sssd-devel October 2013

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[PATCH] PROXY: Fix memory hierarchy when enumerating services
by Jakub Hrozek 22 Oct '13

22 Oct '13

Enumerating services with the proxy backend didn't work, a local variable was used as a talloc context..

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[PATCH] krb5: Use right function to free data
by Lukas Slebodnik 22 Oct '13

22 Oct '13

ehlo, This patch fixes warning reported by clang static analyzer. Simple patch is attached. LS

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[INI][PATCHES] Allow c-style comments in config files
by Dmitri Pal 21 Oct '13

21 Oct '13

Hello The following patch set addresses ticket https://fedorahosted.org/sssd/ticket/2108 Please see commit messages for more details about what each patch does. Please follow the order of the patches in the set. -- Thank you, Dmitri Pal Sr. Engineering Manager for IdM portfolio Red Hat Inc. ------------------------------- Looking to carve out IT costs? www.redhat.com/carveoutcosts/

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SSSD Internals Document published
by Yassir Elley 21 Oct '13

21 Oct '13

The SSSD team has published an SSSD Internals Document, which can be found at https://fedorahosted.org/sssd/wiki/InternalsDocs. If there are any mistakes in the document, feel free to modify the document. >From the Introduction to the document: " The purpose of this document is to give a basic description of the internals of the SSSD implementation. The material in this document is accurate as of SSSD 1.10. It is assumed that the reader is already familiar with the external usage of SSSD. The intended audience of this document are new contributors to the SSSD project. This document is not intended to be comprehensive. For additional details on specific features, please refer to the various Design Documents. This document does not discuss the details of building, installing, and debugging SSSD. More information on these topics can be found in the Developer Pages, and the Documentation. To be most useful, this document should be updated as appropriate, and reviewed at regular intervals. In order to better understand the material and make things more concrete, this document starts by describing a specific use case (and configuration) that will be discussed throughout the document. The document starts with a high level end-to-end overview, and then deep-dives into detailed descriptions. The document is organized into the following sections: Active Directory Use Case: specifies use case used throughout the document System Overview: end-to-end SSSD overview, including short descriptions of components Advanced Topics: offline operation, multiple domains, trust relationships SSSD Wrappers: SBus, SDAP Common Data Structures: data structures used by each SSSD process Component Details: gory details of each component Appendix: tevent, function descriptions, filesystem locations, helpful links " Regards, Yassir.

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Design Discussion: Improving AD provider access control
by Jakub Hrozek 20 Oct '13

