1 /* Copyright (c) 2014 The Chromium OS Authors. All rights reserved.
2  * Use of this source code is governed by a BSD-style license that can be
3  * found in the LICENSE file.
4  *
5  * Misc functions which need access to vb2_context but are not public APIs
6  */
7 
8 #include "2sysincludes.h"
9 #include "2api.h"
10 #include "2common.h"
11 #include "2misc.h"
12 #include "2nvstorage.h"
13 #include "2secdata.h"
14 #include "2sha.h"
15 #include "2rsa.h"
16 
vb2_validate_gbb_signature(uint8_t * sig)17 int vb2_validate_gbb_signature(uint8_t *sig) {
18 	const static uint8_t sig_xor[VB2_GBB_SIGNATURE_SIZE] =
19 			VB2_GBB_XOR_SIGNATURE;
20 	int i;
21 	for (i = 0; i < VB2_GBB_SIGNATURE_SIZE; i++) {
22 		if (sig[i] != (sig_xor[i] ^ VB2_GBB_XOR_CHARS[i]))
23 			return VB2_ERROR_GBB_MAGIC;
24 	}
25 	return VB2_SUCCESS;
26 }
27 
vb2_workbuf_from_ctx(struct vb2_context * ctx,struct vb2_workbuf * wb)28 void vb2_workbuf_from_ctx(struct vb2_context *ctx, struct vb2_workbuf *wb)
29 {
30 	vb2_workbuf_init(wb, ctx->workbuf + ctx->workbuf_used,
31 			 ctx->workbuf_size - ctx->workbuf_used);
32 }
33 
vb2_read_gbb_header(struct vb2_context * ctx,struct vb2_gbb_header * gbb)34 int vb2_read_gbb_header(struct vb2_context *ctx, struct vb2_gbb_header *gbb)
35 {
36 	int rv;
37 
38 	/* Read the entire header */
39 	rv = vb2ex_read_resource(ctx, VB2_RES_GBB, 0, gbb, sizeof(*gbb));
40 	if (rv)
41 		return rv;
42 
43 	/* Make sure it's really a GBB */
44 	rv = vb2_validate_gbb_signature(gbb->signature);
45 	if (rv)
46 		return rv;
47 
48 	/* Check for compatible version */
49 	if (gbb->major_version != VB2_GBB_MAJOR_VER)
50 		return VB2_ERROR_GBB_VERSION;
51 
52 	/* Current code is not backwards-compatible to 1.0 headers */
53 	if (gbb->minor_version == 0)
54 		return VB2_ERROR_GBB_TOO_OLD;
55 
56 	/*
57 	 * Header size should be at least as big as we expect.  It could be
58 	 * bigger, if the header has grown.
59 	 */
60 	if (gbb->header_size < sizeof(*gbb))
61 		return VB2_ERROR_GBB_HEADER_SIZE;
62 
63 	return VB2_SUCCESS;
64 }
65 
vb2_fail(struct vb2_context * ctx,uint8_t reason,uint8_t subcode)66 void vb2_fail(struct vb2_context *ctx, uint8_t reason, uint8_t subcode)
67 {
68 	struct vb2_shared_data *sd = vb2_get_sd(ctx);
69 
70 	/* If NV data hasn't been initialized, initialize it now */
71 	if (!(sd->status & VB2_SD_STATUS_NV_INIT))
72 		vb2_nv_init(ctx);
73 
74 	/* See if we were far enough in the boot process to choose a slot */
75 	if (sd->status & VB2_SD_STATUS_CHOSE_SLOT) {
76 
77 		/* Boot failed */
78 		vb2_nv_set(ctx, VB2_NV_FW_RESULT, VB2_FW_RESULT_FAILURE);
79 
80 		/* Use up remaining tries */
81 		vb2_nv_set(ctx, VB2_NV_TRY_COUNT, 0);
82 
83 		/*
84 		 * Try the other slot next time.  We'll alternate
85 		 * between slots, which may help if one or both slots is
86 		 * flaky.
87 		 */
88 		vb2_nv_set(ctx, VB2_NV_TRY_NEXT, 1 - sd->fw_slot);
89 
90 		/*
91 		 * If we didn't try the other slot last boot, or we tried it
92 		 * and it didn't fail, try it next boot.
