Only allow webhook to send requests to allowed hosts (#17482)

modules/hostmatcher/hostmatcher.go

@@ -0,0 +1,94 @@
+// Copyright 2021 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package hostmatcher
+
+import (
+	"net"
+	"path/filepath"
+	"strings"
+
+	"code.gitea.io/gitea/modules/util"
+)
+
+// HostMatchList is used to check if a host or IP is in a list.
+// If you only need to do wildcard matching, consider to use modules/matchlist
+type HostMatchList struct {
+	hosts  []string
+	ipNets []*net.IPNet
+}
+
+// MatchBuiltinAll all hosts are matched
+const MatchBuiltinAll = "*"
+
+// MatchBuiltinExternal A valid non-private unicast IP, all hosts on public internet are matched
+const MatchBuiltinExternal = "external"
+
+// MatchBuiltinPrivate RFC 1918 (10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16) and RFC 4193 (FC00::/7). Also called LAN/Intranet.
+const MatchBuiltinPrivate = "private"
+
+// MatchBuiltinLoopback 127.0.0.0/8 for IPv4 and ::1/128 for IPv6, localhost is included.
+const MatchBuiltinLoopback = "loopback"
+
+// ParseHostMatchList parses the host list HostMatchList
+func ParseHostMatchList(hostList string) *HostMatchList {
+	hl := &HostMatchList{}
+	for _, s := range strings.Split(hostList, ",") {
+		s = strings.ToLower(strings.TrimSpace(s))
+		if s == "" {
+			continue
+		}
+		_, ipNet, err := net.ParseCIDR(s)
+		if err == nil {
+			hl.ipNets = append(hl.ipNets, ipNet)
+		} else {
+			hl.hosts = append(hl.hosts, s)
+		}
+	}
+	return hl
+}
+
+// MatchesHostOrIP checks if the host or IP matches an allow/deny(block) list
+func (hl *HostMatchList) MatchesHostOrIP(host string, ip net.IP) bool {
+	var matched bool
+	host = strings.ToLower(host)
+	ipStr := ip.String()
+loop:
+	for _, hostInList := range hl.hosts {
+		switch hostInList {
+		case "":
+			continue
+		case MatchBuiltinAll:
+			matched = true
+			break loop
+		case MatchBuiltinExternal:
+			if matched = ip.IsGlobalUnicast() && !util.IsIPPrivate(ip); matched {
+				break loop
+			}
+		case MatchBuiltinPrivate:
+			if matched = util.IsIPPrivate(ip); matched {
+				break loop
+			}
+		case MatchBuiltinLoopback:
+			if matched = ip.IsLoopback(); matched {
+				break loop
+			}
+		default:
+			if matched, _ = filepath.Match(hostInList, host); matched {
+				break loop
+			}
+			if matched, _ = filepath.Match(hostInList, ipStr); matched {
+				break loop
+			}
+		}
+	}
+	if !matched {
+		for _, ipNet := range hl.ipNets {
+			if matched = ipNet.Contains(ip); matched {
+				break
+			}
+		}
+	}
+	return matched
+}