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1 \chapter{Grid computing}
2 % Authenticatie is gebaseerd op PKI
3 % Authorisatie is gebaseerd op DN's, VOMS
4 % Grid heeft dit en dat, maar onze basis is PKI.
5 % Authenticatie: persoonlijke certificaten, VOMS, SAML statements en
6 \section{Authentication \& authorization mechanisms}
7 Grid computing requires a mechanism to authorize users' access to Grid resources. This authorization can be granted at different levels depending on different types of credentials supplied by - or associated with - the user and which service he or she tries to access.
9 The various Grid middleware stacks rely heavily on X.509 certificates \cite{rfc2459} as the 'lingua Franca' for authenticating users.
10 It's a personal SSL certificate that can be traced back to the issuer, a \textit{Certificate Authority} (CA).
11 \glossary{name={CA}, description={Certificate Authority}}
12 This creates a \textit{Public Key Infrastructure} (PKI) \cite{rfc3280} which can be used to enable a Single sign-on (SSO) solution.
13 \glossary{name={SSO}, description={Single sign-on}}
14 \glossary{name={PKI}, description={Public Key Infrastructure}}
15 The certificates used on Grid systems are \textit{Proxy Certificates} \cite{rfc3820} which are signed by the user and are valid for shorter periods of time to diminish the value of stolen certificates.
16 These proxy certificates can be traced back to the user they belong to, providing end-to-end accountability.
18 % SSO, delegation -> trace
20 % VOMS doet registratie van gebruikers op basis van hun DN, groepsstructuur en rollen toekennen
21 % Signed attribute certificates uit te geven.
22 % FQANS zijn onderdeel van de VOMS attributes.
23 \subsection{Virtual Organizations}
24 Because of scalability issues Grid authentication is mostly based on group affiliation.
25 The group affiliations are expressed in several tiers, the most high level of which is a \textit{Virtual Organization} (VO).
26 \glossary{name={VO}, description={Virtual Organization}}
27 VO's appear to work like regular organizations, but are not explicitly connected by location, employer or other affiliation.
28 However, they collaborate and present themselves as a unified organization.
30 \subsubsection{Virtual Organization Management Service}
31 VO's can make use of a \textit{Virtual Organization Management Service} (VOMS) to manage and register their users.
32 \glossary{name={VOMS}, description={Virtual Organization Management Service}}
33 Users should apply to a VOMS with their Grid certificate, which must contain the name of the user in the certificate's Subject \textit{Distinguished Name} (DN).
34 \glossary{name={DN}, description={Distinguished Name}}
36 Based on a user's Grid certificate credentials - specifically, the Subject DN - the VOMS service can give a user signed tokens to claim group membership when interacting with Grid services.
37 In this interaction the VOMS server acts as an \textit{Attribute Authority} (AA), which distributes signed attributes to the user in the form of an \textit{Attribute Certificate} (AC) \cite{rfc3281}.
38 The Attribute Certificate also specifies the group, subgroup, roles and capabilities of the holder.
39 \glossary{name={AA}, description={Attribute Authority}}
40 \glossary{name={AC}, description={Attribute Certificate}}
41 To create a VOMS AC, a VOMS service amends the user's proxy certificate with signed VOMS tokens, which include \textit{Fully Qualified Attribute Name}s (FQANs) \cite{fqan}.
42 \glossary{name={FQAN}, description={Fully Qualified Attribute Name}}
44 As an analogy, in this capacity the Grid certificate is like a passport that is used to obtain a membership card (AC) of a certain club (VO).
45 Once the identity of the holder has been verified, the membership card is all that is needed to access club facilities. Their identity can be established from these \textit{attribute credentials}.
47 A user can be authenticated to belong to a VO group by tracing this information back to a trusted VOMS server certificate (an \textit{Attribute Signing Certificate} \cite{rfc3281}), which has in turn been signed by a trusted CA.
48 Based on these signed attributes a user is authenticated to belong to a project group in a certain role.
49 This authentication solution requires the trusted VOMS server certificates to be available to all services that need to verify VOMS attributes.
51 %VOMS defines groups, roles and capabilities.
