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// Copyright 2019 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be found in the LICENSE file.
#include <stddef.h>
#include <stdint.h>
#include <zircon/errors.h>
#include <zircon/types.h>
#include <digest/digest.h>
#include <digest/node-digest.h>
namespace digest {
namespace internal {
// |digest::internal::HashListBase| contains common hash list code. Callers MUST NOT use this class
// directly. See |digest::HashListCreator| and |digest::HashListVerifier| below.
class HashListBase {
HashListBase() = default;
virtual ~HashListBase() = default;
size_t data_off() const { return data_off_; }
size_t data_len() const { return data_len_; }
size_t list_off() const { return list_off_; }
size_t list_len() const { return list_len_; }
// Gets or sets relevant NodeDigest fields.
uint64_t GetNodeId() const { return; }
size_t GetNodeSize() const { return node_digest_.node_size(); }
size_t GetDigestSize() const { return node_digest_.len(); }
void SetNodeId(uint64_t id) { node_digest_.set_id(id); }
zx_status_t SetNodeSize(size_t node_size) { return node_digest_.SetNodeSize(node_size); }
// Returns true if |data_off| is aligned to a node boundary.
bool IsAligned(size_t data_off) const { return node_digest_.IsAligned(data_off); }
// Modifies |data_off| and |buf_len| to be aligned to the minimum number of nodes that covered
// their original range.
zx_status_t Align(size_t *data_off, size_t *buf_len) const;
// Sets the length of data this hash list will represent. The maxium possible size is
// |SIZE_MAX - NodeSize + 1|, i.e. the maximum node-aligned value of type |size_t|.
zx_status_t SetDataLength(size_t data_len);
// Returns the corresponding offset in the hash list for an offset in the data. This method
// does not check if |data_off| is within bounds.
size_t GetListOffset(size_t data_off) const;
// Returns the minimum size needed to hold a hash list for the given |data_len|. Note that this
// differs from |list_len()| in that it returns what's needed, whereas the latter returns what
// the list length currently is.
size_t GetListLength() const;
void set_list_len(size_t list_len) { list_len_ = list_len; }
// Checks range given by |data_off| and |buf_len| is valid.
virtual bool IsValidRange(size_t data_off, size_t buf_len);
// Handle the |buf_len| bytes from |buf|, corresponding to the data sequence starting at
// |data_off|.
zx_status_t ProcessData(const uint8_t *buf, size_t buf_len, size_t data_off);
// Process the next digest in the hash list, e.g. write a digest when creating, or compare when
// verifying. The no-argument version simply invokes the second version with the current digest.
// The second version is implemented in derived classes.
void HandleOne();
virtual void HandleOne(const Digest &digest) {}
zx_status_t Check(size_t off, size_t len, size_t max, size_t *out = nullptr) const;
// Digest object used to create hashes to store or check.
NodeDigest node_digest_;
// Offset and length of data represented by the hash list.
size_t data_off_ = 0;
size_t data_len_ = 0;
// Contents, offset, and length of the hash list.
size_t list_off_ = 0;
size_t list_len_ = 0;
// |digest::internal::HashList| contains code templated on the list type. Callers MUST NOT use this
// class directly. See |digest::HashListCreator| and |digest::HashListVerifier| below.
template <typename T>
class HashList : public HashListBase {
static_assert(sizeof(T) == sizeof(uint8_t), "Do not invoke HashList directly.");
T *list() const { return list_; }
// Registers |list| as a hash list for |data_len_| bytes of data.
zx_status_t SetList(T *list, size_t list_len);
T *list_ = nullptr;
} // namespace internal
// |digest::HashListCreator| creates hash lists for data.
// Example (without error checking):
// HashListCreator creator;
// creator.SetDataLength(data_len);
// size_t list_len = creator.GetListLength();
// uint8_t *list = malloc(list_len); // or other allocation routine
// creator.SetList(list, list_len);
// creator.Append(&data[0], partial_len1);
// creator.Append(&data[partial_len1], partial_len2);
class HashListCreator : public internal::HashList<uint8_t> {
// Reads |buf_len| bytes of data from |buf| and appends digests to the hash |list|.
zx_status_t Append(const void *buf, size_t buf_len);
// Writes a single calculated digest to the appropriate position in the list.
void HandleOne(const Digest &digest) override;
// |digest::HashListVerifier| verifies data against a hash list.
// Example (without error checking):
// HashListVerifier verifier;
// verifier.SetDataLength(data_len);
// verifier.SetList(list, list_len);
// verifier.Align(&data_off, &partial_len);
// return verifier.Verify(&data[data_off], partial_len) == ZX_OK;
class HashListVerifier : public internal::HashList<const uint8_t> {
// Reads |buf_len| bytes of data from |buf|, calculates digests for each node of data, and
// compares them to the digests stored in the hash list. |data_off| must be node-aligned.
// |buf_len| must be node-aligned, or reach the end of the data. See also |Align|.
zx_status_t Verify(const void *buf, size_t buf_len, size_t data_off);
// Verification ranges must start on a node boundary, and end on a node boundary or the end of the
// data.
bool IsValidRange(size_t data_off, size_t buf_len) override;
// Compares a single calculated digest to the corresponding one in the list.
void HandleOne(const Digest &digest) override;
// Used to store the verification result. The verification logic intentionally does NOT short
// circuit; we want the hash checks to be as close to constant time as possible.
bool verified_ = false;
} // namespace digest