thodg/libgit2

diff --git a/include/git2/remote.h b/include/git2/remote.h
index 1827e12..33b7dfd 100644
--- a/include/git2/remote.h
+++ b/include/git2/remote.h
@@ -287,6 +287,19 @@ GIT_EXTERN(int) git_remote_add(git_remote **out, git_repository *repo, const cha
 GIT_EXTERN(void) git_remote_check_cert(git_remote *remote, int check);
 
 /**
+ * Set a credentials acquisition callback for this remote. If the remote is
+ * not available for anonymous access, then you must set this callback in order
+ * to provide credentials to the transport at the time of authentication
+ * failure so that retry can be performed.
+ *
+ * @param remote the remote to configure
+ * @param The credentials acquisition callback to use (defaults to NULL)
+ */
+GIT_EXTERN(void) git_remote_set_cred_acquire_cb(
+	git_remote *remote,
+	git_cred_acquire_cb cred_acquire_cb);
+
+/**
  * Sets a custom transport for the remote. The caller can use this function
  * to bypass the automatic discovery of a transport by URL scheme (i.e.
  * http://, https://, git://) and supply their own transport to be used
@@ -297,7 +310,9 @@ GIT_EXTERN(void) git_remote_check_cert(git_remote *remote, int check);
  * @param remote the remote to configure
  * @param transport the transport object for the remote to use
  */
-GIT_EXTERN(int) git_remote_set_transport(git_remote *remote, git_transport *transport);
+GIT_EXTERN(int) git_remote_set_transport(
+	git_remote *remote,
+	git_transport *transport);
 
 /**
  * Argument to the completion callback which tells it which operation
diff --git a/include/git2/transport.h b/include/git2/transport.h
index fd0d56f..b2bdaae 100644
--- a/include/git2/transport.h
+++ b/include/git2/transport.h
@@ -20,6 +20,54 @@
 GIT_BEGIN_DECL
 
 /*
+ *** Begin interface for credentials acquisition ***
+ */
+
+typedef enum {
+	/* git_cred_userpass_plaintext */
+	GIT_CREDTYPE_USERPASS_PLAINTEXT = 1,
+} git_credtype_t;
+
+/* The base structure for all credential types */
+typedef struct git_cred {
+	git_credtype_t credtype;
+	void (*free)(
+		struct git_cred *cred);
+} git_cred;
+
+/* A plaintext username and password */
+typedef struct git_cred_userpass_plaintext {
+	git_cred parent;
+	char *username;
+	char *password;
+} git_cred_userpass_plaintext;
+
+/**
+ * Creates a new plain-text username and password credential object.
+ *
+ * @param cred The newly created credential object.
+ * @param username The username of the credential.
+ * @param password The password of the credential.
+ */
+GIT_EXTERN(int) git_cred_userpass_plaintext_new(
+	git_cred **cred,
+	const char *username,
+	const char *password);
+
+/**
+ * Signature of a function which acquires a credential object.
+ *
+ * @param cred The newly created credential object.
+ * @param url The resource for which we are demanding a credential.
+ * @param allowed_types A bitmask stating which cred types are OK to return.
+ */
+typedef int (*git_cred_acquire_cb)(
+	git_cred **cred,
+	const char *url,
+	int allowed_types);
+
+/*
+ *** End interface for credentials acquisition ***
  *** Begin base transport interface ***
  */
 
@@ -43,6 +91,7 @@ typedef struct git_transport {
 	 * direction. */
 	int (*connect)(struct git_transport *transport,
 		const char *url,
+		git_cred_acquire_cb cred_acquire_cb,
 		int direction,
 		int flags);
 
diff --git a/src/remote.c b/src/remote.c
index a873a27..98660fe 100644
--- a/src/remote.c
+++ b/src/remote.c
@@ -492,7 +492,7 @@ int git_remote_connect(git_remote *remote, int direction)
 	if (!remote->check_cert)
 		flags |= GIT_TRANSPORTFLAGS_NO_CHECK_CERT;
 
-	if (t->connect(t, url, direction, flags) < 0)
+	if (t->connect(t, url, remote->cred_acquire_cb, direction, flags) < 0)
 		goto on_error;
 
 	remote->transport = t;
@@ -809,6 +809,15 @@ void git_remote_set_callbacks(git_remote *remote, git_remote_callbacks *callback
 			remote->callbacks.data);
 }
 
