1 files changed, 145 insertions, 0 deletions
diff --git a/vendor/github.com/projectatomic/buildah/imagebuildah/chroot_symlink.go b/vendor/github.com/projectatomic/buildah/imagebuildah/chroot_symlink.go
new file mode 100644
index 000000000..b2452b61c
--- /dev/null
+++ b/vendor/github.com/projectatomic/buildah/imagebuildah/chroot_symlink.go
@@ -0,0 +1,145 @@
+package imagebuildah
+
+import (
+	"flag"
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+
+	"github.com/containers/storage/pkg/reexec"
+	"github.com/pkg/errors"
+	"golang.org/x/sys/unix"
+)
+
+const (
+	symlinkChrootedCommand = "chrootsymlinks-resolve"
+	maxSymlinksResolved    = 40
+)
+
+func init() {
+	reexec.Register(symlinkChrootedCommand, resolveChrootedSymlinks)
+}
+
+func resolveChrootedSymlinks() {
+	status := 0
+	flag.Parse()
+	if len(flag.Args()) < 1 {
+		os.Exit(1)
+	}
+	// Our first parameter is the directory to chroot into.
+	if err := unix.Chdir(flag.Arg(0)); err != nil {
+		fmt.Fprintf(os.Stderr, "chdir(): %v\n", err)
+		os.Exit(1)
+	}
+	if err := unix.Chroot(flag.Arg(0)); err != nil {
+		fmt.Fprintf(os.Stderr, "chroot(): %v\n", err)
+		os.Exit(1)
+	}
+
+	// Our second paramter is the path name to evaluate for symbolic links
+	symLink, err := getSymbolicLink(flag.Arg(0), flag.Arg(1))
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "error getting symbolic links: %v\n", err)
+		os.Exit(1)
+	}
+	if _, err := os.Stdout.WriteString(symLink); err != nil {
+		fmt.Fprintf(os.Stderr, "error writing string to stdout: %v\n", err)
+		os.Exit(1)
+	}
+	os.Exit(status)
+}
+
+func resolveSymLink(rootdir, filename string) (string, error) {
+	// The child process expects a chroot and one path that
+	// will be consulted relative to the chroot directory and evaluated
+	// for any symbolic links present.
+	cmd := reexec.Command(symlinkChrootedCommand, rootdir, filename)
+	output, err := cmd.CombinedOutput()
+	if err != nil {
+		return "", errors.Wrapf(err, string(output))
+	}
+
+	// Hand back the resolved symlink, will be "" if a symlink is not found
+	return string(output), nil
+}
+
+// getSymbolic link goes through each part of the path and continues resolving symlinks as they appear.
+// Returns what the whole target path for what "path" resolves to.
+func getSymbolicLink(rootdir, path string) (string, error) {
+	var (
+		symPath          string
+		symLinksResolved int
+	)
+
+	// Splitting path as we need to resolve each parth of the path at a time
+	splitPath := strings.Split(path, "/")
+	if splitPath[0] == "" {
+		splitPath = splitPath[1:]
+		symPath = "/"
+	}
+
+	for _, p := range splitPath {
+		// If we have resolved 40 symlinks, that means something is terribly wrong
+		// will return an error and exit
+		if symLinksResolved >= maxSymlinksResolved {
+			return "", errors.Errorf("have resolved %q symlinks, something is terribly wrong!", maxSymlinksResolved)
+		}
+
+		symPath = filepath.Join(symPath, p)
+		isSymlink, resolvedPath, err := hasSymlink(symPath)
+		if err != nil {
+			return "", errors.Wrapf(err, "error checking symlink for %q", symPath)
+		}
+		// if isSymlink is true, check if resolvedPath is potentially another symlink
+		// keep doing this till resolvedPath is not a symlink and isSymlink is false
+		for isSymlink == true {
+			// Need to keep track of number of symlinks resolved
+			// Will also return an error if the symlink points to itself as that will exceed maxSymlinksResolved
+			if symLinksResolved >= maxSymlinksResolved {
+				return "", errors.Errorf("have resolved %q symlinks, something is terribly wrong!", maxSymlinksResolved)
+			}
+			isSymlink, resolvedPath, err = hasSymlink(resolvedPath)
+			if err != nil {
+				return "", errors.Wrapf(err, "error checking symlink for %q", resolvedPath)
+			}
+			symLinksResolved++
+		}
+		// Assign resolvedPath to symPath. The next part of the loop will append the next part of the original path
+		// and continue resolving
+		symPath = resolvedPath
+		symLinksResolved++
+	}
+	return symPath, nil
+}
+
+// hasSymlink returns true and the target if path is symlink
+// otherwise it returns false and path
+func hasSymlink(path string) (bool, string, error) {
+	info, err := os.Lstat(path)
+	if os.IsNotExist(err) {
+		if err = os.MkdirAll(path, 0755); err != nil {
+			return false, "", errors.Wrapf(err, "error ensuring volume path %q exists", path)
+		}
+		info, err = os.Lstat(path)
+		if err != nil {
+			return false, "", errors.Wrapf(err, "error running lstat on %q", path)
+		}
+	}
+	// Return false and path as path is not a symlink
+	if info.Mode()&os.ModeSymlink != os.ModeSymlink {
+		return false, path, nil
+	}
+
+	// Read the symlink to get what it points to
+	targetDir, err := os.Readlink(path)
+	if err != nil {
+		return false, "", errors.Wrapf(err, "error reading link %q", path)
+	}
+	// if the symlink points to a relative path, prepend the path till now to the resolved path
+	if !filepath.IsAbs(targetDir) {
+		targetDir = filepath.Join(path, targetDir)
+	}
+	// run filepath.Clean to remove the ".." from relative paths
+	return true, filepath.Clean(targetDir), nil
+}