android反編譯apk後,java檔案中出現的一些類似亂碼的問題
阿新 • • 發佈:2019-02-11
概述
java class 反編譯之後,偶爾回碰到一些不正常的程式碼
例如:
label0 :_L1 MISSING_BLOCK_LABEL_30
JVM INSTR ret 7
JVM INSTR tableswitch 1 3: default 269、
JVM INSTR monitorexit
JVM INSTR monitorenter
這些一般是由特殊的for迴圈、try catch finally語句塊、synchronized語句反編譯後產生的。
下面,就簡單介紹一下,一些反編譯後的特殊程式碼的還原規則。
1、Exceptioin的還原
反編譯後的程式碼如下
public boolean f1() { return cal.getTime().after(new Date()); Exception e; e; e.printStackTrace(); return false; }
還原後的Java程式碼
public boolean f1() {
try {
return cal.getTime().after(new Date());
} catch (Exception e) {
e.printStackTrace();
return false;
}
}
2、finally程式碼的還原
反編譯後的Java程式碼如下
還原後的程式碼如下public boolean f2() { boolean flag = cal.getTime().after(new Date()); System.out.println("finally"); return flag; Exception e; e; e.printStackTrace(); System.out.println("finally"); return false; Exception exception; exception; System.out.println("finally"); throw exception; }
public boolean f2() {
try {
return cal.getTime().after(new Date());
} catch (Exception e) { e.printStackTrace();
return false;
} finally {
System.out.println("finally");
}
}
3、MISSING_BLOCK_LABEL_的還原
反編譯後的程式碼
還原後的Java程式碼public Object f22() { Date date = cal.getTime(); System.out.println("finally"); return date; Exception e; e; e.printStackTrace(); System.out.println("finally"); break MISSING_BLOCK_LABEL_45; Exception exception; exception; System.out.println("finally"); throw exception; return null; }
public Object f22() {
try {
return cal.getTime();
} catch (Exception e) {
e.printStackTrace();
} finally {
System.out.println("finally");
} return null;
}
4、異常中:label的還原
反編譯後的程式碼
public String f4() throws Exception {
label0: {
try {
Integer i = new Integer(1);
if(i.intValue() >0) {
System.out.println(i);
break label0;
}
System.err.println(i);
} catch(Exception dae) {
System.err.println(dae);
throw new RuntimeException(dae);
}
return null;
}
return "Hello";
}
注意,這個程式碼有點詭異,實際程式碼如下:
public String f4() throws Exception {
try {
Integer i = new Integer(1);
if (i.intValue() >0) {
System.out.println(i);
} else {
System.err.println(i);
return null;
}
return "Hello";
} catch (Exception dae) {
System.err.println(dae);
throw new RuntimeException(dae);
}
}
5、典型資料庫操作程式碼還原
反編譯後代碼
public HashMap f5() {
Connection conn = null;
HashMap hashmap;
HashMap map = new HashMap();
Class.forName("");
conn = DriverManager.getConnection("jdbc:odbc:");
PreparedStatement pstmt = conn.prepareStatement("select * from table");
pstmt.setString(1, "param");
String columnVallue;
for(ResultSet rs = pstmt.executeQuery();rs.next();map.put(columnVallue, "")) columnVallue = rs.getString("column");
hashmap = map;
if(conn != null) try {
conn.close();
} catch(SQLException sqlce) {
sqlce.printStackTrace();
}
return hashmap;
ClassNotFoundException cnfe;
cnfe;
cnfe.printStackTrace();
if(conn != null)
try {
conn.close();
} catch(SQLException sqlce) {
sqlce.printStackTrace();
}
break MISSING_BLOCK_LABEL_188;
SQLException sqle;
sqle;
sqle.printStackTrace();
if(conn != null) try {
conn.close();
} catch(SQLException sqlce) {
sqlce.printStackTrace();
}
break MISSING_BLOCK_LABEL_188;
Exception exception;
exception;
if(conn != null) try {
conn.close();
} catch(SQLException sqlce) {
sqlce.printStackTrace();
} throw exception;
return null;
}
實際程式碼如下 public HashMap f5() {
Connection conn = null;
try {
HashMap map = new HashMap();
Class.forName("");
conn = DriverManager.getConnection("jdbc:odbc:");
PreparedStatement pstmt = conn.prepareStatement("select * from table");
pstmt.setString(1, "param");
ResultSet rs = pstmt.executeQuery();
while (rs.next()) {
String columnVallue = rs.getString("column");
map.put(columnVallue, "");
}
return map;
} catch (ClassNotFoundException cnfe) {
cnfe.printStackTrace();
} catch (SQLException sqle) {
sqle.printStackTrace();
} finally {
if (conn != null) {
try {
conn.close();
} catch (SQLException sqlce) {
sqlce.printStackTrace();
}
}
}
return null;
}
6、兩層異常巢狀程式碼還原
反編譯後的程式碼
public int f6() {
int i = cal.getTime().compareTo(new Date());
System.out.println("finally");
return i;
Exception e1;
e1;
e1.printStackTrace();
System.out.println("finally");
return -1;
Exception e2;
e2;
e2.printStackTrace();
System.out.println("finally");
return -2;
Exception exception;
exception;
System.out.println("finally");
throw exception;
}
實際程式碼 public int f6() {
try {
try {
return cal.getTime().compareTo(new Date());
} catch (Exception e1) {
e1.printStackTrace();
return -1;
} } catch (Exception e2) {
e2.printStackTrace();
return -2;
} finally {
System.out.println("finally");
}
}
}
7、非常詭異的程式碼
反編譯後的程式碼
public int f7() {
int i = cal.getTime().compareTo(new Date());
}
System.out.println("finally");
return i;
Exception e1;
e1;
e1.printStackTrace();
_L2: System.out.println("finally");
return -1;
Exception e2;
e2;
e2.printStackTrace();
if(true)
goto _L2;
else
goto _L1 _L1:
Exception exception;
exception;
System.out.println("finally");
throw exception;
}
原始程式碼 public int f7() {
try {
try {
return cal.getTime().compareTo(new Date());
} catch (Exception e1) {
e1.printStackTrace();
return -1;
} } catch (Exception e2) {
e2.printStackTrace();
return -1;
} finally {
System.out.println("finally");
}
}