Università degli Studi di Bari Corso di

Università degli Studi di Bari – Corso di Laurea Specialistica in Informatica “Tecnologia dei Servizi “Grid e cloud computing” A. A. 2009/2010 Giorgio Pietro Maggi giorgio. maggi@ba. infn. it, http: //www. ba. infn. it/~maggi Lezione 5 a - 17 Novembre 2009 Il materiale didattico usato in questo corso è stato mutuato da quello utilizzato da Paolo Veronesi per il corso di Griglie Computazionali per la Laurea Specialistica in Informatica tenuto nell’anno accademico 2008/09 presso l’Università degli Studi di Ferrara. Paolo Veronesi paolo. veronesi@cnaf. infn. it, pveronesi@unife. it http: //www. cnaf. infn. it/~pveronesi/unife/ Tecnologia dei Servizi “Grid e cloud computing” - Lezione 005 a 0

Overview Globus Toolkit V 4. 0 p Introduction to Security p n Fundamental Concepts Authentication p Basic Cryptography p Digital Signature p Public Key Infrastructures (PKIs) p Proxies and Temporary Credentials p Tecnologia dei Servizi “Grid e cloud computing” - Lezione 005 a 1

Execution Management • Job description & submission • Scheduling • Resource provisioning Data Services • Common access facilities • Efficient & reliable transport • Replication services Resource Management Self-Management • Discovery • Monitoring • Control • Self-configuration • Self-optimization • Self-healing OGSA Information Services Security • Registry • Notification • Logging/auditing • Cross-organizational users • Trust nobody • Authorized access only OGSA “profiles” Web services foundation Tecnologia dei Servizi “Grid e cloud computing” - Lezione 005 a 2

From SOA to Grid middleware OASIS SOA RM SOA Reference Model OGSA WSA extensions GLOBUS Arch g. Lite Arch GLOBUS g. Lite … … Tecnologia dei Servizi “Grid e cloud computing” - Lezione 005 a 3

Globus is Service-Oriented Infrastructure Technology p Software for service-oriented infrastructure n n n p Tools to build applications that exploit service-oriented infrastructure n p Registries, security, data management, … Open source & open standards n n p Service enable new & existing resources E. g. , GRAM on computer, Grid. FTP on storage system, custom application service Uniform abstractions & mechanisms Each empowers the other eg – monitoring across different protocols is hard Enabler of a rich tool & service ecosystem Tecnologia dei Servizi “Grid e cloud computing” - Lezione 005 a 4

Globus Toolkit V 4. 0 p p Major release on April 29 th 2005 Precious fifteen months spent on design, development, and testing n n n p 1. 8 M lines of code Major contributions from five institutions Hundreds of millions of service calls executed over weeks of continuous operation Significant improvements over GT 3 code base in all dimensions Tecnologia dei Servizi “Grid e cloud computing” - Lezione 005 a 5

Goals for GT 4 p Usability, reliability, scalability, … n n p Consistency with latest standards (WS-*, WSRF, WS-N, etc. ) and Apache platform n p Web service components have quality equal or superior to pre-WS components Documentation at acceptable quality level WS-I Basic (Security) Profile compliant New components, platforms, languages n And links to larger Globus ecosystem Tecnologia dei Servizi “Grid e cloud computing” - Lezione 005 a 6

Griglie Computazionali - Lezione 005 Tecnologia dei Servizi “Grid e cloud computing” - Lezione 005 a 7 7

Glossary p Principal n p Credentials n p Encrypt the message so that only the recipient can understand it Integrity n p Map an entity to some set of privileges Confidentiality n p Verify the identity of the principal Authorization n p Some data providing a proof of identity Authentication n p An entity: a user, a program, or a machine Ensure that the message has not been altered in the transmission Non-repudiation n Impossibility of denying the authenticity of a digital signature Tecnologia dei Servizi “Grid e cloud computing” - Lezione 005 a 8

Introduction to Security Tecnologia dei Servizi “Grid e cloud computing” - Lezione 005 a 9

Security is a process p A risk is n n p a vulnerability and a threat Organizations implement controls over their activities to obtain acceptable residual risk Tecnologia dei Servizi “Grid e cloud computing” - Lezione 005 a 10

Risk-based view of the world p Organizations: Sites, VOs and Grids n n p Each organization is captain of its own ship n p Each has a security process lifecycle Satisfaction jointly and severally However, constrained to interoperate Standards aid interoperation Tecnologia dei Servizi “Grid e cloud computing” - Lezione 005 a 11

