60 lines
2.2 KiB
C++
60 lines
2.2 KiB
C++
/*
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* Copyright 2015 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef SYSTEM_KEYMASTER_HMAC_H_
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#define SYSTEM_KEYMASTER_HMAC_H_
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#include <keymaster/serializable.h>
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namespace keymaster {
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// Only HMAC-SHA256 is supported.
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class HmacSha256 {
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public:
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HmacSha256(){};
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// DigestLength returns the length, in bytes, of the resulting digest.
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size_t DigestLength() const;
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// Initializes this instance using |key|. Call Init only once. It returns
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// false on the second of later calls.
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bool Init(const uint8_t* key, size_t key_length);
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bool Init(const Buffer& key);
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// Sign calculates the HMAC of |data| with the key supplied to the Init
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// method. At most |digest_len| bytes of the resulting digest are written
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// to |digest|.
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bool Sign(const Buffer& data, uint8_t* digest, size_t digest_len) const;
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bool Sign(const uint8_t* data, size_t data_len, uint8_t* digest, size_t digest_len) const;
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// Verify returns true if |digest| is a valid HMAC of |data| using the key
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// supplied to Init. |digest| must be exactly |DigestLength()| bytes long.
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// Use of this method is strongly recommended over using Sign() with a manual
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// comparison (such as memcmp), as such comparisons may result in
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// side-channel disclosures, such as timing, that undermine the cryptographic
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// integrity.
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bool Verify(const Buffer& data, const Buffer& digest) const;
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bool Verify(const uint8_t* data, size_t data_len, const uint8_t* digest,
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size_t digest_len) const;
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private:
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UniquePtr<uint8_t[]> key_;
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size_t key_len_;
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};
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} // namespace keymaster
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#endif // SYSTEM_KEYMASTER_HMAC_H_
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