Limit release asset redirects

internal/gitea/assets.go

@@ -56,6 +56,7 @@ func (c Client) openAsset(ctx context.Context, client *http.Client, base *url.UR
 	}
 	assetURL.Fragment = ""
 	visited := make(map[string]struct{})
+	followed := 0
 	for {
 		key := assetURL.String()
 		if _, exists := visited[key]; exists {
@@ -75,6 +76,10 @@ func (c Client) openAsset(ctx context.Context, client *http.Client, base *url.UR
 			return nil, failure(FailureUnverifiable, "download release asset", 0, err)
 		}
 		if isRedirect(response.StatusCode) {
+			if followed == 10 {
+				_ = response.Body.Close()
+				return nil, failure(FailureUnverifiable, "redirect release asset: redirect limit exceeded", response.StatusCode, errors.New("at most 10 redirects are allowed"))
+			}
 			location, locationErr := response.Location()
 			_ = response.Body.Close()
 			if locationErr != nil || location.User != nil {
@@ -82,6 +87,7 @@ func (c Client) openAsset(ctx context.Context, client *http.Client, base *url.UR
 			}
 			location.Fragment = ""
 			assetURL = location
+			followed++
 			continue
 		}
 		if response.StatusCode < 200 || response.StatusCode >= 300 {

internal/gitea/assets_test.go

@@ -4,15 +4,104 @@ import (
 	"context"
 	"encoding/json"
 	"errors"
+	"fmt"
 	"io"
 	"net/http"
 	"net/http/httptest"
+	"strconv"
+	"strings"
 	"sync/atomic"
 	"testing"
 
 	"go.maximumdirect.net/releasekit/internal/forge"
 )
 
+func TestBackendOpenAssetBoundsRedirects(t *testing.T) {
+	for _, hops := range []int{0, 10, 11} {
+		t.Run(strconv.Itoa(hops), func(t *testing.T) {
+			var requests atomic.Int32
+			server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+				requests.Add(1)
+				if got := r.Header.Get("Authorization"); got != "token fixture-secret-token" {
+					t.Errorf("authorization = %q", got)
+				}
+				step, err := strconv.Atoi(strings.TrimPrefix(r.URL.Path, "/"))
+				if err != nil {
+					t.Errorf("invalid path %q", r.URL.Path)
+					return
+				}
+				if step < hops {
+					http.Redirect(w, r, fmt.Sprintf("/%d", step+1), http.StatusFound)
+					return
+				}
+				_, _ = io.WriteString(w, "asset")
+			}))
+			defer server.Close()
+			backend := NewBackend(testDestination(server.URL), server.Client())
+			stream, err := backend.OpenAsset(t.Context(), assetHandle{downloadURL: "/0"})
+			if hops <= 10 {
+				if err != nil {
+					t.Fatal(err)
+				}
+				body, readErr := io.ReadAll(stream)
+				closeErr := stream.Close()
+				if readErr != nil || closeErr != nil || string(body) != "asset" || requests.Load() != int32(hops+1) {
+					t.Fatalf("body = %q, read = %v, close = %v, requests = %d", body, readErr, closeErr, requests.Load())
+				}
+				return
+			}
+			var failure *forge.Failure
+			if !errors.As(err, &failure) || failure.Kind != forge.FailureUnverifiable || !strings.Contains(err.Error(), "redirect limit") || requests.Load() != 11 || stream != nil {
+				t.Fatalf("stream = %v, error = %v, requests = %d", stream, err, requests.Load())
+			}
+		})
+	}
+}
+
+func TestBackendOpenAssetRedirectReturnsToOrigin(t *testing.T) {
+	var origin *httptest.Server
+	external := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if got := r.Header.Get("Authorization"); got != "" {
+			t.Errorf("cross-origin authorization = %q", got)
+		}
+		http.Redirect(w, r, origin.URL+"/final", http.StatusFound)
+	}))
+	defer external.Close()
+	origin = httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if got := r.Header.Get("Authorization"); got != "token fixture-secret-token" {
+			t.Errorf("origin authorization = %q", got)
+		}
+		if r.URL.Path == "/start" {
+			http.Redirect(w, r, external.URL+"/away", http.StatusFound)
+			return
+		}
+		_, _ = io.WriteString(w, "asset")
+	}))
+	defer origin.Close()
+	stream, err := NewBackend(testDestination(origin.URL), origin.Client()).OpenAsset(t.Context(), assetHandle{downloadURL: "/start"})
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer stream.Close()
+	if body, err := io.ReadAll(stream); err != nil || string(body) != "asset" {
+		t.Fatalf("body = %q, error = %v", body, err)
+	}
+}
+
+func TestBackendOpenAssetRejectsRedirectCycle(t *testing.T) {
+	var requests atomic.Int32
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		requests.Add(1)
+		http.Redirect(w, r, "/loop#different-fragment", http.StatusFound)
+	}))
+	defer server.Close()
+	stream, err := NewBackend(testDestination(server.URL), server.Client()).OpenAsset(t.Context(), assetHandle{downloadURL: "/loop"})
+	var failure *forge.Failure
+	if !errors.As(err, &failure) || failure.Kind != forge.FailureUnverifiable || !strings.Contains(err.Error(), "loop") || requests.Load() != 1 || stream != nil {
+		t.Fatalf("stream = %v, error = %v, requests = %d", stream, err, requests.Load())
+	}
+}
+
 func TestBackendListAssetsRejectsMalformedAttachmentList(t *testing.T) {
 	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		if r.Method != http.MethodGet || r.URL.Path != "/api/v1/repos/owner/project/releases/10/assets" {