Messages in this thread | | | Subject | Re: [RFC][PATCH 0/9] encrypted keys & key control op | From | Mimi Zohar <> | Date | Mon, 11 Nov 2013 07:14:24 -0500 |
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On Mon, 2013-11-04 at 16:22 +0000, David Howells wrote: > 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).
Ok.
> 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).
I see. The key_type structure defines a number of methods, including .instantiate and .update. I would have thought that only .update would be allowed to update an existing key. Instantiating a new key should create a new key or fail, not update a key. I'm sure there is/was a good reason for add_key() to do both.
> 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().
Would this still be the case, if you differentiated between instantiating and updating a key?
> 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.
What is the usecase scenario that would require a reply_buffer?
> 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).
Agreed.
Mimi
> The control op could also be used for other things like pushing a key into a > TPM.
> What do you think? > > David > --- > 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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