diff options
| -rw-r--r-- | crypto/jitterentropy-kcapi.c | 4 | ||||
| -rw-r--r-- | crypto/jitterentropy.c | 233 | ||||
| -rw-r--r-- | crypto/jitterentropy.h | 3 |
3 files changed, 123 insertions, 117 deletions
diff --git a/crypto/jitterentropy-kcapi.c b/crypto/jitterentropy-kcapi.c index 7d1463a1562a..1de730f94683 100644 --- a/crypto/jitterentropy-kcapi.c +++ b/crypto/jitterentropy-kcapi.c @@ -245,7 +245,7 @@ static int jent_kcapi_init(struct crypto_tfm *tfm) crypto_shash_init(sdesc); rng->sdesc = sdesc; - rng->entropy_collector = jent_entropy_collector_alloc(1, 0, sdesc); + rng->entropy_collector = jent_entropy_collector_alloc(0, 0, sdesc); if (!rng->entropy_collector) { ret = -ENOMEM; goto err; @@ -334,7 +334,7 @@ static int __init jent_mod_init(void) desc->tfm = tfm; crypto_shash_init(desc); - ret = jent_entropy_init(desc); + ret = jent_entropy_init(0, 0, desc); shash_desc_zero(desc); crypto_free_shash(tfm); if (ret) { diff --git a/crypto/jitterentropy.c b/crypto/jitterentropy.c index fe9c233ec769..1b99ffaa8c34 100644 --- a/crypto/jitterentropy.c +++ b/crypto/jitterentropy.c @@ -72,6 +72,8 @@ struct rand_data { __u64 prev_time; /* SENSITIVE Previous time stamp */ __u64 last_delta; /* SENSITIVE stuck test */ __s64 last_delta2; /* SENSITIVE stuck test */ + + unsigned int flags; /* Flags used to initialize */ unsigned int osr; /* Oversample rate */ #define JENT_MEMORY_BLOCKS 64 #define JENT_MEMORY_BLOCKSIZE 32 @@ -88,16 +90,9 @@ struct rand_data { /* Repetition Count Test */ unsigned int rct_count; /* Number of stuck values */ - /* Intermittent health test failure threshold of 2^-30 */ - /* From an SP800-90B perspective, this RCT cutoff value is equal to 31. */ - /* However, our RCT implementation starts at 1, so we subtract 1 here. */ -#define JENT_RCT_CUTOFF (31 - 1) /* Taken from SP800-90B sec 4.4.1 */ -#define JENT_APT_CUTOFF 325 /* Taken from SP800-90B sec 4.4.2 */ - /* Permanent health test failure threshold of 2^-60 */ - /* From an SP800-90B perspective, this RCT cutoff value is equal to 61. */ - /* However, our RCT implementation starts at 1, so we subtract 1 here. */ -#define JENT_RCT_CUTOFF_PERMANENT (61 - 1) -#define JENT_APT_CUTOFF_PERMANENT 355 + /* Adaptive Proportion Test cutoff values */ + unsigned int apt_cutoff; /* Intermittent health test failure */ + unsigned int apt_cutoff_permanent; /* Permanent health test failure */ #define JENT_APT_WINDOW_SIZE 512 /* Data window size */ /* LSB of time stamp to process */ #define JENT_APT_LSB 16 @@ -122,6 +117,9 @@ struct rand_data { * zero). */ #define JENT_ESTUCK 8 /* Too many stuck results during init. */ #define JENT_EHEALTH 9 /* Health test failed during initialization */ +#define JENT_ERCT 10 /* RCT failed during initialization */ +#define JENT_EHASH 11 /* Hash self test failed */ +#define JENT_EMEM 12 /* Can't allocate memory for initialization */ /* * The output n bits can receive more than n bits of min entropy, of course, @@ -148,6 +146,48 @@ struct rand_data { ***************************************************************************/ /* + * See the SP 800-90B comment #10b for the corrected cutoff for the SP 800-90B + * APT. + * http://www.untruth.org/~josh/sp80090b/UL%20SP800-90B-final%20comments%20v1.9%2020191212.pdf + * In in the syntax of R, this is C = 2 + qbinom(1 − 2^(−30), 511, 