Secure from Whom and Against What p Secure from whom? n n p From systems administrator? From rogue employee? Mr. H. Acker…? Secure against what? n n Denial of Service? Identity theft? Legally sensitive data acquisition? Or even MPs leaving laptops on the Tube… Tecnologia dei Servizi “Grid e cloud computing” - Lezione 005 a 12

Secure for how long? n “I recommend overwriting a deleted file seven times: the first time with all ones, p the second time with all zeros, p and five times with a cryptographically secure pseudo-random sequence. p n n Recent developments at the National Institute of Standards and Technology with electron-tunnelling microscopes suggest even that might not be enough. Honestly, if your data is sufficiently valuable, assume that it is impossible to erase data completely off magnetic media. Burn or shared media; it's cheaper to buy media new than to lose your secrets…. " § -Applied Cryptography 1996, page 229 Tecnologia dei Servizi “Grid e cloud computing” - Lezione 005 a 13

Secure Technology vs. Secure System p Secure technology ≠ secure system n System using 2048+ bit encryption technology, packet filtering firewalls, PMIs, PKIs… …. on running laptop in unlocked room p … on PC with password on “post-it” on screen/desk p We have heard worse than this, naming no names! p Tecnologia dei Servizi “Grid e cloud computing” - Lezione 005 a 14

A Quote p “…if you think that technology can solve your security problems then you don’t know enough about the technology, and worse you don’t know what your problems are…” § Bruce Schneier, Secrets and Lies in a Digital Networked World Tecnologia dei Servizi “Grid e cloud computing” - Lezione 005 a 15

Definition: Computer Security p “The protection afforded to an automated information system in order to attain the applicable objectives of preserving the integrity, p availability p and confidentiality p n of information system resources (includes hardware, software, firmware, information/data, and telecommunications)” § § Tecnologia dei Servizi “Grid e cloud computing” - Lezione 005 a An Introduction to Computer Security The NIST Handbook 16

Fundamentals p Key terms that are typically associated with security n n n n p Authentication Authorisation Audit/accounting Integrity Fabric Management Confidentiality Privacy Trust All are important for Grids but some applications may have more emphasis on certain concepts than others Tecnologia dei Servizi “Grid e cloud computing” - Lezione 005 a 17

Fundamentals - Authentication p the establishment and safe propagation of a user’s identity in the system n e. g. site X can check that user Y is attempting to gain access to resources p p p does not check what user is allowed to do, only that we know (and can check!) who they are Masquerading always a danger (and realistic possibility) Need for user guidance on security § § n p Password selection Treatment of certificates Hardware tokens … Is anonymity required? Authentication on the Grid is achieved with Public Key Infrastructures (PKIs) Tecnologia dei Servizi “Grid e cloud computing” - Lezione 005 a 18

Fundamentals - Authorisation p concerned with controlling access to services based on policy n n Can this user invoke this service making use of this data? Complementary to authentication p p Many different contenders for authorisation infrastructures n e. g: some software components related to authorization aspects developed as open source projects: p p p Know it is this user, now can we restrict/enforce what they can/cannot do PERMIS VOMS CAS AKENTI Authorisation on the Grid must be scalable Tecnologia dei Servizi “Grid e cloud computing” - Lezione 005 a 19

Fundamentals - Auditing p Auditing/Accounting n the analysis of records of account (e. g. security event logs) to investigate security events, procedures or the records themselves p Includes logging, intrusion detection and auditing of security in managed computer facilities § well established in theory and practice § Grid computing adds the complication that some of the information required by a local audit system may be distributed elsewhere, or may be obscured by layers of indirection § e. g. Grid service making use of federated data resource where data kept and managed remotely p Need tools to support diagnostics § Do we need to log all information? (Can We? More pertinent probably) § How long do we keep it for? § … n Auditing tools are in development for some authorisation infrastructures Tecnologia dei Servizi “Grid e cloud computing” - Lezione 005 a 20

Fundamentals - Integrity p Integrity n Ensuring that data is not modified since it was created, typically of relevance when data is sent over public network p Technical solutions exist to maintain the integrity of data in transit § checksums, PKI support, … p Grid also raises more general questions § e. g. provenance § maintaining the integrity of chains or groups of related data p Integrity can be checked through the use of digital signatures Tecnologia dei Servizi “Grid e cloud computing” - Lezione 005 a 21

