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diff --git a/docs/textdocs/ENCRYPTION.txt b/docs/textdocs/ENCRYPTION.txt deleted file mode 100644 index 046b473e9a..0000000000 --- a/docs/textdocs/ENCRYPTION.txt +++ /dev/null @@ -1,333 +0,0 @@ - LanManager / Samba Password Encryption. - --------------------------------------- - -With the development of LanManager compatible password encryption for -Samba, it is now able to validate user connections in exactly the same -way as a LanManager or Windows NT server. - -This document describes how the SMB password encryption algorithm -works and what issues there are in choosing whether you want to use -it. You should read it carefully, especially the part about security -and the "PROS and CONS" section. - -How does it work ? ------------------- - - LanManager encryption is somewhat similar to UNIX password -encryption. The server uses a file containing a hashed value of a -users password. This is created by taking the users paintext -password, capitalising it, and either truncating to 14 bytes (or -padding to 14 bytes with null bytes). This 14 byte value is used as -two 56 bit DES keys to encrypt a 'magic' eight byte value, forming a -16 byte value which is stored by the server and client. Let this value -be known as the *hashed password*. - -When a client (LanManager, Windows for WorkGroups, Windows 95 or -Windows NT) wishes to mount a Samba drive (or use a Samba resource) it -first requests a connection and negotiates the protocol that the client -and server will use. In the reply to this request the Samba server -generates and appends an 8 byte, random value - this is stored in the -Samba server after the reply is sent and is known as the *challenge*. - -The challenge is different for every client connection. - -The client then uses the hashed password (16 byte value described -above), appended with 5 null bytes, as three 56 bit DES keys, each of -which is used to encrypt the challenge 8 byte value, forming a 24 byte -value known as the *response*. - -In the SMB call SMBsessionsetupX (when user level security is -selected) or the call SMBtconX (when share level security is selected) -the 24 byte response is returned by the client to the Samba server. - -The Samba server then reproduces the above calculation, using it's own -stored value of the 16 byte hashed password (read from the smbpasswd -file - described later) and the challenge value that it kept from the -negotiate protocol reply. It then checks to see if the 24 byte value it -calculates matches the 24 byte value returned to it from the client. - -If these values match exactly, then the client knew the correct -password (or the 16 byte hashed value - see security note below) and -is this allowed access. If not then the client did not know the -correct password and is denied access. - -Note that the Samba server never knows or stores the cleartext of the -users password - just the 16 byte hashed function derived from it. Also -note that the cleartext password or 16 byte hashed value are never -transmitted over the network - thus increasing security. - -IMPORTANT NOTE ABOUT SECURITY ------------------------------ - -The unix and SMB password encryption techniques seem similar on the -surface. This similarity is, however, only skin deep. The unix scheme -typically sends clear text passwords over the nextwork when logging -in. This is bad. The SMB encryption scheme never sends the cleartext -password over the network but it does store the 16 byte hashed value -on disk. This is also bad. Why? Because the 16 byte hashed value is a -"password equivalent". You cannot derive the users password from it, -but it could potentially be used in a modified client to gain access -to a server. This would require considerable technical knowledge on -behalf of the attacker but is perfectly possible. You should thus -treat the smbpasswd file as though it contained the cleartext -passwords of all your users. Its contents must be kept secret, and the -file should be protected accordingly. - -Ideally we would like a password scheme which neither requires plain -text passwords on the net or on disk. Unfortunately this is not -available as Samba is stuck with being compatible with other SMB -systems (WinNT, WfWg, Win95 etc). - - -PROS AND CONS -------------- - -There are advantages and disadvantages to both schemes. - -Advantages of SMB Encryption: ------------------------------ - -- plain text passwords are not passed across the network. Someone using -a network sniffer cannot just record passwords going to the SMB server. - -- WinNT doesn't like talking to a server that isn't using SMB -encrypted passwords. It will refuse to browse the server if the server -is also in user level security mode. It will insist on promting the -user for the password on each connection, which is very annoying. The -only things you can do to stop this is to use SMB encryption. - -Advantages of non-encrypted passwords: --------------------------------------- - -- plain text passwords are not kept on disk. - -- uses same password file as other unix services such as login and -ftp - -- you are probably already using other services (such as telnet and -ftp) which send plain text passwords over the net, so not sending them -for SMB isn't such a big deal. - -- the SMB encryption code in Samba is new and has only had limited -testing. We have tried hard to make it secure but in any new -implementation of a password scheme there is the possability of an -error. - - -The smbpasswd file. -------------------- - - In order for Samba to participate in the above protocol it must -be able to look up the 16 byte hashed value given a user name. -Unfortunately, as the UNIX password value is also a one way hash -function (ie. it is impossible to retrieve the cleartext of the users -password given the UNIX hash of it) then a separate password file -containing this 16 byte value must be kept. To minimise problems with -these two password files, getting out of sync, the UNIX /etc/passwd and -the smbpasswd file, a utility, mksmbpasswd.sh, is provided to generate -a smbpasswd file from a UNIX /etc/passwd file. - -To generate the smbpasswd file from your /etc/passwd file use the -following command :- - -cat /etc/passwd | mksmbpasswd.sh >/usr/local/samba/private/smbpasswd - -If you are running on a system that uses NIS, use - -ypcat passwd | mksmbpasswd.sh >/usr/local/samba/private/smbpasswd - -The mksmbpasswd.sh program is found in the Samba source directory. By -default, the smbpasswd file is stored in :- - -/usr/local/samba/private/smbpasswd - -The owner of the /usr/local/samba/private directory should