52 %These are completely independent of each other.
53 %Roles are meant to be global, associated directly with the AC holder, regardless of group membership.
54 %However, VOMS allows groups and roles to be bound together, using one as a qualifier for the other.
55 %While it is indeed possible to encode groups and roles inside the standard attributes in a format that could represent
56 %this information, there is no way to have the same format also be readable by other AC users without risking misunderstandings. \cite{ac-rfc}
58 \subsection{Pool accounts}
59 Pool accounts are part of a mechanism to map users' Grid certificate credentials to actual user accounts on compute clusters. \cite{gridmapdirsite}
60 These pool accounts are generic user accounts that are mapped to the remote user based on the credentials in their certificate.
61 The various sets of pool accounts are created by site administrators, which are then 'loaned' to users working in certain roles.
62 The pool accounts are not associated with a user up to this point.
64 When a pool account is in use, there is a strong link between the pool account and the user credentials that were mapped to it.
65 % pool accounts zijn niet geassocieerd met gebruiker totdat die is langsgekomen/gemapped
66 % gebruikers zijn op deze manier sterk verbonden met het UNIX account
67 %This facilitates late binding between users within a VO and the concrete UNIX accounts they use to do work on the Grid.
68 The role and associated capabilities a user takes on are determined by the signed VOMS attributes present in a user's proxy certificate. \cite{nikhefwebsite:gridwikiindex}
71 \subsection{Fully Qualified Attribute Names}
72 \textit{Fully Qualified Attribute Names} (FQANs) are explicit and unambiguous strings that can describe the group and subgroup a user is associated with.
73 These can be given out by a VOMS service through an Attribute Certificate.
74 Besides group affiliation, roles and capabilities can be attributed to the user.
75 By being affiliated with a certain group, a user can claim authorization at a grid service.
76 %In VOMS AC's komen FQANS voor
77 %FQAN is 1 string die beschrijving geeft van de VO groepen, subgroepen, rollen en capabilities
78 % binnen iedere groep kun je aparte rollen aanwijzen
79 % als je die rollen bezit mag je de authorizatie claimen bij een service
80 % mag meer tekst bij
82 \begin{table}[h]
83 \begin{center}
84 \begin{tabular}{ | c | c | c | c | }
85 \hline
86 VO & group & subgroup & role \\
87 \hline
88 /fred.example.org & /production & /optimization & /Role=Admin \\
89 \hline
90 \end{tabular}
91 \end{center}
92 \caption[FQAN fields]{A table showing examples of the FQAN fields VO, group, subgroup, role and capability}
93 \end{table}
95 % Mensen moeten zich via email aanmelden bij de VOMS-server
96 % Alle grid services en VOMS servers hebben een push-model waarin je je certificate upload. De services moeten deze informatie verifieren.
98 %All Grid services have a push model that requires users to provide a certificate which is then verified by the service. This is done by tracing back the proxy certificate and all its signed credentials to the VOMS server certificate, and tracing the user certificate back to the issuing CA.
100 \pagebreak
102 \subsection{Grid credentials}
103 % Basis van de authenticatie is gebaseerd op de persoonlijke certificaten.
104 % Die zijn uitbreidbaar.
105 %
107 Multiple authentication mechanisms must be supported due to the scale and breadth of the Grid use cases.
108 Many different organizations worldwide develop Grid middleware, policies and infrastructure and each organization brings their own use cases, motivations and expertise to the table.
110 %breed -> veel verschillende groepen schrijven middleware en hebben ieder hun eigen use-cases te verwerken daarin EN diverse achtergronden en motivaties
112 % Bepaalde technieken, evolutie ervan, adoptie/penetratie van technieken die we hebben.
113 % Open standaarden die we zoveel mogelijk willen ondersteunen.
114 % SAML is heel nieuw, PKI bestaat al heel lang, en daarbij: proxy delegations.
115 % Door Delegation of credentials from your certificate to a WMS zodat die service functioneert als een agent.
116 % Alleen de private key van de delegation blijft over op de WMS. Je eigen private key van je op jouw naam staande certificate wordt niet overdragen aan de agent.
