Dropbear 2024.85

Download tarballs from
https://matt.ucc.asn.au/dropbear/releases/dropbear-2024.85.tar.bz2 or
https://dropbear.nl/mirror/releases/dropbear-2024.85.tar.bz2
The tarball is reproducible from git with release.sh

This release fixes build regressions in 2024.84

• Fix build failure when SHA1 is disabled, thanks to Peter Krefting

• Fix build failure when DROPBEAR_CLI_PUBKEY_AUTH disabled, thanks to
  Sergey Ponomarev

• Update debian/ directory with changed paths

Dropbear 2024.84

Download tarballs from https://matt.ucc.asn.au/dropbear/releases/dropbear-2024.84.tar.bz2 or
https://mirror.dropbear.nl/mirror/releases/dropbear-2024.84.tar.bz2
The tarball is reproducible from git with release.sh

Features and Changes:

Note >> for compatibility/configuration changes

• >> Only use /etc/shadow when a user has x as the crypt in /etc/passwd.
  This is the documented behaviour of passwd(5) so should be consistent with
  other programs. Thanks to Paulo Cabral for the report.
  Note that any users without x as the crypt will not be able
  to log in with /etc/shadow, in cases were the existing configuration
  differs.

• Support -o StrictHostKeyChecking, patch from Sergey Ponomarev

• Support -o BatchMode, from Sergey Ponomarev and Hans Harder

• Support various other -o options compatible with OpenSSH, from
  Sergey Ponomarev. Includes -o PasswordAuthentication

• Add dbclient config file support, ~/.ssh/dropbear_config
  Thanks to tjkolev
  Disabled by default, set #define DROPBEAR_USE_SSH_CONFIG 1

• Add support for unix socket forwarding (destination) on
  the server, thanks to WangYi for the implementation

• Add option to bind to interface, from Diederik De Coninck

• Ignore unsupported arguments in dropbearkey, allow running
  binary as 'ssh-key'. From Sergey Ponomarev

• Save a public key file on generation with dropbearkey.
  -C can be used for a comment, and choose a default key
  type (ed25519 first preference).
  Thanks to Sergey Ponomarev

• Allow inetd to run in non-syslog modes. Thanks to Laurent Bercot
  for the report

• Allow user's own gid in PTY permissions, lets Dropbear work as non-root
  even if /dev/pts isn't mounted with gid=5

• src/distrooptions.h can now be used as another config file.
  This can be used by distributions for customisations (separate
  to the build directory's localoptions.h)

Fixes:

• dbclient host >> output would previously overwrite "output", instead of
  appending. Thanks for the report from eSotoIoT

• Add "Strict KEX" support. This mitigates a SSH protocol flaw which lets
  a MITM attacker silently remove packets immediately after the
  first key exchange. At present the flaw does not seem to reduce Dropbear's
  security (the only packet affected would be a server-sig-algs extension,
  which is used for compatibility not security).
  For Dropbear, chacha20-poly1305 is the only affected cipher.
  Both sides of the connection must support Strict KEX for it to be used.

  The protocol flaw is tracked as CVE-2023-48795, details
  at https://terrapin-attack.com . Thanks to the researchers Fabian Bäumer,
  Marcus Brinkmann, and Jörg Schwenk. Thanks to OpenSSH for specifying
  strict KEX mode.

• Fix blocking while closing forwarded TCP sessions. Noticable
  when many connections are being forwarded. Reported and
  tested by GektorUA. Github #230

• Don't offer RSA (then fail) if there is no RSA key. Regression in 2020.79
  Github #219

• Fix missing response to remote TCP requests when it is disabled.
  Patch from Justin Chen. Github #254

• Fix building with DROPBEAR_RSA disabled

• /proc/timer_list is no longer used for entropy, it was a bottleneck.
  Thanks to Aleksei Plotnikov for the report.

