Security on Grid: Simone Campana LCG Experiment Integration and Support CERNIT INFNCNAF

1
Security on Grid Simone CampanaLCG
Experiment Integration and Support CERN-IT /
INFN-CNAF
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)

3
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)

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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

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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)

6
Cryptography
K1
K2
Encryption
Decryption
M
C
M

• Mathematical algorithm that provides important
  building blocks for the implementation of a
  security infrastructure
• Symbology
• Plaintext M
• Cyphertext C
• Encryption with key K1 E K1(M) C
• Decryption with key K2 D K2(C) M
• Algorithms
• Symmetric K1 K2
• Asymmetric K1 ? K2

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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(n2)
• Examples
• DES
• 3DES
• Rijndael (AES)
• Blowfish
• Kerberos

Paul
John
ciao
3r
ciao
3r
Paul
John
ciao
3r
ciao
3r
8
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)

Paul
John
ciao
3r
ciao
3r
Paul
John
ciao
cy7
ciao
cy7
John keys
Paul keys
private
public
private
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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)

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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)
• given M, it must be easy to calculate H(M) h
• given h, it must be difficult to calculateM
  H-1(h)
• 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.

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Digital Signature

• 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.
• John calculates the hash of the message and
  verifies it with the one received by A and
  decyphered with As public key.
• If hashes equal message wasnt modified Paul
  cannot
• repudiate it.

Paul
This is some message
Hash(A)
Digital Signature
John
Hash(B)
Hash(A)
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Digital Certificates

• Pauls digital signature is safe if
• Pauls private key is not compromised
• John knows Pauls public key
• How can John be sure that Pauls public key is
  really Pauls public key and not someone elses?
• A third party guarantees the correspondence
  between public key and owners identity.
• Both A and B must trust this third party
• Two models
• X.509 hierarchical organization
• PGP web of trust.

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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.

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X.509

• The third party is called Certification
  Authority (CA).
• Issue Digital Certificates for users, programs
  and machines
• Check the identity and the personal data of the
  requestor
• Registration Authorities (RAs) do the actual
  validation
• CAs periodically publish a list of compromised
  certificates
• Certificate Revocation Lists (CRL) contain all
  the revoked certificates yet to expire
• CA certificates are self-signed

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X.509 Certificates

• An X.509 Certificate contains
• owners public key
• identity of the owner
• info on the CA
• time of validity
• Serial number
• digital signature of the CA

Structure of a X.509 certificate
Public key
SubjectCCH, OCERN, OUGRID, CNAndrea Sciaba
8968 Issuer CCH, OCERN, OUGRID, CNCERN
CA Expiration date Aug 26 080814 2005
GMT Serial number 625 (0x271)
CA Digital signature
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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)

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GRID Security the players
Grid
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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

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The Grid Security Infrastructure (GSI)
John
Paul
Based on X.509 PKI

• every user/host/service has an X.509 certificate
• certificates are signed by trusted (by the local
  sites) CAs
• every Grid transaction is mutually authenticated
• John sends his certificate
• Paul verifies signature in Johns certificate
• Paul sends to John a challenge string
• John encrypts the challenge string with his
  private key
• John sends encrypted challenge to Paul
• Paul uses Johns public key to decrypt the
  challenge.
• Paul compares the decrypted string with the
  original challenge
• If they match, Paul verified Johns identity and
  John can not repudiate it.

VERY IMPORTANT Private keys must be stored
only in protected places AND in encrypted form
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Certificate request more details

• Egee/LCG recognizes a given set of CAs
• https//lcg-registrar.cern.ch/pki_certificates.htm
  l
• How do you request a certificate depends on your
  CA
• For GILDA, have a look at the Demo Video
• https//gilda.ct.infn.it/video/Certification/Allpr
  oxy.html (Flash)
• https//gilda.ct.infn.it/video/Certification/AllCe
  rtproxy.ram (Real)

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Certificate Request
User generatespublic/privatekey pair.
CA confirms identity, signs certificate and sends
back to user.
CertRequest Public Key
Certification Authority
Cert
Private Key encrypted on local disk
User send public key to CA along with proof of
identity.
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Certificate Information

• To get cert information run grid-cert-info
• scampana_at_grid019 grid-cert-info -subject
• /CCH/OCERN/OUGRID/CNSimone Campana 7461
• Options for printing cert information-all -sta
  rtdate-subject -enddate-issuer -help

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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 ltlifetime of credentialgt
• -bits ltlength of keygt
• -help

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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.
• Users private key not exposed after proxy has
  been signed

• Proxy placed in /tmp
• 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!

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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

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Delegation and limited proxy

• Delegation remote creation of a (second level)
  proxy credential
• New key pair generated remotely on server
• Client 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

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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 lthost_namegt
• -s lthost_namegt specifies the hostname of the
  myproxy server
• myproxy-info
• Get information about stored long living proxy
• myproxy-get-delegation
• Get a new proxy from the MyProxy server
• myproxy-destroy
• Chech out the myproxy-xxx - - help option
• A dedicated service on the RB can renew
  automatically the proxy
• contacts the myproxy server

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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_ultidgt)
• 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/certi
  ficates)

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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)

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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

... "/CCH/OCERN/OUGRID/CNSimone Campana 7461"
.dteam "/CCH/OCERN/OUGRID/CNAndrea Sciaba
8968" .cms "/CCH/OCERN/OUGRID/CNPatricia
Mendez Lorenzo-ALICE" .alice ...
/etc/grid-security/grid-mapfile
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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

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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

"/VOcms/GROUP/cms"
.cms "/VOcms/GROUP/cms/prod"
.cmsprod "/VOcms/GROUP/cms/prod/ROLEmanager"
.cmsprodman
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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)

34
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?contr
  ibId78sessionId23confId0

35
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
• 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

36
GSS-API

• The client initiates a context and prepares a
  token for the server
• The token is sent to the server
• The server interprets the token and prepares a
  new one to be sent to the client
• The token is sent to the client
• Iterate process until authentication process
  succeeds or fails

• The client wraps a message for the server and
  sends it
• The server receives the message and unwraps it
• The server sends a confirmation message to the
  client (MIC)
• The client verifies the MIC

37
GSS-API data types

• Integers OM_uint32
• Strings typedef struct gss_buffer_struct
• size_t length
• void value
• gss_buffer_desc, gss_buffer_t
• Names gss_name_t
• OIDs typedef struct gss_OID_desc_struct
• OM_uint32 length
• void value
• gss_OID_desc, gss_OID
• OID sets typedef struct gss_set_desc_struct
• size_t count
• gsss_OID elements
• gss_OID_set_desc, gss_OID_set
• Credentials gss_cred_id_t
• Contexts gss_ctx_id_t

38
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_at_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)

39
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()

40
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()

41
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

42
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()

43
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()

44
GSS Assist

• Simpler functions for
• Credential handle creation
• major_status globus_gss_assist_acquire_cred(min
  or_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_FLAGGSS_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
45
Further Information

• Grid
• LCG Security http//proj-lcg-security.web.cern.c
  h/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/ge
  neral/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.chart
  ers/pkix-charter.html
• PKCS http//www.rsasecurity.com/rsalabs/pkcs/ind
  ex.html