http: simplify authentication mechanisms

Hold an individual authentication context instead of trying to maintain
all the contexts; we can select the preferred context during the initial
negotiation.

Subsequent authentication steps will re-use the chosen authentication
(until such time as it's rejected) instead of trying to manage multiple
contexts when all but one will never be used (since we can only
authenticate with a single mechanism at a time.)

Also, when we're given a 401 or 407 in the middle of challenge/response
handling, short-circuit immediately without incrementing the retry
count.  The multi-step authentication is expected, and not a "retry" and
should not be penalized as such.

This means that we don't need to keep the contexts around and ensures
that we do not unnecessarily fail for too many retries when we have
challenge/response auth on a proxy and a server and potentially
redirects in play as well.

src/transports/http.c

@@ -77,12 +77,14 @@ typedef struct {
 	git_net_url url;
 	git_stream *stream;
 
-	git_http_authtype_t server_types;
+	git_http_authtype_t authtypes;
+	git_credtype_t credtypes;
+
 	git_cred *cred;
 	unsigned url_cred_presented : 1;
 
 	git_vector auth_challenges;
-	git_vector auth_contexts;
+	git_http_auth_context *auth_context;
 } http_server;
 
 typedef struct {
@@ -125,79 +127,24 @@ typedef struct {
 	size_t *bytes_read;
 } parser_context;
 
-static bool credtype_match(git_http_auth_scheme *scheme, void *data)
-{
-	unsigned int credtype = *(unsigned int *)data;
-
-	return !!(scheme->credtypes & credtype);
-}
-
-static bool challenge_match(git_http_auth_scheme *scheme, void *data)
-{
-	const char *scheme_name = scheme->name;
-	const char *challenge = (const char *)data;
-	size_t scheme_len;
-
-	scheme_len = strlen(scheme_name);
-	return (strncasecmp(challenge, scheme_name, scheme_len) == 0 &&
-		(challenge[scheme_len] == '\0' || challenge[scheme_len] == ' '));
-}
-
-typedef struct {
-	git_http_authtype_t server_types;
-	unsigned int credtype;
-} authmatch_data;
-
-static bool auth_match(git_http_auth_scheme *scheme, void *_data)
-{
-	authmatch_data *data = (authmatch_data *)_data;
-
-	return !!(data->server_types & scheme->type) &&
-	       !!(scheme->credtypes & data->credtype);
-}
-
-static int auth_context_match(
-	git_http_auth_context **out,
-	http_server *server,
-	bool (*scheme_match)(git_http_auth_scheme *scheme, void *data),
-	void *data)
+static git_http_auth_scheme *scheme_for_challenge(const char *challenge)
 {
 	git_http_auth_scheme *scheme = NULL;
-	git_http_auth_context *context = NULL, *c;
 	size_t i;
 
-	*out = NULL;
-
 	for (i = 0; i < ARRAY_SIZE(auth_schemes); i++) {
-		if (scheme_match(&auth_schemes[i], data)) {
-			scheme = &auth_schemes[i];
-			break;
-		}
-	}
+		const char *scheme_name = auth_schemes[i].name;
+		size_t scheme_len;
 
-	if (!scheme)
-		return 0;
-
-	/* See if authentication has already started for this scheme */
-	git_vector_foreach(&server->auth_contexts, i, c) {
-		if (c->type == scheme->type) {
-			context = c;
+		scheme_len = strlen(scheme_name);
+		if (strncasecmp(challenge, scheme_name, scheme_len) == 0 &&
+		    (challenge[scheme_len] == '\0' || challenge[scheme_len] == ' ')) {
+			scheme = &auth_schemes[i];
 			break;
 		}
 	}
 
-	if (!context) {
-		if (scheme->init_context(&context, &server->url) < 0)
-			return -1;
-		else if (!context)
-			return 0;
-		else if (git_vector_insert(&server->auth_contexts, context) < 0)
-			return -1;
-	}
-
-	*out = context;
-
-	return 0;
+	return scheme;
 }
 
 static int apply_credentials(
@@ -205,43 +152,13 @@ static int apply_credentials(
 	http_server *server,
 	const char *header_name)
 {
-	git_cred *cred = server->cred;
-	git_http_auth_context *context;
-	authmatch_data data = {0};
 	git_buf token = GIT_BUF_INIT;
 	int error = 0;
 
