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STANFORD UNIVERSITY

INFORMATION TECHNOLOGY SERVICES

WebAuth 4.4.0 Announcement

The ITS WebAuth team is pleased to announce Stanford WebAuth 4.4.0. This is a major new feature release, particularly for the WebKDC and WebLogin components.

Users of WebAuth who build it against Heimdal for the underlying Kerberos library should be aware that a bug in encoding Kerberos ticket flags was fixed in this release in a way that may cause compatibility problems. As of WebAuth 4.4.0, Kerberos tickets are encoded the same with both MIT and Heimdal, as was the original intention, and all components understand both the new and the buggy encoding. However, older versions built against Heimdal only understand the buggy encoding. You should upgrade mod_webauth modules built against Heimdal before upgrading a WebKDC built against Heimdal to ensure that ticket flags are decoded correctly.

Users of WebAuthForceLogin should be aware of the behavior change described in the detailed release notes below. We believe this behavior change will generally be a UI improvement, avoiding pointless multiple logins when a user goes to multiple force-login sites in close succession, but some sites may wish to disable support for multi-stage login processes to get back the previous behavior.

For documentation and downloads of WebAuth 4.4.0, see:

<http://webauth.stanford.edu/>

New Debian packages built against Apache 2.4 have been uploaded to Debian experimental.

The user-visible changes in this release are:

  • The WebKDC and WebLogin server now support allowing a user to assert an authorization identity other than their own identity. This can be used to allow a user to access a test account on a particular WebAuth Application Server, pretend to be another user for testing or administrative reasons, or otherwise use an identity other than their own. This support is disabled by default; to enable it, set the WebKdcIdentityAcl Apache directive to the path to an ACL file describing acceptable combinations of authentication and authorization identities for each site. See the WebKdcIdentityAcl documentation in the mod_webkdc manual for more information. Updates to the confirm and possibly the login templates in WebLogin will also be required. See the sample templates for the new parameters and fields.

  • mod_webauth by default ignores the new authorization identities (and old versions will always ignore them) except for recording the authorization identity in the new environment variable WEBAUTH_AUTHZ_USER. There is a new mod_webauth Apache directive, WebAuthTrustAuthzIdentity, which can be enabled to set REMOTE_USER to the authorization identity instead of the authentication identity and to use the authorization identity for access control (such as mod_webauthldap privilege group lookups). WEBAUTH_USER will always be set to the authentication identity. This directive is allowed in .htaccess files (if authentication overrides are allowed) as well as anywhere in the main Apache configuration. Authorization identities will still be ignored if WebAuthSubjectAuthType is set to krb5.

  • Add new mod_webkdc Apache directive WebKdcLoginTimeLimit, which controls the time limit for completing a multi-step login process (such as with multifactor authentication) and how recently authentication must have occurred to count for session factors and forced login. The default value is five minutes, matching the previous default behavior for multifactor logins.

  • WebAuthForceLogin no longer forces re-entry of the user's password if the user has done an interactive authentication within the WebKdcLoginTimeLimit interval (five minutes by default). Initial authentication factors also count as session factors for single sign-on authentications within that time interval. This allows WebAuthForceLogin to work in combination with other features such as multi-step authentication processes and authorization identities and improves the user experience when simultaneously visiting multiple sites with forced login set. To disable this behavior and always force reauthentication, WebKdcLoginTimeLimit can be set to 0s, but this will make multi-stage login processes, such as multifactor, impossible.

  • Add replay detection to WebLogin. When enabled, only one username and password authentication is permitted with a given request token, and further authentications with the same request token are rejected as replays. This can protect against an attacker using the back button in an abandoned browser to replay the form submission on the WebLogin server. This support requires a memcached server be available for data storage and the Perl modules Cache::Memcached and Digest::SHA. The latter is available as part of Perl since 5.9.3.

  • Add rate limiting of login attempts in WebLogin. If enabled, after a configured number of failed login attempts, all password authentications for a given username will be rejected (valid or not) until a configurable interval of time has passed. This support also requires a memcached server for data storage and the Perl module Cache::Memcached.

  • The WebLogin error template has two new parameters: err_lockout and err_replay, corresponding to a replayed authentication and an account that was locked out due to too many login failures. Local templates should be updated to handle those parameters, particularly if either of these features are in use.

