package vm import ( "crypto/elliptic" "encoding/binary" "encoding/json" "errors" "fmt" "io" "io/ioutil" "math" "math/big" "os" "text/tabwriter" "unicode/utf8" "github.com/nspcc-dev/neo-go/pkg/core/interop/interopnames" "github.com/nspcc-dev/neo-go/pkg/crypto/keys" "github.com/nspcc-dev/neo-go/pkg/encoding/bigint" "github.com/nspcc-dev/neo-go/pkg/smartcontract/callflag" "github.com/nspcc-dev/neo-go/pkg/smartcontract/nef" "github.com/nspcc-dev/neo-go/pkg/smartcontract/trigger" "github.com/nspcc-dev/neo-go/pkg/util" "github.com/nspcc-dev/neo-go/pkg/vm/opcode" "github.com/nspcc-dev/neo-go/pkg/vm/stackitem" ) type errorAtInstruct struct { ip int op opcode.Opcode err interface{} } func (e *errorAtInstruct) Error() string { return fmt.Sprintf("error encountered at instruction %d (%s): %s", e.ip, e.op, e.err) } func newError(ip int, op opcode.Opcode, err interface{}) *errorAtInstruct { return &errorAtInstruct{ip: ip, op: op, err: err} } // StateMessage is a vm state message which could be used as additional info for example by cli. type StateMessage string const ( // MaxInvocationStackSize is the maximum size of an invocation stack. MaxInvocationStackSize = 1024 // MaxTryNestingDepth is the maximum level of TRY nesting allowed, // that is you can't have more exception handling contexts than this. MaxTryNestingDepth = 16 // MaxStackSize is the maximum number of items allowed to be // on all stacks at once. MaxStackSize = 2 * 1024 maxSHLArg = stackitem.MaxBigIntegerSizeBits ) // SyscallHandler is a type for syscall handler. type SyscallHandler = func(*VM, uint32) error // VM represents the virtual machine. type VM struct { state State // callback to get interop price getPrice func(opcode.Opcode, []byte) int64 istack *Stack // invocation stack. estack *Stack // execution stack. uncaughtException stackitem.Item // exception being handled refs *refCounter gasConsumed int64 GasLimit int64 // SyscallHandler handles SYSCALL opcode. SyscallHandler func(v *VM, id uint32) error // LoadToken handles CALLT opcode. LoadToken func(id int32) error trigger trigger.Type // Invocations is a script invocation counter. Invocations map[util.Uint160]int } // New returns a new VM object ready to load AVM bytecode scripts. func New() *VM { return NewWithTrigger(trigger.Application) } // NewWithTrigger returns a new VM for executions triggered by t. func NewWithTrigger(t trigger.Type) *VM { vm := &VM{ state: NoneState, istack: NewStack("invocation"), refs: newRefCounter(), trigger: t, SyscallHandler: defaultSyscallHandler, Invocations: make(map[util.Uint160]int), } vm.estack = vm.newItemStack("evaluation") return vm } func (v *VM) newItemStack(n string) *Stack { s := NewStack(n) s.refs = v.refs return s } // SetPriceGetter registers the given PriceGetterFunc in v. // f accepts vm's Context, current instruction and instruction parameter. func (v *VM) SetPriceGetter(f func(opcode.Opcode, []byte) int64) { v.getPrice = f } // GasConsumed returns the amount of GAS consumed during execution. func (v *VM) GasConsumed() int64 { return v.gasConsumed } // AddGas consumes specified amount of gas. It returns true iff gas limit wasn't exceeded. func (v *VM) AddGas(gas int64) bool { v.gasConsumed += gas return v.GasLimit < 0 || v.gasConsumed <= v.GasLimit } // Estack returns the evaluation stack so interop hooks can utilize this. func (v *VM) Estack() *Stack { return v.estack } // Istack returns the invocation stack so interop hooks can utilize this. func (v *VM) Istack() *Stack { return v.istack } // LoadArgs loads in the arguments used in the Mian entry point. func (v *VM) LoadArgs(method []byte, args []stackitem.Item) { if len(args) > 0 { v.estack.PushVal(args) } if method != nil { v.estack.PushVal(method) } } // PrintOps prints the opcodes of the current loaded program to stdout. func (v *VM) PrintOps(out io.Writer) { if out == nil { out = os.Stdout } w := tabwriter.NewWriter(out, 0, 0, 4, ' ', 0) fmt.Fprintln(w, "INDEX\tOPCODE\tPARAMETER\t") realctx := v.Context() ctx := realctx.Copy() ctx.ip = 0 ctx.nextip = 0 for { cursor := "" instr, parameter, err := ctx.Next() if ctx.ip == realctx.ip { cursor = "<<" } if err != nil { fmt.Fprintf(w, "%d\t%s\tERROR: %s\t%s\n", ctx.ip, instr, err, cursor) break } var desc = "" if parameter != nil { switch instr { case opcode.JMP, opcode.JMPIF, opcode.JMPIFNOT, opcode.CALL, opcode.JMPEQ, opcode.JMPNE, opcode.JMPGT, opcode.JMPGE, opcode.JMPLE, opcode.JMPLT, opcode.JMPL, opcode.JMPIFL, opcode.JMPIFNOTL, opcode.CALLL, opcode.JMPEQL, opcode.JMPNEL, opcode.JMPGTL, opcode.JMPGEL, opcode.JMPLEL, opcode.JMPLTL, opcode.PUSHA, opcode.ENDTRY, opcode.ENDTRYL: desc = getOffsetDesc(ctx, parameter) case opcode.TRY, opcode.TRYL: catchP, finallyP := getTryParams(instr, parameter) desc = fmt.Sprintf("catch %s, finally %s", getOffsetDesc(ctx, catchP), getOffsetDesc(ctx, finallyP)) case opcode.INITSSLOT: desc = fmt.Sprint(parameter[0]) case opcode.CONVERT, opcode.ISTYPE: typ := stackitem.Type(parameter[0]) desc = fmt.Sprintf("%s (%x)", typ, parameter[0]) case opcode.INITSLOT: desc = fmt.Sprintf("%d local, %d arg", parameter[0], parameter[1]) case opcode.SYSCALL: name, err := interopnames.FromID(GetInteropID(parameter)) if err != nil { name = "not found" } desc = fmt.Sprintf("%s (%x)", name, parameter) case