• ProCurve Switch 2510G-24 configure connection https and telnet Hi, i've a switch HP, i want to change the browsing from http to https. Crypto key generate ssh rsa. Optionally, use the 'bits' option after rsa to specify how big of a key you want.
• Ssh-keygen defaults to RSA therefore there is no need to specify it with the -t option. It provides the best compatibility of all algorithms but requires the key size to be larger to provide sufficient security. Minimum key size is 1024 bits, default is 3072 (see ssh-keygen(1)) and maximum is 16384. If you wish to generate a stronger RSA key pair (e.g. To guard against cutting-edge.

1. Assign a local login (operator) and enable (manager) password.

   At a minimum, HP recommends that you always assign at least a manager password to the switch. Otherwise, under some circumstances, anyone with Telnet, web, or serial port access could modify the switch configuration.

   To configure local passwords:

   You can configure both the operator and manager password with one command.

   Syntax:

   Configuring local passwords

2. Generate the switch public and private key pair.

   A public and private host key pair must be generated on the switch. The switch uses this key pair along with a dynamically generated session key pair to negotiate an encryption method and session with an SSH client trying to connect to the switch.

   The host key pair is stored in the switch flash memory, and only the public key in this pair is readable. The public key should be added to a 'known hosts' file (for example, $HOME/.ssh/known_hosts on UNIX systems) on the SSH clients which should have access to the switch. Some SSH client applications automatically add the switch public key to a 'known hosts' file. Other SSH applications require you to manually create a known hosts file and place the switch public key in the file. See the documentation for your SSH client application for more details.

   (The session key pair mentioned above is not visible on the switch. It is a temporary, internally generated pair used for a particular switch/client session, and then discarded.)

   NOTE: When generating a host key pair on the switch, the switch places the key pair in flash memory and not in the running-config file. Also, the switch maintains the key pair across reboots, including power cycles. Consider this key pair to be 'permanent' and avoid re-generating the key pair without a compelling reason. Otherwise, you must re-introduce the switch public key on all management stations you have set up for SSH access to the switch using the earlier pair. Removing (zeroing) the switch public/private key pair renders the switch unable to engage in SSH operation and automatically disables IP SSH on the switch. To verify whether SSH is enabled, execute show ip ssh. However, any active SSH sessions will continue to run, unless explicitly terminated with the CLI kill command. To generate or erase the switch public/private host key pair:

   Because the host key pair is stored in flash instead of the running-config file, it is not necessary to use write memory to save the key pair. Erasing the key pair automatically disables SSH.

   Syntax:

   crypto key generate <autorun-key[rsa] cert[rsa] <keysize> [ssh][dsa rsa]bits <keysize>>

   Installs authentication files for ssh or https server, or for autorun.

   Install RSA key for autorun. See 'Configuring Autorun on the Switch' in the Management and Configuration Guide for more information.

   Install RSA key for https certificate.

   Use your SSL enabled browser to access the switch using the switch IP address or DNS name (if allowed by your browser). See the documentation provided with the browser application for more information.

   Install host key for ssh server. Specify the key type as DSA or RSA.

   Specify the key size (in bits).

   zeroize <ssh cert autorun[rsa]>

   Erases the switch public/private key pair and disables SSH operation.

   Displays switch public key. Displays the version 1 and version 2 views of the key.

   See SSH client public-key authentication for information about public keys saved in a configuration file.

   Displays hashes of the switch public key in phonetic format, see “Displaying the Public Key:”.

   Displays fingerprints of the switch public key in hexadecimal format, see “Displaying the Public Key:”.

   Example:

   To generate and display a new key:

   Example of generating a public/private host key pair for the switch

   To compare the switch key to the key stored in your client's known-hosts file, note that the formatting and comments need not match.

   NOTE: 'Zeroizing' the switch key automatically disables SSH (sets ip ssh to no). Thus, if you zeroize the key and then generate a new key, you must also re-enable SSH with the ip ssh command before the switch can resume SSH operation.

   Configuring key lengths:

   The crypto key generate ssh command allows you to specify the type and length of the generated host key. The size of the host key is platform-dependent as different switches have different amounts of processing power. The size is represented by the <keysize> parameter and has the values shown in . The default value is used if keysize is not specified.

   RSA/DSA values for various HP networking switches

   Platform	Maximum RSA Key Size (in bits)	DSA Key Size (in bits)
   5400/3500/6200/8200/2900	1024, 2048, 3072 Default: 2048	1024
   4200/2900/2810/2610/2510	1024, 2048 Default: 2048	1024
   5300/2800/3400/2600	896	512

3. Provide the switch public key to clients.

   When an SSH client contacts the switch for the first time, the client will challenge the connection unless you have already copied the key into the client's 'known host' file. Copying the switch key in this way reduces the chance that an unauthorized device can pose as the switch to learn your access passwords. The most secure way to acquire the switch public key for distribution to clients is to use a direct, serial connection between the switch and a management device (laptop, PC, or UNIX workstation), as described below.

