| /* |
| * Copyright (C) 2016 The Android Open Source Project |
| * |
| * Permission is hereby granted, free of charge, to any person |
| * obtaining a copy of this software and associated documentation |
| * files (the "Software"), to deal in the Software without |
| * restriction, including without limitation the rights to use, copy, |
| * modify, merge, publish, distribute, sublicense, and/or sell copies |
| * of the Software, and to permit persons to whom the Software is |
| * furnished to do so, subject to the following conditions: |
| * |
| * The above copyright notice and this permission notice shall be |
| * included in all copies or substantial portions of the Software. |
| * |
| * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, |
| * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF |
| * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND |
| * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS |
| * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN |
| * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN |
| * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE |
| * SOFTWARE. |
| */ |
| |
| #include "avb_atx_validate.h" |
| |
| #include <libavb/avb_rsa.h> |
| #include <libavb/avb_sha.h> |
| #include <libavb/avb_sysdeps.h> |
| #include <libavb/avb_util.h> |
| |
| /* The most recent unlock challenge generated. */ |
| static uint8_t last_unlock_challenge[AVB_ATX_UNLOCK_CHALLENGE_SIZE]; |
| static bool last_unlock_challenge_set = false; |
| |
| /* Computes the SHA256 |hash| of |length| bytes of |data|. */ |
| static void sha256(const uint8_t* data, |
| uint32_t length, |
| uint8_t hash[AVB_SHA256_DIGEST_SIZE]) { |
| AvbSHA256Ctx context; |
| avb_sha256_init(&context); |
| avb_sha256_update(&context, data, length); |
| uint8_t* tmp = avb_sha256_final(&context); |
| avb_memcpy(hash, tmp, AVB_SHA256_DIGEST_SIZE); |
| } |
| |
| /* Computes the SHA512 |hash| of |length| bytes of |data|. */ |
| static void sha512(const uint8_t* data, |
| uint32_t length, |
| uint8_t hash[AVB_SHA512_DIGEST_SIZE]) { |
| AvbSHA512Ctx context; |
| avb_sha512_init(&context); |
| avb_sha512_update(&context, data, length); |
| uint8_t* tmp = avb_sha512_final(&context); |
| avb_memcpy(hash, tmp, AVB_SHA512_DIGEST_SIZE); |
| } |
| |
| /* Computes the SHA256 |hash| of a NUL-terminated |str|. */ |
| static void sha256_str(const char* str, uint8_t hash[AVB_SHA256_DIGEST_SIZE]) { |
| sha256((const uint8_t*)str, avb_strlen(str), hash); |
| } |
| |
| /* Verifies structure and |expected_hash| of permanent |attributes|. */ |
| static bool verify_permanent_attributes( |
| const AvbAtxPermanentAttributes* attributes, |
| const uint8_t expected_hash[AVB_SHA256_DIGEST_SIZE]) { |
| uint8_t hash[AVB_SHA256_DIGEST_SIZE]; |
| |
| if (attributes->version != 1) { |
| avb_error("Unsupported permanent attributes version.\n"); |
| return false; |
| } |
| sha256((const uint8_t*)attributes, sizeof(AvbAtxPermanentAttributes), hash); |
| if (0 != avb_safe_memcmp(hash, expected_hash, AVB_SHA256_DIGEST_SIZE)) { |
| avb_error("Invalid permanent attributes.\n"); |
| return false; |
| } |
| return true; |
| } |
| |
| /* Verifies the format, key version, usage, and signature of a certificate. */ |
| static bool verify_certificate( |
| const AvbAtxCertificate* certificate, |
| const uint8_t authority[AVB_ATX_PUBLIC_KEY_SIZE], |
| uint64_t minimum_key_version, |
| const uint8_t expected_usage[AVB_SHA256_DIGEST_SIZE]) { |
| const AvbAlgorithmData* algorithm_data; |
| uint8_t certificate_hash[AVB_SHA512_DIGEST_SIZE]; |
| |
| if (certificate->signed_data.version != 1) { |
| avb_error("Unsupported certificate format.\n"); |
| return false; |
| } |
