/src/connectedhomeip/src/crypto/SessionKeystore.h

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/*
 *    Copyright (c) 2023 Project CHIP Authors
 *    All rights reserved.
 *
 *    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.
 */

#pragma once

#include <crypto/CHIPCryptoPAL.h>
#include <lib/support/Span.h>

namespace chip {
namespace Crypto {

/**
 * @brief Interface for deriving session keys and managing their lifetime.
 *
 * The session keystore interface provides an abstraction that allows the application to store
 * session keys in a secure environment. It uses the concept of key handles that isolate the
 * application from the actual key material.
 *
 * @note Refactor has begun to refactor this API into two disctinct APIs : SymmetrycKeyStore & SessionKeyDerivation
 *       Work has not been completed so the  SessionKeystore has APIs that shouldn't go together for the time being
 *       The SessionKeystore APIs are split into two sections, one for each futur API.
 */
class SessionKeystore
{
public:
    virtual ~SessionKeystore() {}

    /****************************
     * SymmetricKeyStore APIs
     *****************************/

    /**
     * @brief Import raw key material and return a key handle for a key that be used to do AES 128 encryption.
     *
     * @note This method should only be used when using the raw key material in the Matter stack
     * cannot be avoided. Ideally, crypto interfaces should allow platforms to perform all the
     * cryptographic operations in a secure environment.
     *
     * If the method returns no error, the application is responsible for destroying the handle
     * using the DestroyKey() method when the key is no longer needed.
     */
    virtual CHIP_ERROR CreateKey(const Symmetric128BitsKeyByteArray & keyMaterial, Aes128KeyHandle & key) = 0;

    /**
     * @brief Import raw key material and return a key handle for a key that can be used to do 128-bit HMAC.
     *
     * @note This method should only be used when using the raw key material in the Matter stack
     * cannot be avoided. Ideally, crypto interfaces should allow platforms to perform all the
     * cryptographic operations in a secure environment.
     *
     * If the method returns no error, the application is responsible for destroying the handle
     * using the DestroyKey() method when the key is no longer needed.
     */
    virtual CHIP_ERROR CreateKey(const Symmetric128BitsKeyByteArray & keyMaterial, Hmac128KeyHandle & key) = 0;

    /**
     * @brief Import raw key material and return a key handle for an HKDF key.
     *
     * @note This method should only be used when using the raw key material in the Matter stack
     * cannot be avoided. Ideally, crypto interfaces should allow platforms to perform all the
     * cryptographic operations in a secure environment.
     *
     * If the method returns no error, the application is responsible for destroying the handle
     * using the DestroyKey() method when the key is no longer needed.
     */
    virtual CHIP_ERROR CreateKey(const ByteSpan & keyMaterial, HkdfKeyHandle & key) = 0;

    /**
     * @brief Destroy key.
     *
     * The method can take an uninitialized handle in which case it is a no-op.
     * As a result of calling this method, the handle is put in the uninitialized state.
     */
    virtual void DestroyKey(Symmetric128BitsKeyHandle & key) = 0;

    /**
     * @brief Destroy key.
     *
     * The method can take an uninitialized handle in which case it is a no-op.
     * As a result of calling this method, the handle is put in the uninitialized state.
     */
    virtual void DestroyKey(HkdfKeyHandle & key) = 0;

    /****************************
     * SessionKeyDerivation APIs
     *****************************/

    /**
     * @brief Derive key from a session establishment's `SharedSecret`.
     *
     * Use `Crypto_KDF` (HKDF) primitive as defined in the Matter specification to derive
     * a symmetric (AES) key from the session establishment's `SharedSecret`.
     *
     * If the method returns no error, the caller is responsible for destroying the symmetric key
     * using the DestroyKey() method when the key is no longer needed.
     */
    virtual CHIP_ERROR DeriveKey(const P256ECDHDerivedSecret & secret, const ByteSpan & salt, const ByteSpan & info,
                                 Aes128KeyHandle & key) = 0;

