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[stm32, aes, cryp, pka] Zeroize AES registers after performing operation and on cleanup #48

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Merged
aidangarske merged 1 commit into from
Jun 22, 2026
Merged

[stm32, aes, cryp, pka] Zeroize AES registers after performing operation and on cleanup #48

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93 changes: 58 additions & 35 deletions src/crypto/stm32n6_cryp.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -195,6 +195,22 @@ static void WriteIv16(size_t base, const uint8_t *iv)
whal_Reg_Write(base, CRYP_IV1RR_REG, whal_LoadBe32(iv + 12));
}

static void ZeroKeyIv(size_t base)
{
whal_Reg_Write(base, CRYP_K0LR_REG, 0);
whal_Reg_Write(base, CRYP_K0RR_REG, 0);
whal_Reg_Write(base, CRYP_K1LR_REG, 0);
whal_Reg_Write(base, CRYP_K1RR_REG, 0);
whal_Reg_Write(base, CRYP_K2LR_REG, 0);
whal_Reg_Write(base, CRYP_K2RR_REG, 0);
whal_Reg_Write(base, CRYP_K3LR_REG, 0);
whal_Reg_Write(base, CRYP_K3RR_REG, 0);
whal_Reg_Write(base, CRYP_IV0LR_REG, 0);
whal_Reg_Write(base, CRYP_IV0RR_REG, 0);
whal_Reg_Write(base, CRYP_IV1LR_REG, 0);
whal_Reg_Write(base, CRYP_IV1RR_REG, 0);
}

static void WriteBlock(size_t base, const uint8_t *in)
{
whal_Reg_Write(base, CRYP_DINR_REG, whal_LoadBe32(in));
Expand Down Expand Up @@ -351,6 +367,7 @@ whal_Error whal_Stm32n6_Cryp_Deinit(whal_Crypto *dev)
{
(void)dev;
Disable(whal_Stm32n6_Cryp_Dev.base);
ZeroKeyIv(whal_Stm32n6_Cryp_Dev.base);
return WHAL_SUCCESS;
}

Expand Down Expand Up @@ -386,7 +403,7 @@ whal_Error whal_Stm32n6_CrypAesEcb_Oneshot(whal_AesEcb *dev,
err = PrepareDecryptionKey(base, key, keySz, keySizeBits,
cfg->timeout);
if (err)
return err;
goto cleanup;
ConfigureMode(base, CRYP_ALGOMODE_AES_ECB, CRYP_ALGODIR_DECRYPT,
keySizeBits, 0, 0, 0);
Enable(base);
Expand All @@ -397,12 +414,14 @@ whal_Error whal_Stm32n6_CrypAesEcb_Oneshot(whal_AesEcb *dev,
WriteKey(base, key, keySz);
err = WaitKeyValid(base, cfg->timeout);
if (err)
return err;
goto cleanup;
Enable(base);
}

Comment thread
aidangarske marked this conversation as resolved.
err = Process_BlockCipher(in, out, sz);
cleanup:
Disable(base);
ZeroKeyIv(base);
return err;
}

Expand Down Expand Up @@ -488,7 +507,7 @@ whal_Error whal_Stm32n6_CrypAesCbc_Oneshot(whal_AesCbc *dev,
err = PrepareDecryptionKey(base, key, keySz, keySizeBits,
cfg->timeout);
if (err)
return err;
goto cleanup;
ConfigureMode(base, CRYP_ALGOMODE_AES_CBC, CRYP_ALGODIR_DECRYPT,
keySizeBits, 0, 0, 0);
WriteIv16(base, (const uint8_t *)iv);
Expand All @@ -501,12 +520,14 @@ whal_Error whal_Stm32n6_CrypAesCbc_Oneshot(whal_AesCbc *dev,
WriteKey(base, key, keySz);
err = WaitKeyValid(base, cfg->timeout);
if (err)
return err;
goto cleanup;
Enable(base);
}

err = Process_BlockCipher(in, out, sz);
cleanup:
Disable(base);
ZeroKeyIv(base);
return err;
}

