Adding upstream version 1:2.3.21+dfsg1.upstream/1%2.3.21+dfsg1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

11 files changed, 3270 insertions, 0 deletions

diff --git a/src/lib-imap-urlauth/Makefile.am b/src/lib-imap-urlauth/Makefile.am
new file mode 100644
index 0000000..6734b72
--- /dev/null
+++ b/src/lib-imap-urlauth/Makefile.am
@@ -0,0 +1,29 @@
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diff --git a/src/lib-imap-urlauth/Makefile.in b/src/lib-imap-urlauth/Makefile.in
new file mode 100644
index 0000000..9ff6efa
--- /dev/null
+++ b/src/lib-imap-urlauth/Makefile.in
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+	imap-urlauth-backend.c \
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+
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+	-rm -f ./$(DEPDIR)/imap-urlauth-connection.Plo
+	-rm -f ./$(DEPDIR)/imap-urlauth-fetch.Plo
+	-rm -f ./$(DEPDIR)/imap-urlauth.Plo
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diff --git a/src/lib-imap-urlauth/imap-urlauth-backend.c b/src/lib-imap-urlauth/imap-urlauth-backend.c
new file mode 100644
index 0000000..de2b9c9
--- /dev/null
+++ b/src/lib-imap-urlauth/imap-urlauth-backend.c
@@ -0,0 +1,174 @@
+/* Copyright (c) 2013-2018 Dovecot authors, see the included COPYING file */
+
+#include "lib.h"
+#include "buffer.h"
+#include "hex-binary.h"
+#include "randgen.h"
+#include "mail-user.h"
+#include "mail-storage.h"
+#include "mailbox-list-iter.h"
+#include "imap-urlauth-private.h"
+#include "imap-urlauth-backend.h"
+
+#define IMAP_URLAUTH_KEY MAILBOX_ATTRIBUTE_PREFIX_DOVECOT"imap-urlauth"
+
+static int
+imap_urlauth_backend_trans_set_mailbox_key(struct mailbox *box,
+					   unsigned char mailbox_key_r[IMAP_URLAUTH_KEY_LEN],
+					   const char **client_error_r,
+					   enum mail_error *error_code_r)
+{
+	struct mail_attribute_value urlauth_key;
+	const char *mailbox_key_hex = NULL;
+	int ret;
+
+	if (mailbox_open(box) < 0) {
+		*client_error_r = mailbox_get_last_error(box, error_code_r);
+		return -1;
+	}
+
+	struct mailbox_transaction_context *t =
+		mailbox_transaction_begin(box,
+				MAILBOX_TRANSACTION_FLAG_EXTERNAL,
+				__func__);
+
+	/* create new key */
+	random_fill(mailbox_key_r, IMAP_URLAUTH_KEY_LEN);
+	mailbox_key_hex = binary_to_hex(mailbox_key_r,
+					IMAP_URLAUTH_KEY_LEN);
+	i_zero(&urlauth_key);
+	urlauth_key.value = mailbox_key_hex;
+	ret = mailbox_attribute_set(t, MAIL_ATTRIBUTE_TYPE_PRIVATE,
+				    IMAP_URLAUTH_KEY, &urlauth_key);
+
+	if (mailbox_transaction_commit(&t) < 0) {
+		*client_error_r = mailbox_get_last_error(box, error_code_r);
+		ret = -1;
+	}
+
+	return ret;
+}
+
+static int
+imap_urlauth_backend_trans_get_mailbox_key(struct mailbox *box,
+					   bool create,
+					   unsigned char mailbox_key_r[IMAP_URLAUTH_KEY_LEN],
+					   const char **client_error_r,
+					   enum mail_error *error_code_r)
+{
+	struct mail_user *user = mail_storage_get_user(mailbox_get_storage(box));
+	struct mail_attribute_value urlauth_key;
+	const char *mailbox_key_hex = NULL;
+	buffer_t key_buf;
+	int ret;
+
+	*client_error_r = "Internal server error";
+	*error_code_r = MAIL_ERROR_TEMP;
+
+	ret = mailbox_attribute_get(box, MAIL_ATTRIBUTE_TYPE_PRIVATE,
+				    IMAP_URLAUTH_KEY, &urlauth_key);
+	if (ret < 0)
+		return -1;
+
+	e_debug(user->event, "imap-urlauth: %skey found for mailbox %s",
+		(ret > 0 ? "" : "no "), mailbox_get_vname(box));
+
+	if (ret == 0) {
+		if (!create)
+			return 0;
+
+		ret = imap_urlauth_backend_trans_set_mailbox_key(box,
+								 mailbox_key_r,
+								 client_error_r,
+								 error_code_r);
+
+		if (ret < 0)
+			return -1;
+		e_debug(user->event, "imap-urlauth: created key for mailbox %s",
+			mailbox_get_vname(box));
+	} else {
+		/* read existing key */
+		buffer_create_from_data(&key_buf, mailbox_key_r,
+					IMAP_URLAUTH_KEY_LEN);
+		mailbox_key_hex = urlauth_key.value;
+		if (strlen(mailbox_key_hex) != 2*IMAP_URLAUTH_KEY_LEN ||
+		    hex_to_binary(mailbox_key_hex, &key_buf) < 0 ||
+		    key_buf.used != IMAP_URLAUTH_KEY_LEN) {
+			i_error("imap-urlauth: key found for mailbox %s is invalid",
+				mailbox_get_vname(box));
+			return -1;
+		}
+	}
+	return 1;
+}
+
+int imap_urlauth_backend_get_mailbox_key(struct mailbox *box, bool create,
+					 unsigned char mailbox_key_r[IMAP_URLAUTH_KEY_LEN],
+					 const char **client_error_r,
+					 enum mail_error *error_code_r)
+{
+	int ret;
+
+	ret = imap_urlauth_backend_trans_get_mailbox_key(box, create,
+							 mailbox_key_r,
+							 client_error_r,
+							 error_code_r);
+	return ret;
+}
+
+int imap_urlauth_backend_reset_mailbox_key(struct mailbox *box)
+{
+	struct mailbox_transaction_context *t;
+	int ret;
+
+	t = mailbox_transaction_begin(box, MAILBOX_TRANSACTION_FLAG_EXTERNAL,
+				      __func__);
+	ret = mailbox_attribute_unset(t, MAIL_ATTRIBUTE_TYPE_PRIVATE,
+				      IMAP_URLAUTH_KEY);
+	if (mailbox_transaction_commit(&t) < 0)
+		ret = -1;
+	return ret;
+}
+
+static int imap_urlauth_backend_mailbox_reset_key(struct mailbox *box)
+{
+	const char *errstr;
+	enum mail_error error;
+
+	if (mailbox_open(box) < 0) {
+		errstr = mailbox_get_last_internal_error(box, &error);
+		if (error == MAIL_ERROR_NOTFOUND || error == MAIL_ERROR_PERM)
+			return 0;
+		i_error("urlauth key reset: Couldn't open mailbox %s: %s",
+			mailbox_get_vname(box), errstr);
+		return -1;
+	}
+	return imap_urlauth_backend_reset_mailbox_key(box);
+}
+
+int imap_urlauth_backend_reset_all_keys(struct mail_user *user)
+{ 
+	const char *const patterns[] = { "*", NULL };
+	struct mailbox_list_iterate_context *iter;
+	const struct mailbox_info *info;
+	struct mailbox *box;
+	int ret = 0;
+
+	iter = mailbox_list_iter_init_namespaces(user->namespaces, patterns,
+						 MAIL_NAMESPACE_TYPE_MASK_ALL,
+						 MAILBOX_LIST_ITER_NO_AUTO_BOXES |
+						 MAILBOX_LIST_ITER_SKIP_ALIASES |
+						 MAILBOX_LIST_ITER_RETURN_NO_FLAGS);
+	while ((info = mailbox_list_iter_next(iter)) != NULL) {
+		box = mailbox_alloc(info->ns->list, info->vname, 0);
+		if (imap_urlauth_backend_mailbox_reset_key(box) < 0)
+			ret = -1;
+		mailbox_free(&box);
+	}
+	if (mailbox_list_iter_deinit(&iter) < 0) {
+		i_error("urlauth key reset: Couldn't iterate mailboxes: %s",
+			mailbox_list_get_last_internal_error(user->namespaces->list, NULL));
+		ret = -1;
+	}
+	return ret;
+}
diff --git a/src/lib-imap-urlauth/imap-urlauth-backend.h b/src/lib-imap-urlauth/imap-urlauth-backend.h
new file mode 100644
index 0000000..b76ecc5
--- /dev/null
+++ b/src/lib-imap-urlauth/imap-urlauth-backend.h
@@ -0,0 +1,16 @@
+#ifndef IMAP_URLAUTH_BACKEND_H
+#define IMAP_URLAUTH_BACKEND_H
+
+#define IMAP_URLAUTH_KEY_LEN 64
+
+struct imap_urlauth_backend;
+
+int imap_urlauth_backend_get_mailbox_key(struct mailbox *box, bool create,
+					 unsigned char mailbox_key_r[IMAP_URLAUTH_KEY_LEN],
+					 const char **client_error_r,
+					 enum mail_error *error_code_r);
+int imap_urlauth_backend_reset_mailbox_key(struct mailbox *box);
+int imap_urlauth_backend_reset_all_keys(struct mail_user *user);
+
+#endif
+
diff --git a/src/lib-imap-urlauth/imap-urlauth-connection.c b/src/lib-imap-urlauth/imap-urlauth-connection.c
new file mode 100644
index 0000000..5fce6f7
--- /dev/null
+++ b/src/lib-imap-urlauth/imap-urlauth-connection.c
@@ -0,0 +1,1027 @@
+/* Copyright (c) 2013-2018 Dovecot authors, see the included COPYING file */
+
+#include "lib.h"
+#include "llist.h"
+#include "str.h"
+#include "str-sanitize.h"
+#include "strescape.h"
+#include "ioloop.h"
+#include "safe-mkstemp.h"
+#include "hostpid.h"
+#include "net.h"
+#include "istream.h"
+#include "ostream.h"
+#include "write-full.h"
+#include "array.h"
+#include "aqueue.h"
+#include "mail-user.h"
+#include "imap-urlauth-fetch.h"
+
+#include "imap-urlauth-connection.h"
+
+enum imap_urlauth_state {
+	IMAP_URLAUTH_STATE_DISCONNECTED = 0,
+	IMAP_URLAUTH_STATE_AUTHENTICATING,
+	IMAP_URLAUTH_STATE_AUTHENTICATED,
+	IMAP_URLAUTH_STATE_SELECTING_TARGET,
+	IMAP_URLAUTH_STATE_UNSELECTING_TARGET,
+	IMAP_URLAUTH_STATE_READY,
+	IMAP_URLAUTH_STATE_REQUEST_PENDING,
+	IMAP_URLAUTH_STATE_REQUEST_WAIT,
+};
+
+struct imap_urlauth_request {
+	struct imap_urlauth_target *target;
+	struct imap_urlauth_request *prev, *next;
+	
+	char *url;
+	enum imap_urlauth_fetch_flags flags;
+
+	char *bodypartstruct;
+
+	imap_urlauth_request_callback_t *callback;
+	void *context;
+
+	bool binary_has_nuls;
+};
+
+struct imap_urlauth_target {
+	struct imap_urlauth_target *prev, *next;
+
+	char *userid;
+
+	struct imap_urlauth_request *requests_head, *requests_tail;
+};
+
+struct imap_urlauth_connection {
+	int refcount;
+
+	char *path, *service, *session_id;
+	struct mail_user *user;
+
+	int fd;
+	struct istream *input;
+	struct ostream *output;
+	struct io *io;
+
+	struct timeout *to_reconnect, *to_idle, *to_response;
+	time_t last_reconnect;
+	unsigned int reconnect_attempts;
+	unsigned int idle_timeout_msecs;
+
+	char *literal_temp_path;
+	int literal_fd;
+	buffer_t *literal_buf;
+	uoff_t literal_size, literal_bytes_left;
+
+	enum imap_urlauth_state state;
+
+	/* userid => target struct */
