| // Copyright 2016 The Chromium Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #ifndef BASE_UNGUESSABLE_TOKEN_H_ |
| #define BASE_UNGUESSABLE_TOKEN_H_ |
| |
| #include <stdint.h> |
| #include <string.h> |
| #include <iosfwd> |
| #include <tuple> |
| |
| #include "base/base_export.h" |
| #include "base/hash/hash.h" |
| #include "base/logging.h" |
| #include "base/token.h" |
| |
| namespace base { |
| |
| struct UnguessableTokenHash; |
| |
| // UnguessableToken is, like Token, a randomly chosen 128-bit value. Unlike |
| // Token however, a new UnguessableToken must always be generated at runtime |
| // from a cryptographically strong random source (or copied or serialized and |
| // deserialized from another such UnguessableToken). It can be used as part of a |
| // larger aggregate type, or as an ID in and of itself. |
| // |
| // UnguessableToken can be used to implement "Capability-Based Security". |
| // In other words, UnguessableToken can be used when the resource associated |
| // with the ID needs to be protected against manipulation by other untrusted |
| // agents in the system, and there is no other convenient way to verify the |
| // authority of the agent to do so (because the resource is part of a table |
| // shared across processes, for instance). In such a scheme, knowledge of the |
| // token value in and of itself is sufficient proof of authority to carry out |
| // an operation against the associated resource. |
| // |
| // Use Create() for creating new UnguessableTokens. |
| // |
| // NOTE: It is illegal to send empty UnguessableTokens across processes, and |
| // sending/receiving empty tokens should be treated as a security issue. |
| // If there is a valid scenario for sending "no token" across processes, |
| // base::Optional should be used instead of an empty token. |
| class BASE_EXPORT UnguessableToken { |
| public: |
| // Create a unique UnguessableToken. |
| static UnguessableToken Create(); |
| |
| // Returns a reference to a global null UnguessableToken. This should only be |
| // used for functions that need to return a reference to an UnguessableToken, |
| // and should not be used as a general-purpose substitute for invoking the |
| // default constructor. |
| static const UnguessableToken& Null(); |
| |
| // Return a UnguessableToken built from the high/low bytes provided. |
| // It should only be used in deserialization scenarios. |
| // |
| // NOTE: If the deserialized token is empty, it means that it was never |
| // initialized via Create(). This is a security issue, and should be handled. |
| static UnguessableToken Deserialize(uint64_t high, uint64_t low); |
| |
| // Creates an empty UnguessableToken. |
| // Assign to it with Create() before using it. |
| constexpr UnguessableToken() = default; |
| |
| // NOTE: Serializing an empty UnguessableToken is an illegal operation. |
| uint64_t GetHighForSerialization() const { |
| DCHECK(!is_empty()); |
| return token_.high(); |
| } |
| |
| // NOTE: Serializing an empty UnguessableToken is an illegal operation. |
| uint64_t GetLowForSerialization() const { |
| DCHECK(!is_empty()); |
| return token_.low(); |
| } |
| |
| bool is_empty() const { return token_.is_zero(); } |
| |
| // Hex representation of the unguessable token. |
| std::string ToString() const { return token_.ToString(); } |
| |
| explicit operator bool() const { return !is_empty(); } |
| |
| bool operator<(const UnguessableToken& other) const { |
| return token_ < other.token_; |
| } |
| |
| bool operator==(const UnguessableToken& other) const { |
| return token_ == other.token_; |
| } |
| |
| bool operator!=(const UnguessableToken& other) const { |
| return !(*this == other); |
| } |
| |
| private: |
| friend struct UnguessableTokenHash; |
| explicit UnguessableToken(const Token& token); |
| |
| base::Token token_; |
| }; |
| |
| BASE_EXPORT std::ostream& operator<<(std::ostream& out, |
| const UnguessableToken& token); |
| |
| // For use in std::unordered_map. |
| struct UnguessableTokenHash { |
| size_t operator()(const base::UnguessableToken& token) const { |
| DCHECK(token); |
| return TokenHash()(token.token_); |
| } |
| }; |
| |
| } // namespace base |
| |
| #endif // BASE_UNGUESSABLE_TOKEN_H_ |