tls: introduce a wrap function

Introduce `git_tls_stream_wrap` which will take an existing `stream`
with an already connected socket and begin speaking TLS on top of it.
This is useful if you've built a connection to a proxy server and you
wish to begin CONNECT over it to tunnel a TLS connection.

Also update the pluggable TLS stream layer so that it can accept a
registration structure that provides an `init` and `wrap` function,
instead of a single initialization function.

include/git2/sys/stream.h

@@ -40,18 +40,48 @@ typedef struct git_stream {
 	void (*free)(struct git_stream *);
 } git_stream;
 
-typedef int (*git_stream_cb)(git_stream **out, const char *host, const char *port);
+typedef struct {
+	/** The `version` field should be set to `GIT_STREAM_VERSION`. */
+	int version;
+
+	/**
+	 * Called to create a new TLS connection to a given host.
+	 *
+	 * @param out The created TLS stream
+	 * @param host The hostname to connect to; may be a hostname or
+	 *             IP address
+	 * @param port The port to connect to; may be a port number or
+	 *             service name
+	 * @return 0 or an error code
+	 */
+	int (*init)(git_stream **out, const char *host, const char *port);
+
+	/**
+	 * Called to create a new TLS connection on top of the given
+	 * stream.  May be used to proxy a TLS stream over a CONNECT
+	 * session.
+	 *
+	 * @param out The created TLS stream
+	 * @param in An existing stream to add TLS to
+	 * @param host The hostname that the stream is connected to,
+	 *             for certificate validation
+	 * @return 0 or an error code
+	 */
+	int (*wrap)(git_stream **out, git_stream *in, const char *host);
+} git_stream_registration;
 
 /**
- * Register a TLS stream constructor for the library to use
+ * Register TLS stream constructors for the library to use
  *
- * If a constructor is already set, it will be overwritten. Pass
- * `NULL` in order to deregister the current constructor.
+ * If a registration structure is already set, it will be overwritten.
+ * Pass `NULL` in order to deregister the current constructor and return
+ * to the system defaults.
  *
- * @param ctor the constructor to use
+ * @param registration the registration data
  * @return 0 or an error code
  */
-GIT_EXTERN(int) git_stream_register_tls(git_stream_cb ctor);
+GIT_EXTERN(int) git_stream_register_tls(
+	git_stream_registration *registration);
 
 GIT_END_DECL
 

src/global.c

@@ -12,6 +12,7 @@
 #include "sysdir.h"
 #include "filter.h"
 #include "merge_driver.h"
+#include "streams/tls.h"
 #include "streams/curl.h"
 #include "streams/mbedtls.h"
 #include "streams/openssl.h"
@@ -67,6 +68,7 @@ static int init_common(void)
 		(ret = git_filter_global_init()) == 0 &&
 		(ret = git_merge_driver_global_init()) == 0 &&
 		(ret = git_transport_ssh_global_init()) == 0 &&
+		(ret = git_tls_stream_global_init()) == 0 &&
 		(ret = git_openssl_stream_global_init()) == 0 &&
 		(ret = git_curl_stream_global_init()) == 0 &&
 		(ret = git_mbedtls_stream_global_init()) == 0)

src/streams/mbedtls.c

@@ -242,6 +242,7 @@ static int verify_server_cert(mbedtls_ssl_context *ssl)
 typedef struct {
 	git_stream parent;
 	git_stream *io;
+	int owned;
 	bool connected;
 	char *host;
 	mbedtls_ssl_context *ssl;
@@ -254,7 +255,7 @@ int mbedtls_connect(git_stream *stream)
 	int ret;
 	mbedtls_stream *st = (mbedtls_stream *) stream;
 
-	if ((ret = git_stream_connect(st->io)) < 0)
+	if (st->owned && (ret = git_stream_connect(st->io)) < 0)
 		return ret;
 
 	st->connected = true;
@@ -345,37 +346,37 @@ int mbedtls_stream_close(git_stream *stream)
 
 	st->connected = false;
 
