Expose an API 'ssh_server_init_kex' which allows one to change the set of
key exchange, hostkey, ciphers, MACs, and compression algorithms currently
configured for the ssh_session at hand, after having started the
'ssh_handle_key_exchange' process.
One can use this API from the already-existing 'connect_status_function'
callback to dynamically modify the set of algorithms used after having
received the client banner, but before sending out the initial KEXINIT
message.
For example, one might want to prevent advertising the curve25519 key
exchange algorithm for older OpenSSH clients due to interop bugs.
Fixes T25
Signed-off-by: Jon Simons <jon@jonsimons.org>
Reviewed-by: Andreas Schneider <asn@cryptomilk.org>
Summary:
Based on Dirkjan's original patch series here:
* https://www.libssh.org/archive/libssh/2015-08/0000029.html
Here the changes are adapted for the current master
branch, and expanded to include libgcrypt support.
Co-Authored-By: Dirkjan Bussink <d.bussink@gmail.com>
Signed-off-by: Jon Simons <jon@jonsimons.org>
Reviewed-by: Andreas Schneider <asn@cryptomilk.org>
Test Plan:
* Ran pkd tests for libcrypto and libgcrypt builds.
* Ran client torture_algorithms.c tests for libcrypto and libgcrypt builds.
* Tested across multiple libgcrypts ("1.6.3" and "1.7.6-beta").
Reviewers: aris, asn
Tags: #libssh
Differential Revision: https://bugs.libssh.org/D7
Having "ssh_" prefix in the functions' name will avoid possible clashes
when compiling libssh statically.
Signed-off-by: Fabiano Fidêncio <fidencio@redhat.com>
Reviewed-by: Andreas Schneider <asn@cryptomilk.org>
Having "ssh_" prefix in the functions' name will avoid possible clashes
when compiling libssh statically.
Signed-off-by: Fabiano Fidêncio <fidencio@redhat.com>
Reviewed-by: Andreas Schneider <asn@cryptomilk.org>
Having "ssh_" prefix in the functions' name will avoid possible clashes
when compiling libssh statically.
Signed-off-by: Fabiano Fidêncio <fidencio@redhat.com>
Reviewed-by: Andreas Schneider <asn@cryptomilk.org>
Return SSH_OK for the case that an incoming SSH_MSG_KEXDH_INIT should be
ignored. That is, for the case that the initial 'first_kex_packet_follows'
guess is incorrect. Before this change sessions served with libssh can be
observed to error out unexpectedly early when testing with dropbear clients
that send an incompatible guess.
Signed-off-by: Jon Simons <jon@jonsimons.org>
Reviewed-by: Andreas Schneider <asn@cryptomilk.org>
The state validation in the packet handlers for SSH_MSG_NEWKEYS and
SSH_MSG_KEXDH_REPLY had a bug which did not raise an error.
The issue has been found and reported by Mariusz Ziule.
Signed-off-by: Aris Adamantiadis <aris@0xbadc0de.be>
Reviewed-by: Andreas Schneider <asn@cryptomilk.org>
Fix a missing 'buffer_pack' formatter in 'ssh_message_auth_interactive_request'.
With this fix the 'examples/samplesshd-kbdint' program is working again for me.
Signed-off-by: Jon Simons <jon@jonsimons.org>
Reviewed-by: Andreas Schneider <asn@cryptomilk.org>
Ensure to honor the 'first_kex_packet_follow' field when processing
KEXINIT messages in the 'ssh_packet_kexinit' callback. Until now
libssh would assume that this field is always unset (zero). But
some clients may set this (dropbear at or beyond version 2013.57),
and it needs to be included when computing the session ID.
Also include logic for handling wrongly-guessed key exchange algorithms.
Save whether a client's guess is wrong in a new field in the session
struct: when set, the next KEX_DHINIT message to be processed will be
ignored per RFC 4253, 7.1.
While here, update both 'ssh_packet_kexinit' and 'make_sessionid' to
use softabs with a 4 space indent level throughout, and also convert
various error-checking to store intermediate values into an explicit
'rc'.
Patch adjusted from original to ensure that client tests remain passing
(ie 'torture_connect'): restrict the changes in 'ssh_packet_kexinit'
only for the 'server_kex' case.
Signed-off-by: Jon Simons <jon@jonsimons.org>
Reviewed-by: Andreas Schneider <asn@cryptomilk.org>
Ensure to honor the 'first_kex_packet_follow' field when processing
KEXINIT messages in the 'ssh_packet_kexinit' callback. Until now
libssh would assume that this field is always unset (zero). But
some clients may set this (dropbear at or beyond version 2013.57),
and it needs to be included when computing the session ID.
Also include logic for handling wrongly-guessed key exchange algorithms.
Save whether a client's guess is wrong in a new field in the session
struct: when set, the next KEX_DHINIT message to be processed will be
ignored per RFC 4253, 7.1.
While here, update both 'ssh_packet_kexinit' and 'make_sessionid' to
use softabs with a 4 space indent level throughout, and also convert
various error-checking to store intermediate values into an explicit
'rc'.
Signed-off-by: Jon Simons <jon@jonsimons.org>
Reviewed-by: Andreas Schneider <asn@cryptomilk.org>
The commit fixes this build warning:
====
src/server.c:223:8: warning: ‘privkey’ may be used uninitialized in this function [-Wmaybe-uninitialized]
rc = ssh_pki_export_privkey_to_pubkey(*privkey, &pubkey);
^
src/server.c:243:11: note: ‘privkey’ was declared here
ssh_key privkey;
====
Signed-off-by: Luka Perkov <luka.perkov@sartura.hr>
Reviewed-by: Andreas Schneider <asn@cryptomilk.org>
During the transition to strncat in ssh_message_auth_reply_default,
an invalid strlen comparison was added which causes the function
to fail whenever it's called.
Signed-off-by: Andrew Collins <bsderandrew@gmail.com>
Reviewed-by: Andreas Schneider <asn@cryptomilk.org>