   The public key generated by the switch consists of three parts, separated by one blank space each:

   A public key generated by the switch

   With a direct serial connection from a management station to the switch:

   1. Use a terminal application such as HyperTerminal to display the switch public key with the show crypto host public-key command, see Example of generating a public/private host key pair for the switch.

   2. Bring up the SSH client's 'known host' file in a text editor such as Notepad as straight ASCII text, and copy the switch public key into the file.

   3. Ensure that there are no changes or breaks in the text string. A public key must be an unbroken ASCII string. Line breaks are not allowed (changes in the line breaks will corrupt the Key.) For example, if you are using Windows® Notepad, ensure that Word Wrap (in the Edit menu) is disabled, and that the key text appears on a single line.

      Example of a correctly formatted public key

   4. Add any data required by your SSH client application. For example, before saving the key to an SSH client's 'known hosts' file you may have to insert the switch IP address:

      Example of a switch public key edited to include the switch’s IP address

      For more on this topic, see the documentation provided with your SSH client application.

   Displaying the Public Key:

   The switch provides three options for displaying its public key. This is helpful if you need to visually verify that the public key the switch is using for authenticating itself to a client matches the copy of this key in the client's 'known hosts' file:

   • Non-encoded ASCII numeric string:

     Requires a client ability to display the keys in the 'known hosts' file in the ASCII format. This method is tedious and error-prone due to the length of the keys. See Example of a correctly formatted public key.

   • Phonetic hash:

     Outputs the key as a relatively short series of alphabetic character groups. Requires a client ability to convert the key to this format.

   • Hexadecimal hash:

     Outputs the key as a relatively short series of hexadecimal numbers. Requires a parallel client ability.

   For example, on the switch, generate the phonetic and hexadecimal versions of the switch public key as follows:

   Visual phonetic and hexadecimal conversions of the switch public key

   The two commands shown in Visual phonetic and hexadecimal conversions of the switch public key convert the displayed format of the switch (host) public key for easier visual comparison of the switch public key to a copy of the key in a client's 'known host' file. The switch has only one RSA host key. The 'babble' and 'fingerprint' options produce two hashes for the key--one that corresponds to the challenge hash you will see if connecting with a v1 client, and the other corresponding to the hash you will see if connecting with a v2 client. These hashes do not correspond to different keys, but differ only because of the way v1 and v2 clients compute the hash of the same RSA key. The switch always uses an ASCII version of its public key, without babble or fingerprint conversion, for file storage and default display format.

4. Enable SSH on the switch and anticipate SSH client contact behavior.

   The ip ssh command enables or disables SSH on the switch, and modifies parameters the switch uses for transactions with clients. After you enable SSH, the switch can authenticate itself to SSH clients.

   NOTE: Before enabling SSH on the switch you must generate the switch public/private key pair. If not yet done, see Generate the switch public and private key pair. When configured for SSH, the switch uses its host public key to authenticate itself to SSH clients.For SSH clients to authenticate themselves to the switch, configure SSH on the switch for client public-key authentication at the login (operator) level. To enhance security also configure local, TACACS+, or RADIUS authentication at the enable (manager) level. See Step 5.

   SSH client contact behavior:

   At the first contact between the switch and an SSH client, if the switch public key has not been copied into the client, then the client's first connection to the switch will question the connection and, for security reasons, provide the option of accepting or refusing. If it is safe to assume that an unauthorized device is not using the switch IP address in an attempt to gain access to the client's data or network, the connection can be accepted. (As a more secure alternative, the client can be directly connected to the switch serial port to download the switch public key into the client.)

   NOTE:When an SSH client connects to the switch for the first time, it is possible for a 'man-in-the-middle' attack; that is, for an unauthorized device to pose undetected as the switch, and learn the usernames and passwords controlling access to the switch. This possibility can be removed by directly connecting the management station to the switch serial port, using a show command to display the switch public key, and copying the key from the display into a file. This requires a knowledge of where the client stores public keys, plus the knowledge of what key editing and file format might be required by the client application. However, if the first contact attempt between a client and the switch does not pose a security problem, this is unnecessary.

   Enabling SSH on the switch:

   1. Generate a public/private key pair if you have not already done so. See Generate the switch public and private key pair.

   2. Execute the ip ssh command.

   Disabling SSH on the switch:

   Perform either of the following:

   • Execute no ip ssh.

   • Zeroize the switch existing key pair, see “To generate or erase the switch public/private host key pair:” for more details.

     Syntax:

     Enables or disables SSH on the switch.

