Ufdjrw

I'm upgrading from Spring Security 4.x to 5.x.

The ReflectionSaltSource from Spring 4 lets us configure a custom salt. But that's removed in Spring Security 5. I then found out that I should use MessageDigestPasswordEncoder. It has a long detailed java-doc but unfortunately the doc is a bag of words without conveying any structured information (I tried multiple times; my bad if I was ignorant).

Anyways I thought I should do the following based on my limited understanding.

Old system with 4.x - myEncodedPassword and mySalt are passed separately to the encoder.

New System with 5.x - Pass one field with the value mySaltmyEncodedPassword to the MessageDigestPasswordEncoder

However, that did not work. The Problem was that when MessageDigestPasswordEncoder sees mySaltencodedPassword, it uses mySalt (with the ) as the salt instead of using mySalt as the salt . I'm confused.

Here's a coding example. I used Groovy to reduce noise.

@Grab(group='org.springframework.security', module='spring-security-core', version='5.1.4.RELEASE')
import org.springframework.security.crypto.password.MessageDigestPasswordEncoder

String password = 'myPassword'
String salt_1 = 'mySalt'
String salt_2 = 'mySalt'
// http://www.lorem-ipsum.co.uk/hasher.php generated below hashes
String encodedPasswordWithSalt_1 = '57bc828628811a10496215e217b7ae9b714c859fc7a8b1c678c9a0cc40aac422'
String encodedPasswordWithSalt_2 = 'a18b53fc58843def1e08e00a718f40d6f8eda0b97ef97824b5078c1fad93c0c5'

MessageDigestPasswordEncoder encoder = new MessageDigestPasswordEncoder('SHA-256')
println "expected=true, actual=" + encoder.matches(password, "$salt_1$encodedPasswordWithSalt_1") // <--- expected to match but did not
println "expected=false, actual=" + encoder.matches(password, "$salt_1$encodedPasswordWithSalt_2") // <--- why does this match?

The output is

expected=true, actual=false
expected=false, actual=true

I'm hoping to find a way to support SHA256 with custom and separate salt for each user password.

If anyone's interested, I created a ticket on GitHub - https://github.com/spring-projects/spring-security/issues/6594 . No solution so far. I will update here if there's any. So this is still an unanswered question.

I guess the issue is in the org.springframework.security.crypto.password.MessageDigestPasswordEncoder class

By debugging it in the method private String extractSalt(String prefixEncodedPassword) they try to extract salt by returning prefixEncodedPassword.substring(start, end + 1); where start is the index of the prefix while end is the index of suffix and it stops to the first suffix it matches so what happens in your code?

It happens this:

MessageDigestPasswordEncoder encoder = new MessageDigestPasswordEncoder('SHA-256')
println "expected=true, actual=" + encoder.matches(password, "$salt_1$encodedPasswordWithSalt_1") //It's not matched because the extracted salt will be mySalt and not mySalt
println "expected=false, actual=" + encoder.matches(password, "$salt_1$encodedPasswordWithSalt_2") //It's matched because the extracted salt will be mySalt and not mySalt

I state I don't know if it's a bug or not, in any case in your scenario it should be enough to properly investigate and properly modify the method

private String extractSalt(String prefixEncodedPassword) 
 int start = prefixEncodedPassword.indexOf(PREFIX);
 if (start != 0) 
 return "";
 
 int end = prefixEncodedPassword.indexOf(SUFFIX, start);
 if (end < 0) 
 return "";
 
 return prefixEncodedPassword.substring(start, end + 1);
 

This method is inside the org.springframework.security.crypto.password.MessageDigestPasswordEncoder class

I hope it's useful

Angelo