  • In WebLogin, set single sign-on cookies if present even when displaying an error. This establishes single sign-on when errors are returned after authentication, such as authentication rejected errors from the user information service. Without this behavior, if the custom error sent the user to another page that also required authentication, the user would have to log in again and may given up, thinking that authentication was looping.

  • Support two additional WebLogin configuration settings: @REMUSER_LOCAL_REALMS and @REMUSER_PERMITTED_REALMS. These provide the equivalent of WebKdcLocalRealms and WebKdcPermittedRealms for Apache REMOTE_USER authentication handled by the WebLogin front-end (such as when using Negotiate-Auth with mod_auth_kerb). Previously, there was only a @REMUSER_REALMS setting, which combined both meanings. @REMUSER_REALMS continues to be supported for backward compatibility, but will only be used if the more-specific variable is not set. Patch from Tom Jones.

  • Fix encoding of Kerberos credentials containing addresses or authdata when built against MIT Kerberos. WebAuth 4.3.0 and later would fail to encode those credentials properly. This bug only affects people using credential delegation with either Active Directory or with Kerberos configured to add addresses to tickets, which are relatively rare configurations.

  • Fix encoding of ticket flags with Heimdal Kerberos and tolerate the old, incorrect encoding. All previous versions of WebAuth, when built with Heimdal, encoded the ticket flags on the wire with the flag bits reversed (matching the in-memory Heimdal format). Prior to this version, flags would be lost when reading credentials encoded via MIT Kerberos with Heimdal or vice versa. As of this release, the portable flag encoding used for ticket caches is used when writing credentials with both MIT and Heimdal, and the flag order is detected when decoding credentials and fixed if necessary. If you use delegated credentials and link with Heimdal Kerberos, upgrade mod_webauth prior to upgrading the WebKDC to ensure the ticket flags are conveyed correctly.

  • Fix mapping of WebKDC error codes to names when reporting errors in WebLogin, fixing mostly cosmetic Perl warnings in the WebLogin server logs.

  • Document the WebAuthRequireSSL configuration directive. Under normal circumstances, this directive should always be left on (the default) to avoid serious security vulnerabilities, but there are some specific situations where it may be necessary to turn it off.

  • Add webauth_token_encrypt and webauth_token_decrypt to the public API, including the Perl API. These functions provide access to the low-level token encryption and decryption routines. Normally, the high-level webauth_token_{encode,decode} functions will be used instead, but these functions are useful for constructing low-level tests.

  • The webauth_base64_* functions have been removed from libwebauth, as have the corresponding Perl bindings. For C programs, use the apr_base64_* functions from APR-Util instead. For Perl programs, use MIME::Base64.

  • The webauth_attr_*, webauth_attrs_*, and webauth_hex_* functions have been removed from libwebauth, as have the corresponding Perl bindings. These functions provided a low-level interface to internal WebAuth data structures that is no longer necessary.

  • Remove webauth.h. The only remaining contents of interest to clients were the WebAuth protocol error constants, which have now moved to webauth/tokens.h.

  • Add public webauth_keyring_encode and webauth_keyring_decode functions that encode and decode keyrings into the serialization format used for storing them in files. These are useful for sending WebAuth keyrings over other protocols. Add a corresponding keyring_decode method to the Perl WebAuth class and encode and decode methods to the WebAuth::Keyring class.

  • The WA_TK_*, WA_TT_*, and WA_SA_* preprocessor constants are no longer provided by webauth.h. These contained a subset of the encoding rules for the WebAuth wire protocol, but were not really useful to clients of the library.

  • The WA_ERR_KEYRING_* error codes have changed to WA_ERR_FILE_* and will be used for any errors inside the WebAuth library when reading or writing to files. Now that WebAuth can report rich error messages, there is no need for the codes to be this specific. Add new WA_ERR_FILE_NOT_FOUND error, which replaces WA_ERR_KEYRING_OPENREAD when the error is due to the file not existing.

  • Update to rra-c-util 4.7:

    • Fix probing for Heimdal's libroken to work with older versions.
    • Checked asprintf variants are now void functions and cannot fail.
    • Include a replacement strndup for systems that don't have it.
Last modified Wednesday, 19-Dec-2012 10:31:01 PM

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