Add check for certificate validity

go test -v -run TestCerts

certifi_test.go

@@ -4,11 +4,104 @@
 
 package gocertifi
 
-import "testing"
+import (
+	"crypto/x509"
+	"encoding/pem"
+	"testing"
+	"time"
+)
 
 func TestGetCerts(t *testing.T) {
 	certPool, err := CACerts()
 	if certPool == nil || err != nil || len(certPool.Subjects()) == 0 {
 		t.Errorf("Failed to return the certificates.")
 	}
 }
+
+func parsePEM(pemCerts []byte) (certs []*x509.Certificate, err error) {
+	for len(pemCerts) > 0 {
+		var block *pem.Block
+		block, pemCerts = pem.Decode(pemCerts)
+		if block == nil {
+			break
+		}
+		if block.Type != "CERTIFICATE" || len(block.Headers) != 0 {
+			continue
+		}
+
+		cert, err := x509.ParseCertificate(block.Bytes)
+		if err != nil {
+			return nil, err
+		}
+		certs = append(certs, cert)
+	}
+	return
+}
+
+func checkRootCertsPEM(t *testing.T, pemCerts []byte, when time.Time) (ok bool) {
+	now := time.Now()
+	t.Logf("Checking certificate validity on %s...", when)
+	certs, err := parsePEM(pemCerts)
+	if err != nil {
+		t.Error(err)
+		return false
+	}
+
+	roots := x509.NewCertPool()
+	for _, cert := range certs {
+		roots.AddCert(cert)
+	}
+
+	var minExpires time.Time
+	ok = true
+	for _, cert := range certs {
+		if !cert.IsCA {
+			t.Errorf("\u274C %s: not a certificate authority", cert.Subject)
+		}
+		// This check of keyusage is based on my understanding of key usage purposes
+		// https://cabforum.org/wp-content/uploads/CA-Browser-Forum-BR-1.8.0.pdf
+		// Section 1.4.2 has no usage restrictions
+		if cert.KeyUsage&(x509.KeyUsage(-1)^(x509.KeyUsageCertSign|x509.KeyUsageCRLSign|x509.KeyUsageDigitalSignature)) != 0 {
+			t.Logf("\u26A0 %s key usage %#x (see constants at https://golang.org/pkg/crypto/x509/#KeyUsage)", cert.Subject, cert.KeyUsage)
+		} else if cert.KeyUsage&(x509.KeyUsageCertSign|x509.KeyUsageCRLSign) == 0 {
+			// If the certificate authority is not allowed to sign certificates, why is it here?
+			// https://cabforum.org/baseline-requirements-certificate-contents/#CA-Certificates
+			t.Logf("\u26A0 %s key usage %#x (see constants at https://golang.org/pkg/crypto/x509/#KeyUsage)", cert.Subject, cert.KeyUsage)
+		}
+		if minExpires.IsZero() || cert.NotAfter.Before(minExpires) {
+			minExpires = cert.NotAfter
+		}
+		// Check that the certificate is valid now
+		if cert.NotBefore.After(now) {
+			t.Errorf("\u274C %s: fails NotBefore check: %s", cert.Subject, cert.NotBefore)
+			continue
+		}
+		if cert.NotAfter.Before(now) {
+			t.Errorf("\u274C %s: fails NotAfter check: \033[31m%s\033[m", cert.Subject, cert.NotAfter)
+			// ... and that it will still be valid later
+		} else if cert.NotAfter.Before(when) {
+			t.Logf("\u26A0 %s: fails NotAfter check: \033[31m%s\033[m", cert.Subject, cert.NotAfter)
+			continue
+		}
+		_, err := cert.Verify(x509.VerifyOptions{
+			Roots:       roots,
+			CurrentTime: when,
+		})
+		if err != nil {
+			t.Errorf("\u274C %s: %s", cert.Subject, err)
+			ok = false
+		} else {
+			t.Logf("\u2705 %s (expires: %s)", cert.Subject, cert.NotAfter)
+		}
+	}
+	if ok {
+		t.Log("Success.")
+		t.Logf("MinExpire: %s", minExpires)
+	}
+	return
+}
+
+func TestCerts(t *testing.T) {
+	// Check that certificates will still be valid in 3 months
+	checkRootCertsPEM(t, []byte(pemcerts), time.Now().AddDate(0, 3, 0))
+}