x509roots/nss: manually exclude a confusingly constrained root

Fixes golang/go#61963

Change-Id: I16920d160af74772ef5aa650d1274e07c3ca9adc
Reviewed-on: https://go-review.googlesource.com/c/crypto/+/562475
Reviewed-by: Filippo Valsorda <filippo@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>

Author: rolandshoemaker

x509roots/fallback/bundle.go

@@ -147,6 +147,20 @@ func parseTrustClass(s *bufio.Scanner) ([sha1.Size]byte, *trustObj, error) {
 	return h, to, nil
 }
 
+// manualExclusions contains a map of SHA1 fingerprints of roots that we manually exclude
+// from the bundle for various reasons.
+var manualExclusions = map[string]bool{
+	// TUBITAK Kamu SM SSL Kok Sertifikasi - Surum 1
+	// We exclude this root because mozilla manually constrains this root to
+	// issue names under .tr, but this information is only encoded in the CCADB
+	// IncludedCACertificateReport, in a field the format of which is
+	// undocumented, and is only used for this particular certificate. Rather
+	// than adding special parsing for this, we skip it. When code constraint
+	// support is available, we may also want to simply add a manual constraint,
+	// rather than a manual exclusion.
+	"3143649becce27eced3a3f0b8f0de4e891ddeeca": true,
+}
+
 // Parse parses a NSS certdata.txt formatted file, returning only
 // trusted serverAuth roots, as well as any additional constraints. This parser
 // is very opinionated, only returning roots that are currently trusted for
@@ -248,6 +262,9 @@ func Parse(r io.Reader) ([]*Certificate, error) {
 		if !e.trust.trusted {
 			continue
 		}
+		if manualExclusions[fmt.Sprintf("%x", h)] {
+			continue
+		}
 		nssCert := &Certificate{X509: e.cert.c}
 		if e.cert.DistrustAfter != nil {
 			nssCert.Constraints = append(nssCert.Constraints, DistrustAfter(*e.cert.DistrustAfter))