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fix: force-zero secret buffers before free #1099

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fix: force-zero secret buffers before free #1099

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2 changes: 2 additions & 0 deletions apps/wolfsshd/wolfsshd.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1946,6 +1946,8 @@ static int SHELL_Subsystem(WOLFSSHD_CONNECTION* conn, WOLFSSH* ssh,
}
}

ForceZero(channelBuffer, sizeof channelBuffer);
ForceZero(shellBuffer, sizeof shellBuffer);
(void)conn;
return WS_SUCCESS;
}
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4 changes: 2 additions & 2 deletions src/agent.c
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Expand Up @@ -1582,10 +1582,10 @@ void wolfSSH_AGENT_ID_free(WOLFSSH_AGENT_ID* id, void* heap)

if (id != NULL) {
if (id->keyBuffer != NULL) {
WMEMSET(id->keyBuffer, 0, id->keyBufferSz);
ForceZero(id->keyBuffer, id->keyBufferSz);
WFREE(id->keyBuffer, heap, DYNTYPE_STRING);
}
WMEMSET(id, 0, sizeof(WOLFSSH_AGENT_ID));
ForceZero(id, sizeof(WOLFSSH_AGENT_ID));
WFREE(id, heap, DYNTYPE_AGENT_ID);
}

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38 changes: 37 additions & 1 deletion src/internal.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1558,6 +1558,10 @@ void SshResourceFree(WOLFSSH* ssh, void* heap)
HandshakeInfoFree(ssh->handshake, heap);
ForceZero(&ssh->keys, sizeof(Keys));
ForceZero(&ssh->peerKeys, sizeof(Keys));
ForceZero(ssh->h, sizeof(ssh->h));
ssh->hSz = 0;
ForceZero(ssh->sessionId, sizeof(ssh->sessionId));
ssh->sessionIdSz = 0;
if (ssh->rng) {
wc_FreeRng(ssh->rng);
WFREE(ssh->rng, heap, DYNTYPE_RNG);
Expand Down Expand Up @@ -2794,6 +2798,11 @@ static int SetHostPrivateKey(WOLFSSH_CTX* ctx,
}

if (destIdx >= WOLFSSH_MAX_PVT_KEYS) {
/* CTX is full and keyId is new: der cannot be stored, so this
* function takes ownership and zeroizes+frees it to avoid leaking
* the private key material. */
ForceZero(der, derSz);
WFREE(der, ctx->heap, dynamicType);
ret = WS_CTX_KEY_COUNT_E;
}
else {
Expand Down Expand Up @@ -3552,6 +3561,8 @@ void ChannelDelete(WOLFSSH_CHANNEL* channel, void* heap)
if (channel->origin)
WFREE(channel->origin, heap, DYNTYPE_STRING);
#endif /* WOLFSSH_FWD */
if (channel->inputBuffer.buffer)
ForceZero(channel->inputBuffer.buffer, channel->inputBuffer.bufferSz);
WFREE(channel->inputBuffer.buffer,
channel->inputBuffer.heap, DYNTYPE_BUFFER);
if (channel->command)
Expand Down Expand Up @@ -6664,6 +6675,9 @@ static int KeyAgreeEcdhMlKem_client(WOLFSSH* ssh, byte hashId,
ret);
}

/* Zero the ML-KEM private key material in handshake->x now that
* decapsulation is done, matching the DH path's post-use ForceZero. */
ForceZero(ssh->handshake->x, ssh->handshake->xSz);
wc_MlKemKey_Free(&kem);

/* Replace the concatenated shared secrets with the hash. That
Expand Down Expand Up @@ -8274,8 +8288,11 @@ static int DoUserAuthRequestRsa(WOLFSSH* ssh, WS_UserAuthData_PublicKey* pk,
WFREE(key, ssh->ctx->heap, DYNTYPE_PUBKEY);
}
if (encDigest) {
ForceZero(encDigest, MAX_ENCODED_SIG_SZ);
WFREE(encDigest, ssh->ctx->heap, DYNTYPE_BUFFER);
}
#else
ForceZero(encDigest, sizeof(encDigest));
#endif

WLOG(WS_LOG_DEBUG, "Leaving DoUserAuthRequestRsa(), ret = %d", ret);
Expand Down Expand Up @@ -8435,8 +8452,11 @@ static int DoUserAuthRequestRsaCert(WOLFSSH* ssh, WS_UserAuthData_PublicKey* pk,
WFREE(key, ssh->ctx->heap, DYNTYPE_PUBKEY);
}
if (encDigest) {
ForceZero(encDigest, MAX_ENCODED_SIG_SZ);
WFREE(encDigest, ssh->ctx->heap, DYNTYPE_BUFFER);
}
#else
ForceZero(encDigest, sizeof(encDigest));
#endif

WLOG(WS_LOG_DEBUG, "Leaving DoUserAuthRequestRsaCert(), ret = %d", ret);
Expand Down Expand Up @@ -9477,6 +9497,8 @@ static int DoUserAuthRequestPublicKey(WOLFSSH* ssh, WS_UserAuthData* authData,
ret = WS_INVALID_ALGO_ID;
}
}

ForceZero(digest, sizeof(digest));
}

if (ret != WS_SUCCESS) {
Expand Down Expand Up @@ -14059,9 +14081,14 @@ static int SignHRsa(WOLFSSH* ssh, byte* sig, word32* sigSz,
&sigKey->sk.rsa.key, heap, "SignHRsa");
}

