1 /*
2 * Copyright (c) 2011-2018 Apple Inc. All rights reserved.
3 *
4 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
5 *
6 * This file contains Original Code and/or Modifications of Original Code
7 * as defined in and that are subject to the Apple Public Source License
8 * Version 2.0 (the 'License'). You may not use this file except in
9 * compliance with the License. The rights granted to you under the License
10 * may not be used to create, or enable the creation or redistribution of,
11 * unlawful or unlicensed copies of an Apple operating system, or to
12 * circumvent, violate, or enable the circumvention or violation of, any
13 * terms of an Apple operating system software license agreement.
14 *
15 * Please obtain a copy of the License at
16 * http://www.opensource.apple.com/apsl/ and read it before using this file.
17 *
18 * The Original Code and all software distributed under the License are
19 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
20 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
21 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
22 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
23 * Please see the License for the specific language governing rights and
24 * limitations under the License.
25 *
26 * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
27 */
28
29 #include <string.h>
30
31 #include <arm/pmap.h>
32
33 #include <kern/debug.h>
34 #include <kern/trustcache.h>
35 #include <kern/misc_protos.h>
36
37 #include <libkern/section_keywords.h>
38
39 #include <mach/machine/vm_types.h>
40
41 #include <pexpert/device_tree.h>
42
43 #include <sys/cdefs.h>
44
45 // All the external+engineering trust caches (accepting only one on RELEASE).
46 SECURITY_READ_ONLY_LATE(static struct serialized_trust_caches *)pmap_serialized_trust_caches = NULL;
47
48 // Shortcut to the first (= non-engineering, and therefore "static") trust cache.
49 SECURITY_READ_ONLY_LATE(static struct trust_cache_module1 *)pmap_static_trust_cache = NULL;
50
51 #if CONFIG_SECOND_STATIC_TRUST_CACHE
52 SECURITY_READ_ONLY_LATE(static struct trust_cache_module1 *)pmap_secondary_static_trust_cache = NULL;
53 #endif
54
55 // The EXTRADATA segment is where we find the external trust cache.
56 extern vm_offset_t segEXTRADATA;
57 extern unsigned long segSizeEXTRADATA;
58
59 void
trust_cache_init(void)60 trust_cache_init(void)
61 {
62 size_t const locked_down_dt_size = SecureDTIsLockedDown() ? PE_state.deviceTreeSize : 0;
63 size_t const len = segSizeEXTRADATA - locked_down_dt_size;
64
65 if (len == 0) {
66 // We allow no trust cache at all.
67 printf("No external trust cache found (region len is 0).");
68 return;
69 }
70
71 pmap_serialized_trust_caches = (struct serialized_trust_caches*)(segEXTRADATA +
72 locked_down_dt_size);
73
74 uint8_t const *region_end = (uint8_t*)pmap_serialized_trust_caches + len;
75
76 /* Validate the trust cache region for consistency.
77 *
78 * Technically, this shouldn't be necessary because any problem
79 * here would indicate that iBoot is either broken or compromised,
80 * but we do it anyway to assist in development, and for defense
81 * in depth.
82 */
83
84 if (len < sizeof(struct serialized_trust_caches)) {
85 panic("short serialized trust cache region: %zu", len);
86 }
87
88 printf("%d external trust cache modules available.\n", pmap_serialized_trust_caches->num_caches);
89
90 if (len < (sizeof(struct serialized_trust_caches) +
91 pmap_serialized_trust_caches->num_caches * sizeof(uint32_t))) {
92 panic("serialized trust cache region too short for its %d entries: %zu",
93 pmap_serialized_trust_caches->num_caches, len);
94 }
95
96 uint8_t *module_end = (uint8_t*)pmap_serialized_trust_caches;
97
98 for (uint32_t i = 0; i < pmap_serialized_trust_caches->num_caches; i++) {
99 struct trust_cache_module1 *module = (struct trust_cache_module1*)
100 ((uint8_t*)pmap_serialized_trust_caches + pmap_serialized_trust_caches->offsets[i]);
101
102 if ((uint8_t*)module < module_end) {
103 panic("trust cache module %d overlaps previous module", i);
104 }
105
106 module_end = (uint8_t*)(module + 1);
107
108 if (module_end > region_end) {
109 panic("trust cache module %d too short for header", i);
110 }
111
112 if (module->version != 1) {
113 panic("trust cache module %d has unsupported version %d", i, module->version);
114 }
115
116 module_end += module->num_entries * sizeof(struct trust_cache_entry1);
117
118 if (module_end > region_end) {
119 panic("trust cache module %d too short for its %u entries", i, module->num_entries);
120 }
121
122 printf("external trust cache module %d with %d entries\n", i, module->num_entries);
123
124 if (i == 0) {
125 pmap_static_trust_cache = module;
126 }
127 #if CONFIG_SECOND_STATIC_TRUST_CACHE
128 else if (i == 1) {
129 pmap_secondary_static_trust_cache = module;
130 }
131 #endif
132 }
133 }
134
135
136 // Lookup cdhash in a trust cache module.
137 // Suitable for all kinds of trust caches (but loadable ones are currently different).
138 bool
lookup_in_trust_cache_module(struct trust_cache_module1 const * const module,uint8_t const cdhash[CS_CDHASH_LEN],uint8_t * const hash_type,uint8_t * const flags)139 lookup_in_trust_cache_module(
140 struct trust_cache_module1 const * const module,
141 uint8_t const cdhash[CS_CDHASH_LEN],
142 uint8_t * const hash_type,
143 uint8_t * const flags)
144 {
145 size_t lim;
146 struct trust_cache_entry1 const *base = &module->entries[0];
147
148 struct trust_cache_entry1 const *entry = NULL;
149
150 bool found = false;
151
152 /* Initialization already (redundantly) verified the size of the module for us. */
153 for (lim = module->num_entries; lim != 0; lim >>= 1) {
154 entry = base + (lim >> 1);
155 int cmp = memcmp(cdhash, entry->cdhash, CS_CDHASH_LEN);
156 if (cmp == 0) {
157 found = true;
158 break;
159 }
160 if (cmp > 0) { /* key > p: move right */
161 base = entry + 1;
162 lim--;
163 } /* else move left */
164 }
165
166 if (found) {
167 *hash_type = entry->hash_type;
168 *flags = entry->flags;
169 return true;
170 }
171
172 return false;
173 }
174
175 MARK_AS_PMAP_TEXT uint32_t
lookup_in_static_trust_cache(const uint8_t cdhash[CS_CDHASH_LEN])176 lookup_in_static_trust_cache(const uint8_t cdhash[CS_CDHASH_LEN])
177 {
178 /* We will cram those into a single return value, because output parameters require
179 * some contortion. */
180 uint8_t hash_type = 0, flags = 0;
181 uint32_t engineering_trust_cache_index = 1;
182
183 if (pmap_static_trust_cache != NULL) {
184 // The one real new static trust cache.
185 if (lookup_in_trust_cache_module(pmap_static_trust_cache, cdhash, &hash_type, &flags)) {
186 return (hash_type << TC_LOOKUP_HASH_TYPE_SHIFT) |
187 (flags << TC_LOOKUP_FLAGS_SHIFT) |
188 (TC_LOOKUP_FOUND << TC_LOOKUP_RESULT_SHIFT);
189 }
190 #if CONFIG_SECOND_STATIC_TRUST_CACHE
191 if (pmap_secondary_static_trust_cache != NULL &&
192 lookup_in_trust_cache_module(pmap_secondary_static_trust_cache, cdhash, &hash_type, &flags)) {
193 return (hash_type << TC_LOOKUP_HASH_TYPE_SHIFT) |
194 (flags << TC_LOOKUP_FLAGS_SHIFT) |
195 (TC_LOOKUP_FOUND << TC_LOOKUP_RESULT_SHIFT);
196 }
197 engineering_trust_cache_index = (pmap_secondary_static_trust_cache != NULL) ? 2 : 1;
198 #endif
199
200 // Engineering Trust Caches.
201 if (pmap_serialized_trust_caches->num_caches > engineering_trust_cache_index) {
202 for (uint32_t i = engineering_trust_cache_index; i < pmap_serialized_trust_caches->num_caches; i++) {
203 struct trust_cache_module1 const *module =
204 (struct trust_cache_module1 const *)(
205 (uint8_t*)pmap_serialized_trust_caches + pmap_serialized_trust_caches->offsets[i]);
206
207 if (lookup_in_trust_cache_module(module, cdhash, &hash_type, &flags)) {
208 return (hash_type << TC_LOOKUP_HASH_TYPE_SHIFT) |
209 (flags << TC_LOOKUP_FLAGS_SHIFT) |
210 (TC_LOOKUP_FOUND << TC_LOOKUP_RESULT_SHIFT);
211 }
212 }
213 }
214 }
215
216 return 0;
217 }
218