opcode.PUSHINT8, opcode.PUSHINT16, opcode.PUSHINT32, opcode.PUSHINT64, opcode.PUSHINT128, opcode.PUSHINT256: val := bigint.FromBytes(parameter) desc = fmt.Sprintf("%d (%x)", val, parameter) case opcode.LDLOC, opcode.STLOC, opcode.LDARG, opcode.STARG, opcode.LDSFLD, opcode.STSFLD: desc = fmt.Sprintf("%d (%x)", parameter[0], parameter) default: if utf8.Valid(parameter) { desc = fmt.Sprintf("%x (%q)", parameter, parameter) } else { desc = fmt.Sprintf("%x", parameter) } } } fmt.Fprintf(w, "%d\t%s\t%s\t%s\n", ctx.ip, instr, desc, cursor) if ctx.nextip >= len(ctx.prog) { break } } w.Flush() } func getOffsetDesc(ctx *Context, parameter []byte) string { offset, rOffset, err := calcJumpOffset(ctx, parameter) if err != nil { return fmt.Sprintf("ERROR: %v", err) } return fmt.Sprintf("%d (%d/%x)", offset, rOffset, parameter) } // AddBreakPoint adds a breakpoint to the current context. func (v *VM) AddBreakPoint(n int) { ctx := v.Context() ctx.breakPoints = append(ctx.breakPoints, n) } // AddBreakPointRel adds a breakpoint relative to the current // instruction pointer. func (v *VM) AddBreakPointRel(n int) { ctx := v.Context() v.AddBreakPoint(ctx.nextip + n) } // LoadFileWithFlags loads a program in NEF format from the given path, ready to execute it. func (v *VM) LoadFileWithFlags(path string, f callflag.CallFlag) error { b, err := ioutil.ReadFile(path) if err != nil { return err } nef, err := nef.FileFromBytes(b) if err != nil { return err } v.Load(nef.Script) return nil } // Load initializes the VM with the program given. func (v *VM) Load(prog []byte) { v.LoadWithFlags(prog, callflag.NoneFlag) } // LoadWithFlags initializes the VM with the program and flags given. func (v *VM) LoadWithFlags(prog []byte, f callflag.CallFlag) { // Clear all stacks and state, it could be a reload. v.istack.Clear() v.estack.Clear() v.state = NoneState v.gasConsumed = 0 v.LoadScriptWithFlags(prog, f) } // LoadScript loads a script from the internal script table. It // will immediately push a new context created from this script to // the invocation stack and starts executing it. func (v *VM) LoadScript(b []byte) { v.LoadScriptWithFlags(b, callflag.NoneFlag) } // LoadScriptWithFlags loads script and sets call flag to f. func (v *VM) LoadScriptWithFlags(b []byte, f callflag.CallFlag) { v.checkInvocationStackSize() ctx := NewContextWithParams(b, 0, -1, 0) v.estack = v.newItemStack("estack") ctx.estack = v.estack ctx.tryStack = NewStack("exception") ctx.callFlag = f ctx.static = newSlot(v.refs) ctx.callingScriptHash = v.GetCurrentScriptHash() v.istack.PushVal(ctx) } // LoadScriptWithHash if similar to the LoadScriptWithFlags method, but it also loads // given script hash directly into the Context to avoid its recalculations and to make // is possible to override it for deployed contracts with special hashes (the function // assumes that it is used for deployed contracts setting context's parameters // accordingly). It's up to user of this function to make sure the script and hash match // each other. func (v *VM) LoadScriptWithHash(b []byte, hash util.Uint160, f callflag.CallFlag) { shash := v.GetCurrentScriptHash() v.LoadScriptWithCallingHash(shash, b, hash, f, true, 0) } // LoadScriptWithCallingHash is similar to LoadScriptWithHash but sets calling hash explicitly. // It should be used for calling from native contracts. func (v *VM) LoadScriptWithCallingHash(caller util.Uint160, b []byte, hash util.Uint160, f callflag.CallFlag, hasReturn bool, paramCount uint16) { v.LoadScriptWithFlags(b, f) ctx := v.Context() ctx.scriptHash = hash ctx.callingScriptHash = caller if hasReturn { ctx.RetCount = 1 } else { ctx.RetCount = 0 } ctx.ParamCount = int(paramCount) } // Context returns the current executed context. Nil if there is no context, // which implies no program is loaded. func (v *VM) Context() *Context { if v.istack.Len() == 0 { return nil } return v.istack.Peek(0).Value().(*Context) } // PopResult is used to pop the first item of the evaluation stack. This allows // us to test compiler and vm in a bi-directional way. func (v *VM) PopResult() interface{} { e := v.estack.Pop() if e != nil { return e.Value() } return nil } // Stack returns json formatted representation of the given stack. func (v *VM) Stack(n string) string { var s *Stack if n == "istack" { s = v.istack } if n == "estack" { s = v.estack } b, _ := json.MarshalIndent(s, "", " ") return string(b) } // State returns the state for the VM. func (v *VM) State() State { return v.state } // Ready returns true if the VM ready to execute the loaded program. // Will return false if no program is loaded. func (v *VM) Ready() bool { return v.istack.Len() > 0 } // Run starts the execution of the loaded program. func (v *VM) Run() error { if !v.Ready() { v.state = FaultState return errors.New("no program loaded") } if v.state.HasFlag(FaultState) { // VM already ran something and failed, in general its state is // undefined in this case so we can't run anything. return errors.New("VM has failed") } // HaltState (the default) or BreakState are safe to continue. v.state = NoneState for { switch { case v.state.HasFlag(FaultState): // Should be caught and reported already by the v.Step(), // but we're checking here anyway just in case. return errors.New("VM has failed") case v.state.HasFlag(HaltState), v.state.HasFlag(BreakState): // Normal