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Define "MCP Sandbox Interface" and implement limactl mcp serve
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,83 @@ | ||
| // SPDX-FileCopyrightText: Copyright The Lima Authors | ||
| // SPDX-License-Identifier: Apache-2.0 | ||
|
|
||
| package main | ||
|
|
||
| import ( | ||
| "fmt" | ||
| "runtime" | ||
| "strings" | ||
|
|
||
| "github.com/modelcontextprotocol/go-sdk/mcp" | ||
| "github.com/spf13/cobra" | ||
|
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| "github.com/lima-vm/lima/v2/pkg/mcp/toolset" | ||
| "github.com/lima-vm/lima/v2/pkg/store" | ||
| "github.com/lima-vm/lima/v2/pkg/version" | ||
| ) | ||
|
|
||
| func newMcpCommand() *cobra.Command { | ||
| cmd := &cobra.Command{ | ||
| Use: "mcp", | ||
| Short: "Model Context Protocol", | ||
| GroupID: advancedCommand, | ||
| } | ||
| cmd.AddCommand( | ||
| newMcpServeCommand(), | ||
| // TODO: `limactl mcp install-gemini` ? | ||
| ) | ||
| return cmd | ||
| } | ||
|
|
||
| func newMcpServeCommand() *cobra.Command { | ||
| cmd := &cobra.Command{ | ||
| Use: "serve INSTANCE", | ||
| Short: "Serve MCP over stdio", | ||
| Long: `Serve MCP over stdio. | ||
|
|
||
| Expected to be executed via an AI agent, not by a human`, | ||
| Args: WrapArgsError(cobra.MaximumNArgs(1)), | ||
| RunE: mcpServeAction, | ||
| } | ||
| return cmd | ||
| } | ||
|
|
||
| func mcpServeAction(cmd *cobra.Command, args []string) error { | ||
| ctx := cmd.Context() | ||
| instName := DefaultInstanceName | ||
| if len(args) > 0 { | ||
| instName = args[0] | ||
| } | ||
| inst, err := store.Inspect(instName) | ||
| if err != nil { | ||
| return err | ||
| } | ||
| ts, err := toolset.New(inst) | ||
| if err != nil { | ||
| return err | ||
| } | ||
| impl := &mcp.Implementation{ | ||
| Name: "lima", | ||
| Title: "Lima VM, for sandboxing local command executions and file I/O operations", | ||
| Version: version.Version, | ||
| } | ||
| serverOpts := &mcp.ServerOptions{ | ||
| Instructions: `This MCP server provides tools for sandboxing local command executions and file I/O operations, | ||
| by wrapping them in Lima VM (https://lima-vm.io). | ||
|
|
||
| Use these tools to avoid accidentally executing malicious codes directly on the host. | ||
| `, | ||
| } | ||
| if runtime.GOOS != "linux" { | ||
| serverOpts.Instructions += fmt.Sprintf(` | ||
|
|
||
| NOTE: the guest OS of the VM is Linux, while the host OS is %s. | ||
| `, strings.ToTitle(runtime.GOOS)) | ||
| } | ||
| server := mcp.NewServer(impl, serverOpts) | ||
| if err = ts.RegisterServer(server); err != nil { | ||
| return err | ||
| } | ||
| transport := mcp.NewStdioTransport() | ||
| return server.Run(ctx, transport) | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,49 @@ | ||
| // SPDX-FileCopyrightText: Copyright The Lima Authors | ||
| // SPDX-License-Identifier: Apache-2.0 | ||
|
|
||
| // Portion of AI prompt texts from: | ||
| // - https://github.com/google-gemini/gemini-cli/blob/v0.1.12/docs/tools/file-system.md | ||
| // | ||
| // SPDX-FileCopyrightText: Copyright 2025 Google LLC | ||
|
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| package msi | ||
|
|
||
| import ( | ||
| "io/fs" | ||
| "time" | ||
|
|
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| "github.com/modelcontextprotocol/go-sdk/mcp" | ||
| ) | ||
|
|
||
| var ListDirectory = &mcp.Tool{ | ||
| Name: "list_directory", | ||
| Description: `Lists the names of files and subdirectories directly within a specified directory path.`, | ||
| } | ||
|
|
||
| type ListDirectoryParams struct { | ||
| Path string `json:"path" jsonschema:"The absolute path to the directory to list."` | ||
| } | ||
|
|
||
| // ListDirectoryResultEntry is similar to [io/fs.FileInfo]. | ||
| type ListDirectoryResultEntry struct { | ||
| Name string `json:"name" jsonschema:"base name of the file"` | ||
| Size *int64 `json:"size,omitempty" jsonschema:"length in bytes for regular files; system-dependent for others"` | ||
| Mode *fs.FileMode `json:"mode,omitempty" jsonschema:"file mode bits"` | ||
| ModTime *time.Time `json:"time,omitempty" jsonschema:"modification time"` | ||
