|Reported by:||Douglas R. Reno||Owned by:||thomas|
New minor version
OpenSSH 8.3 has just been released. It will be available from the mirrors listed at https://www.openssh.com/ shortly. OpenSSH is a 100% complete SSH protocol 2.0 implementation and includes sftp client and server support. Once again, we would like to thank the OpenSSH community for their continued support of the project, especially those who contributed code or patches, reported bugs, tested snapshots or donated to the project. More information on donations may be found at: https://www.openssh.com/donations.html Future deprecation notice ========================= It is now possible to perform chosen-prefix attacks against the SHA-1 algorithm for less than USD$50K. For this reason, we will be disabling the "ssh-rsa" public key signature algorithm by default in a near-future release. This algorithm is unfortunately still used widely despite the existence of better alternatives, being the only remaining public key signature algorithm specified by the original SSH RFCs. The better alternatives include: * The RFC8332 RSA SHA-2 signature algorithms rsa-sha2-256/512. These algorithms have the advantage of using the same key type as "ssh-rsa" but use the safe SHA-2 hash algorithms. These have been supported since OpenSSH 7.2 and are already used by default if the client and server support them. * The ssh-ed25519 signature algorithm. It has been supported in OpenSSH since release 6.5. * The RFC5656 ECDSA algorithms: ecdsa-sha2-nistp256/384/521. These have been supported by OpenSSH since release 5.7. To check whether a server is using the weak ssh-rsa public key algorithm, for host authentication, try to connect to it after removing the ssh-rsa algorithm from ssh(1)'s allowed list: ssh -oHostKeyAlgorithms=-ssh-rsa user@host If the host key verification fails and no other supported host key types are available, the server software on that host should be upgraded. A future release of OpenSSH will enable UpdateHostKeys by default to allow the client to automatically migrate to better algorithms. Users may consider enabling this option manually. Vendors of devices that implement the SSH protocol should ensure that they support the new signature algorithms for RSA keys.  "SHA-1 is a Shambles: First Chosen-Prefix Collision on SHA-1 and Application to the PGP Web of Trust" Leurent, G and Peyrin, T (2020) https://eprint.iacr.org/2020/014.pdf Security ======== * scp(1): when receiving files, scp(1) could be become desynchronised if a utimes(2) system call failed. This could allow file contents to be interpreted as file metadata and thereby permit an adversary to craft a file system that, when copied with scp(1) in a configuration that caused utimes(2) to fail (e.g. under a SELinux policy or syscall sandbox), transferred different file names and contents to the actual file system layout. Exploitation of this is not likely as utimes(2) does not fail under normal circumstances. Successful exploitation is not silent - the output of scp(1) would show transfer errors followed by the actual file(s) that were received. Finally, filenames returned from the peer are (since openssh-8.0) matched against the user's requested destination, thereby disallowing a successful exploit from writing files outside the user's selected target glob (or directory, in the case of a recursive transfer). This ensures that this attack can achieve no more than a hostile peer is already able to achieve within the scp protocol. Potentially-incompatible changes ================================ This release includes a number of changes that may affect existing configurations: * sftp(1): reject an argument of "-1" in the same way as ssh(1) and scp(1) do instead of accepting and silently ignoring it. Changes since OpenSSH 8.2 ========================= The focus of this release is bug fixing. New Features ------------ * sshd(8): make IgnoreRhosts a tri-state option: "yes" to ignore rhosts/shosts, "no" allow rhosts/shosts or (new) "shosts-only" to allow .shosts files but not .rhosts. * sshd(8): allow the IgnoreRhosts directive to appear anywhere in a sshd_config, not just before any Match blocks; bz3148 * ssh(1): add %TOKEN percent expansion for the LocalFoward and RemoteForward keywords when used for Unix domain socket forwarding. bz#3014 * all: allow loading public keys from the unencrypted envelope of a private key file if no corresponding public key file is present. * ssh(1), sshd(8): prefer to use chacha20 from libcrypto where possible instead of the (slower) portable C