draft-ietf-kitten-gssapi-store-cred-04.txt   rfc5588.txt 
NETWORK WORKING GROUP N. Williams Network Working Group N. Williams
Internet-Draft Sun Request for Comments: 5588 Sun
Intended status: Standards Track March 9, 2009 Generic Security Service Application Program Interface (GSS-API)
Expires: September 10, 2009 Extension for Storing Delegated Credentials
GSS-API Extension for Storing Delegated Credentials
draft-ietf-kitten-gssapi-store-cred-04.txt
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material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at This document defines a new function for the Generic Security Service
http://www.ietf.org/ietf/1id-abstracts.txt. Application Program Interface (GSS-API), which allows applications to
store delegated (and other) credentials in the implicit GSS-API
credential store. This is needed for GSS-API applications to use
delegated credentials as they would use other credentials.
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Abstract
This document defines a new function for the GSS-API which allows
applications to store delegated (and other) credentials in the
implicit GSS-API credential store. This is needed for GSS-API
applications to use delegated credentials as they would use other
credentials.
Table of Contents Table of Contents
1. Conventions used in this document . . . . . . . . . . . . . . 3 1. Introduction ....................................................2
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Conventions Used in This Document ...............................3
3. GSS_Store_cred() . . . . . . . . . . . . . . . . . . . . . . . 5 3. GSS_Store_cred() ................................................3
4. C-Bindings . . . . . . . . . . . . . . . . . . . . . . . . . . 7 4. C-Bindings ......................................................5
5. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 5. Examples ........................................................6
6. IANA considerations . . . . . . . . . . . . . . . . . . . . . 9 6. Security Considerations .........................................6
7. Security considerations . . . . . . . . . . . . . . . . . . . 10 7. Normative References ............................................7
8. Normative References . . . . . . . . . . . . . . . . . . . . . 11
Author's Address . . . . . . . . . . . . . . . . . . . . . . . 12
1. Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
2. Introduction 1. Introduction
The GSS-API [RFC2743] clearly assumes that credentials exist in an The GSS-API [RFC2743] clearly assumes that credentials exist in an
implicit store whence they can be acquired using GSS_Acquire_cred() implicit store whence they can be acquired using GSS_Acquire_cred()
and GSS_Add_cred() or through use of the default credential. and GSS_Add_cred() or through use of the default credential.
Multiple credential stores may exist on a given host, but only one Multiple credential stores may exist on a given host, but only one
store may be accessed by GSS_Acquire_cred() and GSS_Add_cred() at any store may be accessed by GSS_Acquire_cred() and GSS_Add_cred() at any
given time. given time.
This assumption can be seen in sections 1.1.1.2 and 1.1.1.3 of This assumption can be seen in Sections 1.1.1.2 and 1.1.1.3 of
[RFC2743] as well as in section 3.5 of [RFC2744]. [RFC2743] as well as in Section 3.5 of [RFC2744].
Applications may be able to change the credential store from which Applications may be able to change the credential store from which
credentials can be acquired, either by changing user contexts (where credentials can be acquired, either by changing user contexts (where
the applications have the privilege to do so) or by other means the applications have the privilege to do so) or by other means
(where a user may have multiple credential stores). (where a user may have multiple credential stores).
Some GSS-API acceptor applications always change user contexts, after Some GSS-API acceptor applications always change user contexts, after
accepting a GSS-API security context and making appropriate accepting a GSS-API security context and making appropriate
authorization checks, to the user context corresponding to the authorization checks, to the user context corresponding to the
initiator principal name or to a context requested by the initiator. initiator principal name or to a context requested by the initiator.
