Validate object ids in the local blobstore to block path traversal

Why: Local.Put joined the caller-supplied id straight into the store directory, and store.UpdateArtifactContent feeds the HTTP path parameter into it, so a traversal id (encoded ../ in the artifact path) reaches an arbitrary-path file write; Get/Delete took stored refs unvalidated too. The 2026-09-30 deep security scan flagged the unsanitized join as the one actionable finding after triage.
Evidence: new internal/blobstore tests cover rejection of empty/dot/dotdot/traversal/absolute/backslash/NUL ids with no residue in the store dir, a normal Put/Get/Delete roundtrip, and refusal of out-of-store refs for Get and Delete; go vet ./... and go test -count=1 ./... pass.
Impact: internal/blobstore only; plain-filename ids (the only form produced today via newID and artifact path params) keep working; no schema, API, or caller change.
Refs: Dev-side task fix/blobstore-id-hardening (gitlink pin follows after combined verification)

internal/blobstore/blobstore.go

@@ -7,6 +7,7 @@ import (
 	"fmt"
 	"os"
 	"path/filepath"
+	"strings"
 	"sync"
 )
 
@@ -31,8 +32,30 @@ func NewLocal(dir string) (*Local, error) {
 	return &Local{dir: dir}, nil
 }
 
+// validID 只接受纯文件名形态的对象 id：非空、不含路径分隔符、非 . / ..。
+// Put 的 id 可能是上层透传的用户输入（如工件路径参数），先在此挡住路径穿越。
+func validID(id string) bool {
+	if id == "" || id == "." || id == ".." || filepath.IsAbs(id) {
+		return false
+	}
+	return !strings.ContainsAny(id, `/\`) && !strings.ContainsRune(id, 0)
+}
+
+// contains 判断路径是否落在对象目录内：Get/Delete 收的是入库引用，
+// 做包含性检查作为纵深防御，引用被篡改时也不读/删目录外文件。
+func (l *Local) contains(p string) bool {
+	rel, err := filepath.Rel(l.dir, filepath.Clean(p))
+	if err != nil {
+		return false
+	}
+	return rel != ".." && !strings.HasPrefix(rel, ".."+string(filepath.Separator))
+}
+
 // Put 临时文件 → rename 原子写：崩溃只可能残留 .tmp 孤立文件，不产生半写对象。
 func (l *Local) Put(id string, content []byte) (string, error) {
+	if !validID(id) {
+		return "", fmt.Errorf("blobstore: invalid object id %q", id)
+	}
 	final := filepath.Join(l.dir, id)
 	tmp := final + ".tmp-" + id
 	if err := os.WriteFile(tmp, content, 0o644); err != nil {
@@ -48,6 +71,9 @@ func (l *Local) Put(id string, content []byte) (string, error) {
 }
 
 func (l *Local) Get(ref string) ([]byte, error) {
+	if !l.contains(ref) {
+		return nil, fmt.Errorf("blobstore: ref %s escapes object store", filepath.Base(ref))
+	}
 	b, err := os.ReadFile(ref)
 	if os.IsNotExist(err) {
 		return nil, fmt.Errorf("blobstore: object %s not found", filepath.Base(ref))
@@ -56,6 +82,9 @@ func (l *Local) Get(ref string) ([]byte, error) {
 }
 
 func (l *Local) Delete(ref string) error {
+	if !l.contains(ref) {
+		return fmt.Errorf("blobstore: ref %s escapes object store", filepath.Base(ref))
+	}
 	err := os.Remove(ref)
 	if os.IsNotExist(err) {
 		return nil

internal/blobstore/blobstore_test.go

@@ -0,0 +1,71 @@
+package blobstore
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+)
+
+func newTestLocal(t *testing.T) *Local {
+	t.Helper()
+	l, err := NewLocal(t.TempDir())
+	if err != nil {
+		t.Fatalf("NewLocal: %v", err)
+	}
+	return l
+}
+
+func TestLocalPutRejectsUnsafeIDs(t *testing.T) {
+	l := newTestLocal(t)
+	for _, id := range []string{"", ".", "..", "../evil", "../../etc/passwd", "/abs", "a/b", `a\b`, "id\x00x"} {
+		if _, err := l.Put(id, []byte("x")); err == nil {
+			t.Fatalf("Put(%q) 应拒绝却成功了", id)
+		}
+	}
+	entries, err := os.ReadDir(l.dir)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(entries) != 0 {
+		t.Fatalf("对象目录不应有残留: %v", entries)
+	}
+}
+
+func TestLocalPutGetDeleteRoundtrip(t *testing.T) {
+	l := newTestLocal(t)
+	ref, err := l.Put("art_abc123", []byte("hello"))
+	if err != nil {
+		t.Fatalf("Put: %v", err)
+	}
+	if !strings.HasPrefix(filepath.Base(ref), "art_abc123") {
+		t.Fatalf("ref 意外: %q", ref)
+	}
+	got, err := l.Get(ref)
+	if err != nil {
+		t.Fatalf("Get: %v", err)
+	}
+	if string(got) != "hello" {
+		t.Fatalf("内容不符: %q", got)
+	}
+	if err := l.Delete(ref); err != nil {
+		t.Fatalf("Delete: %v", err)
+	}
+	if _, err := l.Get(ref); err == nil {
+		t.Fatal("删除后 Get 应失败")
+	}
+}
+
+func TestLocalGetDeleteRejectOutsideRef(t *testing.T) {
+	l := newTestLocal(t)
+	outside := filepath.Join(t.TempDir(), "outside.txt")
+	if err := os.WriteFile(outside, []byte("secret"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := l.Get(outside); err == nil {
+		t.Fatal("Get 目录外引用应拒绝")
+	}
+	if err := l.Delete(outside); err == nil {
+		t.Fatal("Delete 目录外引用应拒绝")
+	}
+}