Skip to content

fix: prevent path traversal in DownloadActionOutputs and validate symlink targets #650

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
mohammadmseet-hue wants to merge 1 commit into
base: master
Choose a base branch
from
+21 −2
Open

fix: prevent path traversal in DownloadActionOutputs and validate symlink targets #650

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
23 changes: 21 additions & 2 deletions go/pkg/client/cas_download.go
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -9,6 +9,7 @@ import (
"path/filepath"
"sort"
"strconv"
"strings"
"sync"
"time"

Expand Down Expand Up @@ -147,7 +148,21 @@ func (c *Client) DownloadOutputs(ctx context.Context, outs map[string]*TreeOutpu
}
}
for _, out := range symlinks {
if err := os.Symlink(out.SymlinkTarget, filepath.Join(outDir, out.Path)); err != nil {
symlinkPath, err := getAbsPath(outDir, out.Path)
if err != nil {
return fullStats, err
}
// Validate that the symlink target resolves within outDir to prevent
// symlink-based path traversal (e.g. target = "/etc/shadow").
target := out.SymlinkTarget
if !filepath.IsAbs(target) {
target = filepath.Join(filepath.Dir(symlinkPath), target)
}
target = filepath.Clean(target)
if target != outDir && !strings.HasPrefix(target, outDir+string(filepath.Separator)) {
return fullStats, fmt.Errorf("symlink target %q resolves to %q which is outside output directory %q", out.SymlinkTarget, target, outDir)
}
if err := os.Symlink(out.SymlinkTarget, symlinkPath); err != nil {
return fullStats, err
}
}
Expand Down Expand Up @@ -522,7 +537,11 @@ func (c *Client) DownloadActionOutputs(ctx context.Context, resPb *repb.ActionRe
}
// Remove the existing output directories before downloading.
for _, dir := range resPb.OutputDirectories {
if err := os.RemoveAll(filepath.Join(outDir, dir.Path)); err != nil {
absPath, err := getAbsPath(outDir, dir.Path)
if err != nil {
return nil, err
}
if err := os.RemoveAll(absPath); err != nil {
return nil, err
}
}
Expand Down