1 files changed, 869 insertions, 0 deletions

diff --git a/src/pop3/pop3-client.c b/src/pop3/pop3-client.c
new file mode 100644
index 0000000..4bdbea2
--- /dev/null
+++ b/src/pop3/pop3-client.c
@@ -0,0 +1,869 @@
+/* Copyright (c) 2002-2018 Dovecot authors, see the included COPYING file */
+
+#include "pop3-common.h"
+#include "array.h"
+#include "ioloop.h"
+#include "net.h"
+#include "iostream.h"
+#include "istream.h"
+#include "ostream.h"
+#include "iostream-rawlog.h"
+#include "crc32.h"
+#include "str.h"
+#include "llist.h"
+#include "hostpid.h"
+#include "file-dotlock.h"
+#include "var-expand.h"
+#include "master-service.h"
+#include "mail-storage.h"
+#include "mail-storage-service.h"
+#include "mail-autoexpunge.h"
+#include "pop3-commands.h"
+#include "mail-search-build.h"
+#include "mail-namespace.h"
+
+#include <unistd.h>
+
+/* max. length of input command line (spec says 512) */
+#define MAX_INBUF_SIZE 2048
+
+/* Disconnect client when it sends too many bad commands in a row */
+#define CLIENT_MAX_BAD_COMMANDS 20
+
+/* Disconnect client after idling this many milliseconds */
+#define CLIENT_IDLE_TIMEOUT_MSECS (10*60*1000)
+/* If client starts idling for this many milliseconds, commit the current
+   transaction. This allows the mailbox to become unlocked. */
+#define CLIENT_COMMIT_TIMEOUT_MSECS (10*1000)
+
+#define POP3_LOCK_FNAME "dovecot-pop3-session.lock"
+#define POP3_SESSION_DOTLOCK_STALE_TIMEOUT_SECS (60*5)
+
+extern struct pop3_client_vfuncs pop3_client_vfuncs;
+
+struct pop3_module_register pop3_module_register = { 0 };
+
+struct client *pop3_clients;
+unsigned int pop3_client_count;
+
+static enum mail_sort_type pop3_sort_program[] = {
+	MAIL_SORT_POP3_ORDER,
+	MAIL_SORT_END
+};
+
+static const struct dotlock_settings session_dotlock_set = {
+	.timeout = 10,
+	.stale_timeout = POP3_SESSION_DOTLOCK_STALE_TIMEOUT_SECS,
+	.lock_suffix = "",
+	.use_io_notify = TRUE
+};
+
+static void client_input(struct client *client);
+static int client_output(struct client *client);
+
+static void client_commit_timeout(struct client *client)
+{
+	if (client->cmd != NULL) {
+		/* Can't commit while commands are running */
+		return;
+	}
+
+	(void)mailbox_transaction_commit(&client->trans);
+	client->trans = mailbox_transaction_begin(client->mailbox, 0, __func__);
+}
+
+static void client_idle_timeout(struct client *client)
+{
+	if (client->cmd != NULL) {
+		client_destroy(client, t_strdup_printf(
+			"Client has not read server output for for %"PRIdTIME_T" secs",
+			ioloop_time - client->last_output));
+	} else {
+		client_send_line(client, "-ERR Disconnected for inactivity.");
+		client_destroy(client, t_strdup_printf(
+			"Inactivity - no input for %"PRIdTIME_T" secs",
+			ioloop_time - client->last_input));
+	}
+}
+
+static int
+pop3_mail_get_size(struct client *client, struct mail *mail, uoff_t *size_r)
+{
+	int ret;
+
+	if (!client->set->pop3_fast_size_lookups)
+		return mail_get_virtual_size(mail, size_r);
+
+	/* first try to get the virtual size */
+	mail->lookup_abort = MAIL_LOOKUP_ABORT_READ_MAIL;
+	ret = mail_get_virtual_size(mail, size_r);
+	mail->lookup_abort = MAIL_LOOKUP_ABORT_NEVER;
+	if (ret == 0)
+		return 0;
+
+	if (mailbox_get_last_mail_error(mail->box) != MAIL_ERROR_LOOKUP_ABORTED)
+		return -1;
+
+	/* virtual size not available with a fast lookup.
