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Diffstat (limited to '')
| -rw-r--r-- | nts_ke_server.c | 1036 |
1 files changed, 1036 insertions, 0 deletions
diff --git a/nts_ke_server.c b/nts_ke_server.c new file mode 100644 index 0000000..3fe99db --- /dev/null +++ b/nts_ke_server.c @@ -0,0 +1,1036 @@ +/* + chronyd/chronyc - Programs for keeping computer clocks accurate. + + ********************************************************************** + * Copyright (C) Miroslav Lichvar 2020, 2022 + * + * 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. + * + ********************************************************************** + + ======================================================================= + + NTS-KE server + */ + +#include "config.h" + +#include "sysincl.h" + +#include "nts_ke_server.h" + +#include "array.h" +#include "conf.h" +#include "clientlog.h" +#include "local.h" +#include "logging.h" +#include "memory.h" +#include "ntp_core.h" +#include "nts_ke_session.h" +#include "privops.h" +#include "siv.h" +#include "socket.h" +#include "sched.h" +#include "sys.h" +#include "util.h" + +#define SERVER_TIMEOUT 2.0 + +#define MAX_COOKIE_NONCE_LENGTH 16 + +#define KEY_ID_INDEX_BITS 2 +#define MAX_SERVER_KEYS (1U << KEY_ID_INDEX_BITS) +#define FUTURE_KEYS 1 + +#define DUMP_FILENAME "ntskeys" +#define DUMP_IDENTIFIER "NKS1\n" +#define OLD_DUMP_IDENTIFIER "NKS0\n" + +#define INVALID_SOCK_FD (-7) + +typedef struct { + uint32_t key_id; +} ServerCookieHeader; + +typedef struct { + uint32_t id; + unsigned char key[SIV_MAX_KEY_LENGTH]; + SIV_Algorithm siv_algorithm; + SIV_Instance siv; + int nonce_length; +} ServerKey; + +typedef struct { + uint32_t key_id; + uint32_t siv_algorithm; + unsigned char key[SIV_MAX_KEY_LENGTH]; + IPAddr client_addr; + uint16_t client_port; + uint16_t _pad; +} HelperRequest; + +/* ================================================== */ + +static ServerKey server_keys[MAX_SERVER_KEYS]; +static int current_server_key; +static double last_server_key_ts; +static int key_rotation_interval; + +static int server_sock_fd4; +static int server_sock_fd6; + +static int helper_sock_fd; +static int is_helper; + +static int initialised = 0; + +/* Array of NKSN instances */ +static ARR_Instance sessions; +static NKSN_Credentials server_credentials; + +/* ================================================== */ + +static int handle_message(void *arg); + +/* ================================================== */ + +static int +handle_client(int sock_fd, IPSockAddr *addr) +{ + NKSN_Instance inst, *instp; + int i; + + /* Leave at least half of the descriptors which can handled by select() + to other use */ + if (sock_fd > FD_SETSIZE / 2) { + DEBUG_LOG("Rejected connection from %s (%s)", + UTI_IPSockAddrToString(addr), "too many descriptors"); + return 0; + } + + /* Find an unused server slot or one with an already stopped session */ + for (i = 0, inst = NULL; i < ARR_GetSize(sessions); i++) { + instp = ARR_GetElement(sessions, i); + if (!