Add clientapi tests (#2916)

This PR
- adds several tests for the clientapi, mostly around `/register` and
auth fallback.
- removes the now deprecated `homeserver` field from responses to
`/register` and `/login`
- slightly refactors auth fallback handling

internal/validate_test.go

@@ -0,0 +1,170 @@
+package internal
+
+import (
+	"net/http"
+	"reflect"
+	"strings"
+	"testing"
+
+	"github.com/matrix-org/dendrite/clientapi/jsonerror"
+	"github.com/matrix-org/gomatrixserverlib"
+	"github.com/matrix-org/util"
+)
+
+func Test_validatePassword(t *testing.T) {
+	tests := []struct {
+		name      string
+		password  string
+		wantError error
+		wantJSON  *util.JSONResponse
+	}{
+		{
+			name:      "password too short",
+			password:  "shortpw",
+			wantError: ErrPasswordWeak,
+			wantJSON:  &util.JSONResponse{Code: http.StatusBadRequest, JSON: jsonerror.WeakPassword(ErrPasswordWeak.Error())},
+		},
+		{
+			name:      "password too long",
+			password:  strings.Repeat("a", maxPasswordLength+1),
+			wantError: ErrPasswordTooLong,
+			wantJSON:  &util.JSONResponse{Code: http.StatusBadRequest, JSON: jsonerror.BadJSON(ErrPasswordTooLong.Error())},
+		},
+		{
+			name:     "password OK",
+			password: util.RandomString(10),
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			gotErr := ValidatePassword(tt.password)
+			if !reflect.DeepEqual(gotErr, tt.wantError) {
+				t.Errorf("validatePassword() = %v, wantJSON %v", gotErr, tt.wantError)
+			}
+
+			if got := PasswordResponse(gotErr); !reflect.DeepEqual(got, tt.wantJSON) {
+				t.Errorf("validatePassword() = %v, wantJSON %v", got, tt.wantJSON)
+			}
+		})
+	}
+}
+
+func Test_validateUsername(t *testing.T) {
+	tooLongUsername := strings.Repeat("a", maxUsernameLength)
+	tests := []struct {
+		name      string
+		localpart string
+		domain    gomatrixserverlib.ServerName
+		wantErr   error
+		wantJSON  *util.JSONResponse
+	}{
+		{
+			name:      "empty username",
+			localpart: "",
+			domain:    "localhost",
+			wantErr:   ErrUsernameInvalid,
+			wantJSON: &util.JSONResponse{
+				Code: http.StatusBadRequest,
+				JSON: jsonerror.InvalidUsername(ErrUsernameInvalid.Error()),
+			},
+		},
+		{
+			name:      "invalid username",
+			localpart: "INVALIDUSERNAME",
+			domain:    "localhost",
+			wantErr:   ErrUsernameInvalid,
+			wantJSON: &util.JSONResponse{
+				Code: http.StatusBadRequest,
+				JSON: jsonerror.InvalidUsername(ErrUsernameInvalid.Error()),
+			},
+		},
+		{
+			name:      "username too long",
+			localpart: tooLongUsername,
+			domain:    "localhost",
+			wantErr:   ErrUsernameTooLong,
+			wantJSON: &util.JSONResponse{
+				Code: http.StatusBadRequest,
+				JSON: jsonerror.BadJSON(ErrUsernameTooLong.Error()),
+			},
+		},
+		{
+			name:      "localpart starting with an underscore",
+			localpart: "_notvalid",
+			domain:    "localhost",
+			wantErr:   ErrUsernameUnderscore,
+			wantJSON: &util.JSONResponse{
+				Code: http.StatusBadRequest,
+				JSON: jsonerror.InvalidUsername(ErrUsernameUnderscore.Error()),
+			},
+		},
+		{
+			name:      "valid username",
+			localpart: "valid",
+			domain:    "localhost",
+		},
+		{
+			name:      "complex username",
+			localpart: "f00_bar-baz.=40/",
+			domain:    "localhost",
+		},
+		{
+			name:      "rejects emoji username 💥",
+			localpart: "💥",
+			domain:    "localhost",
+			wantErr:   ErrUsernameInvalid,
+			wantJSON: &util.JSONResponse{
+				Code: http.StatusBadRequest,
+				JSON: jsonerror.InvalidUsername(ErrUsernameInvalid.Error()),
+			},
+		},
+		{
+			name:      "special characters are allowed",
+			localpart: "/dev/null",
+			domain:    "localhost",
+		},
+		{
+			name:      "special characters are allowed 2",
+			localpart: "i_am_allowed=1",
+			domain:    "localhost",
+		},
+		{
+			name:      "not all special characters are allowed",
+			localpart: "notallowed#", // contains #
+			domain:    "localhost",
+			wantErr:   ErrUsernameInvalid,
+			wantJSON: &util.JSONResponse{
+				Code: http.StatusBadRequest,
+				JSON: jsonerror.InvalidUsername(ErrUsernameInvalid.Error()),
+			},
+		},
+		{
+			name:      "username containing numbers",
+			localpart: "hello1337",
+			domain:    "localhost",
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			gotErr := ValidateUsername(tt.localpart, tt.domain)
+			if !reflect.DeepEqual(gotErr, tt.wantErr) {
+				t.Errorf("ValidateUsername() = %v, wantErr %v", gotErr, tt.wantErr)
+			}
+			if gotJSON := UsernameResponse(gotErr); !reflect.DeepEqual(gotJSON, tt.wantJSON) {
+				t.Errorf("UsernameResponse() = %v, wantJSON %v", gotJSON, tt.wantJSON)
+			}
+
+			// Application services are allowed usernames starting with an underscore
+			if tt.wantErr == ErrUsernameUnderscore {
+				return
+			}
+			gotErr = ValidateApplicationServiceUsername(tt.localpart, tt.domain)
+			if !reflect.DeepEqual(gotErr, tt.wantErr) {
+				t.Errorf("ValidateUsername() = %v, wantErr %v", gotErr, tt.wantErr)
+			}
+			if gotJSON := UsernameResponse(gotErr); !reflect.DeepEqual(gotJSON, tt.wantJSON) {
+				t.Errorf("UsernameResponse() = %v, wantJSON %v", gotJSON, tt.wantJSON)
+			}
+		})
+	}
+}