udhcpc: add support for DHCP option 212 (RFC 5969)
[oweals/busybox.git] / networking / ftpd.c
index 675324803b6fcea5a34d6eddbd99f89268234342..e38138c0a85b1b4d8ef0e753597ab323c5113ae9 100644 (file)
@@ -4,12 +4,30 @@
  *
  * Author: Adam Tkac <vonsch@gmail.com>
  *
- * Licensed under GPLv2, see file LICENSE in this tarball for details.
+ * Licensed under GPLv2, see file LICENSE in this source tree.
  *
  * Only subset of FTP protocol is implemented but vast majority of clients
- * should not have any problem. You have to run this daemon via inetd.
+ * should not have any problem.
+ *
+ * You have to run this daemon via inetd.
  */
 
+//usage:#define ftpd_trivial_usage
+//usage:       "[-wvS] [-t N] [-T N] [DIR]"
+//usage:#define ftpd_full_usage "\n\n"
+//usage:       "Anonymous FTP server\n"
+//usage:       "\n"
+//usage:       "ftpd should be used as an inetd service.\n"
+//usage:       "ftpd's line for inetd.conf:\n"
+//usage:       "       21 stream tcp nowait root ftpd ftpd /files/to/serve\n"
+//usage:       "It also can be ran from tcpsvd:\n"
+//usage:       "       tcpsvd -vE 0.0.0.0 21 ftpd /files/to/serve\n"
+//usage:     "\n       -w      Allow upload"
+//usage:     "\n       -v      Log errors to stderr. -vv: verbose log"
+//usage:     "\n       -S      Log errors to syslog. -SS: verbose log"
+//usage:     "\n       -t,-T   Idle and absolute timeouts"
+//usage:     "\n       DIR     Change root to this directory"
+
 #include "libbb.h"
 #include <syslog.h>
 #include <netinet/tcp.h>
 /* Convert a constant to 3-digit string, packed into uint32_t */
 enum {
        /* Shift for Nth decimal digit */
-       SHIFT2 =  0 * BB_LITTLE_ENDIAN + 24 * BB_BIG_ENDIAN,
-       SHIFT1 =  8 * BB_LITTLE_ENDIAN + 16 * BB_BIG_ENDIAN,
-       SHIFT0 = 16 * BB_LITTLE_ENDIAN + 8 * BB_BIG_ENDIAN,
+       SHIFT2  =  0 * BB_LITTLE_ENDIAN + 24 * BB_BIG_ENDIAN,
+       SHIFT1  =  8 * BB_LITTLE_ENDIAN + 16 * BB_BIG_ENDIAN,
+       SHIFT0  = 16 * BB_LITTLE_ENDIAN + 8 * BB_BIG_ENDIAN,
+       /* And for 4th position (space) */
+       SHIFTsp = 24 * BB_LITTLE_ENDIAN + 0 * BB_BIG_ENDIAN,
 };
 #define STRNUM32(s) (uint32_t)(0 \
        | (('0' + ((s) / 1 % 10)) << SHIFT0) \
        | (('0' + ((s) / 10 % 10)) << SHIFT1) \
        | (('0' + ((s) / 100 % 10)) << SHIFT2) \
 )
+#define STRNUM32sp(s) (uint32_t)(0 \
+       | (' ' << SHIFTsp) \
+       | (('0' + ((s) / 1 % 10)) << SHIFT0) \
+       | (('0' + ((s) / 10 % 10)) << SHIFT1) \
+       | (('0' + ((s) / 100 % 10)) << SHIFT2) \
+)
+
+#define MSG_OK "Operation successful\r\n"
+#define MSG_ERR "Error\r\n"
 
 struct globals {
        int pasv_listen_fd;
-       int proc_self_fd;
+#if !BB_MMU
+       int root_fd;
+#endif
        int local_file_fd;
-       int start_time;
-       int abs_timeout;
-       int timeout;
+       unsigned end_time;
+       unsigned timeout;
+       unsigned verbose;
        off_t local_file_pos;
        off_t restart_pos;
        len_and_sockaddr *local_addr;
@@ -88,9 +119,16 @@ struct globals {
 #if ENABLE_FEATURE_FTP_WRITE
        char *rnfr_filename;
 #endif
-};
+       /* We need these aligned to uint32_t */
+       char msg_ok [(sizeof("NNN " MSG_OK ) + 3) & 0xfffc];
+       char msg_err[(sizeof("NNN " MSG_ERR) + 3) & 0xfffc];
+} FIX_ALIASING;
 #define G (*(struct globals*)&bb_common_bufsiz1)
-#define INIT_G() do { } while (0)
+#define INIT_G() do { \
+       /* Moved to main */ \
+       /*strcpy(G.msg_ok  + 4, MSG_OK );*/ \
+       /*strcpy(G.msg_err + 4, MSG_ERR);*/ \
+} while (0)
 
 
 static char *
@@ -141,6 +179,12 @@ replace_char(char *str, char from, char to)
        return p - str;
 }
 
+static void
+verbose_log(const char *str)
+{
+       bb_error_msg("%.*s", (int)strcspn(str, "\r\n"), str);
+}
+
 /* NB: status_str is char[4] packed into uint32_t */
 static void
 cmdio_write(uint32_t status_str, const char *str)
@@ -148,35 +192,47 @@ cmdio_write(uint32_t status_str, const char *str)
        char *response;
        int len;
 
