table of contents
| DACS_AUTHENTICATE(8) | DACS Web Services Manual | DACS_AUTHENTICATE(8) |
NAME¶
dacs_authenticate - DACS authentication service
SYNOPSIS¶
dacs_authenticate [dacsoptions[1]]
DESCRIPTION¶
This web service is part of the DACS suite.
The dacs_authenticate web service is an authentication "driver" for DACS. When it receives a request to authenticate a user, it usually invokes one or more authentication modules, depending on its configuration. Successful authentication assigns a DACS user identity to the user and roles modules may be invoked to determine the roles with which the identity is associated; DACS credentials are generated and returned to the user. The caller of dacs_authenticate can be redirected to a configured URL, called the post-authentication handler (or just the handler), depending on whether authentication fails or succeeds.
General DACS configuration directives are discussed in dacs.conf(5)[2]. Configuration directives specific to authentication are described here.
DACS expressions are described in dacs.exprs(5)[3].
dacs_authenticate might be called from an HTML form, directly through a link on a web page, indirectly by DACS HTTP Authentication[4], or from middleware. See the distribution's html/examples[5] directory for examples of simple login pages.
Command line authentication functionality is provided by dacsauth(1)[6]. Other authentication mechanisms are provided by dacs_auth_agent(8)[7], dacs_auth_transfer(8)[8], and dacscookie(1)[9].
Authentication¶
Authentication is the procedure by which a claimed identity is confirmed. Following successful authentication, DACS credentials may be created that represent the identity. For maximum convenience and interoperability in a web environment, DACS credentials are usually encapsulated within an HTTP cookie and transmitted over a TCP/IP connection secured by SSL/TLS. Any secure method of transporting credentials can be used instead, however, such as the value of an HTTP extension-header entity-header field in a request message sent over a VPN.
While dacs_authenticate provides powerful and flexible ways to combine and compose a variety of authentication methods, most DACS jurisdictions will configure only one method, or perhaps just a few methods, in simple ways.
To help integrate DACS seamlessly within a web site, dacs_authenticate allows handlers to be configured. Handlers allow various exceptions to be caught and processed so that an appropriate flow of control can occur. For example, if authentication succeeds the user can be redirected to a specific page, including the one originally requested before the exception occurred.
Authentication succeeds (and the user is authenticated) if and only if:
An incorrect password, for instance, is not considered to be an error; it will cause its Auth clause to fail but depending on the control directives that have been configured, the user may still be successfully authenticated by some other Auth clause. True errors are fatal and cause dacs_authenticate to terminate without issuing credentials and possibly without invoking a handler.
If a DACS identity reauthenticates, the user agent is expected to replace the old credentials with new ones; if re-authentication fails (e.g., the password is incorrect), the old credentials should continue to exist. If a user establishes multiple concurrent identities, the user agent is expected to send all credentials with each service request in accordance with the relevant standards. This is standard behaviour for most common web browsers.
As an efficiency measure, the authentication architecture allows an authentication module to return roles.
Names
Please refer to dacs(1)[14] for details about naming, identities, and roles.
Credentials and Cookies
DACS credentials are cryptographically protected XML documents (credentials.dtd[15]). They have been carefully designed to make it extremely difficult for an attacker to generate valid credentials, modify captured credentials to impersonate another user, or obtain greater access rights without being detected. DACS is careful to not produce log information or error messages that might benefit an attacker.
User agents and other software outside of DACS do not need to decrypt the credentials and do not possess the required encryption key.
New credentials are created and returned to the user after successful authentication. The lifetime of each set of credentials is independently configurable, but they are intended to be fairly transitory. If a user reauthenticates, new credentials different than previous credentials might well be returned (e.g., with different roles).
DACS does not verify that a user's browser is configured to accept cookies - this is the responsibility of the DACS administrator (by supplying client-side code to test that cookies have been enabled, for instance). Failure to accept cookies may cause some features to be unavailable or work incorrectly. Also note that despite what DACS (or any other program) tells a browser about the lifetime of an HTTP cookie, browsers may be configured to impose a shorter lifetime and can delete a cookie at any time.
Security
In some environments this constraint is a good idea, but in general it is of dubious value so enable it with care. For instance, where a user is behind a firewall or router that has multiple IP addresses, successive service requests might legitimately not appear to be coming from the same address and some requests would be denied if this constraint were enabled. In situations where credentials are being forwarded between web services they might be rejected. In the case of DHCP or dial-up Internet access, a user might be issued credentials, reboot, and then be assigned a different IP address; the user would be forced to reauthenticate. Also, more than one user may be associated with a particular IP address, as when a Network Address Translation (NAT) facility such as natd(8)[17] is used, so the check does not guarantee uniqueness.
All DACS jurisdictions within the same federation share an algorithm and key to encrypt and decrypt credentials. The cryptographically secure, symmetric encryption function Rijndael (the Advanced Encryption Standard[20] (AES) algorithm and Federal Information Processing Standard[21]) is currently used. The same 128 bit key is used by all DACS jurisdictions. AES also supports 192 and 256 bit key lengths and either can be configured at build-time.
A cryptographically secure message authentication code (MAC) is used to detect modification of credentials. A key different from the encryption key is used. The Keyed-Hash Message Authentication Code (HMAC, FIPS 198[22], RFC 2104[23], RFC 4635[24], RFC 4868[25]), is employed using the 160-bit NIST[26] secure hash standard, SHA-1 (FIPS 180-1[27], RFC 4634[28], RFC 6234[29]). In addition to SHA-1, SHA-224, SHA-256, SHA-384, and SHA-512 (FIPS 180-4[30]) can be used; they may be configured at build-time.
Security
DACS can be configured to use the less secure but widely-used and somewhat more efficient MD5 algorithm[31] instead, although it is deprecated and it will eventually be removed.
The AES key length and HMAC digest algorithm used by a federation can be changed at any time, perhaps forcing some users to reauthenticate, but the same key length and digest algorithm must be used throughout a federation.
The Netscape HTTP Cookies Specification[32] defines the syntax and semantics of the HTTP response header that a web server sends to a client; this syntax is used by default, but the COOKIE_SYNTAX[33] argument can be used to request a different syntax. The Netscape format is as follows:
Set-Cookie: NAME=VALUE; expires=DATE; path=PATH; domain=DOMAIN_NAME; secure
DACS formulates these response headers as follows.
The NAME attribute of an authentication cookie returned to the user (e.g., by dacs_authenticate) has the following default format:
DACS:federation-name::[jurisdiction-name]:[username]
where federation-name is the official name assigned to the federation for which the cookie is valid, jurisdiction-name is the name of the authenticating jurisdiction, and username is the authenticated name of the user. If the jurisdiction-name is omitted, the username must also be omitted. Semicolons, commas, and whitespace within the name must be URL-style encoded. Colons are not allowed in any of the name components. Here is an example of a cookie name:
DACS:EXAMPLE::METALOGIC:rick@example.com
DACS can also return HTTP cookies for other purposes. The NAME attribute of these cookies has the same format as an authentication cookie but is followed by a colon and a keyword; e.g., DACS:EXAMPLE:::SELECTED.
The default format of the NAME attribute can be overridden through the COOKIE_NAME_TERMINATORS[34] directive.
The VALUE attribute of a cookie is a printable text encoding of credentials.
Security
The value of the domain attribute associated with the cookie is dependent on the uniform domain name scheme chosen for the jurisdictions. The value will be configured to be the most specific tail string that tail matches all participating domain names. For example, if the uniform domain name scheme has hostnames of the form xxx.example.com, yyy.example.com, and zzz.example.com, then the value of the attribute will be example.com. This will ensure that the user agent sends the cookie with any service request directed to a hostname ending in example.com.
Tip
The HTTP cookie specifications appear to say that a cookie having a domain attribute of example.com should not be sent to a host of the same name, yet both Mozilla and IE (and perhaps other browsers) do just that. Without this behaviour, it would not be possible to use a single domain name with multiple DACS jurisdictions below it; that is, given domain=example.com, it is expected that jurisdictions can be identified by URI path prefixes such as example.com/metalogic, example.com/test, and so on.
When operating securely (see the SECURE_MODE[37] directive in dacs.conf(5)[2]) or when an authentication request is sent over SSL/TLS, the secure attribute will be present so that the cookie will only be transmitted if the communications channel with the host is a secure one. At present, browsers define this to mean that secure cookies will only be sent to HTTPS (HTTP over SSL/TLS) servers.
Web Service Arguments¶
In addition to the standard CGI arguments[38], dacs_authenticate understands the following CGI arguments. Some arguments are optional, while others are required depending on the authentication configuration. An invalid argument value will usually cause authentication to fail immediately. Unrecognized arguments are ignored.
AUTH_ID
AUTH_PROMPT_VAR_PREFIX
AUTH_TRANSID
AUTHORIZATION
AUXILIARY
COOKIE_SYNTAX
Note
RFC 2109[40], RFC 2965[41], and RFC 6265[42] forbid the following characters from appearing within an HTTP cookie's NAME attribute:
( ) < > @ , ; : \ " / [ ] ? = { }
Additionally, the space, tab, and all US-ASCII control characters (octets 0 - 31) and DEL (127) are disallowed (refer to the definition of a token in RFC 2616[43], S2.2). By default, DACS currently follows the original Netscape spec syntax in this respect and produces cookies that are invalid according to RFC 2109, RFC 2965, and RFC 6265 because colons are used within cookie names[44]. While this limitation does not appear to cause problems for web browsers in practice, it may be noteworthy for users of some cookie handling APIs. When necessary, the cookie name format can be customized using the COOKIE_NAME_TERMINATORS[34] directive.
DACS_AUTH_SUCCESS_HANDLER
DACS_BROWSER
DACS_DEBUG
ENABLE_AUTH_HANDLERS
OPERATION
PASSWORD
USERNAME
WWW_AUTHENTICATE
Auth Clause Directives¶
Each Auth clause in a DACS configuration file contains directives that describe a procedure for authenticating users. Some of these directives are common to all authentication modules, while others are understood only by a certain module; for example, LDAP_USERNAME_URL[48] is only meaningful to the local_ldap_authenticate[49] module. The general-purpose OPTION[50] directive may sometimes be used to specify an argument to an authentication module.
Important
The order in which the Auth clauses appear is significant. See the CONTROL[11] directive.
Every Auth element must have an id attribute. Its value is merely a label (an alphabetic followed by zero or more alphanumerics, hyphens, and underscores) that allows the clause to be referenced. Each id attribute value must be unique (case-sensitively) within the Jurisdiction section that contains it.
