Re: Question - seeding the hw pseudo random number generator
Am Donnerstag, 23. März 2017, 10:44:06 CEST schrieb Herbert Xu: Hi Herbert, > On Thu, Mar 23, 2017 at 09:23:07AM +0100, Corentin Labbe wrote: > > Problem with this conversion, a huge regression for user space. > > Using hwrng is simple as cat /dev/hwrng. > > Using algif_rng via AF_ALG is ... unusable for the moment. > > Perhaps creating an user space tool (prng-tool which provide a cat > > /dev/hwrng replacement) is mandatory before any convertion. > Stephan may have a tool to do this. Stephan? I added the application kcapi-rng to HEAD of [1]. Create the application with the --enable-kcapi-rngapp configure option. $ kcapi-rng Kernel Crypto API Random Number Gatherer Kernel Crypto API interface library version: libkcapi pre-release 0.13.1 Reported numeric version number 130080 Usage: -b --bytes Number of bytes to generate (required option) -h --help This help information --versionPrint version -v --verboseVerbose logging, multiple options increase verbosity Data provided at stdin is used to seed the DRNG [1] https://github.com/smuellerDD/libkcapi/ Ciao Stephan
Re: Question - seeding the hw pseudo random number generator
Am Donnerstag, 23. März 2017, 10:44:06 CET schrieb Herbert Xu: Hi Herbert, > On Thu, Mar 23, 2017 at 09:23:07AM +0100, Corentin Labbe wrote: > > Problem with this conversion, a huge regression for user space. > > Using hwrng is simple as cat /dev/hwrng. > > Using algif_rng via AF_ALG is ... unusable for the moment. > > Perhaps creating an user space tool (prng-tool which provide a cat > > /dev/hwrng replacement) is mandatory before any convertion. > Stephan may have a tool to do this. Stephan? Creating such tool is more or less trivial. It simply requires the invocation of kcapi_rng_init, kcapi_rng_seed, kcapi_rng_generate and eventually kcapi_rng_destroy from [1]. I can write such a tool if requested. I see one change we need to add to algif_rng.c: currently the caller must provide the specific name of the DRNG to be used. With such a tool, the caller does not care about the type of DRNG. Thus, rng_bind should be changed such that if name is NULL, it should use crypto_get_default_rng(). This would alleviate the caller from selecting "the right" DRNG. [1] http://www.chronox.de/libkcapi.html Ciao Stephan
Re: Question - seeding the hw pseudo random number generator
Am Donnerstag, 23. März 2017, 09:03:23 CET schrieb Harald Freudenberger: Hi Harald, > I'll have a look on it. Currently the s390/crypto/prng seeds itself with > an algorithm based on the jitter of the very fine granular hardware > clock of a s390 machine. There were some thoughts and measurements > by an mathematician which let to this algorithm. It takes a page and simply writes 512 times the high-res time stamp using get_tod_clock_fast into it. Effectively it uses the same fundamental noise source as the jitterentropy. (A couple of months ago I had to perform an SP800-90B assessment on exactly that code path. :-) ) > However, long-term > the s390 platform will provide some kind of true hardware random number > generator and the idea is to use this for seeding the prng. The question is just that it provides a device file nobody else provides. And the question is whether to consolidate it. If it is a DRNG, the discussion is about consolidating it behind AF_ALG. If it is an RNG with its own noise source (i.e. it provides entropic data by itself), it should rather be placed into drivers/char/hw_random and use the hw-random framework. This framework will also ensure that it may seed the /dev/random device kernel-internally. Ciao Stephan
Re: Question - seeding the hw pseudo random number generator
On Thu, Mar 23, 2017 at 09:23:07AM +0100, Corentin Labbe wrote: > > Problem with this conversion, a huge regression for user space. > Using hwrng is simple as cat /dev/hwrng. > Using algif_rng via AF_ALG is ... unusable for the moment. > Perhaps creating an user space tool (prng-tool which provide a cat /dev/hwrng > replacement) is mandatory before any convertion. Stephan may have a tool to do this. Stephan? Thanks, -- Email: Herbert XuHome Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
Re: Question - seeding the hw pseudo random number generator
On Mon, Mar 20, 2017 at 09:28:58PM +0800, Herbert Xu wrote: > On Mon, Mar 20, 2017 at 12:19:32PM +0530, PrasannaKumar Muralidharan wrote: > > > > AF_ALG interface for rng does have seeding support. I think hw_random > > does not provide seeding support intentionally as I understand that > > True RNG need not require seeding (please correct me if I am wrong). > > Yes. We should be converting PRNGs in hwrng over to algif_rng. > Problem with this conversion, a huge regression for user space. Using hwrng is simple as cat /dev/hwrng. Using algif_rng via AF_ALG is ... unusable for the moment. Perhaps creating an user space tool (prng-tool which provide a cat /dev/hwrng replacement) is mandatory before any convertion. Regards
