44 lines
1.5 KiB
Java
44 lines
1.5 KiB
Java
package org.thoughtcrime.securesms.crypto;
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import android.support.annotation.NonNull;
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import java.io.File;
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import java.io.FileInputStream;
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import java.io.IOException;
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import java.io.InputStream;
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import java.security.InvalidAlgorithmParameterException;
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import java.security.InvalidKeyException;
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import java.security.NoSuchAlgorithmException;
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import javax.crypto.Cipher;
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import javax.crypto.CipherInputStream;
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import javax.crypto.Mac;
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import javax.crypto.NoSuchPaddingException;
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import javax.crypto.spec.IvParameterSpec;
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import javax.crypto.spec.SecretKeySpec;
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public class ModernDecryptingPartInputStream {
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public static InputStream createFor(@NonNull AttachmentSecret attachmentSecret, @NonNull byte[] random, @NonNull File file)
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throws IOException
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{
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try {
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Mac mac = Mac.getInstance("HmacSHA256");
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mac.init(new SecretKeySpec(attachmentSecret.getModernKey(), "HmacSHA256"));
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FileInputStream fileInputStream = new FileInputStream(file);
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byte[] iv = new byte[16];
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byte[] key = mac.doFinal(random);
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Cipher cipher = Cipher.getInstance("AES/CTR/NoPadding");
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cipher.init(Cipher.DECRYPT_MODE, new SecretKeySpec(key, "AES"), new IvParameterSpec(iv));
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return new CipherInputStream(fileInputStream, cipher);
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} catch (NoSuchAlgorithmException | InvalidKeyException | InvalidAlgorithmParameterException | NoSuchPaddingException e) {
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throw new AssertionError(e);
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}
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}
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}
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