+	   fallback to trying the physical size */
+	mail->lookup_abort = MAIL_LOOKUP_ABORT_READ_MAIL;
+	ret = mail_get_physical_size(mail, size_r);
+	mail->lookup_abort = MAIL_LOOKUP_ABORT_NEVER;
+	if (ret == 0)
+		return 0;
+
+	if (mailbox_get_last_mail_error(mail->box) != MAIL_ERROR_LOOKUP_ABORTED)
+		return -1;
+
+	/* no way to quickly get the size. fallback to doing a slow virtual
+	   size lookup */
+	return mail_get_virtual_size(mail, size_r);
+}
+
+static void
+msgnum_to_seq_map_add(ARRAY_TYPE(uint32_t) *msgnum_to_seq_map,
+		      struct client *client, struct mail *mail,
+		      unsigned int msgnum)
+{
+	uint32_t seq;
+
+	if (mail->seq == msgnum+1)
+		return;
+
+	if (!array_is_created(msgnum_to_seq_map))
+		i_array_init(msgnum_to_seq_map, client->messages_count);
+
+	/* add any messages between this and the previous one that had
+	   a POP3 order defined */
+	seq = array_count(msgnum_to_seq_map) + 1;
+	for (; seq <= msgnum; seq++)
+		array_push_back(msgnum_to_seq_map, &seq);
+	array_push_back(msgnum_to_seq_map, &mail->seq);
+}
+
+static int read_mailbox(struct client *client, uint32_t *failed_uid_r)
+{
+        struct mailbox_status status;
+        struct mailbox_transaction_context *t;
+	struct mail_search_args *search_args;
+	struct mail_search_arg *sarg;
+	struct mail_search_context *ctx;
+	struct mail *mail;
+	uoff_t size;
+	ARRAY(uoff_t) message_sizes;
+	ARRAY_TYPE(uint32_t) msgnum_to_seq_map = ARRAY_INIT;
+	unsigned int msgnum;
+	int ret = 1;
+
+	*failed_uid_r = 0;
+
+	mailbox_get_open_status(client->mailbox, STATUS_UIDVALIDITY, &status);
+	client->uid_validity = status.uidvalidity;
+	client->messages_count = status.messages;
+
+	t = mailbox_transaction_begin(client->mailbox, 0, __func__);
+
+	search_args = mail_search_build_init();
+	if (client->deleted_kw != NULL) {
+		sarg = mail_search_build_add(search_args, SEARCH_KEYWORDS);
+		sarg->match_not = TRUE;
+		sarg->value.str = p_strdup(search_args->pool,
+					   client->set->pop3_deleted_flag);
+		i_array_init(&client->all_seqs, 32);
+	} else {
+		mail_search_build_add_all(search_args);
+	}
+	mail_search_args_init(search_args, client->mailbox, TRUE, NULL);
+
+	ctx = mailbox_search_init(t, search_args, pop3_sort_program,
+				  client->set->pop3_fast_size_lookups ? 0 :
+				  MAIL_FETCH_VIRTUAL_SIZE, NULL);
+	mail_search_args_unref(&search_args);
+
+	client->last_seen_pop3_msn = 0;
+	client->total_size = 0;
+	i_array_init(&message_sizes, client->messages_count);
+
+	msgnum = 0;
+	while (mailbox_search_next(ctx, &mail)) {
+		if (pop3_mail_get_size(client, mail, &size) < 0) {
+			ret = mail->expunged ? 0 : -1;
+			*failed_uid_r = mail->uid;
+			break;
+		}
+		if (array_is_created(&client->all_seqs))
+			seq_range_array_add(&client->all_seqs, mail->seq);
+		msgnum_to_seq_map_add(&msgnum_to_seq_map, client, mail, msgnum);
+
+		if ((mail_get_flags(mail) & MAIL_SEEN) != 0)
+			client->last_seen_pop3_msn = msgnum + 1;