be set to -root, and the permissions on it should be set to :- - -r-x------ - -The command - -chmod 500 /usr/local/samba/private - -will do the trick. Likewise, the smbpasswd file inside the private -directory should be owned by root and the permissions on is should be -set to - -rw------- - -by the command :- - -chmod 600 smbpasswd. - -The format of the smbpasswd file is - -username:uid:XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX:Long name:user home dir:user shell - -Although only the username, uid, and XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX -sections are significant and are looked at in the Samba code. - -It is *VITALLY* important that there by 32 'X' characters between the -two ':' characters - the smbpasswd and Samba code will fail to validate -any entries that do not have 32 characters between ':' characters. - -When the password file is created all users have password entries -consisting of 32 'X' characters. By default this disallows any access -as this user. When a user has a password set, the 'X' characters change -to 32 ascii hexadecimal digits (0-9, A-F). These are an ascii -representation of the 16 byte hashed value of a users password. - -To set a user to have no password (not recommended), edit the file -using vi, and replace the first 11 characters with the asci text - -NO PASSWORD - -Eg. To clear the password for user bob, his smbpasswd file entry would -look like : - -bob:100:NO PASSWORDXXXXXXXXXXXXXXXXXXXXX:Bob's full name:/bobhome:/bobshell - -If you are allowing users to use the smbpasswd command to set their own -passwords, you may want to give users NO PASSWORD initially so they do -not have to enter a previous password when changing to their new -password (not recommended). - -Note : This file should be protected very carefully. Anyone with -access to this file can (with enough knowledge of the protocols) gain -access to your SMB server. The file is thus more sensitive than a -normal unix /etc/passwd file. - -The smbpasswd Command. ----------------------- - - The smbpasswd command maintains the 32 byte password field in -the smbpasswd file. If you wish to make it similar to the unix passwd -or yppasswd programs, install it in /usr/local/samba/bin (or your main -Samba binary directory) and make it setuid root. - -Note that if you do not do this then the root user will have to set all -users passwords. - -To set up smbpasswd as setuid root, change to the Samba binary install -directory and then type (as root) : - -chown root smbpasswd -chmod 4555 smbpasswd - -If smbpasswd is installed as setuid root then you would use it as -follows. - -smbpasswd -Old SMB password: <type old alue here - just hit return if there is NO PASSWORD> -New SMB Password: < type new value > -Repeat New SMB Password: < re-type new value > - -If the old value does not match the current value stored for that user, -or the two new values do not match each other, then the password will -not be changed. - -If invoked by an ordinary user it will only allow the user to change -his or her own Samba password. - -If run by the root user smbpasswd may take an optional argument, -specifying the user name whose SMB password you wish to change. Note -that when run as root smbpasswd does not prompt for or check the old -password value, thus allowing root to set passwords for users who have -forgotten their passwords. - -smbpasswd is designed to work in the same way and be familiar to UNIX -users who use the passwd or yppasswd commands. - -NOTE. As smbpasswd is designed to be installed as setuid root I would -appreciate it if everyone examined the source code to look for -potential security flaws. A setuid program, if not written properly can -be an open door to a system cracker. Please help make this program -secure by reporting all problems to me (the author, Jeremy Allison). - -My email address is :- - -jra@vantive.com - -Setting up Samba to support LanManager Encryption. --------------------------------------------------- - -This is a very brief description on how to setup samba to support -password encryption. More complete instructions will probably be added -later. - -1) get and compile the libdes libraries. the source is available from -nimbus.anu.edu.au in pub/tridge/libdes/libdes.tar.92-10-13.gz - -2) enable the encryption stuff in the Samba makefile, making sure you -point it to the libdes library and include file (it needs des.h) -The entries you need to uncomment are the four lines after the comment :- - -# This is for SMB encrypted (lanman) passwords. - -Note that you may have to change the variable DES_BASE to -point at the place where you installed the DES library. - -3) compile and install samba as usual - -4) f your system can't compile the module getsmbpass.c then remove the --DSMBGETPASS define from the Makefile. - -5) enable encrypted passwords in smb.conf by adding the line -"encrypt passwords = yes" in the [global] section - -6) create the initial smbpasswd password file in the place you -specified in the Makefile. A simple way to do this based on your -existing Makefile (assuming it is in a reasonably standard format) is -like this: - -cat /etc/passwd | mksmbpasswd.sh > /usr/local/samba/private/smbpasswd - -Change ownership of private and smbpasswd to root. - -chown -R root /usr/local/samba/private - -Set the correct permissions on /usr/local/samba/private - -chmod 500 /usr/local/samba/private - -Set the correct permissions on /usr/local/samba/private/smbpasswd - -chmod 600 /usr/local/samba/private/smbpasswd - -note that the mksmbpasswd.sh script is in the samba source directory. - -If this fails then you will find that you will need entries that look -like this: - -# SMB password file. -tridge:148:XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX:Andrew Tridgell:/home/tridge:/bin/tcsh - -note that the uid and username fields must be right. Also, you must get -the number of X's right (there should be 32). - -If you wish, install the smbpasswd program as suid root. - -chown root /usr/local/samba/bin/smbpasswd -chmod 4555 /usr/local/samba/bin/smbpasswd - -7) set the passwords for users using the smbpasswd command. For -example, as root you could do "smbpasswd tridge" - -8) try it out! - -Note that you can test things using smbclient, as it also now supports -encryption. - -NOTE TO USA Sites that Mirror Samba ------------------------------------ - -The DES library is considered a munition in the USA. Under US Law it is -illegal to export this software, or to put it in a freely available ftp -site. - -Please do not mirror the DES directory from the site on nimbus.anu.edu.au - -Thank you, - -Jeremy Allison. - |