terms of network interactions is unspecified.
2.4.1: GSS_Display_status call
Inputs:
o status_value INTEGER, -- GSS-API major_status or minor_status
-- return value
o status_type INTEGER, -- 1 if major_status, 2 if minor_status
o mech_type OBJECT IDENTIFIER -- mech_type to be used for
-- minor_status translation
Outputs:
o major_status INTEGER,
o minor_status INTEGER,
o status_string_set SET OF OCTET STRING -- required calls for
-- release by caller are specific to language bindings
Return major_status codes:
o GSS_S_COMPLETE indicates that a valid printable status
representation (possibly representing more than one status event
encoded within the status_value) is available in the returned
status_string_set.
o GSS_S_BAD_MECH indicates that translation in accordance with an
unsupported mech_type was requested, so translation could not be
performed.
o GSS_S_BAD_STATUS indicates that the input status_value was
invalid, or that the input status_type carried a value other than 1
or 2, so translation could not be performed.
o GSS_S_FAILURE indicates that the requested operation could not be
performed for reasons unspecified at the GSS-API level.
Provides a means for callers to translate GSS-API-returned major and
minor status codes into printable string representations. Note: some
language bindings may employ an iterative approach in order to emit
successive status components; this approach is acceptable but not
required for conformance with the current specification.
Although not contemplated in [RFC-2078], it has been observed that
some existing GSS-API implementations return GSS_S_CONTINUE_NEEDED
status when iterating through successive messages returned from
GSS_Display_status(). This behavior is deprecated;
GSS_S_CONTINUE_NEEDED should be returned only by
GSS_Init_sec_context() and GSS_Accept_sec_context(). For maximal
portability, however, it is recommended that defensive callers be
able to accept and ignore GSS_S_CONTINUE_NEEDED status if indicated
by GSS_Display_status() or any other call other than
GSS_Init_sec_context() or GSS_Accept_sec_context().
2.4.2: GSS_Indicate_mechs call
Input:
o (none)
Outputs:
o major_status INTEGER,
o minor_status INTEGER,
o mech_set SET OF OBJECT IDENTIFIER -- caller must release
-- with GSS_Release_oid_set()
Return major_status codes:
o GSS_S_COMPLETE indicates that a set of available mechanisms has
been returned in mech_set.
o GSS_S_FAILURE indicates that the requested operation could not be
performed for reasons unspecified at the GSS-API level.
Allows callers to determine the set of mechanism types available on
the local system. This call is intended for support of specialized
callers who need to request non-default mech_type sets from GSS-API
calls which accept input mechanism type specifiers.
2.4.3: GSS_Compare_name call
Inputs:
o name1 INTERNAL NAME,
o name2 INTERNAL NAME
Outputs:
o major_status INTEGER,
o minor_status INTEGER,
o name_equal BOOLEAN
Return major_status codes:
o GSS_S_COMPLETE indicates that name1 and name2 were comparable, and
that the name_equal result indicates whether name1 and name2
represent the same entity.
o GSS_S_BAD_NAMETYPE indicates that the two input names' types are
different and incomparable, so that the comparison operation could
not be completed.
o GSS_S_BAD_NAME indicates that one or both of the input names was
ill-formed in terms of its internal type specifier, so the comparison
operation could not be completed.
o GSS_S_FAILURE indicates that the call's operation could not be
performed for reasons unspecified at the GSS-API level.
Allows callers to compare two internal name representations to
determine whether they refer to the same entity. If either name
presented to GSS_Compare_name() denotes an anonymous principal,
GSS_Compare_name() shall indicate FALSE. It is not required that
either or both inputs name1 and name2 be MNs; for some
implementations and cases, GSS_S_BAD_NAMETYPE may be returned,
indicating name incomparability, for the case where neither input
name is an MN.
2.4.4: GSS_Display_name call
Inputs:
o name INTERNAL NAME
Outputs:
o major_status INTEGER,
o minor_status INTEGER,
o name_string OCTET STRING, -- caller must release
-- with GSS_Release_buffer()
o name_type OBJECT IDENTIFIER -- caller should treat
-- as read-only; does not need to be released
Return major_status codes:
o GSS_S_COMPLETE indicates that a valid printable name
representation is available in the returned name_string.
o GSS_S_BAD_NAME indicates that the contents of the provided name
were inconsistent with the internally-indicated name type, so no
printable representation could be generated.
o GSS_S_FAILURE indicates that the requested operation could not be
performed for reasons unspecified at the GSS-API level.
Allows callers to translate an internal name representation into a
printable form with associated namespace type descriptor. The syntax
of the printable form is a local matter.
If the input name represents an anonymous identity, a reserved value
(GSS_C_NT_ANONYMOUS) shall be returned for name_type.
The GSS_C_NO_OID name type is to be returned only when the
corresponding internal name was created through import with
GSS_C_NO_OID. It is acceptable for mechanisms to normalize names
imported with GSS_C_NO_OID into other supported types and, therefore,
to display them with types other than GSS_C_NO_OID.
