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Add independent ciper and MAC algorithms negotiation for each direction #952

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176 changes: 123 additions & 53 deletions src/internal.c
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Original file line number Diff line number Diff line change
Expand Up @@ -571,13 +571,9 @@ static HandshakeInfo* HandshakeInfoNew(void* heap)
heap, DYNTYPE_HS);
if (newHs != NULL) {
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WMEMSET(newHs, 0, sizeof(HandshakeInfo));
newHs->expectMsgId = MSGID_NONE;
newHs->kexId = ID_NONE;
newHs->kexHashId = WC_HASH_TYPE_NONE;
newHs->pubKeyId = ID_NONE;
newHs->encryptId = ID_NONE;
newHs->macId = ID_NONE;
newHs->blockSz = MIN_BLOCK_SZ;
newHs->peerBlockSz = MIN_BLOCK_SZ;
newHs->eSz = (word32)sizeof(newHs->e);
newHs->xSz = (word32)sizeof(newHs->x);
#ifndef WOLFSSH_NO_DH_GEX_SHA256
Expand Down Expand Up @@ -2659,19 +2655,17 @@ static int GenerateKeys(WOLFSSH* ssh, byte hashId, byte doKeyPad)
sK->encKey, sK->encKeySz,
ssh->k, ssh->kSz, ssh->h, ssh->hSz,
ssh->sessionId, ssh->sessionIdSz, doKeyPad);
if (ret == WS_SUCCESS) {
if (!ssh->handshake->aeadMode) {
ret = GenerateKey(hashId, 'E',
cK->macKey, cK->macKeySz,
ssh->k, ssh->kSz, ssh->h, ssh->hSz,
ssh->sessionId, ssh->sessionIdSz, doKeyPad);
if (ret == WS_SUCCESS) {
ret = GenerateKey(hashId, 'F',
sK->macKey, sK->macKeySz,
ssh->k, ssh->kSz, ssh->h, ssh->hSz,
ssh->sessionId, ssh->sessionIdSz, doKeyPad);
}
}
if (ret == WS_SUCCESS && cK->macKeySz > 0) {
ret = GenerateKey(hashId, 'E',
cK->macKey, cK->macKeySz,
ssh->k, ssh->kSz, ssh->h, ssh->hSz,
ssh->sessionId, ssh->sessionIdSz, doKeyPad);
}
if (ret == WS_SUCCESS && sK->macKeySz > 0) {
ret = GenerateKey(hashId, 'F',
sK->macKey, sK->macKeySz,
ssh->k, ssh->kSz, ssh->h, ssh->hSz,
ssh->sessionId, ssh->sessionIdSz, doKeyPad);
}

#ifdef SHOW_SECRETS
Expand Down Expand Up @@ -4250,6 +4244,18 @@ static int DoKexInit(WOLFSSH* ssh, byte* buf, word32 len, word32* idx)
word32 cannedAlgoNamesSz;
word32 skipSz = 0;
word32 begin;
/* handshake->keys/encryptId/... always represent the LOCAL endpoint's
* outgoing direction; peer* counterparts represent the peer's outgoing
* (= our incoming) direction. Server: local=S2C, peer=C2S.
* Client: local=C2S, peer=S2C. These aliases let the four enc/MAC
* parse sections store results without inline side checks, and keep the
* fields consistent with what GenerateKeys/SendNewKeys/DoNewKeys expect. */
byte *c2sEncryptId = NULL, *c2sAeadMode = NULL, *c2sBlockSz = NULL,
*c2sMacId = NULL, *c2sMacSz = NULL;
Keys *c2sKeys = NULL;
byte *s2cEncryptId = NULL, *s2cAeadMode = NULL, *s2cBlockSz = NULL,
*s2cMacId = NULL, *s2cMacSz = NULL;
Keys *s2cKeys = NULL;

WLOG(WS_LOG_DEBUG, "Entering DoKexInit()");

