tftpd: fix download: we must change user AFTER bind

tftp_protocol                                       1466    1468      +2

diff --git a/networking/tftp.c b/networking/tftp.c
index 5fac487..bea215c 100644 (file)
--- a/networking/tftp.c
+++ b/networking/tftp.c
@@ -83,9 +83,7 @@ enum {
 struct globals {
        /* u16 TFTP_ERROR; u16 reason; both network-endian, then error text: */
        uint8_t error_pkt[4 + 32];
-#if ENABLE_TFTPD
        char *user_opt;
-#endif
        /* used in tftpd_main(), a bit big for stack: */
        char block_buf[TFTP_BLKSIZE_DEFAULT];
 };
@@ -183,7 +181,7 @@ static int tftp_protocol(
        int open_mode, local_fd;
        int retries, waittime_ms;
        int io_bufsize = blksize + 4;
-       char *cp;
+       char *cp = cp; /* for compiler */
        /* Can't use RESERVE_CONFIG_BUFFER here since the allocation
         * size varies meaning BUFFERS_GO_ON_STACK would fail */
        /* We must keep the transmit and receive buffers seperate */
@@ -194,40 +192,8 @@ static int tftp_protocol(
        socket_fd = xsocket(peer_lsa->u.sa.sa_family, SOCK_DGRAM, 0);
        setsockopt_reuseaddr(socket_fd);
 
-#if ENABLE_TFTPD
-       if (user_opt) {
-               struct passwd *pw = getpwnam(user_opt); /* initgroups, setgid, setuid */
-               if (!pw)
-                       bb_error_msg_and_die("unknown user '%s'", user_opt);
-               change_identity(pw);
-       }
-#endif
-
-       if (CMD_PUT(option_mask32)) {
-               open_mode = O_RDONLY;
-       } else {
-               open_mode = O_WRONLY | O_TRUNC | O_CREAT;
-#if ENABLE_TFTPD
-               if ((option_mask32 & (TFTPD_OPT+TFTPD_OPT_c)) == TFTPD_OPT) {
-                       /* tftpd without -c */
-                       open_mode = O_WRONLY | O_TRUNC;
-               }
-#endif
-       }
-       if (!(option_mask32 & TFTPD_OPT)) {
-               local_fd = CMD_GET(option_mask32) ? STDOUT_FILENO : STDIN_FILENO;
-               if (NOT_LONE_DASH(local_file))
-                       local_fd = xopen(local_file, open_mode);
-       } else {
-               local_fd = open_or_warn(local_file, open_mode);
-               if (local_fd < 0) {
-                       /*error_pkt_reason = ERR_NOFILE/ERR_ACCESS?*/
-                       strcpy(error_pkt_str, "can't open file");
-                       goto send_err_pkt;
-               }
-       }
-
        block_nr = 1;
+
        if (!ENABLE_TFTP || our_lsa) {
                /* tftpd */
 
@@ -258,9 +224,48 @@ static int tftp_protocol(
                         * that is, for "block 0" which is our OACK pkt */
                        opcode = TFTP_OACK;
                        cp = xbuf + 2;
+                       /* to be continued, see below */
+               }
+#endif
+               if (user_opt) {
+                       struct passwd *pw = getpwnam(user_opt);
+                       if (!pw)
+                               bb_error_msg_and_die("unknown user '%s'", user_opt);
+                       change_identity(pw); /* initgroups, setgid, setuid */
+               }
+       }
+
+       /* Open local file (must be after changing user) */
+       if (CMD_PUT(option_mask32)) {
+               open_mode = O_RDONLY;
+       } else {
+               open_mode = O_WRONLY | O_TRUNC | O_CREAT;
+#if ENABLE_TFTPD
+               if ((option_mask32 & (TFTPD_OPT+TFTPD_OPT_c)) == TFTPD_OPT) {
+                       /* tftpd without -c */
+                       open_mode = O_WRONLY | O_TRUNC;
+               }
+#endif
+       }
+       if (!(option_mask32 & TFTPD_OPT)) {
+               local_fd = CMD_GET(option_mask32) ? STDOUT_FILENO : STDIN_FILENO;
+               if (NOT_LONE_DASH(local_file))
+                       local_fd = xopen(local_file, open_mode);
+       } else {
+               local_fd = open_or_warn(local_file, open_mode);
+               if (local_fd < 0) {
+                       /*error_pkt_reason = ERR_NOFILE/ERR_ACCESS?*/
+                       strcpy(error_pkt_str, "can't open file");
+                       goto send_err_pkt;
+               }
+       }
+
+       if (!ENABLE_TFTP || our_lsa) {
+#if ENABLE_FEATURE_TFTP_BLOCKSIZE
+               if (blksize != TFTP_BLKSIZE_DEFAULT) {
+                       /* Create and send OACK packet. continued */
                        goto add_blksize_opt;
                }
-               /* else: just fall into while (1) loop below */
 #endif
        } else {
                /* tftp */