+void git_remote_set_cred_acquire_cb(
+	git_remote *remote,
+	git_cred_acquire_cb cred_acquire_cb)
+{
+	assert(remote);
+
+	remote->cred_acquire_cb = cred_acquire_cb;
+}
+
 int git_remote_set_transport(git_remote *remote, git_transport *transport)
 {
 	assert(remote && transport);
diff --git a/src/remote.h b/src/remote.h
index b0df2d6..6a90bfc 100644
--- a/src/remote.h
+++ b/src/remote.h
@@ -22,6 +22,7 @@ struct git_remote {
 	git_vector refs;
 	struct git_refspec fetch;
 	struct git_refspec push;
+	git_cred_acquire_cb cred_acquire_cb;
 	git_transport *transport;
 	git_repository *repo;
 	git_remote_callbacks callbacks;
diff --git a/src/transports/cred.c b/src/transports/cred.c
new file mode 100644
index 0000000..5529537
--- /dev/null
+++ b/src/transports/cred.c
@@ -0,0 +1,57 @@
+/*
+ * Copyright (C) 2009-2012 the libgit2 contributors
+ *
+ * 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.h"
+#include "smart.h"
+
+static void plaintext_free(struct git_cred *cred)
+{
+	git_cred_userpass_plaintext *c = (git_cred_userpass_plaintext *)cred;
+	int pass_len = strlen(c->password);
+
+	git__free(c->username);
+
+	/* Zero the memory which previously held the password */
+	memset(c->password, 0x0, pass_len);
+	git__free(c->password);
+
+	git__free(c);
+}
+
+int git_cred_userpass_plaintext_new(
+	git_cred **cred,
+	const char *username,
+	const char *password)
+{
+	git_cred_userpass_plaintext *c;
+
+	if (!cred)
+		return -1;
+
+	c = (git_cred_userpass_plaintext *)git__malloc(sizeof(git_cred_userpass_plaintext));
+	GITERR_CHECK_ALLOC(c);
+
+	c->parent.credtype = GIT_CREDTYPE_USERPASS_PLAINTEXT;
+	c->parent.free = plaintext_free;
+	c->username = git__strdup(username);
+
+	if (!c->username) {
+		git__free(c);
+		return -1;
+	}
+
+	c->password = git__strdup(password);
+
+	if (!c->password) {
+		git__free(c->username);
+		git__free(c);
+		return -1;
+	}
+
+	*cred = &c->parent;
+	return 0;
+}
\ No newline at end of file
diff --git a/src/transports/http.c b/src/transports/http.c
index f33cad7..4b48779 100644
--- a/src/transports/http.c
+++ b/src/transports/http.c
@@ -10,6 +10,7 @@
 #include "http_parser.h"
 #include "buffer.h"
 #include "netops.h"
+#include "smart.h"
 
 static const char *prefix_http = "http://";
 static const char *prefix_https = "https://";
@@ -18,15 +19,23 @@ static const char *upload_pack_ls_service_url = "/info/refs?service=git-upload-p
 static const char *upload_pack_service_url = "/git-upload-pack";
 static const char *get_verb = "GET";
 static const char *post_verb = "POST";
+static const char *basic_authtype = "Basic";
 
 #define OWNING_SUBTRANSPORT(s) ((http_subtransport *)(s)->parent.subtransport)
 
+#define PARSE_ERROR_GENERIC	-1
+#define PARSE_ERROR_REPLAY	-2
+
 enum last_cb {
 	NONE,
 	FIELD,
 	VALUE
 };
 
+typedef enum {
+	GIT_HTTP_AUTH_BASIC = 1,
+} http_authmechanism_t;
+
 typedef struct {
 	git_smart_subtransport_stream parent;
 	const char *service;
@@ -37,11 +46,13 @@ typedef struct {
 
 typedef struct {
 	git_smart_subtransport parent;
-	git_transport *owner;
+	transport_smart *owner;
 	gitno_socket socket;
 	const char *path;
 	char *host;
-	char *port;	
+	char *port;
+	git_cred *cred;
+	http_authmechanism_t auth_mechanism;
 	unsigned connected : 1,
 		use_ssl : 1,
 		no_check_cert : 1;
@@ -50,14 +61,14 @@ typedef struct {
 	http_parser parser;
 	http_parser_settings settings;
 	gitno_buffer parse_buffer;
-	git_buf parse_temp;
+	git_buf parse_header_name;
+	git_buf parse_header_value;
 	char parse_buffer_data[2048];
 	char *content_type;
+	git_vector www_authenticate;
 	enum last_cb last_cb;
-	int parse_error;	
-	unsigned parse_finished : 1,
-		ct_found : 1,
-		ct_finished : 1;
+	int parse_error;
+	unsigned parse_finished : 1;
 } http_subtransport;
 
 typedef struct {
@@ -70,10 +81,42 @@ typedef struct {
 	size_t *bytes_read;
 } parser_context;
 
