1 Commits

Author	SHA1	Message	Date
Stephan Mueller	5afdfd22e6	crypto: algif_rng - add random number generator support ... 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@chronox.de> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>	2014-12-29 21:37:59 +11:00