github.com/mre-fog/trillianxx@v1.1.2-0.20180615153820-ae375a99d36a/merkle/objhasher/objhasher.go (about)

     1  // Copyright 2017 Google Inc. All Rights Reserved.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  // Package objhasher provides generic object hashing functionality.
    16  package objhasher
    17  
    18  import (
    19  	"crypto"
    20  	"fmt"
    21  
    22  	"github.com/benlaurie/objecthash/go/objecthash"
    23  	"github.com/google/trillian"
    24  	"github.com/google/trillian/merkle/hashers"
    25  	"github.com/google/trillian/merkle/rfc6962"
    26  )
    27  
    28  func init() {
    29  	hashers.RegisterLogHasher(trillian.HashStrategy_OBJECT_RFC6962_SHA256, NewLogHasher(rfc6962.New(crypto.SHA256)))
    30  }
    31  
    32  type objmaphasher struct {
    33  	hashers.MapHasher
    34  }
    35  
    36  type objloghasher struct {
    37  	hashers.LogHasher
    38  }
    39  
    40  // NewMapHasher returns a new ObjectHasher based on the passed in MapHasher
    41  func NewMapHasher(baseHasher hashers.MapHasher) hashers.MapHasher {
    42  	return &objmaphasher{
    43  		MapHasher: baseHasher,
    44  	}
    45  }
    46  
    47  // NewLogHasher returns a new ObjectHasher based on the passed in MapHasher
    48  func NewLogHasher(baseHasher hashers.LogHasher) hashers.LogHasher {
    49  	return &objloghasher{
    50  		LogHasher: baseHasher,
    51  	}
    52  }
    53  
    54  // HashLeaf returns the object hash of leaf, which must be a JSON object.
    55  func (o *objloghasher) HashLeaf(leaf []byte) ([]byte, error) {
    56  	hash, err := objecthash.CommonJSONHash(string(leaf))
    57  	if err != nil {
    58  		return nil, fmt.Errorf("CommonJSONHash(%s): %v", leaf, err)
    59  	}
    60  	return hash[:], err
    61  }
    62  
    63  // HashLeaf returns the object hash of leaf, which must be a JSON object.
    64  func (o *objmaphasher) HashLeaf(treeID int64, index []byte, leaf []byte) ([]byte, error) {
    65  	hash, err := objecthash.CommonJSONHash(string(leaf))
    66  	if err != nil {
    67  		return nil, fmt.Errorf("CommonJSONHash(%s): %v", leaf, err)
    68  	}
    69  	return hash[:], nil
    70  }