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dacs - a distributed access control system


dacs [-v | --verbose] [--dumpenv] [--license] [--version]

dacs dacs-command [dacsoptions[1]] [...]

dacs-command [-u uri-prefix | -uj jurisdiction-name | -un | -up jurisdiction-name | -us]
[-c dacs.conf]
[-sc site.conf] [-ll logging-level] [-format fmt] [-q] [-t] [-Dname=value]
[-v | --verbose] [--dumpenv] [--enable-dump] [--license] [--std] [--version]


This program is part of the DACS suite.

DACS is a general-purpose, Web-based authentication and access control system. It provides
single sign-on functionality and flexible access control to content and services provided
by web servers. DACS consists of an Apache module (mod_auth_dacs[2]) through which Apache
communicates with DACS to make access control decisions, a suite of CGI programs that
provide DACS web services, and a collection of utility commands that provide various
support and administrative functions for DACS. Some of these utilities, such as
dacshttp(1)[3] and sslclient(1)[4], are completely general-purpose.

The DACS access control engine and authentication components can also be used from the
command line, within a CGI environment or completely independently of the Web.

For important information about DACS, including installation instructions, please see
dacs.readme(7)[5] and dacs.install(7)[6].

About DACS
This software is provided by Dss "as is" and any express or implied warranties,
including, but not limited to, the implied warranties of merchantability, fitness for
a particular purpose, or non-infringement, are disclaimed. In no event shall Dss be
liable for any direct, indirect, incidental, special, exemplary, or consequential
damages (including, but not limited to, procurement of substitute goods or services;
loss of use, data, or profits; or business interruption) however caused and on any
theory of liability, whether in contract, strict liability, or tort (including
negligence or otherwise) arising in any way out of the use of this software, even if
advised of the possibility of such damage.

By convention, the names of all DACS web services begin with the prefix "dacs_" (e.g.,
dacs_conf). Starting with release 1.4.17, all commands that implement DACS functionality
begin with the prefix "dacs" (e.g., dacsconf). Many DACS web services have command
analogues. The names of web services that are used internally by DACS (i.e., they are
never called directly by users) begin with "local_" (e.g., local_passwd_authenticate).
General-purpose web services and commands do not follow a naming convention, other than
not using any of the previously mentioned prefixes.

The document type definitions (DTDs) that are maintained in the dtd-xsd directory are used
to document file formats or describe the arguments to a DACS web service or its reply. In
the current implementation, these DTD files are not used during XML validation. Attributes
of type CDATA may have additional constraints on their values; consult the relevant
documentation. The files are technically not valid DTDs, because they lack a document type
declaration (DOCTYPE); an appropriate DOCTYPE is generated programmatically at the time a
DTD is emitted.

DACS does not prevent certain kinds of attacks against web sites, such as Denial of
service attacks[7], Cross-site scripting (XSS)[8] or Cross-site request forgery
(CSRF)[9]. When combined with appropriate web site protective measures, however, DACS
does provide mechanisms to make these types of attacks more difficult.

About the Manual Pages
The technical documentation for DACS consists of a set of manual pages. In the HTML
collection, an index page[10] includes a table of contents, links to special annotations
within the technical documentation, and lists of variables, configuration directives, and
XML Document Type Definitions.

Each HTML manual page contains a font size selection tool near its bottom. If
JavaScript is enabled, the currently selected font size can be changed and a global
preference set. To choose a font size for the current page, click on one of the four
boxes. To make the current selection your preference across manual pages, site visits,
and browser sessions, click on the "set" button, which will set an HTTP cookie. If a
preference has not been set in this way (i.e., there is no cookie) and a manual page
is visited with the query parameter DACSMANFONT set to 0, 1, 2, or 3 (representing
smallest to largest point sizes), the corresponding font will be selected and the
preference automatically set (if a preference has been set, the parameter is ignored).

Areas of the documentation labeled "Security" discuss important security considerations;
please pay special attention to them. Areas labeled "Tip" provide pointers to time-saving
(and sometimes aggravation-reducing) techniques and recommended practices.

In pathnames and URLs that appear in examples, the text "..." represents text that has
been omitted because it is not relevant to the discussion at hand, or which may vary
depending on configuration details, such as where something has been installed (e.g.,

Unless otherwise stated, URLs used in examples are fictitious and most likely will not
work. The reserved domain name example.com is often used (RFC 2606[11]).