-static int gen_request(git_buf *buf, const char *path, const char *host, const char *op,
-                       const char *service, const char *service_url, ssize_t content_length)
+static int apply_basic_credential(git_buf *buf, git_cred *cred)
+{
+	git_cred_userpass_plaintext *c = (git_cred_userpass_plaintext *)cred;
+	git_buf raw = GIT_BUF_INIT;
+	int error = -1;
+
+	git_buf_printf(&raw, "%s:%s", c->username, c->password);
+
+	if (git_buf_oom(&raw) ||
+		git_buf_puts(buf, "Authorization: Basic ") < 0 ||
+		git_buf_put_base64(buf, git_buf_cstr(&raw), raw.size) < 0 ||
+		git_buf_puts(buf, "\r\n") < 0)
+		goto on_error;
+
+	error = 0;
+
+on_error:
+	if (raw.size)
+		memset(raw.ptr, 0x0, raw.size);
+
+	git_buf_free(&raw);
+	return error;
+}
+
+static int gen_request(
+	git_buf *buf,
+	const char *path,
+	const char *host,
+	git_cred *cred,
+	http_authmechanism_t auth_mechanism,
+	const char *op,
+	const char *service,
+	const char *service_url,
+	ssize_t content_length)
 {
-	if (path == NULL) /* Is 'git fetch http://host.com/' valid? */
+	if (!path)
 		path = "/";
 
 	git_buf_printf(buf, "%s %s%s HTTP/1.1\r\n", op, path, service_url);
@@ -86,6 +129,13 @@ static int gen_request(git_buf *buf, const char *path, const char *host, const c
 	} else {
 		git_buf_puts(buf, "Accept: */*\r\n");
 	}
+
+	/* Apply credentials to the request */
+	if (cred && cred->credtype == GIT_CREDTYPE_USERPASS_PLAINTEXT &&
+		auth_mechanism == GIT_HTTP_AUTH_BASIC &&
+		apply_basic_credential(buf, cred) < 0)
+		return -1;
+
 	git_buf_puts(buf, "\r\n");
 
 	if (git_buf_oom(buf))
@@ -94,88 +144,157 @@ static int gen_request(git_buf *buf, const char *path, const char *host, const c
 	return 0;
 }
 
+static int parse_unauthorized_response(
+	git_vector *www_authenticate,
+	int *allowed_types,
+	http_authmechanism_t *auth_mechanism)
+{
+	unsigned i;
+	char *entry;
+
+	git_vector_foreach(www_authenticate, i, entry) {
+		if (!strncmp(entry, basic_authtype, 5) &&
+			(entry[5] == '\0' || entry[5] == ' ')) {
+			*allowed_types |= GIT_CREDTYPE_USERPASS_PLAINTEXT;
+			*auth_mechanism = GIT_HTTP_AUTH_BASIC;
+		}
+	}
+
+	return 0;
+}
+
+static int on_header_ready(http_subtransport *t)
+{
+	git_buf *name = &t->parse_header_name;
+	git_buf *value = &t->parse_header_value;
+	char *dup;
+
+	if (!t->content_type && !strcmp("Content-Type", git_buf_cstr(name))) {
+		t->content_type = git__strdup(git_buf_cstr(value));
+		GITERR_CHECK_ALLOC(t->content_type);
+	}
+	else if (!strcmp("WWW-Authenticate", git_buf_cstr(name))) {
+		dup = git__strdup(git_buf_cstr(value));
+		GITERR_CHECK_ALLOC(dup);
+		git_vector_insert(&t->www_authenticate, dup);
+	}
+
+	return 0;
+}
+
 static int on_header_field(http_parser *parser, const char *str, size_t len)
 {
 	parser_context *ctx = (parser_context *) parser->data;
 	http_subtransport *t = ctx->t;
-	git_buf *buf = &t->parse_temp;
 
-	if (t->last_cb == VALUE && t->ct_found) {
-		t->ct_finished = 1;
-		t->ct_found = 0;
-		t->content_type = git__strdup(git_buf_cstr(buf));
-		GITERR_CHECK_ALLOC(t->content_type);
-		git_buf_clear(buf);
-	}
+	/* 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;
 
-	if (t->ct_found) {
-		t->last_cb = FIELD;
-		return 0;
-	}
+	if (NONE == t->last_cb || VALUE == t->last_cb)
+		git_buf_clear(&t->parse_header_name);
 
-	if (t->last_cb != FIELD)
-		git_buf_clear(buf);
+	if (git_buf_put(&t->parse_header_name, str, len) < 0)
+		return t->parse_error = PARSE_ERROR_GENERIC;
 
-	git_buf_put(buf, str, len);
 	t->last_cb = FIELD;
-
-	return git_buf_oom(buf);
+	return 0;
 }
 
 static int on_header_value(http_parser *parser, const char *str, size_t len)
 {
 	parser_context *ctx = (parser_context *) parser->data;
 	http_subtransport *t = ctx->t;
-	git_buf *buf = &t->parse_temp;
 
-	if (t->ct_finished) {
-		t->last_cb = VALUE;
-		return 0;
-	}
+	assert(NONE != t->last_cb);
 