Expand Down Expand Up @@ -601,11 +622,13 @@ whal_Error whal_Stm32n6_CrypAesCtr_Oneshot(whal_AesCtr *dev,
WriteKey(base, key, keySz);
err = WaitKeyValid(base, cfg->timeout);
if (err)
return err;
goto cleanup;
Enable(base);

err = Process_BlockCipher(in, out, sz);
cleanup:
Disable(base);
ZeroKeyIv(base);
return err;
}

Expand Down Expand Up @@ -776,12 +799,12 @@ whal_Error whal_Stm32n6_CrypAesGcm_Oneshot(whal_AesGcm *dev,
err = GcmInit((const uint8_t *)key, keySz,
keySizeBits, algoDir, (const uint8_t *)iv);
if (err)
return err;
goto cleanup;

/* Header phase */
err = GcmHeaderPhase((const uint8_t *)aad, aadSz);
if (err)
return err;
goto cleanup;

/* Payload phase */
if (sz > 0) {
Expand Down Expand Up @@ -815,10 +838,8 @@ whal_Error whal_Stm32n6_CrypAesGcm_Oneshot(whal_AesGcm *dev,
}

err = WaitOutputReady(base, cfg->timeout);
if (err) {
Disable(base);
return err;
}
if (err)
goto cleanup;

if (remain >= 16) {
ReadBlock(base, outPtr);
Expand Down Expand Up @@ -847,17 +868,17 @@ whal_Error whal_Stm32n6_CrypAesGcm_Oneshot(whal_AesGcm *dev,
whal_Reg_Write(base, CRYP_DINR_REG, (uint32_t)payloadBits);

err = WaitOutputReady(base, cfg->timeout);
if (err) {
Disable(base);
return err;
}
if (err)
goto cleanup;

ReadBlock(base, tagBuf);
for (i = 0; i < tagSz; i++)
((uint8_t *)tag)[i] = tagBuf[i];

cleanup:
Disable(base);
return WHAL_SUCCESS;
ZeroKeyIv(base);
return err;
}

whal_Error whal_Stm32n6_CrypAesGcm_Start(whal_AesGcm *dev,
Expand Down Expand Up @@ -998,6 +1019,7 @@ whal_Error whal_Stm32n6_CrypAesGcm_Finalize(whal_AesGcm *dev,
err = WaitOutputReady(base, cfg->timeout);
if (err) {
Disable(base);
ZeroKeyIv(base);
return err;
}

Expand All @@ -1006,6 +1028,7 @@ whal_Error whal_Stm32n6_CrypAesGcm_Finalize(whal_AesGcm *dev,
((uint8_t *)tag)[i] = tagBuf[i];

Disable(base);
ZeroKeyIv(base);
return WHAL_SUCCESS;
}

Expand Down Expand Up @@ -1053,12 +1076,12 @@ whal_Error whal_Stm32n6_CrypAesGmac_Oneshot(whal_AesGmac *dev,
keySizeBits, CRYP_ALGODIR_ENCRYPT,
(const uint8_t *)iv);
if (err)
return err;
goto cleanup;

/* Header phase */
err = GcmHeaderPhase((const uint8_t *)aad, aadSz);
if (err)
return err;
goto cleanup;

/* Final phase */
Disable(base);
Expand All @@ -1076,17 +1099,17 @@ whal_Error whal_Stm32n6_CrypAesGmac_Oneshot(whal_AesGmac *dev,
whal_Reg_Write(base, CRYP_DINR_REG, 0);

err = WaitOutputReady(base, cfg->timeout);
if (err) {
Disable(base);
return err;
}
if (err)
goto cleanup;

ReadBlock(base, tagBuf);
for (i = 0; i < tagSz; i++)
((uint8_t *)tag)[i] = tagBuf[i];

cleanup:
Disable(base);
return WHAL_SUCCESS;
ZeroKeyIv(base);
return err;
}

const whal_AesGmacDriver whal_Stm32n6_Cryp_GmacDriver = {
Expand Down Expand Up @@ -1187,14 +1210,14 @@ whal_Error whal_Stm32n6_CrypAesCcm_Oneshot(whal_AesCcm *dev,
WriteKey(base, key, keySz);
err = WaitKeyValid(base, cfg->timeout);
if (err)
return err;
goto cleanup;
Enable(base);