     [cipher <cipher-type>]

     Specify a cipher type to use for connection.

     Valid types are:

     • aes128-cbc

     • 3des-cbc

     • aes192-cbc

     • aes256-cbc

     • aes128-ctr

     • aes192-ctr

     • aes256-ctr

     Default: All cipher types are available.

     Use the no form of the command to disable a cipher type.

     Enable/disable secure file transfer capability. https://viocz.over-blog.com/2020/10/toyota-prius-family-pack-sims-3-download.html. SCP and SFTP secure file transfer will not function unless SSH is also enabled.

     [ip-version <4 6 4or6>]

     Select the IP mode to run in. The mode 'ip-version 4' only accepts connections from IPv4 clients. The mode 'ip-version 6' only accepts connections from IPv6 clients. The mode 'ip-version 4or6' accepts connections from both IPv4 and IPv6 clients.

     Default: ip-version 4 or 6

     Allows configuration of the set of MACs that can be selected. Valid types are:

     • hmac-md5

     • hmac-sha1

     • hmac-sha1-96

     • hmac-md5-96

     Default: All MAC types are available.

     Use the no form of the command to disable a MAC type.

     The TCP port number for SSH connections.

     Default: 22.

     Sets the maximum length of time (in seconds) allowed for initial protocol negotiation and authentication.

     Default: 120 seconds

     NOTE:HP recommends using the default TCP port number (22). However, you can use ip ssh port to specify any TCP port for SSH connections except those reserved for other purposes. Examples of reserved port numbers reserved IP ports are 23 (Telnet) and 80 (http). Some other reserved TCP ports on the switch are 49, 80, 1506, and 1513.

     Enabling IP SSH and displaying the SSH configuration

     CAUTION:Protect your private key file from access by anyone other than yourself. If someone can access your private key file, they can penetrate SSH security on the switch by appearing to be you. SSH does not protect the switch from unauthorized access via the WebAgent, Telnet, SNMP, or the serial port. While WebAgent and Telnet access can be restricted by the use of passwords local to the switch, if you are unsure of the security this provides, you may want to disable web-based and/or Telnet access (no web-management and no Telnet). If you need to increase SNMP security, use SNMP version 3 only. To increase the security of your web interface see the section on SSL. For an additional security measure, see the authorized IP managers feature in the Management and Configuration Guide for your switch. To protect against unauthorized access to the serial port (and the Clear button, which removes local password protection), keep physical access to the switch restricted to authorized personnel.

5. Configure the switch for SSH authentication.

   Note that all methods in this section result in authentication of the switch public key by an SSH client. However only Option B below results in the switch also authenticating the client's public key. Also, for a more detailed discussion of the topics in this section, see SSH client public-key authentication notes.

   NOTE:HP recommends that you always assign a manager-level (enable) password to the switch. Without this level of protection, any user with Telnet, web, or serial port access to the switch can change the switch configuration. If you configure only an operator password, entering the operator password through telnet, web, ssh or serial port access enables full manager privileges. See Assign a local login (operator) and enable (manager) password.

   Option A: Configuring SSH access for password-only SSH authentication:

   When configured with this option, the switch uses its public key to authenticate itself to a client, but uses only passwords for client authentication.

   Syntax:

   aaa authentication ssh login <local tacacs radius>[<local none>]

   Configures a password method for the primary and secondary login (operator) access. If you do not specify an optional secondary method, it defaults to none. If the primary method is local, the secondary method must be none.

   aaa authentication ssh enable <local tacacs radius>[<local none>]

   Configures a password method for the primary and secondary enable (manager) access. If you do not specify an optional secondary method, it defaults to none. If the primary method is local, the secondary method must be none.

   Option B: Configuring the switch for client Public-Key SSH authentication

   If configured with this option, the switch uses its public key to authenticate itself to a client, but the client must also provide a client public key for the switch to authenticate. This option requires the additional step of copying a client public-key file from a TFTP or SFTP server into the switch. This means that before you can use this option, you must:

   1. Create a key pair on an SSH client.

   2. Copy the client's public key into a public-key file (which can contain up to 10 client public keys.)

   3. Copy the public-key file into a TFTP or SFTP server accessible to the switch and download the file to the switch.

   For more on these topics, see SSH client public-key authentication notes.

   With steps a-c complete and SSH properly configured on the switch, if an SSH client contacts the switch, login authentication automatically occurs first, using the switch and client public keys. After the client gains login access, the switch controls client access to the manager level by requiring the passwords configured earlier by the aaa authentication ssh enable command.

   Syntax:

   Copies a public-key file into the switch.

   Configures the switch to authenticate a client public key at the login level with an optional secondary password method.

