pam_user_map module throws syntax error if group name contains backslash

When using active directory, group names can have backslashes when specified in the "domain account format". See here for more information:

https://docs.microsoft.com/en-us/windows/desktop/ad/getting-the-domain-account-style-name-of-a-group

"getent group" on Linux is capable of interpreting backslashes in group names when AD is configured. For example, the following command properly gets the information about the AD group:

getent group mydomain\\my-dba-group

However, the pam_user_map module does not seem to support this format at the moment. If /etc/security/user_map.conf contains a line like the following:

@mydomain\\my-dba-group: mysqldba 

Then the module would throw an error like the following:

Aug 28 17:22:02 ip-10-156-191-170 mysqld: pam_user_map(mysql:auth): Syntax error at /etc/security/user_map.conf:5

The same error is seen if only a single backslash is used in the group name. e.g.:

@mydomain\my-dba-group: mysqldba 

The workaround is to set a default domain in the system's AD configuration.