--compress algorithm
**DEPRECATED** Enable a compression algorithm. Compression is generally
not recommended. VPN tunnels which use compression are susceptible to
- the VORALCE attack vector.
+ the VORALCE attack vector. See also the :code:`migrate` parameter below.
The ``algorithm`` parameter may be :code:`lzo`, :code:`lz4`,
- :code:`lz4-v2`, :code:`stub`, :code:`stub-v2` or empty.
+ :code:`lz4-v2`, :code:`stub`, :code:`stub-v2`, :code:`migrate` or empty.
LZO and LZ4 are different compression algorithms, with LZ4 generally
offering the best performance with least CPU usage.
Note: the :code:`stub` (or empty) option is NOT compatible with the older
option ``--comp-lzo no``.
+ Using :code:`migrate` as compression algorithm enables a special migration mode.
+ It allows migration away from the ``--compress``/``--comp-lzo`` options to no compression.
+ This option sets the server to no compression mode and the server behaves identical to
+ a server without a compression option for all clients without a compression in their
+ config. However, if a client is detected that indicates that compression is used (via OCC),
+ the server will automatically add ``--push compress stub-v2`` to the client specific
+ configuration if supported by the client and otherwise switch to ``comp-lzo no``
+ and add ``--push comp-lzo`` to the client specific configuration.
+
***Security Considerations***
Compression and encryption is a tricky combination. If an attacker knows
#define COMP_F_ADVERTISE_STUBS_ONLY (1<<3) /* tell server that we only support compression stubs */
#define COMP_F_ALLOW_STUB_ONLY (1<<4) /* Only accept stub compression, even with COMP_F_ADVERTISE_STUBS_ONLY
* we still accept other compressions to be pushed */
+#define COMP_F_MIGRATE (1<<5) /* push stub-v2 or comp-lzo no when we see a client with comp-lzo in occ */
/*
multi_client_connect_setenv(m, mi);
}
+/**
+ * Do the necessary modification for doing the compress migrate. This is
+ * implemented as a connect handler as it fits the modify config for a client
+ * paradigm and also is early enough in the chain to be overwritten by another
+ * ccd/script to do compression on a special client.
+ */
+static enum client_connect_return
+multi_client_connect_compress_migrate(struct multi_context *m,
+ struct multi_instance *mi,
+ bool deferred,
+ unsigned int *option_types_found)
+{
+#ifdef USE_COMP
+ struct options *o = &mi->context.options;
+ const char *const peer_info = mi->context.c2.tls_multi->peer_info;
+
+ if (!peer_info)
+ {
+ return CC_RET_SUCCEEDED;
+ }
+
+ if (o->comp.flags & COMP_F_MIGRATE && mi->context.c2.tls_multi->remote_usescomp)
+ {
+ if(strstr(peer_info, "IV_COMP_STUBv2=1"))
+ {
+ push_option(o, "compress stub-v2", M_USAGE);
+ }
+ else
+ {
+ /* Client is old and does not support STUBv2 but since it
+ * announced comp-lzo via OCC we assume it uses comp-lzo, so
+ * switch to that and push the uncompressed variant. */
+ push_option(o, "comp-lzo no", M_USAGE);
+ o->comp.alg = COMP_ALG_STUB;
+ *option_types_found |= OPT_P_COMP;
+ }
+ }
+#endif
+ return CC_RET_SUCCEEDED;
+}
+
/**
* Try to source a dynamic config file from the
* --client-config-dir directory.
bool from_deferred, unsigned int *option_types_found);
static const multi_client_connect_handler client_connect_handlers[] = {
+ multi_client_connect_compress_migrate,
multi_client_connect_source_ccd,
multi_client_connect_call_plugin_v1,
multi_client_connect_call_plugin_v2,
options->comp.alg = COMP_ALGV2_UNCOMPRESSED;
options->comp.flags |= COMP_F_ADVERTISE_STUBS_ONLY;
}
+ else if (streq(p[1], "migrate"))
+ {
+ options->comp.alg = COMP_ALG_UNDEF;
+ options->comp.flags = COMP_F_MIGRATE;
+
+ }
else if (options->comp.flags & COMP_F_ALLOW_STUB_ONLY)
{
/* Also printed on a push to hint at configuration problems */
#include "ssl_verify.h"
#include "ssl_backend.h"
#include "ssl_ncp.h"
+#include "ssl_util.h"
#include "auth_token.h"
#include "memdbg.h"
return ret;
}
+#ifdef USE_COMP
+static bool
+write_compat_local_options(struct buffer *buf, const char *options)
+{
+ struct gc_arena gc = gc_new();
+ const char *local_options = options_string_compat_lzo(options, &gc);
+ bool ret = write_string(buf, local_options, TLS_OPTIONS_LEN);
+ gc_free(&gc);
+ return ret;
+}
+#endif
+
/**
* Handle the writing of key data, peer-info, username/password, OCC
* to the TLS control channel (cleartext).
