add aliases.IsValid for name checks

aliases/names.go

@@ -0,0 +1,42 @@
+// SPDX-License-Identifier: MIT
+
+package aliases
+
+import (
+	"fmt"
+)
+
+// IsValid decides weather an alias is okay for use or not.
+// The room spec defines it as _labels valid under RFC 1035_ ( https://ssb-ngi-pointer.github.io/rooms2/#alias-string )
+// but that can be mostly any string since DNS is a 8bit binary protocol,
+// as long as it's shorter then 63 charachters.
+//
+// Right now it's pretty basic set of charachters (a-z, A-Z, 0-9).
+// In theory we could be more liberal but there is a bunch of stuff to figure out,
+// like homograph attacks (https://en.wikipedia.org/wiki/IDN_homograph_attack),
+// if we would decide to allow full utf8 unicode.
+func IsValid(alias string) bool {
+	if len(alias) > 63 {
+		return false
+	}
+
+	var valid = true
+	for _, char := range alias {
+		if char >= '0' && char <= '9' { // is an ASCII number
+			continue
+		}
+
+		if char >= 'a' && char <= 'z' { // is an ASCII char between a and z
+			continue
+		}
+
+		if char >= 'A' && char <= 'Z' { // is an ASCII upper-case char between a and z
+			continue
+		}
+
+		fmt.Println("found", char)
+		valid = false
+		break
+	}
+	return valid
+}

aliases/names_test.go

@@ -0,0 +1,31 @@
+// SPDX-License-Identifier: MIT
+
+package aliases
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestIsValid(t *testing.T) {
+	a := assert.New(t)
+
+	cases := []struct {
+		alias string
+		valid bool
+	}{
+		{"basic", true},
+		{"no spaces", false},
+		{"no.dots", false},
+		{"#*!(! nope", false},
+
+		// too long
+		{"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA", false},
+	}
+
+	for i, tc := range cases {
+		yes := IsValid(tc.alias)
+		a.Equal(tc.valid, yes, "wrong for %d: %s", i, tc.alias)
+	}
+}

muxrpc/handlers/alias/register.go

@@ -56,7 +56,9 @@ func (h Handler) Register(ctx context.Context, req *muxrpc.Request) (interface{}
 	}
 
 	// check alias is valid
-	// if !aliases.IsValid(confirmation.Alias) { ... }
+	if !aliases.IsValid(confirmation.Alias) {
+		return nil, fmt.Errorf("registerAlias: invalid alias")
+	}
 
 	// get the user from the muxrpc connection
 	userID, err := network.GetFeedRefFromAddr(req.RemoteAddr())