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  1. RHEL
  2. RHEL-83277

HMAC-SHA1 reasonable but insecure

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    • CentOS Stream 10
    • crypto-policies
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    • rhel-security-crypto
    • ssg_security
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      According to Red Hat Insights, an important security incident with critical likelihood is raised when a machine uses the DEFAULT crypto policy ("SSH security is decreased when insecure cipher or hmac is enabled in the crypto policy")

      According to the DEFAULT crypto policy, up to RHEL10 /cs10, "# SHA1 is allowed in HMAC where collision resistance does not matter."

      This is inconvenient as a user, it means the distro is shipped with insecure standard (according to the vendor audit tool, that ships the same distro... but other audit tools raise the same "issue" ) and so I need to update this myself to comply.
      Adding to the annoyance there is no module NO-HMAC-SHA1 shipped (as there used to be, a NO-SHA1) so I need to craft a policy myself, which is error prone.

      Is it possible to update the DEFAULT policy so that hmac-sha1 is forbidden in ssh mac? or at least provide a module for convenience? Thanks!!

      $ rpm -q -a crypto-policies\*
      crypto-policies-20250214-1.gitfd9b9b9.el10.noarch
      crypto-policies-scripts-20250214-1.gitfd9b9b9.el10.noarch
      $ update-crypto-policies --show
      DEFAULT
      $ sudo sshd -T | grep mac
      macs hmac-sha2-256-etm@openssh.com,hmac-sha1-etm@openssh.com,umac-128-etm@openssh.com,hmac-sha2-512-etm@openssh.com,hma-sha2-256,hmac-sha1,umac-128@openssh.com,hmac-sha2-512
      

              asosedki@redhat.com Alexander Sosedkin
              frigault Francois Rigault
              Alexander Sosedkin Alexander Sosedkin
              Ondrej Moris Ondrej Moris
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                Created:
                Updated:
                Resolved: