• Sandrine Bailleux's avatar
    Fix type of cot_desc_ptr · 2efb7ddc
    Sandrine Bailleux authored
    
    The chain of trust description and the pointer pointing to its first
    element were incompatible, thus requiring an explicit type cast for
    the assignment.
    
    - cot_desc was an array of
      const pointers to const image descriptors.
    
    - cot_desc_ptr was a const pointer to
      (non-constant) pointers to const image descriptors.
    
    Thus, trying to assign cot_desc to cot_desc_ptr (with no cast) would
    generate the following compiler warning:
    
    drivers/auth/tbbr/tbbr_cot.c:826:14: warning: initialization discards
      ‘const’ qualifier from pointer target type [-Wdiscarded-qualifiers]
     REGISTER_COT(cot_desc);
                  ^~~~~~~~
    
    Change-Id: Iae62dd1bdb43fe379e3843d96461d47cc2f68a06
    Signed-off-by: default avatarSandrine Bailleux <sandrine.bailleux@arm.com>
    2efb7ddc
auth_mod.c 11.4 KB
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424
/*
 * Copyright (c) 2015-2019, ARM Limited and Contributors. All rights reserved.
 *
 * SPDX-License-Identifier: BSD-3-Clause
 */

#include <assert.h>
#include <stdint.h>
#include <string.h>

#include <platform_def.h>

#include <common/debug.h>
#include <common/tbbr/cot_def.h>
#include <drivers/auth/auth_common.h>
#include <drivers/auth/auth_mod.h>
#include <drivers/auth/crypto_mod.h>
#include <drivers/auth/img_parser_mod.h>
#include <plat/common/platform.h>

/* ASN.1 tags */
#define ASN1_INTEGER                 0x02

#define return_if_error(rc) \
	do { \
		if (rc != 0) { \
			return rc; \
		} \
	} while (0)

#pragma weak plat_set_nv_ctr2

/* Pointer to CoT */
extern const auth_img_desc_t *const *const cot_desc_ptr;
extern unsigned int auth_img_flags[MAX_NUMBER_IDS];

static int cmp_auth_param_type_desc(const auth_param_type_desc_t *a,
		const auth_param_type_desc_t *b)
{
	if ((a->type == b->type) && (a->cookie == b->cookie)) {
		return 0;
	}
	return 1;
}

/*
 * This function obtains the requested authentication parameter data from the
 * information extracted from the parent image after its authentication.
 */
static int auth_get_param(const auth_param_type_desc_t *param_type_desc,
			  const auth_img_desc_t *img_desc,
			  void **param, unsigned int *len)
{
	int i;

	if (img_desc->authenticated_data == NULL)
		return 1;

	for (i = 0 ; i < COT_MAX_VERIFIED_PARAMS ; i++) {
		if (0 == cmp_auth_param_type_desc(param_type_desc,
				img_desc->authenticated_data[i].type_desc)) {
			*param = img_desc->authenticated_data[i].data.ptr;
			*len = img_desc->authenticated_data[i].data.len;
			return 0;
		}
	}

	return 1;
}

/*
 * Authenticate an image by matching the data hash
 *
 * This function implements 'AUTH_METHOD_HASH'. To authenticate an image using
 * this method, the image must contain:
 *
 *   - The data to calculate the hash from
 *
 * The parent image must contain:
 *
 *   - The hash to be matched with (including hash algorithm)
 *
 * For a successful authentication, both hashes must match. The function calls
 * the crypto-module to check this matching.
 *
 * Parameters:
 *   param: parameters to perform the hash authentication
 *   img_desc: pointer to image descriptor so we can know the image type
 *             and parent image
 *   img: pointer to image in memory
 *   img_len: length of image (in bytes)
 *
 * Return:
 *   0 = success, Otherwise = error
 */
static int auth_hash(const auth_method_param_hash_t *param,
		     const auth_img_desc_t *img_desc,
		     void *img, unsigned int img_len)
{
	void *data_ptr, *hash_der_ptr;
	unsigned int data_len, hash_der_len;
	int rc = 0;

	/* Get the hash from the parent image. This hash will be DER encoded
	 * and contain the hash algorithm */
	rc = auth_get_param(param->hash, img_desc->parent,
			&hash_der_ptr, &hash_der_len);
	return_if_error(rc);

	/* Get the data to be hashed from the current image */
	rc = img_parser_get_auth_param(img_desc->img_type, param->data,
			img, img_len, &data_ptr, &data_len);
	return_if_error(rc);

