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Re: [Linux-ima-devel] [PATCH v5 2/3] Create IMA machine owner and blacklist keyrings;
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From: Dmitry K. <dmi...@gm...> - 2015-11-17 16:46:41
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On Mon, Nov 16, 2015 at 3:10 PM, Mimi Zohar <zo...@li...> wrote:
> On Mon, 2015-11-02 at 00:32 +0200, Petko Manolov wrote:
>> This option creates IMA MOK and blacklist keyrings. IMA MOK is an
>> intermediate keyring that sits between .system and .ima keyrings,
>> effectively forming a simple CA hierarchy. To successfully import a key
>> into .ima_mok it must be signed by a key which CA is in .system keyring.
>> On turn any key that needs to go in .ima keyring must be signed by CA in
>> either .system or .ima_mok keyrings. IMA MOK is empty at kernel boot.
>>
>> IMA blacklist keyring contains all revoked IMA keys. It is consulted
>> before any other keyring. If the search is successful the requested
>> operation is rejected and error is returned to the caller.
>
> Adding a key to the black list will prevent any new file integrity
> verification from succeeding. This does not address files that have
> already been verified and the results are already in the iint cache.
>
> The iint is a red-black tree. One method would be to walk the entire
> tree clearing the cache info. Another method would be to include a
> timestamp in the iint and lazily clear the iint cache info when next
> accessed. Are there any other solutions?
>
> Mimi
>
It would be possible compare verification timestamp to "blacklist"
update timestamp.
And if it was updated after, invalidate file verification....
Dmitry
>
>> Signed-off-by: Petko Manolov <pe...@mi...>
>> ---
>> crypto/asymmetric_keys/x509_public_key.c | 2 ++
>> include/keys/system_keyring.h | 24 ++++++++++++++
>> security/integrity/digsig_asymmetric.c | 14 +++++++++
>> security/integrity/ima/Kconfig | 18 +++++++++++
>> security/integrity/ima/Makefile | 1 +
>> security/integrity/ima/ima_mok.c | 54 ++++++++++++++++++++++++++++++++
>> 6 files changed, 113 insertions(+)
>> create mode 100644 security/integrity/ima/ima_mok.c
>>
>> diff --git a/crypto/asymmetric_keys/x509_public_key.c b/crypto/asymmetric_keys/x509_public_key.c
>> index 1970966..66dcf30 100644
>> --- a/crypto/asymmetric_keys/x509_public_key.c
>> +++ b/crypto/asymmetric_keys/x509_public_key.c
>> @@ -319,6 +319,8 @@ static int x509_key_preparse(struct key_preparsed_payload *prep)
>> goto error_free_cert;
>> } else if (!prep->trusted) {
>> ret = x509_validate_trust(cert, get_system_trusted_keyring());
>> + if (ret)
>> + ret = x509_validate_trust(cert, get_ima_mok_keyring());
>> if (!ret)
>> prep->trusted = 1;
>> }
>> diff --git a/include/keys/system_keyring.h b/include/keys/system_keyring.h
>> index b20cd88..39fd38c 100644
>> --- a/include/keys/system_keyring.h
>> +++ b/include/keys/system_keyring.h
>> @@ -35,4 +35,28 @@ extern int system_verify_data(const void *data, unsigned long len,
>> enum key_being_used_for usage);
>> #endif
>>
>> +#ifdef CONFIG_IMA_MOK_KEYRING
>> +extern struct key *ima_mok_keyring;
>> +extern struct key *ima_blacklist_keyring;
>> +
>> +static inline struct key *get_ima_mok_keyring(void)
>> +{
>> + return ima_mok_keyring;
>> +}
>> +static inline struct key *get_ima_blacklist_keyring(void)
>> +{
>> + return ima_blacklist_keyring;
>> +}
>> +#else
>> +static inline struct key *get_ima_mok_keyring(void)
>> +{
>> + return NULL;
>> +}
>> +static inline struct key *get_ima_blacklist_keyring(void)
>> +{
>> + return NULL;
>> +}
>> +#endif /* CONFIG_IMA_MOK_KEYRING */
>> +
>> +
>> #endif /* _KEYS_SYSTEM_KEYRING_H */
>> diff --git a/security/integrity/digsig_asymmetric.c b/security/integrity/digsig_asymmetric.c
>> index 4fec181..5ade2a7 100644
>> --- a/security/integrity/digsig_asymmetric.c
>> +++ b/security/integrity/digsig_asymmetric.c
>> @@ -17,6 +17,7 @@
>> #include <linux/key-type.h>
>> #include <crypto/public_key.h>
>> #include <keys/asymmetric-type.h>
>> +#include <keys/system_keyring.h>
>>
>> #include "integrity.h"
>>
>> @@ -32,9 +33,22 @@ static struct key *request_asymmetric_key(struct key *keyring, uint32_t keyid)
>>
>> pr_debug("key search: \"%s\"\n", name);
>>
>> + key = get_ima_blacklist_keyring();
>> + if (key) {
>> + key_ref_t kref;
>> +
>> + kref = keyring_search(make_key_ref(key, 1),
>> + &key_type_asymmetric, name);
>> + if (!IS_ERR(kref)) {
>> + pr_err("Key '%s' is in ima_blacklist_keyring\n", name);
>> + return ERR_PTR(-EKEYREJECTED);
>> + }
>> + }
>> +
>> if (keyring) {
>> /* search in specific keyring */
>> key_ref_t kref;
>> +
>> kref = keyring_search(make_key_ref(keyring, 1),
>> &key_type_asymmetric, name);
>> if (IS_ERR(kref))
>> diff --git a/security/integrity/ima/Kconfig b/security/integrity/ima/Kconfig
>> index 59e215f..a489340 100644
>> --- a/security/integrity/ima/Kconfig
>> +++ b/security/integrity/ima/Kconfig
>> @@ -142,6 +142,24 @@ config IMA_TRUSTED_KEYRING
>> This option requires that all keys added to the .ima
>> keyring be signed by a key on the system trusted keyring.
