**diff options**

author | Stephan MÃ¼ller <smueller@chronox.de> | 2019-05-29 21:24:25 +0200 |
---|---|---|

committer | Herbert Xu <herbert@gondor.apana.org.au> | 2019-06-06 14:38:57 +0800 |

commit | d9d67c87ad37218be65f4cea3ecd7e0312735e78 (patch) | |

tree | 1bd3f1281c20262d2f8359942d3503af875cc203 /crypto/jitterentropy.c | |

parent | d8ea98aa3cd4646945a2a9b647c2502b1e2dcdec (diff) |

crypto: jitter - update implementation to 2.1.2

The Jitter RNG implementation is updated to comply with upstream version
2.1.2. The change covers the following aspects:
* Time variation measurement is conducted over the LFSR operation
instead of the XOR folding
* Invcation of stuck test during initialization
* Removal of the stirring functionality and the Von-Neumann
unbiaser as the LFSR using a primitive and irreducible polynomial
generates an identical distribution of random bits
This implementation was successfully used in FIPS 140-2 validations
as well as in German BSI evaluations.
This kernel implementation was tested as follows:
* The unchanged kernel code file jitterentropy.c is compiled as part
of user space application to generate raw unconditioned noise
data. That data is processed with the NIST SP800-90B non-IID test
tool to verify that the kernel code exhibits an equal amount of noise
as the upstream Jitter RNG version 2.1.2.
* Using AF_ALG with the libkcapi tool of kcapi-rng the Jitter RNG was
output tested with dieharder to verify that the output does not
exhibit statistical weaknesses. The following command was used:
kcapi-rng -n "jitterentropy_rng" -b 100000000000 | dieharder -a -g 200
* The unchanged kernel code file jitterentropy.c is compiled as part
of user space application to test the LFSR implementation. The
LFSR is injected a monotonically increasing counter as input and
the output is fed into dieharder to verify that the LFSR operation
does not exhibit statistical weaknesses.
* The patch was tested on the Muen separation kernel which returns
a more coarse time stamp to verify that the Jitter RNG does not cause
regressions with its initialization test considering that the Jitter
RNG depends on a high-resolution timer.
Tested-by: Reto Buerki <reet@codelabs.ch>
Signed-off-by: Stephan Mueller <smueller@chronox.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

Diffstat (limited to 'crypto/jitterentropy.c')

