dhcp_options.c   [plain text]

/*
 * Copyright (c) 2002-2007 Apple Inc. All rights reserved.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
 * 
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. The rights granted to you under the License
 * may not be used to create, or enable the creation or redistribution of,
 * unlawful or unlicensed copies of an Apple operating system, or to
 * circumvent, violate, or enable the circumvention or violation of, any
 * terms of an Apple operating system software license agreement.
 * 
 * Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this file.
 * 
 * The Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
 * Please see the License for the specific language governing rights and
 * limitations under the License.
 * 
 * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
 */
/*
 * dhcp_options.c
 * - routines to parse and access dhcp options
 *   and create new dhcp option areas
 * - handles overloaded areas as well as vendor-specific options
 *   that are encoded using the RFC 2132 encoding
 */

/* 
 * Modification History
 *
 * March 15, 2002	Dieter Siegmund (dieter@apple)
 * - imported from bootp project
 */

#include <string.h>
#include <sys/types.h>
#include <sys/param.h>
#include <netinet/in.h>
#include <sys/malloc.h>
#include <libkern/libkern.h>

#include <netinet/dhcp.h>
#include <netinet/dhcp_options.h>

#ifdef	DHCP_DEBUG
#define	dprintf(x) printf x;
#else	/* !DHCP_DEBUG */
#define	dprintf(x)
#endif	/* DHCP_DEBUG */

static __inline__ void
my_free(void * ptr)
{
    _FREE(ptr, M_TEMP);
}

static __inline__ void *
my_malloc(int size)
{
    void * data;
    MALLOC(data, void *, size, M_TEMP, M_WAITOK);
    return (data);
}

static __inline__ void *
my_realloc(void * oldptr, int oldsize, int newsize)
{
    void * data;

    MALLOC(data, void *, newsize, M_TEMP, M_WAITOK);
    bcopy(oldptr, data, oldsize);
    my_free(oldptr);
    return (data);
}

/*
 * Functions: ptrlist_*
 * Purpose:
 *   A dynamically growable array of pointers.
 */

#define PTRLIST_NUMBER		16

static void
ptrlist_init(ptrlist_t * list)
{
    bzero(list, sizeof(*list));
    return;
}

static void
ptrlist_free(ptrlist_t * list)
{
    if (list->array)
	my_free(list->array);
    ptrlist_init(list);
    return;
}

static int
ptrlist_count(ptrlist_t * list)
{
    if (list == NULL || list->array == NULL)
	return (0);

    return (list->count);
}

static const void *
ptrlist_element(ptrlist_t * list, int i)
{
    if (list->array == NULL)
	return (NULL);
    if (i < list->count)
	return (list->array[i]);
    return (NULL);
}


static boolean_t
ptrlist_grow(ptrlist_t * list)
{
    if (list->array == NULL) {
	if (list->size == 0)
	    list->size = PTRLIST_NUMBER;
	list->count = 0;
	list->array = my_malloc(sizeof(*list->array) * list->size);
    }
    else if (list->size == list->count) {
	dprintf(("doubling %d to %d\n", list->size, list->size * 2));
	list->array = my_realloc(list->array, 
				 sizeof(*list->array) * list->size,
				 sizeof(*list->array) * list->size * 2);
	list->size *= 2;
    }
    if (list->array == NULL)
	return (FALSE);
    return (TRUE);
}

static boolean_t
ptrlist_add(ptrlist_t * list, const void * element)
{
    if (ptrlist_grow(list) == FALSE)
	return (FALSE);

    list->array[list->count++] = element;
    return (TRUE);
}

/* concatenates extra onto list */
static boolean_t
ptrlist_concat(ptrlist_t * list, ptrlist_t * extra)
{
    if (extra->count == 0)
	return (TRUE);

    if ((extra->count + list->count) > list->size) {
	int old_size = list->size;

	list->size = extra->count + list->count;
	if (list->array == NULL)
	    list->array = my_malloc(sizeof(*list->array) * list->size);
	else
	    list->array = my_realloc(list->array, old_size,
				     sizeof(*list->array) * list->size);
    }
    if (list->array == NULL)
	return (FALSE);
    bcopy(extra->array, list->array + list->count, 
	  extra->count * sizeof(*list->array));
    list->count += extra->count;
    return (TRUE);
}


