| Internet-Draft | IBM i Telnet Enhancements | September 2022 |
| Garvey, et al. | Expires 1 April 2023 | [Page] |
This obsoletes RFC 4777 with an enhanced Automatic Sign-On a password hash, recommended Telnet security considerations using TLS and update on how non-complient 5250 negotiations are handled.¶
This document updates IBM i Telnet support to include a new Automatic Sign-On and Password Hash available with systems running with V7R5M0 or later and configured to use Password Level (QPWDLVL) 4 for the user profile passwords.¶
In addition, this document updates Security Considerations for the Telnet server and client to recomend securing the Telnet session using Transport Layer Security (TLS).¶
This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.¶
Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet-Drafts is at https://datatracker.ietf.org/drafts/current/.¶
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."¶
This Internet-Draft will expire on 1 April 2023.¶
Copyright (c) 2022 IETF Trust and the persons identified as the document authors. All rights reserved.¶
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The IBM i Telnet server enables clients to negotiate both terminal and printer device names through Telnet Environment Options Negotiations [RFC1572].¶
This allows Telnet servers and clients to exchange environment information using a set of standard or custom variables. By using a combination of both standard VARs and custom USERVARs, the IBM i Telnet server allows client Telnet to request a pre-defined specific device by name.¶
If no pre-defined device exists, then the device will be created, with client Telnet having the option to negotiate device attributes, such as the code page, character set, keyboard type, etc.¶
Since printers can also be negotiated as a device name, terminal types have been defined to request printers. For example, you can negotiate "IBM-3812-1" and "IBM-5553-B01" as valid TERMINAL-TYPE options [RFC1091].¶
Finally, the IBM i Telnet server will allow exchange of user profile and password information, where the password may be in either plain text or hash form. If a valid combination of profile and password is received, then the client is allowed to bypass the sign- on panel. The local server setting of the QRMTSIGN system value must be either *VERIFY or *SAMEPRF for the bypass of the sign-on panel to succeed.¶
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 [RFC2119] and [RFC8174] when, and only when, they appear in all capitals, as shown here.¶
The Password Level (QPWDLVL) system value is an OS wide system configuration for the IBM i system that defines what characters are allowed and the maximum length for user profile passwords. This also determines how the system generates one-way password hashs on the system that are used when authenticating all sign-on requests.¶
The Remote Sign-On Control (QRMTSIGN) system value specifies how the system handles automatic sign-on requests.¶
Telnet server option negotiation [RFC855] typically begins with the issuance, by the server, of an invitation to engage in terminal type negotiation with the Telnet client (DO TERMINAL-TYPE) [RFC1091].¶
The client and server then enter into a series of sub-negotiations to determine the level of terminal support that will be used. After the terminal type is agreed upon, the client and server will normally negotiate a required set of additional options (EOR [RFC885], BINARY [RFC856], SGA [RFC858]) that are required to support "transparent mode" or full screen 5250/3270 block mode support. As soon as the required options have been negotiated, the server will suspend further negotiations and begin with initializing the actual virtual device on the IBM i. A typical exchange might start as follows:¶
IBM i Telnet server Enhanced Telnet client
-------------------------- -------------------------
IAC DO TERMINAL-TYPE -->
<-- IAC WILL TERMINAL-TYPE
IAC SB TERMINAL-TYPE SEND
IAC SE -->
IAC SB TERMINAL-TYPE IS
<-- IBM-5555-C01 IAC SE
IAC DO EOR -->
<-- IAC WILL EOR
<-- IAC DO EOR
IAC WILL EOR -->
.
.
(other negotiations) .
Actual bytes transmitted in the above example are shown in hex below.
IBM i Telnet server Enhanced Telnet client
-------------------------- -------------------------
FF FD 18 -->
<-- FF FB 18
FF FA 18 01 FF F0 -->
FF FA 18 00 49 42 4D 2D
35 35 35 35 2D 43 30 31
<-- FF F0
FF FD 19 -->
<-- FF FB 19
<-- FF FD 19
FF FB 19 -->
.
.
(other negotiations) .
¶
Some negotiations are symmetrical between client and server, and some are negotiated in one direction only. Also, it is permissible and common practice to bundle more than one response or request, or to combine a request with a response, so in practice the actual exchange may look different from what is shown above.¶
In order to accommodate the environment option negotiations, the server will bundle an environment option invitation along with the standard terminal type invitation request to the client.¶
A client should either send a negative acknowledgment (WONT NEW- ENVIRON), or at some point after completing terminal-type negotiations, but before completing the full set of negotiations required for 5250 transparent mode, engage in environment option sub-negotiation with the server. A maximum of 1024 bytes of environment strings may be sent to the server. A recommended sequence might look like the following:¶
IBM i Telnet server Enhanced Telnet client
-------------------------- -------------------------
IAC DO NEW-ENVIRON
IAC DO TERMINAL-TYPE -->
(2 requests bundled)
<-- IAC WILL NEW-ENVIRON
IAC SB NEW-ENVIRON SEND
VAR IAC SE -->
IAC SB NEW-ENVIRON IS
VAR "USER" VALUE "JONES"
USERVAR "DEVNAME"
VALUE "MYDEVICE07"
<-- IAC SE
<-- IAC WILL TERMINAL-TYPE
(do the terminal type
sequence first)
IAC SB TERMINAL-TYPE SEND
IAC SE -->
IAC SB TERMINAL-TYPE IS
<-- IBM-5555-C01 IAC SE
(terminal type negotiations
completed)
IAC DO EOR -->
(server will continue
with normal transparent
mode negotiations)
<-- IAC WILL EOR
.
.
(other negotiations) .
¶
Actual bytes transmitted in the above example are shown in hex below.¶
IBM i Telnet server Enhanced Telnet client
-------------------------- -------------------------
FF FD 27
FF FD 18 -->
(2 requests bundled)
<-- FF FB 27
FF FA 27 01 00 FF F0 -->
FF FA 27 00 00 55 53 45
52 01 4A 4F 4E 45 53 03
44 45 56 4E 41 4D 45 01
4D 59 44 45 56 49 43 45
<-- 30 37 FF F0
<-- FF FB 18
(do the terminal type
sequence first)
FF FA 18 01 FF F0 -->
FF FA 18 00 49 42 4D 2D
35 35 35 35 2D 43 30 31
<-- FF F0
FF FD 19 -->
(server will continue
with normal transparent
mode negotiations)
<-- FF FB 19
.
.
(other negotiations) .
¶
Telnet environment options defines 6 standard VARs: USER, JOB, ACCT, PRINTER, SYSTEMTYPE, and DISPLAY. The USER standard VAR will hold the value of the IBM i user profile name to be used in Automatic Sign-On requests. The Telnet server will make no direct use of the additional 5 VARs, nor are any of them required to be sent. All standard VARs and their values that are received by the Telnet server will be placed in a buffer, along with any USERVARs received (described below), and made available to a registered initialization exit program to be used for any purpose desired.¶
There are some reasons you may want to send NEW-ENVIRON negotiations prior to TERMINAL-TYPE negotiations. With an IBM i Telnet server, several virtual device modes can be negotiated: 1) VTxxx device, 2) 3270 device, and 3) 5250 device. The virtual device mode selected depends on the TERMINAL-TYPE negotiated plus any other Telnet option negotiations necessary to support those modes. The IBM i Telnet server will create the desired virtual device at the first opportunity it thinks it has all the requested attributes needed to create the device. This can be as early as completion of the TERMINAL-TYPE negotiations.¶
For the case of Transparent mode (5250 device), the moment TERMINAL- TYPE, BINARY, and EOR options are negotiated, the Telnet server will go create the virtual device. Receiving any NEW-ENVIRON negotiations after these option negotiations are complete will result in the NEW- ENVIRON negotiations having no effect on device attributes, as the virtual device will have already been created.¶
So, for Transparent mode, NEW-ENVIRON negotiations are effectively closed once EOR is negotiated, since EOR is generally the last option done.¶
For other devices modes (such as VTxxx or 3270), you cannot be sure when the IBM i Telnet server thinks it has all the attributes to create the device. Recall that NEW-ENVIRON negotiations are optional, and therefore the IBM i Telnet server need not wait for any NEW-ENVIRON options prior to creating the virtual device. It is in the clients' best interest to send NEW-ENVIRON negotiations as soon as possible, preferably before TERMINAL-TYPE is negotiated. That way, the client can be sure that the requested attributes were received before the virtual device is created.¶
Telnet environment option USERVARs have been defined to allow a compliant Telnet client more control over the Telnet server virtual device on the IBM i and to provide information to the Telnet server about the client. These USERVARs allow the client Telnet to create or select a previously created virtual device. If the virtual device does not exist and must be created, then the USERVAR variables are used to create and initialize the device attributes. If the virtual device already exists, the device attributes are modified.¶