117 % Het proxy certificate is cryptografisch verbonden, omdat jij de signer bent.
118 Support for these mechanisms has evolved over the past decade, and gradually got more flexible.
119 % Het gebruik van de authenticatie technieken heeft relatie tot volwassenheid en evolutie van authenticatie technieken en de use cases (refereer naar delegation). Open standaarden zijn vereist.
121 % End-to-end security: dat je de chain van de worker node kunt terugleiden naar de persoon die de job submitte.
122 % Vanwege de schaalbaarheid maken we vooral authorisatie beslissingen op basis van groepen.
123 % Mensen die in die groep zitten worden impliciet vertrouwd.
124 % VOMS: Virtual Organization staat min of meer 1:1 tot een experiment of een project.
125 % Binnen de VO kennen we groepen, subgroepen en rollen. Aan ieder van deze kunnen personen worden toegewezen, en ook services en resources.
126 % Individu moet zich registeren bij een VO, en als je geregistreerd bent kun je gesignede tokens ophalen.
127 % User genereert een certificate en laat hem signen door een CA.
128 % User kan een proxy certificate maken van z'n user cert.
129 % Daarmee authenticeer je jezelfd bij de VOMS server (standaard mutual SSL authentication) en vraag je de groepen van jouw VO en evt. rollen.
130 % De server zoekt die credentials bij elkaar en signed ze met zijn private key. Vervolgens stuurt ie de gesignede blob (VOMS attribute Certificate of VOMS AC) terug naar de client.
131 % Nu ga je een nieuwe proxy delegation maken, en tijdens het signing request worden de VOMS AC embedded in de CSR als X.509v3 extensies.
132 % Dit geheel wordt nu gesigned als een reguliere met jouw eigen private key.
134 % VOMS AC's zijn gebaseerd op RFC 3281.
135 % Certificates waren gebaseerd op RFC 3280, maar nu is dat RFC 5280
137 % Nu heb je een VOMS-enabled certificate (VOMS proxy).
138 % Attributes in een VOMS proxy zijn:
139 % Van de VOMS server die signed: de URI, de DN, de signer van de DN.
140 % Dus je hebt twee dingen om te controleren: de cert van de VOMS (naar de CA) en de signer (ook CA) van de DN.
142 % IGTF is een samenwerking van 3 grote grid (igtf.net)
143 % PKI + personal certificates.
144 % Binnen de rest van VOMS certificate attributes heb je ook FQANS die vertellen welke groep en/of rol voor jou van toepassing is. Wordt ook gesigned door de VOMS service.
145 % (Dan heb je ook nog een name-value pair voor mogelijk extra attributen.)
148 % Nog 2 dingen die in je VOMS proxy kunnen zitten:
149 % Public key van de voms service.
150 % Serial number van jouw persoonlijke certificaat.
151 % Jouw subject DN.
154 % Zo is er een linkt te leggen tussen:
155 % Jouw subject DN, jouw CA, en jouw serial number van jouw certificaat.
156 % Zo ontstaat er een link tussen de persoon, de signature van de CA en het certificaat van de gebruiker. Dit gaat het stelen van voms-attributes tegen want voms attributes zitten als extensie in je proxy certificaat en dus hebben ze een sterke binding nodig met de eigenaar van het certificaat.
158 % VOMS AC
159 % DN, FQAN, CA, serial number, secret sauce.
160 Different types of credentials that can be used are:
161 \begin{description}
162 \item[Personal, host and service X.509 certificates] % Wie ben je
163 {The Subject \textit{Distinguished Name} (DN). This uniquely identifies a user, host or service through a PKI infrastructure which includes identity-vetting by a trusted third party.
164 }
166 \item[VOMS attributes]{
167 The DN information is used to query a certain VOMS server associated with the project, which returns an \textit{Attribute Certificate} \cite{rfc3281} in which each field and the Attribute Certificate as a whole are signed by the VOMS server.
168 }
170 % Op basis van de info in het certificaat (je DN) en VOMS credentials (FQAN) worden user geauthoriseerd.
171 % (Wie ben je, voor welke groep werk je, wat is je rol).