20 Oct '13

Hi, I created a design page that describes a proposed way of improving the current AD provider access control. The main ticket that tracks the work is https://fedorahosted.org/sssd/ticket/2082 and the full design page can be found here: https://fedorahosted.org/sssd/wiki/DesignDocs/ActiveDirectoryAccessControl Comments and review are mostly welcome. For your convenience, the text of the design page is also copied below, in wiki syntax: == Active Directory client access control == Related ticket(s): * [https://fedorahosted.org/sssd/ticket/2082 RFE:Add a new option ad_access_filter] * [https://fedorahosted.org/sssd/ticket/1975 RFE:Change the default of ldap_access_order] * [https://fedorahosted.org/sssd/ticket/1977 issues when combining the AD provider and ldap_access_filter] Somewhat related: * [https://fedorahosted.org/sssd/ticket/2083 Document the best practices for AD access control] === Problem Statement === The recommended way of connecting a Linux client to an Active Directory domain is using the [http://jhrozek.fedorapeople.org/sssd/1.11.0/man/sssd-ad.5.html AD provider]. However, in the default configuration of the Active Directory provider, only account expiration is checked. Very often, the administrator needs to restrict the access to the client machine further, limiting the access to a certain user, group of users, or using some other custom filtering mechanism. In order to do so, the administrator is required to use an alternative access control provider. However, none of the alternatives provide the full required functionality for all users resolvable by the AD provider, moreover they are hard to configure. This design page proposes extension of the AD access provider to address these concerns. === Current access control options === With the existing SSSD, the administrator has two basic means to restrict access control to the Linux client - using the [http://jhrozek.fedorapeople.org/sssd/1.11.0/man/sssd-simple.5.html simple access control provider] or configuring the LDAP access control provider. Each approach has its pros and cons. ==== Using the simple access provider ==== The simple access provider grants or denies access based on the contents of allow and deny lists. There are separate lists for user and group names as well as allowed and denied objects. The following example shows configuration that grants access to user named `tux` and group called `linuxadmins`. {{{ access_provider = simple simple_allow_users = tux simple_allow_groups = linuxadmins }}} * Pros: * Easy to configure * Realmd provides an interface to configure the simple access provider using its CLI * Cons: * Account expiration is not checked * Limited expresiveness. No way to combine several clauses * Does not align with the LDAP structure the Active Directory uses ==== Using the LDAP access provider ==== The LDAP access provider offers a way to configure the access control decision based on whether the user matches a preconfigured filter. Moreover, the LDAP access provider also offers chaining other LDAP based checks. For the vanilla AD environment, only account expiration check applies. The following example illustrates configuration that allows access to those users, who are members of group named `linuxadmins` AND have a valid home directory set using the `ldap_access_filter` directive. The users who match the configured filter are also checked whether they are expired (`ldap_access_order` contains `expire`). {{{ access_provider = ldap ldap_access_order = filter, expire ldap_account_expire_policy = ad ldap_access_filter = (&(memberOf=cn=admins,ou=groups,dc=example,dc=com)(unixHomeDirectory=*)) ldap_sasl_mech = GSSAPI ldap_sasl_authid = CLIENT_SHORTNAME$(a)EXAMPLE.COM ldap_schema = ad }}} * Pros: * Allows the administrator to base access control on a custom LDAP filter, making it possible to combine several conditions * Conditions are not limited to user names or group membership * Cons: * Nontrivial and clumsy configuration that must include several low level LDAP settings, otherwise set automatically by the AD provider. Defeats the whole purpose of the AD provider * The admin needs to combine AD and LDAP providers. Judging by experience from triaging support cases with Red Hat support, this is a problem for many admins. * Account expiration check must be configured separately, which is not obvious * No support for users from trusted AD domains * No realmd integration === Proposed solution === The proposal is to add a new access filter configuration option to the existing AD access provider. Adding the option to the AD provider would greatly simplify the configuration when compared to the LDAP access control, while maintaining the full expresiveness of `ldap_access_filter`. The new option would be called `ad_access_filter`. If the new option was set, then the AD access provider would first match the entry against the filter in that option. If the entry matched, then the account would be checked for expiration. The following exapmple illustrates an example similar to the one above, using the proposed AD options: {{{ access_provider = ad ad_access_filter = (&(memberOf=cn=admins,ou=groups,dc=example,dc=com)(unixHomeDirectory=*)) }}} The main advantage is simplified configuration. The admin doesn't have to know or understand what "SASL ID" is. In comparison with the two legacy solutions explained above: * Pros * Easy and intuitive configuration. Only one provider type is configured * Sane defaults - always checks for expiration, also checks access filter if configured that way * Would support users and groups from trusted domains by leveraging the existing AD provider infrastructure * Cons * No realmd integration === Realmd integration === After a short discussion with the realmd upstream maintainer, it was decided that these options do not fit the realmd use-cases well. If the user needs to use such advanced techniques as LDAP filters, chances are that he doesn't need a tool like realmd to set them up in the config file. === Implementation details === 1. The default value of what AD access_provider is set to should be changed * Currently, if `access_provider` is not set explicitly, the default is `permit`, thus allowing even expired accounts * The new default would be `ad`, checking account expiration even with a minimal configuration 1. A new option would be added. The new option would be called `ad_access_filter` 1. The LDAP access provider must be extended to allow connecting to a GC and support subdomains in general * Pass in `struct sdap_domain` and `id_conn` instead of using the connection from `sdap_id_ctx` directly * The code must not read the `sss_domain_info` from `be_ctx` but only from `sdap_domain` in order to support subdomain users 1. The AD access provider must call the improved LDAP access provider internally with the right connection * The default should be GC * If POSIX attributes are in use and GC lookup wouldn't match, optionally fall back to LDAP. This fallback could be tried just once to speed up subsequent access control 1. The default chain of LDAP access filter the AD provider sets internally must be changed. * Currently AD provider sets `ldap_access_order=expire`. If (and only if) `ad_access_filter` was set, the LDAP chain would become `ldap_access_order=filter,expire` ==== Parsing the `ad_access_filter` option ==== 1. The `ad_access_filter` option is a comma-separated list of filters that apply globally, per-domain or per-forest. The most specific match is used 1. If the `ad_access_filter` value starts with an opening bracket `(`, it is used as a filter for all entries from all domains and forests * example: `(&(memberOf=cn=admins,ou=groups,dc=example,dc=com)(unixHomeDirectory=*))` 1. More advanced format can be used to restrict the filter to a specific domain or a specific forest. This format is `KEYWORD:NAME:FILTER` * KEYWORD can be one of `DOM` or `FOREST` * KEYWORD can be missing * NAME is a label. * if KEYWORD equals `DOM` or missing completely, the filter is applied for users from domain named NAME only * if KEYWORD equals `FOREST`, the filter is applied on users from forest named NAME only * examples of valid filters are: * apply filter on domain called dom1 only: * `dom1:(memberOf=cn=admins,ou=groups,dc=dom1,dc=com)` * apply filter on domain called dom2 only: * `DOM:dom2:(memberOf=cn=admins,ou=groups,dc=dom2,dc=com)` * apply filter on forest called EXAMPLE.COM only: * `FOREST:EXAMPLE.COM:(memberOf=cn=admins,ou=groups,dc=example,dc=com)` 1. If no filter matches the user's domain, access is denied * example `ad_access_filter = dom1:(memberOf=cn=admins,ou=groups,dc=dom1,dc=com), dom2:(memberOf=cn=admins,ou=groups,dc=dom2,dc=com)`, user logs in from dom3 === Contingency plan === None needed. The existing options would still exist and function as they do now. === How to test === 1. Check that `access_provider=ad` without any other options allows non-expired users 1. Check that `access_provider=ad` without any other options denies expired users 1. Test that setting `ad_access_filter` restricts access to users who match the filter * test that an expired user, even though he matches the filter, is denied access * this test must include users from the primary domain as well as a sub domain * Different filters should be tested to make sure the most speficic filter applies * example: add a restrictive filter for dom1 and permissive filter without specifying the domain. A user from dom1 must be denied access, while a user from other domain must be allowed access 1. When access is denied, the SSSD PAM responder must return a reasonable return code (6) === Future and optional enhancements === In the future, we should extend the `access_provider` option itself and allow chaining access providers. This enhancement would allow even more flexibility and would allow the administrator to combine different access providers, but is outside the scope of the change described by this design page. === Author(s) === * Jakub Hrozek <jhrozek(a)redhat.com> * Sumit Bose <sbose(a)redhat.com>