    /**
     * @brief Derive session keys from a session establishment's `SharedSecret`.
     *
     * Use `Crypto_KDF` (HKDF) primitive as defined in the Matter specification to derive symmetric
     * (AES) session keys for both directions, and the attestation challenge from the session
     * establishment's `SharedSecret`.
     *
     * If the method returns no error, the caller is responsible for destroying the symmetric keys
     * using the DestroyKey() method when the keys are no longer needed. On failure, the method is
     * responsible for releasing all keys that it allocated so far.
     */
    virtual CHIP_ERROR DeriveSessionKeys(const ByteSpan & secret, const ByteSpan & salt, const ByteSpan & info,
                                         Aes128KeyHandle & i2rKey, Aes128KeyHandle & r2iKey,
                                         AttestationChallenge & attestationChallenge) = 0;

    /**
     * @brief Derive session keys from a session establishment's `SharedSecret`.
     *
     * Use Crypto_KDF (HKDF) primitive as defined in the Matter specification to derive symmetric
     * (AES) session keys for both directions, and the attestation challenge from the session
     * establishment's `SharedSecret`, represented as the key handle.
     *
     * If the method returns no error, the caller is responsible for destroying the symmetric keys
     * using the DestroyKey() method when the keys are no longer needed. On failure, the method is
     * responsible for releasing all keys that it allocated so far.
     */
    virtual CHIP_ERROR DeriveSessionKeys(const HkdfKeyHandle & secretKey, const ByteSpan & salt, const ByteSpan & info,
                                         Aes128KeyHandle & i2rKey, Aes128KeyHandle & r2iKey,
                                         AttestationChallenge & attestationChallenge) = 0;

    /**
     * @brief Persistently store an ICD key.
     *
     * If input is already a persistent key handle, the function is a no-op and the original handle is returned.
     * If input is a volatile key handle, key is persisted and the handle may be updated.
     *
     * If the method returns no error, the application is responsible for destroying the handle
     * using the DestroyKey() method when the key is no longer needed.
     */
    virtual CHIP_ERROR PersistICDKey(Symmetric128BitsKeyHandle & key) { return CHIP_NO_ERROR; }
};

/**
 * @brief RAII class to hold a temporary key handle that is destroyed on scope exit.
 */
template <class KeyHandleType>
class AutoReleaseSymmetricKey
{
public:
    explicit AutoReleaseSymmetricKey(SessionKeystore & keystore) : mKeystore(keystore) {}
    ~AutoReleaseSymmetricKey() { mKeystore.DestroyKey(mKeyHandle); }

    KeyHandleType & KeyHandle() { return mKeyHandle; }

private:
    SessionKeystore & mKeystore;
    KeyHandleType mKeyHandle;
};