-	if (t->last_cb == VALUE)
-		git_buf_put(buf, str, len);
+	if (FIELD == t->last_cb)
+		git_buf_clear(&t->parse_header_value);
 
-	if (t->last_cb == FIELD && !strcmp(git_buf_cstr(buf), "Content-Type")) {
-		t->ct_found = 1;
-		git_buf_clear(buf);
-		git_buf_put(buf, str, len);
-	}
+	if (git_buf_put(&t->parse_header_value, str, len) < 0)
+		return t->parse_error = PARSE_ERROR_GENERIC;
 
 	t->last_cb = VALUE;
-
-	return git_buf_oom(buf);
+	return 0;
 }
 
 static int on_headers_complete(http_parser *parser)
 {
 	parser_context *ctx = (parser_context *) parser->data;
 	http_subtransport *t = ctx->t;
-	git_buf *buf = &t->parse_temp;
+	http_stream *s = ctx->s;
+	git_buf buf = GIT_BUF_INIT;
 
-	/* The content-type is text/plain for 404, so don't validate */
-	if (parser->status_code == 404) {
-		git_buf_clear(buf);
-		return 0;
+	/* 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;
+
+	/* Check for an authentication failure. */
+	if (parser->status_code == 401 &&
+		get_verb == s->verb &&
+		t->owner->cred_acquire_cb) {
+		int allowed_types = 0;
+
+		if (parse_unauthorized_response(&t->www_authenticate,
+			&allowed_types, &t->auth_mechanism) < 0)
+			return t->parse_error = PARSE_ERROR_GENERIC;
+
+		if (allowed_types &&
+			(!t->cred || 0 == (t->cred->credtype & allowed_types))) {
+
+			if (t->owner->cred_acquire_cb(&t->cred,
+					t->owner->url,
+					allowed_types) < 0)
+				return PARSE_ERROR_GENERIC;
+
+			assert(t->cred);
+
+			/* Successfully acquired a credential. */
+			return t->parse_error = PARSE_ERROR_REPLAY;
+		}
 	}
 
-	if (t->content_type == NULL) {
-		t->content_type = git__strdup(git_buf_cstr(buf));
-		if (t->content_type == NULL)
-			return t->parse_error = -1;
+	/* Check for a 200 HTTP status code. */
+	if (parser->status_code != 200) {
+		giterr_set(GITERR_NET,
+			"Unexpected HTTP status code: %d",
+			parser->status_code);
+		return t->parse_error = PARSE_ERROR_GENERIC;
 	}
 
-	git_buf_clear(buf);
-	git_buf_printf(buf, "application/x-git-%s-advertisement", ctx->s->service);
-	if (git_buf_oom(buf))
-		return t->parse_error = -1;
+	/* The response must contain a Content-Type header. */
+	if (!t->content_type) {
+		giterr_set(GITERR_NET, "No Content-Type header in response");
+		return t->parse_error = PARSE_ERROR_GENERIC;
+	}
 
-	if (strcmp(t->content_type, git_buf_cstr(buf))) {
-		giterr_set(GITERR_NET, "Invalid content-type: %s", t->content_type);
-		return t->parse_error = -1;
+	/* The Content-Type header must match our expectation. */
+	if (get_verb == s->verb)
+		git_buf_printf(&buf,
+			"application/x-git-%s-advertisement",
+			ctx->s->service);
+	else
+		git_buf_printf(&buf,
+			"application/x-git-%s-result",
+			ctx->s->service);
+
+	if (git_buf_oom(&buf))
+		return t->parse_error = PARSE_ERROR_GENERIC;
+
+	if (strcmp(t->content_type, git_buf_cstr(&buf))) {
+		git_buf_free(&buf);
+		giterr_set(GITERR_NET,
+			"Invalid Content-Type: %s",
+			t->content_type);
+		return t->parse_error = PARSE_ERROR_GENERIC;
 	}
 
-	git_buf_clear(buf);
+	git_buf_free(&buf);
+
 	return 0;
 }
 
@@ -186,11 +305,6 @@ static int on_message_complete(http_parser *parser)
 
 	t->parse_finished = 1;
 
-	if (parser->status_code == 404) {
-		giterr_set(GITERR_NET, "Remote error: %s", git_buf_cstr(&t->parse_temp));
-		t->parse_error = -1;
-	}
-
 	return 0;
 }
 
@@ -201,7 +315,7 @@ static int on_body_fill_buffer(http_parser *parser, const char *str, size_t len)
 
 	if (ctx->buf_size < len) {
 		giterr_set(GITERR_NET, "Can't fit data in the buffer");
-		return t->parse_error = -1;
+		return t->parse_error = PARSE_ERROR_GENERIC;
 	}
 
 	memcpy(ctx->buffer, str, len);
@@ -212,6 +326,36 @@ static int on_body_fill_buffer(http_parser *parser, const char *str, size_t len)
 	return 0;
 }
 