The following configuration directives are recognized by dacs_authenticate within any Auth clause (see dacs.conf(5)[51] for general information about directives).
Auth Clause Common Directives Index:
CONTROL (Required1)
The first Auth clause that appears after configuration merging (see dacs.conf(5)[54]) is the "top" or first module in the stack, the next one is the second module in the stack, and so on.
The value of this directive is a case-insensitive keyword that can be abbreviated up to the indicated minimum:
For example, the keywords require and required are equivalent.
The control flow of authentication module processing is as follows:
If the AUTH_ID argument is not given, then all Auth clauses with the user_sufficient control are disabled - none of their directives are evaluated - and any sufficient controlled clauses are processed normally. If the AUTH_ID is present, then only an Auth clause with a user_sufficient control and an exactly matching id attribute is used. There can be at most one such Auth clause; all other Auth clauses having a user_sufficient or sufficient control is disabled. In all other respects, an enabled user_sufficient Auth clause is processed as for the sufficient control;
CREDENTIALS_LIFETIME_SECS (Optional1)
EXIT* (Optional1)
EXPR (Optional1)
FLAGS (Optional1)
The only value currently recognized is the keyword ident.
Important
If there is more than one Auth clause, the ident flag should ordinarily be specified in at least one of them to indicate that the username returned by the module, if authentication is successful, is to become the "current" username. Those Auth clauses without the ident flag will not change the current username. After the last Auth clause is processed, the current username is used in the resulting credentials.
The ${Auth::CURRENT_USERNAME} variable (see below) is updated only if there is exactly one Auth clause or if the ident flag is given. This update occurs immediately prior to execution of any EXIT* directive.
If ident is not specified in any successfully processed Auth clause (i.e., one where authentication succeeds), the username returned by the last successfully processed clause is used. If the ident flag is specified in one or more successfully processed clauses, the username returned by the last such module will be used.
INIT* (Optional1)
OPTION (Optional)
For example, this directive causes SAMBA_PORT=139 to be passed as a POST method parameter:
OPTION "SAMBA_PORT=139"
OPTION* (Optional)
PASSWORD_AUDIT (Optional)
The directive value can be a variable name, which is matched exactly against the PASSWORD or AUXILIARY arguments, or a keyword in one of the OPTION directives within the same clause. In this form, the PASSWORD_CONSTRAINTS directive must be configured and its value is used as the constraint. In the second form, the directive value is a variable name as in the first form, followed by spaces or tabs, followed by the constraint string to use in the syntax of PASSWORD_CONSTRAINTS. Consider the following directives:
PASSWORD_CONSTRAINTS "8L,1C,1P" <Auth id="auth1">
URL "https://foo.example.com/cgi-bin/dacs/local_woof_authenticate"
STYLE "pass"
CONTROL "sufficient"
PASSWORD_AUDIT "PASSWORD 10L"
PASSWORD_AUDIT "AUXILIARY" </Auth>
Here, the PASSWORD argument must be at least ten characters long but AUXILIARY must only be eight characters long and include an upper case character and punctuation.
Note
Not all authentication modules require a PASSWORD argument, such as local_cas_authenticate[58] in its interactive mode. This directive is ignored if the argument is not passed to the module.
PREDICATE (Optional1)
This directive provides a way to effectively enable or disable a module based on run time context. This can be used to configure layered authentication or risk-based authentication because a predicate can examine various aspects of an authentication request, such as the USERNAME, current date and time, IP address from where the request originates, and so on.
STYLE (Required1)
cas
cert[ificate]
digest
expr
infocard
managed_infocard
nat[ive]
pass[word]
passwd
prompt[ed]
selfissued_infocard
simple
tgma
This style is implemented by the local_tgma_authenticate[68] authentication module.
set_roles
add_roles
URL (Optional1)
URL* (Optional1)
The difference between the two directives is that the value of URL* is an expression that is evaluated immediately before the module is invoked to determine the URL to be used.
In the current implementation, the standard set of modules must run within the context of a DACS jurisdiction. This is not an architectural limitation, however.
Tip
Some authentication modules are available as built-in components of dacs_authenticate and dacsauth. These modules are identified by specific relative URLs. A module's description will provide its built-in name when this capability is available. The built-in capability will automatically be provided if the module has been enabled at build-time.
Although it will be more efficient (and possibly more secure) to use a built-in module, they are executed on the same host as dacs_authenticate thereby giving up some flexibility because access control rules are not applied to them (other than the one for dacs_authenticate), and dacs_authenticate may need to be executed setuid root or setgid www so that it can access password files. When an external module is used, it is subject to normal DACS access control rules. In contrast to a built-in module, the additional level of indirection makes it simple to substitute a custom version of an external module. The same comments apply to dacsauth.
Here is an example of a configuration that will authenticate using Unix user names and passwords:
<Auth id="passwd">
URL "https://foo.example.com:8443/cgi-bin/dacs/local_unix_authenticate"
STYLE "pass"
CONTROL "sufficient" </Auth>
In the following example, dacs_authenticate will first try to authenticate using a Unix login name and password; if that fails, it will then try a DACS account name and password.
<Auth id="passwd">
URL "https://foo.example.com:8443/cgi-bin/dacs/local_unix_authenticate"
STYLE "pass"
CONTROL "sufficient" </Auth> <Auth id="passwd2">
URL "https://foo2.example.com/cgi-bin/dacs/local_passwd_authenticate"
STYLE "pass"
CONTROL "sufficient" </Auth>
The preceding example can be changed to try authenticating using a DACS account name and password if and only if the AUXILIARY argument has the value "guest" (which might have been provided when the user selected a button on a login form):
<Auth id="passwd">
URL "https://foo.example.com:8443/cgi-bin/dacs/local_unix_authenticate"
STYLE "pass"
CONTROL "sufficient"
PREDICATE '${Args::AUXILIARY} ne "guest"' </Auth> <Auth id="passwd2">
URL "https://foo2.example.com/cgi-bin/dacs/local_passwd_authenticate"
STYLE "pass"
CONTROL "sufficient"
PREDICATE '${Args::AUXILIARY} eq "guest"' </Auth>
In this example, a jurisdiction offers users a choice from among three authentication methods: a Google(TM) account, a Windows NTLM account, or a DACS password-based account. The jurisdiction's login form would be written to provide the appropriate AUTH_ID argument for the corresponding method;
# For AUTH_ID=google <Auth id="google">
URL "local_http_authenticate"
STYLE "password"
CONTROL "user_sufficient"
OPTION 'AUTH_URL="https://www.google.com/accounts/ClientLogin"'
OPTION 'AUTH_METHOD=POST'
OPTION 'USERNAME_PARAMETER="Email"'
OPTION 'PASSWORD_PARAMETER="Passwd"'
OPTION 'service=xapi'
OPTION "source=DSS-DACS-1.4" </Auth> # For AUTH_ID=ntlm <Auth id="ntlm">
URL "local__ntlm_authenticate"
STYLE "password"
CONTROL "user_sufficient"
OPTION 'SAMBA_SERVER="samba.example.com"'
OPTION 'SAMBA_PORT="139"'
EXIT* '${Auth::CURRENT_USERNAME}=strtr(${Auth::CURRENT_USERNAME}, "a-z", "A-Z")' </Auth> # For AUTH_ID=passwd <Auth id="passwd">
URL "local_passwd_authenticate"
STYLE "password"
CONTROL "user_sufficient" </Auth>
Initialization and the Auth Namespace¶
dacs_authenticate uses a variable namespace called Auth to make authentication-related context available to its configuration directives (see dacs.exprs(5)[71]). Aspects of dacs_authenticate's behaviour can be controlled by modifying these variables. This namespace disappears when dacs_authenticate terminates. The next section describes how these variables are used.
Additionally, all environment variables are accessible through the Env namespace (e.g., ${Env::REMOTE_ADDR}) during authentication processing.
Authentication Clause Control Flow¶
Auth clauses are processed in the order in which they appear in the configuration file, subject to the semantics of the CONTROL directives.
dacs_authenticate is typically configured so that the last thing it does is to redirect its caller to an appropriate web page. If authentication is successful, any AUTH_SUCCESS[72] expression is evaluated and the AUTH_SUCCESS_HANDLER[73] directive is consulted; if authentication fails, the AUTH_ERROR_HANDLER[74] and AUTH_FAIL_DELAY_SECS[75] directives are used. This behaviour is partially under the control of the caller through the DACS_AUTH_SUCCESS_HANDLER[76] and ENABLE_AUTH_HANDLERS[77] arguments, however.
Tip
To redirect the newly authenticated user to a web page based on the user's identity, jurisdiction, roles, or other contextual state, configure AUTH_SUCCESS_HANDLER to specify the URL of a DACS-wrapped CGI program. After examining environment variables automatically passed to it by DACS or its query arguments, this program can emit an appropriate redirect. To test this, configure:
AUTH_SUCCESS_HANDLER "url /cgi-bin/dacs/dacs_prenv"
(making sure that dacs_prenv(8)[78] has been installed) and examine the information that is available.
An Auth clause is processed in a sequence of steps, and with various hooks to provide fine-grained control. Only advanced DACS administrators usually need to be concerned with this level of detail.
Before the first clause is examined, the variable ${Auth::CURRENT_USERNAME} is set to the empty string; this variable is automatically updated by dacs_authenticate. The contents of the Args, DACS, Conf, and Env namespaces[71] are made available to all expressions evaluated during authentication module processing. Processing of each Auth clause is performed in the following sequence:
If the URL* directive is used instead, it is evaluated to obtain the URL to be invoked; if an error occurs, authentication terminates.
If the clause's STYLE is not expr, the authentication module is invoked.
The username passed to the module, or returned by the module, becomes the tentative DACS username and the variable ${Auth::CURRENT_USERNAME} is set to it. If the variable ${Auth::ROLES} is set to a valid role descriptor, it becomes the current tentative roles for the user.
EXIT* '${Auth::CURRENT_USERNAME}="bobo"'
completely ignores the username returned by the module and simply assigns one, while this directive:
EXIT* '${Auth::CURRENT_USERNAME} = \
strtr(${Auth::CURRENT_USERNAME}, "A-Z", "a-z")'
converts all upper case characters in the username returned by the module to their lower case equivalents.
The value of ${Auth::CURRENT_USERNAME} when the last module has been processed is the username that will be assigned to a successfully authenticated user. If set, the value of ${Auth::CREDENTIALS_LIFETIME_SECS} will be used as the lifetime of the generated credentials; if not set, the value returned by the last successful authentication module is used (typically that of the module's CREDENTIALS_LIFETIME_SECS directive), if available, or the jurisdiction's CREDENTIALS_LIFETIME_SECS directive's value.
