Pull request: dhcpd: imp normalization, validation

Updates #3056.

Squashed commit of the following:

commit 875954fc8d59980a39b03032007cbc15d87801ea
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Wed May 5 19:54:24 2021 +0300

    all: imp err msgs

commit c6ea471038ce28f608084b59d3447ff64124260f
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Wed May 5 17:55:12 2021 +0300

    dhcpd: imp normalization, validation

internal/dnsforward/clientid.go

@@ -2,6 +2,7 @@ package dnsforward
 
 import (
 	"crypto/tls"
+	"errors"
 	"fmt"
 	"path"
 	"strings"
@@ -15,7 +16,8 @@ import (
 func ValidateClientID(clientID string) (err error) {
 	err = aghnet.ValidateDomainNameLabel(clientID)
 	if err != nil {
-		return fmt.Errorf("invalid client id: %w", err)
+		// Replace the domain name label wrapper with our own.
+		return fmt.Errorf("invalid client id %q: %w", clientID, errors.Unwrap(err))
 	}
 
 	return nil

internal/dnsforward/clientid_test.go

@@ -117,8 +117,8 @@ func TestProcessClientID(t *testing.T) {
 		hostSrvName:  "example.com",
 		cliSrvName:   "!!!.example.com",
 		wantClientID: "",
-		wantErrMsg: `client id check: invalid client id: invalid char '!' ` +
-			`at index 0 in "!!!"`,
+		wantErrMsg: `client id check: invalid client id "!!!": ` +
+			`invalid char '!' at index 0`,
 		wantRes:   resultCodeError,
 		strictSNI: true,
 	}, {
@@ -128,9 +128,9 @@ func TestProcessClientID(t *testing.T) {
 		cliSrvName: `abcdefghijklmnopqrstuvwxyz0123456789abcdefghijklmno` +
 			`pqrstuvwxyz0123456789.example.com`,
 		wantClientID: "",
-		wantErrMsg: `client id check: invalid client id: "abcdefghijklmno` +
-			`pqrstuvwxyz0123456789abcdefghijklmnopqrstuvwxyz0123456789" ` +
-			`is too long, max: 63`,
+		wantErrMsg: `client id check: invalid client id "abcdefghijklmno` +
+			`pqrstuvwxyz0123456789abcdefghijklmnopqrstuvwxyz0123456789": ` +
+			`label is too long, max: 63`,
 		wantRes:   resultCodeError,
 		strictSNI: true,
 	}, {
@@ -238,8 +238,8 @@ func TestProcessClientID_https(t *testing.T) {
 		name:         "invalid_client_id",
 		path:         "/dns-query/!!!",
 		wantClientID: "",
-		wantErrMsg: `client id check: invalid client id: invalid char '!' ` +
-			`at index 0 in "!!!"`,
+		wantErrMsg: `client id check: invalid client id "!!!": ` +
+			`invalid char '!' at index 0`,
 		wantRes: resultCodeError,
 	}}
 

internal/dnsforward/dnsforward_test.go

@@ -1166,8 +1166,9 @@ func TestNewServer(t *testing.T) {
 		in: DNSCreateParams{
 			LocalDomain: "!!!",
 		},
-		wantErrMsg: `local domain: invalid domain name label at index 0: ` +
-			`invalid char '!' at index 0 in "!!!"`,
+		wantErrMsg: `local domain: validating domain name "!!!": ` +
+			`invalid domain name label at index 0: ` +
+			`validating label "!!!": invalid char '!' at index 0`,
 	}}
 
 	for _, tc := range testCases {