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RFC 5024

ODETTE File Transfer Protocol 2.0

Pages: 135
Informational
Errata
Obsoletes:  2204
Updated by:  8996
Part 3 of 4 – Pages 69 to 99
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Top   ToC   RFC5024 - Page 69   prevText

6. File Services

6.1. Overview

ODETTE-FTP provides services for compressing, encrypting, and signing files. These services should generally be performed off line, outside of the ODETTE-FTP communications session for performance reasons, although this is not a strict requirement. ODETTE-FTP requires that the following steps must be performed in this exact sequence, although any of steps 2, 3, or 4 may be omitted. Step 1 is required only if any of steps 2, 3, or 4 are performed: 1. Insert record length indicators (V format files only; see Section 6.5) 2. Sign 3. Compress 4. Encrypt The cipher suite for the encryption and signing algorithms is assigned by bilateral agreement. Secured and/or compressed files must be enveloped. The envelope contains additional information about the service used that is necessary for a receiving party to fully process the file. The [CMS] content types used are: EnvelopedData - Indicates encrypted data CompressedData - Indicates compressed data SignedData - Indicates signed content Data - Indicates unstructured data For signed or encrypted data, the encapsulated content type (eContentType field) is id-data.

6.2. File Signing

Files that are to be signed are enveloped according to the file enveloping format (SFIDENV). Generally, this will be as a [CMS] package. A file may be signed more than once to ease the changeover between old and new certificates.
Top   ToC   RFC5024 - Page 70
   It is recommended that the envelope does not contain the public
   certificate of the signer.  Where files are sent to the same
   recipient continuously, it would serve no benefit to repeatedly send
   the same certificate.  Both the original file data and signature are
   stored within the [CMS] package.

6.3. File Encryption

Files that are to be encrypted are enveloped according to the file enveloping format (SFIDENV). Generally, this will be as a [CMS] package. It is recommended that encryption should be performed before the ODETTE-FTP session starts because a large file takes a long time to encrypt and could cause session time outs, even on high-performance machines. Likewise, decryption of the file should occur outside of the session. However, an application may choose to allow in-session encryption and decryption for very small files.

6.4. File Compression

Files that are to be compressed are enveloped according to the file enveloping format (SFIDENV). Generally, this will be as a [CMS] package using the [CMS-Compression] data type, which uses the [ZLIB] compression algorithm by default. Unlike the buffer compression method, this method operates on a whole file. Because of the increased levels of compression, file level compression essentially deprecates the older buffer compression inside ODETTE-FTP. The buffer compression is kept for backwards compatibility.

6.5. V Format Files - Record Lengths

A file that has been signed, compressed, and/or encrypted will have lost its record structure, so ODETTE-FTP will not be able to insert the End of Record Flag in subrecord headers in Data Exchange Buffers. To preserve the record structure, V format files must have record headers inserted into them prior to signing, compression, or encryption. These 2-byte binary numbers, in network byte order, indicate the length of each record, allowing the receiving system, where appropriate, to recreate the files complete with the original variable-length records. Note that the header bytes hold the number of data bytes in the record and don't include themselves.
Top   ToC   RFC5024 - Page 71
   This is only applicable to V format files, which themselves are
   typically only of concern for mainframes.

7. ODETTE-FTP Data Exchange Buffer

7.1. Overview

Virtual Files are transmitted by mapping the Virtual File records into Data Exchange Buffers, the maximum length of which was negotiated between the ODETTE-FTP entities via the Start Session (SSID) commands exchanged during the Start Session phase of the protocol. Virtual File records may be of arbitrary length. A simple compression scheme is defined for strings of repeated characters. An example of the use of the Data Exchange Buffer can be found in Appendix A.

7.2. Data Exchange Buffer Format

For transmission of Virtual File records, data is divided into subrecords, each of which is preceded by a 1-octet Subrecord Header. The Data Exchange Buffer is made up of the initial Command Character followed by pairs of Subrecord Headers and subrecords, as follows. o-------------------------------------------------------- | C | H | | H | | H | | / | M | D | SUBRECORD | D | SUBRECORD | D | SUBRECORD | /_ | D | R | | R | | R | | / o------------------------------------------------------- CMD The Data Exchange Buffer Command Character, 'D'. HDR A 1-octet Subrecord Header defined as follows: 0 1 2 3 4 5 6 7 o-------------------------------o | E | C | | | o | F | C O U N T | | R | | | o-------------------------------o
Top   ToC   RFC5024 - Page 72
      Bits

       0     End of Record Flag

             Set to indicate that the next subrecord is the last
             subrecord of the current record.

             Unstructured files are transmitted as a single record; in
             this case, the flag acts as an end-of-file marker.

       1     Compression Flag

             Set to indicate that the next subrecord is compressed.

      2-7    Subrecord Count

             The number of octets in the Virtual File represented by the
             next subrecord expressed as a binary value.

             For uncompressed data, this is simply the length of the
             subrecord.

             For compressed data, this is the number of times that the
             single octet in the following subrecord must be inserted in
             the Virtual File.

             As 6 bits are available, the next subrecord may represent
             between 0 and 63 octets of the Virtual File.

7.3. Buffer Filling Rules

A Data Exchange Buffer may be any length up to the value negotiated in the Start Session exchange. Virtual File records may be concatenated within one Data Exchange Buffer or split across a number of buffers. A subrecord is never split between two Exchange Buffers. If the remaining space in the current Exchange Buffer is insufficient to contain the next 'complete' subrecord, one of the following strategies should be used: 1. Truncate the Exchange Buffer, and put the complete subrecord (preceded by its header octet) in a new Exchange Buffer. 2. Split the subrecord into two, filling the remainder of the Exchange Buffer with the first new subrecord and starting a new Exchange Buffer with the second.
Top   ToC   RFC5024 - Page 73
   A record of length zero may appear anywhere in the Exchange Buffer.

   A subrecord of length zero may appear anywhere in the record and/or
   the Exchange Buffer.

