PowerShell调用Invoke-RestMethod遇GZip头部魔术数错误求助

我调用某API时，Postman能正常执行，但用PowerShell的Invoke-RestMethod会报错：

Invoke-RestMethod : The magic number in GZip header is not correct. Make sure you are passing in a GZip stream.

已知API返回的响应头：

Connection: close
Content-Encoding: gzip, deflate
Content-Type: application/xml; charset=utf-8
Content-Length: 11778
Date: Fri, 07 Jul 2023 12:49:25 GMT

以下是我编写的PowerShell脚本：

[Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12
$userAgent = [Microsoft.PowerShell.Commands.PSUserAgent]::Chrome
$headers = New-Object "System.Collections.Generic.Dictionary[[String],[String]]"
$headers.Add("Authorization", "Bearer $token")
$headers.Add("Accept", "*/*")
$headers.Add("Accept-Encoding", "gzip, deflate")
$headers.Add("Host", "b-fleet03.bellequipment.com:8080")

$response3 = Invoke-RestMethod 'https://b-fleet03.bellequipment.com:8080/Fleet' -Method 'POST' -Headers $headers -ContentType "text/plain; charset=utf-8" -UserAgent $userAgent

$response3 

脚本变体：

[Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12
$userAgent = [Microsoft.PowerShell.Commands.PSUserAgent]::Chrome
$headers = New-Object "System.Collections.Generic.Dictionary[[String],[String]]"
$headers.Add("Authorization", "Bearer $token")
$headers.Add("Accept", "*/*")
([System.Net.HttpRequestHeader]::AcceptEncoding, "gzip")
$headers.Add("Accept-Encoding", "gzip, deflate")
$headers.Add("Host", "b-fleet03.bellequipment.com:8080")

$response3 = Invoke-RestMethod 'https://b-fleet03.bellequipment.com:8080/Fleet' -Method 'POST' -Headers $headers -ContentType "text/plain; charset=utf-8" -UserAgent $userAgent

$response3 

Postman成功调用的请求及响应信息：

POST https://b-fleet03.bellequipment.com:8080/Fleet
200
1633 ms

Request Headers
loco: besa
Authorization: Bearer XXXXXXXXX
User-Agent: PostmanRuntime/7.32.3
Accept: */*
Postman-Token: 29e59bd1-8d66-4140-9d10-90b3447e9694
Host: b-fleet03.bellequipment.com:8080
Accept-Encoding: gzip, deflate, br
Connection: keep-alive
Content-Length: 0

Response Headers
Connection: close
Content-Encoding: gzip, deflate
Content-Type: application/xml; charset=utf-8
Content-Length: 11779
Date: Mon, 10 Jul 2023 13:55:20 GMT

问题分析 #

这个错误的核心原因是：API返回了gzip+deflate双重压缩的响应，但Invoke-RestMethod默认的解压逻辑无法正确解析这种嵌套压缩的流。另外你的请求和Postman还有两处关键差异：

• 缺少Postman里的loco: besa请求头，这可能是API的必填标识
• 你指定了Content-Type: text/plain但POST没有正文，而Postman是Content-Length: 0的空请求

修复方案 #

方案一：简化请求头，让PowerShell自动处理编码

移除手动添加的Accept-Encoding，让PowerShell自动协商编码，避免触发API的双重压缩返回；同时补上缺失的loco头，调整空请求的处理：

[Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12

$headers = [System.Collections.Generic.Dictionary[string,string]]::new()
$headers.Add("Authorization", "Bearer $token")
$headers.Add("loco", "besa") # 补上Postman里的必填头
$headers.Add("Accept", "*/*")

# 明确传递空请求体，匹配Postman的Content-Length:0
$response3 = Invoke-RestMethod 'https://b-fleet03.bellequipment.com:8080/Fleet' `
    -Method 'POST' `
    -Headers $headers `
    -UserAgent [Microsoft.PowerShell.Commands.PSUserAgent]::Chrome `
    -Body $null

$response3

方案二：手动处理双重压缩（方案一无效时用）

如果API强制返回双重压缩响应，就需要跳过PowerShell的自动解压，手动处理两层压缩流：

[Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12

# 创建底层请求对象，禁用自动解压
$request = [System.Net.HttpWebRequest]::Create('https://b-fleet03.bellequipment.com:8080/Fleet')
$request.Method = 'POST'
$request.Headers.Add("Authorization", "Bearer $token")
$request.Headers.Add("loco", "besa")
$request.Accept = "*/*"
$request.UserAgent = [Microsoft.PowerShell.Commands.PSUserAgent]::Chrome
$request.AutomaticDecompression = [System.Net.DecompressionMethods]::None

# 发送空请求体
$request.ContentLength = 0
$response = $request.GetResponse()

# 先解压deflate层，再解压gzip层
$stream = $response.GetResponseStream()
$deflateStream = New-Object System.IO.Compression.DeflateStream($stream, [System.IO.Compression.CompressionMode]::Decompress)
$gzipStream = New-Object System.IO.Compression.GZipStream($deflateStream, [System.IO.Compression.CompressionMode]::Decompress)

# 读取并转换为XML对象
$reader = New-Object System.IO.StreamReader($gzipStream)
$responseContent = $reader.ReadToEnd()
$xmlContent = [xml]$responseContent
$xmlContent

# 关闭资源
$reader.Close()
$gzipStream.Close()
$deflateStream.Close()
$response.Close()

内容的提问来源于stack exchange，提问作者user3232808