Merge pull request #4870 from libgit2/ethomson/proxy

Add builtin proxy support for the http transport

22 files changed, 956 insertions, 746 deletions

diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 8ba3aa590..5ad8b1447 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -125,17 +125,6 @@ IF (WIN32 AND WINHTTP)
 
 	LIST(APPEND LIBGIT2_LIBS "rpcrt4" "crypt32" "ole32")
 	LIST(APPEND LIBGIT2_PC_LIBS "-lrpcrt4" "-lcrypt32" "-lole32")
-ELSE ()
-	IF (CURL)
-		FIND_PKGLIBRARIES(CURL libcurl)
-	ENDIF ()
-	IF (CURL_FOUND)
-		SET(GIT_CURL 1)
-		LIST(APPEND LIBGIT2_SYSTEM_INCLUDES ${CURL_INCLUDE_DIRS})
-		LIST(APPEND LIBGIT2_LIBS ${CURL_LIBRARIES})
-		LIST(APPEND LIBGIT2_PC_LIBS ${CURL_LDFLAGS})
-	ENDIF()
-	ADD_FEATURE_INFO(cURL GIT_CURL "cURL for HTTP proxy support")
 ENDIF()
 
 IF (USE_HTTPS)
diff --git a/src/features.h.in b/src/features.h.in
index f414c5843..694a61c02 100644
--- a/src/features.h.in
+++ b/src/features.h.in
@@ -22,7 +22,6 @@
 
 #cmakedefine GIT_GSSAPI 1
 #cmakedefine GIT_WINHTTP 1
-#cmakedefine GIT_CURL 1
 
 #cmakedefine GIT_HTTPS 1
 #cmakedefine GIT_OPENSSL 1
diff --git a/src/global.c b/src/global.c
index d33772e91..86a35a2ff 100644
--- a/src/global.c
+++ b/src/global.c
@@ -12,7 +12,7 @@
 #include "sysdir.h"
 #include "filter.h"
 #include "merge_driver.h"
-#include "streams/curl.h"
+#include "streams/registry.h"
 #include "streams/mbedtls.h"
 #include "streams/openssl.h"
 #include "thread-utils.h"
@@ -67,8 +67,8 @@ 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_stream_registry_global_init()) == 0 &&
 		(ret = git_openssl_stream_global_init()) == 0 &&
-		(ret = git_curl_stream_global_init()) == 0 &&
 		(ret = git_mbedtls_stream_global_init()) == 0)
 		ret = git_mwindow_global_init();
 