8. Stream Transmission Buffer

8.1. Introduction

To utilise the TCP stream, a Stream Transmission Buffer (STB) is created by adding a Stream Transmission Header (STH) to the start of all Command and Data Exchange Buffers before they are passed to the TCP transport service. This allows the receiving ODETTE-FTP to recover the original Exchange Buffers. Note: The Stream Transmission Buffer is not used when using ODETTE- FTP over an X.25 network. This is because ODETTE-FTP can rely on the fact that the Network Service will preserve the sequence and boundaries of data units transmitted through the network and that the Network Service will pass the length of the data unit to the receiving ODETTE-FTP. TCP offers a stream-based connection that does not provide these functions. The Stream Transmission Buffer is composed of an STH and an OEB. o-----+-----------------+-----+--------------------+-----+------ | STH | OEB | STH | OEB | STH | OEB/ o-----+-----------------+-----+--------------------+-----+---- STH - Stream Transmission Header OEB - ODETTE-FTP Exchange Buffer

8.2. Stream Transmission Header Format

The Stream Transmission Header is shown below. The fields are transmitted from left to right. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Version| Flags | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Top   ToC   RFC5024 - Page 74
   Version

      Value: 0001 (binary)

             Stream Transmission Header version number.

   Flags

      Value: 0000 (binary)

             Reserved for future use.

   Length

      Range: 5 - 100003 (decimal)

      The length of the Stream Transmission Buffer (STH+OEB).

      The smallest STB is 5 octets consisting of a 4-octet header
      followed by a 1-octet Exchange Buffer such as a Change Direction
      (CD) command.

      The maximum Exchange Buffer length that can be negotiated is 99999
      octets (Section 5.3.2) giving an STB length of 100003.

      The length is expressed as a binary number in network byte order.

   It is expected that implementations of this protocol will follow the
   Internet robustness principle of being conservative in what is sent
   and liberal in what is accepted.

9. Protocol State Machine

9.1. ODETTE-FTP State Machine

The operation of an ODETTE-FTP entity is formally defined by the State Machine presented below. There are five State and Transition tables, and for each table additional information is given in the associated Predicate and Action lists. The response of an ODETTE-FTP entity to the receipt of an event is defined by a Transition table entry indexed by the Event/State intersection within the appropriate state table. Each Transition table entry defines the actions taken, events generated, and new state entered. Predicates may be used within a table entry to select the correct response on the basis of local information held by the entity.
Top   ToC   RFC5024 - Page 75
   A Transition table contains the following fields:

     Index (I)   State transition index.

     Predicate   A list of predicates used to select between different
                 possible transitions.  The predicates are defined in
                 the Predicate and Action lists.

     Actions     A list of actions taken by the entity.  The actions are
                 defined in the Predicate and Action lists.

     Events      Output events generated by the entity.

     Next State  The new state of the entity.

9.2. Error Handling

The receipt of an event in a given state may be invalid for three reasons. 1. The case is impossible by design of the state automata, denoted 'X' in the state tables. For example, a timer that has not been set cannot run out. 2. The event is the result of an error in the Network Service implementation, also denoted 'X' in the state tables. The Network Service implementation is considered to be correct. 3. For all other cases, the event is considered to be a User Error, denoted "U" in the state tables. The state tables define the conditions under which a User event is valid, thus preventing the generation of a protocol error by the ODETTE-FTP entity as a result of a User Monitor error. The reaction of the entity to such errors is undefined and regarded as a local implementation issue. The state tables also allow protocol errors due to the receipt of invalid Exchange Buffers, to be detected. In such cases, the reaction of the entity to the error is defined.
Top   ToC   RFC5024 - Page 76

9.3. States

The Command Mode is strictly a half-duplex flip-flop mode. A_NC_ONLY Responder, Network Connection opened The Responder has sent its Ready Message (SSRM) and is waiting for Start Session (SSID) from the Initiator. A_WF_CONRS Responder Waiting for F_CONNECT_RS The Responder has received the Initiator's Start Session (SSID) and is waiting for a response (F_CONNECT_RS) from its User Monitor. CDSTWFCD CD_RQ stored in WF_CD state Since the User Monitor doesn't see the WF_CD state, it may send a Change Direction request (F_CD_RQ) before the ODETTE-FTP receives a Change Direction (CD) command. CLIP Close Input Pending The Listener has received an End File (EFID) command and is waiting for the Close File response (F_CLOSE_FILE_RS) from its User Monitor. CLOP Close Out Pending The Speaker has sent an End File (EFID) command and is waiting for an End File Answer (EFPA or EFNA). ERSTWFCD End to End Response stored in WF_CD state Since the User Monitor doesn't see the WF_CD state, it may send F_EERP_RQ, before ODETTE-FTP receives a Change Direction (CD) command. IDLE Connection IDLE IDLELI Idle Listener IDLELICD Idle Listener, F_CD_RQ Received The ODETTE-FTP entity has become the Listener after receiving a Change Direction request (F_CD_RQ) from the User Monitor. The receipt of an End Session (ESID) is valid in this state.
Top   ToC   RFC5024 - Page 77
   IDLESP      Idle Speaker

   IDLESPCD    Idle Speaker, F_CD_IND Sent

               The ODETTE-FTP entity has sent a Change Direction
               indication (F_CD_IND) to the User Monitor.  A Change
               Direction request (F_CD_RQ) is invalid in this state.

   I_WF_NC     Initiator Waiting for Network Connection

               The Initiator has requested a new network connection and
               is waiting for a Connection confirmation (N_CON_CF) from
               the Network Service.

   I_WF_RM     Initiator Waiting for Ready Message

               Before sending Start Session (SSID), the Initiator must
               wait for a Ready Message (SSRM) from the Responder.

   I_WF_SSID   Initiator Waiting for SSID

               The Initiator has sent a Start Session (SSID) command and
               is waiting for Start Session from the Responder.

   NRSTWFCD    Negative End Response stored in WF_CD state

               Since the User Monitor doesn't see the WF_CD state, it
               may send F_NERP_RQ, before ODETTE-FTP receives a Change
               Direction (CD) command.

   OPI         Open Input (Data Transfer Phase)

               The Listener is waiting for the Speaker to send a Data
               Exchange Buffer.

   OPIP        Open Input Pending

               The Listener has received a Start File (SFID) command and
               is waiting for the Start File response (F_START_FILE_RS)
               from its User Monitor.