-       /* FTP allegedly uses telnet protocol for command link.
+       /* FTP uses telnet protocol for command link.
         * In telnet, 0xff is an escape char, and needs to be escaped: */
        response = escape_text((char *) &status_str, str, (0xff << 8) + '\r');
 
-       /* ?! does FTP send embedded LFs as NULs? wow */
+       /* FTP sends embedded LFs as NULs */
        len = replace_char(response, '\n', '\0');
 
        response[len++] = '\n'; /* tack on trailing '\n' */
        xwrite(STDOUT_FILENO, response, len);
+       if (G.verbose > 1)
+               verbose_log(response);
        free(response);
 }
 
 static void
-cmdio_write_ok(int status)
+cmdio_write_ok(unsigned status)
 {
-       fdprintf(STDOUT_FILENO, "%u Operation successful\r\n", status);
+       *(uint32_t *) G.msg_ok = status;
+       xwrite(STDOUT_FILENO, G.msg_ok, sizeof("NNN " MSG_OK) - 1);
+       if (G.verbose > 1)
+               verbose_log(G.msg_ok);
 }
+#define WRITE_OK(a) cmdio_write_ok(STRNUM32sp(a))
 
 /* TODO: output strerr(errno) if errno != 0? */
 static void
-cmdio_write_error(int status)
+cmdio_write_error(unsigned status)
 {
-       fdprintf(STDOUT_FILENO, "%u Error\r\n", status);
+       *(uint32_t *) G.msg_err = status;
+       xwrite(STDOUT_FILENO, G.msg_err, sizeof("NNN " MSG_ERR) - 1);
+       if (G.verbose > 0)
+               verbose_log(G.msg_err);
 }
+#define WRITE_ERR(a) cmdio_write_error(STRNUM32sp(a))
 
 static void
 cmdio_write_raw(const char *p_text)
 {
        xwrite_str(STDOUT_FILENO, p_text);
+       if (G.verbose > 1)
+               verbose_log(p_text);
 }
 
 static void
@@ -185,7 +241,7 @@ timeout_handler(int sig UNUSED_PARAM)
        off_t pos;
        int sv_errno = errno;
 
-       if (monotonic_sec() - G.start_time > G.abs_timeout)
+       if ((int)(monotonic_sec() - G.end_time) >= 0)
                goto timed_out;
 
        if (!G.local_file_fd)
@@ -228,10 +284,10 @@ static void
 handle_cwd(void)
 {
        if (!G.ftp_arg || chdir(G.ftp_arg) != 0) {
-               cmdio_write_error(FTP_FILEFAIL);
+               WRITE_ERR(FTP_FILEFAIL);
                return;
        }
-       cmdio_write_ok(FTP_CWDOK);
+       WRITE_OK(FTP_CWDOK);
 }
 
 static void
@@ -244,12 +300,12 @@ handle_cdup(void)
 static void
 handle_stat(void)
 {
-       cmdio_write_raw(STR(FTP_STATOK)"-FTP server status:\r\n"
+       cmdio_write_raw(STR(FTP_STATOK)"-Server status:\r\n"
                        " TYPE: BINARY\r\n"
                        STR(FTP_STATOK)" Ok\r\n");
 }
 
-/* TODO: implement FEAT. Example:
+/* Examples of HELP and FEAT:
 # nc -vvv ftp.kernel.org 21
 ftp.kernel.org (130.239.17.4:21) open
 220 Welcome to ftp.kernel.org.
@@ -273,16 +329,15 @@ HELP
 214 Help OK.
 */
 static void
-handle_help(void)
+handle_feat(unsigned status)
 {
-       cmdio_write_raw(STR(FTP_HELP)"-Commands:\r\n"
-                       " ALLO CDUP CWD EPSV HELP LIST\r\n"
-                       " MODE NLST NOOP PASS PASV PORT PWD QUIT\r\n"
-                       " REST RETR SIZE STAT STRU SYST TYPE USER\r\n"
-#if ENABLE_FEATURE_FTP_WRITE
-                       " APPE DELE MKD RMD RNFR RNTO STOR STOU\r\n"
-#endif
-                       STR(FTP_HELP)" Ok\r\n");
+       cmdio_write(status, "-Features:");
+       cmdio_write_raw(" EPSV\r\n"
+                       " PASV\r\n"
+                       " REST STREAM\r\n"
+                       " MDTM\r\n"
+                       " SIZE\r\n");
+       cmdio_write(status, " Ok");
 }
 
 /* Download commands */
@@ -318,7 +373,7 @@ ftpdataio_get_pasv_fd(void)
        remote_fd = accept(G.pasv_listen_fd, NULL, 0);
 
        if (remote_fd < 0) {
-               cmdio_write_error(FTP_BADSENDCONN);
+               WRITE_ERR(FTP_BADSENDCONN);
                return remote_fd;
        }
 
@@ -358,7 +413,7 @@ static int
 port_or_pasv_was_seen(void)
 {
        if (!pasv_active() && !port_active()) {
-               cmdio_write_raw(STR(FTP_BADSENDCONN)" Use PORT or PASV first\r\n");
+               cmdio_write_raw(STR(FTP_BADSENDCONN)" Use PORT/PASV first\r\n");
                return 0;
        }
 
