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SSL/TLS: blind private key DER
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When WOLFSSL_BLIND_PRIVATE_KEY is defined, blind the private key DER
encoding so that stored private key data is always changing.
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@SparkiDev
SparkiDev committed May 13, 2024
1 parent f24ebdd commit b7eca57
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Showing 8 changed files with 403 additions and 24 deletions.
151 changes: 148 additions & 3 deletions src/internal.c
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Original file line number Diff line number Diff line change
Expand Up @@ -266,6 +266,49 @@ static int SSL_hmac(WOLFSSL* ssl, byte* digest, const byte* in, word32 sz,
#endif /* !WOLFSSL_NO_TLS12 */


#if !defined(NO_CERT) && defined(WOLFSSL_BLIND_PRIVATE_KEY)
int wolfssl_priv_der_blind(WC_RNG* rng, DerBuffer* key, DerBuffer** mask)
{
int ret = 0;
WC_RNG local_rng;

if (key != NULL) {
if (*mask != NULL) {
FreeDer(mask);
}
ret = AllocDer(mask, key->length, key->type, key->heap);
if ((ret == 0) && (rng == NULL)) {
if (wc_InitRng(&local_rng) != 0) {
ret = RNG_FAILURE_E;
}
else {
rng = &local_rng;
}
}
if (ret == 0) {
ret = wc_RNG_GenerateBlock(rng, (*mask)->buffer, (*mask)->length);
}
if (ret == 0) {
xorbuf(key->buffer, (*mask)->buffer, (*mask)->length);
}

if (rng == &local_rng) {
wc_FreeRng(rng);
}
}

return ret;
}

void wolfssl_priv_der_unblind(DerBuffer* key, DerBuffer* mask)
{
if (key != NULL) {
xorbuf(key->buffer, mask->buffer, mask->length);
}
}
#endif


#if defined(WOLFSSL_RENESAS_FSPSM_TLS) || defined(WOLFSSL_RENESAS_TSIP_TLS)
#include <wolfssl/wolfcrypt/port/Renesas/renesas_cmn.h>
#endif
Expand Down Expand Up @@ -2604,11 +2647,17 @@ void SSL_CtxResourceFree(WOLFSSL_CTX* ctx)
ForceZero(ctx->privateKey->buffer, ctx->privateKey->length);
}
FreeDer(&ctx->privateKey);
#ifdef WOLFSSL_BLIND_PRIVATE_KEY
FreeDer(&ctx->privateKeyMask);
#endif
#ifdef WOLFSSL_DUAL_ALG_CERTS
if (ctx->altPrivateKey != NULL && ctx->altPrivateKey->buffer != NULL) {
ForceZero(ctx->altPrivateKey->buffer, ctx->altPrivateKey->length);
}
FreeDer(&ctx->altPrivateKey);
#ifdef WOLFSSL_BLIND_PRIVATE_KEY
FreeDer(&ctx->altPrivateKeyMask);
#endif
#endif /* WOLFSSL_DUAL_ALG_CERTS */
#ifdef OPENSSL_ALL
wolfSSL_EVP_PKEY_free(ctx->privateKeyPKey);
Expand Down Expand Up @@ -6763,14 +6812,45 @@ int SetSSL_CTX(WOLFSSL* ssl, WOLFSSL_CTX* ctx, int writeDup)
#ifdef WOLFSSL_TLS13
ssl->buffers.certChainCnt = ctx->certChainCnt;
#endif
#ifndef WOLFSSL_BLIND_PRIVATE_KEY
ssl->buffers.key = ctx->privateKey;
#else
if (ctx->privateKey != NULL) {
AllocCopyDer(&ssl->buffers.key, ctx->privateKey->buffer,
ctx->privateKey->length, ctx->privateKey->type,
ctx->privateKey->heap);
ssl->buffers.weOwnKey = 1;
/* Blind the private key for the SSL with new random mask. */
wolfssl_priv_der_unblind(ssl->buffers.key, ctx->privateKeyMask);
ret = wolfssl_priv_der_blind(ssl->rng, ssl->buffers.key,
&ssl->buffers.keyMask);
if (ret != 0) {
return ret;
}
}
#endif
ssl->buffers.keyType = ctx->privateKeyType;
ssl->buffers.keyId = ctx->privateKeyId;
ssl->buffers.keyLabel = ctx->privateKeyLabel;
ssl->buffers.keySz = ctx->privateKeySz;
ssl->buffers.keyDevId = ctx->privateKeyDevId;
#ifdef WOLFSSL_DUAL_ALG_CERTS
ssl->buffers.altKey = ctx->altPrivateKey;
#ifndef WOLFSSL_BLIND_PRIVATE_KEY
ssl->buffers.altKey = ctx->altPrivateKey;
#else
if (ctx->altPrivateKey != NULL) {
AllocCopyDer(&ssl->buffers.altkey, ctx->altPrivateKey->buffer,
ctx->altPrivateKey->length, ctx->altPrivateKey->type,
ctx->altPrivateKey->heap);
/* Blind the private key for the SSL with new random mask. */
wolfssl_priv_der_unblind(ssl->buffers.altKey, ctx->altPrivateKeyMask);
ret = wolfssl_priv_der_blind(ssl->rng, ssl->buffers.altKey,
&ssl->buffers.altKeyMask);
if (ret != 0) {
return ret;
}
}
#endif
ssl->buffers.altKeyType = ctx->altPrivateKeyType;
ssl->buffers.altKeyId = ctx->altPrivateKeyId;
ssl->buffers.altKeyLabel = ctx->altPrivateKeyLabel;
Expand Down Expand Up @@ -8518,8 +8598,14 @@ void FreeHandshakeResources(WOLFSSL* ssl)
}
#endif /* !NO_DH */