The USERVARs defined to accomplish this are:¶
USERVAR VALUE EXAMPLE DESCRIPTION
-------- ---------------- -------------- -------------------
DEVNAME us-ascii char(x) MYDEVICE07 Display device name
KBDTYPE us-ascii char(3) USB Keyboard type
CODEPAGE us-ascii char(y) 437 Code page
CHARSET us-ascii char(y) 1212 Character set
IBMSENDCONFREC us-ascii char(3) YES | NO Startup Response
Record desired
IBMASSOCPRT us_ascii char(x) RFCPRT Printer associated
with display
device
x - up to a maximum of 10 characters
y - up to a maximum of 5 characters
¶
For a description of the KBDTYPE, CODEPAGE, and CHARSET parameters and their permissible values, refer to Chapter 8 in the Communications Configuration Reference [COMM-CONFIG] and also to National language keyboard types and SBCS code pages [NLS-SUPPORT].¶
The CODEPAGE and CHARSET USERVARs must be associated with a KBDTYPE USERVAR. If either CODEPAGE or CHARSET are sent without KBDTYPE, they will default to system values. A default value for KBDTYPE can be sent to force CODEPAGE and CHARSET values to be used.¶
IBM i system objects such as device names, user profiles, programs, libraries, etc., are required to be specified in English uppercase. This includes:¶
any letter (A-Z), any number (0-9), special characters (# $ _ @)¶
Therefore, where us-ascii is specified for VAR or USERVAR values, it is recommended that uppercase ASCII values be sent, which will be converted to Extended Binary Coded Decimal Interchange Code (EBCDIC) by the Telnet server.¶
A special case occurs for password hashes (described in the next section), where both the initial password and user profile used to build the password hash must be EBCDIC English uppercase, in order to be properly authenticated by the Telnet server.¶
The IBMASSOCPRT USERVAR is used to provide the device name of a printer that will be associated with the display device that is created. The device description of the printer name provided must currently exist on the Telnet server system. The IBMSENDCONFREC USERVAR is used by the enhanced Telnet client to inform the Telnet server that a display Startup Response Record should be sent to the client. This record communicates the name of the actual display device acquired. If the attempt is unsuccessful, the reason code will be set to provide additional information on why the attempt failed. In addition to the device name and reason code, the Startup Response Record will contain the name of the Telnet server system.¶
For more details on the Startup Response Record, see Section 11 of this document.¶
To allow password hashes, IBMRSEED and IBMSUBSPW USERVARs will be used to exchange seed and substitute passwords information. IBMRSEED will carry a random seed to be used for the Data Encryption Standard (DES), Secure Hash Algorithm (SHA-1) and Password-based Key Derivation Function 2 (PBKDF2) [RFC8018] with Hashed Message Authentication Mode (HMAC) Secure Hash Algorithm (SHA-512) password hash. IBMSUBSPW will carry the password hash.¶
The DES algorithm uses the same 7-step DES-based password substitution scheme as APPC and Access Client Solutions (ACS). For a description of DES, refer to Federal Information Processing Standards Publications (FIPS) 46-2 [FIPS-46-2] and 81 [FIPS-81].¶
The SHA hash is described in Federal Information Processing Standards Publication 180-4 [FIPS-180-4].¶
The SHA-512 hash is described in Federal Information Processing Standards Publication 140-2 [FIPS-140-2].¶
The HMAC: Keyed-Hashing for Message Authentication is described by [RFC2104] published in 1997¶
The FIPS documents can be found at the Federal Information Processing Standards Publications link: https://www.nist.gov/itl/publications-0/federal-information- processing-standards-fips¶
If password hash exchange is not required, plain text password exchange is permitted using the same USERVARs defined for hash. For this case, the random client seed should be set either to an empty value (preferred method) or to hexadecimal zeros to indicate the password is not hashd, but is plain text.¶
It should be noted that security of plain text password exchange cannot be guaranteed unless the network is physically protected, a trusted network (such as an intranet) or if Transport Layer Security (TLS) is configured for the Telnet server and used by the Telnet client. If your network is vulnerable to IP address spoofing or directly connected to the Internet, you should engage in password hash exchange to validate a client's identity.¶
Additional VARs and USERVARs have also been defined to allow an Automatic Sign-On user greater control over their startup environment, similar to what is supported using the Open Virtual Terminal (QTVOPNVT) API [VTAPI].¶
The standard VARs supported to accomplish this are:¶
VAR VALUE EXAMPLE DESCRIPTION -------- ---------------- ---------------- ------------------- USER us-ascii char(x) USERXYZ User profile name x - up to a maximum of 10 characters¶
The custom USERVARs defined to accomplish this are:¶
USERVAR VALUE EXAMPLE DESCRIPTION
-------- ---------------- ---------------- -----------------
IBMRSEED binary(8) 8-byte hex field Random client
seed
IBMSUBSPW binary(y) hex field Substitute
password hash
IBMCURLIB us-ascii char(x) QGPL Current library
IBMIMENU us-ascii char(x) MAIN Initial menu
IBMPROGRAM us-ascii char(x) QCMD Program to call
x - up to a maximum of 10 characters
y - up to a maximum of 128 bytes
¶
In order to communicate the server random seed value to the client, the server will request a USERVAR name made up of a fixed part (the 8 characters "IBMRSEED") immediately followed by an 8-byte hexadecimal variable part, which is the server random seed. The client generates its own 8-byte random seed value and uses both seeds to hash the password. Both the password hash and the client random seed value are then sent to the server for authentication. Telnet environment option rules will need to be adhered to when transmitting the client random seed and substituted password values to the server. Specifically, since a typical environment string is a variable length hexadecimal field, the hexadecimal fields are required to be escaped and/or byte stuffed according to the [RFC854], where any single byte could be misconstrued as a Telnet IAC or other Telnet option negotiation control character. The client must escape and/or byte stuff any bytes that could be seen as a Telnet environment option, specifically VAR, VALUE, ESC, and USERVAR.¶
If you use the IBMSENDCONFREC USERVAR, as described in Section 4 of this document, with a value of YES along with the Automatic Sign-On USERVARs described above, you will receive a Startup Response Record that will contain a response code informing your Telnet client of the success or failure of the Automatic Sign-On attempt. See Section 10 of this document for details on the Startup Response Record.¶
The following illustrates the password hash case:¶
IBM i Telnet server Enhanced Telnet client
-------------------------- -------------------------------
IAC DO NEW-ENVIRON -->
<-- IAC WILL NEW-ENVIRON
IAC SB NEW-ENVIRON SEND
USERVAR "IBMRSEEDxxxxxxxx"
USERVAR "IBMSUBSPW"
VAR USERVAR IAC SE -->
IAC SB NEW-ENVIRON IS
VAR "USER" VALUE "DUMMYUSR"
USERVAR "IBMRSEED" VALUE "yyyyyyyy"
USERVAR "IBMSUBSPW" VALUE "zzzzzzzz"
<-- IAC SE
.
.
(other negotiations) .
¶
In this example, "xxxxxxxx" is an 8-byte hexadecimal random server seed, "yyyyyyyy" is an 8-byte hexadecimal random client seed, and "zzzzzzzz" is an 8-byte hexadecimal hashed password (if the DES algorithm was used), a 20-byte hexadecimal hashed password (if the SHA-1 algorithm was used) or a 64-byte hexadecimal hashed password (if the PBKDF2 with HMAC SHA-512 hash algorithm was used). If the password is not valid, then the sign-on panel is not bypassed. If the password is expired, then the sign-on panel is not bypassed.¶
Actual bytes transmitted in the above example are shown in hex below, where the server seed is "7D3E488F18080404", the client seed is "4E4142334E414233", and the DES hashed password is "DFB0402F22ABA3BA". The user profile used to generate the hashed password is "44554D4D59555352" (DUMMYUSR), with a plain text password of "44554D4D595057" (DUMMYPW).¶
IBM i Telnet server Enhanced Telnet client
-------------------------- -------------------------
FF FD 27 -->
<-- FF FB 27
FF FA 27 01 03 49 42 4D
52 53 45 45 44 7D 3E 48
8F 18 08 04 04 03 49 42
4D 53 55 42 53 50 57 03
00 FF F0 -->
FF FA 27 00 00 55 53 45
52 01 44 55 4D 4D 59 55
53 52 03 49 42 4D 52 53
45 45 44 01 4E 41 42 33
4E 41 42 33 03 49 42 4D
53 55 42 53 50 57 01 DF
B0 40 2F 22 AB A3 BA FF
<-- F0
¶
The following illustrates the plain text case:¶
IBM i Telnet server Enhanced Telnet client
-------------------------- -------------------------
IAC DO NEW-ENVIRON -->
<-- IAC WILL NEW-ENVIRON
IAC SB NEW-ENVIRON SEND
USERVAR "IBMRSEEDxxxxxxxx"
USERVAR "IBMSUBSPW"
VAR USERVAR IAC SE -->
IAC SB NEW-ENVIRON IS
VAR "USER" VALUE "DUMMYUSR"
USERVAR "IBMRSEED" VALUE
USERVAR "IBMSUBSPW" VALUE "yyyyyyyy"
<-- IAC SE
.
.
(other negotiations) .
