Ralf Hildebrandt wrote:

Using slapd 2.5.13+dfsg-1ubuntu1 on ubuntu 22.10:

The password hashes are differing between what "slappasswd" and "openssl dgst" emit:

$ slappasswd -s secret -h '{SHA256}' -o module-path=/usr/lib/ldap -o module-load=pw-sha2 {SHA256}WIrrpN3OjEVOUf6yrH1j+o+ODuUuNBo979Od4UXnu54=

$ echo -n "secret" | openssl dgst -sha256 -binary | openssl enc -base64 K7gNU3sdo+OL0wNhqoVWhr3g6s1xYv72ol/pe/Unols=

With SHA512 on the other hand, the hash generated by different programs is identical:

$ slappasswd -s secret -h '{SHA512}' -o module-path=/usr/lib/ldap -o module-load=pw-sha2 {SHA512}vSsar3708Jvp9Szi2NWZZ02Bqp1qRCFpbcTZPdBhnWgs5WtNZKnvCXdhztmeD2cmW192CF5bDufKRpayrW/isg==

$ echo -n "secret" | openssl dgst -sha512 -binary | openssl enc -base64 vSsar3708Jvp9Szi2NWZZ02Bqp1qRCFpbcTZPdBhnWgs5WtNZKnvCXdhztmeD2cm W192CF5bDufKRpayrW/isg==

On an older box (ubuntu 20.04) with slapd 2.4.49+dfsg-2ubuntu1.9 we're seeing:

$ slappasswd -s secret -h '{SHA256}' -o module-path=/usr/lib/ldap -o module-load=pw-sha2 {SHA256}K7gNU3sdo+OL0wNhqoVWhr3g6s1xYv72ol/pe/Unols= $ echo -n "secret" | openssl dgst -sha256 -binary | openssl enc -base64 K7gNU3sdo+OL0wNhqoVWhr3g6s1xYv72ol/pe/Unols=

So why is the SHA256 password hash generated by the 2.5.13 slappasswd command different from the hashes generated by the other programs/versions?

The source code for the pw-sha2 module hasn't changed since 2015 at least. There's no difference between 2.4 and 2.5.

The variable here is your OS and compiler versions. I get the same result as you on ubuntu 22 with the default compile options. If I compile the module with only "-g" and no optimization, I get a different result. So the compiler is doing something screwy.

Note that the sha2.c used in the pw module comes from https://aarongifford.com/computers/sha.html and is unmodified. Probably you should report a bug to the gcc project.