Security on Grid: User Interface, Internals and APIs Simone Campana LCG Experiment Integration and Support CERN IT.

Security on Grid: User Interface, Internals and APIs Simone Campana LCG Experiment Integration and Support CERN IT

First Latinamerican Grid Workshop, Merida (VE) – 15-20 November 2004 - 2 Overview Glossary Encryption Symmetric algorithms Asymmetric algorithms: PKI Certificates Digital Signatures X509 certificates Grid Security Basic concepts Grid Security Infrastructure Proxy certificates Command line interfaces Virtual Organisation Concept of VO and authorization VOMS, LCAS, LCMAPS C/C++ interfaces (GSS-API, GSS Assist)

First Latinamerican Grid Workshop, Merida (VE) – 15-20 November 2004 - 4 Glossary Principal An entity: a user, a program, or a machine Credentials Some data providing a proof of identity Authentication Verify the identity of the principal Authorization Map an entity to some set of privileges Confidentiality Encrypt the message so that only the recipient can understand it Integrity Ensure that the message has not been altered in the transmission Non-repudiation Impossibility of denying the authenticity of a digital signature

First Latinamerican Grid Workshop, Merida (VE) – 15-20 November 2004 - 5 Overview Glosary Encryption Symmetric algorithms Asymmetric algorithms: PKI Certificates Digital Signatures X509 certificates Grid Security Basic concepts Grid Security Infrastructure Proxy certificates Command line interfaces Virtual Organisation Concept of VO and authorization VOMS, LCAS, LCMAPS C/C++ interfaces (GSS-API, GSS Assist)

First Latinamerican Grid Workshop, Merida (VE) – 15-20 November 2004 - 6 Cryptography Mathematical algorithm that provides important building blocks for the implementation of a security infrastructure Symbology 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 Symmetric Symmetric: K 1 = K 2 Asymmetric Asymmetric: K 1 ≠ K 2 K2K2 K1K1 Encryption Decryption MCM

First Latinamerican Grid Workshop, Merida (VE) – 15-20 November 2004 - 7 Public Key Infrastructure Provides authentication, integrity, confidentiality, non-repudiation Asymmetric encryption Digital signatures A hash derived from the message and encrypted with the signer’s private key Signature checked decrypting with the signer’s public key Allows key exchange in an insecure medium using a trust mode Keys trusted only if signed by a trusted third party (Certification Authority) A CA certifies that a key belongs to a given principal Certificate Public key + principal information + CA signature X.509 format most used PKI used by SSL, PGP, WS security, S/MIME, etc. Encrypted text Private Key Public Key Clear text message

First Latinamerican Grid Workshop, Merida (VE) – 15-20 November 2004 - 8 Symmetric Algoritms The same key is used for encryption and decryption Advantages: Fast Disadvantages: how to distribute the keys? the number of keys is O(n 2 ) Examples: DES 3DES Rijndael (AES) Blowfish Kerberos AB ciao3$rciao AB 3$rciao3$r

First Latinamerican Grid Workshop, Merida (VE) – 15-20 November 2004 - 9 Public Key Algorithms Every user has two keys: one private and one public: it is impossible to derive the private key from the public one; a message encrypted by one key can be decripted only by the other one. No exchange of secrets is necessary 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: Diffie-Helmann (1977) RSA (1978) B’s keys public private A’s keys publicprivate AB ciao3$rciao AB cy7ciao 3$r cy7

First Latinamerican Grid Workshop, Merida (VE) – 15-20 November 2004 - 11 One-Way Hash Functions Functions (H) that given as input a variable-length message (M) produce as output a string of fixed length (h) the length of h must be at least 128 bits (to avoid birthday attacks) 1. given M, it must be easy to calculate H(M) = h 2. given h, it must be difficult to calculate M = H -1 (h) 3. given M, it must be difficult to find M’ such that H(M) = H(M’) Examples: SNEFRU: hash of 128 or 256 bits; MD4/MD5: hash of 128 bits; SHA (Standard FIPS): hash of 160 bits.

First Latinamerican Grid Workshop, Merida (VE) – 15-20 November 2004 - 12 Digital Signature A calculates the h hh hash of the message A encrypts the hash using his private key: the encrypted hash is the d dd digital signature. A sends the signed message to B. B calculates the hash of the message and v vv verifies it with the one received by A and decyphered with A’s p pp public key. If the two hashes are equal, the message wasn’t modified and A cannot repudiate it. B This is some message Digital Signature A This is some message Digital Signature This is some message Digital Signature Hash(A) A’s keys publicprivate Hash(B) Hash(A) = ?

