Ubuntu Manpage: eCryptfs - an enterprise-class cryptographic filesystem for linux

Provided by: ecryptfs-utils_111-0ubuntu1.1_amd64

NAME

       eCryptfs - an enterprise-class cryptographic filesystem for linux

SYNOPSIS

       mount -t ecryptfs [SRC DIR] [DST DIR] -o [OPTIONS]

DESCRIPTION

       eCryptfs  is a POSIX-compliant enterprise-class stacked cryptographic filesystem for Linux. It is derived
       from Erez Zadok's Cryptfs, implemented through the FiST framework  for  generating  stacked  filesystems.
       eCryptfs  extends  Cryptfs  to  provide  advanced  key  management  and policy features.  eCryptfs stores
       cryptographic metadata in the header of each file written, so that encrypted files can be copied  between
       hosts;  the  file  will  be  decryptable  with  the proper key, and there is no need to keep track of any
       additional information aside from what is already in the encrypted file itself. Think of  eCryptfs  as  a
       sort of "gnupgfs."

OPTIONS

KERNEL OPTIONS

Parameters that apply to the eCryptfs kernel module.

ecryptfs_sig=(fekek_sig)
Specify the signature of the mount wide authentication token. The authentication token must be in
the kernel keyring before the mount is performed. ecryptfs-manager or the eCryptfs mount helper
can be used to construct the authentication token and add it to the keyring prior to mounting.

ecryptfs_fnek_sig=(fnek_sig)
Specify the signature of the mount wide authentication token used for filename crypto. The
authentication must be in the kernel keyring before mounting.

ecryptfs_cipher=(cipher)
Specify the symmetric cipher to be used on a per file basis

ecryptfs_key_bytes=(key_bytes)
Specify the keysize to be used with the selected cipher. If the cipher only has one keysize the
keysize does not need to be specified.

ecryptfs_passthrough
Allows for non-eCryptfs files to be read and written from within an eCryptfs mount. This option is
turned off by default.

no_sig_cache
Do not check the mount key signature against the values in the user's ~/.ecryptfs/sig-cache.txt
file. This is useful for such things as non-interactive setup scripts, so that the mount helper
does not stop and prompt the user in the event that the key sig is not in the cache.

ecryptfs_encrypted_view
This option provides a unified encrypted file format of the eCryptfs files in the lower mount
point. Currently, it is only useful if the lower mount point contains files with the metadata
stored in the extended attribute. Upon a file read in the upper mount point, the encrypted
version of the file will be presented with the metadata in the file header instead of the xattr.
Files cannot be opened for writing when this option is enabled.

ecryptfs_xattr
Store the metadata in the extended attribute of the lower files rather than the header region of
the lower files.

verbose
Log ecryptfs information to /var/log/messages. Do not run eCryptfs in verbose-mode unless you are
doing so for the sole purpose of development, since secret values will be written out to the
system log in that case.

MOUNT HELPER OPTIONS

Parameters that apply to the eCryptfs mount helper.

key=(keytype):[KEY MODULE OPTIONS]
Specify the type of key to be used when mounting eCryptfs.

ecryptfs_enable_filename_crypto=(y/n)
Specify whether filename encryption should be enabled. If not, the mount helper will not prompt
the user for the filename encryption key signature (default).

verbosity=0/1
If verbosity=1, the mount helper will ask you for missing values (default). Otherwise, if
verbosity=0, it will not ask for missing values and will fail if required values are omitted.

KEY MODULE OPTIONS

Parameters that apply to individual key modules have the alias for the key module in the prefix of
the parameter name. Key modules are pluggable, and which key modules are available on any given
system is dependent upon whatever happens to be installed in /usr/lib*/ecryptfs/.

passphrase_passwd=(passphrase)
The actual password is passphrase. Since the password is visible to utilities (like ps under Unix)
this form should only be used where security is not important.

passphrase_passwd_file=(filename)
The password should be specified in a file with passphrase_passwd_file=(passphrase). It is highly
recommended that the file be stored on a secure medium such as a personal usb key.

passphrase_passwd_fd=(file descriptor)
The password is specified through the specified file descriptor.

passphrase_salt=(hex value)
The salt should be specified as a 16 digit hex value.

openssl_keyfile=(filename)
The filename should be the filename of a file containing an RSA SSL key.

openssl_passwd_file=(filename)
The password should be specified in a file with openssl_passwd=(openssl-password). It is highly
recommended that the file be stored on a secure medium such as a personal usb key.

openssl_passwd_fd=(file descriptor)
The password is specified through the specified file descriptor.

openssl_passwd=(password)
The password can be specified on the command line. Since the password is visible in the process
list, it is highly recommended to use this option only for testing purposes.

EXAMPLE

       The following command will layover mount eCryptfs on /secret with a passphrase contained in a file stored
       on secure media mounted at /mnt/usb/.

       mount -t ecryptfs -o key=passphrase:passphrase_passwd_file=/mnt/usb/file.txt /secret /secret

       Where file.txt contains the contents "passphrase_passwd=[passphrase]".

NOTES

       Do not run eCryptfs in verbose-mode unless you are doing so for the sole purpose  of  development,  since
       secret  values  will be written out to the system log in that case. Make certain that your eCryptfs mount
       covers all locations where your applications may write sensitive  data.  In  addition,  use  dm-crypt  to
       encrypt your swap space with a random key on boot, or see ecryptfs-setup-swap(1).

       Passphrases have a maximum length of 64 characters.

BUGS

       Please     post     bug     reports     to     the     eCryptfs    bug    tracker    on    Launchpad.net:
       https://bugs.launchpad.net/ecryptfs/+filebug.

       For kernel bugs, please follow the procedure detailed in Documentation/oops-tracing.txt to help us figure
       out what is happening.

AUTHOR

       This  manpage  was  (re-)written  by Dustin Kirkland <kirkland@ubuntu.com> for Ubuntu systems (but may be
       used by others).  Permission is granted to copy, distribute and/or modify this document under  the  terms
       of  the  GNU  General  Public  License,  Version  2  or  any later version published by the Free Software
       Foundation.

       On Debian systems, the complete text of the GNU General Public License can be found in /usr/share/common-
       licenses/GPL.