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In the case of delegated credential handles however, such credentials In the case of delegated credential handles however, such credentials
do not exist in the acceptor's credential store or in the credential do not exist in the acceptor's credential store or in the credential
stores of the user contexts to which the acceptor application might stores of the user contexts to which the acceptor application might
change. The GSS-API provides no mechanism by which delegated change. The GSS-API provides no mechanism by which delegated
credential handles can be made available for acquisition through credential handles can be made available for acquisition through
GSS_Acquire_cred()/GSS_Add_cred(). The GSS-API also does not provide GSS_Acquire_cred()/GSS_Add_cred(). The GSS-API also does not provide
any credential import/export interfaces like the GSS-API context any credential import/export interfaces like the GSS-API context
import/export interfaces. import/export interfaces.
Thus acceptors are limited to making only direct use of delegated Thus, acceptors are limited to making only direct use of delegated
credential handles and only with GSS_Init_sec_context(), credential handles and only with GSS_Init_sec_context(),
GSS_Inquire_cred*() and GSS_Release_cred(). This limitation is GSS_Inquire_cred*(), and GSS_Release_cred(). This limitation is
particularly onerous on Unix systems where a call to exec() to particularly onerous on Unix systems where a call to exec() to
replace the process image obliterates any delegated credentials replace the process image obliterates any delegated credentials
handle that may exist in that process. handle that may exist in that process.
In order to make delegated credentials generally as useful as In order to make delegated credentials generally as useful as
credentials that can be acquired with GSS_Acquire_cred() and credentials that can be acquired with GSS_Acquire_cred() and
GSS_Add_cred() a primitive is needed which allows storing of GSS_Add_cred(), a primitive is needed that allows storing of
credentials in the implicit credential store. This primitive we call credentials in the implicit credential store. We call this primitive
"GSS_Store_cred()." "GSS_Store_cred()".
2. Conventions Used in This Document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
3. GSS_Store_cred() 3. GSS_Store_cred()
Inputs: Inputs:
o input_cred_handle CREDENTIAL HANDLE, -- credential to store; MUST o input_cred_handle CREDENTIAL HANDLE, -- credential to store; MUST
NOT be GSS_C_NO_CREDENTIAL NOT be GSS_C_NO_CREDENTIAL.
o cred_usage INTEGER -- 0=INITIATE-AND-ACCEPT, 1=INITIATE-ONLY, o cred_usage INTEGER -- 0=INITIATE-AND-ACCEPT, 1=INITIATE-ONLY,
2=ACCEPT-ONLY 2=ACCEPT-ONLY.
o desired_mech_element OBJECT IDENTIFIER, -- if GSS_C_NULL_OID then o desired_mech_element OBJECT IDENTIFIER, -- if GSS_C_NULL_OID, then
store all the elements of the input_cred_handle, otherwise store store all the elements of the input_cred_handle, otherwise, store
only the element of the corresponding mechanism only the element of the corresponding mechanism.
o overwrite_cred BOOLEAN, -- if TRUE replace any credential for the o overwrite_cred BOOLEAN, -- if TRUE, replace any credential for the
same principal in the credential store same principal in the credential store.
o default_cred BOOLEAN -- if TRUE make the stored credential o default_cred BOOLEAN -- advisory input; if TRUE, make the stored
available as the default credential (for acquisition with credential available as the default credential (for acquisition
GSS_C_NO_NAME as the desired name or for use as with GSS_C_NO_NAME as the desired name or for use as
GSS_C_NO_CREDENTIAL) GSS_C_NO_CREDENTIAL).
Outputs: Outputs:
o major_status INTEGER, o major_status INTEGER.
o minor_status INTEGER, o minor_status INTEGER.
o mech_elements_stored SET OF OBJECT IDENTIFIER, -- the set of o mech_elements_stored SET OF OBJECT IDENTIFIER, -- the set of
mechanism OIDs for which credential elements were successfully mechanism OIDs for which credential elements were successfully
stored stored.
o cred_usage_stored INTEGER -- like cred_usage, but indicates what o cred_usage_stored INTEGER -- like cred_usage, but indicates what
kind of credential was stored (useful when the cred_usage input kind of credential was stored (useful when the cred_usage input
parameter is set to INITIATE-AND-ACCEPT) parameter is set to INITIATE-AND-ACCEPT).
