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- From 97cafd182f5a5c2d13f57d7faeac8432aea9bbf8 Mon Sep 17 00:00:00 2001
- From: David Woodhouse <dwmw2@infradead.org>
- Date: Mon, 10 Jun 2019 12:34:43 +0100
- Subject: [PATCH] Disable encrypt-then-mac where possible with DTLS and OpenSSL
-
- There is pain here. Just don't bother.
-
- Signed-off-by: David Woodhouse <dwmw2@infradead.org>
- ---
- openssl-dtls.c | 12 +++++++++++-
- 1 file changed, 11 insertions(+), 1 deletion(-)
-
- diff --git a/openssl-dtls.c b/openssl-dtls.c
- index 9e3c5d46..646bf71c 100644
- --- a/openssl-dtls.c
- +++ b/openssl-dtls.c
- @@ -406,7 +406,17 @@ int start_dtls_handshake(struct openconnect_info *vpninfo, int dtls_fd)
- cipher = "PSK";
- }
- #endif /* OPENSSL_NO_PSK */
- -
- +#ifdef SSL_OP_NO_ENCRYPT_THEN_MAC
- + /* I'm fairly sure I wasn't lying when I said I had tested
- + * https://github.com/openssl/openssl/commit/e23d5071ec4c7aa6bb2b
- + * against GnuTLS both with and without EtM in 2016.
- + * Nevertheless, in 2019 it seems to be failing to negotiate
- + * at least for DTLS1_BAD_VER against ocserv with GnuTLS 3.6.7.
- + * Just turn it off. Real Cisco servers don't do it for
- + * DTLS1_BAD_VER, and we should be using GCM ciphersuites in
- + * newer versions of DTLS anyway so it's irrelevant. */
- + SSL_CTX_set_options(vpninfo->dtls_ctx, SSL_OP_NO_ENCRYPT_THEN_MAC);
- +#endif
- /* If we don't readahead, then we do short reads and throw
- away the tail of data packets. */
- SSL_CTX_set_read_ahead(vpninfo->dtls_ctx, 1);
- --
- 2.17.1
-
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