+		client->total_size += size;
+		if (client->highest_seq < mail->seq)
+			client->highest_seq = mail->seq;
+
+		array_push_back(&message_sizes, &size);
+		msgnum++;
+	}
+
+	if (mailbox_search_deinit(&ctx) < 0)
+		ret = -1;
+
+	if (ret <= 0) {
+		/* commit the transaction instead of rolling back to make sure
+		   we don't lose data (virtual sizes) added to cache file */
+		(void)mailbox_transaction_commit(&t);
+		array_free(&message_sizes);
+		if (array_is_created(&msgnum_to_seq_map))
+			array_free(&msgnum_to_seq_map);
+		return ret;
+	}
+	i_assert(msgnum <= client->messages_count);
+	client->messages_count = msgnum;
+
+	if (!array_is_created(&client->all_seqs)) {
+		i_array_init(&client->all_seqs, 1);
+		seq_range_array_add_range(&client->all_seqs, 1, msgnum);
+	}
+
+	client->trans = t;
+	client->message_sizes =
+		array_free_without_data(&message_sizes);
+	if (array_is_created(&msgnum_to_seq_map)) {
+		client->msgnum_to_seq_map_count =
+			array_count(&msgnum_to_seq_map);
+		client->msgnum_to_seq_map =
+			array_free_without_data(&msgnum_to_seq_map);
+	}
+	return 1;
+}
+
+static int init_pop3_deleted_flag(struct client *client, const char **error_r)
+{
+	const char *deleted_keywords[2];
+
+	if (client->set->pop3_deleted_flag[0] == '\0')
+		return 0;
+
+	deleted_keywords[0] = client->set->pop3_deleted_flag;
+	deleted_keywords[1] = NULL;
+	if (mailbox_keywords_create(client->mailbox, deleted_keywords,
+				    &client->deleted_kw) < 0) {
+		*error_r = t_strdup_printf(
+			"pop3_deleted_flags: Invalid keyword '%s': %s",
+			client->set->pop3_deleted_flag,
+			mailbox_get_last_internal_error(client->mailbox, NULL));
+		return -1;
+	}
+	return 0;
+}
+
+static int init_mailbox(struct client *client, const char **error_r)
+{
+	uint32_t failed_uid = 0, last_failed_uid = 0;
+	int i, ret = -1;
+
+	for (i = 0;; i++) {
+		if (mailbox_sync(client->mailbox,
+				 MAILBOX_SYNC_FLAG_FULL_READ) < 0) {
+			ret = -1;
+			break;
+		}
+
+		ret = read_mailbox(client, &failed_uid);
+		if (ret > 0)
+			return 0;
+		if (i == 2)
+			break;
+
+		/* well, sync and try again. maybe it works the second time. */
+		last_failed_uid = failed_uid;
+		failed_uid = 0;
+	}
+
+	if (ret < 0) {
+		*error_r = mailbox_get_last_internal_error(client->mailbox, NULL);
+		client_send_storage_error(client);
+	} else {
+		if (failed_uid == last_failed_uid && failed_uid != 0) {
+			/* failed twice in same message */
+			*error_r = t_strdup_printf(
+				"Getting size of message UID=%u failed",
+				failed_uid);
+		} else {
+			*error_r = "Can't sync mailbox: "
+				"Messages keep getting expunged";
+		}
+		client_send_line(client, "-ERR [SYS/TEMP] Couldn't sync mailbox.");
+	}
+	return -1;
+}
+
+static enum uidl_keys parse_uidl_keymask(const char *format)
+{
+	enum uidl_keys mask = 0;
+
+	for (; *format != '\0'; format++) {
+		if (format[0] == '%' && format[1] != '\0') {
+			switch (var_get_key(++format)) {
+			case 'v':
