On Thu, Dec 25, 2014 at 11:00:06PM +0100, Stephan Mueller wrote: > This patch adds the random number generator support for AF_ALG. > > A random number generator's purpose is to generate data without > requiring the caller to provide any data. Therefore, the AF_ALG > interface handler for RNGs only implements a callback handler for > recvmsg. > > The following parameters provided with a recvmsg are processed by the > RNG callback handler: > > * sock - to resolve the RNG context data structure accessing the > RNG instance private to the socket > > * len - this parameter allows userspace callers to specify how > many random bytes the RNG shall produce and return. As the > kernel context for the RNG allocates a buffer of 128 bytes to > store random numbers before copying them to userspace, the len > parameter is checked that it is not larger than 128. If a > caller wants more random numbers, a new request for recvmsg > shall be made. > > The size of 128 bytes is chose because of the following considerations: > > * to increase the memory footprint of the kernel too much (note, > that would be 128 bytes per open socket) > > * 128 is divisible by any typical cryptographic block size an > RNG may have > > * A request for random numbers typically only shall supply small > amount of data like for keys or IVs that should only require > one invocation of the recvmsg function. > > Note, during instantiation of the RNG, the code checks whether the RNG > implementation requires seeding. If so, the RNG is seeded with output > from get_random_bytes. > > A fully working example using all aspects of the RNG interface is > provided at http://www.chronox.de/libkcapi.html > > Signed-off-by: Stephan Mueller <smueller@xxxxxxxxxx> Patch applied. -- Email: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx> Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