Re: Question - seeding the hw pseudo random number generator
On 03/20/2017 02:39 PM, Stephan Müller wrote: > Am Montag, 20. März 2017, 14:28:58 CET schrieb Herbert Xu: > > Hi Herbert, > >> On Mon, Mar 20, 2017 at 12:19:32PM +0530, PrasannaKumar Muralidharan wrote: >>> AF_ALG interface for rng does have seeding support. I think hw_random >>> does not provide seeding support intentionally as I understand that >>> True RNG need not require seeding (please correct me if I am wrong). >> Yes. We should be converting PRNGs in hwrng over to algif_rng. > IMHO this not only applies to the PRNGs in drivers/crypto (which should > simply > register with crypto_register_rngs) but also to ~/hacking/sources/linux/arch/ > s390/crypto/prng.c which exports a /dev/prandom file. > > For the seeding, it may make sense to follow the example given with crypto/ > drbg.c using the add_random_ready_callback function. > > Ciao > Stephan > I'll have a look on it. Currently the s390/crypto/prng seeds itself with an algorithm based on the jitter of the very fine granular hardware clock of a s390 machine. There were some thoughts and measurements by an mathematician which let to this algorithm. However, long-term the s390 platform will provide some kind of true hardware random number generator and the idea is to use this for seeding the prng. regards Harald Freudenberger
Re: Question - seeding the hw pseudo random number generator
On Mon, Mar 20, 2017 at 09:28:58PM +0800, Herbert Xu wrote: > On Mon, Mar 20, 2017 at 12:19:32PM +0530, PrasannaKumar Muralidharan wrote: > > > > AF_ALG interface for rng does have seeding support. I think hw_random > > does not provide seeding support intentionally as I understand that > > True RNG need not require seeding (please correct me if I am wrong). > > Yes. We should be converting PRNGs in hwrng over to algif_rng. The actual hardware block can be seeded from true RNG (taking data from thermal noise) so the solutions (if I understand correctly) for exynos-rng might be: 1. Seed from internal TRNG making it a proper hwrandom device, 2. Convert to AF_ALG and seed with data from user-space through that interface. Thanks for explanation, I'll queue it to my tasks list. Best regards, Krzysztof
Re: Question - seeding the hw pseudo random number generator
Am Montag, 20. März 2017, 14:28:58 CET schrieb Herbert Xu: Hi Herbert, > On Mon, Mar 20, 2017 at 12:19:32PM +0530, PrasannaKumar Muralidharan wrote: > > AF_ALG interface for rng does have seeding support. I think hw_random > > does not provide seeding support intentionally as I understand that > > True RNG need not require seeding (please correct me if I am wrong). > > Yes. We should be converting PRNGs in hwrng over to algif_rng. IMHO this not only applies to the PRNGs in drivers/crypto (which should simply register with crypto_register_rngs) but also to ~/hacking/sources/linux/arch/ s390/crypto/prng.c which exports a /dev/prandom file. For the seeding, it may make sense to follow the example given with crypto/ drbg.c using the add_random_ready_callback function. Ciao Stephan
Re: Question - seeding the hw pseudo random number generator
On Mon, Mar 20, 2017 at 12:19:32PM +0530, PrasannaKumar Muralidharan wrote: > > AF_ALG interface for rng does have seeding support. I think hw_random > does not provide seeding support intentionally as I understand that > True RNG need not require seeding (please correct me if I am wrong). Yes. We should be converting PRNGs in hwrng over to algif_rng. Thanks, -- Email: Herbert XuHome Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
Re: Question - seeding the hw pseudo random number generator
> I looked at Exynos Pseudo Random Nubmer Generator driver > (drivers/char/hw_random/exynos-rng.c) and noticed that it always seeds > the device with jiffies. Then I looked at few other drivers and found > that they do not seed themself (or at least I couldn't find this). HW random interface is meant for true RNG, not pseudo RNG. Actually PRNGs should use AF_ALG interface. I think exynos-rng.c should follow the same. > I think the hw_random API does not provide generic infrastructure for > seeding. > > What is the preferred approach for seeding a PRNG device? Use jiffies or > a fixed value? > > Or maybe the interface should be abandoned in favor of crypto API? AF_ALG interface for rng does have seeding support. I think hw_random does not provide seeding support intentionally as I understand that True RNG need not require seeding (please correct me if I am wrong). Regards, PrasannaKumar