inet_ntop.c

/*	$OpenBSD: inet_ntop.c,v 1.9 2014/02/05 14:20:43 millert Exp $	*/

/*
 * SPDX-License-Identifier: ISC
 *
 * Copyright (c) 1996 by Internet Software Consortium.
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM DISCLAIMS
 * ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE
 * CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT, 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.
 */

#include <config.h>

#if !defined(HAVE_INET_NTOP)

#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <arpa/nameser.h>
#include <string.h>
#include <errno.h>
#include <stdio.h>

#include <sudo_compat.h>

#ifndef EAFNOSUPPORT
# define EAFNOSUPPORT EINVAL
#endif

#ifndef NS_IN6ADDRSZ
# ifdef IN6ADDRSZ
#  define NS_IN6ADDRSZ IN6ADDRSZ
# else
#  define NS_IN6ADDRSZ 16
# endif
#endif
#ifndef NS_INT16SZ
# ifdef INT16SZ
#  define NS_INT16SZ INT16SZ
# else
#  define NS_INT16SZ 2
# endif
#endif

/*
 * WARNING: Don't even consider trying to compile this on a system where
 * sizeof(int) < 4.  sizeof(int) > 4 is fine; all the world's not a VAX.
 */

/* const char *
 * inet_ntop4(src, dst, size)
 *	format an IPv4 address, more or less like inet_ntoa()
 * return:
 *	`dst' (as a const)
 * notes:
 *	(1) uses no statics
 *	(2) takes a unsigned char* not an in_addr as input
 * author:
 *	Paul Vixie, 1996.
 */
static const char *
inet_ntop4(const unsigned char * restrict src, char * restrict dst, socklen_t size)
{
	const char fmt[] = "%u.%u.%u.%u";
	int len;

	len = snprintf(dst, size, fmt, src[0], src[1], src[2], src[3]);
	if (len < 0 || (socklen_t)len >= size) {
		errno = ENOSPC;
		return (NULL);
	}
	return (dst);
}

#ifdef HAVE_STRUCT_IN6_ADDR
/* const char *
 * inet_ntop6(src, dst, size)
 *	convert IPv6 binary address into presentation (printable) format
 * author:
 *	Paul Vixie, 1996.
 */
static const char *
inet_ntop6(const unsigned char * restrict src, char * restrict dst, socklen_t size)
{
	/*
	 * Note that int32_t and int16_t need only be "at least" large enough
	 * to contain a value of the specified size.  On some systems, like
	 * Crays, there is no such thing as an integer variable with 16 bits.
	 * Keep this in mind if you think this function should have been coded
	 * to use pointer overlays.  All the world's not a VAX.
	 */
	char *cp, *ep;
	struct { int base, len; } best, cur;
	unsigned int words[NS_IN6ADDRSZ / NS_INT16SZ];
	int i;
	int advance;

	/*
	 * Preprocess:
	 *	Copy the input (bytewise) array into a wordwise array.
	 *	Find the longest run of 0x00's in src[] for :: shorthanding.
	 */
	memset(words, 0, sizeof(words));
	for (i = 0; i < NS_IN6ADDRSZ; i++)
		words[i / 2] |= (src[i] << ((1 - (i & 1)) << 3));
	best.base = -1;
	best.len = 0;
	cur.base = -1;
	cur.len = 0;
	for (i = 0; i < (NS_IN6ADDRSZ / NS_INT16SZ); i++) {
		if (words[i] == 0) {
			if (cur.base == -1)
				cur.base = i, cur.len = 1;
			else
				cur.len++;
		} else {
			if (cur.base != -1) {
				if (best.base == -1 || cur.len > best.len)
					best = cur;
				cur.base = -1;
			}
		}
	}
	if (cur.base != -1) {
		if (best.base == -1 || cur.len > best.len)
			best = cur;
	}
	if (best.base != -1 && best.len < 2)
		best.base = -1;

	/*
	 * Format the result.
	 */
	cp = dst;
	ep = dst + size;
	for (i = 0; i < (NS_IN6ADDRSZ / NS_INT16SZ) && cp < ep; i++) {
		/* Are we inside the best run of 0x00's? */
		if (best.base != -1 && i >= best.base &&
		    i < (best.base + best.len)) {
			if (i == best.base) {
				if (cp + 1 >= ep) {
					errno = ENOSPC;
					return (NULL);
				}
				*cp++ = ':';
			}
			continue;
		}
		/* Are we following an initial run of 0x00s or any real hex? */
		if (i != 0) {
			if (cp + 1 >= ep) {
				errno = ENOSPC;
				return (NULL);
			}
			*cp++ = ':';
		}
		/* Is this address an encapsulated IPv4? */
		if (i == 6 && best.base == 0 &&
		    (best.len == 6 ||
		    (best.len == 7 && words[7] != 0x0001) ||
		    (best.len == 5 && words[5] == 0xffff))) {
			if (!inet_ntop4(src + 12, cp, (socklen_t)(ep - cp)))
				return (NULL);
			cp += strlen(cp);
			break;
		}
		advance = snprintf(cp, (size_t)(ep - cp), "%x", words[i]);
		if (advance <= 0 || advance >= ep - cp) {
			errno = ENOSPC;
			return (NULL);
		}
		cp += advance;
	}
	/* Was it a trailing run of 0x00's? */
	if (best.base != -1 &&
	    (best.base + best.len) == (NS_IN6ADDRSZ / NS_INT16SZ)) {
		if (cp + 1 >= ep) {
			errno = ENOSPC;
			return (NULL);
		}
		*cp++ = ':';
	}
	if (cp + 1 >= ep) {
		errno = ENOSPC;
		return (NULL);
	}
	*cp++ = '\0';

	return (dst);
}
#endif /* HAVE_STRUCT_IN6_ADDR */

/* const char *
 * inet_ntop(af, src, dst, size)
 *	convert a network format address to presentation format.
 * return:
 *	pointer to presentation format address (`dst'), or NULL (see errno).
 * author:
 *	Paul Vixie, 1996.
 */
const char *
sudo_inet_ntop(int af, const void * restrict src, char * restrict dst, socklen_t size)
{
	switch (af) {
	case AF_INET:
		return (inet_ntop4(src, dst, size));
#ifdef HAVE_STRUCT_IN6_ADDR
	case AF_INET6:
		return (inet_ntop6(src, dst, size));
#endif
	default:
		errno = EAFNOSUPPORT;
		return (NULL);
	}
	/* NOTREACHED */
}

#endif /* !HAVE_INET_NTOP */