/*
 * Functions: dhcpol_* 
 *
 * Purpose:
 *   Routines to parse/access existing options buffers.
 */
boolean_t
dhcpol_add(dhcpol_t * list, const void * element)
{
    return (ptrlist_add((ptrlist_t *)list, element));
}

int
dhcpol_count(dhcpol_t * list)
{
    return (ptrlist_count((ptrlist_t *)list));
}

const void *
dhcpol_element(dhcpol_t * list, int i)
{
    return (ptrlist_element((ptrlist_t *)list, i));
}

void
dhcpol_init(dhcpol_t * list)
{
    ptrlist_init((ptrlist_t *)list);
}

void
dhcpol_free(dhcpol_t * list)
{
    ptrlist_free((ptrlist_t *)list);
}

boolean_t
dhcpol_concat(dhcpol_t * list, dhcpol_t * extra)
{
    return (ptrlist_concat((ptrlist_t *)list, (ptrlist_t *)extra));
}

/*
 * Function: dhcpol_parse_buffer
 *
 * Purpose:
 *   Parse the given buffer into DHCP options, returning the
 *   list of option pointers in the given dhcpol_t.
 *   Parsing continues until we hit the end of the buffer or
 *   the end tag.
 */
boolean_t
dhcpol_parse_buffer(dhcpol_t * list, const void * buffer, int length)
{
    int			len;
    const uint8_t *	scan;
    uint8_t		tag;

    dhcpol_init(list);

    len = length;
    tag = dhcptag_pad_e;
    for (scan = (const uint8_t *)buffer; tag != dhcptag_end_e && len > 0; ) {

	tag = scan[DHCP_TAG_OFFSET];

	switch (tag) {
	  case dhcptag_end_e:
	      /* remember that it was terminated */
	      dhcpol_add(list, scan);
	      scan++;
	      len--;
	      break;
	  case dhcptag_pad_e: /* ignore pad */
	      scan++;
	      len--;
	      break;
	  default: {
	      uint8_t	option_len = scan[DHCP_LEN_OFFSET];
	    
	      dhcpol_add(list, scan);
	      len -= (option_len + 2);
	      scan += (option_len + 2);
	      break;
	  }
	}
    }
    if (len < 0) {
	/* ran off the end */
	dprintf(("dhcp_options: parse failed near tag %d", tag));
	dhcpol_free(list);
	return (FALSE);
    }
    return (TRUE);
}

/*
 * Function: dhcpol_find
 *
 * Purpose:
 *   Finds the first occurence of the given option, and returns its
 *   length and the option data pointer.
 *
 *   The optional start parameter allows this function to 
 *   return the next start point so that successive
 *   calls will retrieve the next occurence of the option.
 *   Before the first call, *start should be set to 0.
 */
const void *
dhcpol_find(dhcpol_t * list, int tag, int * len_p, int * start)
{
    int 	i = 0;

    if (tag == dhcptag_end_e || tag == dhcptag_pad_e)
	return (NULL);

    if (start)
	i = *start;

    for (; i < dhcpol_count(list); i++) {
	const uint8_t * 	option = dhcpol_element(list, i);
	
	if (option[DHCP_TAG_OFFSET] == tag) {
	    if (len_p)
		*len_p = option[DHCP_LEN_OFFSET];
	    if (start)
		*start = i + 1;
	    return (option + DHCP_OPTION_OFFSET);
	}
    }
    return (NULL);
}

#if 0
/*
 * Function: dhcpol_get
 * 
 * Purpose:
 *   Accumulate all occurences of the given option into a
 *   malloc'd buffer, and return its length.  Used to get
 *   all occurrences of a particular option in a single
 *   data area.
 * Note:
 *   Use _FREE(val, M_TEMP) to free the returned data area.
 */
void *
dhcpol_get(dhcpol_t * list, int tag, int * len_p)
{
    int 	i;
    char *	data = NULL;
    int		data_len = 0;

    if (tag == dhcptag_end_e || tag == dhcptag_pad_e)
	return (NULL);

    for (i = 0; i < dhcpol_count(list); i++) {
	const uint8_t * 	option = dhcpol_element(list, i);
	
	if (option[DHCP_TAG_OFFSET] == tag) {
	    int len = option[DHCP_LEN_OFFSET];

	    if (data_len == 0) {
		data = my_malloc(len);
	    }
	    else {
		data = my_realloc(data, data_len, data_len + len);
	    }
		FIX ME: test data NULL
	    bcopy(option + DHCP_OPTION_OFFSET, data + data_len, len);
	    data_len += len;
	}
    }
    *len_p = data_len;
    return (data);
}
#endif