   Default: none

   Syntax:

   aaa authentication ssh enable <local tacacs radius> <local none>

   Configures a password method for the primary and secondary enable (manager) access. If you do not specify an optional secondary method, it defaults to none.

   If the primary access method is local, you can only specify none for a secondary access method.

   NOTE: The configuration of SSH clients' public keys is stored in flash memory on the switch. You also can save SSH client public-key configurations to a configuration file by entering the following commands: include-credentials write memory For more information about saving security credentials to a configuration file, see Saving security credentials in a config file.

   Example:

   Assume you have a client public-key file named Client-Keys.pub (on a TFTP server at 10.33.18.117) ready for downloading to the switch. For SSH access to the switch allow only clients having a private key that matches a public key found in Client-Keys.pub. For manager-level (enable) access for successful SSH clients use TACACS+ for primary password authentication and local for secondary password authentication, with a manager username of '1eader' and a password of 'm0ns00n'. To set up this operation, configure the switch in a manner similar to the following:

   Configuring for SSH access requiring a client public-key match and manager passwords

   SSH configuration and client public-key listing from figure shows how to check the results of the above commands.

   SSH configuration and client public-key listing from figure

6. Use an SSH client to access the switch.

   Test the SSH configuration on the switch to ensure that you have the level of SSH operation needed for the switch. If you have problems, see 'RADIUS-related problems' in the Management and Configuration Guide for your switch.

I'm learning Linux, and currently SSH. But there are details that I don't really understand. I've seen and understood how Diffie-Hellman key exchanges work from a mathematical point of view, but w. Jan 26, 2018  The ip ssh rsa keypair-name command enables an SSH connection using the Rivest, Shamir, and Adleman (RSA) keys that you have configured. Previously, SSH was linked to the first RSA keys that were generated (that is, SSH was enabled when the first RSA key pair was generated). This behavior still exists, but by using the ip ssh rsa keypair-name command, you can overcome this behavior. Secure Shell (SSH) may generate an additional RSA key pair if you generate a key pair on a router having no RSA keys. Router(config)# crypto key generate rsa general-keys The name for the keys will be: myrouter.example.com Choose the size of the key modulus in the range of 360 to 2048 for your General Purpose Keys. Choosing a key modulus.

This article or section needs expansion.

SSH keys can serve as a means of identifying yourself to an SSH server using public-key cryptography and challenge-response authentication. The major advantage of key-based authentication is that in contrast to password authentication it is not prone to brute-force attacks and you do not expose valid credentials, if the server has been compromised.[1]

Furthermore SSH key authentication can be more convenient than the more traditional password authentication. When used with a program known as an SSH agent, SSH keys can allow you to connect to a server, or multiple servers, without having to remember or enter your password for each system.

Key-based authentication is not without its drawbacks and may not be appropriate for all environments, but in many circumstances it can offer some strong advantages. A general understanding of how SSH keys work will help you decide how and when to use them to meet your needs.

This article assumes you already have a basic understanding of the Secure Shell protocol and have installed the openssh package.

• 2Generating an SSH key pair
  • 2.1Choosing the authentication key type
  • 2.2Choosing the key location and passphrase
• 3Copying the public key to the remote server
• 4SSH agents
  • 4.1ssh-agent
  • 4.3Keychain
  • 4.4x11-ssh-askpass
  • 4.5pam_ssh
• 5Troubleshooting

Background

SSH keys are always generated in pairs with one known as the private key and the other as the public key. The private key is known only to you and it should be safely guarded. By contrast, the public key can be shared freely with any SSH server to which you wish to connect.

If an SSH server has your public key on file and sees you requesting a connection, it uses your public key to construct and send you a challenge. This challenge is an encrypted message and it must be met with the appropriate response before the server will grant you access. What makes this coded message particularly secure is that it can only be understood by the private key holder. While the public key can be used to encrypt the message, it cannot be used to decrypt that very same message. Only you, the holder of the private key, will be able to correctly understand the challenge and produce the proper response.

This challenge-response phase happens behind the scenes and is invisible to the user. As long as you hold the private key, which is typically stored in the ~/.ssh/ directory, your SSH client should be able to reply with the appropriate response to the server.

A private key is a guarded secret and as such it is advisable to store it on disk in an encrypted form. When the encrypted private key is required, a passphrase must first be entered in order to decrypt it. While this might superficially appear as though you are providing a login password to the SSH server, the passphrase is only used to decrypt the private key on the local system. The passphrase is not transmitted over the network.

Generating an SSH key pair

An SSH key pair can be generated by running the ssh-keygen command, defaulting to 3072-bit RSA (and SHA256) which the ssh-keygen(1) man page says is 'generally considered sufficient' and should be compatible with virtually all clients and servers:

The randomart image was introduced in OpenSSH 5.1 as an easier means of visually identifying the key fingerprint.

