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<Network Working Group> Larry Zhu
Internet Draft Karthik Jaganathan
Updates: 1964 Microsoft
Category: Standards Track Sam Hartman
draft-ietf-krb-wg-gssapi-cfx-04.txt MIT
November 21, 2003
Expires: May 21, 2004
The Kerberos Version 5 GSS-API Mechanism: Version 2
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of [RFC-2026].
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts. Internet-Drafts are draft documents valid for a maximum of
six months and may be updated, replaced, or obsoleted by other
documents at any time. It is inappropriate to use Internet-Drafts
as reference material or to cite them other than as "work in
progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
Abstract
This memo defines protocols, procedures, and conventions to be
employed by peers implementing the Generic Security Service
Application Program Interface (GSS-API as specified in [RFC-2743])
when using the Kerberos Version 5 mechanism (as specified in
[KRBCLAR]).
[RFC-1964] is updated and incremental changes are proposed in
response to recent developments such as the introduction of Kerberos
crypto framework [KCRYPTO]. These changes support the inclusion of
new cryptosystems based on crypto profiles [KCRYPTO], by defining
new per-message tokens along with their encryption and checksum
algorithms.
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 [RFC-2119].
1. Introduction
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Kerberos Version 5 GSS-API November 2003
[KCRYPTO] defines a generic framework for describing encryption and
checksum types to be used with the Kerberos protocol and associated
protocols.
[RFC-1964] describes the GSS-API mechanism for Kerberos Version 5.
It defines the format of context establishment, per-message and
context deletion tokens and uses algorithm identifiers for each
cryptosystem in per message and context deletion tokens.
The approach taken in this document obviates the need for algorithm
identifiers. This is accomplished by using the same encryption
algorithm, specified by the crypto profile [KCRYPTO] for the session
key or subkey that is created during context negotiation, and its
required checksum algorithm. Message layouts of the per-message
tokens are therefore revised to remove algorithm indicators and also
to add extra information to support the generic crypto framework
[KCRYPTO].
Tokens transferred between GSS-API peers for security context
establishment are also described in this document. The data
elements exchanged between a GSS-API endpoint implementation and the
Kerberos KDC are not specific to GSS-API usage and are therefore
defined within [KRBCLAR] rather than within this specification.
The new token formats specified in this memo MUST be used with all
"newer" encryption types [KRBCLAR] and MAY be used with "older"
encryption types, provided that the initiator and acceptor know,
from the context establishment, that they can both process these new
token formats.
"Newer" encryption types are those which have been specified along
with or since the new Kerberos cryptosystem specification [KCRYPTO],
as defined in section 3.1.3 of [KRBCLAR]. The list of not-newer
encryption types is as follows [KCRYPTO]:
Encryption Type Assigned Number
----------------------------------------------
des-cbc-crc 1
des-cbc-md4 2
des-cbc-md5 3
des3-cbc-md5 5
des3-cbc-sha1 7
dsaWithSHA1-CmsOID 9
md5WithRSAEncryption-CmsOID 10
sha1WithRSAEncryption-CmsOID 11
rc2CBC-EnvOID 12
rsaEncryption-EnvOID 13
rsaES-OAEP-ENV-OID 14
des-ede3-cbc-Env-OID 15
des3-cbc-sha1-kd 16
rc4-hmac 23
Note that in this document, the term "little endian order" is used
for brevity to refer to the least-significant-octet-first encoding,
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while the term "big endian order" is for the most-significant-octet-
first encoding.
2. Key Derivation for Per-Message Tokens
To limit the exposure of a given key, [KCRYPTO] adopted "one-way"
"entropy-preserving" derived keys, for different purposes or key
usages, from a base key or protocol key.
This document defines four key usage values below that are used to
derive a specific key for signing and sealing messages, from the
session key or subkey [KRBCLAR] created during the context
establishment.
