Source file src/github.com/Microsoft/hcsshim/internal/guest/storage/crypt/utilities.go

Documentation: github.com/Microsoft/hcsshim/internal/guest/storage/crypt

     1  //go:build linux
     2  // +build linux
     3  
     4  package crypt
     5  
     6  import (
     7  	"bytes"
     8  	"crypto/rand"
     9  	"fmt"
    10  	"io"
    11  	"os"
    12  )
    13  
    14  func zeroFirstBlock(path string, blockSize int) error {
    15  	fout, err := os.OpenFile(path, os.O_WRONLY, 0)
    16  	if err != nil {
    17  		return fmt.Errorf("failed to open file for zero'ing: %w", err)
    18  	}
    19  	defer fout.Close()
    20  
    21  	size, err := fout.Seek(0, io.SeekEnd)
    22  	if err != nil {
    23  		return fmt.Errorf("error seeking end of %s: %w", path, err)
    24  	}
    25  	if size < int64(blockSize) {
    26  		return fmt.Errorf("file size is smaller than minimum expected: %d < %d", size, blockSize)
    27  	}
    28  
    29  	_, err = fout.Seek(0, io.SeekStart)
    30  	if err != nil {
    31  		return fmt.Errorf("error seeking start of %s: %w", path, err)
    32  	}
    33  
    34  	zeros := bytes.Repeat([]byte{0}, blockSize)
    35  	if _, err := fout.Write(zeros); err != nil {
    36  		return fmt.Errorf("failed to zero-out bytes: %w", err)
    37  	}
    38  	return nil
    39  }
    40  
    41  // generateKeyFile generates a file with random values.
    42  func generateKeyFile(path string, size int64) error {
    43  	// The crypto.rand interface generates random numbers using /dev/urandom
    44  	keyArray := make([]byte, size)
    45  	_, err := rand.Read(keyArray[:])
    46  	if err != nil {
    47  		return fmt.Errorf("failed to generate key slice: %w", err)
    48  	}
    49  
    50  	if err := os.WriteFile(path, keyArray[:], 0644); err != nil {
    51  		return fmt.Errorf("failed to save key to file: %w", err)
    52  	}
    53  	return nil
    54  }
    55  

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