From patchwork Tue May 10 07:04:48 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Arne Schwabe X-Patchwork-Id: 2443 Return-Path: Delivered-To: patchwork@openvpn.net Delivered-To: patchwork@openvpn.net Received: from director12.mail.ord1d.rsapps.net ([172.30.191.6]) by backend41.mail.ord1d.rsapps.net with LMTP id sPc2A4CbemLdLwAAqwncew (envelope-from ) for ; Tue, 10 May 2022 13:06:08 -0400 Received: from proxy9.mail.ord1d.rsapps.net ([172.30.191.6]) by director12.mail.ord1d.rsapps.net with LMTP id WPNSFoCbemKgdQAAIasKDg (envelope-from ) for ; Tue, 10 May 2022 13:06:08 -0400 Received: from smtp17.gate.ord1d ([172.30.191.6]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) by proxy9.mail.ord1d.rsapps.net with LMTPS id uLwaFoCbemJ1awAA7h+8OQ (envelope-from ) for ; Tue, 10 May 2022 13:06:08 -0400 X-Spam-Threshold: 95 X-Spam-Score: 0 X-Spam-Flag: NO X-Virus-Scanned: OK X-Orig-To: openvpnslackdevel@openvpn.net X-Originating-Ip: [216.105.38.7] Authentication-Results: smtp17.gate.ord1d.rsapps.net; iprev=pass policy.iprev="216.105.38.7"; spf=pass smtp.mailfrom="openvpn-devel-bounces@lists.sourceforge.net" smtp.helo="lists.sourceforge.net"; dkim=fail (signature verification failed) header.d=sourceforge.net; dkim=fail (signature verification failed) header.d=sf.net; dmarc=none (p=nil; dis=none) header.from=rfc2549.org X-Suspicious-Flag: YES X-Classification-ID: 7b635200-d083-11ec-9693-5254008de1cb-1-1 Received: from [216.105.38.7] ([216.105.38.7:34762] helo=lists.sourceforge.net) by smtp17.gate.ord1d.rsapps.net (envelope-from ) (ecelerity 4.2.38.62370 r(:)) with ESMTPS (cipher=DHE-RSA-AES256-GCM-SHA384) id 4B/7C-01072-F7B9A726; Tue, 10 May 2022 13:06:07 -0400 Received: from [127.0.0.1] (helo=sfs-ml-4.v29.lw.sourceforge.com) by sfs-ml-4.v29.lw.sourceforge.com with esmtp (Exim 4.94.2) (envelope-from ) id 1noTID-0002DQ-Cj; Tue, 10 May 2022 17:04:59 +0000 Received: from [172.30.20.202] (helo=mx.sourceforge.net) by sfs-ml-4.v29.lw.sourceforge.com with esmtps (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1noTIB-0002DJ-PK for openvpn-devel@lists.sourceforge.net; Tue, 10 May 2022 17:04:58 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=sourceforge.net; s=x; h=Content-Transfer-Encoding:MIME-Version:References: In-Reply-To:Message-Id:Date:Subject:To:From:Sender:Reply-To:Cc:Content-Type: Content-ID:Content-Description:Resent-Date:Resent-From:Resent-Sender: Resent-To:Resent-Cc:Resent-Message-ID:List-Id:List-Help:List-Unsubscribe: List-Subscribe:List-Post:List-Owner:List-Archive; bh=GXs6gJ9xUd5azOQronnVRDnRC3UQQkSR9jPU/Yk0nco=; b=WYJ/TXVY71wL5ytF7cMCI8wYgc S3+E2zgYK7Agp7E7lfaFfqwk3O5FgGknfXBrwOopZxZ3XNbfFQPKLYYotQzReeI25jYQSNPzcJPOF BJjPBkiGmLKOPSdkadAgrWVWfT3rFnP48fcsriTuxmW6/VVveMi/t3hQh2vbHiEQhk4k=; DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=sf.net; s=x ; h=Content-Transfer-Encoding:MIME-Version:References:In-Reply-To:Message-Id: Date:Subject:To:From:Sender:Reply-To:Cc:Content-Type:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Id:List-Help:List-Unsubscribe:List-Subscribe: List-Post:List-Owner:List-Archive; bh=GXs6gJ9xUd5azOQronnVRDnRC3UQQkSR9jPU/Yk0nco=; b=i+f/tjjBdt591m+z5ZI7Pime2l IhdW37DSRTyfd8h8f6fhNbDenfFSRVWtZYGeMABopJPsxSg4JCDJ42nK5ZT6wcuggQ9de6tpUbmMC trxA5xD7rMQ0yrEvR5krJDpxa89lFRxjkiP7U/Q1D1NhL69wQIv2dQfdomjTCvP+H3OA=; Received: from mail.blinkt.de ([192.26.174.232]) by sfi-mx-2.v28.lw.sourceforge.com with esmtps (TLS1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.94.2) id 1noTI8-0003Lq-BE for openvpn-devel@lists.sourceforge.net; Tue, 10 May 2022 17:04:58 +0000 Received: from kamera.blinkt.de ([2001:638:502:390:20c:29ff:fec8:535c]) by mail.blinkt.de with smtp (Exim 4.95 (FreeBSD)) (envelope-from ) id 1noTI0-000J76-NO for openvpn-devel@lists.sourceforge.net; Tue, 10 May 2022 19:04:48 +0200 Received: (nullmailer pid 1856513 invoked by uid 10006); Tue, 10 May 2022 17:04:48 -0000 From: Arne Schwabe To: openvpn-devel@lists.sourceforge.net Date: Tue, 10 May 2022 19:04:48 +0200 Message-Id: <20220510170448.1856465-1-arne@rfc2549.