Authenticating Using an Expression¶
Rather than using an authentication module, the expr style of authentication involves evaluating an expression. The value of the expression is the DACS username to associate with the user. If no value is returned, an invalid value is returned, or an error occurs, the Auth clause fails.
Here is a simple example that is unlikely to be used in practice. If the PASSWORD argument is "xyzzy", then authentication will succeed and the user will be assigned the DACS username bobo.
<Auth id="expr1">
STYLE "expr"
CONTROL "sufficient"
EXPR '${Args::PASSWORD} eq "xyzzy" ? "bobo" : ""' </Auth>
This example illustrates how an expression can be used to read a password (its hex-encoded SHA-256 hash, actually) from a file and compare it with the one provided in the service request. Each user has his own password file that consists of a single line of text containing the hash. If a username is given that does not have a corresponding password file, or if the hash of the provided password does not match the stored one, the Auth clause will fail, otherwise the given username is returned as the authenticated name.
<Auth id="expr5">
STYLE "expr"
EXPR '${pwd} = get("/usr/local/dacs/pwd/pwd." . ${Args::USERNAME}); \
digest(${Args::PASSWORD}, 0, sha256) eq decode(hex, ${pwd}) \
? ${Args::USERNAME} : ""'
CONTROL "sufficient"
</Auth>
The expression can also assign a valid role string to ${Auth::ROLES} to establish roles for the user (in conjunction with the add_roles[69] or set_roles[70] style modifier):
<Auth id="expr2">
STYLE "expr,add_roles"
CONTROL "sufficient"
EXPR '${Auth::ROLES}="foo,bar"; ${Args::PASSWORD} eq \
"xyzzy" ? "bobo" : ""' </Auth>
This style of authentication can be a useful alternative to the cert style with the local_cert_authenticate module. If the client has provided an X.509 certificate that has been adequately verified by the web server, then in many cases all that remains to be done is to assign a syntactically valid DACS username to the client. Environment variables[79] created by mod_ssl[80] can be referenced as ${Auth::ssl_variable_name}. Something such as the following might be suitable:
<Auth id="expr3">
STYLE "expr"
CONTROL "sufficient"
EXPR '${Auth::SSL_CLIENT_VERIFY} eq "SUCCESS" and
${Auth::SSL_CLIENT_S_DN_Email:ei} \
? ${Auth::SSL_CLIENT_S_DN_Email:i} : ""' </Auth>
Another application of this style of authentication is where it is the location of the user that is important rather than the user's identity per se. For example, if a system administrator needs to restrict access to a web server to the hosts in a lab or desktops in a group of offices (that presumably share a subnet) but does not require individual users to authenticate, a configuration like the following might be adequate:
<Auth id="expr4">
STYLE "expr"
CONTROL "sufficient"
EXPR '${Auth::CURRENT_USERNAME} = "user-${Env::REMOTE_ADDR}"' </Auth>
A user would not provide a username or a password; by simply clicking on a link that invokes dacs_authenticate, a user from the computer with IP address 10.0.0.213 (for example) would be assigned the identity user-10.0.0.213. Access control rules could be expressed in terms of those identities or the corresponding IP addresses.
Middleware Support¶
As with most DACS web services, the FORMAT argument can be used to request a particular type of output (see dacs.services(8)[81]) from dacs_authenticate. If any XML type is specified, the reply from dacs_authenticate will conform to the DTD dacs_auth_reply.dtd[82]. The reply indicates whether the user has been successfully authenticated or not. If authentication was successful, a description of the new credentials is returned as a dacs_current_credentials element, (as described by dacs_current_credentials.dtd[83]). If authentication was unsuccessful because of a transient error condition, a reason may optionally be provided.
Security
This reason is solely used to inform the user; it should not reveal any details that might compromise security.
Authentication modules return an auth_reply.dtd[84] document to dacs_authenticate.
Authentication Modules¶
Important
DACS provides a set of authentication modules. At the time DACS is compiled, some standard modules are enabled by default while others needed must be specifically enabled (see dacs.install(7)[85]). You should not enable authentication modules that you do not plan to use.
Security
Each authentication module is called with the following arguments. Authentication modules are always invoked using the POST method.
AUXILIARY
DACS_JURISDICTION
DACS_VERSION
PASSWORD
USERNAME
Directives
SSL/TLS environment variables
Transaction state data
Authentication Module Index:
local_apache_authenticate
The local_apache_authenticate module is used to authenticate against password files used by the Apache mod_authn_file[86], mod_auth_digest[87], or mod_authn_dbm[88] modules. These password files are managed by Apache's htpasswd(1)[89], htdigest(1)[90], and htdbm(1)[91] utilities, respectively. An administrator can configure DACS to use an existing htpasswd file, for instance, and so avoid dealing with creating and managing a duplicate set of usernames and passwords.
If HTTP Basic authentication (RFC 2617[60]) is used, the STYLE should be password. If Digest authentication is used, because no password is passed to DACS, the STYLE for this module should be configured as digest.
The following configuration options are recognized by this module. They should be provided using the OPTION directive.
AUTH_MODULE
AUTH_FILE
Note
This pathname is resolved on the host that runs this module. This should eventually be extended to accept a DACS virtual filestore URI.
DBM_TYPE
Notes
Here is an example configuration that uses an htpasswd-managed file for authentication:
HTTP_AUTH_ENABLE "yes" HTTP_AUTH "Basic \"DACS Basic Auth Area\" /restricted/*" <Auth id="apache-htpasswd"> URL "https://example.com/cgi-bin/dacs/local_apache_authenticate" STYLE "pass" CONTROL "sufficient" OPTION "AUTH_FILE=/usr/local/apache2/conf/passwords" OPTION "AUTH_MODULE=mod_auth" </Auth>
If the passwords were kept in a Berkeley DB database instead, the configuration might look like:
HTTP_AUTH_ENABLE "yes" HTTP_AUTH "Basic \"DACS Basic Auth Area\" /restricted/*" <Auth id="apache-htpasswd"> URL "https://example.com/cgi-bin/dacs/local_apache_authenticate" STYLE "pass" CONTROL "sufficient" OPTION "AUTH_FILE=/usr/local/apache2/conf/passwords.db" OPTION "AUTH_MODULE=mod_auth_dbm" OPTION "DBM_TYPE=db" </Auth>
This example configuration is similar; the difference is that the username and password obtained through HTTP Basic authentication are verified against a Unix account:
HTTP_AUTH_ENABLE "yes" HTTP_AUTH "Basic \"DACS Basic Auth Area\" /private/*" <Auth id="basic"> URL "https://example.com/cgi-bin/dacs/local_unix_authenticate" STYLE "pass" CONTROL "sufficient" </Auth>
This example configures HTTP Digest authentication and references an htdigest-managed file:
HTTP_AUTH_ENABLE "yes" HTTP_AUTH "Digest \"DACS Digest Auth Area\" /digest/*" <Auth id="apache-htdigest"> URL "apache" STYLE "digest" CONTROL "sufficient" OPTION "AUTH_FILE=/usr/local/apache2/conf/passwords.digest" OPTION "AUTH_MODULE=mod_auth_digest" </Auth>
Tip
A built-in version of this module can be selected by using the URL local_apache_authenticate or just apache.
local_cas_authenticate
This module coordinates with a specified Central Authentication Service (CAS)[93] server to authenticate a user that is purportedly known to that server. The module implements the client side of the CAS 2.0 Protocol[94] and can be used in two different modes: interactive and non-interactive.
Interactive mode is employed if neither a USERNAME nor a PASSWORD argument is given to dacs_authenticate. When dacs_authenticate is called, whether directly or as the result of redirection after access was denied to an unauthenticated user, it redirects the user to a CAS login page. After successful CAS authentication (which may return a ticket granting cookie to the user's browser), CAS redirects the user to dacs_authenticate, passing it the CAS session ticket as an argument called ticket. After successfully validating the session ticket at the CAS server, DACS authentication succeeds.
Security
When interactive mode is used, DACS does not see the username and password, only CAS does. The username is obtained by the module as part of the session ticket validation protocol. This mode of operation is similar to, but simpler than, the OpenID[95] Authentication protocol.
A variant of this flow of control can occur if the user has authenticated against the CAS server outside of DACS and therefore holds a ticket granting cookie. This cookie will automatically be sent by the user's browser when it is redirected to the CAS server; as a result, the CAS server may not prompt the user to authenticate.
In non-interactive mode, both a USERNAME and a PASSWORD argument are passed to dacs_authenticate. This module will use these arguments to authenticate the user against the CAS server. In this mode, no ticket granting cookie will be returned to the user. This mode can be used with the DACS HTTP authentication[4] feature.
The STYLE should be configured as cas for this module.
The following module-specific OPTION directive value is understood:
CAS_SERVER_URI (Required1)
<Auth id="CAS"> URL "cas" STYLE "cas" CONTROL "sufficient" OPTION "CAS_SERVER_URI=https://cas.example.com/castest" </Auth>
The module recognizes the following arguments (which are automatically passed to it as necessary by dacs_authenticate):
CAS_TICKET (Required1-C)
CAS_REDIRECT_ARGS (Optional1)
CAS_SERVER_URI (Required1-C)
Note
The local_cas_authenticate module extends the response of the validate service of the CAS protocol to allow a role descriptor string (role_string) to be returned. If authentication succeeds, the standard service returns the following text: yes\nusername\n
An invalid role string is discarded. If these roles should be used, it will be necessary to use either the set_roles[70] or add_roles[69] style modifier with the STYLE[96] directive.
Tip
The authentication procedure described by the CAS protocol is notable because the authentication material provided by the user in interactive mode does not flow through DACS; in particular, DACS does not see a user's password when this module is used. This may be an important consideration in some environments.
Because the protocol implemented by this module is general purpose and relatively simple, writing middleware that implements a subset of the server-side CAS protocol to interface with this module may be a sensible solution for DACS administrators who require a CAS-like control flow but do not want to use actual CAS server-side software. The user would be redirected to the middleware component by local_cas_authenticate to perform the /login service; then it would prompt and authenticate the user, and redirect the user to a URL provided to it by local_cas_authenticate; then local_cas_authenticate would call the middleware component directly, this time to perform the /validate service. The usual flow of control within DACS would follow.
A simple script for testing and working with local_cas_authenticate is available in src/cas_middleware_test.
