Visudo utility contains build-in capabilities to detect any error while editing this file. Afterwards, save the file by pressing :wq! Another method that can be used in order to allow a regular account with root powers, would be to add the regular user to system group called wheel and uncomment the wheel group from sudoers file by removing the sign at the beginning of the line.
The process of adding a new user is pretty straightforward. Just run adduser command and follow the interactive prompt in order to finalize the process. In order to modify the personal information of a user account, run the chpass command against a username and update the file.
Save the file opened with vi editor by pressing :wq! To change an account default shell, first list all present shells in your system and then execute chsh command as illustrated below.
First run ifconfig -a command to display a list of all NICs and identify the name of the interface you want to edit. Services can be managed in FreeBSD via service command. To list all system-wide enabled services issue the following command.
To enable or disable a FreeBSD daemon during boot initialization process, use sysrc command. To disable a service system-wide, append the NO flag for the disabled daemon as presented below. The daemons flags are case insensitive. Is worth mentioning that some services on FreeBSD require special attention. For example, if you want to only disable Syslog daemon network socket, issue the following command. You can combine the two flags to display all network sockets as illustrated in the below screenshot.
But of course if there is something more simple And the question why my command does not work remains In that case, you are over-complicating things. I have sshd running on Windows and it works but I don't use it from ages, the service is disabled.
Read cygwin documentation on cygwin site, if I remember I followed the instructions there to install it. FreeBSD has nothing to do with your problem, ssh works as is. Try to reinstall cygwin and follow the instructions, if I'm right a sshd user must be created on windows in order to make it works. This user is used internally by cygwin, it will not be the user you specify to login to the system. Not correct: I want the opposite way. It was not a password problem but an uppercase problem in the Windows user name; It is "gabriel" on the FreeBSD side and "Gabriel" on the Windows side.
I will now consider the passwordless logins and proceed to implement my project. For Phoenix, I do not think my goal is as difficult as the one he is thinking of, because I have to backup computers at hours when they do not work. There are a few problems with "always working" programs, for instance Outlook, but there are turnarounds.
Thank you for everybody's help Gabier. You must log in or register to reply here. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
By continuing to use this site, you are consenting to our use of cookies. This is called "insecure mode" because immutable file flags may be turned off and all devices may be read from or written to. The security level will remain at -1 unless it is altered through sysctl or by a setting in the startup scripts. See security 7 and init 8 for more information on these settings and the available security levels. Increasing the securelevel can break Xorg and cause other issues. Be prepared to do some debugging.
The net. The default behavior is to return an RST to show a port is closed. Changing the default provides some level of protection against ports scans, which are used to determine which applications are running on a system. Set net. Refer to blackhole 4 for more information about these settings. Since these packets are not required, set net. Source routing is a method for detecting and accessing non-routable addresses on the internal network.
This should be disabled as non-routable addresses are normally not routable on purpose. To disable this feature, set net. When a machine on the network needs to send messages to all hosts on a subnet, an ICMP echo request message is sent to the broadcast address. However, there is no reason for an external host to perform such an action.
To reject all external broadcast requests, set net. Some additional settings are documented in security 7. Since a password is only used once in OPIE, a discovered password is of little use to an attacker. OPIE uses three different types of passwords. The second is the one-time password which is generated by opiekey.
The third type of password is the "secret password" which is used to generate one-time passwords. There are two other pieces of data that are important to OPIE. One is the "seed" or "key", consisting of two letters and five digits. The other is the "iteration count", a number between 1 and OPIE creates the one-time password by concatenating the seed and the secret password, applying the MD5 hash as many times as specified by the iteration count, and turning the result into six short English words which represent the one-time password.
The authentication system keeps track of the last one-time password used, and the user is authenticated if the hash of the user-provided password is equal to the previous password. Since a one-way hash is used, it is impossible to generate future one-time passwords if a successfully used password is captured.
The iteration count is decremented after each successful login to keep the user and the login program in sync. When the iteration count gets down to 1 , OPIE must be reinitialized.
There are a few programs involved in this process. A one-time password, or a consecutive list of one-time passwords, is generated by passing an iteration count, a seed, and a secret password to opiekey 1. In addition to initializing OPIE, opiepasswd 1 is used to change passwords, iteration counts, or seeds. This section describes four different sorts of operations.
The first is how to set up one-time-passwords for the first time over a secure connection. The second is how to use opiepasswd over an insecure connection. The third is how to log in over an insecure connection. The fourth is how to generate a number of keys which can be written down or printed out to use at insecure locations. When prompted, enter the secret password which will be used to generate the one-time login keys.
It must be between 10 and characters long. Remember this password. The ID line lists the login name unfurl , default iteration count , and default seed to When logging in, the system will remember these parameters and display them, meaning that they do not have to be memorized. The last line lists the generated one-time password which corresponds to those parameters and the secret password.
At the next login, use this one-time password. To initialize or change the secret password on an insecure system, a secure connection is needed to some place where opiekey can be run. This might be a shell prompt on a trusted machine.
