src/lda/main.c

/* Copyright (c) 2005-2018 Dovecot authors, see the included COPYING file */

#include "lib.h"
#include "lib-signals.h"
#include "ioloop.h"
#include "env-util.h"
#include "istream.h"
#include "istream-seekable.h"
#include "path-util.h"
#include "safe-mkstemp.h"
#include "eacces-error.h"
#include "ipwd.h"
#include "str.h"
#include "str-sanitize.h"
#include "strescape.h"
#include "unichar.h"
#include "rfc822-parser.h"
#include "message-address.h"
#include "smtp-address.h"
#include "settings-parser.h"
#include "master-service.h"
#include "master-service-settings.h"
#include "mail-storage-service.h"
#include "mail-namespace.h"
#include "raw-storage.h"
#include "mail-deliver.h"
#include "mail-send.h"
#include "mbox-from.h"
#include "smtp-submit-settings.h"
#include "lda-settings.h"

#include <stdio.h>
#include <sysexits.h>

#define DEFAULT_ENVELOPE_SENDER \
    SMTP_ADDRESS_LITERAL("MAILER-DAEMON", NULL)

/* After buffer grows larger than this, create a temporary file to /tmp
   where to read the mail. */
#define MAIL_MAX_MEMORY_BUFFER (1024*128)

static const char *wanted_headers[] = {
    "From", "To", "Message-ID", "Subject", "Return-Path",
    NULL
};

static int seekable_fd_callback(const char **path_r, void *context)
{
    struct mail_deliver_context *ctx = context;
    string_t *path;
    int fd;

    path = t_str_new(128);
    mail_user_set_get_temp_prefix(path, ctx->rcpt_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 struct istream *
create_raw_stream(struct mail_deliver_context *ctx,
          int fd, time_t *mtime_r)
{
    struct istream *input, *input2, *input_list[2];
    const unsigned char *data;
    const char *error;
    char *sender = NULL;
    size_t i, size;
    int ret, tz;

    *mtime_r = (time_t)-1;
    fd_set_nonblock(fd, FALSE);

    input = i_stream_create_fd(fd, 4096);
    input->blocking = TRUE;
    /* If input begins with a From-line, drop it */
    ret = i_stream_read_bytes(input, &data, &size, 5);
    if (ret > 0 && memcmp(data, "From ", 5) == 0) {
        /* skip until the first LF */
        i_stream_skip(input, 5);
        while (i_stream_read_more(input, &data, &size) > 0) {
            for (i = 0; i < size; i++) {
                if (data[i] == '\n')
                    break;
            }
            if (i != size) {
                (void)mbox_from_parse(data, i, mtime_r, &tz,
                              &sender);
                i_stream_skip(input, i + 1);
                break;
            }
            i_stream_skip(input, size);
        }
    }

    if (sender != NULL && ctx->mail_from == NULL) {
        struct smtp_address *mail_from = NULL;
        /* use the envelope sender from From_-line, but only if it
           hasn't been specified with -f already. */
        if (smtp_address_parse_mailbox(ctx->pool,
            sender, 0, &mail_from, &error) < 0) {
            i_warning("Failed to parse address from `From_'-line: %s",
                  error);
        }
        ctx->mail_from = mail_from;
    }
    i_free(sender);

    if (input->v_offset == 0) {
        input2 = input;
        i_stream_ref(input2);
    } else {
        input2 = i_stream_create_limit(input, (uoff_t)-1);
    }
    i_stream_unref(&input);

    input_list[0] = input2; input_list[1] = NULL;
    input = i_stream_create_seekable(input_list, MAIL_MAX_MEMORY_BUFFER,
                     seekable_fd_callback, ctx);
    i_stream_unref(&input2);
    return input;
}

static struct mail *
lda_raw_mail_open(struct mail_deliver_context *ctx, const char *path)
{
    struct mail_user *raw_mail_user;
    struct mailbox *box;
    struct mailbox_transaction_context *t;
    struct mail *mail;
    struct mailbox_header_lookup_ctx *headers_ctx;
    const struct smtp_address *mail_from;
    struct istream *input;
    void **sets;
    time_t mtime;
    int ret;

    sets = master_service_settings_get_others(master_service);
    raw_mail_user =
        raw_storage_create_from_set(ctx->rcpt_user->set_info, sets[0]);

