Provided by: inn2_2.6.1-4build1_amd64 
NAME
readers.conf - Access control and configuration for nnrpd
DESCRIPTION
readers.conf in pathetc specifies access control for nnrpd(8). It controls who is allowed
to connect as a news reader and what they're allowed to do after they connect. nnrpd
reads this file when it starts up. This generally means that any changes take effect
immediately on all subsequent connections, but nnrpd may have to be restarted if you use
the -D option. (The location pathetc/readers.conf is only the default; the same format
applies to any file specified with "nnrpd -c".)
There are two types of entries in readers.conf: parameter/value pairs and configuration
groups. Blank lines and anything after a number sign ("#") are ignored, unless the
character "#" is escaped with "\". The maximum number of characters on each line is
8,191.
Parameter/value pairs consist of a keyword immediately followed by a colon, at least one
whitespace character, and a value. The case of the parameter is significant (parameter
should generally be in all lowercase), and a parameter may contain any characters except
colon, "#", and whitespace. An example:
hosts: *.example.com
Values that contain whitespace should be quoted with double quotes, as in:
hosts: "*.example.com, *.example.net"
If the parameter does not contain whitespace, such as:
hosts: *.example.com,*.example.net
it's not necessary to quote it, although you may wish to anyway for clarity.
There is no way to continue a line on the next line, and therefore no way to have a single
parameter with a value longer than about 8,180 characters.
Many parameters take a boolean value. For all such parameters, the value may be specified
as "true", "yes", or "on" to turn it on and may be any of "false", "no", or "off" to turn
it off. The case of these values is not significant.
There are two basic types of configuration groups, auth and access. The auth group
provides mechanisms to establish the identity of the user, who they are. The access group
determines, given the user's identity, what that user is permitted to do. Writing a
readers.conf file for your setup is a two-step process: first assigning an identity to
each incoming connection using auth groups, and then giving each identity appropriate
privileges with access group. We recommend not intermingling auth groups and access
groups in the config file; it is often more sensible (in the absence of the key parameter)
to put all of the auth groups first, and all of the access groups below.
A user identity, as established by an auth group, looks like an e-mail address; in other
words, it's in the form "<username>@<domain>" (or sometimes just "<username>" if no domain
is specified.
If nnrpdauthsender is set in inn.conf, the user identity is also put into the Sender:
header of posts made by that user. See the documentation of that option in inn.conf(5)
for more details.
An auth group definition looks like:
auth <name> {
hosts: <host-wildmat>
auth: <auth-program>
res: <res-program>
default: <defuser>
default-domain: <defdomain>
# ...possibly other settings
}
The <name> is used as a label for the group and is only for documentation purposes. (If
your syslog configuration records the "news.debug" facility, the <name> will appear in the
debugging output of nnrpd. Examining that output can be very helpful in understanding why
your configuration doesn't do what you expect it to.)
A given auth group applies only to hosts whose name or IP address matches the wildmat
expression given with the hosts: parameter (comma-separated wildmat expressions allowed,
but "@" is not supported). Rather than wildmat expressions, you may also use CIDR
notation to match any IP address in a netblock; for example, "10.10.10.0/24" will match
any IP address between 10.10.10.0 and 10.10.10.255 inclusive.
If compiled against the TLS/SSL or SASL libraries, an auth group with the require_ssl
parameter set to true only applies if the incoming connection is using an encryption
layer, either from the beginning if the -S flag was passed to nnrpd, or after a successful
use of STARTTLS, or after a successful authentication using a SASL mechanism which
negotiates an encryption layer.
For any connection from a host that matches that wildmat expression or netblock, each
<res-program> (multiple res: lines may be present in a block; they are run in sequence
until one succeeds), if any, is run to determine the identity of the user just from the
connection information. If all the resolvers fail, or if the res: parameter isn't
present, the user is assigned an identity of "<defuser>@<defdomain>"; in other words, the
values of the default: and default-domain: parameters are used. If <res-program> only
returns a username, <defdomain> is used as the domain.
