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diff --git a/third_party/heimdal/doc/standardisation/draft-ietf-krb-wg-gssapi-cfx-04.txt b/third_party/heimdal/doc/standardisation/draft-ietf-krb-wg-gssapi-cfx-04.txt new file mode 100644 index 00000000000..7d407186511 --- /dev/null +++ b/third_party/heimdal/doc/standardisation/draft-ietf-krb-wg-gssapi-cfx-04.txt @@ -0,0 +1,884 @@ + + +<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 + + + +Zhu Internet Draft 1 + 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, + + +Zhu Internet Draft 2 + Kerberos Version 5 GSS-API November 2003 + + + 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 + + +Zhu Internet Draft 3 + 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 + + +Zhu Internet Draft 4 + Kerberos Version 5 GSS-API November 2003 + + + 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 + + +Zhu Internet Draft 5 + 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 + + +Zhu Internet Draft 6 + Kerberos Version 5 GSS-API November 2003 + + + 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 + + +Zhu Internet Draft 7 + 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. + + +Zhu Internet Draft 8 + Kerberos Version 5 GSS-API November 2003 + + + 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 + + +Zhu Internet Draft 9 + Kerberos Version 5 GSS-API November 2003 + + + 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 + + +Zhu Internet Draft 10 + Kerberos Version 5 GSS-API November 2003 + + + + 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] + + +Zhu Internet Draft 11 + 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 + + +Zhu Internet Draft 12 + 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. + + +Zhu Internet Draft 13 + 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 + + + + + + + + + + + + + + + + + + + + + + + + + + +Zhu Internet Draft 14 + Kerberos Version 5 GSS-API November 2003 + + + +Full Copyright Statement + + Copyright (C) The Internet Society (date). All Rights Reserved. + + This document and translations of it may be copied and furnished to + others, and derivative works that comment on or otherwise explain it + or assist in its implementation may be prepared, copied, published + and distributed, in whole or in part, without restriction of any + kind, provided that the above copyright notice and this paragraph + are included on all such copies and derivative works. However, this + document itself may not be modified in any way, such as by removing + the copyright notice or references to the Internet Society or other + Internet organizations, except as needed for the purpose of + developing Internet standards in which case the procedures for + copyrights defined in the Internet Standards process must be + followed, or as required to translate it into languages other than + English. + + The limited permissions granted above are perpetual and will not be + revoked by the Internet Society or its successors or assigns. + + This document and the information contained herein is provided on an + "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING + TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING + BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION + HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF + MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. + + + + + + + + + + + + + + + + + + + + + + + + + + +Zhu Internet Draft 15 |