Expand Down Expand Up @@ -4292,6 +4298,35 @@ static int DoKexInit(WOLFSSH* ssh, byte* buf, word32 len, word32* idx)
begin = *idx;
side = ssh->ctx->side;

if (side == WOLFSSH_ENDPOINT_SERVER) {
c2sEncryptId = &ssh->handshake->peerEncryptId;
c2sAeadMode = &ssh->handshake->peerAeadMode;
c2sBlockSz = &ssh->handshake->peerBlockSz;
c2sMacId = &ssh->handshake->peerMacId;
c2sMacSz = &ssh->handshake->peerMacSz;
c2sKeys = &ssh->handshake->peerKeys;
s2cEncryptId = &ssh->handshake->encryptId;
s2cAeadMode = &ssh->handshake->aeadMode;
s2cBlockSz = &ssh->handshake->blockSz;
s2cMacId = &ssh->handshake->macId;
s2cMacSz = &ssh->handshake->macSz;
s2cKeys = &ssh->handshake->keys;
}
else {
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c2sEncryptId = &ssh->handshake->encryptId;
c2sAeadMode = &ssh->handshake->aeadMode;
c2sBlockSz = &ssh->handshake->blockSz;
c2sMacId = &ssh->handshake->macId;
c2sMacSz = &ssh->handshake->macSz;
c2sKeys = &ssh->handshake->keys;
s2cEncryptId = &ssh->handshake->peerEncryptId;
s2cAeadMode = &ssh->handshake->peerAeadMode;
s2cBlockSz = &ssh->handshake->peerBlockSz;
s2cMacId = &ssh->handshake->peerMacId;
s2cMacSz = &ssh->handshake->peerMacSz;
s2cKeys = &ssh->handshake->peerKeys;
}

/* Check that the cookie exists inside the message */
if (begin + COOKIE_SZ > len) {
/* error, out of bounds */
Expand Down Expand Up @@ -4391,6 +4426,24 @@ static int DoKexInit(WOLFSSH* ssh, byte* buf, word32 len, word32* idx)
ret = WS_MATCH_ENC_ALGO_E;
}
}
if (ret == WS_SUCCESS) {
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*c2sEncryptId = algoId;
*c2sAeadMode = AeadModeForId(algoId);
*c2sBlockSz = BlockSzForId(algoId);
c2sKeys->encKeySz = KeySzForId(algoId);
if (!*c2sAeadMode) {
c2sKeys->ivSz = *c2sBlockSz;
}
else {
/* Reaching here requires an AEAD cipher ID, which requires
* WOLFSSH_NO_AES_GCM to be unset, hence WOLFSSH_NO_AEAD unset
* (see internal.h). */
c2sKeys->ivSz = AEAD_NONCE_SZ;
*c2sMacSz = *c2sBlockSz;
*c2sMacId = ID_NONE;
c2sKeys->macKeySz = 0;
}
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}
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/* Enc Algorithms - Server to Client */
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@aidangarske aidangarske Apr 28, 2026

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🟠 [Medium] Asymmetric S2C-only encryption-algo mismatch error path is untested · path

Pre-PR, the S2C encryption algorithm was matched against the C2S-chosen algorithm only (MatchIdLists(side, list, listSz, &algoId, 1)). Post-PR, S2C is matched independently against ssh->algoListCipher via cannedList. This introduces a NEW failure mode: C2S successfully matches but S2C does not (or vice versa) — yielding WS_MATCH_ENC_ALGO_E from the S2C block. The new tests in TestIndependentAlgoNegotiation/...Client only cover the success paths for asymmetric cipher selection; no test exercises asymmetric mismatch where one direction agrees and the other fails. Grep confirms WS_MATCH_ENC_ALGO_E has zero references in tests/.

Fix: Add a regress.c test that builds a kex_init payload where the C2S cipher list contains an algorithm in the local algoListCipher but the S2C cipher list does not (e.g., local accepts aes128-cbc,aes256-ctr; payload offers C2S=aes128-cbc, S2C=3des-cbc). Verify wolfSSH_TestDoKexInit returns WS_MATCH_ENC_ALGO_E. Mirror the test for the inverse case (C2S fails, S2C succeeds).

