chrony/nts_ntp_client.c
Miroslav Lichvar 1daa40a2f7 nts: use shorter NTS-KE retry interval when network is down
When chronyd configured with an NTS source not specified as offline and
resolvable without network was started before the network was up, it was
using an unnecessarily long NTS-KE retry interval, same as if the server
was refusing the connections.

When the network is down, the connect() call made from NKC_Start() on
the non-blocking TCP socket should fail with a different error than
EINPROGRESS and cause NKC_Start() to return with failure. Add a constant
2-second retry interval (matching default iburst) for this case.
2023-02-27 11:43:22 +01:00

716 lines
19 KiB
C

/*
chronyd/chronyc - Programs for keeping computer clocks accurate.
**********************************************************************
* Copyright (C) Miroslav Lichvar 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.
*
**********************************************************************
=======================================================================
Client NTS-NTP authentication
*/
#include "config.h"
#include "sysincl.h"
#include "nts_ntp_client.h"
#include "conf.h"
#include "logging.h"
#include "memory.h"
#include "ntp.h"
#include "ntp_ext.h"
#include "ntp_sources.h"
#include "nts_ke_client.h"
#include "nts_ntp.h"
#include "nts_ntp_auth.h"
#include "sched.h"
#include "siv.h"
#include "util.h"
/* Maximum length of all cookies to avoid IP fragmentation */
#define MAX_TOTAL_COOKIE_LENGTH (8 * 108)
/* Retry interval for NTS-KE start (which doesn't generate network traffic) */
#define RETRY_INTERVAL_KE_START 2.0
/* Magic string of files containing keys and cookies */
#define DUMP_IDENTIFIER "NNC0\n"
struct NNC_Instance_Record {
/* Address of NTS-KE server */
IPSockAddr nts_address;
/* Hostname or IP address for certificate verification */
char *name;
/* ID of trusted certificates */
uint32_t cert_set;
/* Configured NTP port */
uint16_t default_ntp_port;
/* Address of NTP server (can be negotiated in NTS-KE) */
IPSockAddr ntp_address;
NKC_Instance nke;
SIV_Instance siv;
int nke_attempts;
double next_nke_attempt;
double last_nke_success;
NKE_Context context;
unsigned int context_id;
NKE_Cookie cookies[NTS_MAX_COOKIES];
int num_cookies;
int cookie_index;
int auth_ready;
int nak_response;
int ok_response;
unsigned char nonce[NTS_MIN_UNPADDED_NONCE_LENGTH];
unsigned char uniq_id[NTS_MIN_UNIQ_ID_LENGTH];
};
/* ================================================== */
static void save_cookies(NNC_Instance inst);
static void load_cookies(NNC_Instance inst);
/* ================================================== */
static void
reset_instance(NNC_Instance inst)
{
if (inst->nke)
NKC_DestroyInstance(inst->nke);
inst->nke = NULL;
if (inst->siv)
SIV_DestroyInstance(inst->siv);
inst->siv = NULL;
inst->nke_attempts = 0;
inst->next_nke_attempt = 0.0;
inst->last_nke_success = 0.0;
memset(&inst->context, 0, sizeof (inst->context));
inst->context_id = 0;
memset(inst->cookies, 0, sizeof (inst->cookies));
inst->num_cookies = 0;
inst->cookie_index = 0;
inst->auth_ready = 0;
inst->nak_response = 0;
inst->ok_response = 1;
memset(inst->nonce, 0, sizeof (inst->nonce));
memset(inst->uniq_id, 0, sizeof (inst->uniq_id));
}
/* ================================================== */
NNC_Instance
NNC_CreateInstance(IPSockAddr *nts_address, const char *name, uint32_t cert_set, uint16_t ntp_port)
{
NNC_Instance inst;
inst = MallocNew(struct NNC_Instance_Record);
inst->nts_address = *nts_address;
inst->name = Strdup(name);
inst->cert_set = cert_set;
