xref: /titanic_44/usr/src/uts/sun4v/io/n2rng/n2rng_provider.c (revision 2b4a78020b9c38d1b95e2f3fefa6d6e4be382d1f)
1 /*
2  * CDDL HEADER START
3  *
4  * The contents of this file are subject to the terms of the
5  * Common Development and Distribution License (the "License").
6  * You may not use this file except in compliance with the License.
7  *
8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9  * or http://www.opensolaris.org/os/licensing.
10  * See the License for the specific language governing permissions
11  * and limitations under the License.
12  *
13  * When distributing Covered Code, include this CDDL HEADER in each
14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15  * If applicable, add the following below this CDDL HEADER, with the
16  * fields enclosed by brackets "[]" replaced with your own identifying
17  * information: Portions Copyright [yyyy] [name of copyright owner]
18  *
19  * CDDL HEADER END
20  */
21 /*
22  * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
23  * Use is subject to license terms.
24  */
25 
26 #include <sys/types.h>
27 #include <sys/sysmacros.h>
28 #include <sys/modctl.h>
29 #include <sys/conf.h>
30 #include <sys/devops.h>
31 #include <sys/cmn_err.h>
32 #include <sys/kmem.h>
33 #include <sys/stat.h>
34 #include <sys/open.h>
35 #include <sys/file.h>
36 #include <sys/cpuvar.h>
37 #include <sys/disp.h>
38 #include <sys/hsvc.h>
39 #include <sys/machsystm.h>
40 #include <sys/ksynch.h>
41 #include <sys/hypervisor_api.h>
42 #include <sys/n2rng.h>
43 #include <sys/sha1.h>
44 #include <sys/ddi.h>  /* near end to get min and max macros right */
45 #include <sys/sunddi.h>
46 #include <rng/fips_random.h>
47 
48 /* n must be a power of 2 */
49 #define	ROUNDUP(k, n)		(((k) + (n) - 1) & ~((n) - 1))
50 
51 /*
52  * Policy.  ENTROPY_STARVATION is the maximum number of calls each
53  * FIPS instance will accept without successfully getting more
54  * entropy.  It needs to be large enough to allow RNG operations to
55  * not stall because of health checks, etc.  But we don't want it too
56  * large.  FIPS 186-2 change 1 (5 October 2001) states that no more
57  * that 2,000,000 DSA signatures (done using this algorithm) should be
58  * done without reseeding.  We make sure we add 64 bits of entropy at
59  * most every 10000 operations, hence we will have stirred in 160 bits
60  * of entropy at most once every 30000 operations.  Normally, we stir
61  * in 64 bits of entropy for every number generated.
62  */
63 #define	ENTROPY_STARVATION	10000ULL
64 
65 
66 int
67 fips_random(n2rng_t *n2rng, uint8_t *out, size_t nbytes)
68 {
69 	int			i;
70 	fipsrandomstruct_t	*frsp;
71 	int			rv;
72 	union {
73 		uint32_t	as32[SHA1WORDS];
74 		uint64_t	as64[ROUNDUP(SHA1WORDS, 2) >> 1];
75 	} entropy = {0};
76 	uint32_t		tempout[SHA1WORDS];
77 
78 
79 	for (i = 0; i < nbytes; i += SHA1BYTES) {
80 		frsp = &n2rng->n_frs.fipsarray[
81 		    atomic_inc_32_nv(&n2rng->n_frs.fips_round_robin_j) %
82 		    N2RNG_FIPS_INSTANCES];
83 		/*
84 		 * Since in the new scheme of things, the RNG latency
85 		 * will be high on reads after the first, we get just
86 		 * one word of entropy per call.
87 		 */
88 		if ((rv = n2rng_getentropy(n2rng, (void *)&entropy.as64[1],
89 		    sizeof (uint64_t))) != 0) {
90 
91 			/*
92 			 * If all rngs have failed, dispatch task to unregister
93 			 * from kcf and put the driver in an error state.  If
94 			 * recoverable errors persist, a configuration retry
95 			 * will be initiated.
