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#!/usr/bin/env pwsh |
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# Send an email using Powershell. |
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# Usage: sendmail.ps1 [attachment 1 [attachment 2 [... attachment N]]] |
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# |
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# This is a POC on how to send an email using Powershell. The script should work |
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# on all platforms. The information required for the script to work is all |
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# supplied via environment variables. |
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# |
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# Env Vars |
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# smtp_host |
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# smtp_port (best if you let the implementation decide) |
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# smtp_tls: |
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# 'F' to insist on secure connection (default) |
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# 'O' for opportunistic |
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# 'N' to disable (default if $smtp_host is "localhost") |
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# smtp_tls_cert |
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# smtp_username |
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# smtp_password |
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# mail_from (required) |
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# mail_to (required) |
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# mail_subject (required) |
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# |
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# Example |
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#```pwsh |
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# echo 'Hi! it going? Testing my Powershell script.' | \ |
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# smtp_host=smtp.gmail.com \ |
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# [email protected] \ |
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# smtp_password='0123456789' \ |
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# [email protected] \ |
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# [email protected] \ |
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# mail_subject='Sent using Powershell' \ |
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# sendmail.ps1 \ |
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# doc.pdf |
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#``` |
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using namespace System |
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using namespace System.Net |
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using namespace System.Security.Cryptography |
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Set-StrictMode -Version Latest |
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$ErrorActionPreference = "Stop" |
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$PSDefaultParameterValues['*:ErrorAction'] = 'Stop' |
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<# |
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.SYNOPSIS |
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Get an environment variable and unset it |
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.PARAMETER Name |
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The name of the environment variable to read and unset |
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.PARAMETER Required |
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If set, throw FileNotFoundException if the environment variable requested is not |
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set |
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.NOTES |
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The purpose of the function is to get and scrub off the password passed as an |
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env var in one go. To preserve the env var, use `GetEnvironmentVariable()` |
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directly. |
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#> |
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function FetchEnv ([string]$Name, [bool]$Required = $false) { |
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$RetVal = [Environment]::GetEnvironmentVariable($Name) |
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[Environment]::SetEnvironmentVariable($Name, '') |
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if ( $RetVal ) { |
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return $RetVal |
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} |
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else { |
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if ($Required) { |
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throw New-Object IO.FileNotFoundException ("${Name}: unset env var") |
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} |
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else { |
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return $null |
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} |
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} |
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} |
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<# |
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.SYNOPSIS |
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Read data from STDIN until EOF and return data as decoded string |
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#> |
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function ExhaustStdin () { |
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$stream = New-Object IO.StreamReader ( [Console]::OpenStandardInput() ) |
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return $stream.ReadToEnd() |
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} |
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###################################################################### |
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# Execution starts here |
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###################################################################### |
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# Compose a message |
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$mail = New-Object Mail.MailMessage ( |
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(FetchEnv "mail_from" $true), |
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(FetchEnv "mail_to" $true), |
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(FetchEnv "mail_subject" $true), |
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(ExhaustStdin)) # This is the part where the mail body is read from STDIN |
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# Add attachments |
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foreach ($file in $args) { |
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[string]$file = $file |
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$a = New-Object Mail.Attachment ( |
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$file, |
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# Treat all attachments as binary |
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[System.Net.Mime.MediaTypeNames+Application]::Octet) |
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# Timestamp support |
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$a.ContentDisposition.CreationDate = [IO.File]::GetCreationTime($file) |
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$a.ContentDisposition.ModificationDate = [IO.File]::GetLastWriteTime($file) |
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$a.ContentDisposition.ReadDate = [IO.File]::GetLastAccessTime($file) |
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$mail.Attachments.Add($a) |
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} |
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# Set up credentials |
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$client_cred = New-Object NetworkCredential ( |
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(FetchEnv "smtp_username"), |
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(FetchEnv "smtp_password")) |
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# Set up client TLS cert |
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$tls_cert = FetchEnv("smtp_tls_cert") |
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if ($null -ne $tls_cert) { |
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$cert_chain = New-Object X509Certificates.X509Certificate ( $tls_cert ) |
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} |
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else { |
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$cert_chain = $null |
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} |
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# Read target SMTP host |
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$smtp_host = FetchEnv "smtp_host" |
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if (!$smtp_host) { |
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$smtp_host = "localhost" |
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} |
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# Set up SMTP client object |
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$smtp = New-Object Mail.SmtpClient ($smtp_host) |
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if ($cert_chain) { |
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$smtp.ClientCertificates.Add($cert_chain) |
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} |
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$smtp.Credentials = $client_cred |
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$smtp_port = FetchEnv "smtp_port" |
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if ($smtp_port) { |
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$smtp.Port = [int]$smtp_port |
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} |
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$tlsmode = FetchEnv "smtp_tls" |
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if (!$tlsmode) { |
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# Determine the "tlsmode" to default to |
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if ($smtp_host -eq "localhost") { |
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# No need to waste computing power on TLS. |
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# Unless you're paranoid and don't trust the hosts file. |
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$tlsmode = "N" |
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} |
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else { |
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# Transmitting plain text data on the internet nowadays is no-brainer. |
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# Most email services will refuse anyway. |
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$tlsmode = "F" |
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} |
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} |
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# Set `$smtp.EnableSsl` based on `$tlsmode` |
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if ($tlsmode -eq "F" -or $tlsmode -eq "O") { |
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$smtp.EnableSsl = $true |
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} |
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elseif ($tlsmode -eq "N") { |
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$smtp.EnableSsl = $false |
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} |
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try { |
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$smtp.Send($mail) |
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} |
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catch { |
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if ($tlsmode -eq "O") { |
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# Opportunistic tlsmode. Try again with TLS disabled. |
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# Please think twice and fix the problem before resorting to this bit. |
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$smtp.EnableSsl = $false |
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$smtp.Send($mail) |
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} |
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else { |
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# Let the script die |
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throw $_ |
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} |
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} |
