diff options
Diffstat (limited to 'crypto/jitterentropy.c')
| -rw-r--r-- | crypto/jitterentropy.c | 144 |
1 files changed, 52 insertions, 92 deletions
diff --git a/crypto/jitterentropy.c b/crypto/jitterentropy.c index 93bff3213823..22f48bf4c6f5 100644 --- a/crypto/jitterentropy.c +++ b/crypto/jitterentropy.c @@ -85,10 +85,14 @@ struct rand_data { * bit generation */ /* Repetition Count Test */ - int rct_count; /* Number of stuck values */ + unsigned int rct_count; /* Number of stuck values */ - /* Adaptive Proportion Test for a significance level of 2^-30 */ + /* Intermittent health test failure threshold of 2^-30 */ +#define JENT_RCT_CUTOFF 30 /* 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 */ +#define JENT_RCT_CUTOFF_PERMANENT 60 +#define JENT_APT_CUTOFF_PERMANENT 355 #define JENT_APT_WINDOW_SIZE 512 /* Data window size */ /* LSB of time stamp to process */ #define JENT_APT_LSB 16 @@ -97,8 +101,6 @@ struct rand_data { unsigned int apt_count; /* APT counter */ unsigned int apt_base; /* APT base reference */ unsigned int apt_base_set:1; /* APT base reference set? */ - - unsigned int health_failure:1; /* Permanent health failure */ }; /* Flags that can be used to initialize the RNG */ @@ -169,19 +171,26 @@ static void jent_apt_insert(struct rand_data *ec, unsigned int delta_masked) return; } - if (delta_masked == ec->apt_base) { + if (delta_masked == ec->apt_base) ec->apt_count++; - if (ec->apt_count >= JENT_APT_CUTOFF) - ec->health_failure = 1; - } - ec->apt_observations++; if (ec->apt_observations >= JENT_APT_WINDOW_SIZE) jent_apt_reset(ec, 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; +} + +static int jent_apt_failure(struct rand_data *ec) +{ + return (ec->apt_count >= JENT_APT_CUTOFF) ? 1 : 0; +} + /*************************************************************************** * Stuck Test and its use as Repetition Count Test * @@ -206,55 +215,14 @@ static void jent_apt_insert(struct rand_data *ec, unsigned int delta_masked) */ static void jent_rct_insert(struct rand_data *ec, int stuck) { - /* - * If we have a count less than zero, a previous RCT round identified - * a failure. We will not overwrite it. - */ - if (ec->rct_count < 0) - return; - if (stuck) { ec->rct_count++; - - /* - * The cutoff value is based on the following consideration: - * alpha = 2^-30 as recommended in FIPS 140-2 IG 9.8. - * 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 64 * OSR deltas for inserting them into - * the entropy pool which should then have (close to) 64 bits - * of entropy. - * - * 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. - */ - if ((unsigned int)ec->rct_count >= (31 * ec->osr)) { - ec->rct_count = -1; - ec->health_failure = 1; - } } else { + /* Reset RCT */ ec->rct_count = 0; } } -/* - * Is there an RCT health test failure? - * - * @ec [in] Reference to entropy collector - * - * @return - * 0 No health test failure - * 1 Permanent health test failure - */ -static int jent_rct_failure(struct rand_data *ec) -{ - if (ec->rct_count < 0) - return 1; - return 0; -} - static inline __u64 jent_delta(__u64 prev, __u64 next) { #define JENT_UINT64_MAX (__u64)(~((__u64) 0)) @@ -303,18 +271,26 @@ static int jent_stuck(struct rand_data *ec, __u64 current_delta) return 0; } -/* - * Report any health test failures - * - * @ec [in] Reference to entropy collector - * - * @return - * 0 No health test failure - * 1 Permanent health test failure - */ +/* RCT health test failure detection */ +static int jent_rct_permanent_failure(struct rand_data *ec) +{ + return (ec->rct_count >= JENT_RCT_CUTOFF_PERMANENT) ? 1 : 0; +} + +static int jent_rct_failure(struct rand_data *ec) +{ + return (ec->rct_count >= JENT_RCT_CUTOFF) ? 1 : 0; +} + +/* Report of health test failures */ static int jent_health_failure(struct rand_data *ec) { - return ec->health_failure; + return jent_rct_failure(ec) | jent_apt_failure(ec); +} + +static int jent_permanent_health_failure(struct rand_data *ec) +{ + return jent_rct_permanent_failure(ec) | jent_apt_permanent_failure(ec); } /*************************************************************************** @@ -600,8 +576,8 @@ static void jent_gen_entropy(struct rand_data *ec) * * The following error codes can occur: * -1 entropy_collector is NULL - * -2 RCT failed - * -3 APT test failed + * -2 Intermittent health failure + * -3 Permanent health failure */ int jent_read_entropy(struct rand_data *ec, unsigned char *data, unsigned int len) @@ -616,39 +592,23 @@ int jent_read_entropy(struct rand_data *ec, unsigned char *data, jent_gen_entropy(ec); - if (jent_health_failure(ec)) { - int ret; - - if (jent_rct_failure(ec)) - ret = -2; - else - ret = -3; - + if (jent_permanent_health_failure(ec)) { /* - * Re-initialize the noise source - * - * If the health test fails, the Jitter RNG remains - * in failure state and will return a health failure - * during next invocation. + * At this point, the Jitter RNG instance is considered + * as a failed instance. There is no rerun of the + * startup test any more, because the caller + * is assumed to not further use this instance. */ - if (jent_entropy_init()) - return ret; - - /* Set APT to initial state */ - jent_apt_reset(ec, 0); - ec->apt_base_set = 0; - - /* Set RCT to initial state */ - ec->rct_count = 0; - - /* Re-enable Jitter RNG */ - ec->health_failure = 0; - + return -3; + } else if (jent_health_failure(ec)) { /* - * Return the health test failure status to the - * caller as the generated value is not appropriate. + * Perform startup health tests and return permanent + * error if it fails. */ - return ret; + if (jent_entropy_init()) + return -3; + + return -2; } if ((DATA_SIZE_BITS / 8) < len) |