Tip
A built-in version of this module can be selected by using the URL local_cas_authenticate or just cas.
local_cert_authenticate
The local_cert_authenticate module authenticates a user that supplies an acceptable X.509 client certificate via SSL/TLS. Apache must be appropriately configured to request and verify client certificates, check for revocation, and so on (see SSLVerifyClient[97] and related directives). As part of the SSL/TLS protocol, Apache's mod_ssl[80] module verifies that the client possesses the private key that corresponds to the client certificate. Apache will usually be configured to verify the correctness and suitability of the client certificate. Apache directives such as SSLRequire[98] might be used, for example.
The STYLE should be configured as certificate for this module.
The verification of the client certificate done by Apache may be sufficient, in which case the only remaining configuration task for the Auth clause is to assign a username and possibly extract role information from the certificate; it may impose additional tests on the certificate, however, by inspecting its fields. If verification beyond the ability of mod_ssl[80] is required, or if it needs to be performed on a system other than where the web server is running, local_cert_authenticate can execute an external program to decide whether the client certificate is suitable for authentication. This program is currently limited to OpenSSL[99] but this may be generalized in future versions.
To ensure that local_cert_authenticate is able to obtain information contained within the client certificate, Apache must be configured so that StdEnvVars and ExportCertData are enabled in an appropriate SSLOptions[100] directive, such as the following:
SSLOptions +StdEnvVars +ExportCertData
The following configuration directives are specific to this module:
CERT_CA_PATH (Required1)
CERT_DUMP_CLIENT (Optional1)
CERT_NAME_ATTR (Optional1)
To illustrate this, consider the following configuration:
VFS "[certmap]dacs-kwv-fs:/usr/local/dacs/federations/certnamemap" <Auth id="cert">
URL "https://example.com/cgi-bin/dacs/local_cert_authenticate"
STYLE "cert"
CONTROL "sufficient"
CERT_CA_PATH "/usr/local/apache2/conf/ssl.crt"
CERT_NAME_ATTR "SSL_CLIENT_S_DN_CN" </Auth>
with the file /usr/local/dacs/federations/certnamemap containing the two lines:
Clark Kent:superman Bruce Wayne:batman
Given the configuration above, if the value of the SSL_CLIENT_S_DN_CN environment variable is "Clark Kent", the username returned by the module will be "superman".
As with any module, an expression can be used within an Auth clause to modify or override the value returned by a module.
CERT_OPENSSL_PATH (Optional1)
Security
The lifetime of credentials obtained through the local authentication service may be independent of the validity period of the certificate presented for authentication. It is therefore possible for the certificate to expire before the DACS credentials. The local authentication service might take this into consideration before granting access and when computing a lifetime for the resulting DACS credentials.
local_grid_authenticate
This module works in concert with the dacsgrid(1)[101] utility to provide users with one-time passwords. It is also an approximation of the "something you have" factor of two-factor authentication.
The STYLE should be configured as password for this module.
Please refer to dacsgrid(1)[101] for a complete description.
In addition to the usual USERNAME argument, the module requires the PASSWORD argument to be the user's response to the challenge and the AUXILIARY argument to be the encoded challenge. The latter two arguments must be produced by dacsgrid(1)[101].
The following OPTION directive values are understood:
AUTH_GRID_CHALLENGE_SECS (Optional1)
AUTH_GRID_LIFETIME_SECS (Optional1)
Tip
A built-in version of this module can be selected by using the URL local_grid_authenticate or just grid.
local_http_authenticate
This module authenticates by invoking a given (non-interactive) web service with specified arguments. If the web service reports success by returning HTTP status code 200 (see RFC 2616[43], Section 10), then the module succeeds, otherwise it fails. No session is established with the web service and no additional requests are made to it.
In its simple (default) mode of operation, any output returned by the web service is discarded, including cookies. The web service is used solely to determine whether a username/password is correct. In its alternate mode, the web service can return a document that specifies a replacement username, lifetime of generated credentials, and a role string.
This module can be used to authenticate against any existing web service that follows the expected protocol, or provide a way to add a new, custom authentication method to DACS.
The STYLE should be configured as password for this module.
The following OPTION directive values are understood:
AUTH_URL (Required1)
AUTH_METHOD (Optional1)
PASSWORD_PARAMETER (Optional1)
USERNAME_PARAMETER (Optional1)
USE_AUTH_REPLY (Optional1)
Any other OPTION directive values are simply passed to the invoked web service, including any duplicate argument names.
For Google[102](TM) account authentication[103], for instance, the following configuration might be used:
<Auth id="google"> URL "local_http_authenticate" STYLE "password" CONTROL "required" OPTION 'AUTH_URL="https://www.google.com/accounts/ClientLogin"' OPTION 'USERNAME_PARAMETER=Email' OPTION 'PASSWORD_PARAMETER=Passwd' OPTION 'service=xapi' OPTION "source=DSS-DACS-1.4" </Auth>
This web service returns an HTTP status code of 200 if the correct username and password are given (i.e., login succeeded), and 403 if login fails. If ClientLogin fails and requests a CAPTCHA challenge the request will not be passed back to the user.
Note
One of the reasons for inclusion of this module is to support reuse of accounts widely used by the public. Google(TM) provides exactly the right interface needed by systems such as DACS. As of 20-April-2012, Google has officially deprecated ClientLogin. Accounts provided by eBay[104](TM)and Yahoo![105]®, for instance, do not appear to be directly usable in this way. In some cases, dacs_auth_transfer(8)[8] may be a better approach than this module.
The following outlines a trivial example of authentication using the USE_AUTH_REPLY directive. Assume that the following shell script can be invoked as http://example.com/cgi-bin/myauth:
#! /bin/sh /bin/cat <<HERE <?xml version="1.0" encoding="US-ASCII"?> <!DOCTYPE auth_reply SYSTEM "http://example.com/dacs/dtd-xsd/auth_reply.dtd"> <auth_reply> <ok username="guest"> <roles_reply> <ok roles="bigwheel,mediumwheel,littlewheel"/> </roles_reply> </ok> </auth_reply> HERE exit 0
Also assume the following Auth clause has been configured:
<Auth id="http"> URL "local_http_authenticate" STYLE "password,set_roles" CONTROL "required" OPTION 'AUTH_URL="http://example.com/cgi-bin/myauth"' OPTION 'AUTH_METHOD=GET' OPTION 'USE_AUTH_REPLY="YES"' </Auth>
Invoking this URL will always successfully authenticate any user and issue credentials for the identity JUR1:guest with roles bigwheel,mediumwheel,littlewheel:
This expression[3] is equivalent:
% dacsexpr -e 'dacsauth("-m http passwd,set_roles suff -OAUTH_URL=http://bsd9.dss.ca/cgi-bin/dacs/http_auth \
-OAUTH_METHOD=GET -OUSE_AUTH_REPLY=yes -u test -p test")'
{"result",1,"identity","DSS::BSD9:guest","roles","bigwheel,mediumwheel,littlewheel"}
Tip
A built-in version of this module can be selected by using the URL local_http_authenticate or just http.
local_infocard_authenticate
Deprecated
In early 2011, Microsoft announced[106] that it would not support CardSpace[107] (aka, Infocards and Information Cards) starting with Windows 8[108]. CardSpace has been the most widely available identity selector for using Information Cards.
The implementation of Infocards support within DACS remains in the code base and is documented, but is no longer being actively tested and maintained (neither are the demos). Support for Information Cards within DACS will likely be removed eventually. You may notice that other Infocard and CardSpace related projects have been terminated and their web pages are out of date or no longer available.
References: On the Demise of CardSpace[109]; Open Cardspace opportunity[110]; Personal Reflections on the CardSpace Journey[111]; From CardSpace to Verified Claims[112]; Change will come: the present is untenable[113]; The Clay Feet of Giants?[114]; RIP, Windows CardSpace. Hello, U-Prove[115]; and U-Prove[116].
The local_infocard_authenticate module performs DACS authentication using an Information Card[62] (InfoCard) previously registered at the jurisdiction. Self-issued InfoCards are registered using dacs_infocard(8)[64] or dacsinfocard(1)[63]. Managed InfoCards are also supported, provided they have been registered using dacs_managed_infocard(8)[65] and include a dacs_identity claim in the DACS namespace. DACS aims to conform to Identity Selector Interoperability Profile (ISIP) 1.5[117].
A DACS role descriptor string[118] can be associated with a managed InfoCard through the dacs_roles claim name in the DACS namespace (see dacs_infocard(8)[119]. These roles can be associated with new credentials via the add_roles[69] and set_roles[70] modifiers.
Security
At present, to be valid for authentication, the dacs_identity claim value must specify a user at the current jurisdiction; that is, it cannot specify an identity at a jurisdiction other than the one where authentication is being performed.
The authentication style infocard causes the module to accept either type of InfoCard - the type of InfoCard actually used will be available in the resulting credentials. The styles managed_infocard and selfissued_infocard tell the module to limit authentication to managed InfoCards or self-issued InfoCards, respectively. When invoked as a web service, local_infocard_authenticate understands an optional argument, TYPE, that may have the value "selfissued" or "managed" to restrict authentication to the corresponding InfoCard type; the default behaviour accepts either type of InfoCard.
Tip
The expression-based authentication style[120], which does not call this module, provides an alternative way to support InfoCard-based authentication. It is somewhat more complicated to use, however, and may require a small amount of programming.
For additional information about InfoCards, please refer to:
Tip
A built-in version of this module can be selected by using the URL local_infocard_authenticate or just infocard.
local_ldap_authenticate
The local_ldap_authenticate module performs DACS authentication using the Lightweight Directory Access Protocol, also known as LDAP, (see RFC 2251[128], RFC 2252[129], RFC 2253[130], RFC 3377[131], and many others). This form of authentication can be used with Microsoft's Active Directory (ADS)[132]. OpenLDAP[133] is used to supply LDAP client support.
The STYLE should be configured as password for this module.
In general, authentication using LDAP is challenging because an LDAP name (a distinguished name, or DN) is typically long and often has a site-specific structure. For this reason, this module often requires more local expertise for configuring and testing than other DACS authentication modules. At least a basic familiarity with LDAP will be required to configure this module.
The module implements two different approaches to authentication:
Regardless of the approach, after successful authentication it may be necessary to map the USERNAME or the DN into a valid DACS username.
