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Fix stdio client transport CLI argument escaping. (#811)

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* Fix stdio client transport CLI argument escaping.

* Fix failing Windows test.

* Add more test cases and refine escaping logic.

* Fix test failures in mono

* Style fixes

* Tweak stdio test

* Tweak tests further
This commit is contained in:
Eirik Tsarpalis 2025-09-25 14:46:39 +03:00 • committed by GitHub
commit d8768de302
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GPG key ID: B5690EEEBB952194
5 changed files with 137 additions and 14 deletions
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1
ModelContextProtocol.slnx
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@ -56,6 +56,7 @@
<File Path="global.json" />
<File Path="LICENSE" />
<File Path="logo.png" />
<File Path="Makefile" />
<File Path="nuget.config" />
<File Path="README.MD" />
</Folder>

24
src/ModelContextProtocol.Core/Client/StdioClientTransport.cs
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@ -90,13 +90,13 @@ public sealed partial class StdioClientTransport : IClientTransport
#if NET
foreach (string arg in arguments)
{
startInfo.ArgumentList.Add(arg);
startInfo.ArgumentList.Add(EscapeArgumentString(arg));
}
#else
StringBuilder argsBuilder = new();
foreach (string arg in arguments)
{
PasteArguments.AppendArgument(argsBuilder, arg);
PasteArguments.AppendArgument(argsBuilder, EscapeArgumentString(arg));
}
startInfo.Arguments = argsBuilder.ToString();
@ -236,6 +236,26 @@ public sealed partial class StdioClientTransport : IClientTransport
}
}
private static string EscapeArgumentString(string argument) =>
RuntimeInformation.IsOSPlatform(OSPlatform.Windows) && !ContainsWhitespaceRegex.IsMatch(argument) ?
WindowsCliSpecialArgumentsRegex.Replace(argument, static match => "^" + match.Value) :
argument;
private const string WindowsCliSpecialArgumentsRegexString = "[&^><|]";
#if NET
private static Regex WindowsCliSpecialArgumentsRegex => GetWindowsCliSpecialArgumentsRegex();
private static Regex ContainsWhitespaceRegex => GetContainsWhitespaceRegex();
[GeneratedRegex(WindowsCliSpecialArgumentsRegexString, RegexOptions.CultureInvariant)]
private static partial Regex GetWindowsCliSpecialArgumentsRegex();
[GeneratedRegex(@"\s", RegexOptions.CultureInvariant)]
private static partial Regex GetContainsWhitespaceRegex();
#else
private static Regex WindowsCliSpecialArgumentsRegex { get; } = new(WindowsCliSpecialArgumentsRegexString, RegexOptions.Compiled | RegexOptions.CultureInvariant);
private static Regex ContainsWhitespaceRegex { get; } = new(@"\s", RegexOptions.Compiled | RegexOptions.CultureInvariant);
#endif
[LoggerMessage(Level = LogLevel.Information, Message = "{EndpointName} connecting.")]
private static partial void LogTransportConnecting(ILogger logger, string endpointName);

25
tests/ModelContextProtocol.TestServer/Program.cs
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File diff suppressed because one or more lines are too long

3
tests/ModelContextProtocol.Tests/PlatformDetection.cs
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@ -1,6 +1,9 @@
using System.Runtime.InteropServices;
namespace ModelContextProtocol.Tests;
internal static class PlatformDetection
{
public static bool IsMonoRuntime { get; } = Type.GetType("Mono.Runtime") is not null;
public static bool IsWindows { get; } = RuntimeInformation.IsOSPlatform(OSPlatform.Windows);
}