inst->default_ntp_port = ntp_port;
inst->ntp_address.ip_addr = nts_address->ip_addr;
inst->ntp_address.port = ntp_port;
inst->siv = NULL;
inst->nke = NULL;
reset_instance(inst);
/* Try to reload saved keys and cookies */
load_cookies(inst);
return inst;
}
/* ================================================== */
void
NNC_DestroyInstance(NNC_Instance inst)
{
save_cookies(inst);
reset_instance(inst);
Free(inst->name);
Free(inst);
}
/* ================================================== */
static int
check_cookies(NNC_Instance inst)
{
/* Force a new NTS-KE session if a NAK was received without a valid response,
or the keys encrypting the cookies need to be refreshed */
if (inst->num_cookies > 0 &&
((inst->nak_response && !inst->ok_response) ||
SCH_GetLastEventMonoTime() - inst->last_nke_success > CNF_GetNtsRefresh())) {
inst->num_cookies = 0;
DEBUG_LOG("Dropped cookies");
}
return inst->num_cookies > 0;
}
/* ================================================== */
static int
set_ntp_address(NNC_Instance inst, NTP_Remote_Address *negotiated_address)
{
NTP_Remote_Address old_address, new_address;
old_address = inst->ntp_address;
new_address = *negotiated_address;
if (new_address.ip_addr.family == IPADDR_UNSPEC)
new_address.ip_addr = inst->nts_address.ip_addr;
if (new_address.port == 0)
new_address.port = inst->default_ntp_port;
if (UTI_CompareIPs(&old_address.ip_addr, &new_address.ip_addr, NULL) == 0 &&
old_address.port == new_address.port)
/* Nothing to do */
return 1;
if (NSR_UpdateSourceNtpAddress(&old_address, &new_address) != NSR_Success) {
LOG(LOGS_ERR, "Could not change %s to negotiated address %s",
UTI_IPToString(&old_address.ip_addr), UTI_IPToString(&new_address.ip_addr));
return 0;
}
inst->ntp_address = new_address;
return 1;
}
/* ================================================== */
static void
update_next_nke_attempt(NNC_Instance inst, int failed_start, double now)
{
int factor, interval;
if (failed_start) {
inst->next_nke_attempt = now + RETRY_INTERVAL_KE_START;
return;
}
if (!inst->nke)
return;
factor = NKC_GetRetryFactor(inst->nke);
interval = MIN(factor + inst->nke_attempts - 1, NKE_MAX_RETRY_INTERVAL2);
inst->next_nke_attempt = now + UTI_Log2ToDouble(interval);
}
/* ================================================== */
static int
get_cookies(NNC_Instance inst)
{
NTP_Remote_Address ntp_address;
int got_data, failed_start = 0;
double now;
assert(inst->num_cookies == 0);
now = SCH_GetLastEventMonoTime();
/* Create and start a new NTS-KE session if not already present */
if (!inst->nke) {
if (now < inst->next_nke_attempt) {
DEBUG_LOG("Limiting NTS-KE request rate (%f seconds)",
inst->next_nke_attempt - now);
return 0;
}
inst->nke = NKC_CreateInstance(&inst->nts_address, inst->name, inst->cert_set);
inst->nke_attempts++;
if (!NKC_Start(inst->nke))
failed_start = 1;
}
update_next_nke_attempt(inst, failed_start, now);
/* Wait until the session stops */
if (NKC_IsActive(inst->nke))
return 0;
assert(sizeof (inst->cookies) / sizeof (inst->cookies[0]) == NTS_MAX_COOKIES);
/* Get the new keys, cookies and NTP address if the session was successful */
got_data = NKC_GetNtsData(inst->nke, &inst->context,
inst->cookies, &inst->num_cookies, NTS_MAX_COOKIES,
&ntp_address);
NKC_DestroyInstance(inst->nke);
inst->nke = NULL;
if (!got_data)
return 0;
if (inst->siv)
SIV_DestroyInstance(inst->siv);
inst->siv = NULL;
inst->context_id++;
/* Force a new session if the NTP address is used by another source, with
an expectation that it will eventually get a non-conflicting address */
