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XMSS/Falcon: zeroize secret working state and key buffers before free #11372

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XMSS/Falcon: zeroize secret working state and key buffers before free #11372

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3 changes: 3 additions & 0 deletions wolfcrypt/src/falcon.c
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Original file line number Diff line number Diff line change
Expand Up @@ -9540,6 +9540,9 @@ int wc_Falcon_PrivateKeyDecode(const byte* input, word32* inOutIdx,
}
}

/* Zeroize the decoded private key before free (matches every other secret
* temporary in this file); pubKey is public and needs no scrubbing. */
ForceZero(privKey, FALCON_MAX_PRV_KEY_SIZE);
XFREE(privKey, NULL, DYNAMIC_TYPE_TMP_BUFFER);
XFREE(pubKey, NULL, DYNAMIC_TYPE_TMP_BUFFER);
return ret;
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14 changes: 14 additions & 0 deletions wolfcrypt/src/wc_xmss.c
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Original file line number Diff line number Diff line change
Expand Up @@ -787,6 +787,8 @@ static WC_INLINE int wc_xmsskey_signupdate(XmssKey* key, byte* sig,
/* Free state after use. */
wc_xmss_state_free(state);
}
/* Zeroize working state before free. */
ForceZero(state, sizeof(XmssState));
WC_FREE_VAR_EX(state, key->heap, DYNAMIC_TYPE_TMP_BUFFER);
}
}
Expand Down Expand Up @@ -1284,6 +1286,8 @@ int wc_XmssKey_MakeKey(XmssKey* key, WC_RNG* rng)
/* Free state after use. */
wc_xmss_state_free(state);
}
/* Zeroize working state before free. */
ForceZero(state, sizeof(XmssState));
WC_FREE_VAR_EX(state, key->heap, DYNAMIC_TYPE_TMP_BUFFER);
}
}
Expand All @@ -1305,6 +1309,14 @@ int wc_XmssKey_MakeKey(XmssKey* key, WC_RNG* rng)
key->state = WC_XMSS_STATE_OK;
}

/* Zeroize the secret seed (SK_seed || SK_PRF) before freeing the buffer. */
#ifdef WOLFSSL_SMALL_STACK
if (seed != NULL) {
ForceZero(seed, 3U * key->params->n);
}
#else
ForceZero(seed, sizeof(seed));
#endif
WC_FREE_VAR_EX(seed, key->heap, DYNAMIC_TYPE_TMP_BUFFER);
return ret;
}
Expand Down Expand Up @@ -2015,6 +2027,8 @@ int wc_XmssKey_Verify(XmssKey* key, const byte* sig, word32 sigLen,
/* Free state after use. */
wc_xmss_state_free(state);
}
/* Zeroize working state before free. */
ForceZero(state, sizeof(XmssState));
WC_FREE_VAR_EX(state, key->heap, DYNAMIC_TYPE_TMP_BUFFER);
}
}
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