The passwd(4) man page contains a list of valid formats for the config/passwd property in the name service switch. Adding ad to these configurations is supported. However, changing AD user passwords through the passwd command is not supported. If found in the passwd entry during a password update, ad is skipped. Use the kpasswd command to update AD user passwords.
You can add the ad search order to existing valid password and group entries in name service switch. For example:
# svccfg -s svc:/system/name-service/switch:default svc:/system/name-service/switch:default> setprop config/password = astring: "files nis ad" svc:/system/name-service/switch:default> setprop config/group = astring: "files nis ad" svc:/system/name-service/switch:default> refresh svc:/system/name-service/switch:default> quit