How can I retrieve a salt from LDAP?

Question

The organization that I work for uses PPolicy (an OpenLDAP module) to automatically salt and hash passwords. Unfortunately, I don't have access to the machine running the OpenLDAP server, so i can't look at the config file. From what I've seen though, pretty much everything appears to be setup using the default settings.

I'd like to be able to retrieve the salt for a specific user. If I look at the user's attributes, userPassword is the SSHA password. I don't see anything about a salt for that specific user. I ended up looking at the LDAP schema and I see nothing about salts there either.

If you were to guess where the salt were being stored for each user, where would it be? I understand this is vague and probably not a lot of information, but I can't find anywhere in the OpenLDAP docs that explain where exactly the unique salts are stored. Perhaps someone who has configured an OpenLDAP server before would know where the default location is.

Thank you.

Answer 1

The post of Syon did help me a lot, thanks for that! I thought a working test would be a nice extra for someone else struggling with this topic ;).

public class SshaPasswordVerifyTest {
    private final static int SIZE_SHA1_HASH = 20;

    @Test
    public void itShouldVerifyPassword() throws Exception{
        String password = "YouNeverGuess!";
        String encodedPasswordWithSSHA = "{SSHA}M6HeeJAbwUCzuLwXbq00Fc3n3XcxFI8KjQkqeg==";
        Assert.assertEquals(encodedPasswordWithSSHA, getSshaDigestFor(password, getSalt(encodedPasswordWithSSHA)));
    }

    // The salt is the remaining part after the SHA1_hash
    private byte[] getSalt(String encodedPasswordWithSSHA){
        byte[] data = Base64.getMimeDecoder().decode(encodedPasswordWithSSHA.substring(6));
        return Arrays.copyOfRange(data, SIZE_SHA1_HASH, data.length);
    }

    private String getSshaDigestFor(String password, byte[] salt) throws Exception{
        // create a SHA1 digest of the password + salt
        MessageDigest crypt = MessageDigest.getInstance("SHA-1");
        crypt.reset();
        crypt.update(password.getBytes(Charset.forName("UTF-8")));
        crypt.update(salt);
        byte[] hash = crypt.digest();

        // concatenate the hash with the salt
        byte[] hashPlusSalt = new byte[hash.length + salt.length];
        System.arraycopy(hash, 0, hashPlusSalt, 0, hash.length);
        System.arraycopy(salt, 0, hashPlusSalt, hash.length, salt.length);

        // prepend the SSHA tag + base64 encode the result
        return "{SSHA}" + Base64.getEncoder().encodeToString(hashPlusSalt);
    }
}