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-rw-r--r--nts_ntp_client.c709
1 files changed, 709 insertions, 0 deletions
diff --git a/nts_ntp_client.c b/nts_ntp_client.c
new file mode 100644
index 0000000..34412a6
--- /dev/null
+++ b/nts_ntp_client.c
@@ -0,0 +1,709 @@
+/*
+ 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)
+
+/* 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, double now)
+{
+ int factor, interval;
+
+ 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;
+ double now;
+ int got_data;
+
+ 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++;
+ update_next_nke_attempt(inst, now);
+
+ if (!NKC_Start(inst->nke))
+ return 0;
+ }
+
+ update_next_nke_attempt(inst, 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;
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-16 12:26:53 +0000