/* Feed B0 to start the CBC-MAC; CRYPEN auto-clears when init completes. */
WriteBlock(base, b0);
err = WaitCrypEnClear(base, cfg->timeout);
if (err)
return err;
goto cleanup;

/* Header phase (AAD) */
if (aadSz > 0) {
Expand Down Expand Up @@ -1226,7 +1249,7 @@ whal_Error whal_Stm32n6_CrypAesCcm_Oneshot(whal_AesCcm *dev,

err = WaitBusyClear(base, cfg->timeout);
if (err)
return err;
goto cleanup;
}

/* Payload phase */
Expand Down Expand Up @@ -1261,10 +1284,8 @@ whal_Error whal_Stm32n6_CrypAesCcm_Oneshot(whal_AesCcm *dev,
}

err = WaitOutputReady(base, cfg->timeout);
if (err) {
Disable(base);
return err;
}
if (err)
goto cleanup;

if (remain >= 16) {
ReadBlock(base, outPtr);
Expand All @@ -1288,17 +1309,17 @@ whal_Error whal_Stm32n6_CrypAesCcm_Oneshot(whal_AesCcm *dev,
WriteBlock(base, ctr0);

err = WaitOutputReady(base, cfg->timeout);
if (err) {
Disable(base);
return err;
}
if (err)
goto cleanup;

ReadBlock(base, tagBuf);
for (i = 0; i < tagSz; i++)
((uint8_t *)tag)[i] = tagBuf[i];

cleanup:
Disable(base);
return WHAL_SUCCESS;
ZeroKeyIv(base);
return err;
}

whal_Error whal_Stm32n6_CrypAesCcm_Start(whal_AesCcm *dev,
Expand Down Expand Up @@ -1504,6 +1525,7 @@ whal_Error whal_Stm32n6_CrypAesCcm_Finalize(whal_AesCcm *dev,
err = WaitOutputReady(base, cfg->timeout);
if (err) {
Disable(base);
ZeroKeyIv(base);
return err;
}

Expand All @@ -1512,6 +1534,7 @@ whal_Error whal_Stm32n6_CrypAesCcm_Finalize(whal_AesCcm *dev,
((uint8_t *)tag)[i] = tagBuf[i];

Disable(base);
ZeroKeyIv(base);
return WHAL_SUCCESS;
}

Expand Down
29 changes: 29 additions & 0 deletions src/crypto/stm32wb_aes.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -150,6 +150,24 @@ static void WriteIv(size_t base, const uint8_t *iv)
whal_Reg_Write(base, AES_IVR0_REG, whal_LoadBe32(iv + 12));
}

/* Wipe key and IV/counter material from the peripheral registers. Callers must
Comment thread
aidangarske marked this conversation as resolved.
* clear EN first (key registers are only writable while disabled). */
static void ZeroKeyIv(size_t base)
{
whal_Reg_Write(base, AES_KEYR7_REG, 0);
whal_Reg_Write(base, AES_KEYR6_REG, 0);
whal_Reg_Write(base, AES_KEYR5_REG, 0);
whal_Reg_Write(base, AES_KEYR4_REG, 0);
whal_Reg_Write(base, AES_KEYR3_REG, 0);
whal_Reg_Write(base, AES_KEYR2_REG, 0);
whal_Reg_Write(base, AES_KEYR1_REG, 0);
whal_Reg_Write(base, AES_KEYR0_REG, 0);
whal_Reg_Write(base, AES_IVR3_REG, 0);
whal_Reg_Write(base, AES_IVR2_REG, 0);
whal_Reg_Write(base, AES_IVR1_REG, 0);
whal_Reg_Write(base, AES_IVR0_REG, 0);
}

static void WriteBlock(size_t base, const uint8_t *in)
{
whal_Reg_Write(base, AES_DINR_REG, whal_LoadBe32(in));
Expand Down Expand Up @@ -265,6 +283,7 @@ whal_Error whal_Stm32wb_Aes_Deinit(whal_Crypto *dev)
{
(void)dev;
DisableAes((whal_Crypto *)&whal_Stm32wb_Aes_Dev);
ZeroKeyIv(whal_Stm32wb_Aes_Dev.base);
return WHAL_SUCCESS;
}