+				mask |= UIDL_UIDVALIDITY;
+				break;
+			case 'u':
+				mask |= UIDL_UID;
+				break;
+			case 'm':
+				mask |= UIDL_MD5;
+				break;
+			case 'f':
+				mask |= UIDL_FILE_NAME;
+				break;
+			case 'g':
+				mask |= UIDL_GUID;
+				break;
+			}
+		}
+	}
+	return mask;
+}
+
+static void pop3_lock_session_refresh(struct client *client)
+{
+	if (file_dotlock_touch(client->session_dotlock) < 0) {
+		client_send_line(client,
+			"-ERR [SYS/TEMP] Couldn't update POP3 session lock.");
+		client_destroy(client, "Couldn't lock POP3 session");
+	}
+}
+
+int pop3_lock_session(struct client *client)
+{
+	const struct mail_storage_settings *mail_set =
+		mail_storage_service_user_get_mail_set(client->service_user);
+	struct dotlock_settings dotlock_set;
+	enum mailbox_list_path_type type;
+	const char *dir, *path;
+	int ret;
+
+	if (mailbox_list_get_root_path(client->inbox_ns->list,
+				       MAILBOX_LIST_PATH_TYPE_INDEX, &dir)) {
+		type = MAILBOX_LIST_PATH_TYPE_INDEX;
+	} else if (mailbox_list_get_root_path(client->inbox_ns->list,
+					      MAILBOX_LIST_PATH_TYPE_DIR, &dir)) {
+		type = MAILBOX_LIST_PATH_TYPE_DIR;
+	} else {
+		i_error("pop3_lock_session: Storage has no root/index directory, "
+			"can't create a POP3 session lock file");
+		return -1;
+	}
+	if (mailbox_list_mkdir_root(client->inbox_ns->list, dir, type) < 0) {
+		i_error("pop3_lock_session: Couldn't create root directory %s: %s",
+			dir, mailbox_list_get_last_internal_error(client->inbox_ns->list, NULL));
+		return -1;
+	}
+	path = t_strdup_printf("%s/"POP3_LOCK_FNAME, dir);
+
+	dotlock_set = session_dotlock_set;
+	dotlock_set.use_excl_lock = mail_set->dotlock_use_excl;
+	dotlock_set.nfs_flush = mail_set->mail_nfs_storage;
+
+	ret = file_dotlock_create(&dotlock_set, path, 0,
+				  &client->session_dotlock);
+	if (ret < 0)
+		i_error("file_dotlock_create(%s) failed: %m", path);
+	else if (ret > 0) {
+		client->to_session_dotlock_refresh =
+			timeout_add(POP3_SESSION_DOTLOCK_STALE_TIMEOUT_SECS*1000,
+				    pop3_lock_session_refresh, client);
+	}
+	return ret;
+}
+
+struct client *client_create(int fd_in, int fd_out,
+			     struct mail_user *user,
+			     struct mail_storage_service_user *service_user,
+			     const struct pop3_settings *set)
+{
+	struct client *client;
+	pool_t pool;
+
+	/* always use nonblocking I/O */
+	net_set_nonblock(fd_in, TRUE);
+	net_set_nonblock(fd_out, TRUE);
+
+	pool = pool_alloconly_create("pop3 client", 256);
+	client = p_new(pool, struct client, 1);
+	client->pool = pool;
+	client->service_user = service_user;
+	client->v = pop3_client_vfuncs;
+	client->set = set;
+	client->fd_in = fd_in;
+	client->fd_out = fd_out;
+	client->input = i_stream_create_fd(fd_in, MAX_INBUF_SIZE);
+	client->output = o_stream_create_fd(fd_out, SIZE_MAX);
+	o_stream_set_no_error_handling(client->output, TRUE);
+	o_stream_set_flush_callback(client->output, client_output, client);
+
