 *
 * RFC 1902: Structure of Management Information for SNMPv2
 *
 */

/**********************************************************************
 *
 *           Copyright 1997 by Carnegie Mellon University
 * 
 *                       All Rights Reserved
 * 
 * Permission to use, copy, modify, and distribute this software and its
 * documentation for any purpose and without fee is hereby granted,
 * provided that the above copyright notice appear in all copies and that
 * both that copyright notice and this permission notice appear in
 * supporting documentation, and that the name of CMU not be
 * used in advertising or publicity pertaining to distribution of the
 * software without specific, written prior permission.
 * 
 * CMU DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING
 * ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL
 * CMU BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR
 * ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
 * WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
 * ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
 * SOFTWARE.
 * 
 * Author: Ryan Troll <ryan+@andrew.cmu.edu>
 * 
 **********************************************************************/

#include "config.h"

#include <stdio.h>

#if HAVE_UNISTD_H
#include <unistd.h>
#endif
#if HAVE_STDLIB_H
#include <stdlib.h>
#endif
#if HAVE_SYS_TYPES_H
#include <sys/types.h>
#endif
#if HAVE_CTYPE_H
#include <ctype.h>
#endif
#if HAVE_GNUMALLOC_H
#include <gnumalloc.h>
#elif HAVE_MALLOC_H
#include <malloc.h>
#endif
#if HAVE_MEMORY_H
#include <memory.h>
#endif
#ifdef HAVE_STRING_H
#include <string.h>
#endif
#ifdef HAVE_STRINGS_H
#include <strings.h>
#endif
#if HAVE_BSTRING_H
#include <bstring.h>
#endif
#if HAVE_SYS_SOCKET_H
#include <sys/socket.h>
#endif
#if HAVE_NETINET_IN_H
#include <netinet/in.h>
#endif
#if HAVE_ARPA_INET_H
#include <arpa/inet.h>
#endif
#if HAVE_SYS_TIME_H
#include <sys/time.h>
#endif
#if HAVE_NETDB_H
#include <netdb.h>
#endif

#include "snmp.h"
#include "asn1.h"
#include "snmp_error.h"
#include "snmp_vars.h"
#include "snmp_pdu.h"
#include "snmp_msg.h"
#include "snmp_api_error.h"

#include "util.h"

/* #define DEBUG_PDU 1 */
/* #define DEBUG_PDU_DECODE 1 */
/* #define DEBUG_PDU_ENCODE 1 */

#define ASN_PARSE_ERROR(x) {  return(x); }

/**********************************************************************/

/* Create a PDU.
 */

struct snmp_pdu *
snmp_pdu_create(int command)
{
    struct snmp_pdu *pdu;

#ifdef DEBUG_PDU
    snmplib_debug(8, "PDU:  Creating\n");
#endif

    pdu = (struct snmp_pdu *) xmalloc(sizeof(struct snmp_pdu));
    if (pdu == NULL) {
	snmp_set_api_error(SNMPERR_OS_ERR);
	return (NULL);
    }
    memset((char *) pdu, '\0', sizeof(struct snmp_pdu));

    pdu->command = command;
    pdu->errstat = SNMP_DEFAULT_ERRSTAT;
    pdu->errindex = SNMP_DEFAULT_ERRINDEX;
    pdu->address.sin_addr.s_addr = SNMP_DEFAULT_ADDRESS;
    pdu->enterprise = NULL;
    pdu->enterprise_length = 0;
    pdu->variables = NULL;

#ifdef DEBUG_PDU
    snmplib_debug(8, "PDU:  Created %x\n", (unsigned int) pdu);
#endif

    return (pdu);
}

/**********************************************************************/

/* Clone an existing PDU.
 */
struct snmp_pdu *
snmp_pdu_clone(struct snmp_pdu *Src)
{
    struct snmp_pdu *Dest;

#ifdef DEBUG_PDU
    snmplib_debug(8, "PDU %x:  Cloning\n", (unsigned int) Src);
#endif