+static void clear_parser_state(http_subtransport *t)
+{
+	unsigned i;
+	char *entry;
+
+	http_parser_init(&t->parser, HTTP_RESPONSE);
+	gitno_buffer_setup(&t->socket,
+		&t->parse_buffer,
+		t->parse_buffer_data,
+		sizeof(t->parse_buffer_data));
+
+	t->last_cb = NONE;
+	t->parse_error = 0;
+	t->parse_finished = 0;
+
+	git_buf_free(&t->parse_header_name);
+	git_buf_init(&t->parse_header_name, 0);
+
+	git_buf_free(&t->parse_header_value);
+	git_buf_init(&t->parse_header_value, 0);
+
+	git__free(t->content_type);
+	t->content_type = NULL;
+
+	git_vector_foreach(&t->www_authenticate, i, entry)
+		git__free(entry);
+
+	git_vector_free(&t->www_authenticate);
+}
+
 static int http_stream_read(
 	git_smart_subtransport_stream *stream,
 	char *buffer,
@@ -219,17 +363,22 @@ static int http_stream_read(
 	size_t *bytes_read)
 {
 	http_stream *s = (http_stream *)stream;
-	http_subtransport *t = OWNING_SUBTRANSPORT(s);	
+	http_subtransport *t = OWNING_SUBTRANSPORT(s);
 	git_buf request = GIT_BUF_INIT;
 	parser_context ctx;
 
+replay:
 	*bytes_read = 0;
 
 	assert(t->connected);
 
 	if (!s->sent_request) {
-		if (gen_request(&request, t->path, t->host, s->verb, s->service, s->service_url, 0) < 0) {
-			giterr_set(GITERR_NET, "Failed to generate request");			
+		clear_parser_state(t);
+
+		if (gen_request(&request, t->path, t->host,
+				t->cred, t->auth_mechanism, s->verb,
+				s->service, s->service_url, 0) < 0) {
+			giterr_set(GITERR_NET, "Failed to generate request");
 			return -1;
 		}
 
@@ -239,7 +388,7 @@ static int http_stream_read(
 		}
 
 		git_buf_free(&request);
-		s->sent_request = 1;		
+		s->sent_request = 1;
 	}
 
 	t->parse_buffer.offset = 0;
@@ -250,10 +399,11 @@ static int http_stream_read(
 	if (gitno_recv(&t->parse_buffer) < 0)
 		return -1;
 
-	/* This call to http_parser_execute will result in invocations of the on_* family of
-		* callbacks. The most interesting of these is on_body_fill_buffer, which is called
-		* when data is ready to be copied into the target buffer. We need to marshal the
-		* buffer, buf_size, and bytes_read parameters to this callback. */
+	/* This call to http_parser_execute will result in invocations of the on_*
+	 * family of callbacks. The most interesting of these is
+	 * on_body_fill_buffer, which is called when data is ready to be copied
+	 * into the target buffer. We need to marshal the buffer, buf_size, and
+	 * bytes_read parameters to this callback. */
 	ctx.t = t;
 	ctx.s = s;
 	ctx.buffer = buffer;
@@ -262,11 +412,23 @@ static int http_stream_read(
 
 	/* Set the context, call the parser, then unset the context. */
 	t->parser.data = &ctx;
-	http_parser_execute(&t->parser, &t->settings, t->parse_buffer.data, t->parse_buffer.offset);
+
+	http_parser_execute(&t->parser,
+		&t->settings,
+		t->parse_buffer.data,
+		t->parse_buffer.offset);
+
 	t->parser.data = NULL;
 
+	/* If there was a handled authentication failure, then parse_error
+	 * will have signaled us that we should replay the request. */
+	if (PARSE_ERROR_REPLAY == t->parse_error) {
+		s->sent_request = 0;
+		goto replay;
+	}
+
 	if (t->parse_error < 0)
-		return t->parse_error;
+		return -1;
 
 	return 0;
 }
@@ -277,7 +439,7 @@ static int http_stream_write(
 	size_t len)
 {
 	http_stream *s = (http_stream *)stream;
-	http_subtransport *t = OWNING_SUBTRANSPORT(s);	
+	http_subtransport *t = OWNING_SUBTRANSPORT(s);
 	git_buf request = GIT_BUF_INIT;
 
 	assert(t->connected);
@@ -287,7 +449,11 @@ static int http_stream_write(
 	assert(!s->sent_request);
 
 	if (!s->sent_request) {
-		if (gen_request(&request, t->path, t->host, s->verb, s->service, s->service_url, len) < 0) {
+		clear_parser_state(t);
+
+		if (gen_request(&request, t->path, t->host,
+				t->cred, t->auth_mechanism, s->verb,
+				s->service, s->service_url, len) < 0) {
 			giterr_set(GITERR_NET, "Failed to generate request");
 			return -1;
 		}
@@ -316,9 +482,10 @@ static void http_stream_free(git_smart_subtransport_stream *stream)
 	git__free(s);
 }
 