*instp) { + /* NULL handler arg will be replaced with the session instance */ + inst = NKSN_CreateInstance(1, NULL, handle_message, NULL); + *instp = inst; + break; + } else if (NKSN_IsStopped(*instp)) { + inst = *instp; + break; + } + } + + if (!inst) { + DEBUG_LOG("Rejected connection from %s (%s)", + UTI_IPSockAddrToString(addr), "too many connections"); + return 0; + } + + assert(server_credentials); + + if (!NKSN_StartSession(inst, sock_fd, UTI_IPSockAddrToString(addr), + server_credentials, SERVER_TIMEOUT)) + return 0; + + return 1; +} + +/* ================================================== */ + +static void +update_key_siv(ServerKey *key, SIV_Algorithm algorithm) +{ + if (!key->siv || key->siv_algorithm != algorithm) { + if (key->siv) + SIV_DestroyInstance(key->siv); + key->siv_algorithm = algorithm; + key->siv = SIV_CreateInstance(algorithm); + key->nonce_length = MIN(SIV_GetMaxNonceLength(key->siv), MAX_COOKIE_NONCE_LENGTH); + } + + if (!key->siv || !SIV_SetKey(key->siv, key->key, SIV_GetKeyLength(key->siv_algorithm))) + LOG_FATAL("Could not set SIV key"); +} + +/* ================================================== */ + +static void +handle_helper_request(int fd, int event, void *arg) +{ + SCK_Message *message; + HelperRequest *req; + IPSockAddr client_addr; + ServerKey *key; + int sock_fd; + + /* Receive the helper request with the NTS-KE session socket. + With multiple helpers EAGAIN errors are expected here. */ + message = SCK_ReceiveMessage(fd, SCK_FLAG_MSG_DESCRIPTOR); + if (!message) + return; + + sock_fd = message->descriptor; + if (sock_fd < 0) { + /* Message with no descriptor is a shutdown command */ + SCH_QuitProgram(); + return; + } + + if (!initialised) { + DEBUG_LOG("Uninitialised helper"); + SCK_CloseSocket(sock_fd); + return; + } + + if (message->length != sizeof (HelperRequest)) + LOG_FATAL("Invalid helper request"); + + req = message->data; + + /* Extract the current server key and client address from the request */ + key = &server_keys[current_server_key]; + key->id = ntohl(req->key_id); + assert(sizeof (key->key) == sizeof (req->key)); + memcpy(key->key, req->key, sizeof (key->key)); + UTI_IPNetworkToHost(&req->client_addr, &client_addr.ip_addr); + client_addr.port = ntohs(req->client_port); + + update_key_siv(key, ntohl(req->siv_algorithm)); + + if (!handle_client(sock_fd, &client_addr)) { + SCK_CloseSocket(sock_fd); + return; + } + + DEBUG_LOG("Accepted helper request fd=%d", sock_fd); +} + +/* ================================================== */ + +static void +accept_connection(int listening_fd, int event, void *arg) +{ + SCK_Message message; + IPSockAddr addr; + int log_index, sock_fd; + struct timespec now; + + sock_fd = SCK_AcceptConnection(listening_fd, &addr); + if (sock_fd < 0) + return; + + if (!NCR_CheckAccessRestriction(&addr.ip_addr)) { + DEBUG_LOG("Rejected connection from %s (%s)", + UTI_IPSockAddrToString(&addr), "access denied"); + SCK_CloseSocket(sock_fd); + return; + } + + SCH_GetLastEventTime(&now, NULL, NULL); + + log_index = CLG_LogServiceAccess(CLG_NTSKE, &addr.ip_addr, &now); + if (log_index >= 0 && CLG_LimitServiceRate(CLG_NTSKE, log_index)) { + DEBUG_LOG("Rejected connection from %s (%s)", + UTI_IPSockAddrToString(&addr), "rate limit"); + SCK_CloseSocket(sock_fd); + return; + } + + /* Pass the socket to a helper process if enabled. Otherwise, handle the + client in the main process. */ + if (helper_sock_fd != INVALID_SOCK_FD) { + HelperRequest req; + + memset(&req, 0, sizeof (req)); + + /* Include the current server key and client address in the request */ + req.key_id = htonl(server_keys[current_server_key].id); + req.siv_algorithm = htonl(server_keys[current_server_key].siv_algorithm); + assert(sizeof (req.key) == sizeof (server_keys[current_server_key].key)); + memcpy(req.key, server_keys[current_server_key].key, sizeof (req.key)); + UTI_IPHostToNetwork(&addr.ip_addr, &req.client_addr); + req.client_port = htons(addr.port); + + SCK_InitMessage(&message, SCK_ADDR_UNSPEC); + message.data = &req; + message.length = sizeof (req); + message.descriptor = sock_fd; + + errno = 0; + if (!SCK_SendMessage(helper_sock_fd, &message, SCK_FLAG_MSG_DESCRIPTOR)) { + /* If sending failed with EPIPE, it means all helpers closed their end of + the socket (e.g. due to a fatal error) */ + if (errno == EPIPE) + LOG_FATAL("NTS-KE helpers failed"); + SCK_CloseSocket(sock_fd); + return; + } + + SCK_CloseSocket(sock_fd); + } else { + if (!handle_client(sock_fd, &addr)) { + SCK_CloseSocket(sock_fd); + return; + } + } + + DEBUG_LOG("Accepted connection from %s fd=%d", UTI_IPSockAddrToString(&addr), sock_fd); +} + +/* ================================================== */ + +static int +open_socket(int family) +{ + IPSockAddr local_addr; + int backlog, sock_fd; + char *iface; + + if (!SCK_IsIpFamilyEnabled(family)) + return INVALID_SOCK_FD; + + CNF_GetBindAddress(family, &local_addr.ip_addr); + local_addr.port = CNF_GetNtsServerPort(); + iface = CNF_GetBindNtpInterface(); + + sock_fd = SCK_OpenTcpSocket(NULL, &local_addr, iface, 0); + if (sock_fd < 0) { + LOG(LOGS_ERR, "Could not open NTS-KE socket on %s", UTI_IPSockAddrToString(&local_addr)); + return INVALID_SOCK_FD; + } + + /* Set the maximum number of waiting connections on the socket to the maximum + number of concurrent sessions */ + backlog = MAX(CNF_GetNtsServerProcesses(), 1) * CNF_GetNtsServerConnections(); + + if (!SCK_ListenOnSocket(sock_fd, backlog)) { + SCK_CloseSocket(sock_fd); + return INVALID_SOCK_FD; + } + + SCH_AddFileHandler(sock_fd, SCH_FILE_INPUT, accept_connection, NULL); + + return sock_fd; +} + +/* ================================================== */ + +static void +helper_signal(int x) +{ + SCH_QuitProgram(); +} + +/* ================================================== */ + +static int +prepare_response(NKSN_Instance session, int error, int next_protocol, int aead_algorithm) +{ + NKE_Context context; + NKE_Cookie cookie; + char *ntp_server; + uint16_t datum; + int i; + + DEBUG_LOG("NTS KE response: error=%d next=%d aead=%d", error, next_protocol, aead_algorithm); + + NKSN_BeginMessage(session); + + if (error >= 0) { + datum = htons(error); + if (!NKSN_AddRecord(session, 1, NKE_RECORD_ERROR, &datum, sizeof (datum))) + return 0; + } else if (next_protocol < 0) { + if (!NKSN_AddRecord(session, 1, NKE_RECORD_NEXT_PROTOCOL, NULL, 0)) + return 0; + } else if (aead_algorithm < 0) { + datum = htons(next_protocol); + if (!NKSN_AddRecord(session, 1, NKE_RECORD_NEXT_PROTOCOL, &datum, sizeof (datum))) + return 0; + if (!NKSN_AddRecord(session, 1, NKE_RECORD_AEAD_ALGORITHM, NULL, 0)) + return 0; + } else { + datum = htons(next_protocol); + if (!NKSN_AddRecord(session, 1, NKE_RECORD_NEXT_PROTOCOL, &datum, sizeof (datum))) + return 0; + + datum = htons(aead_algorithm); + if (!NKSN_AddRecord(session, 1, NKE_RECORD_AEAD_ALGORITHM, &datum, sizeof (datum))) + return 0; + + if (CNF_GetNTPPort() != NTP_PORT) { + datum = htons(CNF_GetNTPPort()); + if (!NKSN_AddRecord(session, 1, NKE_RECORD_NTPV4_PORT_NEGOTIATION, &datum, sizeof (datum))) + return 0; + } + + ntp_server = CNF_GetNtsNtpServer(); + if (ntp_server) { + if (!NKSN_AddRecord(session, 1, NKE_RECORD_NTPV4_SERVER_NEGOTIATION, + ntp_server, strlen(ntp_server))) + return 