In instructions and examples, a '%' is generally used to signify a command line prompt:

% date
Sun Apr 1 15:33:11 PDT 2007

Sometimes another character is used to signify a prompt, however, such as when
demonstrating the interactive mode of dacsexpr(1)[12]:

> 1 + 1

An extended form of BNF notation[13] is used to describe syntax concisely. We hope it is
both understandable and familiar, but some inconsistencies and ambiguities may occur
throughout the documentation; this is being improved slowly. A term in a production may
include a regular expression type specification, with '+' meaning one or more occurrences
of the term, and '*' zero or more occurrences. Any one of a set of characters is specified
within square brackets, and a range of consecutive characters (in ASCII code sequence) is
separated by a hyphen (e.g., [A-Za-z0-9\-_]+ means "one or more alphabetic characters,
digits, hyphens, or underscores"). In other contexts, square brackets indicate an optional
term. Single and double quotes specify literal characters. Note that XML DTDs use their
own syntax, which is somewhat different, and in some cases grammars followed in relevant
RFCs are respected for clarity or in examples.

Key Concepts
Some of the key concepts used throughout the DACS documentation are defined in this

A persistent record that associates an identity (or username) with state information
about the account (such as whether the account is enabled or disabled), information
that is required to authenticate the identity (such as a digest of a password string),
and possibly other sign-on related information. Note that DACS identities do not
necessarily have a corresponding account. DACS does not provide mechanisms to
administer "foreign" account types; for instance, although it can authenticate against
them, it cannot create or list Unix or Windows accounts.

The procedure by which a person or program obtains credentials that represent a DACS
identity, usually by asserting a DACS username that represents an identity and
providing information that only that identity is likely to know or possess. After
successful authentication, a person or program is said to have authenticated. DACS
can interface with a wide variety of authentication methods and provides some of its
own; new methods can easily be added.

The procedure that determines, in a particular context, whether a request for a given
resource or object should be allowed. If an identity is authorized to perform a
certain operation on the object, access is granted, otherwise it is denied. Access
control rules are one method of describing which identity or identities should be
granted - or denied - access to a particular resource. Coarse-grained access control
involves making a high-level decision of whether access to an object should be
granted; this is usually an all-or-nothing decision. Fine-grained access control is
used within a program to decide whether access to a lower-level resource (some data,
an administrative function, a menu) should be granted.

Note that unlike some systems, DACS does not predetermine which resources a particular
user (identity) can and cannot access; that is, an administrator does not make a list
of what rights each user has. Authorization is always determined by rule evaluation,
in real time, when a user requests a resource. The only exemptions to this are some
optional features: Authorization Caching[14] and Rlinks[15].

If authentication is successful, DACS returns information that can be used in
subsequent operations to represent the authenticated identity. Credentials contain
information about the identity, such as its name, and meta information, such as the
time at which the credentials expire and become invalid. Credentials are protected
cryptographically so that they are difficult to forge or alter. They must be kept
secret, so that the identity cannot be used by anyone other than its owner, and must
accompany a request made to a server so that DACS knows who is making the request. The
particular mechanism used for this is not important provided credentials cannot be
copied and reused; transporting credentials using the payload of an HTTP cookie over
an SSL connection is typical, although sending credentials as the value of an HTTP
extension header is another possibility.

Although there is no specific limit on the size of credentials as far as DACS is
concerned, since they can be encapsulated within an HTTP cookie and returned to a
browser, constraints on cookies imposed by browsers should be carefully considered.

Any jurisdiction can understand credentials produced by any other jurisdiction within
the same federation. Therefore, a user only needs to be authenticated once to access
web services at any jurisdiction using that identity.

Note that in DACS, credentials do not give their owner any rights or convey any
authorization; DACS is not a capability-based system[16]. Credentials simply represent
a DACS identity.

Refer to dacs_authenticate(8)[17] for details.

current request
The event that has triggered the authorization check being processed by
dacs_acs(8)[18] is referred to as the current request. For a request for a
DACS-wrapped web resource, this will be the HTTP request that is received by the web
server for the resource. In situations where dacs_acs is not involved, such as when
dacscheck(1)[19] or dacsexpr(1)[12] are used, the current request and its context are
specified by command line arguments or are obtained from the execution

dacs_acs uses ${DACS::URI} as the path component of the current request. It is
obtained from Apache's uri element of the current request_rec. This is the string that
is used to match against access control rules.

