add component to fetch all URLs from CCADB

ccadb/ccadb.go

@@ -0,0 +1,289 @@
+package ccadb
+
+import (
+	"context"
+	"crypto/x509"
+	_ "embed"
+	"encoding/base64"
+	"encoding/csv"
+	"encoding/json"
+	"encoding/pem"
+	"errors"
+	"fmt"
+	"io"
+	"log"
+	"net/http"
+	"slices"
+	"time"
+
+	"github.com/letsencrypt/boulder/crl/checker"
+	"github.com/letsencrypt/crl-monitor/cmd"
+	"github.com/letsencrypt/crl-monitor/idp"
+)
+
+//go:embed intermediates.pem
+var allIssuers []byte
+
+const (
+	CCADBAllCertificatesCSVURL cmd.EnvVar = "CCADB_ALL_CERTIFICATES_CSV_URL"
+	CRLAgeLimit                cmd.EnvVar = "CRL_AGE_LIMIT"
+	CAOwner                    cmd.EnvVar = "CA_OWNER"
+)
+
+// Checker fetches the AllCertificatesRecordsReport from CCADB, filters for a
+// specific CA Owner (defaults to 'Internet Security Research Group'), and
+// fetches all CRLs found.
+//
+// It checks that the CRLs:
+//   - Are not too old
+//   - Have an issuingDistributionPoint that matches the URL from which they
+//     were fetched
+//   - Have a valid signature based on their issuer SKID from CCADB
+//     (full issuer certificates for ISRG are embedded in this binary)
+//   - Don't have duplicate serial numbers across different CRLs
+type Checker struct {
+	allCertificatesCSVURL string
+	caOwner               string
+	crlAgeLimit           time.Duration
+
+	// Map from SKID (bytes cast to string) to issuer.
+	issuers map[string]*x509.Certificate
+}
+
+func NewFromEnv() (*Checker, error) {
+	ccadbAllCertificatesCSVURL := "https://ccadb.my.salesforce-sites.com/ccadb/AllCertificateRecordsCSVFormatv2"
+	allCertsCSV, ok := CCADBAllCertificatesCSVURL.LookupEnv()
+	if ok {
+		ccadbAllCertificatesCSVURL = allCertsCSV
+	}
+
+	caOwner := "Internet Security Research Group"
+	owner, ok := CAOwner.LookupEnv()
+	if ok {
+		caOwner = owner
+	}
+
+	ageLimitDuration := 24 * time.Hour
+	crlAgeLimit, ok := CRLAgeLimit.LookupEnv()
+	if ok {
+		var err error
+		ageLimitDuration, err = time.ParseDuration(crlAgeLimit)
+		if err != nil {
+			return nil, fmt.Errorf("parsing age limit: %s", err)
+		}
+	}
+
+	issuers, err := parseIssuers()
+	if err != nil {
+		return nil, err
+	}
+
+	return &Checker{
+		allCertificatesCSVURL: ccadbAllCertificatesCSVURL,
+		caOwner:               caOwner,
+		crlAgeLimit:           ageLimitDuration,
+		issuers:               issuers,
+	}, nil
+}
+
+func (c *Checker) Check(ctx context.Context) error {
+	crlURLs, err := c.getCRLURLs(ctx, c.allCertificatesCSVURL, c.caOwner)
+	if err != nil {
+		return err
+	}
+
+	var crls, entries, bytes int
+
+	serials := make(map[string]*x509.RevocationList)
+
+	var errs []error
+	for skid, urls := range crlURLs {
+		for _, url := range urls {
+			crls++
+			issuer := c.issuers[skid]
+			if issuer == nil {
+				return fmt.Errorf("no issuer found for skid %x", skid)
+			}
+			crl, err := checkCRL(ctx, url, issuer, c.crlAgeLimit)
+			if err != nil {
+				errs = append(errs, fmt.Errorf("fetching %s: %s", url, err))
+				continue
+			}
+
+			// Check for duplicates across different CRLs (or within a CRL).
+			// Cap any given CRL at 1M entries to limit memory use.
+			for i, entry := range crl.RevokedCertificateEntries {
+				if i > 1_000_000 {
+					break
+				}
+				serialByteString := string(entry.SerialNumber.Bytes())
+				if otherCRL, ok := serials[serialByteString]; ok {
+					otherCRLURL, err := idp.Get(otherCRL)
+					if err != nil {
+						return err
+					}
+					errs = append(errs, fmt.Errorf("serial %x seen on multiple CRLs: %s and %s", entry.SerialNumber, otherCRLURL, url))
+				}
+				serials[serialByteString] = crl
+			}
+
+			age := time.Since(crl.ThisUpdate).Round(time.Minute)
+			nextUpdate := time.Until(crl.NextUpdate).Round(time.Hour)
+			entries += len(crl.RevokedCertificateEntries)
+			bytes += len(crl.Raw)
+			log.Printf("crl %q: %d entries, %d bytes, age %gm, nextUpdate %gh", url, len(crl.RevokedCertificateEntries), len(crl.Raw), age.Minutes(), nextUpdate.Hours())
+		}
+	}
+
+	log.Printf("%d CRLs had %d entries and %d bytes", crls, entries, bytes)
+	return errors.Join(errs...)