exit from this loop. return nil case v.state == NoneState: if err := v.Step(); err != nil { return err } default: v.state = FaultState return errors.New("unknown state") } // check for breakpoint before executing the next instruction ctx := v.Context() if ctx != nil && ctx.atBreakPoint() { v.state = BreakState } } } // Step 1 instruction in the program. func (v *VM) Step() error { ctx := v.Context() op, param, err := ctx.Next() if err != nil { v.state = FaultState return newError(ctx.ip, op, err) } return v.execute(ctx, op, param) } // StepInto behaves the same as “step over” in case if the line does not contain a function. Otherwise // the debugger will enter the called function and continue line-by-line debugging there. func (v *VM) StepInto() error { ctx := v.Context() if ctx == nil { v.state = HaltState } if v.HasStopped() { return nil } if ctx != nil && ctx.prog != nil { op, param, err := ctx.Next() if err != nil { v.state = FaultState return newError(ctx.ip, op, err) } vErr := v.execute(ctx, op, param) if vErr != nil { return vErr } } cctx := v.Context() if cctx != nil && cctx.atBreakPoint() { v.state = BreakState } return nil } // StepOut takes the debugger to the line where the current function was called. func (v *VM) StepOut() error { var err error if v.state == BreakState { v.state = NoneState } expSize := v.istack.len for v.state == NoneState && v.istack.len >= expSize { err = v.StepInto() } if v.state == NoneState { v.state = BreakState } return err } // StepOver takes the debugger to the line that will step over a given line. // If the line contains a function the function will be executed and the result returned without debugging each line. func (v *VM) StepOver() error { var err error if v.HasStopped() { return err } if v.state == BreakState { v.state = NoneState } expSize := v.istack.len for { err = v.StepInto() if !(v.state == NoneState && v.istack.len > expSize) { break } } if v.state == NoneState { v.state = BreakState } return err } // HasFailed returns whether VM is in the failed state now. Usually used to // check status after Run. func (v *VM) HasFailed() bool { return v.state.HasFlag(FaultState) } // HasStopped returns whether VM is in Halt or Failed state. func (v *VM) HasStopped() bool { return v.state.HasFlag(HaltState) || v.state.HasFlag(FaultState) } // HasHalted returns whether VM is in Halt state. func (v *VM) HasHalted() bool { return v.state.HasFlag(HaltState) } // AtBreakpoint returns whether VM is at breakpoint. func (v *VM) AtBreakpoint() bool { return v.state.HasFlag(BreakState) } // GetInteropID converts instruction parameter to an interop ID. func GetInteropID(parameter []byte) uint32 { return binary.LittleEndian.Uint32(parameter) } // execute performs an instruction cycle in the VM. Acting on the instruction (opcode). func (v *VM) execute(ctx *Context, op opcode.Opcode, parameter []byte) (err error) { // Instead of polluting the whole VM logic with error handling, we will recover // each panic at a central point, putting the VM in a fault state and setting error. defer func() { if errRecover := recover(); errRecover != nil { v.state = FaultState err = newError(ctx.ip, op, errRecover) } else if v.refs.size > MaxStackSize { v.state = FaultState err = newError(ctx.ip, op, "stack is too big") } }() if v.getPrice != nil && ctx.ip < len(ctx.prog) { v.gasConsumed += v.getPrice(op, parameter) if v.GasLimit >= 0 && v.gasConsumed > v.GasLimit { panic("gas limit is exceeded") } } if op <= opcode.PUSHINT256 { v.estack.PushVal(bigint.FromBytes(parameter)) return } switch op { case opcode.PUSHM1, opcode.PUSH0, opcode.PUSH1, opcode.PUSH2, opcode.PUSH3, opcode.PUSH4, opcode.PUSH5, opcode.PUSH6, opcode.PUSH7, opcode.PUSH8, opcode.PUSH9, opcode.PUSH10, opcode.PUSH11, opcode.PUSH12, opcode.PUSH13, opcode.PUSH14, opcode.PUSH15, opcode.PUSH16: val := int(op) - int(opcode.PUSH0) v.estack.PushVal(val) case opcode.PUSHDATA1, opcode.PUSHDATA2, opcode.PUSHDATA4: v.estack.PushVal(parameter) case opcode.PUSHA: n := getJumpOffset(ctx, parameter) ptr := stackitem.NewPointerWithHash(n, ctx.prog, ctx.ScriptHash()) v.estack.PushVal(ptr) case opcode.PUSHNULL: v.estack.PushVal(stackitem.Null{}) case opcode.ISNULL: _, ok := v.estack.Pop().value.(stackitem.Null) v.estack.PushVal(ok) case opcode.ISTYPE: res := v.estack.Pop().Item() v.estack.PushVal(res.Type() == stackitem.Type(parameter[0])) case opcode.CONVERT: typ := stackitem.Type(parameter[0]) item := v.estack.Pop().Item() result, err := item.Convert(typ) if err != nil { panic(err) } v.estack.PushVal(result) case opcode.INITSSLOT: if parameter[0] == 0 { panic("zero argument") } ctx.static.init(int(parameter[0])) case opcode.INITSLOT: if ctx.local != nil || ctx.arguments != nil { panic("already initialized") } if parameter[0] == 0 && parameter[1] == 0 { panic("zero argument") } if parameter[0] > 0 { ctx.local = v.newSlot(int(parameter[0])) } if parameter[1] > 0 { sz := int(parameter[1]) ctx.arguments = v.newSlot(sz) for i := 0; i < sz; i++ { ctx.arguments.Set(i, v.estack.Pop().Item()) } } case opcode.LDSFLD0, opcode.LDSFLD1, opcode.LDSFLD2, opcode.LDSFLD3, opcode.LDSFLD4, opcode.LDSFLD5, opcode.LDSFLD6: item := ctx.static.Get(int(op - opcode.LDSFLD0)) v.estack.PushVal(item) case opcode.LDSFLD: item := ctx.static.Get(int(parameter[0])) v.estack.PushVal(item) case opcode.STSFLD0, opcode.STSFLD1, opcode.STSFLD2, opcode.STSFLD3, opcode.STSFLD4, opcode.STSFLD5, opcode.STSFLD6: item := v.estack.Pop().Item() ctx.static.Set(int(op-opcode.STSFLD0), item) case opcode.STSFLD: item := v.estack.Pop().Item() ctx.static.Set(int(parameter[0]), item) case opcode.LDLOC0, opcode.LDLOC1, opcode.LDLOC2, opcode.LDLOC3, opcode.LDLOC4, opcode.LDLOC5, opcode.LDLOC6: item := ctx.local.Get(int(op - opcode.LDLOC0)) v.estack.PushVal(item) case opcode.LDLOC: item := ctx.local.Get(int(parameter[0])) v.estack.PushVal(item) case opcode.STLOC0, opcode.STLOC1, opcode.STLOC2, opcode.STLOC3, opcode.STLOC4, opcode.STLOC5, opcode.STLOC6: item := v.estack.Pop().Item() ctx.local.Set(int(op-opcode.STLOC0), item) case opcode.STLOC: item := v.estack.Pop().Item() ctx.local.Set(int(parameter[0]), item) case opcode.LDARG0, opcode.LDARG1, opcode.LDARG2, opcode.LDARG3, opcode.LDARG4, opcode.LDARG5, opcode.LDARG6: item := ctx.arguments.Get(int(op - opcode.LDARG0)) v.estack.PushVal(item) case opcode.LDARG: item := ctx.arguments.Get(int(parameter[0])) v.estack.PushVal(item) case opcode.STARG0, opcode.STARG1, opcode.STARG2, opcode.STARG3, opcode.STARG4, opcode.STARG5, opcode.STARG6: item := v.estack.Pop().Item() ctx.arguments.Set(int(op-opcode.STARG0), item) case opcode.STARG: item := v.estack.Pop().Item() ctx.arguments.Set(int(parameter[0]), item) case opcode.NEWBUFFER: n := toInt(v.estack.Pop().BigInt()) if n < 0 || n > stackitem.MaxSize { panic("invalid size") } v.estack.PushVal(stackitem.NewBuffer(make([]byte, n))) case opcode.MEMCPY: n := toInt(v.estack.Pop().BigInt()) if n < 0 { panic("invalid size") } si := toInt(v.estack.Pop().BigInt()) if si < 0 { panic("invalid source index") } src := v.estack.Pop().Bytes() if sum := si + n; sum < 0 || sum > len(src) { panic("size is too big") } di := toInt(v.estack.Pop().BigInt()) if di < 0 { panic("invalid destination index") } dst := v.estack.Pop().value.(*stackitem.Buffer).Value().([]byte) if sum := di + n; sum < 0 || sum > len(dst) { panic("size is too big") } copy(dst[di:], src[si:si+n]) case opcode.CAT: b := v.estack.Pop().Bytes() a := v.estack.Pop().Bytes() l := len(a) + len(b) if l > stackitem.MaxSize { panic(fmt.Sprintf("too big item: %d", l)) } ab := make([]byte, l) copy(ab, a) copy(ab[len(a):], b) v.estack.PushVal(stackitem.NewBuffer(ab)) case opcode.SUBSTR: l := int(v.estack.Pop().BigInt().Int64()) if l < 0 { panic("negative length") } o := int(v.estack.Pop().BigInt().Int64()) if o < 0 { panic("negative index") } s := v.estack.Pop().Bytes() last := l + o if last > len(s) { panic("invalid offset") } res := make([]byte, l) copy(res, s[o:last]) v.estack.PushVal(stackitem.NewBuffer(res)) case opcode.LEFT: l := int(v.estack.Pop().BigInt().Int64()) if l < 0 { panic("negative length") } s := v.estack.Pop().Bytes() if t := len(s); l > t { panic("size is too big") } res := make([]byte, l) copy(res, s[:l]) v.estack.PushVal(stackitem.NewBuffer(res)) case opcode.RIGHT: l := int(v.estack.Pop().BigInt().Int64()) if l < 0 { panic("negative length") } s := v.estack.Pop().Bytes() res := make([]byte, l) copy(res, s[len(s)-l:]) v.estack.PushVal(stackitem.NewBuffer(res)) case opcode.DEPTH: v.estack.PushVal(v.estack.Len()) case opcode.DROP: if v.estack.Len() < 1 { panic("stack is too small") } v.estack.Pop() case opcode.NIP: elem := v.estack.RemoveAt(1) if elem == nil { panic("no second element found") } case opcode.XDROP: n := int(v.estack.Pop().BigInt().Int64()) if n < 0 { panic("invalid length") } e := v.estack.RemoveAt(n) if e == nil { panic("bad index") } case opcode.CLEAR: v.estack.Clear() case opcode.DUP: v.estack.Push(v.estack.Dup(0)) case opcode.OVER: a := v.estack.Dup(1) if a == nil { panic("no second element found") } v.estack.Push(a) case opcode.PICK: n := int(v.estack.Pop().BigInt().Int64()) if n < 0 { panic("negative stack item returned") } a := v.estack.Dup(n) if a == nil { panic("no nth element found") } v.estack.Push(a) case opcode.TUCK: a := v.estack.Dup(0) if a == nil { panic("no top-level element found") } if v.estack.Len() < 2 { panic("can't TUCK with a one-element stack") } v.estack.InsertAt(a, 2) case opcode.SWAP: err := v.estack.Swap(1, 0) if err != nil { panic(err.Error()) } case opcode.ROT: err := v.estack.Roll(2) if err != nil { panic(err.Error()) } case opcode.ROLL: n := int(v.estack.Pop().BigInt().Int64()) err := v.estack.Roll(n) if err != nil { panic(err.Error()) } case opcode.REVERSE3, opcode.REVERSE4, opcode.REVERSEN: n := 3 switch op { case opcode.REVERSE4: n = 4 case opcode.REVERSEN: n = int(v.estack.Pop().BigInt().Int64()) } if err := v.estack.ReverseTop(n); err != nil { panic(err.Error()) } // Bit operations. case opcode.INVERT: // inplace e := v.estack.Peek(0) i := e.BigInt() e.value = stackitem.Make(i.Not(i)) case opcode.AND: b := v.estack.Pop().BigInt() a := v.estack.Pop().BigInt() v.estack.PushVal(new(big.Int).And(b, a)) case opcode.OR: b := v.estack.Pop().BigInt() a := v.estack.Pop().BigInt() v.estack.PushVal(new(big.Int).Or(b, a)) case opcode.XOR: b := v.estack.Pop().BigInt() a := v.estack.Pop().BigInt() v.estack.PushVal(new(big.Int).Xor(b, a)) case opcode.EQUAL, opcode.NOTEQUAL: b := v.estack.Pop() if b == nil { panic("no top-level element found") } a := v.estack.Pop() if a == nil { panic("no second-to-the-top element found") } v.estack.PushVal(a.value.Equals(b.value) == (op == opcode.EQUAL)) // Numeric operations. case opcode.SIGN: x := v.estack.Pop().BigInt() v.estack.PushVal(x.Sign()) case opcode.ABS: x := v.estack.Pop().BigInt() v.estack.PushVal(x.Abs(x)) case opcode.NEGATE: x := v.estack.Pop().BigInt() v.estack.PushVal(x.Neg(x)) case opcode.INC: x := v.estack.Pop().BigInt() a := new(big.Int).Add(x, big.NewInt(1)) v.estack.PushVal(a) case opcode.DEC: x := v.estack.Pop().BigInt() a := new(big.Int).Sub(x, big.NewInt(1)) v.estack.PushVal(a) case opcode.ADD: a := v.estack.Pop().BigInt() b := v.estack.Pop().BigInt() c := new(big.Int).Add(a, b) v.estack.PushVal(c) case opcode.SUB: b := v.estack.Pop().BigInt() a := v.estack.Pop().BigInt() c := new(big.Int).Sub(a, b) v.estack.PushVal(c) case opcode.MUL: a := v.estack.Pop().BigInt() b := v.estack.Pop().BigInt() c := new(big.Int).Mul(a, b) v.estack.PushVal(c) case opcode.DIV: b := v.estack.Pop().BigInt() a := v.estack.Pop().BigInt() v.estack.PushVal(new(big.Int).Quo(a, b)) case opcode.MOD: b := v.estack.Pop().BigInt() a := v.estack.Pop().BigInt() v.estack.PushVal(new(big.Int).Rem(a, b)) case opcode.POW: exp := v.estack.Pop().BigInt() a := v.estack.Pop().BigInt() if ei := exp.Int64(); !exp.IsInt64() || ei > math.MaxInt32 || ei < 0 { panic("invalid exponent") } v.estack.PushVal(new(big.Int).Exp(a, exp, nil)) case opcode.SQRT: a := v.estack.Pop().BigInt() if a.Sign() == -1 { panic("negative value") } v.estack.PushVal(new(big.Int).Sqrt(a)) case opcode.SHL, opcode.SHR: b := v.estack.Pop().BigInt().Int64() if b == 0 { return } else if b < 0 || b > maxSHLArg { panic(fmt.Sprintf("operand must be between %d and %d", 0, maxSHLArg)) } a := v.estack.Pop().BigInt() var item big.Int if op == opcode.SHL { item.Lsh(a, uint(b)) } else { item.Rsh(a, uint(b)) } v.estack.PushVal(&item) case opcode.NOT: x := v.estack.Pop().Bool() v.estack.PushVal(!x) case opcode.BOOLAND: b := v.estack.Pop().Bool() a := v.estack.Pop().Bool() v.estack.PushVal(a && b) case opcode.BOOLOR: b := v.estack.Pop().Bool() a := v.estack.Pop().Bool() v.estack.PushVal(a || b) case opcode.NZ: x := v.estack.Pop().BigInt() v.estack.PushVal(x.Sign() != 0) case opcode.NUMEQUAL: b := v.estack.Pop().BigInt() a := v.estack.Pop().BigInt() v.estack.PushVal(a.Cmp(b) == 0) case opcode.NUMNOTEQUAL: b := v.estack.Pop().BigInt() a := v.estack.Pop().BigInt() v.estack.PushVal(a.Cmp(b) != 0) case opcode.LT, opcode.LE, opcode.GT, opcode.GE: eb := v.estack.Pop() ea := v.estack.Pop() _, aNil := ea.Item().(stackitem.Null) _, bNil := eb.Item().(stackitem.Null) res := !aNil && !bNil if res { cmp := ea.BigInt().Cmp(eb.BigInt()) switch op { case opcode.LT: res = cmp == -1 case opcode.LE: res = cmp <= 0 case opcode.GT: res = cmp == 1 case opcode.GE: res = cmp >= 0 } } v.estack.PushVal(res) case opcode.MIN: b := v.estack.Pop().BigInt() a := v.estack.Pop().BigInt() val := a if a.Cmp(b) == 1 { val = b } v.estack.PushVal(val) case opcode.MAX: b := v.estack.Pop().BigInt() a := v.estack.Pop().BigInt() val := a if a.Cmp(b) == -1 { val = b } v.estack.PushVal(val) case opcode.WITHIN: b := v.estack.Pop().BigInt() a := v.estack.Pop().BigInt() x := v.estack.Pop().BigInt() v.estack.PushVal(a.Cmp(x) <= 0 && x.Cmp(b) == -1) // Object operations case opcode.NEWARRAY0: v.estack.PushVal(stackitem.NewArray([]stackitem.Item{})) case opcode.NEWARRAY, opcode.NEWARRAYT: item := v.estack.Pop() n := item.BigInt().Int64() if n > stackitem.MaxArraySize { panic("too long array") } typ := stackitem.AnyT if op == opcode.NEWARRAYT { typ = stackitem.Type(parameter[0]) } items := makeArrayOfType(int(n), typ) v.estack.PushVal(stackitem.NewArray(items)) case opcode.NEWSTRUCT0: v.estack.PushVal(stackitem.NewStruct([]stackitem.Item{})) case opcode.NEWSTRUCT: item := v.estack.Pop() n := item.BigInt().Int64() if n > stackitem.MaxArraySize { panic("too long struct") } items := makeArrayOfType(int(n), stackitem.AnyT) v.estack.PushVal(stackitem.NewStruct(items)) case opcode.APPEND: itemElem := v.estack.Pop() arrElem := v.estack.Pop() val := cloneIfStruct(itemElem.value) switch t := arrElem.value.(type) { case *stackitem.Array: if t.Len() >= stackitem.MaxArraySize { panic("too long array") } t.Append(val) case *stackitem.Struct: if t.Len() >= stackitem.MaxArraySize { panic("too long struct") } t.Append(val) default: panic("APPEND: not of underlying type Array") } v.refs.Add(val) case opcode.PACK: n := int(v.estack.Pop().BigInt().Int64()) if n < 0 || n > v.estack.Len() || n > stackitem.MaxArraySize { panic("OPACK: invalid length") } items := make([]stackitem.Item, n) for i := 0; i < n; i++ { items[i] = v.estack.Pop().value } v.estack.PushVal(items) case opcode.UNPACK: a := v.estack.Pop().Array() l := len(a) for i := l - 1; i >= 0; i-- { v.estack.PushVal(a[i]) } v.estack.PushVal(l) case opcode.PICKITEM: key := v.estack.Pop() validateMapKey(key) obj := v.estack.Pop() index := int(key.BigInt().Int64()) switch t := obj.value.(type) { // Struct and Array items have their underlying value as []Item. case *stackitem.Array, *stackitem.Struct: arr := t.Value().([]stackitem.Item) if index < 0 || index >= len(arr) { panic("PICKITEM: invalid index") } item := arr[index].Dup() v.estack.PushVal(item) case *stackitem.Map: index := t.Index(key.Item()) if index < 0 { panic("invalid key") } v.estack.Push(&Element{value: t.Value().