validate sphincs key consistency

Author: JeremiahM37

wolfcrypt/src/sphincs.c

@@ -711,12 +711,46 @@ int wc_sphincs_export_key(sphincs_key* key, byte* priv, word32 *privSz,
  */
 int wc_sphincs_check_key(sphincs_key* key)
 {
+    int ret;
+    word32 keySize;
+    word32 pubSize;
+
     if (key == NULL) {
         return BAD_FUNC_ARG;
     }
 
-    /* Assume everything is fine. */
-    return 0;
+    if ((key->optim != FAST_VARIANT) && (key->optim != SMALL_VARIANT)) {
+        return BAD_FUNC_ARG;
+    }
+
+    if (key->level == 1) {
+        keySize = SPHINCS_LEVEL1_KEY_SIZE;
+        pubSize = SPHINCS_LEVEL1_PUB_KEY_SIZE;
+    }
+    else if (key->level == 3) {
+        keySize = SPHINCS_LEVEL3_KEY_SIZE;
+        pubSize = SPHINCS_LEVEL3_PUB_KEY_SIZE;
+    }
+    else if (key->level == 5) {
+        keySize = SPHINCS_LEVEL5_KEY_SIZE;
+        pubSize = SPHINCS_LEVEL5_PUB_KEY_SIZE;
+    }
+    else {
+        return BAD_FUNC_ARG;
+    }
+
+    if (!key->pubKeySet || !key->prvKeySet) {
+        return PUBLIC_KEY_E;
+    }
+
+    /* SPHINCS+ secret key format ends with PK.seed || PK.root, which is the
+     * public key. Compare it against the stored public key. */
+    ret = XMEMCMP(key->p, key->k + keySize - pubSize, pubSize);
+    if (ret != 0) {
+        ret = PUBLIC_KEY_E;
+    }
+
+    return ret;
 }
 
 /* Returns the size of a sphincs private key.