ACL: some documentation inside redis.conf.

redis.conf

@@ -501,6 +501,94 @@ replica-priority 100
 # can be easily a long string from /dev/urandom or whatever, so by using a
 # long and unguessable password no brute force attack will be possible.
 
+# Redis ACL users are defined in the following format:
+#
+#   user <username> ... acl rules ...
+#
+# For example:
+#
+#   user worker +@list +@connection ~jobs:* on >ffa9203c493aa99
+#
+# The special username "default" is used for new connections. If this user
+# has the "nopass" rule, then new connections will be immediately authenticated
+# as the "default" user without the need of any password provided via the
+# AUTH command. Otherwise if the "default" user is not flagged with "nopass"
+# the connections will start in not authenticated state, and will require
+# AUTH (or the HELLO command AUTH option) in order to be authenticated and
+# start to work.
+#
+# The ACL rules that describe what an user can do are the following:
+#
+#  on           Enable the user: it is possible to authenticate as this user.
+#  off          Disable the user: it's no longer possible to authenticate
+#               with this user, however the already authenticated connections
+#               will still work.
+#  +<command>   Allow the execution of that command
+#  -<command>   Disallow the execution of that command
+#  +@<category> Allow the execution of all the commands in such category
+#               with valid categories are like @admin, @set, @sortedset, ...
+#               and so forth, see the full list in the server.c file where
+#               the Redis command table is described and defined.
+#               The special category @all means all the commands, but currently
+#               present in the server, and that will be loaded in the future
+#               via modules.
+#  +<command>|subcommand    Allow a specific subcommand of an otherwise
+#                           disabled command. Note that this form is not
+#                           allowed as negative like -DEBUG|SEGFAULT, but
+#                           only additive starting with "+".
+#  allcommands  Alias for +@all. Note that it implies the ability to execute
+#               all the future commands loaded via the modules system.
+#  nocommands   Alias for -@all.
+#  ~<pattern>   Add a pattern of keys that can be mentioned as part of
+#               commands. For instance ~* allows all the keys. The pattern
+#               is a glob-style pattern like the one of KEYS.
+#               It is possible to specify multiple patterns.
+#  allkeys      Alias for ~*
+#  resetkeys    Flush the list of allowed keys patterns.
+#  ><password>  Add this passowrd to the list of valid password for the user.
+#               For example >mypass will add "mypass" to the list.
+#               This directive clears the "nopass" flag (see later).
+#  <<password>  Remove this password from the list of valid passwords.
+#  nopass       All the set passwords of the user are removed, and the user
+#               is flagged as requiring no password: it means that every
+#               password will work against this user. If this directive is
+#               used for the default user, every new connection will be
+#               immediately authenticated with the default user without
+#               any explicit AUTH command required. Note that the "resetpass"
+#               directive will clear this condition.
+#  resetpass    Flush the list of allowed passwords. Moreover removes the
+#               "nopass" status. After "resetpass" the user has no associated
+#               passwords and there is no way to authenticate without adding
+#               some password (or setting it as "nopass" later).
+#  reset        Performs the following actions: resetpass, resetkeys, off,
+#               -@all. The user returns to the same state it has immediately
+#               after its creation.
+#
+# ACL rules can be specified in any order: for instance you can start with
+# passwords, then flags, or key patterns. However note that the additive
+# and subtractive rules will CHANGE MEANING depending on the ordering.
+# For instance see the following example:
+#
+#   user alice on +@all -DEBUG ~* >somepassword
+#
+# This will allow "alice" to use all the commands with the exception of the
+# DEBUG command, since +@all added all the commands to the set of the commands
+# alice can use, and later DEBUG was removed. However if we invert the order
+# of two ACL rules the result will be different:
+#
+#   user alice on -DEBUG +@all ~* >somepassword
+#
+# Now DEBUG was removed when alice had yet no commands in the set of allowed
+# commands, later all the commands are added, so the user will be able to
+# execute everything.
+#
+# Basically ACL rules are processed left-to-right.
+#
+# For more information about ACL configuration please refer to
+# the Redis web site at https://redis.io/topics/acl
+
+# Using an external ACL file
+#
 # Instead of configuring users here in this file, it is possible to use
 # a stand-alone file just listing users. The two methods cannot be mixed:
 # if you configure users here and at the same time you activate the exteranl