Other DACS components determine the current HTTP request by examining several
environment variables: HTTP_HOST (or SERVER_NAME and SERVER_PORT), REQUEST_URI,

The value of ${DACS::URI} and the path component of ${Env::REQUEST_URI} are not
necessarily the same. After an internal redirect, for example, the latter's value is
from the original URL, while the former's is from the target of the redirection.

The current request string is important because it may be used to determine the
current federation[21] and current jurisdiction[22], and because it is used when
searching for the access control rule to apply to the request.

Consisting of CGI-based web services, an Apache 2.0/2.2 module, and a collection of
utilities, DACS provides authentication and authorization functionality. Transparent,
coarse-grained role-based access control is available for web resources.

Programmatic, general-purpose role-based access control is available for virtually any
program (using dacscheck(1)[19]). This is completely decoupled from Apache.

DACS administrator
An individual (or individuals) responsible for managing the operation of DACS is
called a DACS administrator (sometimes just "the administrator"). This individual is
not necessarily a system administrator (e.g., superuser or root), although a small
number of optional components of DACS must execute as user or group root. The DACS
administrator need not be an Apache administrator; once Apache has been configured for
DACS it typically requires very few modifications thereafter. The DACS administrator
is responsible for configuring and testing DACS (probably installing and upgrading it,
too), managing user accounts and access control rules, safeguarding security, backing
up configuration and data files, and so on. The design of DACS allows some delegation
of responsibility, largely based on file permissions. When invoked as a web service,
each of the identities configured as a ADMIN_IDENTITY[23] is effectively a DACS
administrator; in this context, the system superuser has no significance.

DACS identity
Each authenticated user is assigned a name that consists of the name of the
authenticating jurisdiction, its federation name, and a username. Each of these naming
components must be syntactically correct. In some contexts the federation name is
implicit; sometimes the jurisdiction name is also implicit. Entities such as
individuals (people, but also programs, devices, etc.), federations, jurisdictions,
and groups have names. It is the responsibility of jurisdictions to authenticate
users. The syntax, meanings, and uniqueness of names is also a jurisdictional issue,
and perhaps a federation-wide issue as well.

Each real world entity typically has a unique DACS identity, but this is left up to
authenticating jurisdictions. Two or more identities are distinct if they do not refer
to the same real world individual. Federated identity or single sign-on (SSO) is the
ability to recognize a user identity across jurisdictions and even across federations.

Keep in mind that regardless of the authentication method and account information
used, two identical usernames (relative to the same jurisdiction and taking into
account NAME_COMPARE[24]) are implicitly assumed to refer to the same identity by
DACS. For instance, someone who authenticated as auggie by providing the correct
Unix password is virtually indistinguishable from someone who authenticated as
auggie using an Information Card. User credentials include information about the
authentication method involved in their creation and the user()[25] function can
be used to obtain this information, but it would be unwise to base identities on
this. It is strongly advised that a new DACS jurisdiction carefully develop an
extensible plan for user naming.

A web resource is said to be DACS-wrapped if the web server responsible for the
resource calls DACS (more specifically, dacs_acs(8)[18]) to make an access control
decision whenever it receives a request for the resource.

A DACS federation consists of one or more jurisdictions. The jurisdictions comprising
a federation coordinate information sharing through light-weight business practices
implemented as a requirement of membership in a DACS federation; in other words, the
members of a federation typically agree to observe certain rules of conduct to
preserve overall security and so that users can obtain maximum benefit. A federation
consisting of just one jurisdiction is not unusual.

item type
An item type is a name that maps to a VFS[26] (virtual filestore) specification that
configures how and where data is stored. The level of indirection that they provide
means that access control rules, for example, can be configured to be in regular
files, a Berkeley DB database, a remote database accessed by HTTP, and so on - all
that is required is that the item type acls be properly configured. Some item types
(like acls) are reserved and have special meaning to DACS, while others can be used by
a DACS administrator for other purposes. An item type name is case sensitive and
consists of alphanumerics, hyphens, and underscores, but must begin with an alphabetic

A DACS jurisdiction is an autonomous administrative entity that authenticates its
users, provides web services, or both. It may correspond to an organization,
department, web server, or virtual host. Jurisdictions are sometimes created simply as
an administrative convenience. Each jurisdiction is assigned a unique name within a

A user's home jurisdiction is a jurisdiction that can authenticate that user. In
situations where a user has multiple credentials obtained from different
jurisdictions, the effective home jurisdiction for a request depends on which
credentials are selected during authorization processing. Configuration directives are
available to restrict the number of sets of credentials that may accompany a request.

user agent
A user agent is client-side software that interacts with other software (a server
application, typically) on behalf of a user. A user is often a person but can also be
software. A web browser, which is used to interact with a web server, is an example of
a user agent.

