draft-ietf-asid-ldapv3-tls-00.txt   draft-ietf-asid-ldapv3-tls-01.txt 
ASID Working Group Jeff Hodges, Stanford ASID Working Group Jeff Hodges, Stanford
INTERNET-DRAFT RL "Bob" Morgan, Stanford INTERNET-DRAFT RL "Bob" Morgan, Stanford
Mark Wahl, Critical Angle Inc. Mark Wahl, Critical Angle Inc.
May, 1997 June, 1997
Lightweight Directory Access Protocol (v3): Lightweight Directory Access Protocol (v3):
Extension for Transport Layer Security Extension for Transport Layer Security
draft-ietf-asid-ldapv3-tls-00.txt draft-ietf-asid-ldapv3-tls-01.txt
1. Status of this Memo 1. Status of this Memo
This document is an Internet-Draft. Internet-Drafts are working docu- This document is an Internet-Draft. Internet-Drafts are working docu-
ments of the Internet Engineering Task Force (IETF), its areas, and its ments of the Internet Engineering Task Force (IETF), its areas, and its
working groups. Note that other groups may also distribute working working groups. Note that other groups may also distribute working
documents as Internet-Drafts. documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
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To learn the current status of any Internet-Draft, please check the To learn the current status of any Internet-Draft, please check the
``1id-abstracts.txt'' listing contained in the Internet- Drafts Shadow ``1id-abstracts.txt'' listing contained in the Internet- Drafts Shadow
Directories on ds.internic.net (US East Coast), nic.nordu.net (Europe), Directories on ds.internic.net (US East Coast), nic.nordu.net (Europe),
ftp.isi.edu (US West Coast), or munnari.oz.au (Pacific Rim). ftp.isi.edu (US West Coast), or munnari.oz.au (Pacific Rim).
2. Abstract 2. Abstract
This document defines the "Start Transport Layer Security (TLS) Opera- This document defines the "Start Transport Layer Security (TLS) Opera-
tion" for LDAP [LDAPv3, TLS]. This operation provides for TLS establish- tion" for LDAP [LDAPv3, TLS]. This operation provides for TLS establish-
ment in an LDAP association and is defined in terms of an LDAP extended ment in an LDAP association and is defined in terms of an LDAP extended
operation. request.
The key words "MUST", "SHOULD", and "MAY" used in this document are to The key words "MUST", "SHOULD", and "MAY" used in this document are to
be interpreted as described in [Bradner97]. be interpreted as described in [Bradner97].
3. The Start TLS Operation 3. The Start TLS Operation
3.1. Requesting TLS Establishment 3.1. Requesting TLS Establishment
A client may perform a Start TLS operation by transmitting an LDAP PDU A client may perform a Start TLS operation by transmitting an LDAP PDU
containing an ExtendedRequest [LDAPv3] specifying the OID for the Start containing an ExtendedRequest [LDAPv3] specifying the OID for the Start
TLS operation: TLS operation:
[To Be Determined] 1.3.6.1.4.1.1466.20037
An LDAP ExtendedRequest is defined as follows: An LDAP ExtendedRequest is defined as follows:
ExtendedRequest ::= [APPLICATION 23] SEQUENCE { ExtendedRequest ::= [APPLICATION 23] SEQUENCE {
requestName [0] LDAPOID, requestName [0] LDAPOID,
requestValue [1] OCTET STRING OPTIONAL } requestValue [1] OCTET STRING OPTIONAL }
A Start TLS extended request is formed by setting the requestName field A Start TLS extended request is formed by setting the requestName field
to the OID string given above. The requestValue field is absent. The to the OID string given above. The requestValue field is absent. The
client MUST NOT send any PDUs on this connection following this request client MUST NOT send any PDUs on this connection following this request
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MUST be set to the same string as that present in the Start TLS extended MUST be set to the same string as that present in the Start TLS extended
request. The response field is absent. The server MUST set the request. The response field is absent. The server MUST set the
resultCode of the standardResponse field to either success or one of the resultCode of the standardResponse field to either success or one of the
other values outlined in section 3.3. other values outlined in section 3.3.
