MemZero: Add more checks of buffers.

Added wc_MemZero_Add calls and wc_MemZero_Check calls wheter ForceZero is used.
Fixed a couple of places that had the wrong size.

Author: SparkiDev

src/dtls.c

@@ -571,10 +571,21 @@ static void FindPskSuiteFromExt(const WOLFSSL* ssl, TLSX* extensions,
                 byte psk_key[MAX_PSK_KEY_LEN];
                 word32 psk_keySz;
                 byte foundSuite[SUITE_LEN];
+            #ifdef WOLFSSL_CHECK_MEM_ZERO
+                /* Register before the key is populated so any future path that
+                 * fails to clear it before scope exit is caught. Baseline the
+                 * buffer so it is defined at registration time. */
+                XMEMSET(psk_key, 0, sizeof(psk_key));
+                wc_MemZero_Add("FindPskSuiteFromExt psk_key", psk_key,
+                    sizeof(psk_key));
+            #endif
                 ret = FindPskSuite(ssl, current, psk_key, &psk_keySz,
                         suites->suites + i, &found, foundSuite);
                 /* Clear the key just in case */
                 ForceZero(psk_key, sizeof(psk_key));
+            #ifdef WOLFSSL_CHECK_MEM_ZERO
+                wc_MemZero_Check(psk_key, sizeof(psk_key));
+            #endif
                 if (ret == 0 && found) {
                     pskInfo->cipherSuite0 = foundSuite[0];
                     pskInfo->cipherSuite  = foundSuite[1];

src/pk.c

@@ -4933,6 +4933,13 @@ static int _DH_compute_key(unsigned char* key, const WOLFSSL_BIGNUM* otherPub,
         if (privSz <= 0) {
             ret = WOLFSSL_FATAL_ERROR;
         }
+    #if defined(WOLFSSL_CHECK_MEM_ZERO) && !defined(WOLFSSL_SMALL_STACK)
+        /* Register as soon as the stack array holds the private key so any
+         * future path that fails to zeroize it before exit is caught. */
+        else {
+            wc_MemZero_Add("_DH_compute_key priv", priv, (word32)privSz);
+        }
+    #endif
     }
     if (ret == 0) {
         /* Get the public key into the array. */
@@ -4996,6 +5003,9 @@ static int _DH_compute_key(unsigned char* key, const WOLFSSL_BIGNUM* otherPub,
         {
             /* Zeroize sensitive data. */
             ForceZero(priv, (word32)privSz);
+        #if defined(WOLFSSL_CHECK_MEM_ZERO) && !defined(WOLFSSL_SMALL_STACK)
+            wc_MemZero_Check(priv, sizeof(priv));
+        #endif
         }
     }
     WC_FREE_VAR_EX(pub, NULL, DYNAMIC_TYPE_PUBLIC_KEY);
@@ -7226,6 +7236,14 @@ int wolfSSL_PEM_do_header(EncryptedInfo* cipher, unsigned char* data, long* len,
         if (passwordSz < 0) {
             ret = 0;
         }
+    #ifdef WOLFSSL_CHECK_MEM_ZERO
+        /* Register as soon as the stack buffer holds the secret so any future
+         * path that fails to zeroize it before exit is caught. */
+        else if (passwordSz > 0) {
+            wc_MemZero_Add("wolfSSL_PEM_do_header password", password,
+                (word32)passwordSz);
+        }
+    #endif
     }
 
     if (ret == 1) {
@@ -7239,6 +7257,9 @@ int wolfSSL_PEM_do_header(EncryptedInfo* cipher, unsigned char* data, long* len,
     if (passwordSz > 0) {
         /* Ensure password is erased from memory. */
         ForceZero(password, (word32)passwordSz);
+    #ifdef WOLFSSL_CHECK_MEM_ZERO
+        wc_MemZero_Check(password, NAME_SZ);
+    #endif
     }
 
     return ret;
@@ -7476,6 +7497,14 @@ static int pem_write_mem_pkcs8privatekey(byte** pem, int* pemSz,
                 res = 0;
             }
             passwd = password;
+        #ifdef WOLFSSL_CHECK_MEM_ZERO
+            /* Register as soon as the stack buffer holds the secret so any
+             * future path that fails to zeroize it before exit is caught. */
+            if (passwdSz > 0) {
+                wc_MemZero_Add("pem_write_mem_pkcs8privatekey password",
+                    password, (word32)passwdSz);
+            }
+        #endif
         }
 
         if (res == 1) {
@@ -7489,6 +7518,9 @@ static int pem_write_mem_pkcs8privatekey(byte** pem, int* pemSz,
         /* Zeroize the password from memory. */
         if ((password == passwd) && (passwdSz > 0)) {
             ForceZero(password, (word32)passwdSz);
+        #ifdef WOLFSSL_CHECK_MEM_ZERO
+            wc_MemZero_Check(password, NAME_SZ);
+        #endif
         }
     }
     else if ((res == 1) && (enc == NULL)) {

src/sniffer.c

@@ -7594,6 +7594,22 @@ static int parseKeyLogFile(const char* fileName, char* error)
         return WOLFSSL_SNIFFER_ERROR;
     }
 
