[RFC PATCH v1] fscrypt: support encrypted and trusted keys

[Ahmad Fatoum]

Hello Jarkko,

On 29.07.21 00:22, Jarkko Sakkinen wrote:
> On Tue, Jul 27, 2021 at 04:43:49PM +0200, Ahmad Fatoum wrote:
>> For both v1 and v2 key setup mechanisms, userspace supplies the raw key
>> material to the kernel after which it is never again disclosed to
>> userspace.
>>
>> Use of encrypted and trusted keys offers stronger guarantees:
>> The key material is generated within the kernel and is never disclosed to
>> userspace in clear text and, in the case of trusted keys, can be
>> directly rooted to a trust source like a TPM chip.
>>
>> Add support for trusted and encrypted keys by repurposing
>> fscrypt_add_key_arg::raw to hold the key description when the new
>> FSCRYPT_KEY_ARG_TYPE_DESC flag is supplied. The location of the flag
>> was previously reserved and enforced by ioctl code to be zero, so this
>> change won't break backwards compatibility.
>>
>> Corresponding userspace patches are available for fscryptctl:
>> https://github.com/google/fscryptctl/pull/23
>>
>> Signed-off-by: Ahmad Fatoum <a.fatoum at pengutronix.de>
>> ---
>> key_extract_material used by this patch is added in
>> <cover.b2fdd70b830d12853b12a12e32ceb0c8162c1346.1626945419.git-series.a.fatoum at pengutronix.de>
>> which still awaits feedback.
>>
>> Sending this RFC out anyway to get some feedback from the fscrypt
>> developers whether this is the correct way to go about it.
>>
>> To: "Theodore Y. Ts'o" <tytso at mit.edu>
>> To: Jaegeuk Kim <jaegeuk at kernel.org>
>> To: Eric Biggers <ebiggers at kernel.org>
>> Cc: Jarkko Sakkinen <jarkko at kernel.org>
>> Cc: James Morris <jmorris at namei.org>
>> Cc: "Serge E. Hallyn" <serge at hallyn.com>
>> Cc: James Bottomley <jejb at linux.ibm.com>
>> Cc: Mimi Zohar <zohar at linux.ibm.com>
>> Cc: Sumit Garg <sumit.garg at linaro.org>
>> Cc: David Howells <dhowells at redhat.com>
>> Cc: linux-fscrypt at vger.kernel.org
>> Cc: linux-crypto at vger.kernel.org
>> Cc: linux-integrity at vger.kernel.org
>> Cc: linux-security-module at vger.kernel.org
>> Cc: keyrings at vger.kernel.org
>> Cc: linux-kernel at vger.kernel.org
>> ---
>>  Documentation/filesystems/fscrypt.rst | 24 ++++++++---
>>  fs/crypto/keyring.c                   | 59 ++++++++++++++++++++++++---
>>  include/uapi/linux/fscrypt.h          | 16 +++++++-
>>  3 files changed, 87 insertions(+), 12 deletions(-)
>>
>> diff --git a/Documentation/filesystems/fscrypt.rst b/Documentation/filesystems/fscrypt.rst
>> index 44b67ebd6e40..83738af2afa3 100644
>> --- a/Documentation/filesystems/fscrypt.rst
>> +++ b/Documentation/filesystems/fscrypt.rst
>> @@ -681,11 +681,15 @@ It can be executed on any file or directory on the target filesystem,
>>  but using the filesystem's root directory is recommended.  It takes in
>>  a pointer to struct fscrypt_add_key_arg, defined as follows::
>>  
>> +    #define FSCRYPT_KEY_ADD_RAW_ASIS		0
>> +    #define FSCRYPT_KEY_ADD_RAW_DESC		1
> 
> Would be nice to have these documented.

They have explanatory comments in the uAPI header. The Documentation file
purposefully omits these comments and describes each field separately after
the code block. I am just following suit.

FWIW, I intend to drop these flags for v2 anyway.

Cheers,
Ahmad

> 
> /Jarkko
> 


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