173 %\item VOMS credentials (Fully Qualified Attribute Name) % Voor welke groep werk je en welke rol bekleed je
174 % Voorbeelden van VOMS rollen: VO-admins, software updaters / installateurs (Software area directories), production managers (verantwoordelijke voor het processen van de data en monte carlo productie).
175 \item[SAML statements] % Zie je terug in Shibolleth. Altijd terug te leiden naar X.509 certificates. Andere niet-standaard authenticatiemethoden. Komt meer uit de web-hoek.
177 {The \textit{Security Assessment Markup Language} \cite{saml} is an XML standard for exchanging authentication and authorization data between security domains.
178 Grid services try to translate SAML information back to an X.509 certificate, as it remains the 'lingua Franca'.
179 }
180 \glossary{name={SAML}, description={Security Assessment Markup Language}}
181 % Bedoeld om een claim te geven over identiteit
182 % These statements lead users back to a X.509 certificate.
183 % The standard was devised for interoperability between Single Sign-on solutions.}
184 % reference SSO
185 % reference SAML
187 \item[XACML queries] % Te maken met policies en queries op policies. Mag pietje puk gebruik maken van deze resource? XACML: Subject (aram + cert), Action (computing), Resource (storage), Environment (arbitraire omgevingsinformatie).
189 {The \textit{eXtensible Access Control Markup Language} (XACML) is a declarative access control policy language implemented in XML. \cite{xacml}
190 It can be used to define rules based on Subject, Action, Resource, and Environment values.
191 %\subsection{XACML fields}
192 \glossary{name={XACML}, description={eXtensible Access Control Markup Language}}
195 }
196 % reference XACML
198 \end{description}
200 \begin{table}[h]
201 \begin{center}
202 \begin{tabular}{ | c | c | c | c | }
203 \hline
204 Subject & Action & Resource & Environment \\
205 \hline
206 User Aram & wants cycles & on this server & which should run Linux \\
207 \hline
208 \end{tabular}
209 \end{center}
210 \caption[XACML concepts]{A table showing examples of the XACML concepts Subject, Action, Resource, and Environment}
211 \end{table}
214 %\section{XACML examples}
215 %Here's an example of how XACML requests can are used to represent Grid credentials.
216 %\subsection{Subject X.509 id}
217 %\begin{verbatim}
218 %<Attribute
219 %AttributeId="http://authz-interop.org/xacml/subject/subject-x509-id"
220 %DataType="http://www.w3.org/2001/XMLSchema#string">
221 %<AttributeValue>
222 %/O=dutchgrid/O=users/O=nikhef/CN=Oscar Koeroo
223 %</AttributeValue>
224 %</Attribute>
225 %\end{verbatim}
227 %\subsection{Subject X.500 issuer}
228 %\begin{verbatim}
229 %<Attribute
230 %AttributeId="http://authz-interop.org/xacml/subject/subject-x509-issuer"
231 %DataType="http://www.w3.org/2001/XMLSchema#string">
232 %<AttributeValue>
233 %/C=NL/O=NIKHEF/CN=NIKHEF medium-security certification auth
234 %</AttributeValue>
235 %</Attribute>
236 %\end{verbatim}
239 %\subsection{Subject VO}
240 %\begin{verbatim}
241 %<Attribute
242 %AttributeId="http://authz-interop.org/xacml/subject/vo"
243 %DataType="http://www.w3.org/2001/XMLSchema#string">
244 %<AttributeValue>gin.ggf.org</AttributeValue>
245 %</Attribute>
246 %\end{verbatim}
249 % PEPd -> Policy Enforcement Point daemon
250 % PDP -> Policy Decision Point
251 % PAP -> Policy Administration Point
254 \pagebreak
256 \section{Grid security middleware and services}
257 %\subsection{ADAM}
258 %% No longer used.
259 %ADAM stands for \textit{AmPS Data Analysis Method}, which as the name implies was first developed to process data generated by the AmPS \textit{Amsterdam Pulse Stretcher}.
260 %\glossary{name={ADAM}, description={AmPS Data Analysis Method}}
261 %\glossary{name={AmPS}, description={Amsterdam Pulse Stretcher}}
262 %It was not designed as a security middleware, but it does have a pluggable architecture to extend its functionality.
