Jose Quaresma via lists.openembedded.org <quaresma.jose= gmail....@lists.openembedded.org> escreveu (sexta, 5/07/2024 à(s) 11:34):
> > > Richard Purdie <richard.pur...@linuxfoundation.org> escreveu (quinta, > 4/07/2024 à(s) 21:27): > >> On Thu, 2024-07-04 at 13:46 +0100, Jose Quaresma via >> lists.openembedded.org wrote: >> > Release notes at https://www.openssh.com/txt/release-9.8 >> > >> > Security >> > ======== >> > >> > This release contains fixes for two security problems, one critical >> > and one minor. >> > >> > 1) Race condition in sshd(8) >> > >> > A critical vulnerability in sshd(8) was present in Portable OpenSSH >> > versions between 8.5p1 and 9.7p1 (inclusive) that may allow arbitrary >> > code execution with root privileges. >> > >> > Successful exploitation has been demonstrated on 32-bit Linux/glibc >> > systems with ASLR. Under lab conditions, the attack requires on >> > average 6-8 hours of continuous connections up to the maximum the >> > server will accept. Exploitation on 64-bit systems is believed to be >> > possible but has not been demonstrated at this time. It's likely that >> > these attacks will be improved upon. >> > >> > Exploitation on non-glibc systems is conceivable but has not been >> > examined. Systems that lack ASLR or users of downstream Linux >> > distributions that have modified OpenSSH to disable per-connection >> > ASLR re-randomisation (yes - this is a thing, no - we don't >> > understand why) may potentially have an easier path to exploitation. >> > OpenBSD is not vulnerable. >> > >> > We thank the Qualys Security Advisory Team for discovering, reporting >> > and demonstrating exploitability of this problem, and for providing >> > detailed feedback on additional mitigation measures. >> > >> > 2) Logic error in ssh(1) ObscureKeystrokeTiming >> > >> > In OpenSSH version 9.5 through 9.7 (inclusive), when connected to an >> > OpenSSH server version 9.5 or later, a logic error in the ssh(1) >> > ObscureKeystrokeTiming feature (on by default) rendered this feature >> > ineffective - a passive observer could still detect which network >> > packets contained real keystrokes when the countermeasure was active >> > because both fake and real keystroke packets were being sent >> > unconditionally. >> > >> > This bug was found by Philippos Giavridis and also independently by >> > Jacky Wei En Kung, Daniel Hugenroth and Alastair Beresford of the >> > University of Cambridge Computer Lab. >> > >> > Worse, the unconditional sending of both fake and real keystroke >> > packets broke another long-standing timing attack mitigation. Since >> > OpenSSH 2.9.9 sshd(8) has sent fake keystoke echo packets for >> > traffic received on TTYs in echo-off mode, such as when entering a >> > password into su(8) or sudo(8). This bug rendered these fake >> > keystroke echoes ineffective and could allow a passive observer of >> > a SSH session to once again detect when echo was off and obtain >> > fairly limited timing information about keystrokes in this situation >> > (20ms granularity by default). >> > >> > This additional implication of the bug was identified by Jacky Wei >> > En Kung, Daniel Hugenroth and Alastair Beresford and we thank them >> > for their detailed analysis. >> > >> > This bug does not affect connections when ObscureKeystrokeTiming >> > was disabled or sessions where no TTY was requested. >> > >> > Future deprecation notice >> > ========================= >> > >> > OpenSSH plans to remove support for the DSA signature algorithm in >> > early 2025. This release disables DSA by default at compile time. >> > >> > DSA, as specified in the SSHv2 protocol, is inherently weak - being >> > limited to a 160 bit private key and use of the SHA1 digest. Its >> > estimated security level is only 80 bits symmetric equivalent. >> > >> > OpenSSH has disabled DSA keys by default since 2015 but has retained >> > run-time optional support for them. DSA was the only mandatory-to- >> > implement algorithm in the SSHv2 RFCs, mostly because alternative >> > algorithms were encumbered by patents when the SSHv2 protocol