¶
In this example, "xxxxxxxx" is an 8-byte hexadecimal random server seed, and "yyyyyyyyyy" is a 128-byte us-ascii client plain text password. If the password has expired, then the sign-on panel is not bypassed.¶
Actual bytes transmitted in the above example are shown in hex below, where the server seed is "7D3E488F18080404", the client seed is empty, and the plain text password is "44554D4D595057" (DUMMYPW). The user profile used is "44554D4D59555352" (DUMMYUSR).¶
IBM i Telnet server Enhanced Telnet client
-------------------------- -------------------------
FF FD 27 -->
<-- FF FB 27
FF FA 27 01 03 49 42 4D
52 53 45 45 44 7D 3E 48
8F 18 08 04 04 03 49 42
4D 53 55 42 53 50 57 03
00 FF F0 -->
FF FA 27 00 00 55 53 45
52 01 44 55 4D 4D 59 55
53 52 03 49 42 4D 52 53
45 45 44 01 03 49 42 4D
53 55 42 53 50 57 01 44
<-- 55 4D 4D 59 50 57 FF F0
¶
Both APPC and Access Client Solutions (ACS) use well-known DES algorithms to create the password hash. An enhanced Telnet Client can generate compatible password hashes if it follows these steps, details of which can be found in the Federal Information Processing Standards 46-2 [FIPS-46-2].¶
The user's password must be left justified in an 8-byte variable and padded to the right with '40'X up to an 8-byte length. If the user's password is 8 bytes in length, no padding will occur. For computing password substitutes for passwords of length 9 and 10, see "Handling passwords of length 9 and 10" below. Passwords less than 1 byte or greater than 10 bytes in length are not valid. Please note that if password is not in EBCDIC, it must be converted to EBCDIC uppercase.¶
Padded_PW = Left justified user password padded to the right with '40'X to 8 bytes.¶
The padded password is Exclusive OR'ed with 8 bytes of '55'X.¶
XOR_PW = Padded_PW xor '5555555555555555'X¶
The entire 8-byte result is shifted 1 bit to the left; the left- most bit value is discarded, and the rightmost bit value is cleared to 0.¶
SHIFT_RESULT = XOR_PW << 1¶
Encrypt user identifier¶
PW_TOKEN = DES_ECB_mode(SHIFT_RESULT, /* key */
userID_in_EBCDIC_uppercase /* data */
)
¶
This shifted result is used as key to the Data Encryption Standard (Federal Information Processing Standards 46-2 [FIPS-46-2]) to encipher the user identifier. When the user identifier is less than 8 bytes, it is left justified in an 8-byte variable and padded to the right with '40'X. When the user identifier is 9 or 10 bytes, it is first padded to the right with '40'X to a length of 10 bytes. Then bytes 9 and 10 are "folded" into bytes 1-8 using the following algorithm:¶
Bit 0 is the high-order bit (i.e., has value of '80'X). Byte 1, bits 0 and 1 are replaced with byte 1, bits 0 and 1 Exclusive OR'ed with byte 9, bits 0 and 1. Byte 2, bits 0 and 1 are replaced with byte 2, bits 0 and 1 Exclusive OR'ed with byte 9, bits 2 and 3. Byte 3, bits 0 and 1 are replaced with byte 3, bits 0 and 1 Exclusive OR'ed with byte 9, bits 4 and 5. Byte 4, bits 0 and 1 are replaced with byte 4, bits 0 and 1 Exclusive OR'ed with byte 9, bits 6 and 7. Byte 5, bits 0 and 1 are replaced with byte 5, bits 0 and 1 Exclusive OR'ed with byte 10, bits 0 and 1. Byte 6, bits 0 and 1 are replaced with byte 6, bits 0 and 1 Exclusive OR'ed with byte 10, bits 2 and 3. Byte 7, bits 0 and 1 are replaced with byte 7, bits 0 and 1 Exclusive OR'ed with byte 10, bits 4 and 5. Byte 8, bits 0 and 1 are replaced with byte 8, bits 0 and 1 Exclusive OR'ed with byte 10, bits 6 and 7.¶
User identifiers greater than 10 bytes or less than 1 byte are not the result of this encryption ID, known as PW_TOKEN in the paper.¶
Increment PWSEQs and store it.¶
Each LU must maintain a pair of sequence numbers for ATTACHs sent and received on each session. Each time an ATTACH is generated, (and password substitutes are in use on the session) the sending sequence number, PWSEQs, is incremented and saved for the next time. Both values are set to zero at BIND time. So the first use of PWSEQs has the value of 1 and increases by one with each use. A new field is added to the ATTACH to carry this sequence number. However, in certain error conditions, it is possible for the sending side to increment the sequence number, and the receiver may not increment it. When the sender sends a subsequent ATTACH, the receiver will detect a missing sequence. This is allowed. However the sequence number received must always be larger than the previous one, even if some are missing.¶
The maximum number of consecutive missing sequence numbers allowed is 16. If this is exceeded, the session is unbound with a protocol violation.¶
Note: The sequence number must be incremented for every ATTACH sent. However, the sequence number field is only required to be included in the FMH5 if a password substitute is sent (byte 4, bit 3 on).¶
Get modified random value:¶
RDrSEQ = RDr + PWSEQs /* RDr is server seed. */¶
The current value of PWSEQs is added to RDr, the random value received from the partner LU on this session, yielding RDrSEQ, essentially a predictably modified value of the random value received from the partner LU at BIND time.¶
Generate DES value¶
PW_SUB = DES_CBC_mode(PW_TOKEN, /* key */
(RDrSEQ, /* 8 bytes */
RDs, /* 8 bytes */
ID xor RDrSEQ, /* 16 bytes */
PWSEQs, /* 8 bytes */
) /* data */
)
¶
The PW_TOKEN is used as a key to the DES function to generate an 8-byte value for the following string of inputs. The DES CBC mode Initialization Vector (IV) used is 8 bytes of '00'X.¶
This is similar to the process used on LU-LU verification as described in the Enhanced LU-LU Bind Security. The resulting enciphered random data is the 'password substitute'.¶
Handling passwords of length 9 and 10¶
Example DES Password Hash Calculation¶
ID: USER123
Password: ABCDEFG
Server seed: '7D4C2319F28004B2'X
Client seed: '08BEF662D851F4B1'X
PWSEQs: 1 (PWSEQs is a sequence number needed in the
7-step algorithm, and it is always one for
Telnet)
DES Encrypted Password should be: '5A58BD50E4DD9B5F'X
¶
An Enhanced Telnet Client can generate SHA-1 password hash if it follows these steps.¶
Convert the user identifier to uppercase UTF-16 (CCSID 13488) format (if it is not already in this format).¶
The user identifier must be left justified in a 10-byte variable and padded to the right with spaces (' ') up to a 10-byte length prior to converting it to UTF-16. If the user's password is 10 bytes in length, no padding will occur. User identifiers of less than 1 byte or greater than 10 bytes in length are not valid. The user identifier will be 20 bytes in length after conversion to UTF-16, so the variable that will hold the UTF-16 user identifier should have a length of 20 bytes.¶
Ensure the password is in UTF-16 (CCSID 13488) format (if it is not already in this format).¶
The user's password must be left justified in a 128-byte variable. It does not need to be padded to the right with spaces up to a 128-byte length. Passwords less than 1 byte or greater than 128 bytes in length are not valid. The password will be 2 times its original length after conversion to UTF-16, so the maximum length of the variable that will hold the UTF-16 password is 256 bytes.¶
Create a 20-byte password token as follows:¶
PW_token = SHA-1(uppercase_utf16_userid, /* 20 bytes */
utf16_password) /* from 2 to 256 bytes */
¶
The actual routine to be used to perform the SHA-1 processing is dependent on the programming language being used. For example, if using the Java language, then use the java.security class to perform the actual SHA-1 processing.¶
The PW_token will be used in subsequent step to actually generate the final password hash.¶
Create the 20-byte password hash as follows:¶
PW_SUB = SHA-1(PW_token, /* 20 bytes */
serverseed, /* 8 bytes */
clientseed, /* 8 bytes */
uppercase_utf16_userid, /* 20 bytes */
PWSEQ) /* 8 bytes */
¶
The actual routine to be used to perform the SHA-1 processing is dependent on the programming language being used. For example, if using the Java language, then use the java.security class to perform the actual SHA-1 processing.¶
Example SHA-1 Password Hash Calculation:¶
ID: USER123
Password: AbCdEfGh123?+
Server seed: '3E3A71C78795E5F5'X
Client seed: 'B1C806D5D377D994'X
PWSEQs: 1 (PWSEQs is a sequence number needed in the
SHA-1 hash, and it is always one for Telnet)
¶
SHA Encrypted Password should be:¶
'E7FAB5F034BEDA42E91F439DD07532A24140E3DD'X¶
An Enhanced Telnet Client can generate a PBKDF2 with HMAC SHA-512 password hash if it follows these steps.¶
Convert the user identifier to uppercase UTF-16 (CCSID 13488) (if it is not already in this format).¶
The user identifier must be left justified in a 10-byte variable and padded to the right with spaces (' ') up to a 10-byte length prior to converting it to UTF-16 (CCSID 13488). If the user's password is 10 bytes in length, no padding will occur. User identifiers of less than 1 byte or greater than 10 bytes in length are not valid. The user identifier will be 20 bytes in length after conversion to UTF-16, so the variable that will hold the UTF-16 user identifier should have a length of 20 bytes.¶
Convert the password to UTF-16 (CCSID 13488) format (if it is not already in this format).¶
The user's password must be left justified in a 128-byte variable. It does not need to be padded to the right with spaces up to a 128-byte length. Passwords less than 1 byte or greater than 128 bytes in length are not valid. The password will be 2 times its original length after conversion to UTF-16, so the maximum length of the variable that will hold the UTF-16 password is 256 bytes.¶
Convert the UTF-16 password to UTF-8 (CCSID 1208) format. The UTF-8 password will encode using 1 to 512 bytes.¶
Generate the salt value:¶
Fill a 28-byte variable with UTF-16 (CCSID 13488) blanks (0x0020).¶
Copy the UTF-16 user ID value into the first 20 bytes of the 28-byte blank filled variable.¶
Copy the last 8 bytes (last 4 characters) of the UTF-16 password value into the last 8 bytes of the 28-byte variable. If the password is less than 4 characters, then copy the entire UTF-16 password value.¶
Calculate a SHA-256 hash on the 28-byte variable to produce the 32-byte salt value.¶
Create a 64-byte password token as follows:¶
PW_token = PBKDF2 with HMAC SHA-512(
Data = utf8_password /* from 1 to 512 bytes from Step #3 */
Data Length = Length of UTF-8 password value
Iterations = 10022
Initialization vector length = 32
Initialization vector (salt value) /* 32 bytes generated
in Step #4 */
¶
The actual routine to be used to perform the PBKDF2 with HMAC SHA-512 processing is dependent on the programming language being used. For example, if using the Java language, then use the java.security class to perform the actual PBKDF2 with HMAC SHA-512 processing.¶
The PW_token will be used in subsequent step to actually generate the final password hash.¶
Create the 64-byte password hash as follows:¶
PW_SUB = SHA-512(PW_token, /* 64 bytes */
serverseed, /* 8 bytes */
clientseed, /* 8 bytes */
uppercase_utf16_userid, /* 20 bytes */
PWSEQ) /* 8 bytes */
¶
The actual routine to be used to perform the SHA-512 processing is dependent on the programming language being used. For example, if using the Java language, then use the java.security class to perform the actual SHA-512 processing.¶
Example PBKDF2 with HMAC SHA-512 Password hash Calculation¶
ID: USER123
Password: AbCdEfGh123?+
Salt generated:
'AFD1D1EC977FF49E7E88B6CC114E0E18
1DA6A56FE4C66598952EF22F88C37B4D'X
PBKDF2 with HMAC SHA-512 Encrypted Password should be:
'C5DD3B0245DBB729492254704EA8A2AA
386611BCBADDFD150E5BECB47D3AF854
3D5F03DAD7CC9B32B830063D0B3EE526
A29D65DA522D0053EF8571F572F84338'X
Server seed: '3E3A71C78795E5F5'X
Client seed: 'B1C806D5D377D994'X
PWSEQs: '0000000000000001'X
(PWSEQs is a sequence number needed in the SHA-512 hash.
