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78 lines
3.5 KiB
78 lines
3.5 KiB
From 286e015bf0d30530707a5e7b3b871509f2ab50d7 Mon Sep 17 00:00:00 2001
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From: Eneas U de Queiroz <cote2004-github@yahoo.com>
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Date: Thu, 27 Sep 2018 08:44:39 -0300
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Subject: Add OPENSSL_PREFER_CHACHA_OVER_GCM option
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This enables a compile-time option to prefer ChaCha20-Poly1305 over
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AES-GCM in the openssl default ciphersuite, which is useful in systems
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without AES specific CPU instructions.
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OPENSSL_PREFER_CHACHA_OVER_GCM must be defined to enable it.
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Note that this does not have the same effect as the
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SL_OP_PRIORITIZE_CHACHA option, which prioritizes ChaCha20-Poly1305 only
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when the client has it on top of its ciphersuite preference.
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Signed-off-by: Eneas U de Queiroz <cote2004-github@yahoo.com>
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--- a/include/openssl/ssl.h
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+++ b/include/openssl/ssl.h
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@@ -173,9 +173,15 @@ extern "C" {
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# define SSL_DEFAULT_CIPHER_LIST "ALL:!COMPLEMENTOFDEFAULT:!eNULL"
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/* This is the default set of TLSv1.3 ciphersuites */
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# if !defined(OPENSSL_NO_CHACHA) && !defined(OPENSSL_NO_POLY1305)
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-# define TLS_DEFAULT_CIPHERSUITES "TLS_AES_256_GCM_SHA384:" \
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- "TLS_CHACHA20_POLY1305_SHA256:" \
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- "TLS_AES_128_GCM_SHA256"
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+# ifdef OPENSSL_PREFER_CHACHA_OVER_GCM
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+# define TLS_DEFAULT_CIPHERSUITES "TLS_CHACHA20_POLY1305_SHA256:" \
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+ "TLS_AES_256_GCM_SHA384:" \
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+ "TLS_AES_128_GCM_SHA256"
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+# else
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+# define TLS_DEFAULT_CIPHERSUITES "TLS_AES_256_GCM_SHA384:" \
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+ "TLS_CHACHA20_POLY1305_SHA256:" \
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+ "TLS_AES_128_GCM_SHA256"
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+# endif
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# else
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# define TLS_DEFAULT_CIPHERSUITES "TLS_AES_256_GCM_SHA384:" \
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"TLS_AES_128_GCM_SHA256"
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--- a/ssl/ssl_ciph.c
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+++ b/ssl/ssl_ciph.c
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@@ -1466,11 +1466,29 @@ STACK_OF(SSL_CIPHER) *ssl_create_cipher_
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ssl_cipher_apply_rule(0, SSL_kECDHE, 0, 0, 0, 0, 0, CIPHER_DEL, -1, &head,
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&tail);
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+ /*
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+ * If OPENSSL_PREFER_CHACHA_OVER_GCM is defined, ChaCha20_Poly1305
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+ * will be placed before AES-256. Otherwise, the default behavior of
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+ * preferring GCM over CHACHA is used.
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+ * This is useful for systems that do not have AES-specific CPU
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+ * instructions, where ChaCha20-Poly1305 is 3 times faster than AES.
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+ * Note that this does not have the same effect as the SSL_OP_PRIORITIZE_CHACHA
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+ * option, which prioritizes ChaCha20-Poly1305 only when the client has it on top
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+ * of its ciphersuite preference.
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+ */
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+
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+#ifdef OPENSSL_PREFER_CHACHA_OVER_GCM
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+ ssl_cipher_apply_rule(0, 0, 0, SSL_CHACHA20, 0, 0, 0, CIPHER_ADD, -1,
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+ &head, &tail);
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+ ssl_cipher_apply_rule(0, 0, 0, SSL_AESGCM, 0, 0, 0, CIPHER_ADD, -1,
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+ &head, &tail);
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+#else
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/* Within each strength group, we prefer GCM over CHACHA... */
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ssl_cipher_apply_rule(0, 0, 0, SSL_AESGCM, 0, 0, 0, CIPHER_ADD, -1,
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&head, &tail);
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ssl_cipher_apply_rule(0, 0, 0, SSL_CHACHA20, 0, 0, 0, CIPHER_ADD, -1,
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&head, &tail);
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+#endif
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/*
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* ...and generally, our preferred cipher is AES.
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@@ -1526,7 +1544,7 @@ STACK_OF(SSL_CIPHER) *ssl_create_cipher_
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* Within each group, ciphers remain sorted by strength and previous
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* preference, i.e.,
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* 1) ECDHE > DHE
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- * 2) GCM > CHACHA
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+ * 2) GCM > CHACHA, reversed if OPENSSL_PREFER_CHACHA_OVER_GCM is defined
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* 3) AES > rest
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* 4) TLS 1.2 > legacy
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*
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