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PAM: reorganize the way pam_ecryptfs and pam_mount get their password

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Run pam_unix an additional time rather than switching it from sufficient
to required. This fixes a potential security issue for
ecryptfs/pam_mount users as with pam_deny gone, if cfg.unixAuth = False
then it is possible to login without a password.
This commit is contained in:
obadz 2015-11-21 21:04:11 +00:00
parent 7ae05edcdd
commit a05a340e26
1 changed files with 18 additions and 8 deletions
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26
nixos/modules/security/pam.nix
View file

@ -218,7 +218,7 @@ let
# Samba stuff to the Samba module. This requires that the PAM
# module provides the right hooks.
text = mkDefault
''
(''
# Account management.
account sufficient pam_unix.so
${optionalString config.users.ldap.enable
@ -241,12 +241,22 @@ let
"auth sufficient ${pkgs.pam_u2f}/lib/security/pam_u2f.so"}
${optionalString cfg.usbAuth
"auth sufficient ${pkgs.pam_usb}/lib/security/pam_usb.so"}
'' +
# Modules in this block require having the password set in PAM_AUTHTOK.
# pam_unix is marked as 'sufficient' on NixOS which means nothing will run
# after it succeeds. Certain modules need to run after pam_unix
# prompts the user for password so we run it once with 'required' at an
# earlier point and it will run again with 'sufficient' further down.
# We use try_first_pass the second time to avoid prompting password twice
(optionalString (cfg.unixAuth && (config.security.pam.enableEcryptfs || cfg.pamMount)) ''
auth required pam_unix.so ${optionalString cfg.allowNullPassword "nullok"} likeauth
${optionalString config.security.pam.enableEcryptfs
"auth optional ${pkgs.ecryptfs}/lib/security/pam_ecryptfs.so unwrap"}
${optionalString cfg.pamMount
"auth optional ${pkgs.pam_mount}/lib/security/pam_mount.so"}
'') + ''
${optionalString cfg.unixAuth
"auth ${if (config.security.pam.enableEcryptfs || cfg.pamMount) then "required" else "sufficient"} pam_unix.so ${optionalString cfg.allowNullPassword "nullok"} likeauth"}
${optionalString cfg.pamMount
"auth optional ${pkgs.pam_mount}/lib/security/pam_mount.so"}
${optionalString config.security.pam.enableEcryptfs
"auth required ${pkgs.ecryptfs}/lib/security/pam_ecryptfs.so unwrap"}
"auth sufficient pam_unix.so ${optionalString cfg.allowNullPassword "nullok"} likeauth try_first_pass"}
${optionalString cfg.otpwAuth
"auth sufficient ${pkgs.otpw}/lib/security/pam_otpw.so"}
${optionalString cfg.oathAuth
@ -258,7 +268,7 @@ let
auth [default=die success=done] ${pam_ccreds}/lib/security/pam_ccreds.so action=validate use_first_pass
auth sufficient ${pam_ccreds}/lib/security/pam_ccreds.so action=store use_first_pass
''}
${optionalString (!(config.security.pam.enableEcryptfs || cfg.pamMount)) "auth required pam_deny.so"}
auth required pam_deny.so
# Password management.
password requisite pam_unix.so nullok sha512
@ -306,7 +316,7 @@ let
"session optional ${pkgs.pam_mount}/lib/security/pam_mount.so"}
${optionalString (cfg.enableAppArmor && config.security.apparmor.enable)
"session optional ${pkgs.apparmor-pam}/lib/security/pam_apparmor.so order=user,group,default debug"}
'';
'');
};
};