} // namespace Crypto
} // namespace chip

Line	Count	Source (jump to first uncovered line)
1		/*
2		* Copyright (c) 2023 Project CHIP Authors
3		* All rights reserved.
4		*
5		* Licensed under the Apache License, Version 2.0 (the "License");
6		* you may not use this file except in compliance with the License.
7		* You may obtain a copy of the License at
8		*
9		* http://www.apache.org/licenses/LICENSE-2.0
10		*
11		* Unless required by applicable law or agreed to in writing, software
12		* distributed under the License is distributed on an "AS IS" BASIS,
13		* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14		* See the License for the specific language governing permissions and
15		* limitations under the License.
16		*/
17
18		#pragma once
19
20		#include <crypto/CHIPCryptoPAL.h>
21		#include <lib/support/Span.h>
22
23		namespace chip {
24		namespace Crypto {
25
26		/**
27		* @brief Interface for deriving session keys and managing their lifetime.
28		*
29		* The session keystore interface provides an abstraction that allows the application to store
30		* session keys in a secure environment. It uses the concept of key handles that isolate the
31		* application from the actual key material.
32		*
33		* @note Refactor has begun to refactor this API into two disctinct APIs : SymmetrycKeyStore & SessionKeyDerivation
34		* Work has not been completed so the SessionKeystore has APIs that shouldn't go together for the time being
35		* The SessionKeystore APIs are split into two sections, one for each futur API.
36		*/
37		class SessionKeystore
38		{
39		public:
40	0	virtual ~SessionKeystore() {}
41
42		/****************************
43		* SymmetricKeyStore APIs
44		*****************************/
45
46		/**
47		* @brief Import raw key material and return a key handle for a key that be used to do AES 128 encryption.
48		*
49		* @note This method should only be used when using the raw key material in the Matter stack
50		* cannot be avoided. Ideally, crypto interfaces should allow platforms to perform all the
51		* cryptographic operations in a secure environment.
52		*
53		* If the method returns no error, the application is responsible for destroying the handle
54		* using the DestroyKey() method when the key is no longer needed.
55		*/
56		virtual CHIP_ERROR CreateKey(const Symmetric128BitsKeyByteArray & keyMaterial, Aes128KeyHandle & key) = 0;
57
58		/**
59		* @brief Import raw key material and return a key handle for a key that can be used to do 128-bit HMAC.
60		*
61		* @note This method should only be used when using the raw key material in the Matter stack
62		* cannot be avoided. Ideally, crypto interfaces should allow platforms to perform all the
63		* cryptographic operations in a secure environment.
64		*
65		* If the method returns no error, the application is responsible for destroying the handle
66		* using the DestroyKey() method when the key is no longer needed.
67		*/
68		virtual CHIP_ERROR CreateKey(const Symmetric128BitsKeyByteArray & keyMaterial, Hmac128KeyHandle & key) = 0;
69
70		/**
71		* @brief Import raw key material and return a key handle for an HKDF key.
72		*
73		* @note This method should only be used when using the raw key material in the Matter stack
74		* cannot be avoided. Ideally, crypto interfaces should allow platforms to perform all the
75		* cryptographic operations in a secure environment.
76		*
77		* If the method returns no error, the application is responsible for destroying the handle
78		* using the DestroyKey() method when the key is no longer needed.
79		*/
80		virtual CHIP_ERROR CreateKey(const ByteSpan & keyMaterial, HkdfKeyHandle & key) = 0;
81
82		/**
83		* @brief Destroy key.
84		*
85		* The method can take an uninitialized handle in which case it is a no-op.
86		* As a result of calling this method, the handle is put in the uninitialized state.
87		*/
88		virtual void DestroyKey(Symmetric128BitsKeyHandle & key) = 0;
89
90		/**
91		* @brief Destroy key.
92		*
93		* The method can take an uninitialized handle in which case it is a no-op.
94		* As a result of calling this method, the handle is put in the uninitialized state.
95		*/
96		virtual void DestroyKey(HkdfKeyHandle & key) = 0;
97
98		/****************************
99		* SessionKeyDerivation APIs
100		*****************************/
101
102		/**
103		* @brief Derive key from a session establishment's `SharedSecret`.
