Azure Automation中MSGraph无法识别嵌套邮件附件内容的问题

我有一个Azure Automation Runbook，用于从Outlook邮件中获取附件并在虚拟机上进行转换。近期更新MSGraph密钥后，代码部分功能失效：直接附加的Excel文件可正常处理，但嵌套在邮件附件中的Excel或ZIP文件无法处理。

• 通过Invoke-GraphRequest获取邮件附件列表
• 若附件包含contentBytes字段，直接调用HandleAttachment处理Excel文件
• 处理嵌套邮件附件时，调用$value端点获取RFC822格式内容，尝试通过匹配boundary提取Excel文件，或匹配contentDisposition提取ZIP文件的Base64内容

• 无法匹配到$boundaryMatches或$contentDisposition
• Azure Automation测试面板无法输出调试信息，无法查看$rfc822的内容
• Runbook在处理嵌套附件的函数中无限运行，需手动停止

Write-Host "Downloading attachments:`n`tMessageId: $($mail.internetMessageId)`n`tSubject: $($mail.subject)"
$files = @()

$r_att = Invoke-GraphRequest "https://graph.microsoft.com/v1.0/me/messages/$($mail.id)/attachments" -AccessToken $token

($r_att.Result.Content | ConvertFrom-Json).value | ForEach-Object {
    if ($_.contentBytes) {
        $f = HandleAttachment $_
        if ($f) { $files += $f }
    }
    else {
        Write-Host "Handling nested attachment: $($_.name)"
        $v = Invoke-GraphRequest "https://graph.microsoft.com/v1.0/me/messages/$($mail.id)/attachments/$($_.id)/`$value" -AccessToken $token
        $rfc822 = $v.Result.Content -replace "`r", '' -split "`n"

        $boundaryMatches = $rfc822 | Select-String -Pattern '^Content-Type: multipart/mixed;boundary="?(.*?)"?$' -AllMatches
        if ($boundaryMatches) {
            $boundaryMatches | ForEach-Object {
                $region = $_.Matches[0].Groups[1].Value
                Write-Host "Found boundary: $region"
                $region_start = $rfc822.IndexOf("--$region")
                $region_end = $rfc822.IndexOf("--$($region)--")
                if ($region_start -ne -1 -and $region_end -ne -1) {
                    $content = $rfc822[($region_start + 4) .. ($region_end - 1)]
                    $f = "$([System.IO.Path]::GetTempFileName()).xlsx"
                    [System.IO.File]::WriteAllBytes($f, ($content -join "`r`n").ToCharArray())
                    $files += $f
                }
                else {
                    Write-Warning "Could not find start or end of region for boundary: $region"
                }
            }
        }
        else {
            $contentDisposition = $rfc822 | Select-String -Pattern '^Content-Disposition: attachment; filename=(.*\.zip)$'
            if ($contentDisposition) {
                $zipFileName = $contentDisposition.Matches.Groups[1].Value
                Write-Host "Found zip file: $zipFileName"

                $base64StartLine = $rfc822 | Select-String -Pattern "^Content-Disposition: attachment; filename=$zipFileName" -CaseSensitive

                if ($base64StartLine) {
                    Write-Host "Found start of base64-encoded content"

                    $base64ContentLines = $rfc822[($base64StartLine.LineNumber + 1)..($rfc822.Count - 1)] |
                    Where-Object { $_ -notmatch "^--" } |
                    ForEach-Object { $_.Trim() }

                    $encodedContent = -join $base64ContentLines
                    Write-Host "Base64 Content Preview: $($encodedContent.Substring(0, [Math]::Min(500, $encodedContent.Length)))"

                    try {
                        $decodedContent = [Convert]::FromBase64String($encodedContent)
                        $zipFilePath = Join-Path $env:TEMP $zipFileName
                        [System.IO.File]::WriteAllBytes($zipFilePath, $decodedContent)
                        $files += $zipFilePath
                        Write-Host "Zip file saved to: $zipFilePath"
                    }
                    catch {
                        Write-Warning "Failed to base64-decode content for zip file: $zipFileName"
                        Write-Warning "Error details: $_"
                    }
                }
                else {
                    Write-Warning "Could not find start of base64 encoded content for zip file: $zipFileName"
                }
            }
            else {
                Write-Warning "No zip file found in nested attachment"
            }
        }
    }
}
return $files

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