-rw-r--r-- | crypto/jitterentropy.c | 305 |

1 files changed, 82 insertions, 223 deletions

diff --git a/crypto/jitterentropy.c b/crypto/jitterentropy.c index acf44b2d2d1d..77fa2120fe0c 100644 --- a/crypto/jitterentropy.c +++ b/crypto/jitterentropy.c @@ -2,7 +2,7 @@ * Non-physical true random number generator based on timing jitter -- * Jitter RNG standalone code. * - * Copyright Stephan Mueller <smueller@chronox.de>, 2015 + * Copyright Stephan Mueller <smueller@chronox.de>, 2015 - 2019 * * Design * ====== @@ -47,7 +47,7 @@ /* * This Jitterentropy RNG is based on the jitterentropy library - * version 1.1.0 provided at http://www.chronox.de/jent.html + * version 2.1.2 provided at http://www.chronox.de/jent.html */ #ifdef __OPTIMIZE__ @@ -71,10 +71,7 @@ struct rand_data { #define DATA_SIZE_BITS ((sizeof(__u64)) * 8) __u64 last_delta; /* SENSITIVE stuck test */ __s64 last_delta2; /* SENSITIVE stuck test */ - unsigned int stuck:1; /* Time measurement stuck */ unsigned int osr; /* Oversample rate */ - unsigned int stir:1; /* Post-processing stirring */ - unsigned int disable_unbias:1; /* Deactivate Von-Neuman unbias */ #define JENT_MEMORY_BLOCKS 64 #define JENT_MEMORY_BLOCKSIZE 32 #define JENT_MEMORY_ACCESSLOOPS 128 @@ -89,8 +86,6 @@ struct rand_data { }; /* Flags that can be used to initialize the RNG */ -#define JENT_DISABLE_STIR (1<<0) /* Disable stirring the entropy pool */ -#define JENT_DISABLE_UNBIAS (1<<1) /* Disable the Von-Neuman Unbiaser */ #define JENT_DISABLE_MEMORY_ACCESS (1<<2) /* Disable memory access for more * entropy, saves MEMORY_SIZE RAM for * entropy collector */ @@ -99,19 +94,16 @@ struct rand_data { #define JENT_ENOTIME 1 /* Timer service not available */ #define JENT_ECOARSETIME 2 /* Timer too coarse for RNG */ #define JENT_ENOMONOTONIC 3 /* Timer is not monotonic increasing */ -#define JENT_EMINVARIATION 4 /* Timer variations too small for RNG */ #define JENT_EVARVAR 5 /* Timer does not produce variations of * variations (2nd derivation of time is * zero). */ -#define JENT_EMINVARVAR 6 /* Timer variations of variations is tooi - * small. */ +#define JENT_ESTUCK 8 /* Too many stuck results during init. */ /*************************************************************************** * Helper functions ***************************************************************************/ void jent_get_nstime(__u64 *out); -__u64 jent_rol64(__u64 word, unsigned int shift); void *jent_zalloc(unsigned int len); void jent_zfree(void *ptr); int jent_fips_enabled(void); @@ -140,16 +132,16 @@ static __u64 jent_loop_shuffle(struct rand_data *ec, jent_get_nstime(&time); /* - * mix the current state of the random number into the shuffle - * calculation to balance that shuffle a bit more + * Mix the current state of the random number into the shuffle + * calculation to balance that shuffle a bit more. */ if (ec) time ^= ec->data; /* - * we fold the time value as much as possible to ensure that as many - * bits of the time stamp are included as possible + * We fold the time value as much as possible to ensure that as many + * bits of the time stamp are included as possible. */ - for (i = 0; (DATA_SIZE_BITS / bits) > i; i++) { + for (i = 0; ((DATA_SIZE_BITS + bits - 1) / bits) > i; i++) { shuffle ^= time & mask; time = time >> bits; } @@ -169,38 +161,28 @@ static __u64 jent_loop_shuffle(struct rand_data *ec, * CPU Jitter noise source -- this is the noise source based on the CPU * execution time jitter * - * This function folds the time into one bit units by iterating - * through the DATA_SIZE_BITS bit time value as follows: assume our time value - * is 0xabcd - * 1st loop, 1st shift generates 0xd000 - * 1st loop, 2nd shift generates 0x000d - * 2nd loop, 1st shift generates 0xcd00 - * 2nd loop, 2nd shift generates 0x000c - * 3rd loop, 1st shift generates 0xbcd0 - * 3rd loop, 2nd shift generates 0x000b - * 4th loop, 1st shift generates 0xabcd - * 4th loop, 2nd shift generates 0x000a - * Now, the values at the end of the 2nd shifts are XORed together. + * This function injects the individual bits of the time value into the + * entropy pool using an LFSR. * - * The code is deliberately inefficient and shall stay that way. This function - * is the root cause why the code shall be compiled without