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fix: AES-EAX allow empty plaintext #10251

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fix: AES-EAX allow empty plaintext #10251

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70 changes: 38 additions & 32 deletions wolfcrypt/src/aes.c
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Original file line number Diff line number Diff line change
Expand Up @@ -16779,8 +16779,9 @@ int wc_AesEaxEncryptAuth(const byte* key, word32 keySz, byte* out,
int ret;
int eaxInited = 0;

if (key == NULL || out == NULL || in == NULL || nonce == NULL
|| authTag == NULL || authIn == NULL) {
if (key == NULL || nonce == NULL || authTag == NULL
|| (inSz > 0 && (out == NULL || in == NULL))
|| (authInSz > 0 && authIn == NULL)) {
return BAD_FUNC_ARG;
}

Expand Down Expand Up @@ -16842,8 +16843,9 @@ int wc_AesEaxDecryptAuth(const byte* key, word32 keySz, byte* out,
int ret;
int eaxInited = 0;

if (key == NULL || out == NULL || in == NULL || nonce == NULL
|| authTag == NULL || authIn == NULL) {
if (key == NULL || nonce == NULL || authTag == NULL
|| (inSz > 0 && (out == NULL || in == NULL))
|| (authInSz > 0 && authIn == NULL)) {
return BAD_FUNC_ARG;
}

Expand Down Expand Up @@ -17031,24 +17033,26 @@ int wc_AesEaxEncryptUpdate(AesEax* eax, byte* out,
{
int ret;

if (eax == NULL || out == NULL || in == NULL) {
if (eax == NULL || (inSz > 0 && (out == NULL || in == NULL))) {
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Copilot AI Apr 17, 2026

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wc_AesEaxEncryptUpdate still doesn't validate authIn when authInSz > 0. If the function later CMAC-updates AAD when authInSz is non-zero, passing authIn == NULL will result in a NULL dereference. Fix by extending the argument validation to also require authIn != NULL when authInSz > 0 (mirroring the one-shot Auth functions).

Suggested change
if (eax == NULL || (inSz > 0 && (out == NULL || in == NULL))) {
if (eax == NULL || (inSz > 0 && (out == NULL || in == NULL)) ||
(authInSz > 0 && authIn == NULL)) {

Copilot uses AI. Check for mistakes.
return BAD_FUNC_ARG;
}

/*
* Encrypt the plaintext using AES CTR
* C = CTR(M)
*/
if ((ret = wc_AesCtrEncrypt(&eax->aes, out, in, inSz)) != 0) {
return ret;
}
if (inSz > 0) {
/*
* Encrypt the plaintext using AES CTR
* C = CTR(M)
*/
if ((ret = wc_AesCtrEncrypt(&eax->aes, out, in, inSz)) != 0) {
return ret;
}

/*
* update OMAC with new ciphertext
* C' = OMAC^2_K(C)
*/
if ((ret = wc_CmacUpdate(&eax->ciphertextCmac, out, inSz)) != 0) {
return ret;
/*
* update OMAC with new ciphertext
* C' = OMAC^2_K(C)
*/
if ((ret = wc_CmacUpdate(&eax->ciphertextCmac, out, inSz)) != 0) {
return ret;
}
}

/* If there exists new auth data, update the OMAC for that as well */
Expand Down Expand Up @@ -17076,24 +17080,26 @@ int wc_AesEaxDecryptUpdate(AesEax* eax, byte* out,
{
int ret;

if (eax == NULL || out == NULL || in == NULL) {
if (eax == NULL || (inSz > 0 && (out == NULL || in == NULL))) {
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Copilot AI Apr 17, 2026

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wc_AesEaxDecryptUpdate has the same gap as EncryptUpdate: there is no guard ensuring authIn != NULL when authInSz > 0. If the function proceeds to CMAC-update AAD for non-zero authInSz, this can crash. Add a length-gated NULL check for authIn in the argument validation.

Suggested change
if (eax == NULL || (inSz > 0 && (out == NULL || in == NULL))) {
if (eax == NULL || (inSz > 0 && (out == NULL || in == NULL)) ||
(authInSz > 0 && authIn == NULL)) {

Copilot uses AI. Check for mistakes.
return BAD_FUNC_ARG;
}

/*
* Decrypt the plaintext using AES CTR
* C = CTR(M)
*/
if ((ret = wc_AesCtrEncrypt(&eax->aes, out, in, inSz)) != 0) {
return ret;
}
if (inSz > 0) {
/*
* Decrypt the plaintext using AES CTR
* C = CTR(M)
*/
if ((ret = wc_AesCtrEncrypt(&eax->aes, out, in, inSz)) != 0) {
return ret;
}

/*
* update OMAC with new ciphertext
* C' = OMAC^2_K(C)
*/
if ((ret = wc_CmacUpdate(&eax->ciphertextCmac, in, inSz)) != 0) {
return ret;
/*
* update OMAC with new ciphertext
* C' = OMAC^2_K(C)
*/
if ((ret = wc_CmacUpdate(&eax->ciphertextCmac, in, inSz)) != 0) {
return ret;
}
}

/* If there exists new auth data, update the OMAC for that as well */
Expand Down
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