-static int http_stream_alloc(http_subtransport *t, git_smart_subtransport_stream **stream)
+static int http_stream_alloc(http_subtransport *t,
+	git_smart_subtransport_stream **stream)
 {
-	http_stream *s;	
+	http_stream *s;
 
 	if (!stream)
 		return -1;
@@ -396,7 +563,8 @@ static int http_action(
 			t->use_ssl = 1;
 		}
 
-		if ((ret = gitno_extract_host_and_port(&t->host, &t->port, url, default_port)) < 0)
+		if ((ret = gitno_extract_host_and_port(&t->host, &t->port,
+				url, default_port)) < 0)
 			return ret;
 
 		t->path = strchr(url, '/');
@@ -412,15 +580,10 @@ static int http_action(
 
 		if (gitno_connect(&t->socket, t->host, t->port, flags) < 0)
 			return -1;
-	
-		t->parser.data = t;
-
-		http_parser_init(&t->parser, HTTP_RESPONSE);
-		gitno_buffer_setup(&t->socket, &t->parse_buffer, t->parse_buffer_data, sizeof(t->parse_buffer_data));
 
 		t->connected = 1;
 	}
-	
+
 	t->parse_finished = 0;
 	t->parse_error = 0;
 
@@ -432,7 +595,7 @@ static int http_action(
 		case GIT_SERVICE_UPLOADPACK:
 			return http_uploadpack(t, stream);
 	}
-	
+
 	*stream = NULL;
 	return -1;
 }
@@ -441,14 +604,20 @@ static void http_free(git_smart_subtransport *smart_transport)
 {
 	http_subtransport *t = (http_subtransport *) smart_transport;
 
-	git_buf_free(&t->parse_temp);
-	git__free(t->content_type);
+	clear_parser_state(t);
+
+	if (t->cred) {
+		t->cred->free(t->cred);
+		t->cred = NULL;
+	}
+
 	git__free(t->host);
 	git__free(t->port);
 	git__free(t);
 }
 
-int git_smart_subtransport_http(git_smart_subtransport **out, git_transport *owner)
+int git_smart_subtransport_http(git_smart_subtransport **out,
+	git_transport *owner)
 {
 	http_subtransport *t;
 	int flags;
@@ -459,7 +628,7 @@ int git_smart_subtransport_http(git_smart_subtransport **out, git_transport *own
 	t = (http_subtransport *)git__calloc(sizeof(http_subtransport), 1);
 	GITERR_CHECK_ALLOC(t);
 
-	t->owner = owner;
+	t->owner = (transport_smart *)owner;
 	t->parent.action = http_action;
 	t->parent.free = http_free;
 
diff --git a/src/transports/local.c b/src/transports/local.c
index 5a279ef..0a63a12 100644
--- a/src/transports/local.c
+++ b/src/transports/local.c
@@ -130,7 +130,11 @@ on_error:
  * Try to open the url as a git directory. The direction doesn't
  * matter in this case because we're calulating the heads ourselves.
  */
-static int local_connect(git_transport *transport, const char *url, int direction, int flags)
+static int local_connect(
+	git_transport *transport,
+	const char *url,
+	git_cred_acquire_cb cred_acquire_cb,
+	int direction, int flags)
 {
 	git_repository *repo;
 	int error;
@@ -138,6 +142,8 @@ static int local_connect(git_transport *transport, const char *url, int directio
 	const char *path;
 	git_buf buf = GIT_BUF_INIT;
 
+	GIT_UNUSED(cred_acquire_cb);
+
 	t->url = git__strdup(url);
 	GITERR_CHECK_ALLOC(t->url);
 	t->direction = direction;
diff --git a/src/transports/smart.c b/src/transports/smart.c
index b9c90df..8f9715a 100644
--- a/src/transports/smart.c
+++ b/src/transports/smart.c
@@ -52,7 +52,12 @@ static int git_smart__set_callbacks(
 	return 0;
 }
 
-static int git_smart__connect(git_transport *transport, const char *url, int direction, int flags)
+static int git_smart__connect(
+	git_transport *transport,
+	const char *url,
+	git_cred_acquire_cb cred_acquire_cb,
+	int direction,
+	int flags)
 {
 	transport_smart *t = (transport_smart *)transport;
 	git_smart_subtransport_stream *stream;
@@ -66,6 +71,7 @@ static int git_smart__connect(git_transport *transport, const char *url, int dir
 
 	t->direction = direction;
 	t->flags = flags;
+	t->cred_acquire_cb = cred_acquire_cb;
 
