ftpd: security tightened up:
PORT is not allowed on !IPv4 PORT must have IP == peer's IP upload is allowed only into regular files function old new delta ftpd_main 1815 2019 +204 handle_upload_common 260 306 +46 ------------------------------------------------------------------------------ (add/remove: 0/0 grow/shrink: 2/0 up/down: 250/0) Total: 250 bytes
This commit is contained in:
Denis Vlasenko
parent
7a6766428e
commit
f2160b6a09
@ -66,9 +66,9 @@
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/* Convert a constant to 3-digit string, packed into uint32_t */
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enum {
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/* Shift for Nth decimal digit */
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SHIFT0 = 16 * BB_LITTLE_ENDIAN + 8 * BB_BIG_ENDIAN,
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SHIFT1 = 8 * BB_LITTLE_ENDIAN + 16 * BB_BIG_ENDIAN,
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SHIFT2 = 0 * BB_LITTLE_ENDIAN + 24 * BB_BIG_ENDIAN,
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SHIFT1 = 8 * BB_LITTLE_ENDIAN + 16 * BB_BIG_ENDIAN,
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SHIFT0 = 16 * BB_LITTLE_ENDIAN + 8 * BB_BIG_ENDIAN,
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};
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#define STRNUM32(s) (uint32_t)(0 \
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| (('0' + ((s) / 1 % 10)) << SHIFT0) \
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@ -76,47 +76,6 @@ enum {
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| (('0' + ((s) / 100 % 10)) << SHIFT2) \
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)
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enum {
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OPT_l = (1 << 0),
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OPT_1 = (1 << 1),
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OPT_v = (1 << 2),
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OPT_S = (1 << 3),
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OPT_w = (1 << 4),
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#define mk_const4(a,b,c,d) (((a * 0x100 + b) * 0x100 + c) * 0x100 + d)
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#define mk_const3(a,b,c) ((a * 0x100 + b) * 0x100 + c)
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const_ALLO = mk_const4('A', 'L', 'L', 'O'),
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const_APPE = mk_const4('A', 'P', 'P', 'E'),
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const_CDUP = mk_const4('C', 'D', 'U', 'P'),
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const_CWD = mk_const3('C', 'W', 'D'),
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const_DELE = mk_const4('D', 'E', 'L', 'E'),
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const_EPSV = mk_const4('E', 'P', 'S', 'V'),
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const_HELP = mk_const4('H', 'E', 'L', 'P'),
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const_LIST = mk_const4('L', 'I', 'S', 'T'),
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const_MKD = mk_const3('M', 'K', 'D'),
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const_MODE = mk_const4('M', 'O', 'D', 'E'),
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const_NLST = mk_const4('N', 'L', 'S', 'T'),
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const_NOOP = mk_const4('N', 'O', 'O', 'P'),
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const_PASS = mk_const4('P', 'A', 'S', 'S'),
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const_PASV = mk_const4('P', 'A', 'S', 'V'),
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const_PORT = mk_const4('P', 'O', 'R', 'T'),
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const_PWD = mk_const3('P', 'W', 'D'),
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const_QUIT = mk_const4('Q', 'U', 'I', 'T'),
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const_REST = mk_const4('R', 'E', 'S', 'T'),
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const_RETR = mk_const4('R', 'E', 'T', 'R'),
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const_RMD = mk_const3('R', 'M', 'D'),
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const_RNFR = mk_const4('R', 'N', 'F', 'R'),
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const_RNTO = mk_const4('R', 'N', 'T', 'O'),
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const_SIZE = mk_const4('S', 'I', 'Z', 'E'),
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const_STAT = mk_const4('S', 'T', 'A', 'T'),
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const_STOR = mk_const4('S', 'T', 'O', 'R'),
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const_STOU = mk_const4('S', 'T', 'O', 'U'),
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const_STRU = mk_const4('S', 'T', 'R', 'U'),
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const_SYST = mk_const4('S', 'Y', 'S', 'T'),
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const_TYPE = mk_const4('T', 'Y', 'P', 'E'),
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const_USER = mk_const4('U', 'S', 'E', 'R'),
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};
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struct globals {
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char *p_control_line_buf;
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len_and_sockaddr *local_addr;
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@ -182,21 +141,16 @@ replace_char(char *str, char from, char to)
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return p - str;
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}
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/* NB: status_str is char[4] packed into uint32_t */
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static void
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cmdio_write(uint32_t status_str, const char *str)
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{
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union {
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char buf[4];
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uint32_t v32;
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} u;
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char *response;
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int len;
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u.v32 = status_str;
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/* FTP allegedly uses telnet protocol for command link.