>>
>> +config IMA_MOK_KEYRING
>> + bool "Create IMA machine owner keys (MOK) and blacklist keyrings"
>> + select SYSTEM_TRUSTED_KEYRING
>> + select IMA_TRUSTED_KEYRING
>> + default y
>> + help
>> + This option creates IMA MOK and blacklist keyrings. IMA MOK is an
>> + intermediate keyring that sits between .system and .ima keyrings,
>> + effectively forming a simple CA hierarchy. To successfully import a
>> + key into .ima_mok it must be signed by a key which CA is in .system
>> + keyring. On turn any key that needs to go in .ima keyring must be
>> + signed by CA in either .system or .ima_mok keyrings. IMA MOK is empty
>> + at kernel boot.
>> +
>> + IMA blacklist keyring contains all revoked IMA keys. It is consulted
>> + before any other keyring. If the search is successful the requested
>> + operation is rejected and error is returned to the caller.
>> +
>> config IMA_LOAD_X509
>> bool "Load X509 certificate onto the '.ima' trusted keyring"
>> depends on IMA_TRUSTED_KEYRING
>> diff --git a/security/integrity/ima/Makefile b/security/integrity/ima/Makefile
>> index d79263d..a8539f9 100644
>> --- a/security/integrity/ima/Makefile
>> +++ b/security/integrity/ima/Makefile
>> @@ -8,3 +8,4 @@ obj-$(CONFIG_IMA) += ima.o
>> ima-y := ima_fs.o ima_queue.o ima_init.o ima_main.o ima_crypto.o ima_api.o \
>> ima_policy.o ima_template.o ima_template_lib.o
>> ima-$(CONFIG_IMA_APPRAISE) += ima_appraise.o
>> +obj-$(CONFIG_IMA_MOK_KEYRING) += ima_mok.o
>> diff --git a/security/integrity/ima/ima_mok.c b/security/integrity/ima/ima_mok.c
>> new file mode 100644
>> index 0000000..18e37f5
>> --- /dev/null
>> +++ b/security/integrity/ima/ima_mok.c
>> @@ -0,0 +1,54 @@
>> +/*
>> + * Copyright (C) 2015 Juniper Networks, Inc.
>> + *
>> + * Author:
>> + * Petko Manolov <pet...@ko...>
>> + *
>> + * This program is free software; you can redistribute it and/or
>> + * modify it under the terms of the GNU General Public License as
>> + * published by the Free Software Foundation, version 2 of the
>> + * License.
>> + *
>> + */
>> +
>> +#include <linux/export.h>
>> +#include <linux/kernel.h>
>> +#include <linux/sched.h>
>> +#include <linux/cred.h>
>> +#include <linux/err.h>
>> +#include <linux/module.h>
>> +#include <keys/asymmetric-type.h>
>> +
>> +
>> +struct key *ima_mok_keyring;
>> +struct key *ima_blacklist_keyring;
>> +
>> +/*
>> + * Allocate the IMA MOK and blacklist keyrings
>> + */
>> +__init int ima_mok_init(void)
>> +{
>> + pr_notice("Allocating IMA MOK and blacklist keyrings.\n");
>> +
>> + ima_mok_keyring = keyring_alloc(".ima_mok",
>> + KUIDT_INIT(0), KGIDT_INIT(0), current_cred(),
>> + (KEY_POS_ALL & ~KEY_POS_SETATTR) |
>> + KEY_USR_VIEW | KEY_USR_READ |
>> + KEY_USR_WRITE | KEY_USR_SEARCH,
>> + KEY_ALLOC_NOT_IN_QUOTA, NULL);
>> +
>> + ima_blacklist_keyring = keyring_alloc(".ima_blacklist",
>> + KUIDT_INIT(0), KGIDT_INIT(0), current_cred(),
>> + (KEY_POS_ALL & ~KEY_POS_SETATTR) |
>> + KEY_USR_VIEW | KEY_USR_READ |
>> + KEY_USR_WRITE | KEY_USR_SEARCH,
>> + KEY_ALLOC_NOT_IN_QUOTA, NULL);
>> +
>> + if (IS_ERR(ima_mok_keyring) || IS_ERR(ima_blacklist_keyring))
>> + panic("Can't allocate IMA MOK or blacklist keyrings.");
>> + set_bit(KEY_FLAG_TRUSTED_ONLY, &ima_mok_keyring->flags);
>> + set_bit(KEY_FLAG_TRUSTED_ONLY, &ima_blacklist_keyring->flags);
>> + return 0;
>> +}
>> +
>> +module_init(ima_mok_init);
>
>
--
Thanks,
Dmitry
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