This is always one for Telnet)
SHA-512 Password substitue hash should be:
'81AE4149D6EBCDA8FBF2DFC5D5585D4F
6F14D12C6F42A8A8ECD7AEB9AE4D5924
6CF602E08612752203CB0550D5F70D41
176BD3CCB044E337222706023D5C4A75'X
¶
An IBM i Telnet server specific USERVAR defined below will contain the complete Generic Security Services (GSS) token for use on the IBM i. Enhanced Telnet clients will need to obtain the Kerberos services ticket from a Key Distribution Center (KDC). Implementation steps for acquiring the Kerberos services ticket will be limited to the Microsoft Security Support Provider Interface (SSPI) example below. For information on Kerberos services tickets, refer to your Network Authentication Service (NAS) documentation.¶
The custom USERVAR defined is:¶
USERVAR VALUE EXAMPLE DESCRIPTION --------- ------------- -------------------- ------------------- IBMTICKET binary(16384) 16384-byte hex field Kerberos services token¶
Several other USERVARs, as defined in Section 4, can be used along with the IBMTICKET USERVAR to allow a user greater control over their startup environment.¶
The custom USERVARs defined to accomplish this are:¶
USERVAR VALUE EXAMPLE DESCRIPTION -------- ---------------- ---------------- ----------------- IBMCURLIB us-ascii char(x) QGPL Current library IBMIMENU us-ascii char(x) MAIN Initial menu IBMPROGRAM us-ascii char(x) QCMD Program to call x - up to a maximum of 10 characters¶
If you use the IBMSENDCONFREC USERVAR, as described in Section 4, with a value of YES along with the Kerberos ticket USERVARs described above, you will receive a Startup Response Record that will contain a response code informing your Telnet client of the success or failure of the Kerberos validation attempt. See Section 10 for details on the Startup Response Record.¶
The following Microsoft SSPI example illustrates how to get the client security token, which contains the Kerberos services ticket.¶
Get a handle to the user's credentials:¶
PSecurityFunctionTable pSSPI_;
CredHandle credHandle;
TimeStamp timeStamp;
ss = pSSPI_->AcquireCredentialsHandle(
NULL, // Principal
"Kerberos", // PackageName
SECPKG_CRED_OUTBOUND, // CredentialUse
NULL, // LogonID
NULL, // AuthData
NULL, // GetKeyFnc
NULL, // GetKeyArg
&credHandle, // CredHandle
&timeStamp); // ExpireTime
¶
Initialize security context to "request delegation". Mutual authentication is also requested, although it is not required and may not be performed.¶
CtxtHandle newContext;
unsigned long contextAttr;
unsigned char token[16384] ;
unsigned long tokenLen = sizeof(token);
SecBuffer sbo = {tokenLen, SECBUFFER_TOKEN, token};
SecBufferDesc sbdo = {SECBUFFER_VERSION, 1, &sbo}
pSSPI_->InitializeSecurityContext(
&credHandle, // CredHandle
NULL, // Context
"krbsrv400/fullyqualifiedLowerCaseSystemName",
// ServicePrincipalName
ISC_REQ_CONNECTION|ISC_REQ_DELEGATE|ISC_REQ_MUTUAL_AUTH,
// ContextRequest
NULL, // Reserved
SECURITY_NATIVE_DREP, // DataRep
NULL, // Input
NULL, // Reserved
&newContext, // NewContext
&sbdo, // Output
&contextAttr, // ContextAttr
&timeStamp); // ExpireTime
¶
Free the user credentials handle with FreeCredentialsHandle().¶
Send security token to Telnet Server (padded with escape characters).¶
The following illustrates the Kerberos Token Negotiation:¶
IBM i Telnet server Enhanced Telnet client
-------------------------- -------------------------------
IAC DO NEW-ENVIRON -->
<-- IAC WILL NEW-ENVIRON
IAC SB NEW-ENVIRON SEND
USERVAR "IBMRSEEDxxxxxxxx"
VAR USERVAR IAC SE -->
IAC SB NEW-ENVIRON IS
USERVAR "IBMTICKET" VALUE
"zzzzzzzz..."
<-- IAC SE
.
.
(other negotiations) .
¶
In this example, "xxxxxxxx" is an 8-byte hexadecimal random server seed, and "zzzzzzzz..." is the complete Kerberos services token. If the Kerberos services token is not valid, then the sign-on panel is not bypassed. It should be noted that for the Kerberos token a random server seed is not needed, although it will be sent by the Telnet Server.¶
Actual bytes transmitted in the above example are shown in hex below, where the server seed is "7D3E488F18080404", and the Kerberos services token starts with "DFB0402F22ABA3BA...". The complete Kerberos services token is not shown here, as the length of the token could be 16384 bytes and would make this document extremely large. As described in Section 6, the client must escape and/or byte stuff any Kerberos token bytes, which could be seen as a Telnet environment option [RFC1572], specifically VAR, VALUE, ESC, and USERVAR.¶
IBM i Telnet server Enhanced Telnet client
-------------------------- -------------------------
FF FD 27 -->
<-- FF FB 27
FF FA 27 01 03 49 42 4D
52 53 45 45 44 7D 3E 48
8F 18 08 04 04 00 03 FF
F0 -->
FF FA 27 00 03 49 42 4D
54 49 43 48 45 54 01 DF
B0 40 2F 22 AB A3 BA...
<-- FF F0
¶
Device name collision occurs when a Telnet client sends the Telnet server a virtual device name that it wants to use, but that device is already in use on the server. When this occurs, the Telnet server sends a request to the client asking it to try another device name. The environment option negotiation uses the USERVAR name of DEVNAME to communicate the virtual device name. The following shows how the Telnet server will request the Telnet client to send a different DEVNAME when device name collision occurs.¶
IBM i Telnet server Enhanced Telnet client -------------------------- ------------------------- IAC SB NEW-ENVIRON SEND VAR USERVAR IAC SE -->¶
Server requests all environment variables be sent.¶
IAC SB NEW-ENVIRON IS USERVAR
"DEVNAME" VALUE "MYDEVICE1"
USERVAR "xxxxx" VALUE "xxx"
...
