kernel.git/crypto/jitterentropy.c, branch linux-5.18.y

crypto: jitter - add oversampling of noise source

2021-12-31T07:10:54Z

The output n bits can receive more than n bits of min entropy, of course, but the fixed output of the conditioning function can only asymptotically approach the output size bits of min entropy, not attain that bound. Random maps will tend to have output collisions, which reduces the creditable output entropy (that is what SP 800-90B Section 3.1.5.1.2 attempts to bound). The value "64" is justified in Appendix A.4 of the current 90C draft, and aligns with NIST's in "epsilon" definition in this document, which is that a string can be considered "full entropy" if you can bound the min entropy in each bit of output to at least 1-epsilon, where epsilon is required to be <= 2^(-32). Note, this patch causes the Jitter RNG to cut its performance in half in FIPS mode because the conditioning function of the LFSR produces 64 bits of entropy in one block. The oversampling requires that additionally 64 bits of entropy are sampled from the noise source. If the conditioner is changed, such as using SHA-256, the impact of the oversampling is only one fourth, because for the 256 bit block of the conditioner, only 64 additional bits from the noise source must be sampled. This patch is derived from the user space jitterentropy-library. Signed-off-by: Stephan Mueller Reviewed-by: Simo Sorce Signed-off-by: Herbert Xu

crypto: jitter - quit sample collection loop upon RCT failure

2021-12-11T05:48:06Z

The jitterentropy collection loop in jent_gen_entropy() can in principle run indefinitely without making any progress if it only receives stuck measurements as determined by jent_stuck(). After 31 consecutive stuck samples, the Repetition Count Test (RCT) would fail anyway and the jitterentropy RNG instances moved into ->health_failure == 1 state. jent_gen_entropy()'s caller, jent_read_entropy() would then check for this ->health_failure condition and return an error if found set. It follows that there's absolutely no point in continuing the collection loop in jent_gen_entropy() once the RCT has failed. Make the jitterentropy collection loop more robust by terminating it upon jent_health_failure() so that it won't continue to run indefinitely without making any progress. Signed-off-by: Nicolai Stange Reviewed-by: Stephan Mueller Signed-off-by: Herbert Xu

crypto: jitter - don't limit ->health_failure check to FIPS mode

2021-12-11T05:48:06Z

The jitterentropy's Repetition Count Test (RCT) as well as the Adaptive Proportion Test (APT) are run unconditionally on any collected samples. However, their result, i.e. ->health_failure, will only get checked if fips_enabled is set, c.f. the jent_health_failure() wrapper. I would argue that a RCT or APT failure indicates that something's seriously off and that this should always be reported as an error, independently of whether FIPS mode is enabled or not: it should be up to callers whether or not and how to handle jitterentropy failures. Make jent_health_failure() to unconditionally return ->health_failure, independent of whether fips_enabled is set. Note that fips_enabled isn't accessed from the jitterentropy code anymore now. Remove the linux/fips.h include as well as the jent_fips_enabled() wrapper. Signed-off-by: Nicolai Stange Reviewed-by: Stephan Mueller Signed-off-by: Herbert Xu

crypto: jitter - consider 32 LSB for APT

2021-11-26T05:25:18Z

The APT compares the current time stamp with a pre-set value. The current code only considered the 4 LSB only. Yet, after reviews by mathematicians of the user space Jitter RNG version >= 3.1.0, it was concluded that the APT can be calculated on the 32 LSB of the time delta. Thi change is applied to the kernel. This fixes a bug where an AMD EPYC fails this test as its RDTSC value contains zeros in the LSB. The most appropriate fix would have been to apply a GCD calculation and divide the time stamp by the GCD. Yet, this is a significant code change that will be considered for a future update. Note, tests showed that constantly the GCD always was 32 on these systems, i.e. the 5 LSB were always zero (thus failing the APT since it only considered the 4 LSB for its calculation). Signed-off-by: Stephan Mueller Signed-off-by: Herbert Xu

crypto: jitter - drop kernel-doc notation

2021-09-17T03:05:09Z

Drop "begin kernel-doc (/**)" entries in jitterentropy.c since they are not in kernel-doc format and they cause many complaints (warnings) from scripts/kernel-doc. Signed-off-by: Randy Dunlap Cc: Stephan Mueller Cc: Herbert Xu Cc: "David S. Miller" Cc: linux-crypto@vger.kernel.org Signed-off-by: Herbert Xu

