vendor: update golang.org/x/crypto v0.0.0-20200128174031-69ecbb4d6d5d (CVE-2020-7919)

Includes 69ecbb4d6d
(forward-port of 8b5121be2f),
which fixes CVE-2020-7919:

- Panic in crypto/x509 certificate parsing and golang.org/x/crypto/cryptobyte
  On 32-bit architectures, a malformed input to crypto/x509 or the ASN.1 parsing
  functions of golang.org/x/crypto/cryptobyte can lead to a panic.
  The malformed certificate can be delivered via a crypto/tls connection to a
  client, or to a server that accepts client certificates. net/http clients can
  be made to crash by an HTTPS server, while net/http servers that accept client
  certificates will recover the panic and are unaffected.
  Thanks to Project Wycheproof for providing the test cases that led to the
  discovery of this issue. The issue is CVE-2020-7919 and Go issue golang.org/issue/36837.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

vendor/golang.org/x/crypto/acme/autocert/cache.go

@@ -77,6 +77,7 @@ func (d DirCache) Put(ctx context.Context, name string, data []byte) error {
 		if tmp, err = d.writeTempFile(name, data); err != nil {
 			return
 		}
+		defer os.Remove(tmp)
 		select {
 		case <-ctx.Done():
 			// Don't overwrite the file if the context was canceled.
@@ -116,12 +117,17 @@ func (d DirCache) Delete(ctx context.Context, name string) error {
 }
 
 // writeTempFile writes b to a temporary file, closes the file and returns its path.
-func (d DirCache) writeTempFile(prefix string, b []byte) (string, error) {
+func (d DirCache) writeTempFile(prefix string, b []byte) (name string, reterr error) {
 	// TempFile uses 0600 permissions
 	f, err := ioutil.TempFile(string(d), prefix)
 	if err != nil {
 		return "", err
 	}
+	defer func() {
+		if reterr != nil {
+			os.Remove(f.Name())
+		}
+	}()
 	if _, err := f.Write(b); err != nil {
 		f.Close()
 		return "", err