How do I list and export a private key from a keystore?
9 Answers
A portion of code originally from Example Depot for listing all of the aliases in a key store:
// Load input stream into keystore
keystore.load(is, password.toCharArray());
// List the aliases
Enumeration aliases = keystore.aliases();
for (; aliases.hasMoreElements(); ) {
String alias = (String)aliases.nextElement();
// Does alias refer to a private key?
boolean b = keystore.isKeyEntry(alias);
// Does alias refer to a trusted certificate?
b = keystore.isCertificateEntry(alias);
}
The exporting of private keys came up on the Sun forums a couple of months ago, and u:turingcompleter came up with a DumpPrivateKey class to stitch into your app.
import java.io.FileInputStream;
import java.security.Key;
import java.security.KeyStore;
import sun.misc.BASE64Encoder;
public class DumpPrivateKey {
/**
* Provides the missing functionality of keytool
* that Apache needs for SSLCertificateKeyFile.
*
* @param args <ul>
* <li> [0] Keystore filename.
* <li> [1] Keystore password.
* <li> [2] alias
* </ul>
*/
static public void main(String[] args)
throws Exception {
if(args.length < 3) {
throw new IllegalArgumentException("expected args: Keystore filename, Keystore password, alias, <key password: default same tha
n keystore");
}
final String keystoreName = args[0];
final String keystorePassword = args[1];
final String alias = args[2];
final String keyPassword = getKeyPassword(args,keystorePassword);
KeyStore ks = KeyStore.getInstance("jks");
ks.load(new FileInputStream(keystoreName), keystorePassword.toCharArray());
Key key = ks.getKey(alias, keyPassword.toCharArray());
String b64 = new BASE64Encoder().encode(key.getEncoded());
System.out.println("-----BEGIN PRIVATE KEY-----");
System.out.println(b64);
System.out.println("-----END PRIVATE KEY-----");
}
private static String getKeyPassword(final String[] args, final String keystorePassword)
{
String keyPassword = keystorePassword; // default case
if(args.length == 4) {
keyPassword = args[3];
}
return keyPassword;
}
}
Note: this use Sun package, which is a "bad thing".
If you can download apache commons code, here is a version which will compile without warning:
javac -classpath .:commons-codec-1.4/commons-codec-1.4.jar DumpPrivateKey.java
and will give the same result:
import java.io.FileInputStream;
import java.security.Key;
import java.security.KeyStore;
//import sun.misc.BASE64Encoder;
import org.apache.commons.codec.binary.Base64;
public class DumpPrivateKey {
/**
* Provides the missing functionality of keytool
* that Apache needs for SSLCertificateKeyFile.
*
* @param args <ul>
* <li> [0] Keystore filename.
* <li> [1] Keystore password.
* <li> [2] alias
* </ul>
*/
static public void main(String[] args)
throws Exception {
if(args.length < 3) {
throw new IllegalArgumentException("expected args: Keystore filename, Keystore password, alias, <key password: default same tha
n keystore");
}
final String keystoreName = args[0];
final String keystorePassword = args[1];
final String alias = args[2];
final String keyPassword = getKeyPassword(args,keystorePassword);
KeyStore ks = KeyStore.getInstance("jks");
ks.load(new FileInputStream(keystoreName), keystorePassword.toCharArray());
Key key = ks.getKey(alias, keyPassword.toCharArray());
//String b64 = new BASE64Encoder().encode(key.getEncoded());
String b64 = new String(Base64.encodeBase64(key.getEncoded(),true));
System.out.println("-----BEGIN PRIVATE KEY-----");
System.out.println(b64);
System.out.println("-----END PRIVATE KEY-----");
}
private static String getKeyPassword(final String[] args, final String keystorePassword)
{
String keyPassword = keystorePassword; // default case
if(args.length == 4) {
keyPassword = args[3];
}
return keyPassword;
}
}
You can use it like so:
java -classpath .:commons-codec-1.4/commons-codec-1.4.jar DumpPrivateKey $HOME/.keystore changeit tomcat
If you don't need to do it programatically, but just want to manage your keys, then I've used IBM's free KeyMan tool for a long time now. Very nice for exporting a private key to a PFX file (then you can easily use OpenSSL to manipulate it, extract it, change pwds, etc).
Select your keystore, select the private key entry, then File->Save to a pkcs12 file (*.pfx, typically). You can then view the contents with:
$ openssl pkcs12 -in mykeyfile.pfx -info
First of all, be careful! All of your security depends on the… er… privacy of your private keys. Keytool doesn't have key export built in to avoid accidental disclosure of this sensitive material, so you might want to consider some extra safeguards that could be put in place to protect your exported keys.
Here is some simple code that gives you unencrypted PKCS #8 PrivateKeyInfo that can be used by OpenSSL (see the -nocrypt option of its pkcs8 utility):
KeyStore keys = ...
char[] password = ...
Enumeration<String> aliases = keys.aliases();
while (aliases.hasMoreElements()) {
String alias = aliases.nextElement();
if (!keys.isKeyEntry(alias))
continue;
Key key = keys.getKey(alias, password);
if ((key instanceof PrivateKey) && "PKCS#8".equals(key.getFormat())) {
/* Most PrivateKeys use this format, but check for safety. */
try (FileOutputStream os = new FileOutputStream(alias + ".key")) {
os.write(key.getEncoded());
os.flush();
}
}
}
If you need other formats, you can use a KeyFactory to get a transparent key specification for different types of keys. Then you can get, for example, the private exponent of an RSA private key and output it in your desired format. That would make a good topic for a follow-up question.
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