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20220422142953.3805364-16-arne@rfc2549.org> References: <20220422142953.3805364-16-arne@rfc2549.org> MIME-Version: 1.0 X-Spam-Report: Spam detection software, running on the system "util-spamd-1.v13.lw.sourceforge.com", has NOT identified this incoming email as spam. The original message has been attached to this so you can view it or label similar future email. If you have any questions, see the administrator of that system for details. Content preview: This ensure that control packets are actually smaller than tls-mtu. Since OpenVPN will consider a control message packet complete when the TLS record is complete, we have to ensure that the SSL librar [...] Content analysis details: (0.3 points, 6.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- 0.0 SPF_HELO_NONE SPF: HELO does not publish an SPF Record 0.2 HEADER_FROM_DIFFERENT_DOMAINS From and EnvelopeFrom 2nd level mail domains are different 0.0 SPF_NONE SPF: sender does not publish an SPF Record X-Headers-End: 1noTI8-0003Lq-BE Subject: [Openvpn-devel] [PATCH v2 25/28] Ensure that control channel packet are respecting tls-mtu X-BeenThere: openvpn-devel@lists.sourceforge.net X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: openvpn-devel-bounces@lists.sourceforge.net X-getmail-retrieved-from-mailbox: Inbox This ensure that control packets are actually smaller than tls-mtu. Since OpenVPN will consider a control message packet complete when the TLS record is complete, we have to ensure that the SSL library will still write one record, so the receiving side will only be able to get/read the control message content when a TLS record is complete. To achieve this goal, this commit does: - Splitting one read from TLS library into multiple control channel packets, splitting one TLS record into multiple control packets. - increase allowed number of outstanding packets to 6 from 4 on the sender side. This is still okay with older implementation as receivers will have room for 8. - calculate the overhead for control channel message to allow staying below that threshold. - remove maxlen from key_state_read_ciphertext and related functions as we now always allow control channel messages to be up to TLS_CHANNEL_BUF_SIZE in size and longer limit this by the mtu of control packets as the implemented splitting will take care of larger payloads from the SSL library Patch v2: avoid assertion about to large buffer by sticking to 1250 max control size in this commit and leaving larger sizes for the --tls-mtu commit. Also fix various other small problems and grammer fixes. Signed-off-by: Arne Schwabe --- src/openvpn/reliable.c | 57 ++++++++++---- src/openvpn/reliable.h | 32 +++++++- src/openvpn/ssl.c | 152 +++++++++++++++++++++++++++++++++----- src/openvpn/ssl_backend.h | 8 +- src/openvpn/ssl_mbedtls.c | 14 +--- src/openvpn/ssl_openssl.c | 16 ++-- src/openvpn/ssl_pkt.h | 4 +- 7 files changed, 215 insertions(+), 68 deletions(-) diff --git a/src/openvpn/reliable.c b/src/openvpn/reliable.c index 372444350..9b2b2fc6f 100644 --- a/src/openvpn/reliable.c +++ b/src/openvpn/reliable.c @@ -41,6 +41,14 @@ #include "memdbg.h" +/* calculates test - base while allowing for base or test wraparound. test is + * assumed to be higher than base */ +static inline packet_id_type +subtract_pid(const packet_id_type test, const packet_id_type base) +{ + return test - base; +} + /* * verify that test - base < extent while allowing for base or test wraparound */ @@ -49,22 +57,7 @@ reliable_pid_in_range1(const packet_id_type test, const packet_id_type base, const unsigned int extent) { - if (test >= base) - { - if (test - base < extent) - { - return true; - } - } - else - { - if ((test+0x80000000u) - (base+0x80000000u) < extent) - { - return true; - } - } - - return false; + return subtract_pid(test, base) < extent; } /* @@ -496,6 +489,38 @@ reliable_get_buf(struct reliable *rel) return NULL; } +/* Counts the number of free buffers in output that can be potientially used + * for sending */ +int +reliable_get_num_output_sequenced_available(struct reliable *rel) +{ + struct gc_arena gc = gc_new(); + packet_id_type min_id = 