If the user later authenticates via the AUTHINFO USER/PASS commands, the provided username
and password are passed to each <auth-program> (multiple auth, perl_auth, or python_auth
lines may be present in a block; they are run in sequence until one succeeds), if any. If
one succeeds and returns a different identity than the one assigned at the time of the
connection, it is matched against the available access groups again and the actions the
user is authorized to do may change. The most common <auth-program> to use is ckpasswd,
which supports several ways of checking passwords including using PAM. See the
ckpasswd(8) man page for more details.
When matching auth groups, the last auth group in the file that matches a given connection
and username/password combination is used.
An access group definition usually looks like:
access <name> {
users: <identity-wildmat>
newsgroups: <group-wildmat>
# ...possibly other settings
}
Again, <name> is just for documentation purposes. This says that all users whose identity
matches <identity-wildmat> can read and post to all newsgroups matching <group-wildmat>
(as before, comma-separated wildmat expressions are allowed, but "@" is not supported).
Alternately, you can use the form:
access <name> {
users: <identity-wildmat>
read: <read-wildmat>
post: <post-wildmat>
}
and matching users will be able to read any group that matches <read-wildmat> and post to
any group that matches <post-wildmat>. You can also set several other things in the
access group as well as override various inn.conf(5) parameters for just a particular
group of users.
Just like with auth groups, when matching access groups the last matching one in the file
is used to determine the user's permissions. There is an exception to this rule: if the
auth group which matched the client contains a perl_access: or python_access: parameter,
then the script given as argument is used to dynamically generate an access group. This
new access group is then used to determine the access rights of the client; the access
groups in the file are ignored.
There is one additional special case to be aware of. When forming particularly complex
authentication and authorization rules, it is sometimes useful for the identities provided
by a given auth group to only apply to particular access groups; in other words, rather
than checking the identity against the users: parameter of every access group, it's
checked against the users: parameter of only some specific access groups. This is done
with the key: parameter. For example:
auth example {
key: special
hosts: *.example.com
default: <SPECIAL>
}
access example {
key: special
users: <SPECIAL>
newsgroups: *
}
In this case, the two key: parameters bind this auth group with this access group. For
any incoming connection matching "*.example.com" (assuming there isn't any later auth
group that also matches such hosts), no access group that doesn't have "key: special" will
even be considered. Similarly, the above access group will only be checked if the user
was authenticated with an auth group containing "key: special". This mechanism normally
isn't useful; there is almost always a better way to achieve the same result.
Also note in the example that there's no default-domain: parameter, which means that no
domain is appended to the default username and the identity for such connections is just
"<SPECIAL>". Note that some additional add-ons to INN may prefer that authenticated
identities always return a full e-mail address (including a domain), so you may want to
set up your system that way.
Configuration files can be included in other configuration files via the syntax:
include <filename>
The file named <filename> is then included. This syntax is allowed only at top-level.
Below is the full list of allowable parameters for auth groups and access groups, and
after that are some examples that may make this somewhat clearer.
AUTH GROUP PARAMETERS
An auth group without at least one of the res:, auth:, perl_auth:, python_auth:, or
default: parameters makes no sense (and in practice will just be ignored).
hosts:
A comma-separated list of remote hosts, wildmat patterns matching either hostnames or
IP addresses, or IP netblocks specified in CIDR notation. If a user connects from a
host that doesn't match this parameter, this auth group will not match the connection
and is ignored.
Note that if you have a large number of patterns that can't be merged into broader
patterns (such as a large number of individual systems scattered around the net that
should have access), the hosts: parameter may exceed the maximum line length of 8,192
characters. In that case, you'll need to break that auth group into multiple auth
groups, each with a portion of the hosts listed in its hosts: parameter, and each
assigning the same user identity.
All hosts match if this parameter is not given.
localaddress:
A comma-separated list of local host or address patterns with the same syntax as the
same as with the hosts: parameter. If this parameter is specified, its auth group
will only match connections made to a matching local interface. (Obviously, this is
only useful for servers with multiple interfaces.)
All local addresses match if this parameter is not given.
res:
A simple command line for a user resolver (shell metacharacters are not supported).
