Internet Assigned Numbers Authority

Secure Shell (SSH) Protocol Parameters

Created
2005-06-02
Last Updated
2024-01-26
Available Formats

XML

HTML

Plain text

Registries included below

Message Numbers

Registration Procedure(s)
Standards Action
Reference
[RFC4250]
Available Formats

CSV
Value Message ID Reference
0 Reserved
1 SSH_MSG_DISCONNECT [RFC4253]
2 SSH_MSG_IGNORE [RFC4253]
3 SSH_MSG_UNIMPLEMENTED [RFC4253]
4 SSH_MSG_DEBUG [RFC4253]
5 SSH_MSG_SERVICE_REQUEST [RFC4253]
6 SSH_MSG_SERVICE_ACCEPT [RFC4253]
7 SSH_MSG_EXT_INFO [RFC8308]
8 SSH_MSG_NEWCOMPRESS [RFC8308]
9-19 Unassigned (Transport layer generic)
20 SSH_MSG_KEXINIT [RFC4253]
21 SSH_MSG_NEWKEYS [RFC4253]
22-29 Unassigned (Algorithm negotiation)
30-49 Reserved (key exchange method specific) [RFC4251]
50 SSH_MSG_USERAUTH_REQUEST [RFC4252]
51 SSH_MSG_USERAUTH_FAILURE [RFC4252]
52 SSH_MSG_USERAUTH_SUCCESS [RFC4252]
53 SSH_MSG_USERAUTH_BANNER [RFC4252]
54-59 Unassigned (User authentication generic)
60 SSH_MSG_USERAUTH_INFO_REQUEST [RFC4256]
61 SSH_MSG_USERAUTH_INFO_RESPONSE [RFC4256]
62-79 Reserved (User authentication method specific) [RFC4251]
80 SSH_MSG_GLOBAL_REQUEST [RFC4254]
81 SSH_MSG_REQUEST_SUCCESS [RFC4254]
82 SSH_MSG_REQUEST_FAILURE [RFC4254]
83-89 Unassigned (Connection protocol generic)
90 SSH_MSG_CHANNEL_OPEN [RFC4254]
91 SSH_MSG_CHANNEL_OPEN_CONFIRMATION [RFC4254]
92 SSH_MSG_CHANNEL_OPEN_FAILURE [RFC4254]
93 SSH_MSG_CHANNEL_WINDOW_ADJUST [RFC4254]
94 SSH_MSG_CHANNEL_DATA [RFC4254]
95 SSH_MSG_CHANNEL_EXTENDED_DATA [RFC4254]
96 SSH_MSG_CHANNEL_EOF [RFC4254]
97 SSH_MSG_CHANNEL_CLOSE [RFC4254]
98 SSH_MSG_CHANNEL_REQUEST [RFC4254]
99 SSH_MSG_CHANNEL_SUCCESS [RFC4254]
100 SSH_MSG_CHANNEL_FAILURE [RFC4254]
101-127 Unassigned (Channel related messages)
128-191 Reserved (for client protocols)
192-255 Reserved for Private Use (local extensions)

Disconnection Messages Reason Codes and Descriptions

Expert(s)
Peter Yee, Markus Stenberg
Reference
[RFC4250][RFC9519]
Note
SSH_MSG_DISCONNECT 'description' and 'reason code' values
    
Available Formats

CSV
Range Registration Procedures
0x00000001-0xFDFFFFFF Expert Review
0xFE000000-0xFFFFFFFF Reserved for Private Use
Reason Code Symbolic Name Reference
0x00000000 Reserved
0x00000001 SSH_DISCONNECT_HOST_NOT_ALLOWED_TO_CONNECT [RFC4253]
0x00000002 SSH_DISCONNECT_PROTOCOL_ERROR [RFC4253]
0x00000003 SSH_DISCONNECT_KEY_EXCHANGE_FAILED [RFC4253]
0x00000004 SSH_DISCONNECT_RESERVED [RFC4253]
0x00000005 SSH_DISCONNECT_MAC_ERROR [RFC4253]
0x00000006 SSH_DISCONNECT_COMPRESSION_ERROR [RFC4253]
0x00000007 SSH_DISCONNECT_SERVICE_NOT_AVAILABLE [RFC4253]
0x00000008 SSH_DISCONNECT_PROTOCOL_VERSION_NOT_SUPPORTED [RFC4253]
0x00000009 SSH_DISCONNECT_HOST_KEY_NOT_VERIFIABLE [RFC4253]
0x0000000A SSH_DISCONNECT_CONNECTION_LOST [RFC4253]
0x0000000B SSH_DISCONNECT_BY_APPLICATION [RFC4253]
0x0000000C SSH_DISCONNECT_TOO_MANY_CONNECTIONS [RFC4253]
0x0000000D SSH_DISCONNECT_AUTH_CANCELLED_BY_USER [RFC4253]
0x0000000E SSH_DISCONNECT_NO_MORE_AUTH_METHODS_AVAILABLE [RFC4253]
0x0000000F SSH_DISCONNECT_ILLEGAL_USER_NAME [RFC4253]
0x00000010-0xFDFFFFFF Unassigned
0xFE000000-0xFFFFFFFF Reserved for Private Use

