CONC-567 Schannel - handle SEC_I_RENEGOTIATE, prepare for TLSv1.3

There is no real renegotiation in TLSv1.3 protocol, so it is
some internal schannel thing, that makes DecryptMessage() to return
SEC_I_RENEGOTIATE, to replay a handshake step.

This pops up when TLSv1.3 is enabled.

libmariadb/secure/ma_schannel.c

@@ -100,6 +100,13 @@ SECURITY_STATUS ma_schannel_handshake_loop(MARIADB_PVIO *pvio, my_bool InitialRe
     return SEC_E_INSUFFICIENT_MEMORY;
 
   cbIoBuffer = 0;
+
+  if (!InitialRead && pExtraData->cbBuffer)
+  {
+    memcpy(IoBuffer, pExtraData->pvBuffer,pExtraData->cbBuffer);
+    cbIoBuffer= pExtraData->cbBuffer;
+  }
+
   fDoRead = InitialRead;
 
   /* handshake loop: We will leave if handshake is finished
@@ -282,6 +289,8 @@ SECURITY_STATUS ma_schannel_client_handshake(MARIADB_TLS *ctls)
   SecBufferDesc	BufferOut;
   SecBuffer  BuffersOut;
 
+  SecBufferDesc *pBuffersIn= NULL;
+
   if (!ctls || !ctls->pvio)
     return 1;
 
@@ -445,7 +454,7 @@ SECURITY_STATUS ma_schannel_read_decrypt(MARIADB_PVIO *pvio,
     } while (sRet == SEC_E_INCOMPLETE_MESSAGE); /* Continue reading until full message arrives */
 
 
-    if (sRet != SEC_E_OK)
+    if (sRet != SEC_E_OK && sRet != SEC_I_RENEGOTIATE)
     {
       ma_schannel_set_sec_error(pvio, sRet);
       return sRet;
@@ -462,7 +471,7 @@ SECURITY_STATUS ma_schannel_read_decrypt(MARIADB_PVIO *pvio,
     }
 
 
-    if (sctx->dataBuf.cbBuffer)
+    if (sctx->dataBuf.cbBuffer || sRet == SEC_I_RENEGOTIATE)
     {
       assert(sctx->dataBuf.pvBuffer);
       /*
@@ -470,12 +479,13 @@ SECURITY_STATUS ma_schannel_read_decrypt(MARIADB_PVIO *pvio,
         Store the rest (if any) to be processed next time.
       */
       nbytes = MIN(sctx->dataBuf.cbBuffer, ReadBufferSize);
-      memcpy((char *)ReadBuffer, sctx->dataBuf.pvBuffer, nbytes);
+      if (nbytes)
+        memcpy((char *)ReadBuffer, sctx->dataBuf.pvBuffer, nbytes);
       sctx->dataBuf.cbBuffer -= (unsigned long)nbytes;
       sctx->dataBuf.pvBuffer = (char *)sctx->dataBuf.pvBuffer + nbytes;
 
       *DecryptLength = (DWORD)nbytes;
-      return SEC_E_OK;
+      return sRet;
     }
     // No data buffer, loop
   }

libmariadb/secure/schannel.c

@@ -472,13 +472,50 @@ ssize_t ma_tls_read(MARIADB_TLS *ctls, const uchar* buffer, size_t length)
   SC_CTX *sctx= (SC_CTX *)ctls->ssl;
   MARIADB_PVIO *pvio= ctls->pvio;
   DWORD dlength= 0;
-  SECURITY_STATUS status = ma_schannel_read_decrypt(pvio, &sctx->hCtxt, &dlength, (uchar *)buffer, (DWORD)length);
+  SECURITY_STATUS status;
-  if (status == SEC_I_CONTEXT_EXPIRED)
+  SecBuffer tmp_extra_buf= {0};
-    return 0; /* other side shut down the connection. */
-  if (status == SEC_I_RENEGOTIATE)
-    return -1; /* Do not handle renegotiate yet */
 
-  return (status == SEC_E_OK)? (ssize_t)dlength : -1;
+retry:
+  status= ma_schannel_read_decrypt(pvio, &sctx->hCtxt, &dlength,
+                                  (uchar *) buffer, (DWORD) length);
+  if (tmp_extra_buf.cbBuffer)
+  {
+    /*
+      This memory was allocated in renegotiation processing
+      below, free it.
+    */
+    LocalFree(tmp_extra_buf.pvBuffer);
+    tmp_extra_buf.cbBuffer= 0;
+  }
+  switch (status) {
+  case SEC_E_OK:
+    return (ssize_t) dlength;
+  case SEC_I_CONTEXT_EXPIRED:
+    /* Other side shut down the connection. */
+    return 0;
+  case SEC_I_RENEGOTIATE:
+    /* Rerun handshake steps */
+    tmp_extra_buf= sctx->extraBuf;
+    tmp_extra_buf.BufferType= SECBUFFER_TOKEN;
+    sctx->extraBuf.cbBuffer= 0;
+    sctx->extraBuf.pvBuffer= NULL;
+    status= ma_schannel_handshake_loop(pvio, FALSE, &tmp_extra_buf);
+    sctx->extraBuf= tmp_extra_buf;
+    if (status != SEC_E_OK)
+      return -1;
+    /*
+      If decrypt returned some decrypted bytes prior to
+      renegotiation,  return them.
+      Otherwise, retry the read-decrypt again
+    */
+    if (dlength)
+      return dlength;
+
+    goto retry;
+
+  default:
+    return -1;
+  }
 }
 
 ssize_t ma_tls_write(MARIADB_TLS *ctls, const uchar* buffer, size_t length)