    mail_from = ctx->mail_from != NULL ?
        ctx->mail_from : DEFAULT_ENVELOPE_SENDER;
    if (path == NULL) {
        input = create_raw_stream(ctx, 0, &mtime);
        i_stream_set_name(input, "stdin");
        ret = raw_mailbox_alloc_stream(raw_mail_user, input, mtime,
                           smtp_address_encode(mail_from), &box);
        i_stream_unref(&input);
    } else {
        ret = raw_mailbox_alloc_path(raw_mail_user, path, (time_t)-1,
                         smtp_address_encode(mail_from), &box);
    }
    if (ret < 0) {
        i_fatal("Can't open delivery mail as raw: %s",
            mailbox_get_last_internal_error(box, NULL));
    }
    mail_user_unref(&raw_mail_user);

    t = mailbox_transaction_begin(box, 0, __func__);
    headers_ctx = mailbox_header_lookup_init(box, wanted_headers);
    mail = mail_alloc(t, 0, headers_ctx);
    mailbox_header_lookup_unref(&headers_ctx);
    mail_set_seq(mail, 1);
    return mail;
}

static void
lda_set_rcpt_to(struct mail_deliver_context *ctx,
        const struct smtp_address *rcpt_to, const char *user,
        const char *rcpt_to_source)
{
    const char *error;

    if (rcpt_to == NULL &&
        *ctx->set->lda_original_recipient_header != '\0') {
        rcpt_to = mail_deliver_get_address(ctx->src_mail,
                    ctx->set->lda_original_recipient_header);
        rcpt_to_source = t_strconcat(
            ctx->set->lda_original_recipient_header, " header", NULL);
    }
    if (rcpt_to == NULL) {
        struct smtp_address *user_addr;

        if (smtp_address_parse_username(ctx->pool, user,
            &user_addr, &error) < 0) {
            i_fatal_status(EX_USAGE,
                "Cannot obtain SMTP address from username `%s': %s",
                user, error);
        }
        if (user_addr->domain == NULL)
            user_addr->domain = ctx->set->hostname;
        rcpt_to = user_addr;
        rcpt_to_source = "user@hostname";
    }

    ctx->rcpt_params.orcpt.addr = rcpt_to;
    if (ctx->rcpt_to == NULL)
        ctx->rcpt_to = rcpt_to;

    if (ctx->rcpt_user->mail_debug) {
        i_debug("Destination address: %s (source: %s)",
            smtp_address_encode_path(rcpt_to), rcpt_to_source);
    }
}

static void failure_exit_callback(int *status)
{
    /* we want all our exit codes to be sysexits.h compatible.
       if we failed because of a logging related error, we most likely
       aren't writing to stderr, so try writing there to give some kind of
       a clue what's wrong. FATAL_LOGOPEN failure already wrote to
       stderr, so don't duplicate it. */
    switch (*status) {
    case FATAL_LOGWRITE:
        fputs("Failed to write to log file", stderr);
        break;
    case FATAL_LOGERROR:
        fputs("Internal logging error", stderr);
        break;
    case FATAL_LOGOPEN:
    case FATAL_OUTOFMEM:
    case FATAL_EXEC:
    case FATAL_DEFAULT:
        break;
    default:
        return;
    }
    *status = EX_TEMPFAIL;
}

static void print_help(void)
{
    printf(
"Usage: dovecot-lda [-c <config file>] [-a <address>] [-d <username>] [-p <path>]\n"
"                   [-f <envelope sender>] [-m <mailbox>] [-e] [-k]\n");
}

int main(int argc, char *argv[])
{
    const struct setting_parser_info *set_roots[] = {
        &smtp_submit_setting_parser_info,
        &lda_setting_parser_info,
        NULL
    };
    struct mail_deliver_context ctx;
    enum mail_storage_service_flags service_flags = 0;
    const char *user, *errstr, *path;
    struct lda_settings *lda_set;
    struct smtp_submit_settings *smtp_set;
    struct smtp_address *rcpt_to, *final_rcpt_to, *mail_from;
    struct mail_storage_service_ctx *storage_service;
    struct mail_storage_service_user *service_user;
    struct mail_storage_service_input service_input;
    const struct var_expand_table *var_table;
    struct mail_storage *storage;
    const char *user_source = "", *rcpt_to_source = "";
    uid_t process_euid;
    bool stderr_rejection = FALSE;
    int ret, c;
    enum mail_error error;

    if (getuid() != geteuid() && geteuid() == 0) {
        /* running setuid - don't allow this if the binary is
           executable by anyone */
        struct stat st;

