Basics for nftables

Signed-off-by: Georg Pfuetzenreuter <mail@georg-pfuetzenreuter.net>

go.mod

@@ -3,7 +3,18 @@ module nftables-http-api
 go 1.22.6
 
 require (
+	github.com/google/nftables v0.2.0
 	github.com/gorilla/mux v1.8.1
 	golang.org/x/crypto v0.26.0
 	gopkg.in/yaml.v3 v3.0.1
 )
+
+require (
+	github.com/google/go-cmp v0.6.0 // indirect
+	github.com/josharian/native v1.1.0 // indirect
+	github.com/mdlayher/netlink v1.7.2 // indirect
+	github.com/mdlayher/socket v0.5.0 // indirect
+	golang.org/x/net v0.22.0 // indirect
+	golang.org/x/sync v0.6.0 // indirect
+	golang.org/x/sys v0.23.0 // indirect
+)

go.sum

@@ -1,7 +1,25 @@
+github.com/google/go-cmp v0.6.0 h1:ofyhxvXcZhMsU5ulbFiLKl/XBFqE1GSq7atu8tAmTRI=
+github.com/google/go-cmp v0.6.0/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
+github.com/google/nftables v0.2.0 h1:PbJwaBmbVLzpeldoeUKGkE2RjstrjPKMl6oLrfEJ6/8=
+github.com/google/nftables v0.2.0/go.mod h1:Beg6V6zZ3oEn0JuiUQ4wqwuyqqzasOltcoXPtgLbFp4=
 github.com/gorilla/mux v1.8.1 h1:TuBL49tXwgrFYWhqrNgrUNEY92u81SPhu7sTdzQEiWY=
 github.com/gorilla/mux v1.8.1/go.mod h1:AKf9I4AEqPTmMytcMc0KkNouC66V3BtZ4qD5fmWSiMQ=
+github.com/josharian/native v1.1.0 h1:uuaP0hAbW7Y4l0ZRQ6C9zfb7Mg1mbFKry/xzDAfmtLA=
+github.com/josharian/native v1.1.0/go.mod h1:7X/raswPFr05uY3HiLlYeyQntB6OO7E/d2Cu7qoaN2w=
+github.com/mdlayher/netlink v1.7.2 h1:/UtM3ofJap7Vl4QWCPDGXY8d3GIY2UGSDbK+QWmY8/g=
+github.com/mdlayher/netlink v1.7.2/go.mod h1:xraEF7uJbxLhc5fpHL4cPe221LI2bdttWlU+ZGLfQSw=
+github.com/mdlayher/socket v0.5.0 h1:ilICZmJcQz70vrWVes1MFera4jGiWNocSkykwwoy3XI=
+github.com/mdlayher/socket v0.5.0/go.mod h1:WkcBFfvyG8QENs5+hfQPl1X6Jpd2yeLIYgrGFmJiJxI=
+github.com/vishvananda/netns v0.0.0-20180720170159-13995c7128cc h1:R83G5ikgLMxrBvLh22JhdfI8K6YXEPHx5P03Uu3DRs4=
+github.com/vishvananda/netns v0.0.0-20180720170159-13995c7128cc/go.mod h1:ZjcWmFBXmLKZu9Nxj3WKYEafiSqer2rnvPr0en9UNpI=
 golang.org/x/crypto v0.26.0 h1:RrRspgV4mU+YwB4FYnuBoKsUapNIL5cohGAmSH3azsw=
 golang.org/x/crypto v0.26.0/go.mod h1:GY7jblb9wI+FOo5y8/S2oY4zWP07AkOJ4+jxCqdqn54=
+golang.org/x/net v0.22.0 h1:9sGLhx7iRIHEiX0oAJ3MRZMUCElJgy7Br1nO+AMN3Tc=
+golang.org/x/net v0.22.0/go.mod h1:JKghWKKOSdJwpW2GEx0Ja7fmaKnMsbu+MWVZTokSYmg=
+golang.org/x/sync v0.6.0 h1:5BMeUDZ7vkXGfEr1x9B4bRcTH4lpkTkpdh0T/J+qjbQ=
+golang.org/x/sync v0.6.0/go.mod h1:Czt+wKu1gCyEFDUtn0jG5QVvpJ6rzVqr5aXyt9drQfk=
+golang.org/x/sys v0.23.0 h1:YfKFowiIMvtgl1UERQoTPPToxltDeZfbj4H7dVUCwmM=
+golang.org/x/sys v0.23.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=

