1. Instead of storing a single STH per log, we now store one verified
STH and any number of unverified STHs. When we process a log, we verify
each unverified STH using a consistency proof with the verified STH,
and only delete it if it successfully verifies. We set the verified
STH to the largest STH which we've successfully verified.
This has two important benefits. First, we never ever delete an STH
unless we can successfully verify it (previously, we would forget about
an STH under certain error conditions). Second, it lays the groundwork
for STH pollination. Upon reception of an STH, we can simply drop it in
the log's unverified_sths directory (assuming the signature is valid),
and Cert Spotter will audit it.
There is no more "evidence" directory; if a consistency proof fails,
the STHs will already be present elsewhere in the state directory.
2. We now persist a MerkleTreeBuilder between each run of Cert Spotter,
instead of rebuilding it every time from the consistency proof. This is
not intrinsically better, but it makes the code simpler considering we
can now fetch numerous consistency proofs per run.
3. To accommodate the above changes, the state directory has a brand
new layout. The state directory is now versioned, and Cert Spotter
will automatically migrate old state directories to the new layout.
This migration logic will be removed in a future Cert Spotter release.
As a bonus, the code is generally cleaner now :-)
If -all_time is specified, scan the entirety of all logs, even
existing logs. This matches user expectation better. Previously,
-all_time had no impact on existing logs.
The first time Cert Spotter is run, do not scan any logs, unless
-all_time is specified. This avoids a several hour wait the first
time Cert Spotter is run. If the user is interested in knowing
about existing certificates, they can use the certspotter.com API
or crt.sh. This is the same as existing behavior.
When a new log is added, scan it in its entirety even if -all_time is
not specified, so users are alerted to interesting certificates in the
new log. Hopefully new logs will be small and this won't take too long!
Previously, new logs were not scanned in their entirety unless -all_time
was specified.
Closes: #5
An io.Reader does not guarantee that it can read all bytes possible
to fill the input buffer. Thus, we should use io.ReadFull here instead.
Cherry-picked from ddfd4a2b2d89e20f0a7c63c88420aaa419d4d95c
of https://github.com/google/certificate-transparency
Andrew Ayer