代理背后的 Express

When running an Express app behind a reverse proxy, some of the Express APIs may return different values than expected. In order to adjust for this, the trust proxy application setting may be used to expose information provided by the reverse proxy in the Express APIs. The most common issue is express APIs that expose the client’s IP address may instead show an internal IP address of the reverse proxy.

When configuring the trust proxy setting, it is important to understand the exact setup of the reverse proxy. Since this setting will trust values provided in the request, it is important that the combination of the setting in Express matches how the reverse proxy operates.

在代理背后运行 Express 应用程序时，可使用 app.set() 将应用程序变量 trust proxy 设置为下表中所列的某个值。

类型值
布尔

如果为 true，那么客户机的 IP 地址将用作 X-Forwarded-* 头中最左侧的条目。 如果为 false，那么该应用程序将被视为直接面对因特网，而客户机的 IP 地址则派生自 req.connection.remoteAddress。这是缺省设置。

If false, the app is understood as directly facing the client and the client’s IP address is derived from req.socket.remoteAddress. This is the default setting.

When setting to true, it is important to ensure that the last reverse proxy trusted is removing/overwriting all of the following HTTP headers: X-Forwarded-For, X-Forwarded-Host, and X-Forwarded-Proto, otherwise it may be possible for the client to provide any value.
IP addresses

An IP address, subnet, or an array of IP addresses and subnets to trust as being a reverse proxy. The following list shows the pre-configured subnet names:

  • loopback - 127.0.0.1/8, ::1/128
  • linklocal - 169.254.0.0/16, fe80::/10
  • uniquelocal - 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16, fc00::/7

您可以按以下某种方法设置 IP 地址：

app.set('trust proxy', 'loopback') // specify a single subnet
app.set('trust proxy', 'loopback, 123.123.123.123') // specify a subnet and an address
app.set('trust proxy', 'loopback, linklocal, uniquelocal') // specify multiple subnets as CSV
app.set('trust proxy', ['loopback', 'linklocal', 'uniquelocal']) // specify multiple subnets as an array

如果指定 IP 地址或子网，那么会在地址确定过程中排除这些项，而将最接近应用程序服务器的不受信任的 IP 地址确定为客户机的 IP 地址。 This works by checking if req.socket.remoteAddress is trusted. If so, then each address in X-Forwarded-For is checked from right to left until the first non-trusted address.
数字

Use the address that is at most n number of hops away from the Express application. req.socket.remoteAddress is the first hop, and the rest are looked for in the X-Forwarded-For header from right to left. A value of 0 means that the first untrusted address would be req.socket.remoteAddress, i.e. there is no reverse proxy.

When using this setting, it is important to ensure there are not multiple, different-length paths to the Express application such that the client can be less than the configured number of hops away, otherwise it may be possible for the client to provide any value.
Function

Custom trust implementation.

app.set('trust proxy', (ip) => {
  if (ip === '127.0.0.1' || ip === '123.123.123.123') return true // trusted IPs
  else return false
})

Enabling trust proxy will have the following impact:

trust proxy 设置由使用 proxy-addr 包实现。有关更多信息，请参阅其文档。 For more information, see its documentation.

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