Channel Connection Failure Reason Codes and Descriptions

Expert(s)
Peter Yee, Markus Stenberg
Reference
[RFC4250][RFC9519]
Note
'reason code' values and 'description' values
    
Available Formats

CSV
Range Registration Procedures
0x00000001-0xFDFFFFFF Expert Review
0xFE000000-0xFFFFFFFF Reserved for Private Use
Reason Code Symbolic Name Reference
0x00000000 Reserved
0x00000001 SSH_OPEN_ADMINISTRATIVELY_PROHIBITED [RFC4254]
0x00000002 SSH_OPEN_CONNECT_FAILED [RFC4254]
0x00000003 SSH_OPEN_UNKNOWN_CHANNEL_TYPE [RFC4254]
0x00000004 SSH_OPEN_RESOURCE_SHORTAGE [RFC4254]
0x00000005-0xFDFFFFFF Unassigned
0xFE000000-0xFFFFFFFF Reserved for Private Use

Extended Channel Data Transfer data_type_code and Data

Expert(s)
Peter Yee, Markus Stenberg
Reference
[RFC4250][RFC9519]
Note
'data_type_code' values and 'data' values
    
Available Formats

CSV
Range Registration Procedures
0x00000001-0xFDFFFFFF Expert Review
0xFE000000-0xFFFFFFFF Reserved for Private Use
data_type_code Symbolic Name Reference
0x00000000 Reserved
0x00000001 SSH_EXTENDED_DATA_STDERR [RFC4254]
0x00000002-0xFDFFFFFF Unassigned
0xFE000000-0xFFFFFFFF Reserved for Private Use

Pseudo-Terminal Encoded Terminal Modes

Registration Procedure(s)
Expert Review
Expert(s)
Peter Yee, Markus Stenberg
Reference
[RFC4250][RFC9519]
Note
opcode and argument values which make up the "encoded terminal modes" values
    
