implement error handling for buffer reads

proto/lux_buffer.go

@@ -2,6 +2,7 @@ package proto
 
 import (
 	"encoding/binary"
+	"fmt"
 )
 
 var NO = binary.BigEndian
@@ -85,11 +86,14 @@ func (buf *LuxBuffer) WriteBytes(bytes []byte) {
 	copy(buf.WriteNext(len(bytes)), bytes)
 }
 
-func (buf *LuxBuffer) ReadNext(size int) []byte {
+func (buf *LuxBuffer) ReadNext(size int) ([]byte, error) {
+	if buf.offset+size > buf.len {
+		return nil, fmt.Errorf("ReadNext %d+%d > %d", buf.offset, size, buf.len)
+	}
 	next := buf.data[buf.offset : buf.offset+size]
 	buf.offset += size
 
-	return next
+	return next, nil
 }
 
 func (buf *LuxBuffer) Skip(skip int) {
@@ -97,23 +101,40 @@ func (buf *LuxBuffer) Skip(skip int) {
 }
 
 // explicit copy of read bytes
-func (buf *LuxBuffer) CopyBytes(size int) []byte {
+func (buf *LuxBuffer) CopyBytes(size int) ([]byte, error) {
+	bytes, err := buf.ReadNext(size)
+	if err != nil {
+		return nil, err
+	}
+
 	read := make([]byte, size)
-	copy(read, buf.ReadNext(size))
+	copy(read, bytes)
 
-	return read
+	return read, nil
 }
 
-func (buf *LuxBuffer) ReadUint16() uint16 {
+func (buf *LuxBuffer) ReadUint16() (uint16, error) {
-	return NO.Uint16(buf.ReadNext(2))
+	rd, err := buf.ReadNext(2)
+	if err != nil {
+		return 0, err
+	}
+	return NO.Uint16(rd), nil
 }
 
-func (buf *LuxBuffer) ReadUint32() uint32 {
+func (buf *LuxBuffer) ReadUint32() (uint32, error) {
-	return NO.Uint32(buf.ReadNext(4))
+	rd, err := buf.ReadNext(4)
+	if err != nil {
+		return 0, err
+	}
+	return NO.Uint32(rd), nil
 }
 
-func (buf *LuxBuffer) ReadUint64() uint64 {
+func (buf *LuxBuffer) ReadUint64() (uint64, error) {
-	return NO.Uint64(buf.ReadNext(8))
+	rd, err := buf.ReadNext(8)
+	if err != nil {
+		return 0, err
+	}
+	return NO.Uint64(rd), nil
 }
 
 func (buf *LuxBuffer) WriteUint16(val uint16) {
@@ -131,14 +152,21 @@ func (buf *LuxBuffer) WriteUint64(val uint64) {
 // variable-length blocks can cause misaligned size,
 // so we make method for them, forcing padding
 
-func (buf *LuxBuffer) ReadVarBlock() []byte {
+func (buf *LuxBuffer) ReadVarBlock() ([]byte, error) {
-	len := buf.ReadUint16()
+	len, err := buf.ReadUint16()
-	bytes := buf.ReadNext(int(len))
+	if err != nil {
+		return nil, err
+	}
+	bytes, err := buf.ReadNext(int(len))
+	if err != nil {
+		return nil, err
+	}
+
 	if len%2 != 0 {
 		buf.Skip(1) // skip padding
 	}
 
-	return bytes
+	return bytes, nil
 }
 
 func (buf *LuxBuffer) WriteVarBlock(bytes []byte) {
@@ -152,8 +180,12 @@ func (buf *LuxBuffer) WriteVarBlock(bytes []byte) {
 }
 
 // strings in LUX protocol format will be padded to align of 2
-func (buf *LuxBuffer) ReadString() string {
+func (buf *LuxBuffer) ReadString() (string, error) {
-	return string(buf.ReadVarBlock())
+	block, err := buf.ReadVarBlock()
+	if err != nil {
+		return "", err
+	}
+	return string(block), nil
 }
 
 func (buf *LuxBuffer) WriteString(val string) {

proto/lux_type.go

@@ -6,3 +6,12 @@ const (
 	LuxTypeHost = 0
 	LuxTypeNode
 )
+
+func (luxType *LuxType) Read(rd *LuxBuffer) error {
+	if val, err := rd.ReadUint16(); err != nil {
+		return err
+	} else {
+		*luxType = LuxType(val)
+		return nil
+	}
+}

tests/lux_buffer_test.go

@@ -29,16 +29,16 @@ func TestInts(t *testing.T) {
 	wd.WriteUint64(69)
 	wd.WriteUint32(2967279234)
 
-	if rd := wd.ReadUint16(); rd != 1234 {
+	if rd, _ := wd.ReadUint16(); rd != 1234 {
 		t.Fatal(rd)
 	}
-	if rd := wd.ReadUint16(); rd != 4321 {
+	if rd, _ := wd.ReadUint16(); rd != 4321 {
 		t.Fatal(rd)
 	}
-	if rd := wd.ReadUint64(); rd != 69 {
+	if rd, _ := wd.ReadUint64(); rd != 69 {
 		t.Fatal(rd)
 	}
-	if rd := wd.ReadUint32(); rd != 2967279234 {
+	if rd, _ := wd.ReadUint32(); rd != 2967279234 {
 		t.Fatal(rd)
 	}
 }
@@ -48,13 +48,26 @@ func TestStrings(t *testing.T) {
 	wd.WriteString("a")     // 4
 	wd.WriteString("hello") // 8
 
-	if rd := wd.ReadString(); rd != "a" {
+	if rd, _ := wd.ReadString(); rd != "a" {
 		t.Fatal(rd)
 	}
-	if rd := wd.ReadString(); rd != "hello" {
+	if rd, _ := wd.ReadString(); rd != "hello" {
 		t.Fatal(rd)
 	}
 	if wd.Length() != 12 {
 		t.Fatalf("string misaligned size: %d\n", wd.Length())
 	}
 }
+
+func TestReadOverrun(t *testing.T) {
+	rd := proto.FromSlice(make([]byte, 2))
+	if _, err := rd.ReadNext(3); err == nil {
+		t.Fatalf("no error when rd.ReadNext(3) for %d\n", rd.Length())
+	}
+
+	rd = proto.FromSlice(make([]byte, 1))
+	rd.ReadNext(1)
+	if _, err := rd.ReadNext(1); err == nil {
+		t.Fatalf("no error when reading at offset 1 of 1 byte buffer\n")
+	}
+}