diff --git a/src/streams/curl.c b/src/streams/curl.c
deleted file mode 100644
index 3c0af3b04..000000000
--- a/src/streams/curl.c
+++ /dev/null
@@ -1,385 +0,0 @@
-/*
- * Copyright (C) the libgit2 contributors. All rights reserved.
- *
- * This file is part of libgit2, distributed under the GNU GPL v2 with
- * a Linking Exception. For full terms see the included COPYING file.
- */
-
-#include "streams/curl.h"
-
-#ifdef GIT_CURL
-
-#include <curl/curl.h>
-
-#include "stream.h"
-#include "git2/transport.h"
-#include "buffer.h"
-#include "global.h"
-#include "vector.h"
-#include "proxy.h"
-
-/* This is for backwards compatibility with curl<7.45.0. */
-#ifndef CURLINFO_ACTIVESOCKET
-# define CURLINFO_ACTIVESOCKET CURLINFO_LASTSOCKET
-# define GIT_CURL_BADSOCKET -1
-# define git_activesocket_t long
-#else
-# define GIT_CURL_BADSOCKET CURL_SOCKET_BAD
-# define git_activesocket_t curl_socket_t
-#endif
-
-typedef struct {
-	git_stream parent;
-	CURL *handle;
-	curl_socket_t socket;
-	char curl_error[CURL_ERROR_SIZE + 1];
-	git_cert_x509 cert_info;
-	git_strarray cert_info_strings;
-	git_proxy_options proxy;
-	git_cred *proxy_cred;
-} curl_stream;
-
-int git_curl_stream_global_init(void)
-{
-	if (curl_global_init(CURL_GLOBAL_ALL) != 0) {
-		giterr_set(GITERR_NET, "could not initialize curl");
-		return -1;
-	}
-
-	/* `curl_global_cleanup` is provided by libcurl */
-	git__on_shutdown(curl_global_cleanup);
-	return 0;
-}
-
-static int seterr_curl(curl_stream *s)
-{
-	giterr_set(GITERR_NET, "curl error: %s\n", s->curl_error);
-	return -1;
-}
-
-GIT_INLINE(int) error_no_credentials(void)
-{
-	giterr_set(GITERR_NET, "proxy authentication required, but no callback provided");
-	return GIT_EAUTH;
-}
-
-static int apply_proxy_creds(curl_stream *s)
-{
-	CURLcode res;
-	git_cred_userpass_plaintext *userpass;
-
-	if (!s->proxy_cred)
-		return GIT_ENOTFOUND;
-
-	userpass = (git_cred_userpass_plaintext *) s->proxy_cred;
-	if ((res = curl_easy_setopt(s->handle, CURLOPT_PROXYUSERNAME, userpass->username)) != CURLE_OK)
-		return seterr_curl(s);
-	if ((res = curl_easy_setopt(s->handle, CURLOPT_PROXYPASSWORD, userpass->password)) != CURLE_OK)
-		return seterr_curl(s);
-
-	return 0;
-}
-
-static int ask_and_apply_proxy_creds(curl_stream *s)
-{
-	int error;
-	git_proxy_options *opts = &s->proxy;
-
-	if (!opts->credentials)
-		return error_no_credentials();
-
-	/* TODO: see if PROXYAUTH_AVAIL helps us here */
-	git_cred_free(s->proxy_cred);
-	s->proxy_cred = NULL;
-	giterr_clear();
-	error = opts->credentials(&s->proxy_cred, opts->url, NULL, GIT_CREDTYPE_USERPASS_PLAINTEXT, opts->payload);
-	if (error == GIT_PASSTHROUGH)
-		return error_no_credentials();
-	if (error < 0) {
-		if (!giterr_last())
-			giterr_set(GITERR_NET, "proxy authentication was aborted by the user");
-		return error;
-	}
-
-	if (s->proxy_cred->credtype != GIT_CREDTYPE_USERPASS_PLAINTEXT) {
-		giterr_set(GITERR_NET, "credentials callback returned invalid credential type");
-		return -1;
-	}
-
-	return apply_proxy_creds(s);
-}
-
-static int curls_connect(git_stream *stream)
-{
-	curl_stream *s = (curl_stream *) stream;
-	git_activesocket_t sockextr;
-	long connect_last = 0;
-	int failed_cert = 0, error;
-	bool retry_connect;
-	CURLcode res;
-
-	/* Apply any credentials we've already established */
-	error = apply_proxy_creds(s);
-	if (error < 0 && error != GIT_ENOTFOUND)
-		return seterr_curl(s);
-
-	do {
-		retry_connect = 0;
-		res = curl_easy_perform(s->handle);
-
-		curl_easy_getinfo(s->handle, CURLINFO_HTTP_CONNECTCODE, &connect_last);
-
-		/* HTTP 407 Proxy Authentication Required */
-		if (connect_last == 407) {
-			if ((error = ask_and_apply_proxy_creds(s)) < 0)
-				return error;
-
-			retry_connect = true;
-		}
-	} while (retry_connect);
-
-	if (res != CURLE_OK && res != CURLE_PEER_FAILED_VERIFICATION)
-		return seterr_curl(s);
-	if (res == CURLE_PEER_FAILED_VERIFICATION)
-		failed_cert = 1;
-
-	if ((res = curl_easy_getinfo(s->handle, CURLINFO_ACTIVESOCKET, &sockextr)) != CURLE_OK) {
-		return seterr_curl(s);
-	}
-
-	if (sockextr == GIT_CURL_BADSOCKET) {
-		giterr_set(GITERR_NET, "curl socket is no longer valid");
-		return -1;
-	}
-
-	s->socket = sockextr;
-
-	if (s->parent.encrypted && failed_cert)
-		return GIT_ECERTIFICATE;
-
-	return 0;
-}
-
-static int curls_certificate(git_cert **out, git_stream *stream)
-{
-	int error;
-	CURLcode res;
-	struct curl_slist *slist;
-	struct curl_certinfo *certinfo;
-	git_vector strings = GIT_VECTOR_INIT;
-	curl_stream *s = (curl_stream *) stream;
-
-	if ((res = curl_easy_getinfo(s->handle, CURLINFO_CERTINFO, &certinfo)) != CURLE_OK)
-		return seterr_curl(s);
-
-	/* No information is available, can happen with SecureTransport */
-	if (certinfo->num_of_certs == 0) {
-		s->cert_info.parent.cert_type = GIT_CERT_NONE;
-		s->cert_info.data             = NULL;
-		s->cert_info.len              = 0;
-		return 0;
-	}
-
-	if ((error = git_vector_init(&strings, 8, NULL)) < 0)
-		return error;
-
-	for (slist = certinfo->certinfo[0]; slist; slist = slist->next) {
-		char *str = git__strdup(slist->data);
-		GITERR_CHECK_ALLOC(str);
-		git_vector_insert(&strings, str);
-	}
-
-	/* Copy the contents of the vector into a strarray so we can expose them */
-	s->cert_info_strings.strings = (char **) strings.contents;
-	s->cert_info_strings.count   = strings.length;
-
-	s->cert_info.parent.cert_type = GIT_CERT_STRARRAY;
-	s->cert_info.data             = &s->cert_info_strings;
-	s->cert_info.len              = strings.length;
-
-	*out = &s->cert_info.parent;
-
-	return 0;
-}
-
-static int curls_set_proxy(git_stream *stream, const git_proxy_options *proxy_opts)
-{
-	int error;
-	CURLcode res;
-	curl_stream *s = (curl_stream *) stream;
-
-	git_proxy_options_clear(&s->proxy);
-	if ((error = git_proxy_options_dup(&s->proxy, proxy_opts)) < 0)
-		return error;
-
-	if ((res = curl_easy_setopt(s->handle, CURLOPT_PROXY, s->proxy.url)) != CURLE_OK)
-		return seterr_curl(s);
-
-	if ((res = curl_easy_setopt(s->handle, CURLOPT_PROXYAUTH, CURLAUTH_ANY)) != CURLE_OK)
-		return seterr_curl(s);
-
-	return 0;
-}
-
-static int wait_for(curl_socket_t fd, bool reading)
-{
-	int ret;
-	fd_set infd, outfd, errfd;
-
-	FD_ZERO(&infd);
-	FD_ZERO(&outfd);
-	FD_ZERO(&errfd);
-
-	assert(fd >= 0);
-	FD_SET(fd, &errfd);
-	if (reading)
-		FD_SET(fd, &infd);
-	else
-		FD_SET(fd, &outfd);
-
-	if ((ret = select(fd + 1, &infd, &outfd, &errfd, NULL)) < 0) {
-		giterr_set(GITERR_OS, "error in select");
-		return -1;
-	}
-
-	return 0;
-}
-
-static ssize_t curls_write(git_stream *stream, const char *data, size_t len, int flags)
-{
-	int error;
-	size_t off = 0, sent;
-	CURLcode res;
-	curl_stream *s = (curl_stream *) stream;
-
-	GIT_UNUSED(flags);
-
-	do {
-		if ((error = wait_for(s->socket, false)) < 0)
-			return error;
-
-		res = curl_easy_send(s->handle, data + off, len - off, &sent);
-		if (res == CURLE_OK)
-			off += sent;
-	} while ((res == CURLE_OK || res == CURLE_AGAIN) && off < len);
-
-	if (res != CURLE_OK)
-		return seterr_curl(s);
-
-	return len;
-}
-
-static ssize_t curls_read(git_stream *stream, void *data, size_t len)
-{
-	int error;
-	size_t read;
-	CURLcode res;
-	curl_stream *s = (curl_stream *) stream;
-
-	do {
-		if ((error = wait_for(s->socket, true)) < 0)
-			return error;
-
-		res = curl_easy_recv(s->handle, data, len, &read);
-	} while (res == CURLE_AGAIN);
-
-	if (res != CURLE_OK)
-		return seterr_curl(s);
-
-	return read;
-}
-
-static int curls_close(git_stream *stream)
-{
-	curl_stream *s = (curl_stream *) stream;
-
-	if (!s->handle)
-		return 0;
-
-	curl_easy_cleanup(s->handle);
-	s->handle = NULL;
-	s->socket = 0;
-
-	return 0;
-}
-
-static void curls_free(git_stream *stream)
-{
-	curl_stream *s = (curl_stream *) stream;
-
-	curls_close(stream);
-	git_strarray_free(&s->cert_info_strings);
-	git_proxy_options_clear(&s->proxy);
-	git_cred_free(s->proxy_cred);
-	git__free(s);
-}
-
-int git_curl_stream_new(git_stream **out, const char *host, const char *port)
-{
-	curl_stream *st;
-	CURL *handle;
-	int iport = 0, error;
-
-	st = git__calloc(1, sizeof(curl_stream));
-	GITERR_CHECK_ALLOC(st);
-
-	handle = curl_easy_init();
-	if (handle == NULL) {
-		giterr_set(GITERR_NET, "failed to create curl handle");
-		git__free(st);
-		return -1;
-	}
-
-	if ((error = git__strntol32(&iport, port, strlen(port), NULL, 10)) < 0) {
-		git__free(st);
-		return error;
-	}
-
-	curl_easy_setopt(handle, CURLOPT_URL, host);
-	curl_easy_setopt(handle, CURLOPT_ERRORBUFFER, st->curl_error);
-	curl_easy_setopt(handle, CURLOPT_PORT, iport);
-	curl_easy_setopt(handle, CURLOPT_CONNECT_ONLY, 1);
-	curl_easy_setopt(handle, CURLOPT_SSL_VERIFYPEER, 1);
-	curl_easy_setopt(handle, CURLOPT_CERTINFO, 1);
-	curl_easy_setopt(handle, CURLOPT_HTTPPROXYTUNNEL, 1);
-	curl_easy_setopt(handle, CURLOPT_PROXYAUTH, CURLAUTH_ANY);
-
-	/* curl_easy_setopt(handle, CURLOPT_VERBOSE, 1); */
-
-	st->parent.version = GIT_STREAM_VERSION;
-	st->parent.encrypted = 0; /* we don't encrypt ourselves */
-	st->parent.proxy_support = 1;
-	st->parent.connect = curls_connect;
-	st->parent.certificate = curls_certificate;
-	st->parent.set_proxy = curls_set_proxy;
-	st->parent.read = curls_read;
-	st->parent.write = curls_write;
-	st->parent.close = curls_close;
-	st->parent.free = curls_free;
-	st->handle = handle;
-
-	*out = (git_stream *) st;
-	return 0;
-}
-
-#else
-
-#include "stream.h"
-
-int git_curl_stream_global_init(void)
-{
-	return 0;
-}
-
-int git_curl_stream_new(git_stream **out, const char *host, const char *port)
-{
-	GIT_UNUSED(out);
-	GIT_UNUSED(host);
-	GIT_UNUSED(port);
-
-	giterr_set(GITERR_NET, "curl is not supported in this version");
-	return -1;
-}
-
-
-#endif
diff --git a/src/streams/curl.h b/src/streams/curl.h
deleted file mode 100644
index 511cd894a..000000000
--- a/src/streams/curl.h
+++ /dev/null
@@ -1,17 +0,0 @@
-/*
- * Copyright (C) the libgit2 contributors. All rights reserved.
- *
- * This file is part of libgit2, distributed under the GNU GPL v2 with
- * a Linking Exception. For full terms see the included COPYING file.
- */
-#ifndef INCLUDE_streams_curl_h__
-#define INCLUDE_streams_curl_h__
-
-#include "common.h"
-
-#include "git2/sys/stream.h"
-
-extern int git_curl_stream_global_init(void);
-extern int git_curl_stream_new(git_stream **out, const char *host, const char *port);
-
-#endif
diff --git a/src/streams/mbedtls.c b/src/streams/mbedtls.c
index bd7bd3126..d22f77069 100644
--- a/src/streams/mbedtls.c
+++ b/src/streams/mbedtls.c
@@ -18,10 +18,6 @@
 #include "git2/transport.h"
 #include "util.h"
 
-#ifdef GIT_CURL
-# include "streams/curl.h"
-#endif
-
 #ifndef GIT_DEFAULT_CERT_LOCATION
 #define GIT_DEFAULT_CERT_LOCATION NULL
 #endif
@@ -242,6 +238,7 @@ 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 +251,7 @@ 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 +342,37 @@ 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 +402,42 @@ 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);
+
+	if ((error = git_socket_stream_new(&stream, host, port)) < 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;
@@ -453,23 +480,4 @@ int git_mbedtls_stream_global_init(void)
 	return 0;
 }
 
-int git_mbedtls_stream_new(git_stream **out, const char *host, const char *port)
-{
-	GIT_UNUSED(out);
-	GIT_UNUSED(host);
-	GIT_UNUSED(port);
-
-	giterr_set(GITERR_SSL, "mbedTLS is not supported in this version");
-	return -1;
-}
-
-int git_mbedtls__set_cert_location(const char *path, int is_dir)
-{
-	GIT_UNUSED(path);
-	GIT_UNUSED(is_dir);
-
-	giterr_set(GITERR_SSL, "mbedTLS is not supported in this version");
-	return -1;
-}
-
 #endif
diff --git a/src/streams/mbedtls.h b/src/streams/mbedtls.h
index 7283698ff..7de94b9fb 100644
--- a/src/streams/mbedtls.h
+++ b/src/streams/mbedtls.h
@@ -13,8 +13,11 @@
 
 extern int git_mbedtls_stream_global_init(void);
 
-extern int git_mbedtls_stream_new(git_stream **out, const char *host, const char *port);
-
+#ifdef GIT_MBEDTLS
 extern int git_mbedtls__set_cert_location(const char *path, int is_dir);
 
+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);
+#endif
+
 #endif
diff --git a/src/streams/openssl.c b/src/streams/openssl.c
index a68f9a9cc..bc129217d 100644
--- a/src/streams/openssl.c
+++ b/src/streams/openssl.c
@@ -19,10 +19,6 @@
 #include "git2/transport.h"
 #include "git2/sys/openssl.h"
 
