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// Copyright (C) 2023 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 (
"bytes"
"context"
"crypto/sha256"
"encoding/hex"
"errors"
"fmt"
"io/fs"
"os"
"path/filepath"
"software.sslmate.com/src/certspotter"
"software.sslmate.com/src/certspotter/ct"
"software.sslmate.com/src/certspotter/loglist"
"software.sslmate.com/src/certspotter/merkletree"
)
type logEntry struct {
Log *loglist.Log
Index uint64
LeafInput []byte
ExtraData []byte
LeafHash merkletree.Hash
}
func processLogEntry(ctx context.Context, config *Config, entry *logEntry) error {
leaf, err := ct.ReadMerkleTreeLeaf(bytes.NewReader(entry.LeafInput))
if err != nil {
return processMalformedLogEntry(ctx, config, entry, fmt.Errorf("error parsing Merkle Tree Leaf: %w", err))
}
switch leaf.TimestampedEntry.EntryType {
case ct.X509LogEntryType:
return processX509LogEntry(ctx, config, entry, leaf.TimestampedEntry.X509Entry)
case ct.PrecertLogEntryType:
return processPrecertLogEntry(ctx, config, entry, leaf.TimestampedEntry.PrecertEntry)
default:
return processMalformedLogEntry(ctx, config, entry, fmt.Errorf("unknown log entry type %d", leaf.TimestampedEntry.EntryType))
}
}
func processX509LogEntry(ctx context.Context, config *Config, entry *logEntry, cert ct.ASN1Cert) error {
certInfo, err := certspotter.MakeCertInfoFromRawCert(cert)
if err != nil {
return processMalformedLogEntry(ctx, config, entry, fmt.Errorf("error parsing X.509 certificate: %w", err))
}
chain, err := ct.UnmarshalX509ChainArray(entry.ExtraData)
if err != nil {
return processMalformedLogEntry(ctx, config, entry, fmt.Errorf("error parsing extra_data for X.509 entry: %w", err))
}
chain = append([]ct.ASN1Cert{cert}, chain...)
if precertTBS, err := certspotter.ReconstructPrecertTBS(certInfo.TBS); err == nil {
certInfo.TBS = precertTBS
} else {
return processMalformedLogEntry(ctx, config, entry, fmt.Errorf("error reconstructing precertificate TBSCertificate: %w", err))
}
return processCertificate(ctx, config, entry, certInfo, chain)
}
func processPrecertLogEntry(ctx context.Context, config *Config, entry *logEntry, precert ct.PreCert) error {
certInfo, err := certspotter.MakeCertInfoFromRawTBS(precert.TBSCertificate)
if err != nil {
return processMalformedLogEntry(ctx, config, entry, fmt.Errorf("error parsing precert TBSCertificate: %w", err))
}
chain, err := ct.UnmarshalPrecertChainArray(entry.ExtraData)
if err != nil {
return processMalformedLogEntry(ctx, config, entry, fmt.Errorf("error parsing extra_data for precert entry: %w", err))
}
if _, err := certspotter.ValidatePrecert(chain[0], precert.TBSCertificate); err != nil {
return processMalformedLogEntry(ctx, config, entry, fmt.Errorf("precertificate in extra_data does not match TBSCertificate in leaf_input: %w", err))
}
return processCertificate(ctx, config, entry, certInfo, chain)
}
func processCertificate(ctx context.Context, config *Config, entry *logEntry, certInfo *certspotter.CertInfo, chain []ct.ASN1Cert) error {
identifiers, err := certInfo.ParseIdentifiers()
if err != nil {
return processMalformedLogEntry(ctx, config, entry, err)
}
matched, watchItem := config.WatchList.Matches(identifiers)
if !matched {
return nil
}
cert := &discoveredCert{
WatchItem: watchItem,
LogEntry: entry,
Info: certInfo,
Chain: chain,
TBSSHA256: sha256.Sum256(certInfo.TBS.Raw),
SHA256: sha256.Sum256(chain[0]),
PubkeySHA256: sha256.Sum256(certInfo.TBS.PublicKey.FullBytes),
Identifiers: identifiers,
}
var notifiedPath string
if config.SaveCerts {
hexFingerprint := hex.EncodeToString(cert.SHA256[:])
prefixPath := filepath.Join(config.StateDir, "certs", hexFingerprint[0:2])
var (
notifiedFilename = "." + hexFingerprint + ".notified"
certFilename = hexFingerprint + ".pem"
jsonFilename = hexFingerprint + ".v1.json"
textFilename = hexFingerprint + ".txt"
legacyCertFilename = hexFingerprint + ".cert.pem"
legacyPrecertFilename = hexFingerprint + ".precert.pem"
)
for _, filename := range []string{notifiedFilename, legacyCertFilename, legacyPrecertFilename} {
if fileExists(filepath.Join(prefixPath, filename)) {
return nil
}
}
if err := os.Mkdir(prefixPath, 0777); err != nil && !errors.Is(err, fs.ErrExist) {
return fmt.Errorf("error creating directory in which to save certificate %x: %w", cert.SHA256, err)
}
notifiedPath = filepath.Join(prefixPath, notifiedFilename)
cert.CertPath = filepath.Join(prefixPath, certFilename)
cert.JSONPath = filepath.Join(prefixPath, jsonFilename)
cert.TextPath = filepath.Join(prefixPath, textFilename)
if err := cert.save(); err != nil {
return fmt.Errorf("error saving certificate %x: %w", cert.SHA256, err)
}
} else {
// TODO-4: save cert to temporary files, and defer their unlinking
}
if err := notify(ctx, config, cert); err != nil {
return fmt.Errorf("error notifying about discovered certificate for %s (%x): %w", cert.WatchItem, cert.SHA256, err)
}
if notifiedPath != "" {
if err := os.WriteFile(notifiedPath, nil, 0666); err != nil {
return fmt.Errorf("error saving certificate %x: %w", cert.SHA256, err)
}
}
return nil
}
func processMalformedLogEntry(ctx context.Context, config *Config, entry *logEntry, parseError error) error {
dirPath := filepath.Join(config.StateDir, "logs", entry.Log.LogID.Base64URLString(), "malformed_entries")
malformed := &malformedLogEntry{
Entry: entry,
Error: parseError.Error(),
EntryPath: filepath.Join(dirPath, fmt.Sprintf("%d.json", entry.Index)),
TextPath: filepath.Join(dirPath, fmt.Sprintf("%d.txt", entry.Index)),
}
if err := malformed.save(); err != nil {
return fmt.Errorf("error saving malformed log entry %d in %s (%q): %w", entry.Index, entry.Log.URL, parseError, err)
}
if err := notify(ctx, config, malformed); err != nil {
return fmt.Errorf("error notifying about malformed log entry %d in %s (%q): %w", entry.Index, entry.Log.URL, parseError, err)
}
return nil
}
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