if (ret == WS_SUCCESS) {
Expand All @@ -4399,31 +4452,32 @@ static int DoKexInit(WOLFSSH* ssh, byte* buf, word32 len, word32* idx)
ret = GetNameList(list, &listSz, buf, len, &begin);
}
if (ret == WS_SUCCESS) {
algoId = MatchIdLists(side, list, listSz, &algoId, 1);
cannedAlgoNamesSz = AlgoListSz(ssh->algoListCipher);
cannedListSz = (word32)sizeof(cannedList);
ret = GetNameListRaw(cannedList, &cannedListSz,
(const byte*)ssh->algoListCipher, cannedAlgoNamesSz);
}
if (ret == WS_SUCCESS) {
algoId = MatchIdLists(side, list, listSz, cannedList, cannedListSz);
if (algoId == ID_UNKNOWN) {
WLOG(WS_LOG_DEBUG, "Unable to negotiate Encryption Algo S2C");
ret = WS_MATCH_ENC_ALGO_E;
}
}
if (ret == WS_SUCCESS) {
ssh->handshake->encryptId = algoId;
ssh->handshake->aeadMode = AeadModeForId(algoId);
ssh->handshake->blockSz = BlockSzForId(algoId);
ssh->handshake->keys.encKeySz =
ssh->handshake->peerKeys.encKeySz =
KeySzForId(algoId);
if (!ssh->handshake->aeadMode) {
ssh->handshake->keys.ivSz =
ssh->handshake->peerKeys.ivSz =
ssh->handshake->blockSz;
*s2cEncryptId = algoId;
*s2cAeadMode = AeadModeForId(algoId);
*s2cBlockSz = BlockSzForId(algoId);
s2cKeys->encKeySz = KeySzForId(algoId);
if (!*s2cAeadMode) {
s2cKeys->ivSz = *s2cBlockSz;
}
else {
#ifndef WOLFSSH_NO_AEAD
ssh->handshake->keys.ivSz =
ssh->handshake->peerKeys.ivSz =
AEAD_NONCE_SZ;
ssh->handshake->macSz = ssh->handshake->blockSz;
#endif
/* Same invariant as C2S: AEAD cipher ID implies !WOLFSSH_NO_AEAD. */
s2cKeys->ivSz = AEAD_NONCE_SZ;
*s2cMacSz = *s2cBlockSz;
*s2cMacId = ID_NONE;
s2cKeys->macKeySz = 0;
}
}

Expand All @@ -4433,7 +4487,7 @@ static int DoKexInit(WOLFSSH* ssh, byte* buf, word32 len, word32* idx)
listSz = (word32)sizeof(list);
ret = GetNameList(list, &listSz, buf, len, &begin);
}
if (ret == WS_SUCCESS && !ssh->handshake->aeadMode) {
if (ret == WS_SUCCESS && !*c2sAeadMode) {
cannedAlgoNamesSz = AlgoListSz(ssh->algoListMac);
cannedListSz = (word32)sizeof(cannedList);
ret = GetNameListRaw(cannedList, &cannedListSz,
Expand All @@ -4445,6 +4499,11 @@ static int DoKexInit(WOLFSSH* ssh, byte* buf, word32 len, word32* idx)
WLOG(WS_LOG_DEBUG, "Unable to negotiate MAC Algo C2S");
ret = WS_MATCH_MAC_ALGO_E;
}
else {
*c2sMacId = algoId;
*c2sMacSz = MacSzForId(algoId);
c2sKeys->macKeySz = KeySzForId(algoId);
}
}
}

Expand All @@ -4454,18 +4513,22 @@ static int DoKexInit(WOLFSSH* ssh, byte* buf, word32 len, word32* idx)
listSz = (word32)sizeof(list);
ret = GetNameList(list, &listSz, buf, len, &begin);
}
if (ret == WS_SUCCESS && !ssh->handshake->aeadMode) {
algoId = MatchIdLists(side, list, listSz, &algoId, 1);
if (algoId == ID_UNKNOWN) {
WLOG(WS_LOG_DEBUG, "Unable to negotiate MAC Algo S2C");
ret = WS_MATCH_MAC_ALGO_E;
}
else {
ssh->handshake->macId = algoId;
ssh->handshake->macSz = MacSzForId(algoId);
ssh->handshake->keys.macKeySz =
ssh->handshake->peerKeys.macKeySz =
KeySzForId(algoId);
if (ret == WS_SUCCESS && !*s2cAeadMode) {
cannedAlgoNamesSz = AlgoListSz(ssh->algoListMac);
cannedListSz = (word32)sizeof(cannedList);
ret = GetNameListRaw(cannedList, &cannedListSz,
(const byte*)ssh->algoListMac, cannedAlgoNamesSz);
if (ret == WS_SUCCESS) {
algoId = MatchIdLists(side, list, listSz, cannedList, cannedListSz);
if (algoId == ID_UNKNOWN) {
WLOG(WS_LOG_DEBUG, "Unable to negotiate MAC Algo S2C");
ret = WS_MATCH_MAC_ALGO_E;
}
else {
*s2cMacId = algoId;
*s2cMacSz = MacSzForId(algoId);
s2cKeys->macKeySz = KeySzForId(algoId);
}
}
}
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🟠 [Medium] Asymmetric S2C-only MAC-algo mismatch error path is untested · path

