NAME

       nss_wrapper - A wrapper for the user, group and hosts NSS API

SYNOPSIS

       LD_PRELOAD=libnss_wrapper.so NSS_WRAPPER_PASSWD=/path/to/passwd
       NSS_WRAPPER_GROUP=/path/to/group NSS_WRAPPER_HOSTS=/path/to/host ./myapplication

DESCRIPTION

       There are projects which provide daemons needing to be able to create, modify and delete
       Unix users. Or just switch user ids to interact with the system e.g. a user space file
       server. To be able to test that you need the privilege to modify the passwd and groups
       file. With nss_wrapper it is possible to define your own passwd and groups file which will
       be used by software to act correctly while under test.

       If you have a client and server under test they normally use functions to resolve network
       names to addresses (dns) or vice versa. The nss_wrappers allow you to create a hosts file
       to setup name resolution for the addresses you use with socket_wrapper.

       •   Provides information for user and group accounts.

       •   Network name resolution using a hosts file.

       •   Loading and testing of NSS modules.

LIMITATIONS

       Some calls in nss_wrapper will only work if uid_wrapper is loaded and active. One of this
       functions is initgroups() which needs to run setgroups() to set the groups for the user.
       setgroups() is wrapped by uid_wrapper.

ENVIRONMENT VARIABLES

       NSS_WRAPPER_PASSWD, NSS_WRAPPER_GROUP
           For user and group accounts you need to create two files: passwd and group. The format
           of the passwd file is described in man 5 passwd and the group file in man 5 group. So
           you can fill these files with made up accounts. You point nss_wrapper to them using
           the two variables NSS_WRAPPER_PASSWD=/path/to/your/passwd and
           NSS_WRAPPER_GROUP=/path/to/your/group.

       NSS_WRAPPER_HOSTS
           If you also need to emulate network name resolution in your enviornment, especially
           with socket_wrapper, you can write a hosts file. The format is described in man 5
           hosts. Then you can point nss_wrapper to your hosts file using:
           NSS_WRAPPER_HOSTS=/path/to/your/hosts

       NSS_WRAPPER_HOSTNAME
           If you need to return a hostname which is different from the one of your machine is
           using you can use: NSS_WRAPPER_HOSTNAME=test.example.org

       NSS_WRAPPER_MODULE_SO_PATH, NSS_WRAPPER_MODULE_FN_PREFIX
           If you have a project which also provides user and group information out of a
           database, you normally write your own nss modules. nss_wrapper is able to load nss
           modules and ask them first before looking into the faked passwd and group file. To
           point nss_wrapper to the module you can do that using
           NSS_WRAPPER_MODULE_SO_PATH=/path/to/libnss_yourmodule.so. As each nss module has a
           special prefix like _nss_winbind_getpwnam() you need to set the prefix too so
           nss_wrapper can load the functions with NSS_WRAPPER_MODULE_FN_PREFIX=<prefix>.

       For _nss_winbind_getpwnam() this would be:

           NSS_WRAPPER_MODULE_FN_PREFIX=winbind

       NSS_WRAPPER_DEBUGLEVEL
           If you need to see what is going on in nss_wrapper itself or try to find a bug, you
           can enable logging support in nss_wrapper if you built it with debug symbols.

           •   0 = ERROR

           •   1 = WARNING

           •   2 = DEBUG

           •   3 = TRACE

       NSS_WRAPPER_DISABLE_DEEPBIND
           This allows you to disable deep binding in nss_wrapper. This is useful for running
           valgrind tools or sanitizers like (address, undefined, thread).

EXAMPLE

           $ echo "bob:x:1000:1000:bob gecos:/home/test/bob:/bin/false" > passwd
           $ echo "root:x:65534:65532:root gecos:/home/test/root:/bin/false" >> passwd
           $ echo "users:x:1000:" > group
           $ echo "root:x:65532:" >> group
           $ LD_PRELOAD=libnss_wrapper.so NSS_WRAPPER_PASSWD=passwd \
             NSS_WRAPPER_GROUP=group getent passwd bob
           bob:x:1000:1000:bob gecos:/home/test/bob:/bin/false
           $ LD_PRELOAD=libnss_wrapper.so NSS_WRAPPER_HOSTNAME=test.example.org hostname
           test.example.org

AUTHOR

       Samba Team
           Author.

                                            2019-05-21                             NSS_WRAPPER(1)