-	return git_stream_close(st->io);
+	return st->owned ? git_stream_close(st->io) : 0;
 }
 
 void mbedtls_stream_free(git_stream *stream)
 {
 	mbedtls_stream *st = (mbedtls_stream *) stream;
 
+	if (st->owned)
+		git_stream_free(st->io);
+
 	git__free(st->host);
 	git__free(st->cert_info.data);
-	git_stream_free(st->io);
 	mbedtls_ssl_free(st->ssl);
 	git__free(st->ssl);
 	git__free(st);
 }
 
-int git_mbedtls_stream_new(git_stream **out, const char *host, const char *port)
+static int mbedtls_stream_wrap(
+	git_stream **out,
+	git_stream *in,
+	const char *host,
+	int owned)
 {
-	int error;
 	mbedtls_stream *st;
+	int error;
 
 	st = git__calloc(1, sizeof(mbedtls_stream));
 	GITERR_CHECK_ALLOC(st);
 
-#ifdef GIT_CURL
-	error = git_curl_stream_new(&st->io, host, port);
-#else
-	error = git_socket_stream_new(&st->io, host, port);
-#endif
-
-	if (error < 0)
-		goto out_err;
+	st->io = in;
+	st->owned = owned;
 
 	st->ssl = git__malloc(sizeof(mbedtls_ssl_context));
 	GITERR_CHECK_ALLOC(st->ssl);
@@ -405,12 +406,48 @@ int git_mbedtls_stream_new(git_stream **out, const char *host, const char *port)
 
 out_err:
 	mbedtls_ssl_free(st->ssl);
+	git_stream_close(st->io);
 	git_stream_free(st->io);
 	git__free(st);
 
 	return error;
 }
 
+int git_mbedtls_stream_wrap(
+	git_stream **out,
+	git_stream *in,
+	const char *host)
+{
+	return mbedtls_stream_wrap(out, in, host, 0);
+}
+
+int git_mbedtls_stream_new(
+	git_stream **out,
+	const char *host,
+	const char *port)
+{
+	git_stream *stream;
+	int error;
+
+	assert(out && host && port);
+
+#ifdef GIT_CURL
+	error = git_curl_stream_new(&stream, host, port);
+#else
+	error = git_socket_stream_new(&stream, host, port);
+#endif
+
+	if (error < 0)
+		return error;
+
+	if ((error = mbedtls_stream_wrap(out, stream, host, 1)) < 0) {
+		git_stream_close(stream);
+		git_stream_free(stream);
+	}
+
+	return error;
+}
+
 int git_mbedtls__set_cert_location(const char *path, int is_dir)
 {
 	int ret = 0;

src/streams/mbedtls.h

@@ -14,6 +14,7 @@
 extern int git_mbedtls_stream_global_init(void);
 
 extern int git_mbedtls_stream_new(git_stream **out, const char *host, const char *port);
+extern int git_mbedtls_stream_wrap(git_stream **out, git_stream *in, const char *host);
 
 extern int git_mbedtls__set_cert_location(const char *path, int is_dir);
 

src/streams/openssl.c

@@ -569,6 +569,7 @@ cleanup:
 typedef struct {
 	git_stream parent;
 	git_stream *io;
+	int owned;
 	bool connected;
 	char *host;
 	SSL *ssl;
@@ -583,7 +584,7 @@ int openssl_connect(git_stream *stream)
 	BIO *bio;
 	openssl_stream *st = (openssl_stream *) stream;
 
-	if ((ret = git_stream_connect(st->io)) < 0)
+	if (st->owned && (ret = git_stream_connect(st->io)) < 0)
 		return ret;
 
 	bio = BIO_new(git_stream_bio_method);
@@ -682,43 +683,43 @@ int openssl_close(git_stream *stream)
 
 	st->connected = false;
 
-	return git_stream_close(st->io);
+	return st->owned ? git_stream_close(st->io) : 0;
 }
 
 void openssl_free(git_stream *stream)
 {
 	openssl_stream *st = (openssl_stream *) stream;
 
+	if (st->owned)
+		git_stream_free(st->io);
+
 	SSL_free(st->ssl);
 	git__free(st->host);
 	git__free(st->cert_info.data);
-	git_stream_free(st->io);
 	git__free(st);
 }
 
