Indirectly support the searching of certificates and private keys in

local machine certificate stores

 * Support the passing in of arbitrary names for system certificate
   stores when leveraging the Windows certificate store integration.

 * Note that while the stores are still opened within the
   CERT_SYSTEM_STORE_CURRENT_USER context, "all current user certificate
   stores except the Current User/Personal store inherit the contents of
   local machine certificate stores." This means that certificates and
   private keys added to local machine certificate stores can still be
   accessed through the credential helper.

 * Do a case-insensitive comparison of the system store name passed in
   with the predefined system store names (as defined in the Microsoft
   documentation). If there is a match, canonicalize the case so that it
   can be used to open a valid system certificate store. Otherwise, use
   the provided name (assuming that the user has created a custom
   certificate store with that name).

aws_signing_helper/signer.go

@@ -36,15 +36,25 @@ type SignerParams struct {
 }
 
 type CertIdentifier struct {
-	Subject      string
-	Issuer       string
-	SerialNumber *big.Int
+	Subject         string
+	Issuer          string
+	SerialNumber    *big.Int
+	SystemStoreName string // Only relevant in the case of Windows
 }
 
 var (
 	// ErrUnsupportedHash is returned by Signer.Sign() when the provided hash
 	// algorithm isn't supported.
 	ErrUnsupportedHash = errors.New("unsupported hash algorithm")
+
+	// Predefined system store names.
+	// See: https://learn.microsoft.com/en-us/windows/win32/seccrypto/system-store-locations
+	SystemStoreNames = []string{
+		"MY",
+		"Root",
+		"Trust",
+		"CA",
+	}
 )
 
 // Interface that all signers will have to implement

aws_signing_helper/windows_cert_store_signer.go

@@ -142,10 +142,11 @@ func (secStatus securityStatus) Error() string {
 	return fmt.Sprintf("SECURITY_STATUS %d", int(secStatus))
 }
 
-// Gets the certificates that match the given CertIdentifier within the user's "MY" certificate store.
+// Gets the certificates that match the given CertIdentifier within the user's specified system
+// certificate store. By default, that is "MY".
 // If there is only a single matching certificate, then its chain will be returned too
 func GetMatchingCertsAndChain(certIdentifier CertIdentifier) (store windows.Handle, certCtx *windows.CertContext, certChain []*x509.Certificate, certContainers []CertificateContainer, err error) {
-	storeName, err := windows.UTF16PtrFromString("MY")
+	storeName, err := windows.UTF16PtrFromString(certIdentifier.SystemStoreName)
 	if err != nil {
 		return 0, nil, nil, nil, errors.New("unable to UTF-16 encode personal certificate store name")
 	}

cmd/credentials.go

@@ -27,6 +27,7 @@ var (
 	privateKeyId        string
 	certificateBundleId string
 	certSelector        string
+	systemStoreName     string
 
 	libPkcs11 string
 
@@ -65,12 +66,16 @@ func initCredentialsSubCommand(subCmd *cobra.Command) {
 	subCmd.PersistentFlags().StringVar(&certificateBundleId, "intermediates", "", "Path to intermediate certificate bundle file")
 	subCmd.PersistentFlags().StringVar(&certSelector, "cert-selector", "", "JSON structure to identify a certificate from a certificate store. "+
 		"Can be passed in either as string or a file name (prefixed by \"file://\")")
+	subCmd.PersistentFlags().StringVar(&systemStoreName, "system-store-name", "MY", "Name of the system store to search for within the "+
+		"CERT_SYSTEM_STORE_CURRENT_USER context. By default, its value will be \"MY\". Note that this flag is only relevant for Windows "+
+		"certificate stores and will be ignored otherwise")
 	subCmd.PersistentFlags().StringVar(&libPkcs11, "pkcs11-lib", "", "Library for smart card / cryptographic device (OpenSC or vendor specific)")
 	subCmd.PersistentFlags().BoolVar(&reusePin, "reuse-pin", false, "Use the CKU_USER PIN as the CKU_CONTEXT_SPECIFIC PIN for "+
 		"private key objects, when they are first used to sign. If the CKU_USER PIN doesn't work as the CKU_CONTEXT_SPECIFIC PIN "+
 		"for a given private key object, fall back to prompting the user")
 
 	subCmd.MarkFlagsMutuallyExclusive("private-key", "cert-selector")
+	subCmd.MarkFlagsMutuallyExclusive("private-key", "system-store-name")
 	subCmd.MarkFlagsMutuallyExclusive("cert-selector", "intermediates")
 	subCmd.MarkFlagsMutuallyExclusive("cert-selector", "reuse-pin")
 }
@@ -173,9 +178,12 @@ func PopulateCertIdentifierFromCertSelectorStr(certSelectorStr string) (helper.C
 
