Fix SSPI login when multiple roundtrips are required

This fixes SSPI login failures showing "The function
requested is not supported", often showing up when connecting
to localhost. The reason was not properly updating the SSPI
handle when multiple roundtrips were required to complete the
authentication sequence.

Report and analysis by Ahmed Shinwari, patch by Magnus Hagander

diff --git a/src/backend/libpq/auth.c b/src/backend/libpq/auth.c
index dd5f6914f7dc28f5c8bd3c3e53710a0331e5be28..8c76eafef5668c320b2bd1a54c6ef7e34d2f2d40 100644 (file)
--- a/src/backend/libpq/auth.c
+++ b/src/backend/libpq/auth.c
@@ -1257,16 +1257,22 @@ pg_SSPI_recvauth(Port *port)
                                                  _("could not accept SSPI security context"), r);
                }
 
+               /*
+                * Overwrite the current context with the one we just received.
+                * If sspictx is NULL it was the first loop and we need to allocate
+                * a buffer for it. On subsequent runs, we can just overwrite the
+                * buffer contents since the size does not change.
+                */
                if (sspictx == NULL)
                {
                        sspictx = malloc(sizeof(CtxtHandle));
                        if (sspictx == NULL)
                                ereport(ERROR,
                                                (errmsg("out of memory")));
-
-                       memcpy(sspictx, &newctx, sizeof(CtxtHandle));
                }
 
+               memcpy(sspictx, &newctx, sizeof(CtxtHandle));
+
                if (r == SEC_I_CONTINUE_NEEDED)
                        elog(DEBUG4, "SSPI continue needed");