If a full path is not given, the program executed must be in the pathbin/auth/resolv
directory. A resolver is an authentication program which attempts to figure out the
identity of the connecting user using nothing but the connection information (in other
words, the user has not provided a username and password). An examples of a resolver
would be a program that assigns an identity from an ident callback or from the user's
hostname.
One auth group can have multiple res: parameters, and they will be tried in the order
they're listed. The results of the first successful one will be used.
Alternatively, a res block can be used instead of a res: paramater. The recognized
parameters in such res blocks are:
log:
A string to log in pathlog/news.notice (with "res also-log:" prepended) before the
resolver is tried. One res group can have multiple log: parameters, and they will
be logged in the order they're listed.
program:
This parameter is mandatory in a res block. Its meaning is the same as the res:
parameter used directly in an auth block.
auth <auth-name> {
res: <res-program>
}
is therefore equivalent to:
auth <auth-name> {
res <res-name> {
program: <res-program>
}
}
auth:
A simple command line for a user authenticator (shell metacharacters are not
supported). If a full path is not given, the program executed must be located in the
pathbin/auth/passwd directory. An authenticator is a program used to handle a user-
supplied username and password, via a mechanism such as AUTHINFO USER/PASS. Like with
res:, one auth group can have multiple auth: parameters; they will be tried in order
and the results of the first successful one will be used. See also perl_auth: below.
The most common authenticator to use is ckpasswd(8); see its man page for more
information.
perl_auth:
A path to a perl script for authentication. The perl_auth: parameter works exactly
like auth:, except that it calls the named script using the perl hook rather then an
external program. Multiple/mixed use of the auth, perl_auth, and python_auth
parameters is permitted within any auth group; each line is tried in the order it
appears. perl_auth: has more power than auth: in that it provides the authentication
program with additional information about the client and the ability to return an
error string and a username. This parameter is only valid if INN is compiled with
Perl support (--with-perl passed to configure). More information may be found in
doc/hook-perl.
python_auth:
A Python script for authentication. The python_auth parameter works exactly like
auth, except that it calls the named script (without its ".py" extension) using the
Python hook rather then an external program. Multiple/mixed use of the auth,
perl_auth, and python_auth parameters is permitted within any auth group; each line is
tried in the order it appears. python_auth has more power than auth in that it
provides the authentication program with additional information about the client and
the ability to return an error string and a username. This parameter is only valid if
INN is compiled with Python support (--with-python passed to configure). More
information may be found in doc/hook-python.
default:
The default username for connections matching this auth group. This is the username
assigned to the user at connection time if all resolvers fail or if there are no res:
parameters. Note that it can be either a bare username, in which case default-domain:
(if present) is appended after an "@", or a full identity string containing an "@", in
which case it will be used verbatim.
default-domain:
The default domain string for this auth group. If a user resolver or authenticator
doesn't provide a domain, or if the default username is used and it doesn't contain a
"@", this domain is used to form the user identity. (Note that for a lot of setups,
it's not really necessary for user identities to be qualified with a domain name, in
which case there's no need to use this parameter.)
key:
If this parameter is present, any connection matching this auth group will have its
privileges determined only by the subset of access groups containing a matching key
parameter.
require_ssl:
If set to true, an incoming connection only matches this auth group if it is
encrypted, either from the beginning if the -S flag was passed to nnrpd, or after a
successful use of STARTTLS, or after a successful authentication using a SASL
mechanism which negotiates an encrypted layer. This parameter is only valid if INN is
compiled with TLS/SSL or SASL support (by default if the OpenSSL SSL and crypto
libraries or the Cyrus SASL library are found at configure time, otherwise see the
--with-openssl and --with-sasl flags passed to configure).
perl_access:
A path to a perl script for dynamically generating an access group. If an auth group
matches successfully and contains a perl_access parameter, then the argument perl
script will be used to create an access group. This group will then determine the
access rights of the client, overriding any access groups in readers.conf. If and
only if a sucessful auth group contains the perl_access parameter, readers.conf access
groups are ignored and the client's rights are instead determined dynamically. This
parameter is only valid if INN is compiled with Perl support (--with-perl passed to
configure). More information may be found in the file doc/hook-perl.
