This changes the "no" setting of allow-compression to also refuse framing. This
is important for our DCO implementation as these do not implement framing.
This behaviour surfaced when a commercial VPN provider was pushing
"comp-lzo no" to a client with DCO. While we are technically at fault here
for announcing comp-lzo no support by announcing IV_LZO_STUB=1, the
VPN provider continues to push "comp-lzo no" even in absense of that
flag.
As the new default we default to allow-compression stub-only if a stub option
is found in the config and to allow-compression no otherwise. This ensures
that we only enable DCO when no compression framing is used.
Signed-off-by: Arne Schwabe <a...@rfc2549.org>
---
Changes.rst | 5 +++
doc/man-sections/protocol-options.rst | 3 ++
src/openvpn/comp.c | 32 +++++++++--------
src/openvpn/comp.h | 2 +-
src/openvpn/dco.c | 4 +--
src/openvpn/options.c | 50 +++++++++++++++++++++------
6 files changed, 66 insertions(+), 30 deletions(-)
diff --git a/Changes.rst b/Changes.rst
index c5335ce93..3a573cc9a 100644
--- a/Changes.rst
+++ b/Changes.rst
@@ -223,6 +223,11 @@ User-visible Changes
compatibility with older versions. See the manual page on the
``--compat-mode`` for details.
+- (OpenVPN 2.6.1) ``--allow-compression no`` has been changed to not allow
+ compression or compression framing at all now and is the new default.
+ Use ``--allow-compression stub-only`` for the old ``no`` behaviour of OpenVPN
+ 2.5 and OpenVPN 2.6.0.
+
Common errors with OpenSSL 3.0 and OpenVPN 2.6
----------------------------------------------
Both OpenVPN 2.6 and OpenSSL 3.0 tighten the security considerable, so some
diff --git a/doc/man-sections/protocol-options.rst
b/doc/man-sections/protocol-options.rst
index 248f65cfd..76c323413 100644
--- a/doc/man-sections/protocol-options.rst
+++ b/doc/man-sections/protocol-options.rst
@@ -25,6 +25,9 @@ configured in a compatible way between both the local and
remote side.
compression at the same time is not a feasible option.
:code:`no` (default)
+ OpenVPN will refuse any compression or compression framing (stub).
+
+ :code:`stub-only`
OpenVPN will refuse any non-stub compression.
:code:`yes`
diff --git a/src/openvpn/comp.c b/src/openvpn/comp.c
index 3b8d78996..c7ec6c7f5 100644
--- a/src/openvpn/comp.c
+++ b/src/openvpn/comp.c
@@ -134,27 +134,29 @@ comp_print_stats(const struct compress_context *compctx,
struct status_output *s
void
comp_generate_peer_info_string(const struct compress_options *opt, struct
buffer *out)
{
- if (opt)
+ if (!opt || opt->flags & COMP_F_ALLOW_NOCOMP_ONLY)
+ {
+ return;
+ }
+
+ bool lzo_avail = false;
+ if (!(opt->flags & COMP_F_ADVERTISE_STUBS_ONLY))
{
- bool lzo_avail = false;
- if (!(opt->flags & COMP_F_ADVERTISE_STUBS_ONLY))
- {
#if defined(ENABLE_LZ4)
- buf_printf(out, "IV_LZ4=1\n");
- buf_printf(out, "IV_LZ4v2=1\n");
+ buf_printf(out, "IV_LZ4=1\n");
+ buf_printf(out, "IV_LZ4v2=1\n");
#endif
#if defined(ENABLE_LZO)
- buf_printf(out, "IV_LZO=1\n");
- lzo_avail = true;
+ buf_printf(out, "IV_LZO=1\n");
+ lzo_avail = true;
#endif
- }
- if (!lzo_avail)
- {
- buf_printf(out, "IV_LZO_STUB=1\n");
- }
- buf_printf(out, "IV_COMP_STUB=1\n");
- buf_printf(out, "IV_COMP_STUBv2=1\n");
}
+ if (!lzo_avail)
+ {
+ buf_printf(out, "IV_LZO_STUB=1\n");
+ }
+ buf_printf(out, "IV_COMP_STUB=1\n");
+ buf_printf(out, "IV_COMP_STUBv2=1\n");
}
#endif /* USE_COMP */
diff --git a/src/openvpn/comp.h b/src/openvpn/comp.h
index 685f40391..027fa0593 100644
--- a/src/openvpn/comp.h
+++ b/src/openvpn/comp.h
@@ -60,7 +60,7 @@
* 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 */
#define COMP_F_ALLOW_ASYM (1<<6) /* Compression was explicitly set
to allow asymetric compression */
-
+#define COMP_F_ALLOW_NOCOMP_ONLY (1<<7) /* Do not allow compression framing
like stub v2 or comp-lzo no. Breaks DCO */
/*
* Length of prepended prefix on compressed packets
