This patch allows for giving strongSwan only the runtime capabilities it
needs, rather than full root privileges.
Adds preprocessor directives which allow strongSwan to be configured to
1) start up as a non-root user
2) avoid modprobe()'ing IPsec kernel modules into the kernel, which
would normally require root or CAP_SYS_MODULE
Additionally, some small mods to charon/libstrongswan ensure that charon
fully supports starting as a non-root user.
Tested with strongSwan 5.5.3.
As it turns out, getpwnam_r, getgrnam_r, and friends will return
ERANGE if _any_ user or group on the system is larger than will fit
into the scratch buffer you pass to them.
This reworks the resolve_uid and resolve_gid methods plus
init_supplementary_groups to use a variable-size buffer that is grown
until the results fit.
Based on a patch by Evan Broder.
Closesstrongswan/strongswan#12.
Tobias Brunner