You can also add an optional comment field to the public key with the -C switch, to more easily identify it in places such as ~/.ssh/known_hosts, ~/.ssh/authorized_keys and ssh-add -L output. For example:

will add a comment saying which user created the key on which machine and when.

Choosing the authentication key type

OpenSSH supports several signing algorithms (for authentication keys) which can be divided in two groups depending on the mathematical properties they exploit:

1. DSA and RSA, which rely on the practical difficulty of factoring the product of two large prime numbers,
2. ECDSA and Ed25519, which rely on the elliptic curve discrete logarithm problem. (example)

Elliptic curve cryptography (ECC) algorithms are a more recent addition to public key cryptosystems. One of their main advantages is their ability to provide the same level of security with smaller keys, which makes for less computationally intensive operations (i.e. faster key creation, encryption and decryption) and reduced storage and transmission requirements.

OpenSSH 7.0 deprecated and disabled support for DSA keys due to discovered vulnerabilities, therefore the choice of cryptosystem lies within RSA or one of the two types of ECC.

#RSA keys will give you the greatest portability, while #Ed25519 will give you the best security but requires recent versions of client & server[2]^{[dead link 2020-04-02 ⓘ]}. #ECDSA is likely more compatible than Ed25519 (though still less than RSA), but suspicions exist about its security (see below).

RSA

ssh-keygen defaults to RSA therefore there is no need to specify it with the -t option. It provides the best compatibility of all algorithms but requires the key size to be larger to provide sufficient security.

Minimum key size is 1024 bits, default is 3072 (see ssh-keygen(1)) and maximum is 16384.

If you wish to generate a stronger RSA key pair (e.g. to guard against cutting-edge or unknown attacks and more sophisticated attackers), simply specify the -b option with a higher bit value than the default:

Be aware though that there are diminishing returns in using longer keys.[3][4] The GnuPG FAQ reads: 'If you need more security than RSA-2048 offers, the way to go would be to switch to elliptical curve cryptography — not to continue using RSA'.[5]

On the other hand, the latest iteration of the NSA Fact Sheet Suite B Cryptography^{[dead link 2020-04-02 ⓘ]} suggests a minimum 3072-bit modulus for RSA while '[preparing] for the upcoming quantum resistant algorithm transition'.[6]

ECDSA

The Elliptic Curve Digital Signature Algorithm (ECDSA) was introduced as the preferred algorithm for authentication in OpenSSH 5.7. Some vendors also disable the required implementations due to potential patent issues.

There are two sorts of concerns with it:

1. Political concerns, the trustworthiness of NIST-produced curves being questioned after revelations that the NSA willingly inserts backdoors into softwares, hardware components and published standards were made; well-known cryptographers haveexpresseddoubts about how the NIST curves were designed, and voluntary tainting has already beenproved in the past.
2. Technical concerns, about the difficulty to properly implement the standard and the slowness and design flaws which reduce security in insufficiently precautious implementations.

Both of those concerns are best summarized in libssh curve25519 introduction. Although the political concerns are still subject to debate, there is a clear consensus that #Ed25519 is technically superior and should therefore be preferred.

Ed25519

Ed25519 was introduced in OpenSSH 6.5 of January 2014: 'Ed25519 is an elliptic curve signature scheme that offers better security than ECDSA and DSA and good performance'. Its main strengths are its speed, its constant-time run time (and resistance against side-channel attacks), and its lack of nebulous hard-coded constants.[7] See also this blog post by a Mozilla developer on how it works.

It is already implemented in many applications and libraries and is the default key exchange algorithm (which is different from key signature) in OpenSSH.

Ed25519 key pairs can be generated with:

There is no need to set the key size, as all Ed25519 keys are 256 bits.

Keep in mind that older SSH clients and servers may not support these keys.

Choosing the key location and passphrase

Upon issuing the ssh-keygen command, you will be prompted for the desired name and location of your private key. By default, keys are stored in the ~/.ssh/ directory and named according to the type of encryption used. You are advised to accept the default name and location in order for later code examples in this article to work properly.

When prompted for a passphrase, choose something that will be hard to guess if you have the security of your private key in mind. A longer, more random password will generally be stronger and harder to crack should it fall into the wrong hands.

It is also possible to create your private key without a passphrase. While this can be convenient, you need to be aware of the associated risks. Without a passphrase, your private key will be stored on disk in an unencrypted form. Anyone who gains access to your private key file will then be able to assume your identity on any SSH server to which you connect using key-based authentication. Furthermore, without a passphrase, you must also trust the root user, as he can bypass file permissions and will be able to access your unencrypted private key file at any time.