+	p_array_init(&client->module_contexts, client->pool, 5);
+        client->last_input = ioloop_time;
+	client->to_idle = timeout_add(CLIENT_IDLE_TIMEOUT_MSECS,
+				      client_idle_timeout, client);
+	client->to_commit = timeout_add(CLIENT_COMMIT_TIMEOUT_MSECS,
+					client_commit_timeout, client);
+
+	client->user = user;
+
+	client->mail_set = mail_user_set_get_storage_set(user);
+	client->uidl_keymask =
+		parse_uidl_keymask(client->mail_set->pop3_uidl_format);
+	if (client->uidl_keymask == 0)
+		i_fatal("Invalid pop3_uidl_format");
+
+	if (var_has_key(set->pop3_logout_format, 'u', "uidl_change")) {
+		/* logging uidl_change. we need hashes of the UIDLs */
+		client->message_uidls_save = TRUE;
+	} else if (strcmp(set->pop3_uidl_duplicates, "allow") != 0) {
+		/* UIDL duplicates aren't allowed, so we'll need to
+		   keep track of them */
+		client->message_uidls_save = TRUE;
+	}
+
+	pop3_client_count++;
+	DLLIST_PREPEND(&pop3_clients, client);
+
+	if (hook_client_created != NULL)
+		hook_client_created(&client);
+
+	return client;
+}
+
+void client_create_finish(struct client *client)
+{
+	if (client->set->rawlog_dir[0] != '\0') {
+		(void)iostream_rawlog_create(client->set->rawlog_dir,
+					     &client->input, &client->output);
+	}
+	client->io = io_add_istream(client->input, client_input, client);
+}
+
+int client_init_mailbox(struct client *client, const char **error_r)
+{
+        enum mailbox_flags flags;
+	const char *ident, *errmsg;
+
+	/* refresh proctitle before a potentially long-running init_mailbox() */
+	pop3_refresh_proctitle();
+
+	flags = MAILBOX_FLAG_POP3_SESSION;
+	if (!client->set->pop3_no_flag_updates)
+		flags |= MAILBOX_FLAG_DROP_RECENT;
+	client->mailbox = mailbox_alloc(client->inbox_ns->list, "INBOX", flags);
+	if (mailbox_open(client->mailbox) < 0) {
+		*error_r = t_strdup_printf("Couldn't open INBOX: %s",
+			mailbox_get_last_internal_error(client->mailbox, NULL));
+		client_send_storage_error(client);
+		return -1;
+	}
+
+	if (init_pop3_deleted_flag(client, &errmsg) < 0 ||
+	    init_mailbox(client, &errmsg) < 0) {
+		*error_r = t_strdup_printf("Couldn't init INBOX: %s", errmsg);
+		return -1;
+	}
+
+	if (!client->set->pop3_no_flag_updates && client->messages_count > 0)
+		client->seen_bitmask = i_malloc(MSGS_BITMASK_SIZE(client));
+
+	ident = mail_user_get_anvil_userip_ident(client->user);
+	if (ident != NULL) {
+		master_service_anvil_send(master_service, t_strconcat(
+			"CONNECT\t", my_pid, "\tpop3/", ident, "\n", NULL));
+		client->anvil_sent = TRUE;
+	}
+	return 0;
+}
+
+static const char *client_build_uidl_change_string(struct client *client)
+{
+	uint32_t i, old_hash, new_hash;
+	unsigned int old_msg_count, new_msg_count;
+
+	if (client->message_uidls == NULL) {
+		/* UIDL command not given */
+		return "";
+	}
+
+	/* 1..new-1 were probably left to mailbox by previous POP3 session */
+	old_msg_count = client->lowest_retr_pop3_msn > 0 ?