2.4.5: GSS_Import_name call
Inputs:
o input_name_string OCTET STRING,
o input_name_type OBJECT IDENTIFIER
Outputs:
o major_status INTEGER,
o minor_status INTEGER,
o output_name INTERNAL NAME -- caller must release with
-- GSS_Release_name()
Return major_status codes:
o GSS_S_COMPLETE indicates that a valid name representation is
output in output_name and described by the type value in
output_name_type.
o GSS_S_BAD_NAMETYPE indicates that the input_name_type is
unsupported by the applicable underlying GSS-API mechanism(s), so the
import operation could not be completed.
o GSS_S_BAD_NAME indicates that the provided input_name_string is
ill-formed in terms of the input_name_type, so the import operation
could not be completed.
o GSS_S_BAD_MECH indicates that the input presented for import was
an exported name object and that its enclosed mechanism type was not
recognized or was unsupported by the GSS-API implementation.
o GSS_S_FAILURE indicates that the requested operation could not be
performed for reasons unspecified at the GSS-API level.
Allows callers to provide a name representation as a contiguous octet
string, designate the type of namespace in conjunction with which it
should be parsed, and convert that representation to an internal form
suitable for input to other GSS-API routines. The syntax of the
input_name_string is defined in conjunction with its associated name
type; depending on the input_name_type, the associated
input_name_string may or may not be a printable string. If the
input_name_type's value is GSS_C_NO_OID, a mechanism-specific default
printable syntax (which shall be specified in the corresponding GSS-
V2 mechanism specification) is assumed for the input_name_string;
other input_name_type values as registered by GSS-API implementations
can be used to indicate specific non-default name syntaxes. Note: The
input_name_type argument serves to describe and qualify the
interpretation of the associated input_name_string; it does not
specify the data type of the returned output_name.
If a mechanism claims support for a particular name type, its
GSS_Import_name() operation shall be able to accept all possible
values conformant to the external name syntax as defined for that
name type. These imported values may correspond to:
(1) locally registered entities (for which credentials may be
acquired),
(2) non-local entities (for which local credentials cannot be
acquired, but which may be referenced as targets of initiated
security contexts or initiators of accepted security contexts), or
to
(3) neither of the above.
Determination of whether a particular name belongs to class (1), (2),
or (3) as described above is not guaranteed to be performed by the
GSS_Import_name() function.
The internal name generated by a GSS_Import_name() operation may be a
single-mechanism MN, and is likely to be an MN within a single-
mechanism implementation, but portable callers must not depend on
this property (and must not, therefore, assume that the output from
GSS_Import_name() can be passed directly to GSS_Export_name() without
first being processed through GSS_Canonicalize_name()).
2.4.6: GSS_Release_name call
Inputs:
o name INTERNAL NAME
Outputs:
o major_status INTEGER,
o minor_status INTEGER
Return major_status codes:
o GSS_S_COMPLETE indicates that the storage associated with the
input name was successfully released.
o GSS_S_BAD_NAME indicates that the input name argument did not
contain a valid name.
o GSS_S_FAILURE indicates that the requested operation could not be
performed for reasons unspecified at the GSS-API level.
Allows callers to release the storage associated with an internal
name representation. This call's specific behavior depends on the
language and programming environment within which a GSS-API
implementation operates, and is therefore detailed within applicable
bindings specifications; in particular, implementation and invocation
of this call may be superfluous (and may be omitted) within bindings
where memory management is automatic.
2.4.7: GSS_Release_buffer call
Inputs:
o buffer OCTET STRING
Outputs:
o major_status INTEGER,
o minor_status INTEGER
Return major_status codes:
o GSS_S_COMPLETE indicates that the storage associated with the
input buffer was successfully released.
o GSS_S_FAILURE indicates that the requested operation could not be
performed for reasons unspecified at the GSS-API level.
Allows callers to release the storage associated with an OCTET STRING
buffer allocated by another GSS-API call. This call's specific
behavior depends on the language and programming environment within
which a GSS-API implementation operates, and is therefore detailed
within applicable bindings specifications; in particular,
implementation and invocation of this call may be superfluous (and
may be omitted) within bindings where memory management is automatic.
2.4.8: GSS_Release_OID_set call
Inputs:
o buffer SET OF OBJECT IDENTIFIER
Outputs:
o major_status INTEGER,
o minor_status INTEGER
Return major_status codes:
o GSS_S_COMPLETE indicates that the storage associated with the
input object identifier set was successfully released.
o GSS_S_FAILURE indicates that the requested operation could not be
performed for reasons unspecified at the GSS-API level.
Allows callers to release the storage associated with an object
identifier set object allocated by another GSS-API call. This call's
specific behavior depends on the language and programming environment
within which a GSS-API implementation operates, and is therefore
detailed within applicable bindings specifications; in particular,
implementation and invocation of this call may be superfluous (and
may be omitted) within bindings where memory management is automatic.
2.4.9: GSS_Create_empty_OID_set call
Inputs:
o (none)
Outputs:
o major_status INTEGER,
o minor_status INTEGER,
o oid_set SET OF OBJECT IDENTIFIER -- caller must release
-- with GSS_Release_oid_set()
Return major_status codes:
o GSS_S_COMPLETE indicates successful completion
o GSS_S_FAILURE indicates that the operation failed
Creates an object identifier set containing no object identifiers, to
which members may be subsequently added using the
GSS_Add_OID_set_member() routine. These routines are intended to be
used to construct sets of mechanism object identifiers, for input to
GSS_Acquire_cred().