| IsDir *bool `json:"is_dir,omitempty" jsonschema:"true for a directory"` | ||
| } | ||
|
|
||
| type ListDirectoryResult struct { | ||
| Entries []ListDirectoryResultEntry `json:"entries" jsonschema:"The directory content entries."` | ||
| } | ||
|
|
||
| var ReadFile = &mcp.Tool{ | ||
| Name: "read_file", | ||
| Description: `Reads and returns the content of a specified file.`, | ||
| } | ||
|
|
||
| type ReadFileParams struct { | ||
| Path string `json:"path" jsonschema:"The absolute path to the file to read."` | ||
| // Offset *int `json:"offset,omitempty" jsonschema:"For text files, the 0-based line number to start reading from. Requires limit to be set."` | ||
| // Limit *int `json:"limit,omitempty" jsonschema:"For text files, the maximum number of lines to read. If omitted, reads a default maximum (e.g., 2000 lines) or the entire file if feasible."` | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,23 @@ | ||
| // SPDX-FileCopyrightText: Copyright The Lima Authors | ||
| // SPDX-License-Identifier: Apache-2.0 | ||
|
|
||
| // Package msi provides the "MCP Sandbox Interface" (tentative) | ||
| // that should be reusable for other projects too. | ||
| // | ||
| // MCP Sandbox Interface defines MCP (Model Context Protocol) tools | ||
| // that can be used for reading, writing, and executing local files | ||
| // with an appropriate sandboxing technology. The sandboxing technology | ||
| // can be more secure and/or efficient than the default tools provided | ||
| // by an AI agent. | ||
| // | ||
| // MCP Sandbox Interface was inspired by Gemini CLI's built-in tools. | ||
| // https://github.com/google-gemini/gemini-cli/tree/v0.1.12/docs/tools | ||
| // | ||
| // Notable differences from Gemini CLI's built-in tools: | ||
| // - the output format is JSON, not a plain text | ||
| // - [RunShellCommandParams].Command is a string slice, not a string | ||
| // - [RunShellCommandParams].Directory is a absolute path, not a relative path | ||
| // - [RunShellCommandParams].Directory must not be empty | ||
| // | ||
| // Eventually, this package may be split to a separate repository. | ||
| package msi | ||
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,29 @@ | ||
| // SPDX-FileCopyrightText: Copyright The Lima Authors | ||
| // SPDX-License-Identifier: Apache-2.0 | ||
|
|
||
| // Portion of AI prompt texts from: | ||
| // - https://github.com/google-gemini/gemini-cli/blob/v0.1.12/docs/tools/shell.md | ||
| // | ||
| // SPDX-FileCopyrightText: Copyright 2025 Google LLC | ||
|
|
||
| package msi | ||
|
|
||
| import "github.com/modelcontextprotocol/go-sdk/mcp" | ||
|
|
||
| var RunShellCommand = &mcp.Tool{ | ||
| Name: "run_shell_command", | ||
| Description: `Executes a given shell command.`, | ||
| } | ||
|
|
||
| type RunShellCommandParams struct { | ||
| Command []string `json:"command" jsonschema:"The exact shell command to execute. Defined as a string slice, unlike Gemini's run_shell_command that defines it as a single string."` | ||
| Description string `json:"description,omitempty" jsonschema:"A brief description of the command's purpose, which will be potentially shown to the user."` | ||
| Directory string `json:"directory" jsonschema:"The absolute directory in which to execute the command. Unlike Gemini's run_shell_command, this must not be a relative path, and must not be empty."` | ||
| } | ||
|
|
||
| type RunShellCommandResult struct { | ||
| Stdout string `json:"stdout" jsonschema:"Output from the standard output stream."` | ||
| Stderr string `json:"stderr" jsonschema:"Output from the standard error stream."` | ||
| Error string `json:"error,omitempty" jsonschema:"Any error message reported by the subprocess."` | ||
| ExitCode *int `json:"exit_code,omitempty" jsonschema:"Exit code of the command."` | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,70 @@ | ||
| // SPDX-FileCopyrightText: Copyright The Lima Authors | ||
| // SPDX-License-Identifier: Apache-2.0 | ||
|
|
||
| package toolset | ||
|
|
||
| import ( | ||
| "context" | ||
| "encoding/json" | ||
| "io" | ||
|
|
||