+		client->lowest_retr_pop3_msn - 1 : client->messages_count;
+	for (i = 0, old_hash = 0; i < old_msg_count; i++)
+		old_hash ^= crc32_str(client->message_uidls[i]);
+
+	/* assume all except deleted messages were sent to POP3 client */
+	if (!client->deleted) {
+		for (i = 0, new_hash = 0; i < client->messages_count; i++)
+			new_hash ^= crc32_str(client->message_uidls[i]);
+	} else {
+		for (i = 0, new_hash = 0; i < client->messages_count; i++) {
+			if ((client->deleted_bitmask[i / CHAR_BIT] &
+			     (1 << (i % CHAR_BIT))) != 0)
+				continue;
+			new_hash ^= crc32_str(client->message_uidls[i]);
+		}
+	}
+
+	new_msg_count = client->messages_count - client->deleted_count;
+	if (old_hash == new_hash && old_msg_count == new_msg_count)
+		return t_strdup_printf("%u/%08x", old_msg_count, old_hash);
+	else {
+		return t_strdup_printf("%u/%08x -> %u/%08x",
+				       old_msg_count, old_hash,
+				       new_msg_count, new_hash);
+	}
+}
+
+static const char *client_stats(struct client *client)
+{
+	const char *uidl_change = "";
+	if (var_has_key(client->set->pop3_logout_format,
+			'o', "uidl_change"))
+		uidl_change = client_build_uidl_change_string(client);
+
+	const struct var_expand_table logout_tab[] = {
+		{ 'p', dec2str(client->top_bytes), "top_bytes" },
+		{ 't', dec2str(client->top_count), "top_count" },
+		{ 'b', dec2str(client->retr_bytes), "retr_bytes" },
+		{ 'r', dec2str(client->retr_count), "retr_count" },
+		{ 'd', !client->delete_success ? "0" :
+		       dec2str(client->deleted_count), "deleted_count" },
+		{ 'm', dec2str(client->messages_count), "message_count" },
+		{ 's', dec2str(client->total_size), "message_bytes" },
+		{ 'i', dec2str(client->input->v_offset), "input" },
+		{ 'o', dec2str(client->output->offset), "output" },
+		{ 'u', uidl_change, "uidl_change" },
+		{ '\0', !client->delete_success ? "0" :
+		        dec2str(client->deleted_size), "deleted_bytes" },
+		{ '\0', NULL, NULL }
+	};
+	const struct var_expand_table *user_tab =
+		mail_user_var_expand_table(client->user);
+	const struct var_expand_table *tab =
+		t_var_expand_merge_tables(logout_tab, user_tab);
+	string_t *str;
+	const char *error;
+
+	str = t_str_new(128);
+	if (var_expand_with_funcs(str, client->set->pop3_logout_format,
+				  tab, mail_user_var_expand_func_table,
+				  client->user, &error) < 0) {
+		i_error("Failed to expand pop3_logout_format=%s: %s",
+			client->set->pop3_logout_format, error);
+	}
+	return str_c(str);
+}
+
+void client_destroy(struct client *client, const char *reason)
+{
+	client->v.destroy(client, reason);
+}
+
+static void client_default_destroy(struct client *client, const char *reason)
+{
+	i_assert(!client->destroyed);
+
+	client->destroyed = TRUE;
+
+	if (client->seen_change_count > 0)
+		(void)client_update_mails(client);
+
+	if (!client->disconnected) {
+		if (reason == NULL) {
+			reason = io_stream_get_disconnect_reason(client->input,
+								 client->output);
+		}
+		i_info("Disconnected: %s %s", reason, client_stats(client));
+	}
+
+	if (client->cmd != NULL) {
+		/* deinitialize command */
+		i_stream_close(client->input);
+		o_stream_close(client->output);
+		client->cmd(client);
+		i_assert(client->cmd == NULL);
+	}
+
+	if (client->trans != NULL) {
+		/* client didn't QUIT, but we still want to save any changes
+		   done in this transaction. especially the cached virtual
+		   message sizes. */
+		(void)mailbox_transaction_commit(&client->trans);
+	}
+	if (array_is_created(&client->all_seqs))
+		array_free(&client->all_seqs);
