mirror of
https://github.com/pgpainless/pgpainless.git
synced 2024-11-01 10:05:59 +01:00
89 lines
4.1 KiB
Markdown
89 lines
4.1 KiB
Markdown
# Passwords
|
|
|
|
In Java based applications, passing passwords as `String` objects has the
|
|
[disadvantage](https://stackoverflow.com/a/8881376/11150851) that you have to rely on garbage collection to clean up
|
|
once they are no longer used.
|
|
For that reason, `char[]` is the preferred method for dealing with passwords.
|
|
Once a password is no longer used, the character array can simply be overwritten to remove the sensitive data from
|
|
memory.
|
|
|
|
## Passphrase
|
|
PGPainless uses a wrapper class `Passphrase`, which takes care for the wiping of unused passwords:
|
|
|
|
```java
|
|
Passphrase passphrase = new Passphrase(new char[] {'h', 'e', 'l', 'l', 'o'});
|
|
assertTrue(passphrase.isValid());
|
|
|
|
assertArrayEquals(new char[] {'h', 'e', 'l', 'l', 'o'}, passphrase.getChars()):
|
|
|
|
// Once we are done, we can clean the data
|
|
passphrase.clear();
|
|
|
|
assertFalse(passphrase.isValid());
|
|
assertNull(passphrase.getChars());
|
|
```
|
|
|
|
Furthermore, `Passphrase` can also wrap empty passphrases, which increases null-safety of the API:
|
|
|
|
```java
|
|
Passphrase empty = Passphrase.emptyPassphrase();
|
|
assertTrue(empty.isValid());
|
|
assertTrue(empty.isEmpty());
|
|
assertNull(empty.getChars());
|
|
|
|
empty.clear();
|
|
|
|
assertFalse(empty.isValid());
|
|
```
|
|
|
|
## SecretKeyRingProtector
|
|
|
|
There are certain operations that require you to provide the passphrase for a key.
|
|
Examples are decryption of messages, or creating signatures / certifications.
|
|
|
|
The primary way of telling PGPainless, which password to use for a certain key is the `SecretKeyRingProtector`
|
|
interface which maps `Passphrases` to (sub-)keys.
|
|
There are multiple implementations of this interface, which may or may not suite your needs:
|
|
|
|
```java
|
|
// If your key is not password protected, this implementation is for you:
|
|
SecretKeyRingProtector unprotected = SecretKeyRingProtector
|
|
.unprotectedKeys();
|
|
|
|
// If you use a single passphrase for all (sub-) keys, take this:
|
|
SecretKeyRingProtector singlePassphrase = SecretKeyRingProtector
|
|
.unlockAnyKeyWith(passphrase);
|
|
|
|
// If you want to be flexible, use this:
|
|
CachingSecretKeyRingProtector flexible = SecretKeyRingProtector
|
|
.defaultSecretKeyRingProtector(passphraseCallback);
|
|
```
|
|
|
|
`SecretKeyRingProtector.unprotectedKeys()` will return an empty passphrase for any key.
|
|
It is best used when dealing with unencrypted secret keys.
|
|
|
|
`SecretKeyRingProtector.unlockAnyKeyWith(passphrase)` will return the same exact passphrase for any given key.
|
|
You should use this if you have a single key with a static passphrase.
|
|
|
|
The last example shows how to instantiate the `CachingSecretKeyRingProtector` with a `SecretKeyPassphraseProvider`
|
|
as argument.
|
|
As the name suggests, the `CachingSecretKeyRingProtector` caches passphrases it knows about in a map.
|
|
That way, you only have to provide the passphrase for a certain key only once, after which it will be remembered.
|
|
If you try to unlock a protected secret key for which no passphrase is cached, the `getPassphraseFor()` method of
|
|
the `SecretKeyPassphraseProvider` callback will be called to interactively ask for the missing passphrase.
|
|
Afterwards, the acquired passphrase will be cached for future use.
|
|
|
|
:::{note}
|
|
While especially the `CachingSecretKeyRingProtector` can handle multiple keys without problems, it is advised
|
|
to use individual `SecretKeyRingProtector` objects per key.
|
|
The reason for this is, that internally the 64bit key-id is used to resolve `Passphrase` objects and collisions are not
|
|
unlikely in this key-space.
|
|
Furthermore, multiple OpenPGP keys could contain the same subkey, but with different passphrases set.
|
|
If the same `SecretKeyRingProtector` is used for two OpenPGP keys with the same subkey, but different passwords,
|
|
the key-id collision will cause the password to be overwritten for one of the keys, which might result in issues.
|
|
See `FLO-04-004 WP2` of the [2021 security audit](https://cure53.de/pentest-report_pgpainless.pdf) for more details.
|
|
:::
|
|
|
|
Most `SecretKeyRingProtector` implementations can be instantiated with custom `KeyRingProtectionSettings`.
|
|
By default, most implementations use `KeyRingProtectionSettings.secureDefaultSettings()` which corresponds to iterated
|
|
and salted S2K using AES256 and SHA256 with an iteration count of 65536.
|