Fix for duplicate SANs in signed certificates

builtin/logical/pki/backend_test.go

@@ -2131,10 +2131,21 @@ func runTestSignVerbatim(t *testing.T, keyType string) {
 	if err != nil {
 		t.Fatal(err)
 	}
+	oidExtensionSubjectAltName = []int{2, 5, 29, 17}
 	csrReq := &x509.CertificateRequest{
 		Subject: pkix.Name{
 			CommonName: "foo.bar.com",
 		},
+		// Check that otherName extensions are not duplicated (see hashicorp/vault#16700).
+		// If these extensions are duplicated, sign-verbatim will fail when parsing the signed certificate on Go 1.19+ (see golang/go#50988).
+		// On older versions of Go this test will fail due to an explicit check for duplicate otherNames later in this test.
+		ExtraExtensions: []pkix.Extension{
+			{
+				Id:       oidExtensionSubjectAltName,
+				Critical: false,
+				Value:    []byte{0x30, 0x26, 0xA0, 0x24, 0x06, 0x0A, 0x2B, 0x06, 0x01, 0x04, 0x01, 0x82, 0x37, 0x14, 0x02, 0x03, 0xA0, 0x16, 0x0C, 0x14, 0x75, 0x73, 0x65, 0x72, 0x6E, 0x61, 0x6D, 0x65, 0x40, 0x65, 0x78, 0x61, 0x6D, 0x70, 0x6C, 0x65, 0x2E, 0x63, 0x6F, 0x6D},
+			},
+		},
 	}
 	csr, err := x509.CreateCertificateRequest(rand.Reader, csrReq, key)
 	if err != nil {
@@ -2285,6 +2296,19 @@ func runTestSignVerbatim(t *testing.T, keyType string) {
 		t.Fatalf("expected a single cert, got %d", len(certs))
 	}
 	cert = certs[0]
+
+	// Fallback check for duplicate otherName, necessary on Go versions before 1.19.
+	// We assume that there is only one SAN in the original CSR and that it is an otherName.
+	san_count := 0
+	for _, ext := range cert.Extensions {
+		if ext.Id.Equal(oidExtensionSubjectAltName) {
+			san_count += 1
+		}
+	}
+	if san_count != 1 {
+		t.Fatalf("expected one SAN extension, got %d", san_count)
+	}
+
 	notAfter := cert.NotAfter.Format(time.RFC3339)
 	if notAfter != "9999-12-31T23:59:59Z" {
 		t.Fatal(fmt.Errorf("not after from certificate is not matching with input parameter"))

changelog/16700.txt

@@ -0,0 +1,3 @@
+```release-note:bug
+secrets/pki: Fixes duplicate otherName in certificates created by the sign-verbatim endpoint.
+```

sdk/helper/certutil/helpers.go

@@ -1033,7 +1033,10 @@ func selectSignatureAlgorithmForECDSA(pub crypto.PublicKey, signatureBits int) x
 	}
 }
 
-var oidExtensionBasicConstraints = []int{2, 5, 29, 19}
+var (
+	oidExtensionBasicConstraints = []int{2, 5, 29, 19}
+	oidExtensionSubjectAltName   = []int{2, 5, 29, 17}
+)
 
 // CreateCSR creates a CSR with the default rand.Reader to
 // generate a cert/keypair. This is currently only meant
@@ -1208,7 +1211,7 @@ func signCertificate(data *CreationBundle, randReader io.Reader) (*ParsedCertBun
 		certTemplate.URIs = data.CSR.URIs
 
 		for _, name := range data.CSR.Extensions {
-			if !name.Id.Equal(oidExtensionBasicConstraints) {
+			if !name.Id.Equal(oidExtensionBasicConstraints) && !(len(data.Params.OtherSANs) > 0 && name.Id.Equal(oidExtensionSubjectAltName)) {
 				certTemplate.ExtraExtensions = append(certTemplate.ExtraExtensions, name)
 			}
 		}