-int git_openssl_stream_new(git_stream **out, const char *host, const char *port)
+static int openssl_stream_wrap(
+	git_stream **out,
+	git_stream *in,
+	const char *host,
+	int owned)
 {
-	int error;
 	openssl_stream *st;
 
+	assert(out && in && host);
+
 	st = git__calloc(1, sizeof(openssl_stream));
 	GITERR_CHECK_ALLOC(st);
 
-	st->io = NULL;
-#ifdef GIT_CURL
-	error = git_curl_stream_new(&st->io, host, port);
-#else
-	error = git_socket_stream_new(&st->io, host, port);
-#endif
-
-	if (error < 0)
-		goto out_err;
+	st->io = in;
+	st->owned = owned;
 
 	st->ssl = SSL_new(git__ssl_ctx);
 	if (st->ssl == NULL) {
 		giterr_set(GITERR_SSL, "failed to create ssl object");
-		error = -1;
-		goto out_err;
+		git__free(st);
+		return -1;
 	}
 
 	st->host = git__strdup(host);
@@ -737,10 +738,33 @@ int git_openssl_stream_new(git_stream **out, const char *host, const char *port)
 
 	*out = (git_stream *) st;
 	return 0;
+}
 
-out_err:
-	git_stream_free(st->io);
-	git__free(st);
+int git_openssl_stream_wrap(git_stream **out, git_stream *in, const char *host)
+{
+	return openssl_stream_wrap(out, in, host, 0);
+}
+
+int git_openssl_stream_new(git_stream **out, const char *host, const char *port)
+{
+	git_stream *stream = NULL;
+	int error;
+
+	assert(out && host && port);
+
+#ifdef GIT_CURL
+	error = git_curl_stream_new(&stream, host, port);
+#else
+	error = git_socket_stream_new(&stream, host, port);
+#endif
+
+	if (error < 0)
+		return error;
+
+	if ((error = openssl_stream_wrap(out, stream, host, 1)) < 0) {
+		git_stream_close(stream);
+		git_stream_free(stream);
+	}
 
 	return error;
 }

src/streams/openssl.h

@@ -14,6 +14,7 @@
 extern int git_openssl_stream_global_init(void);
 
 extern int git_openssl_stream_new(git_stream **out, const char *host, const char *port);
+extern int git_openssl_stream_wrap(git_stream **out, git_stream *in, const char *host);
 
 extern int git_openssl__set_cert_location(const char *file, const char *path);
 

src/streams/stransport.c

@@ -34,8 +34,8 @@ static int stransport_error(OSStatus ret)
 	giterr_set(GITERR_NET, "SecureTransport error: %s", CFStringGetCStringPtr(message, kCFStringEncodingUTF8));
 	CFRelease(message);
 #else
-    giterr_set(GITERR_NET, "SecureTransport error: OSStatus %d", (unsigned int)ret);
-    GIT_UNUSED(message);
+	giterr_set(GITERR_NET, "SecureTransport error: OSStatus %d", (unsigned int)ret);
+	GIT_UNUSED(message);
 #endif
 
 	return -1;
@@ -44,6 +44,7 @@ static int stransport_error(OSStatus ret)
 typedef struct {
 	git_stream parent;
 	git_stream *io;
+	int owned;
 	SSLContextRef ctx;
 	CFDataRef der_data;
 	git_cert_x509 cert_info;
@@ -57,7 +58,7 @@ static int stransport_connect(git_stream *stream)
 	SecTrustResultType sec_res;
 	OSStatus ret;
 
-	if ((error = git_stream_connect(st->io)) < 0)
+	if (st->owned && (error = git_stream_connect(st->io)) < 0)
 		return error;
 
 	ret = SSLHandshake(st->ctx);
@@ -226,41 +227,38 @@ static int stransport_close(git_stream *stream)
 	if (ret != noErr && ret != errSSLClosedGraceful)
 		return stransport_error(ret);
 
-	return git_stream_close(st->io);
+	return st->owned ? git_stream_close(st->io) : 0;
 }
 
 static void stransport_free(git_stream *stream)
 {
 	stransport_stream *st = (stransport_stream *) stream;
 