<-- IAC SE
¶
Client sends all environment variables, including DEVNAME. Server tries to select device MYDEVICE1. If the device is already in use, server requests DEVNAME be sent again.¶
IAC SB NEW-ENVIRON SEND USERVAR "DEVNAME" IAC SE -->¶
Server sends a request for a single environment variable: DEVNAME¶
IAC SB NEW-ENVIRON IS USERVAR
<-- "DEVNAME" VALUE "MYDEVICE2" IAC SE
¶
Client sends one environment variable, calculating a new value of MYDEVICE2. If MYDEVICE2 is different from the last request, then server tries to select device MYDEVICE2, else server disconnects client. If MYDEVICE2 is also in use, server will send DEVNAME request again and keep doing so until it receives a device that is not in use, or the same device name twice in row.¶
Telnet environment option USERVARs have been defined to allow a compliant Telnet client more control over the Telnet server virtual device on the IBM i. These USERVARs allow the client Telnet to select a previously created virtual device or auto-create a new virtual device with requested attributes.¶
This makes the enhancements available to any Telnet client that chooses to support these negotiations.¶
The USERVARs defined to accomplish this are:¶
USERVAR VALUE EXAMPLE DESCRIPTION ------------- ---------------- ---------------- ------------------- DEVNAME us-ascii char(x) PRINTER1 Printer device name IBMIGCFEAT us-ascii char(6) 2424J0 IGC feature (DBCS) IBMMSGQNAME us-ascii char(x) QSYSOPR *MSGQ name IBMMSGQLIB us-ascii char(x) QSYS *MSGQ library IBMFONT us-ascii char(x) 12 Font IBMFORMFEED us-ascii char(1) C | U | A Formfeed IBMTRANSFORM us-ascii char(1) 1 | 0 Transform IBMMFRTYPMDL us-ascii char(x) *IBM42023 Mfg. type and model IBMPPRSRC1 binary(1) 1-byte hex field Paper source 1 IBMPPRSRC2 binary(1) 1-byte hex field Paper source 2 IBMENVELOPE binary(1) 1-byte hex field Envelope hopper IBMASCII899 us-ascii char(1) 1 | 0 ASCII 899 support IBMWSCSTNAME us-ascii char(x) *NONE WSCST name IBMWSCSTLIB us-ascii char(x) *LIBL WSCST library x - up to a maximum of 10 characters The "IBM" prefix on the USERVARs denotes IBM i-specific attributes.¶
The DEVNAME USERVAR is used for both displays and printers. The IBMFONT and IBMASCII899 are used only for SBCS environments.¶
For a description of most of these parameters (drop the "IBM" from the USERVAR) and their permissible values, refer to Chapter 8 in the Communications Configuration Reference [COMM-CONFIG].¶
The IBMIGCFEAT supports the following variable DBCS language identifiers in position 5 (positions 1-4 must be '2424'; position 6 must be '0'):¶
'J' = Japanese 'K' = Korean 'C' = Traditional Chinese 'S' = Simplified Chinese¶
The IBMTRANSFORM and IBMASCII899 values correspond to:¶
'1' = Yes '0' = No¶
The IBMFORMFEED values correspond to:¶
'C' = Continuous 'U' = Cut 'A' = Autocut¶
The IBMPPRSRC1, IBMPPRSRC2, and IBMENVELOPE custom USERVARs do not map directly to their descriptions in Chapter 8 in the Communications Configuration Reference [COMM-CONFIG]. To map these, use the index listed here:¶
IBMPPRSRC1 HEX IBMPPRSRC2 HEX IBMENVELOPE HEX ---------- ----- ---------- ----- ----------- ----- *NONE 'FF'X *NONE 'FF'X *NONE 'FF'X *MFRTYPMDL '00'X *MFRTYPMDL '00'X *MFRTYPMDL '00'X *LETTER '01'X *LETTER '01'X *B5 '06'X *LEGAL '02'X *LEGAL '02'X *MONARCH '09'X *EXECUTIVE '03'X *EXECUTIVE '03'X *NUMBER9 '0A'X *A4 '04'X *A4 '04'X *NUMBER10 '0B'X *A5 '05'X *A5 '05'X *C5 '0C'X *B5 '06'X *B5 '06'X *DL '0D'X *CONT80 '07'X *CONT80 '07'X *CONT132 '08'X *CONT132 '08'X *A3 '0E'X *A3 '0E'X *B4 '0F'X *B4 '0F'X *LEDGER '10'X *LEDGER '10'X¶
Telnet options are defined for the printer pass-through mode of operation. To enable printer pass-through mode, both the client and server must agree to support at least the Transmit-Binary, End-Of- Record, and Terminal-Type Telnet options. The following are new terminal types for printers:¶
TERMINAL-TYPE DESCRIPTION ------------- ------------------- IBM-5553-B01 Double-Byte printer IBM-3812-1 Single-Byte printer¶
Specific characteristics of the IBM-5553-B01 or IBM-3812-1 printers are specified through the USERVAR IBMMFRTYPMDL, which specifies the manufacturer type and model.¶
An example of a typical negotiation process to establish printer pass-through mode of operation is shown below. In this example, the server initiates the negotiation by sending the DO TERMINAL-TYPE request.¶
For DBCS environments, if IBMTRANSFORM is set to 1 (use Host Print Transform), then the virtual device created is 3812, not 5553. Therefore, IBM-3812-1 (and not IBM-5553-B01) should be negotiated for TERMINAL-TYPE.¶
IBM i Telnet server Enhanced Telnet client
-------------------------- --------------------------
IAC DO NEW-ENVIRON -->
<-- IAC WILL NEW-ENVIRON
IAC SB NEW-ENVIRON SEND
VAR USERVAR IAC SE -->
IAC SB NEW-ENVIRON IS
USERVAR "DEVNAME" VALUE "PCPRINTER"
USERVAR "IBMMSGQNAME" VALUE "QSYSOPR"
USERVAR "IBMMSGQLIB" VALUE "*LIBL"
USERVAR "IBMTRANSFORM" VALUE "0"
USERVAR "IBMFONT" VALUE "12"
USERVAR "IBMFORMFEED" VALUE "C"
USERVAR "IBMPPRSRC1" VALUE ESC '01'X
USERVAR "IBMPPRSRC2" VALUE '04'X
USERVAR "IBMENVELOPE" VALUE IAC 'FF'X
<-- IAC SE
IAC DO TERMINAL-TYPE -->
<-- IAC WILL TERMINAL-TYPE
IAC SB TERMINAL-TYPE SEND
IAC SE -->
IAC SB TERMINAL-TYPE IS IBM-3812-1
<-- IAC SE
IAC DO BINARY -->
<-- IAC WILL BINARY
IAC DO EOR -->
<-- IAC WILL EOR
¶
Some points about the above example. The IBMPPRSRC1 value requires escaping the value using ESC according to Telnet environment options [RFC1572]. The IBMPPRSRC2 does not require an ESC character since '04'X has no conflict with environment options. Finally, to send 'FF'X for the IBMENVELOPE value, escape the 'FF'X value by using another 'FF'X (called "doubling"), so as not to have the value interpreted as a Telnet character per the Telnet protocol specification [RFC885].¶
Actual bytes transmitted in the above example are shown in hex below.¶
IBM i Telnet server Enhanced Telnet client
-------------------------- --------------------------
FF FD 27 -->
<-- FF FB 27
FF FA 27 01 00 03 FF F0 -->
FF FA 27 00 03 44 45 56
4E 41 4D 45 01 50 43 50
52 49 4E 54 45 52 03 49
42 4D 4D 53 47 51 4E 41
4D 45 01 51 53 59 53 4F
50 52 03 49 42 4D 4D 53
47 51 4C 49 42 01 2A 4C
49 42 4C 03 49 42 4D 54
52 41 4E 53 46 4F 52 4D
01 30 03 49 42 4D 46 4F
4E 54 01 31 32 03 49 42
4D 46 4F 52 4D 46 45 45
44 01 43 03 49 42 4D 50
50 52 53 52 43 31 01 02
01 03 49 42 4D 50 50 52
53 52 43 32 01 04 03 49
42 4D 45 4E 56 45 4C 4F
<-- 50 45 01 FF FF FF F0
FF FD 18 -->
<-- FF FB 18
FF FA 18 01 FF F0 -->
FF FA 18 00 49 42 4D 2D
<-- 33 38 31 32 2D 31 FF F0
FF FD 00 -->
<-- FF FB 00
FF FD 19 -->
FF FB 19
¶
Once Telnet negotiation for a 5250 pass-through mode is completed, the IBM i Telnet server will initiate a virtual device (printer or display) power-on sequence on behalf of the Telnet client. The Telnet server will supply a Startup Response Record to the Telnet client with the status of the device power-on sequence, indicating success or failure of the virtual device power-on sequence.¶
This section shows an example of two Startup Response Records. The source device is a type 3812 model 01 printer with the name "PCPRINTER" on the target system "TARGET".¶
Figure 1 shows an example of a successful response; Figure 2 shows an example of an error response.¶
The response record in Figure 1 was sent by an IBM i. It is an example of the target sending back a successful Startup Response Record.¶
+------------------------------------------------------------------+ | +----- Pass-Through header | | | +--- Response data | | | | +---- Start diagnostic information| | | | | | | +----------++----------++--------------------------------------- | | | || || | | 004912A090000560060020C0003D0000C9F9F0F2E3C1D9C7C5E34040D7C3D7D9 | | | | T A R G E T P C P R | | +------+ | | Response Code (I902) | | | | ---------------------------------------------------------------- | | | | C9D5E3C5D9400000000000000000000000000000000000000000000000000000 | | I N T E R | | | | +------- End of diagnostic information | | | | | -----------------+ | | | | | 000000000000000000 | +------------------------------------------------------------------+
- '0049'X = Length pass-through data, including this length field - '12A0'X = GDS LU6.2 header - '90000560060020C0003D0000'X = Fixed value fields - 'C9F9F0F2'X = Response Code (I902) - 'E3C1D9C7C5E34040'X = System Name (TARGET) - 'D7C3D7D9C9D5E3C5D940'X = Object Name (PCPRINTER)¶
The response record in Figure 2 is one that reports an error. The virtual device named "PCPRINTER" is not available on the target system "TARGET" because the device is not available. You would normally see this error if the printer were already assigned to another Telnet session.¶
+------------------------------------------------------------------+ | +----- Pass-Through header | | | +--- Response data | | | | +---- Start diagnostic information| | | | | | | +----------++----------++--------------------------------------- | | | || || | | 004912A09000056006008200003D0000F8F9F0F2E3C1D9C7C5E34040D7C3D7D9 | | | | T A R G E T P C P R | | +------+ | | Response Code (8902) | | | | ---------------------------------------------------------------- | | | | C9D5E3C5D9400000000000000000000000000000000000000000000000000000 | | I N T E R | | | | +------- End of diagnostic information | | | | | -----------------+ | | | | | 000000000000000000 | +------------------------------------------------------------------+
