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This document describes two abstract Generic Security Service Application Program Interface (GSS-API) interfaces used to encapsulate and decapsulate context tokens, and their C bindings.
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1.
Introduction
2.
Conventions used in this document
3.
GSS_Encapsulate_Token call
3.1.
gss_encapsulate_token
4.
GSS_Decapsulate_token call
4.1.
gss_decapsulate_token
5.
IANA Considerations
6.
Security Considerations
7.
References
7.1.
Normative References
7.2.
Informative References
§
Authors' Addresses
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Generic Security Service Application Program Interface (GSS-API) [RFC2743] (Linn, J., “Generic Security Service Application Program Interface Version 2, Update 1,” January 2000.) is a framework that provides security services to applications using a variety of authentication mechanisms. There are widely implemented C bindings [RFC2743] (Linn, J., “Generic Security Service Application Program Interface Version 2, Update 1,” January 2000.) for the abstract interface.
For initial context tokens a mechanism-independent token format may be used, see section 3.1 of [RFC2743] (Linn, J., “Generic Security Service Application Program Interface Version 2, Update 1,” January 2000.). Some protocols, e.g., SASL GS2 [I‑D.ietf‑sasl‑gs2] (Josefsson, S. and N. Williams, “Using GSS-API Mechanisms in SASL: The GS2 Mechanism Family,” January 2010.), needs the ability to add and remove the token header from context tokens. This document adds GSS-API interfaces so that GSS-API libraries can provide this functionality.
The intention is that text from this specification should be possible to use for implementation documentation, and for this reason this entire document should be considered a code component.
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The document uses terms from, and is structured in a similar way as, [RFC2743] (Linn, J., “Generic Security Service Application Program Interface Version 2, Update 1,” January 2000.) and [RFC2744] (Wray, J., “Generic Security Service API Version 2 : C-bindings,” January 2000.).
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Inputs:
o input_token OCTET STRING -- buffer with token data to
encapsulate
o token_oid OBJECT IDENTIFIER -- object identifier of mechanism
for the token
Outputs:
o major_status INTEGER
o output_token OCTET STRING -- Encapsulated token data; caller
must release with GSS_Release_buffer()
Return major_status codes:
o GSS_S_COMPLETE indicates successful completion, and that
output parameters holds correct information.
o GSS_S_FAILURE indicates that encapsulation failed for
reasons unspecified at the GSS-API level.
GSS_Encapsulate_token() is used to add the mechanism-independent
token header to GSS-API context token data.
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OM_uint32 gss_encapsulate_token (
const gss_buffer_t input_token,
const gss_OID token_oid,
gss_buffer_t output_token);
Purpose:
Add the mechanism-independent token header to GSS-API context
token data.
Parameters:
input_token buffer, opaque, read
Buffer with GSS-API context token data.
token_oid Object ID, read
Object identifier of token.
output_token buffer, opaque, modify
Encapsulated token data; caller must
release with gss_release_buffer().
Function value: GSS status code
GSS_S_COMPLETE Indicates successful completion, and
that output parameters holds correct
information.
GSS_S_FAILURE Indicates that encapsulation failed for
reasons unspecified at the GSS-API level.
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Inputs:
o input_token OCTET STRING -- buffer with token to decapsulate
o token_oid OBJECT IDENTIFIER -- expected object identifier
of token
Outputs:
o major_status INTEGER
o output_token OCTET STRING -- Decapsulated token data; caller
must release with GSS_Release_buffer()
Return major_status codes:
o GSS_S_COMPLETE indicates successful completion, and that
output parameters holds correct information.
o GSS_S_DEFECTIVE_TOKEN means that the token failed
consistency checks (e.g., OID mismatch or ASN.1 DER length
errors).
o GSS_S_FAILURE indicates that decapsulation failed for
reasons unspecified at the GSS-API level.
GSS_Decapsulate_token() is used to remove the mechanism-
independent token header from an initial GSS-API context token.
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OM_uint32
gss_decapsulate_token (
const gss_buffer_t input_token,
const gss_OID token_oid,
gss_buffer_t output_token)
Purpose:
Remove the mechanism-independent token header from an initial
GSS-API context token.
Parameters:
input_token buffer, opaque, read
Buffer with GSS-API context token.
token_oid Object ID, read
Expected object identifier of token.
output_token buffer, opaque, modify
Decapsulated token data; caller must
release with gss_release_buffer().
Function value: GSS status code
GSS_S_COMPLETE Indicates successful completion, and
that output parameters holds correct
information.
GSS_S_DEFECTIVE_TOKEN Means that the token failed consistency
checks (e.g., OID mismatch or ASN.1 DER
length errors).
GSS_S_FAILURE Indicates that decapsulation failed for
reasons unspecified at the GSS-API level.
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None.
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Implementations needs to treat input as potentially untrustworthy for purposes of dereferencing memory objects to avoid security vulnerabilities. In particular, ASN.1 DER length fields is a common source of mistakes.
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| [RFC2743] | Linn, J., “Generic Security Service Application Program Interface Version 2, Update 1,” RFC 2743, January 2000 (TXT). |
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| [RFC2744] | Wray, J., “Generic Security Service API Version 2 : C-bindings,” RFC 2744, January 2000 (TXT). |
| [I-D.ietf-sasl-gs2] | Josefsson, S. and N. Williams, “Using GSS-API Mechanisms in SASL: The GS2 Mechanism Family,” draft-ietf-sasl-gs2-20 (work in progress), January 2010 (TXT). |
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| Simon Josefsson | |
| SJD AB | |
| Hagagatan 24 | |
| Stockholm 113 47 | |
| SE | |
| Email: | simon@josefsson.org |
| URI: | http://josefsson.org/ |
| Love Hornquist Astrand | |
| Apple, Inc. | |
| Email: | lha@apple.com |