Android 证书安装流程分析

一.证书在源码中的路径

5.1系统证书(命名是 openssl x509 -subject_hash_old -in filename)
libcore/luni/src/main/files/cacerts

7.1及以后系统证书
/system/ca-certificates/files

二.证书在固件中的路径

/system/etc/security/cacerts

三.手动安装流程

设置-->安全-->从SD卡安装证书：
在AndroidManif.xml里

packages/apps/CertInstaller
CertInstallerMain打开Document，选择证书文件，选择好后。启动CerInstaller
然后根据证书类型区分createPkcs12PasswordDialog和createNameCredentialDialog，看个简单的createNameCredentialDialog

try {
    startActivityForResult(
            mCredentials.createSystemInstallIntent(),   //Intent intent = new Intent("com.android.credentials.INSTALL");
            REQUEST_SYSTEM_INSTALL_CODE);
} catch (ActivityNotFoundException e) {
    Log.w(TAG, "systemInstall(): " + e);
    toastErrorAndFinish(R.string.cert_not_saved);
}

看intent，又到了Settings的CredentialStorage

Settings/src/com/android/settings/CredentialStorage.java    installIfAvailable
添加证书：Settings/src/com/android/settings/CredentialStorage.java    installIfAvailable()
删除证书：Settings/src/com/android/settings/TrustedCredentialsSettings.java   AliasOperation#doInBackground
显示证书：Settings/src/com/android/settings/TrustedCredentialsSettings.java   AdapterData#AliasLoader#doInBackground   
证书内容：Settings/src/com/android/settings/TrustedCredentialsSettings.java  CertHolder  SslCertificate

安装类型两种： userKey和Ca证书(pk12要处理密码)
CertInstaller\src\com\android\certinstaller\CredentialHelper.java

异常码：
机器未设置密码锁
机器未解锁
锁屏方式不符合要求还是packages/apps/CertInstaller/CertInstallerMain，startActivityForResult结果回调

if (requestCode == REQUEST_SYSTEM_INSTALL_CODE) {
    if (resultCode == RESULT_OK) {
        Log.d(TAG, "credential is added: " + mCredentials.getName());
        Toast.makeText(this, getString(R.string.cert_is_added,
                mCredentials.getName()), Toast.LENGTH_LONG).show();

        if (mCredentials.hasCaCerts()) {
            // more work to do, don't finish just yet
            new InstallCaCertsToKeyChainTask().execute();
            return;
        }
        setResult(RESULT_OK);
    } else {
        Log.d(TAG, "credential not saved, err: " + resultCode);
        toastErrorAndFinish(R.string.cert_not_saved);
    }
}

如果是CaCerts，还要进行 new InstallCaCertsToKeyChainTask().execute() --> mCredentials.installCaCertsToKeyChain --> keyChainService.installCaCertificate
keyChainService实现在packages/apps/KeyChain  mTrustedCertificateStore.installCertificate
external/conscrypt/src/platform/java/org/conscrypt/TrustedCertificateStore   installCertificate --> writeCertificate

四.c层
system/security/keystore/keystore.cpp

添加证书  installIfAvailable -> mKeyStore.put -> mBinder.insert （这里还是java层）
                    -> KeyStoreProxy::insert -> KeyStore::put  (这里getEncryptionKey用到一个AESkey，哪里来的？)

五.为什么要锁屏密码
以设置密码为例
Settings/src/com/android/settings/ChooseLockPassword.java  mLockPatternUtils.saveLockPassword
frameworks/base/core/java/com/android/internal/widget/LockPatternUtils.java  getLockSettings().setLockPassword
frameworks/base/services/core/java/com/android/server/LockSettingsService.java  setLockPassword -> maybeUpdateKeystore  -> ks.passwordUid
    -> 到keystore.cpp的password_uid 
    
password_uid 有三种状态，其中STATE_UNINITIALIZED和STATE_LOCKED都会调用setupMasterKeys，经锁屏密码设置AESkey
这里就解答了添加证书时的AESKey是哪来的

这个是基于Android5.1分析的，高版本可能文件名不同，但是知道大概位置，搜索下，应该没什么难度

android获取系统证书代码：

    private void listX509Certificate() throws Exception {
        TrustManagerFactory tmf = TrustManagerFactory.getInstance(TrustManagerFactory.getDefaultAlgorithm());
        tmf.init((KeyStore) null); 获取证书列表，keystore需要传null
        for (TrustManager tms : tmf.getTrustManagers()) {
            if (tms instanceof X509TrustManager) {
                X509Certificate[] acceptedIssuers = ((X509TrustManager) tms).getAcceptedIssuers();
                PLog.d( "Number of trusted certificates is "+   acceptedIssuers.length);
                for (X509Certificate x509Certificate : acceptedIssuers) {
                    printCert(x509Certificate);
                }
                break;
            }
        }
    }