Future of Credential Management on the Grid

1
Future of Credential Management on the Grid

• Mary Thompson
• DSD Department Meeting
• Oct 16, 2005

2
PKI package

• Elements
• Diffe-Hellman public/private key cryptography
• X.509 public key certificates
• TLS (Transport Layer Security) protocol
• Public/private key crypto vastly simplified key
  distribution for encrypted communications
• Password/private key is known only to holder, no
  trusted third party is involved
• Good for non-repudiation of digital signatures

3
X.509 Public Key Certificates

• Public certificates binding a name to a public
  key, signed by a trusted authority (CA)
• Private (encrypted) keys prove identity
• Used for authentication by relying parties who
  have previously established trust with the CA.
• X.509 standards
• IETF RFC 2459 1999 - X.509 certificate
• IETF RFC 3280 Apr 2002 - X.509 certificate
  (revised)
• IETF RFC 3820 June 2004 - Proxy certificate
  profile

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Advantages over traditional authentication methods

• No on-line 24/7 secure server needed to
  authenticate users.
• Trust is established between relying parties and
  CA by out-of-band methods. RP has copy of CAs
  public key
• TLS use of certificates to provide authenticated,
  encrypted channel between users and servers.

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Problems - Credential Management

• Security of private keys stored by naïve users on
  local workstation is questionable.
• Difficult for relying party to know when a
  private key may have be comprised.
• Portability of private key
• Use of private key varies by application
• Understanding of private/public key crypto by
  users.
• What key to sign with.
• What key to encrypt with.

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Problems - Certificate Revocation

• CRLs
• Relying parties need to get updates regularly
• TLS does not check revocation out-of-the box
• Many applications do not check for revocation
• OCSP - Online Certificate Status Protocol
• Requires secure on-line 24/7 server
• Pretty new, not all CAs provide the service

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Solutions

• Online credential repositories
• Short-term certificates
• Proxy certificates
• EndEntity certificates generated on demand

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Proxy Certificates

• Invented as part of GSI
• Short-term, non encrypted private keys
• User only types passphrase once
• Dont need to worry about revocation
• Safe enough to store read-only to user
• Created by delegation protocol which works
  between parties or by just one party.
• The delegatee
• generates a new key pair
• Presents a certificate signing request (CSR)
  consisting of the new public key and a DN, and
  signed by the private key
• The delegator
• Verifies the certificate request
• Creates a new X.509 cert, flagged as a proxy cert
  and signs it with the EE private key (i.e. acts
  as a CA)

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Proxy Certs (cont)

• If a relying party agrees, the proxy can
  represent the orginal end entity
• Proxy certs may contain a rights restriction
  extension
• Standardized by IETF RFC 3820, June 2004
• Path validation of proxy certs supported in
  OpenSSL 0.9.8 July 2005

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MyProxy

• Intended to store proxy certificates (1-2 week
  life times)
• Traveling Grid user could delegate a proxy to the
  MyProxy server before leaving home (and access to
  his long-term credential)
• Could then delegate short-term (12-hrs) certs
  from MyProxy to other host from which he wanted
  to start a Globus job.
• Also used by Grid Portals to get a certificate on
  behalf of a user and to renew certificates used
  by long running jobs

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Kerberos CA (KCA)

• Developed at Fermi Lab to grant X.509
  certificates to authorized Kerberos users.
• Use site user registry to provide Grid usable
  credentials
• Been in use for a few years.

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Unmet needs

• Fusion Grid
• Get credential management out of users hands
• Decided to wrap classic MyProxy in Web scripts to
  allow requesting and management of long term
  credentials via a grid-integrated Web interface.
• NERSC
• Get automatic certificate generation for all
  their users
• Get a handle on OTP usage
• Pushed for MyProxy to support an on-line CA,
  similar in concept to KCA but not Kerberos based.

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Extensions to MyProxy

• Storing of long term credentials
• Originally only stored by admin interface (run as
  same user on same host)
• Recently it has added a message interface to
  store and retrieve long-term credentials
• Alternative authentication schemes
• Originally - used the passphrase to decrypt the
  stored key, or established off-line trust with
  Portals using PKI.
• Now has added PAM authentication, including
  Kerberos, OTP, system passwords, etc. (done
  independently by Jim Basney and Monte)

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Extensions to MyProxy (cont)

• Includes an on-line CA
• Issues a limited term credential for
  authenticated users. (just released Montes work)
• Provide mapping from user id to DN
• Gridmap files
• LDAP interface (pending - Monte again)

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One Solution - FusionGridCredential repository
for long-term credentials

• User goes through Web interface to register with
  FusionGrid.
• Credential manager gets credential in standard
  way
• Call ESNet run CA to get a certificate
• Certificate request vetted by RA
• CM stores credential in secure MyProxy server
  encrypted with user chosen passphrase
• Users uses credential by retrieving a proxy with
  MyProxy-logon command. (authenticates against
  stored long-term credential)
• Authorized Portals can also retrieve proxies,
  with or without knowing user passphrase
• The MyProxy server a little more user
  information comprises the VOs user registry

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Second Solution - NERSCMyProxy Online CA

• User is already entered in NERSC user base.
• User does a MyProxy-logon to get a proxy
  credential.
• MyProxy authenticates user against a PAM auth
  module of NERSCs choice, e.g. OTP system.
• MyProxy CA module maps user id to DN, via gridmap
  file or LDAP directory and creates limited term
  credential which is stored in MyProxy repository.
• MyProxy issues proxy to user.
• Work in progress - Steve Chan

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Advantages of Repositories

• Eliminates need for users to securely store and
  manage certificates.
• Provides a portable way for users to access
  certificates.
• Long term certificates can be revoked (sort of)
  by removing from repository.
• Short term certificates can ignore revocation.
• Keys are more secure, or at least compromises are
  more likely to be noticed and dealt with. (all
  certificates revoked and/or reissued)
• Facilitates Portal use of certificates for
  authentication and Grid service use.

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Acceptance by Grid

• PMA federations (CA Policy Management
  Authorities)
• TAGPMA (The Americas Grid PMA)
• EUGridPMA (European Grid)
• APGridPMA (Asia Pacific Grid)
• Three have now joined in International Grid Trust
  Federation (ITFG)
• to allow scientific researchers to identify
  themselves to any grid resource in the world
  using just a single online identity.
• They support two certificate policies
• Classic PKI - private key must never leave
  holders possession
• Short-lived Credential Generation Service profile
  - written to accommodate KCA, will cover MyProxy
  CA as well.

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My Conclusions

• Absence of on-line authentication server not very
  important in Grid environment.
• Desire to use Grid certificates for non-reputable
  digital signatures not evident.
• Scientists intolerant of difficult to remember
  certificate procedures.
• Relying parties happier with private key security
  on key servers than on users workstations.
• Credential managers are the wave of the future
  for Grids and other VOs.