The following configuration directives are specific to this module:
LDAP_ADMIN_PASSWORD (Optional1)
LDAP_ADMIN_URL (Required1-C)
LDAP_ADMIN_URL
"ldap://example.com/cn=Administrator, cn=Users, dc=example, dc=com"
LDAP_BIND_METHOD (Required1-C)
LDAP_ROLES_SELECTOR* (Optional)
An example:
LDAP_ROLES_SELECTOR* '"${LDAP::attrname}" eq "memberOf" \
? strtr(ldap(rdn_attrvalue, \
ldap(dn_index, "${LDAP::attrvalue}", 1)), " ", "_") \
: ""'
For each instance of the entry's memberOf attribute, this expression selects the least significant (left-most) component of the attribute value (a DN) using ldap()[134] and converts spaces to underscores. If the user's entry contains:
memberOf: CN=Domain Guests,CN=Users,DC=example,DC=com memberOf: CN=Guests,CN=Builtin,DC=example,DC=com
the resulting roles would be Domain_Guests and Guests.
Note
These roles are discarded unless the STYLE[96] directive for this module allows the roles to be incorporated into the user's credentials.
LDAP_SEARCH_FILTER (Required1-C)
LDAP_SEARCH_FILTER* (Required1-C)
LDAP_SEARCH_FILTER* '"(sAMAccountName=${Args::USERNAME})"'
LDAP_SEARCH_ROOT_DN (Required1-C)
LDAP_TIMEOUT_SECS (Optional1)
LDAP_USERNAME_EXPR* (Optional1)
LDAP_USERNAME_EXPR* '"${LDAP::sAMAccountName}"'
LDAP_USERNAME_URL (Optional1)
LDAP_USERNAME_URL
'"ldap://example.com/cn=Auggie%20Doggie, cn=Users, dc=example, dc=com"'
Security
The ldaps scheme is not implemented. Communication between this module and the LDAP server should use a secure channel or at least not be snoopable.
LDAP_USERNAME_URL* (Optional1)
LDAP_USERNAME_URL*
'"ldap://example.com/cn=${Args::USERNAME}, cn=Users, dc=example, dc=com"'
Tip
Before using LDAP authentication with DACS, you should first make sure that your LDAP server is functioning as you expect and that the host that will run the local_ldap_authenticate module can communicate with the LDAP server.
One way to do this is to use the ldapsearch(1)[138] command (found in the clients/tools directory of the OpenLDAP distribution) to bind to the directory and perform some searches. You should run this command on the same machine that will be running DACS's LDAP authentication module (local_ldap_authenticate). Some of the information that you obtain from this exercise may be helpful when you configure DACS to use this form of authentication.
Here are some examples to try - you must adapt the names for your environment:
% ./ldapsearch -h win2k.example.com -x -b "dc=example,dc=com" \
-D "CN=Administrator,CN=Users,DC=example,DC=com" -W -LLL % ./ldapsearch -h win2k.example.com -x -b "dc=example,dc=com" \
-D "CN=Auggie Doggie,CN=Users,DC=example,DC=com" -W -LLL % ./ldapsearch -h win2k.example.com -x -b "dc=example,dc=com" \
-D "CN=Administrator,CN=Users,DC=example,DC=com" -W -LLL \
"(cn=Administrator)" memberOf % ./ldapsearch -h win2k.example.com -x -b "dc=example,dc=com" \
-D "CN=Administrator,CN=Users,DC=example,DC=com" -W -LLL \
"(sAMAccountName=auggie)"
In these examples, the LDAP server runs on a host named win2k.example.com (so change win2k.example.com, example, and com), and it expects a user named "Auggie Doggie" to exist and have the account name "auggie" (again, change to names that exist in your LDAP directory). You should be prompted for the LDAP password (in Windows, that will be the login password) for either Administrator or a user named "Auggie Doggie", depending on the argument that follows the -D flag.
The following configuration illustrates authentication using this module:
<Auth id="ldap">
URL "https://example.com/cgi-bin/dacs/local_ldap_authenticate"
STYLE "password,add_roles"
CONTROL "required"
LDAP_BIND_METHOD "direct"
LDAP_USERNAME_URL* '"ldap://windows.example.com/cn=" \
. encode(url, ${Args::USERNAME}) . ",cn=Users,dc=example,dc=com"'
LDAP_USERNAME_EXPR* '"${LDAP::sAMAccountName}"'
LDAP_ROLES_SELECTOR* '"${LDAP::attrname}" eq "memberOf" \
? strtr(ldap(rdn_attrvalue, \
ldap(dn_index, "${LDAP::attrvalue}", 1)), " ", "_") \
: 0' </Auth>
Here, the LDAP authentication module will construct a DN by plugging the user-provided USERNAME argument into the template and binding to that DN with the PASSWORD argument. If successful, the DACS username will be the value of the user's entry's sAMAccountName attribute, and roles will extracted from the entry's memberOf attribute values, as described above.
Note
In Windows, the SAM-Account-Name Active Directory attribute value (sAMAccountName) need not be the same as the entry's Common Name; for instance, the former might be "doggie" and the latter "CN=Auggie Doggie". The sAMAccountName must not exceed 20 characters in length and must be unique within the domain. It is composed of printable characters other than the following:
\ / [ ] : ; | = , + * ? < > @ "
The userPrincipalName attribute value is a user account name (or "user login name") that is unique within its domain and a domain name identifying the domain in which the user account is located. The format is the same as a domain-name based email address; e.g., doggie@example.com.
local_native_authenticate
The local_native_authenticate module transfers a user's current, context-dependent web server identity to a DACS identity. The web server will most likely have used HTTP Basic or Digest authentication (RFC 2617[60]). The user, having already been authenticated by the web server at a particular jurisdiction, will automatically be given DACS credentials associated with that jurisdiction and typically having the same username.
The STYLE should be configured as native for this module.
This method of authentication also depends on a CGI helper program (autologin(8)[139]) and appropriate configuration of Apache authentication. The general idea is that the helper program must be executable only by users that have been properly authenticated by the web server (by any Apache method and using any Apache authentication module). The helper program then invokes dacs_authenticate with appropriate arguments; if this module has been enabled and accepts its arguments, the user will be given DACS credentials.
There are no directives or options specific to this module.
local_ntlm_authenticate
The local_ntlm_authenticate module authenticates users through Windows NT LAN Manager using the NTLM protocol [1[140], 2[141]]. This module, which makes use of Samba[142] libraries, provides Windows NTLM authentication[143] based on a username and password. The module does not need to be (and will not usually be) executed on the host running Windows.
For details, please refer to NTLM user authentication in Windows[144].
The STYLE should be configured as password for this module.
The following OPTION directive values are understood:
SAMBA_SERVER (Required1)
SAMBA_PORT (Optional1)
SAMBA_DOMAIN (Optional1)
The module-specific option SAMBA_SERVER must be given to provide the domain name of the host providing the NTLM authentication. The module-specific options SAMBA_DOMAIN and SAMBA_PORT, which are optional, can be used to override the default port(s) used by Samba to contact SAMBA_SERVER.
The following illustrates how this module might be configured:
<Auth id="ntlm">
URL "https://example.com/cgi-bin/dacs/local_ntlm_authenticate"
STYLE "pass"
CONTROL "sufficient"
OPTION 'SAMBA_SERVER="10.0.0.123"'
OPTION 'SAMBA_PORT="139"' </Auth>
Here, dacs_authenticate will invoke the NTLM authentication module at the given URL. That module will try to authenticate the username and password given to it by asking the NTLM service at port 139 on the Windows system at 10.0.0.213.
There are no directives specific to this module.
Security
Attacks against some versions of NTLM have been identified[145]. Communication between this module and the NTLM service should use a secure channel or at least not be snoopable.
Tip
To test whether it is possible to authenticate using a particular username and password, you may be able to use smbclient(1)[146]. For example, if C:\Shared is a network shared folder or HPLaserJ-PS is a shared printer on the Windows machine on which you want to perform authentication, to authenticate as the Administrator try something like:
% smbclient //mywinhost/shared -U Administrator
or to authenticate as the user bob, try:
% smbclient //mywinhost/HPLaserJ-PS -U bob
or to try a more generic "Sharename", try:
% smbclient //mywinhost/NETLOGON -U bob
or to list available services ("Sharenames"), try:
% smbclient -L mywinhost -U bob
In each of these examples, replace mywinhost with the domain name of your Windows server. You should be prompted for the account's password. If smbclient successfully connects and establishes a session using the username and password you provide, then this module should also be able to authenticate that user, otherwise you should see an error message (type exit to leave smbclient).
If smbutil with the identity option happens to be available, try a non-interactive command like:
% smbutil identity //bob:bobspassword@mywinhost
Before you have configured DACS, you can test NTLM authentication from the command line using dacsauth(1)[6]. For example, try something like:
% dacsauth -m ntlm passwd suff -OSAMBA_SERVER="windows.example.com" -prompt -u bob
Change "bob" to the username you want to authenticate and "windows.example.com" to the domain name of the Windows machine where the user's account is. You may also need to specify SAMBA_PORT if a non-standard port is being used. You will be prompted for the password for the user's account The program's exit status indicates success ("ok" is exit status 0) or failure (exit status 1). Repeat this with an invalid password to make sure that it fails.
After you have configured DACS, there is another method of testing local_ntlm_authenticate from the command line. Set the environment variable QUERY_STRING (using your preferred shell's syntax) to something like this:
% export QUERY_STRING="USERNAME=bob&PASSWORD=test&DACS_JURISDICTION=Test\ &SAMBA_SERVER=windows.example.com"
Change "bob" to the username you want to authenticate, "test" to the password for that username, "Test" to the name of the DACS jurisdiction that will perform the authentication, and "windows.example.com" to the domain name of the Windows machine where the user's account is. You may also need to specify SAMBA_PORT. Then from the distribution's src directory:
% ./local_ntlm_auth -uj Test
Use the -u, -uj, or -us flag to specify a jurisdiction that you have configured (see dacs(1)[147]). The output, an XML document, indicates success ("ok", exit status 0) or failure ("failed", exit status 1). Repeat this with an invalid password to make sure that it fails. When you are done, remember to delete the QUERY_STRING environment variable.
local_pam_authenticate
This module makes a local or remote Pluggable Authentication Modules (PAM) infrastructure available for authentication. PAM authenticates a user that is known to the PAM-capable operating system (i.e., a user with an existing account) through one or more PAM authentication service modules that have been configured by the system administrator. Other PAM operations, such as password management, are currently unsupported by DACS. Please refer to X/Open Single Sign-On Service (XSSO) -- Pluggable Authentication[53] for additional information about PAM.
Notes
Although a prototype has been developed, no "native" PAM authentication module for DACS is distributed. Such a module might be used to provide Unix services with DACS authentication and access control functionality, conceptually allowing dacsauth(1)[6] or dacscheck(1)[148] to be used by them. For instance, configuration for ftp authentication that normally uses pam_unix.so might be replaced by a reference to the module, leveraging any password style of DACS authentication, such as local_ldap_authenticate[49].
