## maddy-shadow-helper External helper binary for interaction with shadow passwords database. Unlike maddy-pam-helper it supports only local shadow database but it does not have any C dependencies. ### Installation maddy-shadow-helper is kinda dangerous binary and should not be allowed to be executed by everybody but maddy's user. At the same moment it needs to have access to read-protected files. For this reason installation should be done very carefully to make sure to not introduce any security "holes". #### First method ```shell chown maddy: /usr/bin/maddy-shadow-helper chmod u+x,g-x,o-x /usr/bin/maddy-shadow-helper ``` Also maddy-shadow-helper needs access to /etc/shadow, one of the ways to provide it is to set file capability CAP_DAC_READ_SEARCH: ``` setcap cap_dac_read_search+ep /usr/bin/maddy-shadow-helper ``` #### Second method Another, less restrictive is to make it setuid-root (assuming you have both maddy user and group): ``` chown root:maddy /usr/bin/maddy-shadow-helper chmod u+xs,g+x,o-x /usr/bin/maddy-shadow-helper ``` #### Third method The best way actually is to create `shadow` group and grant access to /etc/shadow to it and then make maddy-shadow-helper setgid-shadow: ``` groupadd shadow chown :shadow /etc/shadow chmod g+r /etc/shadow chown maddy:shadow /usr/bin/maddy-shadow-helper chmod u+x,g+xs /usr/bin/maddy-shadow-helper ``` Pick what works best for you.