+#ifdef WOLFSSL_CHECK_MEM_ZERO
+    /* Register the secret-bearing stack buffers as high as possible (right
+     * after the last early return that bypasses the ForceZeros, i.e. the
+     * fopen failure above) so any future path that fails to clear them before
+     * scope exit is caught. Every exit path below (the in-loop error return
+     * and the normal post-loop return) ForceZeros and Checks each of them, so
+     * exactly one Add is balanced by one Check. Baseline the not-yet-written
+     * buffers so they are defined at registration time (secretHex is already
+     * zero-initialized at declaration). */
+    XMEMSET(secret, 0, sizeof(secret));
+    XMEMSET(line, 0, sizeof(line));
+    wc_MemZero_Add("parseKeyLogFile secret", secret, sizeof(secret));
+    wc_MemZero_Add("parseKeyLogFile secretHex", secretHex, sizeof(secretHex));
+    wc_MemZero_Add("parseKeyLogFile line", line, sizeof(line));
+#endif
+
     while (fgets(line, (int)sizeof(line), file) != NULL) {
         /* RFC 9850 Section 1: ignore empty lines and lines whose first
          * character is the octothorpe ('#') comment marker. */
@@ -7658,6 +7674,11 @@ static int parseKeyLogFile(const char* fileName, char* error)
             ForceZero(secret, SECRET_LENGTH);
             ForceZero(secretHex, sizeof(secretHex));
             ForceZero(line, sizeof(line));
+        #ifdef WOLFSSL_CHECK_MEM_ZERO
+            wc_MemZero_Check(secret, sizeof(secret));
+            wc_MemZero_Check(secretHex, sizeof(secretHex));
+            wc_MemZero_Check(line, sizeof(line));
+        #endif
             return ret;
         }
     }
@@ -7666,6 +7687,11 @@ static int parseKeyLogFile(const char* fileName, char* error)
     ForceZero(secret, SECRET_LENGTH);
     ForceZero(secretHex, sizeof(secretHex));
     ForceZero(line, sizeof(line));
+#ifdef WOLFSSL_CHECK_MEM_ZERO
+    wc_MemZero_Check(secret, sizeof(secret));
+    wc_MemZero_Check(secretHex, sizeof(secretHex));
+    wc_MemZero_Check(line, sizeof(line));
+#endif
     return 0;
 }
 

src/tls13.c

@@ -1054,6 +1054,14 @@ int Tls13_Exporter(WOLFSSL* ssl, unsigned char *out, size_t outLen,
             return BAD_FUNC_ARG;
     }
 
+#ifdef WOLFSSL_CHECK_MEM_ZERO
+    /* Poison and register firstExpand before it is written so that any path
+     * below (all of which funnel through cleanup) is covered. */
+    XMEMSET(firstExpand, 0xff, sizeof(firstExpand));
+    wc_MemZero_Add("Tls13_Exporter firstExpand", firstExpand,
+                   sizeof(firstExpand));
+#endif
+
     /* Derive-Secret(Secret, label, "") */
     ret = Tls13HKDFExpandLabel(ssl, firstExpand, hashLen,
             ssl->arrays->exporterSecret, hashLen,
@@ -1076,6 +1084,9 @@ int Tls13_Exporter(WOLFSSL* ssl, unsigned char *out, size_t outLen,
      * Hash(context_value); wipe both before the stack frame is reclaimed. */
     ForceZero(firstExpand, sizeof(firstExpand));
     ForceZero(hashOut, sizeof(hashOut));
+#ifdef WOLFSSL_CHECK_MEM_ZERO
+    wc_MemZero_Check(firstExpand, sizeof(firstExpand));
+#endif
     return ret;
 }
 #endif
@@ -1533,6 +1544,11 @@ int DeriveTls13Keys(WOLFSSL* ssl, int secret, int side, int store)
     WC_ALLOC_VAR_EX(key_dig, byte, MAX_PRF_DIG, ssl->heap,
         DYNAMIC_TYPE_DIGEST, return MEMORY_E);
 
+#ifdef WOLFSSL_CHECK_MEM_ZERO
+    XMEMSET(key_dig, 0xff, MAX_PRF_DIG);
+    wc_MemZero_Add("DeriveTls13Keys key_dig", key_dig, MAX_PRF_DIG);
+#endif
+
     if (side == ENCRYPT_AND_DECRYPT_SIDE) {
         provision = PROVISION_CLIENT_SERVER;
     }
@@ -1717,7 +1733,9 @@ int DeriveTls13Keys(WOLFSSL* ssl, int secret, int side, int store)
 #endif /* WOLFSSL_DTLS13 */
 
 end:
-    ForceZero(key_dig, (word32)i);
+    /* Zero the whole key_dig buffer (not just the i bytes derived) so no
+     * key-schedule material can linger in the unused tail. */
+    ForceZero(key_dig, MAX_PRF_DIG);
 #ifdef WOLFSSL_SMALL_STACK
     XFREE(key_dig, ssl->heap, DYNAMIC_TYPE_DIGEST);
 #elif defined(WOLFSSL_CHECK_MEM_ZERO)
@@ -6523,6 +6541,13 @@ static int DoPreSharedKeys(WOLFSSL* ssl, const byte* input, word32 inputSz,
 
     (void)suite;
 
+#ifdef WOLFSSL_CHECK_MEM_ZERO
+    /* Poison and register binderKey up front; every exit below (including the
+     * error paths) funnels through the cleanup label which zeroes it. */
+    XMEMSET(binderKey, 0xff, sizeof(binderKey));
+    wc_MemZero_Add("DoPreSharedKeys binderKey", binderKey, sizeof(binderKey));
+#endif
+
     ext = TLSX_Find(ssl->extensions, TLSX_PRE_SHARED_KEY);
     if (ext == NULL) {
         WOLFSSL_MSG("No pre shared extension keys found");
@@ -6739,6 +6764,9 @@ static int DoPreSharedKeys(WOLFSSL* ssl, const byte* input, word32 inputSz,
 cleanup:
     ForceZero(binderKey, sizeof(binderKey));
     ForceZero(binder, sizeof(binder));
+#ifdef WOLFSSL_CHECK_MEM_ZERO
+    wc_MemZero_Check(binderKey, sizeof(binderKey));
+#endif
     WOLFSSL_LEAVE("DoPreSharedKeys", ret);
 
     return ret;