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225 lines
9.4 KiB
225 lines
9.4 KiB
From cf5864f5922e4f40357d9f75a35cd448e671dddf Mon Sep 17 00:00:00 2001 |
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From: Arne Schwabe <arne@rfc2549.org> |
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Date: Fri, 3 Jun 2022 11:52:19 +0200 |
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Subject: [PATCH] Allow running a default configuration with TLS libraries |
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without BF-CBC |
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Modern TLS libraries might drop Blowfish by default or distributions |
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might disable Blowfish in OpenSSL/mbed TLS. We still signal OCC |
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options with BF-CBC compatible strings. To avoid requiring BF-CBC |
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for this, special this one usage of BF-CBC enough to avoid a hard |
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requirement on Blowfish in the default configuration. |
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This patch is cherry-picked from 79ff3f79 and the missing |
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ciphername = "none"; has been added in the OCC code. |
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Due to uncrustify complains, a few extra whitespace fixes had to be |
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done to options.c. |
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Signed-off-by: Arne Schwabe <arne@rfc2549.org> |
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Acked-by: Gert Doering <gert@greenie.muc.de> |
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Message-Id: <20220603095219.637361-1-arne@rfc2549.org> |
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URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg24456.html |
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Signed-off-by: Gert Doering <gert@greenie.muc.de> |
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--- |
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src/openvpn/crypto_backend.h | 2 ++ |
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src/openvpn/init.c | 37 ++++++++++++++++----- |
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src/openvpn/options.c | 62 ++++++++++++++++++++++++++++-------- |
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3 files changed, 80 insertions(+), 21 deletions(-) |
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diff --git a/src/openvpn/crypto_backend.h b/src/openvpn/crypto_backend.h |
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index a9bb38ed..aebda3d6 100644 |
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--- a/src/openvpn/crypto_backend.h |
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+++ b/src/openvpn/crypto_backend.h |
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@@ -256,6 +256,8 @@ const cipher_kt_t *cipher_kt_get(const char *ciphername); |
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* The returned name is normalised to the OpenVPN config name in case the |
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* name differs from the name used by the crypto library. |
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* |
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+ * Returns [null-cipher] in case the cipher_kt is NULL. |
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+ * |
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* @param cipher_kt Static cipher parameters |
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* |
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* @return a statically allocated string describing the cipher. |
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diff --git a/src/openvpn/init.c b/src/openvpn/init.c |
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index da4d60af..b1b7b350 100644 |
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--- a/src/openvpn/init.c |
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+++ b/src/openvpn/init.c |
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@@ -2764,14 +2764,35 @@ do_init_crypto_tls_c1(struct context *c) |
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#endif /* if P2MP */ |
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} |
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- /* Do not warn if we only have BF-CBC in options->ciphername |
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- * because it is still the default cipher */ |
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- bool warn = !streq(options->ciphername, "BF-CBC") |
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- || options->enable_ncp_fallback; |
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- /* Get cipher & hash algorithms */ |
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- init_key_type(&c->c1.ks.key_type, options->ciphername, options->authname, |
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- options->keysize, true, warn); |
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- |
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+ /* |
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+ * BF-CBC is allowed to be used only when explicitly configured |
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+ * as NCP-fallback or when NCP has been disabled or explicitly |
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+ * allowed in the in ncp_ciphers list. |
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+ * In all other cases do not attempt to initialize BF-CBC as it |
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+ * may not even be supported by the underlying SSL library. |
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+ * |
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+ * Therefore, the key structure has to be initialized when: |
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+ * - any non-BF-CBC cipher was selected; or |
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+ * - BF-CBC is selected and NCP is disabled (explicit request to |
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+ * use the BF-CBC cipher); or |
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+ * - BF-CBC is selected, NCP is enabled and fallback is enabled |
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+ * (BF-CBC will be the fallback). |
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+ * - BF-CBC is in data-ciphers and we negotiate to use BF-CBC: |
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+ * If the negotiated cipher and options->ciphername are the |
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+ * same we do not reinit the cipher |
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+ * |
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+ * Note that BF-CBC will still be part of the OCC string to retain |
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+ * backwards compatibility with older clients. |
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+ */ |
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+ if (!streq(options->ciphername, "BF-CBC") || !options->ncp_enabled |
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+ || (options->ncp_enabled && tls_item_in_cipher_list("BF-CBC", options->ncp_ciphers)) |
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+ || options->enable_ncp_fallback) |
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+ { |
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+ /* Do not warn if the if the cipher is used only in OCC */ |
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+ bool warn = !options->ncp_enabled || options->enable_ncp_fallback; |
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+ init_key_type(&c->c1.ks.key_type, options->ciphername, options->authname, |
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+ options->keysize, true, warn); |
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+ } |
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/* Initialize PRNG with config-specified digest */ |
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prng_init(options->prng_hash, options->prng_nonce_secret_len); |
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diff --git a/src/openvpn/options.c b/src/openvpn/options.c |
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index f6ef02ae..2206d9f4 100644 |
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--- a/src/openvpn/options.c |
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+++ b/src/openvpn/options.c |
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@@ -1135,7 +1135,7 @@ parse_hash_fingerprint(const char *str, int nbytes, int msglevel, struct gc_aren |
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#ifndef ENABLE_SMALL |
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static void |
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-show_dhcp_option_list(const char *name, const char * const*array, int len) |
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+show_dhcp_option_list(const char *name, const char *const *array, int len) |
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{ |
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int i; |
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for (i = 0; i < len; ++i) |
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@@ -2288,7 +2288,7 @@ options_postprocess_verify_ce(const struct options *options, |
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if (options->mode == MODE_SERVER) |
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{ |
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#define USAGE_VALID_SERVER_PROTOS "--mode server currently only supports " \ |
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- "--proto values of udp, tcp-server, tcp4-server, or tcp6-server" |