104		*
105		* Use `Crypto_KDF` (HKDF) primitive as defined in the Matter specification to derive
106		* a symmetric (AES) key from the session establishment's `SharedSecret`.
107		*
108		* If the method returns no error, the caller is responsible for destroying the symmetric key
109		* using the DestroyKey() method when the key is no longer needed.
110		*/
111		virtual CHIP_ERROR DeriveKey(const P256ECDHDerivedSecret & secret, const ByteSpan & salt, const ByteSpan & info,
112		Aes128KeyHandle & key) = 0;
113
114		/**
115		* @brief Derive session keys from a session establishment's `SharedSecret`.
116		*
117		* Use `Crypto_KDF` (HKDF) primitive as defined in the Matter specification to derive symmetric
118		* (AES) session keys for both directions, and the attestation challenge from the session
119		* establishment's `SharedSecret`.
120		*
121		* If the method returns no error, the caller is responsible for destroying the symmetric keys
122		* using the DestroyKey() method when the keys are no longer needed. On failure, the method is
123		* responsible for releasing all keys that it allocated so far.
124		*/
125		virtual CHIP_ERROR DeriveSessionKeys(const ByteSpan & secret, const ByteSpan & salt, const ByteSpan & info,
126		Aes128KeyHandle & i2rKey, Aes128KeyHandle & r2iKey,
127		AttestationChallenge & attestationChallenge) = 0;
128
129		/**
130		* @brief Derive session keys from a session establishment's `SharedSecret`.
131		*
132		* Use Crypto_KDF (HKDF) primitive as defined in the Matter specification to derive symmetric
133		* (AES) session keys for both directions, and the attestation challenge from the session
134		* establishment's `SharedSecret`, represented as the key handle.
135		*
136		* If the method returns no error, the caller is responsible for destroying the symmetric keys
137		* using the DestroyKey() method when the keys are no longer needed. On failure, the method is
138		* responsible for releasing all keys that it allocated so far.
139		*/
140		virtual CHIP_ERROR DeriveSessionKeys(const HkdfKeyHandle & secretKey, const ByteSpan & salt, const ByteSpan & info,
141		Aes128KeyHandle & i2rKey, Aes128KeyHandle & r2iKey,
142		AttestationChallenge & attestationChallenge) = 0;
143
144		/**
145		* @brief Persistently store an ICD key.
146		*
147		* If input is already a persistent key handle, the function is a no-op and the original handle is returned.
148		* If input is a volatile key handle, key is persisted and the handle may be updated.
149		*
150		* If the method returns no error, the application is responsible for destroying the handle
151		* using the DestroyKey() method when the key is no longer needed.
152		*/
153	0	virtual CHIP_ERROR PersistICDKey(Symmetric128BitsKeyHandle & key) { return CHIP_NO_ERROR; } Unexecuted instantiation: chip::Crypto::SessionKeystore::PersistICDKey(chip::Crypto::Symmetric128BitsKeyHandle&) Unexecuted instantiation: chip::Crypto::SessionKeystore::PersistICDKey(chip::Crypto::Symmetric128BitsKeyHandle&)
154		};
155
156		/**
157		* @brief RAII class to hold a temporary key handle that is destroyed on scope exit.
158		*/
159		template <class KeyHandleType>
160		class AutoReleaseSymmetricKey
161		{
162		public:
163	0	explicit AutoReleaseSymmetricKey(SessionKeystore & keystore) : mKeystore(keystore) {} Unexecuted instantiation: chip::Crypto::AutoReleaseSymmetricKey<chip::Crypto::Aes128KeyHandle>::AutoReleaseSymmetricKey(chip::Crypto::SessionKeystore&) Unexecuted instantiation: chip::Crypto::AutoReleaseSymmetricKey<chip::Crypto::HkdfKeyHandle>::AutoReleaseSymmetricKey(chip::Crypto::SessionKeystore&)
164	0	~AutoReleaseSymmetricKey() { mKeystore.DestroyKey(mKeyHandle); } Unexecuted instantiation: chip::Crypto::AutoReleaseSymmetricKey<chip::Crypto::Aes128KeyHandle>::~AutoReleaseSymmetricKey() Unexecuted instantiation: chip::Crypto::AutoReleaseSymmetricKey<chip::Crypto::HkdfKeyHandle>::~AutoReleaseSymmetricKey()
165
166	0	KeyHandleType & KeyHandle() { return mKeyHandle; } Unexecuted instantiation: chip::Crypto::AutoReleaseSymmetricKey<chip::Crypto::Aes128KeyHandle>::KeyHandle() Unexecuted instantiation: chip::Crypto::AutoReleaseSymmetricKey<chip::Crypto::HkdfKeyHandle>::KeyHandle()
167
168		private:
169		SessionKeystore & mKeystore;
170		KeyHandleType mKeyHandle;
171		};
172
173		} // namespace Crypto
174		} // namespace chip

Coverage Report

Created: 2025-08-28 06:31