n2rng_provider.c revision fec509a05ddbf645268fe2e537314def7d1b67c8
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fec509a05ddbf645268fe2e537314def7d1b67c8gm * Copyright 2007 Sun Microsystems, Inc. All rights reserved.
fec509a05ddbf645268fe2e537314def7d1b67c8gm * Use is subject to license terms.
fec509a05ddbf645268fe2e537314def7d1b67c8gm#pragma ident "%Z%%M% %I% %E% SMI"
fec509a05ddbf645268fe2e537314def7d1b67c8gm#include <sys/ddi.h> /* near end to get min and max macros right */
fec509a05ddbf645268fe2e537314def7d1b67c8gm/* n must be a power of 2 */
fec509a05ddbf645268fe2e537314def7d1b67c8gm * Policy. ENTROPY_STARVATION is the maximum number of calls each
fec509a05ddbf645268fe2e537314def7d1b67c8gm * FIPS instance will accept without successfully getting more
fec509a05ddbf645268fe2e537314def7d1b67c8gm * entropy. It needs to be large enough to allow RNG operations to
fec509a05ddbf645268fe2e537314def7d1b67c8gm * not stall because of health checks, etc. But we don't want it too
fec509a05ddbf645268fe2e537314def7d1b67c8gm * large. FIPS 186-2 change 1 (5 October 2001) states that no more
fec509a05ddbf645268fe2e537314def7d1b67c8gm * that 2,000,000 DSA signatures (done using this algorithm) should be
fec509a05ddbf645268fe2e537314def7d1b67c8gm * done without reseeding. We make sure we add 64 bits of entropy at
fec509a05ddbf645268fe2e537314def7d1b67c8gm * most every 10000 operations, hence we will have stirred in 160 bits
fec509a05ddbf645268fe2e537314def7d1b67c8gm * of entropy at most once every 30000 operations. Normally, we stir
fec509a05ddbf645268fe2e537314def7d1b67c8gm * in 64 bits of entropy for every number generated.
fec509a05ddbf645268fe2e537314def7d1b67c8gm * Adds val1 and val2 and stores result into sum. The various input
fec509a05ddbf645268fe2e537314def7d1b67c8gm * pointers can be exactly aliased. (They cannot be offset and
fec509a05ddbf645268fe2e537314def7d1b67c8gm * overlapping, but no one would ever do that.) Values are big endian
fec509a05ddbf645268fe2e537314def7d1b67c8gm * by words and native byte order within words. The return value's
fec509a05ddbf645268fe2e537314def7d1b67c8gm * 2-bit is 0 if the result is zero, it's 1 bit is carry out. (This
fec509a05ddbf645268fe2e537314def7d1b67c8gm * is reused code. The return code is not used by n2rng.) Thus,
fec509a05ddbf645268fe2e537314def7d1b67c8gm * calling with both carryin and complement_val2 ones does a
fec509a05ddbf645268fe2e537314def7d1b67c8gm * subtraction. A null sum pointer parameter is allowed. The
fec509a05ddbf645268fe2e537314def7d1b67c8gm * subtraction features were required when this code was orginally
fec509a05ddbf645268fe2e537314def7d1b67c8gm * written so it could do a mod q operation.
fec509a05ddbf645268fe2e537314def7d1b67c8gmadd160(uint32_t *sum, uint32_t const *val1, uint32_t const *val2,
fec509a05ddbf645268fe2e537314def7d1b67c8gm for (i = 4; i >= 0; --i) {
fec509a05ddbf645268fe2e537314def7d1b67c8gm partialsum = val1[i] + (complement_val2 ? ~val2[i] : val2[i]) +
fec509a05ddbf645268fe2e537314def7d1b67c8gm * Computes a new random value, which is stored in x_j; updates XKEY
fec509a05ddbf645268fe2e537314def7d1b67c8gm * in the *rs. XSEED_j is additional input. In principle, we should
fec509a05ddbf645268fe2e537314def7d1b67c8gm * protect XKEY, perhaps by putting it on a non-pagable page, but we
fec509a05ddbf645268fe2e537314def7d1b67c8gm * aways clobber XKEY with fresh entropy just before we use it. And
fec509a05ddbf645268fe2e537314def7d1b67c8gm * step 3d irreversibly updates it just after we use it. The only
fec509a05ddbf645268fe2e537314def7d1b67c8gm * risk is that if an attacker captured the state while the entropy
fec509a05ddbf645268fe2e537314def7d1b67c8gm * generator was broken, the attacker could predict future values.