Available Formats

CSV
Opcode Argument Description Reference Note
0 TTY_OP_END Indicates end of options. [RFC4250]
1 VINTR Interrupt character; 255 if none. Similarly for the other characters. Not all of these characters are supported on all systems. [RFC4254] Section 8
2 VQUIT The quit character (sends SIGQUIT signal on POSIX systems). [RFC4254] Section 8
3 VERASE Erase the character to left of the cursor. [RFC4254] Section 8
4 VKILL Kill the current input line. [RFC4254] Section 8
5 VEOF End-of-file character (sends EOF from the terminal). [RFC4254] Section 8
6 VEOL End-of-line character in addition to carriage return and/or linefeed. [RFC4254] Section 8
7 VEOL2 Additional end-of-line character. [RFC4254] Section 8
8 VSTART Continues paused output (normally control-Q). [RFC4254] Section 8
9 VSTOP Pauses output (normally control-S). [RFC4254] Section 8
10 VSUSP Suspends the current program. [RFC4254] Section 8
11 VDSUSP Another suspend character. [RFC4254] Section 8
12 VREPRINT Reprints the current input line. [RFC4254] Section 8
13 VWERASE Erases a word left of cursor. [RFC4254] Section 8
14 VLNEXT Enter the next character typed literally, even if it is a special character [RFC4254] Section 8
15 VFLUSH Character to flush output. [RFC4254] Section 8
16 VSWTCH Switch to a different shell layer. [RFC4254] Section 8
17 VSTATUS Prints system status line (load, command, pid, etc). [RFC4254] Section 8
18 VDISCARD Toggles the flushing of terminal output. [RFC4254] Section 8
19-29 Unassigned
30 IGNPAR The ignore parity flag. The parameter SHOULD be 0 if this flag is FALSE, and 1 if it is TRUE. [RFC4254] Section 8
31 PARMRK Mark parity and framing errors. [RFC4254] Section 8
32 INPCK Enable checking of parity errors. [RFC4254] Section 8
33 ISTRIP Strip 8th bit off characters. [RFC4254] Section 8
34 INLCR Map NL into CR on input. [RFC4254] Section 8
35 IGNCR Ignore CR on input. [RFC4254] Section 8
36 ICRNL Map CR to NL on input. [RFC4254] Section 8
37 IUCLC Translate uppercase characters to lowercase. [RFC4254] Section 8
38 IXON Enable output flow control. [RFC4254] Section 8
39 IXANY Any char will restart after stop. [RFC4254] Section 8
40 IXOFF Enable input flow control. [RFC4254] Section 8
41 IMAXBEL Ring bell on input queue full. [RFC4254] Section 8
42 IUTF8 Terminal input and output is assumed to be encoded in UTF-8. [RFC8160]
43-49 Unassigned
50 ISIG Enable signals INTR, QUIT, [D]SUSP. [RFC4254] Section 8
51 ICANON Canonicalize input lines. [RFC4254] Section 8
52 XCASE Enable input and output of uppercase characters by preceding their lowercase equivalents with "\". [RFC4254] Section 8
53 ECHO Enable echoing. [RFC4254] Section 8
54 ECHOE Visually erase chars. [RFC4254] Section 8
55 ECHOK Kill character discards current line. [RFC4254] Section 8
56 ECHONL Echo NL even if ECHO is off. [RFC4254] Section 8
57 NOFLSH Don't flush after interrupt. [RFC4254] Section 8
58 TOSTOP Stop background jobs from output. [RFC4254] Section 8
59 IEXTEN Enable extensions. [RFC4254] Section 8
60 ECHOCTL Echo control characters as ^(Char). [RFC4254] Section 8
61 ECHOKE Visual erase for line kill. [RFC4254] Section 8
62 PENDIN Retype pending input. [RFC4254] Section 8
63-69 Unassigned
70 OPOST Enable output processing. [RFC4254] Section 8
71 OLCUC Convert lowercase to uppercase. [RFC4254] Section 8
72 ONLCR Map NL to CR-NL. [RFC4254] Section 8
73 OCRNL Translate carriage return to newline (output). [RFC4254] Section 8
74 ONOCR Translate newline to carriage return-newline (output). [RFC4254] Section 8
75 ONLRET Newline performs a carriage return (output). [RFC4254] Section 8
76-89 Unassigned
90 CS7 7 bit mode. [RFC4254] Section 8
91 CS8 8 bit mode. [RFC4254] Section 8
92 PARENB Parity enable. [RFC4254] Section 8
93 PARODD Odd parity, else even. [RFC4254] Section 8
94-127 Unassigned
128 TTY_OP_ISPEED Specifies the input baud rate in bits per second. [RFC4254] Section 8
129 TTY_OP_OSPEED Specifies the output baud rate in bits per second. [RFC4254] Section 8
130-255 Unassigned

Service Names

Registration Procedure(s)
Expert Review
Expert(s)
Peter Yee, Markus Stenberg
Reference
[RFC4250][RFC9519]
Available Formats

CSV
Service Name Reference
ssh-userauth [RFC4252]
ssh-connection [RFC4254]

Authentication Method Names

Registration Procedure(s)
Expert Review
Expert(s)
Peter Yee, Markus Stenberg
Reference
[RFC4250][RFC9519]
Available Formats

CSV
Method Name Reference Note
publickey [RFC4252] Section 7
password [RFC4252] Section 8
hostbased [RFC4252] Section 9
none [RFC4252] Section 5.2
keyboard-interactive [RFC4256]
gssapi-with-mic [RFC4462]
gssapi-keyex [RFC4462]
gssapi [RFC4462]
external-keyx [RFC4462]

Connection Protocol Channel Types

Registration Procedure(s)
Expert Review
Expert(s)
Peter Yee, Markus Stenberg
Reference
[RFC4250][RFC9519]
Available Formats