/*
 * Function: dhcpol_parse_packet
 *
 * Purpose:
 *    Parse the option areas in the DHCP packet.
 *    Verifies that the packet has the right magic number,
 *    then parses and accumulates the option areas.
 *    First the pkt->dp_options is parsed.  If that contains
 *    the overload option, it parses pkt->dp_file if specified,
 *    then parses pkt->dp_sname if specified.
 */
boolean_t
dhcpol_parse_packet(dhcpol_t * options, const struct dhcp * pkt, int len)
{
    char		rfc_magic[4] = RFC_OPTIONS_MAGIC;

    dhcpol_init(options);	/* make sure it's empty */

    if (len < (sizeof(*pkt) + RFC_MAGIC_SIZE)) {
	dprintf(("dhcp_options: packet is too short: %d < %d\n",
		 len, (int)sizeof(*pkt) + RFC_MAGIC_SIZE));
	return (FALSE);
    }
    if (bcmp(pkt->dp_options, rfc_magic, RFC_MAGIC_SIZE)) {
	dprintf(("dhcp_options: missing magic number\n"));
	return (FALSE);
    }
    if (dhcpol_parse_buffer(options, pkt->dp_options + RFC_MAGIC_SIZE,
			    len - sizeof(*pkt) - RFC_MAGIC_SIZE) == FALSE)
	return (FALSE);
    { /* get overloaded options */
	const uint8_t *	overload;
	int		overload_len;

	overload = dhcpol_find(options, dhcptag_option_overload_e, 
			       &overload_len, NULL);
	if (overload && overload_len == 1) { /* has overloaded options */
	    dhcpol_t	extra;
	    
	    dhcpol_init(&extra);
	    if (*overload == DHCP_OVERLOAD_FILE
		|| *overload == DHCP_OVERLOAD_BOTH) {
		if (dhcpol_parse_buffer(&extra, pkt->dp_file, 
					sizeof(pkt->dp_file))) {
		    dhcpol_concat(options, &extra);
		    dhcpol_free(&extra);
		}
	    }
	    if (*overload == DHCP_OVERLOAD_SNAME
		|| *overload == DHCP_OVERLOAD_BOTH) {
		if (dhcpol_parse_buffer(&extra, pkt->dp_sname, 
					sizeof(pkt->dp_sname))) {
		    dhcpol_concat(options, &extra);
		    dhcpol_free(&extra);
		}
	    }
	}
    }
    return (TRUE);
}

/*
 * Module: dhcpoa
 *
 * Purpose:
 *   Types and functions to create new dhcp option areas.
 */

/*
 * Function: dhcpoa_{init_common, init_no_end, init}
 *
 * Purpose:
 *   Initialize an option area structure so that it can be used
 *   in calling the dhcpoa_* routines.
 */
static void
dhcpoa_init_common(dhcpoa_t * oa_p, void * buffer, int size, int reserve)
{
    bzero(oa_p, sizeof(*oa_p));
    oa_p->oa_buffer = buffer;
    oa_p->oa_size = size;
    oa_p->oa_reserve = reserve;
}

void
dhcpoa_init_no_end(dhcpoa_t * oa_p, void * buffer, int size)
{
    dhcpoa_init_common(oa_p, buffer, size, 0);
    return;
}

int
dhcpoa_size(dhcpoa_t * oa_p)
{
    return (oa_p->oa_size);
}

void
dhcpoa_init(dhcpoa_t * oa_p, void * buffer, int size)
{
    /* initialize the area, reserve space for the end tag */
    dhcpoa_init_common(oa_p, buffer, size, 1);
    return;
}
/*
 * Function: dhcpoa_add
 *
 * Purpose:
 *   Add an option to the option area.
 */
dhcpoa_ret_t
dhcpoa_add(dhcpoa_t * oa_p, dhcptag_t tag, int len, const void * option)
{
    if (len > DHCP_OPTION_SIZE_MAX) {
	dprintf(("tag %d option %d > %d\n", tag, len, DHCP_OPTION_SIZE_MAX));
	return (dhcpoa_failed_e);
    }

    if (oa_p->oa_end_tag) {
	dprintf(("attempt to add data after end tag\n"));
	return (dhcpoa_failed_e);
    }

    switch (tag) {
      case dhcptag_end_e:
	if ((oa_p->oa_offset + 1) > oa_p->oa_size) {
	    /* this can't happen since we're careful to leave space */
	    dprintf(("can't add end tag %d > %d\n",
		     oa_p->oa_offset + oa_p->oa_reserve, oa_p->oa_size));
	    return (dhcpoa_failed_e);
	}
	((uint8_t *)oa_p->oa_buffer)[oa_p->oa_offset + DHCP_TAG_OFFSET] = tag;
	oa_p->oa_offset++;
	oa_p->oa_end_tag = 1;
	break;

      case dhcptag_pad_e:
	/* 1 for pad tag */
	if ((oa_p->oa_offset + oa_p->oa_reserve + 1) > oa_p->oa_size) {
	    dprintf(("can't add pad tag %d > %d\n",
		     oa_p->oa_offset + oa_p->oa_reserve + 1, oa_p->oa_size));
	    return (dhcpoa_full_e);
	}
	((uint8_t *)oa_p->oa_buffer)[oa_p->oa_offset + DHCP_TAG_OFFSET] = tag;
	oa_p->oa_offset++;
	break;