python_access:
A Python script for dynamically generating an access group. If an auth group matches
successfully and contains a python_access parameter, then the argument script (without
its ".py" extension) will be used to create an access group. This group will then
determine the access rights of the client, overriding any access groups in
readers.conf. If and only if a successful auth group contains the python_access
parameter, readers.conf access groups are ignored and the client's rights are instead
determined dynamically. This parameter is only valid if INN is compiled with Python
support (--with-python passed to configure). More information may be found in the
file doc/hook-python.
python_dynamic:
A Python script for applying access control dynamically on a per newsgroup basis. If
an auth group matches successfully and contains a python_dynamic parameter, then the
argument script (without its ".py" extension) will be used to determine the clients
rights each time the user attempts to view a newsgroup, or read or post an article.
Access rights as determined by python_dynamic override the values of access group
parameters such as newsgroups, read and post. This parameter is only valid if INN is
compiled with Python support (--with-python passed to configure). More information
may be found in the file doc/hook-python.
ACCESS GROUP PARAMETERS
users:
The privileges given by this access group apply to any user identity which matches
this comma-separated list of wildmat patterns. If this parameter isn't given, the
access group applies to all users (and is essentially equivalent to "users: *").
newsgroups:
Users that match this access group are allowed to read and post to all newsgroups
matching this comma-separated list of wildmat patterns. The empty string is
equivalent to "newsgroups: *"; if this parameter is missing, the connection will be
rejected (unless read: and/or post: are used instead, see below).
read:
Like the newsgroups: parameter, but the client is only given permission to read the
matching newsgroups. This parameter is often used with post: (below) to specify some
read-only groups; it cannot be used in the same access group with a newsgroups:
parameter. (If read: is used and post: is missing, the client will have only read-
only access.)
post:
Like the newsgroups: parameter, but the client is only given permission to post to the
matching newsgroups. This parameter is often used with read: (above) to define the
patterns for reading and posting separately (usually to give the user permission to
read more newsgroups than they're permitted to post to). It cannot be used in the
same access group with a newsgroups: parameter.
access:
A set of letters specifying the permissions granted to the client. The letters are
chosen from the following set:
R The client may read articles.
P The client may post articles.
I The client may inject articles with IHAVE. Note that in order to inject articles
with the IHAVE command, the user must also have POST permission (the "P" option).
Articles injected with IHAVE are treated as though they were injected with POST,
that is to say such articles must not have been previously injected (they must not
contain headers like Injection-Info:).
A The client may post articles with Approved: headers (in other words, may approve
articles for moderated newsgroups). By default, this is not allowed.
N The client may use the NEWNEWS command, overriding the global setting.
L The client may post to newsgroups that are set to disallow local posting (status
fields "j", "n" and "x" in the active(5) file).
Note that if this parameter is given, allownewnews in inn.conf is ignored for
connections matching this access group and the ability of the client to use NEWNEWS is
entirely determined by the presence of "N" in the access string. If you want to
support NEWNEWS, make sure to include "N" in the access string when you use this
parameter.
Note that if this parameter is given and "R" isn't present in the access string, the
client cannot read regardless of newsgroups: or read: parameters. Similarly, if this
parameter is given and "P" isn't present, the client cannot post. This use of access:
is deprecated and confusing; it's strongly recommended that if the access: parameter
is used, "R" and "P" always be included in the access string and newsgroups:, read:,
and post: be used to control access. (To grant read access but no posting access, one
can have just a read: parameter and no post: parameter.)
key:
If this parameter is present, this access group is only considered when finding
privileges for users matching auth groups with this same key: parameter.
reject_with:
If this parameter is present, a client matching this block will be disconnected with a
"Permission denied" message containing the contents (a "reason" string) of this
parameter. Some newsreaders will then display the reason to the user.
max_rate:
If this parameter is present (and nonzero), it is used for nnrpd's rate-limiting code.
The client will only be able to download at this speed (in bytes/second). Note that
if an encryption layer is being used, limiting is applied to the pre-encryption
datastream.
localtime:
If a Date: or an Injection-Date: header field is not included in a posted article,
nnrpd(8) normally adds these header fields in UTC. If this is set to true, the Date:
header field will be formatted in local time instead. (The Injection-Date: header
field will remain in UTC, though.) This is a boolean value and the default is false.
