sspi: fix memory leaks

Closes #4299

lib/vauth/digest_sspi.c

@@ -61,6 +61,11 @@ bool Curl_auth_is_digest_supported(void)
   status = s_pSecFn->QuerySecurityPackageInfo((TCHAR *) TEXT(SP_NAME_DIGEST),
                                               &SecurityPackage);
 
+  /* Release the package buffer as it is not required anymore */
+  if(status == SEC_E_OK) {
+    s_pSecFn->FreeContextBuffer(SecurityPackage);
+  }
+
   return (status == SEC_E_OK ? TRUE : FALSE);
 }
 

lib/vauth/krb5_sspi.c

@@ -58,6 +58,11 @@ bool Curl_auth_is_gssapi_supported(void)
                                               TEXT(SP_NAME_KERBEROS),
                                               &SecurityPackage);
 
+  /* Release the package buffer as it is not required anymore */
+  if(status == SEC_E_OK) {
+    s_pSecFn->FreeContextBuffer(SecurityPackage);
+  }
+
   return (status == SEC_E_OK ? TRUE : FALSE);
 }
 

lib/vauth/ntlm_sspi.c

@@ -56,6 +56,11 @@ bool Curl_auth_is_ntlm_supported(void)
   status = s_pSecFn->QuerySecurityPackageInfo((TCHAR *) TEXT(SP_NAME_NTLM),
                                               &SecurityPackage);
 
+  /* Release the package buffer as it is not required anymore */
+  if(status == SEC_E_OK) {
+    s_pSecFn->FreeContextBuffer(SecurityPackage);
+  }
+
   return (status == SEC_E_OK ? TRUE : FALSE);
 }
 

lib/vauth/spnego_sspi.c

@@ -59,6 +59,12 @@ bool Curl_auth_is_spnego_supported(void)
                                               TEXT(SP_NAME_NEGOTIATE),
                                               &SecurityPackage);
 
+  /* Release the package buffer as it is not required anymore */
+  if(status == SEC_E_OK) {
+    s_pSecFn->FreeContextBuffer(SecurityPackage);
+  }
+
+
   return (status == SEC_E_OK ? TRUE : FALSE);
 }