fix(s3api): reject empty v4 signed header names (#9910)

Problem: Signature V4 SignedHeaders parsing accepted empty header name segments such as host; or ;host. Malformed Authorization headers could continue into signature verification instead of failing during header parsing.

Root cause: parseSignedHeader only checked that the SignedHeaders value was non-empty, then split it on semicolons without validating each element.

Fix: reject empty or whitespace-only signed header elements with ErrMissingFields before returning the parsed header list.

Reproduction: go test ./weed/s3api -run TestParseSignedHeaderRejectsEmptyHeaderNames -count=1 failed before the fix because SignedHeaders=host; returned ErrNone.

Validation: gofmt -w weed/s3api/auth_signature_v4.go weed/s3api/auth_signature_v4_test.go; git diff --check; go test ./weed/s3api -run TestParseSignedHeaderRejectsEmptyHeaderNames -count=1; go test ./weed/s3api -count=1

Co-authored-by: Codex <noreply@openai.com>

weed/s3api/auth_signature_v4.go

@@ -559,6 +559,10 @@ func extractV4AuthInfoFromQuery(r *http.Request) (*v4AuthInfo, s3err.ErrorCode)
 	if query.Get("X-Amz-Expires") == "" {
 		return nil, s3err.ErrInvalidQueryParams
 	}
+	signedHeaders, errCode := parseSignedHeaderList(query.Get("X-Amz-SignedHeaders"))
+	if errCode != s3err.ErrNone {
+		return nil, errCode
+	}
 
 	// Parse date
 	dateStr := query.Get("X-Amz-Date")
@@ -584,7 +588,7 @@ func extractV4AuthInfoFromQuery(r *http.Request) (*v4AuthInfo, s3err.ErrorCode)
 	return &v4AuthInfo{
 		Signature:     query.Get("X-Amz-Signature"),
 		AccessKey:     credHeader.accessKey,
-		SignedHeaders: strings.Split(query.Get("X-Amz-SignedHeaders"), ";"),
+		SignedHeaders: signedHeaders,
 		Date:          t,
 		Region:        credHeader.scope.region,
 		Service:       credHeader.scope.service,
@@ -716,10 +720,19 @@ func parseSignedHeader(signedHdrElement string) ([]string, s3err.ErrorCode) {
 	if signedHdrFields[0] != "SignedHeaders" {
 		return nil, s3err.ErrMissingSignHeadersTag
 	}
-	if signedHdrFields[1] == "" {
+	return parseSignedHeaderList(signedHdrFields[1])
+}
+
+func parseSignedHeaderList(signedHeadersValue string) ([]string, s3err.ErrorCode) {
+	if signedHeadersValue == "" {
 		return nil, s3err.ErrMissingFields
 	}
-	signedHeaders := strings.Split(signedHdrFields[1], ";")
+	signedHeaders := strings.Split(signedHeadersValue, ";")
+	for _, header := range signedHeaders {
+		if strings.TrimSpace(header) == "" {
+			return nil, s3err.ErrMissingFields
+		}
+	}
 	return signedHeaders, s3err.ErrNone
 }
 

weed/s3api/auth_signature_v4_test.go

@@ -66,6 +66,51 @@ func TestExtractV4AuthInfoFromHeader_S3Tables(t *testing.T) {
 	}
 }
 
+func TestParseSignedHeaderRejectsEmptyHeaderNames(t *testing.T) {
+	cases := []string{
+		"SignedHeaders=host;",
+		"SignedHeaders=;host",
+		"SignedHeaders=host;;x-amz-date",
+	}
+
+	for _, tc := range cases {
+		if _, errCode := parseSignedHeader(tc); errCode != s3err.ErrMissingFields {
+			t.Fatalf("parseSignedHeader(%q) errCode = %v, want %v", tc, errCode, s3err.ErrMissingFields)
+		}
+	}
+}
+
+func TestExtractV4AuthInfoFromQueryRejectsEmptySignedHeaderNames(t *testing.T) {
+	now := time.Now().UTC()
+	cases := []string{
+		"host;",
+		";host",
+		"host;;x-amz-date",
+	}
+
+	for _, tc := range cases {
+		t.Run(tc, func(t *testing.T) {
+			req, err := http.NewRequest(http.MethodGet, "http://localhost/bucket/object", nil)
+			if err != nil {
+				t.Fatalf("NewRequest: %v", err)
+			}
+
+			query := req.URL.Query()
+			query.Set("X-Amz-Algorithm", signV4Algorithm)
+			query.Set("X-Amz-Credential", fmt.Sprintf("AKIAIOSFODNN7EXAMPLE/%s/us-east-1/s3/aws4_request", now.Format(yyyymmdd)))
+			query.Set("X-Amz-Date", now.Format(iso8601Format))
+			query.Set("X-Amz-Expires", "60")
+			query.Set("X-Amz-Signature", "dummy")
+			query.Set("X-Amz-SignedHeaders", tc)
+			req.URL.RawQuery = query.Encode()
+
+			if _, errCode := extractV4AuthInfoFromQuery(req); errCode != s3err.ErrMissingFields {
+				t.Fatalf("extractV4AuthInfoFromQuery(%q) errCode = %v, want %v", tc, errCode, s3err.ErrMissingFields)
+			}
+		})
+	}
+}
+
 func TestBuildPathWithForwardedPrefix(t *testing.T) {
 	tests := []struct {
 		name            string