Return major_status codes: Return major_status codes:
o GSS_S_COMPLETE indicates that the credentials were successfully o GSS_S_COMPLETE indicates that the credentials were successfully
stored. stored.
o GSS_S_CREDENTIALS_EXPIRED indicates that the input credentials had o GSS_S_CREDENTIALS_EXPIRED indicates that the input credentials had
expired or expired before they could be stored. expired or expired before they could be stored.
o GSS_S_NO_CRED indicates that no input credentials were given. o GSS_S_NO_CRED indicates that no input credentials were given.
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for some other reason. The minor status code may provide more for some other reason. The minor status code may provide more
information if a non-GSS_C_NULL_OID desired_mech_element was information if a non-GSS_C_NULL_OID desired_mech_element was
given. given.
GSS_Store_cred() is used to store, in the current credential store, a GSS_Store_cred() is used to store, in the current credential store, a
given credential that has either been acquired from a different given credential that has either been acquired from a different
credential store or been accepted as a delegated credential. credential store or been accepted as a delegated credential.
Specific mechanism elements of a credential can be stored one at a Specific mechanism elements of a credential can be stored one at a
time by specifying a non-GSS_C_NULL_OID mechanism OID as the time by specifying a non-GSS_C_NULL_OID mechanism OID as the
desired_mech_element input argument, in which case the minor status desired_mech_element input argument; in which case, the minor status
output SHOULD have a mechanism-specific value when the major status output SHOULD have a mechanism-specific value when the major status
is not GSS_S_COMPLETE. is not GSS_S_COMPLETE.
The initiator, acceptor or both usages of the input credential may be The initiator, acceptor, or both usages of the input credential may
stored as per the cred_usage input argument. be stored as per the cred_usage input argument.
The credential elements that were actually stored, when the major The credential elements that were actually stored, when the major
status is GSS_S_COMPLETE, are indicated through the cred_usage_stored status is GSS_S_COMPLETE, are indicated through the cred_usage_stored
and mech_elements_stored function outputs. and mech_elements_stored function outputs.
If credentials already exist in the current store for the principal If credentials already exist in the current store for the principal
of the input_cred_handle, then those credentials are not replaced of the input_cred_handle, then those credentials are not replaced
with the input credentials unless the overwrite_cred input argument with the input credentials unless the overwrite_cred input argument
is TRUE. is TRUE.
Finally, if the current credential store has no default credential In the GSS-API, the default credential can be used by using
(that is, no credential that could be acquired for GSS_C_NO_NAME) or GSS_C_NO_CREDENTIAL or a CREDENTIAL handle acquired by calling
if the default_cred input argument is TRUE, and the input credential GSS_Acquire_cred() or GSS_Add_cred() with the desired_name input set
can be successfully stored, then the input credential will be to GSS_C_NO_NAME.
available for acquisition with GSS_C_NO_NAME as the desired name
input to GSS_Acquire_cred() or GSS_Add_cred() as well as for use as If the default_cred input argument is TRUE, and the input credential
GSS_C_NO_CREDENTIAL for the cred_handle inputs to GSS_Inquire_cred(), can be successfully stored, then the input credential SHOULD be
GSS_Inquire_cred_by_mech(), GSS_Init_sec_context() and stored as the default credential (see above).
GSS_Accept_sec_context().
If the current credential store has no default credential (see
above), then the implementation MAY make the stored credentials
available as the default credential regardless of the value of the
default_cred input argument.
4. C-Bindings 4. C-Bindings
The C-bindings for GSS_Store_cred() make use of types from and are The C-Bindings for GSS_Store_cred() make use of types from and are
designed based on the style of the GSS-APIv2 C-Bindings [RFC2744]. designed based on the style of the GSS-APIv2 C-Bindings [RFC2744].