CSV
Channel Type Reference Note
session [RFC4254] Section 6.1
x11 [RFC4254] Section 6.3.2
forwarded-tcpip [RFC4254] Section 7.2
direct-tcpip [RFC4254] Section 7.2

Connection Protocol Global Request Names

Registration Procedure(s)
Expert Review
Expert(s)
Peter Yee, Markus Stenberg
Reference
[RFC4250][RFC9519]
Available Formats

CSV
Request Type Reference Note
tcpip-forward [RFC4254] Section 7.1
cancel-tcpip-forward [RFC4254] Section 7.1

Connection Protocol Channel Request Names

Registration Procedure(s)
Expert Review
Expert(s)
Peter Yee, Markus Stenberg
Reference
[RFC4250][RFC9519]
Available Formats

CSV
Request Type Reference Note
pty-req [RFC4254] Section 6.2
x11-req [RFC4254] Section 6.3.1
env [RFC4254] Section 6.4
shell [RFC4254] Section 6.5
exec [RFC4254] Section 6.5
subsystem [RFC4254] Section 6.5
window-change [RFC4254] Section 6.7
xon-xoff [RFC4254] Section 6.8
signal [RFC4254] Section 6.9
exit-status [RFC4254] Section 6.10
exit-signal [RFC4254] Section 6.10
break [RFC4335]

Signal Names

Registration Procedure(s)
Expert Review
Expert(s)
Peter Yee, Markus Stenberg
Reference
[RFC4250][RFC9519]
Available Formats

CSV
Signal Reference
ABRT [RFC4254]
ALRM [RFC4254]
FPE [RFC4254]
HUP [RFC4254]
ILL [RFC4254]
INT [RFC4254]
KILL [RFC4254]
PIPE [RFC4254]
QUIT [RFC4254]
SEGV [RFC4254]
TERM [RFC4254]
USR1 [RFC4254]
USR2 [RFC4254]

Connection Protocol Subsystem Names

Registration Procedure(s)
Expert Review
Expert(s)
Peter Yee, Markus Stenberg
Reference
[RFC4250][RFC9519]
Available Formats

CSV
Subsystem Name Reference
publickey [RFC4819]
snmp [RFC5592]
netconf [RFC6242]
rpki-rtr [RFC6810]

Key Exchange Method Names

Registration Procedure(s)
Expert Review
Expert(s)
Peter Yee, Markus Stenberg
Reference
[RFC4250][RFC9142][RFC9519]
Note
*All values beginning with the specified string and not containing "@".
    
Note
“OK to Implement” guidance entries for registrations that pre-date 
[RFC9142] are found in Table 12 in Section 4 of [RFC9142].
Available Formats

CSV
Method Name Reference Note OK to Implement
diffie-hellman-group-exchange-sha1 [RFC4419][RFC8270] Section 4.1 SHOULD NOT
diffie-hellman-group-exchange-sha256 [RFC4419][RFC8270] Section 4.2 MAY
diffie-hellman-group1-sha1 [RFC4253] Section 8.1 SHOULD NOT
diffie-hellman-group14-sha1 [RFC4253] Section 8.2 MAY
diffie-hellman-group14-sha256 [RFC8268] MUST
diffie-hellman-group15-sha512 [RFC8268] MAY
diffie-hellman-group16-sha512 [RFC8268] SHOULD
diffie-hellman-group17-sha512 [RFC8268] MAY
diffie-hellman-group18-sha512 [RFC8268] MAY
ecdh-sha2-* [RFC5656] MAY
ecmqv-sha2 [RFC5656] MAY
gss-group1-sha1-* [RFC4462][RFC8732] SHOULD NOT
gss-group14-sha1-* [RFC4462][RFC8732] SHOULD NOT
gss-gex-sha1-* [RFC4462][RFC8732] SHOULD NOT
gss- [RFC4462] Section 2.6 reserved
rsa1024-sha1 [RFC4432] MUST NOT
rsa2048-sha256 [RFC4432] MAY
ext-info-s [RFC8308] Section 2 SHOULD
ext-info-c [RFC8308] Section 2 SHOULD
gss-group14-sha256-* [RFC8732] SHOULD
gss-group15-sha512-* [RFC8732] MAY
gss-group16-sha512-* [RFC8732] MAY
gss-group17-sha512-* [RFC8732] MAY
gss-group18-sha512-* [RFC8732] MAY
gss-nistp256-sha256-* [RFC8732] SHOULD
gss-nistp384-sha384-* [RFC8732] SHOULD
gss-nistp521-sha512-* [RFC8732] SHOULD
gss-curve25519-sha256-* [RFC8732] SHOULD
gss-curve448-sha512-* [RFC8732] MAY
curve25519-sha256 [RFC8731] SHOULD
curve448-sha512 [RFC8731] MAY
ecdh-sha2-nistp256 [RFC5656] SHOULD
ecdh-sha2-nistp384 [RFC5656] SHOULD
ecdh-sha2-nistp521 [RFC5656] SHOULD