Fundamentals - Fabric Management p Fabric Management n consists of the distributed computing, network resources and associated connections that support Grid applications p impacts Grid security in these ways: § an insecure fabric may undermine the security of the Grid § Are all sites fully patched (middleware/OS)? § Can we limit damage of virus infected machine across Grid? § Identify it, quarantine it, anti-virus update/patch, re-instate into VO, … § fabric security measures may impede grid operations § e. g. firewalls may be configured to block essential Grid traffic Tecnologia dei Servizi “Grid e cloud computing” - Lezione 005 a 22

Fundamentals - Confidentiality p is concerned with ensuring that information is not made available to unauthorised individuals, services or processes n It is usually supported by access control within systems, and encryption between systems p Confidentiality is generally well understood, but the Grid introduces the new problem of transferring or signalling the intended protection policy when data staged between systems p Authentication and Authorisation infrastructures usually implement confidentiality, so we are already there! Tecnologia dei Servizi “Grid e cloud computing” - Lezione 005 a 23

Fundamentals - Privacy p particularly significant for projects processing personal information, or subject to ethical restrictions n p e. g. projects dealing with medical, health data Privacy requirements relate to the use of data, in the context of consent established by the data owner n n Privacy is therefore distinct from confidentiality, although it may be supported by confidentiality mechanisms. Grid technology needs a transferable understanding of suitable policies addressing privacy requirements/constraints p Should allow to express how such policies can be § § defined, applied, implemented, enforced, … Tecnologia dei Servizi “Grid e cloud computing” - Lezione 005 a 24

Trust p characteristic allowing one entity to assume that a second entity will behave exactly as the first entity expects p Important distinction between ‘trust management’ systems which implement authorisation, and the wider requirements of trust n e. g. health applications require the agreement between users and resources providers of restrictions that cannot be implemented by access control p n e. g. restrictions on the export of software, or a guarantee that personal data is deleted after use therefore a need to understand represent policy agreements between groups of users and resource providers p such policies may exist inside or outside the system, and are typically not supported by technical mechanisms Tecnologia dei Servizi “Grid e cloud computing” - Lezione 005 a 25

Authentication Intro p Basic Cryptography p Digital Signature p PKI p Proxy p Tecnologia dei Servizi “Grid e cloud computing” - Lezione 005 a 26

Who Am I? ? p I am n n n p The President of the United States The Secretary General of the United Nations David Beckham Keith Richards The girl who served your cup of coffee this morning. . All of these people may need to use a computer n How can we confirm their identities? Tecnologia dei Servizi “Grid e cloud computing” - Lezione 005 a 27

Who am I? ? p I am John Watt (allegedly) n To prove it I have p A Driving Licence § I got by passing my test and producing my passport p A Passport § I went to the passport office with my Birth certificate p A Birth Certificate § I can’t remember getting this! Tecnologia dei Servizi “Grid e cloud computing” - Lezione 005 a 28

Who am I? ? p Is there a logical chain working here? n Note that, generally, the credentials given on the previous page tend to depend on the one below it. p But the DVLA (UK Driving Licence Authority) state on their website: § “Note - Birth certificates are not absolute proof of identity and so we may ask you to provide other evidence to allow us to check your identity. ” § What other evidence? A passport? § But that depends on you producing a birth certificate! § A bank account? § You need a passport for that! p NO! Tecnologia dei Servizi “Grid e cloud computing” - Lezione 005 a 29

Who am I? ? p But they do have one thing in common n They are non-local credentials p p They attempt to define a unique (nationally at least) reference that will establish your identity Do we need something similar for the Grid? ? n n First of all, we need to establish how identity can be proved and securely moved around a network. The Grid community are (in principle) in agreement about how this should be done p But first we need to look at the basics of this system, and it has to do with an age old problem… Tecnologia dei Servizi “Grid e cloud computing” - Lezione 005 a 30

Cryptography K 1 M p p C Decryption M Mathematical algorithm that provides important building blocks for the implementation of a security infrastructure Symbology n n p Encryption K 2 Plaintext: M Cyphertext: C Encryption with key K 1 : E K 1(M) = C Decryption with key K 2 : D K 2(C) = M Algorithms n n Symmetric: K 1 = K 2 Asymmetric: K 1 ≠ K 2 Tecnologia dei Servizi “Grid e cloud computing” - Lezione 005 a 31