fec509a05ddbf645268fe2e537314def7d1b67c8gm * There are two cases: 1. The attack gets root access to a live
fec509a05ddbf645268fe2e537314def7d1b67c8gm * system. But there is no defense against that. 2. The attacker
fec509a05ddbf645268fe2e537314def7d1b67c8gm * gets access to a crash dump. But by then no values are being
fec509a05ddbf645268fe2e537314def7d1b67c8gm * generated.
fec509a05ddbf645268fe2e537314def7d1b67c8gm * Note that XSEEDj is overwritten with sensitive stuff, and must be
fec509a05ddbf645268fe2e537314def7d1b67c8gm * zeroed by the caller. We use two separate symbols (XVAL and
fec509a05ddbf645268fe2e537314def7d1b67c8gm * XSEEDj) to make each step match the notation in FIPS 186-2.
fec509a05ddbf645268fe2e537314def7d1b67c8gmstatic void
fec509a05ddbf645268fe2e537314def7d1b67c8gmfips_random_inner(fipsrandomstruct_t *frsp, uint32_t *x_j,
fec509a05ddbf645268fe2e537314def7d1b67c8gm /* Alias to preserve terminology from FIPS 186-2 */
fec509a05ddbf645268fe2e537314def7d1b67c8gm * K&R section A8.7: If the array has fixed size, the number
fec509a05ddbf645268fe2e537314def7d1b67c8gm * of initializers may not exceed the number of members in the
fec509a05ddbf645268fe2e537314def7d1b67c8gm * array; if there are fewer, the trailing members are
fec509a05ddbf645268fe2e537314def7d1b67c8gm * initialized with 0.
fec509a05ddbf645268fe2e537314def7d1b67c8gm static const char zero[SHA1BLOCKBYTES - SHA1BYTES] = {0};
fec509a05ddbf645268fe2e537314def7d1b67c8gm * Step 3b: XVAL = (XKEY + XSEED_sub_j) mod 2^b. The mod is
fec509a05ddbf645268fe2e537314def7d1b67c8gm * implicit in the 160 bit representation. Note that XVAL and
fec509a05ddbf645268fe2e537314def7d1b67c8gm * XSEED_j are actually the same location.
fec509a05ddbf645268fe2e537314def7d1b67c8gm * Step 3c: x_sub_j = G(t, XVAL) mod q.
fec509a05ddbf645268fe2e537314def7d1b67c8gm SHA1Update(&sha1_context, (unsigned char *)XVAL, SHA1BYTES);
fec509a05ddbf645268fe2e537314def7d1b67c8gm * Filling to 64 bytes is requried by FIPS 186-2 Appendix 3.3.
fec509a05ddbf645268fe2e537314def7d1b67c8gm * It also triggers SHA1Transform (the steps a-e of the spec).
fec509a05ddbf645268fe2e537314def7d1b67c8gm * zero is a const char[], but SHA1update does not declare its
fec509a05ddbf645268fe2e537314def7d1b67c8gm * second parameter const, even though it does not modify it,
fec509a05ddbf645268fe2e537314def7d1b67c8gm * so we cast to suppress a compiler warning.
fec509a05ddbf645268fe2e537314def7d1b67c8gm * The code below directly accesses the state field of
fec509a05ddbf645268fe2e537314def7d1b67c8gm * sha1_context, which is of type SHA1_CTX, defined in sha1.h.
fec509a05ddbf645268fe2e537314def7d1b67c8gm * This has been deemed acceptable, because that typedef is
fec509a05ddbf645268fe2e537314def7d1b67c8gm * Consolidation Private, and n2rng is in the same
fec509a05ddbf645268fe2e537314def7d1b67c8gm * consolidation.
fec509a05ddbf645268fe2e537314def7d1b67c8gm /* copy out to x_j */
fec509a05ddbf645268fe2e537314def7d1b67c8gm for (i = 0; i < 5; i++) {
fec509a05ddbf645268fe2e537314def7d1b67c8gm * Step 3d: XKEY = (1 + XKEY + x_sub_j) mod 2^b. b=160. The
fec509a05ddbf645268fe2e537314def7d1b67c8gm * mod 2^160 is implicit in the 160 bit representation. The
fec509a05ddbf645268fe2e537314def7d1b67c8gm * one is added via the carry-in flag.
