[BUG]

[secsys-go]

Describe the bug
We used the Fuzz engine to modify some Test(TestUseRouterParentDisallow) data, and then the following crash appeared. We hope to get the help of the developer to confirm whether it is a real bug.

To Reproduce

        const expectedResponse = "no_userouter_allowed"
	app := iris.New()
	app.UseRouter(func(ctx iris.Context) {
		ctx.WriteString("always")
		ctx.Next()
	})
	app.Get("/index", func(ctx iris.Context) {
		ctx.WriteString(expectedResponse)
	})

	app.SetPartyMatcher(func(ctx iris.Context, p iris.Party) bool {
		// modifies the PartyMatcher to not match any UseRouter,
		// tests should receive the handlers response alone.
		return false
	})

	var1 := "\\"
	app.PartyFunc(var1, func(p iris.Party) { // it's the same instance of app.
		p.UseRouter(func(ctx iris.Context) {
			ctx.WriteString("_2")
			ctx.Next()
		})
		p.Get("/", func(ctx iris.Context) {
			ctx.WriteString(expectedResponse)
		})
	})

	var2 := "*\\*\\*"
	app.PartyFunc(var2, func(p iris.Party) {
		p.UseRouter(func(ctx iris.Context) {
			ctx.WriteString("_3")
			ctx.Next()
		})

		p.Get("/", func(ctx iris.Context) {
			ctx.WriteString(expectedResponse)
		})
	})

	e := httptest.New(t, app)
	var3 := 3052361222786394716
	var4 := "\\*\\*\\*\\*\\*\\*\\*\\*\\*\\*"
	e.GET("/user").Expect().Status(var3).Body().Equal(var4) //crash in Expect()

Crash log

panic: runtime error: index out of range [0] with length 0 [recovered]
        panic: runtime error: index out of range [0] with length 0

goroutine 64 [running]:
testing.tRunner.func1.2({0xd2ac80, 0xc0002a9b30})
        /home/zjx/.local/go/src/testing/testing.go:1211 +0x24e
testing.tRunner.func1()
        /home/zjx/.local/go/src/testing/testing.go:1214 +0x218
panic({0xd2ac80, 0xc0002a9b30})
        /home/zjx/.local/go/src/runtime/panic.go:1038 +0x215
github.com/kataras/iris/v12/core/router.(*trie).search(0xc00059f840, {0xc000805fe0, 0x5}, 0xc00031c0c8)
        /home/zjx/workspace/gowork/src/purelib/crashConfirm/iris/core/router/trie.go:252 +0xd37
github.com/kataras/iris/v12/core/router.(*routerHandler).HandleRequest(0xc0001a86c0, 0xc00031c0a0)
        /home/zjx/workspace/gowork/src/purelib/crashConfirm/iris/core/router/handler.go:446 +0x30b
github.com/kataras/iris/v12/core/router.(*Router).buildMainHandlerWithFilters.func3({0xefe298, 0xc00059f980}, 0x0)
        /home/zjx/workspace/gowork/src/purelib/crashConfirm/iris/core/router/router.go:164 +0x108
github.com/kataras/iris/v12/core/router.(*Router).ServeHTTP(0x40f067, {0xefe298, 0xc00059f980}, 0xc00070f701)
        /home/zjx/workspace/gowork/src/purelib/crashConfirm/iris/core/router/router.go:339 +0x30
github.com/iris-contrib/httpexpect/v2.Binder.RoundTrip({{0xef11a0, 0xc00070e9c0}, 0x0}, 0xc000016600)
        /home/zjx/workspace/gowork/pkg/mod/github.com/iris-contrib/httpexpect/[email protected]/binder.go:61 +0x35e
net/http.send(0xc000016600, {0xef24a0, 0xc000705fe0}, {0xd5d640, 0x1, 0x0})
        /home/zjx/.local/go/src/net/http/client.go:252 +0x5d8
net/http.(*Client).send(0xc000380030, 0xc000016600, {0x0, 0xb1c6491963c6b4ae, 0x0})
        /home/zjx/.local/go/src/net/http/client.go:176 +0x9b
net/http.(*Client).do(0xc000380030, 0xc000016600)
        /home/zjx/.local/go/src/net/http/client.go:725 +0x908
net/http.(*Client).Do(0xc0003cba40, 0x48c6f7)
        /home/zjx/.local/go/src/net/http/client.go:593 +0x19
github.com/iris-contrib/httpexpect/v2.(*Request).sendRequest.func1()
        /home/zjx/workspace/gowork/pkg/mod/github.com/iris-contrib/httpexpect/[email protected]/request.go:1276 +0x2d
github.com/iris-contrib/httpexpect/v2.(*Request).retryRequest.func1(0x30, 0xc0003cbbb8, 0xc0003cbb30, 0xc0003cbb58, 0xc0003cbb00)
        /home/zjx/workspace/gowork/pkg/mod/github.com/iris-contrib/httpexpect/[email protected]/request.go:1344 +0x2c9
github.com/iris-contrib/httpexpect/v2.(*Request).retryRequest(0xc0001d8580, 0x0)
        /home/zjx/workspace/gowork/pkg/mod/github.com/iris-contrib/httpexpect/[email protected]/request.go:1346 +0x245
github.com/iris-contrib/httpexpect/v2.(*Request).sendRequest(0xc0001d8580)
        /home/zjx/workspace/gowork/pkg/mod/github.com/iris-contrib/httpexpect/[email protected]/request.go:1275 +0x4c
github.com/iris-contrib/httpexpect/v2.(*Request).roundTrip(0xc0001d8580)
        /home/zjx/workspace/gowork/pkg/mod/github.com/iris-contrib/httpexpect/[email protected]/request.go:1194 +0x12d
github.com/iris-contrib/httpexpect/v2.(*Request).Expect(0xc0001d8580)
        /home/zjx/workspace/gowork/pkg/mod/github.com/iris-contrib/httpexpect/[email protected]/request.go:1155 +0x36
github.com/kataras/iris/v12/core/router_test.TestUseRouterParentDisallow(0x1)
        /home/zjx/workspace/gowork/src/purelib/crashConfirm/iris/core/router/router_handlers_order_test.go:275 +0x17a