Name Value
-------------------------------------
KG-USAGE-ACCEPTOR-SEAL 22
KG-USAGE-ACCEPTOR-SIGN 23
KG-USAGE-INITIATOR-SEAL 24
KG-USAGE-INITIATOR-SIGN 25
When the sender is the context acceptor, KG-USAGE-ACCEPTOR-SIGN is
used as the usage number in the key derivation function for deriving
keys to be used in MIC tokens, and KG-USAGE-ACCEPTOR-SEAL is used
for Wrap tokens; similarly when the sender is the context initiator,
KG-USAGE-INITIATOR-SIGN is used as the usage number in the key
derivation function for MIC tokens, KG-USAGE-INITIATOR-SEAL is used
for Wrap Tokens. Even if the Wrap token does not provide for
confidentiality the same usage values specified above are used.
During the context initiation and acceptance sequence, the acceptor
MAY assert a subkey, and if so, subsequent messages MUST use this
subkey as the protocol key and these messages MUST be flagged as
"AcceptorSubkey" as described in section 4.2.2.
3. Quality of Protection
The GSS-API specification [RFC-2743] provides for Quality of
Protection (QOP) values that can be used by applications to request
a certain type of encryption or signing. A zero QOP value is used
to indicate the "default" protection; applications which do not use
the default QOP are not guaranteed to be portable across
implementations or even inter-operate with different deployment
configurations of the same implementation. Using an algorithm that
is different from the one for which the key is defined may not be
appropriate. Therefore, when the new method in this document is
used, the QOP value is ignored.
The encryption and checksum algorithms in per-message tokens are now
implicitly defined by the algorithms associated with the session key
or subkey. Algorithms identifiers as described in [RFC-1964] are
therefore no longer needed and removed from the new token headers.
4. Definitions and Token Formats
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Kerberos Version 5 GSS-API November 2003
This section provides terms and definitions, as well as descriptions
for tokens specific to the Kerberos Version 5 GSS-API mechanism.
4.1. Context Establishment Tokens
All context establishment tokens emitted by the Kerberos V5 GSS-API
mechanism will have the framing shown below:
GSS-API DEFINITIONS ::=
BEGIN
MechType ::= OBJECT IDENTIFIER
-- representing Kerberos V5 mechanism
GSSAPI-Token ::=
-- option indication (delegation, etc.) indicated within
-- mechanism-specific token
[APPLICATION 0] IMPLICIT SEQUENCE {
thisMech MechType,
innerToken ANY DEFINED BY thisMech
-- contents mechanism-specific
-- ASN.1 structure not required
}
END
Where the notation and encoding of this pseudo ASN.1 header, which
is referred as the generic GSS-API token framing later in this
document, are described in [RFC-2743], and the innerToken field
starts with a two-octet token-identifier (TOK_ID) expressed in big
endian order, followed by a Kerberos message.
Here are the TOK_ID values used in the context establishment tokens:
Token TOK_ID Value in Hex
-----------------------------------------
KRB_AP_REQUEST 01 00
KRB_AP_REPLY 02 00
KRB_ERROR 03 00
Where Kerberos message KRB_AP_REQUEST, KRB_AP_REPLY, and KRB_ERROR
are defined in [KRBCLAR].
If an unknown token identifier (TOK_ID) is received in the initial
context estalishment token, the receiver MUST return
GSS_S_CONTINUE_NEEDED major status, and the returned output token
MUST contain a KRB_ERROR message with the error code
KRB_AP_ERR_MSG_TYPE [KRBCLAR].
4.1.1. Authenticator Checksum
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The authenticator in the KRB_AP_REQ message MUST include the
optional sequence number and the checksum field. The checksum field
is used to convey service flags, channel bindings, and optional
delegation information. The checksum type MUST be 0x8003. The
length of the checksum MUST be 24 octets when delegation is not
used. When delegation is used, a ticket-granting ticket will be
transferred in a KRB_CRED message. This ticket SHOULD have its
forwardable flag set. The KRB_CRED message MUST be encrypted in the
session key of the ticket used to authenticate the context.
