github.com/apernet/quic-go@v0.43.1-0.20240515053213-5e9e635fd9f0/fuzzing/internal/helper/helper.go (about)

     1  package helper
     2  
     3  import (
     4  	"crypto"
     5  	"crypto/rand"
     6  	"crypto/sha1"
     7  	"crypto/tls"
     8  	"crypto/x509"
     9  	"crypto/x509/pkix"
    10  	"encoding/hex"
    11  	"math/big"
    12  	"os"
    13  	"path/filepath"
    14  	"time"
    15  )
    16  
    17  // NthBit gets the n-th bit of a byte (counting starts at 0).
    18  func NthBit(val uint8, n int) bool {
    19  	if n < 0 || n > 7 {
    20  		panic("invalid value for n")
    21  	}
    22  	return val>>n&0x1 == 1
    23  }
    24  
    25  // WriteCorpusFile writes data to a corpus file in directory path.
    26  // The filename is calculated from the SHA1 sum of the file contents.
    27  func WriteCorpusFile(path string, data []byte) error {
    28  	// create the directory, if it doesn't exist yet
    29  	if _, err := os.Stat(path); os.IsNotExist(err) {
    30  		if err := os.MkdirAll(path, os.ModePerm); err != nil {
    31  			return err
    32  		}
    33  	}
    34  	hash := sha1.Sum(data)
    35  	return os.WriteFile(filepath.Join(path, hex.EncodeToString(hash[:])), data, 0o644)
    36  }
    37  
    38  // WriteCorpusFileWithPrefix writes data to a corpus file in directory path.
    39  // In many fuzzers, the first n bytes are used to control.
    40  // This function prepends n zero-bytes to the data.
    41  func WriteCorpusFileWithPrefix(path string, data []byte, n int) error {
    42  	return WriteCorpusFile(path, append(make([]byte, n), data...))
    43  }
    44  
    45  // GenerateCertificate generates a self-signed certificate.
    46  // It returns the certificate and a x509.CertPool containing that certificate.
    47  func GenerateCertificate(priv crypto.Signer) (*tls.Certificate, *x509.CertPool, error) {
    48  	template := x509.Certificate{
    49  		SerialNumber:          big.NewInt(1),
    50  		Subject:               pkix.Name{Organization: []string{"quic-go fuzzer"}},
    51  		NotBefore:             time.Now().Add(-24 * time.Hour),
    52  		NotAfter:              time.Now().Add(30 * 24 * time.Hour),
    53  		KeyUsage:              x509.KeyUsageKeyEncipherment | x509.KeyUsageDigitalSignature,
    54  		ExtKeyUsage:           []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},
    55  		DNSNames:              []string{"localhost"},
    56  		BasicConstraintsValid: true,
    57  	}
    58  	derBytes, err := x509.CreateCertificate(rand.Reader, &template, &template, priv.Public(), priv)
    59  	if err != nil {
    60  		return nil, nil, err
    61  	}
    62  	cert, err := x509.ParseCertificate(derBytes)
    63  	if err != nil {
    64  		return nil, nil, err
    65  	}
    66  	certPool := x509.NewCertPool()
    67  	certPool.AddCert(cert)
    68  	return &tls.Certificate{
    69  		Certificate: [][]byte{derBytes},
    70  		PrivateKey:  priv,
    71  	}, certPool, nil
    72  }