Make duplicate digits in codes fungible (due to bad DTMF parsing).

To get optimally low keyspace reduction I should only replace up to a doubling, but its ok for now.

Author: Zemnmez

ts/pulumi/zemn.me/api/server/BUILD.bazel

@@ -22,6 +22,7 @@ go_oapi_codegen(
 go_library(
     name = "server",
     srcs = [
+        "TestRemoveDuplicateDigits.go",
         "api.gen.go",
         "callbox_settings.go",
         "date.go",

ts/pulumi/zemn.me/api/server/TestRemoveDuplicateDigits.go

@@ -0,0 +1,26 @@
+package apiserver
+
+import "testing"
+
+func TestRemoveDuplicateDigits(t *testing.T) {
+	tests := []struct {
+		input    string
+		expected string
+	}{
+		{"112233445566", "123456"},
+		{"1111111", "1"},
+		{"121212", "121212"},
+		{"", ""},
+		{"a111b222c", "a1b2c"},
+		{"a1b2c3", "a1b2c3"},
+		{"1234444555", "12345"},
+		{"00aa00", "0aa0"},
+	}
+
+	for _, tt := range tests {
+		result := removeDuplicateDigits(tt.input)
+		if result != tt.expected {
+			t.Errorf("removeDuplicateDigits(%q) = %q; expected %q", tt.input, result, tt.expected)
+		}
+	}
+}

ts/pulumi/zemn.me/api/server/phone.go

@@ -8,6 +8,7 @@ import (
 	"net/http"
 	"os"
 	"time"
+	"unicode"
 
 	"github.com/nyaruka/phonenumbers"
 	"github.com/twilio/twilio-go/twiml"
@@ -136,6 +137,26 @@ func (s *Server) GetPhoneInit(rw http.ResponseWriter, rq *http.Request) {
 	}
 }
 
+func removeDuplicateDigits(input string) string {
+	var result []rune
+	var lastDigit rune
+	inDigitSeq := false
+
+	for _, r := range input {
+		if unicode.IsDigit(r) {
+			if !inDigitSeq || r != lastDigit {
+				result = append(result, r)
+			}
+			lastDigit = r
+			inDigitSeq = true
+		} else {
+			result = append(result, r)
+			inDigitSeq = false
+		}
+	}
+	return string(result)
+}
+
 func (s *Server) handleEntryViaCode(w http.ResponseWriter, rq *http.Request, params GetPhoneHandleEntryParams) (success bool, err error) {
 	codes, err := s.getLatestEntryCodes(rq.Context())
 	if err != nil {
@@ -150,7 +171,7 @@ func (s *Server) handleEntryViaCode(w http.ResponseWriter, rq *http.Request, par
 
 	for _, code := range codes {
 		if success = subtle.ConstantTimeCompare(
-			[]byte(code.Code), []byte(digits),
+			[]byte(removeDuplicateDigits(code.Code)), []byte(removeDuplicateDigits(digits)),
 		) == 1; success {
 			break
 		}