 // Populates a CertIdentifier using a cert selector
 // Note that this method can take in a file name as a the cert selector
-func PopulateCertIdentifier(certSelector string) (helper.CertIdentifier, error) {
-	var certIdentifier helper.CertIdentifier
-	var err error
+func PopulateCertIdentifier(certSelector string, systemStoreName string) (helper.CertIdentifier, error) {
+	var (
+		certIdentifier helper.CertIdentifier
+		err            error
+	)
+
 	if certSelector != "" {
 		if strings.HasPrefix(certSelector, "file://") {
 			certSelectorFile, err := ioutil.ReadFile(strings.TrimPrefix(certSelector, "file://"))
@@ -193,13 +201,24 @@ func PopulateCertIdentifier(certSelector string) (helper.CertIdentifier, error)
 			}
 		}
 	}
+	matchedPredefinedSystemStoreName := false
+	for _, predefinedSystemStoreName := range helper.SystemStoreNames {
+		if strings.EqualFold(systemStoreName, predefinedSystemStoreName) {
+			certIdentifier.SystemStoreName = predefinedSystemStoreName
+			matchedPredefinedSystemStoreName = true
+			break
+		}
+	}
+	if !matchedPredefinedSystemStoreName {
+		certIdentifier.SystemStoreName = systemStoreName
+	}
 
 	return certIdentifier, err
 }
 
 // Populate CredentialsOpts that is used to aggregate all the information required to call CreateSession
 func PopulateCredentialsOptions() error {
-	certIdentifier, err := PopulateCertIdentifier(certSelector)
+	certIdentifier, err := PopulateCertIdentifier(certSelector, systemStoreName)
 	if err != nil {
 		return err
 	}

cmd/read_certificate_data.go

@@ -18,6 +18,9 @@ func init() {
 	readCertificateDataCmd.PersistentFlags().StringVar(&certificateId, "certificate", "", "Path to certificate file")
 	readCertificateDataCmd.PersistentFlags().StringVar(&certSelector, "cert-selector", "", "JSON structure to identify a certificate from a certificate store."+
 		" Can be passed in either as string or a file name (prefixed by \"file://\")")
+	readCertificateDataCmd.PersistentFlags().StringVar(&systemStoreName, "system-store-name", "MY", "Name of the system store to search for within the "+
+		"CERT_SYSTEM_STORE_CURRENT_USER context. By default, its value will be \"MY\". Note that this flag is only relevant for Windows "+
+		"certificate stores and will be ignored otherwise")
 	readCertificateDataCmd.PersistentFlags().StringVar(&libPkcs11, "pkcs11-lib", "", "Library for smart card / cryptographic device (OpenSC or vendor specific)")
 	readCertificateDataCmd.PersistentFlags().BoolVar(&debug, "debug", false, "To print debug output")
 }
@@ -43,7 +46,7 @@ var readCertificateDataCmd = &cobra.Command{
 	Long: `Diagnostic command to read certificate data, either from files or 
     from a certificate store`,
 	Run: func(cmd *cobra.Command, args []string) {
-		certIdentifier, err := PopulateCertIdentifier(certSelector)
+		certIdentifier, err := PopulateCertIdentifier(certSelector, systemStoreName)
 		if err != nil {
 			log.Println("unable to populate CertIdentifier")
 			os.Exit(1)

cmd/sign_string.go

@@ -78,6 +78,9 @@ func init() {
 	signStringCmd.PersistentFlags().BoolVar(&debug, "debug", false, "To print debug output")
 	signStringCmd.PersistentFlags().StringVar(&certSelector, "cert-selector", "", "JSON structure to identify a certificate from a certificate store. "+
 		"Can be passed in either as string or a file name (prefixed by \"file://\")")
+	signStringCmd.PersistentFlags().StringVar(&systemStoreName, "system-store-name", "MY", "Name of the system store to search for within the "+
+		"CERT_SYSTEM_STORE_CURRENT_USER context. By default, its value will be \"MY\". Note that this flag is only relevant for Windows "+
+		"certificate stores and will be ignored otherwise")
 	signStringCmd.PersistentFlags().StringVar(&libPkcs11, "pkcs11-lib", "", "Library for smart card / cryptographic device (default: p11-kit-proxy.{so, dll, dylib})")
 	signStringCmd.PersistentFlags().BoolVar(&reusePin, "reuse-pin", false, "Use the CKU_USER PIN as the CKU_CONTEXT_SPECIFIC PIN for "+
 		"private key objects, when they are first used to sign. If the CKU_USER PIN doesn't work as the CKU_CONTEXT_SPECIFIC PIN "+