@@ -377,7 +432,7 @@ bind_for_passive_mode(void)
        G.pasv_listen_fd = fd = xsocket(G.local_addr->u.sa.sa_family, SOCK_STREAM, 0);
        setsockopt_reuseaddr(fd);
 
-       set_nport(G.local_addr, 0);
+       set_nport(&G.local_addr->u.sa, 0);
        xbind(fd, &G.local_addr->u.sa, G.local_addr->len);
        xlisten(fd, 1);
        getsockname(fd, &G.local_addr->u.sa, &G.local_addr->len);
@@ -402,7 +457,7 @@ handle_pasv(void)
                addr = xstrdup("0.0.0.0");
        replace_char(addr, '.', ',');
 
-       response = xasprintf(STR(FTP_PASVOK)" Entering Passive Mode (%s,%u,%u)\r\n",
+       response = xasprintf(STR(FTP_PASVOK)" PASV ok (%s,%u,%u)\r\n",
                        addr, (int)(port >> 8), (int)(port & 255));
        free(addr);
        cmdio_write_raw(response);
@@ -417,26 +472,11 @@ handle_epsv(void)
        char *response;
 
        port = bind_for_passive_mode();
-       response = xasprintf(STR(FTP_EPSVOK)" EPSV Ok (|||%u|)\r\n", port);
+       response = xasprintf(STR(FTP_EPSVOK)" EPSV ok (|||%u|)\r\n", port);
        cmdio_write_raw(response);
        free(response);
 }
 
-/* libbb candidate */
-static
-len_and_sockaddr* get_peer_lsa(int fd)
-{
-       len_and_sockaddr *lsa;
-       socklen_t len = 0;
-
-       if (getpeername(fd, NULL, &len) != 0)
-               return NULL;
-       lsa = xzalloc(LSA_LEN_SIZE + len);
-       lsa->len = len;
-       getpeername(fd, &lsa->u.sa, &lsa->len);
-       return lsa;
-}
-
 static void
 handle_port(void)
 {
@@ -459,7 +499,7 @@ handle_port(void)
 #endif
        ) {
  bail:
-               cmdio_write_error(FTP_BADCMD);
+               WRITE_ERR(FTP_BADCMD);
                return;
        }
 
@@ -501,17 +541,17 @@ handle_port(void)
        G.port_addr = xdotted2sockaddr(raw, port);
 #else
        G.port_addr = get_peer_lsa(STDIN_FILENO);
-       set_nport(G.port_addr, port);
+       set_nport(&G.port_addr->u.sa, htons(port));
 #endif
-       cmdio_write_ok(FTP_PORTOK);
+       WRITE_OK(FTP_PORTOK);
 }
 
 static void
 handle_rest(void)
 {
        /* When ftp_arg == NULL simply restart from beginning */
-       G.restart_pos = G.ftp_arg ? xatoi_u(G.ftp_arg) : 0;
-       cmdio_write_ok(FTP_RESTOK);
+       G.restart_pos = G.ftp_arg ? xatoi_positive(G.ftp_arg) : 0;
+       WRITE_OK(FTP_RESTOK);
 }
 
 static void
@@ -532,13 +572,13 @@ handle_retr(void)
        /* O_NONBLOCK is useful if file happens to be a device node */
        local_file_fd = G.ftp_arg ? open(G.ftp_arg, O_RDONLY | O_NONBLOCK) : -1;
        if (local_file_fd < 0) {
-               cmdio_write_error(FTP_FILEFAIL);
+               WRITE_ERR(FTP_FILEFAIL);
                return;
        }
 
        if (fstat(local_file_fd, &statbuf) != 0 || !S_ISREG(statbuf.st_mode)) {
                /* Note - pretend open failed */
-               cmdio_write_error(FTP_FILEFAIL);
+               WRITE_ERR(FTP_FILEFAIL);
                goto file_close_out;
        }
        G.local_file_fd = local_file_fd;
@@ -553,7 +593,7 @@ handle_retr(void)
                xlseek(local_file_fd, offset, SEEK_SET);
 
        response = xasprintf(
-               " Opening BINARY mode data connection for %s (%"OFF_FMT"u bytes)",
+               " Opening BINARY connection for %s (%"OFF_FMT"u bytes)",
                G.ftp_arg, statbuf.st_size);
        remote_fd = get_remote_transfer_fd(response);
        free(response);
@@ -563,9 +603,9 @@ handle_retr(void)
        bytes_transferred = bb_copyfd_eof(local_file_fd, remote_fd);
        close(remote_fd);
        if (bytes_transferred < 0)
-               cmdio_write_error(FTP_BADSENDFILE);
+               WRITE_ERR(FTP_BADSENDFILE);
        else
-               cmdio_write_ok(FTP_TRANSFEROK);
+               WRITE_OK(FTP_TRANSFEROK);
 
  file_close_out:
        close(local_file_fd);
@@ -577,39 +617,76 @@ handle_retr(void)
 static int
 popen_ls(const char *opt)
 {
-       char *cwd;
-       const char *argv[5] = { "ftpd", opt, NULL, G.ftp_arg, NULL };
+       const char *argv[5];
        struct fd_pair outfd;
        pid_t pid;
 
