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Merged
Travis Plunk (TravisEz13) merged 2 commits into from
Aug 20, 2026
+242 −72
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Improve PowerShell Remoting Argument Validation #27870

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46a0463
Fix PowerShell Remoting Argument Generation (#158)
tgauth Aug 7, 2026
766c64e
Import LINQ for RunspaceConnectionInfo (#173)
Aug 10, 2026
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148 changes: 100 additions & 48 deletions src/System.Management.Automation/engine/remoting/common/RunspaceConnectionInfo.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -14,6 +14,7 @@
using System.Management.Automation.Remoting.Client;
using System.Management.Automation.Tracing;
using System.Net;
using System.Linq;
using System.Net.Sockets;
using System.Reflection;
using System.Runtime.InteropServices;
Expand Down Expand Up @@ -2285,7 +2286,8 @@ internal int StartSSHProcess(
StringUtil.Format(RemotingErrorIdStrings.KeyFileNotFound, this.KeyFilePath));
}

startInfo.ArgumentList.Add(string.Create(CultureInfo.InvariantCulture, $@"-i ""{this.KeyFilePath}"""));
startInfo.ArgumentList.Add("-i");
startInfo.ArgumentList.Add(this.KeyFilePath);
}

// pass "-l login_name" command line argument to ssh if UserName is set
Expand All @@ -2298,33 +2300,39 @@ internal int StartSSHProcess(
// convert DOMAIN\user to user@DOMAIN
var domainName = parts[0];
var userName = parts[1];
startInfo.ArgumentList.Add(string.Create(CultureInfo.InvariantCulture, $@"-l {userName}@{domainName}"));
startInfo.ArgumentList.Add("-l");
startInfo.ArgumentList.Add($"{userName}@{domainName}");
}
else
{
startInfo.ArgumentList.Add(string.Create(CultureInfo.InvariantCulture, $@"-l {this.UserName}"));
startInfo.ArgumentList.Add("-l");
startInfo.ArgumentList.Add(this.UserName);
}
}

// pass "-p port" command line argument to ssh if Port is set
// if Port is not set, then ssh will use Port from ssh_config if defined else 22 by default
if (this.Port != 0)
{
startInfo.ArgumentList.Add(string.Create(CultureInfo.InvariantCulture, $@"-p {this.Port}"));
startInfo.ArgumentList.Add("-p");
startInfo.ArgumentList.Add(this.Port.ToString(CultureInfo.InvariantCulture));
}

// pass "-o option=value" command line argument to ssh if options are provided
if (this.Options != null)
{
foreach (DictionaryEntry pair in this.Options)
{
startInfo.ArgumentList.Add(string.Create(CultureInfo.InvariantCulture, $@"-o {pair.Key}={pair.Value}"));
startInfo.ArgumentList.Add("-o");
startInfo.ArgumentList.Add($"{pair.Key}={pair.Value}");
}
}

// pass "-s destination command" command line arguments to ssh where command is the subsystem to invoke on the destination
// note that ssh expects IPv6 addresses to not be enclosed in square brackets so trim them if present
startInfo.ArgumentList.Add(string.Create(CultureInfo.InvariantCulture, $@"-s {this.ComputerName.TrimStart('[').TrimEnd(']')} {this.Subsystem}"));
startInfo.ArgumentList.Add("-s");
startInfo.ArgumentList.Add(this.ComputerName.TrimStart('[').TrimEnd(']'));
startInfo.ArgumentList.Add(this.Subsystem);

startInfo.WorkingDirectory = Path.GetDirectoryName(filePath);
startInfo.CreateNoWindow = true;
Expand Down Expand Up @@ -2414,7 +2422,7 @@ internal static int StartSSHProcess(
}

string filename = startInfo.FileName;
string[] argv = ParseArgv(startInfo);
string[] argv = startInfo.ArgumentList.Prepend(filename).ToArray();
string[] envp = CopyEnvVariables(startInfo);
string cwd = !string.IsNullOrWhiteSpace(startInfo.WorkingDirectory) ? startInfo.WorkingDirectory : null;

