Fix edge case with isCA

Signed-off-by: Maartje Eyskens <maartje@eyskens.me>

pkg/internal/apis/certmanager/validation/certificaterequest.go

@@ -63,6 +63,9 @@ func ValidateCertificateRequestSpec(crSpec *cmapi.CertificateRequestSpec, fldPat
 		} else {
 			// only compare usages if set on CR and in the CSR
 			if len(crSpec.Usages) > 0 && len(csr.Extensions) > 0 && validateCSRContent && !reflect.DeepEqual(crSpec.Usages, defaultInternalKeyUsages) {
+				if crSpec.IsCA {
+					crSpec.Usages = ensureCertSignIsSet(crSpec.Usages)
+				}
 				csrUsages, err := getCSRKeyUsage(crSpec, fldPath, csr, el)
 				if len(err) > 0 {
 					el = append(el, err...)
@@ -156,3 +159,16 @@ func isUsageEqual(a, b []cmapi.KeyUsage) bool {
 
 	return util.EqualUnsorted(aStrings, bStrings)
 }
+
+// ensureCertSignIsSet adds UsageCertSign in case it is not set
+// TODO: add a mutating webhook to make sure this is always set
+// when isCA is true.
+func ensureCertSignIsSet(list []cmapi.KeyUsage) []cmapi.KeyUsage {
+	for _, usage := range list {
+		if usage == cmapi.UsageCertSign {
+			return list
+		}
+	}
+
+	return append(list, cmapi.UsageCertSign)
+}

pkg/internal/apis/certmanager/validation/certificaterequest_test.go

@@ -75,6 +75,26 @@ func TestValidateCertificateRequestSpec(t *testing.T) {
 			},
 			want: []*field.Error{},
 		},
+		{
+			name: "Test csr that is CA with usages set",
+			crSpec: &cminternal.CertificateRequestSpec{
+				Request:   mustGenerateCSR(t, gen.Certificate("test", gen.SetCertificateDNSNames("example.com"), gen.SetCertificateKeyUsages(cmapi.UsageAny, cmapi.UsageDigitalSignature, cmapi.UsageKeyEncipherment, cmapi.UsageCertSign), gen.SetCertificateIsCA(true))),
+				IssuerRef: validIssuerRef,
+				IsCA:      true,
+				Usages:    []cminternal.KeyUsage{cminternal.UsageAny, cminternal.UsageDigitalSignature, cminternal.UsageKeyEncipherment, cminternal.UsageCertSign},
+			},
+			want: []*field.Error{},
+		},
+		{
+			name: "Test csr that is CA but no cert sign in usages",
+			crSpec: &cminternal.CertificateRequestSpec{
+				Request:   mustGenerateCSR(t, gen.Certificate("test", gen.SetCertificateDNSNames("example.com"), gen.SetCertificateKeyUsages(cmapi.UsageAny, cmapi.UsageDigitalSignature, cmapi.UsageKeyEncipherment, cmapi.UsageClientAuth, cmapi.UsageServerAuth), gen.SetCertificateIsCA(true))),
+				IssuerRef: validIssuerRef,
+				IsCA:      true,
+				Usages:    []cminternal.KeyUsage{cminternal.UsageAny, cminternal.UsageDigitalSignature, cminternal.UsageKeyEncipherment, cminternal.UsageClientAuth, cminternal.UsageServerAuth},
+			},
+			want: []*field.Error{},
+		},
 		{
 			name: "Error on csr not having all usages",
 			crSpec: &cminternal.CertificateRequestSpec{