1/*
2 * Copyright (C) 2015 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License
15 */
16
17package libcore.util;
18
19import sun.security.pkcs.PKCS7;
20import sun.security.pkcs.SignerInfo;
21
22import java.io.IOException;
23import java.io.InputStream;
24import java.security.NoSuchAlgorithmException;
25import java.security.PublicKey;
26import java.security.SignatureException;
27import java.security.cert.X509Certificate;
28import java.util.Set;
29
30public class RecoverySystem {
31    private RecoverySystem() {
32    }
33
34    /**
35     * Verifies that the signature computed from {@code contentStream} matches
36     * that specified in {@code blockStream}. The public key of the certificates specified
37     * in the PCKS7 block must match
38     */
39    public static void verify(InputStream blockStream, InputStream contentStream,
40                              Set<X509Certificate> trustedCerts)
41            throws IOException, SignatureException, NoSuchAlgorithmException {
42        PKCS7 block = new PKCS7(blockStream);
43
44        // Take the first certificate from the signature (packages
45        // should contain only one).
46        X509Certificate[] certificates = block.getCertificates();
47        if (certificates == null || certificates.length == 0) {
48            throw new SignatureException("signature contains no certificates");
49        }
50        X509Certificate cert = certificates[0];
51        PublicKey signatureKey = cert.getPublicKey();
52
53        SignerInfo[] signerInfos = block.getSignerInfos();
54        if (signerInfos == null || signerInfos.length == 0) {
55            throw new SignatureException("signature contains no signedData");
56        }
57        SignerInfo signerInfo = signerInfos[0];
58
59        boolean verified = false;
60        for (X509Certificate c : trustedCerts) {
61            if (c.getPublicKey().equals(signatureKey)) {
62                verified = true;
63                break;
64            }
65        }
66
67        if (!verified) {
68            throw new SignatureException("signature doesn't match any trusted key");
69        }
70
71        SignerInfo verifyResult = block.verify(signerInfo, contentStream);
72        if (verifyResult == null) {
73            throw new SignatureException("signature digest verification failed");
74        }
75    }
76}
77