freebsd-src/crypto
Ed Maste 8c22023ca5 ssh: disable RSA/SHA-1 signatures
From OpenSSH 8.8p1's release notes:

---

Potentially-incompatible changes
================================

This release disables RSA signatures using the SHA-1 hash algorithm
by default. This change has been made as the SHA-1 hash algorithm is
cryptographically broken, and it is possible to create chosen-prefix
hash collisions for <USD$50K [1]

For most users, this change should be invisible and there is
no need to replace ssh-rsa keys. OpenSSH has supported RFC8332
RSA/SHA-256/512 signatures since release 7.2 and existing ssh-rsa keys
will automatically use the stronger algorithm where possible.

Incompatibility is more likely when connecting to older SSH
implementations that have not been upgraded or have not closely tracked
improvements in the SSH protocol. For these cases, it may be necessary
to selectively re-enable RSA/SHA1 to allow connection and/or user
authentication via the HostkeyAlgorithms and PubkeyAcceptedAlgorithms
options. For example, the following stanza in ~/.ssh/config will enable
RSA/SHA1 for host and user authentication for a single destination host:

    Host old-host
        HostkeyAlgorithms +ssh-rsa
	PubkeyAcceptedAlgorithms +ssh-rsa

We recommend enabling RSA/SHA1 only as a stopgap measure until legacy
implementations can be upgraded or reconfigured with another key type
(such as ECDSA or Ed25519).

[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

---

Relnotes:	Yes
Sponsored by:	The FreeBSD Foundation
2021-12-19 11:03:45 -05:00
..
heimdal kerberos.8: Replace dead link 2021-05-16 01:37:09 -04:00
openssh ssh: disable RSA/SHA-1 signatures 2021-12-19 11:03:45 -05:00
openssl OpenSSL: Merge OpenSSL 1.1.1m 2021-12-14 16:03:52 -05:00
README

$FreeBSD$

This directory is for the EXACT same use as src/contrib, except it
holds crypto sources.  In other words, this holds raw sources obtained
from various third party vendors, with FreeBSD patches applied.  No
compilation is done from this directory, it is all done from the
src/secure directory.  The separation between src/contrib and src/crypto
is the result of an old USA law, which made these sources export
controlled, so they had to be kept separate.