First Latinamerican Grid Workshop, Merida (VE) – 15-20 November 2004 - 13 Digital Certificates A’s digital signature is safe if: 1. A’s private key is not compromised 2. B knows A’s public key How can B be sure that A’s public key is really A’s public key and not someone else’s? A third party guarantees the correspondence between public key and owner’s identity, by signing a document which contains the owner’s identity and his public key (Digital Certificate) Both A and B must trust this third party Two models: X.509: hierarchical organization; PGP: “web of trust”.

First Latinamerican Grid Workshop, Merida (VE) – 15-20 November 2004 - 14 PGP “web of trust” A B C D E F 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.

First Latinamerican Grid Workshop, Merida (VE) – 15-20 November 2004 - 15 X.509 Certification Authority The “third party” is called Certification Authority (CA). Issue certificates for users, programs and machines Check the identity and the personal data of the requestor Registration Authorities (RAs) do the actual validation CA’s periodically publish a list of compromised certificates Certificate Revocation Lists (CRL) They contain all the revoked certificates yet to expire Online Certificate Status Protocol (OCSP). CA certificates are self-signed

First Latinamerican Grid Workshop, Merida (VE) – 15-20 November 2004 - 16 X.509 Certificates An X.509 Certificate contains: owner’s public key; identity of the owner; info on the CA; time of validity; Serial number; digital signature of the CA Public key Subject:C=CH, O=CERN, OU=GRID, CN=Andrea Sciaba 8968 Issuer: C=CH, O=CERN, OU=GRID, CN=CERN CA Expiration date: Aug 26 08:08:14 2005 GMT Serial number: 625 (0x271) CA Digital signature Structure of a X.509 certificate

First Latinamerican Grid Workshop, Merida (VE) – 15-20 November 2004 - 18 GRID Security: the players Large and dynamic population Different accounts at different sites Personal and confidential data Heterogeneous privileges (roles) Desire Single Sign-On Users “Group” data Access Patterns Membership “Groups” Sites Heterogeneous Resources Access Patterns Local policies Membership Grid

First Latinamerican Grid Workshop, Merida (VE) – 15-20 November 2004 - 19 The Risks Launch attacks to other sites Large distributed farms of machines Illegal or inappropriate data distribution and access sensitive information Massive distributed storage capacity Disruption by exploiting security holes Complex, heterogeneous and dynamic environment Damage caused by viruses, worms etc. Highly connected and novel infrastructure

First Latinamerican Grid Workshop, Merida (VE) – 15-20 November 2004 - 20 The Grid Security Infrastructure (GSI) every user/host/service has an X.509 certificate; certificates are signed by trusted (by the local sites) CA’s; every Grid transaction is mutually authenticated: 1. A sends his certificate; 2. B verifies signature in A’s certificate; 3. B sends to A a challenge string; 4. A encrypts the challenge string with his private key; 5. A sends encrypted challenge to B 6. B uses A’s public key to decrypt the challenge. 7. B compares the decrypted string with the original challenge 8. If they match, B verified A’s identity and A can not repudiate it. A B A’s certificate Verify CA signature Random phrase Encrypt with A’ s private key Encrypted phrase Decrypt with A’ s public key Compare with original phrase Based on X.509 PKI: VERY IMPORTANT Private keys Private keys must be stored only: protected in protected placesAND encrypted in encrypted form

First Latinamerican Grid Workshop, Merida (VE) – 15-20 November 2004 - 21 Certificate request … more details Egee/LCG recognizes a given set of CAs https://lcg-registrar.cern.ch/pki_certificates.html How do you request a certificate depends on your CA The certificate request is created together with the certificate private key (encrypted by a pass phrase) For GILDA, have a look at the Demo Video: https://gilda.ct.infn.it/video/Certification/Allproxy.html (Flash) https://gilda.ct.infn.it/video/Certification/Allproxy.html https://gilda.ct.infn.it/video/Certification/AllCertproxy.ram (Real) https://gilda.ct.infn.it/video/Certification/AllCertproxy.ram

First Latinamerican Grid Workshop, Merida (VE) – 15-20 November 2004 - 22 Certificate Request Private Key encrypted on local disk Cert Request Public Key ID Cert User generates public/private key pair. User send public key to CA along with proof of identity. CA confirms identity, signs certificate and sends back to user.