- '0049'X = Length pass-through data, including this length field - '12A0'X = GDS LU6.2 header - '90000560060020C0003D0000'X = Fixed value fields - 'F8F9F0F2'X = Response Code (8902) - 'E3C1D9C7C5E34040'X = System Name (TARGET) - 'D7C3D7D9C9D5E3C5D940'X = Object Name (PCPRINTER)¶
The Response Record can be used in conjunction with the DEVNAME Environment variable to allow client emulators to inform users of connection failures. In addition, this combination could be used by client emulators that accept multiple device names to try on session connections. The client would be able to walk through a list of possible device names and provide feedback based on the response code(s) received for each device name that was rejected.¶
The following sequence shows a negotiation between the client and the server in which a named device "RFCTEST" is requested by the client. The device name is already assigned to an existing condition. The server responds with the Response Record showing an 8902 response code. The client could use this information to inform the user that the device name just tried was already in use. Following the Response Record the server would then invite the client to try another device name. Because the same device name was used again by the client, the server closed the session.¶
IBM i Telnet server Enhanced Telnet client
-------------------------- -------------------------
IAC DO NEW-ENVIRON -->
<-- IAC WILL NEW-ENVIRON
IAC DO TERMINAL-TYPE -->
<-- IAC WILL TERMINAL-TYPE
IAC SB NEW-ENVIRON SEND
USERVAR "IBMRSEEDxxxxxxxx"
VAR USERVAR IAC SE -->
IAC SB NEW-ENVIRON IS
USERVAR "DEVNAME"
VALUE "RFCTEST"
USERVAR "IBMSENDCONFREC"
VALUE "YES"
<-- IAC SE
IAC SB TERMINAL-TYPE SEND
IAC SE -->
IAC SB TERMINAL-TYPE IS
<-- IBM-3180-2 IAC SE
(terminal type negotiations
completed)
IAC DO EOR -->
<-- IAC WILL EOR
IAC WILL EOR -->
<-- IAC DO EOR
IAC DO BINARY -->
<-- IAC WILL BINARY
IAC WILL BINARY -->
<-- IAC DO BINARY
(73 BYTE RFC 1205 RECORD
WITH 8902 ERROR CODE) -->
IAC SB NEW-ENVIRON SEND
USERVAR "DEVNAME"
IAC SE -->
IAC SB NEW-ENVIRON IS
USERVAR "DEVNAME"
VALUE "RFCTEST"
USERVAR "IBMSENDCONFREC"
VALUE "YES"
<-- IAC SE
(server closes connection)
¶
Actual bytes transmitted in the above example are shown in hex below.¶
IBM i Telnet server Enhanced Telnet client
-------------------------- --------------------------
FF FD 27 -->
<-- FF FB 27
FF FD 18 -->
<-- FF FB 18
FF FA 27 01 03 49 42 4D
52 53 45 45 44 C4 96 67
76 9A 23 E3 34 00 03 FF
F0 -->
FF FA 27 00 03 44 45 56
4E 41 4D 45 01 52 46 43
54 45 53 54 03 49 42 4D
53 45 4E 44 43 4F 4E 46
52 45 43 01 59 45 53 FF
<-- F0
FF FA 18 01 FF F0 -->
<-- FF FA 18 00 49 42 4D 2D
33 31 38 30 2D 32 FF F0
FF FD 19 -->
<-- FF FB 19
FF FB 19 -->
<-- FF FD 19
FF FD 00 -->
<-- FF FB 00
FF FB 00 -->
<-- FF FD 00
00 49 12 A0 90 00 05 60
06 00 20 C0 00 3D 00 00
F8 F9 F0 F2 D9 E2 F0 F3
F5 40 40 40 00 00 00 00
00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00
00 00 00 00 00 00 00 00
00 FF EF -->
FF FA 27 01 03 44 45 56
4E 41 4D 45 FF F0 -->
<-- FF FA 27 00 03 44 45 56
4E 41 4D 45 01 52 46 43
54 45 53 54 03 49 42 4D
53 45 4E 44 43 4F 4E 46
52 45 43 01 59 45 53 FF
F0
¶
The Start-Up Response Record success response codes:¶
CODE DESCRIPTION
---- ------------------------------------------------------
I901 Virtual device has less function than source device.
I902 Session successfully started.
I906 Automatic Sign-On requested, but not allowed.
Session still allowed; a sign-on screen will be
coming.
¶
The Start-Up Response Record error response codes:¶
CODE DESCRIPTION ---- ------------------------------------------------------ 2702 Device description not found. 2703 Controller description not found. 2777 Damaged device description. 8901 Device not varied on. 8902 Device not available. 8903 Device not valid for session. 8906 Session initiation failed. 8907 Session failure. 8910 Controller not valid for session. 8916 No matching device found. 8917 Not authorized to object. 8918 Job canceled. 8920 Object partially damaged. 8921 Communications error. 8922 Negative response received. 8923 Start-up record built incorrectly. 8925 Creation of device failed. 8928 Change of device failed. 8929 Vary on or vary off failed. 8930 Message queue does not exist. 8934 Start-up for S/36 WSF received. 8935 Session rejected. 8936 Security failure on session attempt. 8937 Automatic Sign-On rejected. 8940 Automatic configuration failed or not allowed. I904 Source system at incompatible release.¶
The Start-Up Response Record error response codes for non-Kerberos Services Token Automatic Sign-On:¶
CODE DESCRIPTION ---- ------------------------------------------------------ 0001 System error. 0002 Userid unknown (deprecated). 0003 Userid disabled. 0004 Userid not found or password not correct 0005 Password/passphrase/token is expired. 0008 Next invalid password/passphrase/token will revoke userid.¶
The Start-Up Response Record error response codes for Kerberos Services Token Automatic Sign-On support:¶
CODE DESCRIPTION
---- ------------------------------------------------------
0001 User profile is disabled.
0002 Kerberos principal maps to a system user profile.
0003 Enterprise Identity Map (EIM) configuration error.
0004 EIM does not map Kerberos principal to user profile.
0005 EIM maps Kerberos principal to multiple user profiles.
0006 EIM maps Kerberos principal to user profile not found on
system.
1000 None of the requested mechanisms are supported by the
local system.
2000 The input name is not formatted properly or is not valid.
6000 The received input token contains an incorrect signature.
7000 No credentials available or credentials valid for context
init only.
9000 Consistency checks performed on the input token failed.
A000 Consistency checks on the cred structure failed.
B000 Credentials are no longer valid.
D000 The runtime failed for reasons that are not defined at the
GSS level.
¶
In the case where the USERVAR, DEVNAME USERVAR, IBMSENDCONFREC USERVAR, IBMSUBSPW USERVAR, and IBMRSEED USERVAR are all used together, any device errors will take precedence over automatic sign-on errors. That is:¶
If the requested named device is not available or an error occurs when attempting to create the device on the server system, a device related return code (i.e., 8902) will be sent to the client system in the display confirmation record.¶
If the requested named device is available or no errors occur when attempting to create the device on the server system, an automatic sign-on return code (i.e., 0002) will be sent to the client system in the display confirmation record.¶
Device Negotiation is terminated when any non Telnet option data is received from the Telnet client before a successful I09x Start-Up Response Record response code is issued, including during Device Name Collision Processing. The device terminal type defaults to VT100 mode. Any negotiated TERMINAL-TYPE is ignored.¶
The information in this section applies to the pass-through session after the receipt of startup confirmation records is complete.¶
Following is the printer header interface used by Telnet.¶
+------------------------------------------------------------------+ | +-- Length of structure (LLLL) | | | | | | +-- GDS identifier | | | | | | | | +-- Data flow record | | | | | | | | | | +-- Length of pass-through specific header (LL) | | | | | | | | | | | | +-- Flags | | | | | | | | | | | | | | +-- Printer operation code | | | | | | | | | | | | | | | | +-- Diagnostic field - zero pad to| | | | | | | | | LL specified | | | | | | | | | | | | | | | | | | +-- Printer data | | | | | | | | | | | | +--+ +--+ +--+ ++ +--+ ++ +----------+ +----------------+ | | | | | | | | || | | || | | | | | | xxxx 12A0 xxxx xx xxxx xx xxxxxxxxxxxx ... print data ... | | | +------------------------------------------------------------------+
BYTES 0-1: Length of structure including this field (LLLL)
BYTES 2-3: GDS Identifier ('12A0'X)
BYTE 4-5: Data flow record
<t>
This field contains flags that describe what type of
data pass-through should be expected to be found
following this header. Generally, bits 0-2 in the first
byte are mutually exclusive (that is, if one of them is
set to '1'B, the rest will be set to '0'B.) The bits and
their meanings follow.<t>
<artwork name="" type="" align="left" alt=""><![CDATA[
BIT DESCRIPTION
0 Start-Up confirmation
1 Termination record
2 Start-Up Record
3 Diagnostic information included
4 - 5 Reserved
6 Reserved
7 Printer record
8 - 13 Reserved
14 Client-originated (inbound) printer record
15 Server-originated (outbound) printer record
BYTE 6: Length printer pass-through header including this field
(LL)
BYTES 7-8: Flags
BYTE 7 BITS: xxxx x111 --> Reserved
xxxx 1xxx --> Last of chain
