Mercurial > dropbear
view filelist.txt @ 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 | d32bcb5c557d |
| children |
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This file is out of date - it remains here in case it is still of use. The basic naming convention is svr- and cli- for seperate parts, then common- for common parts. Some files have no prefix. A brief rundown on which files do what, and their corresponding sections in the IETF drafts. The .c files usually have corresponding .h files. Transport layer draft-ietf-secsh-transport-16.txt =============== session.c Contains the main select() loop, and handles setting up/closing down ssh connections algo.c Framework for handling various ciphers/hashes/algos, and choosing between the lists of client/server preferred ones kex.c Key exchange routines, used at startup to negotiate which algorithms to use, and also to obtain session keys. This also runs when rekeying during the connection. packet.c Handles the basic packet encryption/decryption, and switching to the appropriate packet handlers. Called from session.c's main select loop. service.c Handles service requests (userauth or connection) Authentication draft-ietf-secsh-userauth-17.txt ============== auth.c General auth handling, including user checking etc, passes different auth types to auth{passwd,pubkey} authpasswd.c Handles /etc/passwd or /etc/shadow auth authpubkey.c Handles ~/.ssh/authorized_keys auth Connection draft-ietf-secsh-connect-17.txt ========== channel.c Channel handling routines - each shell/tcp conn/agent etc is a channel. chansession.c Handles shell/exec requests sshpty.c From OpenSSH, allocates PTYs etc termcodes.c Mapping of POSIX terminal codes to SSH terminal codes loginrec.c From OpenSSH, handles utmp/wtmp logging x11fwd.c Handles X11 forwarding agentfwd.c Handles auth-agent forwarding requests localtcpfwd.c Handles -L style tcp forwarding requests, setting up the listening port and also handling connections to that port (and subsequent channels) Program-related =============== dbmulti.c Combination binary chooser main() function dbutil.c Various utility functions, incl logging, memory etc dropbearconvert.c Conversion from dropbear<->openssh keys, uses keyimport.c to do most of the work dropbearkey.c Generates keys, calling gen{dss,rsa} keyimport.c Modified from PuTTY, converts between key types main.c dropbear's main(), handles listening, forking for new connections, child-process limits runopts.c Parses commandline options options.h Compile-time feature selection config.h Features selected from configure debug.h Compile-time selection of debug features includes.h Included system headers etc Generic Routines ================ signkey.c A generic handler for pubkeys, switches to dss or rsa depending on the key type rsa.c RSA asymmetric crypto routines dss.c DSS asymmetric crypto routines ed25519.c Ed25519 asymmetric crypto routines gened25519.c Ed25519 key generation gendss.c DSS key generation genrsa.c RSA key generation bignum.c Some bignum helper functions queue.c A queue, used to enqueue encrypted packets to send random.c PRNG, based on /dev/urandom or prngd atomicio.c From OpenSSH, does `blocking' IO on non-blocking fds buffer.c Buffer-usage routines, with size checking etc vim:set ts=8: