Android通过签名判断是否系统编译的apk

Android平台编译用到的签名公私钥文件存在以下目录：

build/target/product/security

里面包含四对公私钥：

media.pk8、media.pk8、platform.pk8、platform.pk8、shared.pk8、shared.pk8、testkey.pk8、testkey.pk8

系统编译出来的apk，根据策略不同，会选用不同的签名文件。

第三方的apk一般为保证不被篡改和正常升级，都有自己固定的签名文件，不会和Android平台的相同。

所以通过apk的签名可以判断这个应用是否为本系统自带应用。

签名文件分析：

可以通过下面命令来显示公钥的详细信息：

openssl x509 -in build/target/product/security/testkey.x509.pem -text -noout

显示结果如下：

Certificate:

Data:

Version: 3 (0x2)

Serial Number: 10623618503190643167 (0x936eacbe07f201df)

Signature Algorithm: sha1WithRSAEncryption

Issuer: C=US, ST=California, L=Mountain View, O=Android, OU=Android, CN=Android/emailAddress=android@android.com

Validity

Not Before: Feb 29 01:33:46 2008 GMT

Not After : Jul 17 01:33:46 2035 GMT

Subject: C=US, ST=California, L=Mountain View, O=Android, OU=Android, CN=Android/emailAddress=android@android.com

Subject Public Key Info:

Public Key Algorithm: rsaEncryption

Public-Key: (2048 bit)

Modulus:

00:d6:93:19:04:de:c6:0b:24:b1:ed:c7:62:e0:d9:

d8:25:3e:3e:cd:6c:eb:1d:e2:ff:06:8c:a8:e8:bc:

a8:cd:6b:d3:78:6e:a7:0a:a7:6c:e6:0e:bb:0f:99:

35:59:ff:d9:3e:77:a9:43:e7:e8:3d:4b:64:b8:e4:

fe:a2:d3:e6:56:f1:e2:67:a8:1b:bf:b2:30:b5:78:

c2:04:43:be:4c:72:18:b8:46:f5:21:15:86:f0:38:

a1:4e:89:c2:be:38:7f:8e:be:cf:8f:ca:c3:da:1e:

e3:30:c9:ea:93:d0:a7:c3:dc:4a:f3:50:22:0d:50:

08:07:32:e0:80:97:17:ee:6a:05:33:59:e6:a6:94:

ec:2c:b3:f2:84:a0:a4:66:c8:7a:94:d8:3b:31:09:

3a:67:37:2e:2f:64:12:c0:6e:6d:42:f1:58:18:df:

fe:03:81:cc:0c:d4:44:da:6c:dd:c3:b8:24:58:19:

48:01:b3:25:64:13:4f:bf:de:98:c9:28:77:48:db:

f5:67:6a:54:0d:81:54:c8:bb:ca:07:b9:e2:47:55:

33:11:c4:6b:9a:f7:6f:de:ec:cc:8e:69:e7:c8:a2:

d0:8e:78:26:20:94:3f:99:72:7d:3c:04:fe:72:99:

1d:99:df:9b:ae:38:a0:b2:17:7f:a3:1d:5b:6a:fe:

e9:1f

Exponent: 3 (0x3)

X509v3 extensions:

X509v3 Subject Key Identifier:

48:59:00:56:3D:27:2C:46:AE:11:86:05:A4:74:19:AC:09:CA:8C:11

X509v3 Authority Key Identifier:

keyid:48:59:00:56:3D:27:2C:46:AE:11:86:05:A4:74:19:AC:09:CA:8C:11

DirName:/C=US/ST=California/L=Mountain View/O=Android/OU=Android/CN=Android/emailAddress=android@android.com

serial:93:6E:AC:BE:07:F2:01:DF

X509v3 Basic Constraints:

CA:TRUE

Signature Algorithm: sha1WithRSAEncryption

7a:af:96:8c:eb:50:c4:41:05:51:18:d0:da:ab:af:01:5b:8a:

76:5a:27:a7:15:a2:c2:b4:4f:22:14:15:ff:da:ce:03:09:5a:

bf:a4:2d:f7:07:08:72:6c:20:69:e5:c3:6e:dd:ae:04:00:be:

29:45:2c:08:4b:c2:7e:b6:a1:7e:ac:9d:be:18:2c:20:4e:b1:

53:11:f4:55:d8:24:b6:56:db:e4:dc:22:40:91:2d:75:86:fe:

88:95:1d:01:a8:fe:b5:ae:5a:42:60:53:5d:f8:34:31:05:24:

22:46:8c:36:e2:2c:2a:5e:f9:94:d6:1d:d7:30:6a:e4:c9:f6:

95:1b:a3:c1:2f:1d:19:14:dd:c6:1f:1a:62:da:2d:f8:27:f6:

03:fe:a5:60:3b:2c:54:0d:bd:7c:01:9c:36:ba:b2:9a:42:71:

c1:17:df:52:3c:db:c5:f3:81:7a:49:e0:ef:a6:0c:bd:7f:74:

17:7e:7a:4f:19:3d:43:f4:22:07:72:66:6e:4c:4d:83:e1:bd:

5a:86:08:7c:f3:4f:2d:ec:21:e2:45:ca:6c:2b:b0:16:e6:83:

63:80:50:d2:c4:30:ee:a7:c2:6a:1c:49:d3:76:0a:58:ab:7f:

1a:82:cc:93:8b:48:31:38:43:24:bd:04:01:fa:12:16:3a:50:

57:0e:68:4d

我们可以通过其中的Serial Number: 10623618503190643167 (0x936eacbe07f201df)

代码如下：

//media,platform,shared,testkey
private static String mRomSingnum[] = {"17490167175725919310","12941516320735154170","17485000800801945210","10623618503190643167"};

public static boolean isRomSign(Context context) {
try {
PackageInfo packageInfo = context.getPackageManager()
.getPackageInfo(context.getPackageName(),
PackageManager.GET_SIGNATURES);
Signature[] signs = packageInfo.signatures;
Signature sign = signs[0];
String signNumber = parseSignature(sign.toByteArray());
for(String num:mRomSingnum) {
if(num.equals(signNumber)) {
return true;
}
}
} catch (Exception e) {
e.printStackTrace();
}
return false;
}

private static String parseSignature(byte[] signature) {
try {
CertificateFactory certFactory = CertificateFactory
.getInstance("X.509");
X509Certificate cert = (X509Certificate) certFactory
.generateCertificate(new ByteArrayInputStream(signature));
//String pubKey = cert.getPublicKey().toString();
String signNumber = cert.getSerialNumber().toString();
return signNumber;
} catch (CertificateException e) {
e.printStackTrace();
}
return null;
}