Encryption Algorithm Names

Registration Procedure(s)
Expert Review
Expert(s)
Peter Yee, Markus Stenberg
Reference
[RFC4250][RFC9519]
Available Formats

CSV
Encryption Algorithm Name Reference Note
3des-cbc [RFC4253] Section 6.3
blowfish-cbc [RFC4253] Section 6.3
twofish256-cbc [RFC4253] Section 6.3
twofish-cbc [RFC4253] Section 6.3
twofish192-cbc [RFC4253] Section 6.3
twofish128-cbc [RFC4253] Section 6.3
aes256-cbc [RFC4253] Section 6.3
aes192-cbc [RFC4253] Section 6.3
aes128-cbc [RFC4253] Section 6.3
serpent256-cbc [RFC4253] Section 6.3
serpent192-cbc [RFC4253] Section 6.3
serpent128-cbc [RFC4253] Section 6.3
arcfour [RFC8758] HISTORIC
idea-cbc [RFC4253] Section 6.3
cast128-cbc [RFC4253] Section 6.3
none [RFC4253] Section 6.3
des-cbc [FIPS-46-3] HISTORIC, See page 4
arcfour128 [RFC8758] HISTORIC
arcfour256 [RFC8758] HISTORIC
aes128-ctr [RFC4344]
aes192-ctr [RFC4344]
aes256-ctr [RFC4344]
3des-ctr [RFC4344]
blowfish-ctr [RFC4344]
twofish128-ctr [RFC4344]
twofish192-ctr [RFC4344]
twofish256-ctr [RFC4344]
serpent128-ctr [RFC4344]
serpent192-ctr [RFC4344]
serpent256-ctr [RFC4344]
idea-ctr [RFC4344]
cast128-ctr [RFC4344]
AEAD_AES_128_GCM [RFC5647] Section 6.1
AEAD_AES_256_GCM [RFC5647] Section 6.2

MAC Algorithm Names

Registration Procedure(s)
Expert Review
Expert(s)
Peter Yee, Markus Stenberg
Reference
[RFC4250][RFC9519]
Available Formats

CSV
MAC Algorithm Name Reference Note
hmac-sha1 [RFC4253] Section 6.4
hmac-sha1-96 [RFC4253] Section 6.4
hmac-md5 [RFC4253] Section 6.4
hmac-md5-96 [RFC4253] Section 6.4
none [RFC4253] Section 6.4
AEAD_AES_128_GCM [RFC5647] Section 6.1
AEAD_AES_256_GCM [RFC5647] Section 6.2
hmac-sha2-256 [RFC6668] Section 2
hmac-sha2-512 [RFC6668] Section 2

Public Key Algorithm Names

Registration Procedure(s)
Expert Review
Expert(s)
Peter Yee, Markus Stenberg
Reference
[RFC4250][RFC9519]
Note
*All values beginning with the specified string and not containing "@".
    
