feat(sdk/vm): disallow calling internal realms (#3794)

continuation of #3774, fixes #2190.

gno.land/pkg/sdk/vm/msgs.go

@@ -120,6 +120,9 @@ func (msg MsgCall) ValidateBasic() error {
 	if !gno.IsRealmPath(msg.PkgPath) {
 		return ErrInvalidPkgPath("pkgpath must be of a realm")
 	}
+	if _, isInt := gno.IsInternalPath(msg.PkgPath); isInt {
+		return ErrInvalidPkgPath("pkgpath must not be of an internal package")
+	}
 	if msg.Func == "" { // XXX
 		return ErrInvalidExpr("missing function to call")
 	}

gno.land/pkg/sdk/vm/msg_test.go → gno.land/pkg/sdk/vm/msgs_test.go

@@ -164,6 +164,20 @@ func TestMsgCall_ValidateBasic(t *testing.T) {
 			},
 			expectErr: InvalidPkgPathError{},
 		},
+		{
+			name: "pkgPath should not be an internal path",
+			msg: MsgCall{
+				Caller:  caller,
+				PkgPath: "gno.land/r/demo/avl/internal/sort",
+				Func:    funcName,
+				Args:    args,
+				Send: std.Coins{std.Coin{
+					Denom:  "ugnot",
+					Amount: 1000,
+				}},
+			},
+			expectErr: InvalidPkgPathError{},
+		},
 		{
 			name: "missing function name to call",
 			msg: MsgCall{

gnovm/pkg/gnolang/helpers.go

@@ -28,6 +28,22 @@ func IsRealmPath(pkgPath string) bool {
 		!ReGnoRunPath.MatchString(pkgPath)
 }
 
+// IsInternalPath determines whether the given pkgPath refers to an internal
+// package, that may not be called directly or imported by packages that don't
+// share the same root.
+//
+// If isInternal is true, base will be set to the root of the internal package,
+// which must also be an ancestor or the same path that imports the given
+// internal package.
+func IsInternalPath(pkgPath string) (base string, isInternal bool) {
+	// Restrict imports to /internal packages to a package rooted at base.
+	var suff string
+	base, suff, isInternal = strings.Cut(pkgPath, "/internal")
+	// /internal should be either at the end, or be a part: /internal/
+	isInternal = isInternal && (suff == "" || suff[0] == '/')
+	return
+}
+
 // IsPurePackagePath determines whether the given pkgpath is for a published Gno package.
 // It only considers "pure" those starting with gno.land/p/, so it returns false for
 // stdlib packages and MsgRun paths.

gnovm/pkg/gnolang/preprocess.go

@@ -4822,10 +4822,7 @@ func tryPredefine(store Store, pkg *PackageNode, last BlockNode, d Decl) (un Nam
 			panic("cannot import stdlib internal/ package outside of standard library")
 		}
 
-		// Restrict imports to /internal packages to a package rooted at base.
-		base, suff, isInternal := strings.Cut(d.PkgPath, "/internal")
-		// /internal should be either at the end, or be a part: /internal/
-		isInternal = isInternal && (suff == "" || suff[0] == '/')
+		base, isInternal := IsInternalPath(d.PkgPath)
 		if isInternal &&
 			pkg.PkgPath != base &&
 			!strings.HasPrefix(pkg.PkgPath, base+"/") {