-	git_stream_free(st->io);
+	if (st->owned)
+		git_stream_free(st->io);
+
 	CFRelease(st->ctx);
 	if (st->der_data)
 		CFRelease(st->der_data);
 	git__free(st);
 }
 
-int git_stransport_stream_new(git_stream **out, const char *host, const char *port)
+static int stransport_wrap(
+	git_stream **out,
+	git_stream *in,
+	const char *host,
+	int owned)
 {
 	stransport_stream *st;
-	int error;
 	OSStatus ret;
 
-	assert(out && host);
+	assert(out && in && host);
 
 	st = git__calloc(1, sizeof(stransport_stream));
 	GITERR_CHECK_ALLOC(st);
 
-#ifdef GIT_CURL
-	error = git_curl_stream_new(&st->io, host, port);
-#else
-	error = git_socket_stream_new(&st->io, host, port);
-#endif
-
-	if (error < 0){
-		git__free(st);
-		return error;
-	}
+	st->io = in;
+	st->owned = owned;
 
 	st->ctx = SSLCreateContext(NULL, kSSLClientSide, kSSLStreamType);
 	if (!st->ctx) {
@@ -295,4 +293,36 @@ int git_stransport_stream_new(git_stream **out, const char *host, const char *po
 	return 0;
 }
 
+int git_stransport_stream_wrap(
+	git_stream **out,
+	git_stream *in,
+	const char *host)
+{
+	return stransport_wrap(out, in, host, 0);
+}
+
+int git_stransport_stream_new(git_stream **out, const char *host, const char *port)
+{
+	git_stream *stream = NULL;
+	int error;
+
+	assert(out && host);
+
+#ifdef GIT_CURL
+	error = git_curl_stream_new(&stream, host, port);
+#else
+	error = git_socket_stream_new(&stream, host, port);
+#endif
+
+	if (!error)
+		error = stransport_wrap(out, stream, host, 1);
+
+	if (error < 0 && stream) {
+		git_stream_close(stream);
+		git_stream_free(stream);
+	}
+
+	return error;
+}
+
 #endif

src/streams/stransport.h

@@ -12,5 +12,6 @@
 #include "git2/sys/stream.h"
 
 extern int git_stransport_stream_new(git_stream **out, const char *host, const char *port);
+extern int git_stransport_stream_wrap(git_stream **out, git_stream *in, const char *host);
 
 #endif

src/streams/tls.c

@@ -5,41 +5,124 @@
  * a Linking Exception. For full terms see the included COPYING file.
  */
 
-#include "streams/tls.h"
-
 #include "git2/errors.h"
 
+#include "common.h"
+#include "global.h"
+#include "streams/tls.h"
 #include "streams/mbedtls.h"
 #include "streams/openssl.h"
 #include "streams/stransport.h"
 
-static git_stream_cb tls_ctor;
+struct git_tls_stream_registration {
+	git_rwlock lock;
+	git_stream_registration callbacks;
+};
 
-int git_stream_register_tls(git_stream_cb ctor)
+static struct git_tls_stream_registration stream_registration;
+
+static void shutdown_ssl(void)
 {
-	tls_ctor = ctor;
+	git_rwlock_free(&stream_registration.lock);
+}
 
+int git_tls_stream_global_init(void)
+{
+	if (git_rwlock_init(&stream_registration.lock) < 0)
+		return -1;
+
+	git__on_shutdown(shutdown_ssl);
+	return 0;
+}
+
+int git_stream_register_tls(git_stream_registration *registration)
+{
+	assert(!registration || registration->init);
+
+	if (git_rwlock_wrlock(&stream_registration.lock) < 0) {
+		giterr_set(GITERR_OS, "failed to lock stream registration");
+		return -1;
+	}
+
+	if (registration)
+		memcpy(&stream_registration.callbacks, registration,
+		    sizeof(git_stream_registration));
+	else
+		memset(&stream_registration.callbacks, 0,
+		    sizeof(git_stream_registration));
+
+	git_rwlock_wrunlock(&stream_registration.lock);
 	return 0;
 }
 
 int git_tls_stream_new(git_stream **out, const char *host, const char *port)
 {
+	int (*init)(git_stream **, const char *, const char *) = NULL;
 
