From f308251acdc539acb370aeccf46b0ec5587129c1 Mon Sep 17 00:00:00 2001 From: Arne Schwabe Date: Thu, 8 Oct 2020 13:59:59 +0200 Subject: [PATCH] Allow 'none' cipher being specified in --data-ciphers Although we want to get rid of none as cipher, we still have not deprecated it. In order to use it currently you need --ncp-disable together with --cipher none to use the none cipher otherwise OpenVPN will spit out an error about an unrecognised cipher in --data-ciphers. In our current situation allowing none to be specified in data-ciphers is the lesser evil. This commit also fixes that we use '[null-cipher]' instead 'none' when setting remote_cipher. Note that negotiating to cipher 'none' can the same the same problems with frame size calculation as any other non AEAD cipher. If --cipher none is also specified in the configuration, the workaround of commit e539c95dc will also apply to cipher none. Patch V2: Also work correctly if remote_cipher is NULL. Patch V3: fix unit tests, add note about corner case Signed-off-by: Arne Schwabe Acked-by: Gert Doering Message-Id: <20201008115959.21151-1-arne@rfc2549.org> URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg21181.html Signed-off-by: Gert Doering (cherry picked from commit c018fc00be25aee5921d234531f87753a3a7aec7) --- src/openvpn/ssl.c | 8 ++++++++ src/openvpn/ssl_ncp.c | 18 ++++++++++++++++-- tests/unit_tests/openvpn/test_ncp.c | 14 ++++++++++++-- 3 files changed, 36 insertions(+), 4 deletions(-) diff --git a/src/openvpn/ssl.c b/src/openvpn/ssl.c index f16114c2a..c6ba8124d 100644 --- a/src/openvpn/ssl.c +++ b/src/openvpn/ssl.c @@ -2484,6 +2484,14 @@ key_method_2_read(struct buffer *buf, struct tls_multi *multi, struct tls_sessio multi->remote_ciphername = options_string_extract_option(options, "cipher", NULL); + /* In OCC we send '[null-cipher]' instead 'none' */ + if (multi->remote_ciphername + && strcmp(multi->remote_ciphername, "[null-cipher]") == 0) + { + free(multi->remote_ciphername); + multi->remote_ciphername = string_alloc("none", NULL); + } + if (tls_session_user_pass_enabled(session)) { /* Perform username/password authentication */ diff --git a/src/openvpn/ssl_ncp.c b/src/openvpn/ssl_ncp.c index 55496395d..45bddbe0d 100644 --- a/src/openvpn/ssl_ncp.c +++ b/src/openvpn/ssl_ncp.c @@ -110,7 +110,15 @@ mutate_ncp_cipher_list(const char *list, struct gc_arena *gc) * e.g. replacing AeS-128-gCm with AES-128-GCM */ const cipher_kt_t *ktc = cipher_kt_get(token); - if (!ktc) + if (strcmp(token, "none") == 0) + { + msg(M_WARN, "WARNING: cipher 'none' specified for --data-ciphers. " + "This allows negotiation of NO encryption and " + "tunnelled data WILL then be transmitted in clear text " + "over the network! " + "PLEASE DO RECONSIDER THIS SETTING!"); + } + if (!ktc && strcmp(token, "none") != 0) { msg(M_WARN, "Unsupported cipher in --data-ciphers: %s", token); error_found = true; @@ -118,6 +126,12 @@ mutate_ncp_cipher_list(const char *list, struct gc_arena *gc) else { const char *ovpn_cipher_name = cipher_kt_name(ktc); + if (ktc == NULL) + { + /* NULL resolves to [null-cipher] but we need none for + * data-ciphers */ + ovpn_cipher_name = "none"; + } if (buf_len(&new_list)> 0) { @@ -325,4 +339,4 @@ check_pull_client_ncp(struct context *c, const int found) "to this server."); return false; } -} \ No newline at end of file +} diff --git a/tests/unit_tests/openvpn/test_ncp.c b/tests/unit_tests/openvpn/test_ncp.c index a4334c89c..4077be5e8 100644 --- a/tests/unit_tests/openvpn/test_ncp.c +++ b/tests/unit_tests/openvpn/test_ncp.c @@ -50,7 +50,9 @@ test_check_ncp_ciphers_list(void **state) struct gc_arena gc = gc_new(); bool have_chacha = cipher_kt_get("CHACHA20-POLY1305"); - + assert_string_equal(mutate_ncp_cipher_list("none", &gc), "none"); + assert_string_equal(mutate_ncp_cipher_list("AES-256-GCM:none", &gc), + "AES-256-GCM:none"); assert_string_equal(mutate_ncp_cipher_list(aes_ciphers, &gc), aes_ciphers); @@ -139,7 +141,7 @@ test_poor_man(void **state) char *best_cipher; const char *serverlist = "CHACHA20_POLY1305:AES-128-GCM"; - const char *serverlistbfcbc = "CHACHA20_POLY1305:AES-128-GCM:BF-CBC"; + const char *serverlistbfcbc = "CHACHA20_POLY1305:AES-128-GCM:BF-CBC:none"; best_cipher = ncp_get_best_cipher(serverlist, "IV_YOLO=NO\nIV_BAR=7", @@ -166,6 +168,14 @@ test_poor_man(void **state) assert_string_equal(best_cipher, "AES-128-GCM"); + best_cipher = ncp_get_best_cipher(serverlist, NULL, + "none", &gc); + assert_ptr_equal(best_cipher, NULL); + + best_cipher = ncp_get_best_cipher(serverlistbfcbc, NULL, + "none", &gc); + assert_string_equal(best_cipher, "none"); + best_cipher = ncp_get_best_cipher(serverlist, NULL,NULL, &gc); assert_ptr_equal(best_cipher, NULL); -- 2.47.2