optimization. This - * function not only acts as folding operation, but this function's execution - * is used to measure the CPU execution time jitter. Any change to the loop in - * this function implies that careful retesting must be done. + * The code is deliberately inefficient with respect to the bit shifting + * and shall stay that way. This function is the root cause why the code + * shall be compiled without optimization. This function not only acts as + * folding operation, but this function's execution is used to measure + * the CPU execution time jitter. Any change to the loop in this function + * implies that careful retesting must be done. * * Input: * @ec entropy collector struct -- may be NULL - * @time time stamp to be folded + * @time time stamp to be injected * @loop_cnt if a value not equal to 0 is set, use the given value as number of * loops to perform the folding * * Output: - * @folded result of folding operation + * updated ec->data * * @return Number of loops the folding operation is performed */ -static __u64 jent_fold_time(struct rand_data *ec, __u64 time, - __u64 *folded, __u64 loop_cnt) +static __u64 jent_lfsr_time(struct rand_data *ec, __u64 time, __u64 loop_cnt) { unsigned int i; __u64 j = 0; @@ -217,15 +199,34 @@ static __u64 jent_fold_time(struct rand_data *ec, __u64 time, if (loop_cnt) fold_loop_cnt = loop_cnt; for (j = 0; j < fold_loop_cnt; j++) { - new = 0; + new = ec->data; for (i = 1; (DATA_SIZE_BITS) >= i; i++) { __u64 tmp = time << (DATA_SIZE_BITS - i); tmp = tmp >> (DATA_SIZE_BITS - 1); + + /* + * Fibonacci LSFR with polynomial of + * x^64 + x^61 + x^56 + x^31 + x^28 + x^23 + 1 which is + * primitive according to + * http://poincare.matf.bg.ac.rs/~ezivkovm/publications/primpol1.pdf + * (the shift values are the polynomial values minus one + * due to counting bits from 0 to 63). As the current + * position is always the LSB, the polynomial only needs + * to shift data in from the left without wrap. + */ + tmp ^= ((new >> 63) & 1); + tmp ^= ((new >> 60) & 1); + tmp ^= ((new >> 55) & 1); + tmp ^= ((new >> 30) & 1); + tmp ^= ((new >> 27) & 1); + tmp ^= ((new >> 22) & 1); + new <<= 1; new ^= tmp; } } - *folded = new; + ec->data = new; + return fold_loop_cnt; } @@ -258,7 +259,6 @@ static __u64 jent_fold_time(struct rand_data *ec, __u64 time, */ static unsigned int jent_memaccess(struct rand_data *ec, __u64 loop_cnt) { - unsigned char *tmpval = NULL; unsigned int wrap = 0; __u64 i = 0; #define MAX_ACC_LOOP_BIT 7 @@ -278,7 +278,7 @@ static unsigned int jent_memaccess(struct rand_data *ec, __u64 loop_cnt) acc_loop_cnt = loop_cnt; for (i = 0; i < (ec->memaccessloops + acc_loop_cnt); i++) { - tmpval = ec->mem + ec->memlocation; + unsigned char *tmpval = ec->mem + ec->memlocation; /* * memory access: just add 1 to one byte, * wrap at 255 -- memory access implies read @@ -316,7 +316,7 @@ static unsigned int jent_memaccess(struct rand_data *ec, __u64 loop_cnt) * 0 jitter measurement not stuck (good bit) * 1 jitter measurement stuck (reject bit) */ -static void jent_stuck(struct rand_data *ec, __u64 current_delta) +static int jent_stuck(struct rand_data *ec, __u64 current_delta) { __s64 delta2 = ec->last_delta - current_delta; __s64 delta3 = delta2 - ec->last_delta2; @@ -325,14 +325,15 @@ static void jent_stuck(struct rand_data *ec, __u64 current_delta) ec->last_delta2 = delta2; if (!current_delta || !delta2 || !delta3) - ec->stuck = 1; + return 1; + + return 0; } /** * This is the heart of the entropy generation: calculate time deltas and - * use the CPU jitter in the time deltas. The jitter is folded into one - * bit. You can call this function the "random bit generator" as it - * produces one random bit per invocation. + * use the CPU jitter in the time deltas. The jitter is injected into the + * entropy pool. * * WARNING: ensure that ->prev_time is primed before using the output * of this function! This can be done by calling this function @@ -341,12 +342,11 @@ static void jent_stuck(struct rand_data *ec, __u64 current_delta) * Input: * @entropy_collector Reference to entropy collector * - * @return One random bit + * @return result of stuck test */ -static __u64 jent_measure_jitter(struct rand_data *ec) +static int jent_measure_jitter(struct rand_data *ec) { __u64 time = 0; - __u64 data = 0; __u64 current_delta = 0; /* Invoke one noise source before time measurement to add variations */ @@ -360,109 +360,11 @@ static __u64 jent_measure_jitter(struct rand_data *ec) current_delta = time - ec->prev_time; ec->prev_time = time; - /* Now call the next noise sources which also folds the data */ - jent_fold_time(ec, current_delta, &data, 0); - - /* - * Check whether we have a stuck measurement. The enforcement - * is performed after the stuck value has been mixed into the - * entropy pool. - */ - jent_stuck(ec, current_delta); - - return data; -} - -/** - * Von Neuman unbias as explained in RFC 4086 section 4.2. As shown in the - * documentation of that RNG, the bits from jent_measure_jitter are considered - * independent which implies that the Von Neuman unbias operation is applicable. - * A proof of the Von-Neumann unbias operation to remove skews is given in the - * document "A proposal for: Functionality classes for random number - * generators", version 2.0 by Werner Schindler, section 5.4.1. - * - * Input: - * @entropy_collector Reference to entropy collector - * - * @return One random bit - */ -static __u64 jent_unbiased_bit(struct rand_data *entropy_collector) -{ - do { - __u64 a = jent_measure_jitter(entropy_collector); - __u64 b = jent_measure_jitter(entropy_collector); - - if (a == b) - continue; - if (1 == a) - return 1; - else - return 0; - } while (1); -} - -/** - * Shuffle the pool a bit by mixing some value with a bijective function (XOR) - * into the pool. - * - * The function generates a mixer value that depends on the bits set and the - * location of the set bits in the random number generated by the entropy - * source. Therefore, based on the generated random number, this mixer value - * can have 2**64 different values. That mixer value is initialized with the - * first two SHA-1 constants. After obtaining the mixer value, it is XORed into - * the random number. - * - * The mixer value is not assumed to contain any entropy. But due to the XOR - * operation, it can also not destroy any entropy present in the entropy pool. - * - * Input: - * @entropy_collector Reference to entropy collector - */ -static void jent_stir_pool(struct rand_data *entropy_collector) -{ - /* - * to shut up GCC on 32 bit, we have to initialize the 64 variable - * with two 32 bit variables - */ - union c { - __u64 u64; - __u32 u32[2]; - }; - /* - * This constant is derived from the first two 32 bit initialization - * vectors of SHA-1 as defined in FIPS 180-4 section 5.3.1 - */ - union c constant; - /* - * The start value of the mixer variable is derived from the third - * and fourth 32 bit initialization vector of SHA-1 as defined in - * FIPS 180-4 section 5.3.1 - */ - union c mixer; - unsigned int i = 0; - - /* - * Store the SHA-1 constants in reverse order to make up the 64 bit - * value -- this applies to a little endian system, on a big endian - * system, it reverses as expected. But this really does not matter - * as we do not rely on the specific numbers. We just pick the SHA-1 - * constants as they have a good mix of bit set and unset. - */ - constant.u32[1] = 0x67452301; - constant.u32[0] = 0xefcdab89; - mixer.u32[1] = 0x98badcfe; - mixer.u32[0] = 0x10325476; + /* Now call the next noise sources which also injects the data */ + jent_lfsr_time(ec, current_delta, 0); - for (i = 0; i < DATA_SIZE_BITS; i++) { - /* - * get the i-th bit of the input random number and only XOR - * the constant into the mixer value when that bit is set - */ - if ((entropy_collector->data >> i) & 1) - mixer.u64 ^= constant.u64; - mixer.u64 = jent_rol64(mixer.u64, 1); - } - entropy_collector->data ^= mixer.u64; + /* Check whether we have a stuck measurement. */ + return jent_stuck(ec, current_delta); } /** @@ -480,48 +382,9 @@ static void jent_gen_entropy(struct rand_data *ec) jent_measure_jitter(ec); while (1) { - __u64 data = 0; - - if (ec->disable_unbias == 1) - data = jent_measure_jitter(ec); - else - data = jent_unbiased_bit(ec); - - /* enforcement of the jent_stuck test */ - if (ec->stuck) { - /* - * We only mix in the bit considered not appropriate - * without the LSFR. The reason is that if we apply - * the LSFR and we do not rotate, the 2nd bit with LSFR - * will