The S2C MAC negotiation was rewritten from MatchIdLists(side, list, listSz, &algoId, 1) (which forced S2C to equal C2S) to an independent match against ssh->algoListMac. The new failure path WS_MATCH_MAC_ALGO_E can now trigger when C2S MAC matches but S2C MAC does not (and vice versa for the C2S branch at lines 4484-4508). Neither branch's WS_MATCH_MAC_ALGO_E return is exercised by any test. Grep across the repo confirms no test references WS_MATCH_MAC_ALGO_E.

Fix: Add a regress.c test that supplies asymmetric MAC lists where one direction shares no entries with ssh->algoListMac (e.g., local accepts hmac-sha1,hmac-sha2-256; payload offers C2S=hmac-sha1, S2C=hmac-md5). Assert wolfSSH_TestDoKexInit returns WS_MATCH_MAC_ALGO_E. Cover the inverse C2S-mismatch case as well.


Expand Down Expand Up @@ -6207,11 +6270,11 @@ static int DoNewKeys(WOLFSSH* ssh, byte* buf, word32 len, word32* idx)
}

if (ret == WS_SUCCESS) {
ssh->peerEncryptId = ssh->handshake->encryptId;
ssh->peerMacId = ssh->handshake->macId;
ssh->peerBlockSz = ssh->handshake->blockSz;
ssh->peerMacSz = ssh->handshake->macSz;
ssh->peerAeadMode = ssh->handshake->aeadMode;
ssh->peerEncryptId = ssh->handshake->peerEncryptId;
ssh->peerMacId = ssh->handshake->peerMacId;
ssh->peerBlockSz = ssh->handshake->peerBlockSz;
ssh->peerMacSz = ssh->handshake->peerMacSz;
ssh->peerAeadMode = ssh->handshake->peerAeadMode;
WMEMCPY(&ssh->peerKeys, &ssh->handshake->peerKeys, sizeof(Keys));

switch (ssh->peerEncryptId) {
Expand Down Expand Up @@ -17896,6 +17959,13 @@ int wolfSSH_TestDoKexInit(WOLFSSH* ssh, byte* buf, word32 len, word32* idx)
return DoKexInit(ssh, buf, len, idx);
}

int wolfSSH_TestGenerateKeys(WOLFSSH* ssh)
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🔵 [Low] wolfSSH_TestGenerateKeys NULL-argument validation is untested · test

The newly added test helper validates ssh == NULL || ssh->handshake == NULL and returns WS_BAD_ARGUMENT, but no test in tests/regress.c (or anywhere else) calls it with NULL inputs to verify the guard. All four new test sites (TestGenerateKeysSplit, TestGenerateKeysSplitClient sub-tests A and B) invoke it only after AssertNotNull(ssh->handshake). While the function is test-only infrastructure, a sibling invariant check is cheap to add.

Fix: Add a one-line assertion in regress.c (e.g., inside or adjacent to TestGenerateKeysSplit): AssertIntEQ(wolfSSH_TestGenerateKeys(NULL), WS_BAD_ARGUMENT); and a second call with a freshly-created WOLFSSH* whose handshake has been freed/nulled to verify the second branch.

{
if (ssh == NULL || ssh->handshake == NULL)
return WS_BAD_ARGUMENT;
return GenerateKeys(ssh, (enum wc_HashType)ssh->handshake->kexHashId, 1);
}

int wolfSSH_TestDoKexDhInit(WOLFSSH* ssh, byte* buf, word32 len, word32* idx)
{
return DoKexDhInit(ssh, buf, len, idx);
Expand Down
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