263 %The core component was a framework that got raw data as input from the detectors and used specific plug-ins to perform detector specific analysis. \cite{adampage}
265 \begin{figure}[hp]
266 \centering
267 \includegraphics[width=\textwidth]{scas}
268 \caption[SCAS diagram]%
269 {A diagram showing the architecture of a SCAS-based authenticating \& authorization installation}
270 \label{fig:scas}
271 \end{figure}
273 \subsection{gLExec}
274 %By the virtue of the pilot job framework use case a Worker Node has now become a new entry point to the cluster.
275 % reference naar suEXEC
276 gLExec is a pluggable suEXEC-like \cite{suexec} wrapper program that requests a mapping between Grid credentials and Unix user accounts and groups.
277 It can enforce this mapping to wrapped executables by modifying the \textit{uid} and \textit{gid}s of the executing process to the ones the user is mapped to, before passing execution to the wrapped binary.
278 gLExec will authenticate credentials using a callout to LCAS and LCMAPS.
279 It can act as both a light-weight 'gatekeeper' on the Compute Element or be used on the Worker Node for late-binding (pilot job) use cases. Please see appendix \ref{use_cases} for a description of possible use cases.
280 Through the SCAS client in LCMAPS, a central mapping and authorization service like SCAS (or any interoperable SAML2XACML2 service) can be used. \cite{nikhefwebsite:gridwikiglexec}
282 \subsection{LCAS}
283 The \textit{Local Centre Authorization Service} (LCAS) makes binary ('yes' or 'no') authorization decisions at the site and resource level.
284 \glossary{name={LCAS}, description={Local Centre Authorization Service}}
285 %In making this decision it can use a variety of inputs, among which are:
287 %\begin{itemize}
288 %\item The 'Grid' name of the user. The user's X.509 certificate Subject, also known as the \textit{Distinguished Name} (DN)
289 %\item Any VO attributes the user has like VOMS \cite{vomssite} \textit{Fully Qualified Attribute Name}s (FQANs)
290 %\item The name of the executable the user intends to execute
291 %\end{itemize}
293 It supports basic black and white list functionality, but also more complex VOMS-based expressions, based on the GACL \cite{gaclsite:home} language.
294 The framework fetches data, stores it, and through static means offers structures to plug-ins that contain the following values:
296 \begin{itemize}
297 \item X.509 certificate chain string (in PEM \cite{rfc1421} format) \cite{rfc2459}
298 \item \textit{Resource Specification Language} (RSL) string \cite{globus-rsl}
299 \item \textit{Distinguished Name} (DN) string \cite{rfc5280}
300 \item Globus GSS Credential structure \cite{rfc2743}
301 \end{itemize}
302 \glossary{name={RSL}, description={Resource Specification Language}}
303 \glossary{name={PEM}, description={Privacy Enhanced Mail}}
304 \glossary{name={GACL}, description={Grid Access Control Library}}
306 \subsubsection{Plug-ins}
307 The plug-ins that LCAS executes must all exit successfully before authorization can continue. \cite{nikhefwebsite:gridwikiindex}
309 \begin{description}
310 %\item[Gridlist]{A plug-in that maps allowed users to pool accounts using the gridmapfile \cite{gridmapfile}}
311 \item[Timeslots]{A plug-in that makes authorization decisions based on the time of day a job request is received \cite{timeslots}}
312 \item[Userban]{A plug-in that checks a file that contains a list of Subject DNs of users to be banned from the site \cite{userban}}
313 \item[Userallow]{A plug-in that checks a file that contains a list of Subject DNs of users to be allowed to the site. \cite{userallow}}
314 \item[Check executable]{A plug-in that checks if the executable requested is whitelisted by the service. \cite{userallow}}
315 \item[LCAS VOMS]{Works like the userallow plug-in, execpt it verifies the FQANs present in a proxy certificate instead of the Subject DN. These were added to the certificate by a VOMS service. With this plug-in, more complex policies for authorization can also be expressed in the GACL \cite{gaclsite:home} language.}
316 \end{description}
318 \glossary{name={RSL}, description={Resource Specification Language}}
319 \glossary{name={GACL}, description={Grid Access Control Library}}
320 % i.e. the plug-ins must be true if logically AND-ed.