([]stackitem.MapElement)[index].Value.Dup()}) default: arr := obj.Bytes() if index < 0 || index >= len(arr) { panic("PICKITEM: invalid index") } item := arr[index] v.estack.PushVal(int(item)) } case opcode.SETITEM: item := v.estack.Pop().value key := v.estack.Pop() validateMapKey(key) obj := v.estack.Pop() switch t := obj.value.(type) { // Struct and Array items have their underlying value as []Item. case *stackitem.Array, *stackitem.Struct: arr := t.Value().([]stackitem.Item) index := int(key.BigInt().Int64()) if index < 0 || index >= len(arr) { panic("SETITEM: invalid index") } v.refs.Remove(arr[index]) arr[index] = item v.refs.Add(arr[index]) case *stackitem.Map: if i := t.Index(key.value); i >= 0 { v.refs.Remove(t.Value().([]stackitem.MapElement)[i].Value) } else if t.Len() >= stackitem.MaxArraySize { panic("too big map") } t.Add(key.value, item) v.refs.Add(item) case *stackitem.Buffer: index := toInt(key.BigInt()) if index < 0 || index >= t.Len() { panic("invalid index") } bi, err := item.TryInteger() b := toInt(bi) if err != nil || b < math.MinInt8 || b > math.MaxUint8 { panic("invalid value") } t.Value().([]byte)[index] = byte(b) default: panic(fmt.Sprintf("SETITEM: invalid item type %s", t)) } case opcode.REVERSEITEMS: item := v.estack.Pop() switch t := item.value.(type) { case *stackitem.Array, *stackitem.Struct: a := t.Value().([]stackitem.Item) for i, j := 0, len(a)-1; i < j; i, j = i+1, j-1 { a[i], a[j] = a[j], a[i] } case *stackitem.Buffer: slice := t.Value().([]byte) for i, j := 0, t.Len()-1; i < j; i, j = i+1, j-1 { slice[i], slice[j] = slice[j], slice[i] } default: panic(fmt.Sprintf("invalid item type %s", t)) } case opcode.REMOVE: key := v.estack.Pop() validateMapKey(key) elem := v.estack.Pop() switch t := elem.value.(type) { case *stackitem.Array: a := t.Value().([]stackitem.Item) k := int(key.BigInt().Int64()) if k < 0 || k >= len(a) { panic("REMOVE: invalid index") } v.refs.Remove(a[k]) t.Remove(k) case *stackitem.Struct: a := t.Value().([]stackitem.Item) k := int(key.BigInt().Int64()) if k < 0 || k >= len(a) { panic("REMOVE: invalid index") } v.refs.Remove(a[k]) t.Remove(k) case *stackitem.Map: index := t.Index(key.Item()) // NEO 2.0 doesn't error on missing key. if index >= 0 { v.refs.Remove(t.Value().([]stackitem.MapElement)[index].Value) t.Drop(index) } default: panic("REMOVE: invalid type") } case opcode.CLEARITEMS: elem := v.estack.Pop() switch t := elem.value.(type) { case *stackitem.Array: for _, item := range t.Value().([]stackitem.Item) { v.refs.Remove(item) } t.Clear() case *stackitem.Struct: for _, item := range t.Value().([]stackitem.Item) { v.refs.Remove(item) } t.Clear() case *stackitem.Map: for i := range t.Value().([]stackitem.MapElement) { v.refs.Remove(t.Value().([]stackitem.MapElement)[i].Value) } t.Clear() default: panic("CLEARITEMS: invalid type") } case opcode.POPITEM: arr := v.estack.Pop().Item() elems := arr.Value().([]stackitem.Item) index := len(elems) - 1 elem := elems[index] switch item := arr.(type) { case *stackitem.Array: item.Remove(index) case *stackitem.Struct: item.Remove(index) } v.refs.Remove(elem) v.estack.PushVal(elem) case opcode.SIZE: elem := v.estack.Pop() // Cause there is no native (byte) item type here, hence we need to check // the type of the item for array size operations. switch t := elem.Value().(type) { case []stackitem.Item: v.estack.PushVal(len(t)) case []stackitem.MapElement: v.estack.PushVal(len(t)) default: v.estack.PushVal(len(elem.Bytes())) } case opcode.JMP, opcode.JMPL, opcode.JMPIF, opcode.JMPIFL, opcode.JMPIFNOT, opcode.JMPIFNOTL, opcode.JMPEQ, opcode.JMPEQL, opcode.JMPNE, opcode.JMPNEL, opcode.JMPGT, opcode.JMPGTL, opcode.JMPGE, opcode.JMPGEL, opcode.JMPLT, opcode.JMPLTL, opcode.JMPLE, opcode.JMPLEL: offset := getJumpOffset(ctx, parameter) cond := true switch op { case opcode.JMP, opcode.JMPL: case opcode.JMPIF, opcode.JMPIFL, opcode.JMPIFNOT, opcode.JMPIFNOTL: cond = v.estack.Pop().Bool() == (op == opcode.JMPIF || op == opcode.JMPIFL) default: b := v.estack.Pop().BigInt() a := v.estack.Pop().BigInt() cond = getJumpCondition(op, a, b) } if cond { v.Jump(ctx, offset) } case opcode.CALL, opcode.CALLL: // Note: jump offset must be calculated regarding to new context, // but it is cloned and thus has the same script and instruction pointer. v.call(ctx, getJumpOffset(ctx, parameter)) case opcode.CALLA: ptr := v.estack.Pop().Item().(*stackitem.Pointer) if ptr.ScriptHash() != ctx.ScriptHash() { panic("invalid script in pointer") } v.call(ctx, ptr.Position()) case opcode.CALLT: id := int32(binary.LittleEndian.Uint16(parameter)) if err := v.LoadToken(id); err != nil { panic(err) } case opcode.SYSCALL: interopID := GetInteropID(parameter) err := v.SyscallHandler(v, interopID) if err != nil { panic(fmt.Sprintf("failed to invoke syscall %d: %s", interopID, err)) } case opcode.RET: oldCtx := v.istack.Pop().Value().(*Context) oldEstack := v.estack v.unloadContext(oldCtx) if v.istack.Len() == 0 { v.state = HaltState break } newEstack := v.Context().estack if oldEstack != newEstack { if oldCtx.RetCount >= 0 && oldEstack.Len() != oldCtx.RetCount { panic(fmt.Errorf("invalid return values count: expected %d, got %d", oldCtx.RetCount, oldEstack.Len())) } rvcount := oldEstack.Len() for i := rvcount; i > 0; i-- { elem := oldEstack.RemoveAt(i - 1) newEstack.Push(elem) } v.estack = newEstack } case opcode.NEWMAP: v.estack.Push(&Element{value: stackitem.NewMap()}) case opcode.KEYS: item := v.estack.Pop() if item == nil { panic("no argument") } m, ok := item.value.