-       cwd = xrealloc_getcwd_or_warn(NULL);
+       argv[0] = "ftpd";
+       argv[1] = opt; /* "-l" or "-1" */
+#if BB_MMU
+       argv[2] = "--";
+#else
+       /* NOMMU ftpd ls helper chdirs to argv[2],
+        * preventing peer from seeing real root. */
+       argv[2] = xrealloc_getcwd_or_warn(NULL);
+#endif
+       argv[3] = G.ftp_arg;
+       argv[4] = NULL;
+
+       /* Improve compatibility with non-RFC conforming FTP clients
+        * which send e.g. "LIST -l", "LIST -la", "LIST -aL".
+        * See https://bugs.kde.org/show_bug.cgi?id=195578 */
+       if (ENABLE_FEATURE_FTPD_ACCEPT_BROKEN_LIST
+        && G.ftp_arg && G.ftp_arg[0] == '-'
+       ) {
+               const char *tmp = strchr(G.ftp_arg, ' ');
+               if (tmp) /* skip the space */
+                       tmp++;
+               argv[3] = tmp;
+       }
+
        xpiped_pair(outfd);
 
-       /*fflush(NULL); - so far we dont use stdio on output */
-       pid = vfork();
-       switch (pid) {
-       case -1:  /* failure */
-               bb_perror_msg_and_die("vfork");
-       case 0:  /* child */
-               /* NB: close _first_, then move fds! */
+       /*fflush_all(); - so far we dont use stdio on output */
+       pid = BB_MMU ? xfork() : xvfork();
+       if (pid == 0) {
+               /* child */
+#if !BB_MMU
+               /* On NOMMU, we want to execute a child - copy of ourself.
+                * In chroot we usually can't do it. Thus we chdir
+                * out of the chroot back to original root,
+                * and (see later below) execute bb_busybox_exec_path
+                * relative to current directory */
+               if (fchdir(G.root_fd) != 0)
+                       _exit(127);
+               /*close(G.root_fd); - close_on_exec_on() took care of this */
+#endif
+               /* NB: close _first_, then move fd! */
                close(outfd.rd);
                xmove_fd(outfd.wr, STDOUT_FILENO);
+               /* Opening /dev/null in chroot is hard.
+                * Just making sure STDIN_FILENO is opened
+                * to something harmless. Paranoia,
+                * ls won't read it anyway */
                close(STDIN_FILENO);
-               /* xopen("/dev/null", O_RDONLY); - chroot may lack it! */
-               if (fchdir(G.proc_self_fd) == 0) {
-                       close(G.proc_self_fd);
-                       argv[2] = cwd;
-                       /* ftpd ls helper chdirs to argv[2],
-                        * preventing peer from seeing /proc/self
-                        */
-                       execv("exe", (char**) argv);
-               }
+               dup(STDOUT_FILENO); /* copy will become STDIN_FILENO */
+#if BB_MMU
+               /* memset(&G, 0, sizeof(G)); - ls_main does it */
+               exit(ls_main(ARRAY_SIZE(argv) - 1, (char**) argv));
+#else
+               /* + 1: we must use relative path here if in chroot.
+                * For example, execv("/proc/self/exe") will fail, since
+                * it looks for "/proc/self/exe" _relative to chroot!_ */
+               execv(bb_busybox_exec_path + 1, (char**) argv);
                _exit(127);
+#endif
        }
 
        /* parent */
        close(outfd.wr);
-       free(cwd);
+#if !BB_MMU
+       free((char*)argv[2]);
+#endif
        return outfd.rd;
 }
 
@@ -631,40 +708,42 @@ handle_dir_common(int opts)
        /* -n prevents user/groupname display,
         * which can be problematic in chroot */
        ls_fd = popen_ls((opts & LONG_LISTING) ? "-l" : "-1");
-       ls_fp = fdopen(ls_fd, "r");
-       if (!ls_fp) /* never happens. paranoia */
-               bb_perror_msg_and_die("fdopen");
+       ls_fp = xfdopen_for_read(ls_fd);
 
        if (opts & USE_CTRL_CONN) {
                /* STAT <filename> */
-               cmdio_write_raw(STR(FTP_STATFILE_OK)"-Status follows:\r\n");
+               cmdio_write_raw(STR(FTP_STATFILE_OK)"-File status:\r\n");
                while (1) {
-                       line = xmalloc_fgetline(ls_fp);
+                       line = xmalloc_fgetline(ls_fp);
                        if (!line)
                                break;
-                       cmdio_write(0, line); /* hack: 0 results in no status at all */
+                       /* Hack: 0 results in no status at all */
+                       /* Note: it's ok that we don't prepend space,
+                        * ftp.kernel.org doesn't do that too */
+                       cmdio_write(0, line);
                        free(line);
                }
-               cmdio_write_ok(FTP_STATFILE_OK);
+               WRITE_OK(FTP_STATFILE_OK);
        } else {
                /* LIST/NLST [<filename>] */
-               int remote_fd = get_remote_transfer_fd(" Here comes the directory listing");
+               int remote_fd = get_remote_transfer_fd(" Directory listing");
                if (remote_fd >= 0) {
                        while (1) {
-                               line = xmalloc_fgetline(ls_fp);
+                               line = xmalloc_fgetline(ls_fp);
                                if (!line)
                                        break;
                                /* I've seen clients complaining when they
                                 * are fed with ls output with bare '\n'.
                                 * Pity... that would be much simpler.
                                 */
+/* TODO: need to s/LF/NUL/g here */
                                xwrite_str(remote_fd, line);
                                xwrite(remote_fd, "\r\n", 2);
                                free(line);
                        }
                }
                close(remote_fd);
-               cmdio_write_ok(FTP_TRANSFEROK);
+               WRITE_OK(FTP_TRANSFEROK);
        }
        fclose(ls_fp); /* closes ls_fd too */
 }
@@ -676,6 +755,13 @@ handle_list(void)
 static void
 handle_nlst(void)
 {
+       /* NLST returns list of names, "\r\n" terminated without regard
+        * to the current binary flag. Names may start with "/",
+        * then they represent full names (we don't produce such names),
+        * otherwise names are relative to current directory.
+        * Embedded "\n" are replaced by NULs. This is safe since names
+        * can never contain NUL.
+        */
        handle_dir_common(0);
 }
 static void
@@ -684,20 +770,63 @@ handle_stat_file(void)
        handle_dir_common(LONG_LISTING + USE_CTRL_CONN);
 }
 