An iteration count is needed, where is probably a good value, and the seed can either be specified or the randomly-generated one used. On the insecure connection, the machine being initialized, use opiepasswd 1 :.
To accept the default seed, press Return. Before entering an access password, move over to the secure connection and give it the same parameters:. Switch back over to the insecure connection, and copy the generated one-time password over to the relevant program. The OPIE prompts provides a useful feature.
If Return is pressed at the password prompt, the prompt will turn echo on and display what is typed. This can be useful when attempting to type in a password by hand from a printout. At this point, generate the one-time password to answer this login prompt. This must be done on a trusted system where it is safe to run opiekey 1.
This command needs the iteration count and the seed as command line options. Use cut-and-paste from the login prompt on the machine being logged in to. Sometimes there is no access to a trusted machine or secure connection. In this case, it is possible to use opiekey 1 to generate a number of one-time passwords beforehand. For example:. The -n 5 requests five keys in sequence, and 30 specifies what the last iteration number should be.
Note that these are printed out in reverse order of use. The really paranoid might want to write the results down by hand; otherwise, print the list. Each line shows both the iteration count and the one-time password.
Scratch off the passwords as they are used. Refer to opieaccess 5 for more information on this file and which security considerations to be aware of when using it. If no rules in opieaccess are matched, the default is to deny non-OPIE logins. It can be configured to provide logging support, return messages, and connection restrictions for the server daemons under the control of inetd.
Refer to tcpd 8 for more information about TCP Wrapper and its features. TCP Wrapper should not be considered a replacement for a properly configured firewall. Instead, TCP Wrapper should be used in conjunction with a firewall and other security enhancements in order to provide another layer of protection in the implementation of a security policy. Unlike other implementations of TCP Wrapper, the use of hosts. The default configuration in FreeBSD is to allow all connections to the daemons started with inetd.
Basic configuration usually takes the form of daemon : address : action , where daemon is the daemon which inetd started, address is a valid hostname, IP address, or an IPv6 address enclosed in brackets [ ] , and action is either allow or deny. TCP Wrapper uses a first rule match semantic, meaning that the configuration file is scanned from the beginning for a matching rule.
When a match is found, the rule is applied and the search process stops. TCP Wrapper provides advanced options to allow more control over the way connections are handled. In some cases, it may be appropriate to return a comment to certain hosts or daemon connections. In other cases, a log entry should be recorded or an email sent to the administrator.
Other situations may require the use of a service for local connections only. This is all possible through the use of configuration options known as wildcards, expansion characters, and external command execution. Suppose that a situation occurs where a connection should be denied yet a reason should be sent to the host who attempted to establish that connection.
That action is possible with twist. When a connection attempt is made, twist executes a shell command or script. An example exists in hosts. In this example, the message "You are not allowed to use daemon name from hostname. This is useful for sending a reply back to the connection initiator right after the established connection is dropped. Any message returned must be wrapped in quote " characters. It may be possible to launch a denial of service attack on the server if an attacker floods these daemons with connection requests.
Another possibility is to use spawn. Like twist , spawn implicitly denies the connection and may be used to run external shell commands or scripts. Unlike twist , spawn will not send a reply back to the host who established the connection. For example, consider the following configuration:. In this example, all connection requests to Sendmail which have an IP address that varies from its hostname will be denied:. When adding new configuration lines, make sure that any unneeded entries for that daemon are commented out in hosts.
Kerberos is a network authentication protocol which was originally created by the Massachusetts Institute of Technology MIT as a way to securely provide authentication across a potentially hostile network.
The Kerberos protocol uses strong cryptography so that both a client and server can prove their identity without sending any unencrypted secrets over the network.
Kerberos can be described as an identity-verifying proxy system and as a trusted third-party authentication system. After a user authenticates with Kerberos, their communications can be encrypted to assure privacy and data integrity.
The only function of Kerberos is to provide the secure authentication of users and servers on the network. It does not provide authorization or auditing functions.
It is recommended that Kerberos be used with other security methods which provide authorization and audit services. The current version of the protocol is version 5, described in RFC Several free implementations of this protocol are available, covering a wide range of operating systems.
MIT continues to develop their Kerberos package. It is commonly used in the US as a cryptography product, and has historically been subject to US export regulations. The Heimdal Kerberos implementation was explicitly developed outside of the US to avoid export regulations. In Kerberos users and services are identified as "principals" which are contained within an administrative grouping, called a "realm". Use real domain names when setting up Kerberos, even if it will run internally.
This avoids DNS problems and assures inter-operation with other Kerberos realms. The Key Distribution Center KDC is the centralized authentication service that Kerberos provides, the "trusted third party" of the system.
It is the computer that issues Kerberos tickets, which are used for clients to authenticate to servers. As the KDC is considered trusted by all other computers in the Kerberos realm, it has heightened security concerns.