DACS needs to name a variety of things so that they can be referred to in expressions,
access control rules, configuration directives, and so on. While the URI syntax is used to
name some kinds of objects within DACS, DACS also has its own concise naming schemes.

The terms current federation (current jurisdiction) and this federation (this
jurisdiction) are used in the documentation to refer to the federation (jurisdiction)
associated with the configuration context in effect while DACS processes a request.

In general, the federation-name component of a name is optional; if absent, the
current federation is assumed. Similarly, the jurisdiction-name may be elided and the
current jurisdiction is implied.





The federation-name (usually obtained from a FEDERATION_NAME[27] configuration
directive) must begin with an alphabetic character and is followed by zero or more
alphanumerics, hyphens, and underscores. A federation-name is ordinarily treated case
sensitively (but see the NAME_COMPARE[24] configuration directive and the user()[25]
function for alternate behaviours). There is no a priori limit on its length.

The FEDERATION_DOMAIN[28] directive specifies the domain name suffix common to all
jurisdictions in a federation.


[[federation-name:: | [::]] jurisdiction-name:



The jurisdiction-name (usually obtained from a JURISDICTION_NAME[29] configuration
directive) must begin with an alphabetic character and is followed by zero or more
alphanumerics, hyphens, and underscores. A jurisdiction-name is ordinarily treated
case sensitively (but see the NAME_COMPARE[24] configuration directive and the
user()[25] function for alternate behaviours). There is no a priori limit on its


[[[federation-name:: | [::]] jurisdiction-name]:username



A full DACS identity includes a federation name component and a jurisdiction name
component, in addition to the username. It is provided to DACS-wrapped programs as the
value of the DACS_IDENTITY[30] environment variable.

The username component, which is available to CGI programs as the value of the
DACS_USERNAME[31] environment variable, consists of one or more ASCII characters from
the set of upper and lower case alphabetics, digits, and the following punctuation

! # $ % & ' - . ; ? @ [ ^ _ ` { }

All characters having a value less than 041 (octal) or greater than 0176 (octal) are
invalid, as are the following characters:

* , : + ( ) ~ < > = | \ / "

· In addition to the alphanumeric characters, RFC 2396[32] allows only the
following characters ("pchar") to appear in the path component of a URI:

- _ . ! ~ * ' ( ) % : @ & = + $ ,

· Some valid email addresses are not valid DACS usernames. For example,
*bob*@example.com, "(bob)"@example.com, and \(bob\)@example.com are valid
mailbox names as defined by RFC 822[33] (Appendix D) and discussed in RFC
3696[34] (Section 3), but both are invalid as DACS usernames. Unless quoted,
the local-part component of an email address, which precedes the "@" character
in the addr-spec, may not contain any of:

( ) < > @ , ; : \ " . [ ]

Additionally, the space and all US-ASCII control characters (octets 0 - 31)
and DEL (127) are disallowed. Without quotes, the local-part may consist of
any combination of alphabetics, digits, or any of the following characters:

! # $ % & ' * + - / = ? ^ _ ` . { | } ~

A period (".") may be used, but may not start or end the local-part, nor may
two or more consecutive periods appear. Within double quotes, any ASCII
character may appear if properly quoted (e.g., Auggie."
".O."\'".[email protected]). The maximum length of the local-part is 64
characters, and the maximum length of the domain component that appears after
the "@" character is 255 characters.

There is currently no way to "quote" a DACS username, so some safe encoding
method or transformation must be applied to these names.

· DACS may create identities for internal use having username components that
include characters that are normally invalid.

· A username is case sensitive (but see the NAME_COMPARE[24] configuration
directive and the user()[25] function for alternate behaviours). There is no a
priori limit on its length.