322 \subsection{LCMAPS}
323 %Unix (like) systems only understand Unix UID, GID and Secondary GID
324 %credentials. As the lingua Franca is X.509 (with VOMS credentials), these
325 %credentials will need to be translated to Unix credentials.
326 %Based on the Unix credentials, batch system schedulers can do their work as
327 %batch systems have never (yet) been Griddified to natively handle X.509
328 %and/or VOMS credentials.
330 LCMAPS is the \textit{Local Credential Mapping Service}.
331 \glossary{name={LCMAPS}, description={Local Credential Mapping Service}}
332 It takes care of translating Grid credentials to Unix credentials local to a Grid site.
333 It ensures that different individuals on the Grid maintain distinct, isolated Unix accounts using the pool account mechanism \cite{gridmapdirsite}.
334 This mechanism can be extended to dynamic groups when needed.
335 Using group mappings based on the user's VO attributes, scheduling priority decisions can be made.
337 The LCMAPS framework hosts a list of specific credential types in its core.
338 These are offered to the plug-ins via an API.
339 Each plug-in has a specific task to perform, like in the previous frameworks.
340 The plug-ins are able to write intermediate results or final results into the core memory of the framework.
341 The LCMAPS framework has two failover mechanisms in the execution of its loaded plug-ins that can be defined by the configuration file.
342 The first failover mechanism is similar to a state machine.
343 If a plug-in executes and its execution was a success, then progress to plug-in 'a'.
344 Otherwise progress to plug-in 'b'.
345 The state machine must end with a successful result.
346 The second failover mechanism is to define (execution) policies.
347 Each complete state machine is an execution policy.
348 If multiple policies are defined and if the calling application allows it, then on a failure of such policy the framework can select the next policy to execute.
349 Between policy switch the internal memory (with the intermediate results) will be erased. \cite{nikhefwebsite:gridwikiindex}
351 % BEGIN oscar
352 A set of user credentials, e.g. the DN and combination of group and role affiliations listed in the VOMS credentials, will be linked to a specific pool account.
353 A pool account is a regular Unix account that is already present on a system and is already setup to have certain particular privileges of a particular group of users that might also have a specific role e.g. a Production manager of Software Manager.
354 In its initial state a pool account is not associated to any user.
355 During the mapping process a user's credentials are mapped to a specific pool account which means that the selected free pool account is strongly tied to the set of user credentials.
356 When a user returns to the same site with the same set of credentials the user will be mapped to the same Unix account again.
359 \subsubsection{Plug-ins}
360 The plug-ins that LCMAPS executes must all exit successfully before authorization can continue. \cite{nikhefwebsite:gridwikiindex}
362 \begin{description}
363 %\item[Gridlist]{A plug-in that maps users to pool accounts using the gridmapfile \cite{gridmapfile}}
364 \item[Local account]{Maps the supplied user credentials (i.e. a Subject DN or VOMS-signed FQANs) to a local user account on a target system \cite{localaccount}}
365 \item[Pool account]{Maps the supplied user credentials (i.e. a Subject DN or VOMS-signed FQANs) to a pool account on a target system \cite{poolaccount}}
366 \item[POSIX enforcement]{A plug-in that applies acquired credential information to procure a Unix user account on a target system. Verifies that the account was successfully attained. \cite{posix_enf}}
367 \item[LDAP enforcement]{A plug-in that applies acquired credential information in a target LDAP database \cite{ldap_enf}}
368 \item[Verify proxy]{This plug-in can verify the validity and authenticity of the incoming Grid credentials, and enforce life time constraints on the proxy}
369 \end{description}
371 \subsection{SCAS}
372 The \textit{Site Central Authorization Service} makes authorization and mapping decisions upon the presented credentials.
373 %It uses HTTPS authentication to authenticate a client, based on the credentials in their Grid certificate. %(as regular user or pilot job user) and present user credentials.