        if (stat(argv[0], &st) < 0) {
            fprintf(stderr, "stat(%s) failed: %s\n",
                argv[0], strerror(errno));
            return EX_TEMPFAIL;
        } else if ((st.st_mode & 1) != 0 && (st.st_mode & 04000) != 0) {
            fprintf(stderr, "%s must not be both world-executable "
                "and setuid-root. This allows root exploits. "
                "See http://wiki2.dovecot.org/LDA#multipleuids\n",
                argv[0]);
            return EX_TEMPFAIL;
        }
    }

    i_set_failure_exit_callback(failure_exit_callback);

    master_service = master_service_init("lda",
        MASTER_SERVICE_FLAG_STANDALONE |
        MASTER_SERVICE_FLAG_DONT_LOG_TO_STDERR |
        MASTER_SERVICE_FLAG_NO_INIT_DATASTACK_FRAME,
        &argc, &argv, "a:d:ef:m:p:r:");

    i_zero(&ctx);
    ctx.session = mail_deliver_session_init();
    ctx.pool = ctx.session->pool;
    ctx.rcpt_default_mailbox = "INBOX";
    path = NULL;

    user = getenv("USER");
    mail_from = final_rcpt_to = rcpt_to = NULL;
    while ((c = master_getopt(master_service)) > 0) {
        switch (c) {
        case 'a':
            /* original recipient address */
            if (smtp_address_parse_path(ctx.pool, optarg,
                SMTP_ADDRESS_PARSE_FLAG_ALLOW_LOCALPART |
                    SMTP_ADDRESS_PARSE_FLAG_BRACKETS_OPTIONAL,
                &rcpt_to, &errstr) < 0) {
                i_fatal_status(EX_USAGE,
                    "Invalid -a parameter: %s", errstr);
            }
            rcpt_to_source = "-a parameter";
            break;
        case 'd':
            /* destination user */
            user = optarg;
            service_flags |= MAIL_STORAGE_SERVICE_FLAG_USERDB_LOOKUP;
            break;
        case 'e':
            stderr_rejection = TRUE;
            break;
        case 'f':
            /* envelope sender address */
            if (smtp_address_parse_path(ctx.pool, optarg,
                SMTP_ADDRESS_PARSE_FLAG_BRACKETS_OPTIONAL,
                &mail_from, &errstr) < 0) {
                i_fatal_status(EX_USAGE,
                    "Invalid -f parameter: %s", errstr);
            }
            break;
        case 'm':
            /* destination mailbox.
               Ignore -m "". This allows doing -m ${extension}
               in Postfix to handle user+mailbox */
            if (*optarg != '\0') T_BEGIN {
                if (!uni_utf8_str_is_valid(optarg)) {
                    i_fatal("Mailbox name not UTF-8: %s",
                        optarg);
                }
                ctx.rcpt_default_mailbox = optarg;
            } T_END;
            break;
        case 'p':
            /* input path */
            if (t_abspath(optarg, &path, &errstr) < 0) {
                i_fatal("t_abspath(%s) failed: %s",
                    optarg, errstr);
            }
            break;
        case 'r':
            /* final recipient address */
            if (smtp_address_parse_path(ctx.pool, optarg,
                SMTP_ADDRESS_PARSE_FLAG_ALLOW_LOCALPART |
                SMTP_ADDRESS_PARSE_FLAG_BRACKETS_OPTIONAL,
                &final_rcpt_to, &errstr) < 0) {
                i_fatal_status(EX_USAGE,
                    "Invalid -a parameter: %s", errstr);
            }
            break;
        default:
            print_help();
            return EX_USAGE;
        }
    }
    if (optind != argc) {
        print_help();
        i_fatal_status(EX_USAGE, "Unknown argument: %s", argv[optind]);
    }

    process_euid = geteuid();
    if ((service_flags & MAIL_STORAGE_SERVICE_FLAG_USERDB_LOOKUP) != 0)
        ;
    else if (process_euid != 0) {
        /* we're non-root. get our username and possibly our home. */
        struct passwd pw;
        const char *home;