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[INI] [PATCHES] Add UTF 8/16/32 conversion
by Dmitri Pal 19 Oct '13

19 Oct '13

Hello, The attached patches address ticket https://fedorahosted.org/sssd/ticket/2106 The patches do not define new flags as suggested in the ticket. As we discussed with Nalin we try to detect the encoding based on the BOM and do the right thing without flags. If we see that this is not enough we will add flags but that would add a new function so such change would be destined for a bigger release. For now I think the use case is addressed. If we see the need to other use cases we will open other tickets. The patch depends on the previous set of patches that deal with C-Style comments. I also found some other unrelated issue that I logged as a separate ticket. https://fedorahosted.org/sssd/ticket/2119 -- Thank you, Dmitri Pal Sr. Engineering Manager for IdM portfolio Red Hat Inc. ------------------------------- Looking to carve out IT costs? www.redhat.com/carveoutcosts/

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automatic renewal of TGT for IPA users
by Qing Chang 18 Oct '13

18 Oct '13

In sssd InternalsDocs, there is a statement: "SSSD can automatically renew the TGT at a configurable interval". Can someone give me a pointer as how I can configure sssd to do it? I am using krenew for the same effect, thought a native way would be much better... Many thanks, Qing

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[PATCHES] struct sockaddr casting
by Michal Židek 17 Oct '13

