Fix issues found during src/ code review

- ECH: add bounds check on hpkePubkeyLen against HPKE_Npk_MAX to
  prevent heap buffer overflow from untrusted ECH config data

- Sniffer: fix reassembly memory limit check typo, MaxRecoveryMemory -1
  should be MaxRecoveryMemory != -1

- Sniffer: add bounds check in IPv6 extension header parsing loop to
  prevent OOB read when next_header never matches TCP or NO_NEXT_HEADER

- Sniffer: validate tlsFragOffset + rhSize against tlsFragSize before
  XMEMCPY in both TLS handshake fragment reassembly paths

- Internal: use WC_SAFE_SUM_WORD32 in GrowAnOutputBuffer to prevent
  integer overflow on allocation size, matching existing pattern in
  GrowOutputBuffer

Author: LinuxJedi

src/internal.c

@@ -11294,6 +11294,7 @@ static WC_INLINE int GrowAnOutputBuffer(WOLFSSL* ssl,
 #else
     const byte align = WOLFSSL_GENERAL_ALIGNMENT;
 #endif
+    word32 newSz = 0;
 
 #if WOLFSSL_GENERAL_ALIGNMENT > 0
     /* the encrypted data will be offset from the front of the buffer by
@@ -11304,8 +11305,13 @@ static WC_INLINE int GrowAnOutputBuffer(WOLFSSL* ssl,
         align *= 2;
 #endif
 
-    tmp = (byte*)XMALLOC(size + outputBuffer->length + align,
-                             ssl->heap, DYNAMIC_TYPE_OUT_BUFFER);
+    if (!WC_SAFE_SUM_WORD32(outputBuffer->length, (word32)size, newSz))
+        return BUFFER_E;
+#if WOLFSSL_GENERAL_ALIGNMENT > 0
+    if (!WC_SAFE_SUM_WORD32(newSz, align, newSz))
+        return BUFFER_E;
+#endif
+    tmp = (byte*)XMALLOC(newSz, ssl->heap, DYNAMIC_TYPE_OUT_BUFFER);
     WOLFSSL_MSG("growing output buffer");
 
     if (tmp == NULL)
@@ -11318,7 +11324,7 @@ static WC_INLINE int GrowAnOutputBuffer(WOLFSSL* ssl,
 #ifdef WOLFSSL_STATIC_MEMORY
     /* can be from IO memory pool which does not need copy if same buffer */
     if (outputBuffer->length && tmp == outputBuffer->buffer) {
-        outputBuffer->bufferSize = size + outputBuffer->length;
+        outputBuffer->bufferSize = newSz - align;
         return 0;
     }
 #endif
@@ -11339,7 +11345,7 @@ static WC_INLINE int GrowAnOutputBuffer(WOLFSSL* ssl,
 
     outputBuffer->buffer = tmp;
     outputBuffer->dynamicFlag = 1;
-    outputBuffer->bufferSize = size + outputBuffer->length;
+    outputBuffer->bufferSize = newSz - align;
     return 0;
 }
 #endif

src/sniffer.c

@@ -2146,8 +2146,13 @@ static int CheckIp6Hdr(Ip6Hdr* iphdr, IpInfo* info, int length, char* error)
             exthdrsz += hdrsz;
             exthdr = (Ip6ExtHdr*)((byte*)exthdr + hdrsz);
         }
-        while (exthdr->next_header != TCP_PROTOCOL &&
+        while (exthdrsz < length &&
+                exthdr->next_header != TCP_PROTOCOL &&
                 exthdr->next_header != NO_NEXT_HEADER);
+        if (exthdrsz >= length) {
+            SetError(PACKET_HDR_SHORT_STR, error, NULL, 0);
+            return WOLFSSL_FATAL_ERROR;
+        }
     }
 
 #ifndef WOLFSSL_SNIFFER_WATCH
@@ -4571,6 +4576,10 @@ static int DoHandShake(const byte* input, int* sslBytes,
 
 #ifdef HAVE_MAX_FRAGMENT
     if (session->tlsFragBuf) {
+        if (session->tlsFragOffset + rhSize > session->tlsFragSize) {
+            SetError(HANDSHAKE_INPUT_STR, error, session, FATAL_ERROR_STATE);
+            return WOLFSSL_FATAL_ERROR;
+        }
         XMEMCPY(session->tlsFragBuf + session->tlsFragOffset, input, rhSize);
         session->tlsFragOffset += rhSize;
         *sslBytes -= rhSize;
@@ -4625,6 +4634,10 @@ static int DoHandShake(const byte* input, int* sslBytes,
             *sslBytes += HANDSHAKE_HEADER_SZ;
         }
 
+        if (session->tlsFragOffset + rhSize > session->tlsFragSize) {
+            SetError(HANDSHAKE_INPUT_STR, error, session, FATAL_ERROR_STATE);
+            return WOLFSSL_FATAL_ERROR;
+        }
         XMEMCPY(session->tlsFragBuf + session->tlsFragOffset, input, rhSize);
         session->tlsFragOffset += rhSize;
         *sslBytes -= rhSize;
@@ -5622,7 +5635,7 @@ static int AddToReassembly(byte from, word32 seq, const byte* sslFrame,
         if (end >= curr->begin)
             end = curr->begin - 1;
 
-        if (MaxRecoveryMemory -1 &&
+        if (MaxRecoveryMemory != -1 &&
                       (int)(*reassemblyMemory + sslBytes) > MaxRecoveryMemory) {
             SetError(REASSEMBLY_MAX_STR, error, session, FATAL_ERROR_STATE);
             return WOLFSSL_FATAL_ERROR;

src/ssl_ech.c

@@ -580,6 +580,10 @@ int SetEchConfigsEx(WOLFSSL_EchConfig** outputConfigs, void* heap,
         ato16(echConfig, &hpkePubkeyLen);
         echConfig += 2;
         /* hpke public_key */
+        if (hpkePubkeyLen > HPKE_Npk_MAX) {
+            ret = BUFFER_E;
+            break;
+        }
         XMEMCPY(workingConfig->receiverPubkey, echConfig, hpkePubkeyLen);
         echConfig += hpkePubkeyLen;
         /* cipherSuitesLen */