freebsd-dev/usr.sbin/ctld/chap.c

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/*-
* Copyright (c) 2014 The FreeBSD Foundation
* All rights reserved.
*
* This software was developed by Edward Tomasz Napierala under sponsorship
* from the FreeBSD Foundation.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. 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 AUTHOR 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 AUTHOR 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 <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include <assert.h>
#include <stdlib.h>
#include <string.h>
#include <netinet/in.h>
#include <resolv.h>
#include <md5.h>
#include "ctld.h"
static void
chap_compute_md5(const char id, const char *secret,
const void *challenge, size_t challenge_len, void *response,
size_t response_len)
{
MD5_CTX ctx;
assert(response_len == CHAP_DIGEST_LEN);
MD5Init(&ctx);
MD5Update(&ctx, &id, sizeof(id));
MD5Update(&ctx, secret, strlen(secret));
MD5Update(&ctx, challenge, challenge_len);
MD5Final(response, &ctx);
}
static int
chap_hex2int(const char hex)
{
switch (hex) {
case '0':
return (0x00);
case '1':
return (0x01);
case '2':
return (0x02);
case '3':
return (0x03);
case '4':
return (0x04);
case '5':
return (0x05);
case '6':
return (0x06);
case '7':
return (0x07);
case '8':
return (0x08);
case '9':
return (0x09);
case 'a':
case 'A':
return (0x0a);
case 'b':
case 'B':
return (0x0b);
case 'c':
case 'C':
return (0x0c);
case 'd':
case 'D':
return (0x0d);
case 'e':
case 'E':
return (0x0e);
case 'f':
case 'F':
return (0x0f);
default:
return (-1);
}
}
static int
chap_b642bin(const char *b64, void **binp, size_t *bin_lenp)
{
char *bin;
int b64_len, bin_len;
b64_len = strlen(b64);
bin_len = (b64_len + 3) / 4 * 3;
bin = calloc(bin_len, 1);
if (bin == NULL)
log_err(1, "calloc");
bin_len = b64_pton(b64, bin, bin_len);
if (bin_len < 0) {
log_warnx("malformed base64 variable");
free(bin);
return (-1);
}
*binp = bin;
*bin_lenp = bin_len;
return (0);
}
/*
* XXX: Review this _carefully_.
*/
static int
chap_hex2bin(const char *hex, void **binp, size_t *bin_lenp)
{
int i, hex_len, nibble;
bool lo = true; /* As opposed to 'hi'. */
char *bin;
size_t bin_off, bin_len;
if (strncasecmp(hex, "0b", strlen("0b")) == 0)
return (chap_b642bin(hex + 2, binp, bin_lenp));
if (strncasecmp(hex, "0x", strlen("0x")) != 0) {
log_warnx("malformed variable, should start with \"0x\""
" or \"0b\"");
return (-1);
}
hex += strlen("0x");
hex_len = strlen(hex);
if (hex_len < 1) {
log_warnx("malformed variable; doesn't contain anything "
"but \"0x\"");
return (-1);
}
bin_len = hex_len / 2 + hex_len % 2;
bin = calloc(bin_len, 1);
if (bin == NULL)
log_err(1, "calloc");
bin_off = bin_len - 1;
for (i = hex_len - 1; i >= 0; i--) {
nibble = chap_hex2int(hex[i]);
if (nibble < 0) {
log_warnx("malformed variable, invalid char \"%c\"",
hex[i]);
free(bin);
return (-1);
}
assert(bin_off < bin_len);
if (lo) {
bin[bin_off] = nibble;
lo = false;
} else {
bin[bin_off] |= nibble << 4;
bin_off--;
lo = true;
}
}
*binp = bin;
*bin_lenp = bin_len;
return (0);
}
#ifdef USE_BASE64
static char *
chap_bin2hex(const char *bin, size_t bin_len)
{
unsigned char *b64, *tmp;
size_t b64_len;
b64_len = (bin_len + 2) / 3 * 4 + 3; /* +2 for "0b", +1 for '\0'. */
b64 = malloc(b64_len);
if (b64 == NULL)
log_err(1, "malloc");
tmp = b64;
tmp += sprintf(tmp, "0b");
b64_ntop(bin, bin_len, tmp, b64_len - 2);
return (b64);
}
#else
static char *
chap_bin2hex(const char *bin, size_t bin_len)
{
unsigned char *hex, *tmp, ch;
size_t hex_len;
size_t i;
hex_len = bin_len * 2 + 3; /* +2 for "0x", +1 for '\0'. */
hex = malloc(hex_len);
if (hex == NULL)
log_err(1, "malloc");
tmp = hex;
tmp += sprintf(tmp, "0x");
for (i = 0; i < bin_len; i++) {
ch = bin[i];
tmp += sprintf(tmp, "%02x", ch);
}
return (hex);
}
#endif /* !USE_BASE64 */
struct chap *
chap_new(void)
{
struct chap *chap;
chap = calloc(sizeof(*chap), 1);
if (chap == NULL)
log_err(1, "calloc");
/*
* Generate the challenge.