There is a huge selection of open source and vendor-supplied PAM authentication modules for a wide variety of platforms, including some that provide functionality similar to that of DACS authentication modules [GNU/Linux[150], FreeBSD[151], macOS[152]]. For example, pam_unix(8)[153] performs essentially the same authentication function as local_unix_authenticate[154], except that the latter is not interactive (it does not prompt).
The STYLE should be configured as prompted for this module.
Note
While this authentication module has been tested with only a few PAM authentication service modules, in theory it should work with any conformant PAM authentication module. If this module is used, the current implementation does not allow any other authentication modules to be configured for the jurisdiction; this can be partially ameliorated by configuring PAM to try multiple PAM modules (yes, writing "PAM modules" might be incorrect in the same way that "ATM[155] machine" is).
Important
The local_pam_authenticate module depends on functionality provided by pamd(8)[156] running on a PAM-capable system, which does not need to be the same host where local_pam_authenticate is run. The local_pam_authenticate module establishes connections with pamd, which interacts with the pam(3)[52] library. Unlike the other DACS authentication styles, authentication using the prompted style may involve more than one request to dacs_authenticate, each of which supplies additional authentication material.
The prompted authentication style implements a session between the user and the PAM library that consists of a sequence of operations that comprise a PAM transaction. For each operation, dacs_authenticate (via local_pam_authenticate and pamd) supplies the PAM library with authentication material (either initial data or data requested by the PAM library from the previous operation), determines if authentication has succeeded or failed, or whether the user must be prompted for additional data. If the PAM library requires additional data, the user is prompted for it, and the response is submitted to dacs_authenticate in the transaction's next operation.
If PAM requires information from the user, local_pam_authenticate can be configured to prompt for it using one of three methods. The first method is used if the Auth clause has an OPTION directive that configures PAM_HANDLER_URL; the user will be redirected to this URL. The other possibilities are selected by the FORMAT argument (see dacs.services(8)[81]). If any XML type is specified, the reply from dacs_authenticate will conform to the DTD dacs_auth_reply.dtd[82]. If HTML is specified and PAM authentication requires additional information from the user, dacs_authenticate will return a rudimentary HTML form that must be completed and submitted by the user. For example, if pam_unix is configured, dacs_authenticate may emit a web page that prompts for a username (if none was provided with the initial invocation of dacs_authenticate), and after that form has been submitted by the user emit a web page that prompts for a password.
If PAM_HANDLER_URL is configured, the handler to which the administrator redirects users has complete control over user prompting. In most implementations, the handler will emit a web page that includes a form element, with appropriate inputs and hidden variables, which is submitted to the web service named in the service argument (see below). The handler is required to obtain values for a set of requested variables and submit them to a given URL (dacs_authenticate). Each variable has a type, an optional descriptive text label, and a name. The value of PAM_HANDLER_URL may either be an absolute URL or a web service name, beginning with a '/', that is interpreted relative to the current jurisdiction (i.e., the dacs_url[157] is prepended). Query arguments may be included, provided none of the argument names used by dacs_authenticate, described below, are duplicated.
The pamd server requires the handler to respond within 60 seconds (configured at compile time). The local_pam_authenticate module requires pamd to respond to the initial request with the first prompt within 20 seconds (configured at compile time). Should the handler encounter a serious error, it can simply terminate; this will cause pamd to eventually time out, which will abort the PAM transaction.
Security
The handler does not have to be DACS-wrapped, but ideally it should be. If it is, don't forget to add an access control rule to grant access to any user that might authenticate through local_pam_authenticate.
This "prompter" service might be configured as follows:
OPTION "PAM_HANDLER_URL=/dacs_pam_handler"
This will be expanded into a URL that looks something like https://example.com/cgi-bin/dacs/dacs_pam_handler. When a user is redirected to this handler, dacs_authenticate adds the following query arguments:
Any other arguments to the handler should be forwarded to service verbatim. Such arguments include DACS_VERSION, DACS_JURISDICTION, DACS_BROWSER, and ENABLE_AUTH_HANDLERS.
Note
For testing purposes, it may be helpful to set PAM_HANDLER_URL to dacs_prenv, which will display the arguments passed to the handler and other context. The DACS distribution includes an example handler, html/handlers/dacs_pam_handler.
If an HTML form is emitted, its appearance can be customized somewhat through the default stylesheet local_pam_authenticate.css[158]. The content of the generated web page can be customized through the local_pam_authenticate VFS item type. The following items relative to that item type are emitted if they exist:
For example, consider the configuration directive:
VFS "[local_pam_authenticate]dacs-fs:${Conf::DACS_HOME}/pam_auth"
Here, pam_auth is the directory ${Conf::DACS_HOME}/pam_auth. If files named header and trailer exist in that directory, they are expected to contain the initial and final HTML content, respectively. These files consist of text and HTML markup but are not complete HTML documents.
Customization of the HTML form is possible using configuration variables:
For example, the submit button's text can be specified using the directive:
EVAL ${Conf::prompt_submit_label} = " Continue "
Tip
A built-in version of this module can be selected by using the URL local_pam_authenticate or just pam.
local_passwd_authenticate
The local_passwd_authenticate module provides support for DACS identities, strictly private to DACS, through password-protected accounts (similar to what Apache's mod_authn_file[86] and mod_authn_dbm[88] modules do, along with the htpasswd(1)[89] utility). A secure hash of a password is stored rather than the plaintext password itself. Several hashing methods are available (see PASSWORD_DIGEST[159]).
The local_passwd_authenticate module performs authentication by consulting the USERNAME and PASSWORD parameters and comparing them to the information previously stored by the administrator.
Security
This module always requires the PASSWORD argument and will not accept the empty string as a password value (even if that actually is the password). Use local_simple_authenticate[67] for password-less accounts.
The STYLE should be configured as password for this module.
The dacspasswd(1)[160] utility is used to manage these accounts. The item type is "passwds".
The following example configuration, which reflects typical usage, maintains user and password information in a plain text file named /usr/local/dacs/federations/passwd.
VFS "[passwds]dacs-kwv-fs:/usr/local/dacs/federations/passwd"
There are no directives or options specific to this module.
Note
The name "local_passwd_authenticate" may be a little confusing because there are other modules that implement some form of password-based authentication. This module might more appropriately be called "local_dacspasswd_authenticate".
Tip
A built-in version of this module can be selected by using the URL local_passwd_authenticate or just passwd.
local_radius_authenticate
The local_radius_authenticate module supports authentication using RADIUS (Remote Authentication Dial In User Service). The module, acting as a RADIUS client, contacts a RADIUS server to validate the USERNAME and PASSWORD parameters it is given. For details, refer to RFC 2865[161] (also RFC 2866[162], RFC 3162[163], RFC 3579[164], RFC 6929[165], and others).
The STYLE should be configured as password for this module.
The following OPTION directive values are understood:
RADIUS_SERVER (Required1)
RADIUS_PORT (Optional1)
RADIUS_SECRET (Required1)
RADIUS_OK_MSG (Optional1)
RADIUS_TIMEOUT (Optional1)
RADIUS_DEAD_TIME (Optional1)
RADIUS_MAX_TRIES (Optional1)
The following illustrates how this module might be configured:
<Auth id="radius">
URL "https://example.com/cgi-bin/dacs/local_radius_authenticate"
STYLE "passwd"
CONTROL "sufficient"
OPTION 'RADIUS_SERVER=10.0.0.123'
OPTION 'RADIUS_PORT=0'
OPTION 'RADIUS_SECRET=ASecretRadiusPassweird'
OPTION 'RADIUS_OK_MSG="OK DACS."'
OPTION 'RADIUS_TIMEOUT=2'
OPTION 'RADIUS_DEAD_TIME=4'
OPTION 'RADIUS_MAX_TRIES=3' </Auth>
With this configuration, dacs_authenticate will invoke the RADIUS authentication module at the given URL, which will try to authenticate the username and password given to it by asking the RADIUS server at the default port (1812) on the host at 10.0.0.123. The module authenticates itself to the RADIUS server using the password "ASecretRadiusPassweird". If authentication is successful, the module expects the RADIUS server to include the message "OK DACS." in its reply.
Notes
Tip
A built-in version of this module can be selected by using the URL local_radius_authenticate or just radius.
local_simple_authenticate
The local_simple_authenticate module supports DACS identities, strictly private to DACS, through accounts that are not password-protected. The local_simple_authenticate module performs authentication by looking up an account named by the USERNAME argument. In typical use, the username will be an email address, account or membership number, or random character string.
Security
This form of authentication is inherently insecure because no password is provided. It is only appropriate when the consequences of a valid account name being guessed or misappropriated are of little concern, such as for restricted guest accounts. Administrators should not assume that using difficult-to-guess account names with this module offers much security. Keep in mind that depending on the larger context of how these identities are used, these usernames may be publicly visible.
The STYLE should be configured as simple for this module.
The dacspasswd(1)[160] utility is used to manage these accounts. The item type is "simple".
The following example configuration, which reflects typical usage, maintains user account information in a plain text file named /usr/local/dacs/federations/simple_accounts.
VFS "[simple]dacs-kwv-fs:/usr/local/dacs/federations/simple_accounts"
Note
Although it is possible to combine password-protected accounts and password-less accounts in the same VFS object (i.e., with the item types passwds and simple pointing to the same file or database), putting them in separate objects is recommended.
There are no directives or options specific to this module.
Tip
A built-in version of this module can be selected by using the URL local_simple_authenticate or just simple.
local_tgma_authenticate
Experimental. The local_tgma_authenticate module, together with a TGMA server and client validator software, implements strong, interactive mutual authentication without the user having to input a password. The local_tgma_authenticate module supports DACS identities that are strictly private to DACS.
The user begins the authentication procedure by using a simple sign-on page to submit an identity (USERNAME and JURISDICTION). A password is not normally required. A special web-based utility returns a new web page to the user that displays instructions and another form that the user must submit when she is ready to complete the procedure. Next, and within a configurable window of time, the user must prove his ownership of the identity by executing a secure validation protocol. The validation protocol is conducted from a device, such as a smart phone or tablet, which runs the custom validator app and has been configured with account information for the user's identity at the jurisdiction.
