android APK签名过程之CERT.SF分析
MANIFEST.MF文件内容：
Manifest-Version: 1.0 Created-By: 1.0 (Android) Name: res/drawable-xhdpi/ic_launcher.png SHA1-Digest: AfPh3OJoypH966MludSW6f1RHg4= Name: res/menu/main.xml SHA1-Digest: wXc4zBe0Q2LPi4bMr25yy5JJQig= Name: AndroidManifest.xml SHA1-Digest: k3QiLyii25nxkE9q59pXGWI2aTo= Name: res/drawable-mdpi/ic_launcher.png SHA1-Digest: RRxOSvpmhVfCwiprVV/wZlaqQpw= Name: res/drawable-hdpi/ic_launcher.png SHA1-Digest: Nq8q3HeTluE5JNCBpVvNy3BXtJI= Name: res/layout/activity_main.xml SHA1-Digest: qVW+nHovqmEmKpssXKUBidrNDDA= Name: resources.arsc SHA1-Digest: luJu2wwHeH7XAJwms2gIq/pco40= Name: lib/armeabi/libhello-jni.so SHA1-Digest: uFb6Vfi3T/Rq0dvjgCqW7fKKrzM= Name: classes.dex SHA1-Digest: zaipAFvc+AzMSc2nJJG9zIrrfqE= Name: res/drawable-xxhdpi/ic_launcher.png SHA1-Digest: GVIfdEOBv4gEny2T1jDhGGsZOBo=
CERT.SF文件内容：
Signature-Version: 1.0 Created-By: 1.0 (Android) SHA1-Digest-Manifest: KYIkAR4PbCA4w3MLMr7ViERYEC0= Name: res/menu/main.xml SHA1-Digest: 4zwSAYv23t3kqpzCDB/SFXeI+fE= Name: res/drawable-xhdpi/ic_launcher.png SHA1-Digest: cIga++hy5wqjHl9IHSfbg8tqCug= Name: AndroidManifest.xml SHA1-Digest: FZ/sx6NI+BZkCi/hVlBHDLFbKxM= Name: res/drawable-mdpi/ic_launcher.png SHA1-Digest: VY7kOF8E3rn8EUTvQC/DcBEN6kQ= Name: res/drawable-hdpi/ic_launcher.png SHA1-Digest: stS7pUucSY0GgAVoESyO3Y7SanU= Name: res/layout/activity_main.xml SHA1-Digest: bl4WBWN5ooqlzio7tNRqDWt3oWM= Name: resources.arsc SHA1-Digest: tnBvelvdDz0kEBfPf+RjqGfpdn4= Name: classes.dex SHA1-Digest: lxB86ol+PFq8rG2IpToRpZi2JcI= Name: lib/armeabi/libhello-jni.so SHA1-Digest: +rWr7fBTZjm2JnvJytCJCdmdLso= Name: res/drawable-xxhdpi/ic_launcher.png SHA1-Digest: KKqaLh/DVvFp+v1KoaDw7xETvrI=
比较发现CERT.SF比MANIFEST.MF多了一个SHA1-Digest-Manifest的值，这个值其实是MANIFEST.MF文件的SHA1并base64编码的值，可以手动验证，也可以从android源码分析。
打开android源码build/tools/signapk/SignApk.java分析，没有下载android源码的可以在线参考： https://github.com/OESF/Embedded-Master-MIPS/blob/370863733b500b7f0ded111f4b800bce990d69a5/build/tools/signapk/SignApk.java
// CERT.SF
Signature signature = Signature.getInstance("SHA1withRSA");
signature.initSign(privateKey);
je = new JarEntry(CERT_SF_NAME);
je.setTime(timestamp);
outputJar.putNextEntry(je);
writeSignatureFile(manifest, new SignatureOutputStream(outputJar, signature));
/** Write a .SF file with a digest the specified manifest. */
private static void writeSignatureFile(Manifest manifest, OutputStream out) throws IOException, GeneralSecurityException {
Manifest sf = new Manifest();
Attributes main = sf.getMainAttributes();
main.putValue("Signature-Version", "1.0");
main.putValue("Created-By", "1.0 (Android SignApk)");
BASE64Encoder base64 = new BASE64Encoder();
MessageDigest md = MessageDigest.getInstance("SHA1");
PrintStream print = new PrintStream( new DigestOutputStream(new ByteArrayOutputStream(), md), true, "UTF-8"); // Digest of the entire manifest manifest.write(print);
print.flush();
main.putValue("SHA1-Digest-Manifest", base64.encode(md.digest()));
Map<String, Attributes> entries = manifest.getEntries(); for (Map.Entry<String, Attributes> entry : entries.entrySet()) { // Digest of the manifest stanza for this entry.
print.print("Name: " + entry.getKey() + "\r\n"); for (Map.Entry<Object, Object> att : entry.getValue().entrySet()) {
print.print(att.getKey() + ": " + att.getValue() + "\r\n");
}
print.print("\r\n");
print.flush();
Attributes sfAttr = new Attributes();
sfAttr.putValue("SHA1-Digest", base64.encode(md.digest()));
sf.getEntries().put(entry.getKey(), sfAttr);
}
sf.write(out);
}
通过代码可以发现SHA1-Digest-Manifest是MANIFEST.MF文件的SHA1并base64编码的结果。
后面的for循环是对每一项再次SHA1并base64编码，例如：
Name: res/menu/main.xml SHA1-Digest: wXc4zBe0Q2LPi4bMr25yy5JJQig=
注意最后是两个"\r\n"，手动验证也很简单，把上面的字符串保存为文件，并查看文件的HASH值是：E33C12018BF6DEDDE4AA9CC20C1FD2157788F9F1，将其保存为二进制文件并对文件进行一次base64编码，可得4zwSAYv23t3kqpzCDB/SFXeI+fE=
参考：
取得签名工具加载证书库, 取得签名证书链和私钥：
http://www.oschina.net/code/snippet_1434_1503
从CERT.RSA中提取证书 ：
http://www.wangchen.org/2011/01/%E4%BB%8Ecert-rsa%E4%B8%AD%E6%8F%90%E5%8F%96%E8%AF%81%E4%B9%A6/