ndhc/duiaid.c
Nicholas J. Kain 8db8c5589d Replace CMake with GNU Make.
There was previously support for both build systems, but ndhc is
undemanding and there is no point in maintaining a complex
CMake build.
2022-01-22 18:39:41 -05:00

220 lines
7.4 KiB
C

/* duiaid.c - DUID/IAID storage and generation for clientids
*
* Copyright 2014-2018 Nicholas J. Kain <njkain at gmail dot com>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* - Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
*
* - 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.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "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 COPYRIGHT HOLDER OR CONTRIBUTORS 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.
*/
#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <arpa/inet.h>
#include <fcntl.h>
#include <limits.h>
#include <errno.h>
#include "nk/log.h"
#include "nk/random.h"
#include "nk/io.h"
#include "duiaid.h"
#include "ndhc.h"
static void get_duid_path(char *duidfile, size_t dlen)
{
int splen = snprintf(duidfile, dlen, "%s/DUID", state_dir);
if (splen < 0)
suicide("%s: snprintf failed; return=%d", __func__, splen);
if ((size_t)splen >= dlen)
suicide("%s: snprintf dest buffer too small %d >= %zu",
__func__, splen, sizeof dlen);
}
static void get_iaid_path(char *iaidfile, size_t ilen,
const uint8_t hwaddr[static 6], size_t hwaddrlen)
{
if (hwaddrlen != 6)
suicide("%s: Hardware address length=%zu != 6 bytes",
__func__, hwaddrlen);
int splen = snprintf
(iaidfile, ilen,
"%s/IAID-%2.2x:%2.2x:%2.2x:%2.2x:%2.2x:%2.2x",
state_dir, hwaddr[0], hwaddr[1], hwaddr[2],
hwaddr[3], hwaddr[4], hwaddr[5]);
if (splen < 0)
suicide("%s: snprintf failed; return=%d", __func__, splen);
if ((size_t)splen >= ilen)
suicide("%s: snprintf dest buffer too small %d >= %zu",
__func__, splen, sizeof ilen);
}
static int open_duidfile_read(void)
{
char duidfile[PATH_MAX];
get_duid_path(duidfile, sizeof duidfile);
int fd = open(duidfile, O_RDONLY, 0);
if (fd < 0) {
log_line("Failed to open duidfile '%s' for reading: %s",
duidfile, strerror(errno));
}
return fd;
}
static int open_duidfile_write(void)
{
char duidfile[PATH_MAX];
get_duid_path(duidfile, sizeof duidfile);
int fd = open(duidfile, O_WRONLY|O_TRUNC|O_CREAT, 0644);
if (fd < 0)
suicide("Failed to open duidfile '%s' for writing: %s",
duidfile, strerror(errno));
return fd;
}
static int open_iaidfile_read(const uint8_t hwaddr[static 6], size_t hwaddrlen)
{
char iaidfile[PATH_MAX];
get_iaid_path(iaidfile, sizeof iaidfile, hwaddr, hwaddrlen);
int fd = open(iaidfile, O_RDONLY, 0);
if (fd < 0) {
log_line("Failed to open iaidfile '%s' for reading: %s",
iaidfile, strerror(errno));
}
return fd;
}
static int open_iaidfile_write(const uint8_t hwaddr[static 6],
size_t hwaddrlen)
{
char iaidfile[PATH_MAX];
get_iaid_path(iaidfile, sizeof iaidfile, hwaddr, hwaddrlen);
int fd = open(iaidfile, O_WRONLY|O_TRUNC|O_CREAT, 0644);
if (fd < 0)
suicide("Failed to open iaidfile '%s' for writing: %s",
iaidfile, strerror(errno));
return fd;
}
// We use DUID-UUID (RFC6355)
// It is a 16-bit type=4 in network byte order followed by a 128-byte UUID.
// RFC6355 specifies a RFC4122 UUID, but I simply use a 128-byte random
// value, as the complexity of RFC4122 UUID generation is completely
// unwarranted for DHCPv4.
static size_t generate_duid(struct nk_random_state *s,
char *dest, size_t dlen)
{
const size_t tlen = sizeof(uint16_t) + 4 * sizeof(uint32_t);
if (dlen < tlen)
suicide("%s: dlen < %zu", __func__, tlen);
size_t off = 0;
uint16_t typefield = htons(4);
memcpy(dest+off, &typefield, sizeof typefield);
off += sizeof typefield;
for (size_t i = 0; i < 4; ++i) {
uint32_t r32 = nk_random_u32(s);
memcpy(dest+off, &r32, sizeof r32);
off += sizeof r32;
}
return off;
}
// RFC6355 specifies the IAID as a 32-bit value that uniquely identifies
// a hardware link for a given host.
static size_t generate_iaid(struct nk_random_state *s,
char *dest, size_t dlen)
{
if (dlen < sizeof(uint32_t))
suicide("%s: dlen < %zu", __func__, sizeof(uint32_t));
size_t off = 0;
uint32_t r32 = nk_random_u32(s);
memcpy(dest+off, &r32, sizeof r32);
off += sizeof r32;
return off;
}
// Failures are all fatal.
void get_clientid(struct client_state_t *cs,
struct client_config_t *cc)
{
if (cc->clientid_len > 0)
return;
char iaid[sizeof cc->clientid];
char duid[sizeof cc->clientid];
size_t iaid_len;
size_t duid_len;
int fd = open_iaidfile_read(cc->arp, sizeof cc->arp);
if (fd < 0) {
iaid_len = generate_iaid(&cs->rnd_state, iaid, sizeof iaid);
fd = open_iaidfile_write(cc->arp, sizeof cc->arp);
ssize_t r = safe_write(fd, iaid, iaid_len);
if (r < 0 || (size_t)r != iaid_len)
suicide("%s: (%s) failed to write generated IAID.",
cc->interface, __func__);
} else {
ssize_t r = safe_read(fd, iaid, sizeof iaid);
if (r < 0)
suicide("%s: (%s) failed to read IAID from file",
cc->interface, __func__);
iaid_len = (size_t)r;
}
close(fd);
fd = open_duidfile_read();
if (fd < 0) {
duid_len = generate_duid(&cs->rnd_state, duid, sizeof duid);
fd = open_duidfile_write();
ssize_t r = safe_write(fd, duid, duid_len);
if (r < 0 || (size_t)r != duid_len)
suicide("%s: (%s) failed to write generated DUID.",
cc->interface, __func__);
} else {
ssize_t r = safe_read(fd, duid, sizeof duid);
if (r < 0)
suicide("%s: (%s) failed to read DUID from file",
cc->interface, __func__);
duid_len = (size_t)r;
}
close(fd);
const uint8_t cid_type = 255;
size_t cdl = sizeof cid_type + iaid_len + duid_len;
if (cdl > sizeof cc->clientid)
suicide("%s: (%s) clientid length %zu > %zu",
cc->interface, __func__, cdl, sizeof cc->clientid);
uint8_t cid_len = 0;
memcpy(cc->clientid + cid_len, &cid_type, sizeof cid_type);
cid_len += sizeof cid_type;
memcpy(cc->clientid + cid_len, iaid, iaid_len);
cid_len += iaid_len;
memcpy(cc->clientid + cid_len, duid, duid_len);
cid_len += duid_len;
cc->clientid_len = cid_len;
}