    Dest = (struct snmp_pdu *) xmalloc(sizeof(struct snmp_pdu));
    if (Dest == NULL) {
	snmp_set_api_error(SNMPERR_OS_ERR);
	return (NULL);
    }
    xmemcpy((char *) Dest, (char *) Src, sizeof(struct snmp_pdu));

#ifdef DEBUG_PDU
    snmplib_debug(8, "PDU %x:  Created %x\n", (unsigned int) Src, (unsigned int) Dest);
#endif
    return (Dest);
}

/**********************************************************************/

/*
 * If there was an error in the input pdu, creates a clone of the pdu
 * that includes all the variables except the one marked by the errindex.
 * The command is set to the input command and the reqid, errstat, and
 * errindex are set to default values.
 * If the error status didn't indicate an error, the error index didn't
 * indicate a variable, the pdu wasn't a get response message, or there
 * would be no remaining variables, this function will return NULL.
 * If everything was successful, a pointer to the fixed cloned pdu will
 * be returned.
 */
struct snmp_pdu *
snmp_pdu_fix(struct snmp_pdu *pdu, int command)
{
    return (snmp_fix_pdu(pdu, command));
}

struct snmp_pdu *
snmp_fix_pdu(struct snmp_pdu *pdu, int command)
{
    struct variable_list *var, *newvar;
    struct snmp_pdu *newpdu;
    int i;
    int copied = 0;

#ifdef DEBUG_PDU
    snmplib_debug(8, "PDU %x:  Fixing.  Err index is %d\n",
	(unsigned int) pdu, (unsigned int) pdu->errindex);
#endif

    if (pdu->command != SNMP_PDU_RESPONSE ||
	pdu->errstat == SNMP_ERR_NOERROR ||
	pdu->errindex <= 0) {
	snmp_set_api_error(SNMPERR_UNABLE_TO_FIX);
	return (NULL);
    }
    /* clone the pdu */
    newpdu = snmp_pdu_clone(pdu);
    if (newpdu == NULL)
	return (NULL);

    newpdu->variables = 0;
    newpdu->command = command;
    newpdu->reqid = SNMP_DEFAULT_REQID;
    newpdu->errstat = SNMP_DEFAULT_ERRSTAT;
    newpdu->errindex = SNMP_DEFAULT_ERRINDEX;

    /* Loop through the variables, removing whatever isn't necessary */

    var = pdu->variables;
    i = 1;

    /* skip first variable if necessary */
    if (pdu->errindex == i) {
	var = var->next_variable;
	i++;
    }
    if (var != NULL) {

	/* VAR is the first uncopied variable */

	/* Clone this variable */
	newpdu->variables = snmp_var_clone(var);
	if (newpdu->variables == NULL) {
	    snmp_pdu_free(newpdu);
	    return (NULL);
	}
	copied++;

	newvar = newpdu->variables;

	/* VAR has been copied to NEWVAR. */
	while (var->next_variable) {

	    /* Skip the item that was bad */
	    if (++i == pdu->errindex) {
		var = var->next_variable;
		continue;
	    }
	    /* Copy this var */
	    newvar->next_variable = snmp_var_clone(var->next_variable);
	    if (newvar->next_variable == NULL) {
		snmp_pdu_free(newpdu);
		return (NULL);
	    }
	    /* Move to the next one */
	    newvar = newvar->next_variable;
	    var = var->next_variable;
	    copied++;
	}
	newvar->next_variable = NULL;
    }
    /* If we didn't copy anything, free the new pdu. */
    if (i < pdu->errindex || copied == 0) {
	snmp_free_pdu(newpdu);
	snmp_set_api_error(SNMPERR_UNABLE_TO_FIX);
	return (NULL);
    }
#ifdef DEBUG_PDU
    snmplib_debug(8, "PDU %x:  Fixed PDU is %x\n",
	(unsigned int) pdu, (unsigned int) newpdu);
#endif
    return (newpdu);
}


