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Commit 7c475cc7 authored by Alex Klyubin's avatar Alex Klyubin
Browse files

Fix Android Keystore KeyPairGenerator for RSA PSS keys. 

This fixes a bug where key pair generation fails for RSA signing keys
which are not authorized for PKCS#1 signature padding, such as keys
authorized only for the RSA PSS signature padding scheme.

The issue was that the KeyPairGenerator was failing when attempting to
sign the self-signed certificate (needed by Android Keystore) using
PKCS#1 padding for which such keys are not authorized. The solution is
to not attempt to sign these certificates and instead use a fake
signature.

Bug: 21809600
Change-Id: I4f04fcf78174937046d2534e0485c6940eae673f
parent 738241f9

keystore/java/android/security/keystore/AndroidKeyStoreKeyPairGeneratorSpi.java

+30 −0
Original line number Diff line number Diff line
@@ -703,6 +703,36 @@ public abstract class AndroidKeyStoreKeyPairGeneratorSpi extends KeyPairGenerato 
            }

            case KeymasterDefs.KM_ALGORITHM_RSA:

            {

                // Check whether this key is authorized for PKCS#1 signature padding.

                // We use Bouncy Castle to generate self-signed RSA certificates. Bouncy Castle

                // only supports RSA certificates signed using PKCS#1 padding scheme. The key needs

                // to be authorized for PKCS#1 padding or padding NONE which means any padding.

                boolean pkcs1SignaturePaddingSupported = false;

                for (int keymasterPadding : KeyProperties.SignaturePadding.allToKeymaster(

                        spec.getSignaturePaddings())) {

                    if ((keymasterPadding == KeymasterDefs.KM_PAD_RSA_PKCS1_1_5_SIGN)

                            || (keymasterPadding == KeymasterDefs.KM_PAD_NONE)) {

                        pkcs1SignaturePaddingSupported = true;

                        break;

                    }

                }

                if (!pkcs1SignaturePaddingSupported) {

                    // Keymaster doesn't distinguish between encryption padding NONE and signature

                    // padding NONE. In the Android Keystore API only encryption padding NONE is

                    // exposed.

                    for (int keymasterPadding : KeyProperties.EncryptionPadding.allToKeymaster(

                            spec.getEncryptionPaddings())) {

                        if (keymasterPadding == KeymasterDefs.KM_PAD_NONE) {

                            pkcs1SignaturePaddingSupported = true;

                            break;

                        }

                    }

                }

                if (!pkcs1SignaturePaddingSupported) {

                    // Key not authorized for PKCS#1 signature padding -- can't sign

                    return null;

                }



                Set<Integer> availableKeymasterDigests = getAvailableKeymasterSignatureDigests(

                        spec.getDigests(),

                        AndroidKeyStoreBCWorkaroundProvider.getSupportedEcdsaSignatureDigests());