The format of the authenticator checksum field is as follows.
Octet Name Description
-----------------------------------------------------------------
0..3 Lgth Number of octets in Bnd field; Currently
contains hex value 10 00 00 00 (16, represented
in little-endian order)
4..19 Bnd Channel binding information, as described in
section 4.1.1.2.
20..23 Flags Four-octet context-establishment flags in little-
endian order as described in section 4.1.1.1.
24..25 DlgOpt The Delegation Option identifier (=1) [optional]
26..27 Dlgth The length of the Deleg field [optional]
28..n Deleg A KRB_CRED message (n = Dlgth + 29) [optional]
4.1.1.1. Checksum Flags Field
The checksum "Flags" field is used to convey service options or
extension negotiation information. The following context
establishment flags are defined in [RFC-2744].
Flag Name Value
---------------------------------
GSS_C_DELEG_FLAG 1
GSS_C_MUTUAL_FLAG 2
GSS_C_REPLAY_FLAG 4
GSS_C_SEQUENCE_FLAG 8
GSS_C_CONF_FLAG 16
GSS_C_INTEG_FLAG 32
Context establishment flags are exposed to the calling application.
If the calling application desires a particular service option then
it requests that option via GSS_Init_sec_context() [RFC-2743]. An
implementation that supports a particular option or extension SHOULD
then set the appropriate flag in the checksum Flags field.
The most significant eight bits of the checksum flags are reserved
for future use. The receiver MUST ignore unknown checksum flags.
4.1.1.2. Channel Binding Information
Channel bindings are user-specified tags to identify a given context
to the peer application. These tags are intended to be used to
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Kerberos Version 5 GSS-API November 2003
identify the particular communications channel that carries the
context [RFC-2743] [RFC-2744].
When using C language bindings, channel bindings are communicated to
the GSS-API using the following structure [RFC-2744]:
typedef struct gss_channel_bindings_struct {
OM_uint32 initiator_addrtype;
gss_buffer_desc initiator_address;
OM_uint32 acceptor_addrtype;
gss_buffer_desc acceptor_address;
gss_buffer_desc application_data;
} *gss_channel_bindings_t;
The member fields and constants used for different address types are
defined in [RFC-2744].
The "Bnd" field contains the MD5 hash of channel bindings, taken
over all non-null components of bindings, in order of declaration.
Integer fields within channel bindings are represented in little-
endian order for the purposes of the MD5 calculation.
In computing the contents of the Bnd field, the following detailed
points apply:
(1) Each integer field shall be formatted into four octets, using
little endian octet ordering, for purposes of MD5 hash computation.
(2) All input length fields within gss_buffer_desc elements of a
gss_channel_bindings_struct even those which are zero-valued, shall
be included in the hash calculation; the value elements of
gss_buffer_desc elements shall be dereferenced, and the resulting
data shall be included within the hash computation, only for the
case of gss_buffer_desc elements having non-zero length specifiers.
(3) If the caller passes the value GSS_C_NO_BINDINGS instead of a
valid channel binding structure, the Bnd field shall be set to 16
zero-valued octets.
4.2. Per-Message Tokens
Two classes of tokens are defined in this section: "MIC" tokens,
emitted by calls to GSS_GetMIC() and consumed by calls to
GSS_VerifyMIC(), "Wrap" tokens, emitted by calls to GSS_Wrap() and
consumed by calls to GSS_Unwrap().
The new per-message tokens introduced here do not include the
generic GSS-API token framing used by the context establishment
tokens. These new tokens are designed to be used with newer crypto
systems that can, for example, have variable-size checksums.
4.2.1. Sequence Number
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To distinguish intentionally-repeated messages from maliciously-
replayed ones, per-message tokens contain a sequence number field,
which is a 64 bit integer expressed in big endian order. After
sending a GSS_GetMIC() or GSS_Wrap() token, the sender's sequence
numbers are incremented by one.