This parameter permits to handle a relatively unusual corner case. It is mostly a
tool for people who want to disclose their local time zone (it can be useful
information in certain types of discussions), but whose clients don't for some reason,
and who can arrange for the server to be in the same time zone as the client.
newsmaster:
Used as the contact address in the help message returned by nnrpd(8), if the
virtualhost: parameter is set to true.
strippath:
If set to true, any Path: header provided by a user in a post is stripped rather than
used as the beginning of the Path: header of the article. This is a boolean value and
the default is false.
perlfilter:
If set to false, posts made by these users do not pass through the Perl filter even if
it is otherwise enabled. This is a boolean value and the default is true.
pythonfilter:
If set to false, posts made by these users do not pass through the Python filter even
if it is otherwise enabled. This is a boolean value and the default is true.
virtualhost:
Set this parameter to true in order to make nnrpd behave as if it is running on a
server with a different name than it actually is. If you set this parameter to true,
you must also set either pathhost: or domain: in the relevant access group in
readers.conf to something different than is set in inn.conf. All articles displayed
to clients will then have their Path: and Xref: headers altered to appear to be from
the server named in pathhost: or domain: (whichever is set), and posted articles will
use that server name in the Path:, Message-ID:, and Injection-Info: headers.
Note that setting this parameter requires the server modify all posts before
presenting them to the client and therefore may decrease performance slightly.
In addition, all of the following parameters are valid in access groups and override the
global setting in inn.conf. See inn.conf(5) for the descriptions of these parameters:
addinjectiondate, addinjectionpostingaccount, addinjectionpostinghost,
backoff_auth, backoff_db, backoff_k, backoff_postfast, backoff_postslow,
backoff_trigger, checkincludedtext, clienttimeout, complaints, domain,
fromhost, localmaxartsize, moderatormailer, nnrpdauthsender, nnrpdcheckart,
nnrpdoverstats, nnrpdposthost, nnrpdpostport, organization, pathhost,
readertrack, spoolfirst, strippostcc.
SUMMARY
Here's a basic summary of what happens when a client connects:
• All auth groups are scanned and the ones that don't match the client (due to hosts,
localaddress, require_ssl, etc.) are eliminated.
• The remaining auth groups are scanned from the last to the first, and an attempt is made
to apply it to the current connection. This means running res: programs, if any, and
otherwise applying default:. The first auth group (starting from the bottom) to return
a valid user is kept as the active auth group.
• If no auth groups yield a valid user (none have default: parameters or successful res:
programs) but some of the auth groups have auth: lines (indicating a possibility that
the user can authenticate and then obtain permissions), the connection is considered to
have no valid auth group (which means that the access groups are ignored completely) but
the connection isn't closed. Instead, 480 is returned for everything until the user
authenticates.
• When the user authenticates, the auth groups are rescanned, and only the matching ones
which contain at least one auth, perl_auth, or python_auth line are considered. These
auth groups are scanned from the last to the first, running auth: programs and
perl_auth: or python_auth: scripts. The first auth group (starting from the bottom) to
return a valid user is kept as the active auth group.
• Regardless of how an auth group is established, as soon as one is, that auth group is
used to assign a user identity by taking the result of the successful res, auth,
perl_auth, or python_auth line (or the default: if necessary), and appending the
default-domain if necessary. (If the perl_access: or python_access: parameter is
present, see below.)
• Finally, an access group is selected by scanning the access groups from bottom up and
finding the first match. (If the established auth group contained a perl_access: or
python_access line, the dynamically generated access group returned by the script is
used instead.) User permissions are granted based on the established access group.
EXAMPLES
Probably the simplest useful example of a complete readers.conf, this gives permissions to
read and post to all groups to any connections from the "example.com" domain, and no
privileges for anyone connecting elsewhere:
auth example.com {
hosts: "*.example.com, example.com"
default: "<EXAMPLE>"
}
access full {
users: "<EXAMPLE>"
newsgroups: *
}
Note that the above access realm could also be written without the users: key, in which
case it applies to any user identity (though in this example, the user identity that will
be assigned to all matching connections is "<EXAMPLE>"). It is however recommended to
keep an explicit users: key so as to better view to whom the access block applies.