was >> > specified. >> > >> > This has not been the case for decades at this point and better >> > algorithms are well supported by all actively-maintained SSH >> > implementations. We do not consider the costs of maintaining DSA >> > in OpenSSH to be justified and hope that removing it from OpenSSH >> > can accelerate its wider deprecation in supporting cryptography >> > libraries. >> > >> > This release, and its deactivation of DSA by default at compile-time, >> > marks the second step in our timeline to finally deprecate DSA. The >> > final step of removing DSA support entirely is planned for the first >> > OpenSSH release of 2025. >> > >> > DSA support may be re-enabled in OpenBSD by setting "DSAKEY=yes" >> > in Makefile.inc. To enable DSA support in portable OpenSSH, pass >> > the "--enable-dsa-keys" option to configure. >> > >> > Potentially-incompatible changes >> > -------------------------------- >> > >> > * all: as mentioned above, the DSA signature algorithm is now >> > disabled at compile time. >> > >> > * sshd(8): the server will now block client addresses that >> > repeatedly fail authentication, repeatedly connect without ever >> > completing authentication or that crash the server. See the >> > discussion of PerSourcePenalties below for more information. >> > Operators of servers that accept connections from many users, or >> > servers that accept connections from addresses behind NAT or >> > proxies may need to consider these settings. >> > >> > * sshd(8): the server has been split into a listener binary, >> > sshd(8), >> > and a per-session binary "sshd-session". This allows for a much >> > smaller listener binary, as it no longer needs to support the SSH >> > protocol. As part of this work, support for disabling privilege >> > separation (which previously required code changes to disable) and >> > disabling re-execution of sshd(8) has been removed. Further >> > separation of sshd-session into additional, minimal binaries is >> > planned for the future. >> > >> > * sshd(8): several log messages have changed. In particular, some >> > log messages will be tagged with as originating from a process >> > named "sshd-session" rather than "sshd". >> > >> > * ssh-keyscan(1): this tool previously emitted comment lines >> > containing the hostname and SSH protocol banner to standard error. >> > This release now emits them to standard output, but adds a new >> > "-q" flag to silence them altogether. >> > >> > * sshd(8): (portable OpenSSH only) sshd will no longer use argv[0] >> > as the PAM service name. A new "PAMServiceName" sshd_config(5) >> > directive allows selecting the service name at runtime. This >> > defaults to "sshd". bz2101 >> > >> > * (portable OpenSSH only) Automatically-generated files, such as >> > configure, config.h.in, etc will now be checked in to the portable >> > OpenSSH git release branch (e.g. V_9_8). This should ensure that >> > the contents of the signed release branch exactly match the >> > contents of the signed release tarball. >> > >> > Changes since OpenSSH 9.7 >> > ========================= >> > >> > This release contains mostly bugfixes. >> > >> > New features >> > ------------ >> > >> > * sshd(8): as described above, sshd(8) will now penalise client >> > addresses that, for various reasons, do not successfully complete >> > authentication. This feature is controlled by a new sshd_config(5) >> > PerSourcePenalties option and is on by default. >> > >> > sshd(8) will now identify situations where the session did not >> > authenticate as expected. These conditions include when the client >> > repeatedly attempted authentication unsucessfully (possibly >> > indicating an attack against one or more accounts, e.g. password >> > guessing), or when client behaviour caused sshd to crash (possibly >> > indicating attempts to exploit bugs in sshd). >> > >> > When such a condition is observed, sshd will record a penalty of >> > some duration (e.g. 30 seconds) against the client's address. If >> > this time is above a minimum configurable threshold, then all >> > connections from the client