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char/lrng: add interface for gathering of raw entropy
The test interface allows a privileged process to capture the raw unconditioned noise that is collected by the LRNG for statistical analysis. Such testing allows the analysis how much entropy the interrupt noise source provides on a given platform. Extracted noise data is not used to seed the LRNG. This is a test interface and not appropriate for production systems. Yet, the interface is considered to be sufficiently secured for production systems. Access to the data is given through the lrng_raw debugfs file. The data buffer should be multiples of sizeof(u32) to fill the entire buffer. Using the option lrng_testing.boot_test=1 the raw noise of the first 1000 entropy events since boot can be sampled. This test interface allows generating the data required for analysis whether the LRNG is in compliance with SP800-90B sections 3.1.3 and 3.1.4. In addition, the test interface allows gathering of the concatenated raw entropy data to verify that the concatenation works appropriately. This includes sampling of the following raw data: * high-resolution time stamp * Jiffies * IRQ number * IRQ flags * return instruction pointer * interrupt register state * array logic batching the high-resolution time stamp * enabling the runtime configuration of entropy source entropy rates Also, a testing interface to support ACVT of the hash implementation is provided. The reason why only hash testing is supported (as opposed to also provide testing for the DRNG) is the fact that the LRNG software hash implementation contains glue code that may warrant testing in addition to the testing of the software ciphers via the kernel crypto API. Also, for testing the CTR-DRBG, the underlying AES implementation would need to be tested. However, such AES test interface cannot be provided by the LRNG as it has no means to access the AES operation. Finally, the execution duration for processing a time stamp can be obtained with the LRNG raw entropy interface. If a test interface is not compiled, its code is a noop which has no impact on the performance. CC: Torsten Duwe <duwe@lst.de> CC: "Eric W. Biederman" <ebiederm@xmission.com> CC: "Alexander E. Patrakov" <patrakov@gmail.com> CC: "Ahmed S. Darwish" <darwish.07@gmail.com> CC: "Theodore Y. Ts'o" <tytso@mit.edu> CC: Willy Tarreau <w@1wt.eu> CC: Matthew Garrett <mjg59@srcf.ucam.org> CC: Vito Caputo <vcaputo@pengaru.com> CC: Andreas Dilger <adilger.kernel@dilger.ca> CC: Jan Kara <jack@suse.cz> CC: Ray Strode <rstrode@redhat.com> CC: William Jon McCann <mccann@jhu.edu> CC: zhangjs <zachary@baishancloud.com> CC: Andy Lutomirski <luto@kernel.org> CC: Florian Weimer <fweimer@redhat.com> CC: Lennart Poettering <mzxreary@0pointer.de> CC: Nicolai Stange <nstange@suse.de> CC: Alexander Lobakin <alobakin@mailbox.org> Reviewed-by: Roman Drahtmueller <draht@schaltsekun.de> Tested-by: Marcelo Henrique Cerri <marcelo.cerri@canonical.com> Tested-by: Neil Horman <nhorman@redhat.com> Signed-off-by: Stephan Mueller <smueller@chronox.de>
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