98
tests/ModelContextProtocol.Tests/Transport/StdioClientTransportTests.cs
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@ -1,4 +1,5 @@
using ModelContextProtocol.Client;
using ModelContextProtocol.Protocol;
using ModelContextProtocol.Tests.Utils;
using System.Runtime.InteropServices;
using System.Text;
@ -15,17 +16,14 @@ public class StdioClientTransportTests(ITestOutputHelper testOutputHelper) : Log
string id = Guid.NewGuid().ToString("N");
StdioClientTransport transport = RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ?
new(new() { Command = "cmd", Arguments = ["/C", $"echo \"{id}\" >&2"] }, LoggerFactory) :
new(new() { Command = "ls", Arguments = [id] }, LoggerFactory);
new(new() { Command = "cmd", Arguments = ["/c", $"echo {id} >&2 & exit /b 1"] }, LoggerFactory) :
new(new() { Command = "sh", Arguments = ["-c", $"echo {id} >&2; exit 1"] }, LoggerFactory);
IOException e = await Assert.ThrowsAsync<IOException>(() => McpClient.CreateAsync(transport, loggerFactory: LoggerFactory, cancellationToken: TestContext.Current.CancellationToken));
if (!RuntimeInformation.IsOSPlatform(OSPlatform.OSX))
{
Assert.Contains(id, e.ToString());
}
await Assert.ThrowsAsync<IOException>(() => McpClient.CreateAsync(transport, loggerFactory: LoggerFactory, cancellationToken: TestContext.Current.CancellationToken));
}
[Fact(Skip = "Platform not supported by this test.", SkipUnless = nameof(IsStdErrCallbackSupported))]
// [Fact(Skip = "Platform not supported by this test.", SkipUnless = nameof(IsStdErrCallbackSupported))]
[Fact]
public async Task CreateAsync_ValidProcessInvalidServer_StdErrCallbackInvoked()
{
string id = Guid.NewGuid().ToString("N");
@ -43,12 +41,92 @@ public class StdioClientTransportTests(ITestOutputHelper testOutputHelper) : Log
};
StdioClientTransport transport = RuntimeInformation.IsOSPlatform(OSPlatform.Windows) ?
new(new() { Command = "cmd", Arguments = ["/C", $"echo \"{id}\" >&2"], StandardErrorLines = stdErrCallback }, LoggerFactory) :
new(new() { Command = "ls", Arguments = [id], StandardErrorLines = stdErrCallback }, LoggerFactory);
new(new() { Command = "cmd", Arguments = ["/c", $"echo {id} >&2 & exit /b 1"], StandardErrorLines = stdErrCallback }, LoggerFactory) :
new(new() { Command = "sh", Arguments = ["-c", $"echo {id} >&2; exit 1"], StandardErrorLines = stdErrCallback }, LoggerFactory);
await Assert.ThrowsAsync<IOException>(() => McpClient.CreateAsync(transport, loggerFactory: LoggerFactory, cancellationToken: TestContext.Current.CancellationToken));
Assert.InRange(count, 1, int.MaxValue);
Assert.Contains(id, sb.ToString());
}
[Theory]
[InlineData(null)]
[InlineData("argument with spaces")]
[InlineData("&")]
[InlineData("|")]
[InlineData(">")]
[InlineData("<")]
[InlineData("^")]
[InlineData(" & ")]
[InlineData(" | ")]
[InlineData(" > ")]
[InlineData(" < ")]
[InlineData(" ^ ")]
[InlineData("& ")]
[InlineData("| ")]
[InlineData("> ")]
[InlineData("< ")]
[InlineData("^ ")]
[InlineData(" &")]
[InlineData(" |")]
[InlineData(" >")]
[InlineData(" <")]
[InlineData(" ^")]
[InlineData("^&<>|")]
[InlineData("^&<>| ")]
[InlineData(" ^&<>|")]
[InlineData("\t^&<>")]
[InlineData("^&\t<>")]
[InlineData("ls /tmp | grep foo.txt > /dev/null")]
[InlineData("let rec Y f x = f (Y f) x")]
[InlineData("value with \"quotes\" and spaces")]
[InlineData("C:\\Program Files\\Test App\\app.dll")]
[InlineData("C:\\EndsWithBackslash\\")]
[InlineData("--already-looks-like-flag")]
[InlineData("-starts-with-dash")]
[InlineData("name=value=another")]
[InlineData("$(echo injected)")]
[InlineData("value-with-\"quotes\"-and-\\backslashes\\")]
[InlineData("http://localhost:1234/callback?foo=1&bar=2")]
public async Task EscapesCliArgumentsCorrectly(string? cliArgumentValue)
{
if (PlatformDetection.IsMonoRuntime && cliArgumentValue?.EndsWith("\\") is true)
{
Assert.Skip("mono runtime does not handle arguments ending with backslash correctly.");
}
string cliArgument = $"--cli-arg={cliArgumentValue}";
StdioClientTransportOptions options = new()
{
Name = "TestServer",
Command = (PlatformDetection.IsMonoRuntime, PlatformDetection.IsWindows) switch
{
(true, _) => "mono",
(_, true) => "TestServer.exe",
_ => "dotnet",
},
Arguments = (PlatformDetection.IsMonoRuntime, PlatformDetection.IsWindows) switch
{
(true, _) => ["TestServer.exe", cliArgument],
(_, true) => [cliArgument],
_ => ["TestServer.dll", cliArgument],
},
};
var transport = new StdioClientTransport(options, LoggerFactory);
// Act: Create client (handshake) and list tools to ensure full round trip works with the argument present.
await using var client = await McpClient.CreateAsync(transport, loggerFactory: LoggerFactory, cancellationToken: TestContext.Current.CancellationToken);
var tools = await client.ListToolsAsync(cancellationToken: TestContext.Current.CancellationToken);
// Assert
Assert.NotNull(tools);
Assert.NotEmpty(tools);
var result = await client.CallToolAsync("echoCliArg", cancellationToken: TestContext.Current.CancellationToken);
var content = Assert.IsType<TextContentBlock>(Assert.Single(result.Content));
Assert.Equal(cliArgumentValue ?? "", content.Text);
}
}