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/ctcrypto/key.go

@@ -0,0 +1,67 @@
+// Copyright (C) 2025 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 ctcrypto
+
+import (
+	"bytes"
+	"crypto"
+	"crypto/ecdsa"
+	"crypto/rsa"
+	"crypto/x509"
+	"fmt"
+
+	"software.sslmate.com/src/certspotter/tlstypes"
+)
+
+type PublicKey []byte
+
+func (key PublicKey) Verify(input SignatureInput, signature tlstypes.DigitallySigned) error {
+	parsedKey, err := x509.ParsePKIXPublicKey(key)
+	if err != nil {
+		return fmt.Errorf("error parsing log key: %w", err)
+	}
+	switch key := parsedKey.(type) {
+	case *rsa.PublicKey:
+		if signature.Algorithm.Signature != tlstypes.RSA {
+			return fmt.Errorf("log key is RSA but this is not an RSA signature")
+		}
+		if signature.Algorithm.Hash != tlstypes.SHA256 {
+			return fmt.Errorf("unsupported hash algorithm %v (only SHA-256 is allowed in CT)", signature.Algorithm.Hash)
+		}
+		if rsa.VerifyPKCS1v15((*rsa.PublicKey)(key), crypto.SHA256, input[:], signature.Signature) != nil {
+			return fmt.Errorf("RSA signature is incorrect")
+		}
+		return nil
+
+	case *ecdsa.PublicKey:
+		if signature.Algorithm.Signature != tlstypes.ECDSA {
+			return fmt.Errorf("log key is ECDSA but this is not an ECDSA signature")
+		}
+		if signature.Algorithm.Hash != tlstypes.SHA256 {
+			return fmt.Errorf("unsupported hash algorithm %v (only SHA-256 is allowed in CT)", signature.Algorithm.Hash)
+		}
+		if !ecdsa.VerifyASN1((*ecdsa.PublicKey)(key), input[:], signature.Signature) {
+			return fmt.Errorf("ECDSA signature is incorrect")
+		}
+
+	default:
+		return fmt.Errorf("unsupported public key type %T (CT only allows RSA and ECDSA)", key)
+	}
+	return nil
+}
+
+func (key PublicKey) MarshalBinary() ([]byte, error) {
+	return bytes.Clone(key), nil
+}
+
+func (key *PublicKey) UnmarshalBinary(data []byte) error {
+	*key = bytes.Clone(data)
+	return nil
+}

third_party/certspotter/ctcrypto/signatures.go

@@ -0,0 +1,55 @@
+// Copyright (C) 2025 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 ctcrypto
+
+import (
+	"crypto/sha256"
+	"golang.org/x/crypto/cryptobyte"
+
+	"software.sslmate.com/src/certspotter/cttypes"
+)
+
+type SignatureInput [32]byte
+
+func MakeSignatureInput(message []byte) SignatureInput {
+	return sha256.Sum256(message)
+}
+
+func SignatureInputForPrecertSCT(sct *cttypes.SignedCertificateTimestamp, precert cttypes.PreCert) SignatureInput {
+	var builder cryptobyte.Builder
+	builder.AddValue(sct.SCTVersion)
+	builder.AddValue(cttypes.CertificateTimestampSignatureType)
+	builder.AddUint64(sct.Timestamp)
+	builder.AddValue(cttypes.PrecertEntryType)
+	builder.AddValue(&precert)
+	builder.AddValue(sct.Extensions)
+	return MakeSignatureInput(builder.BytesOrPanic())
+}
+
+func SignatureInputForCertSCT(sct *cttypes.SignedCertificateTimestamp, cert cttypes.ASN1Cert) SignatureInput {
+	var builder cryptobyte.Builder
+	builder.AddValue(sct.SCTVersion)
+	builder.AddValue(cttypes.CertificateTimestampSignatureType)
+	builder.AddUint64(sct.Timestamp)
+	builder.AddValue(cttypes.X509EntryType)
+	builder.AddValue(cert)
+	builder.AddValue(sct.Extensions)
+	return MakeSignatureInput(builder.BytesOrPanic())
+}
+
+func SignatureInputForSTH(sth *cttypes.SignedTreeHead) SignatureInput {
+	var builder cryptobyte.Builder
+	builder.AddValue(cttypes.V1)
+	builder.AddValue(cttypes.TreeHashSignatureType)
+	builder.AddUint64(sth.Timestamp)
+	builder.AddUint64(sth.TreeSize)
+	builder.AddBytes(sth.RootHash[:])
+	return MakeSignatureInput(builder.BytesOrPanic())
+}