KEYS: encrypted: Instantiate key with user-provided decrypted data

For availability and performance reasons master keys often need to be
released outside of a Key Management Service (KMS) to clients. It
would be beneficial to provide a mechanism where the
wrapping/unwrapping of data encryption keys (DEKs) is not dependent
on a remote call at runtime yet security is not (or only minimally)
compromised. Master keys could be securely stored in the Kernel and
be used to wrap/unwrap keys from Userspace.

The encrypted.c class supports instantiation of encrypted keys with
either an already-encrypted key material, or by generating new key
material based on random numbers. This patch defines a new datablob
format: [<format>] <master-key name> <decrypted data length>
<decrypted data> that allows to inject and encrypt user-provided
decrypted data. The decrypted data must be hex-ascii encoded.

Signed-off-by: Yael Tzur <yaelt@google.com>
Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
Reviewed-by: Sumit Garg <sumit.garg@linaro.org>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>

1 files changed, 19 insertions, 6 deletions

diff --git a/Documentation/security/keys/trusted-encrypted.rst b/Documentation/security/keys/trusted-encrypted.rst
index 80d5a5af62a1..f614dad7de12 100644
--- a/Documentation/security/keys/trusted-encrypted.rst
+++ b/Documentation/security/keys/trusted-encrypted.rst
@@ -107,12 +107,13 @@ Encrypted Keys
 --------------
 
 Encrypted keys do not depend on a trust source, and are faster, as they use AES
-for encryption/decryption. New keys are created from kernel-generated random
-numbers, and are encrypted/decrypted using a specified ‘master’ key. The
-‘master’ key can either be a trusted-key or user-key type. The main disadvantage
-of encrypted keys is that if they are not rooted in a trusted key, they are only
-as secure as the user key encrypting them. The master user key should therefore
-be loaded in as secure a way as possible, preferably early in boot.
+for encryption/decryption. New keys are created either from kernel-generated
+random numbers or user-provided decrypted data, and are encrypted/decrypted
+using a specified ‘master’ key. The ‘master’ key can either be a trusted-key or
+user-key type. The main disadvantage of encrypted keys is that if they are not
+rooted in a trusted key, they are only as secure as the user key encrypting
+them. The master user key should therefore be loaded in as secure a way as
+possible, preferably early in boot.
 
 
 Usage
@@ -199,6 +200,8 @@ Usage::
 
     keyctl add encrypted name "new [format] key-type:master-key-name keylen"
         ring
+    keyctl add encrypted name "new [format] key-type:master-key-name keylen
+        decrypted-data" ring
     keyctl add encrypted name "load hex_blob" ring
     keyctl update keyid "update key-type:master-key-name"
 
@@ -303,6 +306,16 @@ Load an encrypted key "evm" from saved blob::
     82dbbc55be2a44616e4959430436dc4f2a7a9659aa60bb4652aeb2120f149ed197c564e0
     24717c64 5972dcb82ab2dde83376d82b2e3c09ffc
 
+Instantiate an encrypted key "evm" using user-provided decrypted data::
+
+    $ keyctl add encrypted evm "new default user:kmk 32 `cat evm_decrypted_data.blob`" @u
+    794890253
+
+    $ keyctl print 794890253
+    default user:kmk 32 2375725ad57798846a9bbd240de8906f006e66c03af53b1b382d
+    bbc55be2a44616e4959430436dc4f2a7a9659aa60bb4652aeb2120f149ed197c564e0247
+    17c64 5972dcb82ab2dde83376d82b2e3c09ffc
+
 Other uses for trusted and encrypted keys, such as for disk and file encryption
 are anticipated.  In particular the new format 'ecryptfs' has been defined
 in order to use encrypted keys to mount an eCryptfs filesystem.  More details