-#ifdef GIT_CURL
-# include "streams/curl.h"
-#endif
-
 #ifndef GIT_WIN32
 # include <sys/types.h>
 # include <sys/socket.h>
@@ -569,6 +565,7 @@ cleanup:
 typedef struct {
 	git_stream parent;
 	git_stream *io;
+	int owned;
 	bool connected;
 	char *host;
 	SSL *ssl;
@@ -583,7 +580,7 @@ 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 +679,43 @@ 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 +734,27 @@ 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);
+
+	if ((error = git_socket_stream_new(&stream, host, port)) < 0)
+		return error;
+
+	if ((error = openssl_stream_wrap(out, stream, host, 1)) < 0) {
+		git_stream_close(stream);
+		git_stream_free(stream);
+	}
 
 	return error;
 }
@@ -775,23 +789,4 @@ int git_openssl_set_locking(void)
 	return -1;
 }
 
-int git_openssl_stream_new(git_stream **out, const char *host, const char *port)
-{
-	GIT_UNUSED(out);
-	GIT_UNUSED(host);
-	GIT_UNUSED(port);
-
-	giterr_set(GITERR_SSL, "openssl is not supported in this version");
-	return -1;
-}
-
-int git_openssl__set_cert_location(const char *file, const char *path)
-{
-	GIT_UNUSED(file);
-	GIT_UNUSED(path);
-
-	giterr_set(GITERR_SSL, "openssl is not supported in this version");
-	return -1;
-}
-
 #endif
diff --git a/src/streams/openssl.h b/src/streams/openssl.h
index 496d7efbf..826d1efbc 100644
--- a/src/streams/openssl.h
+++ b/src/streams/openssl.h
@@ -13,8 +13,11 @@
 
 extern int git_openssl_stream_global_init(void);
 
-extern int git_openssl_stream_new(git_stream **out, const char *host, const char *port);
-
+#ifdef GIT_OPENSSL
 extern int git_openssl__set_cert_location(const char *file, const char *path);
 
+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);
+#endif
+
 #endif
diff --git a/src/streams/registry.c b/src/streams/registry.c
new file mode 100644
index 000000000..02fd3491b
--- /dev/null
+++ b/src/streams/registry.c
@@ -0,0 +1,116 @@
+/*
+ * Copyright (C) the libgit2 contributors. All rights reserved.
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+
+#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"
+
+struct stream_registry {
+	git_rwlock lock;
+	git_stream_registration callbacks;
+	git_stream_registration tls_callbacks;
+};
+
+static struct stream_registry stream_registry;
+
+static void shutdown_stream_registry(void)
+{
+	git_rwlock_free(&stream_registry.lock);
+}
+
+int git_stream_registry_global_init(void)
+{
+	if (git_rwlock_init(&stream_registry.lock) < 0)
+		return -1;
+
+	git__on_shutdown(shutdown_stream_registry);
+	return 0;
+}
+
+GIT_INLINE(void) stream_registration_cpy(
+	git_stream_registration *target,
+	git_stream_registration *src)
+{
+	if (src)
+		memcpy(target, src, sizeof(git_stream_registration));
+	else
+		memset(target, 0, sizeof(git_stream_registration));
+}
+
+int git_stream_registry_lookup(git_stream_registration *out, git_stream_t type)
+{
+	git_stream_registration *target;
+	int error = GIT_ENOTFOUND;
+
+	assert(out);
+
+	switch(type) {
+	case GIT_STREAM_STANDARD:
+		target = &stream_registry.callbacks;
+		break;
+	case GIT_STREAM_TLS:
+		target = &stream_registry.tls_callbacks;
+		break;
+	default:
+		assert(0);
+		return -1;
+	}
+
+	if (git_rwlock_rdlock(&stream_registry.lock) < 0) {
+		giterr_set(GITERR_OS, "failed to lock stream registry");
+		return -1;
+	}
+
+	if (target->init) {
+		stream_registration_cpy(out, target);
+		error = 0;
+	}
+
+	git_rwlock_rdunlock(&stream_registry.lock);
+	return error;
+}
+
+int git_stream_register(git_stream_t type, git_stream_registration *registration)
+{
+	assert(!registration || registration->init);
+
+	GITERR_CHECK_VERSION(registration, GIT_STREAM_VERSION, "stream_registration");
+
+	if (git_rwlock_wrlock(&stream_registry.lock) < 0) {
+		giterr_set(GITERR_OS, "failed to lock stream registry");
+		return -1;
+	}
+
+	if ((type & GIT_STREAM_STANDARD) == GIT_STREAM_STANDARD)
+		stream_registration_cpy(&stream_registry.callbacks, registration);
+
+	if ((type & GIT_STREAM_TLS) == GIT_STREAM_TLS)
+		stream_registration_cpy(&stream_registry.tls_callbacks, registration);
+
+	git_rwlock_wrunlock(&stream_registry.lock);
+	return 0;
+}
+
+int git_stream_register_tls(git_stream_cb ctor)
+{
+	git_stream_registration registration = {0};
+
+	if (ctor) {
+		registration.version = GIT_STREAM_VERSION;
+		registration.init = ctor;
+		registration.wrap = NULL;
+
+		return git_stream_register(GIT_STREAM_TLS, &registration);
+	} else {
+		return git_stream_register(GIT_STREAM_TLS, NULL);
+	}
+}
diff --git a/src/streams/registry.h b/src/streams/registry.h
new file mode 100644
index 000000000..adc2b8bdf
--- /dev/null
+++ b/src/streams/registry.h
@@ -0,0 +1,19 @@
+/*
+ * Copyright (C) the libgit2 contributors. All rights reserved.
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+#ifndef INCLUDE_streams_registry_h__
+#define INCLUDE_streams_registry_h__
+
+#include "common.h"
+#include "git2/sys/stream.h"
+
+/** Configure stream registry. */
+int git_stream_registry_global_init(void);
+
+/** Lookup a stream registration. */
+extern int git_stream_registry_lookup(git_stream_registration *out, git_stream_t type);
+
+#endif
diff --git a/src/streams/socket.c b/src/streams/socket.c
index 0c6073b66..732b45940 100644
--- a/src/streams/socket.c
+++ b/src/streams/socket.c
@@ -9,6 +9,7 @@
 
 #include "posix.h"
 #include "netops.h"
+#include "registry.h"
 #include "stream.h"
 
 #ifndef _WIN32
@@ -180,11 +181,14 @@ void socket_free(git_stream *stream)
 	git__free(st);
 }
 
-int git_socket_stream_new(git_stream **out, const char *host, const char *port)
+static int default_socket_stream_new(
+	git_stream **out,
+	const char *host,
+	const char *port)
 {
 	git_socket_stream *st;
 
-	assert(out && host);
+	assert(out && host && port);
 
 	st = git__calloc(1, sizeof(git_socket_stream));
 	GITERR_CHECK_ALLOC(st);
@@ -208,3 +212,29 @@ int git_socket_stream_new(git_stream **out, const char *host, const char *port)
 	*out = (git_stream *) st;
 	return 0;
 }
+
+int git_socket_stream_new(
+	git_stream **out,
+	const char *host,
+	const char *port)
+{
+	int (*init)(git_stream **, const char *, const char *) = NULL;
+	git_stream_registration custom = {0};
+	int error;
+
+	assert(out && host && port);
+
+	if ((error = git_stream_registry_lookup(&custom, GIT_STREAM_STANDARD)) == 0)
+		init = custom.init;
+	else if (error == GIT_ENOTFOUND)
+		init = default_socket_stream_new;
+	else
+		return error;
+
+	if (!init) {
+		giterr_set(GITERR_NET, "there is no socket stream available");
+		return -1;
+	}
+
+	return init(out, host, port);
+}
diff --git a/src/streams/stransport.c b/src/streams/stransport.c
index 15b305745..6626e0f68 100644
--- a/src/streams/stransport.c
+++ b/src/streams/stransport.c
@@ -16,7 +16,6 @@
 #include "git2/transport.h"
 
 #include "streams/socket.h"
-#include "streams/curl.h"
 
 static int stransport_error(OSStatus ret)
 {
@@ -34,8 +33,8 @@ 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 +43,7 @@ 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 +57,7 @@ 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 +226,38 @@ 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 +292,32 @@ 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);
+
+	error = git_socket_stream_new(&stream, host, port);
+
+	if (!error)
+		error = stransport_wrap(out, stream, host, 1);
+
+	if (error < 0 && stream) {
+		git_stream_close(stream);
+		git_stream_free(stream);
+	}
+
+	return error;
+}
+
 #endif
diff --git a/src/streams/stransport.h b/src/streams/stransport.h
index 4c02d07e8..1026e204b 100644
--- a/src/streams/stransport.h
+++ b/src/streams/stransport.h
@@ -11,6 +11,11 @@
 
 #include "git2/sys/stream.h"
 
+#ifdef GIT_SECURE_TRANSPORT
+
 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
 
 #endif
diff --git a/src/streams/tls.c b/src/streams/tls.c
index 1bcb0d984..0ea47fb2f 100644
--- a/src/streams/tls.c
+++ b/src/streams/tls.c
@@ -5,41 +5,69 @@
  * 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/registry.h"
+#include "streams/tls.h"
 #include "streams/mbedtls.h"
 #include "streams/openssl.h"
 #include "streams/stransport.h"
 
