src/pop3-login/client.c

	client.c revision b84eff65e25ae86dfd6f798386577209b94838c6
/* Copyright (c) 2002-2017 Dovecot authors, see the included COPYING file */

#include "login-common.h"
#include "base64.h"
#include "buffer.h"
#include "ioloop.h"
#include "istream.h"
#include "ostream.h"
#include "randgen.h"
#include "hostpid.h"
#include "safe-memset.h"
#include "str.h"
#include "strescape.h"
#include "master-service.h"
#include "client.h"
#include "client-authenticate.h"
#include "auth-client.h"
#include "ssl-proxy.h"
#include "pop3-proxy.h"
#include "pop3-login-settings.h"

/* Disconnect client when it sends too many bad commands */
#define CLIENT_MAX_BAD_COMMANDS 3

static bool cmd_stls(struct pop3_client *client)
{
    client_cmd_starttls(&client->common);
    return TRUE;
}

static bool cmd_quit(struct pop3_client *client)
{
    client_send_reply(&client->common, POP3_CMD_REPLY_OK, "Logging out");
    client_destroy(&client->common, "Aborted login");
    return TRUE;
}

static bool cmd_xclient(struct pop3_client *client, const char *args)
{
    const char *const *tmp;
    in_port_t remote_port;
    bool args_ok = TRUE;

    if (!client->common.trusted) {
        client_send_reply(&client->common, POP3_CMD_REPLY_OK,
                  "You are not from trusted IP - ignoring");
        return TRUE;
    }
    for (tmp = t_strsplit(args, " "); *tmp != NULL; tmp++) {
        if (strncasecmp(*tmp, "ADDR=", 5) == 0) {
            if (net_addr2ip(*tmp + 5, &client->common.ip) < 0)
                args_ok = FALSE;
        } else if (strncasecmp(*tmp, "PORT=", 5) == 0) {
            if (net_str2port(*tmp + 5, &remote_port) < 0)
                args_ok = FALSE;
            else
                client->common.remote_port = remote_port;
        } else if (strncasecmp(*tmp, "SESSION=", 8) == 0) {
            const char *value = *tmp + 8;

            if (strlen(value) <= LOGIN_MAX_SESSION_ID_LEN) {
                client->common.session_id =
                    p_strdup(client->common.pool, value);
            }
        } else if (strncasecmp(*tmp, "TTL=", 4) == 0) {
            if (str_to_uint(*tmp + 4, &client->common.proxy_ttl) < 0)
                args_ok = FALSE;
        } else if (strncasecmp(*tmp, "FORWARD=", 8) == 0) {
            size_t value_len = strlen((*tmp)+8);
            client->common.forward_fields =
                str_new(client->common.preproxy_pool,
                    MAX_BASE64_DECODED_SIZE(value_len));
            if (base64_decode((*tmp)+8, value_len, NULL,
                      client->common.forward_fields) < 0)
                args_ok = FALSE;
        }
    }
    if (!args_ok) {
        client_send_reply(&client->common, POP3_CMD_REPLY_ERROR,
                  "Invalid parameters");
        return TRUE;
    }

    /* args ok, set them and reset the state */
    client_send_reply(&client->common, POP3_CMD_REPLY_OK, "Updated");
    return TRUE;
}

static bool client_command_execute(struct pop3_client *client, const char *cmd,
                   const char *args)
{
    cmd = t_str_ucase(cmd);
    if (strcmp(cmd, "CAPA") == 0)
        return cmd_capa(client, args);
    if (strcmp(cmd, "USER") == 0)
        return cmd_user(client, args);
    if (strcmp(cmd, "PASS") == 0)
        return cmd_pass(client, args);
    if (strcmp(cmd, "AUTH") == 0)
        return cmd_auth(client, args);
    if (strcmp(cmd, "APOP") == 0)
        return cmd_apop(client, args);
    if (strcmp(cmd, "STLS") == 0)
        return cmd_stls(client);
    if (strcmp(cmd, "QUIT") == 0)
        return cmd_quit(client);
    if (strcmp(cmd, "XCLIENT") == 0)
        return cmd_xclient(client, args);
    if (strcmp(cmd, "XOIP") == 0) {
        /* Compatibility with Zimbra's patched nginx */
        return cmd_xclient(client, t_strconcat("ADDR=", args, NULL));
    }

    client_send_reply(&client->common, POP3_CMD_REPLY_ERROR,
              "Unknown command.");
    return FALSE;
}

static void pop3_client_input(struct client *client)
{
    i_assert(!client->authenticating);

    if (!client_read(client))
        return;

    client_ref(client);

    o_stream_cork(client->output);
    /* if a command starts an authentication, stop processing further
       commands until the authentication is finished. */
    while (!client->output->closed && !client->authenticating &&
           auth_client_is_connected(auth_client)) {
        if (!client->v.input_next_cmd(client))
            break;
    }

    if (auth_client != NULL && !auth_client_is_connected(auth_client))
        client->input_blocked = TRUE;

    if (client_unref(&client))
        o_stream_uncork(client->output);
}

static bool pop3_client_input_next_cmd(struct client *client)
{
    struct pop3_client *pop3_client = (struct pop3_client *)client;
    char *line, *args;

    if ((line = i_stream_next_line(client->input)) == NULL)
        return FALSE;

    args = strchr(line, ' ');
    if (args != NULL)
        *args++ = '\0';

    if (client_command_execute(pop3_client, line,
                   args != NULL ? args : ""))
        client->bad_counter = 0;
    else if (++client->bad_counter >= CLIENT_MAX_BAD_COMMANDS) {
        client_send_reply(client, POP3_CMD_REPLY_ERROR,
                  "Too many invalid bad commands.");
        client_destroy(client,
                   "Disconnected: Too many bad commands");
        return FALSE;
    }
    return TRUE;
}