+	struct imap_urlauth_target *targets_head, *targets_tail;
+
+	bool reading_literal:1;
+};
+
+#define IMAP_URLAUTH_RECONNECT_MIN_SECS 2
+#define IMAP_URLAUTH_RECONNECT_MAX_ATTEMPTS 3
+
+#define IMAP_URLAUTH_RESPONSE_TIMEOUT_MSECS 2*60*1000
+
+#define IMAP_URLAUTH_HANDSHAKE "VERSION\timap-urlauth\t2\t0\n"
+
+#define IMAP_URLAUTH_MAX_INLINE_LITERAL_SIZE (1024*32)
+
+static void imap_urlauth_connection_disconnect
+	(struct imap_urlauth_connection *conn, const char *reason);
+static void imap_urlauth_connection_abort
+	(struct imap_urlauth_connection *conn, const char *reason);
+static void imap_urlauth_connection_reconnect
+	(struct imap_urlauth_connection *conn);
+static void imap_urlauth_connection_idle_disconnect
+	(struct imap_urlauth_connection *conn);
+static void imap_urlauth_connection_timeout_abort
+	(struct imap_urlauth_connection *conn);
+static void imap_urlauth_connection_fail
+	(struct imap_urlauth_connection *conn);
+
+struct imap_urlauth_connection *
+imap_urlauth_connection_init(const char *path, const char *service,
+			     struct mail_user *user, const char *session_id,
+			     unsigned int idle_timeout_msecs)
+{
+	struct imap_urlauth_connection *conn;
+
+	conn = i_new(struct imap_urlauth_connection, 1);
+	conn->refcount = 1;
+	conn->service = i_strdup(service);
+	conn->path = i_strdup(path);
+	if (session_id != NULL)
+		conn->session_id = i_strdup(session_id);
+	conn->user = user;
+	conn->fd = -1;
+	conn->literal_fd = -1;
+	conn->idle_timeout_msecs = idle_timeout_msecs;
+	return conn;
+}
+
+void imap_urlauth_connection_deinit(struct imap_urlauth_connection **_conn)
+{
+	struct imap_urlauth_connection *conn = *_conn;
+
+	*_conn = NULL;
+
+	imap_urlauth_connection_abort(conn, NULL);
+
+	i_free(conn->path);
+	i_free(conn->service);
+	if (conn->session_id != NULL)
+		i_free(conn->session_id);
+
+	i_assert(conn->to_idle == NULL);
+	i_assert(conn->to_reconnect == NULL);
+	i_assert(conn->to_response == NULL);
+
+	i_free(conn);
+}
+
+static void
+imap_urlauth_stop_response_timeout(struct imap_urlauth_connection *conn)
+{
+	timeout_remove(&conn->to_response);
+}
+
+static void
+imap_urlauth_start_response_timeout(struct imap_urlauth_connection *conn)
+{
+	imap_urlauth_stop_response_timeout(conn);
+	conn->to_response = timeout_add(IMAP_URLAUTH_RESPONSE_TIMEOUT_MSECS,
+		imap_urlauth_connection_timeout_abort, conn);
+}
+
+static struct imap_urlauth_target *
+imap_urlauth_connection_get_target(struct imap_urlauth_connection *conn,
+				   const char *target_user)
+{
+	struct imap_urlauth_target *target = conn->targets_head;
+
+	while (target != NULL) {
+		if (strcmp(target->userid, target_user) == 0)
+			return target;
+		target = target->next;
+	}
+
+	target = i_new(struct imap_urlauth_target, 1);
+	target->userid = i_strdup(target_user);
+	DLLIST2_APPEND(&conn->targets_head, &conn->targets_tail, target);
+	return target;
+}
+
+static void
+imap_urlauth_target_free(struct imap_urlauth_connection *conn,
+			 struct imap_urlauth_target *target)
+{
+	DLLIST2_REMOVE(&conn->targets_head, &conn->targets_tail, target);
+	i_free(target->userid);
+	i_free(target);
+}
+
+static void
+imap_urlauth_connection_select_target(struct imap_urlauth_connection *conn)
+{
+	struct imap_urlauth_target *target = conn->targets_head;
+	const char *cmd;
+
+	if (target == NULL || conn->state != IMAP_URLAUTH_STATE_AUTHENTICATED)
+		return;
+
+	e_debug(conn->user->event,
+		"imap-urlauth: Selecting target user `%s'", target->userid);
+
+	conn->state = IMAP_URLAUTH_STATE_SELECTING_TARGET;
+	cmd = t_strdup_printf("USER\t%s\n", str_tabescape(target->userid));
+	if (o_stream_send_str(conn->output, cmd) < 0) {
+		i_warning("Error sending USER request to imap-urlauth server: %m");
+		imap_urlauth_connection_fail(conn);
+	}
+
+	imap_urlauth_start_response_timeout(conn);
+}
+
+static void
+imap_urlauth_connection_send_request(struct imap_urlauth_connection *conn)
+{
+	struct imap_urlauth_request *urlreq;
+	string_t *cmd;
+
+	if (conn->targets_head == NULL ||
+	    (conn->targets_head->requests_head == NULL &&
+	     conn->targets_head->next == NULL &&
+	     conn->state == IMAP_URLAUTH_STATE_READY)) {
+		e_debug(conn->user->event,
+			"imap-urlauth: No more requests pending; scheduling disconnect");
+		timeout_remove(&conn->to_idle);
+		if (conn->idle_timeout_msecs > 0) {
+			conn->to_idle =	timeout_add(conn->idle_timeout_msecs,
+				imap_urlauth_connection_idle_disconnect, conn);
+		}
+		return;
+	}
+
+	if (conn->state == IMAP_URLAUTH_STATE_AUTHENTICATED) {
+		imap_urlauth_connection_select_target(conn);
+		return;
+	}
+
+	if (conn->state != IMAP_URLAUTH_STATE_READY)
+		return;
+
+	urlreq = conn->targets_head->requests_head;
+	if (urlreq == NULL) {
+		if (conn->targets_head->next == NULL)
+			return;
+		
+		conn->state = IMAP_URLAUTH_STATE_UNSELECTING_TARGET;
+		imap_urlauth_target_free(conn, conn->targets_head);
+
+		if (o_stream_send_str(conn->output, "END\n") < 0) {
+			i_warning("Error sending END request to imap-urlauth server: %m");
+			imap_urlauth_connection_fail(conn);
+		}
+		imap_urlauth_start_response_timeout(conn);
+		return;
+	}	
+
+	e_debug(conn->user->event,
+		"imap-urlauth: Fetching URL `%s'", urlreq->url);
+
+	cmd = t_str_new(128);
+	str_append(cmd, "URL\t");
+	str_append_tabescaped(cmd, urlreq->url);
+	if ((urlreq->flags & IMAP_URLAUTH_FETCH_FLAG_BODYPARTSTRUCTURE) != 0)
+		str_append(cmd, "\tbpstruct");
+	if ((urlreq->flags & IMAP_URLAUTH_FETCH_FLAG_BINARY) != 0)
+		str_append(cmd, "\tbinary");
+	else if ((urlreq->flags & IMAP_URLAUTH_FETCH_FLAG_BODY) != 0)
+		str_append(cmd, "\tbody");
+	str_append_c(cmd, '\n');
+
+	conn->state = IMAP_URLAUTH_STATE_REQUEST_PENDING;
+	if (o_stream_send(conn->output, str_data(cmd), str_len(cmd)) < 0) {
+		i_warning("Error sending URL request to imap-urlauth server: %m");
+		imap_urlauth_connection_fail(conn);
+	}
+
+	imap_urlauth_start_response_timeout(conn);
+}
+
+struct imap_urlauth_request *
+imap_urlauth_request_new(struct imap_urlauth_connection *conn,
+			 const char *target_user, const char *url,
+			 enum imap_urlauth_fetch_flags flags,
+			 imap_urlauth_request_callback_t *callback,
+			 void *context)
+{
+	struct imap_urlauth_request *urlreq;
+	struct imap_urlauth_target *target;
+
+	target = imap_urlauth_connection_get_target(conn, target_user);
+	
+	urlreq = i_new(struct imap_urlauth_request, 1);
+	urlreq->url = i_strdup(url);
+	urlreq->flags = flags;
+	urlreq->target = target;
+	urlreq->callback = callback;
+	urlreq->context = context;
+
+	DLLIST2_APPEND(&target->requests_head, &target->requests_tail, urlreq);
+
+	timeout_remove(&conn->to_idle);
+	
+	e_debug(conn->user->event,
+		"imap-urlauth: Added request for URL `%s' from user `%s'",
+		url, target_user);
+
+	imap_urlauth_connection_send_request(conn);
+	return urlreq;
+}
+
+static void imap_urlauth_request_free(struct imap_urlauth_request *urlreq)
+{
+	struct imap_urlauth_target *target = urlreq->target;
+
+	DLLIST2_REMOVE(&target->requests_head, &target->requests_tail, urlreq);
+	i_free(urlreq->url);
+	i_free(urlreq->bodypartstruct);
+	i_free(urlreq);
+}
+
+static void imap_urlauth_request_drop(struct imap_urlauth_connection *conn,
+				struct imap_urlauth_request *urlreq)
+{
+	if ((conn->state == IMAP_URLAUTH_STATE_REQUEST_PENDING ||
+			conn->state == IMAP_URLAUTH_STATE_REQUEST_WAIT) &&
+	    conn->targets_head != NULL &&
+	    conn->targets_head->requests_head == urlreq) {
+		/* cannot just drop pending request without breaking
+		   protocol state */
+		return;
+	}
+	imap_urlauth_request_free(urlreq);
+
+}
+
+void imap_urlauth_request_abort(struct imap_urlauth_connection *conn,
+				struct imap_urlauth_request *urlreq)
+{
+	imap_urlauth_request_callback_t *callback;
+
+	callback = urlreq->callback;
+	urlreq->callback = NULL;
+	if (callback != NULL) {
+		T_BEGIN {
+			callback(NULL, urlreq->context);
+		} T_END;
+	}
+
+	imap_urlauth_request_drop(conn, urlreq);
+}
+
+static void
+imap_urlauth_request_fail(struct imap_urlauth_connection *conn,
+			  struct imap_urlauth_request *urlreq,
+			  const char *error)
+{
+	struct imap_urlauth_fetch_reply reply;
+	imap_urlauth_request_callback_t *callback;
+	int ret = 1;
+
+	callback = urlreq->callback;
+	urlreq->callback = NULL;
+	if (callback != NULL) {
+		i_zero(&reply);
+		reply.url = urlreq->url;
+		reply.flags = urlreq->flags;
+		reply.succeeded = FALSE;
+		reply.error = error;
+
+		T_BEGIN {
+			ret = callback(&reply, urlreq->context);
+		} T_END;
+	}
+
+	void *urlreq_context = urlreq->context;
+	imap_urlauth_request_drop(conn, urlreq);
+
+	if (ret < 0) {
+		/* Drop any related requests upon error */
+		imap_urlauth_request_abort_by_context(conn, urlreq_context);
+	}
+
+	if (ret != 0)
+		imap_urlauth_connection_continue(conn);
+}
+
+static void
+imap_urlauth_target_abort(struct imap_urlauth_connection *conn,
+			  struct imap_urlauth_target *target)
+{
+	struct imap_urlauth_request *urlreq, *next;
+
+	urlreq = target->requests_head;
+	while (urlreq != NULL) {
+		next = urlreq->next;
+		imap_urlauth_request_abort(conn, urlreq);