| "github.com/modelcontextprotocol/go-sdk/mcp" | ||
|
|
||
| "github.com/lima-vm/lima/v2/pkg/mcp/msi" | ||
| "github.com/lima-vm/lima/v2/pkg/ptr" | ||
| ) | ||
|
|
||
| func (ts *ToolSet) ListDirectory(ctx context.Context, _ *mcp.ServerSession, | ||
| params *mcp.CallToolParamsFor[msi.ListDirectoryParams], | ||
| ) (*mcp.CallToolResultFor[msi.ListDirectoryResult], error) { | ||
| args := params.Arguments | ||
| guestPath, err := ts.TranslateHostPath(args.Path) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
| guestEnts, err := ts.sftp.ReadDirContext(ctx, guestPath) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
| res := msi.ListDirectoryResult{ | ||
| Entries: make([]msi.ListDirectoryResultEntry, len(guestEnts)), | ||
| } | ||
| for i, f := range guestEnts { | ||
| res.Entries[i].Name = f.Name() | ||
| res.Entries[i].Size = ptr.Of(f.Size()) | ||
| res.Entries[i].Mode = ptr.Of(f.Mode()) | ||
| res.Entries[i].ModTime = ptr.Of(f.ModTime()) | ||
| res.Entries[i].IsDir = ptr.Of(f.IsDir()) | ||
| } | ||
| resJ, err := json.Marshal(res) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
| return &mcp.CallToolResultFor[msi.ListDirectoryResult]{ | ||
| Content: []mcp.Content{&mcp.TextContent{Text: string(resJ)}}, | ||
| }, nil | ||
| } | ||
|
|
||
| func (ts *ToolSet) ReadFile(_ context.Context, _ *mcp.ServerSession, | ||
| params *mcp.CallToolParamsFor[msi.ReadFileParams], | ||
| ) (*mcp.CallToolResultFor[any], error) { | ||
| args := params.Arguments | ||
| guestPath, err := ts.TranslateHostPath(args.Path) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
| f, err := ts.sftp.Open(guestPath) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
| defer f.Close() | ||
| const limitBytes = 32 * 1024 * 1024 | ||
| lr := io.LimitReader(f, limitBytes) | ||
| b, err := io.ReadAll(lr) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
| return &mcp.CallToolResultFor[any]{ | ||
| Content: []mcp.Content{&mcp.TextContent{Text: string(b)}}, | ||
| }, nil | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,52 @@ | ||
| // SPDX-FileCopyrightText: Copyright The Lima Authors | ||
| // SPDX-License-Identifier: Apache-2.0 | ||
|
|
||
| package toolset | ||
|
|
||
| import ( | ||
| "bytes" | ||
| "context" | ||
| "encoding/json" | ||
| "os/exec" | ||
|
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| "github.com/modelcontextprotocol/go-sdk/mcp" | ||
|
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| "github.com/lima-vm/lima/v2/pkg/mcp/msi" | ||
| "github.com/lima-vm/lima/v2/pkg/ptr" | ||
| ) | ||
|
|
||
| func (ts *ToolSet) RunShellCommand(ctx context.Context, _ *mcp.ServerSession, | ||
| params *mcp.CallToolParamsFor[msi.RunShellCommandParams], | ||
| ) (*mcp.CallToolResultFor[msi.RunShellCommandResult], error) { | ||
| args := params.Arguments | ||
| guestPath, err := ts.TranslateHostPath(args.Directory) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
| cmd := exec.CommandContext(ctx, ts.limactl, | ||
| append([]string{"shell", "--workdir=" + guestPath, ts.inst.Name}, | ||
| args.Command...)...) | ||
| var stdout, stderr bytes.Buffer | ||
| cmd.Stdout = &stdout | ||
| cmd.Stderr = &stderr | ||
| cmdErr := cmd.Run() | ||
| res := msi.RunShellCommandResult{ | ||
| Stdout: stdout.String(), | ||
| Stderr: stderr.String(), | ||
| } | ||
| if cmdErr == nil { | ||
| res.ExitCode = ptr.Of(0) | ||
| } else { | ||
| res.Error = cmdErr.Error() | ||
| if st := cmd.ProcessState; st != nil { | ||
| res.ExitCode = ptr.Of(st.ExitCode()) | ||
| } | ||
| } | ||
| resJ, err := json.Marshal(res) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
| return &mcp.CallToolResultFor[msi.RunShellCommandResult]{ | ||
| Content: []mcp.Content{&mcp.TextContent{Text: string(resJ)}}, | ||
| }, nil | ||
| } |
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RFC: "MCP Sandbox Interface" might be a misnomer; it might rather sound like an interface for sandboxing MCP servers, e.g.,
docker run -i --rm example.com/some-mcp-server /usr/bin/some-mcp-serverhttps://github.com/google-gemini/gemini-cli/blob/main/docs/tools/mcp-server.md#docker-based-mcp-server
Alternative names:
Thoughts?