First Latinamerican Grid Workshop, Merida (VE) – 15-20 November 2004 - 23 Certificate Information To get cert information run grid-cert-info [scampana@grid019:~]$ grid-cert-info -subject /C=CH/O=CERN/OU=GRID/CN=Simone Campana 7461 Options for printing cert information -all-startdate -subject-enddate -issuer-help

First Latinamerican Grid Workshop, Merida (VE) – 15-20 November 2004 - 24 X.509 Proxy Certificate GSI extension to X.509 Identity Certificates signed by the normal end entity cert (or by another proxy). Enables single sign-on Support some important features Delegation Mutual authentication Has a limited lifetime (minimized risk of “compromised credentials”) It is created by the grid-proxy-init command: % grid-proxy-init Enter PEM pass phrase: ****** Options for grid-proxy-init: -hours -bits -help

First Latinamerican Grid Workshop, Merida (VE) – 15-20 November 2004 - 25 grid-proxy-init 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 Private Key (Encrypted) Pass Phrase User Proxy certificate file Proxy placed in /tmp, read-only by user 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!

First Latinamerican Grid Workshop, Merida (VE) – 15-20 November 2004 - 26 Proxy again … grid-proxy-init ≡ “login to the Grid” To “logout” you have to destroy your proxy: grid-proxy-destroy This does NOT destroy any proxies that were delegated from this proxy. You cannot revoke a remote proxy Usually create proxies with short lifetimes To gather information about your proxy: grid-proxy-info Options for printing proxy information -subject-issuer -type-timeleft -strength-help

First Latinamerican Grid Workshop, Merida (VE) – 15-20 November 2004 - 27 Delegation and limited proxy Delegation = remote creation of a (second level) proxy credential New key pair generated remotely on server Clients signs proxy cert and returns it Allows remote process to authenticate on behalf of the user Remote process “impersonates” the user The client can elect to delegate a “limited proxy” Each service decides whether it will allow authentication with a limited proxy Job manager service requires a full proxy GridFTP server allows either full or limited proxy to be used

First Latinamerican Grid Workshop, Merida (VE) – 15-20 November 2004 - 28 Long term proxy Proxy has limited lifetime (default is 12 h) Bad idea to have longer proxy However, a grid task might need to use a proxy for a much longer time Grid jobs in HEP Data Challenges on LCG last up to 2 days myproxy server: Allows to create and store a long term proxy certificate: myproxy-init -s -d -n -s: specifies the hostname of the myproxy server -d: server to use the subject of the certificate as the default username -n: avoids the use of a passphrase to access to the long-term proxy –so the WMS can perform the renewals automatically. myproxy-get-delegation -s Get a new proxy from the MyProxy server myproxy-destroy A dedicated service on the RB can renews automatically the proxy contacts the myproxy server

First Latinamerican Grid Workshop, Merida (VE) – 15-20 November 2004 - 29 GSI environment variables User certificate files: Certificate:X509_USER_CERT (default: $HOME/.globus/usercert.pem ) Private key:X509_USER_KEY (default: $HOME/.globus/userkey.pem ) Proxy:X509_USER_PROXY (default: /tmp/x509up_u ) Host certificate files: Certificate:X509_USER_CERT (default: /etc/grid-security/hostcert.pem ) Private key:X509_USER_KEY (default: /etc/grid-security/hostkey.pem ) Trusted certification authority certificates: X509_CERT_DIR(default: /etc/grid-security/certificates )

First Latinamerican Grid Workshop, Merida (VE) – 15-20 November 2004 - 31 Virtual Organizations and authorization Grid users MUST belong to Virtual Organizations What we previously called “Groups” Sets of users belonging to a collaboration List of supported VOs: https://lcg-registrar.cern.ch/virtual_organization.html VOs maintain a list of their members The list is downloaded by Grid machines to map user certificate subjects to local “pool” accounts Sites decide which VOs to accept... "/C=CH/O=CERN/OU=GRID/CN=Simone Campana 7461".dteam "/C=CH/O=CERN/OU=GRID/CN=Andrea Sciaba 8968".cms "/C=CH/O=CERN/OU=GRID/CN=Patricia Mendez Lorenzo-ALICE".alice... /etc/grid-security/grid-mapfile