address will be refused (along with >> > any >> > others in the same PerSourceNetBlockSize CIDR range) until the >> > penalty expire. >> > >> > Repeated offenses by the same client address will accrue greater >> > penalties, up to a configurable maximum. Address ranges may be >> > fully exempted from penalties, e.g. to guarantee access from a set >> > of trusted management addresses, using the new sshd_config(5) >> > PerSourcePenaltyExemptList option. >> > >> > We hope these options will make it significantly more difficult >> > for >> > attackers to find accounts with weak/guessable passwords or >> > exploit >> > bugs in sshd(8) itself. This option is enabled by default. >> > >> > * ssh(8): allow the HostkeyAlgorithms directive to disable the >> > implicit fallback from certificate host key to plain host keys. >> > >> > Bugfixes >> > -------- >> > >> > * misc: fix a number of inaccuracies in the PROTOCOL.* >> > documentation files. GHPR430 GHPR487 >> > >> > * all: switch to strtonum(3) for more robust integer parsing in most >> > places. >> > >> > * ssh(1), sshd(8): correctly restore sigprocmask around ppoll() >> > >> > * ssh-keysign(8): stricter validation of messaging socket fd GHPR492 >> > >> > * sftp(1): flush stdout after writing "sftp>" prompt when not using >> > editline. GHPR480 >> > >> > * sftp-server(8): fix home-directory extension implementation, it >> > previously always returned the current user's home directory >> > contrary to the spec. GHPR477 >> > >> > * ssh-keyscan(1): do not close stdin to prevent error messages when >> > stdin is read multiple times. E.g. >> > echo localhost | ssh-keyscan -f - -f - >> > >> > * regression tests: fix rekey test that was testing the same KEX >> > algorithm repeatedly instead of testing all of them. bz3692 >> > >> > * ssh_config(5), sshd_config(5): clarify the KEXAlgorithms directive >> > documentation, especially around what is supported vs available. >> > bz3701. >> > >> > Portability >> > ----------- >> > >> > * sshd(8): expose SSH_AUTH_INFO_0 always to PAM auth modules >> > unconditionally. The previous behaviour was to expose it only when >> > particular authentication methods were in use. >> > >> > * build: fix OpenSSL ED25519 support detection. An incorrect >> > function >> > signature in configure.ac previously prevented enabling the >> > recently >> > added support for ED25519 private keys in PEM PKCS8 format. >> > >> > * ssh(1), ssh-agent(8): allow the presence of the WAYLAND_DISPLAY >> > environment variable to enable SSH_ASKPASS, similarly to the X11 >> > DISPLAY environment variable. GHPR479 >> > >> > * build: improve detection of the -fzero-call-used-regs compiler >> > flag. bz3673. >> > >> > * build: relax OpenSSL version check to accept all OpenSSL 3.x >> > versions. >> > >> > * sshd(8): add support for notifying systemd on server listen and >> > reload, using a standalone implementation that doesn't depend on >> > libsystemd. bz2641 >> > >> > Signed-off-by: Jose Quaresma <jose.quare...@foundries.io> >> > --- >> > >> > v2: >> > - fix musl build >> > - fix sshd-session packing on openssh-sshd >> > - rebase on top of the CVE-2024-6387 fix sent >> >> Thanks for the fixes. Unfortunately I think there is still one issue >> remaining as the openssh ptests appear to be hanging on both arm and >> x86: >> >> https://autobuilder.yoctoproject.org/typhoon/#/builders/82/builds/6600 >> https://autobuilder.yoctoproject.org/typhoon/#/builders/81/builds/6778 >> >> On a previous build run I ended up stopping them after 24h+ but I >> wasn't sure if that was related to other issues with the update or not. >> It now looks like it is a separate issue :( >> > > I will take a look on this ptests failings. > Thanks for reporting. > I will only be able to return to this next week. I took a quick look at the ptest but I still didn't understand what was wrong. If anyone wants to continue this feel free. Jose > > Jose > > >> >> Cheers, >> >> Richard >> > > > -- > Best regards, > > José Quaresma > > > > -- Best regards, José Quaresma
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