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package buildah
import (
"context"
"fmt"
"io"
"os"
"path/filepath"
"slices"
"strings"
"github.com/containers/buildah/define"
"github.com/containers/buildah/internal/sbom"
"github.com/mattn/go-shellwords"
rspec "github.com/opencontainers/runtime-spec/specs-go"
"github.com/sirupsen/logrus"
)
func stringSliceReplaceAll(slice []string, replacements map[string]string, important []string) (built []string, replacedAnImportantValue bool) {
built = make([]string, 0, len(slice))
for i := range slice {
element := slice[i]
for from, to := range replacements {
previous := element
if element = strings.ReplaceAll(previous, from, to); element != previous {
if len(important) == 0 || slices.Contains(important, from) {
replacedAnImportantValue = true
}
}
}
built = append(built, element)
}
return built, replacedAnImportantValue
}
// sbomScan iterates through the scanning configuration settings, generating
// SBOM files and storing them either in the rootfs or in a local file path.
func (b *Builder) sbomScan(ctx context.Context, options CommitOptions) (imageFiles, localFiles map[string]string, scansDir string, err error) {
// We'll use a temporary per-container directory for this one.
cdir, err := b.store.ContainerDirectory(b.ContainerID)
if err != nil {
return nil, nil, "", err
}
scansDir, err = os.MkdirTemp(cdir, "buildah-scan")
if err != nil {
return nil, nil, "", err
}
defer func() {
if err != nil {
if err := os.RemoveAll(scansDir); err != nil {
logrus.Warnf("removing temporary directory %q: %v", scansDir, err)
}
}
}()
scansSubdir := filepath.Join(scansDir, "scans")
if err = os.Mkdir(scansSubdir, 0o700); err != nil {
return nil, nil, "", err
}
if err = os.Chmod(scansSubdir, 0o777); err != nil {
return nil, nil, "", err
}
// We may be producing sets of outputs using temporary containers, and
// there's no need to create more than one container for any one
// specific scanner image.
scanners := make(map[string]*Builder)
defer func() {
for _, scanner := range scanners {
scannerID := scanner.ContainerID
if err := scanner.Delete(); err != nil {
logrus.Warnf("removing temporary scanner container %q: %v", scannerID, err)
}
}
}()
// Just assume that every scanning method will be looking at the rootfs.
rootfs, err := b.Mount(b.MountLabel)
if err != nil {
return nil, nil, "", err
}
defer func(b *Builder) {
if err := b.Unmount(); err != nil {
logrus.Warnf("unmounting temporary scanner container %q: %v", b.ContainerID, err)
}
}(b)
// Iterate through all of the scanning strategies.
for _, scanSpec := range options.SBOMScanOptions {
// Pull the image and create a container we can run the scanner
// in, unless we've done that already for this scanner image.
scanBuilder, ok := scanners[scanSpec.Image]
if !ok {
builderOptions := BuilderOptions{
FromImage: scanSpec.Image,
ContainerSuffix: "scanner",
PullPolicy: scanSpec.PullPolicy,
BlobDirectory: options.BlobDirectory,
Logger: b.Logger,
SystemContext: options.SystemContext,
MountLabel: b.MountLabel,
ProcessLabel: b.ProcessLabel,
IDMappingOptions: &b.IDMappingOptions,
}
if scanBuilder, err = NewBuilder(ctx, b.store, builderOptions); err != nil {
return nil, nil, "", fmt.Errorf("creating temporary working container to run scanner: %w", err)
}
scanners[scanSpec.Image] = scanBuilder
}
// Now figure out which commands we need to run. First, try to
// parse a command ourselves, because syft's image (at least)
// doesn't include a shell. Build a slice of command slices.
var commands [][]string
for _, commandSpec := range scanSpec.Commands {
// Start by assuming it's shell -c $whatever.
parsedCommand := []string{"/bin/sh", "-c", commandSpec}
if shell := scanBuilder.Shell(); len(shell) != 0 {
parsedCommand = append(slices.Clone(shell), commandSpec)
}
if !strings.ContainsAny(commandSpec, "<>|") { // An imperfect check for shell redirection being used.
// If we can parse it ourselves, though, prefer to use that result,
// in case the scanner image doesn't include a shell.
if parsed, err := shellwords.Parse(commandSpec); err == nil {
parsedCommand = parsed
}
}
commands = append(commands, parsedCommand)
}
// Set up a list of mounts for the rootfs and whichever context
// directories we're told were used.
const rootfsTargetDir = "/.rootfs"
const scansTargetDir = "/.scans"
const contextsTargetDirPrefix = "/.context"
runMounts := []rspec.Mount{
// Our temporary directory, read-write.
{
Type: define.TypeBind,
Source: scansSubdir,
Destination: scansTargetDir,
Options: []string{"rw", "z"},
},
// The rootfs, read-only.