2.4.10: GSS_Add_OID_set_member call
Inputs:
o member_oid OBJECT IDENTIFIER,
o oid_set SET OF OBJECT IDENTIFIER
Outputs:
o major_status INTEGER,
o minor_status INTEGER,
Return major_status codes:
o GSS_S_COMPLETE indicates successful completion
o GSS_S_FAILURE indicates that the operation failed
Adds an Object Identifier to an Object Identifier set. This routine
is intended for use in conjunction with GSS_Create_empty_OID_set()
when constructing a set of mechanism OIDs for input to
GSS_Acquire_cred().
2.4.11: GSS_Test_OID_set_member call
Inputs:
o member OBJECT IDENTIFIER,
o set SET OF OBJECT IDENTIFIER
Outputs:
o major_status INTEGER,
o minor_status INTEGER,
o present BOOLEAN
Return major_status codes:
o GSS_S_COMPLETE indicates successful completion
o GSS_S_FAILURE indicates that the operation failed
Interrogates an Object Identifier set to determine whether a
specified Object Identifier is a member. This routine is intended to
be used with OID sets returned by GSS_Indicate_mechs(),
GSS_Acquire_cred(), and GSS_Inquire_cred().
2.4.12: GSS_Inquire_names_for_mech call
Input:
o input_mech_type OBJECT IDENTIFIER, -- mechanism type
Outputs:
o major_status INTEGER,
o minor_status INTEGER,
o name_type_set SET OF OBJECT IDENTIFIER -- caller must release
-- with GSS_Release_oid_set()
Return major_status codes:
o GSS_S_COMPLETE indicates that the output name_type_set contains a
list of name types which are supported by the locally available
mechanism identified by input_mech_type.
o GSS_S_BAD_MECH indicates that the mechanism identified by
input_mech_type was unsupported within the local implementation,
causing the query to fail.
o GSS_S_FAILURE indicates that the requested operation could not be
performed for reasons unspecified at the GSS-API level.
Allows callers to determine the set of name types which are
supportable by a specific locally-available mechanism.
2.4.13: GSS_Inquire_mechs_for_name call
Inputs:
o input_name INTERNAL NAME,
Outputs:
o major_status INTEGER,
o minor_status INTEGER,
o mech_types SET OF OBJECT IDENTIFIER -- caller must release
-- with GSS_Release_oid_set()
Return major_status codes:
o GSS_S_COMPLETE indicates that a set of object identifiers,
corresponding to the set of mechanisms suitable for processing the
input_name, is available in mech_types.
o GSS_S_BAD_NAME indicates that the input_name was ill-formed and
could not be processed.
o GSS_S_BAD_NAMETYPE indicates that the input_name parameter
contained an invalid name type or a name type unsupported by the
GSS-API implementation.
o GSS_S_FAILURE indicates that the requested operation could not be
performed for reasons unspecified at the GSS-API level.
This routine returns the mechanism set with which the input_name may
be processed.
Each mechanism returned will recognize at least one element within
the name. It is permissible for this routine to be implemented within
a mechanism-independent GSS-API layer, using the type information
contained within the presented name, and based on registration
information provided by individual mechanism implementations. This
means that the returned mech_types result may indicate that a
particular mechanism will understand a particular name when in fact
it would refuse to accept that name as input to
GSS_Canonicalize_name(), GSS_Init_sec_context(), GSS_Acquire_cred(),
or GSS_Add_cred(), due to some property of the particular name rather
than a property of the name type. Thus, this routine should be used
only as a pre-filter for a call to a subsequent mechanism-specific
routine.
2.4.14: GSS_Canonicalize_name call
Inputs:
o input_name INTERNAL NAME,
o mech_type OBJECT IDENTIFIER -- must be explicit mechanism,
-- not "default" specifier or identifier of negotiating mechanism
Outputs:
o major_status INTEGER,
o minor_status INTEGER,
o output_name INTERNAL NAME -- caller must release with
-- GSS_Release_name()
Return major_status codes:
o GSS_S_COMPLETE indicates that a mechanism-specific reduction of
the input_name, as processed by the mechanism identified by
mech_type, is available in output_name.
o GSS_S_BAD_MECH indicates that the identified mechanism is
unsupported for this operation; this may correspond either to a
mechanism wholly unsupported by the local GSS-API implementation or
to a negotiating mechanism with which the canonicalization operation
cannot be performed.
o GSS_S_BAD_NAMETYPE indicates that the input name does not contain
an element with suitable type for processing by the identified
mechanism.
o GSS_S_BAD_NAME indicates that the input name contains an element
with suitable type for processing by the identified mechanism, but
that this element could not be processed successfully.
o GSS_S_FAILURE indicates that the requested operation could not be
performed for reasons unspecified at the GSS-API level.