Changing the private key's passphrase without changing the key

If the originally chosen SSH key passphrase is undesirable or must be changed, one can use the ssh-keygen command to change the passphrase without changing the actual key. This can also be used to change the password encoding format to the new standard.

Managing multiple keys

It is possible — although controversial [8][9] — to use the same SSH key pair for multiple hosts.

On the other hand, it is rather easy to maintain distinct keys for multiple hosts by using the IdentityFile directive in your openSSH config file:

See ssh_config(5) for full description of these options.

Storing SSH keys on hardware tokens

SSH keys can also be stored on a security token like a smart card or a USB token. This has the advantage that the private key is stored securely on the token instead of being stored on disk. When using a security token the sensitive private key is also never present in the RAM of the PC; the cryptographic operations are performed on the token itself. A cryptographic token has the additional advantage that it is not bound to a single computer; it can easily be removed from the computer and carried around to be used on other computers.

Examples are hardware tokens are described in:

• YubiKey#Using a YubiKey with SSH, and

Copying the public key to the remote server

This article or section needs expansion.

Once you have generated a key pair, you will need to copy the public key to the remote server so that it will use SSH key authentication. The public key file shares the same name as the private key except that it is appended with a .pub extension. Note that the private key is not shared and remains on the local machine.

Simple method

If your key file is ~/.ssh/id_rsa.pub you can simply enter the following command.

If your username differs on remote machine, be sure to prepend the username followed by @ to the server name.

If your public key filename is anything other than the default of ~/.ssh/id_rsa.pub you will get an error stating /usr/bin/ssh-copy-id: ERROR: No identities found. In this case, you must explicitly provide the location of the public key.

If the ssh server is listening on a port other than default of 22, be sure to include it within the host argument.

Manual method

By default, for OpenSSH, the public key needs to be concatenated with ~/.ssh/authorized_keys. Begin by copying the public key to the remote server.

The above example copies the public key (id_ecdsa.pub) to your home directory on the remote server via scp. Do not forget to include the : at the end of the server address. Also note that the name of your public key may differ from the example given.

On the remote server, you will need to create the ~/.ssh directory if it does not yet exist and append your public key to the authorized_keys file.

The last two commands remove the public key file from the server and set the permissions on the authorized_keys file such that it is only readable and writable by you, the owner.

SSH agents

If your private key is encrypted with a passphrase, this passphrase must be entered every time you attempt to connect to an SSH server using public-key authentication. Each individual invocation of ssh or scp will need the passphrase in order to decrypt your private key before authentication can proceed.

An SSH agent is a program which caches your decrypted private keys and provides them to SSH client programs on your behalf. In this arrangement, you must only provide your passphrase once, when adding your private key to the agent's cache. This facility can be of great convenience when making frequent SSH connections.

An agent is typically configured to run automatically upon login and persist for the duration of your login session. A variety of agents, front-ends, and configurations exist to achieve this effect. This section provides an overview of a number of different solutions which can be adapted to meet your specific needs.

ssh-agent

ssh-agent is the default agent included with OpenSSH. It can be used directly or serve as the back-end to a few of the front-end solutions mentioned later in this section. When ssh-agent is run, it forks to background and prints necessary environment variables. E.g.

To make use of these variables, run the command through the eval command.

Once ssh-agent is running, you will need to add your private key to its cache:

If your private key is encrypted, ssh-add will prompt you to enter your passphrase. Once your private key has been successfully added to the agent you will be able to make SSH connections without having to enter your passphrase.

In order to start the agent automatically and make sure that only one ssh-agent process runs at a time, add the following to your ~/.bashrc:

This will run a ssh-agent process if there is not one already, and save the output thereof. If there is one running already, we retrieve the cached ssh-agent output and evaluate it which will set the necessary environment variables.

There also exist a number of front-ends to ssh-agent and alternative agents described later in this section which avoid this problem.

Start ssh-agent with systemd user

It is possible to use the systemd/User facilities to start the agent. Use this if you would like your ssh agent to run when you are logged in, regardless of whether x is running.

Add SSH_AUTH_SOCK DEFAULT='${XDG_RUNTIME_DIR}/ssh-agent.socket' to ~/.pam_environment. Then enable or start the service with the --user flag.

ssh-agent as a wrapper program

An alternative way to start ssh-agent (with, say, each X session) is described in this ssh-agent tutorial by UC Berkeley Labs. A basic use case is if you normally begin X with the startx command, you can instead prefix it with ssh-agent like so:

And so you do not even need to think about it you can put an alias in your .bash_aliases file or equivalent:

Doing it this way avoids the problem of having extraneous ssh-agent instances floating around between login sessions. Exactly one instance will live and die with the entire X session.

See the below notes on using x11-ssh-askpass with ssh-add for an idea on how to immediately add your key to the agent.

