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 7799111301f13685fd12674206c8625ee203166f..936cfea10937f1bd5383c2e73a8ea827edc24ee0 100644 (file)
--- a/src/backend/libpq/auth.c
+++ b/src/backend/libpq/auth.c
@@ -1349,16 +1349,22 @@ 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");