faraphel/chrony
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions
chrony/ntp_auth.c
Miroslav Lichvar c1d56ede3f nts: rework update of NTP server address 
In the NTS-NTP client instance, maintain a local copy of the NTP address
instead of using a pointer to the NCR's address, which may change at
unexpected times.

Also, change the NNC_CreateInstance() to accept only the NTP port to
make it clear the initial NTP address is the same as the NTS-KE address
and to make it consistent with NNC_ChangeAddress(), which accepts only
one address.
2021-02-11 09:52:57 +01:00

494 lines
13 KiB
C
Raw Blame History

/*
chronyd/chronyc - Programs for keeping computer clocks accurate.
**********************************************************************
* Copyright (C) Miroslav Lichvar 2019-2020
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of version 2 of the GNU General Public License as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*
**********************************************************************
=======================================================================
NTP authentication
*/
#include "config.h"
#include "sysincl.h"
#include "keys.h"
#include "logging.h"
#include "memory.h"
#include "ntp_auth.h"
#include "ntp_ext.h"
#include "ntp_signd.h"
#include "nts_ntp.h"
#include "nts_ntp_client.h"
#include "nts_ntp_server.h"
#include "srcparams.h"
#include "util.h"
/* Structure to hold authentication configuration and state */
struct NAU_Instance_Record {
NTP_AuthMode mode; /* Authentication mode of NTP packets */
uint32_t key_id; /* Identifier of a symmetric key */
NNC_Instance nts; /* Client NTS state */
};
/* ================================================== */
static int
generate_symmetric_auth(uint32_t key_id, NTP_Packet *packet, NTP_PacketInfo *info)
{
int auth_len, max_auth_len;
if (info->length + NTP_MIN_MAC_LENGTH > sizeof (*packet)) {
DEBUG_LOG("Packet too long");
return 0;
}
/* Truncate long MACs in NTPv4 packets to allow deterministic parsing
of extension fields (RFC 7822) */
max_auth_len = (info->version == 4 ? NTP_MAX_V4_MAC_LENGTH : NTP_MAX_MAC_LENGTH) - 4;
max_auth_len = MIN(max_auth_len, sizeof (*packet) - info->length - 4);
auth_len = KEY_GenerateAuth(key_id, packet, info->length,
(unsigned char *)packet + info->length + 4, max_auth_len);
if (auth_len < NTP_MIN_MAC_LENGTH - 4) {
DEBUG_LOG("Could not generate auth data with key %"PRIu32, key_id);
return 0;
}
*(uint32_t *)((unsigned char *)packet + info->length) = htonl(key_id);
info->auth.mac.start = info->length;
info->auth.mac.length = 4 + auth_len;
info->auth.mac.key_id = key_id;
info->length += info->auth.mac.length;
return 1;
}
/* ================================================== */
static int
check_symmetric_auth(NTP_Packet *packet, NTP_PacketInfo *info)
{
int trunc_len;
if (info->auth.mac.length < NTP_MIN_MAC_LENGTH)
return 0;
trunc_len = info->version == 4 && info->auth.mac.length <= NTP_MAX_V4_MAC_LENGTH ?
NTP_MAX_V4_MAC_LENGTH : NTP_MAX_MAC_LENGTH;
if (!KEY_CheckAuth(info->auth.mac.key_id, packet, info->auth.mac.start,
(unsigned char *)packet + info->auth.mac.start + 4,
info->auth.mac.length - 4, trunc_len - 4))
return 0;
return 1;
}
/* ================================================== */
static int
is_zero_data(unsigned char *data, int length)
{
int i;
for (i = 0; i < length; i++)
if (data[i] != 0)
return 0;
return 1;
}
/* ================================================== */
static NAU_Instance
create_instance(NTP_AuthMode mode)
{
NAU_Instance instance;
instance = MallocNew(struct NAU_Instance_Record);
instance->mode = mode;
instance->key_id = INACTIVE_AUTHKEY;
instance->nts = NULL;
assert(sizeof (instance->key_id) == 4);
return instance;
}
/* ================================================== */
NAU_Instance
NAU_CreateNoneInstance(void)
{
return create_instance(NTP_AUTH_NONE);
}
/* ================================================== */