This routine reduces a GSS-API internal name input_name, which may in
general contain elements corresponding to multiple mechanisms, to a
mechanism-specific Mechanism Name (MN) output_name by applying the
translations corresponding to the mechanism identified by mech_type.
The contents of input_name are unaffected by the
GSS_Canonicalize_name() operation. References to output_name will
remain valid until output_name is released, independent of whether or
not input_name is subsequently released.
2.4.15: GSS_Export_name call
Inputs:
o input_name INTERNAL NAME, -- required to be MN
Outputs:
o major_status INTEGER,
o minor_status INTEGER,
o output_name OCTET STRING -- caller must release
-- with GSS_Release_buffer()
Return major_status codes:
o GSS_S_COMPLETE indicates that a flat representation of the input
name is available in output_name.
o GSS_S_NAME_NOT_MN indicates that the input name contained elements
corresponding to multiple mechanisms, so cannot be exported into a
single-mechanism flat form.
o GSS_S_BAD_NAME indicates that the input name was an MN, but could
not be processed.
o GSS_S_BAD_NAMETYPE indicates that the input name was an MN, but
that its type is unsupported by the GSS-API implementation.
o GSS_S_FAILURE indicates that the requested operation could not be
performed for reasons unspecified at the GSS-API level.
This routine creates a flat name representation, suitable for
bytewise comparison or for input to GSS_Import_name() in conjunction
with the reserved GSS-API Exported Name Object OID, from a internal-
form Mechanism Name (MN) as emitted, e.g., by GSS_Canonicalize_name()
or GSS_Accept_sec_context().
The emitted GSS-API Exported Name Object is self-describing; no
associated parameter-level OID need be emitted by this call. This
flat representation consists of a mechanism-independent wrapper
layer, defined in Section 3.2 of this document, enclosing a
mechanism-defined name representation.
In all cases, the flat name output by GSS_Export_name() to correspond
to a particular input MN must be invariant over time within a
particular installation.
The GSS_S_NAME_NOT_MN status code is provided to enable
implementations to reject input names which are not MNs. It is not,
however, required for purposes of conformance to this specification
that all non-MN input names must necessarily be rejected.
2.4.16: GSS_Duplicate_name call
Inputs:
o src_name INTERNAL NAME
Outputs:
o major_status INTEGER,
o minor_status INTEGER,
o dest_name INTERNAL NAME -- caller must release
-- with GSS_Release_name()
Return major_status codes:
o GSS_S_COMPLETE indicates that dest_name references an internal
name object containing the same name as passed to src_name.
o GSS_S_BAD_NAME indicates that the input name was invalid.
o GSS_S_FAILURE indicates that the requested operation could not be
performed for reasons unspecified at the GSS-API level.
This routine takes input internal name src_name, and returns another
reference (dest_name) to that name which can be used even if src_name
is later freed. (Note: This may be implemented by copying or through
use of reference counts.)
3: Data Structure Definitions for GSS-V2 Usage
Subsections of this section define, for interoperability and
portability purposes, certain data structures for use with GSS-V2.
3.1: Mechanism-Independent Token Format
This section specifies a mechanism-independent level of encapsulating
representation for the initial token of a GSS-API context
establishment sequence, incorporating an identifier of the mechanism
type to be used on that context and enabling tokens to be interpreted
unambiguously at GSS-API peers. Use of this format is required for
initial context establishment tokens of Internet standards-track
GSS-API mechanisms; use in non-initial tokens is optional.
The encoding format for the token tag is derived from ASN.1 and DER
(per illustrative ASN.1 syntax included later within this
subsection), but its concrete representation is defined directly in
terms of octets rather than at the ASN.1 level in order to facilitate
interoperable implementation without use of general ASN.1 processing
code. The token tag consists of the following elements, in order:
1. 0x60 -- Tag for [APPLICATION 0] SEQUENCE; indicates that
-- constructed form, definite length encoding follows.
2. Token length octets, specifying length of subsequent data
(i.e., the summed lengths of elements 3-5 in this list, and of the
mechanism-defined token object following the tag). This element
comprises a variable number of octets:
2a. If the indicated value is less than 128, it shall be
represented in a single octet with bit 8 (high order) set to
"0" and the remaining bits representing the value.
2b. If the indicated value is 128 or more, it shall be
represented in two or more octets, with bit 8 of the first
octet set to "1" and the remaining bits of the first octet
specifying the number of additional octets. The subsequent
octets carry the value, 8 bits per octet, most significant
digit first. The minimum number of octets shall be used to
encode the length (i.e., no octets representing leading zeros
shall be included within the length encoding).
3. 0x06 -- Tag for OBJECT IDENTIFIER
4. Object identifier length -- length (number of octets) of
-- the encoded object identifier contained in element 5,
-- encoded per rules as described in 2a. and 2b. above.
5. Object identifier octets -- variable number of octets,
-- encoded per ASN.1 BER rules:
5a. The first octet contains the sum of two values: (1) the
top-level object identifier component, multiplied by 40
(decimal), and (2) the second-level object identifier
component. This special case is the only point within an
object identifier encoding where a single octet represents
contents of more than one component.
