encrypted-keys: add ecryptfs format support

The 'encrypted' key type defines its own payload format which contains a
symmetric key randomly generated that cannot be used directly to mount
an eCryptfs filesystem, because it expects an authentication token
structure.

This patch introduces the new format 'ecryptfs' that allows to store an
authentication token structure inside the encrypted key payload containing
a randomly generated symmetric key, as the same for the format 'default'.

More details about the usage of encrypted keys with the eCryptfs
filesystem can be found in the file 'Documentation/keys-ecryptfs.txt'.

Signed-off-by: Roberto Sassu <roberto.sassu@polito.it>
Acked-by: Gianluca Ramunno <ramunno@polito.it>
Acked-by: Tyler Hicks <tyhicks@linux.vnet.ibm.com>
Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>

1 files changed, 4 insertions, 2 deletions

diff --git a/Documentation/security/keys-trusted-encrypted.txt b/Documentation/security/keys-trusted-encrypted.txt
index 0afcb50..5f50cca 100644
--- a/Documentation/security/keys-trusted-encrypted.txt
+++ b/Documentation/security/keys-trusted-encrypted.txt
@@ -63,7 +63,7 @@ Usage:
     keyctl add encrypted name "load hex_blob" ring
     keyctl update keyid "update key-type:master-key-name"
 
-format:= 'default'
+format:= 'default | ecryptfs'
 key-type:= 'trusted' | 'user'
 
 
@@ -154,4 +154,6 @@ Load an encrypted key "evm" from saved blob:
     24717c64 5972dcb82ab2dde83376d82b2e3c09ffc
 
 Other uses for trusted and encrypted keys, such as for disk and file encryption
-are anticipated.
+are anticipated.  In particular the new format 'ecryptfs' has been defined in
+in order to use encrypted keys to mount an eCryptfs filesystem.  More details
+about the usage can be found in the file 'Documentation/keys-ecryptfs.txt'.