# run sftp sessions inside a chroot diff --git a/openssh-6.6p1/session.c b/openssh-6.6p1/session.c --- a/openssh-6.6p1/session.c +++ b/openssh-6.6p1/session.c @@ -120,16 +120,18 @@ int do_exec(Session *, const char *); void do_login(Session *, const char *); #ifdef LOGIN_NEEDS_UTMPX static void do_pre_login(Session *s); #endif void do_child(Session *, const char *); void do_motd(void); int check_quietlogin(Session *, const char *); +int chroot_no_tree = 0; + static void do_authenticated1(Authctxt *); static void do_authenticated2(Authctxt *); static int session_pty_req(Session *); /* import */ extern ServerOptions options; extern char *__progname; @@ -827,16 +829,21 @@ do_exec(Session *s, const char *command) "subsystem '%.900s'", s->subsys); } else if (command == NULL) { snprintf(session_type, sizeof(session_type), "shell"); } else { /* NB. we don't log unforced commands to preserve privacy */ snprintf(session_type, sizeof(session_type), "command"); } + if ((s->is_subsystem != SUBSYSTEM_INT_SFTP) && chroot_no_tree) { + logit("You aren't welcomed, go away!"); + exit (1); + } + if (s->ttyfd != -1) { tty = s->tty; if (strncmp(tty, "/dev/", 5) == 0) tty += 5; } verbose("Starting session: %s%s%s for %s from %.200s port %d", session_type, @@ -1463,67 +1470,132 @@ do_nologin(struct passwd *pw) while (fgets(buf, sizeof(buf), f)) fputs(buf, stderr); fclose(f); } exit(254); } /* + * Test if filesystem is mounted nosuid and nodev + */ + +static void +test_nosuid (char * path, dev_t fs) +{ + FILE *f; + struct stat st; + char buf[4096], *s, *on, *mountpoint, *opt; + int nodev, nosuid; + + if (!(f = popen ("/bin/mount", "r"))) + fatal ("%s: popen(\"/bin/mount\", \"r\"): %s", + __func__, strerror (errno)); + for (;;) { + s = fgets (buf, sizeof (buf), f); + if (ferror (f)) + fatal ("%s: read from popen: %s", __func__, + strerror (errno)); + if (!s) { + pclose (f); + fatal ("cannot find filesystem with the chroot directory"); + } + (void) strtok (buf, " "); + on = strtok (NULL, " "); + if (strcmp (on, "on")) { + pclose (f); + fatal ("bad format of mount output"); + } + mountpoint = strtok (NULL, " "); + if (memcmp (path, mountpoint, strlen (mountpoint))) + continue; + if (stat(mountpoint, &st) != 0) { + pclose (f); + fatal("%s: stat(\"%s\"): %s", __func__, + mountpoint, strerror(errno)); + } + if (fs != st.st_dev) + continue; + nodev = nosuid = 0; + for (opt = strtok (NULL, "("); opt; opt = strtok (NULL, " ,)")) { + if (!strcmp (opt, "nodev")) + nodev = 1; + else if (!strcmp (opt, "nosuid")) + nosuid = 1; + else if (!strcmp (opt, "noexec")) + nosuid = 1; + if (nodev && nosuid) { + pclose (f); + return; + } + } + fatal ("chroot into directory without nodev and either noexec or nosuid"); + } +} + +/* * Chroot into a directory after checking it for safety: all path components * must be root-owned directories with strict permissions. */ static void safely_chroot(const char *path, uid_t uid) { const char *cp; char component[MAXPATHLEN]; struct stat st; + int last; if (*path != '/') fatal("chroot path does not begin at root"); if (strlen(path) >= sizeof(component)) fatal("chroot path too long"); /* * Descend the path, checking that each component is a * root-owned directory with strict permissions. */ for (cp = path; cp != NULL;) { - if ((cp = strchr(cp, '/')) == NULL) + if (((last = ((cp = strchr(cp, '/')) == NULL)))) strlcpy(component, path, sizeof(component)); else { cp++; memcpy(component, path, cp - path); component[cp - path] = '\0'; } debug3("%s: checking '%s'", __func__, component); if (stat(component, &st) != 0) fatal("%s: stat(\"%s\"): %s", __func__, component, strerror(errno)); - if (st.st_uid != 0 || (st.st_mode & 022) != 0) + if ((st.st_uid != 0 || (st.st_mode & 022) != 0) && !(last && st.st_uid == uid)) fatal("bad ownership or modes for chroot " "directory %s\"%s\"", cp == NULL ? "" : "component ", component); if (!S_ISDIR(st.st_mode)) fatal("chroot path %s\"%s\" is not a directory", cp == NULL ? "" : "component ", component); - + } + setenv ("TZ", "/etc/localtime", 0); + tzset(); + + if (st.st_uid) { + test_nosuid(path, st.st_dev); + ++chroot_no_tree; } if (chdir(path) == -1) fatal("Unable to chdir to chroot path \"%s\": " "%s", path, strerror(errno)); if (chroot(path) == -1) fatal("chroot(\"%s\"): %s", path, strerror(errno)); if (chdir("/") == -1) fatal("%s: chdir(/) after chroot: %s", __func__, strerror(errno)); + verbose("Changed root directory to \"%s\"", path); } /* Set login name, uid, gid, and groups. */ void do_setusercontext(struct passwd *pw) { char *chroot_path, *tmp; diff --git a/openssh-6.6p1/sftp-chrootenv.h b/openssh-6.6p1/sftp-chrootenv.h new file mode 100644 --- /dev/null +++ b/openssh-6.6p1/sftp-chrootenv.h @@ -0,0 +1,30 @@ +/* + * Copyright (c) 2009 Jan F Chadima. All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * + * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR + * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES + * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. + * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, + * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT + * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, + * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY + * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT + * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF + * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. + */ +#ifndef CHROOTENV_H +#define CHROOTENV_H + +extern int chroot_no_tree; + +#endif + diff --git a/openssh-6.6p1/sftp-common.c b/openssh-6.6p1/sftp-common.c --- a/openssh-6.6p1/sftp-common.c +++ b/openssh-6.6p1/sftp-common.c @@ -42,16 +42,17 @@ #endif #include "xmalloc.h" #include "buffer.h" #include "log.h" #include "sftp.h" #include "sftp-common.h" +#include "sftp-chrootenv.h" /* Clear contents of attributes structure */ void attrib_clear(Attrib *a) { a->flags = 0; a->size = 0; a->uid = 0; @@ -193,23 +194,23 @@ ls_file(const char *name, const struct s int ulen, glen, sz = 0; struct tm *ltime = localtime(&st->st_mtime); char *user, *group; char buf[1024], mode[11+1], tbuf[12+1], ubuf[11+1], gbuf[11+1]; char sbuf[FMT_SCALED_STRSIZE]; time_t now; strmode(st->st_mode, mode); - if (!remote) { + if (!remote && !chroot_no_tree) { user = user_from_uid(st->st_uid, 0); } else { snprintf(ubuf, sizeof ubuf, "%u", (u_int)st->st_uid); user = ubuf; } - if (!remote) { + if (!remote && !chroot_no_tree) { group = group_from_gid(st->st_gid, 0); } else { snprintf(gbuf, sizeof gbuf, "%u", (u_int)st->st_gid); group = gbuf; } if (ltime != NULL) { now = time(NULL); if (now - (365*24*60*60)/2 < st->st_mtime && diff --git a/openssh-6.6p1/sftp-server-main.c b/openssh-6.6p1/sftp-server-main.c --- a/openssh-6.6p1/sftp-server-main.c +++ b/openssh-6.6p1/sftp-server-main.c @@ -17,21 +17,24 @@ #include "includes.h" #include #include #include #include #include +#include #include "log.h" #include "sftp.h" #include "misc.h" +int chroot_no_tree = 0; + void cleanup_exit(int i) { sftp_server_cleanup_exit(i); } int main(int argc, char **argv) diff --git a/openssh-6.6p1/sftp.c b/openssh-6.6p1/sftp.c --- a/openssh-6.6p1/sftp.c +++ b/openssh-6.6p1/sftp.c @@ -109,16 +109,18 @@ struct complete_ctx { char **remote_pathp; }; int remote_glob(struct sftp_conn *, const char *, int, int (*)(const char *, int), glob_t *); /* proto for sftp-glob.c */ extern char *__progname; +int chroot_no_tree = 0; + /* Separators for interactive commands */ #define WHITESPACE " \t\r\n" /* ls flags */ #define LS_LONG_VIEW 0x0001 /* Full view ala ls -l */ #define LS_SHORT_VIEW 0x0002 /* Single row view ala ls -1 */ #define LS_NUMERIC_VIEW 0x0004 /* Long view with numeric uid/gid */ #define LS_NAME_SORT 0x0008 /* Sort by name (default) */ diff --git a/openssh-6.6p1/sshd_config.0 b/openssh-6.6p1/sshd_config.0 --- a/openssh-6.6p1/sshd_config.0 +++ b/openssh-6.6p1/sshd_config.0 @@ -189,16 +189,24 @@ DESCRIPTION session this requires at least a shell, typically sh(1), and basic /dev nodes such as null(4), zero(4), stdin(4), stdout(4), stderr(4), arandom(4) and tty(4) devices. For file transfer sessions using ``sftp'', no additional configuration of the environment is necessary if the in-process sftp server is used, though sessions which use logging do require /dev/log inside the chroot directory (see sftp-server(8) for details). + In the special case when only sftp is used, not ssh nor scp, it + is possible to use ChrootDirectory %h or ChrootDirectory + /some/path/%u. The file system containing this directory must be + mounted with options nodev and either nosuid or noexec. The owner + of the directory should be the user. The ownership of the other + components of the path must fulfill the usual conditions. No adi- + tional files are required to be present in the directory. + The default is not to chroot(2). Ciphers Specifies the ciphers allowed for protocol version 2. Multiple ciphers must be comma-separated. The supported ciphers are: ``3des-cbc'', ``aes128-cbc'', ``aes192-cbc'', ``aes256-cbc'', ``aes128-ctr'', ``aes192-ctr'', ``aes256-ctr'', diff --git a/openssh-6.6p1/sshd_config.5 b/openssh-6.6p1/sshd_config.5 --- a/openssh-6.6p1/sshd_config.5 +++ b/openssh-6.6p1/sshd_config.5 @@ -324,16 +324,27 @@ For file transfer sessions using no additional configuration of the environment is necessary if the in-process sftp server is used, though sessions which use logging do require .Pa /dev/log inside the chroot directory (see .Xr sftp-server 8 for details). .Pp +In the special case when only sftp is used, not ssh nor scp, +it is possible to use +.Cm ChrootDirectory +%h or +.Cm ChrootDirectory +/some/path/%u. The file system containing this directory must be +mounted with options nodev and either nosuid or noexec. The owner of the +directory should be the user. The ownership of the other components of the path +must fulfill the usual conditions. No aditional files are required to be present +in the directory. +.Pp The default is not to .Xr chroot 2 . .It Cm Ciphers Specifies the ciphers allowed for protocol version 2. Multiple ciphers must be comma-separated. The supported ciphers are: .Pp .Dq 3des-cbc ,