5b. Subsequent octets, if required, encode successively-lower
components in the represented object identifier. A component's
encoding may span multiple octets, encoding 7 bits per octet
(most significant bits first) and with bit 8 set to "1" on all
but the final octet in the component's encoding. The minimum
number of octets shall be used to encode each component (i.e.,
no octets representing leading zeros shall be included within a
component's encoding).
(Note: In many implementations, elements 3-5 may be stored and
referenced as a contiguous string constant.)
The token tag is immediately followed by a mechanism-defined token
object. Note that no independent size specifier intervenes following
the object identifier value to indicate the size of the mechanism-
defined token object. While ASN.1 usage within mechanism-defined
tokens is permitted, there is no requirement that the mechanism-
specific innerContextToken, innerMsgToken, and sealedUserData data
elements must employ ASN.1 BER/DER encoding conventions.
The following ASN.1 syntax is included for descriptive purposes only,
to illustrate structural relationships among token and tag objects.
For interoperability purposes, token and tag encoding shall be
performed using the concrete encoding procedures described earlier in
this subsection.
GSS-API DEFINITIONS ::=
BEGIN
MechType ::= OBJECT IDENTIFIER
-- data structure definitions
-- callers must be able to distinguish among
-- InitialContextToken, SubsequentContextToken,
-- PerMsgToken, and SealedMessage data elements
-- based on the usage in which they occur
InitialContextToken ::=
-- option indication (delegation, etc.) indicated within
-- mechanism-specific token
[APPLICATION 0] IMPLICIT SEQUENCE {
thisMech MechType,
innerContextToken ANY DEFINED BY thisMech
-- contents mechanism-specific
-- ASN.1 structure not required
}
SubsequentContextToken ::= innerContextToken ANY
-- interpretation based on predecessor InitialContextToken
-- ASN.1 structure not required
PerMsgToken ::=
-- as emitted by GSS_GetMIC and processed by GSS_VerifyMIC
-- ASN.1 structure not required
innerMsgToken ANY
SealedMessage ::=
-- as emitted by GSS_Wrap and processed by GSS_Unwrap
-- includes internal, mechanism-defined indicator
-- of whether or not encrypted
-- ASN.1 structure not required
sealedUserData ANY
END
3.2: Mechanism-Independent Exported Name Object Format
This section specifies a mechanism-independent level of encapsulating
representation for names exported via the GSS_Export_name() call,
including an object identifier representing the exporting mechanism.
The format of names encapsulated via this representation shall be
defined within individual mechanism drafts. The Object Identifier
value to indicate names of this type is defined in Section 4.7 of
this document.
No name type OID is included in this mechanism-independent level of
format definition, since (depending on individual mechanism
specifications) the enclosed name may be implicitly typed or may be
explicitly typed using a means other than OID encoding.
The bytes within MECH_OID_LEN and NAME_LEN elements are represented
most significant byte first (equivalently, in IP network byte order).
Length Name Description
2 TOK_ID Token Identifier
For exported name objects, this
must be hex 04 01.
2 MECH_OID_LEN Length of the Mechanism OID
MECH_OID_LEN MECH_OID Mechanism OID, in DER
4 NAME_LEN Length of name
NAME_LEN NAME Exported name; format defined in
applicable mechanism draft.
A concrete example of the contents of an exported name object,
derived from the Kerberos Version 5 mechanism, is as follows:
04 01 00 0B 06 09 2A 86 48 86 F7 12 01 02 02 hx xx xx xl pp qq ... zz
04 01 mandatory token identifier
00 0B 2-byte length of the immediately following DER-encoded
ASN.1 value of type OID, most significant octet first
06 09 2A 86 48 86 F7 12 01 02 02 DER-encoded ASN.1 value
of type OID; Kerberos V5
mechanism OID indicates
Kerberos V5 exported name
in Detail: 06 Identifier octet (6=OID)
09 Length octet(s)
2A 86 48 86 F7 12 01 02 02 Content octet(s)
hx xx xx xl 4-byte length of the immediately following exported
name blob, most significant octet first
pp qq ... zz exported name blob of specified length,
bits and bytes specified in the
(Kerberos 5) GSS-API v2 mechanism spec
4: Name Type Definitions
This section includes definitions for name types and associated
syntaxes which are defined in a mechanism-independent fashion at the
GSS-API level rather than being defined in individual mechanism
specifications.
4.1: Host-Based Service Name Form
This name form shall be represented by the Object Identifier:
{iso(1) member-body(2) United States(840) mit(113554) infosys(1)
"gssapi(2) generic(1) service_name(4)}.
The recommended symbolic name for this type is
"GSS_C_NT_HOSTBASED_SERVICE".
For reasons of compatibility with existing implementations, it is
recommended that this OID be used rather than the alternate value as
included in [RFC-2078]:
{1(iso), 3(org), 6(dod), 1(internet), 5(security), 6(nametypes),
2(gss-host-based-services)}
While it is not recommended that this alternate value be emitted on
output by GSS implementations, it is recommended that it be accepted
on input as equivalent to the recommended value.