 	if (GIT_DIR_FETCH == direction)
 	{
diff --git a/src/transports/smart.h b/src/transports/smart.h
index 5784713..046bc89 100644
--- a/src/transports/smart.h
+++ b/src/transports/smart.h
@@ -99,6 +99,7 @@ typedef void (*packetsize_cb)(int received, void *payload);
 typedef struct {
 	git_transport parent;
 	char *url;
+	git_cred_acquire_cb cred_acquire_cb;
 	int direction;
 	int flags;
 	git_transport_message_cb progress_cb;
diff --git a/src/transports/winhttp.c b/src/transports/winhttp.c
index 0411a70..ef47616 100644
--- a/src/transports/winhttp.c
+++ b/src/transports/winhttp.c
@@ -30,6 +30,7 @@ static const char *upload_pack_ls_service_url = "/info/refs?service=git-upload-p
 static const char *upload_pack_service_url = "/git-upload-pack";
 static const wchar_t *get_verb = L"GET";
 static const wchar_t *post_verb = L"POST";
+static const wchar_t *basic_authtype = L"Basic";
 static const wchar_t *pragma_nocache = L"Pragma: no-cache";
 static const int no_check_cert_flags = SECURITY_FLAG_IGNORE_CERT_CN_INVALID |
 	SECURITY_FLAG_IGNORE_CERT_DATE_INVALID |
@@ -37,6 +38,10 @@ static const int no_check_cert_flags = SECURITY_FLAG_IGNORE_CERT_CN_INVALID |
 
 #define OWNING_SUBTRANSPORT(s) ((winhttp_subtransport *)(s)->parent.subtransport)
 
+typedef enum {
+	GIT_WINHTTP_AUTH_BASIC = 1,
+} winhttp_authmechanism_t;
+
 typedef struct {
 	git_smart_subtransport_stream parent;
 	const char *service;
@@ -49,16 +54,75 @@ typedef struct {
 
 typedef struct {
 	git_smart_subtransport parent;
-	git_transport *owner;
+	transport_smart *owner;
 	const char *path;
 	char *host;
 	char *port;
+	git_cred *cred;
+	int auth_mechanism;
 	HINTERNET session;
 	HINTERNET connection;
 	unsigned use_ssl : 1,
 		no_check_cert : 1;
 } winhttp_subtransport;
 
+static int apply_basic_credential(HINTERNET request, git_cred *cred)
+{
+	git_cred_userpass_plaintext *c = (git_cred_userpass_plaintext *)cred;
+	git_buf buf = GIT_BUF_INIT, raw = GIT_BUF_INIT;
+	wchar_t *wide = NULL;
+	int error = -1, wide_len;
+
+	git_buf_printf(&raw, "%s:%s", c->username, c->password);
+
+	if (git_buf_oom(&raw) ||
+		git_buf_puts(&buf, "Authorization: Basic ") < 0 ||
+		git_buf_put_base64(&buf, git_buf_cstr(&raw), raw.size) < 0)
+		goto on_error;
+
+	wide_len = MultiByteToWideChar(CP_UTF8,	MB_ERR_INVALID_CHARS,
+		git_buf_cstr(&buf),	-1, NULL, 0);
+
+	if (!wide_len) {
+		giterr_set(GITERR_OS, "Failed to measure string for wide conversion");
+		goto on_error;
+	}
+
+	wide = (wchar_t *)git__malloc(wide_len * sizeof(wchar_t));
+
+	if (!wide)
+		goto on_error;
+
+	if (!MultiByteToWideChar(CP_UTF8, MB_ERR_INVALID_CHARS,
+		git_buf_cstr(&buf), -1, wide, wide_len)) {
+		giterr_set(GITERR_OS, "Failed to convert string to wide form");
+		goto on_error;
+	}
+
+	if (!WinHttpAddRequestHeaders(request, wide, (ULONG) -1L, WINHTTP_ADDREQ_FLAG_ADD)) {
+		giterr_set(GITERR_OS, "Failed to add a header to the request");
+		goto on_error;
+	}
+
+	error = 0;
+
+on_error:
+	/* We were dealing with plaintext passwords, so clean up after ourselves a bit. */
+	if (wide)
+		memset(wide, 0x0, wide_len * sizeof(wchar_t));
+
+	if (buf.size)
+		memset(buf.ptr, 0x0, buf.size);
+
+	if (raw.size)
+		memset(raw.ptr, 0x0, raw.size);
+
+	git__free(wide);
+	git_buf_free(&buf);
+	git_buf_free(&raw);
+	return error;
+}
+
 static int winhttp_stream_connect(winhttp_stream *s)
 {
 	winhttp_subtransport *t = OWNING_SUBTRANSPORT(s);
@@ -127,6 +191,13 @@ static int winhttp_stream_connect(winhttp_stream *s)
 		}
 	}
 