+}
+
+func checkCRL(ctx context.Context, url string, issuer *x509.Certificate, ageLimit time.Duration) (*x509.RevocationList, error) {
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, url, nil)
+	if err != nil {
+		return nil, err
+	}
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode != http.StatusOK {
+		return nil, fmt.Errorf("HTTP status code %d", resp.StatusCode)
+	}
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return nil, fmt.Errorf("reading CRL body: %s", err)
+	}
+	crl, err := x509.ParseRevocationList(body)
+	if err != nil {
+		return nil, err
+	}
+
+	idp, err := idp.Get(crl)
+	if err != nil {
+		return nil, err
+	}
+
+	if idp != url {
+		return nil, fmt.Errorf("CRL fetched from %s had mismatched IDP %s", url, idp)
+	}
+
+	return crl, checker.Validate(crl, issuer, ageLimit)
+}
+
+// returns a map from issuer SKID to list of URLs
+func (c Checker) getCRLURLs(ctx context.Context, csvURL string, owner string) (map[string][]string, error) {
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, csvURL, nil)
+	if err != nil {
+		return nil, err
+	}
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode != http.StatusOK {
+		return nil, fmt.Errorf("HTTP status code %d", resp.StatusCode)
+	}
+	reader := csv.NewReader(resp.Body)
+	header, err := reader.Read()
+	if err != nil {
+		return nil, err
+	}
+
+	var ownerIndex, crlIndex, skidIndex, certificateNameIndex int
+	for i, name := range header {
+		if name == "CA Owner" {
+			ownerIndex = i
+		}
+		if name == "JSON Array of Partitioned CRLs" {
+			crlIndex = i
+		}
+		if name == "Subject Key Identifier" {
+			skidIndex = i
+		}
+		if name == "Certificate Name" {
+			certificateNameIndex = i
+		}
+	}
+	allCRLs := make(map[string][]string)
+	for {
+		record, err := reader.Read()
+		if err == io.EOF {
+			break
+		}
+		if err != nil {
+			return nil, err
+		}
+		if record[ownerIndex] != owner {
+			continue
+		}
+		crlJSON := record[crlIndex]
+		if crlJSON == "" {
+			continue
+		}
+		var crls []string
+		err = json.Unmarshal([]byte(crlJSON), &crls)
+		if err != nil {
+			return nil, err
+		}
+		// Roots have a CRL list containing a single ""
+		if len(crls) == 1 && crls[0] == "" {
+			continue
+		}
+		certificateName := record[certificateNameIndex]
+		skidBase64 := record[skidIndex]
+		skid, err := base64.StdEncoding.DecodeString(skidBase64)
+		if err != nil {
+			return nil, err
+		}
+		if len(skid) == 0 {
+			return nil, fmt.Errorf("no skid for %q", certificateName)
+		}
+		stringSKID := string(skid)
+		if c.issuers[stringSKID] == nil {
+			return nil, fmt.Errorf("CCADB contained %q with SKID %x, but that SKID is not in embedded issuers file. Might need update and rebuild this binary",
+				certificateName, skid)
+		}
+		// An issuer can show up multiple times, under different cross-signs. However
+		// it must have the same list of CRLs each time.
+		if c := allCRLs[stringSKID]; c != nil && !slices.Equal(c, crls) {
+			return nil, fmt.Errorf("CCADB contained %q with SKID %x multiple times with different CRLs", certificateName, skid)
+		}
+		allCRLs[stringSKID] = crls
+	}
+
+	if len(allCRLs) == 0 {
+		return nil, fmt.Errorf("no records found in CCADB for CA Owner %q", owner)
+	}
+	return allCRLs, nil
+}
+
+// getIssuers parses the embedded PEM file containing multiple intermediates.
+//
+// The file should contain an entry for every issuer that is listed in the
+// CCADB All Certificates list for the relevant CA Organization.
+//
+// Returns a map from SubjectKeyId (cast from []byte to string) to the
+// matching intermediate.
+func parseIssuers() (map[string]*x509.Certificate, error) {
+	ret := make(map[string]*x509.Certificate)
+
+	remaining := allIssuers
+	for {
+		var block *pem.Block
+		block, remaining = pem.Decode(remaining)
+		if block == nil {
+			return ret, nil
+		}
+
+		cert, err := x509.ParseCertificate(block.Bytes)
+		if err != nil {
+			return nil, err
+		}
+
+		ret[string(cert.SubjectKeyId)] = cert
+	}
+}