+	if (client->deleted_kw != NULL)
+		mailbox_keywords_unref(&client->deleted_kw);
+	if (client->mailbox != NULL)
+		mailbox_free(&client->mailbox);
+	if (client->anvil_sent) {
+		master_service_anvil_send(master_service, t_strconcat(
+			"DISCONNECT\t", my_pid, "\tpop3/",
+			mail_user_get_anvil_userip_ident(client->user),
+			"\n", NULL));
+	}
+
+	if (client->session_dotlock != NULL)
+		file_dotlock_delete(&client->session_dotlock);
+	timeout_remove(&client->to_session_dotlock_refresh);
+
+	pool_unref(&client->uidl_pool);
+	i_free(client->message_sizes);
+	i_free(client->deleted_bitmask);
+	i_free(client->seen_bitmask);
+	i_free(client->msgnum_to_seq_map);
+
+	io_remove(&client->io);
+	timeout_remove(&client->to_idle);
+	timeout_remove(&client->to_commit);
+
+	i_stream_destroy(&client->input);
+	o_stream_destroy(&client->output);
+
+	fd_close_maybe_stdio(&client->fd_in, &client->fd_out);
+
+	/* Autoexpunging might run for a long time. Disconnect the client
+	   before it starts, and refresh proctitle so it's clear that it's
+	   doing autoexpunging. We've also sent DISCONNECT to anvil already,
+	   because this is background work and shouldn't really be counted
+	   as an active POP3 session for the user. */
+	pop3_refresh_proctitle();
+	mail_user_autoexpunge(client->user);
+	mail_user_deinit(&client->user);
+	mail_storage_service_user_unref(&client->service_user);
+
+	pop3_client_count--;
+	DLLIST_REMOVE(&pop3_clients, client);
+	pool_unref(&client->pool);
+
+	master_service_client_connection_destroyed(master_service);
+	pop3_refresh_proctitle();
+}
+
+static void client_destroy_timeout(struct client *client)
+{
+	client_destroy(client, NULL);
+}
+
+void client_disconnect(struct client *client, const char *reason)
+{
+	if (client->disconnected)
+		return;
+
+	client->disconnected = TRUE;
+	i_info("Disconnected: %s %s", reason, client_stats(client));
+
+	(void)o_stream_flush(client->output);
+
+	i_stream_close(client->input);
+	o_stream_close(client->output);
+
+	timeout_remove(&client->to_idle);
+	client->to_idle = timeout_add(0, client_destroy_timeout, client);
+}
+
+void client_send_line(struct client *client, const char *fmt, ...)
+{
+	va_list va;
+	ssize_t ret;
+
+	if (client->output->closed)
+		return;
+
+	va_start(va, fmt);
+
+	T_BEGIN {
+		string_t *str;
+
+		str = t_str_new(256);
+		str_vprintfa(str, fmt, va);
+		str_append(str, "\r\n");
+
+		ret = o_stream_send(client->output,
+				    str_data(str), str_len(str));
+		i_assert(ret < 0 || (size_t)ret == str_len(str));
+	} T_END;
+	if (ret >= 0) {
+		if (!POP3_CLIENT_OUTPUT_FULL(client))
+			client->last_output = ioloop_time;
+		else if (client->io != NULL) {
+			/* no more input until client has read
+			   our output */
+			io_remove(&client->io);
+
+			/* If someone happens to flush output, we want to get
+			   our IO handler back in flush callback */
+			o_stream_set_flush_pending(client->output, TRUE);
+		}
+	}
+	va_end(va);
+}
+
+void client_send_storage_error(struct client *client)
+{
+	const char *errstr;
+	enum mail_error error;
+
+	if (mailbox_is_inconsistent(client->mailbox)) {
+		client_send_line(client, "-ERR [SYS/TEMP] Mailbox is in inconsistent "
+				 "state, please relogin.");
+		client_disconnect(client, "Mailbox is in inconsistent state.");
+		return;
+	}
+
+	errstr = mailbox_get_last_error(client->mailbox, &error);
+	switch (error) {
+	case MAIL_ERROR_TEMP:
+	case MAIL_ERROR_NOQUOTA:
+	case MAIL_ERROR_INUSE:
+		client_send_line(client, "-ERR [SYS/TEMP] %s", errstr);
+		break;
+	default:
