ctcloud: CertSpotter-backed CT cloud-resource monitor

Single stateless Go process that consumes CT logs via embedded (patched)
CertSpotter internals, classifies cloud/database/storage DNS identifiers
in-process with a zero-allocation classifier, enriches via round-robin DNS
resolvers with CNAME following, and batch-writes useful findings to PostgreSQL.

- third_party/certspotter: 2-hunk IdentifierSink patch, no stdout/JSON/files
- internal/classify: AWS/Azure/GCP/Firebase/Cloudflare R2/DigitalOcean/Supabase/OCI
- internal/dns: sharded bounded TTL cache, multi-resolver load balancing + failover
- internal/pipeline: bounded queues, dedup, direct-priority load shedding
- internal/store: pgx batch writer, Postgres CT checkpoints (no cert contents)
- internal/probe: optional non-destructive reachability checks (off by default)
- Docker: distroless non-root, read-only rootfs, no app volume, resource limits
- tests enforce 0 allocs/op on the classifier and sink hot path

third_party/certspotter/monitor/state.go

@@ -0,0 +1,91 @@
+// Copyright (C) 2024 Opsmate, Inc.
+//
+// This Source Code Form is subject to the terms of the Mozilla
+// Public License, v. 2.0. If a copy of the MPL was not distributed
+// with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
+//
+// This software is distributed WITHOUT A WARRANTY OF ANY KIND.
+// See the Mozilla Public License for details.
+
+package monitor
+
+import (
+	"context"
+	"time"
+
+	"software.sslmate.com/src/certspotter/cttypes"
+	"software.sslmate.com/src/certspotter/loglist"
+	"software.sslmate.com/src/certspotter/merkletree"
+)
+
+type LogState struct {
+	DownloadPosition *merkletree.CollapsedTree `json:"download_position"`
+	VerifiedPosition *merkletree.CollapsedTree `json:"verified_position"`
+	VerifiedSTH      *cttypes.SignedTreeHead   `json:"verified_sth"`
+	LastSuccess      time.Time                 `json:"last_success"`
+}
+
+func (state *LogState) rewindDownloadPosition() {
+	position := state.VerifiedPosition.Clone()
+	state.DownloadPosition = &position
+}
+
+func (state *LogState) advanceVerifiedPosition() {
+	position := state.DownloadPosition.Clone()
+	state.VerifiedPosition = &position
+}
+
+// Methods are safe to call concurrently.
+type StateProvider interface {
+	// Initialize the state.  Called before any other method in this interface.
+	// Idempotent: returns nil if the state is already initialized.
+	Prepare(context.Context) error
+
+	// Initialize the state for the given log.  Called before any other method
+	// with the log ID.  Idempotent: returns nil if log state already initialized.
+	PrepareLog(context.Context, LogID) error
+
+	// Store log state for retrieval by LoadLogState.
+	StoreLogState(context.Context, LogID, *LogState) error
+
+	// Load log state that was previously stored with StoreLogState.
+	// Returns nil, nil if StoreLogState has not been called yet for this log.
+	LoadLogState(context.Context, LogID) (*LogState, error)
+
+	// Store STH for retrieval by LoadSTHs.  If an STH with the same
+	// timestamp and root hash is already stored, this STH can be ignored.
+	StoreSTH(context.Context, LogID, *cttypes.SignedTreeHead) (*StoredSTH, error)
+
+	// Load all STHs for this log previously stored with StoreSTH.
+	// The returned slice must be sorted by tree size.
+	LoadSTHs(context.Context, LogID) ([]*StoredSTH, error)
+
+	// Remove an STH so it is no longer returned by LoadSTHs.
+	RemoveSTH(context.Context, LogID, *cttypes.SignedTreeHead) error
+
+	// Store a DER-encoded issuer certificate with the given fingerprint for
+	// retrieval by LoadIssuer.  Returns nil if the issuer has already been stored.
+	StoreIssuer(context.Context, *[32]byte, []byte) error
+
+	// Retrieve a DER-encoded issuer certificate previously stored with StoreIssuer.
+	// Returns nil, nil if this issuer certificate has not been stored.
+	LoadIssuer(context.Context, *[32]byte) ([]byte, error)
+
+	// Called when a certificate matching the watch list is discovered.
+	NotifyCert(context.Context, *DiscoveredCert) error
+
+	// Called when certspotter fails to parse a log entry.
+	NotifyMalformedEntry(context.Context, *LogEntry, error) error
+
+	// Called when a health check fails.  The log is nil if the
+	// feailure is not associated with a log.
+	NotifyHealthCheckFailure(context.Context, *loglist.Log, HealthCheckFailure) error
+
+	// Called when a non-fatal error occurs.  The log is nil if the error is
+	// not associated with a log.  Note that most errors are transient, and
+	// certspotter will retry the failed operation later.
+	NotifyError(context.Context, *loglist.Log, error) error
+
+	// Retrieve the specified number of most recent errors.
+	GetErrors(context.Context, *loglist.Log, int) (string, error)
+}