ftpd: simplify PORT check by assuming IP = peer's IP.

 Should be as safe as before this change.

function                                             old     new   delta
ftpd_main                                           2115    2025     -90

1 files changed, 27 insertions, 1 deletions

diff --git a/networking/ftpd.c b/networking/ftpd.c
index d63fd9bed..675324803 100644
--- a/networking/ftpd.c
+++ b/networking/ftpd.c
@@ -422,21 +422,42 @@ handle_epsv(void)
         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)
 {
         unsigned port, port_hi;
         char *raw, *comma;
+#ifdef WHY_BOTHER_WE_CAN_ASSUME_IP_MATCHES
         socklen_t peer_ipv4_len;
         struct sockaddr_in peer_ipv4;
         struct in_addr port_ipv4_sin_addr;
+#endif
 
         port_pasv_cleanup();
 
         raw = G.ftp_arg;
 
         /* PORT command format makes sense only over IPv4 */
-        if (!raw || G.local_addr->u.sa.sa_family != AF_INET) {
+        if (!raw
+#ifdef WHY_BOTHER_WE_CAN_ASSUME_IP_MATCHES
+         || G.local_addr->u.sa.sa_family != AF_INET
+#endif
+        ) {
  bail:
                 cmdio_write_error(FTP_BADCMD);
                 return;
@@ -459,6 +480,7 @@ handle_port(void)
                 goto bail;
         port |= port_hi << 8;
 
+#ifdef WHY_BOTHER_WE_CAN_ASSUME_IP_MATCHES
         replace_char(raw, ',', '.');
 
         /* We are verifying that PORT's IP matches getpeername().
@@ -477,6 +499,10 @@ handle_port(void)
                 goto bail;
 
         G.port_addr = xdotted2sockaddr(raw, port);
+#else
+        G.port_addr = get_peer_lsa(STDIN_FILENO);
+        set_nport(G.port_addr, port);
+#endif
         cmdio_write_ok(FTP_PORTOK);
 }