openssl: recreate the OpenSSL 1.1 BIO interface for older versions

We want to program against the interface, so recreate it when we compile
against pre-1.1 versions.

src/openssl_stream.c

@@ -13,6 +13,7 @@
 #include "posix.h"
 #include "stream.h"
 #include "socket_stream.h"
+#include "openssl_stream.h"
 #include "netops.h"
 #include "git2/transport.h"
 #include "git2/sys/openssl.h"
@@ -71,12 +72,20 @@ static void shutdown_ssl_locking(void)
 
 #endif /* GIT_THREADS */
 
+static BIO_METHOD *git_stream_bio_method;
+static int init_bio_method(void);
+
 /**
  * This function aims to clean-up the SSL context which
  * we allocated.
  */
 static void shutdown_ssl(void)
 {
+	if (git_stream_bio_method) {
+		BIO_meth_free(git_stream_bio_method);
+		git_stream_bio_method = NULL;
+	}
+
 	if (git__ssl_ctx) {
 		SSL_CTX_free(git__ssl_ctx);
 		git__ssl_ctx = NULL;
@@ -121,6 +130,13 @@ int git_openssl_stream_global_init(void)
 		git__ssl_ctx = NULL;
 		return -1;
 	}
+
+	if (init_bio_method() < 0) {
+		SSL_CTX_free(git__ssl_ctx);
+		git__ssl_ctx = NULL;
+		return -1;
+	}
+
 #endif
 
 	git__on_shutdown(shutdown_ssl);
@@ -156,14 +172,8 @@ int git_openssl_set_locking(void)
 
 static int bio_create(BIO *b)
 {
-#if OPENSSL_VERSION_NUMBER < 0x10100000L
-	b->init = 1;
-	b->num = 0;
-	b->ptr = NULL;
-	b->flags = 0;
-#else
 	BIO_set_init(b, 1);
-#endif
+	BIO_set_data(b, NULL);
 
 	return 1;
 }
@@ -173,36 +183,22 @@ static int bio_destroy(BIO *b)
 	if (!b)
 		return 0;
 
-#if OPENSSL_VERSION_NUMBER < 0x10100000L
-	b->init = 0;
-	b->num = 0;
-	b->ptr = NULL;
-	b->flags = 0;
-#else
-	BIO_set_init(b, 0);
 	BIO_set_data(b, NULL);
-#endif
 
 	return 1;
 }
 
 static int bio_read(BIO *b, char *buf, int len)
 {
-#if OPENSSL_VERSION_NUMBER < 0x10100000L
-	git_stream *io = (git_stream *) b->ptr;
-#else
 	git_stream *io = (git_stream *) BIO_get_data(b);
-#endif
+
 	return (int) git_stream_read(io, buf, len);
 }
 
 static int bio_write(BIO *b, const char *buf, int len)
 {
-#if OPENSSL_VERSION_NUMBER < 0x10100000L
-	git_stream *io = (git_stream *) b->ptr;
-#else
 	git_stream *io = (git_stream *) BIO_get_data(b);
-#endif
+
 	return (int) git_stream_write(io, buf, len, 0);
 }
 
@@ -231,21 +227,22 @@ static int bio_puts(BIO *b, const char *str)
 	return bio_write(b, str, strlen(str));
 }
 
-#if OPENSSL_VERSION_NUMBER < 0x10100000L
-static BIO_METHOD git_stream_bio_method = {
-	BIO_TYPE_SOURCE_SINK,
-	"git_stream",
-	bio_write,
-	bio_read,
-	bio_puts,
-	bio_gets,
-	bio_ctrl,
-	bio_create,
-	bio_destroy
-};
-#else
-static BIO_METHOD *git_stream_bio_method = NULL;
-#endif
+static int init_bio_method(void)
+{
+	/* Set up the BIO_METHOD we use for wrapping our own stream implementations */
+	git_stream_bio_method = BIO_meth_new(BIO_TYPE_SOURCE_SINK | BIO_get_new_index(), "git_stream");
+	GITERR_CHECK_ALLOC(git_stream_bio_method);
+
+	BIO_meth_set_write(git_stream_bio_method, bio_write);
+	BIO_meth_set_read(git_stream_bio_method, bio_read);
+	BIO_meth_set_puts(git_stream_bio_method, bio_puts);
+	BIO_meth_set_gets(git_stream_bio_method, bio_gets);
+	BIO_meth_set_ctrl(git_stream_bio_method, bio_ctrl);
+	BIO_meth_set_create(git_stream_bio_method, bio_create);
+	BIO_meth_set_destroy(git_stream_bio_method, bio_destroy);
+
+	return 0;
+}
 
 static int ssl_set_error(SSL *ssl, int error)
 {
@@ -466,27 +463,12 @@ int openssl_connect(git_stream *stream)
 
 	st->connected = true;
 