4.2.2. Flags Field
The "Flags" field is a one-octet integer used to indicate a set of
attributes for the protected message. For example, one flag is
allocated as the direction-indicator, thus preventing an adversary
from sending back the same message in the reverse direction and
having it accepted.
The meanings of bits in this field (the least significant bit is bit
0) are as follows:
Bit Name Description
---------------------------------------------------------------
0 SentByAcceptor When set, this flag indicates the sender
is the context acceptor. When not set,
it indicates the sender is the context
initiator.
1 Sealed When set in Wrap tokens, this flag
indicates confidentiality is provided
for. It SHALL NOT be set in MIC tokens.
2 AcceptorSubkey A subkey asserted by the context acceptor
is used to protect the message.
The rest of available bits are reserved for future use and MUST be
cleared. The receiver MUST ignore unknown flags.
4.2.3. EC Field
The "EC" (Extra Count) field is a two-octet integer field expressed
in big endian order.
In Wrap tokens with confidentiality, the EC field is used to encode
the number of octets in the filler, as described in section 4.2.4.
In Wrap tokens without confidentiality, the EC field is used to
encode the number of octets in the trailing checksum, as described
in section 4.2.4.
4.2.4. Encryption and Checksum Operations
The encryption algorithms defined by the crypto profiles provide for
integrity protection [KCRYPTO]. Therefore no separate checksum is
needed.
The result of decryption can be longer than the original plaintext
[KCRYPTO] and the extra trailing octets are called "crypto-system
garbage". However, given the size of any plaintext data, one can
always find the next (possibly larger) size so that, when padding
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Kerberos Version 5 GSS-API November 2003
the to-be-encrypted text to that size, there will be no crypto-
system garbage added [KCRYPTO].
In Wrap tokens that provide for confidentiality, the first 16 octets
of the Wrap token (the "header", as defined in section 4.2.6), are
appended to the plaintext data before encryption. Filler octets can
be inserted between the plaintext data and the "header", and the
values and size of the filler octets are chosen by implementations,
such that there is no crypto-system garbage present after the
decryption. The resulting Wrap token is {"header" |
encrypt(plaintext-data | filler | "header")}, where encrypt() is the
encryption operation (which provides for integrity protection)
defined in the crypto profile [KCRYPTO], and the RRC field in the
to-be-encrypted header contains the hex value 00 00.
In Wrap tokens that do not provide for confidentiality, the checksum
is calculated first over the to-be-signed plaintext data, and then
the first 16 octets of the Wrap token (the "header", as defined in
section 4.2.6). Both the EC field and the RRC field in the token
header are filled with zeroes for the purpose of calculating the
checksum. The resulting Wrap token is {"header" | plaintext-data |
get_mic(plaintext-data | "header")}, where get_mic() is the
checksum operation for the required checksum mechanism of the chosen
encryption mechanism defined in the crypto profile [KCRYPTO].
The parameters for the key and the cipher-state in the encrypt() and
get_mic() operations have been omitted for brevity.
For MIC tokens, the checksum is first calculated over the to-be-
signed plaintext data, and then the first 16 octets of the MIC
token, where the checksum mechanism is the required checksum
mechanism of the chosen encryption mechanism defined in the crypto
profile [KCRYPTO].
The resulting Wrap and MIC tokens bind the data to the token header,
including the sequence number and the direction indicator.
4.2.5. RRC Field
The "RRC" (Right Rotation Count) field in Wrap tokens is added to
allow the data to be encrypted in-place by existing [SSPI]
applications that do not provide an additional buffer for the
trailer (the cipher text after the in-place-encrypted data) in
addition to the buffer for the header (the cipher text before the
in-place-encrypted data). The resulting Wrap token in the previous
section, excluding the first 16 octets of the token header, is
rotated to the right by "RRC" octets. The net result is that "RRC"
octets of trailing octets are moved toward the header. Consider the
following as an example of this rotation operation: Assume that the
RRC value is 3 and the token before the rotation is {"header" | aa |
bb | cc | dd | ee | ff | gg | hh}, the token after rotation would be
{"header" | ff | gg | hh | aa | bb | cc | dd | ee }, where {aa | bb
| cc |...| hh} is used to indicate the octet sequence.