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* In telnet, 0xff is an escape char, and needs to be escaped: */
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response = escape_text(u.buf, str, (0xff << 8) + '\r');
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response = escape_text((char *) &status_str, str, (0xff << 8) + '\r');
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/* ?! does FTP send embedded LFs as NULs? wow */
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len = replace_char(response, '\n', '\0');
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@ -444,46 +398,58 @@ handle_epsv(void)
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static void
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handle_port(void)
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{
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unsigned short port;
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char *raw, *port_part;
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len_and_sockaddr *lsa;
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unsigned port, port_hi;
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char *raw, *comma;
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socklen_t peer_ipv4_len;
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struct sockaddr_in peer_ipv4;
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struct in_addr port_ipv4_sin_addr;
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port_pasv_cleanup();
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raw = G.ftp_arg;
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/* Buglets:
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* xatou16 will accept wrong input,
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* xatou16 will exit instead of generating error to peer
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*/
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port_part = strrchr(raw, ',');
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if (port_part == NULL)
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goto bail;
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port = xatou16(&port_part[1]);
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*port_part = '\0';
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port_part = strrchr(raw, ',');
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if (port_part == NULL)
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goto bail;
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port |= xatou16(&port_part[1]) << 8;
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*port_part = '\0';
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replace_char(raw, ',', '.');
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lsa = xdotted2sockaddr(raw, port);
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if (lsa == NULL) {
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/* PORT command format makes sense only over IPv4 */
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if (!raw || G.local_addr->u.sa.sa_family != AF_INET) {
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bail:
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cmdio_write_error(FTP_BADCMD);
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return;
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}
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/* Should we verify that lsa matches getpeername(STDIN)?
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* Otherwise peer can make us open data connections
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* to other hosts (security problem!)
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*/
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comma = strrchr(raw, ',');
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if (comma == NULL)
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goto bail;
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*comma = '\0';
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port = bb_strtou(&comma[1], NULL, 10);
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if (errno || port > 0xff)
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goto bail;
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G.port_addr = lsa;
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comma = strrchr(raw, ',');
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if (comma == NULL)
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goto bail;
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*comma = '\0';
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port_hi = bb_strtou(&comma[1], NULL, 10);
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if (errno || port_hi > 0xff)
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goto bail;
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port |= port_hi << 8;
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replace_char(raw, ',', '.');
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/* We are verifying that PORT's IP matches getpeername().
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* Otherwise peer can make us open data connections
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* to other hosts (security problem!)
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* This code would be too simplistic:
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* lsa = xdotted2sockaddr(raw, port);
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* if (lsa == NULL) goto bail;
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*/
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if (!inet_aton(raw, &port_ipv4_sin_addr))
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goto bail;
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peer_ipv4_len = sizeof(peer_ipv4);
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if (getpeername(STDIN_FILENO, &peer_ipv4, &peer_ipv4_len) != 0)
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goto bail;
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if (memcmp(&port_ipv4_sin_addr, &peer_ipv4.sin_addr, sizeof(struct in_addr)) != 0)
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goto bail;
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G.port_addr = xdotted2sockaddr(raw, port);
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cmdio_write_ok(FTP_PORTOK);
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}
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@ -612,6 +578,8 @@ handle_dir_common(int opts)
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if (!(opts & USE_CTRL_CONN) && !port_or_pasv_was_seen())
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return; /* port_or_pasv_was_seen emitted error response */
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/* -n prevents user/groupname display,
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* which can be problematic in chroot */
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ls_fd = popen_ls((opts & LONG_LISTING) ? "-l" : "-1");
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ls_fp = fdopen(ls_fd, "r");
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if (!ls_fp) /* never happens. paranoia */
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@ -749,11 +717,12 @@ handle_rnto(void)
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static void
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handle_upload_common(int is_append, int is_unique)
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{
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char *tempname = NULL;
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struct stat statbuf;
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char *tempname;
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off_t bytes_transferred;
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off_t offset;
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int local_file_fd;
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int remote_fd;
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off_t offset;
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offset = G.restart_pos;
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G.restart_pos = 0;
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@ -761,6 +730,7 @@ handle_upload_common(int is_append, int is_unique)
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if (!port_or_pasv_was_seen())
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return; /* port_or_pasv_was_seen emitted error response */
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tempname = NULL;
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local_file_fd = -1;
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if (is_unique) {
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tempname = xstrdup(" FILE: uniq.XXXXXX");
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@ -773,13 +743,17 @@ handle_upload_common(int is_append, int is_unique)
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flags = O_WRONLY | O_CREAT;
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local_file_fd = open(G.ftp_arg, flags, 0666);
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}
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if (local_file_fd < 0) {
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if (local_file_fd < 0
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|| fstat(local_file_fd, &statbuf) != 0
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|| !S_ISREG(statbuf.st_mode)
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) {
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cmdio_write_error(FTP_UPLOADFAIL);
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if (local_file_fd >= 0)
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goto close_local_and_bail;
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return;
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}
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/* TODO: paranoia: fstat it, refuse to do anything if it's not a regular file */
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if (offset)
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xlseek(local_file_fd, offset, SEEK_SET);
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@ -787,7 +761,7 @@ handle_upload_common(int is_append, int is_unique)
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free(tempname);
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if (remote_fd < 0)
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goto bail;
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goto close_local_and_bail;
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/* TODO: if we'll implement timeout, this will need more clever handling.
