/
core.go
277 lines (240 loc) · 5.79 KB
/
core.go
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// execute a command, and take care to sanitize the child process environment (conditionally)
package pkg
import (
//nolint
"crypto/md5"
"errors"
"net/http"
//nolint
"crypto/sha1"
"crypto/sha256"
"fmt"
"io/ioutil"
"os"
"os/exec"
"strings"
"github.com/thoas/go-funk"
)
type Digest struct {
SHA1 string
SHA256 string
MD5 string
}
const SHA1 = "sha1"
const MD5 = "md5"
func (d *Digest) For(kind string) string {
switch kind {
case SHA1:
return d.SHA1
case MD5:
return d.MD5
default:
return d.SHA256
}
}
func (d *Digest) Verify(s Signature) (ok bool, expectedHash string) {
switch s.digest {
case SHA1:
return d.SHA1 == s.content, d.SHA1
case MD5:
return d.MD5 == s.content, d.MD5
default:
return d.SHA256 == s.content, d.SHA256
}
}
func (d *Digest) String() string {
return fmt.Sprintf("sha256=%v\nOR: sha1=%v\nOR: md5=%v", d.SHA256, d.SHA1, d.MD5)
}
type Signature struct {
content string
digest string
}
func (s *Signature) String() string {
return fmt.Sprintf("%v=%v", s.digest, s.content)
}
type CheckResult struct {
LookupResult *LookupResult
ValidDigest *Signature
ExpectedDigests []Signature
ActualDigest Digest
Ok bool
}
func (c *CheckResult) Error() error {
if c.Ok {
return nil
}
if c.HasLookupVulns() {
return fmt.Errorf("vulnerable digest: %v", c.ActualDigest)
} else if c.HasValidationVulns() {
return fmt.Errorf("digest mismatch: actual: %v, expected: %v", c.ActualDigest, c.ExpectedDigests)
} else {
return errors.New("unknown result error")
}
}
func (c *CheckResult) HasValidationVulns() bool {
return c.ValidDigest == nil && len(c.ExpectedDigests) > 0
}
func (c *CheckResult) HasLookupVulns() bool {
return c.LookupResult != nil && c.LookupResult.Vulnerable
}
type Lookup interface {
Hash(digest Digest) (LookupResult, error)
Name() string
}
type LookupResult struct {
Vulnerable bool
Message string
Link string
}
type Preflight struct {
Lookup []Lookup
Porcelain *Porcelain
}
func GetLookup() ([]Lookup, error) {
// base lookup is always "no lookup"
lookups := []Lookup{&NoLookup{}}
//
// add: file list lookup
//
if os.Getenv("PF_FILE_LOOKUP") != "" {
lu, err := NewFileLookup(os.Getenv("PF_FILE_LOOKUP"))
if err != nil {
return nil, err
}
lookups = append(lookups, lu)
}
//
// add: virustotal lookup
//
if os.Getenv("PF_VT_TOKEN") != "" {
lu, err := NewVirusTotalLookup(os.Getenv("PF_VT_TOKEN"))
if err != nil {
return nil, err
}
lookups = append(lookups, lu)
}
return lookups, nil
}
func createDigest(s string) Digest {
return Digest{
//nolint
SHA1: fmt.Sprintf("%x", sha1.Sum([]byte(s))),
//nolint
MD5: fmt.Sprintf("%x", md5.Sum([]byte(s))),
SHA256: fmt.Sprintf("%x", sha256.Sum256([]byte(s))),
}
}
func createSignature(sig string) Signature {
sig = strings.Trim(sig, " ") // remove any space-y artifacts
sig = strings.Split(sig, " ")[0] // start up to first space is important, throw away the rest
parts := strings.Split(sig, "=")
signature := Signature{content: sig, digest: "sha256"}
if len(parts) > 1 {
signature = Signature{content: parts[1], digest: strings.ToLower(parts[0])}
}
return signature
}
func NewPreflight(lookup []Lookup) *Preflight {
return &Preflight{
Lookup: lookup,
Porcelain: &Porcelain{},
}
}
func (a *Preflight) Check(script, siglist string) (*CheckResult, error) {
sigs, err := parsehashList(siglist)
if err != nil {
return nil, fmt.Errorf("cannot parse hashlist: %v", err)
}
digest := createDigest(script)
res := funk.Find(sigs, func(s Signature) bool {
ok, _ := digest.Verify(s)
return ok
})
if res == nil {
return &CheckResult{
ExpectedDigests: sigs,
ActualDigest: digest,
ValidDigest: nil,
Ok: false,
}, nil
}
validDigest := res.(Signature)
var lookupResult LookupResult
for li := range a.Lookup {
lookup := a.Lookup[li]
lookupResult, err = lookup.Hash(digest)
if err != nil {
return nil, fmt.Errorf("%v - cannot look up: %v", lookup.Name(), err)
}
if lookupResult.Vulnerable {
break
}
}
return &CheckResult{
ExpectedDigests: sigs,
ActualDigest: digest,
ValidDigest: &validDigest,
LookupResult: &lookupResult,
Ok: !lookupResult.Vulnerable,
}, nil
}
// XXX: windows/powershell needs a different function
func (a *Preflight) ExecPiped(script, sig string) error {
a.Porcelain.Start(a)
check, err := a.Check(script, sig)
if err != nil {
return err
}
if !check.Ok {
a.Porcelain.CheckFailed(check)
return check.Error()
}
a.Porcelain.RunOk()
command := exec.Command("/bin/sh")
command.Stdin = strings.NewReader(script)
command.Stdout = os.Stdout
command.Stderr = os.Stderr
return command.Run()
}
func (a *Preflight) Exec(args []string, sig string) error {
a.Porcelain.Start(a)
s, err := ioutil.ReadFile(args[0])
if err != nil {
return fmt.Errorf("cannot open %v: %v", args[0], err)
}
check, err := a.Check(string(s), sig)
if err != nil {
return err
}
if !check.Ok {
a.Porcelain.CheckFailed(check)
return check.Error()
}
a.Porcelain.RunOk()
//nolint
command := exec.Command(args[0], args[1:]...)
command.Stdin = os.Stdin
command.Stdout = os.Stdout
command.Stderr = os.Stderr
return command.Run()
}
func parsehashList(hashArg string) ([]Signature, error) {
var sigs []string
if strings.Contains(hashArg, ",") {
sigs = strings.Split(hashArg, ",")
} else if strings.HasPrefix(hashArg, "http") {
resp, err := http.Get(hashArg) //nolint
if err != nil {
return nil, fmt.Errorf("cannot parse hash URL: %v", err)
}
defer resp.Body.Close()
res, err := ioutil.ReadAll(resp.Body)
if err != nil {
return nil, fmt.Errorf("cannot read hash URL content: %v", err)
}
sigs = strings.Split(string(res), "\n")
} else {
sigs = []string{hashArg}
}
return funk.Map(sigs, createSignature).([]Signature), nil
}