+		urlreq = next;
+	}
+
+	imap_urlauth_target_free(conn, target);
+}
+
+static void
+imap_urlauth_target_fail(struct imap_urlauth_connection *conn,
+			 struct imap_urlauth_target *target, const char *error)
+{
+	struct imap_urlauth_request *urlreq, *next;
+
+	urlreq = target->requests_head;
+	while (urlreq != NULL) {
+		next = urlreq->next;
+		imap_urlauth_request_fail(conn, urlreq, error);
+		urlreq = next;
+	}
+
+	imap_urlauth_target_free(conn, target);
+}
+
+static void
+imap_urlauth_target_abort_by_context(struct imap_urlauth_connection *conn,
+				     struct imap_urlauth_target *target,
+				     void *context)
+{
+	struct imap_urlauth_request *urlreq, *next;
+
+	/* abort all matching requests */
+	urlreq = target->requests_head;
+	while (urlreq != NULL) {
+		next = urlreq->next;
+		if (urlreq->context == context)
+			imap_urlauth_request_abort(conn, urlreq);
+		urlreq = next;
+	}
+
+	if (target->requests_head == NULL)
+		imap_urlauth_target_free(conn, target);
+}
+
+static void
+imap_urlauth_connection_abort(struct imap_urlauth_connection *conn,
+			      const char *reason)
+{
+	struct imap_urlauth_target *target, *next;
+	
+	if (reason == NULL)
+		reason = "Aborting due to error";
+	imap_urlauth_connection_disconnect(conn, reason);
+
+	/* abort all requests */
+	target = conn->targets_head;
+	while (target != NULL) {
+		next = target->next;
+		imap_urlauth_target_abort(conn, target);
+		target = next;
+	}
+}
+
+void imap_urlauth_request_abort_by_context(struct imap_urlauth_connection *conn,
+					   void *context)
+{
+	struct imap_urlauth_target *target, *next;
+
+	/* abort all matching requests */
+	target = conn->targets_head;
+	while (target != NULL) {
+		next = target->next;
+		imap_urlauth_target_abort_by_context(conn, target, context);
+		target = next;
+	}
+}
+
+static void imap_urlauth_connection_fail(struct imap_urlauth_connection *conn)
+{
+	if (conn->reconnect_attempts > IMAP_URLAUTH_RECONNECT_MAX_ATTEMPTS) {
+		imap_urlauth_connection_abort(conn,
+			"Connection failed and connection attempts exhausted");
+	} else {
+		imap_urlauth_connection_reconnect(conn);
+	}
+}
+
+static int
+imap_urlauth_connection_create_temp_fd(struct imap_urlauth_connection *conn,
+				       const char **path_r)
+{
+	string_t *path;
+	int fd;
+
+	path = t_str_new(128);
+	mail_user_set_get_temp_prefix(path, conn->user->set);
+	fd = safe_mkstemp(path, 0600, (uid_t)-1, (gid_t)-1);
+	if (fd == -1) {
+		i_error("safe_mkstemp(%s) failed: %m", str_c(path));
+		return -1;
+	}
+
+	/* we just want the fd, unlink it */
+	if (i_unlink(str_c(path)) < 0) {
+		/* shouldn't happen.. */
+		i_close_fd(&fd);
+		return -1;
+	}
+
+	*path_r = str_c(path);
+	return fd;
+}
+
+static int
+imap_urlauth_connection_read_literal_init(struct imap_urlauth_connection *conn,
+					  uoff_t size)
+{
+	const char *path;
+
+	i_assert(conn->literal_fd == -1 && conn->literal_buf == NULL);
+
+	if (size <= IMAP_URLAUTH_MAX_INLINE_LITERAL_SIZE) {
+		/* read the literal directly */
+		if (size > 0) {
+			conn->literal_buf =
+				buffer_create_dynamic(default_pool, size);
+		}
+	} else {
+		/* read it into a file */
+		conn->literal_fd =
+			imap_urlauth_connection_create_temp_fd(conn, &path);
+		if (conn->literal_fd == -1)
+			return -1;
+		conn->literal_temp_path = i_strdup(path);
+	}
+
+	conn->literal_size = size;
+	conn->literal_bytes_left = size;
+	conn->reading_literal = TRUE;
+	return 1;
+}
+
+void imap_urlauth_connection_continue(struct imap_urlauth_connection *conn)
+{
+	i_assert(conn->targets_head != NULL);
+	i_assert(conn->targets_head->requests_head != NULL);
+
+	if (conn->state != IMAP_URLAUTH_STATE_REQUEST_WAIT)
+		return;
+
+	conn->state = IMAP_URLAUTH_STATE_READY;
+	imap_urlauth_request_free(conn->targets_head->requests_head);
+
+	imap_urlauth_connection_send_request(conn);
+}
+
+static int
+imap_urlauth_connection_read_literal_data(struct imap_urlauth_connection *conn)
+{
+	const unsigned char *data;
+	size_t size;
+
+	/* read data */
+	data = i_stream_get_data(conn->input, &size);
+	if (size > conn->literal_bytes_left)
+		size = conn->literal_bytes_left;
+
+	/* write to buffer or file */
+	if (size > 0) {
+		if (conn->literal_fd >= 0) {
+			if (write_full(conn->literal_fd, data, size) < 0) {
+				i_error("imap-urlauth: write(%s) failed: %m",
+					conn->literal_temp_path);
+				return -1;
+			}
+		} else {
+			i_assert(conn->literal_buf != NULL);
+			buffer_append(conn->literal_buf, data, size);
+		}
+		i_stream_skip(conn->input, size);
+		conn->literal_bytes_left -= size;
+	}
+
+	/* exit if not finished */
+	if (conn->literal_bytes_left > 0)
+		return 0;
+
+	/* read LF guard */
+	data = i_stream_get_data(conn->input, &size);
+	if (size < 1)
+		return 0;
+
+	/* check LF guard */
+	if (data[0] != '\n') {
+		i_error("imap-urlauth: no LF at end of literal (found 0x%x)",
+			data[0]);
+		return -1;
+	}
+	i_stream_skip(conn->input, 1);
+	return 1;
+}
+
+static void literal_stream_destroy(buffer_t *buffer)
+{
+	buffer_free(&buffer);
+}
+
+static int
+imap_urlauth_fetch_reply_set_literal_stream(struct imap_urlauth_connection *conn,
+					    struct imap_urlauth_fetch_reply *reply)
+{
+	const unsigned char *data;
+	size_t size;
+	uoff_t fd_size;
+
+	if (conn->literal_fd != -1) {
+		reply->input = i_stream_create_fd_autoclose(&conn->literal_fd,
+							    SIZE_MAX);
+		if (i_stream_get_size(reply->input, TRUE, &fd_size) < 1 ||
+		    fd_size != conn->literal_size) {
+			i_stream_unref(&reply->input);
+			i_error("imap-urlauth: Failed to obtain proper size from literal stream");
+			imap_urlauth_connection_abort(conn,
+				"Failed during literal transfer");
+			return -1;
+		}
+	} else {
+		data = buffer_get_data(conn->literal_buf, &size);
+		i_assert(size == conn->literal_size);
+		reply->input = i_stream_create_from_data(data, size);
+		i_stream_add_destroy_callback(reply->input,
+					      literal_stream_destroy,
+					      conn->literal_buf);
+	}
+	reply->size = conn->literal_size;
+	return 0;
+}
+
+static int
+imap_urlauth_connection_read_literal(struct imap_urlauth_connection *conn)
+{
+	struct imap_urlauth_request *urlreq = conn->targets_head->requests_head;
+	struct imap_urlauth_fetch_reply reply;
+	imap_urlauth_request_callback_t *callback;
+	int ret;
+
+	i_assert(conn->reading_literal);
+	i_assert(urlreq != NULL);
+
+	if (conn->literal_size > 0) {
+		ret = imap_urlauth_connection_read_literal_data(conn);
+		if (ret <= 0)
+			return ret;
+	}
+	i_assert(conn->literal_bytes_left == 0);
+
+	/* reply */
+	i_zero(&reply);
+	reply.url = urlreq->url;
+	reply.flags = urlreq->flags;
+	reply.bodypartstruct = urlreq->bodypartstruct;
+	reply.binary_has_nuls = urlreq->binary_has_nuls ? 1 : 0;
+
+	if (conn->literal_size > 0) {
+		if (imap_urlauth_fetch_reply_set_literal_stream(conn, &reply) < 0)
+			return -1;
+	}
+	reply.succeeded = TRUE;
+
+	ret = 1;
+	callback = urlreq->callback;
+	urlreq->callback = NULL;
+	if (callback != NULL) T_BEGIN {
+		ret = callback(&reply, urlreq->context);
+	} T_END;
+
+	if (reply.input != NULL)
+		i_stream_unref(&reply.input);
+
+	if (ret < 0) {
+		/* Drop any related requests upon error */
+		imap_urlauth_request_abort_by_context(conn, urlreq->context);
+	}
+
+	conn->state = IMAP_URLAUTH_STATE_REQUEST_WAIT;
+	if (ret != 0)
+		imap_urlauth_connection_continue(conn);
+
+	/* finished */
+	i_free_and_null(conn->literal_temp_path);
+	conn->literal_fd = -1;
+	conn->literal_buf = NULL;
+	conn->reading_literal = FALSE;
+	return 1;
+}
+
+static int imap_urlauth_input_pending(struct imap_urlauth_connection *conn)
+{
+	struct imap_urlauth_request *urlreq;
+	const char *response, *const *args, *bpstruct = NULL;
+	uoff_t literal_size;
+
+	i_assert(conn->targets_head != NULL);
+	i_assert(conn->targets_head->requests_head != NULL);
+	urlreq = conn->targets_head->requests_head;
+
+	if (conn->reading_literal) {
+		/* Read pending literal; may callback */
+		return imap_urlauth_connection_read_literal(conn);
+	}
+
+	/* "OK"[<metadata-items>]"\t"<literal-size>"\n" or
+	   "NO"["\terror="<error>]"\n" */
+	if ((response = i_stream_next_line(conn->input)) == NULL)
+		return 0;
+	imap_urlauth_stop_response_timeout(conn);
+
+	args = t_strsplit_tabescaped(response);
+	if (args[0] == NULL) {
+		i_error("imap-urlauth: Empty URL response: %s",
+			str_sanitize(response, 80));
+		return -1;
+	}
+
+	if (strcmp(args[0], "OK") != 0 || args[1] == NULL) {
+		if (strcmp(args[0], "NO") == 0) {
+			const char *param = args[1], *error = NULL;
+
+			if (param != NULL &&
+			    strncasecmp(param, "error=", 6) == 0 &&
+			    param[6] != '\0') {
+				error = param+6;
+			}
+			conn->state = IMAP_URLAUTH_STATE_REQUEST_WAIT;
+			imap_urlauth_request_fail(conn,
+				conn->targets_head->requests_head, error);
+			return 1;
+		}
+		i_error("imap-urlauth: Unexpected URL response: %s",
+			str_sanitize(response, 80));
+		return -1;
+	}
+
+	/* read metadata */
+	args++;
+	for (; args[1] != NULL; args++) {
+		const char *param = args[0];
+
+		if (strcasecmp(param, "hasnuls") == 0) {
