From e86bc8b2967484afdb1e96efddb8d91185c4cc2c Mon Sep 17 00:00:00 2001 From: Arne Schwabe Date: Thu, 23 Mar 2023 18:05:59 +0100 Subject: [PATCH] Refuse connection if server pushes an option contradicting allow-compress This removes also the checks in options.c itself as they we now bail out later and no longer need to ignore them during parsing. Change-Id: I872c06f402c35112194ba77c3d6aee78e22547cb Signed-off-by: Arne Schwabe Acked-by: Gert Doering Message-Id: <20230323170601.1256132-2-arne@rfc2549.org> URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg26503.html Signed-off-by: Gert Doering --- Changes.rst | 4 ++++ src/openvpn/comp.c | 29 +++++++++++++++++++++++++++++ src/openvpn/comp.h | 8 ++++++++ src/openvpn/init.c | 8 ++++++++ src/openvpn/multi.c | 8 ++++++++ src/openvpn/options.c | 27 ++++----------------------- 6 files changed, 61 insertions(+), 23 deletions(-) diff --git a/Changes.rst b/Changes.rst index dedb97ee..77bcef26 100644 --- a/Changes.rst +++ b/Changes.rst @@ -232,6 +232,10 @@ User-visible Changes - The ``client-pending-auth`` management command now requires also the key id. The management version has been changed to 5 to indicate this change. +- (OpenVPN 2.6.2) A client will now refuse a connection if pushed compression + settings will contradict the setting of allow-compression as this almost + always results in a non-working connection. + 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/src/openvpn/comp.c b/src/openvpn/comp.c index 3b8d7899..d6d8029d 100644 --- a/src/openvpn/comp.c +++ b/src/openvpn/comp.c @@ -157,4 +157,33 @@ comp_generate_peer_info_string(const struct compress_options *opt, struct buffer } } +bool +check_compression_settings_valid(struct compress_options *info, int msglevel) +{ + if ((info->flags & COMP_F_ALLOW_STUB_ONLY) && comp_non_stub_enabled(info)) + { + msg(msglevel, "Compression is not allowed since allow-compression is " + "set to 'no'"); + return false; + } +#ifndef ENABLE_LZ4 + if (info->alg == COMP_ALGV2_LZ4 || info->alg == COMP_ALG_LZ4) + { + msg(msglevel, "OpenVPN is compiled without LZ4 support. Requested " + "compression cannot be enabled."); + return false; + } +#endif +#ifndef ENABLE_LZO + if (info->alg == COMP_ALG_LZO || info->alg == COMP_ALG_LZ4) + { + msg(msglevel, "OpenVPN is compiled without LZO support. Requested " + "compression cannot be enabled."); + return false; + } +#endif + return true; +} + + #endif /* USE_COMP */ diff --git a/src/openvpn/comp.h b/src/openvpn/comp.h index 685f4039..8636727a 100644 --- a/src/openvpn/comp.h +++ b/src/openvpn/comp.h @@ -196,5 +196,13 @@ comp_non_stub_enabled(const struct compress_options *info) && info->alg != COMP_ALG_UNDEF; } +/** + * Checks if the compression settings are valid. Takes into account the + * flags of allow-compression and also the whether algorithms are compiled + * in + */ +bool +check_compression_settings_valid(struct compress_options *info, int msglevel); + #endif /* USE_COMP */ #endif /* ifndef OPENVPN_COMP_H */ diff --git a/src/openvpn/init.c b/src/openvpn/init.c index 3a6f624f..14859499 100644 --- a/src/openvpn/init.c +++ b/src/openvpn/init.c @@ -2637,6 +2637,14 @@ do_deferred_options(struct context *c, const unsigned int found) #ifdef USE_COMP if (found & OPT_P_COMP) { + if (!check_compression_settings_valid(&c->options.comp, D_PUSH_ERRORS)) + { + msg(D_PUSH_ERRORS, "OPTIONS ERROR: server pushed compression " + "settings that are not allowed and will result " + "in a non-working connection. " + "See also allow-compression in the manual."); + return false; + } msg(D_PUSH_DEBUG, "OPTIONS IMPORT: compression parms modified"); comp_uninit(c->c2.comp_context); c->c2.comp_context = comp_init(&c->options.comp); diff --git a/src/openvpn/multi.c b/src/openvpn/multi.c index 1480bf47..ac090ef5 100644 --- a/src/openvpn/multi.c +++ b/src/openvpn/multi.c @@ -2766,6 +2766,14 @@ multi_connection_established(struct multi_context *m, struct multi_instance *mi) cc_succeeded = false; } +#ifdef USE_COMP + if (!check_compression_settings_valid(&mi->context.options.comp, D_MULTI_ERRORS)) + { + msg(D_MULTI_ERRORS, "MULTI: client has been rejected due to invalid compression options"); + cc_succeeded = false; + } +#endif + if (cc_succeeded) { multi_client_connect_late_setup(m, mi, *option_types_found); diff --git a/src/openvpn/options.c b/src/openvpn/options.c index 2bed4ce9..435e1ca9 100644 --- a/src/openvpn/options.c +++ b/src/openvpn/options.c @@ -3779,6 +3779,9 @@ options_postprocess_mutate(struct options *o, struct env_set *es) /* this depends on o->windows_driver, which is set above */ options_postprocess_mutate_invariant(o); + /* check that compression settings in the options are okay */ + check_compression_settings_valid(&o->comp, M_USAGE); + /* * Save certain parms before modifying options during connect, especially * when using --pull @@ -8405,21 +8408,12 @@ add_option(struct options *options, /* All lzo variants do not use swap */ options->comp.flags &= ~COMP_F_SWAP; -#if defined(ENABLE_LZO) + if (p[1] && streq(p[1], "no")) -#endif { options->comp.alg = COMP_ALG_STUB; options->comp.flags &= ~COMP_F_ADAPTIVE; } -#if defined(ENABLE_LZO) - else if (options->comp.flags & COMP_F_ALLOW_STUB_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; - } else if (p[1]) { if (streq(p[1], "yes")) @@ -8444,7 +8438,6 @@ add_option(struct options *options, options->comp.flags |= COMP_F_ADAPTIVE; } show_compression_warning(&options->comp); -#endif /* if defined(ENABLE_LZO) */ } else if (streq(p[0], "comp-noadapt") && !p[1]) { @@ -8478,23 +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'", alg); - goto err; - } -#if defined(ENABLE_LZO) else if (streq(alg, "lzo")) { options->comp.alg = COMP_ALG_LZO; options->comp.flags &= ~(COMP_F_ADAPTIVE | COMP_F_SWAP); } -#endif -#if defined(ENABLE_LZ4) else if (streq(alg, "lz4")) { options->comp.alg = COMP_ALG_LZ4; @@ -8504,7 +8486,6 @@ add_option(struct options *options, { options->comp.alg = COMP_ALGV2_LZ4; } -#endif else { msg(msglevel, "bad comp option: %s", alg);