#ifndef NO_CERTS
wolfSSL_UnloadCertsKeys(ssl);
#if !defined(NO_CERTS) && !defined(OPENSSL_EXTRA) && \
!defined(WOLFSSL_WPAS_SMALL)
#ifndef WOLFSSL_POST_HANDSHAKE_AUTH
if (ssl->options.side != WOLFSSL_CLIENT_END)
#endif
{
wolfSSL_UnloadCertsKeys(ssl);
}
#endif
#ifdef HAVE_PK_CALLBACKS
#if defined(WOLFSSL_TLS13) && defined(WOLFSSL_POST_HANDSHAKE_AUTH)
Expand Down Expand Up @@ -28322,6 +28408,10 @@ int DecodeAltPrivateKey(WOLFSSL *ssl, word32* length)
ERROR_OUT(NO_PRIVATE_KEY, exit_dapk);
}

#ifdef WOLFSSL_BLIND_PRIVATE_KEY
wolfssl_priv_der_unblind(ssl->buffers.altKey, ssl->buffers.altKeyMask);
#endif

#ifdef WOLF_PRIVATE_KEY_ID
if (ssl->buffers.altKeyDevId != INVALID_DEVID &&
(ssl->buffers.altKeyId || ssl->buffers.altKeyLabel)) {
Expand Down Expand Up @@ -28724,6 +28814,16 @@ int DecodeAltPrivateKey(WOLFSSL *ssl, word32* length)
(void)length;

exit_dapk:
#ifdef WOLFSSL_BLIND_PRIVATE_KEY
if (ret == 0) {
ret = wolfssl_priv_der_blind(ssl->rng, ssl->buffers.altKey,
&ssl->buffers.altKeyMask);
}
else {
wolfssl_priv_der_unblind(ssl->buffers.key, ssl->buffers.keyMask);
}
#endif

if (ret != 0) {
WOLFSSL_ERROR_VERBOSE(ret);
}
Expand Down Expand Up @@ -32746,6 +32846,10 @@ int SendCertificateVerify(WOLFSSL* ssl)
WOLFSSL_START(WC_FUNC_CERTIFICATE_VERIFY_SEND);
WOLFSSL_ENTER("SendCertificateVerify");

#ifdef WOLFSSL_BLIND_PRIVATE_KEY
wolfssl_priv_der_unblind(ssl->buffers.key, ssl->buffers.keyMask);
#endif

#ifdef WOLFSSL_ASYNC_IO
if (ssl->async == NULL) {
ssl->async = (struct WOLFSSL_ASYNC*)
Expand Down Expand Up @@ -32792,6 +32896,10 @@ int SendCertificateVerify(WOLFSSL* ssl)
case TLS_ASYNC_BEGIN:
{
if (ssl->options.sendVerify == SEND_BLANK_CERT) {
#ifdef WOLFSSL_BLIND_PRIVATE_KEY
wolfssl_priv_der_unblind(ssl->buffers.key,
ssl->buffers.keyMask);
#endif
return 0; /* sent blank cert, can't verify */
}