Basic Cryptography p When I were a lad… n My friend would post an important message through my letterbox… 3 VLR PJBII n But we had ‘code wheels’ Rotate the inner wheel by the number of jumps indicated at the beginning of the message p And translate… p 3 YOU SMELL Tecnologia dei Servizi “Grid e cloud computing” - Lezione 005 a 32

Basic Cryptography p What if someone else got hold of the wheel? n n Our plans for world domination are in ruins Because what makes the wheel work is the extra information included with the original encrypted message: 3 VLR PJBII Without this number the message will stay encrypted This number is the encryption ‘key’ p And is transmitted UNENCRYPTED § We could agree this face-to-face, but why not just give the message then? ? What if I was grounded? (happened a lot) p Lets look at this at a slightly more mature level… Tecnologia dei Servizi “Grid e cloud computing” - Lezione 005 a 33

Symmetric Algoritms p p The same key is used for encryption and decryption Advantages: n p Disadvantages: n n p Fast how to distribute the keys? the number of keys is O(n 2) Examples: n n n DES 3 DES Rijndael (AES) Blowfish Kerberos Tecnologia dei Servizi “Grid e cloud computing” - Lezione 005 a Paul ciao John 3$r Paul ciao 3$r ciao John 3$r ciao 34

Basic Cryptography p We need some way of transmitting the key so it can’t be stolen. n Can we encrypt the key? No, but we can do something analogous… n 1) Split the key into two parts, one for encryption and one for decryption 2) Make the encryption key PUBLIC for anyone to use, but keep your decryption key PRIVATE n p Note that in some implementations the private key may also be used to encrypt and the public key to decrypt (see Digital Signatures) Tecnologia dei Servizi “Grid e cloud computing” - Lezione 005 a 35

Public Key Algorithms p Every user has two keys: one private and one public: n n p No exchange of secrets is necessary n n n p it is impossible to derive the private key from the public one; a message encrypted by one key can be decrypted only by the other one. the sender cyphers using the public key of the receiver; the receiver decripts using his private key; the number of keys is O(n). Examples: n n Paul John ciao 3$r Paul 3$r ciao John ciao cy 7 Paul keys public cy 7 ciao John keys public Diffie-Helmann (1977) RSA (1978) Tecnologia dei Servizi “Grid e cloud computing” - Lezione 005 a 36

Solved the key transmission problem p We have solved the key transmission problem by only transmitting an encryption key n Now anyone who wishes to send you a message uses your PUBLIC key to encrypt it, safe in the knowledge that the only person who can decrypt it is the holder of the PRIVATE key (i. e. you!) n The public and private keys are broken apart according to a complex mathematical formula that means it would take months/years to crack messages without the private key. p Tends to outlive credentials issued (e. g. credit cards) Tecnologia dei Servizi “Grid e cloud computing” - Lezione 005 a 37

Symmetric vs. Asymmetric p Symmetric encryption only guarantees privacy n p Asymmetric encryption can be used to authenticate n p The message is still encrypted, but there is no evidence of who encrypted it, nor any guarantee the data has not been tampered with. By encrypting a message with someone’s public key, you can be sure ONLY they will be able to read it. And… n Some level of integrity may be provided (digital signatures) Tecnologia dei Servizi “Grid e cloud computing” - Lezione 005 a 38

Authentication Intro p Basic Cryptography p Digital Signature p PKI p Proxy p Tecnologia dei Servizi “Grid e cloud computing” - Lezione 005 a 39

One-Way Hash Functions p Functions (H) that given as input a variable-length message (M) produce as output a string of fixed length (h) n n p the length of h must be at least 256 bits given M, it must be easy to calculate H(M) = h given h, it must be difficult to calculate M = H-1(h) given M, it must be difficult to find M’ such that H(M) = H(M’) Examples: n n n SNEFRU: hash of 128 or 256 bits; MD 4/MD 5: hash of 128 bits; now MD 6! SHA (Standard FIPS): hash of 160 bits. Tecnologia dei Servizi “Grid e cloud computing” - Lezione 005 a 40

Ex $cat prova 1 testo di prova $ md 5 sum prova 1 909 adc 30 dcc 15239 ac 640 b 52 d 33 a 12 b 2 prova 1 $ cat prova 2 testo di prove $ md 5 sum prova 2 c 89 ee 15 b 2 f 056 edfbef 2 dcb 62 b 2249 aa prova 2 $ ls -l /bin/ls -rwxr-xr-x 1 root 67700 Dec 9 2005 /bin/ls $ md 5 sum /bin/ls 2636 c 546 ce 5 ca 69687 f 5 dfc 74 cc 3175 e Tecnologia dei Servizi “Grid e cloud computing” - Lezione 005 a /bin/ls 41

