talos-op-linux/include/crypto/drbg.h, branch v4.2.2

crypto: drbg - reseed often if seedsource is degraded

2015-06-10T11:14:05+00:00

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 Signed-off-by: Herbert Xu

crypto: drbg - Use callback API for random readiness

2015-06-10T11:14:01+00:00

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 Signed-off-by: Herbert Xu

crypto: drbg - use Jitter RNG to obtain seed

2015-05-27T09:51:53+00:00

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 CC: Theodore Ts'o CC: Sandy Harris Signed-off-by: Stephan Mueller Signed-off-by: Herbert Xu

crypto: drbg - add async seeding operation

2015-05-27T09:51:53+00:00

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 CC: Theodore Ts'o CC: Sandy Harris Signed-off-by: Stephan Mueller Signed-off-by: Herbert Xu

crypto: drbg - prepare for async seeding

2015-05-27T09:51:53+00:00

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 CC: Theodore Ts'o CC: Sandy Harris Signed-off-by: Stephan Mueller Signed-off-by: Herbert Xu

crypto: drbg - Convert to new rng interface

2015-04-22T01:30:17+00:00

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 Acked-by: Stephan Mueller

crypto: drbg - replace spinlock with mutex

2015-04-21T01:14:45+00:00

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 Signed-off-by: Herbert Xu

crypto: drbg - fix maximum value checks on 32 bit systems

2014-08-26T08:58:05+00:00

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 Reported-by: kbuild test robot Signed-off-by: Stephan Mueller Signed-off-by: Herbert Xu

crypto: drbg - remove configuration of fixed values

2014-08-25T12:34:12+00:00

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 Signed-off-by: Herbert Xu

crypto: drbg - Mix a time stamp into DRBG state

2014-07-08T13:18:25+00:00

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 Signed-off-by: Stephan Mueller Signed-off-by: Herbert Xu