Using sudo in an SSH Shell Session

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Demonstrates running a command with sudo in a shell session without an interactive prompt. sudo -S reads the password from stdin and -p "" suppresses the prompt, so piping the password in with echo runs the command as root with no interaction.

Security note: The password appears in the command line, so it may be visible in the remote host's process list and shell history. A passwordless sudo rule for the specific command is preferable where it can be arranged.

integer li_rc
integer li_Success
oleobject loo_Ssh
integer li_Port
string ls_Password
integer li_ChannelNum
oleobject loo_SbCommands
string ls_Commands
integer li_CaseSensitive
string ls_SessionOutput

li_Success = 0

//  This example requires the Chilkat API to have been previously unlocked.
//  See Global Unlock Sample for sample code.

//  Demonstrates running a command with "sudo" in a shell session, supplying the password without
//  an interactive prompt.

loo_Ssh = create oleobject
li_rc = loo_Ssh.ConnectToNewObject("Chilkat.Ssh")
if li_rc < 0 then
    destroy loo_Ssh
    MessageBox("Error","Connecting to COM object failed")
    return
end if

li_Port = 22
li_Success = loo_Ssh.Connect("ssh.example.com",li_Port)
if li_Success = 0 then
    Write-Debug loo_Ssh.LastErrorText
    destroy loo_Ssh
    return
end if

//  Normally you would not hard-code the password in source.  You should instead obtain it
//  from an interactive prompt, environment variable, or a secrets vault.
ls_Password = "mySshPassword"

li_Success = loo_Ssh.AuthenticatePw("mySshLogin",ls_Password)
if li_Success = 0 then
    Write-Debug loo_Ssh.LastErrorText
    destroy loo_Ssh
    return
end if

//  Start a shell session.  QuickShell allocates a PTY, so the shell echoes the commands sent
//  to it and prints a prompt.
li_ChannelNum = loo_Ssh.QuickShell()
if li_ChannelNum < 0 then
    Write-Debug loo_Ssh.LastErrorText
    destroy loo_Ssh
    return
end if

//  Build the command.  "sudo -S" makes sudo read the password from stdin, and "-p" sets the
//  prompt -- setting it to an empty string removes the prompt entirely.  Piping the password in
//  via "echo" therefore runs the command as root with no interaction.
//  
//  Security note: the password appears in the command line, so it can be visible in the remote
//  host's process list and shell history.  Prefer a passwordless sudo rule where possible.
loo_SbCommands = create oleobject
li_rc = loo_SbCommands.ConnectToNewObject("Chilkat.StringBuilder")

loo_SbCommands.Append("echo ~"")
loo_SbCommands.Append(ls_Password)
loo_SbCommands.Append("~" | sudo -S -p ~"~" ls~n")

//  The final command echoes a marker used to detect the end of the output.  The single quotes
//  around 'IS' are a trick: the terminal echo of the typed command includes the quotes, while
//  the command's actual output does not.  Matching the unquoted form therefore matches the real
//  output rather than the echo.
loo_SbCommands.Append("echo THIS 'IS' THE END OF THE SCRIPT~n")

ls_Commands = loo_SbCommands.GetAsString()
li_Success = loo_Ssh.ChannelSendString(li_ChannelNum,ls_Commands,"utf-8")
if li_Success = 0 then
    Write-Debug loo_Ssh.LastErrorText
    destroy loo_Ssh
    destroy loo_SbCommands
    return
end if

//  No more commands will be sent.
li_Success = loo_Ssh.ChannelSendEof(li_ChannelNum)
if li_Success = 0 then
    Write-Debug loo_Ssh.LastErrorText
    destroy loo_Ssh
    destroy loo_SbCommands
    return
end if

//  IMPORTANT: Set a read timeout before receiving until a match.  ReadTimeoutMs defaults to 0,
//  which means no limit -- without it, this call waits forever if the received data never
//  contains a match.
loo_Ssh.ReadTimeoutMs = 15000

li_CaseSensitive = 1
li_Success = loo_Ssh.ChannelReceiveUntilMatch(li_ChannelNum,"THIS IS THE END OF THE SCRIPT","utf-8",li_CaseSensitive)
if li_Success = 0 then
    Write-Debug loo_Ssh.LastErrorText
    destroy loo_Ssh
    destroy loo_SbCommands
    return
end if

//  Close the channel only after the desired output has been received.
li_Success = loo_Ssh.ChannelSendClose(li_ChannelNum)
if li_Success = 0 then
    Write-Debug loo_Ssh.LastErrorText
    destroy loo_Ssh
    destroy loo_SbCommands
    return
end if

li_Success = loo_Ssh.ChannelReceiveToClose(li_ChannelNum)
if li_Success = 0 then
    Write-Debug loo_Ssh.LastErrorText
    destroy loo_Ssh
    destroy loo_SbCommands
    return
end if

ls_SessionOutput = loo_Ssh.GetReceivedText(li_ChannelNum,"utf-8")
if loo_Ssh.LastMethodSuccess = 0 then
    Write-Debug loo_Ssh.LastErrorText
    destroy loo_Ssh
    destroy loo_SbCommands
    return
end if

Write-Debug "--- output ----"
Write-Debug ls_SessionOutput

loo_Ssh.Disconnect()


destroy loo_Ssh
destroy loo_SbCommands