if (!set_ntp_address(inst, &ntp_address)) {
inst->num_cookies = 0;
return 0;
}
inst->last_nke_success = now;
inst->cookie_index = 0;
return 1;
}
/* ================================================== */
int
NNC_PrepareForAuth(NNC_Instance inst)
{
inst->auth_ready = 0;
/* Prepare data for the next request and invalidate any responses to the
previous request */
UTI_GetRandomBytes(inst->uniq_id, sizeof (inst->uniq_id));
UTI_GetRandomBytes(inst->nonce, sizeof (inst->nonce));
/* Get new cookies if there are not any, or they are no longer usable */
if (!check_cookies(inst)) {
if (!get_cookies(inst))
return 0;
}
inst->nak_response = 0;
if (!inst->siv)
inst->siv = SIV_CreateInstance(inst->context.algorithm);
if (!inst->siv ||
!SIV_SetKey(inst->siv, inst->context.c2s.key, inst->context.c2s.length)) {
DEBUG_LOG("Could not set SIV key");
return 0;
}
inst->auth_ready = 1;
return 1;
}
/* ================================================== */
int
NNC_GenerateRequestAuth(NNC_Instance inst, NTP_Packet *packet,
NTP_PacketInfo *info)
{
NKE_Cookie *cookie;
int i, req_cookies;
void *ef_body;
if (!inst->auth_ready)
return 0;
inst->auth_ready = 0;
if (inst->num_cookies <= 0 || !inst->siv)
return 0;
if (info->mode != MODE_CLIENT)
return 0;
cookie = &inst->cookies[inst->cookie_index];
inst->num_cookies--;
inst->cookie_index = (inst->cookie_index + 1) % NTS_MAX_COOKIES;
req_cookies = MIN(NTS_MAX_COOKIES - inst->num_cookies,
MAX_TOTAL_COOKIE_LENGTH / (cookie->length + 4));
if (!NEF_AddField(packet, info, NTP_EF_NTS_UNIQUE_IDENTIFIER,
inst->uniq_id, sizeof (inst->uniq_id)))
return 0;
if (!NEF_AddField(packet, info, NTP_EF_NTS_COOKIE,
cookie->cookie, cookie->length))
return 0;
for (i = 0; i < req_cookies - 1; i++) {
if (!NEF_AddBlankField(packet, info, NTP_EF_NTS_COOKIE_PLACEHOLDER,
cookie->length, &ef_body))
return 0;
memset(ef_body, 0, cookie->length);
}
if (!NNA_GenerateAuthEF(packet, info, inst->siv, inst->nonce, sizeof (inst->nonce),
(const unsigned char *)"", 0, NTP_MAX_V4_MAC_LENGTH + 4))
return 0;
inst->ok_response = 0;
return 1;
}
/* ================================================== */
static int
parse_encrypted_efs(NNC_Instance inst, unsigned char *plaintext, int length)
{
int ef_length, parsed;
for (parsed = 0; parsed < length; parsed += ef_length) {
if (!NEF_ParseSingleField(plaintext, length, parsed, &ef_length, NULL, NULL, NULL)) {
DEBUG_LOG("Could not parse encrypted EF");
return 0;
}
}
return 1;
}
/* ================================================== */
static int
extract_cookies(NNC_Instance inst, unsigned char *plaintext, int length)
{
int ef_type, ef_body_length, ef_length, parsed, index, acceptable, saved;
void *ef_body;
acceptable = saved = 0;
for (parsed = 0; parsed < length; parsed += ef_length) {
if (!NEF_ParseSingleField(plaintext, length, parsed,
&ef_length, &ef_type, &ef_body, &ef_body_length))
return 0;
if (ef_type != NTP_EF_NTS_COOKIE)
continue;
if (ef_length < NTP_MIN_EF_LENGTH || ef_body_length > sizeof (inst->cookies[0].cookie)) {
DEBUG_LOG("Unexpected cookie length %d", ef_body_length);
continue;
}
acceptable++;
if (inst->num_cookies >= NTS_MAX_COOKIES)
continue;
index = (inst->cookie_index + inst->num_cookies) % NTS_MAX_COOKIES;
assert(index >= 0 && index < NTS_MAX_COOKIES);
assert(sizeof (inst->cookies) / sizeof (inst->cookies[0]) == NTS_MAX_COOKIES);
memcpy(inst->cookies[index].cookie, ef_body, ef_body_length);
inst->cookies[index].length = ef_body_length;
inst->num_cookies++;
saved++;
}
DEBUG_LOG("Extracted %d cookies (saved %d)", acceptable, saved);
return acceptable > 0;
}