NAU_Instance
NAU_CreateSymmetricInstance(uint32_t key_id)
{
NAU_Instance instance = create_instance(NTP_AUTH_SYMMETRIC);
instance->key_id = key_id;
if (!KEY_KeyKnown(key_id))
LOG(LOGS_WARN, "Key %"PRIu32" is %s", key_id, "missing");
else if (!KEY_CheckKeyLength(key_id))
LOG(LOGS_WARN, "Key %"PRIu32" is %s", key_id, "too short");
return instance;
}
/* ================================================== */
NAU_Instance
NAU_CreateNtsInstance(IPSockAddr *nts_address, const char *name, uint16_t ntp_port)
{
NAU_Instance instance = create_instance(NTP_AUTH_NTS);
instance->nts = NNC_CreateInstance(nts_address, name, ntp_port);
return instance;
}
/* ================================================== */
void
NAU_DestroyInstance(NAU_Instance instance)
{
if (instance->mode == NTP_AUTH_NTS)
NNC_DestroyInstance(instance->nts);
Free(instance);
}
/* ================================================== */
int
NAU_IsAuthEnabled(NAU_Instance instance)
{
return instance->mode != NTP_AUTH_NONE;
}
/* ================================================== */
int
NAU_GetSuggestedNtpVersion(NAU_Instance instance)
{
/* If the MAC in NTPv4 packets would be truncated, prefer NTPv3 for
compatibility with older chronyd servers */
if (instance->mode == NTP_AUTH_SYMMETRIC &&
KEY_GetAuthLength(instance->key_id) + sizeof (instance->key_id) > NTP_MAX_V4_MAC_LENGTH)
return 3;
return NTP_VERSION;
}
/* ================================================== */
int
NAU_PrepareRequestAuth(NAU_Instance instance)
{
switch (instance->mode) {
case NTP_AUTH_NTS:
if (!NNC_PrepareForAuth(instance->nts))
return 0;
break;
default:
break;
}
return 1;
}
/* ================================================== */
int
NAU_GenerateRequestAuth(NAU_Instance instance, NTP_Packet *request, NTP_PacketInfo *info)
{
switch (instance->mode) {
case NTP_AUTH_NONE:
break;
case NTP_AUTH_SYMMETRIC:
if (!generate_symmetric_auth(instance->key_id, request, info))
return 0;
break;
case NTP_AUTH_NTS:
if (!NNC_GenerateRequestAuth(instance->nts, request, info))
return 0;
break;
default:
assert(0);
}
info->auth.mode = instance->mode;
return 1;
}
/* ================================================== */
int
NAU_ParsePacket(NTP_Packet *packet, NTP_PacketInfo *info)
{
int parsed, remainder, ef_length, ef_type;
unsigned char *data;
data = (void *)packet;
parsed = NTP_HEADER_LENGTH;
remainder = info->length - parsed;
info->ext_fields = 0;
/* Check if this is a plain NTP packet with no extension fields or MAC */
if (remainder <= 0)
return 1;
assert(remainder % 4 == 0);
/* In NTPv3 and older packets don't have extension fields. Anything after
the header is assumed to be a MAC. */
if (info->version <= 3) {
info->auth.mode = NTP_AUTH_SYMMETRIC;
info->auth.mac.start = parsed;
info->auth.mac.length = remainder;
info->auth.mac.key_id = ntohl(*(uint32_t *)(data + parsed));
/* Check if it is an MS-SNTP authenticator field or extended authenticator
field with zeroes as digest */
if (info->version == 3 && info->auth.mac.key_id != 0) {
if (remainder == 20 && is_zero_data(data + parsed + 4, remainder - 4))
info->auth.mode = NTP_AUTH_MSSNTP;
else if (remainder == 72 && is_zero_data(data + parsed + 8, remainder - 8))
info->auth.mode = NTP_AUTH_MSSNTP_EXT;
}
return 1;
}
/* Check for a crypto NAK */
if (remainder == 4 && ntohl(*(uint32_t *)(data + parsed)) == 0) {
info->auth.mode = NTP_AUTH_SYMMETRIC;
info->auth.mac.start = parsed;
info->auth.mac.length = remainder;
info->auth.mac.key_id = 0;
return 1;
}
/* Parse the rest of the NTPv4 packet */
while (remainder > 0) {
/* Check if the remaining data is a MAC */
if (remainder >= NTP_MIN_MAC_LENGTH && remainder <= NTP_MAX_V4_MAC_LENGTH)
break;
/* Check if this is a valid NTPv4 extension field and skip it */
if (!NEF_ParseField(packet, info->length, parsed, &ef_length, &ef_type, NULL, NULL)) {
DEBUG_LOG("Invalid format");
return 0;
}
assert(ef_length > 0 && ef_length % 4 == 0);