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The RRC field is expressed as a two-octet integer in big endian
order.
The rotation count value is chosen by the sender based on
implementation details, and the receiver MUST be able to interpret
all possible rotation count values.
4.2.6. Message Layouts
Per-message tokens start with a two-octet token identifier (TOK_ID)
field, expressed in big endian order. These tokens are defined
separately in subsequent sub-sections.
4.2.6.1. MIC Tokens
Use of the GSS_GetMIC() call yields a token, separate from the user
data being protected, which can be used to verify the integrity of
that data as received. The token has the following format:
Octet no Name Description
-----------------------------------------------------------------
0..1 TOK_ID Identification field. Tokens emitted by
GSS_GetMIC() contain the hex value 04 04
expressed in big endian order in this field.
2 Flags Attributes field, as described in section
4.2.2.
3..7 Filler Contains five octets of hex value FF.
8..15 SND_SEQ Sequence number field in clear text,
expressed in big endian order.
16..last SGN_CKSUM Checksum of octet 0..15 and the "to-be-
signed" data, as described in section 4.2.4.
The Filler field is included in the checksum calculation for
simplicity.
4.2.6.2. Wrap Tokens
Use of the GSS_Wrap() call yields a token, which consists of a
descriptive header, followed by a body portion that contains either
the input user data in plaintext concatenated with the checksum, or
the input user data encrypted. The GSS_Wrap() token has the
following format:
Octet no Name Description
---------------------------------------------------------------
0..1 TOK_ID Identification field. Tokens emitted by
GSS_Wrap() contain the the hex value 05 04
expressed in big endian order in this field.
2 Flags Attributes field, as described in section
4.2.2.
3 Filler Contains the hex value FF.
4..5 EC Contains the "extra count" field, in big
endian order as described in section 4.2.3.
6..7 RRC Contains the "right rotation count" in big
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endian order, as described in section 4.2.5.
8..15 SND_SEQ Sequence number field in clear text,
expressed in big endian order.
16..last Data Encrypted data for Wrap tokens with
confidentiality, or plaintext data followed
by the checksum for Wrap tokens without
confidentiality, as described in section
4.2.4.
4.3. Context Deletion Tokens
Context deletion tokens are empty in this mechanism. Both peers to
a security context invoke GSS_Delete_sec_context() [RFC-2743]
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.
4.4. Token Identifier Assignment Considerations
Token identifiers (TOK_ID) from 0x60 0x00 through 0x60 0xFF
inclusive are reserved and SHALL NOT be assigned. Thus by examining
the first two octets of a token, one can tell unambiguously if it is
wrapped with the generic GSS-API token framing.
5. Parameter Definitions
This section defines parameter values used by the Kerberos V5 GSS-
API mechanism. It defines interface elements in support of
portability, and assumes use of C language bindings per [RFC-2744].
5.1. Minor Status Codes
This section recommends common symbolic names for minor_status
values to be returned by the Kerberos V5 GSS-API mechanism. Use of
these definitions will enable independent implementers to enhance
application portability across different implementations of the
mechanism defined in this specification. (In all cases,
implementations of GSS_Display_status() will enable callers to
convert minor_status indicators to text representations.) Each
implementation should make available, through include files or other
means, a facility to translate these symbolic names into the
concrete values which a particular GSS-API implementation uses to
represent the minor_status values specified in this section.