/* ================================================== */
int
NNC_CheckResponseAuth(NNC_Instance inst, NTP_Packet *packet,
NTP_PacketInfo *info)
{
int ef_type, ef_body_length, ef_length, parsed, plaintext_length;
int has_valid_uniq_id = 0, has_valid_auth = 0;
unsigned char plaintext[NTP_MAX_EXTENSIONS_LENGTH];
void *ef_body;
if (info->ext_fields == 0 || info->mode != MODE_SERVER)
return 0;
/* Accept at most one response per request */
if (inst->ok_response || inst->auth_ready)
return 0;
if (!inst->siv ||
!SIV_SetKey(inst->siv, inst->context.s2c.key, inst->context.s2c.length)) {
DEBUG_LOG("Could not set SIV key");
return 0;
}
for (parsed = NTP_HEADER_LENGTH; parsed < info->length; parsed += ef_length) {
if (!NEF_ParseField(packet, info->length, parsed,
&ef_length, &ef_type, &ef_body, &ef_body_length))
/* This is not expected as the packet already passed parsing */
return 0;
switch (ef_type) {
case NTP_EF_NTS_UNIQUE_IDENTIFIER:
if (ef_body_length != sizeof (inst->uniq_id) ||
memcmp(ef_body, inst->uniq_id, sizeof (inst->uniq_id)) != 0) {
DEBUG_LOG("Invalid uniq id");
return 0;
}
has_valid_uniq_id = 1;
break;
case NTP_EF_NTS_COOKIE:
DEBUG_LOG("Unencrypted cookie");
break;
case NTP_EF_NTS_AUTH_AND_EEF:
if (parsed + ef_length != info->length) {
DEBUG_LOG("Auth not last EF");
return 0;
}
if (!NNA_DecryptAuthEF(packet, info, inst->siv, parsed,
plaintext, sizeof (plaintext), &plaintext_length))
return 0;
if (!parse_encrypted_efs(inst, plaintext, plaintext_length))
return 0;
has_valid_auth = 1;
break;
default:
break;
}
}
if (!has_valid_uniq_id || !has_valid_auth) {
if (has_valid_uniq_id && packet->stratum == NTP_INVALID_STRATUM &&
ntohl(packet->reference_id) == NTP_KOD_NTS_NAK) {
DEBUG_LOG("NTS NAK");
inst->nak_response = 1;
return 0;
}
DEBUG_LOG("Missing NTS EF");
return 0;
}
if (!extract_cookies(inst, plaintext, plaintext_length))
return 0;
inst->ok_response = 1;
/* At this point we know the client interoperates with the server. Allow a
new NTS-KE session to be started as soon as the cookies run out. */
inst->nke_attempts = 0;
inst->next_nke_attempt = 0.0;
return 1;
}
/* ================================================== */
void
NNC_ChangeAddress(NNC_Instance inst, IPAddr *address)
{
save_cookies(inst);
inst->nts_address.ip_addr = *address;
inst->ntp_address.ip_addr = *address;
reset_instance(inst);
DEBUG_LOG("NTS reset");
load_cookies(inst);
}
/* ================================================== */
static void
save_cookies(NNC_Instance inst)
{
char buf[2 * NKE_MAX_COOKIE_LENGTH + 2], *dump_dir, *filename;
struct timespec now;
double context_time;
FILE *f;
int i;
if (inst->num_cookies < 1 || !UTI_IsIPReal(&inst->nts_address.ip_addr))
return;
dump_dir = CNF_GetNtsDumpDir();
if (!dump_dir)
return;
filename = UTI_IPToString(&inst->nts_address.ip_addr);
f = UTI_OpenFile(dump_dir, filename, ".tmp", 'w', 0600);
if (!f)
return;
SCH_GetLastEventTime(&now, NULL, NULL);
context_time = inst->last_nke_success - SCH_GetLastEventMonoTime();
context_time += UTI_TimespecToDouble(&now);
if (fprintf(f, "%s%s\n%.1f\n%s %d\n%u %d ",
DUMP_IDENTIFIER, inst->name, context_time,
UTI_IPToString(&inst->ntp_address.ip_addr), inst->ntp_address.port,
inst->context_id, (int)inst->context.algorithm) < 0 ||
!UTI_BytesToHex(inst->context.s2c.key, inst->context.s2c.length, buf, sizeof (buf)) ||
fprintf(f, "%s ", buf) < 0 ||
!UTI_BytesToHex(inst->context.c2s.key, inst->context.c2s.length, buf, sizeof (buf)) ||
fprintf(f, "%s\n", buf) < 0)
goto error;
for (i = 0; i < inst->num_cookies; i++) {
if (!UTI_BytesToHex(inst->cookies[i].cookie, inst->cookies[i].length, buf, sizeof (buf)) ||