implementation included in OpenSSH. * ssh-keygen(1): add ability to dump the contents of a binary key revocation list via "ssh-keygen -lQf /path" bz#3132 Bugfixes -------- * ssh(1): fix IdentitiesOnly=yes to also apply to keys loaded from a PKCS11Provider; bz#3141 * ssh-keygen(1): avoid NULL dereference when trying to convert an invalid RFC4716 private key. * scp(1): when performing remote-to-remote copies using "scp -3", start the second ssh(1) channel with BatchMode=yes enabled to avoid confusing and non-deterministic ordering of prompts. * ssh(1), ssh-keygen(1): when signing a challenge using a FIDO token, perform hashing of the message to be signed in the middleware layer rather than in OpenSSH code. This permits the use of security key middlewares that perform the hashing implicitly, such as Windows Hello. * ssh(1): fix incorrect error message for "too many known hosts files." bz#3149 * ssh(1): make failures when establishing "Tunnel" forwarding terminate the connection when ExitOnForwardFailure is enabled; bz#3116 * ssh-keygen(1): fix printing of fingerprints on private keys and add a regression test for same. * sshd(8): document order of checking AuthorizedKeysFile (first) and AuthorizedKeysCommand (subsequently, if the file doesn't match); bz#3134 * sshd(8): document that /etc/hosts.equiv and /etc/shosts.equiv are not considered for HostbasedAuthentication when the target user is root; bz#3148 * ssh(1), ssh-keygen(1): fix NULL dereference in private certificate key parsing (oss-fuzz #20074). * ssh(1), sshd(8): more consistency between sets of %TOKENS are accepted in various configuration options. * ssh(1), ssh-keygen(1): improve error messages for some common PKCS#11 C_Login failure cases; bz#3130 * ssh(1), sshd(8): make error messages for problems during SSH banner exchange consistent with other SSH transport-layer error messages and ensure they include the relevant IP addresses bz#3129 * various: fix a number of spelling errors in comments and debug/error messages * ssh-keygen(1), ssh-add(1): when downloading FIDO2 resident keys from a token, don't prompt for a PIN until the token has told us that it needs one. Avoids double-prompting on devices that implement on-device authentication. * sshd(8), ssh-keygen(1): no-touch-required FIDO certificate option should be an extension, not a critical option. * ssh(1), ssh-keygen(1), ssh-add(1): offer a better error message when trying to use a FIDO key function and SecurityKeyProvider is empty. * ssh-add(1), ssh-agent(8): ensure that a key lifetime fits within the values allowed by the wire format (u32). Prevents integer wraparound of the timeout values. bz#3119 * ssh(1): detect and prevent trivial configuration loops when using ProxyJump. bz#3057. Portability ----------- * Detect systems where signals flagged with SA_RESTART will interrupt select(2). POSIX permits implementations to choose whether select(2) will return when interrupted with a SA_RESTART-flagged signal, but OpenSSH requires interrupting behaviour. * Several compilation fixes for HP/UX and AIX. * On platforms that do not support setting process-wide routing domains (all excepting OpenBSD at present), fail to accept a configuration attempts to set one at process start time rather than fatally erroring at run time. bz#3126 * Improve detection of egrep (used in regression tests) on platforms that offer a poor default one (e.g. Solaris). * A number of shell portability fixes for the regression tests. * Fix theoretical infinite loop in the glob(3) replacement implementation. * Fix seccomp sandbox compilation problems for some Linux configurations bz#3085 * Improved detection of libfido2 and some compilation fixes for some configurations when --with-security-key-builtin is selected. Checksums: ========== - SHA1 (openssh-8.3.tar.gz) = 46c63b7ddbe46a0666222f7988c993866c31fcca - SHA256 (openssh-8.3.tar.gz) = M6CnZ+duGs4bzDio8hQNLwyLQChV+3wkUEO8HWLV35c= - SHA1 (/openssh-8.3p1.tar.gz) = 04c7adb9986f16746588db8988b910530c589819 - SHA256 (openssh-8.3p1.tar.gz) = 8r774Ecv5+t10jNA6xdTHLazqsJAdeIGa0H4FOEjh7I= Please note that the SHA256 signatures are base64 encoded and not hexadecimal (which is the default for most checksum tools). The PGP key used to sign the releases is available as RELEASE_KEY.asc from the mirror sites. Reporting Bugs: =============== - Please read https://www.openssh.com/report.html Security bugs should be reported directly to firstname.lastname@example.org
Note that SSH-RSA keys are now deprecated.
Change History (4)
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