Break the clock and watch authentication fail

short · 40 min · Objective 6.4

Task

Time drift presents as a security problem, which is why it consumes so much diagnostic effort. Skew a clock deliberately and observe certificate and token validation failing before anything mentions time.

Steps

  1. Establish a working TLS connection from the guest to the local service, and a working token-based authentication. Record both in lab/net/time.md.
  2. Disable time synchronisation in the guest and set its clock forward by two years. Retry the TLS connection and record the exact error -- note that it blames the certificate, not the clock.
  3. Set the clock back by two years and retry. Record the different error message for the same underlying cause.
  4. Restore the clock to roughly correct but skewed by ten minutes, and retry the token authentication. Record whether it fails and what it says.
  5. Re-enable synchronisation, confirm everything works, and write the diagnostic rule: what to check first when several unrelated systems fail to authenticate at once.

Verify

grep -Eci 'certificate' lab/net/time.md
grep -Eci 'not yet valid|expired' lab/net/time.md
grep -Eci 'token|skew' lab/net/time.md
grep -Eci 'check the clock|clock first|time first' lab/net/time.md

All four non-zero, with two DIFFERENT certificate errors recorded for the forward and backward skew. Both are the same cause wearing different messages, which is exactly why the fault is hard to spot.

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