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authorLinus Torvalds <torvalds@linux-foundation.org>2022-01-11 10:21:35 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2022-01-11 10:21:35 -0800
commit5c947d0dbae8038ec1c8b538891f6475350542ee (patch)
treebd81b14e0cd2212bf885b835d9da39db51a33d43 /crypto/jitterentropy.c
parentMerge tag 'docs-5.17' of git://git.lwn.net/linux (diff)
parentcrypto: af_alg - rewrite NULL pointer check (diff)
downloadlinux-dev-5c947d0dbae8038ec1c8b538891f6475350542ee.tar.xz
linux-dev-5c947d0dbae8038ec1c8b538891f6475350542ee.zip
Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6
Pull crypto updates from Herbert Xu: "Algorithms: - Drop alignment requirement for data in aesni - Use synchronous seeding from the /dev/random in DRBG - Reseed nopr DRBGs every 5 minutes from /dev/random - Add KDF algorithms currently used by security/DH - Fix lack of entropy on some AMD CPUs with jitter RNG Drivers: - Add support for the D1 variant in sun8i-ce - Add SEV_INIT_EX support in ccp - PFVF support for GEN4 host driver in qat - Compression support for GEN4 devices in qat - Add cn10k random number generator support" * 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6: (145 commits) crypto: af_alg - rewrite NULL pointer check lib/mpi: Add the return value check of kcalloc() crypto: qat - fix definition of ring reset results crypto: hisilicon - cleanup warning in qm_get_qos_value() crypto: kdf - select SHA-256 required for self-test crypto: x86/aesni - don't require alignment of data crypto: ccp - remove unneeded semicolon crypto: stm32/crc32 - Fix kernel BUG triggered in probe() crypto: s390/sha512 - Use macros instead of direct IV numbers crypto: sparc/sha - remove duplicate hash init function crypto: powerpc/sha - remove duplicate hash init function crypto: mips/sha - remove duplicate hash init function crypto: sha256 - remove duplicate generic hash init function crypto: jitter - add oversampling of noise source MAINTAINERS: update SEC2 driver maintainers list crypto: ux500 - Use platform_get_irq() to get the interrupt crypto: hisilicon/qm - disable qm clock-gating crypto: omap-aes - Fix broken pm_runtime_and_get() usage MAINTAINERS: update caam crypto driver maintainers list crypto: octeontx2 - prevent underflow in get_cores_bmap() ...
Diffstat (limited to 'crypto/jitterentropy.c')
-rw-r--r--crypto/jitterentropy.c32
1 files changed, 23 insertions, 9 deletions
diff --git a/crypto/jitterentropy.c b/crypto/jitterentropy.c
index 4dc2261cdeef..93bff3213823 100644
--- a/crypto/jitterentropy.c
+++ b/crypto/jitterentropy.c
@@ -117,6 +117,22 @@ struct rand_data {
#define JENT_EHEALTH 9 /* Health test failed during initialization */
#define JENT_ERCT 10 /* RCT failed during initialization */
+/*
+ * 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).
+ */
+#define JENT_ENTROPY_SAFETY_FACTOR 64
+
+#include <linux/fips.h>
#include "jitterentropy.h"
/***************************************************************************
@@ -265,7 +281,6 @@ static int jent_stuck(struct rand_data *ec, __u64 current_delta)
{
__u64 delta2 = jent_delta(ec->last_delta, current_delta);
__u64 delta3 = jent_delta(ec->last_delta2, delta2);
- unsigned int delta_masked = current_delta & JENT_APT_WORD_MASK;
ec->last_delta = current_delta;
ec->last_delta2 = delta2;
@@ -274,7 +289,7 @@ static int jent_stuck(struct rand_data *ec, __u64 current_delta)
* Insert the result of the comparison of two back-to-back time
* deltas.
*/
- jent_apt_insert(ec, delta_masked);
+ jent_apt_insert(ec, current_delta);
if (!current_delta || !delta2 || !delta3) {
/* RCT with a stuck bit */
@@ -299,10 +314,6 @@ static int jent_stuck(struct rand_data *ec, __u64 current_delta)
*/
static int jent_health_failure(struct rand_data *ec)
{
- /* Test is only enabled in FIPS mode */
- if (!jent_fips_enabled())
- return 0;
-
return ec->health_failure;
}
@@ -547,12 +558,15 @@ static int jent_measure_jitter(struct rand_data *ec)
*/
static void jent_gen_entropy(struct rand_data *ec)
{
- unsigned int k = 0;
+ unsigned int k = 0, safety_factor = 0;
+
+ if (fips_enabled)
+ safety_factor = JENT_ENTROPY_SAFETY_FACTOR;
/* priming of the ->prev_time value */
jent_measure_jitter(ec);
- while (1) {
+ while (!jent_health_failure(ec)) {
/* If a stuck measurement is received, repeat measurement */
if (jent_measure_jitter(ec))
continue;
@@ -561,7 +575,7 @@ static void jent_gen_entropy(struct rand_data *ec)
* We multiply the loop value with ->osr to obtain the
* oversampling rate requested by the caller
*/
- if (++k >= (DATA_SIZE_BITS * ec->osr))
+ if (++k >= ((DATA_SIZE_BITS + safety_factor) * ec->osr))
break;
}
}