        home = getenv("HOME");
        if (user != NULL && home != NULL) {
            /* no need for a pw lookup */
            user_source = "USER environment";
        } else if ((ret = i_getpwuid(process_euid, &pw)) > 0) {
            user = t_strdup(pw.pw_name);
            if (home == NULL)
                env_put(t_strconcat("HOME=", pw.pw_dir, NULL));
            user_source = "passwd lookup for process euid";
        } else if (ret < 0) {
            /* temporary failure */
            i_fatal("getpwuid() failed: %m");
        } else if (user == NULL) {
            i_fatal_status(EX_USAGE,
                       "Couldn't lookup our username (uid=%s)",
                       dec2str(process_euid));
        }
    } else {
        i_fatal_status(EX_USAGE,
            "destination user parameter (-d user) not given");
    }
    master_service_init_finish(master_service);

    i_zero(&service_input);
    service_input.module = "lda";
    service_input.service = "lda";
    service_input.username = user;

    service_flags |= MAIL_STORAGE_SERVICE_FLAG_USE_SYSEXITS;
    storage_service = mail_storage_service_init(master_service, set_roots,
                            service_flags);
    mail_deliver_hooks_init();
    /* set before looking up the user (or ideally we'd do this between
       _lookup() and _next(), but don't bother) */
    ctx.delivery_time_started = ioloop_timeval;
    ret = mail_storage_service_lookup_next(storage_service, &service_input,
                           &service_user, &ctx.rcpt_user,
                           &errstr);
    if (ret <= 0) {
        if (ret < 0)
            i_fatal("%s", errstr);
        return EX_NOUSER;
    }

#ifdef SIGXFSZ
        lib_signals_ignore(SIGXFSZ, TRUE);
#endif
    var_table = mail_user_var_expand_table(ctx.rcpt_user);
    smtp_set = mail_storage_service_user_get_set(service_user)[1];
    lda_set = mail_storage_service_user_get_set(service_user)[2];
    ret = settings_var_expand(
        &lda_setting_parser_info,
        lda_set, ctx.rcpt_user->pool, var_table,
        &errstr);
    if (ret > 0) {
        ret = settings_var_expand(
            &smtp_submit_setting_parser_info,
            smtp_set, ctx.rcpt_user->pool, var_table,
            &errstr);
    }
    if (ret <= 0)
        i_fatal("Failed to expand settings: %s", errstr);
    ctx.set = lda_set;
    ctx.smtp_set = smtp_set;

    if (ctx.rcpt_user->mail_debug && *user_source != '\0') {
        i_debug("userdb lookup skipped, username taken from %s",
            user_source);
    }

    ctx.src_mail = lda_raw_mail_open(&ctx, path);
    ctx.mail_from = mail_from;
    ctx.rcpt_to = final_rcpt_to;
    lda_set_rcpt_to(&ctx, rcpt_to, user, rcpt_to_source);

    if (mail_deliver(&ctx, &storage) < 0) {
        if (ctx.tempfail_error != NULL) {
            errstr = ctx.tempfail_error;
            error = MAIL_ERROR_TEMP;
        } else if (storage != NULL) {
            errstr = mail_storage_get_last_error(storage, &error);
        } else {
            /* This shouldn't happen */
            i_error("BUG: Saving failed to unknown storage");
            return EX_TEMPFAIL;
        }

        if (stderr_rejection) {
            /* write to stderr also for tempfails so that MTA
               can log the reason if it wants to. */
            fprintf(stderr, "%s\n", errstr);
        }

        if (error != MAIL_ERROR_NOQUOTA ||
            ctx.set->quota_full_tempfail) {
            /* Saving to INBOX should always work unless
               we're over quota. If it didn't, it's probably a
               configuration problem. */
            return EX_TEMPFAIL;
        }
        ctx.mailbox_full = TRUE;
        ctx.dsn = TRUE;

        /* we'll have to reply with permanent failure */
        mail_deliver_log(&ctx, "rejected: %s",
                 str_sanitize(errstr, 512));

        if (stderr_rejection)
            return EX_NOPERM;
        ret = mail_send_rejection(&ctx, ctx.rcpt_to, errstr);
        if (ret != 0)
            return ret < 0 ? EX_TEMPFAIL : ret;
        /* ok, rejection sent */
    }

    {
        struct mailbox_transaction_context *t =
            ctx.src_mail->transaction;
        struct mailbox *box = ctx.src_mail->box;

        mail_free(&ctx.src_mail);
        mailbox_transaction_rollback(&t);
        mailbox_free(&box);
    }

    mail_user_unref(&ctx.rcpt_user);
    mail_deliver_session_deinit(&ctx.session);

    mail_storage_service_user_unref(&service_user);
    mail_storage_service_deinit(&storage_service);
    master_service_deinit(&master_service);
        return EX_OK;
}