+/* This can be extended to handle MLST, as all info is available
+ * in struct stat for that:
+ * MLST file_name
+ * 250-Listing file_name
+ *  type=file;size=4161;modify=19970214165800; /dir/dir/file_name
+ * 250 End
+ * Nano-doc:
+ * MLST [<file or dir name, "." assumed if not given>]
+ * Returned name should be either the same as requested, or fully qualified.
+ * If there was no parameter, return "" or (preferred) fully-qualified name.
+ * Returned "facts" (case is not important):
+ *  size    - size in octets
+ *  modify  - last modification time
+ *  type    - entry type (file,dir,OS.unix=block)
+ *            (+ cdir and pdir types for MLSD)
+ *  unique  - unique id of file/directory (inode#)
+ *  perm    -
+ *      a: can be appended to (APPE)
+ *      d: can be deleted (RMD/DELE)
+ *      f: can be renamed (RNFR)
+ *      r: can be read (RETR)
+ *      w: can be written (STOR)
+ *      e: can CWD into this dir
+ *      l: this dir can be listed (dir only!)
+ *      c: can create files in this dir
+ *      m: can create dirs in this dir (MKD)
+ *      p: can delete files in this dir
+ *  UNIX.mode - unix file mode
+ */
 static void
-handle_size(void)
+handle_size_or_mdtm(int need_size)
 {
        struct stat statbuf;
-       char buf[sizeof(STR(FTP_STATFILE_OK)" %"OFF_FMT"u\r\n") + sizeof(off_t)*3];
+       struct tm broken_out;
+       char buf[(sizeof("NNN %"OFF_FMT"u\r\n") + sizeof(off_t) * 3)
+               | sizeof("NNN YYYYMMDDhhmmss\r\n")
+       ];
 
        if (!G.ftp_arg
         || stat(G.ftp_arg, &statbuf) != 0
         || !S_ISREG(statbuf.st_mode)
        ) {
-               cmdio_write_error(FTP_FILEFAIL);
+               WRITE_ERR(FTP_FILEFAIL);
                return;
        }
-       sprintf(buf, STR(FTP_STATFILE_OK)" %"OFF_FMT"u\r\n", statbuf.st_size);
+       if (need_size) {
+               sprintf(buf, STR(FTP_STATFILE_OK)" %"OFF_FMT"u\r\n", statbuf.st_size);
+       } else {
+               gmtime_r(&statbuf.st_mtime, &broken_out);
+               sprintf(buf, STR(FTP_STATFILE_OK)" %04u%02u%02u%02u%02u%02u\r\n",
+                       broken_out.tm_year + 1900,
+                       broken_out.tm_mon,
+                       broken_out.tm_mday,
+                       broken_out.tm_hour,
+                       broken_out.tm_min,
+                       broken_out.tm_sec);
+       }
        cmdio_write_raw(buf);
 }
 
@@ -708,30 +837,30 @@ static void
 handle_mkd(void)
 {
        if (!G.ftp_arg || mkdir(G.ftp_arg, 0777) != 0) {
-               cmdio_write_error(FTP_FILEFAIL);
+               WRITE_ERR(FTP_FILEFAIL);
                return;
        }
-       cmdio_write_ok(FTP_MKDIROK);
+       WRITE_OK(FTP_MKDIROK);
 }
 
 static void
 handle_rmd(void)
 {
        if (!G.ftp_arg || rmdir(G.ftp_arg) != 0) {
-               cmdio_write_error(FTP_FILEFAIL);
+               WRITE_ERR(FTP_FILEFAIL);
                return;
        }
-       cmdio_write_ok(FTP_RMDIROK);
+       WRITE_OK(FTP_RMDIROK);
 }
 
 static void
 handle_dele(void)
 {
        if (!G.ftp_arg || unlink(G.ftp_arg) != 0) {
-               cmdio_write_error(FTP_FILEFAIL);
+               WRITE_ERR(FTP_FILEFAIL);
                return;
        }
-       cmdio_write_ok(FTP_DELEOK);
+       WRITE_OK(FTP_DELEOK);
 }
 
 static void
@@ -739,7 +868,7 @@ handle_rnfr(void)
 {
        free(G.rnfr_filename);
        G.rnfr_filename = xstrdup(G.ftp_arg);
-       cmdio_write_ok(FTP_RNFROK);
+       WRITE_OK(FTP_RNFROK);
 }
 
 static void
@@ -749,7 +878,7 @@ handle_rnto(void)
 