• Don't unconditionally enable DROPBEAR_DSS

• Make banner reading failure non-fatal

• Fix DROPBEAR_SVR_MULTIUSER. This appears to have been broken since when it
  was added in 2019. If you're using this let me know (it might be removed
  if I don't hear otherwise). Thanks to davidatrsp

• Fix Y2038 issues

Infrastructure:

• Move source files to src/ subdirectory. Thanks to tjkolev

• Remove more files with "make distclean"

• Add tests for disabled options

Dropbear 2022.83

Download tarballs from
https://matt.ucc.asn.au/dropbear/releases/dropbear-2022.83.tar.bz2 or
https://mirror.dropbear.nl/mirror/dropbear-2022.83.tar.bz2

Features and Changes:

Note >> for compatibility/configuration changes

• >> Disable DROPBEAR_DSS by default
  It is only 1024 bit and uses sha1, most distros disable it by default already.

• Added DROPBEAR_RSA_SHA1 option to allow disabling sha1 rsa signatures.
  >> RSA with sha1 will be disabled in a future release (rsa keys will continue
  to work OK, with sha256 signatures used instead).

• Add option for requiring both password and pubkey (-t)
  Patch from Jackkal

• Add 'no-touch-required' and 'verify-required' options for sk keys
  Patch from Egor Duda

• >> DROPBEAR_SK_KEYS config option now replaces separate DROPBEAR_SK_ECDSA
  and DROPBEAR_SK_ED25519 options.

• Add 'permitopen' option for authorized_keys to restrict forwarded ports
  Patch from Tuomas Haikarainen

• >> Added LTM_CFLAGS configure argument to set flags for building
  bundled libtommath. This also restores the previous arguments used
  in 2020.81 (-O3 -funroll-loops). That gives a big speedup for RSA
  key generation, which regressed in 2022.82.
  There is a tradeoff with code size, so -Os can be used if required.
  #174
  Reported by David Bernard

• Add '-z' flag to disable setting QoS traffic class. This may be necessary
  to work with broken networks or network drivers, exposed after changes to use
  AF21 in 2022.82
  #193
  Reported by yuhongwei380, patch from Petr Štetiar

• Allow overriding user shells with COMPAT_USER_SHELLS
  Based on a patch from Matt Robinson

• Improve permission error message
  Patch from k-kurematsu

• >> Remove HMAC_MD5 entirely

Regression fixes from 2022.82:

• Fix X11 build

• Fix build warning

• Fix compilation when disabling pubkey authentication
  Patch from MaxMougg

• Fix MAX_UNAUTH_CLIENTS regression
  Reported by ptpt52

• Avoid using slower prime testing in bundled libtomcrypt when DSS is disabled
  #174
  Suggested by Steffen Jaeckel

• Fix Dropbear plugin support
  #194
  Reported by Struan Bartlett

Other fixes:

• Fix long standing incorrect compression size check. Dropbear
  (client or server) would erroneously exit with
  "bad packet, oversized decompressed"
  when receiving a compressed packet of exactly the maximum size.

• Fix missing setsid() removed in 2020.79
  #180
  Reported and debugged by m5jt and David Bernard

• Try keyboard-interactive auth before password, in dbclient.
  This was unintentionally changed back in 2013
  #190
  Patch from Michele Giacomoli

• Drain the terminal when reading the fingerprint confirmation response
  #191
  Patch from Michele Giacomoli

• Fix utx wtmp variable typo. This has been wrong for a long time but
  only recently became a problem when wtmp was detected.
  #189
  Patch from Michele Giacomoli

• Improve configure test for hardening options.
  Fixes building on AIX
  #158

• Fix debian/dropbear.init newline
  From wulei-student

Infrastructure:

• Test off-by-default compile options

• Set -Wundef to catch typos in #if statements

Dropbear 2022.82

Download tarballs from
https://matt.ucc.asn.au/dropbear/releases/dropbear-2022.82.tar.bz2 or
https://mirror.dropbear.nl/mirror/dropbear-2022.82.tar.bz2

Features and Changes:

• Implemented OpenSSH format private key handling for dropbearconvert.
  Keys can be read in OpenSSH format or the old PEM format.
  Keys are now written in OpenSSH format rather than PEM.
  ED25519 support is now correct. DSS keys are still PEM format.

