[RFC][PATCH 0/9] encrypted keys & key control op

From: David Howells
Date: Mon Nov 04 2013 - 13:14:27 EST

Hi Mimi, Dmitry,

Here's a series of patches, the last three of which attempt to fix up a
problem with encrypted keys update method. The preceding patches are fixes or
are preparatory for other changes that I want to put underneath.

I really want to make all key types use ->preparse() to avoid a deadlock in
the garbage collector with quota recycling, but encrypted_update() requires
access to the old key - which you can't have in ->preparse() because the
keyring isn't locked (and this lock is the root of the gc deadlock anyway).

Further, the existence of encrypted_update() means that add_key() will
sometimes get things wrong with encrypted keys (add_key() will call ->update()
if a matching key already exists rather than creating a new key). But you
can't pre-search for the existence of a key and mould the payload accordingly
because that means you can race against both add_key() and keyctl_unlink().

My solution is to add a new keyctl function that allows the caller to perform
a type-specific operation on a key:

long keyctl_control(key_serial_t key_id,
const char *command,
char *reply_buffer,
size_t reply_size);

This would then take a NUL-terminated string indicating the command and
arguments and potentially return a reply up to the buffer length.

For instance:

keyctl_control(1234, "encrypted change-master-key fred's key", NULL, 0);

or, from the shell:

keyctl control 1234 "encrypted change-master-key fred's key"

(I think that requiring the command string to be prefixed with the expected
key type is probably a good idea).

The control op could also be used for other things like pushing a key into a

What do you think?

David Howells (9):
KEYS: The RSA public key algorithm needs to select MPILIB
KEYS: Provide a generic instantiation function
KEYS: struct key_preparsed_payload should have two payload pointers
KEYS: Allow expiry time to be set when preparsing a key
KEYS: Call ->free_preparse() even after ->preparse() returns an error
KEYS: Trusted: Use key preparsing
KEYS: Add a keyctl function to alter/control a key in type-dependent way
KEYS: Implement keyctl control for encrypted keys
KEYS: Fix encrypted key type update method

Documentation/security/keys.txt | 48 +++++++-
crypto/asymmetric_keys/Kconfig | 1
crypto/asymmetric_keys/asymmetric_type.c | 27 ----
crypto/asymmetric_keys/x509_public_key.c | 2
include/linux/key-type.h | 11 ++
include/uapi/linux/keyctl.h | 1
security/keys/compat.c | 6 +
security/keys/encrypted-keys/encrypted.c | 111 +++++++++++++-----
security/keys/internal.h | 2
security/keys/key.c | 49 +++++++-
security/keys/keyctl.c | 104 ++++++++++++++++
security/keys/trusted.c | 190 ++++++++++++++----------------
12 files changed, 385 insertions(+), 167 deletions(-)

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