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path: root/include/crypto/drbg.h
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2015-06-10crypto: drbg - reseed often if seedsource is degradedStephan Mueller
As required by SP800-90A, the DRBG implements are reseeding threshold. This threshold is at 2**48 (64 bit) and 2**32 bit (32 bit) as implemented in drbg_max_requests. With the recently introduced changes, the DRBG is now always used as a stdrng which is initialized very early in the boot cycle. To ensure that sufficient entropy is present, the Jitter RNG is added to even provide entropy at early boot time. However, the 2nd seed source, the nonblocking pool, is usually degraded at that time. Therefore, the DRBG is seeded with the Jitter RNG (which I believe contains good entropy, which however is questioned by others) and is seeded with a degradded nonblocking pool. This seed is now used for quasi the lifetime of the system (2**48 requests is a lot). The patch now changes the reseed threshold as follows: up until the time the DRBG obtains a seed from a fully iniitialized nonblocking pool, the reseeding threshold is lowered such that the DRBG is forced to reseed itself resonably often. Once it obtains the seed from a fully initialized nonblocking pool, the reseed threshold is set to the value required by SP800-90A. Signed-off-by: Stephan Mueller <smueller@chronox.de> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2015-06-10crypto: drbg - Use callback API for random readinessStephan Mueller
The get_blocking_random_bytes API is broken because the wait can be arbitrarily long (potentially forever) so there is no safe way of calling it from within the kernel. This patch replaces it with the new callback API which does not have this problem. The patch also removes the entropy buffer registered with the DRBG handle in favor of stack variables to hold the seed data. Signed-off-by: Stephan Mueller <smueller@chronox.de> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2015-05-27crypto: drbg - use Jitter RNG to obtain seedStephan Mueller
During initialization, the DRBG now tries to allocate a handle of the Jitter RNG. If such a Jitter RNG is available during seeding, the DRBG pulls the required entropy/nonce string from get_random_bytes and concatenates it with a string of equal size from the Jitter RNG. That combined string is now the seed for the DRBG. Written differently, the initial seed of the DRBG is now: get_random_bytes(entropy/nonce) || jitterentropy (entropy/nonce) If the Jitter RNG is not available, the DRBG only seeds from get_random_bytes. CC: Andreas Steffen <andreas.steffen@strongswan.org> CC: Theodore Ts'o <tytso@mit.edu> CC: Sandy Harris <sandyinchina@gmail.com> Signed-off-by: Stephan Mueller <smueller@chronox.de> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2015-05-27crypto: drbg - add async seeding operationStephan Mueller
The async seeding operation is triggered during initalization right after the first non-blocking seeding is completed. As required by the asynchronous operation of random.c, a callback function is provided that is triggered by random.c once entropy is available. That callback function performs the actual seeding of the DRBG. CC: Andreas Steffen <andreas.steffen@strongswan.org> CC: Theodore Ts'o <tytso@mit.edu> CC: Sandy Harris <sandyinchina@gmail.com> Signed-off-by: Stephan Mueller <smueller@chronox.de> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2015-05-27crypto: drbg - prepare for async seedingStephan Mueller
In order to prepare for the addition of the asynchronous seeding call, the invocation of seeding the DRBG is moved out into a helper function. In addition, a block of memory is allocated during initialization time that will be used as a scratchpad for obtaining entropy. That scratchpad is used for the initial seeding operation as well as by the asynchronous seeding call. The memory must be zeroized every time the DRBG seeding call succeeds to avoid entropy data lingering in memory. CC: Andreas Steffen <andreas.steffen@strongswan.org> CC: Theodore Ts'o <tytso@mit.edu> CC: Sandy Harris <sandyinchina@gmail.com> Signed-off-by: Stephan Mueller <smueller@chronox.de> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2015-04-22crypto: drbg - Convert to new rng interfaceHerbert Xu
This patch converts the DRBG implementation to the new low-level rng interface. This allows us to get rid of struct drbg_gen by using the new RNG API instead. Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au> Acked-by: Stephan Mueller <smueller@chronox.de>
2015-04-21crypto: drbg - replace spinlock with mutexStephan Mueller