0; + bool min_id_defined = false; + + /* find minimum active packet_id */ + for (int i = 0; i < rel->size; ++i) + { + const struct reliable_entry *e = &rel->array[i]; + if (e->active) + { + if (!min_id_defined || reliable_pid_min(e->packet_id, min_id)) + { + min_id_defined = true; + min_id = e->packet_id; + } + } + } + + int ret = rel->size; + if (min_id_defined) + { + ret -= subtract_pid(rel->packet_id, min_id); + } + gc_free(&gc); + return ret; +} + /* grab a free buffer, fail if buffer clogged by unacknowledged low packet IDs */ struct buffer * reliable_get_buf_output_sequenced(struct reliable *rel) diff --git a/src/openvpn/reliable.h b/src/openvpn/reliable.h index b9863efe3..5b4f75c28 100644 --- a/src/openvpn/reliable.h +++ b/src/openvpn/reliable.h @@ -46,7 +46,7 @@ * be stored in one \c reliable_ack * structure. */ -#define RELIABLE_CAPACITY 8 /**< The maximum number of packets that +#define RELIABLE_CAPACITY 12 /**< The maximum number of packets that * the reliability layer for one VPN * tunnel in one direction can store. */ @@ -93,7 +93,7 @@ struct reliable int size; interval_t initial_timeout; packet_id_type packet_id; - int offset; + int offset; /**< Offset of the bufs in the reliable_entry array */ bool hold; /* don't xmit until reliable_schedule_now is called */ struct reliable_entry array[RELIABLE_CAPACITY]; }; @@ -178,6 +178,20 @@ reliable_ack_empty(struct reliable_ack *ack) return !ack->len; } +/** + * Returns the number of packets that need to be acked. + * + * @param ack The acknowledgment structure to check. + * + * @returns the number of outstanding acks + */ +static inline int +reliable_ack_outstanding(struct reliable_ack *ack) +{ + return ack->len; +} + + /** * Write a packet ID acknowledgment record to a buffer. * @@ -385,6 +399,20 @@ void reliable_mark_deleted(struct reliable *rel, struct buffer *buf); */ struct buffer *reliable_get_buf_output_sequenced(struct reliable *rel); + +/** + * Counts the number of free buffers in output that can be potientially used + * for sending + * + * @param rel The reliable structure in which to search for a free + * entry. + * + * @return the number of buffer that are available for sending without + * breaking ack sequence + * */ +int +reliable_get_num_output_sequenced_available(struct reliable *rel); + /** * Mark the reliable entry associated with the given buffer as * active outgoing. diff --git a/src/openvpn/ssl.c b/src/openvpn/ssl.c index 61dea996d..1e3c500d8 100644 --- a/src/openvpn/ssl.c +++ b/src/openvpn/ssl.c @@ -323,8 +323,10 @@ tls_init_control_channel_frame_parameters(const struct frame *data_channel_frame /* Previous OpenVPN version calculated the maximum size and buffer of a * control frame depending on the overhead of the data channel frame * overhead and limited its maximum size to 1250. We always allocate the - * 1250 buffer size since a lot of code blindly assumes a large buffer - * (e.g. PUSH_BUNDLE_SIZE) and set frame->mtu_mtu as suggestion for the + * TLS_CHANNEL_BUF_SIZE buffer size since a lot of code blindly assumes + * a large buffer (e.g. PUSH_BUNDLE_SIZE) and also our peer might have + * a higher size configured and we still want to be able to receive the + * packets. frame->mtu_mtu is set as suggestion for the maximum packet * size */ frame->buf.payload_size = 1250 + overhead; @@ -334,6 +336,47 @@ tls_init_control_channel_frame_parameters(const struct frame *data_channel_frame frame->tun_mtu = min_int(data_channel_frame->tun_mtu, 1250); } +/** + * calculate the maximum overhead that control channel frames have + * This includes header, op code and everything apart from the + * payload itself. This method is a bit pessimistic and might give higher + * overhead than we actually have */ +static int +calc_control_channel_frame_overhead(const struct tls_session *session) +{ + const struct key_state *ks = &session->key[KS_PRIMARY]; + int overhead = 0; + + /* TCP length field and opcode */ + overhead += 3; + + /* our own session id */ + overhead += SID_SIZE; + + /* ACK array and remote SESSION ID (part of the ACK array) */ + overhead += ACK_SIZE(min_int(reliable_ack_outstanding(ks->rec_ack), CONTROL_SEND_ACK_MAX)); + + /* Message packet id */ + overhead += sizeof(packet_id_type); + + if (session->tls_wrap.mode == TLS_WRAP_CRYPT) + { + overhead += tls_crypt_buf_overhead(); + } + else if (session->tls_wrap.mode == TLS_WRAP_AUTH) + { + overhead += hmac_ctx_size(session->tls_wrap.opt.key_ctx_bi.encrypt.hmac); + overhead += packet_id_size(true); + } + + /* Add the typical UDP overhead for an IPv6 UDP packet. TCP+IPv6 has a + * larger overhead but the risk of a TCP connection getting dropped because + * we try to send a too large packet is basically zero */ + overhead += datagram_overhead(AF_INET6, PROTO_UDP); + + return overhead; +} + void init_ssl_lib(void) { @@ -2619,7 +2662,7 @@ read_incoming_tls_plaintext(struct key_state *ks, struct buffer *buf, { ASSERT(buf_init(buf, 0)); - int status = key_state_read_plaintext(&ks->ks_ssl, buf, TLS_CHANNEL_BUF_SIZE); + int status = key_state_read_plaintext(&ks->ks_ssl, buf); update_time(); if (status == -1) @@ -2638,6 +2681,91 @@ read_incoming_tls_plaintext(struct key_state *ks, struct buffer *buf, return true; } +static bool +write_outgoing_tls_ciphertext(struct tls_session *session, bool *state_change) +{ + struct key_state *ks = &session->key[KS_PRIMARY]; + + int rel_avail = reliable_get_num_output_sequenced_available(ks->send_reliable); + if (rel_avail == 0) + { + return true; + } + + /* We need to determine how much space is actually available in the control + * channel frame */ + + int max_pkt_len = min_int(TLS_CHANNEL_BUF_SIZE, session->opt->frame.tun_mtu); + + + /* Subtract overhead */ + max_pkt_len -= calc_control_channel_frame_overhead(session); + + /* calculate total available length for outgoing tls ciphertext */ + int maxlen = max_pkt_len * rel_avail; + + /* Is first packet one that will have a WKC appended? */ + if (control_packet_needs_wkc(ks)) + { + maxlen -= buf_len(session->tls_wrap.tls_crypt_v2_wkc); + } + + /* Not enough space available to send a full control channel packet */ + if (maxlen < TLS_CHANNEL_BUF_SIZE) + { + if (rel_avail == TLS_RELIABLE_N_SEND_BUFFERS) + { + msg(D_TLS_ERRORS, "--tls-mtu setting to low. Unable to send TLS packets"); + } + msg(D_REL_LOW, "Reliable: Send queue full, postponing TLS send"); + return true; + } + + /* This seems a bit wasteful to allocate every time */ + struct gc_arena gc = gc_new(); + struct buffer tmp = alloc_buf_gc(TLS_CHANNEL_BUF_SIZE, &gc); + + int status = key_state_read_ciphertext(&ks->ks_ssl, &tmp); + + if (status == -1) + { + msg(D_TLS_ERRORS, + "TLS Error: Ciphertext -> reliable TCP/UDP transport read error"); + gc_free(&gc); + return false; + } + if (status == 1) + { + /* Split the TLS ciphertext (TLS record) into multiple small packets + * that respect tls_mtu */ + while (tmp.len) + { + int len = max_pkt_len; + int opcode = P_CONTROL_V1; + if (control_packet_needs_wkc(ks)) + { + opcode = P_CONTROL_WKC_V1; + len = max_int(0, len - buf_len(session->tls_wrap.tls_crypt_v2_wkc)); + } + /* do not send more than available */ + len = min_int(len, tmp.len); + + struct buffer *buf = reliable_get_buf_output_sequenced(ks->send_reliable); + /* we assert here since we checked for its availibility before */ + ASSERT(buf); + buf_copy_n(buf, &tmp, len); + + reliable_mark_active_outgoing(ks->send_reliable, buf, opcode); + INCR_GENERATED; + *state_change = true; + } + dmsg(D_TLS_DEBUG, "Outgoing Ciphertext -> Reliable"); + } + + gc_free(&gc); + return true; +} + static bool tls_process_state(struct tls_multi *multi, @@ -2792,26 +2920,10 @@ tls_process_state(struct tls_multi *multi, buf = reliable_get_buf_output_sequenced(ks->send_reliable); if (buf) { - int status = key_state_read_ciphertext(&ks->ks_ssl, buf, multi->opt.frame.tun_mtu); - - if (status == -1) + if (!write_outgoing_tls_ciphertext(session, &state_change)) { - msg(D_TLS_ERRORS, - "TLS Error: Ciphertext -> reliable TCP/UDP transport read error"); goto error; } - if (status == 1) - { - int opcode = P_CONTROL_V1; - if (control_packet_needs_wkc(ks)) - { - opcode = P_CONTROL_WKC_V1; - } - reliable_mark_active_outgoing(ks->send_reliable, buf, opcode); - INCR_GENERATED; - state_change = true; - dmsg(D_TLS_DEBUG, "Outgoing Ciphertext -> Reliable"); - } } } diff --git a/src/openvpn/ssl_backend.h b/src/openvpn/ssl_backend.h index 1bd336999..215425d41 100644 --- a/src/openvpn/ssl_backend.h +++ b/src/openvpn/ssl_backend.h @@ -461,7 +461,6 @@ int key_state_write_plaintext_const(struct key_state_ssl *ks_ssl, * @param ks_ssl - The security parameter state for this %key * session. * @param buf - A buffer in which to store the ciphertext. - * @param maxlen - The maximum number of bytes to extract. * * @return The return value indicates whether the data was successfully * processed: @@ -470,8 +469,8 @@ int key_state_write_plaintext_const(struct key_state_ssl *ks_ssl, * later to retry. * - \c -1: An error occurred. */ -int key_state_read_ciphertext(struct key_state_ssl *ks_ssl, struct buffer *buf, - int maxlen); +int key_state_read_ciphertext(struct key_state_ssl *ks_ssl, struct buffer *buf); + /** @} name Functions for packets to be sent to a remote OpenVPN peer */ @@ -517,8 +516,7 @@ int key_state_write_ciphertext(struct key_state_ssl *ks_ssl, * later to retry. * - \c -1: An error occurred. */ -int key_state_read_plaintext(struct key_state_ssl *ks_ssl, struct buffer *buf, - int maxlen); +int key_state_read_plaintext(struct key_state_ssl *ks_ssl, struct buffer *buf); /** @} name Functions for packets received from a remote OpenVPN peer */ diff --git a/src/openvpn/ssl_mbedtls.c b/src/openvpn/ssl_mbedtls.c index b0785bae9..ea06cf703 100644 --- a/src/openvpn/ssl_mbedtls.c +++ b/src/openvpn/ssl_mbedtls.c @@ -1285,8 +1285,7 @@ key_state_write_plaintext_const(struct key_state_ssl *ks, const uint8_t *data, i } int -key_state_read_ciphertext(struct key_state_ssl *ks, struct buffer *buf, - int maxlen) +key_state_read_ciphertext(struct key_state_ssl *ks, struct buffer *buf) { int retval = 0; int len = 0; @@ -1304,10 +1303,6 @@ key_state_read_ciphertext(struct key_state_ssl *ks, struct buffer *buf, } len = buf_forward_capacity(buf); - if (maxlen < len) - { - len = maxlen; - } retval = endless_buf_read(&ks->bio_ctx->out, BPTR(buf), len); @@ -1388,8 +1383,7 @@ key_state_write_ciphertext(struct key_state_ssl *ks, struct buffer *buf) } int -key_state_read_plaintext(struct key_state_ssl *ks, struct buffer *buf, - int maxlen) +key_state_read_plaintext(struct key_state_ssl *ks, struct buffer *buf) { int retval = 0; int len = 0; @@ -1407,10 +1401,6 @@ key_state_read_plaintext(struct key_state_ssl *ks, struct buffer *buf, } len = buf_forward_capacity(buf); - if (maxlen < len) - { - len = maxlen; - } retval = mbedtls_ssl_read(ks->ctx, BPTR(buf), len); diff --git a/src/openvpn/ssl_openssl.c b/src/openvpn/ssl_openssl.c index c9ea10d49..92bf60862 100644 --- a/src/openvpn/ssl_openssl.c +++ b/src/openvpn/ssl_openssl.c @@ -1871,7 +1871,7 @@ bio_write_post(const int status, struct buffer *buf) * Read from an OpenSSL BIO in non-blocking mode. */ static int -bio_read(BIO *bio, struct buffer *buf, int maxlen, const char *desc) +bio_read(BIO *bio, struct buffer *buf, const char *desc) { int i; int ret = 0; @@ -1882,10 +1882,6 @@ bio_read(BIO *bio, struct buffer *buf, int maxlen, const char *desc) else { int len = buf_forward_capacity(buf); - if (maxlen < len) - { - len = maxlen; - } /* * BIO_read brackets most of the serious RSA @@ -2012,15 +2008,14 @@ key_state_write_plaintext_const(struct key_state_ssl *ks_ssl, const uint8_t *dat } int -key_state_read_ciphertext(struct key_state_ssl *ks_ssl, struct buffer *buf, - int maxlen) +key_state_read_ciphertext(struct key_state_ssl *ks_ssl, struct buffer *buf) { int ret = 0; perf_push(PERF_BIO_READ_CIPHERTEXT); ASSERT(NULL != ks_ssl); - ret = bio_read(ks_ssl->ct_out, buf, maxlen, "tls_read_ciphertext"); + ret = bio_read(ks_ssl->ct_out, buf, "tls_read_ciphertext"); perf_pop(); return ret; @@ -2042,15 +2037,14 @@ key_state_write_ciphertext(struct key_state_ssl *ks_ssl, struct buffer *buf) } int -key_state_read_plaintext(struct key_state_ssl *ks_ssl, struct buffer *buf, - int maxlen) +key_state_read_plaintext(struct key_state_ssl *ks_ssl, struct