Mercurial > dropbear
view runopts.h @ 1788:1fc0012b9c38
Fix handling of replies to global requests (#112)
The current code assumes that all global requests want / need a reply.
This isn't always true and the request itself indicates if it wants a
reply or not.
It causes a specific problem with [email protected] messages.
These are sent by OpenSSH after authentication to inform the client of
potential other host keys for the host. This can be used to add a new
type of host key or to rotate host keys.
The initial information message from the server is sent as a global
request, but with want_reply set to false. This means that the server
doesn't expect an answer to this message. Instead the client needs to
send a prove request as a reply if it wants to receive proof of
ownership for the host keys.
The bug doesn't cause any current problems with due to how OpenSSH
treats receiving the failure message. It instead treats it as a
keepalive message and further ignores it.
Arguably this is a protocol violation though of Dropbear and it is only
accidental that it doesn't cause a problem with OpenSSH.
The bug was found when adding host keys support to libssh, which is more
strict protocol wise and treats the unexpected failure message an error,
also see https://gitlab.com/libssh/libssh-mirror/-/merge_requests/145
for more information.
The fix here is to honor the want_reply flag in the global request and
to only send a reply if the other side expects a reply.
author | Dirkjan Bussink <d.bussink@gmail.com> |
---|---|
date | Thu, 10 Dec 2020 16:13:13 +0100 |
parents | cc0fc5131c5c |
children | 5120e22882de |
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/* * Dropbear - a SSH2 server * * Copyright (c) 2002,2003 Matt Johnston * 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. */ #ifndef DROPBEAR_RUNOPTS_H_ #define DROPBEAR_RUNOPTS_H_ #include "includes.h" #include "signkey.h" #include "buffer.h" #include "auth.h" #include "tcpfwd.h" typedef struct runopts { #if DROPBEAR_SVR_REMOTETCPFWD || DROPBEAR_CLI_LOCALTCPFWD \ || DROPBEAR_CLI_REMOTETCPFWD int listen_fwd_all; #endif unsigned int recv_window; time_t keepalive_secs; /* Time between sending keepalives. 0 is off */ time_t idle_timeout_secs; /* Exit if no traffic is sent/received in this time */ int usingsyslog; #ifndef DISABLE_ZLIB /* TODO: add a commandline flag. Currently this is on by default if compression * is compiled in, but disabled for a client's non-final multihop stages. (The * intermediate stages are compressed streams, so are uncompressible. */ enum { DROPBEAR_COMPRESS_DELAYED, /* Server only */ DROPBEAR_COMPRESS_ON, DROPBEAR_COMPRESS_OFF, } compress_mode; #endif #if DROPBEAR_USER_ALGO_LIST char *cipher_list; char *mac_list; #endif } runopts; extern runopts opts; int readhostkey(const char * filename, sign_key * hostkey, enum signkey_type *type); void load_all_hostkeys(void); typedef struct svr_runopts { char * bannerfile; int forkbg; /* ports and addresses are arrays of the portcount listening ports. strings are malloced. */ char *ports[DROPBEAR_MAX_PORTS]; unsigned int portcount; char *addresses[DROPBEAR_MAX_PORTS]; int inetdmode; /* Flags indicating whether to use ipv4 and ipv6 */ /* not used yet int ipv4; int ipv6; */ #if DO_MOTD /* whether to print the MOTD */ int domotd; #endif int norootlogin; #ifdef HAVE_GETGROUPLIST /* restrict_group is the group name if group restriction was enabled, NULL otherwise */ char *restrict_group; /* restrict_group_gid is only valid if restrict_group is set */ gid_t restrict_group_gid; #endif int noauthpass; int norootpass; int allowblankpass; unsigned int maxauthtries; #if DROPBEAR_SVR_REMOTETCPFWD int noremotetcp; #endif #if DROPBEAR_SVR_LOCALTCPFWD int nolocaltcp; #endif sign_key *hostkey; int delay_hostkey; char *hostkey_files[MAX_HOSTKEYS]; int num_hostkey_files; buffer * banner; char * pidfile; char * forced_command; #if DROPBEAR_PLUGIN char *pubkey_plugin; char *pubkey_plugin_options; #endif } svr_runopts; extern svr_runopts svr_opts; void svr_getopts(int argc, char ** argv); void loadhostkeys(void); typedef struct cli_runopts { char *progname; char *remotehost; const char *remoteport; char *own_user; char *username; char *cmd; int wantpty; int always_accept_key; int no_hostkey_check; int no_cmd; int backgrounded; int is_subsystem; #if DROPBEAR_CLI_PUBKEY_AUTH m_list *privkeys; /* Keys to use for public-key auth */ #endif #if DROPBEAR_CLI_ANYTCPFWD int exit_on_fwd_failure; #endif #if DROPBEAR_CLI_REMOTETCPFWD m_list * remotefwds; #endif #if DROPBEAR_CLI_LOCALTCPFWD m_list * localfwds; #endif #if DROPBEAR_CLI_AGENTFWD int agent_fwd; int agent_keys_loaded; /* whether pubkeys has been populated with a list of keys held by the agent */ int agent_fd; /* The agent fd is only set during authentication. Forwarded agent sessions have their own file descriptors */ #endif #if DROPBEAR_CLI_NETCAT char *netcat_host; unsigned int netcat_port; #endif #if DROPBEAR_CLI_PROXYCMD char *proxycmd; #endif char *bind_address; char *bind_port; } cli_runopts; extern cli_runopts cli_opts; void cli_getopts(int argc, char ** argv); #if DROPBEAR_USER_ALGO_LIST void parse_ciphers_macs(void); #endif void print_version(void); #endif /* DROPBEAR_RUNOPTS_H_ */