The creation of a shadow copy is intended to only hold a short term lock. But the drawback is that parallel users have a very similar DRBG state which only differs by a high-resolution time stamp. The DRBG will now hold a long term lock. Therefore, the lock is changed to a mutex which implies that the DRBG can only be used in process context. The lock now guards the instantiation as well as the entire DRBG generation operation. Therefore, multiple callers are fully serialized when generating a random number. As the locking is changed to use a long-term lock to avoid such similar DRBG states, the entire creation and maintenance of a shadow copy can be removed. Signed-off-by: Stephan Mueller <smueller@chronox.de> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2014-08-26crypto: drbg - fix maximum value checks on 32 bit systemsStephan Mueller
The maximum values for additional input string or generated blocks is larger than 1<<32. To ensure a sensible value on 32 bit systems, return SIZE_MAX on 32 bit systems. This value is lower than the maximum allowed values defined in SP800-90A. The standard allow lower maximum values, but not larger values. SIZE_MAX - 1 is used for drbg_max_addtl to allow drbg_healthcheck_sanity to check the enforcement of the variable without wrapping. Reported-by: Stephen Rothwell <sfr@canb.auug.org.au> Reported-by: kbuild test robot <fengguang.wu@intel.com> Signed-off-by: Stephan Mueller <smueller@chronox.de> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2014-08-25crypto: drbg - remove configuration of fixed valuesStephan Mueller
SP800-90A mandates several hard-coded values. The old drbg_cores allows the setting of these values per DRBG implementation. However, due to the hard requirement of SP800-90A, these values are now returned globally for each DRBG. The ability to set such values per DRBG is therefore removed. Signed-off-by: Stephan Mueller <smueller@chronox.de> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2014-07-08crypto: drbg - Mix a time stamp into DRBG stateStephan Mueller
The current locking approach of the DRBG tries to keep the protected code paths very minimal. It is therefore possible that two threads query one DRBG instance at the same time. When thread A requests random numbers, a shadow copy of the DRBG state is created upon which the request for A is processed. After finishing the state for A's request is merged back into the DRBG state. If now thread B requests random numbers from the same DRBG after the request for thread A is received, but before A's shadow state is merged back, the random numbers for B will be identical to the ones for A. Please note that the time window is very small for this scenario. To prevent that there is even a theoretical chance for thread A and B having the same DRBG state, the current time stamp is provided as additional information string for each new request. The addition of the time stamp as additional information string implies that now all generate functions must be capable to process a linked list with additional information strings instead of a scalar. CC: Rafael Aquini <aquini@redhat.com> Signed-off-by: Stephan Mueller <smueller@chronox.de> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2014-07-04crypto: drbg - use of kernel linked listStephan Mueller
The DRBG-style linked list to manage input data that is fed into the cipher invocations is replaced with the kernel linked list implementation. The change is transparent to users of the interfaces offered by the DRBG. Therefore, no changes to the testmgr code is needed. Reported-by: kbuild test robot <fengguang.wu@intel.com> Signed-off-by: Stephan Mueller <smueller@chronox.de> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2014-06-20crypto: drbg - header file for DRBGStephan Mueller
The header file includes the definition of: * DRBG data structures with - struct drbg_state as main structure - struct drbg_core referencing the backend ciphers - struct drbg_state_ops callbach handlers for specific code supporting the Hash, HMAC, CTR DRBG implementations - struct drbg_conc defining a linked list for input data - struct drbg_test_data holding the test "entropy" data for CAVS testing and testmgr.c - struct drbg_gen allowing test data, additional information string and personalization string data to be funneled through the kernel crypto API -- the DRBG requires additional parameters when invoking the reset and random number generation requests than intended by the kernel crypto API * wrapper function to the kernel crypto API functions using struct drbg_gen to pass through all data needed for DRBG * wrapper functions to kernel crypto API functions usable for testing code to inject test_data into the DRBG as needed by CAVS testing and testmgr.c. * DRBG flags required for the operation of the DRBG and for selecting the particular DRBG type and backend cipher * getter functions for data from struct drbg_core Signed-off-by: Stephan Mueller <smueller@chronox.de> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>