buffer *buf) { int ret = 0; perf_push(PERF_BIO_READ_PLAINTEXT); ASSERT(NULL != ks_ssl); - ret = bio_read(ks_ssl->ssl_bio, buf, maxlen, "tls_read_plaintext"); + ret = bio_read(ks_ssl->ssl_bio, buf, "tls_read_plaintext"); perf_pop(); return ret; diff --git a/src/openvpn/ssl_pkt.h b/src/openvpn/ssl_pkt.h index 45e0a81f5..9bb3ca958 100644 --- a/src/openvpn/ssl_pkt.h +++ b/src/openvpn/ssl_pkt.h @@ -67,8 +67,8 @@ /* * Define number of buffers for send and receive in the reliability layer. */ -#define TLS_RELIABLE_N_SEND_BUFFERS 4 /* also window size for reliability layer */ -#define TLS_RELIABLE_N_REC_BUFFERS 8 +#define TLS_RELIABLE_N_SEND_BUFFERS 6 /* also window size for reliability layer */ +#define TLS_RELIABLE_N_REC_BUFFERS 12 /* * Used in --mode server mode to check tls-auth signature on initial From patchwork Tue May 10 07:07:41 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Arne Schwabe X-Patchwork-Id: 2444 Return-Path: Delivered-To: patchwork@openvpn.net Delivered-To: patchwork@openvpn.net Received: from director7.mail.ord1d.rsapps.net ([172.27.255.52]) by backend41.mail.ord1d.rsapps.net with LMTP id 8F/3HCGcemLENAAAqwncew (envelope-from ) for ; 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Tue, 10 May 2022 19:07:41 +0200 Received: (nullmailer pid 1856889 invoked by uid 10006); Tue, 10 May 2022 17:07:41 -0000 From: Arne Schwabe To: openvpn-devel@lists.sourceforge.net Date: Tue, 10 May 2022 19:07:41 +0200 Message-Id: <20220510170741.1856843-1-arne@rfc2549.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20220422142953.3805364-17-arne@rfc2549.org> References: <20220422142953.3805364-17-arne@rfc2549.org> MIME-Version: 1.0 X-Spam-Report: Spam detection software, running on the system "util-spamd-2.v13.lw.sourceforge.com", has NOT identified this incoming email as spam. The original message has been attached to this so you can view it or label similar future email. If you have any questions, see the administrator of that system for details. Content preview: Currently control packet size is controlled by tun-mtu in a very non-obvious way since the control overhead is not taken into account and control channel packet will end up with a different size than [...] Content analysis details: (0.2 points, 6.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- 0.0 SPF_NONE SPF: sender does not publish an SPF Record 0.2 HEADER_FROM_DIFFERENT_DOMAINS From and EnvelopeFrom 2nd level mail domains are different 0.0 SPF_HELO_NONE SPF: HELO does not publish an SPF Record -0.0 T_SCC_BODY_TEXT_LINE No description available. X-Headers-End: 1noTKu-0003nI-CV Subject: [Openvpn-devel] [PATCH v2 26/28] Allow setting control channel packet size with tls-mtu X-BeenThere: openvpn-devel@lists.sourceforge.net X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: openvpn-devel-bounces@lists.sourceforge.net X-getmail-retrieved-from-mailbox: Inbox Currently control packet size is controlled by tun-mtu in a very non-obvious way since the control overhead is not taken into account and control channel packet will end up with a different size than data channel packet. Instead we decouple this and introduce tls-mtu which defaults to 1250. Patch v2: rebase on latest patch set Signed-off-by: Arne Schwabe --- Changes.rst | 8 ++++++++ doc/man-sections/link-options.rst | 7 +++++++ src/openvpn/init.c | 8 ++++++-- src/openvpn/mtu.h | 5 +++++ src/openvpn/options.c | 14 ++++++++++++++ src/openvpn/options.h | 1 + src/openvpn/ssl.c | 25 +++++++++++++------------ src/openvpn/ssl.h | 8 +++----- 8 files changed, 57 insertions(+), 19 deletions(-) diff --git a/Changes.rst b/Changes.rst index 67a23c792..f40fc09ae 100644 --- a/Changes.rst +++ b/Changes.rst @@ -79,6 +79,12 @@ Cookie based handshake for UDP server shake. The tls-crypt-v2 option allows controlling if older clients are accepted. +Improved control channel packet size control (``--tls-mtu``) + The size of control channel is no longer tied to + ``--link-mtu``/``--tun-mtu`` and can be set using ``--tls-mtu``. Setting + the size to small sizes no longer breaks the OpenVPN protocol in certain + situation. + Deprecated