	/* Ask the crypto module to verify this hash */
	rc = crypto_mod_verify_hash(data_ptr, data_len,
				    hash_der_ptr, hash_der_len);

	return rc;
}

/*
 * Authenticate by digital signature
 *
 * This function implements 'AUTH_METHOD_SIG'. To authenticate an image using
 * this method, the image must contain:
 *
 *   - Data to be signed
 *   - Signature
 *   - Signature algorithm
 *
 * We rely on the image parser module to extract this data from the image.
 * The parent image must contain:
 *
 *   - Public key (or a hash of it)
 *
 * If the parent image contains only a hash of the key, we will try to obtain
 * the public key from the image itself (i.e. self-signed certificates). In that
 * case, the signature verification is considered just an integrity check and
 * the authentication is established by calculating the hash of the key and
 * comparing it with the hash obtained from the parent.
 *
 * If the image has no parent (NULL), it means it has to be authenticated using
 * the ROTPK stored in the platform. Again, this ROTPK could be the key itself
 * or a hash of it.
 *
 * Return: 0 = success, Otherwise = error
 */
static int auth_signature(const auth_method_param_sig_t *param,
			  const auth_img_desc_t *img_desc,
			  void *img, unsigned int img_len)
{
	void *data_ptr, *pk_ptr, *pk_hash_ptr, *sig_ptr, *sig_alg_ptr;
	unsigned int data_len, pk_len, pk_hash_len, sig_len, sig_alg_len;
	unsigned int flags = 0;
	int rc = 0;

	/* Get the data to be signed from current image */
	rc = img_parser_get_auth_param(img_desc->img_type, param->data,
			img, img_len, &data_ptr, &data_len);
	return_if_error(rc);

	/* Get the signature from current image */
	rc = img_parser_get_auth_param(img_desc->img_type, param->sig,
			img, img_len, &sig_ptr, &sig_len);
	return_if_error(rc);

	/* Get the signature algorithm from current image */
	rc = img_parser_get_auth_param(img_desc->img_type, param->alg,
			img, img_len, &sig_alg_ptr, &sig_alg_len);
	return_if_error(rc);

	/* Get the public key from the parent. If there is no parent (NULL),
	 * the certificate has been signed with the ROTPK, so we have to get
	 * the PK from the platform */
	if (img_desc->parent) {
		rc = auth_get_param(param->pk, img_desc->parent,
				&pk_ptr, &pk_len);
	} else {
		rc = plat_get_rotpk_info(param->pk->cookie, &pk_ptr, &pk_len,
				&flags);
	}
	return_if_error(rc);

	if (flags & (ROTPK_IS_HASH | ROTPK_NOT_DEPLOYED)) {
		/* If the PK is a hash of the key or if the ROTPK is not
		   deployed on the platform, retrieve the key from the image */
		pk_hash_ptr = pk_ptr;
		pk_hash_len = pk_len;
		rc = img_parser_get_auth_param(img_desc->img_type,
					param->pk, img, img_len,
					&pk_ptr, &pk_len);
		return_if_error(rc);

		/* Ask the crypto module to verify the signature */
		rc = crypto_mod_verify_signature(data_ptr, data_len,
						 sig_ptr, sig_len,
						 sig_alg_ptr, sig_alg_len,
						 pk_ptr, pk_len);
		return_if_error(rc);

		if (flags & ROTPK_NOT_DEPLOYED) {
			NOTICE("ROTPK is not deployed on platform. "
				"Skipping ROTPK verification.\n");
		} else {
			/* Ask the crypto-module to verify the key hash */
			rc = crypto_mod_verify_hash(pk_ptr, pk_len,
				    pk_hash_ptr, pk_hash_len);
		}
	} else {
		/* Ask the crypto module to verify the signature */
		rc = crypto_mod_verify_signature(data_ptr, data_len,
						 sig_ptr, sig_len,
						 sig_alg_ptr, sig_alg_len,
						 pk_ptr, pk_len);
	}

	return rc;
}

/*
 * Authenticate by Non-Volatile counter
 *
 * To protect the system against rollback, the platform includes a non-volatile
 * counter whose value can only be increased. All certificates include a counter
 * value that should not be lower than the value stored in the platform. If the
 * value is larger, the counter in the platform must be updated to the new
 * value.
 *
 * Return: 0 = success, Otherwise = error
 */
static int auth_nvctr(const auth_method_param_nv_ctr_t *param,
		      const auth_img_desc_t *img_desc,
		      void *img, unsigned int img_len)
{
	char *p;
	void *data_ptr = NULL;
	unsigned int data_len, len, i;
	unsigned int cert_nv_ctr, plat_nv_ctr;
	int rc = 0;

	/* Get the counter value from current image. The AM expects the IPM
	 * to return the counter value as a DER encoded integer */
	rc = img_parser_get_auth_param(img_desc->img_type, param->cert_nv_ctr,
				       img, img_len, &data_ptr, &data_len);
	return_if_error(rc);

	/* Parse the DER encoded integer */
	assert(data_ptr);
	p = (char *)data_ptr;
	if (*p != ASN1_INTEGER) {
		/* Invalid ASN.1 integer */
		return 1;
	}
	p++;

	/* NV-counters are unsigned integers up to 32-bit */
	len = (unsigned int)(*p & 0x7f);
	if ((*p & 0x80) || (len > 4)) {
		return 1;
	}
	p++;

