From 5819a6c4552b1c3c37f48405ad1dc7d7b4681a8c Mon Sep 17 00:00:00 2001
From: Ajay Kelkar <ajaykelkar@outlook.com>
Date: Thu, 8 Sep 2022 10:41:17 +0200
Subject: [PATCH] feat: helper to extract ip address that isn't on an exclusion
 list (#593)

---
 httpx/client_info.go          | 34 ++++++++++++++++++++++++++++++++++
 httpx/client_info_test.go     | 22 ++++++++++++++++++++++
 httpx/private_ip_validator.go | 20 +++++++++++---------
 stringsx/ptr.go               |  5 +++++
 stringsx/ptr_test.go          | 11 +++++++++++
 5 files changed, 83 insertions(+), 9 deletions(-)
 create mode 100644 httpx/client_info.go
 create mode 100644 httpx/client_info_test.go
 create mode 100644 stringsx/ptr.go
 create mode 100644 stringsx/ptr_test.go

diff --git a/httpx/client_info.go b/httpx/client_info.go
new file mode 100644
index 00000000..cde03185
--- /dev/null
+++ b/httpx/client_info.go
@@ -0,0 +1,34 @@
+package httpx
+
+import (
+	"net"
+	"strings"
+)
+
+func GetClientIPAddress(ipAddresses []string, exclude []string) (string, error) {
+	var res string
+
+	for i := len(ipAddresses) - 1; i >= 0; i-- {
+		var isExcluded bool
+		ip := strings.TrimSpace(ipAddresses[i])
+
+		for _, j := range exclude {
+			_, cidr, err := net.ParseCIDR(j)
+			if err != nil {
+				return "", err
+			}
+
+			if cidr.Contains(net.ParseIP(ip)) {
+				isExcluded = true
+				break
+			}
+		}
+
+		if !isExcluded {
+			res = ip
+			break
+		}
+	}
+
+	return res, nil
+}
diff --git a/httpx/client_info_test.go b/httpx/client_info_test.go
new file mode 100644
index 00000000..270257c9
--- /dev/null
+++ b/httpx/client_info_test.go
@@ -0,0 +1,22 @@
+package httpx
+
+import (
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"strings"
+	"testing"
+)
+
+func TestIgnoresInternalIPs(t *testing.T) {
+	input := "54.155.246.232,10.145.1.10"
+
+	res, err := GetClientIPAddress(strings.Split(input, ","), InternalIPSet)
+	require.NoError(t, err)
+	assert.Equal(t, "54.155.246.232", res)
+}
+
+func TestEmptyInputArray(t *testing.T) {
+	res, err := GetClientIPAddress([]string{}, InternalIPSet)
+	require.NoError(t, err)
+	assert.Equal(t, "", res)
+}
diff --git a/httpx/private_ip_validator.go b/httpx/private_ip_validator.go
index 5760694f..914fd143 100644
--- a/httpx/private_ip_validator.go
+++ b/httpx/private_ip_validator.go
@@ -11,6 +11,16 @@ import (
 	"github.com/pkg/errors"
 )
 
+var InternalIPSet = []string{
+	"127.0.0.0/8",
+	"10.0.0.0/8",
+	"172.16.0.0/12",
+	"192.168.0.0/16",
+	"fd47:1ed0:805d:59f0::/64",
+	"fc00::/7",
+	"::1/128",
+}
+
 // ErrPrivateIPAddressDisallowed is returned when a private IP address is disallowed.
 type ErrPrivateIPAddressDisallowed error
 
@@ -64,15 +74,7 @@ func DisallowIPPrivateAddresses(ipOrHostnameOrURL string) error {
 		ips = append(ips, ip)
 	}
 
-	for _, disabled := range []string{
-		"127.0.0.0/8",
-		"10.0.0.0/8",
-		"172.16.0.0/12",
-		"192.168.0.0/16",
-		"fd47:1ed0:805d:59f0::/64",
-		"fc00::/7",
-		"::1/128",
-	} {
+	for _, disabled := range InternalIPSet {
 		_, cidr, err := net.ParseCIDR(disabled)
 		if err != nil {
 			return err
diff --git a/stringsx/ptr.go b/stringsx/ptr.go
new file mode 100644
index 00000000..4e9d464b
--- /dev/null
+++ b/stringsx/ptr.go
@@ -0,0 +1,5 @@
+package stringsx
+
+func GetPointer(s string) *string {
+	return &s
+}
diff --git a/stringsx/ptr_test.go b/stringsx/ptr_test.go
new file mode 100644
index 00000000..46432f02
--- /dev/null
+++ b/stringsx/ptr_test.go
@@ -0,0 +1,11 @@
+package stringsx
+
+import (
+	"github.com/stretchr/testify/assert"
+	"testing"
+)
+
+func TestGetPointer(t *testing.T) {
+	s := "TestString"
+	assert.Equal(t, &s, GetPointer(s))
+}