github.com/google/trillian-examples@v0.0.0-20240520080811-0d40d35cef0e/binary_transparency/firmware/devices/dummy/common/measurement.go (about)

     1  // Copyright 2020 Google LLC. 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 common
    16  
    17  import (
    18  	"crypto/sha512"
    19  	"fmt"
    20  )
    21  
    22  // ExpectedMeasurement returns the expected on-device measurement hash for the
    23  // given firmware image.
    24  //
    25  // For the dummy device, this is SHA512("dummy"||img)
    26  func ExpectedMeasurement(img []byte) ([]byte, error) {
    27  	hasher := sha512.New()
    28  	if _, err := hasher.Write([]byte("dummy")); err != nil {
    29  		return nil, fmt.Errorf("failed to write measurement domain prefix to hasher: %w", err)
    30  	}
    31  	if _, err := hasher.Write(img); err != nil {
    32  		return nil, fmt.Errorf("failed to write firmware image to hasher: %w", err)
    33  	}
    34  	fwHash := hasher.Sum(nil)
    35  	return fwHash[:], nil
    36  }