• Use SHA256 for key fingerprints

• Reworked -v verbose printing, specifying multiple times will increase
  verbosity. -vvvv is equivalent to the old DEBUG_TRACE -v level, it
  can be configured at compile time in localoptions.h (see default_options.h)
  Lower -v options can be used to check connection progress or algorithm
  negotiation.
  Thanks to Hans Harder for the implementation

  localoptions.h DEBUG_TRACE should be set to 4 for the same result as the
  previous DEBUG_TRACE 1.

• Added server support for U2F/FIDO keys (ecdsa-sk and ed25519-sk) in
  authorized_keys. no-touch-required option isn't allowed yet.
  Thanks to Egor Duda for the implementation

• autoconf output (configure script etc) is now committed to version control.
  It isn't necessary to run "autoconf" any more on a checkout.

• sha1 will be omitted from the build if KEX/signing/MAC algorithms don't
  require it. Instead sha256 is used for random number generation.
  See sysoptions.h to see which algorithms require which hashes.

• Set SSH_PUBKEYINFO environment variable based on the authorized_keys
  entry used for auth. The first word of the comment after the key is used
  (must only have characters a-z A-Z 0-9 .,_-+@)
  Patch from Hans Harder, modified by Matt Johnston

• Let dbclient multihop mode be used with '-J'.
  Patch from Hans Harder

• Allow home-directory relative paths ~/path for various settings
  and command line options.
  *_PRIV_FILENAME DROPBEAR_PIDFILE SFTPSERVER_PATH MOTD_FILENAME
  Thanks to Begley Brothers Inc

  The default DROPBEAR_DEFAULT_CLI_AUTHKEY has now changed, it now needs
  a tilde prefix.

• LANG environment variable is carried over from the Dropbear server process
  From Maxim Kochetkov

• Add /usr/sbin and /sbin to $PATH when logging in as root.
  Patch from Raphaël Hertzog
  https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=903403

• Added client option "-o DisableTrivialAuth". This can be used to prevent
  the server immediately accepting successful authentication (before any auth
  request) which could cause UI confusion and security issues with agent
  forwarding - it isn't clear which host is prompting to use a key.
  CVE-2021-36369 though the description there is a bit confused. It only applies
  to Dropbear as a client.
  Thanks to Manfred Kaiser from Austrian MilCERT

• Add -q client option to hide remote banner, from Hans Harder

• Add -e option to pass all server environment variables to child processes.
  This should be used with caution.
  Patch from Roland Vollgraf (github #118)

• Use DSCP for QoS traffic classes. Priority (tty) traffic is now set to
  AF21 "interactive". Previously TOS classes were used, they are not used by
  modern traffic classifiers. Non-tty traffic is left at default priority.

• Disable dh-group1 key exchange by default. It has been disabled server
  side by default since 2018.

• Removed Twofish cipher

Fixes:

• Fix flushing channel data when pty was allocated (github #85)
  Data wasn't completely transmitted at channel close.
  Reported and initial patch thanks to Yousong Zhou

• Dropbear now re-executes itself rather than just forking for each connection
  (only on Linux). This allows ASLR to randomise address space for each
  connection as a security mitigation. It should not have any visible impact

  • if there are any performance impacts in the wild please report it.

• Check authorized_keys permissions as the user, fixes NFS squash root.
  Patch from Chris Dragan (github #107)

• A missing home directory is now non-fatal, starting in / instead

• Fixed IPv6 [address]:port parsing for dbclient -b
  Reported by Fabio Molinari

• Improve error logging so that they are logged on the server rather than being
  sent to the client over the connection

• Max window size is increased to 10MB, more graceful fallback if it's invalid.

• Fix correctness of Dropbear's handling of global requests.
  Patch from Dirkjan Bussink

• Fix some small bugs found by fuzzers, null pointer dereference crash and leaks
  (post authentication)

• $HOME variable is used before /etc/passwd when expanding paths such as
  ~/.ssh/id_dropbear (for the client). Patch from Matt Robinson

• C89 build fixes from Guillaume Picquet

Infrastructure:

• Improvements to fuzzers. Added post-auth fuzzer, and a mutator that can
  handle the structure of SSH packet streams. Added cifuzz to run on commits
  and pull requests.
  Thanks to OSS-Fuzz for the tools/clusters and reward funding.

• Dropbear source tarballs generated by release.sh are now reproducible from a
  Git or Mercurial checkout, they will be identical on any system. Tested
  on ubuntu and macos.

