Hi devs,

When using multi and schannel (version 7.40), it happens that Curl_schannel_session_free (curl_schannel.c) can be called just after a curl_easy_cleanup but before the Curl_schannel_shutdown is done on a connection. It results that if the ssl credentials are cached, the refcount will not be 0. And then, they are not be freed.

Furthermore, no leak happens when using openSSL. Here's how I managed to counter the leak when using schannel:

(urldata.h)
 
        struct curl_schannel_cred {
        /* . */
          bool session_freed; ///New boolean
        /* . */

(curl_schannel.h)

        void Curl_schannel_session_free(void *ptr)
        {
          struct curl_schannel_cred *cred = ptr;

          if(cred && cred->cached)
          {
            if(cred->refcount == 0)
     {
                s_pSecFn->FreeCredentialsHandle(&cred->cred_handle);
                Curl_safefree(cred);
            }
            else
     {
                cred->session_freed = true;
     }
   }
        }

        int Curl_schannel_shutdown(struct connectdata *conn, int sockindex)
        /* . */
            /* if the handle was not cached and the refcount is zero */
     if((!connssl->cred->cached && connssl->cred->refcount == 0) || connssl->cred->session_freed) {
              infof(data, "schannel: clear credential handle\n");
              s_pSecFn->FreeCredentialsHandle(&connssl->cred->cred_handle);
              Curl_safefree(connssl->cred);
            }
        /* . */

Any thoughts or suggestions are welcome,

Have a wonderful day,

-- 
Jean-Francois Durand
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