-	if (!server->server_types)
-		goto done;
-
-	/* Get or create a context for the best scheme for this cred type */
-	if ((error = auth_context_match(&context, server,
-	    credtype_match, &cred->credtype)) < 0)
+	if (!server->auth_context)
 		goto done;
 
-	if (!context)
-		goto done;
-
-	/*
-	 * If we do have creds, find the first mechanism supported by both
-	 * the server and ourselves that supports the credential type.
-	 */
-	if (!cred)
-		goto done;
-
-	data.server_types = server->server_types;
-	data.credtype = cred->credtype;
-
-	if ((error = auth_context_match(&context, server, auth_match, &data)) < 0)
-		goto done;
-
-	if (!context) {
-		git_error_set(GIT_ERROR_NET, "no suitable mechanism found for authentication");
-		error = -1;
-		goto done;
-	}
-
-	if ((error = context->next_token(&token, context, cred)) < 0)
+	if ((error = server->auth_context->next_token(&token, server->auth_context, server->cred)) < 0)
 		goto done;
 
 	error = git_buf_printf(buf, "%s: %s\r\n", header_name, token.ptr);
@@ -313,32 +230,53 @@ static int gen_request(
 	return 0;
 }
 
-static int parse_authenticate_response(
-	http_server *server,
-	int *allowed_types)
+static int set_authentication_challenge(http_server *server)
+{
+	const char *challenge;
+
+	if (git_vector_length(&server->auth_challenges) > 1) {
+		git_error_set(GIT_ERROR_NET, "received multiple authentication challenges");
+		return -1;
+	}
+
+	challenge = git_vector_get(&server->auth_challenges, 0);
+
+	if (server->auth_context->set_challenge)
+		return server->auth_context->set_challenge(server->auth_context, challenge);
+	else
+		return 0;
+}
+
+static int set_authentication_types(http_server *server)
 {
-	git_http_auth_context *context;
+	git_http_auth_scheme *scheme;
 	char *challenge;
 	size_t i;
 
 	git_vector_foreach(&server->auth_challenges, i, challenge) {
-		if (auth_context_match(&context, server,
-		    challenge_match, challenge) < 0)
-			return -1;
-		else if (!context)
-			continue;
-
-		if (context->set_challenge &&
-			context->set_challenge(context, challenge) < 0)
-			return -1;
-
-		server->server_types |= context->type;
-		*allowed_types |= context->credtypes;
+		if ((scheme = scheme_for_challenge(challenge)) != NULL) {
+			server->authtypes |= scheme->type;
+			server->credtypes |= scheme->credtypes;
+		}
 	}
 
 	return 0;
 }
 
+static int parse_authenticate_response(http_server *server)
+{
+	/*
+	 * If we've begun authentication, give the challenge to the context.
+	 * Otherwise, set up the types to prepare credentials.
+	 */
+	if (git_vector_length(&server->auth_challenges) == 0)
+		return 0;
+	else if (server->auth_context)
+		return set_authentication_challenge(server);
+	else
+		return set_authentication_types(server);
+}
+
 static int on_header_ready(http_subtransport *t)
 {
 	git_buf *name = &t->parse_header_name;
@@ -427,6 +365,17 @@ static int on_header_value(http_parser *parser, const char *str, size_t len)
 	return 0;
 }
 
+static void free_auth_context(http_server *server)
+{
+	if (!server->auth_context)
+		return;
+
+	if (server->auth_context->free)
+		server->auth_context->free(server->auth_context);
+
+	server->auth_context = NULL;
+}
+
 GIT_INLINE(void) free_cred(git_cred **cred)
 {
 	if (*cred) {
@@ -450,6 +399,37 @@ static int apply_url_credentials(
 	return GIT_PASSTHROUGH;
 }
 