*/
static bool
-key_method_2_write(struct buffer *buf, struct tls_session *session)
+key_method_2_write(struct buffer *buf, struct tls_multi *multi, struct tls_session *session)
{
struct key_state *ks = &session->key[KS_PRIMARY]; /* primary key */
/* write options string */
{
+#ifdef USE_COMP
+ if (multi->remote_usescomp && session->opt->mode == MODE_SERVER
+ && multi->opt.comp_options.flags & COMP_F_MIGRATE)
+ {
+ if (!write_compat_local_options(buf, session->opt->local_options))
+ {
+ goto error;
+ }
+ }
+ else
+#endif
if (!write_string(buf, session->opt->local_options, TLS_OPTIONS_LEN))
{
goto error;
free(multi->remote_ciphername);
multi->remote_ciphername =
options_string_extract_option(options, "cipher", NULL);
+ multi->remote_usescomp = strstr(options, ",comp-lzo,");
/* In OCC we send '[null-cipher]' instead 'none' */
if (multi->remote_ciphername
if (!session->opt->disable_occ
&& !options_cmp_equal(options, session->opt->remote_options))
{
- options_warning(options, session->opt->remote_options);
+ const char *remote_options = session->opt->remote_options;
+#ifdef USE_COMP
+ if (multi->opt.comp_options.flags & COMP_F_MIGRATE && multi->remote_usescomp)
+ {
+ msg(D_SHOW_OCC, "Note: 'compress migrate' detected remote peer "
+ "with compression enabled.");
+ remote_options = options_string_compat_lzo(remote_options, &gc);
+ }
+#endif
+
+ options_warning(options, remote_options);
+
if (session->opt->ssl_flags & SSLF_OPT_VERIFY)
{
msg(D_TLS_ERRORS, "Option inconsistency warnings triggering disconnect due to --opt-verify");
if (!buf->len && ((ks->state == S_START && !session->opt->server)
|| (ks->state == S_GOT_KEY && session->opt->server)))
{
- if (!key_method_2_write(buf, session))
+ if (!key_method_2_write(buf, multi, session))
{
goto error;
}
bool use_peer_id;
char *remote_ciphername; /**< cipher specified in peer's config file */
+ bool remote_usescomp; /**< remote announced comp-lzo in OCC string */
/*
* Our session objects.
}
return 0;
}
+
+const char *
+options_string_compat_lzo(const char *options, struct gc_arena *gc)
+{
+ /* Example string without and with comp-lzo, i.e. input/output of this function */
+ /* w/o comp: 'V4,dev-type tun,link-mtu 1457,tun-mtu 1400,proto UDPv4,auth SHA1,keysize 128,key-method 2,tls-server' */
+ /* comp-lzo: 'V4,dev-type tun,link-mtu 1458,tun-mtu 1400,proto UDPv4,comp-lzo,auth SHA1,keysize 128,key-method 2,tls-server' */
+
+ /* Note: since this function is used only in a very limited scope it makes
+ * assumptions how the string looks. Since we locally generated the string
+ * we can make these assumptions */
+
+ /* Check that the link-mtu string is in options */
+ const char *tmp = strstr(options, ",link-mtu");
+ if (!tmp)
+ {
+ return options;
+ }
+
+ /* Get old link_mtu size */
+ int link_mtu;
+ if (sscanf(tmp, ",link-mtu %d,", &link_mtu) != 1 || link_mtu < 100 || link_mtu > 9900)
+ {
+ return options;
+ }
+
+ /* 1 byte for the possibility of 999 to 1000 and 1 byte for the null
+ * terminator */
+ struct buffer buf = alloc_buf_gc(strlen(options) + strlen(",comp-lzo") + 2, gc);
+
+ buf_write(&buf, options, (int)(tmp - options));
+
+ /* Increase link-mtu by one for the comp-lzo opcode */
+ buf_printf(&buf, ",link-mtu %d", link_mtu + 1);
+
+ tmp += strlen(",link-mtu ") + (link_mtu < 1000 ? 3 : 4);
+
+ buf_printf(&buf, "%s,comp-lzo", tmp);
+
+ return BSTR(&buf);
+}
*/
unsigned int
extract_iv_proto(const char *peer_info);
+
+/**
+ * Takes a locally produced OCC string for TLS server mode and modifies as
+ * if the option comp-lzo was enabled. This is to send a client in
+ * comp-lzo migrate mode the expected OCC string.