17 Oct '13

Hello, these are the patches, that solve the casting of sockaddr structure. Patch 0001 - Adds function to filter out special ip addresses (loopback, multicast, linklocal, broadcast) and also a unit test for it. Used in later patches. Patch 0002 and 0003 - Use the function from patch 0001 and properly copy the sockaddr_in structure to avoid alignment warnings. Patch 0004 - Avoid casting of sockaddr to sockaddr_in in tests. Also here is the discussion from diffrent thread, related to sockaddr casting: // PASTE BEGIN >>>>> I tested some compilers and patches work fine with clang and gcc. >>>>> But there are also another compilers in the world >>>>> ant they needn't understand "pragma GCC". This pragma is not standardized. >>>>> >>>>> >>>>> src/providers/dp_dyndns.c(145): warning #161: unrecognized #pragma >>>>> #pragma GCC diagnostic push >>>>> ^ >>>>> >>>>> src/providers/dp_dyndns.c(146): warning #161: unrecognized #pragma >>>>> #pragma GCC diagnostic ignored "-Wcast-align" >>>>> ^ >>>>> >>>>> src/providers/dp_dyndns.c(206): warning #161: unrecognized #pragma >>>>> #pragma GCC diagnostic pop >>>>> ^ >>>>> >>>>> If you are 100% sure about alignment, you can define own macro. >>>>> >>>>> Something like this: >>>>> #define ignore_align(var, dest_type) \ >>>>> (dest_type *)((void*)(var)) >>>>> >>>>> And usage: >>>>> wrapper->refcount = ignore_align(wrapper->ptr + refcount_offset, int); >>>>> >>>>> >>>>> Does anybody have any better ideas? >>>> Compiler specific #pragma should not be used. And I think in general >>>> #pragma should be used with great care. Currently there is only one use >>>> case in sssd in the memcache code to align some structs which make >>>> sense. >>> Indeed, agree 100% >>> >>>> Especially I think ingnoring a warning is not a good idea. If currently >>>> no one has a good idea how to handle the sockaddr and in_addr structs in >>>> a way which does not produce a warning I would prefer to keep the >>>> warning around until someone has a good idea. Imo a comment in the code >>>> that the warning can be ignored would be sufficient for the time being. >>> casting sockaddr is a bug, unless you know for sure it was created as >>> sockaddr_un and then simply casted to sockaddr, but in that case I would >>> consider the casting to pass it around just a different bug. >>> >>> Please use sockaddr_un anywhere you need to perform casts. Pass around >>> sockaddr_un and cast it only at the time of use when needed. >> It is not possible to use sockaddr_un(or sockaddr_storage). >> >> We use function getifaddrs to retrieve addresses of network interfaces. >> >> Manual page says (man 3 getifaddrs) >> -------------------------------------------------------------------------- >> int getifaddrs(struct ifaddrs **ifap); >> >> The getifaddrs() function creates a linked list of structures >> describing the network interfaces of the local system, and stores >> the address of the first item of the list in *ifap. >> The list consists of ifaddrs structures, defined as follows: >> >> struct ifaddrs { >> struct ifaddrs *ifa_next; /* Next item in list */ >> char *ifa_name; /* Name of interface */ >> unsigned int ifa_flags; /* Flags from SIOCGIFFLAGS */ >> struct sockaddr *ifa_addr; /* Address of interface */ >> ^^^^^^^^^^^^^^^ >> We cannot change this type >> struct sockaddr *ifa_netmask; /* Netmask of interface */ >> union { >> struct sockaddr *ifu_broadaddr; >> /* Broadcast address of interface */ >> struct sockaddr *ifu_dstaddr; >> /* Point-to-point destination address */ >> } ifa_ifu; >> #define ifa_broadaddr ifa_ifu.ifu_broadaddr >> #define ifa_dstaddr ifa_ifu.ifu_dstaddr >> void *ifa_data; /* Address-specific data */ >> }; >> >> -------------------------------------------------------------------------- > In this case you should copy the contents of sockaddr to a new variable > of the right type, and not cast. > > Simo. > Yes, this is the only way you can deal with these issues. I remembered this from my experiments with ELAPI 3 years ago. I ran into similar problems with this function and had to copy data. -- Thank you, Dmitri Pal // PASTE END Thank you, Michal

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[PATCH] krb5: Remove warning dereference of a null pointer
by Lukas Slebodnik 17 Oct '13

17 Oct '13

ehlo, coverity and clang report warning "dereference of a null pointer". I think it was false possitive, because we cannot get to the sithuation where "kr->creds == NULL" Patch is attached. Gzipped clang report is attached. (report-pv9WXu.html#Path19) LS

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[PATCH] sdap_idmap: properly handle ranges for external mappings
by Sumit Bose 17 Oct '13

17 Oct '13

Hi, this patch set aims to fix https://fedorahosted.org/sssd/ticket/2105 . But since I had to touch the libsss_idmap code for this I found an issue here as well, which is fixed by the first two patches. bye, Sumit

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sssd-devel October 2013