+		client_send_line(client, "-ERR [SYS/PERM] %s", errstr);
+		break;
+	}
+}
+
+bool client_handle_input(struct client *client)
+{
+	char *line, *args;
+	int ret;
+
+	o_stream_cork(client->output);
+	while (!client->output->closed &&
+	       (line = i_stream_next_line(client->input)) != NULL) {
+		args = strchr(line, ' ');
+		if (args != NULL)
+			*args++ = '\0';
+
+		const struct pop3_command *cmd = pop3_command_find(line);
+		if (cmd == NULL) {
+			client_send_line(client, "-ERR Unknown command: %s", line);
+			ret = -1;
+		} else T_BEGIN {
+			const char *reason_code =
+				event_reason_code_prefix("pop3", "cmd_",
+							 cmd->name);
+			struct event_reason *reason =
+				event_reason_begin(reason_code);
+			ret = client_command_execute(client, cmd,
+						     args != NULL ? args : "");
+			event_reason_end(&reason);
+		} T_END;
+		if (ret >= 0) {
+			client->bad_counter = 0;
+			if (client->cmd != NULL) {
+				o_stream_set_flush_pending(client->output,
+							   TRUE);
+				client->waiting_input = TRUE;
+				break;
+			}
+		} else if (++client->bad_counter > CLIENT_MAX_BAD_COMMANDS) {
+			client_send_line(client, "-ERR Too many bad commands.");
+			client_disconnect(client, "Too many bad commands.");
+		}
+	}
+	o_stream_uncork(client->output);
+
+	if (client->output->closed) {
+		client_destroy(client, NULL);
+		return FALSE;
+	}
+	return TRUE;
+}
+
+static void client_input(struct client *client)
+{
+	if (client->cmd != NULL) {
+		/* we're still processing a command. wait until it's
+		   finished. */
+		io_remove(&client->io);
+		client->waiting_input = TRUE;
+		return;
+	}
+
+	client->waiting_input = FALSE;
+	client->last_input = ioloop_time;
+	timeout_reset(client->to_idle);
+	if (client->to_commit != NULL)
+		timeout_reset(client->to_commit);
+
+	switch (i_stream_read(client->input)) {
+	case -1:
+		/* disconnected */
+		client_destroy(client, NULL);
+		return;
+	case -2:
+		/* line too long, kill it */
+		client_send_line(client, "-ERR Input line too long.");
+		client_destroy(client, "Input line too long");
+		return;
+	}
+
+	(void)client_handle_input(client);
+}
+
+static int client_output(struct client *client)
+{
+	if (o_stream_flush(client->output) < 0) {
+		client_destroy(client, NULL);
+		return 1;
+	}
+
+	client->last_output = ioloop_time;
+	timeout_reset(client->to_idle);
+	if (client->to_commit != NULL)
+		timeout_reset(client->to_commit);
+
+	if (client->cmd != NULL)
+		client->cmd(client);
+
+	if (client->cmd == NULL) {
+		if (o_stream_get_buffer_used_size(client->output) <
+		    POP3_OUTBUF_THROTTLE_SIZE/2 && client->io == NULL &&
+		    !client->input->closed) {
+			/* enable input again */
+			client->io = io_add_istream(client->input, client_input,
+						    client);
+		}
+		if (client->io != NULL && client->waiting_input) {
+			if (!client_handle_input(client)) {
+				/* client got destroyed */
+				return 1;
+			}
+		}
+	}
+
+	if (client->cmd != NULL) {
+		/* command not finished yet */
+		return 0;
+	} else if (client->io == NULL) {
+		/* data still in output buffer, get back here to add IO */
+		return 0;
+	} else {
+		return 1;
+	}
+}
+
+void clients_destroy_all(void)
+{
+	while (pop3_clients != NULL) {
+		mail_storage_service_io_activate_user(pop3_clients->service_user);
+		if (pop3_clients->cmd == NULL) {
+			client_send_line(pop3_clients,
+				"-ERR [SYS/TEMP] Server shutting down.");
+		}
+		client_destroy(pop3_clients, "Server shutting down.");
+	}
+}
+
+struct pop3_client_vfuncs pop3_client_vfuncs = {
+	client_default_destroy
+};