It is recognized that this list may grow over time, and that the
need for additional minor_status codes specific to particular
implementations may arise. It is recommended, however, that
implementations should return a minor_status value as defined on a
mechanism-wide basis within this section when that code is
accurately representative of reportable status rather than using a
separate, implementation-defined code.
5.1.1. Non-Kerberos-specific codes
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GSS_KRB5_S_G_BAD_SERVICE_NAME
/* "No @ in SERVICE-NAME name string" */
GSS_KRB5_S_G_BAD_STRING_UID
/* "STRING-UID-NAME contains nondigits" */
GSS_KRB5_S_G_NOUSER
/* "UID does not resolve to username" */
GSS_KRB5_S_G_VALIDATE_FAILED
/* "Validation error" */
GSS_KRB5_S_G_BUFFER_ALLOC
/* "Couldn't allocate gss_buffer_t data" */
GSS_KRB5_S_G_BAD_MSG_CTX
/* "Message context invalid" */
GSS_KRB5_S_G_WRONG_SIZE
/* "Buffer is the wrong size" */
GSS_KRB5_S_G_BAD_USAGE
/* "Credential usage type is unknown" */
GSS_KRB5_S_G_UNKNOWN_QOP
/* "Unknown quality of protection specified" */
5.1.2. Kerberos-specific-codes
GSS_KRB5_S_KG_CCACHE_NOMATCH
/* "Client principal in credentials does not match
specified name" */
GSS_KRB5_S_KG_KEYTAB_NOMATCH
/* "No key available for specified service principal" */
GSS_KRB5_S_KG_TGT_MISSING
/* "No Kerberos ticket-granting ticket available" */
GSS_KRB5_S_KG_NO_SUBKEY
/* "Authenticator has no subkey" */
GSS_KRB5_S_KG_CONTEXT_ESTABLISHED
/* "Context is already fully established" */
GSS_KRB5_S_KG_BAD_SIGN_TYPE
/* "Unknown signature type in token" */
GSS_KRB5_S_KG_BAD_LENGTH
/* "Invalid field length in token" */
GSS_KRB5_S_KG_CTX_INCOMPLETE
/* "Attempt to use incomplete security context" */
5.2. Buffer Sizes
All implementations of this specification shall be capable of
accepting buffers of at least 16K octets as input to GSS_GetMIC(),
GSS_VerifyMIC(), and GSS_Wrap(), and shall be capable of accepting
the output_token generated by GSS_Wrap() for a 16K octet input
buffer as input to GSS_Unwrap(). Support for larger buffer sizes is
optional but recommended.
6. Backwards Compatibility Considerations
The new token formats defined in this document will only be
recognized by new implementations. To address this, implementations
can always use the explicit sign or seal algorithm in [RFC-1964]
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Kerberos Version 5 GSS-API November 2003
when the key type corresponds to "older" enctypes. An alternative
approach might be to retry sending the message with the sign or seal
algorithm explicitly defined as in [RFC-1964]. However this would
require either the use of a mechanism such as [RFC-2478] to securely
negotiate the method or the use out of band mechanism to choose
appropriate mechanism. For this reason, it is RECOMMENDED that the
new token formats defined in this document SHOULD be used only if
both peers are known to support the new mechanism during context
negotiation because of, for example, the use of "new" enctypes.
GSS_Unwrap() or GSS_Verify_MIC() can process a message token as
follows: it can look at the first octet of the token header, if it
is 0x60 then the token must carry the generic GSS-API pseudo ASN.1
framing, otherwise the first two octets of the token contain the
TOK_ID that uniquely identify the token message format.
7. Security Considerations
Under the current mechanism, no negotiation of algorithm types
occurs, so server-side (acceptor) implementations cannot request
that clients not use algorithm types not understood by the server.
However, administration of the server's Kerberos data (e.g., the
service key) has to be done in communication with the KDC, and it is
from the KDC that the client will request credentials. The KDC
could therefore be given the task of limiting session keys for a
given service to types actually supported by the Kerberos and GSSAPI
software on the server.
