-// Copyright 2016 The Chromium Authors. All rights reserved.
+// Copyright 2016 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include <tuple>
#include "base/base_export.h"
-#include "base/hash/hash.h"
-#include "base/logging.h"
+#include "base/check.h"
+#include "base/containers/span.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.
+// Token, a new UnguessableToken is always generated at runtime from a
+// cryptographically strong random source (or copied or serialized and
+// deserialized from another such UnguessableToken). Also unlike Token, the ==
+// and != operators are constant time. 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.
+// An UnguessableToken is a strong *bearer token*. Bearer tokens are like HTTP
+// cookies: if a caller has the token, the callee thereby considers the caller
+// authorized to request the operation the callee performs.
+//
+// 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 on 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.
+// sending/receiving empty tokens should be treated as a security issue. If
+// there is a valid scenario for sending "no token" across processes, use
+// absl::optional instead of an empty token.
+
class BASE_EXPORT UnguessableToken {
public:
- // Create a unique UnguessableToken.
+ // Create a unique UnguessableToken. It's guaranteed to be nonempty.
static UnguessableToken Create();
// Returns a reference to a global null UnguessableToken. This should only be
// default constructor.
static const UnguessableToken& Null();
- // Return a UnguessableToken built from the high/low bytes provided.
+ // Return an 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
+ // NOTE: If the returned `absl::optional` does not have a value, it means that
+ // `high` and `low` correspond to an `UnguesssableToken` that was never
// initialized via Create(). This is a security issue, and should be handled.
- static UnguessableToken Deserialize(uint64_t high, uint64_t low);
+ static absl::optional<UnguessableToken> Deserialize(uint64_t high,
+ uint64_t low);
// Creates an empty UnguessableToken.
// Assign to it with Create() before using it.
constexpr UnguessableToken() = default;
+ constexpr UnguessableToken(const UnguessableToken&) = default;
+ constexpr UnguessableToken& operator=(const UnguessableToken&) = default;
+ constexpr UnguessableToken(UnguessableToken&&) noexcept = default;
+ constexpr UnguessableToken& operator=(UnguessableToken&&) = default;
+
// NOTE: Serializing an empty UnguessableToken is an illegal operation.
uint64_t GetHighForSerialization() const {
DCHECK(!is_empty());
return token_.low();
}
- bool is_empty() const { return token_.is_zero(); }
+ constexpr 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(); }
+ explicit constexpr operator bool() const { return !is_empty(); }
+
+ span<const uint8_t, 16> AsBytes() const { return token_.AsBytes(); }
- bool operator<(const UnguessableToken& other) const {
+ constexpr 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;
bool operator!=(const UnguessableToken& other) const {
return !(*this == other);
}
+#if defined(UNIT_TEST)
+ static UnguessableToken CreateForTesting(uint64_t high, uint64_t low) {
+ absl::optional<UnguessableToken> token = Deserialize(high, low);
+ DCHECK(token.has_value());
+ return token.value();
+ }
+#endif
+
private:
friend struct UnguessableTokenHash;
explicit UnguessableToken(const Token& token);
projects / platform / framework / web / chromium-efl.git / blobdiff