+			urlreq->binary_has_nuls = TRUE;
+		} else if (strncasecmp(param, "bpstruct=", 9) == 0 &&
+			   param[9] != '\0') {
+			bpstruct = param+9;
+		}
+	}
+
+	/* read literal size */
+	if (str_to_uoff(args[0], &literal_size) < 0) {
+		i_error("imap-urlauth: "
+			"Overflowing unsigned integer value for literal size: %s",
+			args[1]);
+		return -1;
+	}
+
+	/* read literal */
+	if (imap_urlauth_connection_read_literal_init(conn, literal_size) < 0)
+		return -1;
+
+	urlreq->bodypartstruct = i_strdup(bpstruct);
+	return imap_urlauth_connection_read_literal(conn);
+}
+
+static int imap_urlauth_input_next(struct imap_urlauth_connection *conn)
+{
+	const char *response;
+	int ret;
+
+	switch (conn->state) {
+	case IMAP_URLAUTH_STATE_AUTHENTICATING:
+	case IMAP_URLAUTH_STATE_UNSELECTING_TARGET:
+		if ((response = i_stream_next_line(conn->input)) == NULL)
+			return 0;
+		imap_urlauth_stop_response_timeout(conn);
+
+		if (strcasecmp(response, "OK") != 0) {
+			if (conn->state == IMAP_URLAUTH_STATE_AUTHENTICATING)
+				i_error("imap-urlauth: Failed to authenticate to service: "
+					"Got unexpected response: %s", str_sanitize(response, 80));
+			else
+				i_error("imap-urlauth: Failed to unselect target user: "
+					"Got unexpected response: %s", str_sanitize(response, 80));
+			imap_urlauth_connection_abort(conn, NULL);
+			return -1;
+		}
+
+		if (conn->state == IMAP_URLAUTH_STATE_AUTHENTICATING) {
+			e_debug(conn->user->event,
+				"imap-urlauth: Successfully authenticated to service");
+		} else {
+			e_debug(conn->user->event,
+				"imap-urlauth: Successfully unselected target user");
+		}
+
+		conn->state = IMAP_URLAUTH_STATE_AUTHENTICATED;
+		imap_urlauth_connection_select_target(conn);
+		return 0;
+	case IMAP_URLAUTH_STATE_SELECTING_TARGET:
+		if ((response = i_stream_next_line(conn->input)) == NULL)
+			return 0;
+		imap_urlauth_stop_response_timeout(conn);
+
+		i_assert(conn->targets_head != NULL);
+
+		if (strcasecmp(response, "NO") == 0) {
+			e_debug(conn->user->event,
+				"imap-urlauth: Failed to select target user %s",
+				conn->targets_head->userid);
+			imap_urlauth_target_fail(conn, conn->targets_head, NULL);
+
+			conn->state = IMAP_URLAUTH_STATE_AUTHENTICATED;
+			imap_urlauth_connection_select_target(conn);
+			return 0;
+		}
+		if (strcasecmp(response, "OK") != 0) {
+			i_error("imap-urlauth: Failed to select target user %s: "
+				"Got unexpected response: %s", conn->targets_head->userid,
+				str_sanitize(response, 80));
+			imap_urlauth_connection_abort(conn, NULL);
+			return -1;
+		}
+
+		e_debug(conn->user->event,
+			"imap-urlauth: Successfully selected target user %s",
+			conn->targets_head->userid);
+		conn->state = IMAP_URLAUTH_STATE_READY;
+		imap_urlauth_connection_send_request(conn);
+		return 0;
+	case IMAP_URLAUTH_STATE_AUTHENTICATED:
+	case IMAP_URLAUTH_STATE_READY:
+	case IMAP_URLAUTH_STATE_REQUEST_WAIT:
+		if ((response = i_stream_next_line(conn->input)) == NULL)
+			return 0;
+
+		i_error("imap-urlauth: Received input while no requests were pending: %s",
+			str_sanitize(response, 80));
+		imap_urlauth_connection_abort(conn, NULL);
+		return -1;
+	case IMAP_URLAUTH_STATE_REQUEST_PENDING:
+		if ((ret = imap_urlauth_input_pending(conn)) < 0)
+			imap_urlauth_connection_fail(conn);
+		return ret;
+	case IMAP_URLAUTH_STATE_DISCONNECTED:
+		break;
+	}
+	i_unreached();
+}
+
+static void imap_urlauth_input(struct imap_urlauth_connection *conn)
+{
+	i_assert(conn->state != IMAP_URLAUTH_STATE_DISCONNECTED);
+
+	if (conn->input->closed) {
+		/* disconnected */
+		i_error("imap-urlauth: Service disconnected unexpectedly");
+		imap_urlauth_connection_fail(conn);
+		return;
+	}
+
+	switch (i_stream_read(conn->input)) {
+	case -1:
+		/* disconnected */
+		i_error("imap-urlauth: Service disconnected unexpectedly");
+		imap_urlauth_connection_fail(conn);
+		return;
+	case -2:
+		/* input buffer full */
+		i_error("imap-urlauth: Service sent too large input");
+		imap_urlauth_connection_abort(conn, NULL);
+		return;
+	}
+
+	while (!conn->input->closed) {
+		if (imap_urlauth_input_next(conn) <= 0)
+			break;
+	}
+}
+
+static int
+imap_urlauth_connection_do_connect(struct imap_urlauth_connection *conn)
+{
+	string_t *str;
+	int fd;
+
+	if (conn->state != IMAP_URLAUTH_STATE_DISCONNECTED) {
+		imap_urlauth_connection_send_request(conn);
+		return 1;
+	}
+
+	if (conn->user->auth_token == NULL) {
+		i_error("imap-urlauth: cannot authenticate because no auth token "
+			"is available for this session (running standalone?).");
+		imap_urlauth_connection_abort(conn, NULL);
+		return -1;
+	}
+
+	e_debug(conn->user->event, "imap-urlauth: Connecting to service at %s", conn->path);
+
+	i_assert(conn->fd == -1);
+	fd = net_connect_unix(conn->path);
+	if (fd == -1) {
+		i_error("imap-urlauth: net_connect_unix(%s) failed: %m",
+			conn->path);
+		imap_urlauth_connection_abort(conn, NULL);
+		return -1;
+	}
+
+	timeout_remove(&conn->to_reconnect);
+
+	conn->fd = fd;
+	conn->input = i_stream_create_fd(fd, SIZE_MAX);
+	conn->output = o_stream_create_fd(fd, SIZE_MAX);
+	conn->io = io_add(fd, IO_READ, imap_urlauth_input, conn);
+	conn->state = IMAP_URLAUTH_STATE_AUTHENTICATING;
+
+	str = t_str_new(128);
+	str_printfa(str, IMAP_URLAUTH_HANDSHAKE"AUTH\t%s\t%s\t",
+		conn->service, my_pid);
+	str_append_tabescaped(str, conn->user->username);
+	str_append_c(str, '\t');
+	if (conn->session_id != NULL)
+		str_append_tabescaped(str, conn->session_id);
+	str_append_c(str, '\t');
+	str_append_tabescaped(str, conn->user->auth_token);
+	str_append_c(str, '\n');
+	if (o_stream_send(conn->output, str_data(str), str_len(str)) < 0) {
+		i_warning("Error sending handshake to imap-urlauth server: %m");
+		imap_urlauth_connection_abort(conn, NULL);
+		return -1;
+	}
+
+	imap_urlauth_start_response_timeout(conn);
+	return 0;
+}
+
+int imap_urlauth_connection_connect(struct imap_urlauth_connection *conn)
+{
+	conn->reconnect_attempts = 0;
+
+	if (conn->to_reconnect == NULL)
+		return imap_urlauth_connection_do_connect(conn);
+	return 0;
+}
+
+static void imap_urlauth_connection_disconnect
+(struct imap_urlauth_connection *conn, const char *reason)
+{
+	conn->state = IMAP_URLAUTH_STATE_DISCONNECTED;
+
+	if (conn->fd != -1) {
+		if (reason == NULL)
+			e_debug(conn->user->event, "imap-urlauth: Disconnecting from service");
+		else
+			e_debug(conn->user->event, "imap-urlauth: Disconnected: %s", reason);
+
+		io_remove(&conn->io);
+		i_stream_destroy(&conn->input);
+		o_stream_destroy(&conn->output);
+		net_disconnect(conn->fd);
+		conn->fd = -1;
+	}
+	conn->reading_literal = FALSE;
+
+	if (conn->literal_fd != -1) {
+		if (close(conn->literal_fd) < 0)
+			i_error("imap-urlauth: close(%s) failed: %m", conn->literal_temp_path);
+
+		i_free_and_null(conn->literal_temp_path);
+		conn->literal_fd = -1;
+	}
+
+	buffer_free(&conn->literal_buf);
+	timeout_remove(&conn->to_reconnect);
+	timeout_remove(&conn->to_idle);
+	imap_urlauth_stop_response_timeout(conn);
+}
+
+static void
+imap_urlauth_connection_do_reconnect(struct imap_urlauth_connection *conn)
+{
+	if (conn->reconnect_attempts >= IMAP_URLAUTH_RECONNECT_MAX_ATTEMPTS) {
+		imap_urlauth_connection_abort(conn,
+			"Connection failed and connection attempts exhausted");
+		return;
+	}
+
+	if (ioloop_time - conn->last_reconnect < IMAP_URLAUTH_RECONNECT_MIN_SECS) {
+		e_debug(conn->user->event, "imap-urlauth: Scheduling reconnect");
+		timeout_remove(&conn->to_reconnect);
+		conn->to_reconnect =
+			timeout_add(IMAP_URLAUTH_RECONNECT_MIN_SECS*1000,
+				imap_urlauth_connection_do_reconnect, conn);
+	} else {
+		conn->reconnect_attempts++;
+		conn->last_reconnect = ioloop_time;
+		(void)imap_urlauth_connection_do_connect(conn);
+	}
+}
+
+static void
+imap_urlauth_connection_reconnect(struct imap_urlauth_connection *conn)
+{
+	imap_urlauth_connection_disconnect(conn, NULL);
+
+	/* don't reconnect if there are no requests */
+	if (conn->targets_head == NULL)
+		return;
+
+	imap_urlauth_connection_do_reconnect(conn);
+}
+
+static void
+imap_urlauth_connection_idle_disconnect(struct imap_urlauth_connection *conn)
+{
+	imap_urlauth_connection_disconnect(conn, "Idle timeout");
+}
+
+static void
+imap_urlauth_connection_timeout_abort(struct imap_urlauth_connection *conn)
+{
+	imap_urlauth_connection_abort(conn, "Service is not responding");
+}
+
+bool imap_urlauth_connection_is_connected(struct imap_urlauth_connection *conn)
+{
+	return conn->fd != -1 && conn->state != IMAP_URLAUTH_STATE_DISCONNECTED;
+}
diff --git a/src/lib-imap-urlauth/imap-urlauth-connection.h b/src/lib-imap-urlauth/imap-urlauth-connection.h
new file mode 100644
index 0000000..b60186a
--- /dev/null
+++ b/src/lib-imap-urlauth/imap-urlauth-connection.h
@@ -0,0 +1,42 @@
+#ifndef IMAP_URLAUTH_CONNECTION_H
+#define IMAP_URLAUTH_CONNECTION_H
+
+struct imap_urlauth_request;
+struct imap_urlauth_fetch_reply;
+
+typedef int
+imap_urlauth_request_callback_t(struct imap_urlauth_fetch_reply *reply,
+				void *context);
+
+/* If reconnect_callback is specified, it's called when connection is lost.
