Revert the minimal golang version requirement from 1.17 to 1.16 and add a warning in Makefile

.drone.yml

@@ -109,7 +109,7 @@ steps:
     depends_on: [test-frontend]
 
   - name: build-backend-no-gcc
-    image: golang:1.17 # this step is kept as the lowest version of golang that we support
+    image: golang:1.16 # this step is kept as the lowest version of golang that we support
     pull: always
     environment:
       GO111MODULE: on

Makefile

@@ -203,10 +203,13 @@ help:
 go-check:
 	$(eval MIN_GO_VERSION_STR := $(shell grep -Eo '^go\s+[0-9]+\.[0-9.]+' go.mod | cut -d' ' -f2))
 	$(eval MIN_GO_VERSION := $(shell printf "%03d%03d%03d" $(shell echo '$(MIN_GO_VERSION_STR)' | tr '.' ' ')))
-	$(eval GO_VERSION := $(shell printf "%03d%03d%03d" $(shell $(GO) version | grep -Eo '[0-9]+\.[0-9.]+' | tr '.' ' ');))
+	$(eval GO_VERSION_STR := $(shell $(GO) version | grep -Eo '[0-9]+\.[0-9.]+'))
+	$(eval GO_VERSION := $(shell printf "%03d%03d%03d" $(shell echo '$(GO_VERSION_STR)' | tr '.' ' ')))
 	@if [ "$(GO_VERSION)" -lt "$(MIN_GO_VERSION)" ]; then \
-		echo "Gitea requires Go $(MIN_GO_VERSION_STR) or greater to build. You can get it at https://go.dev/dl/"; \
+		echo "Gitea requires Go $(MIN_GO_VERSION_STR) or greater to build, but $(GO_VERSION) was found. You can get an updated version at https://go.dev/dl/"; \
 		exit 1; \
+	else \
+		echo "WARNING: Please ensure Go $(GO_VERSION_STR) is still maintained to avoid possible security problems. You can check it at https://go.dev/dl/"; \
 	fi
 
 .PHONY: git-check

docs/config.yaml

@@ -19,7 +19,7 @@ params:
   author: The Gitea Authors
   website: https://docs.gitea.io
   version: 1.16.4
-  minGoVersion: 1.17
+  minGoVersion: 1.16
   goVersion: 1.18
   minNodeVersion: 12.17
 

go.mod

@@ -1,6 +1,6 @@
 module code.gitea.io/gitea
 
-go 1.17
+go 1.16
 
 require (
 	cloud.google.com/go v0.99.0 // indirect

modules/hostmatcher/hostmatcher.go

@@ -8,6 +8,8 @@ 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.
@@ -102,11 +104,11 @@ func (hl *HostMatchList) checkIP(ip net.IP) bool {
 	for _, builtin := range hl.builtins {
 		switch builtin {
 		case MatchBuiltinExternal:
-			if ip.IsGlobalUnicast() && !ip.IsPrivate() {
+			if ip.IsGlobalUnicast() && !util.IsIPPrivate(ip) {
 				return true
 			}
 		case MatchBuiltinPrivate:
-			if ip.IsPrivate() {
+			if util.IsIPPrivate(ip) {
 				return true
 			}
 		case MatchBuiltinLoopback:

modules/util/net.go

@@ -0,0 +1,19 @@
+// 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 util
+
+import (
+	"net"
+)
+
+// IsIPPrivate for net.IP.IsPrivate.
+func IsIPPrivate(ip net.IP) bool {
+	if ip4 := ip.To4(); ip4 != nil {
+		return ip4[0] == 10 ||
+			(ip4[0] == 172 && ip4[1]&0xf0 == 16) ||
+			(ip4[0] == 192 && ip4[1] == 168)
+	}
+	return len(ip) == net.IPv6len && ip[0]&0xfe == 0xfc
+}