· The recommended practice is for jurisdictions to map their DACS usernames to
lower case during the authentication procedure where possible and when the
mappings are unique. The EXIT*[35] directive may be used for this purpose.


[[federation-name:: | [::]] %[jurisdiction-name]:groupname

A groupname must begin with an alphabetic character and may be followed by any number
of alphanumeric, hyphen ("-"), and underscore ("_") characters.



Roles and Role Descriptors

Role-Descriptor -> Empty-String | Role-List

Role-List -> Role | Role "," Role-List

Role -> Basic-Role | Composite-Role

Basic-Role -> [A-Za-z0-9\-_]+
Composite-Role -> Basic-Role "/" Basic-Role | Basic-Role "/" Composite-Role

Empty-String -> ""

A role descriptor string (also called a role string or a role descriptor) consists of
a comma separated list of roles. The name of a role (a Basic-Role) is constructed from
upper and lower case letters, digits, hyphens, and underscores. A Composite-Role is
constructed from two or more Basic-Role terms, separated by a slash character. Here
are three examples of a role descriptor:


A role descriptor string contains no white space characters and may not begin or
end with a comma or slash character. Two or more consecutive commas are illegal,
as are two or more consecutive slashes.
The setvar()[36] function can be used to separate a composite role into its basic

Please refer to dacs.groups(5)[37] for additional information.

Concise User Syntax

ident -> '{' kwv-list '}' | user
kwv-list -> kwv [',' kwv]*
kwv -> kwv-user | kwv-group | kwv-attr | kwv-ip | kwv-expires
kwv-user -> 'u=' [Q] user [Q]
kwv-group -> 'g=' [Q] groups [Q]
kwv-attr -> 'a=' [Q] attr [Q]
kwv-expires -> 'e=' [Q] expires [Q]
kwv-ip -> 'ip=' [Q] ip-addr [Q]

user -> simple-name | DACS-identity
groups -> group [',' group]*
group -> groupname | role-descriptor
attr -> any-alphabetic
ip-addr -> any-IP-addr
expires -> +rel-secs | date


· Q is an optional (matched) quote character;

· whitespace may optionally precede most tokens;

· a DACS-identity is a full or abbreviated DACS identity[38]

· a simple-name is the username component of a DACS identity (i.e., without any
colons); consequently in this context a "special" name, such as auth, is treated
as :auth

· role-descriptor must be a valid DACS role string and groupname must be a valid
DACS group name (see dacs_authenticate(8)[39] and dacs.groups(5)[40]);

· an IP address is expressed in the Internet standard numeric dot notation (e.g.,; and

· the lifetime of credentials derived from the identity can be expressed either as a
given number of seconds (e.g, "e=+3600") or a given date in one of the following
formats (see strptime(3)[41]):

%a, %d-%b-%Y %H:%M:%S GMT
%b %d, %Y
%b %d

When necessary, dates are interpreted relative to the current time or date. The
lifetime is converted to its canonical form, which is the absolute time and date
in seconds since the Epoch, based on the jurisdiction's clock. A date in the past
can be specified; this might be useful for testing, for instance. If the identity
is not used to create credentials, the expiry date is ignored, although it must be
syntactically correct.

· the only supported attribute value is "a", which means that the identity should be
treated as an ADMIN_IDENTITY[23] (refer to the -admin flag of dacscheck(1)[19]).

A name expressed in the concise syntax, gives a username and, optionally, roles and
attributes for the identity. It is used by dacscheck(1)[19], for instance.

The dacs Utility
DACS utility commands are usually installed as separate binaries, but DACS can (also or
instead) be built with most of them combined into a single binary that is installed as
dacs. The various utility programs may then be run as:

% dacs dacs-command [dacsoptions] [command-options]

For example:

% dacs dacskey -u foo.myfed.com outfile

Running the dacs utility without arguments will show the list of available sub-commands.

Start-up Processing
Most DACS programs perform the following actions when they start:

1. Determine the "mode" in which they should operate; for example, if the REMOTE_ADDR
environment variable is present, programs will in general assume they should run as a
web application rather than as a utility command

2. Process a standard set of command line arguments (dacsoptions[42])

3. Set the process umask to 007 to disallow world access for any created files

4. Disable a core dump so that sensitive information cannot be revealed by examining them
(but see --enable-dump[43])

5. Refuse to operate if any configuration file cannot be found or has an error

6. For web services, make the DACS home directory the current working directory

7. If "secure mode" has been enabled, web services will only process HTTPS requests

8. Verify that the version required by a request is compatible with the version of DACS
receiving the request

9. Process any program-specific command line arguments.

DACS programs make an effort to destroy sensitive information (such as passwords) as soon
as it is no longer needed and not to write potentially sensitive information to log files
unless specifically configured to do so.