xxx1 xxxx --> First of chain
xx1x xxxx --> Printer now ready
x1xx xxxx --> Intervention Required
1xxx xxxx --> Error Indicator
BYTE 8 BITS: xxxx xxxx --> Reserved
BYTE 9: Printer operation code
'01'X Print/Print complete
'02'X Clear Print Buffers
BYTE 10-LL: Diagnostic information (Note 1)
If BYTE 7 = xx1x xxxx, then bytes 10-LL may contain:
Printer ready C9 00 00 00 02
If BYTE 7 = x1xx xxxx, then bytes 10-LL may contain: (Note 2)
Command/parameter not valid C9 00 03 02 2x
Print check C9 00 03 02 3x
Forms check C9 00 03 02 4x
Normal periodic condition C9 00 03 02 5x
Data stream error C9 00 03 02 6x
Machine/print/ribbon check C9 00 03 02 8x
If BYTE 7 = 1xxx xxxx, then bytes 10-LL may contain: (Note 3)
Cancel 08 11 02 00
Invalid print parameter 08 11 02 29
Invalid print command 08 11 02 28
¶
Diagnostic information notes:¶
LL is the length of the structure defined in Byte 6. If no additional data is present, the remainder of the structure must be padded with zeroes.¶
These are printer SIGNAL commands. Further information on these commands may be obtained from the 5494 Remote Control Unit Functions Reference guide [SC30-3533].¶
Refer to your IBM i printer documentation for more specific information on these data stream exceptions. The following are some 3812 and 5553 errors that may be seen:¶
Machine check C9 00 03 02 11
Graphics check C9 00 03 02 26
Print check C9 00 03 02 31
Form jam C9 00 03 02 41
Paper jam C9 00 03 02 47
End of forms C9 00 03 02 50
Printer not ready C9 00 03 02 51
Data stream - class 1 C9 00 03 02 66 loss of text
Data stream - class 2 C9 00 03 02 67 text appearance
Data stream - class 3 C9 00 03 02 68 multibyte control error
Data stream - class 4 C9 00 03 02 69 multibyte control parm
Cover unexpectedly open C9 00 03 02 81
Machine check C9 00 03 02 86
Machine check C9 00 03 02 87
Ribbon check C9 00 03 02 88
¶
These are printer negative responses. Further information on these commands may be obtained from the 5494 Remote Control Unit Functions Reference guide [SC30-3533].¶
The print data will start in byte LL+1.¶
Figure 4 shows the server sending the client data with a print record. This is normally seen following receipt of a Success Response Record, such as the example in Figure 1.¶
+--------------------------------------------------------------------+ | +-- Length of structure (LLLL) | | | +-- GDS identifier | | | | +-- Data flow record | | | | | +-- Length of pass-through specific header (LL) | | | | | | +-- Flags | | | | | | | +-- Printer operation code | | | | | | | | +-- Zero pad to LL specified (0A) | | | | | | | | | +-- Printer data | | | | | | | | | | | | +--+ +--+ +--+ ++ +--+ ++ +----------+ +---------------------------| | | | | | | | || | | || | | | | | 0085 12A0 0101 0A 1800 01 000000000000 34C4012BD20345FF2BD2044C0002| | | | ------------------------------------------------------------ | | | | 2BD2040D00002BD20A8501010201030204022BD20309022BD2061100014A | | | | ------------------------------------------------------------ | | | | 402BD20601010000012BD306F60000FFFF2BD20A48000001000000010100 | | | | ------------------------------------------------------------ | | | | 2BD10705000B0090012BD2044900F02BD206404A403DE02BD2041500F034 | | | | end of printer data | | -------------------------+ | | | | | C4012BD10381FF002BC8034001 | +--------------------------------------------------------------------+
- '0085'X = Logical record length, including this byte (LLLL) - '12A0'X = GDS LU6.2 header - '0101'X = Data flow record (server to client) - '0A'X = Length of pass-through specific header (LL) - '1800'X = First of chain / Last of chain indicators - '01'X = Print - '000000000000'X = Zero pad header to LL specified - '34C401'X = First piece of data for spooled data - Remainder is printer data/commands/orders¶
Figure 5 shows the client sending the server a print complete record. This would normally follow receipt of a print record, such as the example in Figure 4. This indicates successful completion of a print request.¶
+-------------------------------------------------------------------+ | +-- Length of structure (LLLL) | | | +-- GDS identifier | | | | +-- Data flow record | | | | | +-- Length of pass-through specific header (LL) | | | | | | +-- Flags | | | | | | | +-- Printer operation code | | | | | | | | | | +--+ +--+ +--+ ++ +--+ ++ | | | | | | | | || | | || | | 000A 12A0 0102 04 0000 01 | +-------------------------------------------------------------------+
- '000A'X = Logical record length, including this byte (LLLL) - '12A0'X = GDS LU6.2 header - '0102'X = Data flow response record (client to server) - '04'X = Length of pass-through specific header (LL) - '0000'X = Good Response - '01'X = Print Complete¶
Figure 6 shows the server sending the client a null print record. The null print record is the last print command the server sends to the client for a print job, and it indicates to the printer that there is no more data. The null data byte '00'X is optional and in some cases may be omitted (in particular, this scenario occurs in DBCS print streams).¶
This example would normally follow any number of print records, such as the example in Figure 4. This indicates successful completion of a print job. The client normally responds to this null print record with another print complete record, such as in Figure 5.¶
+------------------------------------------------------------------+ | +-- Length of structure (LLLL) | | | +-- GDS identifier | | | | +-- Data flow record | | | | | +-- Length of pass-through specific header (LL) | | | | | | +-- Flags | | | | | | | +-- Printer operation code | | | | | | | | +-- Zero pad to LL specified (0A) | | | | | | | | | +-- Printer data | | | | | | | | | | | | +--+ +--+ +--+ ++ +--+ ++ +----------+ ++ | | | | | | | | || | | || | | || | | 0011 12A0 0101 0A 0800 01 000000000000 00 | +------------------------------------------------------------------+
- '0011'X = Logical record length, including this byte - '12A0'X = GDS LU6.2 header - '0101'X = Data flow record - '0A'X = Length of pass-through specific header (LL) - '0800'X = Last of Chain - '01'X = Print - '000000000000'X = Zero pad header to LL specified - '00'X = Null data byte¶
The next example shows a full print exchange between a Telnet client and server for a 526 byte spooled file. Selective translation of the hexadecimal streams into 1) Telnet negotiations and 2) ASCII/EBCDIC characters is done to aid readability. Telnet negotiations are delimited by '(' and ')' parenthesis characters; ASCII/EBCDIC conversions are bracketed by '|' vertical bar characters.¶
IBM i Telnet server Enhanced Telnet client
------------------------------- ---------------------------------
FFFD27 -->
(IAC DO NEW-ENVIRON)
<-- FFFB27
(IAC WILL NEW-ENVIRON)
FFFD18FFFA270103 49424D5253454544
7EA5DFDDFD300404 0003FFF0 -->
(IAC DO TERMINAL-TYPE
IAC SB NEW-ENVIRON SEND USERVAR
IBMRSEED xxxxxxxx VAR USERVAR
IAC SE)
<-- FFFB18
(IAC WILL TERMINAL-TYPE)
(IAC SB TERMINAL-TYPE SEND IAC
SE)
FFFA27000349424D 52534545447EA5DF
DDFD300404000344 45564E414D450144
554D4D5950525403 49424D4D5347514E
414D450151535953 4F50520349424D4D
5347514C4942012A 4C49424C0349424D
464F4E5401313103 49424D5452414E53
464F524D01310349 424D4D4652545950
4D444C012A485049 490349424D505052
5352433101020103 49424D5050525352
433201040349424D 454E56454C4F5045
01FFFF0349424D41 5343494938393901
<-- 30FFF0
(IAC SB NEW-ENVIRON IS USERVAR
IBMRSEED xxxxxxxx VAR
USERVAR DEVNAME VALUE DUMMYPRT
USERVAR IBMMSGQNAME VALUE
QSYSOPR
USERVAR IBMMSGQLIB VALUE *LIBL
USERVAR IBMFONT VALUE 11
USERVAR IBMTRANSFORM VALUE 1
USERVAR IBMMFRTYPMDL VALUE *HPII
USERVAR IBMPPRSRC1 VALUE
ESC '01'X
USERVAR IBMPPRSRC2 VALUE '04'X
USERVAR IBMENVELOPE VALUE IAC
USERVAR IBMASCII899 VALUE 0
IAC SE)
<-- FFFA180049424D2D 333831322D31FFF0
(IAC SB TERMINAL-TYPE IS
IBM-3812-1 IAC SE)
FFFD19 -->
(IAC DO EOR)
<-- FFFB19
(IAC WILL EOR)
FFFB19 -->
(IAC WILL EOR)
<-- FFFD19
(IAC DO EOR)
FFFD00 -->
(IAC DO BINARY)
<-- FFFB00
(IAC WILL BINARY)
FFFB00 -->
(IAC WILL BINARY)
<-- FFFD00
(IAC DO BINARY)
004912A090000560 060020C0003D0000 | - { |
C9F9F0F2C5D3C3D9 E3D7F0F6C4E4D4D4 |I902ELCRTP06DUMM| (EBCDIC)
E8D7D9E340400000 0000000000000000 |YPRT |
0000000000000000 0000000000000000 | |
0000000000000000 00FFEF --> | |
(73-byte startup success response
record ... IAC EOR)
00DF12A001010A18 0001000000000000 | |
03CD1B451B283130 551B287330703130 | E (10U (s0p10| (ASCII)
2E30306831327630 733062303033541B |.00h12v0s0b003T |
287330421B266440 1B266C304F1B266C |(s0B &d@ &l0O &l|
303038431B266C30 3035431B28733070 |008C &l005C (s0p|
31372E3130683130 7630733062303030 |17.10h10v0s0b000|
541B283130551B28 73307031372E3130 |T (10U (s0p17.10|
6831307630733062 303030541B287330 |h10v0s0b000T (s0|
421B2664401B266C 314F1B266C303035 |B &d@ &l1O &l005|
431B287330703137 2E31306831307630 |C (s0p17.10h10v0|
733062303030541B 266C314F1B287330 |s0b000T &l1O (s0|
7031372E31306831 3076307330623030 |p17.10h10v0s0b00|
30541B2873307031 372E313068313076 |0T (s0p17.10h10v|
3073306230303054 1B266C30303543FF |0s0b000T &l005C |
EF --> | |
(... 223-byte print record ...