Available Formats

CSV
Public Key Algorithm Name Public Key Format Reference Note
ssh-dss ssh-dss [RFC4253] Section 6.6
ssh-rsa ssh-rsa [RFC4253] Section 6.6
rsa-sha2-256 ssh-rsa [RFC8332] Section 3
rsa-sha2-512 ssh-rsa [RFC8332] Section 3
spki-sign-rsa spki-sign-rsa [RFC4253] Section 6.6
spki-sign-dss spki-sign-dss [RFC4253] Section 6.6
pgp-sign-rsa pgp-sign-rsa [RFC4253] Section 6.6
pgp-sign-dss pgp-sign-dss [RFC4253] Section 6.6
null null [RFC4462] Section 5
ecdsa-sha2-* ecdsa-sha2-* [RFC5656]
x509v3-ssh-dss x509v3-ssh-dss [RFC6187]
x509v3-ssh-rsa x509v3-ssh-rsa [RFC6187]
x509v3-rsa2048-sha256 x509v3-rsa2048-sha256 [RFC6187]
x509v3-ecdsa-sha2-* x509v3-ecdsa-sha2-* [RFC6187]
ssh-ed25519 ssh-ed25519 [RFC8709]
ssh-ed448 ssh-ed448 [RFC8709]

Compression Algorithm Names

Registration Procedure(s)
Expert Review
Expert(s)
Peter Yee, Markus Stenberg
Reference
[RFC4250][RFC9519]
Available Formats

CSV
Compression Algorithm Name Reference Note
none [RFC4253] Section 6.2
zlib [RFC4253] Section 6.2

SSH Public-Key File Header Tags

Registration Procedure(s)
Expert Review
Expert(s)
Peter Yee, Markus Stenberg
Reference
[RFC4716][RFC9519]
Note
Tags beginning with x- Reserved for Private Use
    
Available Formats

CSV
Header Tag Reference Note
subject [RFC4716] Section 3.3.1
comment [RFC4716] Section 3.3.2

Publickey Subsystem Request Names

Registration Procedure(s)
Expert Review
Expert(s)
Peter Yee, Markus Stenberg
Reference
[RFC4819][RFC9519]
Available Formats

CSV
Request Name Reference
version [RFC4819]
add [RFC4819]
remove [RFC4819]
list [RFC4819]
listattributes [RFC4819]

Publickey Subsystem Response Names

Registration Procedure(s)
Expert Review
Expert(s)
Peter Yee, Markus Stenberg
Reference
[RFC4819][RFC9519]
Available Formats

CSV
Response Name Reference
version [RFC4819]
status [RFC4819]
publickey [RFC4819]
attribute [RFC4819]

Publickey Subsystem Attributes

Registration Procedure(s)
Expert Review
Expert(s)
Peter Yee, Markus Stenberg
Reference
[RFC4819][RFC9519]
Available Formats

CSV
Attribute Name Reference
comment [RFC4819]
comment-language [RFC4819]
command-override [RFC4819]
subsystem [RFC4819]
x11 [RFC4819]
shell [RFC4819]
exec [RFC4819]
agent [RFC4819]
env [RFC4819]
from [RFC4819]
port-forward [RFC4819]
reverse-forward [RFC4819]

Publickey Subsystem Status Codes

Reference
[RFC4819]
Available Formats

CSV
Range Registration Procedures
0-191 Standards Action
192-255 Reserved for Private Use
Value Status Code Reference
0 SSH_PUBLICKEY_SUCCESS [RFC4819]
1 SSH_PUBLICKEY_ACCESS_DENIED [RFC4819]
2 SSH_PUBLICKEY_STORAGE_EXCEEDED [RFC4819]
3 SSH_PUBLICKEY_VERSION_NOT_SUPPORTED [RFC4819]
4 SSH_PUBLICKEY_KEY_NOT_FOUND [RFC4819]
5 SSH_PUBLICKEY_KEY_NOT_SUPPORTED [RFC4819]
6 SSH_PUBLICKEY_KEY_ALREADY_PRESENT [RFC4819]
7 SSH_PUBLICKEY_GENERAL_FAILURE [RFC4819]
8 SSH_PUBLICKEY_REQUEST_NOT_SUPPORTED [RFC4819]
9 SSH_PUBLICKEY_ATTRIBUTE_NOT_SUPPORTED [RFC4819]
10-191 Standards Action
192-255 Reserved

Extension Names

Registration Procedure(s)
Expert Review
Expert(s)
Peter Yee, Markus Stenberg
Reference
[RFC8308][RFC9519]
Note
Names in the Extension Names table MUST follow the Conventions for 
Names defined in [RFC4250], Section 4.6.1.
    
Available Formats

CSV
Extension Name Reference Note
server-sig-algs [RFC8308] Section 3.1
delay-compression [RFC8308] Section 3.2
no-flow-control [RFC8308] Section 3.3
elevation [RFC8308] Section 3.4