   OPO         Open Out (Data Transfer Phase)

               The Speaker has received a Start File Positive Answer
               (SFPA) and is waiting for a Data (F_DATA_RQ) or Close
               File (F_CLOSE_FILE) request from its User Monitor.
Top   ToC   RFC5024 - Page 78
   OPOP        Open Out Pending

               The Speaker has sent a Start File (SFID) command and is
               waiting for a Start File Answer (SFPA or SFNA).

   OPOWFC      Open Out Wait for Credit

               The Speaker is waiting for a Set Credit (CDT) command
               before sending further Data Exchange buffers.

   RTRP        Ready to Receive (RTR) Pending

               The Listener has received an EERP or a NERP and is
               waiting for the Ready to Receive response (F_RTR_RS) from
               its User Monitor.

   SFSTWFCD    Start File Request stored in WF_CD state.

               Since the User Monitor doesn't see the WF_CD state, it
               may send a Start File request (F_START_FILE_RQ) before
               the ODETTE-FTP receives a Change Direction (CD) command.

   WF_CD       Wait for Change Direction

               The Listener wishes to become the Speaker and is waiting
               for a Change Direction (CD) command after sending an End
               File Positive Answer (EFPA) requesting change direction.

   WF_RTR      Wait for Ready To Receive

               The Speaker has sent an End to End Response (EERP) or a
               Negative End Response (NERP) command and must wait for
               Ready To Receive (RTR) from the Listener.

   WF_NDISC    Wait for N_DISC_IND

               ODETTE-FTP has sent an End Session (ESID) command and is
               waiting for a Disconnection indication (N_DISC_IND) from
               the Network Service.

   WF_SECD     Wait for Security Change Direction

               The Speaker is expecting a Security Change Direction
               (SECD) from the Listener.
Top   ToC   RFC5024 - Page 79
   WF_AUCH     Wait for Authentication Challenge

               The Speaker has sent a Security Change Direction (SECD)
               command and must wait for Authentication Challenge (AUCH)
               from the Listener.

   WF_AURP     Wait for Authentication Response

               The Speaker has sent an Authentication Challenge (AUCH)
               command and must wait for Authentication Response (AURP)
               from the Listener.

9.4. Input Events

User Monitor Input Events (Section 3) F_DATA_RQ F_CONNECT_RQ F_START_FILE_RQ F_CLOSE_FILE_RQ F_EERP_RQ F_CONNECT_RS F_START_FILE_RS(+) F_CLOSE_FILE_RS(+) F_NERP_RQ F_ABORT_RQ F_START_FILE_RS(-) F_CLOSE_FILE_RS(-) F_CD_RQ F_RELEASE_RQ F_RTR_RS Network Input Events (Section 2.2) N_CON_IND N_CON_CF N_DATA_IND N_DISC_IND N_RST_IND Peer ODETTE-FTP Input Events (Section 4) SSID SFID SFPA SFNA EFID EFPA EFNA DATA ESID EERP RTR CD CDT SSRM NERP SECD AUCH AURP Internal Input Events TIME-OUT - Internal ODETTE-FTP timer expires. Input event parameters are denoted I.Event-name.Parameter-name within the state table action and predicate lists. Their value can be examined but not changed by the ODETTE-FTP entity.

9.5. Output Events

User Monitor Output Events (Section 3) F_DATA_IND F_CONNECT_IND F_START_FILE_IND F_CLOSE_FILE_IND F_EERP_IND F_CONNECT_CF F_START_FILE_CF(+) F_CLOSE_FILE_CF(+) F_CD_IND F_ABORT_IND F_START_FILE_CF(-) F_CLOSE_FILE_CF(-) F_NERP_IND F_RELEASE_IND F_DATA_CF F_RTR_CF
Top   ToC   RFC5024 - Page 80
   Network Output Events (Section 2.2)

      N_CON_RQ   N_CON_RS   N_DATA_RQ   N_DISC_RQ

   Peer ODETTE-FTP Output Events (Section 4)

      SSID   SFID   SFPA   SFNA   EFID   EFPA   EFNA
      DATA   ESID   EERP   RTR    CD     CDT    SSRM
      NERP   SECD   AUCH   AURP

   Output event parameters are denoted O.Event-name.Parameter-name
   within the state table action and predicate lists.  Their values can
   be examined and changed by the ODETTE-FTP entity.

9.6. Local Variables

The following variables are maintained by the ODETTE-FTP entity to assist the operation of the protocol. They are denoted V.Variable- name within the state table action and predicate lists. Their value can be examined and changed by the ODETTE-FTP entity. The initial value of each variable is undefined. Variable Type Comments --------------------------------------------------------------------- Buf-size Integer Negotiated Data Exchange Buffer size. Called-addr Address Used to build O.F_CONNECT_IND.Called-addr Calling-addr Address To build O.F_CONNECT_IND.Calling-addr Compression Yes/No Compression in use as agreed. Credit_L Integer Listener's credit counter. Credit_S Integer Speaker's credit counter. Id String Used to build O.SSID.Id Mode Sender-only, Receiver-only, Both. Pswd String Password, used to build O.SSID.Pswd Req-buf Primitive Input event (F_XXX_RQ) stored in WF_CD state. Restart Yes/No Restart in used as agreed. Restart-pos Integer Used only during file opening. Window Integer The credit value negotiated for the session. Caller Yes/No This entity initiated the ODETTE-FTP session. Authentication Yes/No Secure authentication in use as agreed Challenge Binary Random challenge ---------------------------------------------------------------------
Top   ToC   RFC5024 - Page 81

9.7. Local Constants

The following constants define the capabilities of a given ODETTE-FTP entity. They are denoted C.Constant-name within the state table action and predicate lists. Their value can be examined but not changed by the ODETTE-FTP entity. Constant Value Comments --------------------------------------------------------------------- Cap-compression Yes/No Compression supported? Cap-init Initiator Must be Initiator. Responder Must be Responder. Both Can be Initiator or Responder. Cap-mode Sender-only Must be sender. Receiver-only Must be receiver. Both Can be sender or receiver. Max-buf-size 127 < Int < 100000 Maximum Data Exchange Buffer size supported. Max-window 0 < Int < 1000 Local maximum credit value. Cap-restart Yes/No Restart supported? Cap-logic 0, 1, 2 0 = does not support special logic 1 = supports special logic 2 = needs special logic ---------------------------------------------------------------------
Top   ToC   RFC5024 - Page 82