First Latinamerican Grid Workshop, Merida (VE) – 15-20 November 2004 - 32 On the side: user Registration in a VO Import your certificate in your browser If you received a.pem certificate you need to convert it to PKCS12 Use openssl command line (available in each egee/LCG UI) openssl pkcs12 –export –in usercert.pem –inkey userkey.pem –out my_cert.p12 –name ’My Name’ Sign the usage guidelines for the VO You will be registered in the VO-LDAP server (wait for notification) Gilda (and other VO): You receive already a PKCS12 certificate (can import it directly into web browser) For future use, you will need usercert.pem and userkey.pem in a directory ~/.globus on your UI Export the PKCS12 cert to a local dir on UI and use again openssl: openssl pkcs12 -nocerts -in my_cert.p12 -out userkey.pem openssl pkcs12 -clcerts -nokeys -in my_cert.p12 -out usercert.pem

First Latinamerican Grid Workshop, Merida (VE) – 15-20 November 2004 - 33 VOMS, LCAS, LCMAPS Virtual Organization Membership Service Extends the proxy info with VO membership, group, role and capabilities Local Centre Authorization Service (LCAS) Checks if the user is authorized (currently using the grid-mapfile) Checks if the user is banned at the site Checks if at that time the site accepts jobs Local Credential Mapping Service (LCMAPS) Maps grid credentials to local credentials (eg. UNIX uid/gid, AFS tokens, etc.) Currently uses the grid-mapfile (based only on certificate subject) In the near future will map also VOMS group and roles "/VO=cms/GROUP=/cms".cms "/VO=cms/GROUP=/cms/prod".cmsprod "/VO=cms/GROUP=/cms/prod/ROLE=manager".cmsprodman

First Latinamerican Grid Workshop, Merida (VE) – 15-20 November 2004 - 35 Security APIs in egee/LCG Currently, there are no API developed specifically by egee/LCG The existing API come from other projects Authentication Globus GSS-API, GSS Assist, COG Kits Authorization LCAS plugins LCMAPS plugins VOMS API The documentation is generally poor Some development is on the way. Check CHEP 2004: http://indico.cern.ch/contributionDisplay.py?contribId=78&sessionId =23&confId=0

First Latinamerican Grid Workshop, Merida (VE) – 15-20 November 2004 - 36 API: GSS-API and GSS Assist GSS-API (Generic Security Services Application Programming Interface) is a generic API for client-server authentication (RFC-2743, 2744) Traditionally, interfaces to Kerberos Globus interfaced it to GSI Communication is kept separate Unfortunately, rather complicated to use GSS-API as user interface to GSI C API Java API The Globus GSS Assist routines are designed to simplify the use of the GSSAPI

First Latinamerican Grid Workshop, Merida (VE) – 15-20 November 2004 - 37 GSS-API 1.The client initiates a context and prepares a token for the server 2.The token is sent to the server 3.The server interprets the token and prepares a new one to be sent to the client 4.The token is sent to the client 5. Iterate process until authentication process succeeds or fails 1.The client wraps a message for the server and sends it 2.The server receives the message and unwraps it 3. The server sends a confirmation message to the client (MIC) 4.The client verifies the MIC

First Latinamerican Grid Workshop, Merida (VE) – 15-20 November 2004 - 38 GSS-API data types Integers OM_uint32 Strings typedef struct gss_buffer_struct { size_tlength; void*value; } gss_buffer_desc, *gss_buffer_t Names gss_name_t OIDs typedef struct gss_OID_desc_struct { OM_uint32length; void*value; } gss_OID_desc, *gss_OID OID sets typedef struct gss_set_desc_struct { size_tcount; gsss_OIDelements; } gss_OID_set_desc, *gss_OID_set Credentials gss_cred_id_t Contexts gss_ctx_id_t

First Latinamerican Grid Workshop, Merida (VE) – 15-20 November 2004 - 39 More on data types Strings are used for character strings and tokens Names are an opaque representation of a principal Object Identifiers (OIDs) are used for Security mechanisms Quality of Protection (QOP) values Name types GSS_C_NT_HOSTBASED_SERVICE (service@host) GSS_C_NT_USER_NAME (username) Etc. GSS_C_NO_OID for default or null value Status codes OM_uint32 major-status: generic GSS-API routine errors OM_uint32 minor-status: mechanism-specific errors Tokens Context level tokens: used for context establishment Per-message tokens: used for data protection (cryptographic tag, encrypted message)