2^(-1/osr)). + * (The original formula wasn't correct because the first symbol must + * necessarily have been observed, so there is no chance of observing 0 of these + * symbols.) + * + * For the alpha < 2^-53, R cannot be used as it uses a float data type without + * arbitrary precision. A SageMath script is used to calculate those cutoff + * values. + * + * For any value above 14, this yields the maximal allowable value of 512 + * (by FIPS 140-2 IG 7.19 Resolution # 16, we cannot choose a cutoff value that + * renders the test unable to fail). + */ +static const unsigned int jent_apt_cutoff_lookup[15] = { + 325, 422, 459, 477, 488, 494, 499, 502, + 505, 507, 508, 509, 510, 511, 512 }; +static const unsigned int jent_apt_cutoff_permanent_lookup[15] = { + 355, 447, 479, 494, 502, 507, 510, 512, + 512, 512, 512, 512, 512, 512, 512 }; +#define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0])) + +static void jent_apt_init(struct rand_data *ec, unsigned int osr) +{ + /* + * Establish the apt_cutoff based on the presumed entropy rate of + * 1/osr. + */ + if (osr >= ARRAY_SIZE(jent_apt_cutoff_lookup)) { + ec->apt_cutoff = jent_apt_cutoff_lookup[ + ARRAY_SIZE(jent_apt_cutoff_lookup) - 1]; + ec->apt_cutoff_permanent = jent_apt_cutoff_permanent_lookup[ + ARRAY_SIZE(jent_apt_cutoff_permanent_lookup) - 1]; + } else { + ec->apt_cutoff = jent_apt_cutoff_lookup[osr - 1]; + ec->apt_cutoff_permanent = + jent_apt_cutoff_permanent_lookup[osr - 1]; + } +} +/* * Reset the APT counter * * @ec [in] Reference to entropy collector @@ -187,12 +227,12 @@ static void jent_apt_insert(struct rand_data *ec, unsigned int delta_masked) /* APT health test failure detection */ static int jent_apt_permanent_failure(struct rand_data *ec) { - return (ec->apt_count >= JENT_APT_CUTOFF_PERMANENT) ? 1 : 0; + return (ec->apt_count >= ec->apt_cutoff_permanent) ? 1 : 0; } static int jent_apt_failure(struct rand_data *ec) { - return (ec->apt_count >= JENT_APT_CUTOFF) ? 1 : 0; + return (ec->apt_count >= ec->apt_cutoff) ? 1 : 0; } /*************************************************************************** @@ -275,15 +315,28 @@ static int jent_stuck(struct rand_data *ec, __u64 current_delta) return 0; } -/* RCT health test failure detection */ +/* + * The cutoff value is based on the following consideration: + * alpha = 2^-30 or 2^-60 as recommended in SP800-90B. + * In addition, we require an entropy value H of 1/osr as this is the minimum + * entropy required to provide full entropy. + * Note, we collect (DATA_SIZE_BITS + ENTROPY_SAFETY_FACTOR)*osr deltas for + * inserting them into the entropy pool which should then have (close to) + * DATA_SIZE_BITS bits of entropy in the conditioned output. + * + * Note, ec->rct_count (which equals to value B in the pseudo code of SP800-90B + * section 4.4.1) starts with zero. Hence we need to subtract one from the + * cutoff value as calculated following SP800-90B. Thus + * C = ceil(-log_2(alpha)/H) = 30*osr or 60*osr. + */ static int jent_rct_permanent_failure(struct rand_data *ec) { - return (ec->rct_count >= JENT_RCT_CUTOFF_PERMANENT) ? 1 : 0; + return (ec->rct_count >= (60 * ec->osr)) ? 1 : 0; } static int jent_rct_failure(struct rand_data *ec) { - return (ec->rct_count >= JENT_RCT_CUTOFF) ? 1 : 0; + return (ec->rct_count >= (30 * ec->osr)) ? 