Add staticcheck tool

vendor/honnef.co/go/tools/staticcheck/sa1020/sa1020.go

@@ -0,0 +1,94 @@
+package sa1020
+
+import (
+	"go/constant"
+	"net"
+	"strconv"
+	"strings"
+
+	"honnef.co/go/tools/analysis/callcheck"
+	"honnef.co/go/tools/analysis/lint"
+	"honnef.co/go/tools/internal/passes/buildir"
+
+	"golang.org/x/tools/go/analysis"
+)
+
+var SCAnalyzer = lint.InitializeAnalyzer(&lint.Analyzer{
+	Analyzer: &analysis.Analyzer{
+		Name:     "SA1020",
+		Requires: []*analysis.Analyzer{buildir.Analyzer},
+		Run:      callcheck.Analyzer(checkListenAddressRules),
+	},
+	Doc: &lint.RawDocumentation{
+		Title:    `Using an invalid host:port pair with a \'net.Listen\'-related function`,
+		Since:    "2017.1",
+		Severity: lint.SeverityError,
+		MergeIf:  lint.MergeIfAny,
+	},
+})
+
+var Analyzer = SCAnalyzer.Analyzer
+
+var checkListenAddressRules = map[string]callcheck.Check{
+	"net/http.ListenAndServe":    checkValidHostPort(0),
+	"net/http.ListenAndServeTLS": checkValidHostPort(0),
+}
+
+func checkValidHostPort(arg int) callcheck.Check {
+	return func(call *callcheck.Call) {
+		if !ValidHostPort(call.Args[arg].Value) {
+			const MsgInvalidHostPort = "invalid port or service name in host:port pair"
+			call.Args[arg].Invalid(MsgInvalidHostPort)
+		}
+	}
+}
+
+func ValidHostPort(v callcheck.Value) bool {
+	if k := callcheck.ExtractConstExpectKind(v, constant.String); k != nil {
+		s := constant.StringVal(k.Value)
+		if s == "" {
+			return true
+		}
+		_, port, err := net.SplitHostPort(s)
+		if err != nil {
+			return false
+		}
+		// TODO(dh): check hostname
+		if !validatePort(port) {
+			return false
+		}
+	}
+	return true
+}
+
+func validateServiceName(s string) bool {
+	if len(s) < 1 || len(s) > 15 {
+		return false
+	}
+	if s[0] == '-' || s[len(s)-1] == '-' {
+		return false
+	}
+	if strings.Contains(s, "--") {
+		return false
+	}
+	hasLetter := false
+	for _, r := range s {
+		if (r >= 'A' && r <= 'Z') || (r >= 'a' && r <= 'z') {
+			hasLetter = true
+			continue
+		}
+		if r >= '0' && r <= '9' {
+			continue
+		}
+		return false
+	}
+	return hasLetter
+}
+
+func validatePort(s string) bool {
+	n, err := strconv.ParseInt(s, 10, 64)
+	if err != nil {
+		return validateServiceName(s)
+	}
+	return n >= 0 && n <= 65535
+}