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 a3651be744f809c839738f02c57adecb82035960..88d809faff9c390dd7e66af17948f5a13ed95e7f 100644 (file)
--- a/src/backend/libpq/auth.c
+++ b/src/backend/libpq/auth.c
@@ -807,16 +807,22 @@ pg_SSPI_recvauth(Port *port)
                                  gettext_noop("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");