(*stackitem.Map) if !ok { panic("not a Map") } arr := make([]stackitem.Item, 0, m.Len()) for k := range m.Value().([]stackitem.MapElement) { arr = append(arr, m.Value().([]stackitem.MapElement)[k].Key.Dup()) } v.estack.PushVal(arr) case opcode.VALUES: item := v.estack.Pop() if item == nil { panic("no argument") } var arr []stackitem.Item switch t := item.value.(type) { case *stackitem.Array, *stackitem.Struct: src := t.Value().([]stackitem.Item) arr = make([]stackitem.Item, len(src)) for i := range src { arr[i] = cloneIfStruct(src[i]) } case *stackitem.Map: arr = make([]stackitem.Item, 0, t.Len()) for k := range t.Value().([]stackitem.MapElement) { arr = append(arr, cloneIfStruct(t.Value().([]stackitem.MapElement)[k].Value)) } default: panic("not a Map, Array or Struct") } v.estack.PushVal(arr) case opcode.HASKEY: key := v.estack.Pop() validateMapKey(key) c := v.estack.Pop() if c == nil { panic("no value found") } switch t := c.value.(type) { case *stackitem.Array, *stackitem.Struct: index := key.BigInt().Int64() if index < 0 { panic("negative index") } v.estack.PushVal(index < int64(len(c.Array()))) case *stackitem.Map: v.estack.PushVal(t.Has(key.Item())) case *stackitem.Buffer: index := key.BigInt().Int64() if index < 0 { panic("negative index") } v.estack.PushVal(index < int64(t.Len())) default: panic("wrong collection type") } case opcode.NOP: // unlucky ^^ case opcode.THROW: v.throw(v.estack.Pop().Item()) case opcode.ABORT: panic("ABORT") case opcode.ASSERT: if !v.estack.Pop().Bool() { panic("ASSERT failed") } case opcode.TRY, opcode.TRYL: catchP, finallyP := getTryParams(op, parameter) if ctx.tryStack.Len() >= MaxTryNestingDepth { panic("maximum TRY depth exceeded") } cOffset := getJumpOffset(ctx, catchP) fOffset := getJumpOffset(ctx, finallyP) if cOffset == ctx.ip && fOffset == ctx.ip { panic("invalid offset for TRY*") } else if cOffset == ctx.ip { cOffset = -1 } else if fOffset == ctx.ip { fOffset = -1 } eCtx := newExceptionHandlingContext(cOffset, fOffset) ctx.tryStack.PushVal(eCtx) case opcode.ENDTRY, opcode.ENDTRYL: eCtx := ctx.tryStack.Peek(0).Value().(*exceptionHandlingContext) if eCtx.State == eFinally { panic("invalid exception handling state during ENDTRY*") } eOffset := getJumpOffset(ctx, parameter) if eCtx.HasFinally() { eCtx.State = eFinally eCtx.EndOffset = eOffset eOffset = eCtx.FinallyOffset } else { ctx.tryStack.Pop() } v.Jump(ctx, eOffset) case opcode.ENDFINALLY: if v.uncaughtException != nil { v.handleException() return } eCtx := ctx.tryStack.Pop().Value().(*exceptionHandlingContext) v.Jump(ctx, eCtx.EndOffset) default: panic(fmt.Sprintf("unknown opcode %s", op.String())) } return } func (v *VM) unloadContext(ctx *Context) { if ctx.local != nil { ctx.local.Clear() } if ctx.arguments != nil { ctx.arguments.Clear() } currCtx := v.Context() if ctx.static != nil && currCtx != nil && ctx.static != currCtx.static { ctx.static.Clear() } } // getTryParams splits TRY(L) instruction parameter into offsets for catch and finally blocks. func getTryParams(op opcode.Opcode, p []byte) ([]byte, []byte) { i := 1 if op == opcode.TRYL { i = 4 } return p[:i], p[i:] } // getJumpCondition performs opcode specific comparison of a and b. func getJumpCondition(op opcode.Opcode, a, b *big.Int) bool { cmp := a.Cmp(b) switch op { case opcode.JMPEQ, opcode.JMPEQL: return cmp == 0 case opcode.JMPNE, opcode.JMPNEL: return cmp != 0 case opcode.JMPGT, opcode.JMPGTL: return cmp > 0 case opcode.JMPGE, opcode.JMPGEL: return cmp >= 0 case opcode.JMPLT, opcode.JMPLTL: return cmp < 0 case opcode.JMPLE, opcode.JMPLEL: return cmp <= 0 default: panic(fmt.Sprintf("invalid JMP* opcode: %s", op)) } } func (v *VM) throw(item stackitem.Item) { v.uncaughtException = item v.handleException() } // Jump performs jump to the offset. func (v *VM) Jump(ctx *Context, offset int) { ctx.nextip = offset } // Call calls method by offset. It is similar to Jump but also // pushes new context to the invocation stack and increments // invocation counter for the corresponding context script hash. func (v *VM) Call(ctx *Context, offset int) { v.call(ctx, offset) v.Invocations[ctx.ScriptHash()]++ } // call is an internal representation of Call, which does not // affect the invocation counter and is only being used by vm // package. func (v *VM) call(ctx *Context, offset int) { v.checkInvocationStackSize() newCtx := ctx.Copy() newCtx.RetCount = -1 newCtx.local = nil newCtx.arguments = nil newCtx.tryStack = NewStack("exception") newCtx.NEF = ctx.NEF v.istack.PushVal(newCtx) v.Jump(newCtx, offset) } // getJumpOffset returns instruction number in a current context // to a which JMP should be performed. // parameter should have length either 1 or 4 and // is interpreted as little-endian. func getJumpOffset(ctx *Context, parameter []byte) int { offset, _, err := calcJumpOffset(ctx, parameter) if err != nil { panic(err) } return offset } // calcJumpOffset returns absolute and relative offset of JMP/CALL/TRY instructions // either in short (1-byte) or long (4-byte) form. func calcJumpOffset(ctx *Context, parameter []byte) (int, int, error) { var rOffset int32 switch l := len(parameter); l { case 1: rOffset = int32(int8(parameter[0])) case 4: rOffset = int32(binary.LittleEndian.Uint32(parameter)) default: _, curr := ctx.CurrInstr() return 0, 0, fmt.Errorf("invalid %s parameter length: %d", curr, l) } offset := ctx.ip + int(rOffset) if offset < 0 || offset > len(ctx.prog) { return 0, 0, fmt.Errorf("invalid offset %d ip at %d", offset, ctx.ip) } return offset, int(rOffset), nil } func (v *VM) handleException() { pop := 0 ictxv := v.istack.Peek(0) ictx := ictxv.Value().