0; + } + + context.algorithm = aead_algorithm; + + if (!NKSN_GetKeys(session, aead_algorithm, &context.c2s, &context.s2c)) + return 0; + + for (i = 0; i < NKE_MAX_COOKIES; i++) { + if (!NKS_GenerateCookie(&context, &cookie)) + return 0; + if (!NKSN_AddRecord(session, 0, NKE_RECORD_COOKIE, cookie.cookie, cookie.length)) + return 0; + } + } + + if (!NKSN_EndMessage(session)) + return 0; + + return 1; +} + +/* ================================================== */ + +static int +process_request(NKSN_Instance session) +{ + int next_protocol_records = 0, aead_algorithm_records = 0; + int next_protocol_values = 0, aead_algorithm_values = 0; + int next_protocol = -1, aead_algorithm = -1, error = -1; + int i, critical, type, length; + uint16_t data[NKE_MAX_RECORD_BODY_LENGTH / sizeof (uint16_t)]; + + assert(NKE_MAX_RECORD_BODY_LENGTH % sizeof (uint16_t) == 0); + assert(sizeof (uint16_t) == 2); + + while (error < 0) { + if (!NKSN_GetRecord(session, &critical, &type, &length, &data, sizeof (data))) + break; + + switch (type) { + case NKE_RECORD_NEXT_PROTOCOL: + if (!critical || length < 2 || length % 2 != 0) { + error = NKE_ERROR_BAD_REQUEST; + break; + } + + next_protocol_records++; + + for (i = 0; i < MIN(length, sizeof (data)) / 2; i++) { + next_protocol_values++; + if (ntohs(data[i]) == NKE_NEXT_PROTOCOL_NTPV4) + next_protocol = NKE_NEXT_PROTOCOL_NTPV4; + } + break; + case NKE_RECORD_AEAD_ALGORITHM: + if (length < 2 || length % 2 != 0) { + error = NKE_ERROR_BAD_REQUEST; + break; + } + + aead_algorithm_records++; + + for (i = 0; i < MIN(length, sizeof (data)) / 2; i++) { + aead_algorithm_values++; + /* Use the first supported algorithm */ + if (aead_algorithm < 0 && SIV_GetKeyLength(ntohs(data[i])) > 0) + aead_algorithm = ntohs(data[i]); + } + break; + case NKE_RECORD_ERROR: + case NKE_RECORD_WARNING: + case NKE_RECORD_COOKIE: + error = NKE_ERROR_BAD_REQUEST; + break; + default: + if (critical) + error = NKE_ERROR_UNRECOGNIZED_CRITICAL_RECORD; + } + } + + if (error < 0) { + if (next_protocol_records != 1 || next_protocol_values < 1 || + (next_protocol == NKE_NEXT_PROTOCOL_NTPV4 && + (aead_algorithm_records != 1 || aead_algorithm_values < 1))) + error = NKE_ERROR_BAD_REQUEST; + } + + if (!prepare_response(session, error, next_protocol, aead_algorithm)) + return 0; + + return 1; +} + +/* ================================================== */ + +static int +handle_message(void *arg) +{ + NKSN_Instance session = arg; + + return process_request(session); +} + +/* ================================================== */ + +static void +generate_key(int index) +{ + SIV_Algorithm algorithm; + ServerKey *key; + int key_length; + + if (index < 0 || index >= MAX_SERVER_KEYS) + assert(0); + + /* Prefer AES-128-GCM-SIV if available. Note that if older keys loaded + from ntsdumpdir use a different algorithm, responding to NTP requests + with cookies encrypted with those keys will not work if the new algorithm + produces longer cookies (i.e. response would be longer than request). + Switching from AES-SIV-CMAC-256 to AES-128-GCM-SIV is ok. */ + algorithm = SIV_GetKeyLength(AEAD_AES_128_GCM_SIV) > 0 ? + AEAD_AES_128_GCM_SIV : AEAD_AES_SIV_CMAC_256; + + key = &server_keys[index]; + + key_length = SIV_GetKeyLength(algorithm); + if (key_length > sizeof (key->key)) + assert(0); + + UTI_GetRandomBytesUrandom(key->key, key_length); + memset(key->key + key_length, 0, sizeof (key->key) - key_length); + UTI_GetRandomBytes(&key->id, sizeof (key->id)); + + /* Encode the index in the lowest bits of the ID */ + key->id &= -1U << KEY_ID_INDEX_BITS; + key->id |= index; + + update_key_siv(key, algorithm); + + DEBUG_LOG("Generated key %08"PRIX32" (%d)", key->id, (int)key->siv_algorithm); + + last_server_key_ts = SCH_GetLastEventMonoTime(); +} + +/* ================================================== */ + +static void +save_keys(void) +{ + char buf[SIV_MAX_KEY_LENGTH * 2 + 1], *dump_dir; + int i, index, key_length; + double last_key_age; + FILE *f; + + /* Don't save the keys if rotation is disabled to enable an external + management of the keys (e.g. share them with another server) */ + if (key_rotation_interval == 0) + return; + + dump_dir = CNF_GetNtsDumpDir(); + if (!dump_dir) + return; + + f = UTI_OpenFile(dump_dir, DUMP_FILENAME, ".tmp", 'w', 0600); + if (!f) + return; + + last_key_age = SCH_GetLastEventMonoTime() - last_server_key_ts; + + if (fprintf(f, "%s%.1f\n", DUMP_IDENTIFIER, last_key_age) < 0) + goto error; + + for (i = 0; i < MAX_SERVER_KEYS; i++) { + index = (current_server_key + i + 1 + FUTURE_KEYS) % MAX_SERVER_KEYS; + key_length = SIV_GetKeyLength(server_keys[index].siv_algorithm); + + if (key_length > sizeof (server_keys[index].key) || + !UTI_BytesToHex(server_keys[index].key, key_length, buf, sizeof (buf)) || + fprintf(f, "%08"PRIX32" %s %d\n", server_keys[index].id, buf, + (int)server_keys[index].siv_algorithm) < 0) + goto error; + } + + fclose(f); + + /* Rename the temporary file, or remove it if that fails */ + if (!UTI_RenameTempFile(dump_dir, DUMP_FILENAME, ".tmp", NULL)) { + if (!UTI_RemoveFile(dump_dir, DUMP_FILENAME, ".tmp")) + ; + } + + return; + +error: + LOG(LOGS_ERR, "Could not %s %s", "save", "server NTS keys"); + fclose(f); + + if (!UTI_RemoveFile(dump_dir, DUMP_FILENAME, NULL)) + ; +} + +/* ================================================== */ + +#define MAX_WORDS 3 + +static int +load_keys(void) +{ + int i, index, key_length, algorithm = 0, old_ver; + char *dump_dir, line[1024], *words[MAX_WORDS]; + ServerKey new_keys[MAX_SERVER_KEYS]; + double key_age; + FILE *f; + + dump_dir = CNF_GetNtsDumpDir(); + if (!dump_dir) + return 0; + + f = UTI_OpenFile(dump_dir, DUMP_FILENAME, NULL, 'r', 0); + if (!f) + return 0; + + if (!fgets(line, sizeof (line), f) || + (strcmp(line, DUMP_IDENTIFIER) != 0 && strcmp(line, OLD_DUMP_IDENTIFIER) != 0)) + goto error; + + old_ver = strcmp(line, DUMP_IDENTIFIER) != 0; + + if (!fgets(line, sizeof (line), f) || + UTI_SplitString(line, words, MAX_WORDS) != (old_ver ? 2 : 1) || + (old_ver && sscanf(words[0], "%d", &algorithm) != 1) || + sscanf(words[old_ver ? 1 : 0], "%lf", &key_age) != 1) + goto error; + + for (i = 0; i < MAX_SERVER_KEYS && fgets(line, sizeof (line), f); i++) { + if (UTI_SplitString(line, words, MAX_WORDS) != (old_ver ? 2 : 3) || + sscanf(words[0], "%"PRIX32, &new_keys[i].id) != 1 || + (!old_ver && sscanf(words[2], "%d", &algorithm) != 1)) + goto error; + + new_keys[i].siv_algorithm = algorithm; + key_length = SIV_GetKeyLength(algorithm); + + if ((i > 0 && (new_keys[i].id - new_keys[i - 1].id) % MAX_SERVER_KEYS != 1) || + key_length <= 0 || + UTI_HexToBytes(words[1], new_keys[i].key, sizeof (new_keys[i].key)) != key_length) + goto error; + memset(new_keys[i].key + key_length, 0, sizeof (new_keys[i].key) - key_length); + } + + if (i < MAX_SERVER_KEYS) + goto error; + + for (i = 0; i < MAX_SERVER_KEYS; i++) { + index = new_keys[i].id % MAX_SERVER_KEYS; + server_keys[index].id = new_keys[i].id; + memcpy(server_keys[index].key, new_keys[i].key, sizeof (server_keys[index].key)); + + update_key_siv(&server_keys[index], new_keys[i].siv_algorithm); + + DEBUG_LOG("Loaded key %08"PRIX32" (%d)", + server_keys[index].id, (int)server_keys[index].siv_algorithm); + } + + current_server_key = (index + MAX_SERVER_KEYS - FUTURE_KEYS) % MAX_SERVER_KEYS; + last_server_key_ts = SCH_GetLastEventMonoTime() - MAX(key_age, 0.0); + + fclose(f); + + LOG(LOGS_INFO, "Loaded %s", "server NTS keys"); + return 1; + +error: + LOG(LOGS_ERR, "Could not %s %s", "load", "server NTS keys"); + fclose(f); + + return 0; +} + +/* ================================================== */ + +static void +key_timeout(void *arg) +{ + current_server_key = (current_server_key + 1) % MAX_SERVER_KEYS; + generate_key((current_server_key + FUTURE_KEYS) % MAX_SERVER_KEYS); + save_keys(); + + SCH_AddTimeoutByDelay(key_rotation_interval, key_timeout, NULL); +} + +/* ================================================== */ + +static void +run_helper(uid_t uid, gid_t gid, int scfilter_level) +{ + LOG_Severity log_severity; + + /* Finish minimal initialisation and run using the scheduler loop + similarly to the main process */ + + DEBUG_LOG("Helper started"); + + SCK_CloseReusableSockets(); + + /* Suppress a log message about disabled clock control */ + log_severity = LOG_GetMinSeverity(); + LOG_SetMinSeverity(LOGS_ERR); + + SYS_Initialise(0); + LOG_SetMinSeverity(log_severity); + + if (!geteuid() && (uid || gid)) + SYS_DropRoot(uid, gid, SYS_NTSKE_HELPER); + + NKS_Initialise(); + + UTI_SetQuitSignalsHandler(helper_signal, 1); + if (scfilter_level != 0) + SYS_EnableSystemCallFilter(scfilter_level, SYS_NTSKE_HELPER); + + SCH_MainLoop(); + + DEBUG_LOG("Helper exiting"); + + NKS_Finalise(); + SCK_Finalise(); + SYS_Finalise(); + SCH_Finalise(); + LCL_Finalise(); + PRV_Finalise(); + CNF_Finalise(); + LOG_Finalise(); + + UTI_ResetGetRandomFunctions(); + + exit(0); +} + +/* ================================================== */ + +void +NKS_PreInitialise(uid_t uid, gid_t gid, int scfilter_level) +{ + int i, processes, sock_fd1, sock_fd2; + const char **certs, **keys; + char prefix[16]; + pid_t pid; + + helper_sock_fd = INVALID_SOCK_FD; + is_helper = 0; + + if (CNF_GetNtsServerCertAndKeyFiles(&certs, &keys) <= 0) + return; + + processes = CNF_GetNtsServerProcesses(); + if (processes <= 0) + return; + + /* Start helper processes to perform (computationally expensive) NTS-KE + sessions with clients on sockets forwarded from the main process */ + + sock_fd1 = SCK_OpenUnixSocketPair(0, &sock_fd2); + if (sock_fd1 < 0) + LOG_FATAL("Could not open socket pair"); + + for (i = 0; i < processes; i++) { + pid = fork(); + + if (pid < 0) + LOG_FATAL("fork() failed : %s", strerror(errno)); + + if (pid > 0) + continue; + + is_helper = 1; + + UTI_ResetGetRandomFunctions(); + + snprintf(prefix, sizeof (prefix), "nks#%d:", i + 1); + LOG_SetDebugPrefix(prefix); + LOG_CloseParentFd(); + + SCK_CloseSocket(sock_fd1); + SCH_AddFileHandler(sock_fd2, SCH_FILE_INPUT, handle_helper_request, NULL); + + run_helper(uid, gid, scfilter_level); + } + + SCK_CloseSocket(sock_fd2); + helper_sock_fd = sock_fd1; +} + +/* ================================================== */ + +void +NKS_Initialise(void) +{ + const char **certs, **keys; + int i, n_certs_keys; + double key_delay; + + server_sock_fd4 = INVALID_SOCK_FD; + server_sock_fd6 = INVALID_SOCK_FD; + + n_certs_keys = CNF_GetNtsServerCertAndKeyFiles(&certs, &keys); + if (n_certs_keys <= 0) + return; + + if (helper_sock_fd == INVALID_SOCK_FD) { + server_credentials = NKSN_CreateServerCertCredentials(certs, keys, n_certs_keys); + if (!server_credentials) + return; + } else { + server_credentials = NULL; + } + + sessions = ARR_CreateInstance(sizeof (NKSN_Instance)); + for (i = 0; i < CNF_GetNtsServerConnections(); i++) + *(NKSN_Instance *)ARR_GetNewElement(sessions) = NULL; + + /* Generate random keys, even if they will be replaced by reloaded keys, + or unused (in the helper) */ + for (i = 0; i < MAX_SERVER_KEYS; i++) { + server_keys[i].siv = NULL; + generate_key(i); + } + + current_server_key = MAX_SERVER_KEYS - 1; + + if (!is_helper) { + server_sock_fd4 = open_socket(IPADDR_INET4); + server_sock_fd6 = open_socket(IPADDR_INET6); + + key_rotation_interval = MAX(CNF_GetNtsRotate(), 0); + + /* Reload saved keys, or save the new keys */ + if (!load_keys()) + save_keys(); + + if (key_rotation_interval > 0) { + key_delay = key_rotation_interval - (SCH_GetLastEventMonoTime() - last_server_key_ts); + SCH_AddTimeoutByDelay(MAX(key_delay, 0.0), key_timeout, NULL); + } + + /* Warn if keys are not saved, which can cause a flood of requests + after server restart */ + if (!CNF_GetNtsDumpDir()) + LOG(LOGS_WARN, "No ntsdumpdir to save server keys"); + } + + initialised = 1; +} + +/* ================================================== */ + +void +NKS_Finalise(void) +{ + int i; + + if (!initialised) + return; + + if (helper_sock_fd != INVALID_SOCK_FD) { + /* Send the helpers a request to exit */ + for (i = 0; i < CNF_GetNtsServerProcesses(); i++) { + if (!SCK_Send(helper_sock_fd, "", 1, 0)) + ; + } + SCK_CloseSocket(helper_sock_fd); + } + if (server_sock_fd4 != INVALID_SOCK_FD) + SCK_CloseSocket(server_sock_fd4); + if (server_sock_fd6 != INVALID_SOCK_FD) + SCK_CloseSocket(server_sock_fd6); + + if (!is_helper) + save_keys(); + + for (i = 0; i < MAX_SERVER_KEYS; i++) + SIV_DestroyInstance(server_keys[i].siv); + + for (i = 0; i < ARR_GetSize(sessions); i++) { + NKSN_Instance session = *(NKSN_Instance *)ARR_GetElement(sessions, i); + if (session) + NKSN_DestroyInstance(session); + } + ARR_DestroyInstance(sessions); + + if (server_credentials) + NKSN_DestroyCertCredentials(server_credentials); +} + +/* ================================================== */ + +void +NKS_DumpKeys(void) +{ + save_keys(); +} + +/* ================================================== */ + +void +NKS_ReloadKeys(void) +{ + /* Don't load the keys if they are expected to be generated by this server + instance (i.e. they are already loaded) to not delay the next rotation */ + if (key_rotation_interval > 0) + return; + + load_keys(); +} + +/* ================================================== */ + +/* A server cookie consists of key ID, nonce, and encrypted C2S+S2C keys */ + +int +NKS_GenerateCookie(NKE_Context *context, NKE_Cookie *cookie) +{ + unsigned char *nonce, plaintext[2 * NKE_MAX_KEY_LENGTH], *ciphertext; + int plaintext_length, tag_length; + ServerCookieHeader *header; + ServerKey *key; + + if (!initialised) { + DEBUG_LOG("NTS server disabled"); + return 0; + } + + /* The AEAD ID is not encoded in the cookie. It is implied from the key + length (as long as only algorithms