+static int init_auth(http_server *server)
+{
+	git_http_auth_scheme *s, *scheme = NULL;
+	char *c, *challenge = NULL;
+	size_t i;
+
+	git_vector_foreach(&server->auth_challenges, i, c) {
+		s = scheme_for_challenge(c);
+
+		if (s && !!(s->credtypes & server->credtypes)) {
+			scheme = s;
+			challenge = c;
+			break;
+		}
+	}
+
+	if (!scheme) {
+		git_error_set(GIT_ERROR_NET, "no authentication mechanism could be negotiated");
+		return -1;
+	}
+
+	if (scheme->init_context(&server->auth_context, &server->url) < 0)
+		return -1;
+
+	if (server->auth_context->set_challenge &&
+		server->auth_context->set_challenge(server->auth_context, challenge) < 0)
+		return -1;
+
+	return 0;
+}
+
 static int on_auth_required(
 	git_cred **creds,
 	http_parser *parser,
@@ -457,24 +437,24 @@ static int on_auth_required(
 	const char *url,
 	const char *type,
 	git_cred_acquire_cb callback,
-	void *callback_payload,
-	int allowed_types)
+	void *callback_payload)
 {
 	parser_context *ctx = (parser_context *) parser->data;
 	http_subtransport *t = ctx->t;
 	int error = 1;
 
-	if (!allowed_types) {
+	if (!server->credtypes) {
 		git_error_set(GIT_ERROR_NET, "%s requested authentication but did not negotiate mechanisms", type);
 		t->parse_error = PARSE_ERROR_GENERIC;
 		return t->parse_error;
 	}
 
+	free_auth_context(server);
 	free_cred(creds);
 
 	/* Start with URL-specified credentials, if there were any. */
 	if (!server->url_cred_presented && server->url.username && server->url.password) {
-		error = apply_url_credentials(creds, allowed_types, server->url.username, server->url.password);
+		error = apply_url_credentials(creds, server->credtypes, server->url.username, server->url.password);
 		server->url_cred_presented = 1;
 
 		if (error == GIT_PASSTHROUGH) {
@@ -484,7 +464,7 @@ static int on_auth_required(
 	}
 
 	if (error > 0 && callback) {
-		error = callback(creds, url, server->url.username, allowed_types, callback_payload);
+		error = callback(creds, url, server->url.username, server->credtypes, callback_payload);
 
 		if (error == GIT_PASSTHROUGH) {
 			/* treat GIT_PASSTHROUGH as if callback isn't set */
@@ -505,13 +485,18 @@ static int on_auth_required(
 
 	assert(*creds);
 
-	if (!((*creds)->credtype & allowed_types)) {
+	if (!((*creds)->credtype & server->credtypes)) {
 		git_error_set(GIT_ERROR_NET, "%s credential provider returned an invalid cred type", type);
 		t->parse_error = PARSE_ERROR_GENERIC;
 		return t->parse_error;
 	}
 
-	/* Successfully acquired a credential. */
+	/* Successfully acquired a credential. Start an auth context. */
+	if (init_auth(server) < 0) {
+		t->parse_error = PARSE_ERROR_GENERIC;
+		return t->parse_error;
+	}
+
 	t->parse_error = PARSE_ERROR_REPLAY;
 	return 0;
 }
@@ -522,29 +507,39 @@ static int on_headers_complete(http_parser *parser)
 	http_subtransport *t = ctx->t;
 	http_stream *s = ctx->s;
 	git_buf buf = GIT_BUF_INIT;
-	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) {
-		git_error_set(GIT_ERROR_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. */
-	if (VALUE == t->last_cb)
-		if (on_header_ready(t) < 0)
-			return t->parse_error = PARSE_ERROR_GENERIC;
+	if (t->last_cb == VALUE && 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 ||
-	    parse_authenticate_response(&t->server, &server_auth_types) < 0)
+	if (parse_authenticate_response(&t->proxy) < 0 ||
+	    parse_authenticate_response(&t->server) < 0)
 		return t->parse_error = PARSE_ERROR_GENERIC;
 
+	/* If we're in the middle of challenge/response auth, continue */
+	if (parser->status_code == 407 || parser->status_code == 401) {
+		http_server *server = parser->status_code == 407 ? &t->proxy : &t->server;
+
+		if (server->auth_context &&
+		    server->auth_context->is_complete &&
+		    !server->auth_context->is_complete(server->auth_context)) {
+			t->parse_error = PARSE_ERROR_REPLAY;
+			return 0;
+		}
+	}
+
+	/* Enforce a reasonable cap on the number of replays */
+	if (t->replay_count++ >= GIT_HTTP_REPLAY_MAX) {
+		git_error_set(GIT_ERROR_NET, "too many redirects or authentication replays");
+		return t->parse_error = PARSE_ERROR_GENERIC;
+	}
+
 	/* Check for a proxy authentication failure. */
 	if (parser->status_code == 407 && get_verb == s->verb)
 		return on_auth_required(&t->proxy.cred,
@@ -553,8 +548,7 @@ static int on_headers_complete(http_parser *parser)
 		    t->proxy_opts.url,
 		    SERVER_TYPE_PROXY,
 		    t->proxy_opts.credentials,
-		    t->proxy_opts.payload,
-			proxy_auth_types);
+		    t->proxy_opts.payload);
 
