/* * Copyright (c) 2015-2016, ARM Limited and Contributors. All rights reserved. * * SPDX-License-Identifier: BSD-3-Clause */ #include <assert.h> #include <auth_common.h> #include <auth_mod.h> #include <cot_def.h> #include <crypto_mod.h> #include <debug.h> #include <img_parser_mod.h> #include <platform.h> #include <platform_def.h> #include <stdint.h> #include <string.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 cot_desc_ptr; extern unsigned int auth_img_flags[]; 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; 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. */ 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. */ 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, ¶m_ptr, ¶m_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; }