374 The service is a front-end to the LCAS and LCMAPS frameworks and uses HTTPS with mutual authentication to setup a session in which a SAML2-XACML2 request is sent.
375 \glossary{name={SCAS}, description={Site Central Authorization Service}}
378 The SCAS is specifically tailored to solve the use case involving pilot job frameworks. (Please see appendix \ref{use_case_pilot_job}.)
379 %This relatively new use case involves the late binding of the \textit{Worker Node} (WN) resources by sending pilot jobs to all the compute clusters by a production manager.
380 %When the pilot jobs come out of the queue and have started their run, they'll discover if the Worker Node on which they have acquired a job slot meets the criteria specified by the user.
381 %If the job slot criteria can be satisfied the pilot job framework will download the payload from a VO central job repository queue, unpack the payload and start executing the actual job.
383 %In this use case there are two actors: a user and a VO production manager.
384 %The VO production manager who has the responsibility to fill all the queues on the clusters according to the used quotas and taking into account what kind of data is stored nearby the compute cluster.
385 %The user had to submit their analysis jobs to the central queue.
386 %The pilot jobs submitted by the VO production managers will pick up the analysis jobs from the central queue.
388 %As this use case has two actors into play two sets of credentials will need to be authorized.
389 %The gLExec and SCAS are able to do this.
394 % cite OASIS standard saml2-xacml2 .
395 The SCAS will authorize the pilot job framework production manager and it will authorize the payload user using the LCAS framework.
396 Upon successful authorization the user credentials of the payload will be mapped to Unix credentials by LCMAPS and returned in a SAML2-XACML2 \cite{authzinterop} response.
397 In such response there is a binary authorization statement given and optionally XACML obligations can be returned.
399 Obligations are name-spaced identifiers that can contain attributes.
400 Returned XACML obligations are non-repudiable (undeniable) and must be handled by the client who receives them.
401 The XACML convention is to abort the authorization (and mapping) process if the client cannot meet the obligations set by the service.
402 % oscar
406 \subsection{Limitations of existing frameworks}
407 \begin{description}
408 % Behalve de unix credentials zoals we die nu hebben doorgeven, we ook use-cases om dynamisch priority queues en priority scheduling te kunnen doen in verschillende typen batch systems met verschillende batch system scheduler.
409 %\item Software design overly complex, difficult to maintain.
410 % Alleen evaluation manager
411 %\item Strongly oriented towards existing use cases.
412 %\item Unable to handle new use cases.
413 \item[Strong binding to X.509 certificates, VOMS credentials, and Unix \textit{uid}s/\textit{gid}s.]{
414 This limits the types of systems and services the middleware frameworks can interact with.
415 }
416 %\item[No facility to interact with scheduling services]
417 \item[Does not facilitate direct low-level interaction with batch systems and schedulers]{
418 A desired functionality is the on-demand creation of priority queues.
419 It should also be possible to manipulate existing scheduling configurations.
420 }
421 \item[No facility to interact with virtualization frameworks]{
422 %kijk naar sander's e-mail van vanochtend (15 oct. 11:11) onder taken.
423 %describe interaction
424 To enable the scheduling of Virtual Machine execution, a connection to existing virtualization frameworks must be made.
425 The \textit{Open Cloud Computing Interface} (OCCI) API \cite{occi} or OpenNebula toolkit \cite{opennebula} are frameworks that could be incorporated to enable scheduling of virtual machine execution.
426 % plug-in voor het batch systeem
427 }
429 \item[No facility to interact with batch-systems in an arbitrary way]{
430 % Op ieder cluster systeem heb je allerlei trucjes om je systeem in leven te houden, dit maakt een hook voor je.
431 %Het idee is dat je met perl/python scripts systeembeheerders mogelijkheden geven om systeem-specifieke handelingen uit te kunenn voeren. bijv. interacties met lokale accounting systemen
432 Because each cluster configuration is different it would be very beneficial to let system administrators hook their management scripts into the framework.
433 Adding support for high-level scripting languages like Perl or Python should be an effective way to allow this.
434 }
435 % We hebben een datastore. Datastore is toegespitst op X509,VOMS, en Unix credentials
436 %\item Inability to facilitate a shared data store for plug-ins executed in the framework.