      default:
	/* 2 for tag/len */
	if ((oa_p->oa_offset + len + 2 + oa_p->oa_reserve) > oa_p->oa_size) {
	    dprintf(("can't add tag %d (%d > %d)\n", tag,
		     oa_p->oa_offset + len + 2 + oa_p->oa_reserve, 
		     oa_p->oa_size));
	    return (dhcpoa_full_e);
	}
	((uint8_t *)oa_p->oa_buffer)[oa_p->oa_offset + DHCP_TAG_OFFSET] = tag;
	((uint8_t *)oa_p->oa_buffer)[oa_p->oa_offset + DHCP_LEN_OFFSET] = (uint8_t)len;
	if (len) {
	    memcpy(oa_p->oa_buffer + (DHCP_OPTION_OFFSET + oa_p->oa_offset),
		   option, len);
	}
	oa_p->oa_offset += len + DHCP_OPTION_OFFSET;
	break;
    }
    oa_p->oa_option_count++;
    return (dhcpoa_success_e);
}

/*
 * Function: dhcpoa_add_dhcpmsg
 *
 * Purpose:
 *   Add a dhcp message option to the option area.
 */
dhcpoa_ret_t
dhcpoa_add_dhcpmsg(dhcpoa_t * oa_p, dhcp_msgtype_t msgtype)
{
    return (dhcpoa_add(oa_p, dhcptag_dhcp_message_type_e,
		       sizeof(msgtype), &msgtype));
}

int
dhcpoa_used(dhcpoa_t * oa_p)
{
    return (oa_p->oa_offset);
}

int
dhcpoa_freespace(dhcpoa_t * oa_p)
{
    int	freespace;

    freespace = oa_p->oa_size - oa_p->oa_offset - oa_p->oa_reserve;
    if (freespace < 0) {
	freespace = 0;
    }
    return (freespace);
}

int
dhcpoa_count(dhcpoa_t * oa_p)
{
    return (oa_p->oa_option_count);
}

void *
dhcpoa_buffer(dhcpoa_t * oa_p) 
{
    return (oa_p->oa_buffer);
}


#ifdef TEST_DHCP_OPTIONS
char test_empty[] = {
    99, 130, 83, 99,
    255,
};

char test_simple[] = {
    99, 130, 83, 99,
    1, 4, 255, 255, 252, 0,
    3, 4, 17, 202, 40, 1,
    255,
};

char test_vendor[] = {
    99, 130, 83, 99,
    1, 4, 255, 255, 252, 0,
    3, 4, 17, 202, 40, 1,
    43, 6, 1, 4, 1, 2, 3, 4,
    43, 6, 1, 4, 1, 2, 3, 4,
    255,
};

char test_no_end[] = {
    0x63, 0x82, 0x53, 0x63, 0x35, 0x01, 0x05, 0x36, 
    0x04, 0xc0, 0xa8, 0x01, 0x01, 0x33, 0x04, 0x80,
    0x00, 0x80, 0x00, 0x01, 0x04, 0xff, 0xff, 0xff,
    0x00, 0x03, 0x04, 0xc0, 0xa8, 0x01, 0x01, 0x06,
    0x0c, 0x18, 0x1a, 0xa3, 0x21, 0x18, 0x1a, 0xa3,
    0x20, 0x18, 0x5e, 0xa3, 0x21, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
};

char test_too_short[] = {
    0x1 
};
struct test {
    char * 		name;
    char *		data;
    int			len;
    boolean_t		result;
};

struct test tests[] = {
    { "empty", test_empty, sizeof(test_empty), TRUE },
    { "simple", test_simple, sizeof(test_simple), TRUE },
    { "vendor", test_vendor, sizeof(test_vendor), TRUE },
    { "no_end", test_no_end, sizeof(test_no_end), TRUE },
    { "too_short", test_too_short, sizeof(test_too_short), FALSE },
    { NULL, NULL, 0, FALSE },
};


static char buf[2048];

int
main()
{
    int 	i;
    dhcpol_t 	options;
    struct dhcp * pkt = (struct dhcp *)buf;

    dhcpol_init(&options);

    for (i = 0; tests[i].name; i++) {
	printf("\nTest %d: ", i);
	bcopy(tests[i].data, pkt->dp_options, tests[i].len);
	if (dhcpol_parse_packet(&options, pkt, 
				sizeof(*pkt) + tests[i].len)
	    != tests[i].result) {
	    printf("test '%s' FAILED\n", tests[i].name);
	}
	else {
	    printf("test '%s' PASSED\n", tests[i].name);
	}
	dhcpol_free(&options);
    }
    exit(0);
}
#endif /* TEST_DHCP_OPTIONS */