| algorithm_data = avb_get_algorithm_data(AVB_ALGORITHM_TYPE_SHA512_RSA4096); |
| sha512((const uint8_t*)&certificate->signed_data, |
| sizeof(AvbAtxCertificateSignedData), |
| certificate_hash); |
| if (!avb_rsa_verify(authority, |
| AVB_ATX_PUBLIC_KEY_SIZE, |
| certificate->signature, |
| AVB_RSA4096_NUM_BYTES, |
| certificate_hash, |
| AVB_SHA512_DIGEST_SIZE, |
| algorithm_data->padding, |
| algorithm_data->padding_len)) { |
| avb_error("Invalid certificate signature.\n"); |
| return false; |
| } |
| if (certificate->signed_data.key_version < minimum_key_version) { |
| avb_error("Key rollback detected.\n"); |
| return false; |
| } |
| if (0 != avb_safe_memcmp(certificate->signed_data.usage, |
| expected_usage, |
| AVB_SHA256_DIGEST_SIZE)) { |
| avb_error("Invalid certificate usage.\n"); |
| return false; |
| } |
| return true; |
| } |
| |
| /* Verifies signature and fields of a PIK certificate. */ |
| static bool verify_pik_certificate( |
| const AvbAtxCertificate* certificate, |
| const uint8_t authority[AVB_ATX_PUBLIC_KEY_SIZE], |
| uint64_t minimum_version) { |
| uint8_t expected_usage[AVB_SHA256_DIGEST_SIZE]; |
| |
| sha256_str("com.google.android.things.vboot.ca", expected_usage); |
| if (!verify_certificate( |
| certificate, authority, minimum_version, expected_usage)) { |
| avb_error("Invalid PIK certificate.\n"); |
| return false; |
| } |
| return true; |
| } |
| |
| /* Verifies signature and fields of a PSK certificate. */ |
| static bool verify_psk_certificate( |
| const AvbAtxCertificate* certificate, |
| const uint8_t authority[AVB_ATX_PUBLIC_KEY_SIZE], |
| uint64_t minimum_version, |
| const uint8_t product_id[AVB_ATX_PRODUCT_ID_SIZE]) { |
| uint8_t expected_subject[AVB_SHA256_DIGEST_SIZE]; |
| uint8_t expected_usage[AVB_SHA256_DIGEST_SIZE]; |
| |
| sha256_str("com.google.android.things.vboot", expected_usage); |
| if (!verify_certificate( |
| certificate, authority, minimum_version, expected_usage)) { |
| avb_error("Invalid PSK certificate.\n"); |
| return false; |
| } |
| sha256(product_id, AVB_ATX_PRODUCT_ID_SIZE, expected_subject); |
| if (0 != avb_safe_memcmp(certificate->signed_data.subject, |
| expected_subject, |
| AVB_SHA256_DIGEST_SIZE)) { |
| avb_error("PSK: Product ID mismatch.\n"); |
| return false; |
| } |
| return true; |
| } |
| |
| /* Verifies signature and fields of a PUK certificate. */ |
| static bool verify_puk_certificate( |
| const AvbAtxCertificate* certificate, |
| const uint8_t authority[AVB_ATX_PUBLIC_KEY_SIZE], |
| uint64_t minimum_version, |
| const uint8_t product_id[AVB_ATX_PRODUCT_ID_SIZE]) { |
| uint8_t expected_subject[AVB_SHA256_DIGEST_SIZE]; |
| uint8_t expected_usage[AVB_SHA256_DIGEST_SIZE]; |
| |
| sha256_str("com.google.android.things.vboot.unlock", expected_usage); |
| if (!verify_certificate( |
| certificate, authority, minimum_version, expected_usage)) { |
| avb_error("Invalid PUK certificate.\n"); |
| return false; |
| } |
| sha256(product_id, AVB_ATX_PRODUCT_ID_SIZE, expected_subject); |
| if (0 != avb_safe_memcmp(certificate->signed_data.subject, |
| expected_subject, |
| AVB_SHA256_DIGEST_SIZE)) { |
| avb_error("PUK: Product ID mismatch.\n"); |
| return false; |
| } |
| return true; |
| } |
| |
| AvbIOResult avb_atx_validate_vbmeta_public_key( |
| AvbOps* ops, |
| const uint8_t* public_key_data, |
| size_t public_key_length, |
| const uint8_t* public_key_metadata, |
| size_t public_key_metadata_length, |
| bool* out_is_trusted) { |
| AvbIOResult result = AVB_IO_RESULT_OK; |
| AvbAtxPermanentAttributes permanent_attributes; |
| uint8_t permanent_attributes_hash[AVB_SHA256_DIGEST_SIZE]; |
| AvbAtxPublicKeyMetadata metadata; |
| uint64_t minimum_version; |
