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Restore SHA3 client state when the server cannot offload #455

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Merged
Frauschi merged 1 commit into from
Jul 20, 2026
Merged

Restore SHA3 client state when the server cannot offload #455

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53 changes: 49 additions & 4 deletions src/wh_client_crypto.c
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Original file line number Diff line number Diff line change
Expand Up @@ -8695,11 +8695,34 @@ static int _Sha3FinalResponse(whClientContext* ctx, wc_Sha3* sha,
return ret;
}

/* Snapshot of the streaming state the offload path mutates: the Keccak
* state and the locally buffered partial block. */
typedef struct {
uint64_t s[25];
uint8_t t[WC_SHA3_224_BLOCK_SIZE]; /* largest block size: 144 */
uint32_t i;
} _Sha3SavedState;

static void _Sha3SaveState(const wc_Sha3* sha, _Sha3SavedState* saved)
{
saved->i = sha->i;
memcpy(saved->s, sha->s, sizeof(saved->s));
memcpy(saved->t, sha->t, sizeof(saved->t));
}

static void _Sha3RestoreState(wc_Sha3* sha, const _Sha3SavedState* saved)
{
sha->i = (uint8_t)saved->i;
memcpy(sha->s, saved->s, sizeof(saved->s));
memcpy(sha->t, saved->t, sizeof(saved->t));
}

static int _Sha3Oneshot(whClientContext* ctx, wc_Sha3* sha,
const whSha3Variant* v, const uint8_t* in,
uint32_t inLen, uint8_t* out)
{
int ret = WH_ERROR_OK;
int ret = WH_ERROR_OK;
_Sha3SavedState saved;

/* _Sha3UpdatePerCallCapacity (below) reads sha->i, so validate sha here
* rather than relying on the lower-level helper's NULL check. */
Expand All @@ -8713,6 +8736,11 @@ static int _Sha3Oneshot(whClientContext* ctx, wc_Sha3* sha,
return WH_ERROR_BADARGS;
}

/* A server without SHA3 answers NOT_COMPILED_IN, which wolfCrypt maps to
* CRYPTOCB_UNAVAILABLE and re-hashes the same input in software. Snapshot
* so that fallback cannot absorb any of it twice. */
_Sha3SaveState(sha, &saved);

if (in != NULL && inLen > 0) {
uint32_t consumed = 0;
while (ret == WH_ERROR_OK && consumed < inLen) {
Expand Down Expand Up @@ -8745,6 +8773,12 @@ static int _Sha3Oneshot(whClientContext* ctx, wc_Sha3* sha,
} while (ret == WH_ERROR_NOTREADY);
}
}

/* Leave sha as the caller passed it so a fallback starts clean. */
if (ret != WH_ERROR_OK) {
_Sha3RestoreState(sha, &saved);
}

return ret;
}

Expand Down Expand Up @@ -9135,14 +9169,19 @@ static int _Sha3DmaOneshot(whClientContext* ctx, wc_Sha3* sha,
const whSha3Variant* v, const uint8_t* in,
uint32_t inLen, uint8_t* out)
{
int ret = WH_ERROR_OK;
int ret = WH_ERROR_OK;
_Sha3SavedState saved;

/* Mirror _Sha3DmaUpdateRequest's invariant: skipping the update branch on
* (in == NULL && inLen != 0) would silently digest the current state. */
if (in == NULL && inLen != 0) {
* (in == NULL && inLen != 0) would silently digest the current state.
* sha is validated here since _Sha3SaveState dereferences it below. */
if (sha == NULL || (in == NULL && inLen != 0)) {
return WH_ERROR_BADARGS;
}

/* Same fallback hazard as _Sha3Oneshot: snapshot before mutating. */
_Sha3SaveState(sha, &saved);

if (in != NULL && inLen > 0) {
bool sent = false;
ret = _Sha3DmaUpdateRequest(ctx, sha, v, in, inLen, &sent);
Expand All @@ -9160,6 +9199,12 @@ static int _Sha3DmaOneshot(whClientContext* ctx, wc_Sha3* sha,
} while (ret == WH_ERROR_NOTREADY);
}
}

/* Leave sha as the caller passed it so a fallback starts clean. */
if (ret != WH_ERROR_OK) {
_Sha3RestoreState(sha, &saved);
}

return ret;
}

Expand Down
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