OM_uint32 gss_store_cred( OM_uint32 gss_store_cred(
OM_uint32 *minor_status, OM_uint32 *minor_status,
gss_cred_id_t input_cred_handle, gss_cred_id_t input_cred_handle,
gss_cred_usage_t cred_usage, gss_cred_usage_t cred_usage,
const gss_OID desired_mech, const gss_OID desired_mech,
OM_uint32 overwrite_cred, OM_uint32 overwrite_cred,
OM_uint32 default_cred, OM_uint32 default_cred,
gss_OID_set *elements_stored, gss_OID_set *elements_stored,
gss_cred_usage_t *cred_usage_stored) gss_cred_usage_t *cred_usage_stored)
Figure 1 Figure 1
The two boolean arguments, 'overwrite_cred' and 'default_cred' are The two boolean arguments, 'overwrite_cred' and 'default_cred', are
typed as OM_uint32; 0 corresponds to FALSE, non-zero values typed as OM_uint32; 0 corresponds to FALSE, non-zero values
correspond to TRUE. correspond to TRUE.
5. Examples 5. Examples
The intended usage of GSS_Store_cred() is to make delegated The intended usage of GSS_Store_cred() is to make delegated
credentials available to child processes of GSS-API acceptor credentials available to child processes of GSS-API acceptor
applications. Example pseudo-code: applications. Example pseudo-code:
/* /*
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... ...
if (authorize_gss_client(src_name, requested_username)) { if (authorize_gss_client(src_name, requested_username)) {
/* /*
* For Unix-type platforms this may mean calling setuid() and * For Unix-type platforms this may mean calling setuid() and
* it may or may not also mean setting/unsetting such * it may or may not also mean setting/unsetting such
* environment variables as KRB5CCNAME and what not -- all * environment variables as KRB5CCNAME and what not -- all
* OS-specific details. * OS-specific details.
*/ */
if (change_user_context(requested_username)) if (change_user_context(requested_username))
(void) gss_store_creds(&minor_status, deleg_cred, (void) gss_store_cred(&minor_status, deleg_cred,
GSS_C_INITIATE, actual_mech, GSS_C_INITIATE, actual_mech,
0, 1, NULL, NULL); 0, 1, NULL, NULL);
} }
else ... else ...
} }
else ... else ...
6. IANA considerations 6. Security Considerations
There are no IANA considerations in this document.
7. Security considerations
Acceptor applications MUST only store delegated credentials into Acceptor applications MUST only store delegated credentials into
appropriate credential stores and only after proper authorization of appropriate credential stores and only after proper authorization of
the authenticated initiator principal to the requested service(s). the authenticated initiator principal to the requested service(s).
Acceptor applications that have no use for delegated credentials MUST Acceptor applications that have no use for delegated credentials MUST
release them (such acceptor applications that use the GSS-API release them (such acceptor applications that use the GSS-API C-
C-Bindings may simply provide a NULL value for the Bindings may simply provide a NULL value for the
delegated_cred_handle argument to gss_accept_sec_context()). delegated_cred_handle argument to gss_accept_sec_context()).
8. Normative References 7. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2743] Linn, J., "Generic Security Service Application Program [RFC2743] Linn, J., "Generic Security Service Application Program
Interface Version 2, Update 1", RFC 2743, January 2000. Interface Version 2, Update 1", RFC 2743, January 2000.
[RFC2744] Wray, J., "Generic Security Service API Version 2 : [RFC2744] Wray, J., "Generic Security Service API Version 2 :
C-bindings", RFC 2744, January 2000. C-bindings", RFC 2744, January 2000.
Author's Address Author's Address
Nicolas Williams Nicolas Williams
Sun Microsystems Sun Microsystems
5300 Riata Trace Ct 5300 Riata Trace Ct
Austin, TX 78727 Austin, TX 78727
US US
Email: Nicolas.Williams@sun.com EMail: Nicolas.Williams@sun.com
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