prefer libcrypto chacha20-poly1305 where possible

Makefile.in

@@ -103,7 +103,7 @@ LIBSSH_OBJS=${LIBOPENSSH_OBJS} \
 	ssh-ed25519-sk.o ssh-rsa.o dh.o \
 	msg.o progressmeter.o dns.o entropy.o gss-genr.o umac.o umac128.o \
 	ssh-pkcs11.o smult_curve25519_ref.o \
-	poly1305.o chacha.o cipher-chachapoly.o \
+	poly1305.o chacha.o cipher-chachapoly.o cipher-chachapoly-libcrypto.o \
 	ssh-ed25519.o digest-openssl.o digest-libc.o \
 	hmac.o sc25519.o ge25519.o fe25519.o ed25519.o verify.o hash.o \
 	kex.o kexdh.o kexgex.o kexecdh.o kexc25519.o \

cipher-chachapoly-libcrypto.c

@@ -18,6 +18,8 @@
 
 #include "includes.h"
 
+#if defined(HAVE_EVP_CHACHA20) || !defined(HAVE_BROKEN_CHACHA20)
+
 #include <sys/types.h>
 #include <stdarg.h> /* needed for log.h */
 #include <string.h>
@@ -158,3 +160,4 @@ chachapoly_get_length(struct chachapoly_ctx *ctx,
 	*plenp = PEEK_U32(buf);
 	return 0;
 }
+#endif /* defined(HAVE_EVP_CHACHA20) && !defined(HAVE_BROKEN_CHACHA20) */

cipher-chachapoly.c

@@ -18,6 +18,8 @@
 
 #include "includes.h"
 
+#if !defined(HAVE_EVP_CHACHA20) || defined(HAVE_BROKEN_CHACHA20)
+
 #include <sys/types.h>
 #include <stdarg.h> /* needed for log.h */
 #include <string.h>
@@ -130,3 +132,5 @@ chachapoly_get_length(struct chachapoly_ctx *ctx,
 	*plenp = PEEK_U32(buf);
 	return 0;
 }
+
+#endif /* !defined(HAVE_EVP_CHACHA20) || defined(HAVE_BROKEN_CHACHA20) */

configure.ac

@@ -2804,6 +2804,7 @@ if test "x$openssl" = "xyes" ; then
 		EVP_PKEY_get0_RSA \
 		EVP_MD_CTX_new \
 		EVP_MD_CTX_free \
+		EVP_chacha20 \
 	])
 
 	if test "x$openssl_engine" = "xyes" ; then

openbsd-compat/openssl-compat.h

@@ -62,6 +62,12 @@ void ssh_libcrypto_init(void);
 # define OPENSSL_DSA_MAX_MODULUS_BITS	10000
 #endif
 
+#ifdef LIBRESSL_VERSION_NUMBER
+# if LIBRESSL_VERSION_NUMBER >= 0x3010000fL
+#  define HAVE_BROKEN_CHACHA20
+# endif
+#endif
+
 #ifndef OPENSSL_HAVE_EVPCTR
 # define EVP_aes_128_ctr evp_aes_128_ctr
 # define EVP_aes_192_ctr evp_aes_128_ctr