crypto: jitterentropy - Put constants on the right side of the expression

2021-03-26T09:02:35Z

This patch fixes the following checkpatch.pl warnings: crypto/jitterentropy.c:600: WARNING: Comparisons should place the constant on the right side of the test crypto/jitterentropy.c:681: WARNING: Comparisons should place the constant on the right side of the test crypto/jitterentropy.c:772: WARNING: Comparisons should place the constant on the right side of the test crypto/jitterentropy.c:829: WARNING: Comparisons should place the constant on the right side of the test Signed-off-by: Milan Djurovic Reviewed-by: Stephan Mueller Signed-off-by: Herbert Xu

crypto: Replace HTTP links with HTTPS ones

2020-07-23T07:34:20Z

Rationale: Reduces attack surface on kernel devs opening the links for MITM as HTTPS traffic is much harder to manipulate. Deterministic algorithm: For each file: If not .svg: For each line: If doesn't contain `\bxmlns\b`: For each link, `\bhttp://[^# \t\r\n]*(?:\w|/)`: If neither `\bgnu\.org/license`, nor `\bmozilla\.org/MPL\b`: If both the HTTP and HTTPS versions return 200 OK and serve the same content: Replace HTTP with HTTPS. Signed-off-by: Alexander A. Klimov Signed-off-by: Herbert Xu

crypto: jitter - SP800-90B compliance

2020-04-24T07:42:17Z

SP800-90B specifies various requirements for the noise source(s) that may seed any DRNG including SP800-90A DRBGs. In November 2020, SP800-90B will be mandated for all noise sources that provide entropy to DRBGs as part of a FIPS 140-[2|3] validation or other evaluation types. Without SP800-90B compliance, a noise source is defined to always deliver zero bits of entropy. This patch ports the SP800-90B compliance from the user space Jitter RNG version 2.2.0. The following changes are applied: - addition of (an enhanced version of) the repetitive count test (RCT) from SP800-90B section 4.4.1 - the enhancement is due to the fact of using the stuck test as input to the RCT. - addition of the adaptive proportion test (APT) from SP800-90B section 4.4.2 - update of the power-on self test to perform a test measurement of 1024 noise samples compliant to SP800-90B section 4.3 - remove of the continuous random number generator test which is replaced by APT and RCT Health test failures due to the SP800-90B operation are only enforced in FIPS mode. If a runtime health test failure is detected, the Jitter RNG is reset. If more than 1024 resets in a row are performed, a permanent error is returned to the caller. Signed-off-by: Stephan Mueller Signed-off-by: Herbert Xu

crypto: jitter - add header to fix buildwarnings

2019-10-18T07:49:40Z

Fix the following build warnings by adding a header for the definitions shared between jitterentropy.c and jitterentropy-kcapi.c. Fixes the following: crypto/jitterentropy.c:445:5: warning: symbol 'jent_read_entropy' was not declared. Should it be static? crypto/jitterentropy.c:475:18: warning: symbol 'jent_entropy_collector_alloc' was not declared. Should it be static? crypto/jitterentropy.c:509:6: warning: symbol 'jent_entropy_collector_free' was not declared. Should it be static? crypto/jitterentropy.c:516:5: warning: symbol 'jent_entropy_init' was not declared. Should it be static? crypto/jitterentropy-kcapi.c:59:6: warning: symbol 'jent_zalloc' was not declared. Should it be static? crypto/jitterentropy-kcapi.c:64:6: warning: symbol 'jent_zfree' was not declared. Should it be static? crypto/jitterentropy-kcapi.c:69:5: warning: symbol 'jent_fips_enabled' was not declared. Should it be static? crypto/jitterentropy-kcapi.c:74:6: warning: symbol 'jent_panic' was not declared. Should it be static? crypto/jitterentropy-kcapi.c:79:6: warning: symbol 'jent_memcpy' was not declared. Should it be static? crypto/jitterentropy-kcapi.c:93:6: warning: symbol 'jent_get_nstime' was not declared. Should it be static? Signed-off-by: Ben Dooks Reviewed-by: Stephan Mueller

crypto: jitter - fix comments

2019-10-04T15:06:18Z

One should not say "ec can be NULL" and then dereference it. One cannot talk about the return value if the function returns void. Signed-off-by: Alexander E. Patrakov Signed-off-by: Herbert Xu