feat(backend): 提交后端审计修复与配套测试改动

backend/internal/service/upstream_response_limit_test.go

+package service
+
+import (
+	"bytes"
+	"errors"
+	"testing"
+
+	"github.com/Wei-Shaw/sub2api/internal/config"
+	"github.com/stretchr/testify/require"
+)
+
+func TestResolveUpstreamResponseReadLimit(t *testing.T) {
+	t.Run("use default when config missing", func(t *testing.T) {
+		require.Equal(t, defaultUpstreamResponseReadMaxBytes, resolveUpstreamResponseReadLimit(nil))
+	})
+
+	t.Run("use configured value", func(t *testing.T) {
+		cfg := &config.Config{}
+		cfg.Gateway.UpstreamResponseReadMaxBytes = 1234
+		require.Equal(t, int64(1234), resolveUpstreamResponseReadLimit(cfg))
+	})
+}
+
+func TestReadUpstreamResponseBodyLimited(t *testing.T) {
+	t.Run("within limit", func(t *testing.T) {
+		body, err := readUpstreamResponseBodyLimited(bytes.NewReader([]byte("ok")), 2)
+		require.NoError(t, err)
+		require.Equal(t, []byte("ok"), body)
+	})
+
+	t.Run("exceeds limit", func(t *testing.T) {
+		body, err := readUpstreamResponseBodyLimited(bytes.NewReader([]byte("toolong")), 3)
+		require.Nil(t, body)
+		require.Error(t, err)
+		require.True(t, errors.Is(err, ErrUpstreamResponseBodyTooLarge))
+	})
+}

deploy/config.example.yaml

@@ -146,6 +146,15 @@ gateway:
   # Max request body size in bytes (default: 100MB)
   # 请求体最大字节数（默认 100MB）
   max_body_size: 104857600
+  # Max bytes to read for non-stream upstream responses (default: 8MB)
+  # 非流式上游响应体读取上限（默认 8MB）
+  upstream_response_read_max_bytes: 8388608
+  # Max bytes to read for proxy probe responses (default: 1MB)
+  # 代理探测响应体读取上限（默认 1MB）
+  proxy_probe_response_read_max_bytes: 1048576
+  # Enable Gemini upstream response header debug logs (default: false)
+  # 是否开启 Gemini 上游响应头调试日志（默认 false）
+  gemini_debug_response_headers: false
   # Sora max request body size in bytes (0=use max_body_size)
   # Sora 请求体最大字节数（0=使用 max_body_size）
   sora_max_body_size: 268435456