Direct access to the KDC should be limited. While running a KDC requires few computing resources, a dedicated machine acting only as a KDC is recommended for security reasons. In this example, the KDC will use the fully-qualified hostname kerberos.
For large organizations that have their own DNS servers, the above example could be trimmed to:. Next, create the Kerberos database which contains the keys of all principals users and hosts encrypted with a master password.
To create the master key, run kstash and enter a password:. Once the master key has been created, the database should be initialized. The Kerberos administrative tool kadmin 8 can be used on the KDC in a mode that operates directly on the database, without using the kadmind 8 network service, as kadmin -l.
This resolves the chicken-and-egg problem of trying to connect to the database before it is created. Lastly, while still in kadmin , create the first principal using add. Stick to the default options for the principal for now, as these can be changed later with modify.
While there will not be any kerberized daemons running at this point, it is possible to confirm that the KDC is functioning by obtaining a ticket for the principal that was just created:.
The version from the KDC can be used as-is, or it can be regenerated on the new system. This is the main part of "Kerberizing" a service - it corresponds to generating a secret shared between the service and the KDC. The secret is a cryptographic key, stored in a "keytab". It must be transmitted to the server in a secure fashion, as the security of the server can be broken if the key is made public.
It is very important that the keytab is transmitted to the server in a secure fashion: if the key is known by some other party, that party can impersonate any user to the server!
Using kadmin on the server directly is convenient, because the entry for the host principal in the KDC database is also created using kadmin.
Of course, kadmin is a kerberized service; a Kerberos ticket is needed to authenticate to the network service, but to ensure that the user running kadmin is actually present and their session has not been hijacked , kadmin will prompt for the password to get a fresh ticket.
See the section titled "Remote administration" in info heimdal for details on designing access control lists. Instead of enabling remote kadmin access, the administrator could securely connect to the KDC via the local console or ssh 1 , and perform administration locally using kadmin -l.
The keytab can then be securely copied to the server using scp 1 or a removable media. At this point, the server can read encrypted messages from the KDC using its shared key, stored in krb5. It is now ready for the Kerberos-using services to be enabled. After making this change, sshd 8 must be restarted for the new configuration to take effect: service sshd restart. Copy the file in place securely or re-enter it as needed.
Test the client by using kinit , klist , and kdestroy from the client to obtain, show, and then delete a ticket for an existing principal. Kerberos applications should also be able to connect to Kerberos enabled servers.
If that does not work but obtaining a ticket does, the problem is likely with the server and not with the client or the KDC. When testing a Kerberized application, try using a packet sniffer such as tcpdump to confirm that no sensitive information is sent in the clear. Various Kerberos client applications are available.
Users within a realm typically have their Kerberos principal mapped to a local user account. Occasionally, one needs to grant access to a local user account to someone who does not have a matching Kerberos principal. ORG may need access to the local user account webdevelopers. Other principals may also need access to that local account. For example, if the following. Refer to ksu 1 for more information about. The major difference between the MIT and Heimdal implementations is that kadmin has a different, but equivalent, set of commands and uses a different protocol.
Client applications may also use slightly different command line options to accomplish the same tasks. If all the computers in the realm do not have synchronized time settings, authentication may fail. The error message for unresolvable hosts is not intuitive: Kerberos5 refuses authentication because Read req failed: Key table entry not found.
Some operating systems that act as clients to the KDC do not set the permissions for ksu to be setuid root. This means that ksu does not work. This is a permissions problem, not a KDC error. The principal can then use kinit -l to request a ticket with a longer lifetime. When running a packet sniffer on the KDC to aid in troubleshooting while running kinit from a workstation, the Ticket Granting Ticket TGT is sent immediately, even before the password is typed.
This is because the Kerberos server freely transmits a TGT to any unauthorized request. When a user types their password, it is not sent to the KDC, it is instead used to decrypt the TGT that kinit already obtained. If the decryption process results in a valid ticket with a valid time stamp, the user has valid Kerberos credentials. This second layer of encryption allows the Kerberos server to verify the authenticity of each TGT.
Host principals can have a longer ticket lifetime. If the user principal has a lifetime of a week but the host being connected to has a lifetime of nine hours, the user cache will have an expired host principal and the ticket cache will not work as expected.
When setting up krb5. The format used in krb5. Since Kerberos is an all or nothing approach, every service enabled on the network must either be modified to work with Kerberos or be otherwise secured against network attacks. This is to prevent user credentials from being stolen and re-used. An example is when Kerberos is enabled on all remote shells but the non-Kerberized POP3 mail server sends passwords in plain text. The KDC is a single point of failure. This can be done can be done remotely using a s ecure sh ell and a s ecure c o p y or by using remote desktop via the NoMachine software.
We believe remote desktop option is probably most convenient. If you had a department account last semester, you should still have a department account this semester.
For others students, accounts will be created by the second week of class; see your email for the initial password. Look for an email sent from cshelpdesk and, for most students, the week before classes started. This tool will not work unless your account was setup at some point to have its initial temporary password changed.
0コメント