openssh-9.7p1

[Bruce Dubbs]

New point version.

[thomas]

Future deprecation notice

OpenSSH plans to remove support for the DSA signature algorithm in early 2025 and compile-time disable it later this year.

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[3], 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 makes DSA support in OpenSSH compile-time optional, defaulting to on. We intend the next release to change the default to disable DSA at compile time. The first OpenSSH release of 2025 will remove DSA support entirely.

Changes since OpenSSH 9.6

This release contains mostly bugfixes.

New features

• ssh(1), sshd(8): add a "global" ChannelTimeout type that watches all open channels and will close all open channels if there is no traffic on any of them for the specified interval. This is in addition to the existing per-channel timeouts added recently.

This supports situations like having both session and x11 forwarding channels open where one may be idle for an extended period but the other is actively used. The global timeout could close both channels when both have been idle for too long.

• All: make DSA key support compile-time optional, defaulting to on.

Bugfixes

• sshd(8): don't append an unnecessary space to the end of subsystem arguments (bz3667)

• ssh(1): fix the multiplexing "channel proxy" mode, broken when keystroke timing obfuscation was added. (GHPR#463)

• ssh(1), sshd(8): fix spurious configuration parsing errors when options that accept array arguments are overridden (bz3657).

• ssh-agent(1): fix potential spin in signal handler (bz3670)

• Many fixes to manual pages and other documentation, including GHPR#462, GHPR#454, GHPR#442 and GHPR#441.

• Greatly improve interop testing against PuTTY.

Portability

• Improve the error message when the autoconf OpenSSL header check fails (bz#3668)

• Improve detection of broken toolchain -fzero-call-used-regs support (bz3645).

• Fix regress/misc/fuzz-harness fuzzers and make them compile without warnings when using clang16

[thomas]

...
test_sshbuf: ... 103 tests ok
test_sshkey: ... 104 tests ok
test_sshsig: ... 8 tests ok
test_authopt:... 146 tests ok
test_bitmap: .. 2 tests ok
test_conversion: . 1 tests ok
test_kex: ... 398 tests ok
test_hostkeys: ... 18 tests ok
test_match: ... 6 tests ok
test_misc: ... 43 tests ok
make[1]: Verzeichnis „/mnt/tmp/openssh/source/openssh-9.7p1/regress“ wird verlassen
unit tests passed
echo all tests passed
all tests passed

[thomas]

Fixed in [da5da7ae13]