mirrors listed at https://www.openssh.com/.
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[1] 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.
[1] "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.
Update netpgpverify and libnetpgpverify to version 20200503
ensure all exported functions use a unique prfix, so that they don't
conflict with symbols (both data and text) in libcrypto. this works for
statically linked binaries and libraries, rather then the version map which
only works for dynalically-linked.
exported. In particular the following symbols:
DSA_SIG_free
DSA_SIG_new
DSA_do_sign
DSA_do_verify
DSA_free
DSA_new
DSA_size
RSA_check_key
RSA_free
RSA_generate_key
RSA_new
RSA_private_decrypt
RSA_private_encrypt
RSA_public_decrypt
RSA_public_encrypt
conflict with libcrypto and break pkg_add which links against both
libraries.
Firstly, include the correct headers. Then, make sure that requests
never exceed 256 bytes.
Disable a hack for old FreeBSD versions, just in case it actually gets
used.
This should mean that OpenSSL doesn't ever fall back to reading from
/dev/urandom.
XXX pullup, XXX upstream.
*) Fixed segmentation fault in SSL_check_chain()
Server or client applications that call the SSL_check_chain() function
during or after a TLS 1.3 handshake may crash due to a NULL pointer
dereference as a result of incorrect handling of the
"signature_algorithms_cert" TLS extension. The crash occurs if an invalid
or unrecognised signature algorithm is received from the peer. This could
be exploited by a malicious peer in a Denial of Service attack.
(CVE-2020-1967)
[Benjamin Kaduk]
*) Added AES consttime code for no-asm configurations
an optional constant time support for AES was added
when building openssl for no-asm.
Enable with: ./config no-asm -DOPENSSL_AES_CONST_TIME
Disable with: ./config no-asm -DOPENSSL_NO_AES_CONST_TIME
At this time this feature is by default disabled.
It will be enabled by default in 3.0.
[Bernd Edlinger]
*) Revert the change of EOF detection while reading in libssl to avoid
regressions in applications depending on the current way of reporting
the EOF. As the existing method is not fully accurate the change to
reporting the EOF via SSL_ERROR_SSL is kept on the current development
branch and will be present in the 3.0 release.
[Tomas Mraz]
*) Revised BN_generate_prime_ex to not avoid factors 3..17863 in p-1
when primes for RSA keys are computed.
Since we previously always generated primes == 2 (mod 3) for RSA keys,
the 2-prime and 3-prime RSA modules were easy to distinguish, since
N = p*q = 1 (mod 3), but N = p*q*r = 2 (mod 3). Therefore fingerprinting
2-prime vs. 3-prime RSA keys was possible by computing N mod 3.
This avoids possible fingerprinting of newly generated RSA modules.
[Bernd Edlinger]
*) Properly detect EOF while reading in libssl. Previously if we hit an EOF
while reading in libssl then we would report an error back to the
application (SSL_ERROR_SYSCALL) but errno would be 0. We now add
an error to the stack (which means we instead return SSL_ERROR_SSL) and
therefore give a hint as to what went wrong.
[Matt Caswell]
*) Check that ed25519 and ed448 are allowed by the security level. Previously
signature algorithms not using an MD were not being checked that they were
allowed by the security level.
[Kurt Roeckx]
*) Fixed SSL_get_servername() behaviour. The behaviour of SSL_get_servername()
was not quite right. The behaviour was not consistent between resumption
and normal handshakes, and also not quite consistent with historical
behaviour. The behaviour in various scenarios has been clarified and
it has been updated to make it match historical behaviour as closely as
possible.
[Matt Caswell]
*) [VMS only] The header files that the VMS compilers include automatically,
__DECC_INCLUDE_PROLOGUE.H and __DECC_INCLUDE_EPILOGUE.H, use pragmas that
the C++ compiler doesn't understand. This is a shortcoming in the
compiler, but can be worked around with __cplusplus guards.
C++ applications that use OpenSSL libraries must be compiled using the
qualifier '/NAMES=(AS_IS,SHORTENED)' to be able to use all the OpenSSL
functions. Otherwise, only functions with symbols of less than 31
characters can be used, as the linker will not be able to successfully
resolve symbols with longer names.
[Richard Levitte]
*) Corrected the documentation of the return values from the EVP_DigestSign*
set of functions. The documentation mentioned negative values for some
errors, but this was never the case, so the mention of negative values
was removed.
Code that followed the documentation and thereby check with something
like 'EVP_DigestSignInit(...) <= 0' will continue to work undisturbed.
[Richard Levitte]
*) Fixed an an overflow bug in the x64_64 Montgomery squaring procedure
used in exponentiation with 512-bit moduli. No EC algorithms are
affected. Analysis suggests that attacks against 2-prime RSA1024,
3-prime RSA1536, and DSA1024 as a result of this defect would be very
difficult to perform and are not believed likely. Attacks against DH512
are considered just feasible. However, for an attack the target would
have to re-use the DH512 private key, which is not recommended anyway.
Also applications directly using the low level API BN_mod_exp may be
affected if they use BN_FLG_CONSTTIME.
(CVE-2019-1551)
[Andy Polyakov]
*) Added a new method to gather entropy on VMS, based on SYS$GET_ENTROPY.
The presence of this system service is determined at run-time.
[Richard Levitte]
*) Added newline escaping functionality to a filename when using openssl dgst.
This output format is to replicate the output format found in the '*sum'
checksum programs. This aims to preserve backward compatibility.
[Matt Eaton, Richard Levitte, and Paul Dale]
*) Print all values for a PKCS#12 attribute with 'openssl pkcs12', not just
the first value.
[Jon Spillett]
- Add GSSAPIAuthentication and related options
- Add KerberosAuthentication and related options
- Bring in the lengthy but useful comment block about
the side-effect of UsePAM with regards to PermitRootLogin.
- Match the case of the UsePAM keyword used in the manual page and code,
to aid case-sensitive grep etc.
- Remove references to obsole UseLogin and UsePrivilegeSeparation keywords.
- Whitespace police
The first matching entry that sets an option "wins." Therefore more
specific matches should be provided before the "Host *" entry that
matches everything. This way options set in the more specific entry will
not be accidentally made ineffective by the match-all entry.
christos