93 		 */
94 		if (sd->last_fw_slot != 1 - sd->fw_slot ||
95 		    sd->last_fw_result != VB2_FW_RESULT_FAILURE)
96 			return;
97 	}
98 
99 	/*
100 	 * If we're still here, we failed before choosing a slot, or both
101 	 * this slot and the other slot failed in successive boots.  So we
102 	 * need to go to recovery.
103 	 *
104 	 * Set a recovery reason and subcode only if they're not already set.
105 	 * If recovery is already requested, it's a more specific error code
106 	 * than later code is providing and we shouldn't overwrite it.
107 	 */
108 	VB2_DEBUG("Need recovery, reason: %#x / %#x\n", reason, subcode);
109 	if (!vb2_nv_get(ctx, VB2_NV_RECOVERY_REQUEST)) {
110 		vb2_nv_set(ctx, VB2_NV_RECOVERY_REQUEST, reason);
111 		vb2_nv_set(ctx, VB2_NV_RECOVERY_SUBCODE, subcode);
112 	}
113 }
114 
vb2_init_context(struct vb2_context * ctx)115 int vb2_init_context(struct vb2_context *ctx)
116 {
117 	struct vb2_shared_data *sd = vb2_get_sd(ctx);
118 
119 	/* Don't do anything if the context has already been initialized */
120 	if (ctx->workbuf_used)
121 		return VB2_SUCCESS;
122 
123 	/*
124 	 * Workbuf had better be big enough for our shared data struct and
125 	 * aligned.  Not much we can do if it isn't; we'll die before we can
126 	 * store a recovery reason.
127 	 */
128 	if (ctx->workbuf_size < sizeof(*sd))
129 		return VB2_ERROR_INITCTX_WORKBUF_SMALL;
130 	if (!vb2_aligned(ctx->workbuf, VB2_WORKBUF_ALIGN))
131 		return VB2_ERROR_INITCTX_WORKBUF_ALIGN;
132 
133 	/* Initialize the shared data at the start of the work buffer */
134 	memset(sd, 0, sizeof(*sd));
135 	ctx->workbuf_used = sizeof(*sd);
136 	return VB2_SUCCESS;
137 }
138 
vb2_check_recovery(struct vb2_context * ctx)139 void vb2_check_recovery(struct vb2_context *ctx)
140 {
141 	struct vb2_shared_data *sd = vb2_get_sd(ctx);
142 
143 	/*
144 	 * Read the current recovery request, unless there's already been a
145 	 * failure earlier in the boot process.
146 	 */
147 	if (!sd->recovery_reason)
148 		sd->recovery_reason = vb2_nv_get(ctx, VB2_NV_RECOVERY_REQUEST);
149 
150 	/* Clear the recovery request so we don't get stuck in recovery mode */
151 	if (sd->recovery_reason) {
152 		vb2_nv_set(ctx, VB2_NV_RECOVERY_REQUEST,
153 			   VB2_RECOVERY_NOT_REQUESTED);
154 		/*
155 		 * Note that we ignore failures clearing the request.  We only
156 		 * hit this code path if recovery mode has already been
157 		 * requested, so what more can we do?  Don't want to obscure
158 		 * the original reason for going into recovery mode.