Expand Down Expand Up @@ -33196,6 +33304,15 @@ int SendCertificateVerify(WOLFSSL* ssl)
} /* switch(ssl->options.asyncState) */

exit_scv:
#ifdef WOLFSSL_BLIND_PRIVATE_KEY
if (ret == 0) {
ret = wolfssl_priv_der_blind(ssl->rng, ssl->buffers.key,
&ssl->buffers.keyMask);
}
else {
wolfssl_priv_der_unblind(ssl->buffers.key, ssl->buffers.keyMask);
}
#endif

WOLFSSL_LEAVE("SendCertificateVerify", ret);
WOLFSSL_END(WC_FUNC_CERTIFICATE_VERIFY_SEND);
Expand Down Expand Up @@ -33859,6 +33976,10 @@ static int DoSessionTicket(WOLFSSL* ssl, const byte* input, word32* inOutIdx,
WOLFSSL_START(WC_FUNC_SERVER_KEY_EXCHANGE_SEND);
WOLFSSL_ENTER("SendServerKeyExchange");

#ifdef WOLFSSL_BLIND_PRIVATE_KEY
wolfssl_priv_der_unblind(ssl->buffers.key, ssl->buffers.keyMask);
#endif

#ifdef WOLFSSL_ASYNC_IO
if (ssl->async == NULL) {
ssl->async = (struct WOLFSSL_ASYNC*)
Expand Down Expand Up @@ -35415,6 +35536,16 @@ static int DoSessionTicket(WOLFSSL* ssl, const byte* input, word32* inOutIdx,

exit_sske:

#ifdef WOLFSSL_BLIND_PRIVATE_KEY
if (ret == 0) {
ret = wolfssl_priv_der_blind(ssl->rng, ssl->buffers.key,
&ssl->buffers.keyMask);
}
else {
wolfssl_priv_der_unblind(ssl->buffers.key, ssl->buffers.keyMask);
}
#endif

WOLFSSL_LEAVE("SendServerKeyExchange", ret);
WOLFSSL_END(WC_FUNC_SERVER_KEY_EXCHANGE_SEND);

Expand Down Expand Up @@ -38937,6 +39068,10 @@ static int DefTicketEncCb(WOLFSSL* ssl, byte key_name[WOLFSSL_TICKET_NAME_SZ],
WOLFSSL_START(WC_FUNC_CLIENT_KEY_EXCHANGE_DO);
WOLFSSL_ENTER("DoClientKeyExchange");

#ifdef WOLFSSL_BLIND_PRIVATE_KEY
wolfssl_priv_der_unblind(ssl->buffers.key, ssl->buffers.keyMask);
#endif

#ifdef WOLFSSL_ASYNC_CRYPT
if (ssl->async == NULL) {
ssl->async = (struct WOLFSSL_ASYNC*)
Expand Down Expand Up @@ -40131,6 +40266,16 @@ static int DefTicketEncCb(WOLFSSL* ssl, byte key_name[WOLFSSL_TICKET_NAME_SZ],

exit_dcke:

#ifdef WOLFSSL_BLIND_PRIVATE_KEY
if (ret == 0) {
ret = wolfssl_priv_der_blind(ssl->rng, ssl->buffers.key,
&ssl->buffers.keyMask);
}
else {
wolfssl_priv_der_unblind(ssl->buffers.key, ssl->buffers.keyMask);
}
#endif

WOLFSSL_LEAVE("DoClientKeyExchange", ret);
WOLFSSL_END(WC_FUNC_CLIENT_KEY_EXCHANGE_DO);
#ifdef WOLFSSL_ASYNC_CRYPT
Expand Down
3 changes: 2 additions & 1 deletion src/pk.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -11704,7 +11704,8 @@ static int wolfssl_ec_key_int_copy(ecc_key* dst, const ecc_key* src)

if (ret == 0) {
/* Copy private key. */
ret = mp_copy(wc_ecc_key_get_priv(src), wc_ecc_key_get_priv(dst));
ret = mp_copy(wc_ecc_key_get_priv((ecc_key*)src),
wc_ecc_key_get_priv(dst));
if (ret != MP_OKAY) {
WOLFSSL_MSG("mp_copy error");
}
Expand Down
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