| |
| /* Be pessimistic so we can exit early without having to remember to clear. |
| */ |
| *out_is_trusted = false; |
| |
| /* Read and verify permanent attributes. */ |
| result = ops->atx_ops->read_permanent_attributes(ops->atx_ops, |
| &permanent_attributes); |
| if (result != AVB_IO_RESULT_OK) { |
| avb_error("Failed to read permanent attributes.\n"); |
| return result; |
| } |
| result = ops->atx_ops->read_permanent_attributes_hash( |
| ops->atx_ops, permanent_attributes_hash); |
| if (result != AVB_IO_RESULT_OK) { |
| avb_error("Failed to read permanent attributes hash.\n"); |
| return result; |
| } |
| if (!verify_permanent_attributes(&permanent_attributes, |
| permanent_attributes_hash)) { |
| return AVB_IO_RESULT_OK; |
| } |
| |
| /* Sanity check public key metadata. */ |
| if (public_key_metadata_length != sizeof(AvbAtxPublicKeyMetadata)) { |
| avb_error("Invalid public key metadata.\n"); |
| return AVB_IO_RESULT_OK; |
| } |
| avb_memcpy(&metadata, public_key_metadata, sizeof(AvbAtxPublicKeyMetadata)); |
| if (metadata.version != 1) { |
| avb_error("Unsupported public key metadata.\n"); |
| return AVB_IO_RESULT_OK; |
| } |
| |
| /* Verify the PIK certificate. */ |
| result = ops->read_rollback_index( |
| ops, AVB_ATX_PIK_VERSION_LOCATION, &minimum_version); |
| if (result != AVB_IO_RESULT_OK) { |
| avb_error("Failed to read PIK minimum version.\n"); |
| return result; |
| } |
| if (!verify_pik_certificate(&metadata.product_intermediate_key_certificate, |
| permanent_attributes.product_root_public_key, |
| minimum_version)) { |
| return AVB_IO_RESULT_OK; |
| } |
| |
| /* Verify the PSK certificate. */ |
| result = ops->read_rollback_index( |
| ops, AVB_ATX_PSK_VERSION_LOCATION, &minimum_version); |
| if (result != AVB_IO_RESULT_OK) { |
| avb_error("Failed to read PSK minimum version.\n"); |
| return result; |
| } |
| if (!verify_psk_certificate( |
| &metadata.product_signing_key_certificate, |
| metadata.product_intermediate_key_certificate.signed_data.public_key, |
| minimum_version, |
| permanent_attributes.product_id)) { |
| return AVB_IO_RESULT_OK; |
| } |
| |
| /* Verify the PSK is the same key that verified vbmeta. */ |
| if (public_key_length != AVB_ATX_PUBLIC_KEY_SIZE) { |
| avb_error("Public key length mismatch.\n"); |
| return AVB_IO_RESULT_OK; |
| } |
| if (0 != avb_safe_memcmp( |
| metadata.product_signing_key_certificate.signed_data.public_key, |
| public_key_data, |
| AVB_ATX_PUBLIC_KEY_SIZE)) { |
| avb_error("Public key mismatch.\n"); |
| return AVB_IO_RESULT_OK; |
| } |
| |
| /* Report the key versions used during verification. */ |
| ops->atx_ops->set_key_version( |
| ops->atx_ops, |
| AVB_ATX_PIK_VERSION_LOCATION, |
| metadata.product_intermediate_key_certificate.signed_data.key_version); |
| ops->atx_ops->set_key_version( |
| ops->atx_ops, |
| AVB_ATX_PSK_VERSION_LOCATION, |
| metadata.product_signing_key_certificate.signed_data.key_version); |
| |
| *out_is_trusted = true; |
| return AVB_IO_RESULT_OK; |
| } |
| |
| AvbIOResult avb_atx_generate_unlock_challenge( |
| AvbAtxOps* atx_ops, AvbAtxUnlockChallenge* out_unlock_challenge) { |
| AvbIOResult result = AVB_IO_RESULT_OK; |
| AvbAtxPermanentAttributes permanent_attributes; |
| |
| /* We need the permanent attributes to compute the product_id_hash. */ |
| result = atx_ops->read_permanent_attributes(atx_ops, &permanent_attributes); |
| if (result != AVB_IO_RESULT_OK) { |
| avb_error("Failed to read permanent attributes.\n"); |
| return result; |
| } |
| result = atx_ops->get_random( |
| atx_ops, AVB_ATX_UNLOCK_CHALLENGE_SIZE, last_unlock_challenge); |
| if (result != AVB_IO_RESULT_OK) { |
| avb_error("Failed to generate random challenge.\n"); |