 	/* Check for an authentication failure. */
 	if (parser->status_code == 401 && get_verb == s->verb)
@@ -564,8 +558,7 @@ static int on_headers_complete(http_parser *parser)
 		    t->owner->url,
 		    SERVER_TYPE_REMOTE,
 		    t->owner->cred_acquire_cb,
-		    t->owner->cred_acquire_payload,
-		    server_auth_types);
+		    t->owner->cred_acquire_payload);
 
 	/* Check for a redirect.
 	 * Right now we only permit a redirect to the same hostname. */
@@ -840,18 +833,10 @@ 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) {
-		git_error_set(GIT_ERROR_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. */
-	if (VALUE == t->last_cb)
-		if (on_header_ready(t) < 0)
+	if (t->last_cb == VALUE && on_header_ready(t) < 0)
 			return t->parse_error = PARSE_ERROR_GENERIC;
 
 	/*
@@ -859,8 +844,24 @@ static int proxy_headers_complete(http_parser *parser)
 	 * 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)
+	if (parse_authenticate_response(&t->proxy) < 0)
+		return t->parse_error = PARSE_ERROR_GENERIC;
+
+	/* If we're in the middle of challenge/response auth, continue */
+	if (parser->status_code == 407) {
+		if (t->proxy.auth_context &&
+		    t->proxy.auth_context->is_complete &&
+		    !t->proxy.auth_context->is_complete(t->proxy.auth_context)) {
+			t->parse_error = PARSE_ERROR_REPLAY;
+			return 0;
+		}
+	}
+
+	/* Enforce a reasonable cap on the number of replays */
+	if (t->replay_count++ >= GIT_HTTP_REPLAY_MAX) {
+		git_error_set(GIT_ERROR_NET, "too many redirects or authentication replays");
 		return t->parse_error = PARSE_ERROR_GENERIC;
+	}
 
 	/* Check for a proxy authentication failure. */
 	if (parser->status_code == 407)
@@ -870,8 +871,7 @@ static int proxy_headers_complete(http_parser *parser)
 			t->proxy_opts.url,
 			SERVER_TYPE_PROXY,
 			t->proxy_opts.credentials,
-			t->proxy_opts.payload,
-			proxy_auth_types);
+			t->proxy_opts.payload);
 
 	if (parser->status_code != 200) {
 		git_error_set(GIT_ERROR_NET, "unexpected status code from proxy: %d",
@@ -1014,6 +1014,12 @@ static int http_connect(http_subtransport *t)
 		t->proxy.stream = NULL;
 	}
 
+	free_auth_context(&t->server);
+	free_auth_context(&t->proxy);
+
+	t->server.url_cred_presented = false;
+	t->proxy.url_cred_presented = false;
+
 	t->connected = 0;
 
 	if (t->proxy_opts.type == GIT_PROXY_SPECIFIED) {
@@ -1466,19 +1472,6 @@ static int http_action(
 	return -1;
 }
 
-static void free_auth_contexts(git_vector *contexts)
-{
-	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 = GIT_CONTAINER_OF(subtransport, http_subtransport, parent);
@@ -1502,8 +1495,8 @@ static int http_close(git_smart_subtransport *subtransport)
 	free_cred(&t->server.cred);
 	free_cred(&t->proxy.cred);
 
-	free_auth_contexts(&t->server.auth_contexts);
-	free_auth_contexts(&t->proxy.auth_contexts);
+	free_auth_context(&t->server);
+	free_auth_context(&t->proxy);
 
 	t->server.url_cred_presented = false;
 	t->proxy.url_cred_presented = false;
@@ -1522,9 +1515,6 @@ static void http_free(git_smart_subtransport *subtransport)
 	http_subtransport *t = GIT_CONTAINER_OF(subtransport, http_subtransport, parent);
 
 	http_close(subtransport);
-
-	git_vector_free(&t->server.auth_contexts);
-	git_vector_free(&t->proxy.auth_contexts);
 	git__free(t);
 }