dhcp_options.c   [plain text]

/*
 * Copyright (c) 2002-2019 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 <netinet/dhcp.h>
#include <netinet/dhcp_options.h>

#ifndef TEST_DHCP_OPTIONS
#include <libkern/libkern.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;
}
#else
/*
 * To build:
 * xcrun -sdk macosx.internal cc -DTEST_DHCP_OPTIONS -o /tmp/dhcp_options dhcp_options.c -I ..
 */
#include <stdlib.h>
#include <unistd.h>
#include <stdio.h>
#define my_free free
#define my_malloc malloc
#define my_realloc(ptr, old_size, new_size) realloc(ptr, new_size)
#define dprintf(x) printf x;
#endif

/*
 * 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 > DHCP_TAG_OFFSET;) {
		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:
			if (len > DHCP_LEN_OFFSET) {
				uint8_t       option_len;

				option_len = scan[DHCP_LEN_OFFSET];
				dhcpol_add(list, scan);
				len -= (option_len + DHCP_OPTION_OFFSET);
				scan += (option_len + DHCP_OPTION_OFFSET);
			} else {
				len = -1;
			}
			break;
		}
	}
	if (len < 0) {
		/* ran off the end */
		dprintf(("dhcp_options: parse failed near tag %d\n", 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;
}

/*
 * 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;
}

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

char test_short[] = {
	99, 130, 83, 99,
	1,
};

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

struct test tests[] = {
	{ .name = "empty", .data = test_empty, .len = sizeof(test_empty), .result = TRUE },
	{ .name = "simple", .data = test_simple, .len = sizeof(test_simple), .result = TRUE },
	{ .name = "vendor", .data = test_vendor, .len = sizeof(test_vendor), .result = TRUE },
	{ .name = "no_end", .data = test_no_end, .len = sizeof(test_no_end), .result = TRUE },
	{ .name = "no magic", .data = test_no_magic, .len = sizeof(test_no_magic), .result = FALSE },
	{ .name = "short", .data = test_short, .len = sizeof(test_short), .result =  FALSE },
	{ .name = NULL, .data = NULL, .len = 0, .result = FALSE },
};


static char buf[2048];

int
main(void)
{
	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 */