/**********************************************************************/

void
snmp_pdu_free(struct snmp_pdu *pdu)
{
    snmp_free_pdu(pdu);
}

/*
 * Frees the pdu and any xmalloc'd data associated with it.
 */
void
snmp_free_pdu(struct snmp_pdu *pdu)
{
    struct variable_list *vp, *ovp;

    vp = pdu->variables;
    while (vp) {
	ovp = vp;
	vp = vp->next_variable;
	snmp_var_free(ovp);
    }

    if (pdu->enterprise)
	xfree((char *) pdu->enterprise);
    xfree((char *) pdu);
}

/**********************************************************************/

/* Encode this PDU into DestBuf.
 *
 * Returns a pointer to the next byte in the buffer (where the Variable
 * Bindings belong.)
 */

/*
 * RFC 1902: Structure of Management Information for SNMPv2
 *
 *   PDU ::= 
 *    SEQUENCE {
 *      request-id   INTEGER32
 *      error-status INTEGER
 *      error-index  INTEGER
 *      Variable Bindings
 *    }
 *
 * BulkPDU ::=
 *    SEQUENCE {
 *      request-id      INTEGER32
 *      non-repeaters   INTEGER
 *      max-repetitions INTEGER
 *      Variable Bindings
 *    }
 */

/*
 * RFC 1157: A Simple Network Management Protocol (SNMP)
 *
 *   PDU ::= 
 *    SEQUENCE {
 *      request-id   INTEGER
 *      error-status INTEGER
 *      error-index  INTEGER
 *      Variable Bindings
 *    }
 *
 *   TrapPDU ::=
 *    SEQUENCE {
 *      enterprise    NetworkAddress
 *      generic-trap  INTEGER
 *      specific-trap INTEGER
 *      time-stamp    TIMETICKS
 *      Variable Bindings
 *    }
 */

u_char *
snmp_pdu_encode(u_char * DestBuf, int *DestBufLen,
    struct snmp_pdu *PDU)
{
    u_char *bufp;

#ifdef DEBUG_PDU_ENCODE
    snmplib_debug(8, "PDU: Encoding %d\n", PDU->command);
#endif

    /* ASN.1 Header */
    switch (PDU->command) {

/**********************************************************************/
#ifdef TRP_REQ_MSG
    case TRP_REQ_MSG:

	/* SNMPv1 Trap */

	/* enterprise */
	bufp = asn_build_objid(DestBuf, DestBufLen,
	    (u_char) (ASN_UNIVERSAL | ASN_PRIMITIVE | ASN_OBJECT_ID),
	    (oid *) PDU->enterprise, PDU->enterprise_length);
	if (bufp == NULL)
	    return (NULL);

	/* agent-addr */
	bufp = asn_build_string(bufp, DestBufLen,
	    (u_char) (SMI_IPADDRESS | ASN_PRIMITIVE),
	    (u_char *) & PDU->agent_addr.sin_addr.s_addr,
	    sizeof(PDU->agent_addr.sin_addr.s_addr));
	if (bufp == NULL)
	    return (NULL);

	/* generic trap */
	bufp = asn_build_int(bufp, DestBufLen,
	    (u_char) (ASN_UNIVERSAL | ASN_PRIMITIVE | ASN_INTEGER),
	    (int *) &PDU->trap_type, sizeof(PDU->trap_type));
	if (bufp == NULL)
	    return (NULL);

	/* specific trap */
	bufp = asn_build_int(bufp, DestBufLen,
	    (u_char) (ASN_UNIVERSAL | ASN_PRIMITIVE | ASN_INTEGER),
	    (int *) &PDU->specific_type,
	    sizeof(PDU->specific_type));
	if (bufp == NULL)
	    return (NULL);

	/* timestamp */
	bufp = asn_build_unsigned_int(bufp, DestBufLen,
	    (u_char) (SMI_TIMETICKS | ASN_PRIMITIVE),
	    &PDU->time, sizeof(PDU->time));
	if (bufp == NULL)
	    return (NULL);
	break;
#endif

/**********************************************************************/

    case SNMP_PDU_GETBULK:

	/* SNMPv2 Bulk Request */

	/* request id */
	bufp = asn_build_int(DestBuf, DestBufLen,
	    (u_char) (ASN_UNIVERSAL | ASN_PRIMITIVE | ASN_INTEGER),
	    &PDU->reqid, sizeof(PDU->reqid));
	if (bufp == NULL)
	    return (NULL);

	/* non-repeaters */
	bufp = asn_build_int(bufp, DestBufLen,
	    (u_char) (ASN_UNIVERSAL | ASN_PRIMITIVE | ASN_INTEGER),
	    &PDU->non_repeaters,
	    sizeof(PDU->non_repeaters));
	if (bufp == NULL)
	    return (NULL);

	/* max-repetitions */
	bufp = asn_build_int(bufp, DestBufLen,
	    (u_char) (ASN_UNIVERSAL | ASN_PRIMITIVE | ASN_INTEGER),
	    &PDU->max_repetitions,
	    sizeof(PDU->max_repetitions));
	if (bufp == NULL)
	    return (NULL);
	break;

/**********************************************************************/

    default:

	/* Normal PDU Encoding */

	/* request id */
#ifdef DEBUG_PDU_ENCODE
	snmplib_debug(8, "PDU: Request ID %d (0x%x)\n", PDU->reqid, DestBuf);
#endif
	bufp = asn_build_int(DestBuf, DestBufLen,
	    (u_char) (ASN_UNIVERSAL | ASN_PRIMITIVE | ASN_INTEGER),
	    &PDU->reqid, sizeof(PDU->reqid));
	if (bufp == NULL)
	    return (NULL);

	/* error status */
#ifdef DEBUG_PDU_ENCODE
	snmplib_debug(8, "PDU: Error Status %d (0x%x)\n", PDU->errstat, bufp);
#endif
	bufp = asn_build_int(bufp, DestBufLen,
	    (u_char) (ASN_UNIVERSAL | ASN_PRIMITIVE | ASN_INTEGER),
	    &PDU->errstat, sizeof(PDU->errstat));
	if (bufp == NULL)
	    return (NULL);

	/* error index */
#ifdef DEBUG_PDU_ENCODE
	snmplib_debug(8, "PDU: Error index %d (0x%x)\n", PDU->errindex, bufp);
#endif
	bufp = asn_build_int(bufp, DestBufLen,
	    (u_char) (ASN_UNIVERSAL | ASN_PRIMITIVE | ASN_INTEGER),
	    &PDU->errindex, sizeof(PDU->errindex));
	if (bufp == NULL)
	    return (NULL);
	break;
    }				/* End of encoding */

    return (bufp);
}

/**********************************************************************/

/* Decodes PDU from Packet into PDU.
 *
 * Returns a pointer to the next byte of the packet, which is where the
 * Variable Bindings start.
 */
u_char *
snmp_pdu_decode(u_char * Packet,	/* data */
    int *Length,		/* &length */
    struct snmp_pdu * PDU)
{				/* pdu */
    u_char *bufp;
    u_char PDUType;
    u_char ASNType;
#ifdef UNUSED_CODE
    int four;
    oid objid[MAX_NAME_LEN];
#endif

    bufp = asn_parse_header(Packet, Length, &PDUType);
    if (bufp == NULL)
	ASN_PARSE_ERROR(NULL);

#ifdef DEBUG_PDU_DECODE
    snmplib_debug(8, "PDU Type: %d\n", PDUType);
#endif

    PDU->command = PDUType;
    switch (PDUType) {

#ifdef TRP_REQ_MSG
    case TRP_REQ_MSG:

	/* SNMPv1 Trap Message */

	/* enterprise */
	PDU->enterprise_length = MAX_NAME_LEN;
	bufp = asn_parse_objid(bufp, Length,
	    &ASNType, objid, &PDU->enterprise_length);
	if (bufp == NULL)
	    ASN_PARSE_ERROR(NULL);

	PDU->enterprise = (oid *) xmalloc(PDU->enterprise_length * sizeof(oid));
	if (PDU->enterprise == NULL) {
	    snmp_set_api_error(SNMPERR_OS_ERR);
	    return (NULL);
	}
	xmemcpy((char *) PDU->enterprise, (char *) objid,
	    PDU->enterprise_length * sizeof(oid));