-static git_stream_cb tls_ctor;
-
-int git_stream_register_tls(git_stream_cb ctor)
+int git_tls_stream_new(git_stream **out, const char *host, const char *port)
 {
-	tls_ctor = ctor;
+	int (*init)(git_stream **, const char *, const char *) = NULL;
+	git_stream_registration custom = {0};
+	int error;
+
+	assert(out && host && port);
 
-	return 0;
+	if ((error = git_stream_registry_lookup(&custom, GIT_STREAM_TLS)) == 0) {
+		init = custom.init;
+	} else if (error == GIT_ENOTFOUND) {
+#ifdef GIT_SECURE_TRANSPORT
+		init = git_stransport_stream_new;
+#elif defined(GIT_OPENSSL)
+		init = git_openssl_stream_new;
+#elif defined(GIT_MBEDTLS)
+		init = git_mbedtls_stream_new;
+#endif
+	} else {
+		return error;
+	}
+
+	if (!init) {
+		giterr_set(GITERR_SSL, "there is no TLS stream available");
+		return -1;
+	}
+
+	return init(out, host, port);
 }
 
-int git_tls_stream_new(git_stream **out, const char *host, const char *port)
+int git_tls_stream_wrap(git_stream **out, git_stream *in, const char *host)
 {
+	int (*wrap)(git_stream **, git_stream *, const char *) = NULL;
+	git_stream_registration custom = {0};
 
-	if (tls_ctor)
-		return tls_ctor(out, host, port);
+	assert(out && in);
 
+	if (git_stream_registry_lookup(&custom, GIT_STREAM_TLS) == 0) {
+		wrap = custom.wrap;
+	} else {
 #ifdef GIT_SECURE_TRANSPORT
-	return git_stransport_stream_new(out, host, port);
+		wrap = git_stransport_stream_wrap;
 #elif defined(GIT_OPENSSL)
-	return git_openssl_stream_new(out, host, port);
+		wrap = git_openssl_stream_wrap;
 #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;
+		wrap = git_mbedtls_stream_wrap;
 #endif
+	}
+
+	if (!wrap) {
+		giterr_set(GITERR_SSL, "there is no TLS stream available");
+		return -1;
+	}
+
+	return wrap(out, in, host);
 }
diff --git a/src/streams/tls.h b/src/streams/tls.h
index 6d110e8ad..465a6ea89 100644
--- a/src/streams/tls.h
+++ b/src/streams/tls.h
@@ -13,11 +13,19 @@
 
 /**
  * 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
diff --git a/src/transports/auth.c b/src/transports/auth.c
index c8e6adb12..dcc3e09a7 100644
--- a/src/transports/auth.c
+++ b/src/transports/auth.c
@@ -11,7 +11,10 @@
 #include "buffer.h"
 
 static int basic_next_token(
-	git_buf *out, git_http_auth_context *ctx, git_cred *c)
+	git_buf *out,
+	git_http_auth_context *ctx,
+	const char *header_name,
+	git_cred *c)
 {
 	git_cred_userpass_plaintext *cred;
 	git_buf raw = GIT_BUF_INIT;
@@ -29,7 +32,7 @@ static int basic_next_token(
 	git_buf_printf(&raw, "%s:%s", cred->username, cred->password);
 
 	if (git_buf_oom(&raw) ||
-		git_buf_puts(out, "Authorization: Basic ") < 0 ||
+		git_buf_printf(out, "%s: Basic ", header_name) < 0 ||
 		git_buf_encode_base64(out, git_buf_cstr(&raw), raw.size) < 0 ||
 		git_buf_puts(out, "\r\n") < 0)
 		goto on_error;
diff --git a/src/transports/auth.h b/src/transports/auth.h
index 3b8b29eb9..e5cf7eff0 100644
--- a/src/transports/auth.h
+++ b/src/transports/auth.h
@@ -31,7 +31,7 @@ struct git_http_auth_context {
 	int (*set_challenge)(git_http_auth_context *ctx, const char *challenge);
 
 	/** Gets the next authentication token from the context */
-	int (*next_token)(git_buf *out, git_http_auth_context *ctx, git_cred *cred);
+	int (*next_token)(git_buf *out, git_http_auth_context *ctx, const char *header_name, git_cred *cred);
 
 	/** Frees the authentication context */
 	void (*free)(git_http_auth_context *ctx);
diff --git a/src/transports/auth_negotiate.c b/src/transports/auth_negotiate.c
index eeabe8a6d..173ae992e 100644
--- a/src/transports/auth_negotiate.c
+++ b/src/transports/auth_negotiate.c
@@ -73,6 +73,7 @@ static int negotiate_set_challenge(
 static int negotiate_next_token(
 	git_buf *buf,
 	git_http_auth_context *c,
+	const char *header_name,
 	git_cred *cred)
 {
 	http_auth_negotiate_context *ctx = (http_auth_negotiate_context *)c;
@@ -155,7 +156,7 @@ static int negotiate_next_token(
 		goto done;
 	}
 
-	git_buf_puts(buf, "Authorization: Negotiate ");
+	git_buf_printf(buf, "%s: Negotiate ", header_name);
 	git_buf_encode_base64(buf, output_token.value, output_token.length);
 	git_buf_puts(buf, "\r\n");
 
diff --git a/src/transports/http.c b/src/transports/http.c
index 7f9d35012..3a0d2cc02 100644
--- a/src/transports/http.c
+++ b/src/transports/http.c
@@ -21,7 +21,6 @@
 #include "auth_negotiate.h"
 #include "streams/tls.h"
 #include "streams/socket.h"
-#include "streams/curl.h"
 
 git_http_auth_scheme auth_schemes[] = {
 	{ GIT_AUTHTYPE_NEGOTIATE, "Negotiate", GIT_CREDTYPE_DEFAULT, git_http_auth_negotiate },
@@ -37,6 +36,12 @@ static const char *receive_pack_service_url = "/git-receive-pack";
 static const char *get_verb = "GET";
 static const char *post_verb = "POST";
 
+#define AUTH_HEADER_SERVER "Authorization"
+#define AUTH_HEADER_PROXY  "Proxy-Authorization"
+
+#define SERVER_TYPE_REMOTE "remote"
+#define SERVER_TYPE_PROXY  "proxy"
+
 #define OWNING_SUBTRANSPORT(s) ((http_subtransport *)(s)->parent.subtransport)
 
 #define PARSE_ERROR_GENERIC	-1
@@ -62,17 +67,32 @@ typedef struct {
 	unsigned chunk_buffer_len;
 	unsigned sent_request : 1,
 		received_response : 1,
-		chunked : 1,
-		redirect_count : 3;
+		chunked : 1;
 } http_stream;
 
 typedef struct {
+	gitno_connection_data url;
+	git_stream *stream;
+
+	git_cred *cred;
+	git_cred *url_cred;
+
+	git_vector auth_challenges;
+	git_vector auth_contexts;
+} http_server;
+
+typedef struct {
 	git_smart_subtransport parent;
 	transport_smart *owner;
-	git_stream *io;
-	gitno_connection_data connection_data;
+	git_stream *gitserver_stream;
 	bool connected;
 
+	http_server server;
+
+	http_server proxy;
+	char *proxy_url;
+	git_proxy_options proxy_opts;
+
 	/* Parser structures */
 	http_parser parser;
 	http_parser_settings settings;
@@ -81,17 +101,13 @@ typedef struct {
 	git_buf parse_header_value;
 	char parse_buffer_data[NETIO_BUFSIZE];
 	char *content_type;
+	char *content_length;
 	char *location;
-	git_vector www_authenticate;
 	enum last_cb last_cb;
 	int parse_error;
 	int error;
-	unsigned parse_finished : 1;
-
-	/* Authentication */
-	git_cred *cred;
-	git_cred *url_cred;
-	git_vector auth_contexts;
+	unsigned parse_finished : 1,
+	    replay_count : 3;
 } http_subtransport;
 
 typedef struct {
@@ -124,7 +140,7 @@ static bool challenge_match(git_http_auth_scheme *scheme, void *data)
 
 static int auth_context_match(
 	git_http_auth_context **out,
-	http_subtransport *t,
+	http_server *server,
 	bool (*scheme_match)(git_http_auth_scheme *scheme, void *data),
 	void *data)
 {
@@ -145,7 +161,7 @@ static int auth_context_match(
 		return 0;
 
 	/* See if authentication has already started for this scheme */
-	git_vector_foreach(&t->auth_contexts, i, c) {
+	git_vector_foreach(&server->auth_contexts, i, c) {
 		if (c->type == scheme->type) {
 			context = c;
 			break;
@@ -153,11 +169,11 @@ static int auth_context_match(
 	}
 
 	if (!context) {
-		if (scheme->init_context(&context, &t->connection_data) < 0)
+		if (scheme->init_context(&context, &server->url) < 0)
 			return -1;
 		else if (!context)
 			return 0;
-		else if (git_vector_insert(&t->auth_contexts, context) < 0)
+		else if (git_vector_insert(&server->auth_contexts, context) < 0)
 			return -1;
 	}
 
@@ -166,32 +182,36 @@ static int auth_context_match(
 	return 0;
 }
 
-static int apply_credentials(git_buf *buf, http_subtransport *t)
+static int apply_credentials(
+	git_buf *buf,
+	http_server *server,
+	const char *header_name)
 {
-	git_cred *cred = t->cred;
+	git_cred *cred = server->cred;
 	git_http_auth_context *context;
 