This name type is used to represent services associated with host
computers. Support for this name form is recommended to mechanism
designers in the interests of portability, but is not mandated by
this specification. This name form is constructed using two elements,
"service" and "hostname", as follows:
service@hostname
When a reference to a name of this type is resolved, the "hostname"
may (as an example implementation strategy) be canonicalized by
attempting a DNS lookup and using the fully-qualified domain name
which is returned, or by using the "hostname" as provided if the DNS
lookup fails. The canonicalization operation also maps the host's
name into lower-case characters.
The "hostname" element may be omitted. If no "@" separator is
included, the entire name is interpreted as the service specifier,
with the "hostname" defaulted to the canonicalized name of the local
host.
Documents specifying means for GSS integration into a particular
protocol should state either:
(a) that a specific IANA-registered name associated with that
protocol shall be used for the "service" element (this admits, if
needed, the possibility that a single name can be registered and
shared among a related set of protocols), or
(b) that the generic name "host" shall be used for the "service"
element, or
(c) that, for that protocol, fallback in specified order (a, then
b) or (b, then a) shall be applied.
IANA registration of specific names per (a) should be handled in
accordance with the "Specification Required" assignment policy,
defined by BCP 26, RFC2434 as follows: "Values and their meaning
must be documented in an RFCor other available reference, in
sufficient detail so that interoperability between independent
implementations is possible."
4.2: User Name Form
This name form shall be represented by the Object Identifier {iso(1)
member-body(2) United States(840) mit(113554) infosys(1) gssapi(2)
generic(1) user_name(1)}. The recommended mechanism-independent
symbolic name for this type is "GSS_C_NT_USER_NAME". (Note: the same
name form and OID is defined within the Kerberos V5 GSS-API
mechanism, but the symbolic name recommended there begins with a
"GSS_KRB5_NT_" prefix.)
This name type is used to indicate a named user on a local system.
Its syntax and interpretation may be OS-specific. This name form is
constructed as:
username
4.3: Machine UID Form
This name form shall be represented by the Object Identifier {iso(1)
member-body(2) United States(840) mit(113554) infosys(1) gssapi(2)
generic(1) machine_uid_name(2)}. The recommended mechanism-
independent symbolic name for this type is
"GSS_C_NT_MACHINE_UID_NAME". (Note: the same name form and OID is
defined within the Kerberos V5 GSS-API mechanism, but the symbolic
name recommended there begins with a "GSS_KRB5_NT_" prefix.)
This name type is used to indicate a numeric user identifier
corresponding to a user on a local system. Its interpretation is
OS-specific. The gss_buffer_desc representing a name of this type
should contain a locally-significant user ID, represented in host
byte order. The GSS_Import_name() operation resolves this uid into a
username, which is then treated as the User Name Form.
4.4: String UID Form
This name form shall be represented by the Object Identifier {iso(1)
member-body(2) United States(840) mit(113554) infosys(1) gssapi(2)
generic(1) string_uid_name(3)}. The recommended symbolic name for
this type is "GSS_C_NT_STRING_UID_NAME". (Note: the same name form
and OID is defined within the Kerberos V5 GSS-API mechanism, but the
symbolic name recommended there begins with a "GSS_KRB5_NT_" prefix.)
This name type is used to indicate a string of digits representing
the numeric user identifier of a user on a local system. Its
interpretation is OS-specific. This name type is similar to the
Machine UID Form, except that the buffer contains a string
representing the user ID.
4.5: Anonymous Nametype
The following Object Identifier value is provided as a means to
identify anonymous names, and can be compared against in order to
determine, in a mechanism-independent fashion, whether a name refers
to an anonymous principal:
{1(iso), 3(org), 6(dod), 1(internet), 5(security), 6(nametypes),
3(gss-anonymous-name)}
The recommended symbolic name corresponding to this definition is
GSS_C_NT_ANONYMOUS.
4.6: GSS_C_NO_OID
The recommended symbolic name GSS_C_NO_OID corresponds to a null
input value instead of an actual object identifier. Where specified,
it indicates interpretation of an associated name based on a
mechanism-specific default printable syntax.
4.7: Exported Name Object
Name objects of the Mechanism-Independent Exported Name Object type,
as defined in Section 3.2 of this document, will be identified with
the following Object Identifier:
{1(iso), 3(org), 6(dod), 1(internet), 5(security), 6(nametypes),
4(gss-api-exported-name)}
The recommended symbolic name corresponding to this definition is
GSS_C_NT_EXPORT_NAME.
4.8: GSS_C_NO_NAME
The recommended symbolic name GSS_C_NO_NAME indicates that no name is
being passed within a particular value of a parameter used for the
purpose of transferring names. Note: GSS_C_NO_NAME is not an actual
name type, and is not represented by an OID; its acceptability in
lieu of an actual name is confined to specific calls
(GSS_Acquire_cred(), GSS_Add_cred(), and GSS_Init_sec_context()) with
usages as identified within this specification.
5: Mechanism-Specific Example Scenarios
This section provides illustrative overviews of the use of various
candidate mechanism types to support the GSS-API. These discussions
are intended primarily for readers familiar with specific security
technologies, demonstrating how GSS-API functions can be used and
implemented by candidate underlying mechanisms. They should not be
regarded as constrictive to implementations or as defining the only
means through which GSS-API functions can be realized with a
particular underlying technology, and do not demonstrate all GSS-API
features with each technology.