diff --git a/src/openvpn/dco.c b/src/openvpn/dco.c
index 3087a0df8..10337b964 100644
--- a/src/openvpn/dco.c
+++ b/src/openvpn/dco.c
@@ -410,9 +410,7 @@ dco_check_option(int msglevel, const struct options *o)
}
#if defined(USE_COMP)
- if (o->comp.alg != COMP_ALG_UNDEF
- || o->comp.flags & COMP_F_ALLOW_ASYM
- || o->comp.flags & COMP_F_ALLOW_COMPRESS)
+ if (o->comp.alg != COMP_ALG_UNDEF || !(o->comp.flags &
COMP_F_ALLOW_NOCOMP_ONLY))
{
msg(msglevel, "Note: '--allow-compression' is not set to 'no',
disabling data channel offload.");
diff --git a/src/openvpn/options.c b/src/openvpn/options.c
index ab1b01cf7..6550dc52c 100644
--- a/src/openvpn/options.c
+++ b/src/openvpn/options.c
@@ -3628,10 +3628,16 @@ options_set_backwards_compatible_options(struct options
*o)
*
* Disable compression by default starting with 2.6.0 if no other
* compression related option has been explicitly set */
- if (!comp_non_stub_enabled(&o->comp) && !need_compatibility_before(o,
20600)
- && (o->comp.flags == 0))
+ if (!need_compatibility_before(o, 20600) && (o->comp.flags == 0))
{
- o->comp.flags = COMP_F_ALLOW_STUB_ONLY|COMP_F_ADVERTISE_STUBS_ONLY;
+ if (o->comp.alg == COMP_ALG_UNDEF)
+ {
+ o->comp.flags = COMP_F_ALLOW_NOCOMP_ONLY;
+ }
+ else if (!comp_non_stub_enabled(&o->comp))
+ {
+ o->comp.flags = COMP_F_ALLOW_STUB_ONLY |
COMP_F_ADVERTISE_STUBS_ONLY;
+ }
}
#endif
}
@@ -8330,8 +8336,16 @@ add_option(struct options *options,
if (streq(p[1], "no"))
{
- options->comp.flags =
- COMP_F_ALLOW_STUB_ONLY|COMP_F_ADVERTISE_STUBS_ONLY;
+ options->comp.flags = COMP_F_ALLOW_NOCOMP_ONLY;
+ if (comp_non_stub_enabled(&options->comp))
+ {
+ msg(msglevel, "'--allow-compression no' conflicts with "
+ " enabling compression");
+ }
+ }
+ else if (streq(p[1], "stub-only"))
+ {
+ options->comp.flags =
COMP_F_ADVERTISE_STUBS_ONLY|COMP_F_ALLOW_STUB_ONLY;
if (comp_non_stub_enabled(&options->comp))
{
msg(msglevel, "'--allow-compression no' conflicts with "
@@ -8342,7 +8356,7 @@ add_option(struct options *options,
{
/* Also printed on a push to hint at configuration problems */
msg(msglevel, "Cannot set allow-compression to '%s' "
- "after set to 'no'", p[1]);
+ "after set to 'stub-only'", p[1]);
goto err;
}
else if (streq(p[1], "asym"))
@@ -8373,8 +8387,16 @@ add_option(struct options *options,
/* All lzo variants do not use swap */
options->comp.flags &= ~COMP_F_SWAP;
+
+ if (options->comp.flags & COMP_F_ALLOW_NOCOMP_ONLY)
+ {
+ /* Also printed on a push to hint at configuration problems */
+ msg(msglevel, "Cannot set comp-lzo to '%s', "
+ "allow-compression is set to 'no'", p[1]);
+ goto err;
+ }
#if defined(ENABLE_LZO)
- if (p[1] && streq(p[1], "no"))
+ else if (p[1] && streq(p[1], "no"))
#endif
{
options->comp.alg = COMP_ALG_STUB;
@@ -8385,7 +8407,7 @@ add_option(struct options *options,
{
/* Also printed on a push to hint at configuration problems */
msg(msglevel, "Cannot set comp-lzo to '%s', "
- "allow-compression is set to 'no'", p[1]);
+ "allow-compression is set to 'stub-only'", p[1]);
goto err;
}
else if (p[1])
@@ -8428,7 +8450,14 @@ add_option(struct options *options,
VERIFY_PERMISSION(OPT_P_COMP);
if (p[1])
{
- if (streq(p[1], "stub"))
+ if (options->comp.flags & COMP_F_ALLOW_NOCOMP_ONLY)
+ {
+ /* Also printed on a push to hint at configuration problems */
+ msg(msglevel, "Cannot set compress to '%s', "
+ "allow-compression is set to 'no'", p[1]);
+ goto err;
+ }
+ else if (streq(p[1], "stub"))
{
options->comp.alg = COMP_ALG_STUB;
options->comp.flags |=
(COMP_F_SWAP|COMP_F_ADVERTISE_STUBS_ONLY);
@@ -8442,13 +8471,12 @@ add_option(struct options *options,
{
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 */
msg(msglevel, "Cannot set compress to '%s', "
- "allow-compression is set to 'no'", p[1]);
+ "allow-compression is set to 'stub-only'", p[1]);
goto err;
}
#if defined(ENABLE_LZO)
--
2.37.1 (Apple Git-137.1)
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