From 4391b1ba5aaa2348176a9eac0e164721ee0a761a Mon Sep 17 00:00:00 2001
From: Shivaram Lingamneni <slingamn@cs.stanford.edu>
Date: Sun, 22 Dec 2019 09:57:49 -0500
Subject: [PATCH] restrict ASCII mode to printable characters only

---
 irc/strings.go      | 10 ++++++----
 irc/strings_test.go | 48 +++++++++++++++++++++++++++++++++------------
 2 files changed, 42 insertions(+), 16 deletions(-)

diff --git a/irc/strings.go b/irc/strings.go
index 3f9b82c4..32f3f952 100644
--- a/irc/strings.go
+++ b/irc/strings.go
@@ -9,7 +9,6 @@ import (
 	"fmt"
 	"regexp"
 	"strings"
-	"unicode"
 
 	"github.com/oragono/confusables"
 	"golang.org/x/text/cases"
@@ -262,15 +261,18 @@ func CanonicalizeMaskWildcard(userhost string) (expanded string, err error) {
 }
 
 func foldASCII(str string) (result string, err error) {
-	if !IsPureASCII(str) {
+	if !IsPrintableASCII(str) {
 		return "", errInvalidCharacter
 	}
 	return strings.ToLower(str), nil
 }
 
-func IsPureASCII(str string) bool {
+func IsPrintableASCII(str string) bool {
 	for i := 0; i < len(str); i++ {
-		if unicode.MaxASCII < str[i] {
+		// allow space here because it's technically printable;
+		// it will be disallowed later by CasefoldName/CasefoldChannel
+		chr := str[i]
+		if chr < ' ' || chr > '~' {
 			return false
 		}
 	}
diff --git a/irc/strings_test.go b/irc/strings_test.go
index 6780186f..9bb487f5 100644
--- a/irc/strings_test.go
+++ b/irc/strings_test.go
@@ -217,20 +217,24 @@ func TestCanonicalizeMaskWildcard(t *testing.T) {
 	tester("*SHIVARAM*", "*shivaram*!*@*", nil)
 }
 
+func validFoldTester(first, second string, equal bool, folder func(string) (string, error), t *testing.T) {
+	firstFolded, err := folder(first)
+	if err != nil {
+		panic(err)
+	}
+	secondFolded, err := folder(second)
+	if err != nil {
+		panic(err)
+	}
+	foundEqual := firstFolded == secondFolded
+	if foundEqual != equal {
+		t.Errorf("%s and %s: expected equality %t, but got %t", first, second, equal, foundEqual)
+	}
+}
+
 func TestFoldPermissive(t *testing.T) {
 	tester := func(first, second string, equal bool) {
-		firstFolded, err := foldPermissive(first)
-		if err != nil {
-			panic(err)
-		}
-		secondFolded, err := foldPermissive(second)
-		if err != nil {
-			panic(err)
-		}
-		foundEqual := firstFolded == secondFolded
-		if foundEqual != equal {
-			t.Errorf("%s and %s: expected equality %t, but got %t", first, second, equal, foundEqual)
-		}
+		validFoldTester(first, second, equal, foldPermissive, t)
 	}
 	tester("SHIVARAM", "shivaram", true)
 	tester("shIvaram", "shivaraM", true)
@@ -250,3 +254,23 @@ func TestFoldPermissiveInvalid(t *testing.T) {
 		t.Errorf("the null byte should be invalid in identifiers")
 	}
 }
+
+func TestFoldASCII(t *testing.T) {
+	tester := func(first, second string, equal bool) {
+		validFoldTester(first, second, equal, foldASCII, t)
+	}
+	tester("shivaram", "SHIVARAM", true)
+	tester("X|Y", "x|y", true)
+	tester("a != b", "A != B", true)
+}
+
+func TestFoldASCIIInvalid(t *testing.T) {
+	_, err := foldASCII("\x01")
+	if err == nil {
+		t.Errorf("control characters should be invalid in identifiers")
+	}
+	_, err = foldASCII("\x7F")
+	if err == nil {
+		t.Errorf("control characters should be invalid in identifiers")
+	}
+}