features ------------------- ``inetd`` has been removed @@ -141,6 +147,8 @@ User-visible Changes - Option ``--nobind`` is default when ``--client`` or ``--pull`` is used in the configuration - :code:`link_mtu` parameter is removed from environment or replaced with 0 when scripts are called with parameters. This parameter is unreliable and no longer internally calculated. +- control channel packet maximum size is no longer influenced by ``--link-mtu``/``--tun-mtu`` + and must be set by ``--tls-mtu`` now. Overview of changes in 2.5 ========================== diff --git a/doc/man-sections/link-options.rst b/doc/man-sections/link-options.rst index 6473ad423..b084fe082 100644 --- a/doc/man-sections/link-options.rst +++ b/doc/man-sections/link-options.rst @@ -454,3 +454,10 @@ the local and the remote host. if mode server: socket-flags TCP_NODELAY push "socket-flags TCP_NODELAY" + +--tls-mtu size + This option sets the maximum size for control channel packets. OpenVPN will + try to keep its control channel messages below this size but due to some + constraints in the protocol this is not always possible. If the option is + not set, it default to 1250. Valid sizes are between 512 and 2048. + The maximum packet size includes encapsalution overhead like UDP and IP. \ No newline at end of file diff --git a/src/openvpn/init.c b/src/openvpn/init.c index b0c62a859..c86866219 100644 --- a/src/openvpn/init.c +++ b/src/openvpn/init.c @@ -2451,6 +2451,10 @@ frame_finalize_options(struct context *c, const struct options *o) * space */ size_t payload_size = max_int(1500, frame->tun_mtu); + /* we need to be also large enough to hold larger control channel packets + * if configured */ + payload_size = max_int(payload_size, o->ce.tls_mtu); + /* The extra tun needs to be added to the payload size */ if (o->ce.tun_mtu_defined) { @@ -2987,7 +2991,7 @@ do_init_frame_tls(struct context *c) { if (c->c2.tls_multi) { - tls_multi_init_finalize(c->c2.tls_multi, &c->c2.frame); + tls_multi_init_finalize(c->c2.tls_multi, c->options.ce.tls_mtu); ASSERT(c->c2.tls_multi->opt.frame.buf.payload_size <= c->c2.frame.buf.payload_size); frame_print(&c->c2.tls_multi->opt.frame, D_MTU_INFO, @@ -2995,7 +2999,7 @@ do_init_frame_tls(struct context *c) } if (c->c2.tls_auth_standalone) { - tls_init_control_channel_frame_parameters(&c->c2.frame, &c->c2.tls_auth_standalone->frame); + tls_init_control_channel_frame_parameters(&c->c2.tls_auth_standalone->frame, c->options.ce.tls_mtu); frame_print(&c->c2.tls_auth_standalone->frame, D_MTU_INFO, "TLS-Auth MTU parms"); c->c2.tls_auth_standalone->tls_wrap.work = alloc_buf_gc(BUF_SIZE(&c->c2.frame), &c->c2.gc); diff --git a/src/openvpn/mtu.h b/src/openvpn/mtu.h index 7f967e066..86959bd53 100644 --- a/src/openvpn/mtu.h +++ b/src/openvpn/mtu.h @@ -79,6 +79,11 @@ */ #define MSSFIX_DEFAULT 1492 +/* + * Default maximum size of control channel packets + */ +#define TLS_MTU_DEFAULT 1250 + /* * Alignment of payload data such as IP packet or * ethernet frame. diff --git a/src/openvpn/options.c b/src/openvpn/options.c index 9ff384d09..d156e0ed1 100644 --- a/src/openvpn/options.c +++ b/src/openvpn/options.c @@ -815,6 +815,7 @@ init_options(struct options *o, const bool init_gc) o->ce.bind_local = true; o->ce.tun_mtu = TUN_MTU_DEFAULT; o->ce.link_mtu = LINK_MTU_DEFAULT; + o->ce.tls_mtu = TLS_MTU_DEFAULT; o->ce.mtu_discover_type = -1; o->ce.mssfix = 0; o->ce.mssfix_default = true; @@ -1582,6 +1583,7 @@ show_connection_entry(const struct connection_entry *o) SHOW_BOOL(link_mtu_defined); SHOW_INT(tun_mtu_extra); SHOW_BOOL(tun_mtu_extra_defined); + SHOW_INT(tls_mtu); SHOW_INT(mtu_discover_type); @@ -6281,6 +6283,18 @@ add_option(struct options *options, options->ce.tun_mtu_extra = positive_atoi(p[1]); options->ce.tun_mtu_extra_defined = true; } + else if (streq(p[0], "tls-mtu") && p[1] && !p[2]) + { + VERIFY_PERMISSION(OPT_P_MTU|OPT_P_CONNECTION); + int tls_mtu = atoi(p[1]); + if (tls_mtu < 512 || tls_mtu > TLS_CHANNEL_BUF_SIZE) + { + msg(msglevel, "Bad tls-mtu value, must be between %d and %d", + 512, TLS_CHANNEL_BUF_SIZE); + goto