Port thvignore.md (#21)

Author: blkt

rfcs/THV-0021-thvignore.md

@@ -0,0 +1,350 @@
+# **🧱 Technical Design Proposal: `.thvignore`\-Driven Bind Mount Filtering in ToolHive**
+
+> [!NOTE]
+> This was originally [thvignore.md](https://github.com/stacklok/toolhive/blob/f8a7841687a75e08a01d3b1d807ce53b44761e31/docs/proposals/thvignore.md).
+
+---
+
+## **🎯 Goals**
+
+| Objective | Solution |
+| ----- | ----- |
+| Exclude secrets (e.g., `.ssh`, `.env`) from containers while using bind mounts | Use `.thvignore` to drive tmpfs overlays |
+| Maintain real-time access to files like SQLite DBs | Bind mount full directory |
+| Support both global ignore patterns (e.g., user-wide) and per-project rules | Combine global and local `.thvignore` |
+| Provide a consistent, secure experience across all runtimes | Abstract runtime-specific mount behavior in ToolHive's execution layer |
+
+---
+
+## **🗂 Config File Design**
+
+### **🧭 Per-folder config: `.thvignore`**
+
+Lives **next to the files being mounted**.
+
+```shell
+my-folder/
+├── database.db
+├── .ssh/
+└── .thvignore
+```
+
+`.thvignore`:
+
+```
+.ssh/
+*.bak
+.env
+```
+
+### **🌍 Global config: `~/.config/toolhive/thvignore`**
+
+Example:
+
+```
+node_modules/
+.DS_Store
+.idea/
+```
+
+These patterns apply to **all** mounts unless explicitly disabled.
+
+---
+
+## **🧠 Behavior Overview**
+
+### **✅ At runtime:**
+
+1. User runs:
+
+```shell
+thv run --volume ./my-folder:/app server-name
+```
+
+2.
+   ToolHive does the following:
+
+   * Load global ignore file from `~/.config/toolhive/thvignore`
+
+   * Load `./my-folder/.thvignore` (if present)
+
+   * Combine and normalize both sets of patterns
+
+   * For each pattern:
+
+     * Determine full container path (e.g. `/app/.ssh`)
+
+     * Add a `tmpfs` mount over it to the runtime configuration
+
+---
+
+## **🧱 Component Design**
+
+### **🔹 `IgnoreProcessor` (new module in `pkg/ignore/`)**
+
+```go
+package ignore
+
+type IgnoreProcessor struct {
+    GlobalPatterns []string
+    LocalPatterns  []string
+}
+
+func NewIgnoreProcessor() *IgnoreProcessor
+func (ip *IgnoreProcessor) LoadGlobal() error
+func (ip *IgnoreProcessor) LoadLocal(sourceDir string) error
+func (ip *IgnoreProcessor) GetOverlayPaths(bindMount, containerPath string) []string
+func (ip *IgnoreProcessor) ShouldIgnore(path string) bool
+```
+
+*
+  Reads `.gitignore`\-style files using existing Go libraries
+
+* Integrates with ToolHive's existing mount processing pipeline
+
+* Converts ignore patterns into **container absolute paths** (e.g. `/app/.ssh`)
+
+---
+
+### **🔹 Enhanced `runtime.Mount` (in `pkg/container/runtime/types.go`)**
+
+Extend the existing Mount struct to support tmpfs:
+
+```go
+type Mount struct {
+    Source   string
+    Target   string
+    ReadOnly bool
+    Type     string // NEW: "bind" or "tmpfs"
+}
+```
+
+Integration with existing mount processing in `pkg/runner/config_builder.go`:
+
+```go
+func (b *RunConfigBuilder) processVolumeMounts() error {
+    // Existing mount processing...
+    
+    // NEW: Process ignore patterns
+    ignoreProcessor := ignore.NewIgnoreProcessor()
+    ignoreProcessor.LoadGlobal()
+    ignoreProcessor.LoadLocal(sourceDir)
+    
+    overlayPaths := ignoreProcessor.GetOverlayPaths(source, target)
+    for _, overlayPath := range overlayPaths {
+        b.addTmpfsOverlay(overlayPath)
+    }
+}
+```
+
+---
+
+## **🧪 Runtime Support**
+
+Enhanced `convertMounts` function in `pkg/container/docker/client.go`:
+
+```go
+func convertMounts(mounts []runtime.Mount) []mount.Mount {
+    result := make([]mount.Mount, 0, len(mounts))
+    for _, m := range mounts {
+        if m.Type == "tmpfs" {
+            result = append(result, mount.Mount{
+                Type:   mount.TypeTmpfs,
+                Target: m.Target,
+                TmpfsOptions: &mount.TmpfsOptions{
+                    SizeBytes: 1024 * 1024, // 1MB tmpfs for security overlays
+                },
+            })
+        } else {
+            result = append(result, mount.Mount{
+                Type:     mount.TypeBind,
+                Source:   m.Source,
+                Target:   m.Target,
+                ReadOnly: m.ReadOnly,
+            })
+        }
+    }
+    return result
+}
+```
+
+| Runtime | Bind Mount | Tmpfs Overlay |
+| ----- | ----- | ----- |
+| Docker | ✅ `mount.TypeBind` | ✅ `mount.TypeTmpfs` |
+| Podman | ✅ `--mount type=bind` | ✅ `--mount type=tmpfs` |
+| Colima | ✅ `mount.TypeBind` | ✅ `mount.TypeTmpfs` |
+
+---
+
+## **🧰 CLI Integration**
+
+Extend existing `thv run` command flags:
+
+```go
+// In cmd/thv/app/run.go
+var (
+    runIgnoreGlobally     bool
+    runPrintOverlays      bool
+    runIgnoreFile         string
+)
+
+func init() {
+    runCmd.Flags().BoolVar(&runIgnoreGlobally, "ignore-globally", true,
+        "Load global ignore patterns from ~/.config/toolhive/thvignore")
+    runCmd.Flags().BoolVar(&runPrintOverlays, "print-resolved-overlays", false,
+        "Debug: show resolved container paths for tmpfs overlays")
+    runCmd.Flags().StringVar(&runIgnoreFile, "ignore-file", ".thvignore",
+        "Name of the ignore file to look for in source directories")
+}
+```
+
+---
+
+## **🔐 Security Considerations**
+
+* Warn users if sensitive-looking files (`.ssh`, `.env`) are present but not excluded
+
+* Validate ignore patterns to prevent overly broad exclusions
+
+* Integrate with existing permission profile system for defense-in-depth
+
+* Log overlay mount creation for audit purposes
+
+---
+
+## **🎯 Use Cases**
+
+### **🔑 Cloud Provider Credentials**
+
+**Scenario**: Developer working on a project with AWS/GCP credentials that should never be accessible to MCP servers.
+
+```shell
+my-project/
+├── src/
+├── .aws/credentials
+├── .gcp/service-account.json
+├── .env.production
+└── .thvignore
+```
+
+**`.thvignore`**:
+```
+.aws/
+.gcp/
+*.pem
+.env.production
+```
+
+**Result**: MCP server analyzes code in `src/` but cloud credentials are hidden via tmpfs overlays.
+
+---
+
+### **🏢 SSH Keys and Development Secrets**
+
+**Scenario**: Developer's home directory mounted for MCP server to access project files while protecting personal credentials.
+
+```shell
+~/dev-project/
+├── code/
+├── .ssh/id_rsa
+├── .gnupg/
+├── .docker/config.json
+└── .thvignore
+```
+
+**`.thvignore`**:
+```
+.ssh/
+.gnupg/
+.docker/config.json
+.kube/config
+```
+
+**Result**: MCP server can access project code but personal authentication credentials remain protected.
+
+---
+
+### **🤖 AI/ML Model Protection**
+
+**Scenario**: Data scientist using MCP servers for code analysis while protecting sensitive datasets and production models.
+
+```shell
+ml-project/
+├── notebooks/
+├── src/
+├── data/customer-data.csv
+├── models/production-model.pkl
+└── .thvignore
+```
+
+**`.thvignore`**:
+```
+data/*.csv
+models/production-*
+*.pkl
+.kaggle/
+```
+
+**Result**: MCP server can analyze notebooks and source code but cannot access sensitive data or production models.
+
+---
+
+## **📄 Example: Final Runtime Command**
+
+If user runs:
+
+```shell
+thv run --volume ./my-folder:/app server-name
+```
+
+And:
+
+```shell
+# ~/.config/toolhive/thvignore
+node_modules/
+
+# ./my-folder/.thvignore
+.ssh/
+.env
+```
+
+ToolHive generates runtime configuration with:
+
+```go
+// Main bind mount
+runtime.Mount{
+    Source: "/absolute/path/my-folder",
+    Target: "/app",
+    Type: "bind",
+    ReadOnly: false,
+}
+
+// Tmpfs overlays
+runtime.Mount{Target: "/app/.ssh", Type: "tmpfs"}
+runtime.Mount{Target: "/app/.env", Type: "tmpfs"}
+runtime.Mount{Target: "/app/node_modules", Type: "tmpfs"}
+```
+
+Which converts to Docker commands:
+
+```shell
+docker run \
+  -v /absolute/path/my-folder:/app \
+  --tmpfs /app/.ssh:rw,nosuid,nodev,noexec \
+  --tmpfs /app/.env:rw,nosuid,nodev,noexec \
+  --tmpfs /app/node_modules:rw,nosuid,nodev,noexec \
+  my-image
+```
+
+---
+
+## **✅ Summary**
+
+| Feature | Outcome |
+| ----- | ----- |
+| Real-time file access | ✅ via full bind mount |
+| Hidden files (e.g. `.ssh`, `.env`) | ✅ overlaid with tmpfs |
+| Config flexibility | ✅ per-folder \+ global `.thvignore` |
+| Runtime compatibility | ✅ Docker, Podman, Colima |
+| Integration | ✅ Works with existing permission profiles |
+