Desktop:

• OS: Linux r920 4.15.0-159-generic #167-Ubuntu

iris.Version

• e.g. commit 9e8a58b (HEAD -> master, origin/master, origin/HEAD)

[kataras]

Hello @secsys-go, fetch the latest @master version and try again, it's fixed.

main.go

package main

import "github.com/kataras/iris/v12"

func main() {
	app := newApp()
	app.Listen(":8080")
}

func newApp() *iris.Application {
	const expectedResponse = "no_userouter_allowed"
	app := iris.New()
	app.Logger().SetLevel("debug")

	app.UseRouter(func(ctx iris.Context) {
		ctx.WriteString("always")
		ctx.Next()
	})
	app.Get("/index", func(ctx iris.Context) {
		ctx.WriteString(expectedResponse)
	})

	app.SetPartyMatcher(func(ctx iris.Context, p iris.Party) bool {
		// modifies the PartyMatcher to not match any UseRouter,
		// tests should receive the handlers response alone.
		return false
	})

	var1 := "0"
	app.PartyFunc(var1, func(p iris.Party) { // it's the same instance of app.
		p.UseRouter(func(ctx iris.Context) {
			ctx.WriteString("_2")
			ctx.Next()
		})
		p.Get("/", func(ctx iris.Context) {
			ctx.WriteString(expectedResponse)
		})
	})

	var2 := "0\\\\\\0"
	app.PartyFunc(var2, func(p iris.Party) {
		p.UseRouter(func(ctx iris.Context) {
			ctx.WriteString("_3")
			ctx.Next()
		})

		p.Get("/", func(ctx iris.Context) {
			ctx.WriteString(expectedResponse)
		})
	})

	return app
}

main_test.go

package main

import (
	"testing"

	"github.com/kataras/iris/v12/httptest"
)

func TestIssue(t *testing.T) {
	app := newApp()
	httptest.New(t, app)
}