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authorDenys Vlasenko <vda.linux@googlemail.com>2014-06-27 12:24:39 +0200
committerDenys Vlasenko <vda.linux@googlemail.com>2014-06-27 12:24:39 +0200
commita6ae999b3b30ad522272325bac4c69b153150108 (patch)
tree0af61697af6661c9d45c28025f2404c522436278 /networking
parent5f8daefb835687e428215f90d26fdf1f0206149d (diff)
downloadbusybox-a6ae999b3b30ad522272325bac4c69b153150108.tar.gz
ftpd: escape chroot prior to re-executing ls helper
When we merely chdir to saved "real" root fd, exec("proc/self/exe") works for static executables but not for dynamic ones (they can't find their interpreter). With this patch, we also *chroot* to real root. As a bonus, this gives us proper usernames, timezone conversion etc. function old new delta popen_ls 203 259 +56 ftpd_main 2362 2366 +4 Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
Diffstat (limited to 'networking')
-rw-r--r--networking/ftpd.c53
1 files changed, 21 insertions, 32 deletions
diff --git a/networking/ftpd.c b/networking/ftpd.c
index e724734df..839a85d73 100644
--- a/networking/ftpd.c
+++ b/networking/ftpd.c
@@ -620,16 +620,12 @@ popen_ls(const char *opt)
const char *argv[5];
struct fd_pair outfd;
pid_t pid;
-
+#if !BB_MMU
+ int cur_fd = xopen(".", O_RDONLY | O_DIRECTORY);
+#endif
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;
@@ -651,16 +647,6 @@ popen_ls(const char *opt)
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);
@@ -674,19 +660,25 @@ popen_ls(const char *opt)
/* 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);
+ /* On NOMMU, we want to execute a child - copy of ourself
+ * in order to unblock parent after vfork.
+ * In chroot we usually can't re-exec. Thus we escape
+ * out of the chroot back to original root.
+ */
+ if (G.root_fd >= 0) {
+ if (fchdir(G.root_fd) != 0 || chroot(".") != 0)
+ _exit(127);
+ /*close(G.root_fd); - close_on_exec_on() took care of this */
+ }
+ /* Child expects directory to list on fd #3 */
+ xmove_fd(cur_fd, 3);
+ execv(bb_busybox_exec_path, (char**) argv);
_exit(127);
#endif
}
/* parent */
close(outfd.wr);
-#if !BB_MMU
- free((char*)argv[2]);
-#endif
return outfd.rd;
}
@@ -705,8 +697,6 @@ handle_dir_common(int opts)
if (!(opts & USE_CTRL_CONN) && !port_or_pasv_was_seen())
return; /* port_or_pasv_was_seen emitted error response */
- /* -n prevents user/groupname display,
- * which can be problematic in chroot */
ls_fd = popen_ls((opts & LONG_LISTING) ? "-l" : "-1");
ls_fp = xfdopen_for_read(ls_fd);
/* FIXME: filenames with embedded newlines are mishandled */
@@ -1139,11 +1129,10 @@ int ftpd_main(int argc UNUSED_PARAM, char **argv)
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 */
-/* 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*)"--";
+ if (fchdir(3) != 0)
+ _exit(127);
/* memset(&G, 0, sizeof(G)); - ls_main does it */
return ls_main(argc, argv);
}
@@ -1185,9 +1174,9 @@ int ftpd_main(int argc UNUSED_PARAM, char **argv)
G.root_fd = xopen("/", O_RDONLY | O_DIRECTORY);
close_on_exec_on(G.root_fd);
#endif
-
- if (argv[optind]) {
- xchroot(argv[optind]);
+ argv += optind;
+ if (argv[0]) {
+ xchroot(argv[0]);
}
//umask(077); - admin can set umask before starting us