static struct client *pop3_client_alloc(pool_t pool)
{
    struct pop3_client *pop3_client;

    pop3_client = p_new(pool, struct pop3_client, 1);
    return &pop3_client->common;
}

static void pop3_client_create(struct client *client ATTR_UNUSED,
                   void **other_sets ATTR_UNUSED)
{
}

static void pop3_client_destroy(struct client *client)
{
    struct pop3_client *pop3_client = (struct pop3_client *)client;

    i_free_and_null(pop3_client->last_user);
    i_free_and_null(pop3_client->apop_challenge);
}

static char *get_apop_challenge(struct pop3_client *client)
{
    unsigned char buffer[16];
    unsigned char buffer_base64[MAX_BASE64_ENCODED_SIZE(sizeof(buffer)) + 1];
    buffer_t buf;

    if (auth_client_find_mech(auth_client, "APOP") == NULL) {
        /* disabled, no need to present the challenge */
        return NULL;
    }

    auth_client_get_connect_id(auth_client, &client->apop_server_pid,
                   &client->apop_connect_uid);

    random_fill(buffer, sizeof(buffer));
    buffer_create_from_data(&buf, buffer_base64, sizeof(buffer_base64));
    base64_encode(buffer, sizeof(buffer), &buf);
    buffer_append_c(&buf, '\0');

    return i_strdup_printf("<%x.%x.%lx.%s@%s>",
                   client->apop_server_pid,
                   client->apop_connect_uid,
                   (unsigned long)ioloop_time,
                   (const char *)buf.data, my_hostname);
}

static void pop3_client_notify_auth_ready(struct client *client)
{
    struct pop3_client *pop3_client = (struct pop3_client *)client;
    string_t *str;

    client->io = io_add(client->fd, IO_READ, client_input, client);

    str = t_str_new(128);
    if (client->trusted) {
        /* Dovecot extension to avoid extra roundtrip for CAPA */
        str_append(str, "[XCLIENT] ");
    }
    str_append(str, client->set->login_greeting);

    pop3_client->apop_challenge = get_apop_challenge(pop3_client);
    if (pop3_client->apop_challenge != NULL)
        str_printfa(str, " %s", pop3_client->apop_challenge);
    client_send_reply(client, POP3_CMD_REPLY_OK, str_c(str));

    client->banner_sent = TRUE;
}

static void
pop3_client_notify_starttls(struct client *client,
                bool success, const char *text)
{
    if (success)
        client_send_reply(client, POP3_CMD_REPLY_OK, text);
    else
        client_send_reply(client, POP3_CMD_REPLY_ERROR, text);
}

static void pop3_client_starttls(struct client *client ATTR_UNUSED)
{
}

void client_send_reply(struct client *client, enum pop3_cmd_reply reply,
               const char *text)
{
    const char *prefix = "-ERR";

    switch (reply) {
    case POP3_CMD_REPLY_OK:
        prefix = "+OK";
        break;
    case POP3_CMD_REPLY_TEMPFAIL:
        prefix = "-ERR [SYS/TEMP]";
        break;
    case POP3_CMD_REPLY_AUTH_ERROR:
        if (text[0] == '[')
            prefix = "-ERR";
        else
            prefix = "-ERR [AUTH]";
        break;
    case POP3_CMD_REPLY_ERROR:
        break;
    }

    T_BEGIN {
        string_t *line = t_str_new(256);

        str_append(line, prefix);
        str_append_c(line, ' ');
        str_append(line, text);
        str_append(line, "\r\n");

        client_send_raw_data(client, str_data(line), str_len(line));
    } T_END;
}

static void
pop3_client_notify_disconnect(struct client *client,
                  enum client_disconnect_reason reason,
                  const char *text)
{
    if (reason == CLIENT_DISCONNECT_INTERNAL_ERROR)
        client_send_reply(client, POP3_CMD_REPLY_TEMPFAIL, text);
    else
        client_send_reply(client, POP3_CMD_REPLY_ERROR, text);
}

static void pop3_login_die(void)
{
    /* do nothing. pop3 connections typically die pretty quick anyway. */
}

static void pop3_login_preinit(void)
{
    login_set_roots = pop3_login_setting_roots;
}

static void pop3_login_init(void)
{
    /* override the default login_die() */
    master_service_set_die_callback(master_service, pop3_login_die);
}

static void pop3_login_deinit(void)
{
    clients_destroy_all();
}

static struct client_vfuncs pop3_client_vfuncs = {
    pop3_client_alloc,
    pop3_client_create,
    pop3_client_destroy,
    pop3_client_notify_auth_ready,
    pop3_client_notify_disconnect,
    NULL,
    pop3_client_notify_starttls,
    pop3_client_starttls,
    pop3_client_input,
    NULL,
    NULL,
    pop3_client_auth_result,
    pop3_proxy_reset,
    pop3_proxy_parse_line,
    pop3_proxy_error,
    pop3_proxy_get_state,
    client_common_send_raw_data,
    pop3_client_input_next_cmd,
    client_common_default_free,
};

static const struct login_binary pop3_login_binary = {
    .protocol = "pop3",
    .process_name = "pop3-login",
    .default_port = 110,
    .default_ssl_port = 995,

    .client_vfuncs = &pop3_client_vfuncs,
    .preinit = pop3_login_preinit,
    .init = pop3_login_init,
    .deinit = pop3_login_deinit,

    .sasl_support_final_reply = FALSE
};

int main(int argc, char *argv[])
{
    return login_binary_run(&pop3_login_binary, argc, argv);
}