9.8. Session Connection State Table

9.8.1. State Table

o----------------------------------------------------------o | | Other States | | |--------------------------------------------------o | | | WF_SECD | | | |----------------------------------------------o | | | | WF_AURP | | | | |------------------------------------------o | | | | | WF_AUCH | | | | | |--------------------------------------o | | | | | S | A_WF_CONRS | | | | | | |----------------------------------o | | | | | | T | A_NC_ONLY | | | | | | | |------------------------------o | | | | | | | A | I_WF_SSID | | | | | | | | |--------------------------o | | | | | | | | T | I_WF_RM | | | | | | | | | |----------------------o | | | | | | | | | E | I_WF_NC | | | | | | | | | | |------------------o | | | | | | | | | | | IDLE | | | | | | | | | | |==================o---+---+---+---+---+---+---+---+---+---| | | F_CONNECT_RQ | A | X | X | X | X | X | X | X | X | X | | |--------------+---+---+---+---+---+---+---+---+---+---| | E | N_CON_CF | X | C | X | X | X | X | X | X | X | X | | |--------------+---+---+---+---+---+---+---+---+---+---| | V | SSRM | X | X | H | X | X | X | L | L | L | X | | |--------------+---+---+---+---+---+---+---+---+---+---| | E | SSID | X | X | X | D | E | F | L | L | L | F | | |--------------+---+---+---+---+---+---+---+---+---+---| | N | N_CON_IND | B | X | X | X | X | X | X | X | X | X | | |--------------+---+---+---+---+---+---+---+---+---+---| | T | F_CONNECT_RS | X | U | U | U | U | G | X | X | X | U | | |--------------+---+---+---+---+---+---+---+---+---+---| | | ESID | X | X | X | F | X | X | F | F | F | X | | |--------------+---+---+---+---+---+---+---+---+---+---| | | AUCH | X | X | U | U | X | X | I | L | L | U | | |--------------+---+---+---+---+---+---+---+---+---+---| | | AURP | X | X | U | U | X | X | L | K | L | U | | |--------------+---+---+---+---+---+---+---+---+---+---| | | SECD | X | X | U | U | X | X | L | L | J | U | o----------------------------------------------------------o
Top   ToC   RFC5024 - Page 83

9.8.2. Transition Table

I | Predicate Actions Output Events Next State ===o============================================================= A | P1: F_ABORT_IND IDLE | !P1: 1,2 N_CON_RQ I_WF_NC ---+------------------------------------------------------------- B | P3: N_DISC_RQ IDLE | !P3: 2 N_CON_RS | SSRM A_NC_ONLY ---+------------------------------------------------------------- C | 4,2 I_WF_RM ---+------------------------------------------------------------- D | P2 & P8 & P11: 4,2,5 SECD WF_AUCH | P2 & P8 & !P11: 4,2,5 F_CONNECT_CF IDLESP | P2 & !P8: 4,2 ESID(R=12) | F_ABORT_IND(R,AO=L) WF_NDISC | else: 4,2 ESID(R=10) | F_ABORT_IND(R,AO=L) WF_NDISC ---+------------------------------------------------------------- E | P4: 4 N_DISC_RQ IDLE | !P4: 4,2 F_CONNECT_IND A_WF_CONRS ---+------------------------------------------------------------- F | 4 F_ABORT_IND | N_DISC_RQ IDLE ---+------------------------------------------------------------- G | P2 & P9 & P10: 4,2,5 SSID WF_SECD | P2 & !P9 & P10: 4,2,5 SSID IDLELI | !P10: 4,2 ESID(R=12) | F_ABORT_IND(R,AO=L) WF_NDISC | else: 4,2 ESID(R=10) | F_ABORT_IND(R,AO=L) WF_NDISC ---+------------------------------------------------------------- H | 4,2,3 SSID I_WF_SSID ---+------------------------------------------------------------- I | P5: 4,2 AURP WF_SECD | !P5: 4,2 AURP IDLELI ---+------------------------------------------------------------- J | 4,2 AUCH WF_AURP ---+------------------------------------------------------------- K | P6: 4,2 F_CONNECT_CF IDLESP | P7: 4,2 SECD WF_AUCH | else: 4,2 ESID(R=11) | F_ABORT_IND(R,AO=L) WF_NDISC ---+------------------------------------------------------------- L | 4,2 ESID(R=02) | F_ABORT_IND(R,AO=L) WF_NDISC ---+-------------------------------------------------------------
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9.8.3. Predicates and Actions

Predicate P1: (No resources available) OR (C.Cap-init = Responder) OR (C.Cap-mode = Sender-only AND I.F_CONNECT_RQ.Mode = Receiver-only) OR (C.Cap-mode = Receiver-only AND I.F_CONNECT_RQ.Mode = Sender-only) Predicate P2: SSID negotiation is successful (for these, Buf-size, Restart, Compression, Mode, Special logic, and Window, compare the inbound SSID with the local constants to set the local variables. Any incompatibilities result in failure of the negotiation.) Predicate P3: C.Cap-init = Initiator Predicate P4: Mode in SSID incompatible with C.Cap-mode Predicate P5: V.Caller = Yes Predicate P6: (V.Caller = Yes) AND (AURP.Signature verifies with V.Challenge) Predicate P7: (V.Caller = No) AND (AURP.Signature verifies with V.Challenge) Predicate P8: V.Authentication = I.SSID.Authentication Predicate P9: I.F_CONNECT_RS.Authentication = Yes Predicate P10: O.F_CONNECT_IND.Authentication = I.F_CONNECT_RS.Authentication Predicate P11: V.Authentication = Yes Action 1: Set V.Mode from (C.Cap-mode, I.F_CONNECT_RQ.Mode) Set V.Pswd, V.Id, V.Restart, and V.Authentication from I.F_CONNECT_RQ Set V.Buf-size = C.Max-buf-size Set V.Compression = C.Cap-compression Set V.Caller = Yes Build O.N_CON_RQ Action 2: Start inactivity timer Action 3: Set parameters in O.SSID = from local variables
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       Action 4:  Stop timer

