From f7ad927c2059ef9cd1cd6befeb43f26b92f6369f Mon Sep 17 00:00:00 2001 From: Denys Vlasenko Date: Tue, 13 Oct 2015 13:49:53 +0200 Subject: ftpd: make DIR parameter work for non-root too: chdir to it instead of chroot Unfortunately, chroot() works only for root user, because of attacks on setuid binaries (make DIR/lib/ld-linux.so a shell, hardlink to a setuid binary, chroot to DIR, execute it and get root shell). function old new delta ftpd_main 2160 2180 +20 Signed-off-by: Denys Vlasenko --- networking/ftpd.c | 17 ++++++++++++++++- 1 file changed, 16 insertions(+), 1 deletion(-) (limited to 'networking/ftpd.c') diff --git a/networking/ftpd.c b/networking/ftpd.c index 7735b7233..8345ae67c 100644 --- a/networking/ftpd.c +++ b/networking/ftpd.c @@ -1223,11 +1223,26 @@ int ftpd_main(int argc UNUSED_PARAM, char **argv) #endif argv += optind; if (argv[0]) { + const char *basedir = argv[0]; #if !BB_MMU G.root_fd = xopen("/", O_RDONLY | O_DIRECTORY); close_on_exec_on(G.root_fd); #endif - xchroot(argv[0]); + if (chroot(basedir) == 0) + basedir = "/"; +#if !BB_MMU + else { + close(G.root_fd); + G.root_fd = -1; + } +#endif + /* + * If chroot failed, assume that we aren't root, + * and at least chdir to the specified DIR + * (older versions were dying with error message). + * If chroot worked, move current dir to new "/": + */ + xchdir(basedir); } #if ENABLE_FEATURE_FTP_AUTHENTICATION -- cgit v1.2.3