As the only available auth realm only matches hosts in the "example.com" domain, any
connections from other hosts will be rejected immediately.
If you have some systems that should only have read-only access to the server, you can
modify the example above slightly by adding an additional auth and access group:
auth lab {
hosts: "*.lab.example.com"
default: <LAB>
}
access lab {
users: <LAB>
read: *
}
If those are put in the file after the above example, they'll take precedence (because
they're later in the file) for any user coming from a machine in the lab.example.com
domain, everyone will only have read access, not posting access.
Here's a similar example for a news server that accepts connections from anywhere but
requires the user to specify a username and password. The username and password are first
checked against an external database of usernames and passwords, and then against the
system shadow password file:
auth all {
auth: "ckpasswd -d <pathdb in inn.conf>/newsusers"
auth: "ckpasswd -s"
}
access full {
users: *
newsgroups: *
}
When the user first connects, there are no res: keys and no default, so they don't receive
any valid identity and the connection won't match any access groups (even ones with
"users: *"). Such users receive nothing but authentication-required responses from nnrpd
until they authenticate.
If they then later authenticate, the username and password are checked first by running
ckpasswd with the -d option for an external dbm file of encrypted passwords, and then with
the -s option to check the shadow password database (note that this option may require
ckpasswd to be setgid to a shadow group, and there are security considerations; see
ckpasswd(8) for details). If both of those fail, the user will continue to have no
identity; otherwise, an identity will be assigned (usually the supplied username, perhaps
with a domain appended, although an authenticator technically can provide a completely
different username for the identity), and the access group will match, giving full access.
It may be educational to consider how to combine the above examples; general groups always
go first. The order of the auth groups actually doesn't matter, since the "hosts:
example.com" one only matches connections before username/password is sent, and the "auth:
ckpasswd" one only matches after; order would matter if either group applied to both
cases. The order of the access groups in this case does matter, provided the newsgroups:
lines differ; the access group with no users: line needs to be first, with the "users:
<LOCAL>" group after.
Here's an example of another common case: a server that only allows connections from a
local domain and has an additional hierarchy that's password-restricted.
auth "example.com" {
hosts: "*.example.com"
auth: "ckpasswd -d <pathdb in inn.conf>/newsusers"
default: "anonymous"
}
access regular {
newsgroups: "*,!example.restricted.*"
}
access full {
users: "*,!anonymous"
newsgroups: *
}
In this example, unauthenticated users get the identity "anonymous", which matches only
the first access group and hence doesn't get access to the example.restricted.* hierarchy.
Anyone who authenticates using a password in the newsusers file gets full access to all
groups. However, note that the only authentication block is limited to hostnames in the
example.com domain; connections outside of that domain will never be allowed access or an
opportunity to authenticate.
Here's a very complicated example. This is for an organization that has an internal
hierarchy "example.*" only available to local shell users, who are on machines where
identd can be trusted. Dialup users must provide a username and password, which is then
checked against RADIUS. Remote users have to use a username and password that's checked
against a database on the news server. Finally, the admin staff (users "joe" and "jane")
can post anywhere (including the "example.admin.*" groups that are read-only for everyone
else), and are exempted from the Perl filter. For an additional twist, posts from dialup
users have their Sender: header replaced by their authenticated identity.