Some DACS components may call other components using HTTP (possibly over SSL, depending on
configuration). For example, authentication modules may be invoked as web services by
dacs_authenticate(8)[39]. In all cases, these "internal" HTTP calls may not result in a
redirection, such as through a 302 Found status code. Although this can sometimes be an
inconvenience, it is, in part, a security measure.

When debugging a problem that may involve an internal HTTP request (especially related
to authentication), verify that DACS is not receiving a redirect. Internal HTTP
requests may also fail mysteriously because of incorrect or incomplete configuration
of SSL parameters. Internal HTTP requests over SSL use sslclient(1)[4], as does the
dacshttp(1)[3] command. If you suspect that an https-schemed URL may not be working,
debug the problem using sslclient and then dacshttp.

To maintain data consistency, DACS creates exclusive locks using the fcntl(2)[44] system
call on files written in the directory configured through the TEMP_DIRECTORY[45]

Most DACS services and utilities write various kinds of messages to one or more log files.
These messages can be invaluable when trying to figure out what DACS is doing, for
security audits, or to see which DACS-wrapped resources are being accessed and in what

Please refer to dacs.conf(5)[46] for information about configuration directives related to
logging. An assortment of command line flags, described below, are also related to

· DACS can emit log messages before configuration processing is complete and
configuration directives associated with logging are not in effect during this
startup interval.

· Because mod_auth_dacs[2] is an Apache module, the Apache logging directives apply
to it (and not the DACS directives) and its log messages are written to Apache log

· Log files can quickly become large, especially when the logging level is set to
debug or trace levels. Consider daily rotation or truncation.

· The text of a log message may occasionally span several lines.

The default value of the LOG_FORMAT[47] directive, which controls the appearance of log
messages, is defined in include/local.h as LOG_FORMAT_DEFAULT_WEB for DACS web services
and LOG_FORMAT_DEFAULT_CMD for everything else. Here is a typical log message:

[Wed Jul 12 12:37:09 2006] [trace] [83648,1060,-] [dacs_acs:"acslib"] Allow
clause grants access

Audit-Class Log Messages
In the case of audit-class messages, a string within parentheses may sometimes follow
an identity, as in the examples below. This string, called a tracker, associates log
messages with a particular origin and can be used to trace a user's sequence of
service requests using log messages throughout a federation. This can be useful when
debugging, looking for security problems, or forensic analysis.

For an unauthenticated user, the tracker can only be derived heuristically, from
elements of the execution context. The user's IP address, user agent string, and SSL
client certificate, when available, are used. If two of these tracker strings differ,
the requests are typically coming from different hosts, browsers, or users, but this
is not necessarily always the case. Similarly, if the same tracker string is
associated with two log messages, the service requests are not necessarily being
issued by the same user.

For an authenticated user, the tracker string consists of the heuristically-derived
string, followed by a comma, followed by a string uniquely associated with the user's
credentials. This tracker has a high probability of being unique and having a
one-to-one mapping with a particular user.

Consider these (condensed) log file entries:

[Wed Jul 12 15:56:24 2006] [notice] [83963,1067,A] [dacs_acs:"authlib"]
*** Access granted to unauthenticated user (7vJLWzv5) from
for /cgi-bin/dacs/dacs_current_credentials

[Wed Jul 12 15:56:27 2006] [notice] [83965,1073,A] [dacs_acs:"authlib"]
*** Access granted to unauthenticated user (7vJLWzv5) from
for /cgi-bin/dacs/dacs_authenticate

[Wed Jul 12 15:56:27 2006] [debug] [83966,172,A] [dacs_authenticate:"authlib"]
Authentication succeeded for HOME:bobo (7vJLWzv5,wA/Pudyp3f0)

[Wed Jul 12 15:56:30 2006] [notice] [83973,1078,A] [dacs_acs:"authlib"]
*** Access granted to DSS::HOME:bobo (7vJLWzv5,wA/Pudyp3f0)
from for /cgi-bin/dacs/dacs_current_credentials

