Commit 2c0d295e authored by Matt Caswell's avatar Matt Caswell
Browse files

Fix OCSP Status Request extension unbounded memory growth 



A malicious client can send an excessively large OCSP Status Request
extension. If that client continually requests renegotiation,
sending a large OCSP Status Request extension each time, then there will
be unbounded memory growth on the server. This will eventually lead to a
Denial Of Service attack through memory exhaustion. Servers with a
default configuration are vulnerable even if they do not support OCSP.
Builds using the "no-ocsp" build time option are not affected.

I have also checked other extensions to see if they suffer from a similar
problem but I could not find any other issues.

CVE-2016-6304

Issue reported by Shi Lei.

Reviewed-by: default avatarRich Salz <rsalz@openssl.org>
parent 151adf2e

ssl/t1_lib.c

+17 −7
Original line number Diff line number Diff line
@@ -1284,6 +1284,23 @@ int ssl_parse_clienthello_tlsext(SSL *s, unsigned char **p, 
                size -= 2;

                if (dsize > size)

                    goto err;



                /*

                 * We remove any OCSP_RESPIDs from a previous handshake

                 * to prevent unbounded memory growth - CVE-2016-6304

                 */

                sk_OCSP_RESPID_pop_free(s->tlsext_ocsp_ids,

                                        OCSP_RESPID_free);

                if (dsize > 0) {

                    s->tlsext_ocsp_ids = sk_OCSP_RESPID_new_null();

                    if (s->tlsext_ocsp_ids == NULL) {

                        *al = SSL_AD_INTERNAL_ERROR;

                        return 0;

                    }

                } else {

                    s->tlsext_ocsp_ids = NULL;

                }



                while (dsize > 0) {

                    OCSP_RESPID *id;

                    int idsize;
@@ -1303,13 +1320,6 @@ int ssl_parse_clienthello_tlsext(SSL *s, unsigned char **p, 
                        OCSP_RESPID_free(id);

                        goto err;

                    }

                    if (!s->tlsext_ocsp_ids

                        && !(s->tlsext_ocsp_ids =

                             sk_OCSP_RESPID_new_null())) {

                        OCSP_RESPID_free(id);

                        *al = SSL_AD_INTERNAL_ERROR;

                        return 0;

                    }

                    if (!sk_OCSP_RESPID_push(s->tlsext_ocsp_ids, id)) {

                        OCSP_RESPID_free(id);

                        *al = SSL_AD_INTERNAL_ERROR;