-#if OPENSSL_VERSION_NUMBER < 0x10100000L
-	bio = BIO_new(&git_stream_bio_method);
-#else
-	git_stream_bio_method = BIO_meth_new(BIO_TYPE_SOURCE_SINK | BIO_get_new_index(), "git_stream");
-	BIO_meth_set_write(git_stream_bio_method, bio_write);
-	BIO_meth_set_read(git_stream_bio_method, bio_read);
-	BIO_meth_set_puts(git_stream_bio_method, bio_puts);
-	BIO_meth_set_gets(git_stream_bio_method, bio_gets);
-	BIO_meth_set_ctrl(git_stream_bio_method, bio_ctrl);
-	BIO_meth_set_create(git_stream_bio_method, bio_create);
-	BIO_meth_set_destroy(git_stream_bio_method, bio_destroy);
 	bio = BIO_new(git_stream_bio_method);
-#endif
 	GITERR_CHECK_ALLOC(bio);
-#if OPENSSL_VERSION_NUMBER < 0x10100000L
-	bio->ptr = st->io;
-#else
-	BIO_set_data(bio, st->io);
-#endif
 
+	BIO_set_data(bio, st->io);
 	SSL_set_bio(st->ssl, bio, bio);
+
 	/* specify the host in case SNI is needed */
 #ifdef SSL_CTRL_SET_TLSEXT_HOSTNAME
 	SSL_set_tlsext_host_name(st->ssl, st->host);

src/openssl_stream.h

@@ -7,10 +7,107 @@
 #ifndef INCLUDE_openssl_stream_h__
 #define INCLUDE_openssl_stream_h__
 
+#include <openssl/ssl.h>
+#include <openssl/err.h>
+#include <openssl/x509v3.h>
+#include <openssl/bio.h>
+
 #include "git2/sys/stream.h"
 
 extern int git_openssl_stream_global_init(void);
 
 extern int git_openssl_stream_new(git_stream **out, const char *host, const char *port);
 
+/*
+ * OpenSSL 1.1 made BIO opaque so we have to use functions to interact with it
+ * which do not exist in previous versions. We define these inline functions so
+ * we can program against the interface instead of littering the implementation
+ * with ifdefs.
+ */
+# if OPENSSL_VERSION_NUMBER < 0x10100000L
+
+GIT_INLINE(BIO_METHOD*) BIO_meth_new(int type, const char *name)
+{
+	BIO_METHOD *meth = git__calloc(1, sizeof(BIO_METHOD));
+	if (!meth) {
+		return NULL;
+	}
+
+	meth->type = type;
+	meth->name = name;
+
+	return meth;
+}
+
+GIT_INLINE(void) BIO_meth_free(BIO_METHOD *biom)
+{
+	git__free(biom);
+}
+
+GIT_INLINE(int) BIO_meth_set_write(BIO_METHOD *biom, int (*write) (BIO *, const char *, int))
+{
+	biom->bwrite = write;
+	return 1;
+}
+
+GIT_INLINE(int) BIO_meth_set_read(BIO_METHOD *biom, int (*read) (BIO *, char *, int))
+{
+	biom->bread = read;
+	return 1;
+}
+
+GIT_INLINE(int) BIO_meth_set_puts(BIO_METHOD *biom, int (*puts) (BIO *, const char *))
+{
+	biom->bputs = puts;
+	return 1;
+}
+
+GIT_INLINE(int) BIO_meth_set_gets(BIO_METHOD *biom, int (*gets) (BIO *, char *, int))
+
+{
+	biom->bgets = gets;
+	return 1;
+}
+
+GIT_INLINE(int) BIO_meth_set_ctrl(BIO_METHOD *biom, long (*ctrl) (BIO *, int, long, void *))
+{
+	biom->ctrl = ctrl;
+	return 1;
+}
+
+GIT_INLINE(int) BIO_meth_set_create(BIO_METHOD *biom, int (*create) (BIO *))
+{
+	biom->create = create;
+	return 1;
+}
+
+GIT_INLINE(int) BIO_meth_set_destroy(BIO_METHOD *biom, int (*destroy) (BIO *))
+{
+	biom->destroy = destroy;
+	return 1;
+}
+
+GIT_INLINE(int) BIO_get_new_index(void)
+{
+	/* This exists as of 1.1 so before we'd just have 0 */
+	return 0;
+}
+
+GIT_INLINE(void) BIO_set_init(BIO *b, int init)
+{
+	b->init = init;
+}
+
+GIT_INLINE(void) BIO_set_data(BIO *a, void *ptr)
+{
+	a->ptr = ptr;
+}
+
+GIT_INLINE(void*) BIO_get_data(BIO *a)
+{
+	return a->ptr;
+}
+
+# endif
+
 #endif