+   If the callback returns FALSE, reconnection isn't attempted. */
+struct imap_urlauth_connection *
+imap_urlauth_connection_init(const char *path, const char *service,
+			     struct mail_user *user, const char *session_id,
+			     unsigned int idle_timeout_msecs);
+void imap_urlauth_connection_deinit(struct imap_urlauth_connection **conn);
+
+/* Connect to imap-urlauth (even if failed for previous requests). */
+int imap_urlauth_connection_connect(struct imap_urlauth_connection *conn);
+
+/* Continue after request callback returned 0 */
+void imap_urlauth_connection_continue(struct imap_urlauth_connection *conn);
+
+/* Create a new URL fetch request */
+struct imap_urlauth_request *
+imap_urlauth_request_new(struct imap_urlauth_connection *conn,
+			 const char *target_user, const char *url,
+			 enum imap_urlauth_fetch_flags flags,
+			 imap_urlauth_request_callback_t *callback,
+			 void *context);
+/* Abort request */
+void imap_urlauth_request_abort(struct imap_urlauth_connection *conn,
+				struct imap_urlauth_request *urlreq);
+/* Abort all requests with matching context value */
+void imap_urlauth_request_abort_by_context(struct imap_urlauth_connection *conn,
+					   void *context);
+
+/* Returns TRUE if currently connected imap-urlauth service. */
+bool imap_urlauth_connection_is_connected(struct imap_urlauth_connection *conn);
+
+#endif
diff --git a/src/lib-imap-urlauth/imap-urlauth-fetch.c b/src/lib-imap-urlauth/imap-urlauth-fetch.c
new file mode 100644
index 0000000..d5746f1
--- /dev/null
+++ b/src/lib-imap-urlauth/imap-urlauth-fetch.c
@@ -0,0 +1,530 @@
+/* Copyright (c) 2013-2018 Dovecot authors, see the included COPYING file */
+
+#include "lib.h"
+#include "llist.h"
+#include "array.h"
+#include "net.h"
+#include "istream.h"
+#include "mail-user.h"
+#include "mail-error.h"
+#include "mail-storage.h"
+#include "imap-url.h"
+#include "imap-msgpart-url.h"
+#include "imap-urlauth-private.h"
+#include "imap-urlauth-fetch.h"
+#include "imap-urlauth-connection.h"
+
+struct imap_urlauth_fetch_url {
+	struct imap_urlauth_fetch_url *prev, *next;
+
+	char *url;
+	enum imap_urlauth_fetch_flags flags;
+};
+
+struct imap_urlauth_fetch {
+	unsigned int refcount;
+	struct imap_urlauth_context *uctx;
+
+	imap_urlauth_fetch_callback_t *callback;
+	void *context;
+
+	/* local urls */
+	struct imap_urlauth_fetch_url *local_urls_head, *local_urls_tail;
+	struct imap_msgpart_url *local_url;
+
+	unsigned int pending_requests;
+
+	struct {
+		char *url;
+		enum imap_urlauth_fetch_flags flags;
+
+		struct istream *input;
+		uoff_t size;
+
+		char *bodypartstruct;
+		char *error;
+
+		bool succeeded:1;
+		bool binary_has_nuls:1;
+	} pending_reply;
+
+	bool failed:1;
+	bool waiting_local:1;
+	bool waiting_service:1;
+};
+
+static void imap_urlauth_fetch_abort_local(struct imap_urlauth_fetch *ufetch)
+{
+	struct imap_urlauth_fetch_url *url, *url_next;
+
+	if (ufetch->local_url != NULL) {
+		ufetch->pending_requests--;
+		imap_msgpart_url_free(&ufetch->local_url);
+	}
+
+	i_free_and_null(ufetch->pending_reply.url);
+	i_free_and_null(ufetch->pending_reply.bodypartstruct);
+	i_free_and_null(ufetch->pending_reply.error);
+	i_stream_unref(&ufetch->pending_reply.input);
+
+	url = ufetch->local_urls_head;
+	for (; url != NULL; url = url_next) {
+		url_next = url->next;
+		i_free(url->url);
+		i_free(url);
+		ufetch->pending_requests--;
+	}
+	ufetch->local_urls_head = ufetch->local_urls_tail = NULL;
+}
+
+static void imap_urlauth_fetch_abort(struct imap_urlauth_fetch *ufetch)
+{
+	if (ufetch->pending_requests > 0)
+		imap_urlauth_request_abort_by_context(ufetch->uctx->conn, ufetch);
+
+	imap_urlauth_fetch_abort_local(ufetch);
+
+	i_assert(ufetch->pending_requests == 0);
+}
+
+static void imap_urlauth_fetch_fail(struct imap_urlauth_fetch *ufetch)
+{
+	imap_urlauth_fetch_abort(ufetch);
+	ufetch->failed = TRUE;
+}
+
+struct imap_urlauth_fetch *
+imap_urlauth_fetch_init(struct imap_urlauth_context *uctx,
+			imap_urlauth_fetch_callback_t *callback, void *context)
+{
+	struct imap_urlauth_fetch *ufetch;
+
+	ufetch = i_new(struct imap_urlauth_fetch, 1);
+	ufetch->refcount = 1;
+	ufetch->uctx = uctx;
+	ufetch->callback = callback;
+	ufetch->context = context;
+	return ufetch;
+}
+
+static void imap_urlauth_fetch_ref(struct imap_urlauth_fetch *ufetch)
+{
+	i_assert(ufetch->refcount > 0);
+	ufetch->refcount++;
+}
+
+static void imap_urlauth_fetch_unref(struct imap_urlauth_fetch **_ufetch)
+{
+	struct imap_urlauth_fetch *ufetch = *_ufetch;
+
+	i_assert(ufetch->refcount > 0);
+
+	*_ufetch = NULL;
+	if (--ufetch->refcount > 0)
+		return;
+
+	ufetch->refcount++;
+	imap_urlauth_fetch_abort(ufetch);
+	ufetch->refcount--;
+	i_assert(ufetch->refcount == 0);
+
+	/* dont leave the connection in limbo; make sure continue is called */
+	if (ufetch->waiting_service)
+		imap_urlauth_connection_continue(ufetch->uctx->conn);
+	i_free(ufetch);
+}
+
+void imap_urlauth_fetch_deinit(struct imap_urlauth_fetch **_ufetch)
+{
+	imap_urlauth_fetch_unref(_ufetch);
+}
+
+static void
+imap_urlauth_fetch_error(struct imap_urlauth_fetch *ufetch, const char *url,
+			 enum imap_urlauth_fetch_flags url_flags,
+			 const char *error)
+{
+	struct imap_urlauth_fetch_reply reply;
+	int ret;
+
+	ufetch->pending_requests--;
+
+	i_zero(&reply);
+	reply.url = url;
+	reply.flags = url_flags;
+	reply.succeeded = FALSE;
+	reply.error = error;
+
+	T_BEGIN {
+		ret = ufetch->callback(&reply, ufetch->pending_requests == 0,
+				       ufetch->context);
+	} T_END;
+
+	if (ret == 0) {
+		ufetch->waiting_local = TRUE;
+		ufetch->pending_requests++;
+	} else if (ret < 0) {
+		imap_urlauth_fetch_fail(ufetch);
+	}
+}
+
+static void
+imap_urlauth_fetch_local(struct imap_urlauth_fetch *ufetch, const char *url,
+			 enum imap_urlauth_fetch_flags url_flags,
+			 struct imap_url *imap_url)
+{
+	struct imap_urlauth_fetch_reply reply;
+	struct imap_msgpart_open_result mpresult;
+	const char *error, *errormsg = NULL, *bpstruct = NULL;
+	bool debug = ufetch->uctx->user->mail_debug, success;
+	enum mail_error error_code;
+	struct imap_msgpart_url *mpurl = NULL;
+	int ret;
+
+	success = TRUE;
+
+	if (debug)
+		i_debug("Fetching local URLAUTH %s", url);
+
+	if (url_flags == 0)
+		url_flags = IMAP_URLAUTH_FETCH_FLAG_BODY;
+
+	/* fetch URL */
+	if (imap_url == NULL) {
+		ret = imap_urlauth_fetch(ufetch->uctx, url,
+					 &mpurl, &error_code, &error);
+	} else {
+		ret = imap_urlauth_fetch_parsed(ufetch->uctx, imap_url,
+						&mpurl, &error_code, &error);
+	}
+	if (ret <= 0) {
+		if (ret == 0) {
+			errormsg = t_strdup_printf("Failed to fetch URLAUTH \"%s\": %s",
+						   url, error);
+			if (debug)
+				i_debug("%s", errormsg);
+		}
+		success = FALSE;
+	}
+
+	/* fetch metadata */
+	if (success && (url_flags & IMAP_URLAUTH_FETCH_FLAG_BINARY) != 0)
+		imap_msgpart_url_set_decode_to_binary(mpurl);
+	if (success &&
+	    (url_flags & IMAP_URLAUTH_FETCH_FLAG_BODYPARTSTRUCTURE) != 0) {
+		ret = imap_msgpart_url_get_bodypartstructure(mpurl, &bpstruct, &error);
+		if (ret <= 0) {
+			if (ret == 0) {
+				errormsg = t_strdup_printf
+					("Failed to read URLAUTH \"%s\": %s",	url, error);
+				if (debug)
+					i_debug("%s", errormsg);
+			}
+			success = FALSE;
+		}
+	}
+
+	/* if requested, read the message part the URL points to */
+	i_zero(&mpresult);
+	if (success && ((url_flags & IMAP_URLAUTH_FETCH_FLAG_BODY) != 0 ||
+			(url_flags & IMAP_URLAUTH_FETCH_FLAG_BINARY) != 0)) {
+		ret = imap_msgpart_url_read_part(mpurl, &mpresult, &error);
+		if (ret <= 0) {
+			if (ret == 0) {
+				errormsg = t_strdup_printf
+					("Failed to read URLAUTH \"%s\": %s",	url, error);
+				if (debug)
+					i_debug("%s", errormsg);
+			}
+			success = FALSE;
+		}
+	}
+
+	if (debug && success) {
+		if (bpstruct != NULL)
+			i_debug("Fetched URLAUTH yielded BODYPARTSTRUCTURE (%s)", bpstruct);
+		if (mpresult.size == 0 || mpresult.input == NULL)
+			i_debug("Fetched URLAUTH yielded empty result");
+		else {
+			i_debug("Fetched URLAUTH yielded %"PRIuUOFF_T" bytes "
+				"of %smessage data", mpresult.size,
+				(mpresult.binary_decoded_input_has_nuls ? "binary " : ""));
+		}
+	}
+
+	ufetch->pending_requests--;
+
+	if (!success && ret < 0) {
+		if (mpurl != NULL)
+			imap_msgpart_url_free(&mpurl);
+		(void)ufetch->callback(NULL, TRUE, ufetch->context);
+		imap_urlauth_fetch_fail(ufetch);
+		return;
+	}
+
+	i_zero(&reply);
+	reply.url = url;
+	reply.flags = url_flags;
+	reply.error = errormsg;
+	reply.succeeded = success;
+
+	reply.bodypartstruct = bpstruct;
+	reply.binary_has_nuls = mpresult.binary_decoded_input_has_nuls;
+	reply.size = mpresult.size;
+	reply.input = mpresult.input;
+
+	ret = ufetch->callback(&reply, ufetch->pending_requests == 0,
+			       ufetch->context);
+	if (ret == 0) {
+		ufetch->local_url = mpurl;
+		ufetch->waiting_local = TRUE;