       Action 5:  Set V.Mode, V.Restart, V.Compression, V.Buf-size,
                      V.Window, V.Authentication = from SSID

       Action 6:  Set V.Challenge = A random number unique to the
                   session

9.9. Error and Abort State Table

9.9.1. State Table

o--------------------------------------o | | Other States | | S |------------------------------o | | T | WF_NDISC | | | A |--------------------------o | | | T | I_WF_NC | | | | E |----------------------o | | | | | IDLE | | | | |======================o---+---+---+---| | | TIME-OUT | X | X | A | B | | |------------------+---+---+---+---| | E | F_ABORT_RQ | X | A | X | C | | V |------------------+---+---+---+---| | E | N_RST_IND | X | X | A | D | | N |------------------+---+---+---+---| | T | N_DISC_IND | X | E | F | G | | |------------------+---+---+---+---| | | Invalid Buffer | X | X | H | I | o--------------------------------------o
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9.9.2. Transition Table

I | Predicate Actions Output Events Next State ===o================================================================= A | N_DISC_RQ IDLE ---+----------------------------------------------------------------- B | F_ABORT_IND | N_DISC_RQ IDLE ---+----------------------------------------------------------------- C | 1 N_DISC_RQ IDLE ---+----------------------------------------------------------------- D | 1 N_DISC_RQ | F_ABORT_IND IDLE ---+----------------------------------------------------------------- E | F_ABORT_IND IDLE ---+----------------------------------------------------------------- F | 1 IDLE ---+----------------------------------------------------------------- G | 1 F_ABORT_IND IDLE ---+----------------------------------------------------------------- H | WF_NDISC ---+----------------------------------------------------------------- I | 1,2 ESID(R=01) | F_ABORT_IND(R,AO=L) WF_NDISC ---------------------------------------------------------------------

9.9.3. Predicates and Actions

Action 1: Stop inactivity timer Action 2: Start inactivity timer

9.10. Speaker State Table 1

9.10.1. State Table

The following abbreviations are used in the Speaker state table. F_REL_RQ(Ok) - F_RELEASE_RQ Reason = Normal F_REL_RQ(Err) - F_RELEASE_RQ Reason = Error o--------------------------------------------------------------------o | | Other States | | |--------------------------------------------------------------o | | | WF_NDISC | | | |----------------------------------------------------------o | | | | OPOWFC | | |
Top   ToC   RFC5024 - Page 87
  | |------------------------------------------------------o   |   |   |
  | | OPO                                                  |   |   |   |
  |S|--------------------------------------------------o   |   |   |   |
  | | OPOP                                             |   |   |   |   |
  |T|----------------------------------------------o   |   |   |   |   |
  | | CDSTWFCD                                     |   |   |   |   |   |
  |A|------------------------------------------o   |   |   |   |   |   |
  | | SFSTWFCD                                 |   |   |   |   |   |   |
  |T|--------------------------------------o   |   |   |   |   |   |   |
  | | NRSTWFCD                             |   |   |   |   |   |   |   |
  |E|----------------------------------o   |   |   |   |   |   |   |   |
  | | ERSTWFCD                         |   |   |   |   |   |   |   |   |
  | |------------------------------o   |   |   |   |   |   |   |   |   |
  | | WF_CD                        |   |   |   |   |   |   |   |   |   |
  | |--------------------------o   |   |   |   |   |   |   |   |   |   |
  | | WF_RTR                   |   |   |   |   |   |   |   |   |   |   |
  | |----------------------o   |   |   |   |   |   |   |   |   |   |   |
  | | IDLESPCD             |   |   |   |   |   |   |   |   |   |   |   |
  | |------------------o   |   |   |   |   |   |   |   |   |   |   |   |
  | | IDLESP           |   |   |   |   |   |   |   |   |   |   |   |   |
  |=+==============o---+---+---+---+---+---+---+---+---+---+---+---+---|
  | | F_EERP_RQ    | A | A | W | F | W | W | U | U | U | U | U | U | U |
  | |--------------+---+---+---+---+---+---+---+---+---+---+---+---+---|
  | | F_NERP_RQ    | Y | Y | W | Z | W | W | U | U | U | U | U | U | U |
  | |--------------+---+---+---+---+---+---+---+---+---+---+---+---+---|
  | | F_START_     | B | B | W | G | W | W | U | U | U | U | U | X | U |
  | |   FILE_RQ    |   |   |   |   |   |   |   |   |   |   |   |   |   |
  | |--------------+---+---+---+---+---+---+---+---+---+---+---+---+---|
  | | SFPA         | C | C | C | C | C | C | C | C | K | C | C | S | C |
  | |--------------+---+---+---+---+---+---+---+---+---+---+---+---+---|
  |E| SFNA         | C | C | C | C | C | C | C | C | L | C | C | S | C |
  | |--------------+---+---+---+---+---+---+---+---+---+---+---+---+---|
  |V| CD           | C | C | C | H | R | Z1| I | J | C | C | C | S | C |
  | |--------------+---+---+---+---+---+---+---+---+---+---+---+---+---|
  |E| F_DATA_RQ    | U | U | U | U | U | U | U | U | U | M | U | S | U |
  | |--------------+---+---+---+---+---+---+---+---+---+---+---+---+---|
  |N| CDT          | C | C | C | C | C | C | C | C | C | P | O | S | C |
  | |--------------+---+---+---+---+---+---+---+---+---+---+---+---+---|
  |T| F_CD_RQ      | D | U | W | T | W | W | U | U | U | U | U | X | U |
  | |--------------+---+---+---+---+---+---+---+---+---+---+---+---+---|
  | | F_REL_RQ(Ok) | U | E | U | U | U | U | U | U | U | U | U | X | U |
  | |--------------+---+---+---+---+---+---+---+---+---+---+---+---+---|
  | | F_REL_RQ(Err)| Q | Q | Q | Q | Q | Q | Q | Q | Q | Q | Q | S | Q |
  | |--------------+---+---+---+---+---+---+---+---+---+---+---+---+---|
  | | RTR          | C | C | N | C | C | C | C | C | C | C | C | S | C |
  o--------------------------------------------------------------------o
Top   ToC   RFC5024 - Page 88

