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nvd.go
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nvd.go
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// Copyright 2017 clair authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// Package nvd implements a vulnerability metadata appender using the NIST NVD
// database.
package nvd
import (
"bufio"
"compress/gzip"
"encoding/xml"
"errors"
"fmt"
"io"
"io/ioutil"
"net/http"
"os"
"strconv"
"strings"
"time"
log "github.com/sirupsen/logrus"
"github.com/coreos/clair/database"
"github.com/coreos/clair/ext/vulnmdsrc"
"github.com/coreos/clair/pkg/commonerr"
)
const (
dataFeedURL string = "http://static.nvd.nist.gov/feeds/xml/cve/nvdcve-2.0-%s.xml.gz"
dataFeedMetaURL string = "http://static.nvd.nist.gov/feeds/xml/cve/nvdcve-2.0-%s.meta"
appenderName string = "NVD"
logDataFeedName string = "data feed name"
)
type appender struct {
localPath string
dataFeedHashes map[string]string
metadata map[string]NVDMetadata
}
type NVDMetadata struct {
CVSSv2 NVDmetadataCVSSv2
}
type NVDmetadataCVSSv2 struct {
Vectors string
Score float64
}
func init() {
vulnmdsrc.RegisterAppender(appenderName, &appender{})
}
func (a *appender) BuildCache(datastore database.Datastore) error {
var err error
a.metadata = make(map[string]NVDMetadata)
// Init if necessary.
if a.localPath == "" {
// Create a temporary folder to store the NVD data and create hashes struct.
if a.localPath, err = ioutil.TempDir(os.TempDir(), "nvd-data"); err != nil {
return commonerr.ErrFilesystem
}
a.dataFeedHashes = make(map[string]string)
}
// Get data feeds.
dataFeedReaders, dataFeedHashes, err := getDataFeeds(a.dataFeedHashes, a.localPath)
if err != nil {
return err
}
a.dataFeedHashes = dataFeedHashes
// Parse data feeds.
for dataFeedName, dataFeedReader := range dataFeedReaders {
var nvd nvd
if err = xml.NewDecoder(dataFeedReader).Decode(&nvd); err != nil {
log.WithError(err).WithField(logDataFeedName, dataFeedName).Error("could not decode NVD data feed")
return commonerr.ErrCouldNotParse
}
// For each entry of this data feed:
for _, nvdEntry := range nvd.Entries {
// Create metadata entry.
if metadata := nvdEntry.Metadata(); metadata != nil {
a.metadata[nvdEntry.Name] = *metadata
}
}
dataFeedReader.Close()
}
return nil
}
func (a *appender) Append(vulnName string, appendFunc vulnmdsrc.AppendFunc) error {
if nvdMetadata, ok := a.metadata[vulnName]; ok {
appendFunc(appenderName, nvdMetadata, SeverityFromCVSS(nvdMetadata.CVSSv2.Score))
}
return nil
}
func (a *appender) PurgeCache() {
a.metadata = nil
}
func (a *appender) Clean() {
os.RemoveAll(a.localPath)
}
func getDataFeeds(dataFeedHashes map[string]string, localPath string) (map[string]NestedReadCloser, map[string]string, error) {
var dataFeedNames []string
for y := 2002; y <= time.Now().Year(); y++ {
dataFeedNames = append(dataFeedNames, strconv.Itoa(y))
}
// Get hashes for these feeds.
for _, dataFeedName := range dataFeedNames {
hash, err := getHashFromMetaURL(fmt.Sprintf(dataFeedMetaURL, dataFeedName))
if err != nil {
log.WithError(err).WithField(logDataFeedName, dataFeedName).Warning("could not get NVD data feed hash")
// It's not a big deal, no need interrupt, we're just going to download it again then.
continue
}
dataFeedHashes[dataFeedName] = hash
}
// Create io.Reader for every data feed.
dataFeedReaders := make(map[string]NestedReadCloser)
for _, dataFeedName := range dataFeedNames {
fileName := localPath + dataFeedName + ".xml"
if h, ok := dataFeedHashes[dataFeedName]; ok && h == dataFeedHashes[dataFeedName] {
// The hash is known, the disk should contains the feed. Try to read from it.
if localPath != "" {
if f, err := os.Open(fileName); err == nil {
dataFeedReaders[dataFeedName] = NestedReadCloser{
Reader: f,
NestedReadClosers: []io.ReadCloser{f},
}
continue
}
}
// Download data feed.
r, err := http.Get(fmt.Sprintf(dataFeedURL, dataFeedName))
if err != nil {
log.WithError(err).WithField(logDataFeedName, dataFeedName).Error("could not download NVD data feed")
return dataFeedReaders, dataFeedHashes, commonerr.ErrCouldNotDownload
}
// Un-gzip it.
gr, err := gzip.NewReader(r.Body)
if err != nil {
log.WithError(err).WithField(logDataFeedName, dataFeedName).Error("could not read NVD data feed")
return dataFeedReaders, dataFeedHashes, commonerr.ErrCouldNotDownload
}
// Store it to a file at the same time if possible.
if f, err := os.Create(fileName); err == nil {
nrc := NestedReadCloser{
Reader: io.TeeReader(gr, f),
NestedReadClosers: []io.ReadCloser{r.Body, gr, f},
}
dataFeedReaders[dataFeedName] = nrc
} else {
nrc := NestedReadCloser{
Reader: gr,
NestedReadClosers: []io.ReadCloser{gr, r.Body},
}
dataFeedReaders[dataFeedName] = nrc
log.WithError(err).Warning("could not store NVD data feed to filesystem")
}
}
}
return dataFeedReaders, dataFeedHashes, nil
}
func getHashFromMetaURL(metaURL string) (string, error) {
r, err := http.Get(metaURL)
if err != nil {
return "", err
}
defer r.Body.Close()
scanner := bufio.NewScanner(r.Body)
for scanner.Scan() {
line := scanner.Text()
if strings.HasPrefix(line, "sha256:") {
return strings.TrimPrefix(line, "sha256:"), nil
}
}
if err := scanner.Err(); err != nil {
return "", err
}
return "", errors.New("invalid .meta file format")
}
// SeverityFromCVSS converts the CVSS Score (0.0 - 10.0) into a
// database.Severity following the qualitative rating scale available in the
// CVSS v3.0 specification (https://www.first.org/cvss/specification-document),
// Table 14.
//
// The Negligible level is set for CVSS scores between [0, 1), replacing the
// specified None level, originally used for a score of 0.
func SeverityFromCVSS(score float64) database.Severity {
switch {
case score < 1.0:
return database.NegligibleSeverity
case score < 3.9:
return database.LowSeverity
case score < 6.9:
return database.MediumSeverity
case score < 8.9:
return database.HighSeverity
case score <= 10:
return database.CriticalSeverity
}
return database.UnknownSeverity
}