 	/* Apply the credentials given to us in the URL */
-	if (!cred && t->connection_data.user && t->connection_data.pass) {
-		if (!t->url_cred &&
-			git_cred_userpass_plaintext_new(&t->url_cred,
-				t->connection_data.user, t->connection_data.pass) < 0)
+	if (!cred && server->url.user && server->url.pass) {
+		if (!server->url_cred &&
+			git_cred_userpass_plaintext_new(&server->url_cred,
+			    server->url.user, server->url.pass) < 0)
 			return -1;
 
-		cred = t->url_cred;
+		cred = server->url_cred;
 	}
 
 	if (!cred)
 		return 0;
 
 	/* Get or create a context for the best scheme for this cred type */
-	if (auth_context_match(&context, t, credtype_match, &cred->credtype) < 0)
+	if (auth_context_match(&context, server,
+	    credtype_match, &cred->credtype) < 0)
 		return -1;
 
 	if (!context)
 		return 0;
 
-	return context->next_token(buf, context, cred);
+	return context->next_token(buf, context, header_name, cred);
 }
 
 static int gen_request(
@@ -200,17 +220,26 @@ static int gen_request(
 	size_t content_length)
 {
 	http_subtransport *t = OWNING_SUBTRANSPORT(s);
-	const char *path = t->connection_data.path ? t->connection_data.path : "/";
+	const char *path = t->server.url.path ? t->server.url.path : "/";
 	size_t i;
 
-	git_buf_printf(buf, "%s %s%s HTTP/1.1\r\n", s->verb, path, s->service_url);
+	if (t->proxy_opts.type == GIT_PROXY_SPECIFIED)
+		git_buf_printf(buf, "%s %s://%s:%s%s%s HTTP/1.1\r\n",
+			s->verb,
+			t->server.url.use_ssl ? "https" : "http",
+			t->server.url.host,
+			t->server.url.port,
+			path, s->service_url);
+	else
+		git_buf_printf(buf, "%s %s%s HTTP/1.1\r\n",
+			s->verb, path, s->service_url);
 
 	git_buf_puts(buf, "User-Agent: ");
 	git_http__user_agent(buf);
 	git_buf_puts(buf, "\r\n");
-	git_buf_printf(buf, "Host: %s", t->connection_data.host);
-	if (strcmp(t->connection_data.port, gitno__default_port(&t->connection_data)) != 0) {
-		git_buf_printf(buf, ":%s", t->connection_data.port);
+	git_buf_printf(buf, "Host: %s", t->server.url.host);
+	if (strcmp(t->server.url.port, gitno__default_port(&t->server.url)) != 0) {
+		git_buf_printf(buf, ":%s", t->server.url.port);
 	}
 	git_buf_puts(buf, "\r\n");
 
@@ -230,8 +259,12 @@ static int gen_request(
 			git_buf_printf(buf, "%s\r\n", t->owner->custom_headers.strings[i]);
 	}
 
-	/* Apply credentials to the request */
-	if (apply_credentials(buf, t) < 0)
+	/* Apply proxy and server credentials to the request */
+	if (t->proxy_opts.type != GIT_PROXY_NONE &&
+	    apply_credentials(buf, &t->proxy, AUTH_HEADER_PROXY) < 0)
+		return -1;
+
+	if (apply_credentials(buf, &t->server, AUTH_HEADER_SERVER) < 0)
 		return -1;
 
 	git_buf_puts(buf, "\r\n");
@@ -243,16 +276,16 @@ static int gen_request(
 }
 
 static int parse_authenticate_response(
-	git_vector *www_authenticate,
-	http_subtransport *t,
+	http_server *server,
 	int *allowed_types)
 {
 	git_http_auth_context *context;
 	char *challenge;
 	size_t i;
 
-	git_vector_foreach(www_authenticate, i, challenge) {
-		if (auth_context_match(&context, t, challenge_match, challenge) < 0)
+	git_vector_foreach(&server->auth_challenges, i, challenge) {
+		if (auth_context_match(&context, server,
+		    challenge_match, challenge) < 0)
 			return -1;
 		else if (!context)
 			continue;
@@ -273,22 +306,45 @@ static int on_header_ready(http_subtransport *t)
 	git_buf *value = &t->parse_header_value;
 
 	if (!strcasecmp("Content-Type", git_buf_cstr(name))) {
-		if (!t->content_type) {
-			t->content_type = git__strdup(git_buf_cstr(value));
-			GITERR_CHECK_ALLOC(t->content_type);
+		if (t->content_type) {
+			giterr_set(GITERR_NET, "multiple Content-Type headers");
+			return -1;
 		}
+
+		t->content_type = git__strdup(git_buf_cstr(value));
+		GITERR_CHECK_ALLOC(t->content_type);
+	}
+	else if (!strcasecmp("Content-Length", git_buf_cstr(name))) {
+		if (t->content_length) {
+			giterr_set(GITERR_NET, "multiple Content-Length headers");
+			return -1;
+		}
+
+		t->content_length = git__strdup(git_buf_cstr(value));
+		GITERR_CHECK_ALLOC(t->content_length);
+	}
+	else if (!strcasecmp("Proxy-Authenticate", git_buf_cstr(name))) {
+		char *dup = git__strdup(git_buf_cstr(value));
+		GITERR_CHECK_ALLOC(dup);
+
+		if (git_vector_insert(&t->proxy.auth_challenges, dup) < 0)
+			return -1;
 	}
 	else if (!strcasecmp("WWW-Authenticate", git_buf_cstr(name))) {
 		char *dup = git__strdup(git_buf_cstr(value));
 		GITERR_CHECK_ALLOC(dup);
 
-		git_vector_insert(&t->www_authenticate, dup);
+		if (git_vector_insert(&t->server.auth_challenges, dup) < 0)
+			return -1;
 	}
 	else if (!strcasecmp("Location", git_buf_cstr(name))) {
-		if (!t->location) {
-			t->location = git__strdup(git_buf_cstr(value));
-			GITERR_CHECK_ALLOC(t->location);
+		if (t->location) {
+			giterr_set(GITERR_NET, "multiple Location headers");
+			return -1;
 		}
+
+		t->location = git__strdup(git_buf_cstr(value));
+		GITERR_CHECK_ALLOC(t->location);
 	}
 
 	return 0;
@@ -332,13 +388,78 @@ static int on_header_value(http_parser *parser, const char *str, size_t len)
 	return 0;
 }
 
+GIT_INLINE(void) free_cred(git_cred **cred)
+{
+	if (*cred) {
+		git_cred_free(*cred);
+		(*cred) = NULL;
+	}
+}
+
+static int on_auth_required(
+	git_cred **creds,
+	http_parser *parser,
+	const char *url,
+	const char *type,
+	git_cred_acquire_cb callback,
+	void *callback_payload,
+	const char *username,
+	int allowed_types)
+{
+	parser_context *ctx = (parser_context *) parser->data;
+	http_subtransport *t = ctx->t;
+	int ret;
+
+	if (!allowed_types) {
+		giterr_set(GITERR_NET, "%s requested authentication but did not negotiate mechanisms", type);
+		t->parse_error = PARSE_ERROR_GENERIC;
+		return t->parse_error;
+	}
+
+	if (callback) {
+		free_cred(creds);
+		ret = callback(creds, url, username, allowed_types, callback_payload);
+
+		if (ret == GIT_PASSTHROUGH) {
+			/* treat GIT_PASSTHROUGH as if callback isn't set */
+		} else if (ret < 0) {
+			t->error = ret;
+			t->parse_error = PARSE_ERROR_EXT;
+			return t->parse_error;
+		} else {
+			assert(*creds);
+
+			if (!((*creds)->credtype & allowed_types)) {
+				giterr_set(GITERR_NET, "%s credential provider returned an invalid cred type", type);
+				t->parse_error = PARSE_ERROR_GENERIC;
+				return t->parse_error;
+			}
+
+			/* Successfully acquired a credential. */
+			t->parse_error = PARSE_ERROR_REPLAY;
+			return 0;
+		}
+	}
+
+	giterr_set(GITERR_NET, "%s authentication required but no callback set",
+		type);
+	t->parse_error = PARSE_ERROR_GENERIC;
+	return t->parse_error;
+}
+
 static int on_headers_complete(http_parser *parser)
 {
 	parser_context *ctx = (parser_context *) parser->data;
 	http_subtransport *t = ctx->t;
 	http_stream *s = ctx->s;
 	git_buf buf = GIT_BUF_INIT;
-	int error = 0, no_callback = 0, allowed_auth_types = 0;
+	int proxy_auth_types = 0, server_auth_types = 0;
+
+	/* Enforce a reasonable cap on the number of replays */
+	if (t->replay_count++ >= GIT_HTTP_REPLAY_MAX) {
+		giterr_set(GITERR_NET, "too many redirects or authentication replays");
+		return t->parse_error = PARSE_ERROR_GENERIC;
+	}
 
 	/* Both parse_header_name and parse_header_value are populated
 	 * and ready for consumption. */
@@ -346,57 +467,36 @@ static int on_headers_complete(http_parser *parser)
 		if (on_header_ready(t) < 0)
 			return t->parse_error = PARSE_ERROR_GENERIC;
 