9.10.2. Transition Table

I | Predicate Actions Output Events Next State ===o================================================================= A | P5: 1,2,3,18 EERP WF_RTR | !P5: 1,2,3 EERP WF_RTR ---+----------------------------------------------------------------- B | P1: UE | !P1: 1,2,5 SFID OPOP ---+----------------------------------------------------------------- C | 1,2 ESID(R=02) | F_ABORT_IND(R,AO=L) WF_NDISC ---+----------------------------------------------------------------- D | 1,2 CD IDLELICD ---+----------------------------------------------------------------- E | 1,2 ESID(R=00) WF_NDISC ---+----------------------------------------------------------------- F | 4 ERSTWFCD ---+----------------------------------------------------------------- G | P1: UE | !P1: 6 SFSTWFCD ---+----------------------------------------------------------------- H | 1,2 IDLESP ---+----------------------------------------------------------------- I | 1,2,10 SFID OPOP ---+----------------------------------------------------------------- J | 1,2 CD IDLELICD ---+----------------------------------------------------------------- K | P2: 1,2 ESID(R=02) | F_ABORT_IND(R,AO=L) WF_NDISC | !P2: 1,2,7,12 F_START_FILE_CF(+) OPO ---+----------------------------------------------------------------- L | 1,2,8 F_START_FILE_CF(-) IDLESP ---+----------------------------------------------------------------- M | P3: 1,2,11,13 DATA OPOWFC | !P3: 1,2,11,13 DATA | F_DATA_CF OPO ---+----------------------------------------------------------------- N | F_RTR_CF IDLESP ---+----------------------------------------------------------------- O | 12 F_DATA_CF OPO ---+----------------------------------------------------------------- P | Protocol 1,2 ESID(R=02) | Error F_ABORT_IND(R,AO=L) WF_NDISC ---+----------------------------------------------------------------- Q | 1,2 ESID(R) WF_NDISC ---+----------------------------------------------------------------- Continued -->
Top   ToC   RFC5024 - Page 89
    I | Predicate    Actions      Output Events              Next State
   ===o=================================================================
    R |              1,2,9        EERP                       WF_RTR
   ---+-----------------------------------------------------------------
    S |                                                      WF_NDISC
   ---+-----------------------------------------------------------------
    T |                                                      CDSTWFCD
   ---+-----------------------------------------------------------------
    U |                           User Error                 UE
   ---+-----------------------------------------------------------------
    W |                           User Error - Note 1        UE
   ---+-----------------------------------------------------------------
    X |                           Error
   ---+-----------------------------------------------------------------
    Y |  P4 &  P5:   1,2,15,18    NERP                       WF_RTR
      | !P4 & !P5:   1,2,15,14    NERP                       WF_RTR
      |  P4 & !P5:   1,2,15       NERP                       WF_RTR
      | !P4 &  P5:   1,2,15,14,18 NERP                       WF_RTR
   ---+-----------------------------------------------------------------
    Z |              16                                      NRSTWFCD
   ---------------------------------------------------------------------
    Z1| P4:          1,2,17       NERP                       WF_RTR
      | !P4:         1,2,17,14    NERP                       WF_RTR
   ---------------------------------------------------------------------

9.10.3. Predicates and Actions

Predicate P1: (I.F_START_FILE_RQ.Restart-pos > 0 AND V.Restart = No) OR (V.Mode = Receiver-only) Note: Restart requested and not supported for this session. Predicate P2: I.SFPA.Restart-pos > V.Restart-pos Note: Protocol error due to the restart position in the SFPA acknowledgement being greater than the position requested in the SFID request. Predicate P3: V.Credit_S - 1 = 0 Note: Speaker's Credit is exhausted. Predicate P4: No special logic is in use Predicate P5: Signed EERP/NERP requested Action 1: Stop inactivity timer
Top   ToC   RFC5024 - Page 90
       Action 2:  Start inactivity timer

       Action 3:  Build an EERP from F_EERP_RQ

       Action 4:  Store F_EERP_RQ in V.Req-buf

       Action 5:  Build SFID from F_START_FILE_RQ
                  V.Restart-pos = I.F_START_FILE_RQ.Restart-pos

       Action 6:  Store F_START_FILE_RQ in V.Req-buf

       Action 7:  Build F_START_FILE_CF(+) from I.SFPA

       Action 8:  Build F_START_FILE_CF(-) from I.SFNA

       Action 9:  Build EERP from F_EERP_RQ stored in V.Req-buf

       Action 10: Build SFID from F_START_FILE_RQ stored in V.Req-buf
                  Set V.Restart-pos

       Action 11: Build Exchange Buffer

       Action 12: V.Credit_S = V.Window

       Action 13: V.Credit_S = V.Credit_S - 1

       Action 14: Activate CRC-calculus function.  Wrap Exchange buffer
                  in special logic

       Action 15: Build a NERP from F_NERP_RQ

       Action 16: Store F_NERP_RQ in V.Req-buf

       Action 17: Build NERP from F_NERP_RQ stored in V.Req-buf

       Action 18: Sign the contents of NERP/EERP

          Note 1: Whether to accept this "Request/Event" while in this
                  state is a matter of local implementation.  The ODETTE
                  state tables are based on the assumption that this
                  event cannot occur in this state and is considered to
                  be a user error (UE).
Top   ToC   RFC5024 - Page 91

9.11. Speaker State Table 2

9.11.1. State Table

o---------------------------------o | S | CLOP | | T |-------------------------o | | A | OPOWFC | | | T |---------------------o | | | E | OPO | | | |=====================o---+---+---| | E | F_CLOSE_FILE_RQ | A | E | U | | V |-----------------+---+---+---| | E | EFPA | B | B | C | | N |-----------------+---+---+---| | T | EFNA | B | B | D | o---------------------------------o

9.11.2. Transition Table

I | Predicate Actions Output Events Next State ===o================================================================= A | 1,2,5,7 EFID CLOP ---+----------------------------------------------------------------- B | 1,2 ESID(R=02) | F_ABORT_IND(R,AO=L) WF_NDISC ---+----------------------------------------------------------------- C | P1: 1,2,3 F_CLOSE_FILE_CF(+,SP=No) | CD IDLELI | !P1: 1,2,4 F_CLOSE_FILE_CF(+,SP=Yes) IDLESP ---+----------------------------------------------------------------- D | 1,2,6 F_CLOSE_FILE_CF(-) IDLESP ---+----------------------------------------------------------------- E | See Note 1 ---+----------------------------------------------------------------- U | User Error UE ---------------------------------------------------------------------