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+ "--proto values of udp, tcp-server, tcp4-server, or tcp6-server" |
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#ifdef TARGET_ANDROID |
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msg(M_FATAL, "--mode server not supported on Android"); |
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#endif |
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@@ -3103,7 +3103,7 @@ options_postprocess_cipher(struct options *o) |
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if (!o->ncp_enabled) |
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{ |
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msg(M_USAGE, "--ncp-disable needs an explicit --cipher or " |
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- "--data-ciphers-fallback config option"); |
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+ "--data-ciphers-fallback config option"); |
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} |
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msg(M_WARN, "--cipher is not set. Previous OpenVPN version defaulted to " |
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@@ -3681,9 +3681,30 @@ calc_options_string_link_mtu(const struct options *o, const struct frame *frame) |
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{ |
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struct frame fake_frame = *frame; |
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struct key_type fake_kt; |
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- init_key_type(&fake_kt, o->ciphername, o->authname, o->keysize, true, |
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- false); |
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+ |
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frame_remove_from_extra_frame(&fake_frame, crypto_max_overhead()); |
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+ |
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+ |
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+ /* o->ciphername might be BF-CBC even though the underlying SSL library |
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+ * does not support it. For this reason we workaround this corner case |
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+ * by pretending to have no encryption enabled and by manually adding |
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+ * the required packet overhead to the MTU computation. |
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+ */ |
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+ const char *ciphername = o->ciphername; |
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+ |
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+ if (strcmp(o->ciphername, "BF-CBC") == 0) |
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+ { |
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+ /* none has no overhead, so use this to later add only --auth |
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+ * overhead */ |
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+ |
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+ /* overhead of BF-CBC: 64 bit block size, 64 bit IV size */ |
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+ frame_add_to_extra_frame(&fake_frame, 64/8 + 64/8); |
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+ ciphername = "none"; |
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+ } |
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+ |
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+ init_key_type(&fake_kt, ciphername, o->authname, o->keysize, true, |
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+ false); |
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+ |
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crypto_adjust_frame_parameters(&fake_frame, &fake_kt, o->replay, |
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cipher_kt_mode_ofb_cfb(fake_kt.cipher)); |
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frame_finalize(&fake_frame, o->ce.link_mtu_defined, o->ce.link_mtu, |
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@@ -3853,18 +3874,33 @@ options_string(const struct options *o, |
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+ (TLS_SERVER == true) |
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<= 1); |
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- init_key_type(&kt, o->ciphername, o->authname, o->keysize, true, |
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- false); |
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+ /* Skip resolving BF-CBC to allow SSL libraries without BF-CBC |
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+ * to work here in the default configuration */ |
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+ const char *ciphername = o->ciphername; |
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+ int keysize; |
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+ |
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+ if (strcmp(o->ciphername, "BF-CBC") == 0) |
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+ { |
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+ init_key_type(&kt, "none", o->authname, o->keysize, true, |
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+ false); |
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+ keysize = 128; |
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+ } |
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+ else |
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+ { |
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+ init_key_type(&kt, o->ciphername, o->authname, o->keysize, true, |
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+ false); |
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+ ciphername = cipher_kt_name(kt.cipher); |
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+ keysize = kt.cipher_length * 8; |
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+ } |
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/* Only announce the cipher to our peer if we are willing to |
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* support it */ |
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- const char *ciphername = cipher_kt_name(kt.cipher); |
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if (p2p_nopull || !o->ncp_enabled |
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|| tls_item_in_cipher_list(ciphername, o->ncp_ciphers)) |
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{ |
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buf_printf(&out, ",cipher %s", ciphername); |
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} |
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buf_printf(&out, ",auth %s", md_kt_name(kt.digest)); |
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- buf_printf(&out, ",keysize %d", kt.cipher_length * 8); |
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+ buf_printf(&out, ",keysize %d", keysize); |
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if (o->shared_secret_file) |
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{ |
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buf_printf(&out, ",secret"); |
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@@ -6168,9 +6204,9 @@ add_option(struct options *options, |
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} |
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} |
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#ifdef TARGET_LINUX |
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- else if (streq (p[0], "bind-dev") && p[1]) |
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+ else if (streq(p[0], "bind-dev") && p[1]) |
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{ |
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- VERIFY_PERMISSION (OPT_P_SOCKFLAGS); |
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+ VERIFY_PERMISSION(OPT_P_SOCKFLAGS); |
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options->bind_dev = p[1]; |
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} |
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#endif |
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@@ -6248,7 +6284,7 @@ add_option(struct options *options, |
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{ |
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int64_t val = atoll(p[2]); |
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options->inactivity_minimum_bytes = (val < 0) ? 0 : val; |
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- if ( options->inactivity_minimum_bytes > INT_MAX ) |
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+ if (options->inactivity_minimum_bytes > INT_MAX) |
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{ |
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msg(M_WARN, "WARNING: '--inactive' with a 'bytes' value" |
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" >2 Gbyte was silently ignored in older versions. If " |
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@@ -8132,7 +8168,7 @@ add_option(struct options *options, |
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#endif |
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else if (streq(p[0], "providers") && p[1]) |
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{ |
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- for (size_t j = 1; j < MAX_PARMS && p[j] != NULL;j++) |
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+ for (size_t j = 1; j < MAX_PARMS && p[j] != NULL; j++) |
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{ |
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options->providers.names[j] = p[j]; |
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} |
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-- |
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2.31.1 |
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