5.1: Kerberos V5, single-TGT
OS-specific login functions yield a TGT to the local realm Kerberos
server; TGT is placed in a credentials structure for the client.
Client calls GSS_Acquire_cred() to acquire a cred_handle in order to
reference the credentials for use in establishing security contexts.
Client calls GSS_Init_sec_context(). If the requested service is
located in a different realm, GSS_Init_sec_context() gets the
necessary TGT/key pairs needed to traverse the path from local to
target realm; these data are placed in the owner's TGT cache. After
any needed remote realm resolution, GSS_Init_sec_context() yields a
service ticket to the requested service with a corresponding session
key; these data are stored in conjunction with the context. GSS-API
code sends KRB_TGS_REQ request(s) and receives KRB_TGS_REP
response(s) (in the successful case) or KRB_ERROR.
Assuming success, GSS_Init_sec_context() builds a Kerberos-formatted
KRB_AP_REQ message, and returns it in output_token. The client sends
the output_token to the service.
The service passes the received token as the input_token argument to
GSS_Accept_sec_context(), which verifies the authenticator, provides
the service with the client's authenticated name, and returns an
output_context_handle.
Both parties now hold the session key associated with the service
ticket, and can use this key in subsequent GSS_GetMIC(),
GSS_VerifyMIC(), GSS_Wrap(), and GSS_Unwrap() operations.
5.2: Kerberos V5, double-TGT
TGT acquisition as above.
Note: To avoid unnecessary frequent invocations of error paths when
implementing the GSS-API atop Kerberos V5, it seems appropriate to
represent "single-TGT K-V5" and "double-TGT K-V5" with separate
mech_types, and this discussion makes that assumption.
Based on the (specified or defaulted) mech_type,
GSS_Init_sec_context() determines that the double-TGT protocol
should be employed for the specified target. GSS_Init_sec_context()
returns GSS_S_CONTINUE_NEEDED major_status, and its returned
output_token contains a request to the service for the service's TGT.
(If a service TGT with suitably long remaining lifetime already
exists in a cache, it may be usable, obviating the need for this
step.) The client passes the output_token to the service. Note: this
scenario illustrates a different use for the GSS_S_CONTINUE_NEEDED
status return facility than for support of mutual authentication;
note that both uses can coexist as successive operations within a
single context establishment operation.
The service passes the received token as the input_token argument to
GSS_Accept_sec_context(), which recognizes it as a request for TGT.
(Note that current Kerberos V5 defines no intra-protocol mechanism to
represent such a request.) GSS_Accept_sec_context() returns
GSS_S_CONTINUE_NEEDED major_status and provides the service's TGT in
its output_token. The service sends the output_token to the client.
The client passes the received token as the input_token argument to a
continuation of GSS_Init_sec_context(). GSS_Init_sec_context() caches
the received service TGT and uses it as part of a service ticket
request to the Kerberos authentication server, storing the returned
service ticket and session key in conjunction with the context.
GSS_Init_sec_context() builds a Kerberos-formatted authenticator, and
returns it in output_token along with GSS_S_COMPLETE return
major_status. The client sends the output_token to the service.
Service passes the received token as the input_token argument to a
continuation call to GSS_Accept_sec_context().
GSS_Accept_sec_context() verifies the authenticator, provides the
service with the client's authenticated name, and returns
major_status GSS_S_COMPLETE.
GSS_GetMIC(), GSS_VerifyMIC(), GSS_Wrap(), and GSS_Unwrap() as
above.
5.3: X.509 Authentication Framework
This example illustrates use of the GSS-API in conjunction with
public-key mechanisms, consistent with the X.509 Directory
Authentication Framework.
The GSS_Acquire_cred() call establishes a credentials structure,
making the client's private key accessible for use on behalf of the
client.
The client calls GSS_Init_sec_context(), which interrogates the
Directory to acquire (and validate) a chain of public-key
certificates, thereby collecting the public key of the service. The
certificate validation operation determines that suitable integrity
checks were applied by trusted authorities and that those
certificates have not expired. GSS_Init_sec_context() generates a
secret key for use in per-message protection operations on the
context, and enciphers that secret key under the service's public
key.
The enciphered secret key, along with an authenticator quantity
signed with the client's private key, is included in the output_token
from GSS_Init_sec_context(). The output_token also carries a
certification path, consisting of a certificate chain leading from
the service to the client; a variant approach would defer this path
resolution to be performed by the service instead of being asserted
by the client. The client application sends the output_token to the
service.
The service passes the received token as the input_token argument to
GSS_Accept_sec_context(). GSS_Accept_sec_context() validates the
certification path, and as a result determines a certified binding
between the client's distinguished name and the client's public key.
Given that public key, GSS_Accept_sec_context() can process the
input_token's authenticator quantity and verify that the client's
private key was used to sign the input_token. At this point, the
client is authenticated to the service. The service uses its private
key to decipher the enciphered secret key provided to it for per-
message protection operations on the context.
