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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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5e899a1
fix: ChaCha20-Poly1305 Final() allow empty plaintext
MarkAtwood Apr 17, 2026
76e5415
test: update ChaCha20-Poly1305 bad-state test for empty-plaintext fix
MarkAtwood Apr 30, 2026
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3 changes: 2 additions & 1 deletion wolfcrypt/src/chacha20_poly1305.c
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Original file line number Diff line number Diff line change
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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Original file line number Diff line number Diff line change
Expand Up @@ -10766,6 +10766,22 @@ WOLFSSL_TEST_SUBROUTINE wc_test_ret_t chacha20_poly1305_aead_test(void)
0x39, 0x23, 0x36, 0xfe, 0xa1, 0x85, 0x1f, 0x38
};

/* Wycheproof tc2: empty plaintext + empty AAD (valid per RFC 8439 §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
};

byte generatedCiphertext[265]; /* max plaintext2/cipher2 */
byte generatedPlaintext[265]; /* max plaintext2/cipher2 */
byte generatedAuthTag[CHACHA20_POLY1305_AEAD_AUTHTAG_SIZE];
Expand Down Expand Up @@ -10969,10 +10985,16 @@ WOLFSSL_TEST_SUBROUTINE wc_test_ret_t chacha20_poly1305_aead_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 §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;

XMEMSET(generatedCiphertext, 0, sizeof(generatedCiphertext));
XMEMSET(generatedAuthTag, 0, sizeof(generatedAuthTag));
Expand Down
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