This authentication module sends an authentication request message to a TGMA server. The TGMA server executes an authentication protocol with a user's validator and returns the result to the module. The TGMA server is a light-weight daemon that may serve one or more jurisdictions. The mutual authentication protocol, based on Secure Remote Password authentication (RFC 2945[170], RFC 5054[171]), verifies the user's identity using account information available to the module, TGMA server, and the validator. The user's validator confirms the identity of the TGMA server, and indirectly, the jurisdiction. Communication between the TGMA server and the module may use TCP, SSL, or UDP, depending on configuration. Likewise, communication between the TGMA server and a validator may also use TCP, SSL, or UDP. Choice of the networking protocol will depend on security, performance, and connectivity dependencies. An instance of the TGMA server must have network connectivity with both users' validator devices and instances of this authentication module. In a larger organization it will likely run on a firewall or DMZ-located server.
The STYLE should be configured as tgma for this module.
local_token_authenticate
This module works in concert with the dacstoken(1)[172] utility to support one-time passwords. Two-factor authentication, a strong authentication method, is supported by combining hardware token-based one-time passwords ("something you have") with a PIN (a password, "something you know"). Software-based clients may also be used. The implementation follows RFC 4226[173], which has been adopted by OATH[174], and other standards. Please refer to dacstoken(1)[172] for complete details.
The STYLE should be configured as password for this module.
In addition to the usual USERNAME argument, the module requires the PASSWORD argument to be the next one-time password (e.g., the value produced by the user's hardware token). If the user's DACS account has a PIN associated with it, the PIN must be passed as the AUXILIARY argument. The PIN referred to here is the one managed by dacstoken, not a PIN that may be entered into the token device to unlock it.
One-time password generation depends on a secret that is shared between the client and DACS, and a non-repeating value that may be based on synchronized counters or clocks. The client's token can become unsynchronized with the server's state. This can happen for many reasons, such as if a password is generated by the device but not used, if a password or PIN is typed incorrectly, or because of a configuration error. The method can tolerate a configurable deviation of the client's token from the server's state; that is, provided the client's password falls within a window of N from the one expected by DACS, DACS will accept the client's token. For counter-based tokens, only the "forward" side of the window is examined, so DACS can "catch up" to the client.
If the user's password does not fall within the window, it is deemed to have become unsynchronized with local_token_authenticate and authentication will fail. The user can attempt to resynchronize by entering a sequence of passwords as PASSWORD, using a comma to separate them. Three consecutive, valid passwords are required (this number can be configured at build time). If the account has a PIN, it must be provided to enable synchronization. If synchronization succeeds, the user's account information is corrected and the module also reports successful authentication. If synchronization fails, the module also fails and a DACS administrator must be contacted to resynchronize the token.
Note
The token value must be entered exactly as it is displayed on the token. Leading zeroes must be typed, for example, and no spaces or punctuation are allowed. Whenever authentication fails, the user must obtain a new password from the token.
The following OPTION directive value is understood:
ACCEPT_WINDOW (Optional1)
Tip
A built-in version of this module can be selected by using the URL local_token_authenticate or just token.
local_unix_authenticate
The local_unix_authenticate module implements native Unix username/password authentication, allowing a user having a pre-existing Unix account to be authenticated by DACS using the username and password for that account. Normally, the user's hashed password is compared to the string obtained by hashing the PASSWORD argument. But because some platforms do not make stored passwords available to applications (most notably macOS), a second algorithm can be used; if it is enabled and the pam(3)[175] library is available, a simple PAM policy is used to validate the plaintext password provided.
In the password comparison algorithm, the getpwnam(3)[176] library function is passed the USERNAME parameter given to dacs_authenticate. It can be configured for systems with or without shadow passwords. On some Unix systems, when the yp(8)[177] password database is enabled, the getpwnam(3)[176] function will use the YP map "passwd.byname" if the requested password entry is not found in the local database. If the account information is obtained, the PASSWORD parameter is validated.
In the PAM-based algorithm, the USERNAME and PASSWORD parameters given to dacs_authenticate are passed to the PAM module (e.g., pam_unix(8)[153]) that has been configured by an administrator. This method is separate and much simpler than what is provided by local_pam_authenticate[39]. To help protect against misconfiguration, any unexpected behaviour by PAM will cause authentication to fail. For example, the password prompt string produced by PAM must match "Password:", ignoring trailing spaces; currently, this default can only be changed at compile time.
The STYLE should be configured as password for this module.
The following OPTION directive values are understood:
PAM_SERVICE (Optional1)
auth required pam_unix.so no_warn
An existing policy file may be available or it may be necessary to create one. On macOS, for example, /etc/pam.d/chkpasswd contains the following entry, which is sufficient for password validation:
auth required pam_opendirectory.so
To use that file with this module, the following DACS configuration directive would be placed in the appropriate Auth clause:
OPTION "PAM_SERVICE=chkpasswd"
See pam_start(3)[149] and pam.conf(5)[178].
Depending on the operating system, PAM modules might be found in /usr/lib, /usr/lib/pam, or /lib/security.
It is possible to configure the PAM service policy to use a password-based "auth" facility other than the Unix password module, but do so with care.
USE_PAM (Optional1)
Tip
A built-in version of this module can be selected by using the URL local_unix_authenticate or just unix. If the built-in version is used, dacs_authenticate must be setuid root, and if the web-based version is used, local_unix_authenticate must be setuid root, so that the shadow password file can be read and/or the PAM module used. Authentication using this module will fail if it does not execute with sufficient priviledges.
Note
On platforms where encrypted passwords are unavailable, such as macOS, authentication will always fail unless the PAM-based algorithm is available and enabled.
Roles¶
Each user authenticated by DACS may be associated with one or more roles. The syntax of roles and role descriptors[14] is described elsewhere. Role-based group membership is discussed in dacs.groups(5)[179]. Configuration of a Roles clause is optional and if none are specified, an empty role descriptor string will be used. If more than one Roles clause is configured, their role strings are concatenated (duplicates are not removed). If a roles service fails, it is treated as if it returned no roles and processing continues normally.
Like authentication, a modular mechanism is used to find the roles with which a user is associated. A roles module, analogous to an authentication module, can be called by dacs_authenticate to return roles. A roles service returns a roles_reply element (see roles_reply.dtd[180]).
Each Roles element must have an id attribute. Its value is merely a label (an alphabetic followed by zero or more alphanumerics, hyphens, and underscores) that allows the clause to be referenced. The id attribute values must be unique (case-sensitively) within the clause's Jurisdiction section.
Note
A maximum limit is imposed on the length of a role descriptor string. Please refer to the ROLE_STRING_MAX_LENGTH[181] directive.
Roles Clause Directives¶
The roles directives are largely analogous to the authentication directives.
When evaluation of the Roles clauses begins, several variables are available in the Auth namespace to reflect the outcome of authentication. These variables may be useful when determining the user's roles: DACS_USERNAME, DACS_IDENTITY, DACS_JURISDICTION, and DACS_VERSION.
Roles Clause Directives Index:
URL (Optional1)
URL* (Optional1)
INIT* (Optional1)
EXIT* (Optional1)
EXPR (Optional1)
OPTION (Optional)
For example:
OPTION "PASSWORD=bobo"
causes PASSWORD=bobo to be passed as a POST method parameter.
OPTION* (Optional)
PREDICATE (Optional1)
Roles Clause Control Flow¶
If authentication succeeds, Roles clauses are processed in which they appear, but only if set_roles[70] has not been specified for some authentication module's STYLE.
A Roles clause is processed in a sequence of steps, and with various hooks to provide fine-grained control. Before the first clause is examined, the variables ${Auth::CURRENT_ROLES} and ${Auth::LAST_ROLES} are initialized to the role string, if any, obtained during authentication module processing. Processing of each Roles clause proceeds as follows:
The value of ${Auth::CURRENT_ROLES} when the last module has been processed is the roles string that will be used in the generated credentials.
Tip
Some roles modules are available as built-in components of dacs_authenticate. These modules are identified by specific relative URLs; a module's description will provide its built-in name when this capability is available. The built-in capability will automatically be provided if the module has been enabled at build-time. The same applies for dacsauth.
Although it will be more efficient (and possibly more secure) to use a built-in module, they are executed on the same host as dacs_authenticate (thereby giving up some flexibility), access control rules are not applied to them (other than the one for dacs_authenticate), and dacs_authenticate may need to be executed setuid (probably as root) or setgid (as www, for example) so that it can access password files.
Roles Modules¶
If and only if authentication succeeds, DACS can request the user's role descriptor from the jurisdiction. Roles modules are always invoked using the POST method and are passed the following arguments:
DACS_USERNAME
DACS_JURISDICTION
DACS_VERSION
OPTION directives
Roles modules return an roles_reply.dtd[180] document to dacs_authenticate.
Note
Although there is a roles module for obtaining LDAP or ADS roles, you may also get them by authenticating through local_ldap_authenticate[49] or by using a Roles clause with an appropriate EXPR directive.
Roles Module Index:
local_roles
This roles service consults a private list to obtain a username-to-roles mapping using DACS virtual storage (the item type is "roles"). The following example configuration, which reflects typical usage, maintains mappings in a plain text file named /usr/local/dacs/federations/roles.
VFS "[roles]dacs-kwv-fs:/usr/local/dacs/federations/roles"
The file /usr/local/dacs/federations/roles might look something like this:
admin:dacs,admin rick:metalogic,guests bobo:staff,users auggie:staff,users
Here, user auggie is associated with the roles staff and users.
Tip
A built-in version of this module can be selected by using the URL local_roles or just roles.
local_ldap_roles
This roles service returns roles derived from the attributes of a user's LDAP/ADS directory entry. This module is based on local_ldap_authenticate[49]; please consult the description and examples presented with that authentication module for additional information.
Note
The user need not have been authenticated by LDAP/ADS for this module to be used. For example, the user can be authenticated on a Unix system but his roles can come from LDAP/ADS.
The following configuration directives are recognized by this module. They function identically to the directives of the same name used by local_ldap_authenticate[49], so for the most part their descriptions will not be repeated here.
Note
These module directives must be passed using either OPTION[182] or OPTION*[183] directives. Ensure that the option value is properly quoted.
