47 lines
1.5 KiB
Java
47 lines
1.5 KiB
Java
package org.thoughtcrime.securesms.glide;
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import androidx.annotation.NonNull;
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import java.io.IOException;
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import java.security.SecureRandom;
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import okhttp3.Headers;
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import okhttp3.Interceptor;
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import okhttp3.Request;
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import okhttp3.Response;
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/**
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* An interceptor that adds a header with a random amount of bytes to disguise header length.
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*/
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public class PaddedHeadersInterceptor implements Interceptor {
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private static final String PADDING_HEADER = "X-SignalPadding";
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private static final int MIN_RANDOM_BYTES = 1;
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private static final int MAX_RANDOM_BYTES = 64;
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@Override
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public @NonNull Response intercept(@NonNull Chain chain) throws IOException {
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Request padded = chain.request().newBuilder()
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.headers(getPaddedHeaders(chain.request().headers()))
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.build();
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return chain.proceed(padded);
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}
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private @NonNull Headers getPaddedHeaders(@NonNull Headers headers) {
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return headers.newBuilder()
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.add(PADDING_HEADER, getRandomString(new SecureRandom(), MIN_RANDOM_BYTES, MAX_RANDOM_BYTES))
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.build();
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}
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private static @NonNull String getRandomString(@NonNull SecureRandom secureRandom, int minLength, int maxLength) {
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char[] buffer = new char[secureRandom.nextInt(maxLength - minLength) + minLength];
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for (int i = 0 ; i < buffer.length; i++) {
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buffer[i] = (char) (secureRandom.nextInt(74) + 48); // Random char from 0-Z
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}
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return new String(buffer);
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}
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}
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