cancel out the first LSFR application on the - * bad bit. - * - * And we do not rotate as we apply the next bit to the - * current bit location again. - */ - ec->data ^= data; - ec->stuck = 0; + /* If a stuck measurement is received, repeat measurement */ + if (jent_measure_jitter(ec)) continue; - } - - /* - * Fibonacci LSFR with polynom of - * x^64 + x^61 + x^56 + x^31 + x^28 + x^23 + 1 which is - * primitive according to - * http://poincare.matf.bg.ac.rs/~ezivkovm/publications/primpol1.pdf - * (the shift values are the polynom values minus one - * due to counting bits from 0 to 63). As the current - * position is always the LSB, the polynom only needs - * to shift data in from the left without wrap. - */ - ec->data ^= data; - ec->data ^= ((ec->data >> 63) & 1); - ec->data ^= ((ec->data >> 60) & 1); - ec->data ^= ((ec->data >> 55) & 1); - ec->data ^= ((ec->data >> 30) & 1); - ec->data ^= ((ec->data >> 27) & 1); - ec->data ^= ((ec->data >> 22) & 1); - ec->data = jent_rol64(ec->data, 1); /* * We multiply the loop value with ->osr to obtain the @@ -530,8 +393,6 @@ static void jent_gen_entropy(struct rand_data *ec) if (++k >= (DATA_SIZE_BITS * ec->osr)) break; } - if (ec->stir) - jent_stir_pool(ec); } /** @@ -639,12 +500,6 @@ struct rand_data *jent_entropy_collector_alloc(unsigned int osr, osr = 1; /* minimum sampling rate is 1 */ entropy_collector->osr = osr; - entropy_collector->stir = 1; - if (flags & JENT_DISABLE_STIR) - entropy_collector->stir = 0; - if (flags & JENT_DISABLE_UNBIAS) - entropy_collector->disable_unbias = 1; - /* fill the data pad with non-zero values */ jent_gen_entropy(entropy_collector); @@ -656,7 +511,6 @@ void jent_entropy_collector_free(struct rand_data *entropy_collector) jent_zfree(entropy_collector->mem); entropy_collector->mem = NULL; jent_zfree(entropy_collector); - entropy_collector = NULL; } int jent_entropy_init(void) @@ -665,8 +519,9 @@ int jent_entropy_init(void) __u64 delta_sum = 0; __u64 old_delta = 0; int time_backwards = 0; - int count_var = 0; int count_mod = 0; + int count_stuck = 0; + struct rand_data ec = { 0 }; /* We could perform statistical tests here, but the problem is * that we only have a few loop counts to do testing. These @@ -695,12 +550,14 @@ int jent_entropy_init(void) for (i = 0; (TESTLOOPCOUNT + CLEARCACHE) > i; i++) { __u64 time = 0; __u64 time2 = 0; - __u64 folded = 0; __u64 delta = 0; unsigned int lowdelta = 0; + int stuck; + /* Invoke core entropy collection logic */ jent_get_nstime(&time); - jent_fold_time(NULL, time, &folded, 1<<MIN_FOLD_LOOP_BIT); + ec.prev_time = time; + jent_lfsr_time(&ec, time, 0); jent_get_nstime(&time2); /* test whether timer works */ @@ -715,6 +572,8 @@ int jent_entropy_init(void) if (!delta) return JENT_ECOARSETIME; + stuck = jent_stuck(&ec, delta); + /* * up to here we did not modify any variable that will be * evaluated later, but we already performed some work. Thus we @@ -725,14 +584,14 @@ int jent_entropy_init(void) if (CLEARCACHE > i) continue; + if (stuck) + count_stuck++; + /* test whether we have an increasing timer */ if (!(time2 > time)) time_backwards++; - /* - * Avoid modulo of 64 bit integer to allow code to compile - * on 32 bit architectures. - */ + /* use 32 bit value to ensure compilation on 32 bit arches */ lowdelta = time2 - time; if (!(lowdelta % 100)) count_mod++; @@ -743,14 +602,10 @@ int jent_entropy_init(void) * only after the first loop is executed as we need to prime * the old_data value */ - if (i) { - if (delta != old_delta) - count_var++; - if (delta > old_delta) - delta_sum += (delta - old_delta); - else - delta_sum += (old_delta - delta); - } + if (delta > old_delta) + delta_sum += (delta - old_delta); + else + delta_sum += (old_delta - delta); old_delta = delta; } @@ -763,25 +618,29 @@ int jent_entropy_init(void) */ if (3 < time_backwards) return JENT_ENOMONOTONIC; - /* Error if the time variances are always identical */ - if (!delta_sum) - return JENT_EVARVAR; /* * 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_EMINVARVAR; + if ((delta_sum) <= 1) + return JENT_EVARVAR; /* * 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 + * 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; + /* + * 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; + return 0; } |