+		ufetch->pending_requests++;
+	} else {
+
+		if (mpurl != NULL)
+			imap_msgpart_url_free(&mpurl);
+		if (ret < 0)
+			imap_urlauth_fetch_fail(ufetch);
+	}
+}
+
+static int
+imap_urlauth_fetch_request_callback(struct imap_urlauth_fetch_reply *reply,
+				    void *context)
+{
+	struct imap_urlauth_fetch *ufetch =
+		(struct imap_urlauth_fetch *)context;
+	int ret = 1;
+
+	if (ufetch->waiting_local && reply != NULL) {
+		i_assert(ufetch->pending_reply.url == NULL);
+		ufetch->pending_reply.url = i_strdup(reply->url);
+		ufetch->pending_reply.flags = reply->flags;
+		ufetch->pending_reply.bodypartstruct =
+			i_strdup(reply->bodypartstruct);
+		ufetch->pending_reply.error = i_strdup(reply->error);
+		if (reply->input != NULL) {
+			ufetch->pending_reply.input = reply->input;
+			i_stream_ref(ufetch->pending_reply.input);
+		}
+		ufetch->pending_reply.size = reply->size;
+		ufetch->pending_reply.succeeded = reply->succeeded;
+		ufetch->pending_reply.binary_has_nuls = reply->binary_has_nuls;
+		ufetch->waiting_service = TRUE;
+		return 0;
+	}
+
+	ufetch->waiting_local = FALSE;
+	ufetch->pending_requests--;
+
+	imap_urlauth_fetch_ref(ufetch);
+
+	if (!ufetch->failed) {
+		bool last = ufetch->pending_requests == 0 || reply == NULL;
+		ret = ufetch->callback(reply, last, ufetch->context);
+	}
+
+	/* report failure only once */
+	if (ret < 0 || reply == NULL) {
+		if (!ufetch->failed)
+			imap_urlauth_fetch_abort_local(ufetch);
+		ufetch->failed = TRUE;
+	} else if (ret == 0) {
+		ufetch->waiting_service = TRUE;
+		ufetch->pending_requests++;
+	}
+	
+	imap_urlauth_fetch_unref(&ufetch);
+	return ret;
+}
+
+int imap_urlauth_fetch_url(struct imap_urlauth_fetch *ufetch, const char *url,
+			   enum imap_urlauth_fetch_flags url_flags)
+{
+	struct imap_urlauth_context *uctx = ufetch->uctx;
+	enum imap_url_parse_flags url_parse_flags =
+		IMAP_URL_PARSE_ALLOW_URLAUTH;
+	struct mail_user *mail_user = uctx->user;
+	struct imap_url *imap_url;
+	const char *error, *errormsg;
+
+	/* parse the url */
+	if (imap_url_parse(url, NULL, url_parse_flags, &imap_url, &error) < 0) {
+		errormsg = t_strdup_printf(
+			"Failed to fetch URLAUTH \"%s\": %s", url, error);
+		e_debug(mail_user->event, "%s", errormsg);
+		ufetch->pending_requests++;
+		imap_urlauth_fetch_ref(ufetch);
+		imap_urlauth_fetch_error(ufetch, url, url_flags, errormsg);
+		imap_urlauth_fetch_unref(&ufetch);
+		return 1;
+	}
+
+	return imap_urlauth_fetch_url_parsed(ufetch, url, imap_url, url_flags);
+}
+
+int imap_urlauth_fetch_url_parsed(struct imap_urlauth_fetch *ufetch,
+			   const char *url, struct imap_url *imap_url,
+			   enum imap_urlauth_fetch_flags url_flags)
+{
+	struct imap_urlauth_context *uctx = ufetch->uctx;
+	struct mail_user *mail_user = uctx->user;
+	const char *error, *errormsg;
+	int ret = 0;
+
+	ufetch->failed = FALSE;
+	ufetch->pending_requests++;
+
+	imap_urlauth_fetch_ref(ufetch);
+
+	/* if access user and target user match, handle fetch request locally */
+	if (imap_url->userid != NULL &&
+		strcmp(mail_user->username, imap_url->userid) == 0) {
+
+		if (ufetch->waiting_local) {
+			struct imap_urlauth_fetch_url *url_local;
+
+			url_local = i_new(struct imap_urlauth_fetch_url, 1);
+			url_local->url = i_strdup(url);
+			url_local->flags = url_flags;
+
+			DLLIST2_APPEND(&ufetch->local_urls_head,
+				       &ufetch->local_urls_tail, url_local);
+		} else T_BEGIN {
+			imap_urlauth_fetch_local(ufetch, url,
+						 url_flags, imap_url);
+		} T_END;
+		imap_url = NULL;
+	/* don't try to fetch remote URLs that are already known to fail access */
+	} else if (!imap_urlauth_check(uctx, imap_url, TRUE, &error)) {
+		errormsg = t_strdup_printf(
+			"Failed to fetch URLAUTH \"%s\": %s", url, error);
+		e_debug(mail_user->event, "%s", errormsg);
+		imap_urlauth_fetch_error(ufetch, url, url_flags, errormsg);
+		imap_url = NULL;
+	}
+
+	/* create request for url */
+	if (imap_url != NULL && imap_url->userid != NULL) {
+		i_assert(uctx->conn != NULL);
+		(void)imap_urlauth_request_new(uctx->conn, imap_url->userid,
+				url, url_flags,
+				imap_urlauth_fetch_request_callback, ufetch);
+		i_assert(uctx->conn != NULL);
+		if (imap_urlauth_connection_connect(uctx->conn) < 0)
+			ret = -1;
+	}
+	if (ret >= 0)
+		ret = (ufetch->pending_requests > 0 ? 0 : 1);
+
+	imap_urlauth_fetch_unref(&ufetch);
+	return ret;
+}
+
+static bool imap_urlauth_fetch_do_continue(struct imap_urlauth_fetch *ufetch)
+{
+	struct imap_urlauth_fetch_url *url, *url_next;
+	int ret;
+
+	if (ufetch->failed)
+		return FALSE;
+
+	if (!ufetch->waiting_local && !ufetch->waiting_service) {
+		/* not currently waiting for anything */
+		return ufetch->pending_requests > 0;
+	}
+
+	/* we finished a request */
+	ufetch->pending_requests--;
+
+	if (!ufetch->waiting_local) {
+		/* not waiting for local request handling */
+		ufetch->waiting_service = FALSE;
+		imap_urlauth_connection_continue(ufetch->uctx->conn);
+		return ufetch->pending_requests > 0;
+	}
+
+	/* finished local request */
+	if (ufetch->local_url != NULL) {
+		imap_msgpart_url_free(&ufetch->local_url);
+	}
+	ufetch->waiting_local = FALSE;
+
+	/* handle pending remote reply */
+	if (ufetch->pending_reply.url != NULL) {
+		struct imap_urlauth_fetch_reply reply;
+
+		ufetch->pending_requests--;
+
+		i_zero(&reply);
+		reply.url = ufetch->pending_reply.url;
+		reply.flags = ufetch->pending_reply.flags;
+		reply.bodypartstruct = ufetch->pending_reply.bodypartstruct;
+		reply.error = ufetch->pending_reply.error;
+		reply.input = ufetch->pending_reply.input;
+		reply.size = ufetch->pending_reply.size;
+		reply.succeeded = ufetch->pending_reply.succeeded;
+		reply.binary_has_nuls = ufetch->pending_reply.binary_has_nuls;
+
+		ret = ufetch->callback(&reply, ufetch->pending_requests == 0,
+				       ufetch->context);
+
+		if (ufetch->pending_reply.url != NULL)
+			i_free(ufetch->pending_reply.url);
+		if (ufetch->pending_reply.input != NULL)
+			i_stream_unref(&ufetch->pending_reply.input);
+		if (ufetch->pending_reply.bodypartstruct != NULL)
+			i_free(ufetch->pending_reply.bodypartstruct);
+		if (ufetch->pending_reply.error != NULL)
+			i_free(ufetch->pending_reply.error);
+
+		if (ret < 0) {
+			imap_urlauth_fetch_fail(ufetch);
+			return FALSE;
+		} 
+
+		if (ret == 0) {
+			ufetch->waiting_service = TRUE;
+			ufetch->pending_requests++;
+			return TRUE;
+		}
+
+		ufetch->waiting_service = FALSE;
+		imap_urlauth_connection_continue(ufetch->uctx->conn);
+	}
+
+	/* handle pending local urls */
+	url = ufetch->local_urls_head;
+	while (url != NULL) {
+		url_next = url->next;
+		T_BEGIN {
+			imap_urlauth_fetch_local(ufetch, url->url,
+						 url->flags, NULL);
+		} T_END;
+		DLLIST2_REMOVE(&ufetch->local_urls_head,
+			       &ufetch->local_urls_tail, url);
+		i_free(url->url);
+		i_free(url);
+		if (ufetch->waiting_local) 
+			return TRUE;
+		url = url_next;
+	}
+
+	return ufetch->pending_requests > 0;
+}
+
+bool imap_urlauth_fetch_continue(struct imap_urlauth_fetch *ufetch)
+{
+	bool pending;
+
+	imap_urlauth_fetch_ref(ufetch);
+	pending = imap_urlauth_fetch_do_continue(ufetch);
+	imap_urlauth_fetch_unref(&ufetch);
+
+	return pending;
+}
+
+bool imap_urlauth_fetch_is_pending(struct imap_urlauth_fetch *ufetch)
+{
+	return ufetch->pending_requests > 0;
+}
diff --git a/src/lib-imap-urlauth/imap-urlauth-fetch.h b/src/lib-imap-urlauth/imap-urlauth-fetch.h
new file mode 100644
index 0000000..628a95e
--- /dev/null
+++ b/src/lib-imap-urlauth/imap-urlauth-fetch.h
@@ -0,0 +1,56 @@
+#ifndef IMAP_URLAUTH_FETCH_H
+#define IMAP_URLAUTH_FETCH_H
+
+struct imap_url;
+struct imap_urlauth_context;
+struct imap_urlauth_fetch;
+
+enum imap_urlauth_fetch_flags {
+	/* Indicates that this is an extended request */
+	IMAP_URLAUTH_FETCH_FLAG_EXTENDED		= 0x01,
+	/* Fetch body part unmodified */
+	IMAP_URLAUTH_FETCH_FLAG_BODY			= 0x02,
+	/* Fetch body part as binary, i.e. without content encoding */
+	IMAP_URLAUTH_FETCH_FLAG_BINARY			= 0x04,
+	/* Fetch IMAP bodypartstructure */
+	IMAP_URLAUTH_FETCH_FLAG_BODYPARTSTRUCTURE	= 0x08,
+};
+
+struct imap_urlauth_fetch_reply {
+	const char *url;
+	enum imap_urlauth_fetch_flags flags;
+
+	struct istream *input;
+	uoff_t size;
+
+	const char *bodypartstruct;
+	const char *error;
+
+	bool succeeded:1;
+	bool binary_has_nuls:1;
+};
+
+/* Callback to handle fetch reply. Returns 1 if handled completely and ready
+   for next reply, 0 if not all data was processed, and -1 for error. If a
+   callback returns 0, imap_urlauth_fetch_continue() must be called once
+   new replies may be processed. If this is the last request to yield a reply,
+   argument last is TRUE. */
+typedef int
+imap_urlauth_fetch_callback_t(struct imap_urlauth_fetch_reply *reply,
+			      bool last, void *context);
+
+struct imap_urlauth_fetch *
+imap_urlauth_fetch_init(struct imap_urlauth_context *uctx,