-	if (tls_ctor)
-		return tls_ctor(out, host, port);
+	assert(out && host && port);
 
+	if (git_rwlock_rdlock(&stream_registration.lock) < 0) {
+		giterr_set(GITERR_OS, "failed to lock stream registration");
+		return -1;
+	}
+
+	if (stream_registration.callbacks.init) {
+		init = stream_registration.callbacks.init;
+	} else {
 #ifdef GIT_SECURE_TRANSPORT
-	return git_stransport_stream_new(out, host, port);
+		init = git_stransport_stream_new;
 #elif defined(GIT_OPENSSL)
-	return git_openssl_stream_new(out, host, port);
+		init = git_openssl_stream_new;
 #elif defined(GIT_MBEDTLS)
-	return git_mbedtls_stream_new(out, host, port);
-#else
-	GIT_UNUSED(out);
-	GIT_UNUSED(host);
-	GIT_UNUSED(port);
-
-	giterr_set(GITERR_SSL, "there is no TLS stream available");
-	return -1;
+		init = git_mbedtls_stream_new;
 #endif
+	}
+
+	if (git_rwlock_rdunlock(&stream_registration.lock) < 0) {
+		giterr_set(GITERR_OS, "failed to unlock stream registration");
+		return -1;
+	}
+
+	if (!init) {
+		giterr_set(GITERR_SSL, "there is no TLS stream available");
+		return -1;
+	}
+
+	return init(out, host, port);
+}
+
+int git_tls_stream_wrap(git_stream **out, git_stream *in, const char *host)
+{
+	int (*wrap)(git_stream **, git_stream *, const char *) = NULL;
+
+	assert(out && in);
+
+	if (git_rwlock_rdlock(&stream_registration.lock) < 0) {
+		giterr_set(GITERR_OS, "failed to lock stream registration");
+		return -1;
+	}
+
+	if (stream_registration.callbacks.wrap) {
+		wrap = stream_registration.callbacks.wrap;
+	} else {
+#ifdef GIT_SECURE_TRANSPORT
+		wrap = git_stransport_stream_wrap;
+#elif defined(GIT_OPENSSL)
+		wrap = git_openssl_stream_wrap;
+#elif defined(GIT_MBEDTLS)
+		wrap = git_mbedtls_stream_wrap;
+#endif
+	}
+
+	if (git_rwlock_rdunlock(&stream_registration.lock) < 0) {
+		giterr_set(GITERR_OS, "failed to unlock stream registration");
+		return -1;
+	}
+
+	if (!wrap) {
+		giterr_set(GITERR_SSL, "there is no TLS stream available");
+		return -1;
+	}
+
+	return wrap(out, in, host);
 }

src/streams/tls.h

@@ -11,13 +11,24 @@
 
 #include "git2/sys/stream.h"
 
+/** Configure TLS stream functions. */
+int git_tls_stream_global_init(void);
+
 /**
  * Create a TLS stream with the most appropriate backend available for
- * the current platform.
- *
- * This allows us to ask for a SecureTransport or OpenSSL stream
- * according to being on general Unix vs OS X.
+ * the current platform, whether that's SecureTransport on macOS,
+ * OpenSSL or mbedTLS on other Unixes, or something else entirely.
  */
 extern int git_tls_stream_new(git_stream **out, const char *host, const char *port);
 