In the first two of the log messages above, the tracker 7vJLWzv5 appears, meaning that
the two requests probably came from the same (unauthenticated) user. With the third
log message, the user has been authenticated and the tracker 7vJLWzv5,wA/Pudyp3f0 is
used. Because these trackers all share the same prefix, the first two requests
probably also came from someone who authenticated as DSS::HOME:bobo. The last request,
for /cgi-bin/dacs/dacs_current_credentials, definitely came from that user. If this
user were to signout and then issue more service requests anywhere in the federation
DSS, each log message would contain the tracker 7vJLWzv5.

Tracking the requests of anonymous users reliably is difficult to do well. A
cookie-based approach may do better in some situations but has its own drawbacks
(such as being totally ineffective when the user has disabled cookies).

Tracking User Activity
DACS includes a feature, enabled as a build-time option (see dacs.install(7)[48]), whereby
a jurisdiction can track the activity of all of its users (i.e., those users that
authenticate at the jurisdiction). Each successful authentication event, explicit signout
event, and user-submitted web service request event can be recorded at the user's home
jurisdiction in the format defined by dacs_user_info.dtd[49]. This information can be
valuable for getting a better understanding of what is happening in a federation,
including helping to diagnose performance and security issues. It is the basis of features
like displays of recent account activity, and it might also be used to create new
capabilities, such as a concurrent login limit or an adaptive authentication component to
implement layered authentication or risk-based authentication.

To specify where and how a home jurisdiction should maintain these records, the user_info
item type must be defined at that jurisdiction; if it is not defined, no records will be
written at that jurisdiction, although the jurisdiction will still try to send event
records to other jurisdictions. For maximum benefit, the feature should be enabled at all
jurisdictions in a federation since all user activity throughout the federation can then
be logged.

If a jurisdiction wants to monitor the activity of its users at other jurisdictions, it
must allow those jurisdictions to invoke its dacs_vfs(8)[50] service by adding an
appropriate access control rule.

It is critical for any such rule to require the dacs_admin()[51] predicate.

· The dacs_admin(8)[52] tools provides an interface to these records. It should
eventually be extended to collect and organize records found at all jurisdictions
in a federation to facilitate analysis. Because they are text files with a
relatively simple format, administrators should not find it difficult to apply
common text processing tools or write short, custom programs for this purpose.
Commands analogous to last(1)[53], who(1)[54], and sa(8)[55] are being considered.

· Each jurisdiction should write records to its own place (i.e., jurisdictions
should not share the same VFS object for user_info).

· This database will grow indefinitely; an administrator is responsible for rotating
or truncating it. If previous and active sign on information is important (see
dacs_current_credentials(8)[56]), prune only the request records (i.e., the acs
elements). Another acceptable method is to discard (or archive) some proportion of
older records (say, half) and keep some of the newer records.

· The data format is subject to change.

· A directive to enable or disable this feature at run-time may be added.

· Internal administrative events are not recorded.

· Because logging off (via dacs_signout(8)[57]) is optional, the end of a session
can sometimes only be inferred or approximated from the expiry of credentials or
the time of the last recorded event.


DACS programs and web services get much of their run-time configuration information by
reading configuration files and examining environment variables. Some configuration
information can be provided at compile-time. Several command line flags may be used to
override default behaviour.

· All dacsoptions flags are processed left-to-right and must appear before any
command-specific flag or argument. The first flag or argument that is not
recognized as one of the dacsoptions terminates the list.

· The most important dacsoptions are those that specify the location of
configuration files and identify the jurisdiction section to use within a
configuration file. Depending on the program and how it is used, configuration
information may not be needed, may be optional, or may be required.

· At most one of the command line flags to select a jurisdiction section can be
specified. Refer to dacs.conf(5)[46] for additional information on the
configuration file and configuration processing.

Many DACS utilities recognize the following standard options, which are called

-c dacs.conf
This tells DACS where it can find a configuration file for the jurisdiction on whose
behalf it is acting. If this argument is not present, depending on how it was built,
DACS may either try to use a compile-time specified file or it will try to use the
value of the environment variable DACS_CONF[58]. For details, refer to Locating
dacs.conf and site.conf[59].