3.2. "Success" Response 3.2. "Success" Response
If the standardResponse field contains a resultCode of success, this If the standardResponse field contains a resultCode of success, this
indicates that the server is willing and able to negotiate TLS. At this indicates that the server is willing and able to negotiate TLS. At this
point the client, which has ceased to transfer LDAP requests on the con- point the client, which has ceased to transfer LDAP requests on the con-
nection, MUST begin a TLS negotiation. The client will send PDUs in the nection, MUST either begin a TLS negotiation, or close the connection.
TLS Record Protocol directly over the underlying TCP bytestream to the In the former case, the client will send PDUs in the TLS Record Protocol
server. directly over the underlying TCP bytestream to the server.
After the TLS connection is established, both parties MUST individually After the TLS connection is established, both parties MUST individually
decide whether or not to continue based on the privacy level achieved. decide whether or not to continue based on the privacy level achieved.
Ascertaining the TLS connection's privacy level is implementation depen- Ascertaining the TLS connection's privacy level is implementation depen-
dent, and accomplished by communicating with one's respective local TLS dent, and accomplished by communicating with one's respective local TLS
implementation. implementation.
If the client or server decides that the level of authentication or If the client or server decides that the level of authentication or
privacy is not high enough for it to continue, it SHOULD close the TLS privacy is not high enough for it to continue, it SHOULD close the TLS
and LDAP connection as discussed in section 5 [see Open Issues, below]. connection immediately after the TLS negotiation has completed, to
disconnect the TLS service and return to an LDAP state (see section 5,
below). This will cause the client's authorization identity to be reset
to anonymous. The client MAY attempt to Start TLS again, or MAY send an
unbind request, or send any other LDAP request.
3.3. Response other than "success" 3.3. Response other than "success"
If the standardResponse field contains a resultCode other than success, If the standardResponse field contains a resultCode other than success,
this indicates that the server is unwilling or unable to negotiate TLS. this indicates that the server is unwilling or unable to negotiate TLS.
If the Start TLS extended request was not successful, the resultCode If the Start TLS extended request was not successful, the resultCode
will be one of: will be one of:
- operationsError (operations sequencing incorrect; e.g. TLS already - operationsError (operations sequencing incorrect; e.g. TLS already
established) established)
- protocolError (TLS not supported or incorrect PDU structure) - protocolError (TLS not supported or incorrect PDU structure)
- referral (this server doesn't do TLS, try this one) - referral (this server doesn't do TLS, try this one)
- unavailable (e.g. some major problem with TLS, or server is - unavailable (e.g. some major problem with TLS, or server is
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If the Start TLS extended request was not successful, the resultCode If the Start TLS extended request was not successful, the resultCode
will be one of: will be one of:
- operationsError (operations sequencing incorrect; e.g. TLS already - operationsError (operations sequencing incorrect; e.g. TLS already
established) established)
- protocolError (TLS not supported or incorrect PDU structure) - protocolError (TLS not supported or incorrect PDU structure)
- referral (this server doesn't do TLS, try this one) - referral (this server doesn't do TLS, try this one)
- unavailable (e.g. some major problem with TLS, or server is - unavailable (e.g. some major problem with TLS, or server is
shutting down) shutting down)
The server MUST return operationsError if the client violates any of the
Start TLS extended operation sequencing requirements described in sec-
tion 4, below.
If the server does not support TLS (whether by design or by current con- If the server does not support TLS (whether by design or by current con-
figuration), it MUST set the resultCode to protocolError (see section figuration), it MUST set the resultCode to protocolError (see section
4.1.1 of [LDAPv3]), or to referral. The server MUST include an actual 4.1.1 of [LDAPv3]), or to referral. The server MUST include an actual
referral value in the LDAP Result if it returns a resultCode of refer- referral value in the LDAP Result if it returns a resultCode of refer-
ral. The client's current session is unaffected if the the server does ral. The client's current session is unaffected if the server does not
not support TLS. The client MAY proceed with any LDAP operation, or it support TLS. The client MAY proceed with any LDAP operation, or it MAY
MAY close the connection. close the connection.
