Added sanity check for bios clock errors

When bios clock resets to 1979, terminus reads that, determines the threshold
has not been exceeded (because it's a negative number since lastlogin obviously
ahead of 1979), and writes the new lastlogin time, which is in 1979. If ntp
then updates the clock, the user hasn't logged in in over 35 years, likely
exceeding their set threshold.

This puts in a sanity check to ensure the difference between lastlogin and now
is a positive number. If the difference exceeds -1 day, terminus exits since
the system clock is evidently unreliable.

1 files changed, 9 insertions, 0 deletions

diff --git a/src/main.c b/src/main.c
index fa89688..372e011 100644
--- a/src/main.c
+++ b/src/main.c
@@ -209,6 +209,15 @@ int main(int argc, char* argv[]) {
   if((now - lastlogin) > threshold) {
     printf("You're dead!\n");
     exec_cmd(cmd);
+  } else if((lastlogin - now) > -86400) {
+    // Abort if last login is too far in the future.
+    // This should account for when 
+    printf(
+      "Error: Last login appears to be over one day in the future.\n"
+      "This likely means something has gone wrong with the system clock.\n"
+      "Unable to determine current time. Aborting terminus check.\n"
+    );
+    return 2;
   } else {
     if(write_lastlogin(lastlogin_path) == 1) {
       printf("Failure writing lastlogin\n");