96 			 */
97 			if (rv == EPERM) {
98 				n2rng_failure(n2rng);
99 				return (EIO);
100 			}
101 			/* Failure with possible recovery */
102 			entropy.as64[1] = 0;
103 		}
104 
105 		/*
106 		 * The idea here is that a Niagara2 chip is highly
107 		 * parallel, with many strands.  If we have just one
108 		 * instance of the FIPS data, then only one FIPS
109 		 * computation can happen at a time, serializeing all
110 		 * the RNG stuff.  So we make N2RNG_FIPS_INSTANCES,
111 		 * and use them round-robin, with the counter being
112 		 * n2rng->n_frs.fips_round_robin_j.  We increment the
113 		 * counter with an atomic op, avoiding having to have
114 		 * a global muxtex.  The atomic ops are also
115 		 * significantly faster than mutexes.  The mutex is
116 		 * put inside the loop, otherwise one thread reading
117 		 * many blocks could stall all other strands.
118 		 */
119 		frsp = &n2rng->n_frs.fipsarray[
120 		    atomic_inc_32_nv(&n2rng->n_frs.fips_round_robin_j) %
121 		    N2RNG_FIPS_INSTANCES];
122 
123 		mutex_enter(&frsp->mtx);
124 
125 		if (entropy.as64[1] == 0) {
126 			/*
127 			 * If we did not get any entropy, entropyword
128 			 * is zero.  We get a false positive with
129 			 * probablitity 2^-64.  It's not worth a few
130 			 * extra stores and tests eliminate the false
131 			 * positive.
132 			 */
133 			if (++frsp->entropyhunger > ENTROPY_STARVATION) {
134 				mutex_exit(&frsp->mtx);
135 				n2rng_unconfigured(n2rng);
136 				return (EIO);
137 			}
138 		} else {
139 			frsp->entropyhunger = 0;
140 		}
141 
142 		/* nbytes - i is bytes to go */
143 		fips_random_inner(frsp->XKEY, tempout, entropy.as32);
144 		bcopy(tempout, &out[i], min(nbytes - i,  SHA1BYTES));
145 
146 		mutex_exit(&frsp->mtx);
147 	}
148 
149 	/* Zeroize sensitive information */
150 
151 	entropy.as64[1] = 0;
152 	bzero(tempout, SHA1BYTES);
153 
154 	return (0);
155 }
156 
157 /*
158  * Initializes one FIPS RNG instance.  Must be called once for each
159  * instance.
160  */
161 int
162 n2rng_fips_random_init(n2rng_t *n2rng, fipsrandomstruct_t *frsp)
163 {
164 	/*
165 	 * All FIPS-approved algorithms will operate as cryptograpic
166 	 * quality PRNGs even if there is no entropy source.  (In
167 	 * fact, this the only one that accepts entropy on the fly.)
168 	 * One motivation for this is that they system keeps on
169 	 * delivering cryptographic quality random numbers, even if
170 	 * the entropy source fails.
171 	 */
172 
173 	int rv;
174 
175 	rv = n2rng_getentropy(n2rng, (void *)frsp->XKEY, ROUNDUP(SHA1BYTES, 8));
176 	if (rv) {
177 		return (rv);
178 	}
179 	frsp->entropyhunger = 0;
180 	mutex_init(&frsp->mtx, NULL, MUTEX_DRIVER, NULL);
181 
182 	return (0);
183 }
184 
185 void
186 n2rng_fips_random_fini(fipsrandomstruct_t *frsp)
187 {
188 	mutex_destroy(&frsp->mtx);
189 	/*
190 	 * Zeroise fips data.  Not really necessary, since the
191 	 * algorithm has backtracking resistance, but do it anyway.
192 	 */
193 	bzero(frsp, sizeof (fipsrandomstruct_t));
194 }
195