The server MUST return unavailable if it supports TLS but cannot estab- The server MUST return unavailable if it supports TLS but cannot estab-
lish a TLS connection for some reason, e.g. the certificate server not lish a TLS connection for some reason, e.g. the certificate server not
responding, it cannot contact its TLS implementation, or if the server responding, it cannot contact its TLS implementation, or if the server
is in process of shutting down. The client MAY retry the StartTLS opera- is in process of shutting down. The client MAY retry the StartTLS opera-
tion, or it MAY proceed with any other LDAP operation, or it MAY close tion, or it MAY proceed with any other LDAP operation, or it MAY close
the connection. the connection.
4. Sequencing of the Start TLS Operation 4. Sequencing of the Start TLS Operation
The client MAY send the Start TLS extended request at any time once the The client MAY send the Start TLS extended request at any time after
LDAP association has been established, except during a SASL negotiation, establishing an LDAP association, except that in the following cases the
or if TLS is currently established on the connection. client MUST NOT send a Start TLS extended request:
The client may have already completed the bind process when it sends a - if TLS is currently established on the connection, or
Start TLS request, or the client may have not yet bound. - during a multi-stage SASL negotiation, or
- if there are any LDAP operations outstanding on the connection.
The result of violating any of these requirements is described above in
section 3.3.
The client MAY have already perfomed a Bind operation when it sends a
Start TLS request, or the client might have not yet bound.
If the client did not establish a TLS connection before sending any If the client did not establish a TLS connection before sending any
other requests, and the server requires the client to establish a TLS other requests, and the server requires the client to establish a TLS
connection before performing a particular request, the server MUST connection before performing a particular request, the server MUST
reject that request with a confidentialityRequired or strongAuthRequired reject that request with a confidentialityRequired or strongAuthRequired
result. The client MAY send a Start TLS extended request, or it MAY result. The client MAY send a Start TLS extended request, or it MAY
choose to close the connection. choose to close the connection.
5. Closing a TLS Connection 5. Closing a TLS Connection
Closing a TLS connection requires termination of the overlying LDAP 5.1. Graceful Closure
association [see Open Issues, below]. The TLS protocol interactions for
TLS closure are described in [TLS]. The LDAP operations specified below
are described in [LDAPv3]. Either the client or server MAY terminate the TLS connection on an LDAP
association by sending a TLS closure alert. This will leave the LDAP
association intact.
5.1. Client-initiated Closure Before closing a TLS connection, the client MUST either wait for any
outstanding LDAP operations to complete, or explicitly abandon them
[LDAPv3].
A client MAY initiate TLS, and thus LDAP, connection closure at any After the initiator of a close has sent a closure alert, it MUST discard
time. It MAY initiate the termination by first performing an LDAP Unbind any TLS messages until it has received an alert from the other party.
Operation. It MUST then initiate TLS and underlying transport closure It will cease to send TLS Record Protocol PDUs, and following the
according to the procedures required by the particular TLS implementa- reciept of the alert, MAY send and receive LDAP PDUs.
tion being utilized.
5.2. Server-initiated Closure The other party, if it receives a closure alert, MUST immediately
transmit a TLS closure alert. It will subequently cease to send TLS
Record Protocol PDUs, and MAY send and receive LDAP PDUs.
A server MAY initiate TLS, and thus LDAP, connection closure at any 5.2. Abrupt Closure
time. It SHOULD first send an LDAP Notice of Disconnection with the
appropriate resultCode value to the client. It MUST then immediately
initiate TLS and underlying transport closure according to the pro-
cedures required by the particular TLS implementation being utilized.
6. Effects of TLS Establishment on an LDAP Connection Either the client or server MAY abruptly close the entire LDAP associa-
tion and any TLS connection established on it by dropping the underlying
TCP connection. A server MAY beforehand send the client a Notice of
Disconnection [LDAPv3] in this case.
The establishment of TLS into the LDAP protocol stack causes any out- 6. Effects of TLS Establishment on the Client's Authorization Identity
standing requests from the client to be implicitly abandoned. However,
it does not affect the authentication credentials of the client nor its
associated authorization identity. If the client had bound to the
server previously on this association, that authorization identity MUST
remain in force. If the client had not bound, then the connection MUST
remain in an anonymous authentication and authorization state.