err; + } + options->ce.tls_mtu = positive_atoi(p[1]); + } #ifdef ENABLE_FRAGMENT else if (streq(p[0], "mtu-dynamic")) { diff --git a/src/openvpn/options.h b/src/openvpn/options.h index c2937dc37..6615d1c74 100644 --- a/src/openvpn/options.h +++ b/src/openvpn/options.h @@ -123,6 +123,7 @@ struct connection_entry bool tun_mtu_extra_defined; int link_mtu; /* MTU of device over which tunnel packets pass via TCP/UDP */ bool link_mtu_defined; /* true if user overriding parm with command line option */ + int tls_mtu; /* Maximum MTU for the control channel messages */ /* Advanced MTU negotiation and datagram fragmentation options */ int mtu_discover_type; /* used if OS supports setting Path MTU discovery options on socket */ diff --git a/src/openvpn/ssl.c b/src/openvpn/ssl.c index 1e3c500d8..d1708c19b 100644 --- a/src/openvpn/ssl.c +++ b/src/openvpn/ssl.c @@ -296,8 +296,7 @@ tls_limit_reneg_bytes(const char *ciphername, int *reneg_bytes) } void -tls_init_control_channel_frame_parameters(const struct frame *data_channel_frame, - struct frame *frame) +tls_init_control_channel_frame_parameters(struct frame *frame, int tls_mtu) { /* * frame->extra_frame is already initialized with tls_auth buffer requirements, @@ -322,18 +321,20 @@ tls_init_control_channel_frame_parameters(const struct frame *data_channel_frame /* Previous OpenVPN version calculated the maximum size and buffer of a * control frame depending on the overhead of the data channel frame - * overhead and limited its maximum size to 1250. We always allocate the - * TLS_CHANNEL_BUF_SIZE buffer size since a lot of code blindly assumes - * a large buffer (e.g. PUSH_BUNDLE_SIZE) and also our peer might have - * a higher size configured and we still want to be able to receive the - * packets. frame->mtu_mtu is set as suggestion for the maximum packet - * size */ - frame->buf.payload_size = 1250 + overhead; + * overhead and limited its maximum size to 1250. Since control frame + * frames also need to fit into data channel buffer we have the same + * default of 1500 + 100 as data channel buffers have. Increasing + * tls-mtu beyond this limit also increases the data channel buffers */ + frame->buf.payload_size = max_int(1500, tls_mtu) + 100; frame->buf.headroom = overhead; frame->buf.tailroom = overhead; - frame->tun_mtu = min_int(data_channel_frame->tun_mtu, 1250); + frame->tun_mtu = tls_mtu; + + /* Ensure the tun-mtu stays in a valid range */ + frame->tun_mtu = min_int(frame->tun_mtu, TLS_CHANNEL_BUF_SIZE); + frame->tun_mtu = max_int(frame->tun_mtu, 512); } /** @@ -1299,9 +1300,9 @@ tls_multi_init(struct tls_options *tls_options) } void -tls_multi_init_finalize(struct tls_multi *multi, const struct frame *frame) +tls_multi_init_finalize(struct tls_multi *multi, int tls_mtu) { - tls_init_control_channel_frame_parameters(frame, &multi->opt.frame); + tls_init_control_channel_frame_parameters(&multi->opt.frame, tls_mtu); /* initialize the active and untrusted sessions */ tls_session_init(multi, &multi->session[TM_ACTIVE]); diff --git a/src/openvpn/ssl.h b/src/openvpn/ssl.h index 0ba86d3e6..cab5f449e 100644 --- a/src/openvpn/ssl.h +++ b/src/openvpn/ssl.h @@ -156,10 +156,9 @@ struct tls_multi *tls_multi_init(struct tls_options *tls_options); * * @param multi - The \c tls_multi structure of which to finalize * initialization. - * @param frame - The data channel's \c frame structure. + * @param tls_mtu - maximum allowed size for control channel packets */ -void tls_multi_init_finalize(struct tls_multi *multi, - const struct frame *frame); +void tls_multi_init_finalize(struct tls_multi *multi, int tls_mtu); /* * Initialize a standalone tls-auth verification object. @@ -171,8 +170,7 @@ struct tls_auth_standalone *tls_auth_standalone_init(struct tls_options *tls_opt * Setups the control channel frame size parameters from the data channel * parameters */ -void tls_init_control_channel_frame_parameters(const struct frame *data_channel_frame, - struct frame *frame); +void tls_init_control_channel_frame_parameters(struct frame *frame, int tls_mtu); /* * Set local and remote option compatibility strings.