437 % LCAS/LCMAPS hebbben wel een data store, om gegevens te delen
438 % Maar dat ze te specifiek zijn voor bepaalde toepassing
439 % Toegespitst op bepaalde use cases.
440 % Het moet generiek worden.
444 % Uitwijden over wat we van plan zijn
445 % Alles is georienteerd op x509 plus voms naar unix credentials.
448 %\item Opaque and non-intuitive due to the above.
449 \end{description}
452 %\chapter{The new authorization framework}
453 %\chapter{The EES Execution Framework}
454 \pagebreak
455 \section{Argus: the new authorization framework}
456 \subsection{Motivation}
457 Argus aims to improve interoperability between Grid services.
458 It is designed to be more modular than SCAS, and should be able to handle new use cases.
459 The interaction between systems is similar at a high level, but the Argus framework separates the roles and tasks as performed by the SCAS system into more granular, more abstract services.
460 %, like what, why and how?
461 % Abstracter, meerdere componenten. duidelijke rolverdeling
462 % Waarom waarom waarom???
463 %
465 \subsection{Components of the Argus framework}
466 %\section{Architecture of the Argus Authorization Services}
467 \begin{figure}[hp]
468 \centering
469 \includegraphics[width=\textwidth]{argus}
470 \caption[Argus diagram]
471 {A diagram showing the architecture of Argus authorization framework}
472 \label{fig:argus}
473 \end{figure}
475 \subsubsection{Policy Enforcement Point (PEP)}
476 The \textit{Policy Enforcement Point} is the client to the authorization service.
477 It generates an authorization request and forwards it to the PDP for evaluation.
478 The PDP responds with a decision, and a set of obligations the PEP must fulfil.
479 %krijgt een beslissing terug, met obligations die 'ie moet verwerken
481 \subsubsection{Policy Decision Point (PDP)}
482 The \textit{Policy Decision Point} is a policy evaluation engine.
483 The PDP receives authorization requests from Policy Enforcement Points and evaluates these requests against authorization policies retrieved from the PAP.
484 It returns its response to the PEP
486 %antwoord wordt teruggegeven aan een PEP
488 \subsubsection{Policy Administration Point (PAP)}
489 The \textit{Policy Administration Point} provides tools to author, store and manage authorization policies.
490 This service can interact with other PAPs, and can combine external policies with local ones.
491 Interaction with other PAPs can be useful to coordinate policies in dealing with security issues.
492 It provides managed policies to other authorization service components, such as the PDP.
494 % interact met externe (andere PAP's). (Bijv OSCT)
495 % Externe policies kan 'ie combineren met de lokale policies
497 \subsubsection{Execution Environment Service (EES)}
498 The \textit{Execution Environment Service}.
499 The role of the EES is to ensure that an appropriate site-specific execution environment is procured based on the site-agnostic obligations and attributes it receives as input in the form of SAML2-XACML2 requests.
500 It responds to requests from the PDP.
501 It should be able to interact with many kinds of services and systems, for instance:
502 \begin{itemize}
503 \item Mapping users to pool accounts on Unix systems
504 \item Submitting jobs to the Maui queue
505 \item Procuring a VM environment through a virtualization framework
506 \item Executing arbitrary scripts local to the site
507 \end{itemize}
510 % interacties met andere dingen
511 % Pool account mapping
512 % Maui queue
513 % VM procurement
514 % OpenNebula
515 % arbitrary script execution
517 %\subsection{Policy Information Point (PIP)}
518 %The \textit{Policy Information Point} ...
520 \glossary{name={EES}, description={Execution Environment Service}}
521 \nomenclature{EES}{Execution Environment Service}
523 \glossary{name={PDP}, description={Policy Decision Point}}
524 \nomenclature{PDP}{Policy Decision Point}
526 \glossary{name={PAP}, description={Policy Administration Point}}
527 \nomenclature{PAP}{Policy Administration Point}
529 \glossary{name={PIP}, description={Policy Information Point}}
530 \nomenclature[]{PIP}{Policy Information Point}

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