switch (ef_type) {
case NTP_EF_NTS_UNIQUE_IDENTIFIER:
case NTP_EF_NTS_COOKIE:
case NTP_EF_NTS_COOKIE_PLACEHOLDER:
case NTP_EF_NTS_AUTH_AND_EEF:
info->auth.mode = NTP_AUTH_NTS;
break;
default:
DEBUG_LOG("Unknown extension field type=%x", (unsigned int)ef_type);
}
info->ext_fields++;
parsed += ef_length;
remainder = info->length - parsed;
}
if (remainder == 0) {
/* No MAC */
return 1;
} else if (remainder >= NTP_MIN_MAC_LENGTH) {
info->auth.mode = NTP_AUTH_SYMMETRIC;
info->auth.mac.start = parsed;
info->auth.mac.length = remainder;
info->auth.mac.key_id = ntohl(*(uint32_t *)(data + parsed));
return 1;
}
DEBUG_LOG("Invalid format");
return 0;
}
/* ================================================== */
int
NAU_CheckRequestAuth(NTP_Packet *request, NTP_PacketInfo *info, uint32_t *kod)
{
*kod = 0;
switch (info->auth.mode) {
case NTP_AUTH_NONE:
break;
case NTP_AUTH_SYMMETRIC:
if (!check_symmetric_auth(request, info))
return 0;
break;
case NTP_AUTH_MSSNTP:
/* MS-SNTP requests are not authenticated */
break;
case NTP_AUTH_MSSNTP_EXT:
/* Not supported yet */
return 0;
case NTP_AUTH_NTS:
if (!NNS_CheckRequestAuth(request, info, kod))
return 0;
break;
default:
return 0;
}
return 1;
}
/* ================================================== */
int
NAU_GenerateResponseAuth(NTP_Packet *request, NTP_PacketInfo *request_info,
NTP_Packet *response, NTP_PacketInfo *response_info,
NTP_Remote_Address *remote_addr, NTP_Local_Address *local_addr,
uint32_t kod)
{
switch (request_info->auth.mode) {
case NTP_AUTH_NONE:
break;
case NTP_AUTH_SYMMETRIC:
if (!generate_symmetric_auth(request_info->auth.mac.key_id, response, response_info))
return 0;
break;
case NTP_AUTH_MSSNTP:
/* Sign the packet asynchronously by ntp_signd */
if (!NSD_SignAndSendPacket(request_info->auth.mac.key_id, response, response_info,
remote_addr, local_addr))
return 0;
/* Don't send the original packet */
return 0;
case NTP_AUTH_NTS:
if (!NNS_GenerateResponseAuth(request, request_info, response, response_info, kod))
return 0;
break;
default:
DEBUG_LOG("Could not authenticate response auth_mode=%d", (int)request_info->auth.mode);
return 0;
}
response_info->auth.mode = request_info->auth.mode;
return 1;
}
/* ================================================== */
int
NAU_CheckResponseAuth(NAU_Instance instance, NTP_Packet *response, NTP_PacketInfo *info)
{
/* The authentication must match the expected mode */
if (info->auth.mode != instance->mode)
return 0;
switch (info->auth.mode) {
case NTP_AUTH_NONE:
break;
case NTP_AUTH_SYMMETRIC:
/* Check if it is authenticated with the specified key */
if (info->auth.mac.key_id != instance->key_id)
return 0;
/* and that the MAC is valid */
if (!check_symmetric_auth(response, info))
return 0;
break;
case NTP_AUTH_NTS:
if (!NNC_CheckResponseAuth(instance->nts, response, info))
return 0;
break;
default:
return 0;
}
return 1;
}
/* ================================================== */
void
NAU_ChangeAddress(NAU_Instance instance, IPAddr *address)
{
switch (instance->mode) {
case NTP_AUTH_NONE:
case NTP_AUTH_SYMMETRIC:
break;
case NTP_AUTH_NTS:
NNC_ChangeAddress(instance->nts, address);
break;
default:
assert(0);
}
}
/* ================================================== */
void
NAU_DumpData(NAU_Instance instance)
{
switch (instance->mode) {
case NTP_AUTH_NTS:
NNC_DumpData(instance->nts);
break;
default:
break;
}
}
/* ================================================== */
void
NAU_GetReport(NAU_Instance instance, RPT_AuthReport *report)
{
memset(report, 0, sizeof (*report));
report->mode = instance->mode;
report->last_ke_ago = -1;
switch (instance->mode) {
case NTP_AUTH_NONE:
break;
case NTP_AUTH_SYMMETRIC:
report->key_id = instance->key_id;
KEY_GetKeyInfo(instance->key_id, &report->key_type, &report->key_length);
break;
case NTP_AUTH_NTS:
NNC_GetReport(instance->nts, report);
break;
default:
assert(0);
}
}
Reference in a new issue View git blame Copy permalink