        /* If we didn't get a RNFR, throw a wobbly */
        if (G.rnfr_filename == NULL || G.ftp_arg == NULL) {
-               cmdio_write_raw(STR(FTP_NEEDRNFR)" RNFR required first\r\n");
+               cmdio_write_raw(STR(FTP_NEEDRNFR)" Use RNFR first\r\n");
                return;
        }
 
@@ -758,10 +887,10 @@ handle_rnto(void)
        G.rnfr_filename = NULL;
 
        if (retval) {
-               cmdio_write_error(FTP_FILEFAIL);
+               WRITE_ERR(FTP_FILEFAIL);
                return;
        }
-       cmdio_write_ok(FTP_RENAMEOK);
+       WRITE_OK(FTP_RENAMEOK);
 }
 
 static void
@@ -798,7 +927,7 @@ handle_upload_common(int is_append, int is_unique)
         || fstat(local_file_fd, &statbuf) != 0
         || !S_ISREG(statbuf.st_mode)
        ) {
-               cmdio_write_error(FTP_UPLOADFAIL);
+               WRITE_ERR(FTP_UPLOADFAIL);
                if (local_file_fd >= 0)
                        goto close_local_and_bail;
                return;
@@ -817,9 +946,9 @@ handle_upload_common(int is_append, int is_unique)
        bytes_transferred = bb_copyfd_eof(remote_fd, local_file_fd);
        close(remote_fd);
        if (bytes_transferred < 0)
-               cmdio_write_error(FTP_BADSENDFILE);
+               WRITE_ERR(FTP_BADSENDFILE);
        else
-               cmdio_write_ok(FTP_TRANSFEROK);
+               WRITE_OK(FTP_TRANSFEROK);
 
  close_local_and_bail:
        close(local_file_fd);
@@ -850,25 +979,78 @@ handle_stou(void)
 static uint32_t
 cmdio_get_cmd_and_arg(void)
 {
-       size_t len;
+       int len;
        uint32_t cmdval;
        char *cmd;
 
        alarm(G.timeout);
 
        free(G.ftp_cmd);
-       len = 8 * 1024; /* Paranoia. Peer may send 1 gigabyte long cmd... */
-       G.ftp_cmd = cmd = xmalloc_reads(STDIN_FILENO, NULL, &len);
-       if (!cmd)
-               exit(0);
-
-       /* Trailing '\n' is already stripped, strip '\r' */
-       len = strlen(cmd) - 1;
-       while ((ssize_t)len >= 0 && cmd[len] == '\r') {
-               cmd[len] = '\0';
-               len--;
+       {
+               /* Paranoia. Peer may send 1 gigabyte long cmd... */
+               /* Using separate len_on_stk instead of len optimizes
+                * code size (allows len to be in CPU register) */
+               size_t len_on_stk = 8 * 1024;
+               G.ftp_cmd = cmd = xmalloc_fgets_str_len(stdin, "\r\n", &len_on_stk);
+               if (!cmd)
+                       exit(0);
+               len = len_on_stk;
+       }
+
+       /* De-escape telnet: 0xff,0xff => 0xff */
+       /* RFC959 says that ABOR, STAT, QUIT may be sent even during
+        * data transfer, and may be preceded by telnet's "Interrupt Process"
+        * code (two-byte sequence 255,244) and then by telnet "Synch" code
+        * 255,242 (byte 242 is sent with TCP URG bit using send(MSG_OOB)
+        * and may generate SIGURG on our side. See RFC854).
+        * So far we don't support that (may install SIGURG handler if we'd want to),
+        * but we need to at least remove 255,xxx pairs. lftp sends those. */
+       /* Then de-escape FTP: NUL => '\n' */
+       /* Testing for \xff:
+        * Create file named '\xff': echo Hello >`echo -ne "\xff"`
+        * Try to get it:            ftpget -v 127.0.0.1 Eff `echo -ne "\xff\xff"`
+        * (need "\xff\xff" until ftpget applet is fixed to do escaping :)
+        * Testing for embedded LF:
+        * LF_HERE=`echo -ne "LF\nHERE"`
+        * echo Hello >"$LF_HERE"
+        * ftpget -v 127.0.0.1 LF_HERE "$LF_HERE"
+        */
+       {
+               int dst, src;
+
+               /* Strip "\r\n" if it is there */
+               if (len != 0 && cmd[len - 1] == '\n') {
+                       len--;
+                       if (len != 0 && cmd[len - 1] == '\r')
+                               len--;
+                       cmd[len] = '\0';
+               }
+               src = strchrnul(cmd, 0xff) - cmd;
+               /* 99,99% there are neither NULs nor 255s and src == len */
+               if (src < len) {
+                       dst = src;
+                       do {
+                               if ((unsigned char)(cmd[src]) == 255) {
+                                       src++;
+                                       /* 255,xxx - skip 255 */
+                                       if ((unsigned char)(cmd[src]) != 255) {
+                                               /* 255,!255 - skip both */
+                                               src++;
+                                               continue;
+                                       }
+                                       /* 255,255 - retain one 255 */
+                               }
+                               /* NUL => '\n' */
+                               cmd[dst++] = cmd[src] ? cmd[src] : '\n';
+                               src++;
+                       } while (src < len);
+                       cmd[dst] = '\0';
+               }
        }
 