Digital Signature p p p Paul calculates the hash of the message Paul encrypts the hash using his private key: the encrypted hash is the digital signature. Paul sends the signed message to John calculates the hash of the message and verifies it with the one received by A and decyphered with A’s public key. If hashes equal: message wasn’t modified; Paul cannot repudiate it. Paul keys Paul This is some Hash(A) Tecnologia dei Servizi “Grid e cloud computing” - Lezione 005 a message Digital Signature John Hash(B) This is some message =? Hash(A) public This is some Digital Signature private 42

Digital Certificates p Paul’s digital signature is safe if: n n p How can John be sure that Paul’s public key is really Paul’s public key and not someone else’s? n n p Paul’s private key is not compromised John knows Paul’s public key A third party guarantees the correspondence between public key and owner’s identity. Both A and B must trust this third party Two models: n n X. 509: hierarchical organization; PGP: “web of trust”. Tecnologia dei Servizi “Grid e cloud computing” - Lezione 005 a 43

PGP “web of trust” D B F C E A • F knows D and E, who knows A and C, who knows A and B. • F is reasonably sure that the key from A is really from A. Tecnologia dei Servizi “Grid e cloud computing” - Lezione 005 a 44

Public Key Infrastructures (PKIs) p PKIs provide a mechanism for privacy, integrity and authentication using public keys n Implemented with DIGITAL CERTIFICATES p n Issued by a CERTIFICATE AUTHORITY p n Your UNIQUE virtualised identity Entity which administers certificates and issues them correctly X. 509 (1988) is the standard for PKI certificates p Binds a globally unique X 500 distinguished name to a public key § In reality, CAs tend to choose any name they want § Legal disclaimer, liability transfer. A mess, but not critical p Web browser compatible Tecnologia dei Servizi “Grid e cloud computing” - Lezione 005 a 45

X. 509 Certificates • An X. 509 Certificate contains: – owner’s public key; Structure of a X. 509 certificate Public key – identity of the owner; Subject: C=CH, O=CERN, OU=GRID, CN=Andrea Sciaba 8968 – info on the CA; Issuer: C=CH, O=CERN, OU=GRID, CN=CERN CA – time of validity; Expiration date: Aug 26 08: 14 2005 GMT Serial number: 625 (0 x 271) – Serial number; CA Digital signature – digital signature of the CA Tecnologia dei Servizi “Grid e cloud computing” - Lezione 005 a 46

Certificate Authorities p A Certificate Authority (CA) is a third party that signs certificates and ensures that the subject name and public key actually belong to that person n How? The old fashioned way… p Example… The INFN Certificate Authority p § Initial contact – application (online) § Credential verification (IN PERSON) § Go to CA or Regional Authority (RA) § Issue – download (online) § INFN CA requires the application and issuing terminals to be the same ( this is where the PRIVATE key of your certificate is) Tecnologia dei Servizi “Grid e cloud computing” - Lezione 005 a 47

Certificate Authorities p A CA may delegate Regional Operators to confirm people’s identities n p CA records a piece of personal identification for their records n p Saves me having to travel from Bologna to Firenze if I want a certificate Passport, Driving Licence, Staff/Student Matric Card CA extends an existing ID infrastructure Tecnologia dei Servizi “Grid e cloud computing” - Lezione 005 a 48

Certificate Authorities p A CA also is in charge of revoking certificates n CA publishes a Certificate Revocation List Download to your browser p Shows all invalid certificates in the organisation p p A CA MUST be explicitly trusted by the system n n Trusted Root CAs list in Windows Certificate cannot be used until the CA’s root certificate has been accepted as trusted p Accepted very much like Software Licences i. e. nearly always! Tecnologia dei Servizi “Grid e cloud computing” - Lezione 005 a 49

Certificate Authenticity p CAs confirm the certificate’s authenticity by digitally signing it n n CA computes a hash of the certificate using an agreed (non-secret) algorithm CA encrypts this hash with their private key and appends to bottom of certificate Recipient computes their own hash of the info Recipient decrypts the hash the CA sent (with the CA’s public key) and compares with their own p Proves the CA signed the info and the info hasn’t been tampered with § Encryption of the info is optional (for privacy) Tecnologia dei Servizi “Grid e cloud computing” - Lezione 005 a 50