+			imap_urlauth_fetch_callback_t *callback, void *context);
+void imap_urlauth_fetch_deinit(struct imap_urlauth_fetch **ufetch);
+
+int imap_urlauth_fetch_url(struct imap_urlauth_fetch *ufetch, const char *url,
+			   enum imap_urlauth_fetch_flags url_flags);
+int imap_urlauth_fetch_url_parsed(struct imap_urlauth_fetch *ufetch,
+			   const char *url, struct imap_url *imap_url,
+			   enum imap_urlauth_fetch_flags url_flags);
+
+bool imap_urlauth_fetch_continue(struct imap_urlauth_fetch *ufetch);
+bool imap_urlauth_fetch_is_pending(struct imap_urlauth_fetch *ufetch);
+
+#endif
diff --git a/src/lib-imap-urlauth/imap-urlauth-private.h b/src/lib-imap-urlauth/imap-urlauth-private.h
new file mode 100644
index 0000000..3b3622c
--- /dev/null
+++ b/src/lib-imap-urlauth/imap-urlauth-private.h
@@ -0,0 +1,20 @@
+#ifndef IMAP_URLAUTH_PRIVATE_H
+#define IMAP_URLAUTH_PRIVATE_H
+
+#include "imap-urlauth.h"
+
+struct imap_urlauth_context {
+	struct mail_user *user;
+	struct imap_urlauth_connection *conn;
+
+	char *url_host;
+	in_port_t url_port;
+
+	char *access_user;
+	char *access_service;
+	const char **access_applications;
+
+	bool access_anonymous:1;
+};
+
+#endif
diff --git a/src/lib-imap-urlauth/imap-urlauth.c b/src/lib-imap-urlauth/imap-urlauth.c
new file mode 100644
index 0000000..a9c2673
--- /dev/null
+++ b/src/lib-imap-urlauth/imap-urlauth.c
@@ -0,0 +1,486 @@
+/* Copyright (c) 2013-2018 Dovecot authors, see the included COPYING file */
+
+#include "lib.h"
+#include "hostpid.h"
+#include "var-expand.h"
+#include "hmac.h"
+#include "sha1.h"
+#include "randgen.h"
+#include "safe-memset.h"
+#include "mail-storage.h"
+#include "mail-storage-service.h"
+#include "mail-namespace.h"
+#include "mail-user.h"
+#include "imap-url.h"
+#include "imap-msgpart-url.h"
+#include "imap-urlauth-backend.h"
+#include "imap-urlauth-fetch.h"
+#include "imap-urlauth-connection.h"
+
+#include "imap-urlauth-private.h"
+
+#include <time.h>
+
+#define IMAP_URLAUTH_MECH_INTERNAL_VERSION    0x01
+
+#define IMAP_URLAUTH_NORMAL_TIMEOUT_MSECS     5*1000
+#define IMAP_URLAUTH_SPECIAL_TIMEOUT_MSECS    3*60*1000
+
+#define URL_HOST_ALLOW_ANY "*"
+
+struct imap_urlauth_context *
+imap_urlauth_init(struct mail_user *user,
+		  const struct imap_urlauth_config *config)
+{
+	struct imap_urlauth_context *uctx;
+	unsigned int timeout;
+
+	i_assert(*config->url_host != '\0');
+
+	uctx = i_new(struct imap_urlauth_context, 1);
+	uctx->user = user;
+	uctx->url_host = i_strdup(config->url_host);
+	uctx->url_port = config->url_port;
+
+	if (config->access_anonymous)
+		uctx->access_user = i_strdup("anonymous");
+	else
+		uctx->access_user = i_strdup(config->access_user);
+	uctx->access_service = i_strdup(config->access_service);
+	uctx->access_anonymous = config->access_anonymous;
+	if (config->access_applications != NULL &&
+	    *config->access_applications != NULL) {
+		uctx->access_applications =
+			p_strarray_dup(default_pool,
+				       config->access_applications);
+		timeout = IMAP_URLAUTH_SPECIAL_TIMEOUT_MSECS;
+	} else {
+		timeout = IMAP_URLAUTH_NORMAL_TIMEOUT_MSECS;
+	}
+
+	if (config->socket_path != NULL) {
+		uctx->conn = imap_urlauth_connection_init(config->socket_path,
+					config->access_service, user, config->session_id, timeout);
+	}
+	return uctx;
+}
+
+void imap_urlauth_deinit(struct imap_urlauth_context **_uctx)
+{
+	struct imap_urlauth_context *uctx = *_uctx;
+
+	*_uctx = NULL;
+
+	if (uctx->conn != NULL)
+		imap_urlauth_connection_deinit(&uctx->conn);
+	i_free(uctx->url_host);
+	i_free(uctx->access_user);
+	i_free(uctx->access_service);
+	i_free(uctx->access_applications);
+	i_free(uctx);
+}
+
+static const unsigned char *
+imap_urlauth_internal_generate(const char *rumpurl,
+			       const unsigned char mailbox_key[IMAP_URLAUTH_KEY_LEN],
+			       size_t *token_len_r)
+{
+	struct hmac_context hmac;
+	unsigned char *token;
+
+	token = t_new(unsigned char, SHA1_RESULTLEN + 1);
+	token[0] = IMAP_URLAUTH_MECH_INTERNAL_VERSION;
+
+	hmac_init(&hmac, mailbox_key, IMAP_URLAUTH_KEY_LEN, &hash_method_sha1);
+	hmac_update(&hmac, rumpurl, strlen(rumpurl));
+	hmac_final(&hmac, token+1);
+
+	*token_len_r = SHA1_RESULTLEN + 1;
+	return token;
+}
+
+static bool
+imap_urlauth_internal_verify(const char *rumpurl,
+			     const unsigned char mailbox_key[IMAP_URLAUTH_KEY_LEN],
+			     const unsigned char *token, size_t token_len)
+{
+	const unsigned char *valtoken;
+	size_t valtoken_len;
+
+	if (rumpurl == NULL || token == NULL)
+		return FALSE;
+
+	valtoken = imap_urlauth_internal_generate(rumpurl, mailbox_key,
+						  &valtoken_len);
+	/* Note: the token length has timing leak here in any case */
+	if (token_len != valtoken_len)
+		return FALSE;
+
+	return mem_equals_timing_safe(token, valtoken, valtoken_len);
+}
+
+static bool
+access_applications_have_access(struct imap_urlauth_context *uctx,
+				struct imap_url *url, const char *const *access_applications)
+{
+	const char *const *application;
+
+	if (access_applications == NULL)
+		return FALSE;
+
+	application = access_applications;
+	for (; *application != NULL; application++) {
+		const char *app = *application;
+		bool have_userid = FALSE;
+		size_t len = strlen(app);
+
+		if (app[len-1] == '+')
+			have_userid = TRUE;
+
+		if (strncasecmp(url->uauth_access_application, app, len-1) == 0) {
+			if (!have_userid) {
+				/* this access application must have no userid */
+				return url->uauth_access_user == NULL;
+			}
+
+			/* this access application must have a userid */
+			return (!uctx->access_anonymous && url->uauth_access_user != NULL);
+		}
+	}
+	return FALSE;
+}
+
+static bool
+imap_urlauth_check_access(struct imap_urlauth_context *uctx,
+			  struct imap_url *url, bool ignore_unknown,
+			  const char **error_r)
+{
+	const char *userid;
+
+	if (url->uauth_access_application == NULL) {
+		*error_r = "URL is missing URLAUTH";
+		return FALSE;
+	}
+
+	if (strcmp(uctx->access_service, "imap") == 0) {
+		/* these access types are only allowed if URL is accessed through imap */
+		if (strcasecmp(url->uauth_access_application, "user") == 0) {
+			/* user+<access_user> */
+			if (url->uauth_access_user == NULL) {
+				*error_r = "URLAUTH `user' access is missing userid";
+				return FALSE;
+			}
+			if (!uctx->access_anonymous ||
+				  strcasecmp(url->uauth_access_user, uctx->access_user) == 0)
+				return TRUE;
+		} else if (strcasecmp(url->uauth_access_application, "authuser") == 0) {
+			/* authuser */
+			if (!uctx->access_anonymous)
+				return TRUE;
+		} else if (strcasecmp(url->uauth_access_application, "anonymous") == 0) {
+			/* anonymous */
+			return TRUE;
+		} else if (ignore_unknown || access_applications_have_access
+			(uctx, url, uctx->access_applications)) {
+			return TRUE;
+		}
+	} else if (strcmp(uctx->access_service, "submission") == 0) {
+		/* accessed directly through submission service */
+
+		if (strcasecmp(url->uauth_access_application, "submit") != 0) {
+			userid = url->uauth_access_user == NULL ? "" :
+				t_strdup_printf("+%s", url->uauth_access_user);
+			*error_r = t_strdup_printf(
+				"No '%s%s' access allowed for submission service",
+				url->uauth_access_application, userid);
+			return FALSE;
+		} else if (url->uauth_access_user == NULL) {
+			*error_r = "URLAUTH `submit' access is missing userid";
+			return FALSE;
+		} else if (!uctx->access_anonymous &&
+			strcasecmp(url->uauth_access_user, uctx->access_user) == 0) {
+			return TRUE;
+		}
+	}
+
+	userid = url->uauth_access_user == NULL ? "" :
+		t_strdup_printf("+%s", url->uauth_access_user);
+
+	if (uctx->access_anonymous) {
+		*error_r = t_strdup_printf(
+			"No '%s%s' access allowed for anonymous user",
+			url->uauth_access_application, userid);
+	} else {
+		*error_r = t_strdup_printf(
+			"No '%s%s' access allowed for user %s",
+			url->uauth_access_application, userid, uctx->access_user);
+	}
+	return FALSE;
+}
+
+static bool
+imap_urlauth_check_hostport(struct imap_urlauth_context *uctx,
+			    struct imap_url *url, const char **client_error_r)
+{
+	/* validate host */
+	/* FIXME: allow host ip/ip6 as well? */
+	if (strcmp(uctx->url_host, URL_HOST_ALLOW_ANY) != 0 &&
+	    strcmp(url->host.name, uctx->url_host) != 0) {
+		*client_error_r = "Invalid URL: Inappropriate host name";
+		return FALSE;
+	}
+
+	/* validate port */
+	if ((url->port == 0 && uctx->url_port != 143) ||
+	    (url->port != 0 && uctx->url_port != url->port)) {
+		*client_error_r = "Invalid URL: Inappropriate server port";
+		return FALSE;
+	}
+	return TRUE;
+}
+
+int imap_urlauth_generate(struct imap_urlauth_context *uctx,
+			  const char *mechanism, const char *rumpurl,
+			  const char **urlauth_r, const char **client_error_r)
+{
+	struct mail_user *user = uctx->user;
+	enum imap_url_parse_flags url_flags =
+		IMAP_URL_PARSE_ALLOW_URLAUTH;