This does have a drawback for cases where a service principal name
is used both for GSSAPI-based and non-GSSAPI-based communication
(most notably the "host" service key), if the GSSAPI implementation
does not understand (for example) AES [AES-KRB5] but the Kerberos
implementation does. It means that AES session keys cannot be
issued for that service principal, which keeps the protection of
non-GSSAPI services weaker than necessary. KDC administrators
desiring to limit the session key types to support interoperability
with such GSSAPI implementations should carefully weigh the
reduction in protection offered by such mechanisms against the
benefits of interoperability.
8. Acknowledgments
Ken Raeburn and Nicolas Williams corrected many of our errors in the
use of generic profiles and were instrumental in the creation of this
memo.
The text for security considerations was contributed by Ken Raeburn.
Sam Hartman and Ken Raeburn suggested the "floating trailer" idea,
namely the encoding of the RRC field.
Sam Hartman and Nicolas Williams recommended the replacing our
earlier key derivation function for directional keys with different
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Kerberos Version 5 GSS-API November 2003
key usage numbers for each direction as well as retaining the
directional bit for maximum compatibility.
Paul Leach provided numerous suggestions and comments.
Scott Field, Richard Ward, Dan Simon, and Kevin Damour also provided
valuable inputs on this memo.
Jeffrey Hutzelman provided comments on channel bindings and suggested
many editorial changes.
Luke Howard provided implementations of this memo for the Heimdal
code base, and helped inter-operability testing with the Microsoft
code base, together with Love Hornquist Astrand. These experiments
formed the basis of this memo.
Martin Rex provided suggestions of TOK_ID assignment recommendations
thus the token tagging in this memo is unambiguous if the token is
wrapped with the pseudo ASN.1 header.
This document retains some of the text of RFC-1964 in relevant
sections.
9. References
9.1. Normative References
[RFC-2026] Bradner, S., "The Internet Standards Process -- Revision
3", BCP 9, RFC 2026, October 1996.
[RFC-2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC-2743] Linn, J., "Generic Security Service Application Program
Interface Version 2, Update 1", RFC 2743, January 2000.
[RFC-2744] Wray, J., "Generic Security Service API Version 2: C-
bindings", RFC 2744, January 2000.
[RFC-1964] Linn, J., "The Kerberos Version 5 GSS-API Mechanism",
RFC 1964, June 1996.
[KCRYPTO] Raeburn, K., "Encryption and Checksum Specifications for
Kerberos 5", draft-ietf-krb-wg-crypto-05.txt, June, 2003. Work in
progress.
[KRBCLAR] Neuman, C., Kohl, J., Ts'o T., Yu T., Hartman, S.,
Raeburn, K., "The Kerberos Network Authentication Service (V5)",
draft-ietf-krb-wg-kerberos-clarifications-04.txt, February 2002.
Work in progress.
[AES-KRB5] Raeburn, K., "AES Encryption for Kerberos 5", draft-
raeburn-krb-rijndael-krb-05.txt, June 2003. Work in progress.
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Kerberos Version 5 GSS-API November 2003
[RFC-2478] Baize, E., Pinkas D., "The Simple and Protected GSS-API
Negotiation Mechanism", RFC 2478, December 1998.
9.2. Informative References
[SSPI] Leach, P., "Security Service Provider Interface", Microsoft
Developer Network (MSDN), April 2003.
10. Author's Address
Larry Zhu
One Microsoft Way
Redmond, WA 98052 - USA
EMail: LZhu@microsoft.com
Karthik Jaganathan
One Microsoft Way
Redmond, WA 98052 - USA
EMail: karthikj@microsoft.com
Sam Hartman
Massachusetts Institute of Technology
77 Massachusetts Avenue
Cambridge, MA 02139 - USA
Email: hartmans@MIT.EDU
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Kerberos Version 5 GSS-API November 2003
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Zhu Internet Draft 15
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