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SPKM BOF – IETF 67 SSiLKey

SPKM BOF – IETF 67 SSiLKey. Mike Eisler email2mre-ietf AT yahoo.com. Background and Motivation. NFSv4 (and other upper layer protocols) need a certificate-based authentication system TLS (or SSL) is ubiquitous, why doesn’t NFS use TLS?

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SPKM BOF – IETF 67 SSiLKey

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  1. SPKM BOF – IETF 67SSiLKey Mike Eisler email2mre-ietf AT yahoo.com

  2. Background and Motivation • NFSv4 (and other upper layer protocols) need a certificate-based authentication system • TLS (or SSL) is ubiquitous, why doesn’t NFS use TLS? • NFS uses ONC RPC, and ONC RPC does not fit cleanly with TLS • TLS/SSL enabled http servers are abundant, can we leverage that? • Not proposing using https as the transport for NFS

  3. SSiLKey: Session Keys via SSL (aka TLS) • A GSS initiator creates a SSiLKey context token to <svc_name>@<host_name> • Issues an https call to https://<host_name>/SSiLKey/InitialContext/service_name?target=<svc_name>@<host_name> • The https server response is encrypted via TLS, and contains: • Authenticator, in GSS InitialContext form (i.e. the ASN.1 OID for SSiLKey), consisting of • OID of a symmetric encryption algorithm • OID of a one way hash algorithm • Cipher text (wrapped via encryption and HMAC of one way hash algorithms) using service key consisting of • session key between initiator and target • initiator’s certificate (if any) • sequence number (for replay protection) • the session key (same as that in Authenticator) • NFS via RPCSEC_GSS, sends Authenticator NFS server

  4. SSiLKey: Target Processing of Context Token • NFS server, via RPCSEC_GSS, acquires its credentials (a secret symmetric key accessible to the NFS server and the https server) • calls GSS_Accept_Sec_Context() which unwraps cipher text in token • Checks sequence number for replay • If the initiator did not send its certificate, then initiator is anonymous • Initiator will use LIPKEY to authenticate itself • LIPKEY will layer itself over SSiLKey as it does over SPKM-3 • If a certificate was sent, the target maps it an operating environment cred (e.g. UNIX uid, gid, gid list) • My opinion: implementers should add a gss_ctx_to_uid() call to their GSS libraries if they haven’t already • If there is a best practice for mapping certs to uids, use it, otherwise, define one and move on

  5. Parts Needed • Client side: TLS code, http client, SSiLKey GSS initiator • Server side: • https server • SSiLKey CGI scripts or binaries to process SSiLKey request for InitialContext • Tools for creating random service keys, and service key tabs to store them • SSiLKey GSS target

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