[SECURITY] security checker.

[raminfp]

I check security issue, we should fix.

G404 (CWE-338): Use of weak random number generator (math/rand instead of crypto/rand) (Confidence: MEDIUM, Severity: HIGH)
    32:         for i := range b {
  > 33:                 b[i] = letters[rand.Intn(len(letters))]
    34:         }



[/root/fuzzing/golangs/bin/ravro_dcrp/pdf.go:52] - G301 (CWE-276): Expect directory permissions to be 0750 or less (Confidence: HIGH, Severity: MEDIUM)
    51:         if _, err := os.Stat(tmpPath); os.IsNotExist(err) {
  > 52:                 errDir := os.Mkdir(tmpPath, 0777)
    53:                 if errDir != nil {



[/root/fuzzing/golangs/bin/ravro_dcrp/fs.go:61] - G301 (CWE-276): Expect directory permissions to be 0750 or less (Confidence: HIGH, Severity: MEDIUM)
    60: func ensureDir(dirName string) error {
  > 61:         err := os.Mkdir(dirName, 0775)
    62:



[/root/fuzzing/golangs/bin/ravro_dcrp/pdf.go:57] - G306 (CWE-276): Expect WriteFile permissions to be 0600 or less (Confidence: HIGH, Severity: MEDIUM)
    56:         }
  > 57:         err1 := ioutil.WriteFile(tmpPath+strconv.FormatInt(int64(t), 10)+".html", []byte(r.body), 0644)
    58:         if err1 != nil {



[/root/fuzzing/golangs/bin/ravro_dcrp/html.go:10] - G306 (CWE-276): Expect WriteFile permissions to be 0600 or less (Confidence: HIGH, Severity: MEDIUM)

Thanks.