+       if (G.verbose > 1)
+               verbose_log(cmd);
+
        G.ftp_arg = strchr(cmd, ' ');
        if (G.ftp_arg != NULL)
                *G.ftp_arg++ = '\0';
@@ -890,8 +1072,10 @@ enum {
        const_CWD  = mk_const3('C', 'W', 'D'),
        const_DELE = mk_const4('D', 'E', 'L', 'E'),
        const_EPSV = mk_const4('E', 'P', 'S', 'V'),
+       const_FEAT = mk_const4('F', 'E', 'A', 'T'),
        const_HELP = mk_const4('H', 'E', 'L', 'P'),
        const_LIST = mk_const4('L', 'I', 'S', 'T'),
+       const_MDTM = mk_const4('M', 'D', 'T', 'M'),
        const_MKD  = mk_const3('M', 'K', 'D'),
        const_MODE = mk_const4('M', 'O', 'D', 'E'),
        const_NLST = mk_const4('N', 'L', 'S', 'T'),
@@ -915,35 +1099,58 @@ enum {
        const_TYPE = mk_const4('T', 'Y', 'P', 'E'),
        const_USER = mk_const4('U', 'S', 'E', 'R'),
 
+#if !BB_MMU
        OPT_l = (1 << 0),
        OPT_1 = (1 << 1),
-       OPT_v = (1 << 2),
-       OPT_S = (1 << 3),
-       OPT_w = (1 << 4),
+#endif
+       OPT_v = (1 << ((!BB_MMU) * 2 + 0)),
+       OPT_S = (1 << ((!BB_MMU) * 2 + 1)),
+       OPT_w = (1 << ((!BB_MMU) * 2 + 2)) * ENABLE_FEATURE_FTP_WRITE,
 };
 
 int ftpd_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
+#if !BB_MMU
 int ftpd_main(int argc, char **argv)
+#else
+int ftpd_main(int argc UNUSED_PARAM, char **argv)
+#endif
 {
+       unsigned abs_timeout;
+       unsigned verbose_S;
        smallint opts;
 
        INIT_G();
 
-       G.start_time = monotonic_sec();
-       G.abs_timeout = 1 * 60 * 60;
+       abs_timeout = 1 * 60 * 60;
+       verbose_S = 0;
        G.timeout = 2 * 60;
-       opt_complementary = "t+:T+";
-       opts = getopt32(argv, "l1vS" USE_FEATURE_FTP_WRITE("w") "t:T:", &G.timeout, &G.abs_timeout);
-
+       opt_complementary = "t+:T+:vv:SS";
+#if BB_MMU
+       opts = getopt32(argv,   "vS" IF_FEATURE_FTP_WRITE("w") "t:T:", &G.timeout, &abs_timeout, &G.verbose, &verbose_S);
+#else
+       opts = getopt32(argv, "l1vS" IF_FEATURE_FTP_WRITE("w") "t:T:", &G.timeout, &abs_timeout, &G.verbose, &verbose_S);
        if (opts & (OPT_l|OPT_1)) {
                /* Our secret backdoor to ls */
-               memset(&G, 0, sizeof(G));
-/* TODO: pass -n too? */
+/* TODO: pass -n? It prevents user/group resolution, which may not work in chroot anyway */
+/* TODO: pass -A? It shows dot files */
+/* TODO: pass --group-directories-first? would be nice, but ls doesn't do that yet */
                xchdir(argv[2]);
                argv[2] = (char*)"--";
+               /* memset(&G, 0, sizeof(G)); - ls_main does it */
                return ls_main(argc, argv);
        }
-
+#endif
+       if (G.verbose < verbose_S)
+               G.verbose = verbose_S;
+       if (abs_timeout | G.timeout) {
+               if (abs_timeout == 0)
+                       abs_timeout = INT_MAX;
+               G.end_time = monotonic_sec() + abs_timeout;
+               if (G.timeout > abs_timeout)
+                       G.timeout = abs_timeout;
+       }
+       strcpy(G.msg_ok  + 4, MSG_OK );
+       strcpy(G.msg_err + 4, MSG_ERR);
 
        G.local_addr = get_sock_lsa(STDIN_FILENO);
        if (!G.local_addr) {
@@ -963,8 +1170,13 @@ int ftpd_main(int argc, char **argv)
                openlog(applet_name, LOG_PID | LOG_NDELAY, LOG_DAEMON);
                logmode |= LOGMODE_SYSLOG;
        }
+       if (logmode)
+               applet_name = xasprintf("%s[%u]", applet_name, (int)getpid());
 
-       G.proc_self_fd = xopen("/proc/self", O_RDONLY | O_DIRECTORY);
+#if !BB_MMU
+       G.root_fd = xopen("/", O_RDONLY | O_DIRECTORY);
+       close_on_exec_on(G.root_fd);
+#endif
 
        if (argv[optind]) {
                xchdir(argv[optind]);
@@ -979,9 +1191,11 @@ int ftpd_main(int argc, char **argv)
        /* Set up options on the command socket (do we need these all? why?) */
        setsockopt(STDIN_FILENO, IPPROTO_TCP, TCP_NODELAY, &const_int_1, sizeof(const_int_1));
        setsockopt(STDIN_FILENO, SOL_SOCKET, SO_KEEPALIVE, &const_int_1, sizeof(const_int_1));
+       /* Telnet protocol over command link may send "urgent" data,
+        * we prefer it to be received in the "normal" data stream: */
        setsockopt(STDIN_FILENO, SOL_SOCKET, SO_OOBINLINE, &const_int_1, sizeof(const_int_1));
 
