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Generalize CryptoType infrastructure
More consistency between MetadataCrypt and cryptfs, and steps towards supporting Adiantum properly in MetadataCrypt. Test: create private volume on Cuttlefish Bug: 147814592 Change-Id: Ic3993c1fde11b4f5a9e6cc8ee588a7d92241c6ab
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| Original file line number | Diff line number | Diff line change |
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| /* | ||
| * Copyright (C) 2020 The Android Open Source Project | ||
| * | ||
| * Licensed under the Apache License, Version 2.0 (the "License"); | ||
| * you may not use this file except in compliance with the License. | ||
| * You may obtain a copy of the License at | ||
| * | ||
| * http://www.apache.org/licenses/LICENSE-2.0 | ||
| * | ||
| * Unless required by applicable law or agreed to in writing, software | ||
| * distributed under the License is distributed on an "AS IS" BASIS, | ||
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| * See the License for the specific language governing permissions and | ||
| * limitations under the License. | ||
| */ | ||
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| #include "CryptoType.h" | ||
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| #include <string.h> | ||
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| #include <android-base/logging.h> | ||
| #include <cutils/properties.h> | ||
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| namespace android { | ||
| namespace vold { | ||
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| const CryptoType& lookup_crypto_algorithm(const CryptoType table[], int table_len, | ||
| const CryptoType& default_alg, const char* property) { | ||
| char paramstr[PROPERTY_VALUE_MAX]; | ||
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| property_get(property, paramstr, default_alg.get_config_name()); | ||
| for (int i = 0; i < table_len; i++) { | ||
| if (strcmp(paramstr, table[i].get_config_name()) == 0) { | ||
| return table[i]; | ||
| } | ||
| } | ||
| LOG(ERROR) << "Invalid name (" << paramstr << ") for " << property << ". Defaulting to " | ||
| << default_alg.get_config_name() << "."; | ||
| return default_alg; | ||
| } | ||
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| } // namespace vold | ||
| } // namespace android |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,103 @@ | ||
| /* | ||
| * Copyright (C) 2020 The Android Open Source Project | ||
| * | ||
| * Licensed under the Apache License, Version 2.0 (the "License"); | ||
| * you may not use this file except in compliance with the License. | ||
| * You may obtain a copy of the License at | ||
| * | ||
| * http://www.apache.org/licenses/LICENSE-2.0 | ||
| * | ||
| * Unless required by applicable law or agreed to in writing, software | ||
| * distributed under the License is distributed on an "AS IS" BASIS, | ||
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| * See the License for the specific language governing permissions and | ||
| * limitations under the License. | ||
| */ | ||
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| #pragma once | ||
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| #include <stdlib.h> | ||
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| namespace android { | ||
| namespace vold { | ||
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| // Struct representing an encryption algorithm supported by vold. | ||
| // "config_name" represents the name we give the algorithm in | ||
| // read-only properties and fstab files | ||
| // "kernel_name" is the name we present to the Linux kernel | ||
| // "keysize" is the size of the key in bytes. | ||
| struct CryptoType { | ||
| // We should only be constructing CryptoTypes as part of | ||
| // supported_crypto_types[]. We do it via this pseudo-builder pattern, | ||
| // which isn't pure or fully protected as a concession to being able to | ||
| // do it all at compile time. Add new CryptoTypes in | ||
| // supported_crypto_types[] below. | ||
| constexpr CryptoType() : CryptoType(nullptr, nullptr, 0xFFFFFFFF) {} | ||
| constexpr CryptoType set_keysize(size_t size) const { | ||
| return CryptoType(this->config_name, this->kernel_name, size); | ||
| } | ||
| constexpr CryptoType set_config_name(const char* property) const { | ||
| return CryptoType(property, this->kernel_name, this->keysize); | ||
| } | ||
| constexpr CryptoType set_kernel_name(const char* crypto) const { | ||
| return CryptoType(this->config_name, crypto, this->keysize); | ||
| } | ||
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| constexpr const char* get_config_name() const { return config_name; } | ||
| constexpr const char* get_kernel_name() const { return kernel_name; } | ||
| constexpr size_t get_keysize() const { return keysize; } | ||
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| private: | ||
| const char* config_name; | ||
| const char* kernel_name; | ||
| size_t keysize; | ||
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| constexpr CryptoType(const char* property, const char* crypto, size_t ksize) | ||
| : config_name(property), kernel_name(crypto), keysize(ksize) {} | ||
| }; | ||
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| // Use the named android property to look up a type from the table | ||
| // If the property is not set or matches no table entry, return the default. | ||
| const CryptoType& lookup_crypto_algorithm(const CryptoType table[], int table_len, | ||
| const CryptoType& default_alg, const char* property); | ||
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| // Some useful types | ||
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| constexpr CryptoType invalid_crypto_type = CryptoType(); | ||
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| constexpr CryptoType aes_256_xts = CryptoType() | ||
| .set_config_name("aes-256-xts") | ||
| .set_kernel_name("aes-xts-plain64") | ||
| .set_keysize(64); | ||
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| constexpr CryptoType adiantum = CryptoType() | ||
| .set_config_name("adiantum") | ||
| .set_kernel_name("xchacha12,aes-adiantum-plain64") | ||
| .set_keysize(32); | ||
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| // Support compile-time validation of a crypto type table | ||
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| template <typename T, size_t N> | ||
| constexpr size_t array_length(T (&)[N]) { | ||
| return N; | ||
| } | ||
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| constexpr bool isValidCryptoType(size_t max_keylen, const CryptoType& crypto_type) { | ||
| return ((crypto_type.get_config_name() != nullptr) && | ||
| (crypto_type.get_kernel_name() != nullptr) && | ||
| (crypto_type.get_keysize() <= max_keylen)); | ||
| } | ||
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| // Confirms that all supported_crypto_types have a small enough keysize and | ||
| // had both set_config_name() and set_kernel_name() called. | ||
| // Note in C++11 that constexpr functions can only have a single line. | ||
| // So our code is a bit convoluted (using recursion instead of a loop), | ||
| // but it's asserting at compile time that all of our key lengths are valid. | ||
| constexpr bool validateSupportedCryptoTypes(size_t max_keylen, const CryptoType types[], | ||
| size_t len) { | ||
| return len == 0 || (isValidCryptoType(max_keylen, types[len - 1]) && | ||
| validateSupportedCryptoTypes(max_keylen, types, len - 1)); | ||
| } | ||
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| } // namespace vold | ||
| } // namespace android |
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