with different key lengths are + supported). */ + + if (context->c2s.length < 0 || context->c2s.length > NKE_MAX_KEY_LENGTH || + context->s2c.length != context->c2s.length) { + DEBUG_LOG("Invalid key length"); + return 0; + } + + key = &server_keys[current_server_key]; + + header = (ServerCookieHeader *)cookie->cookie; + + header->key_id = htonl(key->id); + + nonce = cookie->cookie + sizeof (*header); + if (key->nonce_length > sizeof (cookie->cookie) - sizeof (*header)) + assert(0); + UTI_GetRandomBytes(nonce, key->nonce_length); + + plaintext_length = context->c2s.length + context->s2c.length; + assert(plaintext_length <= sizeof (plaintext)); + memcpy(plaintext, context->c2s.key, context->c2s.length); + memcpy(plaintext + context->c2s.length, context->s2c.key, context->s2c.length); + + tag_length = SIV_GetTagLength(key->siv); + cookie->length = sizeof (*header) + key->nonce_length + plaintext_length + tag_length; + assert(cookie->length <= sizeof (cookie->cookie)); + ciphertext = cookie->cookie + sizeof (*header) + key->nonce_length; + + if (!SIV_Encrypt(key->siv, nonce, key->nonce_length, + "", 0, + plaintext, plaintext_length, + ciphertext, plaintext_length + tag_length)) { + DEBUG_LOG("Could not encrypt cookie"); + return 0; + } + + return 1; +} + +/* ================================================== */ + +int +NKS_DecodeCookie(NKE_Cookie *cookie, NKE_Context *context) +{ + unsigned char *nonce, plaintext[2 * NKE_MAX_KEY_LENGTH], *ciphertext; + int ciphertext_length, plaintext_length, tag_length; + ServerCookieHeader *header; + ServerKey *key; + uint32_t key_id; + + if (!initialised) { + DEBUG_LOG("NTS server disabled"); + return 0; + } + + if (cookie->length <= (int)sizeof (*header)) { + DEBUG_LOG("Invalid cookie length"); + return 0; + } + + header = (ServerCookieHeader *)cookie->cookie; + + key_id = ntohl(header->key_id); + key = &server_keys[key_id % MAX_SERVER_KEYS]; + if (key_id != key->id) { + DEBUG_LOG("Unknown key %"PRIX32, key_id); + return 0; + } + + tag_length = SIV_GetTagLength(key->siv); + + if (cookie->length <= (int)sizeof (*header) + key->nonce_length + tag_length) { + DEBUG_LOG("Invalid cookie length"); + return 0; + } + + nonce = cookie->cookie + sizeof (*header); + ciphertext = cookie->cookie + sizeof (*header) + key->nonce_length; + ciphertext_length = cookie->length - sizeof (*header) - key->nonce_length; + plaintext_length = ciphertext_length - tag_length; + + if (plaintext_length > sizeof (plaintext) || plaintext_length % 2 != 0) { + DEBUG_LOG("Invalid cookie length"); + return 0; + } + + if (!SIV_Decrypt(key->siv, nonce, key->nonce_length, + "", 0, + ciphertext, ciphertext_length, + plaintext, plaintext_length)) { + DEBUG_LOG("Could not decrypt cookie"); + return 0; + } + + /* Select a supported algorithm corresponding to the key length, avoiding + potentially slow SIV_GetKeyLength() */ + switch (plaintext_length / 2) { + case 16: + context->algorithm = AEAD_AES_128_GCM_SIV; + break; + case 32: + context->algorithm = AEAD_AES_SIV_CMAC_256; + break; + default: + DEBUG_LOG("Unknown key length"); + return 0; + } + + context->c2s.length = plaintext_length / 2; + context->s2c.length = plaintext_length / 2; + assert(context->c2s.length <= sizeof (context->c2s.key)); + + memcpy(context->c2s.key, plaintext, context->c2s.length); + memcpy(context->s2c.key, plaintext + context->c2s.length, context->s2c.length); + + return 1; +} |