Mercurial > dropbear
view svr-tcpfwd.c @ 1930:299f4f19ba19
Add /usr/sbin and /sbin to default root PATH
When dropbear is used in a very restricted environment (such as in a
initrd), the default user shell is often also very restricted
and doesn't take care of setting the PATH so the user ends up
with the PATH set by dropbear. Unfortunately, dropbear always
sets "/usr/bin:/bin" as default PATH even for the root user
which should have /usr/sbin and /sbin too.
For a concrete instance of this problem, see the "Remote Unlocking"
section in this tutorial: https://paxswill.com/blog/2013/11/04/encrypted-raspberry-pi/
It speaks of a bug in the initramfs script because it's written "blkid"
instead of "/sbin/blkid"... this is just because the scripts from the
initramfs do not expect to have a PATH without the sbin directories and
because dropbear is not setting the PATH appropriately for the root user.
I'm thus suggesting to use the attached patch to fix this misbehaviour (I
did not test it, but it's easy enough). It might seem anecdotic but
multiple Kali users have been bitten by this.
From https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=903403
author | Raphael Hertzog <hertzog@debian.org> |
---|---|
date | Mon, 09 Jul 2018 16:27:53 +0200 |
parents | 1d86a58fb52d |
children |
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/* * Dropbear SSH * * Copyright (c) 2002,2003 Matt Johnston * Copyright (c) 2004 by Mihnea Stoenescu * All rights reserved. * * Permission is hereby granted, free of charge, to any person obtaining a copy * of this software and associated documentation files (the "Software"), to deal * in the Software without restriction, including without limitation the rights * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell * copies of the Software, and to permit persons to whom the Software is * furnished to do so, subject to the following conditions: * * The above copyright notice and this permission notice shall be included in * all copies or substantial portions of the Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE * SOFTWARE. */ #include "includes.h" #include "ssh.h" #include "tcpfwd.h" #include "dbutil.h" #include "session.h" #include "buffer.h" #include "packet.h" #include "listener.h" #include "runopts.h" #include "auth.h" #include "netio.h" #if !DROPBEAR_SVR_REMOTETCPFWD /* This is better than SSH_MSG_UNIMPLEMENTED */ void recv_msg_global_request_remotetcp() { unsigned int wantreply = 0; TRACE(("recv_msg_global_request_remotetcp: remote tcp forwarding not compiled in")) buf_eatstring(ses.payload); wantreply = buf_getbool(ses.payload); if (wantreply) { send_msg_request_failure(); } } /* */ #endif /* !DROPBEAR_SVR_REMOTETCPFWD */ static int svr_cancelremotetcp(void); static int svr_remotetcpreq(int *allocated_listen_port); static int newtcpdirect(struct Channel * channel); #if DROPBEAR_SVR_REMOTETCPFWD static const struct ChanType svr_chan_tcpremote = { "forwarded-tcpip", NULL, NULL, NULL, NULL, NULL }; /* At the moment this is completely used for tcp code (with the name reflecting * that). If new request types are added, this should be replaced with code * similar to the request-switching in chansession.c */ void recv_msg_global_request_remotetcp() { char* reqname = NULL; unsigned int namelen; unsigned int wantreply = 0; int ret = DROPBEAR_FAILURE; TRACE(("enter recv_msg_global_request_remotetcp")) if (svr_opts.noremotetcp || !svr_pubkey_allows_tcpfwd()) { TRACE(("leave recv_msg_global_request_remotetcp: remote tcp forwarding disabled")) goto out; } reqname = buf_getstring(ses.payload, &namelen); wantreply = buf_getbool(ses.payload); if (namelen > MAX_NAME_LEN) { TRACE(("name len is wrong: %d", namelen)) goto out; } if (strcmp("tcpip-forward", reqname) == 0) { int allocated_listen_port = 0; ret = svr_remotetcpreq(&allocated_listen_port); /* client expects-port-number-to-make-use-of-server-allocated-ports */ if (DROPBEAR_SUCCESS == ret) { CHECKCLEARTOWRITE(); buf_putbyte(ses.writepayload, SSH_MSG_REQUEST_SUCCESS); buf_putint(ses.writepayload, allocated_listen_port); encrypt_packet(); wantreply = 0; /* avoid out: below sending another reply */ } } else if (strcmp("cancel-tcpip-forward", reqname) == 0) { ret = svr_cancelremotetcp(); } else { TRACE(("reqname isn't tcpip-forward: '%s'", reqname)) } out: if (wantreply) { if (ret == DROPBEAR_SUCCESS) { send_msg_request_success(); } else { send_msg_request_failure(); } } m_free(reqname); TRACE(("leave recv_msg_global_request")) } static int matchtcp(const void* typedata1, const void* typedata2) { const struct TCPListener *info1 = (struct TCPListener*)typedata1; const struct TCPListener *info2 = (struct TCPListener*)typedata2; return (info1->listenport == info2->listenport) && (info1->chantype == info2->chantype) && (strcmp(info1->listenaddr, info2->listenaddr) == 0); } static int svr_cancelremotetcp() { int ret = DROPBEAR_FAILURE; char * bindaddr = NULL; unsigned int addrlen; unsigned int port; struct Listener * listener = NULL; struct TCPListener tcpinfo; TRACE(("enter cancelremotetcp")) bindaddr = buf_getstring(ses.payload, &addrlen); if (addrlen > MAX_HOST_LEN) { TRACE(("addr len too long: %d", addrlen)) goto out; } port = buf_getint(ses.payload); tcpinfo.sendaddr = NULL; tcpinfo.sendport = 0; tcpinfo.listenaddr = bindaddr; tcpinfo.listenport = port; listener = get_listener(CHANNEL_ID_TCPFORWARDED, &tcpinfo, matchtcp); if (listener) { remove_listener( listener ); ret = DROPBEAR_SUCCESS; } out: m_free(bindaddr); TRACE(("leave cancelremotetcp")) return ret; } static int svr_remotetcpreq(int *allocated_listen_port) { int ret = DROPBEAR_FAILURE; char * request_addr = NULL; unsigned int addrlen; struct TCPListener *tcpinfo = NULL; unsigned int port; struct Listener *listener = NULL; TRACE(("enter remotetcpreq")) request_addr = buf_getstring(ses.payload, &addrlen); if (addrlen > MAX_HOST_LEN) { TRACE(("addr len too long: %d", addrlen)) goto out; } port = buf_getint(ses.payload); if (port != 0) { if (port < 1 || port > 65535) { TRACE(("invalid port: %d", port)) goto out; } if (!ses.allowprivport && port < IPPORT_RESERVED) { TRACE(("can't assign port < 1024 for non-root")) goto out; } } tcpinfo = (struct TCPListener*)m_malloc(sizeof(struct TCPListener)); tcpinfo->sendaddr = NULL; tcpinfo->sendport = 0; tcpinfo->listenport = port; tcpinfo->chantype = &svr_chan_tcpremote; tcpinfo->tcp_type = forwarded; tcpinfo->request_listenaddr = request_addr; if (!opts.listen_fwd_all || (strcmp(request_addr, "localhost") == 0) ) { /* NULL means "localhost only" */ tcpinfo->listenaddr = NULL; } else { tcpinfo->listenaddr = m_strdup(request_addr); } ret = listen_tcpfwd(tcpinfo, &listener); if (DROPBEAR_SUCCESS == ret) { tcpinfo->listenport = get_sock_port(listener->socks[0]); *allocated_listen_port = tcpinfo->listenport; } out: if (ret == DROPBEAR_FAILURE) { /* we only free it if a listener wasn't created, since the listener * has to remember it if it's to be cancelled */ m_free(request_addr); m_free(tcpinfo); } TRACE(("leave remotetcpreq")) return ret; } #endif /* DROPBEAR_SVR_REMOTETCPFWD */ #if DROPBEAR_SVR_LOCALTCPFWD const struct ChanType svr_chan_tcpdirect = { "direct-tcpip", newtcpdirect, /* init */ NULL, /* checkclose */ NULL, /* reqhandler */ NULL, /* closehandler */ NULL /* cleanup */ }; /* Called upon creating a new direct tcp channel (ie we connect out to an * address */ static int newtcpdirect(struct Channel * channel) { char* desthost = NULL; unsigned int destport; char* orighost = NULL; unsigned int origport; char portstring[NI_MAXSERV]; unsigned int len; int err = SSH_OPEN_ADMINISTRATIVELY_PROHIBITED; TRACE(("newtcpdirect channel %d", channel->index)) if (svr_opts.nolocaltcp || !svr_pubkey_allows_tcpfwd()) { TRACE(("leave newtcpdirect: local tcp forwarding disabled")) goto out; } desthost = buf_getstring(ses.payload, &len); if (len > MAX_HOST_LEN) { TRACE(("leave newtcpdirect: desthost too long")) goto out; } destport = buf_getint(ses.payload); orighost = buf_getstring(ses.payload, &len); if (len > MAX_HOST_LEN) { TRACE(("leave newtcpdirect: orighost too long")) goto out; } origport = buf_getint(ses.payload); /* best be sure */ if (origport > 65535 || destport > 65535) { TRACE(("leave newtcpdirect: port > 65535")) goto out; } snprintf(portstring, sizeof(portstring), "%u", destport); channel->conn_pending = connect_remote(desthost, portstring, channel_connect_done, channel, NULL, NULL, DROPBEAR_PRIO_NORMAL); err = SSH_OPEN_IN_PROGRESS; out: m_free(desthost); m_free(orighost); TRACE(("leave newtcpdirect: err %d", err)) return err; } #endif /* DROPBEAR_SVR_LOCALTCPFWD */