9.11.3. Predicates and Actions

Predicate P1: (I.EFPA.CD-Request = Yes) Predicate P2: No special logic is in use Action 1: Stop inactivity timer Action 2: Start inactivity timer
Top   ToC   RFC5024 - Page 92
       Action 3:  O.F_CLOSE_FILE_CF(+).Speaker = No

       Action 4:  O.F_CLOSE_FILE_CF(+).Speaker = Yes

       Action 5:  Build EFID from F_CLOSE_FILE_RQ

       Action 6:  Build F_CLOSE_FILE_CF(-) from EFNA

       Action 7:  Set V.Credit_S = 0

       Action 8:  Wrap Exchange buffer in special logic

         Note 1:  In order to respect the "half duplex" property of
                  ODETTE-FTP, it is forbidden to send EFID while in the
                  OPOWFC state.  EFID can be sent only in the OPO state.

                  The ODETTE-FTP implementation must avoid sending EFID
                  (or receiving F_CLOSE_FILE_RQ) while in the OPOWFC
                  state.
Top   ToC   RFC5024 - Page 93

9.12. Listener State Table

9.12.1. State Table

o---------------------------------------------o | | RTRP | | |-------------------------------------o | | | CLIP | | | |---------------------------------o | | | | OPI | | | | S |-----------------------------o | | | | T | OPIP | | | | | A |-------------------------o | | | | | T | IDLELICD | | | | | | E |---------------------o | | | | | | | IDLELI | | | | | | |=====================o---+---+---+---+---+---+ | | SFID | A | A | B | B | B | B | | |-----------------+---+---+---+---+---+---+ | E | DATA | B | B | B | I | B | B | | V |-----------------+---+---+---+---+---+---+ | E | EFID | B | B | B | J | B | B | | N |-----------------+---+---+---+---+---+---+ | T | F_START_FILE_RS | U | U | H | U | U | U | | |-----------------+---+---+---+---+---+---+ | | F_CLOSE_FILE_RS | U | U | U | U | K | U | | |-----------------+---+---+---+---+---+---+ | | CD | C | B | B | B | B | B | | |-----------------+---+---+---+---+---+---+ | | ESID R=Normal | D | F | D | D | D | D | | |-----------------+---+---+---+---+---+---+ | | ESID R=Error | D | D | D | D | D | D | | |-----------------+---+---+---+---+---+---+ | | EERP | E | E | B | B | B | B | | |-----------------+---+---+---+---+---+---+ | | NERP | L | L | B | B | B | B | | |-----------------+---+---+---+---+---+---+ | | F_RTR_RS | U | U | U | U | U | M | o---------------------------------------------o
Top   ToC   RFC5024 - Page 94

9.12.2. Transition Table

I | Predicate Actions Output Events Next State ===o================================================================= A | P1: 1,2 ESID(R=02) | F_ABORT_IND(R,AO=L) WF_NDISC | !P1: 1,2,3 F_START_FILE_IND OPIP ---+----------------------------------------------------------------- B | 1,2 ESID(R=02) | F_ABORT_IND(R,AO=L) WF_NDISC ---+----------------------------------------------------------------- C | 1,2 F_CD_IND IDLESPCD ---+----------------------------------------------------------------- D | 1 F_ABORT_IND(Received | ESID Reason,AO=D) | N_DISC_RQ IDLE ---+----------------------------------------------------------------- E | 1,2,4 F_EERP_IND RTRP ---+----------------------------------------------------------------- F | 1 F_RELEASE_IND | N_DISC_RQ IDLE ---+----------------------------------------------------------------- H | P4: User Error UE | P2 & !P4 & !P5: 1,2,8 SFPA OPI | !P2 & !P4 & !P5: 1,2 SFNA IDLELI | P2 & !P4 & P5: 1,2,5,8 SFPA OPI | !P2 & !P4 & P5: 1,2,5 SFNA IDLELI ---+----------------------------------------------------------------- I | P6: 1,2 ESID(R=02) | F_ABORT_IND(R,A0=L) WF_NDISC | !P5 & !P6 & !P7: 1,2,7 F_DATA_IND (See Note 1) OPI | !P5 & !P6 & P7: 1,2,8 F_DATA_IND | CDT (See Note 1) OPI | P5 & !P6 & P8: 1,2 ESID(R=07) | F_ABORT_IND(R,A0=L) WF_NDISC | P5 & !P6 & !P7 : 1,2,6,7 F_DATA_IND (See Note 1) OPI | & !P8 | P5 & !P6 & P7 : 1,2,5,6,8 F_DATA_IND OPI | & !P8 CDT (See Note 1) ---+----------------------------------------------------------------- J | 1,2 F_CLOSE_FILE_IND CLIP ---+----------------------------------------------------------------- K | P2 & P3 & !P5: 1,2 EFPA(CD-Req) WF_CD | P2 & !P3 & !P5: 1,2 EFPA(no CD) IDLELI | !P2 & !P5: 1,2 EFNA IDLELI | P2 & !P3 & P5: 1,2,5 EFPA(no CD) IDLELI | !P2 & P5: 1,2,5 EFNA IDLELI | P2 & P3 & P5: 1,2,5 EFPA(CD-Req) WF_CD
Top   ToC   RFC5024 - Page 95
   ---+-----------------------------------------------------------------
    L |                    1,2,10     F_NERP_IND                RTRP
   ---+-----------------------------------------------------------------
    M |                    1,2        RTR                       IDLELI
   ---+-----------------------------------------------------------------
    U |                               User Error                UE
   ---------------------------------------------------------------------