ForceZero(digest, sizeof(digest));
#ifdef WOLFSSH_SMALL_STACK
if (encSig != NULL)
if (encSig != NULL) {
ForceZero(encSig, MAX_ENCODED_SIG_SZ);
WFREE(encSig, heap, DYNTYPE_TEMP);
}
#else
ForceZero(encSig, MAX_ENCODED_SIG_SZ);
#endif
WLOG(WS_LOG_DEBUG, "Leaving SignHRsa(), ret = %d", ret);
return ret;
Expand Down Expand Up @@ -14203,6 +14230,7 @@ static int SignHEcdsa(WOLFSSH* ssh, byte* sig, word32* sigSz,
WMEMCPY(sig + idx, s, sSz);
}

ForceZero(digest, sizeof(digest));
#ifdef WOLFSSH_SMALL_STACK
if (r)
WFREE(r, heap, DYNTYPE_BUFFER);
Expand Down Expand Up @@ -16227,6 +16255,8 @@ static int BuildUserAuthRequestRsa(WOLFSSH* ssh,

if (ret == WS_SUCCESS)
begin += keySig->sigSz;

ForceZero(encDigest, sizeof(encDigest));
}
}

Expand All @@ -16238,6 +16268,7 @@ static int BuildUserAuthRequestRsa(WOLFSSH* ssh,
WFREE(checkData, ssh->ctx->heap, DYNTYPE_TEMP);
}

ForceZero(digest, sizeof(digest));
return ret;
} /* END BuildUserAuthRequestRsa */

Expand Down Expand Up @@ -16407,6 +16438,8 @@ static int BuildUserAuthRequestRsaCert(WOLFSSH* ssh,

if (ret == WS_SUCCESS)
begin += keySig->sigSz;

ForceZero(encDigest, sizeof(encDigest));
}
}

Expand All @@ -16418,6 +16451,7 @@ static int BuildUserAuthRequestRsaCert(WOLFSSH* ssh,
WFREE(checkData, ssh->ctx->heap, DYNTYPE_TEMP);
}

ForceZero(digest, sizeof(digest));
WLOG(WS_LOG_DEBUG, "Leaving BuildUserAuthRequestRsaCert(), ret = %d",
ret);
return ret;
Expand Down Expand Up @@ -16685,6 +16719,7 @@ static int BuildUserAuthRequestEcc(WOLFSSH* ssh,
WFREE(checkData, ssh->ctx->heap, DYNTYPE_TEMP);
}

ForceZero(digest, sizeof(digest));
#ifdef WOLFSSH_SMALL_STACK
if (r_ptr)
WFREE(r_ptr, ssh->ctx->heap, DYNTYPE_BUFFER);
Expand Down Expand Up @@ -16945,6 +16980,7 @@ static int BuildUserAuthRequestEccCert(WOLFSSH* ssh,
WFREE(checkData, ssh->ctx->heap, DYNTYPE_TEMP);
}

ForceZero(digest, sizeof(digest));
return ret;
}

Expand Down
4 changes: 4 additions & 0 deletions src/wolfsftp.c
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Original file line number Diff line number Diff line change
Expand Up @@ -850,6 +850,7 @@ static void wolfSSH_SFTP_ClearState(WOLFSSH* ssh, enum WS_SFTP_STATE_ID state)

if (state & STATE_ID_GET) {
if (ssh->getState) {
ForceZero(ssh->getState, sizeof(WS_SFTP_GET_STATE));
WFREE(ssh->getState, ssh->ctx->heap, DYNTYPE_SFTP_STATE);
ssh->getState = NULL;
}
Expand Down Expand Up @@ -928,6 +929,7 @@ static void wolfSSH_SFTP_ClearState(WOLFSSH* ssh, enum WS_SFTP_STATE_ID state)

if (state & STATE_ID_PUT) {
if (ssh->putState) {
ForceZero(ssh->putState, sizeof(WS_SFTP_PUT_STATE));
WFREE(ssh->putState, ssh->ctx->heap, DYNTYPE_SFTP_STATE);
ssh->putState = NULL;
}
Expand Down Expand Up @@ -9775,6 +9777,7 @@ int wolfSSH_SFTP_Get(WOLFSSH* ssh, char* from,
case STATE_GET_CLEANUP:
WLOG(WS_LOG_SFTP, "SFTP GET STATE: CLEANUP");
if (ssh->getState != NULL) {
ForceZero(ssh->getState, sizeof(WS_SFTP_GET_STATE));
WFREE(ssh->getState, ssh->ctx->heap, DYNTYPE_SFTP_STATE);
ssh->getState = NULL;
}
Expand Down Expand Up @@ -9998,6 +10001,7 @@ int wolfSSH_SFTP_Put(WOLFSSH* ssh, char* from, char* to, byte resume,
case STATE_PUT_CLEANUP:
WLOG(WS_LOG_SFTP, "SFTP PUT STATE: CLEANUP");
if (ssh->putState != NULL) {
ForceZero(ssh->putState, sizeof(WS_SFTP_PUT_STATE));
WFREE(ssh->putState, ssh->ctx->heap, DYNTYPE_SFTP_STATE);
ssh->putState = NULL;
}
Expand Down
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