159 		 */
160 	}
161 
162 	/* If forcing recovery, override recovery reason */
163 	if (ctx->flags & VB2_CONTEXT_FORCE_RECOVERY_MODE) {
164 		sd->recovery_reason = VB2_RECOVERY_RO_MANUAL;
165 		sd->flags |= VB2_SD_FLAG_MANUAL_RECOVERY;
166 	}
167 
168 	/* If recovery reason is non-zero, tell caller we need recovery mode */
169 	if (sd->recovery_reason) {
170 		ctx->flags |= VB2_CONTEXT_RECOVERY_MODE;
171 		VB2_DEBUG("We have a recovery request: %#x / %#x\n",
172 			  sd->recovery_reason,
173 			  vb2_nv_get(ctx, VB2_NV_RECOVERY_SUBCODE));
174 	}
175 }
176 
vb2_fw_parse_gbb(struct vb2_context * ctx)177 int vb2_fw_parse_gbb(struct vb2_context *ctx)
178 {
179 	struct vb2_shared_data *sd = vb2_get_sd(ctx);
180 	struct vb2_gbb_header *gbb;
181 	struct vb2_workbuf wb;
182 	int rv;
183 
184 	vb2_workbuf_from_ctx(ctx, &wb);
185 
186 	/* Read GBB into next chunk of work buffer */
187 	gbb = vb2_workbuf_alloc(&wb, sizeof(*gbb));
188 	if (!gbb)
189 		return VB2_ERROR_GBB_WORKBUF;
190 
191 	rv = vb2_read_gbb_header(ctx, gbb);
192 	if (rv)
193 		return rv;
194 
195 	/* Extract the only things we care about at firmware time */
196 	sd->gbb_flags = gbb->flags;
197 	sd->gbb_rootkey_offset = gbb->rootkey_offset;
198 	sd->gbb_rootkey_size = gbb->rootkey_size;
199 	memcpy(sd->gbb_hwid_digest, gbb->hwid_digest, VB2_GBB_HWID_DIGEST_SIZE);
200 
201 	return VB2_SUCCESS;
202 }
203 
vb2_check_dev_switch(struct vb2_context * ctx)204 int vb2_check_dev_switch(struct vb2_context *ctx)
205 {
206 	struct vb2_shared_data *sd = vb2_get_sd(ctx);
207 	uint32_t flags;
208 	uint32_t old_flags;
209 	int is_dev = 0;
210 	int rv;
211 
212 	/* Read secure flags */
213 	rv = vb2_secdata_get(ctx, VB2_SECDATA_FLAGS, &flags);
214 	if (rv)
215 		return rv;
216 
217 	old_flags = flags;
218 
219 	/* Handle dev disable request */
220 	if (vb2_nv_get(ctx, VB2_NV_DISABLE_DEV_REQUEST)) {
221 		flags &= ~VB2_SECDATA_FLAG_DEV_MODE;
222 
223 		/* Clear the request */
224 		vb2_nv_set(ctx, VB2_NV_DISABLE_DEV_REQUEST, 0);
225 	}
226 
227 	/* Check virtual dev switch */
228 	if (flags & VB2_SECDATA_FLAG_DEV_MODE)
229 		is_dev = 1;
230 
231 	/* Handle forcing dev mode via physical switch */
232 	if (ctx->flags & VB2_CONTEXT_FORCE_DEVELOPER_MODE)
233 		is_dev = 1;
234 
235 	/* Check if GBB is forcing dev mode */
236 	if (sd->gbb_flags & VB2_GBB_FLAG_FORCE_DEV_SWITCH_ON)
237 		is_dev = 1;
238 
239 	/* Handle whichever mode we end up in */
240 	if (is_dev) {
241 		/* Developer mode */
242 		sd->flags |= VB2_SD_DEV_MODE_ENABLED;
243 		ctx->flags |= VB2_CONTEXT_DEVELOPER_MODE;
244 
245 		flags |= VB2_SECDATA_FLAG_LAST_BOOT_DEVELOPER;
246 	} else {
247 		/* Normal mode */
248 		flags &= ~VB2_SECDATA_FLAG_LAST_BOOT_DEVELOPER;
249 
250 		/*
251 		 * Disable dev_boot_* flags.  This ensures they will be
252 		 * initially disabled if the user later transitions back into
253 		 * developer mode.
254 		 */
255 		vb2_nv_set(ctx, VB2_NV_DEV_BOOT_USB, 0);
256 		vb2_nv_set(ctx, VB2_NV_DEV_BOOT_LEGACY, 0);
257 		vb2_nv_set(ctx, VB2_NV_DEV_BOOT_SIGNED_ONLY, 0);
258 	}
259 
260 	if (flags != old_flags) {
261 		/*
262 		 * Just changed dev mode state.  Clear TPM owner.  This must be
263 		 * done here instead of simply passing a flag to
264 		 * vb2_check_tpm_clear(), because we don't want to update
265 		 * last_boot_developer and then fail to clear the TPM owner.
266 		 */
267 		rv = vb2ex_tpm_clear_owner(ctx);
268 		if (rv) {
269 			/*
270 			 * Note that this truncates rv to 8 bit.  Which is not
271 			 * as useful as the full error code, but we don't have
272 			 * NVRAM space to store the full 32-bit code.