A problem p Are there any pitfalls to digital certificates? n Can we alter their contents? p n Can we spoof? p p No, the CA signed the certificate thus ensuring its integrity You will need your own CA, and if the application doesn’t trust it, your certificates won’t work. So no. What can we do? n STEAL IT! Someone who holds your digital certificate (and private key) may safely assume your identity on the Grid p This problem isn’t going away. How can we deal with this? p Tecnologia dei Servizi “Grid e cloud computing” - Lezione 005 a 51

Certificate Revocation Lists p list of serial numbers of the certificates n n n which have been revoked are no longer valid and should not be relied upon by any system user p CRLs are usually signed by the issuing CA and therefore carry a digital signature p Type of revocations: n n Non reversible: a certificate is irreversibly revoked Reversible: the certificate is on hold; p this reversible status can be used to notice the temporary invalidity of the certificate, for instance when the user is not sure if the private key has been lost. Tecnologia dei Servizi “Grid e cloud computing” - Lezione 005 a 52

PKI basics p p PKI provides, among other services, an authentication protocol relying on asymmetric encryption. One of the keys is kept private, the other is made public. Public keys are distributed using certificates which are digitally signed by trusted authorities Clear-text Input Cipher-text “An intro to PKI and few deploy hints” Clear-text Output “Py 75 c%bn&*)9|f De^b. Dzj. F@g 5=& nmd. Fgeg. Ms” Encryption “An intro to PKI and few deploy hints” Decryption Different keys Tecnologia dei Servizi “Grid e cloud computing” - Lezione 005 a 53

PKI: Obtaining a Certificate User generates a key pair Priv Public key is submitted to CA for certification User identity verified, Digital signature added, Certificate produced Alice pub DS Certificate is sent to the user Tecnologia dei Servizi “Grid e cloud computing” - Lezione 005 a Certification Server Cert 54

PKI: Authentication with Certificates Certificate is sent for authentication Alice Bob Alice pub DS DS Cert Bob verifies the digital signature on the certificate Cert &er. D 4%@f. T% Priv I Like Flowers Encrypt using private key ? Decrypt using public key in certificate and compare Tecnologia dei Servizi “Grid e cloud computing” - Lezione 005 a I Like Flowers He can trust that the public key really belongs to Alice, but is it Alice standing if front of him ? Bob challenges Alice to encrypt for him a random phrase he generated 55

Authentication Intro p Basic Cryptography p Digital Signature p PKI p Proxy p Tecnologia dei Servizi “Grid e cloud computing” - Lezione 005 a 56

X. 509 Proxy Certificate p Extension to X. 509 Identity Certificates n signed by the normal end entity cert (or by another proxy) Enables single sign-on p Support p n n p Delegation Mutual authentication Has a limited lifetime n minimized risk of “compromised credentials” Tecnologia dei Servizi “Grid e cloud computing” - Lezione 005 a 57

Creating a proxy p Command: grid-proxy-init n n n User enters pass phrase, which is used to decrypt private key Private key is used to sign a proxy certificate with its own, new public/private key pair. User’s private key not exposed after proxy has been signed User certificate file Pass Phrase l Proxy placed in /tmp l l Private Key (Encrypted) User Proxy certificate file the private key of the Proxy is not encrypted: stored in local file: must be readable only by the owner; proxy lifetime is short (typically 12 h) to minimize security risks. NOTE: No network traffic! Tecnologia dei Servizi “Grid e cloud computing” - Lezione 005 a 58

Delegation and limited proxy p Proxy credential n p Delegation = remote creation of a (second level) proxy credential n n p New key pair generated remotely on server Client signs proxy cert and returns it Allows remote process to authenticate on behalf of the user n p the combination of a proxy certificate and its corresponding private key Remote process “impersonates” the user The client can elect to delegate a “limited proxy” n n n Each service decides whether it will allow authentication with a limited proxy Job manager service requires a full proxy Grid. FTP server allows either full or limited proxy to be used Tecnologia dei Servizi “Grid e cloud computing” - Lezione 005 a 59

CONCLUSION p Security is a combination of technical implementation and sociological behaviour p There can be no overall security policy for the Grid – integrate existing site policies p The establishment of identity on the Grid (authentication) is achieved through the use of PKI Certificates and Proxies Tecnologia dei Servizi “Grid e cloud computing” - Lezione 005 a 60