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