273 			 */
274 			vb2_fail(ctx, VB2_RECOVERY_TPM_CLEAR_OWNER, rv);
275 			return rv;
276 		}
277 
278 		/* Save new flags */
279 		rv = vb2_secdata_set(ctx, VB2_SECDATA_FLAGS, flags);
280 		if (rv)
281 			return rv;
282 	}
283 
284 	return VB2_SUCCESS;
285 }
286 
vb2_check_tpm_clear(struct vb2_context * ctx)287 int vb2_check_tpm_clear(struct vb2_context *ctx)
288 {
289 	int rv;
290 
291 	/* Check if we've been asked to clear the owner */
292 	if (!vb2_nv_get(ctx, VB2_NV_CLEAR_TPM_OWNER_REQUEST))
293 		return VB2_SUCCESS;  /* No need to clear */
294 
295 	/* Request applies one time only */
296 	vb2_nv_set(ctx, VB2_NV_CLEAR_TPM_OWNER_REQUEST, 0);
297 
298 	/* Try clearing */
299 	rv = vb2ex_tpm_clear_owner(ctx);
300 	if (rv) {
301 		/*
302 		 * Note that this truncates rv to 8 bit.  Which is not as
303 		 * useful as the full error code, but we don't have NVRAM space
304 		 * to store the full 32-bit code.
305 		 */
306 		vb2_fail(ctx, VB2_RECOVERY_TPM_CLEAR_OWNER, rv);
307 		return rv;
308 	}
309 
310 	/* Clear successful */
311 	vb2_nv_set(ctx, VB2_NV_CLEAR_TPM_OWNER_DONE, 1);
312 	return VB2_SUCCESS;
313 }
314 
vb2_select_fw_slot(struct vb2_context * ctx)315 int vb2_select_fw_slot(struct vb2_context *ctx)
316 {
317 	struct vb2_shared_data *sd = vb2_get_sd(ctx);
318 	uint32_t tries;
319 
320 	/* Get result of last boot */
321 	sd->last_fw_slot = vb2_nv_get(ctx, VB2_NV_FW_TRIED);
322 	sd->last_fw_result = vb2_nv_get(ctx, VB2_NV_FW_RESULT);
323 
324 	/* Save to the previous result fields in NV storage */
325 	vb2_nv_set(ctx, VB2_NV_FW_PREV_TRIED, sd->last_fw_slot);
326 	vb2_nv_set(ctx, VB2_NV_FW_PREV_RESULT, sd->last_fw_result);
327 
328 	/* Clear result, since we don't know what will happen this boot */
329 	vb2_nv_set(ctx, VB2_NV_FW_RESULT, VB2_FW_RESULT_UNKNOWN);
330 
331 	/* Get slot to try */
332 	sd->fw_slot = vb2_nv_get(ctx, VB2_NV_TRY_NEXT);
333 
334 	/* Check try count */
335 	tries = vb2_nv_get(ctx, VB2_NV_TRY_COUNT);
336 
337 	if (sd->last_fw_result == VB2_FW_RESULT_TRYING &&
338 	    sd->last_fw_slot == sd->fw_slot &&
339 	    tries == 0) {
340 		/*
341 		 * We used up our last try on the previous boot, so fall back
342 		 * to the other slot this boot.
343 		 */
344 		sd->fw_slot = 1 - sd->fw_slot;
345 		vb2_nv_set(ctx, VB2_NV_TRY_NEXT, sd->fw_slot);
346 	}
347 
348 	if (tries > 0) {
349 		/* Still trying this firmware */
350 		vb2_nv_set(ctx, VB2_NV_FW_RESULT, VB2_FW_RESULT_TRYING);
351 
352 		/* Decrement non-zero try count */
353 		vb2_nv_set(ctx, VB2_NV_TRY_COUNT, tries - 1);
354 	}
355 
356 	/* Store the slot we're trying */
357 	vb2_nv_set(ctx, VB2_NV_FW_TRIED, sd->fw_slot);
358 
359 	/* Set context flag if we're using slot B */
360 	if (sd->fw_slot)
361 		ctx->flags |= VB2_CONTEXT_FW_SLOT_B;
362 
363 	/* Set status flag */
364 	sd->status |= VB2_SD_STATUS_CHOSE_SLOT;
365 
366 	return VB2_SUCCESS;
367 }
368