Expand Down Expand Up @@ -317,6 +336,7 @@ whal_Error whal_Stm32wb_AesEcb_Oneshot(whal_AesEcb *dev, whal_Crypto_Dir dir,

err = ProcessBlockCipher(crypto, in, out, sz);
DisableAes(crypto);
ZeroKeyIv(base);
return err;
}

Expand Down Expand Up @@ -419,6 +439,7 @@ whal_Error whal_Stm32wb_AesCbc_Oneshot(whal_AesCbc *dev, whal_Crypto_Dir dir,

err = ProcessBlockCipher(crypto, in, out, sz);
DisableAes(crypto);
ZeroKeyIv(base);
return err;
}

Expand Down Expand Up @@ -521,6 +542,7 @@ whal_Error whal_Stm32wb_AesCtr_Oneshot(whal_AesCtr *dev, whal_Crypto_Dir dir,

err = ProcessBlockCipher(crypto, in, out, sz);
DisableAes(crypto);
ZeroKeyIv(base);
return err;
}

Expand Down Expand Up @@ -760,6 +782,7 @@ whal_Error whal_Stm32wb_AesGcm_Oneshot(whal_AesGcm *dev, whal_Crypto_Dir dir,

cleanup:
whal_Reg_Update(base, AES_CR_REG, AES_CR_EN_Msk, 0);
ZeroKeyIv(base);
return err;
}

Expand Down Expand Up @@ -986,6 +1009,7 @@ whal_Error whal_Stm32wb_AesGcm_Finalize(whal_AesGcm *dev,
err = WaitForCCF(base, cfg->timeout);
if (err) {
whal_Reg_Update(base, AES_CR_REG, AES_CR_EN_Msk, 0);
ZeroKeyIv(base);
return err;
}

Expand All @@ -995,6 +1019,7 @@ whal_Error whal_Stm32wb_AesGcm_Finalize(whal_AesGcm *dev,
((uint8_t *)tag)[i] = tagBuf[i];

whal_Reg_Update(base, AES_CR_REG, AES_CR_EN_Msk, 0);
ZeroKeyIv(base);
return WHAL_SUCCESS;
}

Expand Down Expand Up @@ -1133,6 +1158,7 @@ whal_Error whal_Stm32wb_AesGmac_Oneshot(whal_AesGmac *dev,

cleanup:
whal_Reg_Update(base, AES_CR_REG, AES_CR_EN_Msk, 0);
ZeroKeyIv(base);
return err;
}

Expand Down Expand Up @@ -1354,6 +1380,7 @@ whal_Error whal_Stm32wb_AesCcm_Oneshot(whal_AesCcm *dev, whal_Crypto_Dir dir,

cleanup:
whal_Reg_Update(base, AES_CR_REG, AES_CR_EN_Msk, 0);
ZeroKeyIv(base);
return err;
}

Expand Down Expand Up @@ -1615,6 +1642,7 @@ whal_Error whal_Stm32wb_AesCcm_Finalize(whal_AesCcm *dev,
err = WaitForCCF(base, cfg->timeout);
if (err) {
whal_Reg_Update(base, AES_CR_REG, AES_CR_EN_Msk, 0);
ZeroKeyIv(base);
return err;
}

Expand All @@ -1624,6 +1652,7 @@ whal_Error whal_Stm32wb_AesCcm_Finalize(whal_AesCcm *dev,
((uint8_t *)tag)[i] = tagBuf[i];

whal_Reg_Update(base, AES_CR_REG, AES_CR_EN_Msk, 0);
ZeroKeyIv(base);
return WHAL_SUCCESS;
}

Expand Down
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