| return result; |
| } |
| last_unlock_challenge_set = true; |
| out_unlock_challenge->version = 1; |
| sha256(permanent_attributes.product_id, |
| AVB_ATX_PRODUCT_ID_SIZE, |
| out_unlock_challenge->product_id_hash); |
| avb_memcpy(out_unlock_challenge->challenge, |
| last_unlock_challenge, |
| AVB_ATX_UNLOCK_CHALLENGE_SIZE); |
| return result; |
| } |
| |
| AvbIOResult avb_atx_validate_unlock_credential( |
| AvbAtxOps* atx_ops, |
| const AvbAtxUnlockCredential* unlock_credential, |
| bool* out_is_trusted) { |
| AvbIOResult result = AVB_IO_RESULT_OK; |
| AvbAtxPermanentAttributes permanent_attributes; |
| uint8_t permanent_attributes_hash[AVB_SHA256_DIGEST_SIZE]; |
| uint64_t minimum_version; |
| const AvbAlgorithmData* algorithm_data; |
| uint8_t challenge_hash[AVB_SHA512_DIGEST_SIZE]; |
| |
| /* Be pessimistic so we can exit early without having to remember to clear. |
| */ |
| *out_is_trusted = false; |
| |
| /* Sanity check the credential. */ |
| if (unlock_credential->version != 1) { |
| avb_error("Unsupported unlock credential format.\n"); |
| return AVB_IO_RESULT_OK; |
| } |
| |
| /* Read and verify permanent attributes. */ |
| result = atx_ops->read_permanent_attributes(atx_ops, &permanent_attributes); |
| if (result != AVB_IO_RESULT_OK) { |
| avb_error("Failed to read permanent attributes.\n"); |
| return result; |
| } |
| result = atx_ops->read_permanent_attributes_hash(atx_ops, |
| permanent_attributes_hash); |
| if (result != AVB_IO_RESULT_OK) { |
| avb_error("Failed to read permanent attributes hash.\n"); |
| return result; |
| } |
| if (!verify_permanent_attributes(&permanent_attributes, |
| permanent_attributes_hash)) { |
| return AVB_IO_RESULT_OK; |
| } |
| |
| /* Verify the PIK certificate. */ |
| result = atx_ops->ops->read_rollback_index( |
| atx_ops->ops, AVB_ATX_PIK_VERSION_LOCATION, &minimum_version); |
| if (result != AVB_IO_RESULT_OK) { |
| avb_error("Failed to read PIK minimum version.\n"); |
| return result; |
| } |
| if (!verify_pik_certificate( |
| &unlock_credential->product_intermediate_key_certificate, |
| permanent_attributes.product_root_public_key, |
| minimum_version)) { |
| return AVB_IO_RESULT_OK; |
| } |
| |
| /* Verify the PUK certificate. The minimum version is shared with the PSK. */ |
| result = atx_ops->ops->read_rollback_index( |
| atx_ops->ops, AVB_ATX_PSK_VERSION_LOCATION, &minimum_version); |
| if (result != AVB_IO_RESULT_OK) { |
| avb_error("Failed to read PSK minimum version.\n"); |
| return result; |
| } |
| if (!verify_puk_certificate( |
| &unlock_credential->product_unlock_key_certificate, |
| unlock_credential->product_intermediate_key_certificate.signed_data |
| .public_key, |
| minimum_version, |
| permanent_attributes.product_id)) { |
| return AVB_IO_RESULT_OK; |
| } |
| |
| /* Hash the most recent unlock challenge. */ |
| if (!last_unlock_challenge_set) { |
| avb_error("Challenge does not exist.\n"); |
| return AVB_IO_RESULT_OK; |
| } |
| sha512(last_unlock_challenge, AVB_ATX_UNLOCK_CHALLENGE_SIZE, challenge_hash); |
| last_unlock_challenge_set = false; |
| |
| /* Verify the challenge signature. */ |
| algorithm_data = avb_get_algorithm_data(AVB_ALGORITHM_TYPE_SHA512_RSA4096); |
| if (!avb_rsa_verify(unlock_credential->product_unlock_key_certificate |
| .signed_data.public_key, |
| AVB_ATX_PUBLIC_KEY_SIZE, |
| unlock_credential->challenge_signature, |
| AVB_RSA4096_NUM_BYTES, |
| challenge_hash, |
| AVB_SHA512_DIGEST_SIZE, |
| algorithm_data->padding, |
| algorithm_data->padding_len)) { |
| avb_error("Invalid unlock challenge signature.\n"); |
| return AVB_IO_RESULT_OK; |
| } |
| |
| *out_is_trusted = true; |
| return AVB_IO_RESULT_OK; |
| } |