fec509a05ddbf645268fe2e537314def7d1b67c8gm * Since in the new scheme of things, the RNG latency
fec509a05ddbf645268fe2e537314def7d1b67c8gm * will be high on reads after the first, we get just
fec509a05ddbf645268fe2e537314def7d1b67c8gm * one word of entropy per call. And if it fails, we
fec509a05ddbf645268fe2e537314def7d1b67c8gm * just go on, but if the number of successive
fec509a05ddbf645268fe2e537314def7d1b67c8gm * failures gets too big, we fail.
fec509a05ddbf645268fe2e537314def7d1b67c8gm sizeof (uint64_t))) {
fec509a05ddbf645268fe2e537314def7d1b67c8gm /* failure case */
fec509a05ddbf645268fe2e537314def7d1b67c8gm * The idea here is that a Niagara2 chip is highly
fec509a05ddbf645268fe2e537314def7d1b67c8gm * parallel, with many strands. If we have just one
fec509a05ddbf645268fe2e537314def7d1b67c8gm * instance of the FIPS data, then only one FIPS
fec509a05ddbf645268fe2e537314def7d1b67c8gm * computation can happen at a time, serializeing all
fec509a05ddbf645268fe2e537314def7d1b67c8gm * the RNG stuff. So we make N2RNG_FIPS_INSTANCES,
fec509a05ddbf645268fe2e537314def7d1b67c8gm * and use them round-robin, with the counter being
fec509a05ddbf645268fe2e537314def7d1b67c8gm * n2rng->n_frs.fips_round_robin_j. We increment the
fec509a05ddbf645268fe2e537314def7d1b67c8gm * counter with an atomic op, avoiding having to have
fec509a05ddbf645268fe2e537314def7d1b67c8gm * a global muxtex. The atomic ops are also
fec509a05ddbf645268fe2e537314def7d1b67c8gm * significantly faster than mutexes. The mutex is
fec509a05ddbf645268fe2e537314def7d1b67c8gm * put inside the loop, otherwise one thread reading
fec509a05ddbf645268fe2e537314def7d1b67c8gm * many blocks could stall all other strands.
fec509a05ddbf645268fe2e537314def7d1b67c8gm * If we did not get any entropy, entropyword
fec509a05ddbf645268fe2e537314def7d1b67c8gm * is zero. We get a false positive with
fec509a05ddbf645268fe2e537314def7d1b67c8gm * probablitity 2^-64. It's not worth a few
fec509a05ddbf645268fe2e537314def7d1b67c8gm * extra stores and tests eliminate the false
fec509a05ddbf645268fe2e537314def7d1b67c8gm * positive.
fec509a05ddbf645268fe2e537314def7d1b67c8gm "entropy");
fec509a05ddbf645268fe2e537314def7d1b67c8gm /* nbytes - i is bytes to go */
fec509a05ddbf645268fe2e537314def7d1b67c8gm /* Zeroize sensitive information */
fec509a05ddbf645268fe2e537314def7d1b67c8gm return (0);
fec509a05ddbf645268fe2e537314def7d1b67c8gm * Initializes one FIPS RNG instance. Must be called once for each
fec509a05ddbf645268fe2e537314def7d1b67c8gm * instance.
fec509a05ddbf645268fe2e537314def7d1b67c8gmn2rng_fips_random_init(n2rng_t *n2rng, fipsrandomstruct_t *frsp)
fec509a05ddbf645268fe2e537314def7d1b67c8gm * All FIPS-approved algorithms will operate as cryptograpic
fec509a05ddbf645268fe2e537314def7d1b67c8gm * quality PRNGs even if there is no entropy source. (In
fec509a05ddbf645268fe2e537314def7d1b67c8gm * fact, this the only one that accepts entropy on the fly.)
fec509a05ddbf645268fe2e537314def7d1b67c8gm * One motivation for this is that they system keeps on
fec509a05ddbf645268fe2e537314def7d1b67c8gm * delivering cryptographic quality random numbers, even if
fec509a05ddbf645268fe2e537314def7d1b67c8gm * the entropy source fails.
fec509a05ddbf645268fe2e537314def7d1b67c8gm rv = n2rng_getentropy(n2rng, (void *)frsp->XKEY, ROUNDUP(SHA1BYTES, 8));
fec509a05ddbf645268fe2e537314def7d1b67c8gm return (rv);
fec509a05ddbf645268fe2e537314def7d1b67c8gm return (0);
fec509a05ddbf645268fe2e537314def7d1b67c8gm * Zeroise fips data. Not really necessary, since the
fec509a05ddbf645268fe2e537314def7d1b67c8gm * algorithm has backtracking resistance, but do it anyway.