+	/* If we have a credential on the subtransport, apply it to the request */
+	if (t->cred &&
+		t->cred->credtype == GIT_CREDTYPE_USERPASS_PLAINTEXT &&
+		t->auth_mechanism == GIT_WINHTTP_AUTH_BASIC &&
+		apply_basic_credential(s->request, t->cred) < 0)
+		goto on_error;
+
 	/* We've done everything up to calling WinHttpSendRequest. */
 
 	return 0;
@@ -136,6 +207,64 @@ on_error:
 	return -1;
 }
 
+static int parse_unauthorized_response(
+	HINTERNET request,
+	int *allowed_types,
+	int *auth_mechanism)
+{
+	DWORD index, buf_size, last_error;
+	int error = 0;
+	wchar_t *buf = NULL;
+
+	*allowed_types = 0;
+
+	for (index = 0; ; index++) {
+		/* Make a first call to ask for the size of the buffer to allocate
+		 * to hold the WWW-Authenticate header */
+		if (!WinHttpQueryHeaders(request, WINHTTP_QUERY_WWW_AUTHENTICATE,
+			WINHTTP_HEADER_NAME_BY_INDEX, WINHTTP_NO_OUTPUT_BUFFER,
+			&buf_size, &index))
+		{
+			last_error = GetLastError();
+
+			if (ERROR_WINHTTP_HEADER_NOT_FOUND == last_error) {
+				/* End of enumeration */
+				break;
+			} else if (ERROR_INSUFFICIENT_BUFFER == last_error) {
+				git__free(buf);
+				buf = (wchar_t *)git__malloc(buf_size);
+
+				if (!buf) {
+					error = -1;
+					break;
+				}
+			} else {
+				giterr_set(GITERR_OS, "Failed to read WWW-Authenticate header");
+				error = -1;
+				break;
+			}
+		}
+
+		/* Actually receive the data into our now-allocated buffer */
+		if (!WinHttpQueryHeaders(request, WINHTTP_QUERY_WWW_AUTHENTICATE,
+			WINHTTP_HEADER_NAME_BY_INDEX, buf,
+			&buf_size, &index)) {
+			giterr_set(GITERR_OS, "Failed to read WWW-Authenticate header");
+			error = -1;
+			break;
+		}
+
+		if (!wcsncmp(buf, basic_authtype, 5) &&
+			(buf[5] == L'\0' || buf[5] == L' ')) {
+			*allowed_types |= GIT_CREDTYPE_USERPASS_PLAINTEXT;
+			*auth_mechanism = GIT_WINHTTP_AUTH_BASIC;
+		}
+	}
+
+	git__free(buf);
+	return error;
+}
+
 static int winhttp_stream_read(
 	git_smart_subtransport_stream *stream,
 	char *buffer,
@@ -145,6 +274,7 @@ static int winhttp_stream_read(
 	winhttp_stream *s = (winhttp_stream *)stream;
 	winhttp_subtransport *t = OWNING_SUBTRANSPORT(s);
 
+replay:
 	/* Connect if necessary */
 	if (!s->request && winhttp_stream_connect(s) < 0)
 		return -1;
@@ -182,6 +312,31 @@ static int winhttp_stream_read(
 				return -1;
 		}
 
+		/* Handle authentication failures */
+		if (HTTP_STATUS_DENIED == status_code &&
+			get_verb == s->verb && t->owner->cred_acquire_cb) {
+			int allowed_types;
+
+			if (parse_unauthorized_response(s->request, &allowed_types, &t->auth_mechanism) < 0)
+				return -1;
+
+			if (allowed_types &&
+				(!t->cred || 0 == (t->cred->credtype & allowed_types))) {
+
+				if (t->owner->cred_acquire_cb(&t->cred, t->owner->url, allowed_types) < 0)
+					return -1;
+
+				assert(t->cred);
+
+				WinHttpCloseHandle(s->request);
+				s->request = NULL;
+				s->sent_request = 0;
+
+				/* Successfully acquired a credential */
+				goto replay;
+			}
+		}
+
 		if (HTTP_STATUS_OK != status_code) {
 			giterr_set(GITERR_NET, "Request failed with status code: %d", status_code);
 			return -1;
@@ -432,6 +587,11 @@ static void winhttp_free(git_smart_subtransport *smart_transport)
 	git__free(t->host);
 	git__free(t->port);
 
+	if (t->cred) {
+		t->cred->free(t->cred);
+		t->cred = NULL;
+	}
+
 	if (t->connection) {
 		WinHttpCloseHandle(t->connection);
 		t->connection = NULL;
@@ -456,7 +616,7 @@ int git_smart_subtransport_http(git_smart_subtransport **out, git_transport *own
 	t = (winhttp_subtransport *)git__calloc(sizeof(winhttp_subtransport), 1);
 	GITERR_CHECK_ALLOC(t);
 
-	t->owner = owner;
+	t->owner = (transport_smart *)owner;
 	t->parent.action = winhttp_action;
 	t->parent.free = winhttp_free;