(*Context) for ictx != nil { e := ictx.tryStack.Peek(0) for e != nil { ectx := e.Value().(*exceptionHandlingContext) if ectx.State == eFinally || (ectx.State == eCatch && !ectx.HasFinally()) { ictx.tryStack.Pop() e = ictx.tryStack.Peek(0) continue } for i := 0; i < pop; i++ { ctx := v.istack.Pop().Value().(*Context) v.unloadContext(ctx) } if ectx.State == eTry && ectx.HasCatch() { ectx.State = eCatch v.estack.PushVal(v.uncaughtException) v.uncaughtException = nil v.Jump(ictx, ectx.CatchOffset) } else { ectx.State = eFinally v.Jump(ictx, ectx.FinallyOffset) } return } pop++ ictxv = ictxv.Next() if ictxv == nil { break } ictx = ictxv.Value().(*Context) } throwUnhandledException(v.uncaughtException) } // throwUnhandledException gets exception message from the provided stackitem and panics. func throwUnhandledException(item stackitem.Item) { msg := "unhandled exception" switch item.Type() { case stackitem.ArrayT: if arr := item.Value().([]stackitem.Item); len(arr) > 0 { data, err := arr[0].TryBytes() if err == nil { msg = fmt.Sprintf("%s: %q", msg, string(data)) } } default: data, err := item.TryBytes() if err == nil { msg = fmt.Sprintf("%s: %q", msg, string(data)) } } panic(msg) } // CheckMultisigPar checks if sigs contains sufficient valid signatures. func CheckMultisigPar(v *VM, curve elliptic.Curve, h []byte, pkeys [][]byte, sigs [][]byte) bool { if len(sigs) == 1 { return checkMultisig1(v, curve, h, pkeys, sigs[0]) } k1, k2 := 0, len(pkeys)-1 s1, s2 := 0, len(sigs)-1 type task struct { pub *keys.PublicKey signum int } type verify struct { ok bool signum int } worker := func(ch <-chan task, result chan verify) { for { t, ok := <-ch if !ok { return } result <- verify{ signum: t.signum, ok: t.pub.Verify(sigs[t.signum], h), } } } const workerCount = 3 tasks := make(chan task, 2) results := make(chan verify, len(sigs)) for i := 0; i < workerCount; i++ { go worker(tasks, results) } tasks <- task{pub: bytesToPublicKey(pkeys[k1], curve), signum: s1} tasks <- task{pub: bytesToPublicKey(pkeys[k2], curve), signum: s2} sigok := true taskCount := 2 loop: for r := range results { goingForward := true taskCount-- if r.signum == s2 { goingForward = false } if k1+1 == k2 { sigok = r.ok && s1+1 == s2 if taskCount != 0 && sigok { continue } break loop } else if r.ok { if s1+1 == s2 { if taskCount != 0 && sigok { continue } break loop } if goingForward { s1++ } else { s2-- } } var nextSig, nextKey int if goingForward { k1++ nextSig = s1 nextKey = k1 } else { k2-- nextSig = s2 nextKey = k2 } taskCount++ tasks <- task{pub: bytesToPublicKey(pkeys[nextKey], curve), signum: nextSig} } close(tasks) return sigok } func checkMultisig1(v *VM, curve elliptic.Curve, h []byte, pkeys [][]byte, sig []byte) bool { for i := range pkeys { pkey := bytesToPublicKey(pkeys[i], curve) if pkey.Verify(sig, h) { return true } } return false } func cloneIfStruct(item stackitem.Item) stackitem.Item { switch it := item.(type) { case *stackitem.Struct: return it.Clone() default: return it } } func makeArrayOfType(n int, typ stackitem.Type) []stackitem.Item { if !typ.IsValid() { panic(fmt.Sprintf("invalid stack item type: %d", typ)) } items := make([]stackitem.Item, n) for i := range items { switch typ { case stackitem.BooleanT: items[i] = stackitem.NewBool(false) case stackitem.IntegerT: items[i] = stackitem.NewBigInteger(big.NewInt(0)) case stackitem.ByteArrayT: items[i] = stackitem.NewByteArray([]byte{}) default: items[i] = stackitem.Null{} } } return items } func validateMapKey(key *Element) { if key == nil { panic("no key found") } if err := stackitem.IsValidMapKey(key.Item()); err != nil { panic(err) } } func (v *VM) checkInvocationStackSize() { if v.istack.len >= MaxInvocationStackSize { panic("invocation stack is too big") } } // bytesToPublicKey is a helper deserializing keys using cache and panicing on // error. func bytesToPublicKey(b []byte, curve elliptic.Curve) *keys.PublicKey { pkey, err := keys.NewPublicKeyFromBytes(b, curve) if err != nil { panic(err.Error()) } return pkey } // GetCallingScriptHash implements ScriptHashGetter interface. func (v *VM) GetCallingScriptHash() util.Uint160 { return v.Context().callingScriptHash } // GetEntryScriptHash implements ScriptHashGetter interface. func (v *VM) GetEntryScriptHash() util.Uint160 { return v.getContextScriptHash(v.Istack().Len() - 1) } // GetCurrentScriptHash implements ScriptHashGetter interface. func (v *VM) GetCurrentScriptHash() util.Uint160 { return v.getContextScriptHash(0) } // toInt converts an item to a 32-bit int. func toInt(i *big.Int) int { if !i.IsInt64() { panic("not an int32") } n := i.Int64() if n < math.MinInt32 || n > math.MaxInt32 { panic("not an int32") } return int(n) }