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This document describes threee abstract Generic Security Service Application Program Interface (GSS-API) interfaces used to encapsulate/decapsulate context tokens and compare OIDs, 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.
GSS_OID_equal call
5.1.
gss_oid_equal
6.
IANA Considerations
7.
Security Considerations
8.
References
8.1.
Normative References
8.2.
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 [RFC2744] (Wray, J., “Generic Security Service API Version 2 : C-bindings,” 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 two GSS-API interfaces (GSS_Encapsulate_token and GSS_Decapsulate_token) so that GSS-API libraries can provide this functionality.
Being able to compare OIDs is useful, for example when validating that an negotiated mechanism matched the requested one. This document adds one GSS-API interface (GSS_OID_equal) for this purpose.
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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Inputs:
o first_oid OBJECT IDENTIFIER -- first object identifier
to compare
o second_oid OBJECT IDENTIFIER -- second object identifier
to compare
Return codes:
o non-0 when neither OID is GSS_C_NO_OID and the two OIDs
are equal
o 0 otherwise
GSS_OID_equal() is used to add compare two OIDs for equality. The
value GSS_C_NO_OID will not match any OID, including GSS_C_NO_OID
itself.
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extern int
gss_oid_equal (
const gss_OID first_oid,
const gss_OID second_oid
)
Purpose:
Compare two OIDs for equality. The value GSS_C_NO_OID will not
match any OID, including GSS_C_NO_OID itself.
Parameters:
first_oid Object ID, read
First object identifier to compare.
second_oid Object ID, read
Second object identifier to compare.
Function value: GSS status code
non-0 neither OID is GSS_C_NO_OID and the
two OIDs are equal
0 otherwise
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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 |