+	struct imap_url *url;
+	struct imap_msgpart_url *mpurl = NULL;
+	struct mailbox *box;
+	const char *error;
+	enum mail_error error_code;
+	unsigned char mailbox_key[IMAP_URLAUTH_KEY_LEN];
+	const unsigned char *token;
+	size_t token_len;
+	int ret;
+
+	/* validate mechanism */
+	if (strcasecmp(mechanism, "INTERNAL") != 0) {
+		*client_error_r = t_strdup_printf("Unsupported URLAUTH mechanism: %s", mechanism);
+		return 0;
+	}
+
+	/* validate URL */
+	if (imap_url_parse(rumpurl, NULL, url_flags, &url, &error) < 0) {
+		*client_error_r = t_strdup_printf("Invalid URL: %s", error);
+		return 0;
+	}
+
+	if (url->mailbox == NULL || url->uid == 0 || url->search_program != NULL ||
+		url->uauth_rumpurl == NULL || url->uauth_mechanism != NULL) {
+		*client_error_r = "Invalid URL: Must be an URLAUTH rump URL";
+		return 0;
+	}
+
+	/* validate expiry time */
+	if (url->uauth_expire != (time_t)-1) {
+		time_t now = time(NULL);
+
+		if (now > url->uauth_expire) {
+			*client_error_r = t_strdup_printf("URLAUTH has already expired");
+			return 0;
+		}
+	}
+
+	/* validate user */
+	if (url->userid == NULL) {
+		*client_error_r = "Invalid URL: Missing user name";
+		return 0;
+	}
+	if (user->anonymous || strcmp(url->userid, user->username) != 0) {
+		*client_error_r = t_strdup_printf(
+			"Not permitted to generate URLAUTH for user %s",
+			url->userid);
+		return 0;
+	}
+
+	/* validate host:port */
+	if (!imap_urlauth_check_hostport(uctx, url, client_error_r))
+		return 0;
+
+	/* validate mailbox */
+	if ((ret = imap_msgpart_url_create(user, url, &mpurl, &error)) < 0 ||
+	    imap_msgpart_url_verify(mpurl, &error) <= 0) {
+		*client_error_r = t_strdup_printf("Invalid URL: %s", error);
+		if (mpurl != NULL)
+			imap_msgpart_url_free(&mpurl);
+		return ret;
+	}
+	box = imap_msgpart_url_get_mailbox(mpurl);
+
+	/* obtain mailbox key */
+	ret = imap_urlauth_backend_get_mailbox_key(box, TRUE, mailbox_key,
+						   client_error_r, &error_code);
+	if (ret < 0) {
+		imap_msgpart_url_free(&mpurl);
+		return ret;
+	}
+
+	token = imap_urlauth_internal_generate(rumpurl, mailbox_key, &token_len);
+	imap_msgpart_url_free(&mpurl);
+
+	*urlauth_r = imap_url_add_urlauth(rumpurl, mechanism, token, token_len);
+	return 1;
+}
+
+bool imap_urlauth_check(struct imap_urlauth_context *uctx,
+			struct imap_url *url, bool ignore_unknown_access,
+			const char **error_r)
+{
+	/* validate URL fields */
+	if (url->mailbox == NULL || url->uid == 0 ||
+	    url->search_program != NULL || url->uauth_rumpurl == NULL ||
+	    url->uauth_mechanism == NULL) {
+		*error_r = "Invalid URL: Must be a full URLAUTH URL";
+		return FALSE;
+	}
+
+	/* check presence of userid */
+	if (url->userid == NULL) {
+		*error_r = "Invalid URLAUTH: Missing user name";
+		return FALSE;
+	}
+
+	/* validate mechanism */
+	if (strcasecmp(url->uauth_mechanism, "INTERNAL") != 0) {
+		*error_r = t_strdup_printf("Unsupported URLAUTH mechanism: %s",
+					   url->uauth_mechanism);
+		return FALSE;
+	}
+
+	/* validate expiry time */
+	if (url->uauth_expire != (time_t)-1) {
+		time_t now = time(NULL);
+
+		if (now > url->uauth_expire) {
+			*error_r = t_strdup_printf("URLAUTH has expired");
+			return FALSE;
+		}
+	}
+
+	/* validate access */
+	if (!imap_urlauth_check_access(uctx, url, ignore_unknown_access,
+				       error_r))
+		return FALSE;
+	/* validate host:port */
+	if (!imap_urlauth_check_hostport(uctx, url, error_r))
+		return FALSE;
+	return TRUE;
+}
+
+int imap_urlauth_fetch_parsed(struct imap_urlauth_context *uctx,
+			      struct imap_url *url,
+			      struct imap_msgpart_url **mpurl_r,
+			      enum mail_error *error_code_r,
+			      const char **error_r)
+{
+	struct mail_user *user = uctx->user;
+	struct imap_msgpart_url *mpurl;
+	struct mailbox *box;
+	const char *error;
+	unsigned char mailbox_key[IMAP_URLAUTH_KEY_LEN];
+	int ret;
+
+	*mpurl_r = NULL;
+	*error_r = NULL;
+	*error_code_r = MAIL_ERROR_NONE;
+
+	/* check urlauth mechanism, access, userid and authority */
+	if (!imap_urlauth_check(uctx, url, FALSE, error_r)) {
+		*error_code_r = MAIL_ERROR_PARAMS;
+		return 0;
+	}
+
+	/* validate target user */
+	if (user->anonymous || strcmp(url->userid, user->username) != 0) {
+		*error_r = t_strdup_printf("Not permitted to fetch URLAUTH for user %s",
+					   url->userid);
+		*error_code_r = MAIL_ERROR_PARAMS;
+		return 0;
+	}
+
+	/* validate mailbox */
+	if ((ret = imap_msgpart_url_create(user, url, &mpurl, &error)) < 0) {
+		*error_r = t_strdup_printf("Invalid URLAUTH: %s", error);
+		*error_code_r = MAIL_ERROR_PARAMS;
+		return ret;
+	}
+
+	if ((ret = imap_msgpart_url_open_mailbox(mpurl, &box, error_code_r,
+						 &error)) < 0) {
+		*error_r = "Internal server error";
+		imap_msgpart_url_free(&mpurl);
+		return -1;
+	}
+
+	if (ret == 0) {
+		/* RFC says: `If the mailbox cannot be identified, an
+		   authorization token is calculated on the rump URL, using
+		   random "plausible" keys (selected by the server) as needed,
+		   before returning a validation failure. This prevents timing
+		   attacks aimed at identifying mailbox names.' */
+		random_fill(mailbox_key, sizeof(mailbox_key));
+		(void)imap_urlauth_internal_verify(url->uauth_rumpurl,
+			mailbox_key, url->uauth_token, url->uauth_token_size);
+
+		*error_r = t_strdup_printf("Invalid URLAUTH: %s", error);
+		imap_msgpart_url_free(&mpurl);
+		return 0;
+	}
+
+	/* obtain mailbox key */
+	ret = imap_urlauth_backend_get_mailbox_key(box, FALSE, mailbox_key,
+						   error_r, error_code_r);
+	if (ret < 0) {
+		imap_msgpart_url_free(&mpurl);
+		return -1;
+	}
+
+	if (ret == 0 ||
+	    !imap_urlauth_internal_verify(url->uauth_rumpurl, mailbox_key,
+					  url->uauth_token,
+					  url->uauth_token_size)) {
+		*error_r = "URLAUTH verification failed";
+		*error_code_r = MAIL_ERROR_PERM;
+		imap_msgpart_url_free(&mpurl);
+		ret = 0;
+	} else {
+		ret = 1;
+	}
+
+	safe_memset(mailbox_key, 0, sizeof(mailbox_key));
+	*mpurl_r = mpurl;
+	return ret;
+}
+
+int imap_urlauth_fetch(struct imap_urlauth_context *uctx,
+		       const char *urlauth, struct imap_msgpart_url **mpurl_r,
+		       enum mail_error *error_code_r, const char **error_r)
+{
+	struct imap_url *url;
+	enum imap_url_parse_flags url_flags = IMAP_URL_PARSE_ALLOW_URLAUTH;
+	const char *error;
+
+	/* validate URL */
+	if (imap_url_parse(urlauth, NULL, url_flags, &url, &error) < 0) {
+		*error_r = t_strdup_printf("Invalid URLAUTH: %s", error);
+		*error_code_r = MAIL_ERROR_PARAMS;
+		return 0;
+	}
+
+	return imap_urlauth_fetch_parsed(uctx, url, mpurl_r,
+					 error_code_r, error_r);
+}
+
+int imap_urlauth_reset_mailbox_key(struct imap_urlauth_context *uctx ATTR_UNUSED,
+				   struct mailbox *box)
+{
+	return imap_urlauth_backend_reset_mailbox_key(box);
+}
+
+int imap_urlauth_reset_all_keys(struct imap_urlauth_context *uctx)
+{
+	return imap_urlauth_backend_reset_all_keys(uctx->user);
+}
diff --git a/src/lib-imap-urlauth/imap-urlauth.h b/src/lib-imap-urlauth/imap-urlauth.h
new file mode 100644
index 0000000..9c7c30f
--- /dev/null
+++ b/src/lib-imap-urlauth/imap-urlauth.h
@@ -0,0 +1,55 @@
+#ifndef IMAP_URLAUTH_H
+#define IMAP_URLAUTH_H
+
+#include "net.h"
+
+#define IMAP_URLAUTH_SOCKET_NAME "imap-urlauth"
+
+struct imap_url;
+struct imap_msgpart_url;
+struct imap_urlauth_context;
+
+struct imap_urlauth_config {
+	const char *url_host;
+	in_port_t url_port;
+
+	const char *socket_path;
+	const char *session_id;
+
+	/* the user who is requesting access to URLAUTHs */
+	const char *access_user;
+	/* ... is using this service (i.e. imap or submission) */
+	const char *access_service;
+	/* ... represents these applications */
+	const char *const *access_applications;
+	/* ... is anonymous? */
+	bool access_anonymous;
+};
+
+struct imap_urlauth_context *
+imap_urlauth_init(struct mail_user *user,
+		  const struct imap_urlauth_config *config);
+void imap_urlauth_deinit(struct imap_urlauth_context **_uctx);
+
+int imap_urlauth_generate(struct imap_urlauth_context *uctx,
+			  const char *mechanism, const char *rumpurl,
+			  const char **urlauth_r, const char **client_error_r);
+
+bool imap_urlauth_check(struct imap_urlauth_context *uctx,
+			struct imap_url *url, bool ignore_unknown_access,
+			const char **error_r);
+
+int imap_urlauth_fetch_parsed(struct imap_urlauth_context *uctx,
+			      struct imap_url *url,
+			      struct imap_msgpart_url **mpurl_r,
+			      enum mail_error *error_code_r,
+			      const char **error_r);
+int imap_urlauth_fetch(struct imap_urlauth_context *uctx,
+		       const char *urlauth, struct imap_msgpart_url **mpurl_r,
+		       enum mail_error *error_code_r, const char **error_r);
+
+int imap_urlauth_reset_mailbox_key(struct imap_urlauth_context *uctx,
+				   struct mailbox *box);
+int imap_urlauth_reset_all_keys(struct imap_urlauth_context *uctx);
+
+#endif