GnuPG Agent

The gpg-agent has OpenSSH agent emulation. See GnuPG#SSH agent for necessary configuration.

Keychain

Ssh Crypto Key Generate Rsa Number

Keychain is a program designed to help you easily manage your SSH keys with minimal user interaction. It is implemented as a shell script which drives both ssh-agent and ssh-add. A notable feature of Keychain is that it can maintain a single ssh-agent process across multiple login sessions. This means that you only need to enter your passphrase once each time your local machine is booted.

Installation

Install the keychain package.

Configuration

Add a line similar to the following to your shell configuration file, e.g. if using Bash:

In the above example,

• the --eval switch outputs lines to be evaluated by the opening eval command; this sets the necessary environments variables for SSH client to be able to find your agent.
• --quiet will limit output to warnings, errors, and user prompts.

Multiple keys can be specified on the command line, as shown in the example. By default keychain will look for key pairs in the ~/.ssh/ directory, but absolute path can be used for keys in non-standard location. You may also use the --confhost option to inform keychain to look in ~/.ssh/config for IdentityFile settings defined for particular hosts, and use these paths to locate keys.

See keychain --help or keychain(1) for details on setting keychain for other shells.

To test Keychain, simply open a new terminal emulator or log out and back in your session. It should prompt you for the passphrase of the specified private key(s) (if applicable), either using the program set in $SSH_ASKPASS or on the terminal.

Because Keychain reuses the same ssh-agent process on successive logins, you should not have to enter your passphrase the next time you log in or open a new terminal. You will only be prompted for your passphrase once each time the machine is rebooted.

Tips

• keychain expects public key files to exist in the same directory as their private counterparts, with a .pub extension. If the private key is a symlink, the public key can be found alongside the symlink or in the same directory as the symlink target (this capability requires the readlink command to be available on the system).

• to disable the graphical prompt and always enter your passphrase on the terminal, use the --nogui option. This allows to copy-paste long passphrases from a password manager for example.

• if you do not want to be immediately prompted for unlocking the keys but rather wait until they are needed, use the --noask option.

x11-ssh-askpass

The x11-ssh-askpass package provides a graphical dialog for entering your passhrase when running an X session. x11-ssh-askpass depends only on the libx11 and libxt libraries, and the appearance of x11-ssh-askpass is customizable. While it can be invoked by the ssh-add program, which will then load your decrypted keys into ssh-agent, the following instructions will, instead, configure x11-ssh-askpass to be invoked by the aforementioned Keychain script.

Install the keychain and x11-ssh-askpass packages.

Edit your ~/.xinitrc file to include the following lines, replacing the name and location of your private key if necessary. Be sure to place these commands before the line which invokes your window manager.

In the above example, the first line invokes keychain and passes the name and location of your private key. If this is not the first time keychain was invoked, the following two lines load the contents of $HOSTNAME-sh and $HOSTNAME-sh-gpg, if they exist. These files store the environment variables of the previous instance of keychain.

Calling x11-ssh-askpass with ssh-add

The ssh-add manual page specifies that, in addition to needing the DISPLAY variable defined, you also need SSH_ASKPASS set to the name of your askpass program (in this case x11-ssh-askpass). It bears keeping in mind that the default Arch Linux installation places the x11-ssh-askpass binary in /usr/lib/ssh/, which will not be in most people's PATH. This is a little annoying, not only when declaring the SSH_ASKPASS variable, but also when theming. You have to specify the full path everywhere. Both inconveniences can be solved simultaneously by symlinking:

This is assuming that ~/bin is in your PATH. So now in your .xinitrc, before calling your window manager, one just needs to export the SSH_ASKPASS environment variable:

/ubuntu-generate-public-key-from-private.html. and your X resources will contain something like:

Doing it this way works well with the above method on using ssh-agent as a wrapper program. You start X with ssh-agent startx and then add ssh-add to your window manager's list of start-up programs.

Theming

The appearance of the x11-ssh-askpass dialog can be customized by setting its associated X resources. Some examples are the .ad files at https://github.com/sigmavirus24/x11-ssh-askpass. See x11-ssh-askpass(1)^{[dead link 2019-05-05]} for full details.

Alternative passphrase dialogs

There are other passphrase dialog programs which can be used instead of x11-ssh-askpass. The following list provides some alternative solutions.

• ksshaskpass uses the KDE Wallet.
• openssh-askpass uses the Qt library.

pam_ssh

The pam_ssh project exists to provide a Pluggable Authentication Module (PAM) for SSH private keys. This module can provide single sign-on behavior for your SSH connections. On login, your SSH private key passphrase can be entered in place of, or in addition to, your traditional system password. Once you have been authenticated, the pam_ssh module spawns ssh-agent to store your decrypted private key for the duration of the session.

