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wolfcrypt-jni
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JCE: fix Cipher.getOutputSize() for AES/GCM/NoPadding in DECRYPT mode, should remove tag from length

pull/107/head
Chris Conlon 2025-03-19 16:55:14 -06:00
parent ab70102343
commit dbfbe28cab
2 changed files with 71 additions and 4 deletions
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15
src/main/java/com/wolfssl/provider/jce/WolfCryptCipher.java
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@ -303,12 +303,19 @@ public class WolfCryptCipher extends CipherSpi {
if (paddingType == PaddingType.WC_NONE) {
if (cipherMode == CipherMode.WC_GCM) {
/* In AES-GCM mode we append the authentication tag
* to the end of ciphertext */
size = inputLen + this.gcmTagLen;
* to the end of ciphertext, When decrypting, output
* size will have it taken off. */
if (this.direction == OpMode.WC_ENCRYPT) {
size = inputLen + this.gcmTagLen;
}
else {
size = inputLen - this.gcmTagLen;
}
size = Math.max(size, 0);
}
else {
/* wolfCrypt expects input to be padded by application to
* block size, thus output is same size as input */
/* wolfCrypt expects input to be padded by application
* to block size, thus output is same size as input */
size = inputLen;
}
}

60
src/test/java/com/wolfssl/provider/jce/test/WolfCryptCipherTest.java
View File

@ -2250,6 +2250,66 @@ public class WolfCryptCipherTest {
}
}
/**
* Test Cipher("AES/GCM/NoPadding") getOutputSize() method for various
* use cases.
*/
@Test
public void testAesGcmGetOutputSize() throws Exception {
final int TAG_LENGTH_BYTES = 16; /* Default tag length */
final int KEY_LENGTH_BYTES = 16; /* 128-bit AES key */
final int IV_LENGTH_BYTES = 12;
/* Fill key and IV with non-zero values */
byte[] keyBytes = new byte[KEY_LENGTH_BYTES];
java.util.Arrays.fill(keyBytes, (byte) 0x01);
SecretKeySpec key = new SecretKeySpec(keyBytes, "AES");
byte[] iv = new byte[IV_LENGTH_BYTES];
java.util.Arrays.fill(iv, (byte) 0x02);
GCMParameterSpec spec = new GCMParameterSpec(TAG_LENGTH_BYTES * 8, iv);
Cipher cipher = Cipher.getInstance("AES/GCM/NoPadding", jceProvider);
/* Test ENCRYPT with zero-length input */
cipher.init(Cipher.ENCRYPT_MODE, key, spec);
assertEquals("Output size for zero-length input should be tag length",
TAG_LENGTH_BYTES, cipher.getOutputSize(0));
/* Test ENCRYPT with small input, re-init to reset state */
cipher.init(Cipher.ENCRYPT_MODE, key, spec);
assertEquals("Output size should be input length plus tag length",
10 + TAG_LENGTH_BYTES, cipher.getOutputSize(10));
/* Test ENCRYPT with block boundary input */
cipher.init(Cipher.ENCRYPT_MODE, key, spec);
assertEquals("Output size should be input length plus tag length " +
"at block boundary", 16 + TAG_LENGTH_BYTES,
cipher.getOutputSize(16));
/* Test DECRYPT with tag included */
cipher.init(Cipher.DECRYPT_MODE, key, spec);
assertEquals("Output size for decryption should be input length " +
"minus tag length", 10, cipher.getOutputSize(10 + TAG_LENGTH_BYTES));
/* Test ENCRYPT after partial update */
byte[] partialInput = new byte[5];
cipher.init(Cipher.ENCRYPT_MODE, key, spec);
cipher.update(partialInput); /* Process some data */
assertEquals("Output size after update should account for remaining " +
"input plus tag", 10 + TAG_LENGTH_BYTES, cipher.getOutputSize(10));
/* Test getOutputSize() before initialization, expect exception */
Cipher uninitializedCipher = Cipher.getInstance("AES/GCM/NoPadding");
try {
uninitializedCipher.getOutputSize(10);
fail("Expected IllegalStateException for uninitialized cipher");
} catch (IllegalStateException e) {
/* Expected exception */
}
}
@Test
public void testDESedeCbcNoPadding()
throws NoSuchProviderException, NoSuchAlgorithmException,