LDAP_BIND_METHOD (Required1-C)
LDAP_USERNAME_URL (Optional1)
LDAP_USERNAME_URL* (Optional1)
LDAP_ADMIN_URL (Required1-C)
LDAP_ADMIN_PASSWORD (Optional1)
LDAP_SEARCH_ROOT_DN (Required1-C)
LDAP_SEARCH_FILTER (Required1-C)
LDAP_SEARCH_FILTER* (Required1-C)
LDAP_USERNAME_EXPR* (Optional1)
LDAP_ROLES_SELECTOR* (Optional)
LDAP_TIMEOUT_SECS (Optional1)
Here is an example that binds to the directory on x.example.com as the administrator, searches for the entry for the account of the authenticated user, and assigns the user a role from the attribute value of each memberOf attribute in the entry:
<Roles id="ldap_roles"> URL "http://example.com/cgi-bin/dacs/local_ldap_roles" OPTION "LDAP_BIND_METHOD=indirect" OPTION \ 'LDAP_ADMIN_URL="ldap://x.example.com/CN=Administrator,CN=Users,DC=example,DC=com"' OPTION 'LDAP_ADMIN_PASSWORD="secretpassword"' OPTION 'LDAP_SEARCH_ROOT_DN="cn=Users,dc=example,dc=com"' OPTION 'LDAP_SEARCH_FILTER*=\'"(sAMAccountName=${Args::DACS_USERNAME})"\'' OPTION 'LDAP_ROLES_SELECTOR*=\'"${LDAP::attrname}" eq "memberOf" \
? strtr(ldap(rdn_attrvalue, \
ldap(dn_index, "${LDAP::attrvalue}", 1)), " ", "_") \
: ""\'' </Roles>
For example, the resulting role string might look like:
DnsAdmins,Print_Operators,Domain_Admins,Administrators
local_unix_roles
This roles service returns the Unix group membership associated with an authenticated username; that it, the resulting list of roles is the same as would be obtained if the user ran the Unix groups(1)[184].
Note
The user need not have been authenticated as this username on the Unix system where this service is run.
Tip
A built-in version of this module can be selected by using the URL local_unix_roles or just unix.
Related Services¶
The dacs_current_credentials(8)[35] web service displays elements of each set of credentials sent with the request. The dacs_signout(8)[185] service is typically called from a browser to cause one or more cookies (each representing a DACS identity) to be deleted. Cookies are automatically deleted when a browser terminates, but it is sometimes useful to explicitly logoff.
DIAGNOSTICS¶
The program exits 0 if everything was fine, 1 if an error occurred.
NOTES¶
A separate but similar mechanism called "affiliated DACS federations" supports cross-federation single sign-on; see dacs_auth_transfer(8)[8].
dacs_authenticate could be modified to temporarily disable an account after some number of unsuccessful login attempts over a certain time period. The flip side of such a feature is that it could be used in a denial of service attack. Rather than disabling an account, a designated administrator might receive an email notification or a console message might be logged.
It might be worthwhile to include a rule-based mechanism, called after the user has been identified but before credentials are returned, to decide whether authentication should be permitted. This might be used, for example, to restrict a particular user to login from a specified IP address or range of addresses, or limit the time of day at which login is allowed.
BUGS¶
It would be nice to provide assistance to programs that generate login pages. Composing modules should be easier, to make multi-factor authentication more accessible.
SEE ALSO¶
dacsauth(1)[6], dacscred(1)[186], dacscookie(1)[9], dacs.exprs(5)[3], dacs_autologin_ssl(8)[187], autologin(8)[139], dacs_auth_agent(8)[7], dacs_auth_transfer(8)[8], dacs_current_credentials(8)[35], dacs_select_credentials(8)[46], dacs_signout(8)[185], pamd(8)[156]
AUTHOR¶
Distributed Systems Software (www.dss.ca[188])
COPYING¶
Copyright © 2003-2018 Distributed Systems Software. See the LICENSE[189] file that accompanies the distribution for licensing information.
NOTES¶
- 1.
- dacsoptions
- 2.
- dacs.conf(5)
- 3.
- dacs.exprs(5)
- 4.
- HTTP Authentication
- 5.
- html/examples
- 6.
- dacsauth(1)
- 7.
- dacs_auth_agent(8)
- 8.
- dacs_auth_transfer(8)
- 9.
- dacscookie(1)
- 10.
- Auth clause
- 11.
- CONTROL
- 12.
- username
- 13.
- dacs.acls(5)
- 14.
- dacs(1)
- 15.
- credentials.dtd
- 16.
- VERIFY_IP
- 17.
- natd(8)
- 18.
- VERIFY_UA
- 19.
- AUTH_CREDENTIALS_DEFAULT_LIFETIME_SECS
- 20.
- Advanced Encryption Standard
- 21.
- Federal Information Processing Standard
- 22.
- FIPS 198
- 23.
- RFC 2104
- 24.
- RFC 4635
- 25.
- RFC 4868
- 26.
- NIST
- 27.
- FIPS 180-1
- 28.
- RFC 4634
- 29.
- RFC 6234
- 30.
- FIPS 180-4
- 31.
- MD5 algorithm
- 32.
- Netscape HTTP Cookies Specification
- 33.
- COOKIE_SYNTAX
- 34.
- COOKIE_NAME_TERMINATORS
- 35.
- dacs_current_credentials(8)
- 36.
- COOKIE_PATH
- 37.
- SECURE_MODE
- 38.
- standard CGI arguments
- 39.
- local_pam_authenticate
- 40.
- RFC 2109
- 41.
- RFC 2965
- 42.
- RFC 6265
- 43.
- RFC 2616
- 44.
- colons are used within cookie names
- 45.
- dacs_acs(8)
- 46.
- dacs_select_credentials(8)
- 47.
- strtr()
- 48.
- LDAP_USERNAME_URL
- 49.
- local_ldap_authenticate
- 50.
- OPTION
- 51.
- dacs.conf(5)
- 52.
- pam(3)
- 53.
- X/Open Single Sign-On Service (XSSO) preliminary specification
- 54.
- dacs.conf(5)
- 55.
- Authenticating Using an Expression
- 56.
- PASSWORD_CONSTRAINTS
- 57.
- LOG_FILTER
- 58.
- local_cas_authenticate
- 59.
- Central Authentication Service (CAS)
- 60.
- RFC 2617
- 61.
- local_apache_authenticate
- 62.
- Information Card
- 63.
- dacsinfocard(1)
- 64.
- dacs_infocard(8)
- 65.
- dacs_managed_infocard(8)
- 66.
- local_infocard_authenticate
- 67.
- local_simple_authenticate
- 68.
- local_tgma_authenticate
- 69.
- add_roles
- 70.
- set_roles
- 71.
- dacs.exprs(5)
- 72.
- AUTH_SUCCESS
- 73.
- AUTH_SUCCESS_HANDLER
- 74.
- AUTH_ERROR_HANDLER
- 75.
- AUTH_FAIL_DELAY_SECS
- 76.
- DACS_AUTH_SUCCESS_HANDLER
- 77.
- ENABLE_AUTH_HANDLERS
- 78.
- dacs_prenv(8)
- 79.
- Environment variables
- 80.
- mod_ssl
- 81.
- dacs.services(8)
- 82.
- dacs_auth_reply.dtd
- 83.
- dacs_current_credentials.dtd
- 84.
- auth_reply.dtd
- 85.
- dacs.install(7)
- 86.
- mod_authn_file
- 87.
- mod_auth_digest
- 88.
- mod_authn_dbm
- 89.
- htpasswd(1)
- 90.
- htdigest(1)
- 91.
- htdbm(1)
- 92.
- local_native_authenticate
- 93.
- Central Authentication Service (CAS)
- 94.
- CAS 2.0 Protocol
- 95.
- OpenID
- 96.
- STYLE
- 97.
- SSLVerifyClient
- 98.
- SSLRequire
- 99.
- OpenSSL
- 00.
- SSLOptions
- 01.
- dacsgrid(1)
- 02.
- 03.
- account authentication
- 04.
- eBay
- 05.
- Yahoo!
- 06.
- announced
- 07.
- CardSpace
- 08.
- Windows 8
- 09.
- On the Demise of CardSpace
- 10.
- Open Cardspace opportunity
- 11.
- Personal Reflections on the CardSpace Journey
- 12.
- From CardSpace to Verified Claims
- 13.
- Change will come: the present is untenable
- 14.
- The Clay Feet of Giants?
- 15.
- RIP, Windows CardSpace. Hello, U-Prove
- 16.
- U-Prove
- 17.
- Identity Selector Interoperability Profile (ISIP) 1.5
- 18.
- role descriptor string
- 19.
- dacs_infocard(8)
- 20.
- expression-based authentication style
- 21.
- dacs_managed_infocard(8)
- 22.
- dacs.conf(5)
- 23.
- dacs_mex(8)
- 24.
- dacs_sts(8)
- 25.
- Using InfoCards With DACS
- 26.
- Identity Selector Interoperability Profile specification and companion guides
- 27.
- Introducing Windows CardSpace
- 28.
- RFC 2251
- 29.
- RFC 2252
- 30.
- RFC 2253
- 31.
- RFC 3377
- 32.
- Active Directory (ADS)
- 33.
- OpenLDAP
- 34.
- ldap()
- 35.
- LDAP_USERNAME_URL*
- 36.
- RFC 2396
- 37.
- RFC 3986
- 38.
- ldapsearch(1)
- 39.
- autologin(8)
- 40.
- 1
- 41.
- 2
- 42.
- Samba
- 43.
- NTLM authentication
- 44.
- NTLM user authentication in Windows
- 45.
- have been identified
- 46.
- smbclient(1)
- 47.
- dacs(1)
- 48.
- dacscheck(1)
- 49.
- pam_start(3)
- 50.
- GNU/Linux
- 51.
- FreeBSD
- 52.
- macOS
- 53.
- pam_unix(8)
- 54.
- local_unix_authenticate
- 55.
- ATM
- 56.
- pamd(8)
- 57.
- dacs_url
- 58.
- local_pam_authenticate.css
- 59.
- PASSWORD_DIGEST
- 60.
- dacspasswd(1)
- 61.
- RFC 2865
- 62.
- RFC 2866
- 63.
- RFC 3162
- 64.
- RFC 3579
- 65.
- RFC 6929
- 66.
- FreeRADIUS
- 67.
- radiusd(8)
- 68.
- RFC 6614
- 69.
- libradius(3)
- 70.
- RFC 2945
- 71.
- RFC 5054
- 72.
- dacstoken(1)
- 73.
- RFC 4226
- 74.
- OATH
- 75.
- pam(3)
- 76.
- getpwnam(3)
- 77.
- yp(8)
- 78.
- pam.conf(5)
- 79.
- dacs.groups(5)
- 80.
- roles_reply.dtd
- 81.
- ROLE_STRING_MAX_LENGTH
- 82.
- OPTION directive
- 83.
- OPTION* directive
- 84.
- groups(1)
- 85.
- dacs_signout(8)
- 86.
- dacscred(1)
- 87.
- dacs_autologin_ssl(8)
- 88.
- www.dss.ca
- 89.
- LICENSE
| 08/23/2020 | DACS 1.4.40 |