-	/* Capture authentication headers which may be a 401 (authentication
-	 * is not complete) or a 200 (simply informing us that auth *is*
-	 * complete.)
+	/*
+	 * Capture authentication headers for the proxy or final endpoint,
+	 * these may be 407/401 (authentication is not complete) or a 200
+	 * (informing us that auth has completed).
 	 */
-	if (parse_authenticate_response(&t->www_authenticate, t,
-			&allowed_auth_types) < 0)
+	if (parse_authenticate_response(&t->proxy, &proxy_auth_types) < 0 ||
+	    parse_authenticate_response(&t->server, &server_auth_types) < 0)
 		return t->parse_error = PARSE_ERROR_GENERIC;
 
-	/* Check for an authentication failure. */
-	if (parser->status_code == 401 && get_verb == s->verb) {
-		if (!t->owner->cred_acquire_cb) {
-			no_callback = 1;
-		} else {
-			if (allowed_auth_types) {
-				if (t->cred) {
-					t->cred->free(t->cred);
-					t->cred = NULL;
-				}
-
-				error = t->owner->cred_acquire_cb(&t->cred,
-								  t->owner->url,
-								  t->connection_data.user,
-								  allowed_auth_types,
-								  t->owner->cred_acquire_payload);
-
-				/* treat GIT_PASSTHROUGH as if callback isn't set */
-				if (error == GIT_PASSTHROUGH) {
-					no_callback = 1;
-				} else if (error < 0) {
-					t->error = error;
-					return t->parse_error = PARSE_ERROR_EXT;
-				} else {
-					assert(t->cred);
-
-					if (!(t->cred->credtype & allowed_auth_types)) {
-						giterr_set(GITERR_NET, "credentials callback returned an invalid cred type");
-						return t->parse_error = PARSE_ERROR_GENERIC;
-					}
-
-					/* Successfully acquired a credential. */
-					t->parse_error = PARSE_ERROR_REPLAY;
-					return 0;
-				}
-			}
-		}
+	/* Check for a proxy authentication failure. */
+	if (parser->status_code == 407 && get_verb == s->verb)
+		return on_auth_required(&t->proxy.cred,
+		    parser,
+		    t->proxy_opts.url,
+		    SERVER_TYPE_PROXY,
+		    t->proxy_opts.credentials,
+		    t->proxy_opts.payload,
+		    t->proxy.url.user,
+			proxy_auth_types);
 
-		if (no_callback) {
-			giterr_set(GITERR_NET, "authentication required but no callback set");
-			return t->parse_error = PARSE_ERROR_GENERIC;
-		}
-	}
+	/* Check for an authentication failure. */
+	if (parser->status_code == 401 && get_verb == s->verb)
+		return on_auth_required(&t->server.cred,
+		    parser,
+		    t->owner->url,
+		    SERVER_TYPE_REMOTE,
+		    t->owner->cred_acquire_cb,
+		    t->owner->cred_acquire_payload,
+		    t->server.url.user,
+		    server_auth_types);
 
 	/* Check for a redirect.
 	 * Right now we only permit a redirect to the same hostname. */
@@ -407,12 +507,7 @@ static int on_headers_complete(http_parser *parser)
 	     parser->status_code == 308) &&
 	    t->location) {
 
-		if (s->redirect_count >= 7) {
-			giterr_set(GITERR_NET, "too many redirects");
-			return t->parse_error = PARSE_ERROR_GENERIC;
-		}
-
-		if (gitno_connection_data_from_url(&t->connection_data, t->location, s->service_url) < 0)
+		if (gitno_connection_data_from_url(&t->server.url, t->location, s->service_url) < 0)
 			return t->parse_error = PARSE_ERROR_GENERIC;
 
 		/* Set the redirect URL on the stream. This is a transfer of
@@ -424,8 +519,6 @@ static int on_headers_complete(http_parser *parser)
 		t->location = NULL;
 
 		t->connected = 0;
-		s->redirect_count++;
-
 		t->parse_error = PARSE_ERROR_REPLAY;
 		return 0;
 	}
@@ -492,15 +585,19 @@ static int on_body_fill_buffer(http_parser *parser, const char *str, size_t len)
 	if (t->parse_error == PARSE_ERROR_REPLAY)
 		return 0;
 
-	if (ctx->buf_size < len) {
-		giterr_set(GITERR_NET, "can't fit data in the buffer");
-		return t->parse_error = PARSE_ERROR_GENERIC;
+	/* If there's no buffer set, we're explicitly ignoring the body. */
+	if (ctx->buffer) {
+		if (ctx->buf_size < len) {
+			giterr_set(GITERR_NET, "can't fit data in the buffer");
+			return t->parse_error = PARSE_ERROR_GENERIC;
+		}
+
+		memcpy(ctx->buffer, str, len);
+		ctx->buffer += len;
+		ctx->buf_size -= len;
 	}
 
-	memcpy(ctx->buffer, str, len);
 	*(ctx->bytes_read) += len;
-	ctx->buffer += len;
-	ctx->buf_size -= len;
 
 	return 0;
 }
@@ -508,7 +605,7 @@ static int on_body_fill_buffer(http_parser *parser, const char *str, size_t len)
 static void clear_parser_state(http_subtransport *t)
 {
 	http_parser_init(&t->parser, HTTP_RESPONSE);
-	gitno_buffer_setup_fromstream(t->io,
+	gitno_buffer_setup_fromstream(t->server.stream,
 		&t->parse_buffer,
 		t->parse_buffer_data,
 		sizeof(t->parse_buffer_data));
@@ -526,10 +623,14 @@ static void clear_parser_state(http_subtransport *t)
 	git__free(t->content_type);
 	t->content_type = NULL;
 
+	git__free(t->content_length);
+	t->content_length = NULL;
+
 	git__free(t->location);
 	t->location = NULL;
 
-	git_vector_free_deep(&t->www_authenticate);
+	git_vector_free_deep(&t->proxy.auth_challenges);
+	git_vector_free_deep(&t->server.auth_challenges);
 }
 
 static int write_chunk(git_stream *io, const char *buffer, size_t len)
@@ -560,102 +661,350 @@ static int write_chunk(git_stream *io, const char *buffer, size_t len)
 	return 0;
 }
 
-static int apply_proxy_config(http_subtransport *t)
+static int load_proxy_config(http_subtransport *t)
 {
 	int error;
-	git_proxy_t proxy_type;
 
-	if (!git_stream_supports_proxy(t->io))
+	switch (t->owner->proxy.type) {
+	case GIT_PROXY_NONE:
 		return 0;
 
-	proxy_type = t->owner->proxy.type;
-
-	if (proxy_type == GIT_PROXY_NONE)
-		return 0;
+	case GIT_PROXY_AUTO:
+		git__free(t->proxy_url);
+		t->proxy_url = NULL;
 
-	if (proxy_type == GIT_PROXY_AUTO) {
-		char *url;
-		git_proxy_options opts = GIT_PROXY_OPTIONS_INIT;
+		git_proxy_init_options(&t->proxy_opts, GIT_PROXY_OPTIONS_VERSION);
 
-		if ((error = git_remote__get_http_proxy(t->owner->owner, !!t->connection_data.use_ssl, &url)) < 0)
+		if ((error = git_remote__get_http_proxy(t->owner->owner,
+		    !!t->server.url.use_ssl, &t->proxy_url)) < 0)
 			return error;
 
-		opts.credentials = t->owner->proxy.credentials;
-		opts.certificate_check = t->owner->proxy.certificate_check;
-		opts.payload = t->owner->proxy.payload;
-		opts.type = GIT_PROXY_SPECIFIED;
-		opts.url = url;
-		error = git_stream_set_proxy(t->io, &opts);
-		git__free(url);
+		t->proxy_opts.type = GIT_PROXY_SPECIFIED;
+		t->proxy_opts.url = t->proxy_url;
+		t->proxy_opts.credentials = t->owner->proxy.credentials;
+		t->proxy_opts.certificate_check = t->owner->proxy.certificate_check;
+		t->proxy_opts.payload = t->owner->proxy.payload;
+		break;
+
+	case GIT_PROXY_SPECIFIED:
+		memcpy(&t->proxy_opts, &t->owner->proxy, sizeof(git_proxy_options));
+		break;
 
+	default:
+		assert(0);
+		return -1;
+	}
+
+	if ((error = gitno_connection_data_from_url(&t->proxy.url, t->proxy_opts.url, NULL)) < 0)
 		return error;
+
+	if (t->proxy.url.use_ssl) {
+		giterr_set(GITERR_NET, "SSL connections to proxy are not supported");
+		return -1;
 	}
 
-	return git_stream_set_proxy(t->io, &t->owner->proxy);
+	return error;
 }
 
-static int http_connect(http_subtransport *t)
+static int check_certificate(
+	git_stream *stream,
+	gitno_connection_data *url,
+	int is_valid,
+	git_transport_certificate_check_cb cert_cb,
+	void *cert_cb_payload)
 {
+	git_cert *cert;
+	git_error_state last_error = {0};
 	int error;
 
-	if (t->connected &&
-		http_should_keep_alive(&t->parser) &&
-		t->parse_finished)
-		return 0;
+	if ((error = git_stream_certificate(&cert, stream)) < 0)
+		return error;
 