The client calls GSS_GetMIC() or GSS_Wrap() on a data message, which
causes per-message authentication, integrity, and (optional)
confidentiality facilities to be applied to that message. The service
uses the context's shared secret key to perform corresponding
GSS_VerifyMIC() and GSS_Unwrap() calls.
6: Security Considerations
This document specifies a service interface for security facilities
and services; as such, security considerations are considered
throughout the specification. Nonetheless, it is appropriate to
summarize certain specific points relevant to GSS-API implementors
and calling applications. Usage of the GSS-API interface does not in
itself provide security services or assurance; instead, these
attributes are dependent on the underlying mechanism(s) which support
a GSS-API implementation. Callers must be attentive to the requests
made to GSS-API calls and to the status indicators returned by GSS-
API, as these specify the security service characteristics which
GSS-API will provide. When the interprocess context transfer
facility is used, appropriate local controls should be applied to
constrain access to interprocess tokens and to the sensitive data
which they contain.
7: Related Activities
In order to implement the GSS-API atop existing, emerging, and future
security mechanisms:
object identifiers must be assigned to candidate GSS-API
mechanisms and the name types which they support
concrete data element formats and processing procedures must be
defined for candidate mechanisms
Calling applications must implement formatting conventions which will
enable them to distinguish GSS-API tokens from other data carried in
their application protocols.
Concrete language bindings are required for the programming
environments in which the GSS-API is to be employed, as [RFC-1509]
defines for the C programming language and GSS-V1. C Language
bindings for GSS-V2 are defined in [RFC-2744].
8: Referenced Documents
[ISO-7498-2] International Standard ISO 7498-2-1988(E), Security
Architecture.
[ISOIEC-8824] ISO/IEC 8824, "Specification of Abstract Syntax
Notation One (ASN.1)".
[ISOIEC-8825] ISO/IEC 8825, "Specification of Basic Encoding Rules
for Abstract Syntax Notation One (ASN.1)".)
[RFC-1507]: Kaufman, C., "DASS: Distributed Authentication Security
Service", RFC1507, September 1993.
[RFC-1508]: Linn, J., "Generic Security Service Application Program
Interface", RFC1508, September 1993.
[RFC-1509]: Wray, J., "Generic Security Service API: C-bindings",
RFC1509, September 1993.
[RFC-1964]: Linn, J., "The Kerberos Version 5 GSS-API Mechanism",
RFC1964, June 1996.
[RFC-2025]: Adams, C., "The Simple Public-Key GSS-API Mechanism
(SPKM)", RFC2025, October 1996.
[RFC-2078]: Linn, J., "Generic Security Service Application Program
Interface, Version 2", RFC2078, January 1997.
[RFC-2203]: Eisler, M., Chiu, A. and L. Ling, "RPCSEC_GSS Protocol
Specification", RFC2203, September 1997.
[RFC-2744]: Wray, J., "Generic Security Service API Version 2 :
C-bindings", RFC2744, January 2000.
APPENDIX A
MECHANISM DESIGN CONSTRAINTS
The following constraints on GSS-API mechanism designs are adopted in
response to observed caller protocol requirements, and adherence
thereto is anticipated in subsequent descriptions of GSS-API
mechanisms to be documented in standards-track Internet
specifications.
It is strongly recommended that mechanisms offering per-message
protection services also offer at least one of the replay detection
and sequencing services, as mechanisms offering neither of the latter
will fail to satisfy recognized requirements of certain candidate
caller protocols.
APPENDIX B
COMPATIBILITY WITH GSS-V1
It is the intent of this document to define an interface and
procedures which preserve compatibility between GSS-V1 [RFC-1508]
callers and GSS-V2 providers. All calls defined in GSS-V1 are
preserved, and it has been a goal that GSS-V1 callers should be able
to operate atop GSS-V2 provider implementations. Certain detailed
changes, summarized in this section, have been made in order to
resolve omissions identified in GSS-V1.
The following GSS-V1 constructs, while supported within GSS-V2, are
deprecated:
Names for per-message processing routines: GSS_Seal() deprecated
in favor of GSS_Wrap(); GSS_Sign() deprecated in favor of
GSS_GetMIC(); GSS_Unseal() deprecated in favor of GSS_Unwrap();
GSS_Verify() deprecated in favor of GSS_VerifyMIC().
GSS_Delete_sec_context() facility for context_token usage,
allowing mechanisms to signal context deletion, is retained for
compatibility with GSS-V1. For current usage, it is recommended
that both peers to a context invoke GSS_Delete_sec_context()
independently, passing a null output_context_token buffer to
indicate that no context_token is required. Implementations of
GSS_Delete_sec_context() should delete relevant locally-stored
context information.
This GSS-V2 specification adds the following calls which are not
present in GSS-V1:
Credential management calls: GSS_Add_cred(),
GSS_Inquire_cred_by_mech().
Context-level calls: GSS_Inquire_context(), GSS_Wrap_size_limit(),
GSS_Export_sec_context(), GSS_Import_sec_context().
Per-message calls: No new calls. Existing calls have been
renamed.
Support calls: GSS_Create_empty_OID_set(),