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* Perhaps alarm(N) + checking that current position on local_file_fd
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@ -800,7 +774,8 @@ handle_upload_common(int is_append, int is_unique)
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cmdio_write_error(FTP_BADSENDFILE);
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else
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cmdio_write_ok(FTP_TRANSFEROK);
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bail:
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close_local_and_bail:
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close(local_file_fd);
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}
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@ -838,17 +813,18 @@ cmdio_get_cmd_and_arg(void)
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if (!cmd)
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exit(0);
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/* Trailing '\n' is already stripped, strip '\r' */
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len = strlen(cmd) - 1;
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while (len >= 0 && cmd[len] == '\r') {
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while ((ssize_t)len >= 0 && cmd[len] == '\r') {
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cmd[len] = '\0';
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len--;
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}
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G.ftp_arg = strchr(cmd, ' ');
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if (G.ftp_arg != NULL) {
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*G.ftp_arg = '\0';
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G.ftp_arg++;
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}
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if (G.ftp_arg != NULL)
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*G.ftp_arg++ = '\0';
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/* Uppercase and pack into uint32_t first word of the command */
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cmdval = 0;
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while (*cmd)
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cmdval = (cmdval << 8) + ((unsigned char)*cmd++ & (unsigned char)~0x20);
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@ -856,6 +832,47 @@ cmdio_get_cmd_and_arg(void)
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return cmdval;
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}
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#define mk_const4(a,b,c,d) (((a * 0x100 + b) * 0x100 + c) * 0x100 + d)
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#define mk_const3(a,b,c) ((a * 0x100 + b) * 0x100 + c)
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enum {
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const_ALLO = mk_const4('A', 'L', 'L', 'O'),
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const_APPE = mk_const4('A', 'P', 'P', 'E'),
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const_CDUP = mk_const4('C', 'D', 'U', 'P'),
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const_CWD = mk_const3('C', 'W', 'D'),
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const_DELE = mk_const4('D', 'E', 'L', 'E'),
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const_EPSV = mk_const4('E', 'P', 'S', 'V'),
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const_HELP = mk_const4('H', 'E', 'L', 'P'),
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const_LIST = mk_const4('L', 'I', 'S', 'T'),
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const_MKD = mk_const3('M', 'K', 'D'),
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const_MODE = mk_const4('M', 'O', 'D', 'E'),
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const_NLST = mk_const4('N', 'L', 'S', 'T'),
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const_NOOP = mk_const4('N', 'O', 'O', 'P'),
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const_PASS = mk_const4('P', 'A', 'S', 'S'),
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const_PASV = mk_const4('P', 'A', 'S', 'V'),
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const_PORT = mk_const4('P', 'O', 'R', 'T'),
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const_PWD = mk_const3('P', 'W', 'D'),
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const_QUIT = mk_const4('Q', 'U', 'I', 'T'),
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const_REST = mk_const4('R', 'E', 'S', 'T'),
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const_RETR = mk_const4('R', 'E', 'T', 'R'),
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const_RMD = mk_const3('R', 'M', 'D'),
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const_RNFR = mk_const4('R', 'N', 'F', 'R'),
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const_RNTO = mk_const4('R', 'N', 'T', 'O'),
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const_SIZE = mk_const4('S', 'I', 'Z', 'E'),
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const_STAT = mk_const4('S', 'T', 'A', 'T'),
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const_STOR = mk_const4('S', 'T', 'O', 'R'),
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const_STOU = mk_const4('S', 'T', 'O', 'U'),
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const_STRU = mk_const4('S', 'T', 'R', 'U'),
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const_SYST = mk_const4('S', 'Y', 'S', 'T'),
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const_TYPE = mk_const4('T', 'Y', 'P', 'E'),
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const_USER = mk_const4('U', 'S', 'E', 'R'),
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OPT_l = (1 << 0),
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OPT_1 = (1 << 1),
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OPT_v = (1 << 2),
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OPT_S = (1 << 3),
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OPT_w = (1 << 4),
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};
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int ftpd_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
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int ftpd_main(int argc, char **argv)
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{
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@ -865,6 +882,7 @@ int ftpd_main(int argc, char **argv)
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if (opts & (OPT_l|OPT_1)) {
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/* Our secret backdoor to ls */
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/* TODO: pass -n too? */
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xchdir(argv[2]);
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argv[2] = (char*)"--";
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return ls_main(argc, argv);
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