Clear auth context correctly when re-connecting after failed auth attempt.

If authentication over an SSL connection fails, with sslmode=prefer,
libpq will reconnect without SSL and retry. However, we did not clear
the variables related to GSS, SSPI, and SASL authentication state, when
reconnecting. Because of that, the second authentication attempt would
always fail with a "duplicate GSS/SASL authentication request" error.
pg_SSPI_startup did not check for duplicate authentication requests like
the corresponding GSS and SASL functions, so with SSPI, you would leak
some memory instead.

Another way this could manifest itself, on version 10, is if you list
multiple hostnames in the "host" parameter. If the first server requests
Kerberos or SCRAM authentication, but it fails, the attempts to connect to
the other servers will also fail with "duplicate authentication request"
errors.

To fix, move the clearing of authentication state from closePGconn to
pgDropConnection, so that it is cleared also when re-connecting.

Patch by Michael Paquier, with some kibitzing by me.

Backpatch down to 9.3. 9.2 has the same bug, but the code around closing
the connection is somewhat different, so that this patch doesn't apply.
To fix this in 9.2, I think we would need to back-port commit 210eb9b743
first, and then apply this patch. However, given that we only bumped into
this in our own testing, we haven't heard any reports from users about
this, and that 9.2 will be end-of-lifed in a couple of months anyway, it
doesn't seem worth the risk and trouble.

Discussion: https://www.postgresql.org/message-id/CAB7nPqRuOUm0MyJaUy9L3eXYJU3AKCZ-0-03=-aDTZJGV4GyWw@mail.gmail.com

diff --git a/src/interfaces/libpq/fe-auth.c b/src/interfaces/libpq/fe-auth.c
index f30fb04809cd8c877bc16628b31d0c82400f09e9..ad9b0315e13cc6c52c056a366547dcca2ee11067 100644 (file)
--- a/src/interfaces/libpq/fe-auth.c
+++ b/src/interfaces/libpq/fe-auth.c
@@ -416,7 +416,12 @@ pg_SSPI_startup(PGconn *conn, int use_negotiate, int payloadlen)
        TimeStamp       expire;
        char       *host = PQhost(conn);
 
-       conn->sspictx = NULL;
+       if (conn->sspictx)
+       {
+               printfPQExpBuffer(&conn->errorMessage,
+                                       libpq_gettext("duplicate SSPI authentication request\n"));
+               return STATUS_ERROR;
+       }
 
        /*
         * Retrieve credentials handle

diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c
index f2c9bf7a883235734281e462352e6f83ccccf938..77b170af94dfb95ed3c4749e4c67f8a12d25e23c 100644 (file)
--- a/src/interfaces/libpq/fe-connect.c
+++ b/src/interfaces/libpq/fe-connect.c
@@ -406,15 +406,59 @@ pqDropConnection(PGconn *conn, bool flushInput)
 {
        /* Drop any SSL state */
        pqsecure_close(conn);
+
        /* Close the socket itself */
        if (conn->sock != PGINVALID_SOCKET)
                closesocket(conn->sock);
        conn->sock = PGINVALID_SOCKET;
+
        /* Optionally discard any unread data */
        if (flushInput)
                conn->inStart = conn->inCursor = conn->inEnd = 0;
+
        /* Always discard any unsent data */
        conn->outCount = 0;
+
+       /* Free authentication state */
+#ifdef ENABLE_GSS
+       {
+               OM_uint32       min_s;
+
+               if (conn->gctx)
+                       gss_delete_sec_context(&min_s, &conn->gctx, GSS_C_NO_BUFFER);
+               if (conn->gtarg_nam)
+                       gss_release_name(&min_s, &conn->gtarg_nam);
+       }
+#endif
+#ifdef ENABLE_SSPI
+       if (conn->sspitarget)
+       {
+               free(conn->sspitarget);
+               conn->sspitarget = NULL;
+       }
+       if (conn->sspicred)
+       {
+               FreeCredentialsHandle(conn->sspicred);
+               free(conn->sspicred);
+               conn->sspicred = NULL;
+       }
+       if (conn->sspictx)
+       {
+               DeleteSecurityContext(conn->sspictx);
+               free(conn->sspictx);
+               conn->sspictx = NULL;
+       }
+       conn->usesspi = 0;
+#endif
+       if (conn->sasl_state)
+       {
+               /*
+                * XXX: if support for more authentication mechanisms is added, this
+                * needs to call the right 'free' function.
+                */
+               pg_fe_scram_free(conn->sasl_state);
+               conn->sasl_state = NULL;
+       }
 }
 
 
@@ -3475,42 +3519,6 @@ closePGconn(PGconn *conn)
        if (conn->lobjfuncs)
                free(conn->lobjfuncs);
        conn->lobjfuncs = NULL;
-#ifdef ENABLE_GSS
-       {
-               OM_uint32       min_s;
-
-               if (conn->gctx)
-                       gss_delete_sec_context(&min_s, &conn->gctx, GSS_C_NO_BUFFER);
-               if (conn->gtarg_nam)
-                       gss_release_name(&min_s, &conn->gtarg_nam);
-       }
-#endif
-#ifdef ENABLE_SSPI
-       if (conn->sspitarget)
-               free(conn->sspitarget);
-       conn->sspitarget = NULL;
-       if (conn->sspicred)
-       {
-               FreeCredentialsHandle(conn->sspicred);
-               free(conn->sspicred);
-               conn->sspicred = NULL;
-       }
-       if (conn->sspictx)
-       {
-               DeleteSecurityContext(conn->sspictx);
-               free(conn->sspictx);
-               conn->sspictx = NULL;
-       }
-#endif
-       if (conn->sasl_state)
-       {
-               /*
-                * XXX: if support for more authentication mechanisms is added, this
-                * needs to call the right 'free' function.
-                */
-               pg_fe_scram_free(conn->sasl_state);
-               conn->sasl_state = NULL;
-       }
 }
 
 /*