The client MAY request that its authenticated TLS credentials be used as Upon establishment of the TLS connection onto the LDAP association, the
the source for its LDAP authorization identity, or it MAY request use of server MAY base the client's authorization identity on the client's
other credentials. negotiated TLS credentials, overriding any previously established
credentials and authorization identity. Otherwise, any previously esta-
blished credentials and authorization identity MUST remain in force,
including anonymous cedentials and identity in the case where the client
had not previously bound.
Requesting that the server use the negotiated TLS credentials for LDAP A client MAY explicitly request that its authenticated TLS credentials
authorization is accomplished by invoking a Bind request of the SASL be used as the source for its LDAP authorization identity. This is
form with a negotiated mechanism name of "EXTERNAL" [SASL]. The creden- accomplished after TLS establishment by invoking a Bind request of the
tials field MAY contain the client's distinguished name (as an LDAP SASL form with a negotiated mechanism name of "EXTERNAL" [SASL]. The
string). If it does contain a distinguished name, this name MUST match credentials field MAY contain the client's distinguished name (as an
that negotiated by TLS as the client's identity. The client MAY leave LDAP string), or it MAY be empty. If it does contain a distinguished
the credentials field empty. name, this name MUST match the authorization identity negotiated by TLS
as the client's identity. It is a matter of local policy what consti-
tutes a match. In the absence of local policy, the default matching pol-
icy compares for equality. The server MUST reject the Bind operation
with an invalidCredentials resultCode in the Bind response if they do
not match.
The termination of TLS MUST cause the connection to move to an anonymous Closure of the TLS connection MUST cause the LDAP association to move to
authentication and authorization state irregardless of the state esta- an anonymous authentication and authorization state regardless of the
blished over TLS and irregardless of the authentication and authoriza- state established over TLS and regardless of the authentication and
tion state prior to TLS connection establishment. authorization state prior to TLS connection establishment.
7. Security Considerations 7. Security Considerations
The goals of using the TLS protocol with LDAP are to ensure connection The goals of using the TLS protocol with LDAP are to ensure connection
confidentiality and integrity, and to optionally provide for authentica- confidentiality and integrity, and to optionally provide for authentica-
tion. TLS expressly provides these capabilities, as described in [TLS]. tion. TLS expressly provides these capabilities, as described in [TLS].
All security gained via use of the Start TLS operation is gained by the All security gained via use of the Start TLS operation is gained by the
use of TLS itself. The Start TLS operation, on its own, does not provide use of TLS itself. The Start TLS operation, on its own, does not provide
any additional security. any additional security.
The use of TLS does not provide or ensure for confidentiality and/or The use of TLS does not provide or ensure for confidentiality and/or
non-repudiation of the data housed by an LDAP-based directory server. non-repudiation of the data housed by an LDAP-based directory server.
Once established, TLS only provides for and ensures confidentiality and Once established, TLS only provides for and ensures confidentiality and
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tion. TLS expressly provides these capabilities, as described in [TLS]. tion. TLS expressly provides these capabilities, as described in [TLS].
All security gained via use of the Start TLS operation is gained by the All security gained via use of the Start TLS operation is gained by the
use of TLS itself. The Start TLS operation, on its own, does not provide use of TLS itself. The Start TLS operation, on its own, does not provide
any additional security. any additional security.
The use of TLS does not provide or ensure for confidentiality and/or The use of TLS does not provide or ensure for confidentiality and/or
non-repudiation of the data housed by an LDAP-based directory server. non-repudiation of the data housed by an LDAP-based directory server.
Once established, TLS only provides for and ensures confidentiality and Once established, TLS only provides for and ensures confidentiality and
integrity of the operations and data in transit over the LDAP associa- integrity of the operations and data in transit over the LDAP associa-
tion. tion, and only if the implementations on the client and server support
and negotiate it.
The level of security provided though the use of TLS depends directly on The level of security provided though the use of TLS depends directly on
both the quality of the TLS implementation used and the style of usage both the quality of the TLS implementation used and the style of usage
of that implementation. Both parties SHOULD independently ascertain and of that implementation. Both parties SHOULD independently ascertain and
consent to the privacy level achieved once TLS is established and before consent to the privacy level achieved once TLS is established and before
begining use of the TLS connection. For example, the privacy level of begining use of the TLS connection. For example, the privacy level of
the TLS connection might have been negotiated down to plaintext. the TLS connection might have been negotiated down to plaintext.