fprintf(f, "%s\n", buf) < 0)
goto error;
}
fclose(f);
if (!UTI_RenameTempFile(dump_dir, filename, ".tmp", ".nts"))
;
return;
error:
DEBUG_LOG("Could not %s cookies for %s", "save", filename);
fclose(f);
if (!UTI_RemoveFile(dump_dir, filename, ".nts"))
;
}
/* ================================================== */
#define MAX_WORDS 4
static void
load_cookies(NNC_Instance inst)
{
char line[2 * NKE_MAX_COOKIE_LENGTH + 2], *dump_dir, *filename, *words[MAX_WORDS];
unsigned int context_id;
int i, algorithm, port;
double context_time;
struct timespec now;
IPSockAddr ntp_addr;
FILE *f;
dump_dir = CNF_GetNtsDumpDir();
if (!dump_dir)
return;
filename = UTI_IPToString(&inst->nts_address.ip_addr);
f = UTI_OpenFile(dump_dir, filename, ".nts", 'r', 0);
if (!f)
return;
/* Don't load this file again */
if (!UTI_RemoveFile(dump_dir, filename, ".nts"))
;
if (inst->siv)
SIV_DestroyInstance(inst->siv);
inst->siv = NULL;
if (!fgets(line, sizeof (line), f) || strcmp(line, DUMP_IDENTIFIER) != 0 ||
!fgets(line, sizeof (line), f) || UTI_SplitString(line, words, MAX_WORDS) != 1 ||
strcmp(words[0], inst->name) != 0 ||
!fgets(line, sizeof (line), f) || UTI_SplitString(line, words, MAX_WORDS) != 1 ||
sscanf(words[0], "%lf", &context_time) != 1 ||
!fgets(line, sizeof (line), f) || UTI_SplitString(line, words, MAX_WORDS) != 2 ||
!UTI_StringToIP(words[0], &ntp_addr.ip_addr) || sscanf(words[1], "%d", &port) != 1 ||
!fgets(line, sizeof (line), f) || UTI_SplitString(line, words, MAX_WORDS) != 4 ||
sscanf(words[0], "%u", &context_id) != 1 || sscanf(words[1], "%d", &algorithm) != 1)
goto error;
inst->context.algorithm = algorithm;
inst->context.s2c.length = UTI_HexToBytes(words[2], inst->context.s2c.key,
sizeof (inst->context.s2c.key));
inst->context.c2s.length = UTI_HexToBytes(words[3], inst->context.c2s.key,
sizeof (inst->context.c2s.key));
if (inst->context.s2c.length != SIV_GetKeyLength(algorithm) ||
inst->context.c2s.length != inst->context.s2c.length)
goto error;
for (i = 0; i < NTS_MAX_COOKIES && fgets(line, sizeof (line), f); i++) {
if (UTI_SplitString(line, words, MAX_WORDS) != 1)
goto error;
inst->cookies[i].length = UTI_HexToBytes(words[0], inst->cookies[i].cookie,
sizeof (inst->cookies[i].cookie));
if (inst->cookies[i].length == 0)
goto error;
}
inst->num_cookies = i;
ntp_addr.port = port;
if (!set_ntp_address(inst, &ntp_addr))
goto error;
SCH_GetLastEventTime(&now, NULL, NULL);
context_time -= UTI_TimespecToDouble(&now);
if (context_time > 0)
context_time = 0;
inst->last_nke_success = context_time + SCH_GetLastEventMonoTime();
inst->context_id = context_id;
fclose(f);
DEBUG_LOG("Loaded %d cookies for %s", i, filename);
return;
error:
DEBUG_LOG("Could not %s cookies for %s", "load", filename);
fclose(f);
memset(&inst->context, 0, sizeof (inst->context));
inst->num_cookies = 0;
}
/* ================================================== */
void
NNC_DumpData(NNC_Instance inst)
{
save_cookies(inst);
}
/* ================================================== */
void
NNC_GetReport(NNC_Instance inst, RPT_AuthReport *report)
{
report->key_id = inst->context_id;
report->key_type = inst->context.algorithm;
report->key_length = 8 * inst->context.s2c.length;
report->ke_attempts = inst->nke_attempts;
if (report->key_length > 0)
report->last_ke_ago = SCH_GetLastEventMonoTime() - inst->last_nke_success;
else
report->last_ke_ago = -1;
report->cookies = inst->num_cookies;
report->cookie_length = inst->num_cookies > 0 ? inst->cookies[inst->cookie_index].length : 0;
report->nak = inst->nak_response;
}