+ *
+ * Note: This function expects the string to be in the locally generated
+ * format and does not accept arbitrary strings.
+ *
+ * @param options the locally generated OCC string
+ * @param gc gc_arena to allocate the returned string in
+ * @return the modified string or options on error
+ */
+const char *
+options_string_compat_lzo(const char *options, struct gc_arena *gc);
#endif
test_binaries += argv_testdriver buffer_testdriver
endif
-test_binaries += crypto_testdriver packet_id_testdriver auth_token_testdriver ncp_testdriver
+test_binaries += crypto_testdriver packet_id_testdriver auth_token_testdriver ncp_testdriver misc_testdriver
if HAVE_LD_WRAP_SUPPORT
test_binaries += tls_crypt_testdriver
endif
$(openvpn_srcdir)/packet_id.c \
$(openvpn_srcdir)/platform.c \
$(openvpn_srcdir)/ssl_util.c
+
+misc_testdriver_CFLAGS = @TEST_CFLAGS@ \
+ -I$(openvpn_includedir) -I$(compat_srcdir) -I$(openvpn_srcdir)
+
+misc_testdriver_LDFLAGS = @TEST_LDFLAGS@
+
+misc_testdriver_SOURCES = test_misc.c mock_msg.c \
+ mock_get_random.c \
+ $(openvpn_srcdir)/buffer.c \
+ $(openvpn_srcdir)/ssl_util.c \
+ $(openvpn_srcdir)/platform.c
\ No newline at end of file
--- /dev/null
+/*
+ * OpenVPN -- An application to securely tunnel IP networks
+ * over a single UDP port, with support for SSL/TLS-based
+ * session authentication and key exchange,
+ * packet encryption, packet authentication, and
+ * packet compression.
+ *
+ * Copyright (C) 2021 Arne Schwabe <arne@rfc2549.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#elif defined(_MSC_VER)
+#include "config-msvc.h"
+#endif
+
+#include "syshead.h"
+
+#include <stdio.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <stdarg.h>
+#include <string.h>
+#include <setjmp.h>
+#include <cmocka.h>
+
+#include "ssl_util.h"
+
+static void
+test_compat_lzo_string(void **state)
+{
+ struct gc_arena gc = gc_new();
+
+ const char* input = "V4,dev-type tun,link-mtu 1457,tun-mtu 1400,proto UDPv4,auth SHA1,keysize 128,key-method 2,tls-server";
+
+ const char* output = options_string_compat_lzo(input, &gc);
+
+ assert_string_equal(output, "V4,dev-type tun,link-mtu 1458,tun-mtu 1400,proto UDPv4,auth SHA1,keysize 128,key-method 2,tls-server,comp-lzo");
+
+ /* This string is has a much too small link-mtu so we should fail on it" */
+ input = "V4,dev-type tun,link-mtu 2,tun-mtu 1400,proto UDPv4,auth SHA1,keysize 128,key-method 2,tls-server";
+
+ output = options_string_compat_lzo(input, &gc);
+
+ assert_string_equal(input, output);
+
+ /* not matching at all */
+ input = "V4,dev-type tun";
+ output = options_string_compat_lzo(input, &gc);
+
+ assert_string_equal(input, output);
+
+
+ input = "V4,dev-type tun,link-mtu 999,tun-mtu 1400,proto UDPv4,auth SHA1,keysize 128,key-method 2,tls-server";
+ output = options_string_compat_lzo(input, &gc);
+
+ /* 999 -> 1000, 3 to 4 chars */
+ assert_string_equal(output, "V4,dev-type tun,link-mtu 1000,tun-mtu 1400,proto UDPv4,auth SHA1,keysize 128,key-method 2,tls-server,comp-lzo");
+
+};
+
+const struct CMUnitTest misc_tests[] = {
+ cmocka_unit_test(test_compat_lzo_string),
+};
+
+int
+main(void)
+{
+ return cmocka_run_group_tests(misc_tests, NULL, NULL);
+}
projects / thirdparty / openvpn.git / commitdiff