	/* Check the number is not negative */
	if (*p & 0x80) {
		return 1;
	}

	/* Convert to unsigned int. This code is for a little-endian CPU */
	cert_nv_ctr = 0;
	for (i = 0; i < len; i++) {
		cert_nv_ctr = (cert_nv_ctr << 8) | *p++;
	}

	/* Get the counter from the platform */
	rc = plat_get_nv_ctr(param->plat_nv_ctr->cookie, &plat_nv_ctr);
	return_if_error(rc);

	if (cert_nv_ctr < plat_nv_ctr) {
		/* Invalid NV-counter */
		return 1;
	} else if (cert_nv_ctr > plat_nv_ctr) {
		rc = plat_set_nv_ctr2(param->plat_nv_ctr->cookie,
			img_desc, cert_nv_ctr);
		return_if_error(rc);
	}

	return 0;
}

int plat_set_nv_ctr2(void *cookie, const auth_img_desc_t *img_desc __unused,
		unsigned int nv_ctr)
{
	return plat_set_nv_ctr(cookie, nv_ctr);
}

/*
 * Return the parent id in the output parameter '*parent_id'
 *
 * Return value:
 *   0 = Image has parent, 1 = Image has no parent or parent is authenticated
 */
int auth_mod_get_parent_id(unsigned int img_id, unsigned int *parent_id)
{
	const auth_img_desc_t *img_desc = NULL;

	assert(parent_id != NULL);

	/* Get the image descriptor */
	img_desc = cot_desc_ptr[img_id];

	/* Check if the image has no parent (ROT) */
	if (img_desc->parent == NULL) {
		*parent_id = 0;
		return 1;
	}

	/* Check if the parent has already been authenticated */
	if (auth_img_flags[img_desc->parent->img_id] & IMG_FLAG_AUTHENTICATED) {
		*parent_id = 0;
		return 1;
	}

	*parent_id = img_desc->parent->img_id;
	return 0;
}

/*
 * Initialize the different modules in the authentication framework
 */
void auth_mod_init(void)
{
	/* Check we have a valid CoT registered */
	assert(cot_desc_ptr != NULL);

	/* Crypto module */
	crypto_mod_init();

	/* Image parser module */
	img_parser_init();
}

/*
 * Authenticate a certificate/image
 *
 * Return: 0 = success, Otherwise = error
 */
int auth_mod_verify_img(unsigned int img_id,
			void *img_ptr,
			unsigned int img_len)
{
	const auth_img_desc_t *img_desc = NULL;
	const auth_method_desc_t *auth_method = NULL;
	void *param_ptr;
	unsigned int param_len;
	int rc, i;

	/* Get the image descriptor from the chain of trust */
	img_desc = cot_desc_ptr[img_id];

	/* Ask the parser to check the image integrity */
	rc = img_parser_check_integrity(img_desc->img_type, img_ptr, img_len);
	return_if_error(rc);

	/* Authenticate the image using the methods indicated in the image
	 * descriptor. */
	if (img_desc->img_auth_methods == NULL)
		return 1;
	for (i = 0 ; i < AUTH_METHOD_NUM ; i++) {
		auth_method = &img_desc->img_auth_methods[i];
		switch (auth_method->type) {
		case AUTH_METHOD_NONE:
			rc = 0;
			break;
		case AUTH_METHOD_HASH:
			rc = auth_hash(&auth_method->param.hash,
					img_desc, img_ptr, img_len);
			break;
		case AUTH_METHOD_SIG:
			rc = auth_signature(&auth_method->param.sig,
					img_desc, img_ptr, img_len);
			break;
		case AUTH_METHOD_NV_CTR:
			rc = auth_nvctr(&auth_method->param.nv_ctr,
					img_desc, img_ptr, img_len);
			break;
		default:
			/* Unknown authentication method */
			rc = 1;
			break;
		}
		return_if_error(rc);
	}

	/* Extract the parameters indicated in the image descriptor to
	 * authenticate the children images. */
	if (img_desc->authenticated_data != NULL) {
		for (i = 0 ; i < COT_MAX_VERIFIED_PARAMS ; i++) {
			if (img_desc->authenticated_data[i].type_desc == NULL) {
				continue;
			}

			/* Get the parameter from the image parser module */
			rc = img_parser_get_auth_param(img_desc->img_type,
					img_desc->authenticated_data[i].type_desc,
					img_ptr, img_len, &param_ptr, &param_len);
			return_if_error(rc);

			/* Check parameter size */
			if (param_len > img_desc->authenticated_data[i].data.len) {
				return 1;
			}

			/* Copy the parameter for later use */
			memcpy((void *)img_desc->authenticated_data[i].data.ptr,
					(void *)param_ptr, param_len);
		}
	}

	/* Mark image as authenticated */
	auth_img_flags[img_desc->img_id] |= IMG_FLAG_AUTHENTICATED;

	return 0;
}