{
Type: define.TypeBind,
Source: rootfs,
Destination: rootfsTargetDir,
Options: []string{"ro"},
},
}
// Each context directory, also read-only.
for i := range scanSpec.ContextDir {
contextMount := rspec.Mount{
Type: define.TypeBind,
Source: scanSpec.ContextDir[i],
Destination: fmt.Sprintf("%s%d", contextsTargetDirPrefix, i),
Options: []string{"ro"},
}
runMounts = append(runMounts, contextMount)
}
// Set up run options and mounts one time, and reuse it.
runOptions := RunOptions{
Logger: b.Logger,
Isolation: b.Isolation,
SystemContext: options.SystemContext,
Mounts: runMounts,
}
// We'll have to do some text substitutions so that we run the
// right commands, in the right order, pointing at the right
// mount points.
var resolvedCommands [][]string
var resultFiles []string
for _, command := range commands {
// Each command gets to produce its own file that we'll
// combine later if there's more than one of them.
contextDirScans := 0
for i := range scanSpec.ContextDir {
resultFile := filepath.Join(scansTargetDir, fmt.Sprintf("scan%d.json", len(resultFiles)))
// If the command mentions {CONTEXT}...
resolvedCommand, scansContext := stringSliceReplaceAll(command,
map[string]string{
"{CONTEXT}": fmt.Sprintf("%s%d", contextsTargetDirPrefix, i),
"{OUTPUT}": resultFile,
},
[]string{"{CONTEXT}"},
)
if !scansContext {
break
}
// ... resolve the path references and add it to the list of commands.
resolvedCommands = append(resolvedCommands, resolvedCommand)
resultFiles = append(resultFiles, resultFile)
contextDirScans++
}
if contextDirScans == 0 {
resultFile := filepath.Join(scansTargetDir, fmt.Sprintf("scan%d.json", len(resultFiles)))
// If the command didn't mention {CONTEXT}, but does mention {ROOTFS}...
resolvedCommand, scansRootfs := stringSliceReplaceAll(command,
map[string]string{
"{ROOTFS}": rootfsTargetDir,
"{OUTPUT}": resultFile,
},
[]string{"{ROOTFS}"},
)
// ... resolve the path references and add that to the list of commands.
if scansRootfs {
resolvedCommands = append(resolvedCommands, resolvedCommand)
resultFiles = append(resultFiles, resultFile)
}
}
}
// Run all of the commands, one after the other, producing one
// or more files named "scan%d.json" in our temporary directory.
for _, resolvedCommand := range resolvedCommands {
logrus.Debugf("Running scan command %q", resolvedCommand)
if err = scanBuilder.Run(resolvedCommand, runOptions); err != nil {
return nil, nil, "", fmt.Errorf("running scanning command %v: %w", resolvedCommand, err)
}
}
// Produce the combined output files that we need to create, if there are any.
var sbomResult, purlResult string
switch {
case scanSpec.ImageSBOMOutput != "":
sbomResult = filepath.Join(scansSubdir, filepath.Base(scanSpec.ImageSBOMOutput))
case scanSpec.SBOMOutput != "":
sbomResult = filepath.Join(scansSubdir, filepath.Base(scanSpec.SBOMOutput))
default:
sbomResult = filepath.Join(scansSubdir, "sbom-result")
}
switch {
case scanSpec.ImagePURLOutput != "":
purlResult = filepath.Join(scansSubdir, filepath.Base(scanSpec.ImagePURLOutput))
case scanSpec.PURLOutput != "":
purlResult = filepath.Join(scansSubdir, filepath.Base(scanSpec.PURLOutput))
default:
purlResult = filepath.Join(scansSubdir, "purl-result")
}
copyFile := func(destination, source string) error {
dst, err := os.Create(destination)
if err != nil {
return err
}
defer dst.Close()
src, err := os.Open(source)
if err != nil {
return err
}
defer src.Close()
if _, err = io.Copy(dst, src); err != nil {
return fmt.Errorf("copying %q to %q: %w", source, destination, err)
}
return nil
}
err = func() error {
for i := range resultFiles {
thisResultFile := filepath.Join(scansSubdir, filepath.Base(resultFiles[i]))
switch i {
case 0:
// Straight-up copy to create the first version of the final output.
if err = copyFile(sbomResult, thisResultFile); err != nil {
return err
}
// This shouldn't change any contents, but lets us generate the purl file.
err = sbom.Merge(scanSpec.MergeStrategy, thisResultFile, sbomResult, purlResult)
default:
// Hopefully we know how to merge information from the new one into the final output.
err = sbom.Merge(scanSpec.MergeStrategy, sbomResult, thisResultFile, purlResult)
}
}
return err
}()
if err != nil {
return nil, nil, "", err
}
// If these files are supposed to be written to the local filesystem, add
// their contents to the map of files we expect our caller to write.
if scanSpec.SBOMOutput != "" || scanSpec.PURLOutput != "" {
if localFiles == nil {
localFiles = make(map[string]string)
}
if scanSpec.SBOMOutput != "" {
localFiles[scanSpec.SBOMOutput] = sbomResult
}
if scanSpec.PURLOutput != "" {
localFiles[scanSpec.PURLOutput] = purlResult
}
}
// If these files are supposed to be written to the image, create a map of
// their contents so that we can either create a layer diff for them (or
// slipstream them into a squashed layer diff) later.
if scanSpec.ImageSBOMOutput != "" || scanSpec.ImagePURLOutput != "" {
if imageFiles == nil {
imageFiles = make(map[string]string)
}
if scanSpec.ImageSBOMOutput != "" {
imageFiles[scanSpec.ImageSBOMOutput] = sbomResult
}
if scanSpec.ImagePURLOutput != "" {
imageFiles[scanSpec.ImagePURLOutput] = purlResult
}
}
}
return imageFiles, localFiles, scansDir, nil
}
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