To enable single sign-on behavior at the tty login prompt, install the unofficial pam_ssh^AUR package.

Hp Procurve Crypto Key Generate Ssh Rsa

Create a symlink to your private key file and place it in ~/.ssh/login-keys.d/. Replace the id_rsa in the example below with the name of your own private key file.

Edit the /etc/pam.d/login configuration file to include the text highlighted in bold in the example below. The order in which these lines appear is significiant and can affect login behavior.

In the above example, login authentication initially proceeds as it normally would, with the user being prompted to enter his user password. The additional auth authentication rule added to the end of the authentication stack then instructs the pam_ssh module to try to decrypt any private keys found in the ~/.ssh/login-keys.d directory. The try_first_pass option is passed to the pam_ssh module, instructing it to first try to decrypt any SSH private keys using the previously entered user password. If the user's private key passphrase and user password are the same, this should succeed and the user will not be prompted to enter the same password twice. In the case where the user's private key passphrase user password differ, the pam_ssh module will prompt the user to enter the SSH passphrase after the user password has been entered. The optional control value ensures that users without an SSH private key are still able to log in. In this way, the use of pam_ssh will be transparent to users without an SSH private key.

If you use another means of logging in, such as an X11 display manager like SLiM or XDM and you would like it to provide similar functionality, you must edit its associated PAM configuration file in a similar fashion. Packages providing support for PAM typically place a default configuration file in the /etc/pam.d/ directory.

Further details on how to use pam_ssh and a list of its options can be found in the pam_ssh(8) man page.

Using a different password to unlock the SSH key

If you want to unlock the SSH keys or not depending on whether you use your key's passphrase or the (different!) login password, you can modify /etc/pam.d/system-auth to

For an explanation, see [10].

Known issues with pam_ssh

Work on the pam_ssh project is infrequent and the documentation provided is sparse. You should be aware of some of its limitations which are not mentioned in the package itself.

• Versions of pam_ssh prior to version 2.0 do not support SSH keys employing the newer option of ECDSA (elliptic curve) cryptography. If you are using earlier versions of pam_ssh you must use either RSA or DSA keys.

• The ssh-agent process spawned by pam_ssh does not persist between user logins. If you like to keep a GNU Screen session active between logins you may notice when reattaching to your screen session that it can no longer communicate with ssh-agent. This is because the GNU Screen environment and those of its children will still reference the instance of ssh-agent which existed when GNU Screen was invoked but was subsequently killed in a previous logout. The Keychain front-end avoids this problem by keeping the ssh-agent process alive between logins.

pam_exec-ssh

As an alternative to pam_ssh you can use pam_exec-ssh^AUR. It is a shell script that uses pam_exec. Help for configuration can be found upstream.

GNOME Keyring

If you use the GNOME desktop, the GNOME Keyring tool can be used as an SSH agent. See the GNOME Keyring article for further details.

Store SSH keys with Kwallet

Crypto Key Generate Rsa Ssh

For instructions on how to use kwallet to store your SSH keys, see KDE Wallet#Using the KDE Wallet to store ssh key passphrases.

KeePass2 with KeeAgent plugin

KeeAgent is a plugin for KeePass that allows SSH keys stored in a KeePass database to be used for SSH authentication by other programs.

• Supports both PuTTY and OpenSSH private key formats.
• Works with native SSH agent on Linux/Mac and with PuTTY on Windows.

See KeePass#Plugin Installation in KeePass or install the keepass-plugin-keeagent package.

This agent can be used directly, by matching KeeAgent socket: KeePass -> Tools -> Options -> KeeAgent -> Agent mode socket file -> %XDG_RUNTIME_DIR%/keeagent.socket-and environment variable:export SSH_AUTH_SOCK='$XDG_RUNTIME_DIR'/keeagent.socket'.

KeePassXC

The KeePassXC fork of KeePass supports being used as an SSH agent by default. It is also compatible with KeeAgent's database format.

Troubleshooting

Key ignored by the server

• If it appears that the SSH server is ignoring your keys, ensure that you have the proper permissions set on all relevant files.

For the local machine:

For the remote machine:

• If that does not solve the problem you may try temporarily setting StrictModes to no in /etc/ssh/sshd_config. If authentication with StrictModes off is successful, it is likely an issue with file permissions persists.

• Make sure keys in ~/.ssh/authorized_keys are entered correctly and only use one single line.
• Make sure the remote machine supports the type of keys you are using: some servers do not support ECDSA keys, try using RSA or DSA keys instead, see #Generating an SSH key pair.
• You may want to use debug mode and monitor the output while connecting:

Crypto Key Generate Ssh Rsa Bits 2048

See also

• OpenSSH key management: Part 1, Part 2, Part 3

Ssh Crypto Key Generate Rsa Command