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Fix ChaCha20-Poly1305 Final() to allow empty plaintext and AAD #10046

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Fix ChaCha20-Poly1305 Final() to allow empty plaintext and AAD #10046

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dcbd117
fix: ChaCha20-Poly1305 Final() allow empty plaintext
MarkAtwood Apr 17, 2026
933b7c2
test: update ChaCha20-Poly1305 bad-state test for empty-plaintext fix
MarkAtwood Apr 30, 2026
89460fa
test: update API test for Init->Final READY state acceptance
MarkAtwood Jun 4, 2026
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6 changes: 3 additions & 3 deletions tests/api/test_chacha20_poly1305.c
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Original file line number Diff line number Diff line change
Expand Up @@ -526,11 +526,11 @@ int test_wc_ChaCha20Poly1305_Stream(void)
/* wc_ChaCha20Poly1305_Final: NULL aead */
ExpectIntEQ(wc_ChaCha20Poly1305_Final(NULL, outTag),
WC_NO_ERR_TRACE(BAD_FUNC_ARG));
/* wc_ChaCha20Poly1305_Final: wrong state (INIT, not AAD/DATA) */
/* wc_ChaCha20Poly1305_Final: READY state (Init, no UpdateAad/UpdateData)
* is valid -- RFC 8439 Section 2.8 permits empty plaintext + empty AAD. */
ExpectIntEQ(wc_ChaCha20Poly1305_Init(&aead, key, iv,
CHACHA20_POLY1305_AEAD_ENCRYPT), 0);
ExpectIntEQ(wc_ChaCha20Poly1305_Final(&aead, outTag),
WC_NO_ERR_TRACE(BAD_STATE_E));
ExpectIntEQ(wc_ChaCha20Poly1305_Final(&aead, outTag), 0);
#endif
return EXPECT_RESULT();
} /* END test_wc_ChaCha20Poly1305_Stream */
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3 changes: 2 additions & 1 deletion wolfcrypt/src/chacha20_poly1305.c
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Expand Up @@ -275,7 +275,8 @@ int wc_ChaCha20Poly1305_Final(ChaChaPoly_Aead* aead,
if (aead == NULL || outAuthTag == NULL) {
return BAD_FUNC_ARG;
}
if (aead->state != CHACHA20_POLY1305_STATE_AAD &&
if (aead->state != CHACHA20_POLY1305_STATE_READY &&
aead->state != CHACHA20_POLY1305_STATE_AAD &&
aead->state != CHACHA20_POLY1305_STATE_DATA) {
return BAD_STATE_E;
}
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26 changes: 24 additions & 2 deletions wolfcrypt/test/test.c
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Expand Up @@ -11790,6 +11790,22 @@ static wc_test_ret_t chacha20_poly1305_oneshot_test(void)

static wc_test_ret_t chacha20_poly1305_stream_param_test(void)
{
/* Wycheproof tc2: empty plaintext + empty AAD (valid per RFC 8439 Section 2.8) */
WOLFSSL_SMALL_STACK_STATIC const byte key_tc2[] = {
0x80, 0xba, 0x31, 0x92, 0xc8, 0x03, 0xce, 0x96,
0x5e, 0xa3, 0x71, 0xd5, 0xff, 0x07, 0x3c, 0xf0,
0xf4, 0x3b, 0x6a, 0x2a, 0xb5, 0x76, 0xb2, 0x08,
0x42, 0x6e, 0x11, 0x40, 0x9c, 0x09, 0xb9, 0xb0
};
WOLFSSL_SMALL_STACK_STATIC const byte iv_tc2[] = {
0x4d, 0xa5, 0xbf, 0x8d, 0xfd, 0x58, 0x52, 0xc1,
0xea, 0x12, 0x37, 0x9d
};
WOLFSSL_SMALL_STACK_STATIC const byte authTag_tc2[] = {
0x76, 0xac, 0xb3, 0x42, 0xcf, 0x31, 0x66, 0xa5,
0xb6, 0x3c, 0x0c, 0x0e, 0xa1, 0x38, 0x3c, 0x8d
};

const byte* key1 = chacha20_poly1305_test1_key;
const byte* iv1 = chacha20_poly1305_test1_iv;
const byte* aad1 = chacha20_poly1305_test1_aad;
Expand Down Expand Up @@ -11863,10 +11879,16 @@ static wc_test_ret_t chacha20_poly1305_stream_param_test(void)
err = wc_ChaCha20Poly1305_Final(&aead, generatedAuthTag);
if (err != WC_NO_ERR_TRACE(BAD_STATE_E))
return WC_TEST_RET_ENC_EC(err);
aead.state = CHACHA20_POLY1305_STATE_READY;
/* Wycheproof tc2: empty plaintext + empty AAD must succeed (RFC 8439 Section 2.8) */
err = wc_ChaCha20Poly1305_Init(&aead, key_tc2, iv_tc2,
CHACHA20_POLY1305_AEAD_ENCRYPT);
if (err != 0)
return WC_TEST_RET_ENC_EC(err);
err = wc_ChaCha20Poly1305_Final(&aead, generatedAuthTag);
if (err != WC_NO_ERR_TRACE(BAD_STATE_E))
if (err != 0)
return WC_TEST_RET_ENC_EC(err);
if (XMEMCMP(generatedAuthTag, authTag_tc2, sizeof(authTag_tc2)) != 0)
return WC_TEST_RET_ENC_NC;

return 0;
}
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