From 1578904da28ce38d2add729faae257dc43d30044 Mon Sep 17 00:00:00 2001
From: Evgeniy Stratonikov <evgeniy@nspcc.ru>
Date: Fri, 4 Jun 2021 11:47:52 +0300
Subject: [PATCH] compiler: disallow `runtime.Notify` in `Verify` function

Only direct invocations are considered. The check can be disabled
with '--no-events' compiler option.
---
 pkg/compiler/codegen.go       |  6 ++++++
 pkg/compiler/compiler.go      | 11 ++++++++++-
 pkg/compiler/compiler_test.go | 22 ++++++++++++++++++++++
 pkg/compiler/inline.go        | 16 +++++++++++++++-
 4 files changed, 53 insertions(+), 2 deletions(-)

diff --git a/pkg/compiler/codegen.go b/pkg/compiler/codegen.go
index 5fd993f01..921c8008b 100644
--- a/pkg/compiler/codegen.go
+++ b/pkg/compiler/codegen.go
@@ -337,6 +337,12 @@ func isInitFunc(decl *ast.FuncDecl) bool {
 		decl.Type.Results.NumFields() == 0
 }
 
+func (c *codegen) isVerifyFunc(decl *ast.FuncDecl) bool {
+	return decl.Name.Name == "Verify" && decl.Recv == nil &&
+		decl.Type.Results.NumFields() == 1 &&
+		isBool(c.typeOf(decl.Type.Results.List[0].Type))
+}
+
 func (c *codegen) clearSlots(n int) {
 	for i := 0; i < n; i++ {
 		emit.Opcodes(c.prog.BinWriter, opcode.PUSHNULL)
diff --git a/pkg/compiler/compiler.go b/pkg/compiler/compiler.go
index 0545c716e..867e70021 100644
--- a/pkg/compiler/compiler.go
+++ b/pkg/compiler/compiler.go
@@ -59,6 +59,7 @@ type Options struct {
 type buildInfo struct {
 	initialPackage string
 	program        *loader.Program
+	options        *Options
 }
 
 // ForEachPackage executes fn on each package used in the current program
@@ -153,10 +154,18 @@ func Compile(name string, r io.Reader) ([]byte, error) {
 
 // CompileWithDebugInfo compiles a Go program into bytecode and emits debug info.
 func CompileWithDebugInfo(name string, r io.Reader) ([]byte, *DebugInfo, error) {
+	return CompileWithOptions(name, r, &Options{
+		NoEventsCheck: true,
+	})
+}
+
+// CompileWithOptions compiles a Go program into bytecode with provided compiler options.
+func CompileWithOptions(name string, r io.Reader, o *Options) ([]byte, *DebugInfo, error) {
 	ctx, err := getBuildInfo(name, r)
 	if err != nil {
 		return nil, nil, err
 	}
+	ctx.options = o
 	return CodeGen(ctx)
 }
 
@@ -173,7 +182,7 @@ func CompileAndSave(src string, o *Options) ([]byte, error) {
 	if len(o.Ext) == 0 {
 		o.Ext = fileExt
 	}
-	b, di, err := CompileWithDebugInfo(src, nil)
+	b, di, err := CompileWithOptions(src, nil, o)
 	if err != nil {
 		return nil, fmt.Errorf("error while trying to compile smart contract file: %w", err)
 	}
diff --git a/pkg/compiler/compiler_test.go b/pkg/compiler/compiler_test.go
index d77a26012..eb18a1b1e 100644
--- a/pkg/compiler/compiler_test.go
+++ b/pkg/compiler/compiler_test.go
@@ -1,6 +1,7 @@
 package compiler_test
 
 import (
+	"fmt"
 	"io/ioutil"
 	"os"
 	"path"
@@ -175,3 +176,24 @@ func TestEventWarnings(t *testing.T) {
 		require.NoError(t, err)
 	})
 }
+
+func TestNotifyInVerify(t *testing.T) {
+	srcTmpl := `package payable
+		import "github.com/nspcc-dev/neo-go/pkg/interop/runtime"
+		func Verify() bool { runtime.%s("Event"); return true }`
+
+	for _, name := range []string{"Notify", "Log"} {
+		t.Run(name, func(t *testing.T) {
+			src := fmt.Sprintf(srcTmpl, name)
+			_, _, err := compiler.CompileWithOptions("eventTest", strings.NewReader(src),
+				&compiler.Options{ContractEvents: []manifest.Event{{Name: "Event"}}})
+			require.Error(t, err)
+
+			t.Run("suppress", func(t *testing.T) {
+				_, _, err := compiler.CompileWithOptions("eventTest", strings.NewReader(src),
+					&compiler.Options{NoEventsCheck: true})
+				require.NoError(t, err)
+			})
+		})
+	}
+}
diff --git a/pkg/compiler/inline.go b/pkg/compiler/inline.go
index 6c5b676ce..f578888cb 100644
--- a/pkg/compiler/inline.go
+++ b/pkg/compiler/inline.go
@@ -121,7 +121,21 @@ func (c *codegen) inlineCall(f *funcScope, n *ast.CallExpr) {
 }
 
 func (c *codegen) processNotify(f *funcScope, args []ast.Expr) {
-	if f != nil && f.pkg.Path() == interopPrefix+"/runtime" && f.name == "Notify" {
+	if f != nil && f.pkg.Path() == interopPrefix+"/runtime" {
+		if f.name != "Notify" && f.name != "Log" {
+			return
+		}
+
+		if c.scope != nil && c.isVerifyFunc(c.scope.decl) &&
+			c.scope.pkg == c.mainPkg.Pkg && !c.buildInfo.options.NoEventsCheck {
+			c.prog.Err = fmt.Errorf("runtime.%s is not allowed in `Verify`", f.name)
+			return
+		}
+
+		if f.name == "Log" {
+			return
+		}
+
 		// Sometimes event name is stored in a var.
 		// Skip in this case.
 		tv := c.typeAndValueOf(args[0])