nft.go

@@ -0,0 +1,106 @@
+/*
+ * This file is part of nftables-http-api.
+ * Copyright (C) 2024 Georg Pfuetzenreuter <mail@georg-pfuetzenreuter.net>
+ *
+ *  The nftables-http-api program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.
+
+ * This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+
+ * You should have received a copy of the GNU General Public License along with this program. If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package main
+
+import (
+	"github.com/google/nftables"
+	"log"
+)
+
+type nftError struct {
+	Message string
+}
+
+func (nfterr nftError) Error() string {
+	return nfterr.Message
+}
+
+func handleNft(task string, set string) (any, error) {
+	nft, err := nftables.New()
+	if err != nil {
+		log.Println("handleNft():", err)
+		return "", err
+	}
+
+	if task == "get" {
+		nftResult, err := getNftSetElements(nft, set)
+		if err == nil {
+			return nftResult, nil
+		}
+		return nil, err
+	}
+
+	return "", nil
+}
+
+func getNftTable(nft *nftables.Conn) (*nftables.Table, error) {
+	targetTable := "filter" // TODO: make table configurable or smarter
+
+	foundTables, err := nft.ListTables()
+	if err != nil {
+		log.Printf("getNftTable(): %s", err)
+		return nil, err
+	}
+
+	exists := false
+	var table *nftables.Table
+	for _, foundTable := range foundTables {
+		if foundTable.Name == targetTable {
+			exists = true
+			table = foundTable
+			break
+		}
+	}
+
+	if !exists {
+		log.Printf("Table %s does not exist, cannot proceed", targetTable)
+		return nil, nftError{Message: "Table does not exist"}
+	}
+
+	return table, nil
+}
+
+func getNftSet(nft *nftables.Conn, setName string) (*nftables.Set, error) {
+	foundTable, err := getNftTable(nft)
+	if err != nil {
+		return nil, err
+	}
+	foundSet, err := nft.GetSetByName(foundTable, setName)
+	if err != nil || foundSet == nil {
+		log.Printf("Set lookup for %s failed, cannot proceed: %s", setName, err)
+		return nil, err
+	}
+
+	return foundSet, nil
+}
+
+func getNftSetElements(nft *nftables.Conn, setName string) ([]string, error) {
+	set, err := getNftSet(nft, setName)
+	if err != nil {
+		log.Printf("Could not retrieve set elements")
+		return nil, err
+	}
+
+	setElements, err := nft.GetSetElements(set)
+	if err != nil {
+		return nil, err
+	}
+
+	var returnElements []string
+
+	for _, element := range setElements {
+		log.Printf("element: %s", element.Key)
+		returnElements = append(returnElements, string(element.Key))
+	}
+
+	return returnElements, nil
+}

nftables-http-api.go

@@ -13,11 +13,12 @@ package main
 
 import (
 	"flag"
+	"github.com/gorilla/mux"
+	"gopkg.in/yaml.v3"
 	"log"
 	"net/http"
 	"os"
-	"github.com/gorilla/mux"
-	"gopkg.in/yaml.v3"
+	"strings"
 )
 
 var config Config
@@ -102,6 +103,12 @@ func handleSetRoute(w http.ResponseWriter, r *http.Request) {
 	log.Printf("Processing authorized %s request from %s for set %s", method, r.RemoteAddr, set)
 
 	if method == "GET" {
-		doReturn(w, http.StatusOK, "ok")
+		nftResult, err := handleNft("get", set)
+		if err != nil {
+			doReturn(w, http.StatusInternalServerError, "nftables failure")
+		}
+		if nftResult != nil {
+			doReturn(w, http.StatusOK, strings.Join(nftResult.([]string), ""))
+		}
 	}
 }

utils.go

@@ -13,9 +13,11 @@ package main
 
 import (
 	"encoding/json"
-	"log"
-	"net/http"
+	"errors"
 	"golang.org/x/crypto/bcrypt"
+	"log"
+	"net"
+	"net/http"
 )
 
 type Response struct {
@@ -47,3 +49,38 @@ func doCheckToken(token string, hash string) bool {
 		return false
 	}
 }
+
+func parseIPAddress(straddress string) (net.IP, string) {
+	parsedaddress := net.ParseIP(straddress)
+	var address net.IP
+	family, err := getIPAddressFamily(straddress)
+	if err == nil {
+		if family == "ipv4" {
+			address = parsedaddress.To4()
+		} else if family == "ipv6" {
+			address = parsedaddress.To16()
+		} else {
+			log.Println("unknown family, this should not happen")
+			return nil, family
+		}
+		return address, family
+	}
+	log.Println("address parsing failed:", err)
+	return nil, ""
+}
+
+func getIPAddressFamily(ip string) (string, error) {
+	if net.ParseIP(ip) == nil {
+		return "", errors.New("Not an IP address")
+	}
+	for i := 0; i < len(ip); i++ {
+		switch ip[i] {
+		case '.':
+			return "ipv4", nil
+		case ':':
+			return "ipv6", nil
+		}
+	}
+
+	return "", errors.New("unknown error")
+}