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Prevent argument injection in git CLI calls #446

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8d62716
Protect against git refs that look like a CLI flag
pfleidi Feb 20, 2026
bd811de
Merge branch 'main' into protect-against-invalid-git-refs
pfleidi Feb 20, 2026
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3 changes: 3 additions & 0 deletions cmd/entire/cli/git_operations.go
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Original file line number Diff line number Diff line change
Expand Up @@ -291,6 +291,9 @@ func BranchExistsLocally(branchName string) (bool, error) {
// Should be switched back to go-git once we upgrade to go-git v6
// Returns an error if the ref doesn't exist or checkout fails.
func CheckoutBranch(ref string) error {
if strings.HasPrefix(ref, "-") {
return fmt.Errorf("checkout failed: invalid ref %q", ref)
}
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@evisdren evisdren Feb 20, 2026 •
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This is probably okay in the short term.

But I wonder if we should actually split this out into SwitchBranch and CheckoutBranch functions. CheckoutBranch is a bit overloaded. It seems like the intention of the function is just to switch to a local branch or If you go with switch branch, then you can pass in -- <branch> which will treat everything after the -- as a branch name and fail if a - is passed as an evil flag.

The nuance here is that git switch has to handle both commit hashes and branch names. For commit hashes you have to pass in git switch --detach <commithash>, which is actually clearer in my opinion. The challenge is then determining the difference between a commit hash and a branch. You could shell out to a git sub process to do that (most reliable), but that seems wasteful.

The actual better long term strategy here would be to split up the swtich into SwitchBranchWithName() and SwitchBranchWithCommit() and pass in the right argument. That would fully remove the argument injection problem since the argument would always come after a -- and be treated as a literal and make it clearer in the codebase what argument we're passing.

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@pfleidi pfleidi Feb 20, 2026

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Yeah, SwitchBranch would also address the case where legitimate branch names beginning with a - would work and not confuse git unnecessarily.

I like the idea but that might be a change for down the road. What do you think?

ctx := context.Background()
cmd := exec.CommandContext(ctx, "git", "checkout", ref)
if output, err := cmd.CombinedOutput(); err != nil {
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30 changes: 30 additions & 0 deletions cmd/entire/cli/resume_test.go
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Expand Up @@ -5,6 +5,7 @@ import (
"fmt"
"os"
"path/filepath"
"strings"
"testing"

"github.com/entireio/cli/cmd/entire/cli/checkpoint/id"
Expand Down Expand Up @@ -163,6 +164,35 @@ func TestCheckoutBranch(t *testing.T) {
t.Error("CheckoutBranch() expected error for nonexistent branch, got nil")
}
})

t.Run("rejects ref starting with dash to prevent argument injection", func(t *testing.T) {
// "git checkout -b evil" would create a new branch named "evil" instead
// of failing, because git interprets "-b" as a flag.
err := CheckoutBranch("-b evil")
if err == nil {
t.Fatal("CheckoutBranch() should reject refs starting with '-', got nil")
}
if !strings.Contains(err.Error(), "invalid ref") {
t.Errorf("CheckoutBranch() error = %q, want error containing 'invalid ref'", err.Error())
}
})
}

func TestPerformGitResetHard_RejectsArgumentInjection(t *testing.T) {
tmpDir := t.TempDir()
t.Chdir(tmpDir)

setupResumeTestRepo(t, tmpDir, false)

// "git reset --hard -q" would silently reset to HEAD in quiet mode instead
// of failing, because git interprets "-q" as the --quiet flag.
err := performGitResetHard("-q")
if err == nil {
t.Fatal("performGitResetHard() should reject hashes starting with '-', got nil")
}
if !strings.Contains(err.Error(), "invalid commit hash") {
t.Errorf("performGitResetHard() error = %q, want error containing 'invalid commit hash'", err.Error())
}
}

func TestResumeFromCurrentBranch_NoCheckpoint(t *testing.T) {
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3 changes: 3 additions & 0 deletions cmd/entire/cli/rewind.go
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Expand Up @@ -1179,6 +1179,9 @@ func countCommitsBetween(repo *git.Repository, ancestor, descendant plumbing.Has
// Uses the git CLI instead of go-git because go-git's HardReset incorrectly
// deletes untracked directories (like .entire/) even when they're in .gitignore.
func performGitResetHard(commitHash string) error {
if strings.HasPrefix(commitHash, "-") {
return fmt.Errorf("reset failed: invalid commit hash %q", commitHash)
}
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@evisdren evisdren Feb 20, 2026

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pretty much same comment as above

ctx := context.Background()
cmd := exec.CommandContext(ctx, "git", "reset", "--hard", commitHash)
if output, err := cmd.CombinedOutput(); err != nil {
Expand Down