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openscap.go
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openscap.go
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package openscap
import (
"fmt"
docker "github.com/fsouza/go-dockerclient"
"io"
"net/http"
"net/url"
"os"
"os/exec"
"path"
"strings"
"syscall"
)
const (
CPE = "oval:org.open-scap.cpe.rhel:def:"
CPEDict = "/usr/share/openscap/cpe/openscap-cpe-oval.xml"
CVEUrl = "https://www.redhat.com/security/data/metrics/ds/"
DistCVENameFmt = "com.redhat.rhsa-RHEL%d.ds.xml.bz2"
ArfResultFile = "results-arf.xml"
TmpDir = "/tmp"
Linux = "Linux"
OpenSCAP = "OpenSCAP"
ImageShortIDLen = 11
)
var (
RHELDistNumbers = [...]int{5, 6, 7}
)
// rhelDistFunc provides an injectable way to get the rhel dist for testing.
type rhelDistFunc func() (int, error)
// inputCVEFunc provides an injectable way to get the cve file for testing.
type inputCVEFunc func(int) (string, error)
// chrootOscapFunc provides an injectable way to chroot and execute oscap for testing.
type chrootOscapFunc func(...string) ([]byte, error)
// setEnvFunc provides an injectable way to get the cve file for testing.
type setEnvFunc func() error
type defaultOSCAPScanner struct {
// CVEDir is the directory where the CVE file is saved
CVEDir string
// ResultsDir is the directory to which the arf report will be written
ResultsDir string
// Image is the metadata of the inspected image
image *docker.Image
// ImageMountPath is the path where the image to be scanned is mounted
imageMountPath string
rhelDist rhelDistFunc
inputCVE inputCVEFunc
chrootOscap chrootOscapFunc
setEnv setEnvFunc
}
// NewDefaultScanner returns a new OpenSCAP scanner
func NewDefaultScanner(cveDir string, resultsDir string) Scanner {
scanner := &defaultOSCAPScanner{
CVEDir: cveDir,
ResultsDir: resultsDir,
}
scanner.rhelDist = scanner.getRHELDist
scanner.inputCVE = scanner.getInputCVE
scanner.chrootOscap = scanner.oscapChroot
scanner.setEnv = scanner.setOscapChrootEnv
return scanner
}
func (s *defaultOSCAPScanner) getRHELDist() (int, error) {
for _, dist := range RHELDistNumbers {
output, err := s.chrootOscap("oval", "eval", "--id",
fmt.Sprintf("%s%d", CPE, dist), CPEDict)
if err != nil {
return 0, err
}
if strings.Contains(string(output), fmt.Sprintf("%s%d: true", CPE, dist)) {
return dist, nil
}
}
return 0, fmt.Errorf("could not find RHEL dist")
}
func (s *defaultOSCAPScanner) getInputCVE(dist int) (string, error) {
cveName := fmt.Sprintf(DistCVENameFmt, dist)
cveFileName := path.Join(s.CVEDir, cveName)
cveURL, _ := url.Parse(CVEUrl)
cveURL.Path = path.Join(cveURL.Path, cveName)
out, err := os.Create(cveFileName)
if err != nil {
return "", fmt.Errorf("Could not create file %s: %v\n", cveFileName, err)
}
defer out.Close()
resp, err := http.Get(cveURL.String())
if err != nil {
return "", fmt.Errorf("Could not download file %s: %v\n", cveURL, err)
}
defer resp.Body.Close()
_, err = io.Copy(out, resp.Body)
return cveFileName, err
}
func (s *defaultOSCAPScanner) setOscapChrootEnv() error {
for k, v := range map[string]string{
"OSCAP_PROBE_ROOT": s.imageMountPath,
"OSCAP_PROBE_OS_VERSION": "4.2.6-301.fc23.x86_64", // FIXME place holder value
"OSCAP_PROBE_ARCHITECTURE": s.image.Config.Labels["Architecture"],
"OSCAP_PROBE_OS_NAME": Linux,
"OSCAP_PROBE_PRIMARY_HOST_NAME": fmt.Sprintf("docker-image-%s", s.image.ID[:ImageShortIDLen]),
} {
err := os.Setenv(k, v)
if err != nil {
return err
}
}
return nil
}
// Wrapper function for executing oscap
func (s *defaultOSCAPScanner) oscapChroot(oscapArgs ...string) ([]byte, error) {
if err := s.setEnv(); err != nil {
return nil, fmt.Errorf("Unable to set env variables in oscapChroot: %v", err)
}
cmd := exec.Command("oscap", oscapArgs...)
out, err := cmd.CombinedOutput()
if err != nil {
if exitError, ok := err.(*exec.ExitError); ok {
waitStatus := exitError.Sys().(syscall.WaitStatus)
if waitStatus.ExitStatus() == 2 {
// Error code 2 means that OpenSCAP had failed rules
// For our purpose this means success
return out, nil
}
return out, fmt.Errorf("OpenSCAP error: %d: %v\nInput:\n%s\nOutput:\n%s\n",
waitStatus.ExitStatus(), err, oscapArgs, string(out))
}
}
return out, err
}
func (s *defaultOSCAPScanner) Scan(mountPath string, image *docker.Image) error {
fi, err := os.Stat(mountPath)
if err != nil || os.IsNotExist(err) || !fi.IsDir() {
return fmt.Errorf("%s is not a directory, error: %v", mountPath, err)
}
if image == nil {
return fmt.Errorf("image cannot be nil")
}
s.image = image
s.imageMountPath = mountPath
rhelDist, err := s.rhelDist()
if err != nil {
return fmt.Errorf("Unable to get RHEL distribution number: %v\n", err)
}
cveFileName, err := s.inputCVE(rhelDist)
if err != nil {
return fmt.Errorf("Unable to retreive the CVE file: %v\n", err)
}
_, err = s.chrootOscap("xccdf", "eval",
"--results-arf", s.ResultsFileName(),
cveFileName)
return err
}
func (s *defaultOSCAPScanner) ScannerName() string {
return OpenSCAP
}
func (s *defaultOSCAPScanner) ResultsFileName() string {
return path.Join(s.ResultsDir, ArfResultFile)
}