fix: NTP syncs as soon as DHCP has a lease, random origin cookie instead of the unsynced local clock, TLS validates certificates against UTC

programs/include/montauk/ntp.h

@@ -51,42 +51,6 @@ inline uint32_t read_be32(const uint8_t* p) {
            ((uint32_t)p[2] << 8) | (uint32_t)p[3];
 }
 
-inline void write_be64(uint8_t* p, uint64_t value) {
-    for (int i = 7; i >= 0; i--) {
-        p[i] = (uint8_t)value;
-        value >>= 8;
-    }
-}
-
-inline bool is_leap_year(int year) {
-    return (year % 4 == 0 && year % 100 != 0) || (year % 400 == 0);
-}
-
-inline int days_in_month(int month, int year) {
-    static const int days[] = {0, 31, 28, 31, 30, 31, 30,
-                               31, 31, 30, 31, 30, 31};
-    return month == 2 && is_leap_year(year) ? 29 : days[month];
-}
-
-inline int64_t current_unix_seconds() {
-    montauk::abi::DateTime now = {};
-    montauk::gettime(&now);
-    if (now.Year < 1970 || now.Month < 1 || now.Month > 12 ||
-        now.Day < 1 || now.Day > days_in_month(now.Month, now.Year))
-        return 0;
-
-    int64_t days = 0;
-    for (int year = 1970; year < (int)now.Year; year++)
-        days += is_leap_year(year) ? 366 : 365;
-    for (int month = 1; month < (int)now.Month; month++)
-        days += days_in_month(month, now.Year);
-    days += now.Day - 1;
-
-    int64_t local = days * 86400 + (int64_t)now.Hour * 3600 +
-                    (int64_t)now.Minute * 60 + now.Second;
-    return local - (int64_t)montauk::gettz() * 60;
-}
-
 inline bool same_bytes(const uint8_t* a, const uint8_t* b, int count) {
     for (int i = 0; i < count; i++) {
         if (a[i] != b[i]) return false;
@@ -115,14 +79,15 @@ inline int synchronize(const char* server, uint32_t timeout_ms = 5000,
     request[2] = 6;    // poll exponent: 2^6 = 64 seconds
     request[3] = 0xEC; // precision: approximately 2^-20 seconds
 
-    int64_t unix_now = current_unix_seconds();
-    if (unix_now <= 0) {
+    // The transmit timestamp only has to come back in the reply's origin
+    // field, so send a random cookie rather
+    // than the local clock, which may still be invalid before the first sync.
+    uint8_t cookie[8];
+    if (montauk::getrandom(cookie, sizeof(cookie)) != (int64_t)sizeof(cookie)) {
         montauk::closesocket(fd);
         return CLOCK_ERROR;
     }
-    uint64_t transmit_timestamp =
-        ((uint64_t)unix_now + UNIX_EPOCH_DELTA) << 32;
-    write_be64(request + 40, transmit_timestamp);
+    for (int i = 0; i < 8; i++) request[40 + i] = cookie[i];
 
     progress(progress_callback, "Sending NTP request...");
     if (montauk::sendto(fd, request, sizeof(request), server_ip, SERVER_PORT) < 0) {

programs/include/montauk/syscall.h

@@ -505,6 +505,8 @@ namespace montauk {
 
     // Timekeeping (wall-clock)
     inline void gettime(montauk::abi::DateTime* out) { syscall1(montauk::abi::SYS_GETTIME, (uint64_t)out); }
+    // UTC seconds since 1970 (gettime() is local time).
+    inline int64_t get_unix_time() { return syscall0(montauk::abi::SYS_GETUNIXTIME); }
     inline int set_unix_time(int64_t unix_seconds) {
         return (int)syscall1(montauk::abi::SYS_SETUNIXTIME, (uint64_t)unix_seconds);
     }