fix: allow calling internal IP ranges with relevant option

The `ResilientClient` options `ResilientClientDisallowInternalIPs`
and `ResilientClientAllowInternalIPRequestsTo` were not allowing to call
certain IP ranges, like 100.64.0.0/10 properly.

httpx/resilient_client_test.go

@@ -13,6 +13,7 @@ import (
 	"net/url"
 	"sync/atomic"
 	"testing"
+	"time"
 
 	"github.com/hashicorp/go-retryablehttp"
 	"github.com/stretchr/testify/assert"
@@ -33,11 +34,13 @@ func TestNoPrivateIPs(t *testing.T) {
 
 	allowedURL := "http://localhost:" + port + "/foobar"
 	allowedGlob := "http://localhost:" + port + "/glob/*"
+	allowedPrivateIP := "http://100.64.1.1:80" + "/private"
 
 	c := NewResilientClient(
-		ResilientClientWithMaxRetry(1),
+		ResilientClientWithMaxRetry(0),
+		ResilientClientWithConnectionTimeout(10*time.Millisecond),
 		ResilientClientDisallowInternalIPs(),
-		ResilientClientAllowInternalIPRequestsTo(allowedURL, allowedGlob),
+		ResilientClientAllowInternalIPRequestsTo(allowedURL, allowedGlob, allowedPrivateIP),
 	)
 
 	for i := 0; i < 10; i++ {
@@ -49,13 +52,51 @@ func TestNoPrivateIPs(t *testing.T) {
 			"http://localhost:" + port + "/glob/bar":     true,
 			"http://localhost:" + port + "/glob/bar/baz": false,
 			"http://localhost:" + port + "/FOOBAR":       false,
+			allowedPrivateIP:                             true,
+			"http://100.64.8.8:" + port + "/route":       false,
 		} {
 			_, err := c.Get(destination)
 			if !passes {
 				require.Errorf(t, err, "dest = %s", destination)
 				assert.Containsf(t, err.Error(), "is not a permitted destination", "dest = %s", destination)
+			} else if err != nil {
+				assert.NotContainsf(t, err.Error(), "is not a permitted destination", "dest = %s", destination)
+			}
+		}
+	}
+}
+
+func TestAllowPrivateIPs(t *testing.T) {
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+		_, _ = w.Write([]byte("Hello, world!"))
+	}))
+	t.Cleanup(ts.Close)
+
+	target, err := url.ParseRequestURI(ts.URL)
+	require.NoError(t, err)
+
+	_, port, err := net.SplitHostPort(target.Host)
+	require.NoError(t, err)
+
+	c := NewResilientClient(
+		ResilientClientWithMaxRetry(0),
+		ResilientClientWithConnectionTimeout(10*time.Millisecond),
+	)
+
+	for i := 0; i < 10; i++ {
+		for destination, handled := range map[string]bool{
+			"http://127.0.0.1:" + port:               true,
+			"http://localhost:" + port:               true,
+			"http://192.168.178.5:" + port:           false,
+			"http://localhost:" + port + "/glob/bar": true,
+			"http://100.64.1.1:" + port + "/route":   false,
+		} {
+			_, err = c.Get(destination)
+			if handled {
+				require.NoError(t, err)
 			} else {
-				require.NoErrorf(t, err, "dest = %s", destination)
+				require.Error(t, err)
+				assert.NotContainsf(t, err.Error(), "is not a permitted destination", "dest = %s", destination)
 			}
 		}
 	}

httpx/ssrf.go

@@ -8,7 +8,6 @@ import (
 	"net"
 	"net/http"
 	"net/http/httptrace"
-	"net/netip"
 	"time"
 
 	"code.dny.dev/ssrf"
@@ -88,15 +87,10 @@ func init() {
 		ssrf.WithAnyPort(),
 		ssrf.WithNetworks("tcp4", "tcp6"),
 		ssrf.WithAllowedV4Prefixes(
-			netip.MustParsePrefix("10.0.0.0/8"),     // Private-Use (RFC 1918)
-			netip.MustParsePrefix("127.0.0.0/8"),    // Loopback (RFC 1122, Section 3.2.1.3))
-			netip.MustParsePrefix("169.254.0.0/16"), // Link Local (RFC 3927)
-			netip.MustParsePrefix("172.16.0.0/12"),  // Private-Use (RFC 1918)
-			netip.MustParsePrefix("192.168.0.0/16"), // Private-Use (RFC 1918)
+			ssrf.IPv4DeniedPrefixes...,
 		),
 		ssrf.WithAllowedV6Prefixes(
-			netip.MustParsePrefix("::1/128"),  // Loopback (RFC 4193)
-			netip.MustParsePrefix("fc00::/7"), // Unique Local (RFC 4193)
+			ssrf.IPv6DeniedPrefixes...,
 		),
 	).Safe
 	allowInternalAllowIPv6 = otelTransport(t)
@@ -108,15 +102,10 @@ func init() {
 		ssrf.WithAnyPort(),
 		ssrf.WithNetworks("tcp4"),
 		ssrf.WithAllowedV4Prefixes(
-			netip.MustParsePrefix("10.0.0.0/8"),     // Private-Use (RFC 1918)
-			netip.MustParsePrefix("127.0.0.0/8"),    // Loopback (RFC 1122, Section 3.2.1.3))
-			netip.MustParsePrefix("169.254.0.0/16"), // Link Local (RFC 3927)
-			netip.MustParsePrefix("172.16.0.0/12"),  // Private-Use (RFC 1918)
-			netip.MustParsePrefix("192.168.0.0/16"), // Private-Use (RFC 1918)
+			ssrf.IPv4DeniedPrefixes...,
 		),
 		ssrf.WithAllowedV6Prefixes(
-			netip.MustParsePrefix("::1/128"),  // Loopback (RFC 4193)
-			netip.MustParsePrefix("fc00::/7"), // Unique Local (RFC 4193)
+			ssrf.IPv6DeniedPrefixes...,
 		),
 	).Safe
 	t.DialContext = func(ctx context.Context, network, addr string) (net.Conn, error) {