*/
arc4random_buf(chap->chap_challenge, sizeof(chap->chap_challenge));
arc4random_buf(&chap->chap_id, sizeof(chap->chap_id));
return (chap);
}
char *
chap_get_id(const struct chap *chap)
{
char *chap_i;
int ret;
ret = asprintf(&chap_i, "%d", chap->chap_id);
if (ret < 0)
log_err(1, "asprintf");
return (chap_i);
}
char *
chap_get_challenge(const struct chap *chap)
{
char *chap_c;
chap_c = chap_bin2hex(chap->chap_challenge,
sizeof(chap->chap_challenge));
return (chap_c);
}
static int
chap_receive_bin(struct chap *chap, void *response, size_t response_len)
{
if (response_len != sizeof(chap->chap_response)) {
log_debugx("got CHAP response with invalid length; "
"got %zd, should be %zd",
response_len, sizeof(chap->chap_response));
return (1);
}
memcpy(chap->chap_response, response, response_len);
return (0);
}
int
chap_receive(struct chap *chap, const char *response)
{
void *response_bin;
size_t response_bin_len;
int error;
error = chap_hex2bin(response, &response_bin, &response_bin_len);
if (error != 0) {
log_debugx("got incorrectly encoded CHAP response \"%s\"",
response);
return (1);
}
error = chap_receive_bin(chap, response_bin, response_bin_len);
free(response_bin);
return (error);
}
int
chap_authenticate(struct chap *chap, const char *secret)
{
char expected_response[CHAP_DIGEST_LEN];
chap_compute_md5(chap->chap_id, secret,
chap->chap_challenge, sizeof(chap->chap_challenge),
expected_response, sizeof(expected_response));
if (memcmp(chap->chap_response,
expected_response, sizeof(expected_response)) != 0) {
return (-1);
}
return (0);
}
void
chap_delete(struct chap *chap)
{
free(chap);
}
struct rchap *
rchap_new(const char *secret)
{
struct rchap *rchap;
rchap = calloc(sizeof(*rchap), 1);
if (rchap == NULL)
log_err(1, "calloc");
rchap->rchap_secret = checked_strdup(secret);
return (rchap);
}
static void
rchap_receive_bin(struct rchap *rchap, const unsigned char id,
const void *challenge, size_t challenge_len)
{
rchap->rchap_id = id;
rchap->rchap_challenge = calloc(challenge_len, 1);
if (rchap->rchap_challenge == NULL)
log_err(1, "calloc");
memcpy(rchap->rchap_challenge, challenge, challenge_len);
rchap->rchap_challenge_len = challenge_len;
}
int
rchap_receive(struct rchap *rchap, const char *id, const char *challenge)
{
unsigned char id_bin;
void *challenge_bin;
size_t challenge_bin_len;
int error;
id_bin = strtoul(id, NULL, 10);
error = chap_hex2bin(challenge, &challenge_bin, &challenge_bin_len);
if (error != 0) {
log_debugx("got incorrectly encoded CHAP challenge \"%s\"",
challenge);
return (1);
}
rchap_receive_bin(rchap, id_bin, challenge_bin, challenge_bin_len);
free(challenge_bin);
return (0);
}
static void
rchap_get_response_bin(struct rchap *rchap,
void **responsep, size_t *response_lenp)
{
void *response_bin;
size_t response_bin_len = CHAP_DIGEST_LEN;
response_bin = calloc(response_bin_len, 1);
if (response_bin == NULL)
log_err(1, "calloc");
chap_compute_md5(rchap->rchap_id, rchap->rchap_secret,
rchap->rchap_challenge, rchap->rchap_challenge_len,
response_bin, response_bin_len);
*responsep = response_bin;
*response_lenp = response_bin_len;
}
char *
rchap_get_response(struct rchap *rchap)
{
void *response;
size_t response_len;
char *chap_r;
rchap_get_response_bin(rchap, &response, &response_len);
chap_r = chap_bin2hex(response, response_len);
free(response);
return (chap_r);
}
void
rchap_delete(struct rchap *rchap)
{
free(rchap->rchap_secret);
free(rchap->rchap_challenge);
free(rchap);
}