The effect of this flag is to define variable name (which must be syntactically valid)
in the DACS namespace to have the value value. Any quotes around value are retained,
provided the shell has not already stripped them off. This flag may be repeated. These
variables can subsequently be tested during configuration processing and rule
processing; for example, the value of a configuration directive might depend on the
value of a dacsoptions flag. Defining a name that happens to correspond to a
dacsoptions flag has no effect other than to create the variable.

All dacsoptions flags (excluding this one) are automatically added to the DACS
namespace as they are processed. A flag that is a "singleton" (e.g., -q) is initially
assigned a value of one and is incremented on each subsequent appearance. A flag of
the form -flag value is equivalent to -D-flag=value. Unused flags are undefined; if -q
is not given, ${DACS::-q} will not be defined. For those flags that have synonyms, a
variable for each synonym is created. If the name is used, explicitly or implicitly,
later values replace earlier ones.

For example, if the dacsoptions are:

-c www.example.com -v --verbose -Dfoo="baz" -ll debug -D-ll=trace

then variables will be defined as follows:

${DACS::-c} is "www.example.com"
${DACS::-v} is "2"
${DACS::--verbose} is "2"
${DACS::foo} is "\"baz\""
${DACS::-ll} is "trace"

The debugging level will be debug and not trace.

Print all environment variables to stdout and then exit immediately.

By default, DACS web services and most commands disable core dump generation as a
security precaution. Because a core dump can be useful when debugging, this flag
allows it to be created. As programs that are allowed to produce a core dump must
change to the DACS_HOME directory, core dumps will be written there. Use this flag
with care.

-format fmt
The output format is set to fmt, which is one of the following keywords (case
insensitive): file, html, json, php, plain, text, xml, xmldtd, xmlsimple, or
xmlschema. Not all output formats are supported by all programs. This flag overrides
any FORMAT[60] argument to a web service, which in turn overrides a program's default
format. The default format depends on the particular program and way it is invoked.
For additional information, refer to the description of the FORMAT argument[60].

-ll logging-level
The logging level is set to log-level, which is one of the keywords recognized by the
LOG_FILTER[61] directive.

Print the license for DACS to stdout and then exit immediately.

Be quiet. This is equivalent to setting the logging level to warn.

-sc site.conf
This tells DACS that it can find a configuration file for the jurisdiction on whose
behalf it is acting. If this argument is not present, depending on how it was built,
DACS may either try to use a compile-time specified file or it will try to use the
value of the environment variable DACS_CONF[58]. For details, refer to Locating
dacs.conf and site.conf[59].

This flags the end of the common arguments. The next command line argument, if any, is
specific to the program.

Emit tracing information. This is equivalent to setting the logging level to trace.
(Also see debug_dacs[62].)

-u config-uri
This instructs DACS to use config-uri to select the jurisdiction section to use in the
configuration file. For details, refer to The Jurisdiction Section[63].

-uj jurisdiction-name
This instructs DACS to use the jurisdiction name jurisdiction-name to select the
jurisdiction section to use in the configuration file. For details, refer to The
Jurisdiction Section[63].

This instructs DACS not to process site.conf or dacs.conf. This may only be used with
a small number of commands, such as dacsacl(1)[64] and sslclient(1)[4].

-up jurisdiction-name
NOT IMPLEMENTED. This instructs DACS to use the jurisdiction name jurisdiction-name to
select the jurisdiction section to use in the configuration file and tells it that the
web server is acting as a forward proxy; that is, jurisdiction-name does not
necessarily "own" the requested URL. For details, refer to The Jurisdiction

This instructs DACS to use the one-and-only jurisdiction section that appears in the
configuration file. That is, the configuration file must contain exactly one
jurisdiction section and that is the one that should be used. For details, refer to
The Jurisdiction Section[63].

Be more verbose, relative to the current logging level. This flag may be repeated.

Print version information to stderr immediately and then exit. If -v appeared earlier
on the command line, also print version information for each DACS source code file in
this program.

Complete version information is available only for statically linked programs.
Also see dacsversion(1)[65] and dacs_version(8)[66].

If no command line flag is given to specify the jurisdiction section, the value of the
environment variable DEFAULT_JURISDICTION will be used as if given with the -uj flag.
This can be particularly useful when a host has only one jurisdiction configured
because it makes it unnecessary to always specify the jurisdiction for DACS commands.


May be used to determine the applicable jurisdiction.

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