	/* Agent-addr */
	four = 4;
	bufp = asn_parse_string(bufp, Length,
	    &ASNType,
	    (u_char *) & PDU->agent_addr.sin_addr.s_addr,
	    &four);
	if (bufp == NULL)
	    ASN_PARSE_ERROR(NULL);

	/* Generic trap */
	bufp = asn_parse_int(bufp, Length,
	    &ASNType,
	    (int *) &PDU->trap_type,
	    sizeof(PDU->trap_type));
	if (bufp == NULL)
	    ASN_PARSE_ERROR(NULL);

	/* Specific Trap */
	bufp = asn_parse_int(bufp, Length,
	    &ASNType,
	    (int *) &PDU->specific_type,
	    sizeof(PDU->specific_type));
	if (bufp == NULL)
	    ASN_PARSE_ERROR(NULL);

	/* Timestamp */
	bufp = asn_parse_unsigned_int(bufp, Length,
	    &ASNType,
	    &PDU->time, sizeof(PDU->time));
	if (bufp == NULL)
	    ASN_PARSE_ERROR(NULL);
	break;
#endif

/**********************************************************************/

    case SNMP_PDU_GETBULK:

	/* SNMPv2 Bulk Request */

	/* request id */
	bufp = asn_parse_int(bufp, Length,
	    &ASNType,
	    &PDU->reqid, sizeof(PDU->reqid));
	if (bufp == NULL)
	    ASN_PARSE_ERROR(NULL);

	/* non-repeaters */
	bufp = asn_parse_int(bufp, Length,
	    &ASNType,
	    &PDU->non_repeaters, sizeof(PDU->non_repeaters));
	if (bufp == NULL)
	    ASN_PARSE_ERROR(NULL);

	/* max-repetitions */
	bufp = asn_parse_int(bufp, Length,
	    &ASNType,
	    &PDU->max_repetitions, sizeof(PDU->max_repetitions));
	if (bufp == NULL)
	    ASN_PARSE_ERROR(NULL);
	break;

/**********************************************************************/

    default:

	/* Normal PDU Encoding */

	/* request id */
	bufp = asn_parse_int(bufp, Length,
	    &ASNType,
	    &PDU->reqid, sizeof(PDU->reqid));
	if (bufp == NULL)
	    ASN_PARSE_ERROR(NULL);

#ifdef DEBUG_PDU_DECODE
	snmplib_debug(8, "PDU Request ID: %d\n", PDU->reqid);
#endif

	/* error status */
	bufp = asn_parse_int(bufp, Length,
	    &ASNType,
	    &PDU->errstat, sizeof(PDU->errstat));
	if (bufp == NULL)
	    ASN_PARSE_ERROR(NULL);

#ifdef DEBUG_PDU_DECODE
	snmplib_debug(8, "PDU Error Status: %d\n", PDU->errstat);
#endif

	/* error index */
	bufp = asn_parse_int(bufp, Length,
	    &ASNType,
	    &PDU->errindex, sizeof(PDU->errindex));
	if (bufp == NULL)
	    ASN_PARSE_ERROR(NULL);

#ifdef DEBUG_PDU_DECODE
	snmplib_debug(8, "PDU Error Index: %d\n", PDU->errindex);
#endif

	break;
    }

    return (bufp);
}

/*
 * Add a null variable with the requested name to the end of the list of
 * variables for this pdu.
 */
void
snmp_add_null_var(struct snmp_pdu *pdu, oid * name, int name_length)
{
    struct variable_list *vars;
    struct variable_list *ptr;

    vars = snmp_var_new(name, name_length);
    if (vars == NULL) {
	perror("snmp_add_null_var:xmalloc");
	return;
    }
    if (pdu->variables == NULL) {
	pdu->variables = vars;
    } else {

	/* Insert at the end */
	for (ptr = pdu->variables;
	    ptr->next_variable;
	    ptr = ptr->next_variable)
	    /*EXIT */ ;
	ptr->next_variable = vars;
    }

    return;
}