-	if (t->io) {
-		git_stream_close(t->io);
-		git_stream_free(t->io);
-		t->io = NULL;
-		t->connected = 0;
+	giterr_state_capture(&last_error, GIT_ECERTIFICATE);
+
+	error = cert_cb(cert, is_valid, url->host, cert_cb_payload);
+
+	if (error == GIT_PASSTHROUGH && !is_valid)
+		return giterr_state_restore(&last_error);
+	else if (error == GIT_PASSTHROUGH)
+		error = 0;
+	else if (error && !giterr_last())
+		giterr_set(GITERR_NET, "user rejected certificate for %s", url->host);
+
+	giterr_state_free(&last_error);
+	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 gen_connect_req(git_buf *buf, http_subtransport *t)
+{
+	git_buf_printf(buf, "CONNECT %s:%s HTTP/1.1\r\n",
+		t->server.url.host, t->server.url.port);
+
+	git_buf_puts(buf, "User-Agent: ");
+	git_http__user_agent(buf);
+	git_buf_puts(buf, "\r\n");
+
+	git_buf_printf(buf, "Host: %s\r\n", t->proxy.url.host);
+
+	if (apply_credentials(buf, &t->proxy, AUTH_HEADER_PROXY) < 0)
+		return -1;
+
+	git_buf_puts(buf, "\r\n");
+
+	return git_buf_oom(buf) ? -1 : 0;
+}
+
+static int proxy_headers_complete(http_parser *parser)
+{
+	parser_context *ctx = (parser_context *) parser->data;
+	http_subtransport *t = ctx->t;
+	int proxy_auth_types = 0;
+
+	/* Enforce a reasonable cap on the number of replays */
+	if (t->replay_count++ >= GIT_HTTP_REPLAY_MAX) {
+		giterr_set(GITERR_NET, "too many redirects or authentication replays");
+		return t->parse_error = PARSE_ERROR_GENERIC;
 	}
 
-	if (t->connection_data.use_ssl) {
-		error = git_tls_stream_new(&t->io, t->connection_data.host, t->connection_data.port);
-	} else {
-#ifdef GIT_CURL
-		error = git_curl_stream_new(&t->io, t->connection_data.host, t->connection_data.port);
-#else
-		error = git_socket_stream_new(&t->io,  t->connection_data.host, t->connection_data.port);
-#endif
+	/* Both parse_header_name and parse_header_value are populated
+	 * and ready for consumption. */
+	if (VALUE == t->last_cb)
+		if (on_header_ready(t) < 0)
+			return t->parse_error = PARSE_ERROR_GENERIC;
+
+	/*
+	 * Capture authentication headers for the proxy or final endpoint,
+	 * these may be 407/401 (authentication is not complete) or a 200
+	 * (informing us that auth has completed).
+	 */
+	if (parse_authenticate_response(&t->proxy, &proxy_auth_types) < 0)
+		return t->parse_error = PARSE_ERROR_GENERIC;
+
+	/* Check for a proxy authentication failure. */
+	if (parser->status_code == 407)
+		return on_auth_required(&t->proxy.cred,
+			parser,
+			t->proxy_opts.url,
+			SERVER_TYPE_PROXY,
+			t->proxy_opts.credentials,
+			t->proxy_opts.payload,
+			t->proxy.url.user,
+			proxy_auth_types);
+
+	if (parser->status_code != 200) {
+		giterr_set(GITERR_NET, "unexpected status code from proxy: %d",
+			parser->status_code);
+		return t->parse_error = PARSE_ERROR_GENERIC;
 	}
 
-	if (error < 0)
-		return error;
+	if (!t->content_length || strcmp(t->content_length, "0") == 0)
+		t->parse_finished = 1;
+
+	return 0;
+}
+
+static int proxy_connect(
+	git_stream **out, git_stream *proxy_stream, http_subtransport *t)
+{
+	git_buf request = GIT_BUF_INIT;
+	static http_parser_settings proxy_parser_settings = {0};
+	size_t bytes_read = 0, bytes_parsed;
+	parser_context ctx;
+	int error;
 
-	GITERR_CHECK_VERSION(t->io, GIT_STREAM_VERSION, "git_stream");
+	/* Use the parser settings only to parser headers. */
+	proxy_parser_settings.on_header_field = on_header_field;
+	proxy_parser_settings.on_header_value = on_header_value;
+	proxy_parser_settings.on_headers_complete = proxy_headers_complete;
+	proxy_parser_settings.on_message_complete = on_message_complete;
 
-	apply_proxy_config(t);
+replay:
+	clear_parser_state(t);
 
-	error = git_stream_connect(t->io);
+	gitno_buffer_setup_fromstream(proxy_stream,
+		&t->parse_buffer,
+		t->parse_buffer_data,
+		sizeof(t->parse_buffer_data));
 
-	if ((!error || error == GIT_ECERTIFICATE) && t->owner->certificate_check_cb != NULL &&
-	    git_stream_is_encrypted(t->io)) {
-		git_cert *cert;
-		int is_valid = (error == GIT_OK);
+	if ((error = gen_connect_req(&request, t)) < 0)
+		goto done;
 
-		if ((error = git_stream_certificate(&cert, t->io)) < 0)
-			return error;
+	if ((error = git_stream_write(proxy_stream,
+	    request.ptr, request.size, 0)) < 0)
+		goto done;
 
-		giterr_clear();
-		error = t->owner->certificate_check_cb(cert, is_valid, t->connection_data.host, t->owner->message_cb_payload);
+	git_buf_dispose(&request);
 
-		if (error == GIT_PASSTHROUGH)
-			error = is_valid ? 0 : GIT_ECERTIFICATE;
+	while (!bytes_read && !t->parse_finished) {
+		t->parse_buffer.offset = 0;
 
-		if (error < 0) {
-			if (!giterr_last())
-				giterr_set(GITERR_NET, "user cancelled certificate check");
+		if ((error = gitno_recv(&t->parse_buffer)) < 0)
+			goto done;
 
-			return error;
+		/*
+		 * This call to http_parser_execute will invoke the on_*
+		 * callbacks.  Since we don't care about the body of the response,
+		 * we can set our buffer to NULL.
+		 */
+		ctx.t = t;
+		ctx.s = NULL;
+		ctx.buffer = NULL;
+		ctx.buf_size = 0;
+		ctx.bytes_read = &bytes_read;
+
+		/* Set the context, call the parser, then unset the context. */
+		t->parser.data = &ctx;
+
+		bytes_parsed = http_parser_execute(&t->parser,
+			&proxy_parser_settings, t->parse_buffer.data, t->parse_buffer.offset);
+
+		t->parser.data = NULL;
+
+		/* Ensure that we didn't get a redirect; unsupported. */
+		if (t->location) {
+			giterr_set(GITERR_NET, "proxy server sent unsupported redirect during CONNECT");
+			error = -1;
+			goto done;
+		}
+
+		/* Replay the request with authentication headers. */
+		if (PARSE_ERROR_REPLAY == t->parse_error)
+			goto replay;
+
+		if (t->parse_error < 0) {
+			error = t->parse_error == PARSE_ERROR_EXT ? PARSE_ERROR_EXT : -1;
+			goto done;
+		}
+
+		if (bytes_parsed != t->parse_buffer.offset) {
+			giterr_set(GITERR_NET,
+				"HTTP parser error: %s",
+				http_errno_description((enum http_errno)t->parser.http_errno));
+			error = -1;
+			goto done;
 		}
 	}
 
-	if (error < 0)
+	if ((error = git_tls_stream_wrap(out, proxy_stream, t->server.url.host)) == 0)
+		error = stream_connect(*out, &t->server.url,
+		    t->owner->certificate_check_cb,
+			t->owner->message_cb_payload);
+
+	/*
+	 * Since we've connected via a HTTPS proxy tunnel, we don't behave
+	 * as if we have an HTTP proxy.
+	 */
+	t->proxy_opts.type = GIT_PROXY_NONE;
+	t->replay_count = 0;
+
+done:
+	return error;
+}
+
+static int http_connect(http_subtransport *t)
+{
+	gitno_connection_data *url;
+	git_stream *proxy_stream = NULL, *stream = NULL;
+	git_transport_certificate_check_cb cert_cb;
+	void *cb_payload;
+	int error;
+
+	if (t->connected &&
+		http_should_keep_alive(&t->parser) &&
+		t->parse_finished)
+		return 0;
+
+	if ((error = load_proxy_config(t)) < 0)
 		return error;
 