1 : 0; } /* Report of health test failures */ @@ -448,7 +501,7 @@ static void jent_memaccess(struct rand_data *ec, __u64 loop_cnt) * * @return result of stuck test */ -static int jent_measure_jitter(struct rand_data *ec) +static int jent_measure_jitter(struct rand_data *ec, __u64 *ret_current_delta) { __u64 time = 0; __u64 current_delta = 0; @@ -472,6 +525,10 @@ static int jent_measure_jitter(struct rand_data *ec) if (jent_condition_data(ec, current_delta, stuck)) stuck = 1; + /* return the raw entropy value */ + if (ret_current_delta) + *ret_current_delta = current_delta; + return stuck; } @@ -489,11 +546,11 @@ static void jent_gen_entropy(struct rand_data *ec) safety_factor = JENT_ENTROPY_SAFETY_FACTOR; /* priming of the ->prev_time value */ - jent_measure_jitter(ec); + jent_measure_jitter(ec, NULL); while (!jent_health_failure(ec)) { /* If a stuck measurement is received, repeat measurement */ - if (jent_measure_jitter(ec)) + if (jent_measure_jitter(ec, NULL)) continue; /* @@ -554,7 +611,8 @@ int jent_read_entropy(struct rand_data *ec, unsigned char *data, * Perform startup health tests and return permanent * error if it fails. */ - if (jent_entropy_init(ec->hash_state)) + if (jent_entropy_init(ec->osr, ec->flags, + ec->hash_state)) return -3; return -2; @@ -604,11 +662,15 @@ struct rand_data *jent_entropy_collector_alloc(unsigned int osr, /* verify and set the oversampling rate */ if (osr == 0) - osr = 1; /* minimum sampling rate is 1 */ + osr = 1; /* H_submitter = 1 / osr */ entropy_collector->osr = osr; + entropy_collector->flags = flags; entropy_collector->hash_state = hash_state; + /* Initialize the APT */ + jent_apt_init(entropy_collector, osr); + /* fill the data pad with non-zero values */ jent_gen_entropy(entropy_collector); @@ -622,20 +684,14 @@ void jent_entropy_collector_free(struct rand_data *entropy_collector) jent_zfree(entropy_collector); } -int jent_entropy_init(void *hash_state) +int jent_entropy_init(unsigned int osr, unsigned int flags, void *hash_state) { - int i; - __u64 delta_sum = 0; - __u64 old_delta = 0; - unsigned int nonstuck = 0; - int time_backwards = 0; - int count_mod = 0; - int count_stuck = 0; - struct rand_data ec = { 0 }; - - /* Required for RCT */ - ec.osr = 1; - ec.hash_state = hash_state; + struct rand_data *ec; + int i, time_backwards = 0, ret = 0; + + ec = jent_entropy_collector_alloc(osr, flags, hash_state); + if (!ec) + return JENT_EMEM; /* We could perform statistical tests here, but the problem is * that we only have a few loop counts to do testing. These @@ -664,31 +720,28 @@ int jent_entropy_init(void *hash_state) #define TESTLOOPCOUNT 1024 #define CLEARCACHE 100 for (i = 0; (TESTLOOPCOUNT + CLEARCACHE) > i; i++) { - __u64 time = 0; - __u64 time2 = 0; - __u64 delta = 0; - unsigned int lowdelta = 0; - int stuck; + __u64 start_time = 0, end_time = 0, delta = 0; /* Invoke core entropy collection logic */ - jent_get_nstime(&time); - ec.prev_time = time; - jent_condition_data(&ec, time, 0); - jent_get_nstime(&time2); + jent_measure_jitter(ec, &delta); + end_time = ec->prev_time; + start_time = ec->prev_time - delta; /* test whether timer works */ - if (!time || !time2) - return JENT_ENOTIME; - delta = jent_delta(time, time2); + if (!start_time || !end_time) { + ret = JENT_ENOTIME; + goto out; + } + /* * test whether timer