• Added some integration testing using pytest. Currently this has tests
  for various channel handling edge cases, ASLR fork randomisation,
  dropbearconvert, and SSH_PUBKEYINFO

• Set up github actions. This runs the pytest suite and other checks.

  • build matrix includes c89, dropbearmulti, bundled libtom, macos, DEBUG_TRACE
  • test for configure script regeneration
  • build a tarball for external reproducibility

Dropbear 2020.81

• Fix regression in 2020.79 which prevented connecting with some SSH
  implementations. Increase MAX_PROPOSED_ALGO to 50, and print a log
  message if the limit is hit. This fixes interoperability with sshj
  library (used by PyCharm), and GoAnywhere.
  Reported by Pirmin Walthert and Piotr Jurkiewicz

• Fix building with non-GCC compilers, reported by Kazuo Kuroi

• Fix potential long delay in dbclient, found by OSS Fuzz

• Fix null pointer dereference crash, found by OSS Fuzz

• libtommath now uses the same random source as Dropbear (in 2020.79
  and 2020.80 used getrandom() separately)

• Some fuzzing improvements, start of a dbclient fuzzer

Dropbear 2020.80

• Don't block authorized_keys logins with no-X11-forwarding or no-agent-forwarding
  restrictions when X11 or agent forwarding are disabled at compile time.
  This is more of a problem now X11 is disabled by default, reported by Guilhem Moulin

• Reduce binary size by 4kB (x64) when using bundled libtommath

• Define GNU_SOURCE for getrandom() on uclibc, reported by Laurent Bercot and
  Fabrice Fontaine

• Improve checking libtomcrypt version compatibility

• Add some style notes to DEVELOPING.md

Dropbear 2020.79

• Support ed25519 hostkeys and authorized_keys, many thanks to Vladislav Grishenko.
  This also replaces curve25519 with a TweetNaCl implementation that reduces code size.

• Add chacha20-poly1305 authenticated cipher. This will perform faster than AES
  on many platforms. Thanks to Vladislav Grishenko

• Support using rsa-sha2 signatures. No changes are needed to hostkeys/authorized_keys
  entries, existing RSA keys can be used with the new signature format (signatures
  are ephemeral within a session). Old ssh-rsa signatures will no longer
  be supported by OpenSSH in future so upgrading is recommended.

• Use getrandom() call on Linux to ensure sufficient entropy has been gathered at startup.
  Dropbear now avoids reading from the random source at startup, instead waiting until
  the first connection. It is possible that some platforms were running without enough
  entropy previously, those could potentially block at first boot generating host keys.
  The dropbear "-R" option is one way to avoid that.

• Upgrade libtomcrypt to 1.18.2 and libtommath to 1.2.0, many thanks to Steffen Jaeckel for
  updating Dropbear to use the current API. Dropbear's configure script will check
  for sufficient system library versions, otherwise using the bundled versions.

• CBC ciphers, 3DES, hmac-sha1-96, and x11 forwarding are now disabled by default.
  They can be set in localoptions.h if required.
  Blowfish has been removed.

• Support AES GCM, patch from Vladislav Grishenko. This is disabled by default,
  Dropbear doesn't currently use hardware accelerated AES.

• Added an API for specifying user public keys as an authorized_keys replacement.
  See pubkeyapi.h for details, thanks to Fabrizio Bertocci

• Fix idle detection clashing with keepalives, thanks to jcmathews

• Include IP addresses in more early exit messages making it easier for fail2ban
  processing. Patch from Kevin Darbyshire-Bryant

• scp fix for CVE-2018-20685 where a server could modify name of output files

• SSH_ORIGINAL_COMMAND is set for "dropbear -c" forced command too

• Fix writing key files on systems without hard links, from Matt Robinson

• Compatibility fixes for IRIX from Kazuo Kuroi

• Re-enable printing MOTD by default, was lost moving from options.h. Thanks to zciendor

• Call fsync() is called on parent directory when writing key files to ensure they are flushed

• Fix "make install" for manpages in out-of-tree builds, from Gabor Z. Papp

• Some notes are added in DEVELOPER.md