🛡️ Sentinel: [HIGH] Fix SSRF vulnerability in plugin downloader

.jules/sentinel.md

@@ -16,3 +16,8 @@
 **Vulnerability:** Writing fully buffered in-memory data to temporary disk files solely for parsing.
 **Learning:** This increases attack surface, risks disk exhaustion, and violates the principle of least privilege.
 **Prevention:** Refactor parsing functions to accept byte slices or `io.Reader` directly to process data in memory.
+
+## 2024-08-03 - Prevent SSRF with net.Dialer Control Hook
+**Vulnerability:** Relying on `net/url.Parse` to validate URL schemes doesn't fully protect against SSRF (e.g. against cloud metadata services) and custom transports can break 'Happy Eyeballs'.
+**Learning:** Using a `net.Dialer` with a `Control` hook allows inspecting the resolved IP *before* the socket connects, providing a robust way to block targeted IPs (like `169.254.169.254`) without breaking legitimate local use cases.
+**Prevention:** Clone `http.DefaultTransport` and configure its `DialContext` to use a dialer with a Control hook that validates the resolved IP. Block specific cloud metadata endpoints instead of all private IPs.

internal/plugin/manager.go

@@ -7,6 +7,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"io"
+	"net"
 	"net/http"
 	"net/url"
 	"os"
@@ -16,6 +17,7 @@ import (
 	"runtime"
 	"sort"
 	"strings"
+	"syscall"
 	"time"
 
 	"github.com/himattm/prism/internal/fsutil"
@@ -410,7 +412,7 @@ func (m *Manager) addScriptPlugin(owner, repo, pluginName string) error {
 
 	fmt.Printf("Fetching script from: %s\n", rawURL)
 
-	resp, err := http.Get(rawURL)
+	resp, err := secureGet(rawURL)
 	if err != nil {
 		return fmt.Errorf("failed to fetch plugin: %w", err)
 	}
@@ -468,7 +470,7 @@ func (m *Manager) addFromDirectURL(rawURL string) error {
 		return fmt.Errorf("unsupported URL scheme: %s", parsedURL.Scheme)
 	}
 
-	resp, err := http.Get(parsedURL.String())
+	resp, err := secureGet(parsedURL.String())
 	if err != nil {
 		return fmt.Errorf("failed to fetch plugin: %w", err)
 	}
@@ -860,3 +862,33 @@ func CompareVersions(a, b string) int {
 
 	return 0
 }
+
+func secureGet(urlStr string) (*http.Response, error) {
+	dialer := &net.Dialer{
+		Timeout:   30 * time.Second,
+		KeepAlive: 30 * time.Second,
+		Control: func(network, address string, c syscall.RawConn) error {
+			host, _, err := net.SplitHostPort(address)
+			if err != nil {
+				return err
+			}
+			if idx := strings.IndexByte(host, '%'); idx != -1 {
+				host = host[:idx]
+			}
+			ip := net.ParseIP(host)
+			if ip != nil && ip.Equal(net.ParseIP("169.254.169.254")) {
+				return fmt.Errorf("blocked request to cloud metadata IP")
+			}
+			return nil
+		},
+	}
+	transport := http.DefaultTransport.(*http.Transport).Clone()
+	transport.DialContext = dialer.DialContext
+	transport.DisableKeepAlives = true
+
+	client := &http.Client{
+		Timeout:   10 * time.Second,
+		Transport: transport,
+	}
+	return client.Get(urlStr)
+}