... first of chain ...
... last of chain ... IAC EOR)
<-- 000A12A001020400 0001FFEF
(10-byte print complete header)
031012A001010A10 0001000000000000 | |
03FFFF1B451B2831 30551B2873307031 | E (10U (s0p1| (ASCII)
372E313068313076 3073306230303054 |7.10h10v0s0b000T|
1B287330421B2664 401B266C314F1B26 | (s0B &d@ &l1O &|
6C303035431B266C 31481B266C314F1B |l005C &l1H &l1O |
266C3032411B266C 31431B266C303030 |&l02A &l1C &l000|
38451B266C303038 431B266C30303439 |8E &l008C &l0049|
461B266130521B26 6C303035430A0A0A |F &a0R &l005C |
0A0A0A0A1B26612B 3030303130561B26 | &a+00010V &|
6C303035431B2661 2B30303231364820 |l005C &a+00216H |
2020202020202020 2020202020202020 | |
2020202020205072 696E74204B657920 | Print Key |
4F75747075742020 2020202020202020 |Output |
2020202020202020 2020202020202020 | |
2020202020205061 6765202020310D0A | Page 1 |
1B26612B30303231 3648202020203537 | &a+00216H 57|
3639535331205634 52334D3020393830 |69SS1 V4R3M0 980|
373203FFFF392020 2020202020202020 |72 9 |
202020202020454C 4352545030362020 | ELCRTP06 |
2020202020202020 202030332F33312F | 03/31/|
3939202031363A33 303A34350D0A1B26 |99 16:30:45 &|
612B303032313648 0D0A1B26612B3030 |a+00216H &a+00|
3231364820202020 446973706C617920 |216H Display |
4465766963652020 2E202E202E202E20 |Device . . . . |
2E203A2020515041 444556303033510D |. : QPADEV003Q |
0A1B26612B303032 3136482020202055 | &a+00216H U|
73657220202E202E 202E202E202E202E |ser . . . . . .|
202E202E202E202E 203A202052434153 | . . . . : RCAS|
54524F0D0A1B2661 2B3030323136480D |TRO &a+00216H |
0A1B26612B303032 313648204D41494E | &a+00216H MAIN|
2020202020202020 2020202020202020 | |
2020202020202020 20202041532F3430 | AS/40|
30204D61696E204D 656E750D0A1B2661 |0 Main Menu &a|
2B30303203FFFF31 3648202020202020 |+002 16H |
2020202020202020 2020202020202020 | |
2020202020202020 2020202020202020 | |
2020202020202020 2020202020202020 | |
2020202020202053 797374656D3A2020 | System: |
20454C4352545030 360D0A1B26612B30 | ELCRTP06 &a+0|
3032313648205365 6C656374206F6E65 |0216H Select one|
206F662074686520 666F6C6C6F77696E | of the followin|
673A0D0A1B26612B 3030323136480D0A |g: &a+00216H |
1B26612B30303231 3648202020202020 | &a+00216H |
312E205573657220 7461736B730D0A1B |1. User tasks |
26612B3030323136 4820202020202032 |&a+00216H 2|
2E204F6666696365 207461736B730D0A |. Office tasks |
1B26612B30303231 36480D0A1B26612B | &a+00216H &a+|
3030323136482020 20202020342E2046 |00216H 4. F|
696C65732C206C69 627261726965732C |iles, libraries,|
20616EFFEF | an |
(... 784-byte print record ...
... first of chain ... IAC EOR)
<-- 000A12A001020400 0001FFEF
(10-byte print complete header)
020312A001010A00 0001000000000000 | |
64206603FFFF6F6C 646572730D0A1B26 |d f olders &| (ASCII)
612B303032313648 0D0A1B26612B3030 |a+00216H &a+00|
3231364820202020 2020362E20436F6D |216H 6. Com|
6D756E6963617469 6F6E730D0A1B2661 |munications &a|
2B3030323136480D 0A1B26612B303032 |+00216H &a+002|
3136482020202020 20382E2050726F62 |16H 8. Prob|
6C656D2068616E64 6C696E670D0A1B26 |lem handling &|
612B303032313648 202020202020392E |a+00216H 9.|
20446973706C6179 2061206D656E750D | Display a menu |
0A1B26612B303032 3136482020202020 | &a+00216H |
31302E20496E666F 726D6174696F6E20 |10. Information |
417373697374616E 74206F7074696F6E |Assistant option|
730D0A1B26612B30 3032313648202020 |s &a+00216H |
202031312E20436C 69656E7420416363 | 11. Client Acc|
6573732F34303020 7461736B730D0A1B |ess/400 tasks |
26612B3030323136 480D0A1B26612B30 |&a+00216H &a+0|
303231364803ED20 2020202039302E20 |0216H 90. |
5369676E206F6666 0D0A1B26612B3030 |Sign off &a+00|
323136480D0A1B26 612B303032313648 |216H &a+00216H|
2053656C65637469 6F6E206F7220636F | Selection or co|
6D6D616E640D0A1B 26612B3030323136 |mmand &a+00216|
48203D3D3D3E0D0A 1B26612B30303231 |H ===> &a+0021|
36480D0A1B26612B 3030323136482046 |6H &a+00216H F|
333D457869742020 2046343D50726F6D |3=Exit F4=Prom|
707420202046393D 5265747269657665 |pt F9=Retrieve|
2020204631323D43 616E63656C202020 | F12=Cancel |
4631333D496E666F 726D6174696F6E20 |F13=Information |
417373697374616E 740D0A1B26612B30 |Assistant &a+0|
3032313648204632 333D53657420696E |0216H F23=Set in|
697469616C206D65 6E750D0A1B26612B |itial menu &a+|
3030323136480D0A 1B26612B30303231 |00216H &a+0021|
36480D0CFFEF |6H |
(... 515-byte print record ...
IAC EOR)
<-- 000A12A001020400 0001FFEF
(10-byte print complete header)
001412A001010A00 0001000000000000 | |
03021B45FFEF | E | (ASCII)
(... 20-byte print record ...
IAC EOR)
<-- 000A12A001020400 0001FFEF
(10-byte print complete header)
001112A001010A08 0001000000000000
00FFEF -->
(... 17-byte NULL print record ...
... last of chain ... IAC EOR)
<-- 000A12A001020400 0001FFEF
(10-byte print complete header)
¶
Automatic Sign-On and Password Hash SHOULD be used to avoid negotiating with clear text passwords. The hash required depends entrirely on the Password Level (QPWDLVL) system value configured on the IBM i system the Telnet server is running on. The Telnet server uses this to authenticate the substitute password hash. IBM i Systems configured with QPWDLVL 0 or 1 MUST use DES, QPWDLVL 2 or 3 MUST use SHA-1 and QPWDLVL 4 MUST uses PBKDF2 with HMAC SHA-512.¶
The Automatic Sign-On feature provided by this RFC describes a way to hash an automatic signon user profile password. However, while passwords can be hashed by using the IBMRSEED and IBMSUBSPW USERVAR negotiations, users should understand that only the negotiated automatic signon user profile password is hashed and not the entire Telnet data payload.¶
The Automatic Sign-On feature supports plain text passwords, password hashes, and Kerberos tokens. However, Telnet clients using plain text passwords are strongly discouraged.¶
The password hash algorithm required depends on how the IBM i system has configured the Password Level (QPWDLVL) system value. Configuring the system to use a stronger QPWDLVL determines the password hash that is required by the Telnet client as well as all other password authentication methods used on the IBM i system. The QPWDLVL system value is not negotiated with the Telnet client and thus the required Automatic Sign-On and Password Hash required must be determined seperatly from this RFC, such as through external Telnet configuration, parameters, client application install options or other out of band methods.¶
Encryption of the entire Telnet client session requires that Transport Layer Security (TLS) to secure the entire Telnet session data payload. Standard Telnet uses port 23 which is considered obsolete. IBM i provides a secure Telnet port 992 for Transport Layer Security (TLS). Use of secure Telnet is recomended and MUST implement TLS 1.2 [RFC8446] or later. When a TCP connection is established for the "telnets" service (default port 992), a TLS handshake begins immediately. Once the TLS session is established, Telnet negotiation proceeds.¶
Configuring the IBM i system to use the highest version of TLS available on the secure Telnet port 992 and disabling the non secure Telnet port 23 is RECOMENDED to secure all Telnet sessions.¶
IANA registered the terminal types "IBM-3812-1" and "IBM-5553-B01" as a terminal type [RFC1091]. They are used when communicating with IBM i Telnet servers.¶
Thomas E. Murphy, Jr. IBM Corporation Paul F. Rieth IBM Corporation Jeffrey S. Stevens IBM Corporation¶
This RFC relies on the 5250 Telnet Interface [RFC1205] in all examples.¶
This RFC replaces 5250 Telnet Enhancements RFC 4777, adding new PBKDF2 with HMAC SHA-512 hash, IBM i Telent security recomendations and minor corrections.¶
The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the ISOC's procedures with respect to rights in ISOC Documents can be found in BCP 78 and BCP 79.¶