is fine grained enough to provide * delta even when called shortly after each other -- this * implies that we also have a high resolution timer */ - if (!delta) - return JENT_ECOARSETIME; - - stuck = jent_stuck(&ec, delta); + if (!delta || (end_time == start_time)) { + ret = JENT_ECOARSETIME; + goto out; + } /* * up to here we did not modify any variable that will be @@ -700,49 +753,9 @@ int jent_entropy_init(void *hash_state) if (i < CLEARCACHE) continue; - if (stuck) - count_stuck++; - else { - nonstuck++; - - /* - * Ensure that the APT succeeded. - * - * With the check below that count_stuck must be less - * than 10% of the overall generated raw entropy values - * it is guaranteed that the APT is invoked at - * floor((TESTLOOPCOUNT * 0.9) / 64) == 14 times. - */ - if ((nonstuck % JENT_APT_WINDOW_SIZE) == 0) { - jent_apt_reset(&ec, - delta & JENT_APT_WORD_MASK); - } - } - - /* Validate health test result */ - if (jent_health_failure(&ec)) - return JENT_EHEALTH; - /* test whether we have an increasing timer */ - if (!(time2 > time)) + if (!(end_time > start_time)) time_backwards++; - - /* use 32 bit value to ensure compilation on 32 bit arches */ - lowdelta = time2 - time; - if (!(lowdelta % 100)) - count_mod++; - - /* - * ensure that we have a varying delta timer which is necessary - * for the calculation of entropy -- perform this check - * only after the first loop is executed as we need to prime - * the old_data value - */ - if (delta > old_delta) - delta_sum += (delta - old_delta); - else - delta_sum += (old_delta - delta); - old_delta = delta; } /* @@ -752,31 +765,23 @@ int jent_entropy_init(void *hash_state) * should not fail. The value of 3 should cover the NTP case being * performed during our test run. */ - if (time_backwards > 3) - return JENT_ENOMONOTONIC; - - /* - * Variations of deltas of time must on average be larger - * than 1 to ensure the entropy estimation - * implied with 1 is preserved - */ - if ((delta_sum) <= 1) - return JENT_EVARVAR; + if (time_backwards > 3) { + ret = JENT_ENOMONOTONIC; + goto out; + } - /* - * Ensure that we have variations in the time stamp below 10 for at - * least 10% of all checks -- on some platforms, the counter increments - * in multiples of 100, but not always - */ - if ((TESTLOOPCOUNT/10 * 9) < count_mod) - return JENT_ECOARSETIME; + /* Did we encounter a health test failure? */ + if (jent_rct_failure(ec)) { + ret = JENT_ERCT; + goto out; + } + if (jent_apt_failure(ec)) { + ret = JENT_EHEALTH; + goto out; + } - /* - * If we have more than 90% stuck results, then this Jitter RNG is - * likely to not work well. - */ - if ((TESTLOOPCOUNT/10 * 9) < count_stuck) - return JENT_ESTUCK; +out: + jent_entropy_collector_free(ec); - return 0; + return ret; } diff --git a/crypto/jitterentropy.h b/crypto/jitterentropy.h index 4c92176ea2b1..626c6228b7e2 100644 --- a/crypto/jitterentropy.h +++ b/crypto/jitterentropy.h @@ -9,7 +9,8 @@ extern int jent_hash_time(void *hash_state, __u64 time, u8 *addtl, int jent_read_random_block(void *hash_state, char *dst, unsigned int dst_len); struct rand_data; -extern int jent_entropy_init(void *hash_state); +extern int jent_entropy_init(unsigned int osr, unsigned int flags, + void *hash_state); extern int jent_read_entropy(struct rand_data *ec, unsigned char *data, unsigned int len); |