Expand Down Expand Up @@ -2497,46 +2505,6 @@ private static string[] CopyEnvVariables(ProcessStartInfo psi)
return envp;
}

/// <summary>Converts the filename and arguments information from a ProcessStartInfo into an argv array.</summary>
/// <param name="psi">The ProcessStartInfo.</param>
/// <returns>The argv array.</returns>
private static string[] ParseArgv(ProcessStartInfo psi)
{
var argvList = new List<string>();
argvList.Add(psi.FileName);

var argsToParse = string.Join(' ', psi.ArgumentList).Trim();
var argsLength = argsToParse.Length;
for (int i = 0; i < argsLength; )
{
var iStart = i;

switch (argsToParse[i])
{
case '"':
// Special case for arguments within quotes
// Just return argument value within the quotes
while ((++i < argsLength) && argsToParse[i] != '"') { }
if (iStart < argsLength - 1)
{
iStart++;
}

break;

default:
// Common case for parsing arguments with space character delimiter
while ((++i < argsLength) && argsToParse[i] != ' ') { }
break;
}

argvList.Add(argsToParse.Substring(iStart, (i - iStart)));
while ((++i < argsLength) && argsToParse[i] == ' ') { }
}

return argvList.ToArray();
}

internal static unsafe void CreateProcess(
string filename, string[] argv, string[] envp, string cwd,
bool redirectStdin, bool redirectStdout, bool redirectStderr, int creationFlags,
Expand Down Expand Up @@ -2779,7 +2747,7 @@ private static Process CreateProcessWithRedirectedStd(
CultureInfo.InvariantCulture,
@"""{0}"" {1}",
startInfo.FileName,
string.Join(' ', startInfo.ArgumentList));
JoinArguments(startInfo.ArgumentList));

lpStartupInfo.hStdInput = stdInPipeClient;
lpStartupInfo.hStdOutput = stdOutPipeClient;
Expand Down Expand Up @@ -2841,6 +2809,90 @@ private static Process CreateProcessWithRedirectedStd(
}
}

/// <summary>Joins the specified arguments into a single Windows command line.</summary>
/// <param name="arguments">The arguments to join.</param>
/// <returns>The flattened command line arguments.</returns>
private static string JoinArguments(ICollection<string> arguments)
{
var builder = new StringBuilder();
bool first = true;

foreach (string argument in arguments)
{
if (!first)
{
builder.Append(' ');
}

if (argument == null
|| argument.Contains(' ')
|| argument.Contains('"')
|| argument.Contains('\t')
|| argument.Contains('\n')
|| argument.Contains('\r'))
{
Comment thread
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builder.Append(QuoteArgument(argument));
}
else
{
builder.Append(argument);
}

first = false;
}

return builder.ToString();
}

/// <summary>Quotes a single argument for the flattened Windows CreateProcess command line.</summary>
/// <remarks>Handles backslashes in the argument with the following logic:
/// - before a normal character, preserve the run unchanged
/// - before a double-quote, double the run and add one more '\\' to escape the double-quote
/// - at the end of the argument, double the run so trailing '\\' survive the closing quote</remarks>
/// <param name="argument">The argument to quote.</param>
/// <returns>The quoted command line argument.</returns>
private static string QuoteArgument(string argument)
{
argument ??= string.Empty;

var builder = new StringBuilder(argument.Length + 2);
builder.Append('"');

int backslashCount = 0;
foreach (char character in argument)
{
if (character == '\\')
{
backslashCount++;
continue;
}

if (character == '"')
{
builder.Append('\\', (backslashCount * 2) + 1);
builder.Append(character);
backslashCount = 0;
continue;
}

if (backslashCount > 0)
{
builder.Append('\\', backslashCount);
backslashCount = 0;
}

builder.Append(character);
}

if (backslashCount > 0)
{
builder.Append('\\', backslashCount * 2);
}

builder.Append('"');
return builder.ToString();
}

private static SafeFileHandle GetNamedPipeHandle(string pipeName)
{
SafeFileHandle sf = File.OpenHandle(pipeName, FileMode.Open, FileAccess.ReadWrite, FileShare.Inheritable, FileOptions.Asynchronous);
Expand Down
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