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diff --git a/modules/pam_unix/README b/modules/pam_unix/README new file mode 100644 index 0000000..651ed9c --- /dev/null +++ b/modules/pam_unix/README @@ -0,0 +1,190 @@ +pam_unix — Module for traditional password authentication + +━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ + +DESCRIPTION + +This is the standard Unix authentication module. It uses standard calls from +the system's libraries to retrieve and set account information as well as +authentication. Usually this is obtained from the /etc/passwd and the /etc/ +shadow file as well if shadow is enabled. + +The account component performs the task of establishing the status of the +user's account and password based on the following shadow elements: expire, +last_change, max_change, min_change, warn_change. In the case of the latter, it +may offer advice to the user on changing their password or, through the +PAM_AUTHTOKEN_REQD return, delay giving service to the user until they have +established a new password. The entries listed above are documented in the +shadow(5) manual page. Should the user's record not contain one or more of +these entries, the corresponding shadow check is not performed. + +The authentication component performs the task of checking the users +credentials (password). The default action of this module is to not permit the +user access to a service if their official password is blank. + +A helper binary, unix_chkpwd(8), is provided to check the user's password when +it is stored in a read protected database. This binary is very simple and will +only check the password of the user invoking it. It is called transparently on +behalf of the user by the authenticating component of this module. In this way +it is possible for applications like xlock(1) to work without being +setuid-root. The module, by default, will temporarily turn off SIGCHLD handling +for the duration of execution of the helper binary. This is generally the right +thing to do, as many applications are not prepared to handle this signal from a +child they didn't know was fork()d. The noreap module argument can be used to +suppress this temporary shielding and may be needed for use with certain +applications. + +The maximum length of a password supported by the pam_unix module via the +helper binary is PAM_MAX_RESP_SIZE - currently 512 bytes. The rest of the +password provided by the conversation function to the module will be ignored. + +The password component of this module performs the task of updating the user's +password. The default encryption hash is taken from the ENCRYPT_METHOD variable +from /etc/login.defs + +The session component of this module logs when a user logins or leave the +system. + +Remaining arguments, supported by others functions of this module, are silently +ignored. Other arguments are logged as errors through syslog(3). + +OPTIONS + +debug + + Turns on debugging via syslog(3). + +audit + + A little more extreme than debug. + +quiet + + Turns off informational messages namely messages about session open and + close via syslog(3). + +nullok + + The default action of this module is to not permit the user access to a + service if their official password is blank. The nullok argument overrides + this default. + +try_first_pass + + Before prompting the user for their password, the module first tries the + previous stacked module's password in case that satisfies this module as + well. + +use_first_pass + + The argument use_first_pass forces the module to use a previous stacked + modules password and will never prompt the user - if no password is + available or the password is not appropriate, the user will be denied + access. + +nodelay + + This argument can be used to discourage the authentication component from + requesting a delay should the authentication as a whole fail. The default + action is for the module to request a delay-on-failure of the order of two + second. + +use_authtok + + When password changing enforce the module to set the new password to the + one provided by a previously stacked password module (this is used in the + example of the stacking of the pam_cracklib module documented below). + +authtok_type=type + + This argument can be used to modify the password prompt when changing + passwords to include the type of the password. Empty by default. + +nis + + NIS RPC is used for setting new passwords. + +remember=n + + The last n passwords for each user are saved in /etc/security/opasswd in + order to force password change history and keep the user from alternating + between the same password too frequently. The MD5 password hash algorithm + is used for storing the old passwords. Instead of this option the + pam_pwhistory module should be used. + +shadow + + Try to maintain a shadow based system. + +md5 + + When a user changes their password next, encrypt it with the MD5 algorithm. + +bigcrypt + + When a user changes their password next, encrypt it with the DEC C2 + algorithm. + +sha256 + + When a user changes their password next, encrypt it with the SHA256 + algorithm. If the SHA256 algorithm is not known to the crypt(3) function, + fall back to MD5. + +sha512 + + When a user changes their password next, encrypt it with the SHA512 + algorithm. If the SHA512 algorithm is not known to the crypt(3) function, + fall back to MD5. + +blowfish + + When a user changes their password next, encrypt it with the blowfish + algorithm. If the blowfish algorithm is not known to the crypt(3) function, + fall back to MD5. + +rounds=n + + Set the optional number of rounds of the SHA256, SHA512 and blowfish + password hashing algorithms to n. + +broken_shadow + + Ignore errors reading shadow information for users in the account + management module. + +minlen=n + + Set a minimum password length of n characters. The max. for DES crypt based + passwords are 8 characters. + +no_pass_expiry + + When set ignore password expiration as defined by the shadow entry of the + user. The option has an effect only in case pam_unix was not used for the + authentication or it returned authentication failure meaning that other + authentication source or method succeeded. The example can be public key + authentication in sshd. The module will return PAM_SUCCESS instead of + eventual PAM_NEW_AUTHTOK_REQD or PAM_AUTHTOK_EXPIRED. + +Invalid arguments are logged with syslog(3). + +EXAMPLES + +An example usage for /etc/pam.d/login would be: + +# Authenticate the user +auth required pam_unix.so +# Ensure users account and password are still active +account required pam_unix.so +# Change the user's password, but at first check the strength +# with pam_cracklib(8) +password required pam_cracklib.so retry=3 minlen=6 difok=3 +password required pam_unix.so use_authtok nullok md5 +session required pam_unix.so + + +AUTHOR + +pam_unix was written by various people. + |