-       cmdio_write_ok(FTP_GREET);
+       WRITE_OK(FTP_GREET);
        signal(SIGALRM, timeout_handler);
 
 #ifdef IF_WE_WANT_TO_REQUIRE_LOGIN
@@ -1002,14 +1216,14 @@ int ftpd_main(int argc, char **argv)
                                        break;
                                cmdio_write_raw(STR(FTP_NEEDUSER)" Login with USER\r\n");
                        } else if (cmdval == const_QUIT) {
-                               cmdio_write_ok(FTP_GOODBYE);
+                               WRITE_OK(FTP_GOODBYE);
                                return 0;
                        } else {
                                cmdio_write_raw(STR(FTP_LOGINERR)" Login with USER and PASS\r\n");
                        }
                }
        }
-       cmdio_write_ok(FTP_LOGINOK);
+       WRITE_OK(FTP_LOGINOK);
 #endif
 
        /* RFC-959 Section 5.1
@@ -1054,23 +1268,28 @@ int ftpd_main(int argc, char **argv)
                uint32_t cmdval = cmdio_get_cmd_and_arg();
 
                if (cmdval == const_QUIT) {
-                       cmdio_write_ok(FTP_GOODBYE);
+                       WRITE_OK(FTP_GOODBYE);
                        return 0;
                }
                else if (cmdval == const_USER)
-                       cmdio_write_ok(FTP_GIVEPWORD);
+                       /* This would mean "ok, now give me PASS". */
+                       /*WRITE_OK(FTP_GIVEPWORD);*/
+                       /* vsftpd can be configured to not require that,
+                        * and this also saves one roundtrip:
+                        */
+                       WRITE_OK(FTP_LOGINOK);
                else if (cmdval == const_PASS)
-                       cmdio_write_ok(FTP_LOGINOK);
+                       WRITE_OK(FTP_LOGINOK);
                else if (cmdval == const_NOOP)
-                       cmdio_write_ok(FTP_NOOPOK);
+                       WRITE_OK(FTP_NOOPOK);
                else if (cmdval == const_TYPE)
-                       cmdio_write_ok(FTP_TYPEOK);
+                       WRITE_OK(FTP_TYPEOK);
                else if (cmdval == const_STRU)
-                       cmdio_write_ok(FTP_STRUOK);
+                       WRITE_OK(FTP_STRUOK);
                else if (cmdval == const_MODE)
-                       cmdio_write_ok(FTP_MODEOK);
+                       WRITE_OK(FTP_MODEOK);
                else if (cmdval == const_ALLO)
-                       cmdio_write_ok(FTP_ALLOOK);
+                       WRITE_OK(FTP_ALLOOK);
                else if (cmdval == const_SYST)
                        cmdio_write_raw(STR(FTP_SYSTOK)" UNIX Type: L8\r\n");
                else if (cmdval == const_PWD)
@@ -1079,14 +1298,21 @@ int ftpd_main(int argc, char **argv)
                        handle_cwd();
                else if (cmdval == const_CDUP) /* cd .. */
                        handle_cdup();
-               else if (cmdval == const_HELP)
-                       handle_help();
+               /* HELP is nearly useless, but we can reuse FEAT for it */
+               /* lftp uses FEAT */
+               else if (cmdval == const_HELP || cmdval == const_FEAT)
+                       handle_feat(cmdval == const_HELP
+                                       ? STRNUM32(FTP_HELP)
+                                       : STRNUM32(FTP_STATOK)
+                       );
                else if (cmdval == const_LIST) /* ls -l */
                        handle_list();
                else if (cmdval == const_NLST) /* "name list", bare ls */
                        handle_nlst();
-               else if (cmdval == const_SIZE)
-                       handle_size();
+               /* SIZE is crucial for wget's download indicator etc */
+               /* Mozilla, lftp use MDTM (presumably for caching) */
+               else if (cmdval == const_SIZE || cmdval == const_MDTM)
+                       handle_size_or_mdtm(cmdval == const_SIZE);
                else if (cmdval == const_STAT) {
                        if (G.ftp_arg == NULL)
                                handle_stat();
@@ -1121,6 +1347,8 @@ int ftpd_main(int argc, char **argv)
                                handle_appe();
                        else if (cmdval == const_STOU) /* "store unique" */
                                handle_stou();
+                       else
+                               goto bad_cmd;
                }
 #endif
 #if 0
@@ -1139,9 +1367,11 @@ int ftpd_main(int argc, char **argv)
                else {
                        /* Which unsupported commands were seen in the wild?
                         * (doesn't necessarily mean "we must support them")
-                        * lftp 3.6.3: FEAT - is it useful?
-                        *             MDTM - works fine without it anyway
+                        * foo 1.2.3: XXXX - comment
                         */
+#if ENABLE_FEATURE_FTP_WRITE
+ bad_cmd:
+#endif
                        cmdio_write_raw(STR(FTP_BADCMD)" Unknown command\r\n");
                }
        }