Client and server implementors SHOULD take measures to ensure proper Client and server implementors SHOULD take measures to ensure proper
protection of credentials and other confidential data where such meas- protection of credentials and other confidential data where such meas-
ures are not otherwise provided by the TLS implementation. ures are not otherwise provided by the TLS implementation.
Server implementors SHOULD allow for server administrators to elect Server implementors SHOULD allow for server administrators to elect
whether and when connection confidentiality is required and for what whether and when connection confidentiality is required.
portions of the DIT (served by the server) it applies to.
8. References 8. Acknowledgements
The authors thank Tim Howes and Paul Hoffman for their contributions to
this document.
9. References
[Bradner97] [Bradner97]
Scott Bradner, "Key Words for use in RFCs to Indicate Requirement Scott Bradner, "Key Words for use in RFCs to Indicate Requirement
Levels", Internet Draft, RFC 2119. Levels", Internet Draft, RFC 2119.
[LDAPv3] [LDAPv3]
M. Wahl, S. Kille and T. Howes, "Lightweight Directory Access Pro- M. Wahl, S. Kille and T. Howes, "Lightweight Directory Access Pro-
tocol (v3)", Internet Draft, February, 1997. Available as draft- tocol (v3)", Internet Draft, February, 1997. Available as draft-
ietf-asid-ldapv3-protocol-04.txt. ietf-asid-ldapv3-protocol-04.txt.
[TLS]Tim Dierks, C. Allen, "The TLS Protocol Version 1.0", Internet [TLS]Tim Dierks, C. Allen, "The TLS Protocol Version 1.0", Internet
Draft, March 1997. Available as draft-ietf-tls-protocol-03.txt Draft, March 1997. Available as draft-ietf-tls-protocol-03.txt
[SASL]J. Myers, "Simple Authentication and Security Layer (SASL)", [SASL]J. Myers, "Simple Authentication and Security Layer (SASL)",
Internet Draft, April 1997. Available as draft-myers-auth-sasl- Internet Draft, April 1997. Available as draft-myers-auth-sasl-
10.txt 10.txt
9. Open Issues
9.1. TLS Closure
[TLS] discusses TLS closure in section 7.2.1. This section implies that
closing a TLS connection assumes closure of the underlying transport.
Thus, closing TLS, but retaining both the overlying application layer
(LDAP, in this case) and the underlying transport is not explicitly sup-
ported.
Modifications to [TLS] are required if there are requirements for con-
tinuing an LDAP association across a TLS connection closure.
Below is suggested alternative text for the "Closing a TLS Connection"
section of this document that COULD be used if [TLS] is so modified:
Either the client or server MAY terminate the TLS service on the
connection by sending a TLS closure alert. TLS closure has the
effect of abandoning any outstanding LDAP protocol requests.
After the initiator of a close has sent a closure alert, it MUST
discard any TLS messages until it has received an alert from the
other party. It will cease to send TLS Record Protocol PDUs, and
following the reciept of the alert, MAY send and receive LDAP PDUs.
The other party, if it receives a closure alert, MUST immediately
transmit a TLS closure alert. It will subequently cease to send
TLS Record Protocol PDUs, and MAY send and receive LDAP PDUs.
Additionally, below is suggested alternative text for the last paragraph
of the "Success Response" section:
If the client or server decides that the level of authentication or
privacy is not high enough for it to continue, it SHOULD send a TLS
closure alert immediately after the TLS negotiation has completed,
to disconnect the TLS service and return to an LDAP state. (This
will cause the authorization to be reset to anonymous.) The client
MAY attempt to Start TLS again, or MAY send an unbind request, or
send any other LDAP request.
10. Author's Address 10. Author's Address
Jeff Hodges Jeff Hodges
Computing & Communication Services Computing & Communication Services
Stanford University Stanford University
115 Pine Hall 115 Pine Hall
Stanford, CA 94305-4122 Stanford, CA 94305-4122
USA USA
Phone: +1-415-723-2452 Phone: +1-415-723-2452
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