Since this organization has some internal moderated newsgroups, the admin staff can also
post messages with Approved: headers, but other users cannot.
auth default {
auth: "ckpasswd -f <pathdb in inn.conf>/newsusers"
default: <FAIL>
default-domain: example.com
}
auth shell {
hosts: *.shell.example.com
res: ident
auth: "ckpasswd -s"
default: <FAIL>
default-domain: shell.example.com
}
auth dialup {
hosts: *.dialup.example.com
auth: radius
default: <FAIL>
default-domain: dialup.example.com
}
access shell {
users: *@shell.example.com
read: *
post: "*, !example.admin.*"
}
access dialup {
users: *@dialup.example.com
newsgroups: *,!example.*
nnrpdauthsender: true
}
access other {
users: "*@example.com, !<FAIL>@example.com"
newsgroups: *,!example.*
}
access fail {
users: "<FAIL>@*"
newsgroups: !*
}
access admin {
users: "joe@*,jane@*"
newsgroups: *
access: "RPA"
perlfilter: false
}
Note the use of different domains to separate dialup from shell users easily. Another way
to do that would be with key: parameters, but this way provides slightly more intuitive
identity strings. Note also that the fail access group catches not only failing
connections from external users but also failed authentication of shell and dialup users
and dialup users before they've authenticated. The identity string given for, say, dialup
users before RADIUS authentication has been attempted matches both the dialup access group
and the fail access group, since it's "<FAIL>@dialup.example.com", but the fail group is
last so it takes precedence.
The shell auth group has an auth: parameter so that users joe and jane can, if they
choose, use username and password authentication to gain their special privileges even if
they're logged on as a different user on the shell machines (or if ident isn't working).
When they first connect, they'd have the default access for that user, but they could then
send AUTHINFO USER and AUTHINFO PASS in order to get their extended access.
Also note that if the users joe and jane are using their own accounts, they get their
special privileges regardless of how they connect, whether the dialups, the shell
machines, or even externally with a username and password.
Finally, here's a very simple example of a configuration for a public server for a
particular hierarchy.
auth default {
hosts: *
default: <PUBLIC>
}
access default {
users: <PUBLIC>
newsgroups: example.*
}
Notice that clients aren't allowed to read any other groups; this keeps them from getting
access to administrative groups or reading control messages, just as a precaution. When
running a public server like this, be aware that many public hierarchies will later be
pulled down and reinjected into the main Usenet, so it's highly recommended that you also
run a Perl or Python filter to reject any messages crossposted out of your local hierarchy
and any messages containing a Supersedes: header. This will keep messages posted to your
public hierarchy from hurting any of the rest of Usenet if they leak out.
SECURITY CONSIDERATIONS
In general, separate passwords should be used for NNTP wherever possible; the NNTP
protocol itself does not protect passwords from casual interception, and many
implementations (including this one) do not "lock out" accounts or otherwise discourage
password-guessing attacks. So it is best to ensure that a compromised password has
minimal effects.
Authentication using the AUTHINFO USER/PASS commands passes unencrypted over the network.
Extreme caution should therefore be used especially with system passwords (e.g. "auth:
ckpasswd -s"). Passwords can be protected by using NNTP over TLS/SSL or through ssh
tunnels, and this usage can be enforced by a well-considered server configuration that
only permits certain auth groups to be applied in certain cases. One can also
authenticate using a strong SASL mechanism. Here are some ideas:
• To restrict connections on the standard NNTP port (119) to use an encryption layer for
some (or all) of the auth groups to match, use the require_ssl parameter. Note that a
client can use STARTTLS to negotiate an encrypted TLS connection. A secure layer can
also be negotiated during authentication via AUTHINFO SASL.
• If you consider your local network (but not the internet) secure, have some auth
groups with a restrictive hosts: parameter; they would go above, with ones having
global applicability below.
• Consider running nnrpd with the -S flag (either also with -D, or out of "super-server"
like inetd) on the NNTPS port (563) for clients that support TLS/SSL. See nnrpd(8)
for more details about how to configure that. You can use the require_ssl parameter
or the -c flag to specify an alternate readers.conf file if you want a substantially
different configuration for this case.
• If you want to restrict an auth group to only match loopback connections (for users
running newsreaders on localhost or connecting via an ssh tunnel), use the
localaddress: parameter.
HISTORY
Written by Aidan Cully <aidan@panix.com> for InterNetNews. Substantially expanded by Russ
Allbery <eagle@eyrie.org>.
$Id: readers.conf.pod 9977 2015-12-10 20:49:04Z iulius $
SEE ALSO
auth_krb5(8), ckpasswd(8), inn.conf(5), innd(8), newsfeeds(5), nnrpd(8), uwildmat(3).