+	if (t->server.stream) {
+		git_stream_close(t->server.stream);
+		git_stream_free(t->server.stream);
+		t->server.stream = NULL;
+	}
+
+	if (t->proxy.stream) {
+		git_stream_close(t->proxy.stream);
+		git_stream_free(t->proxy.stream);
+		t->proxy.stream = NULL;
+	}
+
+	t->connected = 0;
+
+	if (t->proxy_opts.type == GIT_PROXY_SPECIFIED) {
+		url = &t->proxy.url;
+		cert_cb = t->proxy_opts.certificate_check;
+		cb_payload = t->proxy_opts.payload;
+	} else {
+		url = &t->server.url;
+		cert_cb = t->owner->certificate_check_cb;
+		cb_payload = t->owner->message_cb_payload;
+	}
+
+	if (url->use_ssl)
+		error = git_tls_stream_new(&stream, url->host, url->port);
+	else
+		error = git_socket_stream_new(&stream, url->host, url->port);
+
+	if (error < 0)
+		goto on_error;
+
+	if ((error = stream_connect(stream, url, cert_cb, cb_payload)) < 0)
+		goto on_error;
+
+	/*
+	 * At this point we have a connection to the remote server or to
+	 * a proxy.  If it's a proxy and the remote server is actually
+	 * an HTTPS connection, then we need to build a CONNECT tunnel.
+	 */
+	if (t->proxy_opts.type == GIT_PROXY_SPECIFIED &&
+		t->server.url.use_ssl) {
+		proxy_stream = stream;
+		stream = NULL;
+
+		if ((error = proxy_connect(&stream, proxy_stream, t)) < 0)
+			goto on_error;
+	}
+
+	t->proxy.stream = proxy_stream;
+	t->server.stream = stream;
 	t->connected = 1;
+	t->replay_count = 0;
 	return 0;
+
+on_error:
+	if (stream) {
+		git_stream_close(stream);
+		git_stream_free(stream);
+	}
+
+	if (proxy_stream) {
+		git_stream_close(proxy_stream);
+		git_stream_free(proxy_stream);
+	}
+
+	return error;
 }
 
 static int http_stream_read(
@@ -682,7 +1031,8 @@ replay:
 		if (gen_request(&request, s, 0) < 0)
 			return -1;
 
-		if (git_stream_write(t->io, request.ptr, request.size, 0) < 0) {
+		if (git_stream_write(t->server.stream,
+		    request.ptr, request.size, 0) < 0) {
 			git_buf_dispose(&request);
 			return -1;
 		}
@@ -698,13 +1048,14 @@ replay:
 
 			/* Flush, if necessary */
 			if (s->chunk_buffer_len > 0 &&
-				write_chunk(t->io, s->chunk_buffer, s->chunk_buffer_len) < 0)
+				write_chunk(t->server.stream,
+				    s->chunk_buffer, s->chunk_buffer_len) < 0)
 				return -1;
 
 			s->chunk_buffer_len = 0;
 
 			/* Write the final chunk. */
-			if (git_stream_write(t->io, "0\r\n\r\n", 5, 0) < 0)
+			if (git_stream_write(t->server.stream, "0\r\n\r\n", 5, 0) < 0)
 				return -1;
 		}
 
@@ -803,7 +1154,8 @@ static int http_stream_write_chunked(
 		if (gen_request(&request, s, 0) < 0)
 			return -1;
 
-		if (git_stream_write(t->io, request.ptr, request.size, 0) < 0) {
+		if (git_stream_write(t->server.stream,
+		    request.ptr, request.size, 0) < 0) {
 			git_buf_dispose(&request);
 			return -1;
 		}
@@ -816,14 +1168,15 @@ static int http_stream_write_chunked(
 	if (len > CHUNK_SIZE) {
 		/* Flush, if necessary */
 		if (s->chunk_buffer_len > 0) {
-			if (write_chunk(t->io, s->chunk_buffer, s->chunk_buffer_len) < 0)
+			if (write_chunk(t->server.stream,
+			    s->chunk_buffer, s->chunk_buffer_len) < 0)
 				return -1;
 
 			s->chunk_buffer_len = 0;
 		}
 
 		/* Write chunk directly */
-		if (write_chunk(t->io, buffer, len) < 0)
+		if (write_chunk(t->server.stream, buffer, len) < 0)
 			return -1;
 	}
 	else {
@@ -840,7 +1193,8 @@ static int http_stream_write_chunked(
 
 		/* Is the buffer full? If so, then flush */
 		if (CHUNK_SIZE == s->chunk_buffer_len) {
-			if (write_chunk(t->io, s->chunk_buffer, s->chunk_buffer_len) < 0)
+			if (write_chunk(t->server.stream,
+			    s->chunk_buffer, s->chunk_buffer_len) < 0)
 				return -1;
 
 			s->chunk_buffer_len = 0;
@@ -876,10 +1230,11 @@ static int http_stream_write_single(
 	if (gen_request(&request, s, len) < 0)
 		return -1;
 
-	if (git_stream_write(t->io, request.ptr, request.size, 0) < 0)
+	if (git_stream_write(t->server.stream,
+	    request.ptr, request.size, 0) < 0)
 		goto on_error;
 
-	if (len && git_stream_write(t->io, buffer, len, 0) < 0)
+	if (len && git_stream_write(t->server.stream, buffer, len, 0) < 0)
 		goto on_error;
 
 	git_buf_dispose(&request);
@@ -1010,13 +1365,21 @@ static int http_action(
 	http_subtransport *t = (http_subtransport *)subtransport;
 	int ret;
 
-	if (!stream)
-		return -1;
+	assert(stream);
 
-	if ((!t->connection_data.host || !t->connection_data.port || !t->connection_data.path) &&
-		 (ret = gitno_connection_data_from_url(&t->connection_data, url, NULL)) < 0)
+	/*
+	 * If we've seen a redirect then preserve the location that we've
+	 * been given.  This is important to continue authorization against
+	 * the redirect target, not the user-given source; the endpoint may
+	 * have redirected us from HTTP->HTTPS and is using an auth mechanism
+	 * that would be insecure in plaintext (eg, HTTP Basic).
+	 */
+	if ((!t->server.url.host || !t->server.url.port || !t->server.url.path) &&
+	    (ret = gitno_connection_data_from_url(&t->server.url, url, NULL)) < 0)
 		return ret;
 
+	assert(t->server.url.host && t->server.url.port && t->server.url.path);
+
 	if ((ret = http_connect(t)) < 0)
 		return ret;
 
@@ -1038,41 +1401,55 @@ static int http_action(
 	return -1;
 }
 
-static int http_close(git_smart_subtransport *subtransport)
+static void free_auth_contexts(git_vector *contexts)
 {
-	http_subtransport *t = (http_subtransport *) subtransport;
 	git_http_auth_context *context;
 	size_t i;
 
+	git_vector_foreach(contexts, i, context) {
+		if (context->free)
+			context->free(context);
+	}
+
+	git_vector_clear(contexts);
+}
+
+static int http_close(git_smart_subtransport *subtransport)
+{
+	http_subtransport *t = (http_subtransport *) subtransport;
+
 	clear_parser_state(t);
 
 	t->connected = 0;
 
-	if (t->io) {
-		git_stream_close(t->io);
-		git_stream_free(t->io);
-		t->io = NULL;
+	if (t->server.stream) {
+		git_stream_close(t->server.stream);
+		git_stream_free(t->server.stream);
+		t->server.stream = NULL;
 	}
 
-	if (t->cred) {
-		t->cred->free(t->cred);
-		t->cred = NULL;
+	if (t->proxy.stream) {
+		git_stream_close(t->proxy.stream);
+		git_stream_free(t->proxy.stream);
+		t->proxy.stream = NULL;
 	}
 
-	if (t->url_cred) {
-		t->url_cred->free(t->url_cred);
-		t->url_cred = NULL;
-	}
+	free_cred(&t->server.cred);
+	free_cred(&t->server.url_cred);
+	free_cred(&t->proxy.cred);
+	free_cred(&t->proxy.url_cred);
 
-	git_vector_foreach(&t->auth_contexts, i, context) {
-		if (context->free)
-			context->free(context);
-	}
+	free_auth_contexts(&t->server.auth_contexts);
+	free_auth_contexts(&t->proxy.auth_contexts);
+
+	gitno_connection_data_free_ptrs(&t->server.url);
+	memset(&t->server.url, 0x0, sizeof(gitno_connection_data));
 
-	git_vector_clear(&t->auth_contexts);
+	gitno_connection_data_free_ptrs(&t->proxy.url);
+	memset(&t->proxy.url, 0x0, sizeof(gitno_connection_data));
 
-	gitno_connection_data_free_ptrs(&t->connection_data);
-	memset(&t->connection_data, 0x0, sizeof(gitno_connection_data));
+	git__free(t->proxy_url);
+	t->proxy_url = NULL;
 
 	return 0;
 }
@@ -1083,7 +1460,8 @@ static void http_free(git_smart_subtransport *subtransport)
 
 	http_close(subtransport);
 
-	git_vector_free(&t->auth_contexts);
+	git_vector_free(&t->server.auth_contexts);
+	git_vector_free(&t->proxy.auth_contexts);
 	git__free(t);
 }
 
diff --git a/src/transports/http.h b/src/transports/http.h
index 6c4ecc9a4..b09475755 100644
--- a/src/transports/http.h
+++ b/src/transports/http.h
@@ -10,6 +10,8 @@
 
 #include "buffer.h"
 
+#define GIT_HTTP_REPLAY_MAX 7
+
 GIT_INLINE(int) git_http__user_agent(git_buf *buf)
 {
 	const char *ua = git_libgit2__user_agent();
diff --git a/src/transports/winhttp.c b/src/transports/winhttp.c
index 5e7bde73c..30e2ecb73 100644
--- a/src/transports/winhttp.c
+++ b/src/transports/winhttp.c
@@ -932,7 +932,7 @@ static int winhttp_stream_read(
 
 replay:
 	/* Enforce a reasonable cap on the number of replays */
-	if (++replay_count >= 7) {
+	if (replay_count++ >= GIT_HTTP_REPLAY_MAX) {
 		giterr_set(GITERR_NET, "too many redirects or authentication replays");
 		return -1;
 	}