First Latinamerican Grid Workshop, Merida (VE) – 15-20 November 2004 - 40 Name manipulation Convert a string to a name and vice versa gss_import_name(), gss_display_name() Compare, duplicate names gss_compare_name(), gss_duplicate_name() Generate a Mechanism Name, a mechanism-specific representation of a name gss_canonicalize_name() Export a MN in a format suitable for comparison gss_export_name Destroy a name gss_release_name()

First Latinamerican Grid Workshop, Merida (VE) – 15-20 November 2004 - 41 Credential management Acquire an existing credential by name gss_acquire_cred() If name is GSS_C_NO_NAME, default credential is used Obtain information about a credential gss_inquire_cred(), gss_inquire_cred_by_mech() name, lifetime, usage (INITIATE, ACCEPT, BOTH), mechanisms supported Destroy a credential handle gss_release_cred()

First Latinamerican Grid Workshop, Merida (VE) – 15-20 November 2004 - 42 Context management Establish a secure context gss_init_sec_context(), gss_accept_sec_context() Retrieve residual duration or other info about context gss_context_time(), gss_inquire_context() Export a context from a process to another by means of an interprocess token gss_export_sec_context(), gss_import_sec_context() Destroy a secure context gss_delete_sec_context

First Latinamerican Grid Workshop, Merida (VE) – 15-20 November 2004 - 43 Confidentiality and integrity Generate a cryptographic message integrity code (MIC) for a message to transfer to the peer application gss_get_mic() Verify the received message against the received MIC gss_verify_mic() Embed the MIC in the (possibly encrypted) message gss_wrap() (possibly decrypt and) verify the embedded MIC gss_unwrap()

First Latinamerican Grid Workshop, Merida (VE) – 15-20 November 2004 - 44 Globus extensions Credential import and export To pass credentials from a process to another or storing them Export to 1) an opaque buffer, or 2) a file in GSI native format gss_import_cred(), gss_export_cred() Delegation at any time A lot more flexible than standard GSS-API delegation Delegation at times other than context establishment Possible to delegate credentials different than those used for context establishment: even for different mechanisms! –Ex.: delegate a Kerberos credential over a context established with GSI gss_init_delegation(), gss_accept_delegation()

First Latinamerican Grid Workshop, Merida (VE) – 15-20 November 2004 - 45 GSS Assist Simpler functions for Credential handle creation major_status = globus_gss_assist_acquire_cred(&minor_status, GSS_C_INITIATE, /* or GSS_C_ACCEPT */ &credential_handle); Context establishment major_status = globus_gss_assist_init_sec_context(&minor_status, credential_handle, &context_handle, (char *) server_princ, GSS_C_DELEG_FLAG|GSS_C_MUTUAL_FLAG, &ret_flags, &token_status, globus_gss_assist_token_get_fd, (void *) &socket_fd, globus_gss_assist_token_send_fd, (void *) &socket_fd); Little documentation http://www.globus.org/security/gss_assist.html Pointers to functions to send and receive tokens using sockets

First Latinamerican Grid Workshop, Merida (VE) – 15-20 November 2004 - 46 The Risks http://proj-lcg-security.web.cern.ch/proj-lcg-security/RiskAnalysis/risk.html

First Latinamerican Grid Workshop, Merida (VE) – 15-20 November 2004 - 47 Further Information Grid LCG Security: http://proj-lcg-security.web.cern.ch/proj-lcg-security/ LCG Registration: http://lcg-registrar.cern.ch / Globus Security: http://www.globus.org/security/Background GGF Security: http://www.gridforum.org/security/ GSS-API: http://www.faqs.org/faqs/kerberos-faq/general/section-84.htmlhttp://www.faqs.org/faqs/kerberos-faq/general/section-84.html GSS-API: http://docsun.cites.uiuc.edu/sun_docs/C/solaris_9/SUNWdev/GSSAPIPG/toc.html IETF PKIX charter: http://www.ietf.org/html.charters/pkix-charter.html PKCS: http://www.rsasecurity.com/rsalabs/pkcs/index.html

Security on Grid: User Interface, Internals and APIs Simone Campana LCG Experiment Integration and Support CERN IT.

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Security on Grid: User Interface, Internals and APIs Simone Campana LCG Experiment Integration and Support CERN IT.

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