9.12.3. Predicates and Actions

Predicate P1: (I.SFID.Restart-pos > 0 AND V.Restart = No) OR (V.Mode = Sender-only) Note: Invalid Start File command. Predicate P2: Positive Response Predicate P3: I.F_CLOSE_FILE_RS(+).Speaker = Yes Predicate P4: I.F_START_FILE_RS(+).Restart-pos > V.Restart Predicate P5: Special logic is used Predicate P6: V.Credit_L - 1 < 0 Note: Protocol Error because the Speaker has exceeded its available transmission credit. Predicate P7: V.Credit_L - 1 = 0 Note: The Speaker's credit must be reset before it can send further Data Exchange Buffers. Predicate P8: The calculus of the received CRC indicates an error Action 1: Stop inactivity timer Action 2: Start inactivity timer Action 3: Build F_START_FILE_IND from I.SFID V.Restart-pos = I.SFID.Restart-pos Action 4: Build F_EERP_IND from I.EERP Action 5: Add special logic header to the command to be sent to the Speaker
Top   ToC   RFC5024 - Page 96
       Action 6:  Suppress the special logic header from the data buffer
                  before giving it to the user

       Action 7:  V.Credit_L = V.Credit_L - 1

       Action 8:  V.Credit_L = V.Window

       Action 10: Build F_NERP_IND from I.NERP

         Note 1:  Flow control in case of reception.

                  The ODETTE-FTP Listener must periodically send new
                  credit to the Speaker.  The timing of this operation
                  will depend on:

                  1. The User Monitor's capacity to receive data.
                  2. The number of buffers available to ODETTE-FTP.
                  3. The Speaker's available credit, which must be
                     equal to zero.

9.13. Example

Consider an ODETTE-FTP entity that has sent a Start File (SFID) command and entered the Open Out Pending (OPOP) state. Its response on receiving a Positive Answer (SFPA) is documented in Speaker State Table 1, which shows that transition 'K' should be applied and is interpreted as follows: if (I.SFPA.Restart-pos > V.Restart-pos) then begin // invalid restart Actions: Stop inactivity timer, // reset timer Start inactivity timer; Output: ESID(R=02), // to peer ODETTE-FTP F_ABORT_IND(R,AO=L); // to User Monitor New State: WF_NDISC; end else begin Actions: Stop inactivity timer, // reset timer Start inactivity timer; Build F_START_FILE_CF(+) from I.SFPA V.Credit_S = V.Window // initialise credit Output: F_START_FILE_CF(+); // to User Monitor New State: OPO; end
Top   ToC   RFC5024 - Page 97
   ODETTE-FTP checks the restart position in the received Start File
   Positive Answer (SFPA) command.  If it is invalid, it aborts the
   session by sending an End Session (ESID) command to its peer and an
   Abort indication (F_ABORT_IND) to its User Monitor.  If the restart
   position is valid, a Start File confirmation (F_START_FILE_CF) is
   built and sent to the User Monitor, the credit window is initialised,
   and the Open Out (OPO) state is entered.

10. Miscellaneous

10.1. Algorithm Choice

The choice of algorithms to use for security or compression between partners is for bilateral agreement outside of ODETTE-FTP.

10.2. Cryptographic Algorithms

The algorithms for symmetric and asymmetric cryptography and hashing are represented by a coded value, the cipher suite: Cipher Suite Symmetric Asymmetric Hashing ------------ ----------------- ------------ ------- 01 3DES_EDE_CBC_3KEY RSA_PKCS1_15 SHA-1 02 AES_256_CBC RSA_PKCS1_15 SHA-1 Support of all cipher suites listed here is mandatory. The certificates used must be [X.509] certificates. TripleDES is using Cipher Block Chaining (CBC) mode for added security and uses the Encryption Decryption Encryption (EDE) process with 3 different 64-bit keys. RSA padding is as defined in [PKCS#1]. AES is using a 256-bit key in CBC mode. An extended list of optional cipher suites may be used (Section 10.3), but there is no guarantee that two communicating ODETTE-FTP entities would both support these optional cipher suites.

10.3. Protocol Extensions

The algorithms and file enveloping formats available in ODETTE-FTP may be extended outside of this document.
Top   ToC   RFC5024 - Page 98
   An up-to-date list of cipher suite values for use in ODETTE-FTP is
   maintained by ODETTE International, and published on their website at
   www.odette.org.

10.4. Certificate Services

Certificates and certificate revocation lists may be exchanged as [CMS] enveloped files. It is therefore valid to exchange a [CMS] file that is neither encrypted, compressed, nor signed. It is an application implementation issue to determine the correct course of action on receipt of such a file.

11. Security Considerations

ODETTE-FTP security requires the use of [X.509] certificates. If no security options are agreed for use, the send and receive passwords are sent in plain text. Whilst this is acceptable over X.25 and ISDN networks, this is a risky practice over insecure public networks such as the Internet. All, some, or none of the security options available in ODETTE-FTP may be used. No recommendations for the use of these options are provided in this specification. Whilst use of the highest-strength encryption algorithms may seem admirable, there is often a performance tradeoff to be made, and signing all files and acknowledgements has potential legal implications that should be considered. It should be noted that whilst the security measures ensure that an ODETTE-FTP partner is authenticated, it does not necessarily mean that the partner is authorised. Having proven the identity of a partner, it is an application issue to decide whether that partner is allowed to connect or exchange files. Extracted from [RFC3850]: "When processing certificates, there are many situations where the processing might fail. Because the processing may be done by a user agent, a security gateway, or other program, there is no single way to handle such failures. Just because the methods to handle the failures have not been listed, however, the reader should not assume that they are not important. The opposite is true: if a certificate is not provably valid and associated with the message, the processing software should take immediate and noticeable steps to inform the end user about it.
Top   ToC   RFC5024 - Page 99
   Some of the many situations in which signature and certificate
   checking might fail include the following:

     No certificate chain leads to a trusted CA
     No ability to check the Certificate Revocation List (CRL) for a
      certificate
     An invalid CRL was received
     The CRL being checked is expired
     The certificate is expired
     The certificate has been revoked

   There are certainly other instances where a certificate may be
   invalid, and it is the responsibility of the processing software to
   check them all thoroughly, and to decide what to do if the check
   fails.  See RFC 3280 for additional information on certificate path
   validation."

   The push / pull nature of ODETTE-FTP means that a party can make an
   outbound connection from behind a firewall to another party and
   exchange files in both directions.  There is no need for both
   partners to open ports on their firewalls to allow incoming
   connections; only one party needs to allow incoming connections.

   See Section 1.7 for a discussion of the benefits of session security
   [TLS] versus file security.


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