+/**
+ * Create a TLS stream on top of an existing insecure stream, using
+ * the most appropriate backend available for the current platform.
+ *
+ * This allows us to create a CONNECT stream on top of a proxy;
+ * using SecureTransport on macOS, OpenSSL or mbedTLS on other
+ * Unixes, or something else entirely.
+ */
+extern int git_tls_stream_wrap(git_stream **out, git_stream *in, const char *host);
+
 #endif

src/transports/http.c

@@ -713,10 +713,31 @@ static int check_certificate(
 	return error;
 }
 
+static int stream_connect(
+	git_stream *stream,
+	gitno_connection_data *url,
+	git_transport_certificate_check_cb cert_cb,
+	void *cb_payload)
+{
+	int error;
+
+	GITERR_CHECK_VERSION(stream, GIT_STREAM_VERSION, "git_stream");
+
+	error = git_stream_connect(stream);
+
+	if (error && error != GIT_ECERTIFICATE)
+		return error;
+
+	if (git_stream_is_encrypted(stream) && cert_cb != NULL)
+		error = check_certificate(stream, url, !error, cert_cb, cb_payload);
+
+	return error;
+}
+
 static int http_connect(http_subtransport *t)
 {
 	gitno_connection_data *url;
-	git_stream *stream = NULL;
+	git_stream *proxy_stream = NULL, *stream = NULL;
 	git_transport_certificate_check_cb cert_cb;
 	void *cb_payload;
 	int error;
@@ -744,8 +765,14 @@ static int http_connect(http_subtransport *t)
 	}
 
 #ifdef GIT_CURL
-	error = git_curl_stream_new(&stream,
-	    t->server.url.host, t->server.url.port);
+	if ((error = git_curl_stream_new(&stream,
+	        t->server.url.host, t->server.url.port)) < 0)
+		goto on_error;
+
+	GITERR_CHECK_VERSION(stream, GIT_STREAM_VERSION, "git_stream");
+
+	if ((error = apply_proxy_config_to_stream(stream, &t->proxy_opts)) < 0)
+		goto on_error;
 #else
 	if (url->use_ssl)
 		error = git_tls_stream_new(&stream, url->host, url->port);
@@ -756,20 +783,7 @@ static int http_connect(http_subtransport *t)
 	if (error < 0)
 		goto on_error;
 
-	GITERR_CHECK_VERSION(stream, GIT_STREAM_VERSION, "git_stream");
-
-	if ((error = apply_proxy_config_to_stream(stream, &t->proxy_opts)) < 0)
-		goto on_error;
-
-	error = git_stream_connect(stream);
-
-	if (error && error != GIT_ECERTIFICATE)
-		goto on_error;
-
-	if (git_stream_is_encrypted(stream) && cert_cb != NULL)
-		error = check_certificate(stream, url, !error, cert_cb, cb_payload);
-
-	if (error)
+	if ((error = stream_connect(stream, url, cert_cb, cb_payload)) < 0)
 		goto on_error;
 
 	t->server.stream = stream;
@@ -782,6 +796,11 @@ on_error:
 		git_stream_free(stream);
 	}
 
+	if (proxy_stream) {
+		git_stream_close(proxy_stream);
+		git_stream_free(proxy_stream);
+	}
+
 	return error;
 }
 

tests/core/stream.c

@@ -6,7 +6,7 @@
 static git_stream test_stream;
 static int ctor_called;
 
-static int test_ctor(git_stream **out, const char *host, const char *port)
+static int test_stream_init(git_stream **out, const char *host, const char *port)
 {
 	GIT_UNUSED(host);
 	GIT_UNUSED(port);
@@ -17,13 +17,29 @@ static int test_ctor(git_stream **out, const char *host, const char *port)
 	return 0;
 }
 
+static int test_stream_wrap(git_stream **out, git_stream *in, const char *host)
+{
+	GIT_UNUSED(in);
+	GIT_UNUSED(host);
+
+	ctor_called = 1;
+	*out = &test_stream;
+
+	return 0;
+}
+
 void test_core_stream__register_tls(void)
 {
 	git_stream *stream;
+	git_stream_registration registration = {0};
 	int error;
 
+	registration.version = 1;
+	registration.init = test_stream_init;
+	registration.wrap = test_stream_wrap;
+
 	ctor_called = 0;
-	cl_git_pass(git_stream_register_tls(test_ctor));
+	cl_git_pass(git_stream_register_tls(&registration));
 	cl_git_pass(git_tls_stream_new(&stream, "localhost", "443"));
 	cl_assert_equal_i(1, ctor_called);
 	cl_assert_equal_p(&test_stream, stream);